WO2025204192A1 - Gas shielded arc welding method, gas shielded arc welding system, and welding wire - Google Patents

Abstract

The present invention achieves excellent tip wear resistance regardless of the current range. In this gas shielded arc welding method: a welding wire includes an Fe or Fe-based alloy, a Cu or Cu-based alloy plating, and, on the plated surface, a solid lubricating agent that at least has a layered crystal structure and comprises a sulfide; a feed control method includes a step for controlling at least a welding current in accordance with the tip end position of the welding wire; in the step for controlling at least the welding current, the welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP_AVE during a forward feed period is set to be higher than the predetermined current value; and when a wire position phase based on the tip end position of the welding wire at the time of switching from a reverse feed period to the forward feed period is set to 0 deg, the wire position phase for switching from the low current period to the high current period is set in a range of 280° to 350°.

Description

Gas-shielded arc welding method, gas-shielded arc welding system, and welding wire

The present invention relates to a gas-shielded arc welding method, a gas-shielded arc welding system, and a welding wire.

In consumable electrode gas-shielded arc welding, current is sent to a constantly fed consumable electrode (hereafter also referred to as welding wire) via a contact tip, melting the welding wire and performing arc welding. During this process, the welding wire slides against the contact tip while current is passed through it, resulting in significant wear phenomena, primarily adhesive wear and abrasive wear. Abrasive wear is also known as scratch wear.

This type of wear generally occurs on the contact tip side, which is made of a softer material with a lower melting point than the welding wire. Hereinafter, this wear on the contact tip side will also be referred to as tip wear. Tip wear tends to increase the faster the welding wire feed speed or the more the welding current fluctuates up and down. For this reason, feed control methods that have become increasingly common in recent years have the problem that tip wear is particularly likely to occur, as the welding wire is alternately fed forward and backward at high speed and the welding current also fluctuates.

Patent Document 1 discloses a technology for providing arc welding solid wire with excellent arc stability even when used for long periods of continuous welding, in which the steel material and the copper plating layer have a copper content of 0.05 to 0.30 mass% based on the total mass of the wire, 0.05 to 0.20 g of oil per 1 kg of wire is applied to the wire surface, and the copper plating layer has a circumferential arithmetic mean roughness Rac of 0.25 to 1.00 μm and a longitudinal arithmetic mean roughness Ral of 0.07 to 0.50 μm.

Patent Document 2 discloses a welding power supply that includes a feed control means that controls wire feed while periodically switching between forward and reverse wire feed periods, and a current control means that changes the welding current in accordance with the position of the wire tip, whose distance from the surface of the base metal periodically fluctuates. The feed control means controls the time it takes for the wire tip to move from the closest point, where it is closest to the base metal, to the farthest point, where it is farthest from the base metal, so that it is shorter than the time it takes for the wire tip to move from the farthest point to the closest point. The current control means controls the welding current to provide a low-current period during which the wire tip is reverse-fed, reducing it below a predetermined current value. This technology reduces spatter scattering and wear on the contact tip.

Japanese Patent Application Publication No. 2021-159957 Japanese Patent Application Publication No. 2022-33399

Patent Document 1 describes a technology using a low-current feed control method for welding currents of around 200A. There are different types of feed control welding methods, including one that alternates between forward and reverse feed periods to weld at low currents, based on a short-circuit transition that generates short-circuit periods and arc periods (hereinafter also referred to as a "short-circuit feed control method"), and one that alternates between forward and reverse feed periods to weld at medium currents or higher, based on a globule transition that suppresses the occurrence of short-circuit periods (hereinafter also referred to as a "short-circuit suppression feed control method"). Patent Document 1 describes a short-circuit feed control method, and because it welds at low currents of roughly 250A or less, it does not take into account the effects of adhesive wear.

On the other hand, Patent Document 2 discloses a short-circuit suppression type feed control method suitable for medium current ranges and above, which discloses that reducing the wire feed speed, lengthening the non-current suppression period, and maintaining a low welding current are effective against tip wear. However, because the wire feed speed must be reduced and the current during the non-current suppression period must be kept low, the conditions for application are limited. Specifically, because there are restrictions on increasing the wire feed speed and welding current, no effect against tip wear can be expected for welding in the high current range. Furthermore, it does not specify how effective it is against tip wear, and does not take into account the impact of adhesive wear caused by current fluctuations that occur when current non-suppression periods and current suppression periods are set.

The present invention therefore aims to solve the above-mentioned problems by providing a gas-shielded arc welding method that achieves excellent tip wear resistance regardless of the current range using a feed control method that feeds welding wire at a predetermined average wire feed speed while alternately repeating forward and reverse feed, as well as a welding system and welding wire used in this method.

The present invention consists of the following:

(1) A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire,
In the step of controlling at least the welding current,
the welding current has at least a high current period in which the welding current is higher than the predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP _AVE during the forward feed period is higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding method.

(2) A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
a welding wire feed control device;
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
the feed control device controls at least the welding current in accordance with the tip position of the welding wire;
the welding current has at least a high current period in which the welding current is higher than the predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the feed control device controls the welding current so that an average welding current ITP _AVE during the forward feed period becomes a current higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding system.

(3) A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, controls an average welding current at least during a period of forward feed to be higher than a predetermined current value depending on a tip position of the welding wire, and feeds the welding wire at a predetermined average wire feed speed,
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface.
Welding wire.

According to the present invention, a feed control method in which welding wire is fed at a predetermined average wire feed speed while alternately repeating forward and reverse feed can achieve excellent tip wear resistance regardless of the current range.

FIG. 1 is a conceptual diagram illustrating tip wear. FIG. 2 is a conceptual diagram illustrating the configuration of the welding wire according to this embodiment. FIG. 3 is an explanatory diagram of the timing at which the low current period is provided. FIG. 4 is a diagram showing the wear state of the contact tip when a test is conducted with the current phase changed. FIG. 5 is a schematic diagram showing an example of the configuration of a welding system according to this embodiment. FIG. 6 is a block diagram showing a schematic configuration relating to the control of the welding power source, welding control device, and servo amplifier in this embodiment. FIG. 7 is a graph illustrating the relationship between the wire feed speed, the wire tip position, and the current detection signal in this embodiment. FIG. 8 is a diagram showing the composition of the welding wire in this embodiment. FIG. 9 is a diagram showing conditions for feed control in this embodiment. FIG. 10 is a diagram showing the results of the evaluation test in this embodiment. FIG. 11 is a diagram showing the relationship between the amount of solid lubricant, the square of the current during the normal feeding period, and the amount of wear.

Figure 1 is a conceptual diagram illustrating tip wear.

Contact tips used in gas-shielded arc welding are hollow contact tips with welding wire passing through them. Welding is performed while the welding wire is being fed, but as shown in the figure, the welding wire comes into contact with one side of the contact tip, causing current to flow through it, which causes wear on the contact tip.

The main wear modes that affect chip wear are adhesive wear and abrasive wear. Adhesive wear occurs when two materials adhere to each other at the sliding contact surface, causing the material with the weaker interface bond to be torn off and adhere to one surface. Abrasive wear occurs when the surface protrusions of the harder material at the sliding contact surface mechanically scrape away the opposing material, and when there are hard particles sandwiched between the contact surfaces, the hard particles scrape away both surfaces, causing wear.

Tip wear generally occurs when current flows between an Fe-based welding wire and a Cu-based contact tip. This occurs mainly because the Cu-based material of the contact tip, which has a low melting point, softens or melts due to electrical resistance heat and frictional heat generated by the sliding of the welding wire. The softened or molten Cu adheres to the surface of the welding wire and is expelled from the contact tip. In particular, when the current periodically increases and decreases, as in pulse welding, the Cu-based material of the contact tip repeatedly melts and solidifies, bonding strongly to the welding wire as it solidifies. The Cu on the contact tip side hardens and is then torn off by the welding wire, resulting in significant tip wear. Therefore, the challenge is how to suppress adhesive wear when the welding wire is fed in the forward direction.

The present invention focuses on, first, keeping the interface condition on the contact tip side unchanged during the forward feed period of the welding wire, and, second, preventing Cu from adhering to the contact surface on the welding wire side even if the contact tip softens or melts, and has solved the problem from the perspective of the timing of feeding and current control in the welding wire and feed control method. Below, we will explain the technical features of the welding wire and the timing of feeding and current control in the feed control method.

[Features of welding wire]
2 is a conceptual diagram illustrating the configuration of a welding wire according to this embodiment. The welding wire is made of Fe or an Fe-based alloy (hereinafter, Fe or an Fe-based alloy will be collectively referred to as an Fe-based metal). The surface of the welding wire is plated with Cu or a Cu-based alloy, and at least a solid lubricant having a layered crystal structure and a sulfide is applied to the plated surface. Examples of solid lubricants having a layered crystal structure and a sulfide include molybdenum disulfide (MoS ₂ ) and tungsten disulfide (WS ₂ ). Here, examples of Fe-based alloys include mild steel and stainless steel, and examples of Cu-based alloys include those commonly used for electrodes, such as chromium copper, chromium zirconium copper, and beryllium copper.

[Characteristics of feed and current control in the feed control method]
In the feed control method, the welding current is set to at least a high-current period where the welding current is higher than the predetermined current value and a low-current period where the current is lower than the predetermined current value, and the welding current is controlled to switch to at least the high-current period or the low-current period depending on the tip position of the welding wire, and the welding current is set or controlled so that the average welding current ITP _AVE during the forward feeding period of the welding wire is higher than the predetermined current value. Note that the predetermined current value may be, for example, the average welding current I _AVE . Furthermore, when the wire position phase based on the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, the wire position phase at which the low-current period is switched to the high-current period is set in the range of 280° to 350°.

Due to the characteristics of the welding wire and feed control method conditions described above, it is estimated that the following phenomena (a) to (c) occur at the contact surface between the welding wire and the contact tip (hereinafter simply referred to as the "contact surface") during the forward feed period.

(a) During the forward feeding period of the welding wire, a current equal to or greater than the average welding current I _AVE is applied. At this time, the Fe-based metal side of the welding wire, which has a high electrical resistance, becomes hot due to resistance heat, and the Fe-based metal of the wire and the Cu-based metal of the plating melt.

(b) The molten Fe in the wire and Cu in the plating react with S in the sulfide to produce FeS or Cu ₂ S. FeS has a melting point of 1190°C, and Cu ₂ S has a melting point of 1130°C, and they are substances with good electrical conductivity. During the forward feed period, a current equal to or greater than the average welding current I _AVE is applied, so the FeS and Cu ₂ S melt and come into contact with the solid portion of the sliding welding wire (unmelted Fe-based metal).

(c) The interface between the solid portion of the wire and the molten portion of FeS and Cu ₂ S has poor wettability, making it difficult for the molten portion of FeS and Cu ₂ S to adhere to the solid portion of the sliding wire. In other words, the molten portion of FeS and Cu ₂ S is not expelled from the tip during the forward feed period. Here, FeS and Cu ₂ S act as a liquid lubricant film during the forward feed period, preventing adhesive wear. Furthermore, the liquid lubricant film stabilizes the current-carrying surface, which is also effective for arc stability. Note that, if sulfides are not present on the plating surface, an excellent liquid lubricant film is not formed, and therefore, during the forward feed period, the molten Fe of the welding wire and the Cu of the contact tip adhere to the sliding solid portion of the welding wire and are expelled from the contact tip, resulting in adhesive wear.

[Timing for low current period]
3 is an explanatory diagram of the timing for providing a low current period. In the short circuit suppression type feed control method, it is necessary to provide a low current period due to the nature of the control. In the short circuit suppression type feed control method of the present invention, it is preferable to provide a low current period in the reverse feed period, and it is more preferable that the average welding current during the reverse feed period be equal to or less than the average welding current I _AVE .

By providing a low-current period during the reverse feed period, the molten Fe and Cu, as well as the FeS and Cu ₂ S that react with them, solidify and transfer to the contact tip side. As described above, because FeS and Cu ₂ S do not easily adhere to the welding wire due to their wettability, these solidified substances bond more strongly with the Cu-based metal of the contact tip and are transferred to the contact tip side. This is also evident from the observation of the contact surface on the contact tip side after welding, which will be described later with reference to Figure 4. Therefore, during the low-current period, abrasive wear (mechanical wear) between the solid portion of the wire and the solidified and adhered portion on the contact tip side becomes dominant. The transferred layer on the contact tip side, which has a lower melting point and is softer than the solid portion of the wire, is pushed toward the back of the contact tip by the sliding of the welding wire. At this time, if the timing of switching from the low-current period to the high-current period is appropriate, it will be re-melted during the next forward feed period, and therefore will not affect the wear of the contact tip. Specifically, when the wire position phase is 0° with respect to the tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period, the wire position phase at the time of switching from the low current period to the high current period needs to be set to a timing in the range of 280° to 350°. If this timing is not met, abrasive wear will occur on the contact tip.

Figure 4 shows the wear state of the contact tip when testing with different current phases.

(a) in Figure 4 shows the contact surface of the contact tip after welding under phase conditions in which a peak current is set during the forward feed period and a low current period is set during the reverse feed period, i.e., standard conditions. Under standard conditions, almost no trace of contact with the welding wire was observed on the contact surface of the contact tip.

(b) in Figure 4 shows the contact surface of the contact tip after welding under phase conditions in which the current phase was advanced by 200 degrees from the standard conditions, resulting in a low current period during the forward feed period and a peak current during the reverse feed period. Under phase conditions in which the current phase was advanced by 200 degrees, abrasive wear was observed on the contact surface of the contact tip.

[Ratio of forward feeding period to reverse feeding period]
The ratio of the forward feeding period to the reverse feeding period in one cycle is preferably 1:1, as in this embodiment, or a smaller ratio for the forward feeding period. This shortens the period during which wear is promoted and allows for a high current to be applied to stably generate a liquid lubricant film. In other words, tip wear resistance tends to improve when the ratio is 1:1 or when the forward feeding period is smaller.

Below, we will explain specific wires and specific embodiments of feed control that can achieve more favorable effects on tip wear resistance. Please note that this is merely an example, and is not limited to this as long as the above technical characteristics are met.

[Surface properties of welding wire]
(Welding wire plating)
In order to generate a stable liquid lubricant film during the forward feed period, the welding wire must be plated with Cu or a Cu-based alloy. As mentioned above, since the resistance heat is greatest in the Fe or Fe-based alloy of the welding wire, the molten Cu required to generate the liquid lubricant film must be secured by plating. As will be described later, wires without plating cannot achieve wear resistance, which suggests that the amount of molten Cu required to generate the liquid lubricant film was insufficient. In the present invention, the composition, plating thickness, and amount of plated Cu are not particularly important, and are sufficient as long as they fall within the commonly used range. However, in order to generate a stable liquid lubricant film, the amount of plated Cu is preferably 0.05 to 0.30 mass% of the total mass of the wire.

(sulfide)
The sulfide is preferably applied so as to adhere to the plating surface, and is preferably applied so as to adhere uniformly to the plating surface without bias. Furthermore, the sulfide is a solid lubricant of a layered crystalline structure material, which stabilizes feedability as a solid lubricant up to the contact tip, and acts to generate a liquid lubricant film on the contact surface within the contact tip, suppressing adhesive wear. Examples of solid lubricants that function in this way include molybdenum disulfide (MoS ₂ ) and tungsten disulfide (WS ₂ ). While molybdenum disulfide and tungsten disulfide are stable at room temperature, FeS and Cu ₂ S are more stable at temperatures above 1000°C. Therefore, in the present invention, it is preferable to include either molybdenum disulfide or tungsten disulfide.

Furthermore, to generate a liquid lubricating film, the amount of sulfide applied is preferably 0.05 g or more and 0.40 g or less per 10 kg of welding wire, and more preferably 0.10 g or more and 0.30 g or less. Furthermore, the sulfide is mixed with lubricating oil and applied to the plated surface of the welding wire, and the amount of adhesion can be controlled by adjusting the mixture ratio.

(lubricating oil)
In the present invention, the type and amount of lubricating oil are not particularly limited. Examples of lubricating oils that can be used include animal oils, vegetable oils, or mixtures thereof (collectively referred to as animal and vegetable oils), as well as mineral oils and synthetic oils (collectively referred to as mineral oils). Specific examples of animal and vegetable oils include palm oil, rapeseed oil, castor oil, lard, and beef tallow. Examples of mineral oils include refined petroleum products containing paraffinic hydrocarbons and naphthenic hydrocarbons, which are commonly used as lubricating oils. The amount of lubricating oil may be within a range that ensures stable feeding and prevents the lubricating oil from forming a pool within the power feed tip. For example, the amount may be between 0.4 g and 2.0 g per 10 kg of welding wire.

(Surface solids)
The solid matter present on the surface of the copper plating layer is copper powder that has fallen off the copper plating or re-adhered during the manufacturing process. It may also be a lubricant used during wire drawing. Specific examples include copper powder, calcium- or sodium-based soap, etc. Although this is not a particular issue in the present invention, if there is an excessive amount of solid matter, it may adhere and accumulate inside the conduit liner or power feed tip, potentially causing wire feed to stop. Therefore, it is preferable to limit the total amount of solid matter present on the wire surface to 500 mg or less per 10 kg of wire.

[Wire composition of welding wire]
In the present invention, as described above, the composition of the wire may be Fe or an Fe alloy, and examples thereof include JIS Z 3312:2009 (MAG and MIG welding solid wires for mild steel, high-tensile steel, and low-temperature steel), JIS Z 3313:2009 (flux-cored arc welding wires for mild steel, high-tensile steel, and low-temperature steel), JIS Z 3315:2012 (MAG and MIG welding solid wires for weathering steel), JIS Z 3317:2011 (gas-shielded arc welding filler rods and solid wires for molybdenum steel and chromium-molybdenum steel), JIS Z 3320:2012 (flux-cored arc welding wires for weathering steel), JIS Z 3321:2013 (stainless steel filler rods, solid wires, and steel strips for welding), and JIS Z The composition specified in JIS Z 3323:2007 (Stainless steel arc welding flux-cored wire and filler rod) is applicable. That is, the steel type is preferably mild steel, high-tensile steel, low-temperature steel, molybdenum steel, chromium-molybdenum steel, or stainless steel. In particular, with regard to the feed control method, a composition based on or similar to JIS Z 3312:2009, which has a high Fe content, is more preferable in terms of tip wear resistance. Specifically, the wire composition described below is preferred.

The alloying elements contained in the welding wire according to this embodiment are described in detail below, along with the reasons for their addition and the reasons for limiting their numerical values. In the following description, the content of each element in the welding wire is defined as the content of the element contained as an alloying element relative to the total mass of the welding wire. The welding wire may be a solid wire composed of alloying elements, or a flux-cored wire in which the flux is formed only of metal powder (hereinafter also referred to as a metal-based flux-cored wire). Furthermore, the welding wire may be a flux-cored wire in which the flux contains even a small amount of compounds (mainly oxides, fluorides, etc.) (hereinafter also referred to as a slag-based flux-cored wire). However, from a manufacturing perspective, which makes it easier to apply Cu-based plating to the wire surface, it is more preferable that the welding wire be a solid wire.

In addition, in metal-based flux-cored wire or slag-based flux-cored wire, the alloying elements described below may be contained in the flux-cored wire in the form of metal, in the form of compound, or in the form of both metal and compound, unless otherwise specified. Therefore, regardless of the form in which each of the above elements is contained in the flux-cored wire, they are specified in terms of the converted value of the element itself. For example, in the case of Si, the Si content refers to the sum of the converted Si values of metal Si and Si compounds, and metal Si includes both elemental Si and Si alloys.

(Fe: 90% by mass or more)
In the present invention, Fe in the welding wire is required to generate a liquid lubricant film during the forward feed period. To obtain more stable tip wear resistance, the Fe content is preferably 90 mass% or more, and more preferably 95 mass% or more. On the other hand, to obtain the tip wear resistance effect of the present invention, the welding wire may be made of pure iron, but from the viewpoint of welding workability and the mechanical properties of the weld metal, it is more preferable to set the Fe content to 99 mass% or less and to contain the elements described below.

(C: 0.15% by mass or less (including 0% by mass))
C has a deoxidizing effect, and when C is contained in the welding wire, the effect of improving the mechanical performance of the weld metal can be obtained. The C content can be adjusted appropriately depending on the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain C, and the C content may be 0 mass %.

However, if excessive C is contained in the welding wire, the deoxidizing effect becomes greater, and CO is generated near the arc, which may cause an explosion, resulting in the generation of spatter and an increase in the amount of fumes. Therefore, from the perspective of welding workability, the C content in the welding wire is preferably 0.15 mass% or less, more preferably 0.10 mass% or less, and even more preferably 0.08 mass% or less, relative to the total mass of the welding wire.

(Si: 1.10 mass% or less (including 0 mass%))
Si is a deoxidizer, and when Si is contained in the welding wire, the effect of improving the mechanical performance of the weld metal can be obtained. The Si content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Si, and the Si content may be 0 mass %. Note that, in order to obtain the above effect, the Si content is preferably 0.20 mass % or more.

On the other hand, if the wire contains too much Si, deoxidation will occur and the amount of oxygen in the molten pool will decrease, increasing the surface tension of the droplets and damaging the bead shape. Therefore, the Si content in the welding wire should be 1.10 mass% or less, and preferably 1.00 mass% or less, relative to the total mass of the wire.

(Mn: 2.30 mass% or less (including 0 mass%))
Like Si, Mn is a deoxidizer, and the inclusion of Mn in the welding wire can provide the effect of improving the mechanical properties of the weld metal. The Mn content can be adjusted appropriately depending on the required strength. In this embodiment, however, as long as the strength can be ensured by other elements, the welding wire does not need to contain Mn, and may even contain 0 mass% Mn. However, Mn is suitable for improving mechanical properties, and therefore it is preferable to include Mn preferentially. In order to obtain the above effect, the Mn content is preferably 0.90 mass% or more.

On the other hand, if the Mn content in the wire is excessive, deoxidation will occur and the amount of oxygen in the molten pool will decrease, which will increase the surface tension of the droplets and damage the bead shape. Therefore, the Mn content in the welding wire should be 2.30 mass% or less, and preferably 2.20 mass% or less, relative to the total mass of the wire.

(Ti: 0.30 mass% or less (including 0 mass%))
Ti is an element that has strong deoxidation, denitrification, and desulfurization effects, and is an element that preferentially forms compounds through these effects. The precipitation of these elements in the weld metal structure can have the effect of improving the mechanical performance of the weld metal. The Ti content can be adjusted appropriately depending on the required strength, but in this embodiment, as long as strength can be ensured by other elements, the welding wire does not need to contain Ti, and may even contain 0 mass % Ti. Note that, in order to obtain the above effects, the Ti content is preferably 0.02 mass % or more.

On the other hand, if the welding wire contains an excessive amount of Ti, inclusions in the weld metal will become coarse, which may reduce toughness in particular. Therefore, the Ti content in the welding wire is preferably kept to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

(Al: 0.30 mass% or less (including 0 mass%))
Like Ti, Al is an element that strongly deoxidizes, denitrifies, and desulfurizes, and is an element that preferentially forms compounds through these actions. Precipitation of these compounds in the weld metal structure can provide the effect of improving the mechanical performance of the weld metal. The Al content can be adjusted appropriately depending on the required strength. However, in this embodiment, as long as strength can be ensured by other elements, the welding wire does not need to contain Al, and the content may be 0 mass %. To obtain the above effects, the Al content is preferably 0.02 mass % or more.

On the other hand, if the welding wire contains an excessive amount of Al, inclusions in the weld metal will become coarse, which may reduce toughness in particular. Therefore, the Al content in the welding wire is preferably kept to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

(Zr: 0.30 mass% or less (including 0 mass%))
Like Al and Ti, Zr is an element that strongly deoxidizes, denitrifies, and desulfurizes, and these elements preferentially form compounds through these actions. Precipitation of these elements in the weld metal structure enhances the mechanical performance of the weld metal. The Zr content can be adjusted appropriately depending on the required strength. However, in this embodiment, as long as the strength can be ensured by other elements, the welding wire does not need to contain Zr, and Zr may be 0% by mass. To obtain the above effects, the Zr content is preferably 0.02% by mass or more.

On the other hand, if the welding wire contains an excessive amount of Zr, inclusions in the weld metal will become coarse, which may reduce toughness in particular. Therefore, the Zr content in the welding wire is preferably kept to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

(Mg: 0.30% by mass or less (including 0% by mass))
Like Zr, Al, and Ti, Mg is an element that strongly deoxidizes, denitrifies, and desulfurizes, and is an element that preferentially forms compounds through these actions. Precipitation of these elements in the weld metal structure can provide the effect of improving the mechanical performance of the weld metal. The Mg content can be adjusted appropriately depending on the required strength. However, in this embodiment, as long as strength can be ensured with other elements, the welding wire does not need to contain Mg, and the Mg content may be 0 mass %. To obtain the above effects, the Mg content is preferably 0.02 mass % or more.

On the other hand, if the welding wire contains excessive Mg, inclusions in the weld metal will become coarse, which may reduce toughness in particular. Therefore, the Mg content in the welding wire is preferably kept to 0.30 mass% or less, and more preferably 0.25 mass% or less, relative to the total mass of the wire.

(Ni: 4.75 mass% or less (including 0 mass%))
When the welding wire contains Ni, it is possible to obtain the effect of improving the mechanical properties of the weld metal. The Ni content can be adjusted appropriately depending on the required strength. However, in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain Ni, and the Ni content may be 0 mass %. When using the welding wire according to this embodiment, the Ni content is preferably 4.75 mass % or less with respect to the total mass of the welding wire. By suppressing the Ni content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to prevent the weld metal from becoming excessively strong.

(Cr: 0.60% by mass or less (including 0% by mass))
The inclusion of Cr in the welding wire can provide the effect of improving the mechanical properties of the weld metal. The Cr content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, the welding wire does not need to contain Cr, and the Cr content may be 0 mass %. Note that the Cr content is preferably 0.60 mass % or less with respect to the total mass of the welding wire. By suppressing the Cr content as described above, a balance is achieved with other elements that improve mechanical properties, and excessive strength of the weld metal can be suppressed.

(Mo: 0.90 mass% or less (including 0 mass%))
When Mo is contained in the welding wire, the effect of improving the mechanical performance of the weld metal can be obtained. The Mo content can be adjusted appropriately depending on the required strength. In this embodiment, however, if the strength can be ensured by other elements, Mo does not need to be contained in the welding wire, and it may be 0 mass %. The Mo content is preferably 0.90 mass % or less with respect to the total mass of the welding wire. By suppressing the Mo content as described above, a balance is achieved with other elements that improve mechanical performance, and excessive strength of the weld metal can be suppressed.

(Cu (excluding plated Cu): 0.50% by mass or less (including 0% by mass))
When Cu is contained in the welding wire, the effect of improving the mechanical performance of the weld metal can be obtained. The Cu content can be adjusted appropriately depending on the required strength. In this embodiment, however, as long as the strength can be ensured by other elements, the welding wire does not need to contain Cu, and the Cu content may be 0 mass %. The Cu content in the welding wire is preferably 0.50 mass % or less with respect to the total mass of the welding wire. By suppressing the Cu content as described above, a balance is achieved with other elements that improve mechanical performance, and excessive strength of the weld metal can be suppressed.

(Nb: 0.50 mass% or less (including 0 mass%))
(V: 0.50% by mass or less (including 0% by mass))
The inclusion of Nb and V in the welding wire can provide the effect of improving the mechanical performance of the weld metal. The contents of Nb and V can be adjusted appropriately depending on the required strength. However, in this embodiment, as long as the strength can be ensured by other elements, the welding wire does not need to contain Nb or V, and may contain 0 mass%. The Nb content and V content in the welding wire are preferably 0.50 mass% or less, respectively, with respect to the total mass of the welding wire. By suppressing the Nb content and V content as described above, a balance can be achieved with other elements that improve mechanical performance, and excessive strength of the weld metal can be prevented.

(B: 0.0050% by mass or less (including 0% by mass))
When the welding wire contains B, it is possible to obtain the effect of improving the mechanical properties of the weld metal. The B content can be adjusted appropriately depending on the required strength, but in this embodiment, if the strength can be ensured by other elements, the welding wire does not need to contain B, and the B content may be 0 mass %. The B content is preferably 0.0050 mass % or less with respect to the total mass of the welding wire. By suppressing the B content as described above, a balance is achieved with other elements that improve mechanical properties, and it is possible to suppress the weld metal from becoming excessively strong.

(P: 0.050% by mass or less (including 0% by mass))
(S: 0.050% by mass or less (including 0% by mass))
P and S are elements that affect the cracking susceptibility of the weld metal, and the lower the P and S contents in the welding wire, the better the cracking resistance of the weld metal, so the welding wire according to this embodiment does not need to contain P or S, or it may contain 0 mass %. Note that when the welding wire contains P and S, from the viewpoint of cracking resistance, the P and S contents in the welding wire are preferably 0.050 mass % or less with respect to the total mass of the welding wire.

(Remainder: unavoidable impurities)
In this embodiment, the balance of the alloy elements of the wire preferably used is unavoidable impurities. Examples of unavoidable impurities include O, N, Li, Bi, and As. The content of each of these unavoidable impurities is preferably 0.0100% by mass or less, and more preferably 0.0050% by mass or less, based on the total mass of the wire. Furthermore, the total content of these unavoidable impurities is preferably 0.0200% by mass or less, based on the total mass of the wire.

(wire diameter)
In the welding wire according to the present embodiment, the wire diameter (diameter) is not particularly limited, but a wire having a diameter specified in a welding material standard such as AWS or JIS can be used.

(Wire manufacturing)
The welding wire according to this embodiment is not particularly limited in its manufacturing method, and no special manufacturing conditions are required, and it can be manufactured by a conventional method. For example, in the case of a solid wire, a steel containing the above alloy elements in a specified content is melted to obtain an ingot. Next, the ingot is subjected to hot forging or the like as needed, followed by hot rolling and cold wire drawing to form a wire. The obtained wire is then annealed at a temperature of about 500 to 900°C as needed, pickled, copper plated as needed, and further subjected to finish wire drawing as needed to obtain a target wire diameter. Thereafter, a lubricant is added as needed, and the welding wire can be manufactured.

(Feeding control method)
Next, the conditions for the feed control method according to this embodiment will be described in detail below.

[Welding system]
Next, an embodiment of a system for implementing the feed control method used in the present invention will be described in detail with reference to the drawings. Note that this embodiment is an example of a system using a welding robot, and the welding control method according to the present invention is not limited to the configuration of this embodiment. For example, an automatic welding device using a cart instead of a welding robot body may be applied, or a portable, small welding robot may be applied. Furthermore, in this embodiment, the tip wear suppression effect will be described using as an example the system configuration of a short-circuit suppression type feed control method, in which tip wear is particularly noticeable.

In this embodiment, additive manufacturing technology utilizing the gas-shielded arc welding method of the present invention is also useful, specifically, in wire and arc additive manufacturing (WAAM). The term additive manufacturing is sometimes used broadly to refer to additive manufacturing or rapid prototyping, but in this invention, the term additive manufacturing is used consistently. When the method of the present invention is used in additive manufacturing technology, "welding" can be replaced with "deposition," "additive manufacturing," or "additive manufacturing." For example, when treated as welding, it becomes "welding conditions," but when the present invention is used as additive manufacturing, it can be replaced with "deposition conditions," and when treated as welding, it becomes "welding system," but when the present invention is used as additive manufacturing, it can be replaced with "additive manufacturing system."

FIG. 5 is a schematic diagram showing an example configuration of a welding system 50 according to this embodiment. The welding system 50 includes a welding robot 110, a welding control device 120, a welding power source 140, a controller 150, a servo amplifier 160, a servo motor 170, a push motor 180, and a wire buffer 190. The push motor 180 feeds the welding wire 100.

The welding power source 140 is connected to the welding robot 110 via a positive power cable (not shown) so that electricity can be applied to the welding wire 100, and is connected to the workpiece (hereinafter also referred to as the "base material") 200 via a negative power cable (not shown). This connection is for welding with reverse polarity. To weld with positive polarity, the polarity of the welding power source 140 can be reversed.

Furthermore, the welding power source 140 and push motor 180 are connected by a signal line, allowing the feed speed of the welding wire to be controlled. In the feed control of this embodiment, the push motor 180 rotates only in the forward direction, while the servo motor 170, described below, can be switched between forward and reverse rotation.

Welding robot 110 is equipped with a welding torch 111 as an end effector. Welding torch 111 has a contact tip, i.e., an energization mechanism that energizes welding wire 100. The gas-shielded arc welding method, gas-shielded arc welding system, and welding wire of the present invention provide this contact tip with excellent tip wear resistance. When energized from the contact tip, welding wire 100 generates an arc from its tip, and the resulting heat welds workpiece 200, which is the target of welding.

The welding torch 111 also includes a shielding gas nozzle, which serves as a mechanism for ejecting shielding gas. While there are no particular limitations on the shielding gas, it is preferable that the gas composition be one that exhibits globular transition due to the characteristics of the control used in this embodiment. Specifically, it is preferable that the gas contains at least one of carbon dioxide, nitrogen, hydrogen, and oxygen, which have high potential gradients. From the perspective of versatility, in the case of a mixed gas with argon gas (hereinafter also referred to as "Ar gas"), a system containing at least 10% by volume of carbon dioxide is more preferable, a system containing 90% by volume or more of carbon dioxide is even more preferable, and it is even more preferable to use carbon dioxide alone. The shielding gas is supplied from a shielding gas supply device (not shown).

Servo motor 170 is provided near welding torch 111. Servo amplifier 160 connected to servo motor 170 controls servo motor 170. In this embodiment, welding torch 111 is configured independent of servo motor 170, but the torch may be configured such that servo motor 170 is provided inside welding torch 111. Servo motor 170 switches between forward and reverse rotation based on a forward/reverse feed command, and controls the feed. In addition, servo amplifier 160 enables high-speed calculation processing, and has a forward/reverse feed command generation unit 161, as described below.

A wire buffer 190 is placed between the push motor 180 and the servo motor 170. Because the push motor 180 feeds the wire only in the forward direction and the servo motor 170 feeds the wire in both the forward and reverse directions, the feed directions of the push motor 180 and the servo motor 170 may differ. This can create situations where a large load is easily placed on the wire within the feed path. To ensure proper feed control even in such feed situations, the wire buffer 190 is provided to prevent buckling of the wire.

Furthermore, in this embodiment, the specific configuration of workpiece 200 is not particularly important, and neither are the welding conditions such as joint shape, welding posture, or groove shape. Welding control device 120 mainly controls the operation of welding robot 110. Therefore, welding control device 120 can also be referred to as a robot controller. Welding control device 120 holds teaching data that predefines the operation pattern, welding start position, welding end position, welding conditions, weaving operation, etc. of welding robot 110, and instructs welding robot 110 on these to control the operation of welding robot 110. Furthermore, welding control device 120 provides welding conditions such as welding current, welding voltage, and feed speed to welding power source 140 during welding work in accordance with the teaching data.

As shown in FIG. 5, the welding system 50 of this embodiment is configured such that the welding control device 120 is independent from the welding power source 140, but the welding control device 120 may also be provided within the welding power source 140.

The controller 150 is connected to the welding control device 120 and creates or displays programs for operating the welding robot 110, inputs teaching data, etc. Information input by the user to the controller 150 is provided to the welding control device 120. The controller 150 may also have the function of manually operating the welding robot 110. The connection between the controller 150 and the welding control device 120 may be wired or wireless.

In response to a command from the welding control device 120, the welding power source 140 supplies power to the welding wire 100 and the workpiece 200, thereby generating an arc between the welding wire 100 and the workpiece 200. In addition, in response to a command from the welding control device 120, the welding power source 140 outputs a control signal for the push motor 180.

Next, the functional configuration of welding system 50 according to this embodiment will be described in detail with reference to Figures 6 and 7. Figure 6 is a block diagram showing the general configuration related to the control of welding power source 140, welding control device 120, and servo amplifier 160 according to this embodiment. In the present invention, a device or group of devices having functions related to feed control is referred to as a feed control device. In this embodiment, the configuration of welding power source 140, welding control device 120, and servo amplifier 160 related to feed control is called the feed control device. Figure 7 is a graph illustrating the relationship between wire feed speed, wire tip position, and current detection signal according to this embodiment.

Welding power source 140 is connected to welding control device 120 via digital communication, and welding control device 120 is connected to servo amplifier 160 via digital communication. In other words, servo amplifier 160, welding control device 120, and welding power source 140 are digitally connected in a line configuration in that order. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are indirectly connected via digital communication. Note that servo amplifier 160, welding power source 140, and welding control device 120 may also be connected in a line configuration in that order. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are directly connected via digital communication.

In this embodiment, communication between the welding power source 140 and the welding control device 120 is via CAN (Controller Area Network), which is an industrial field network, and communication between the welding control device 120 and the servo amplifier 160 is via EtherCAT (Ethernet for Control Automation Technology) (registered trademark), which is also an industrial field network, but this is not limited to these.

(Functional configuration of welding power source)
The control system 141 of the welding power source 140 is executed, for example, by the welding control device 120 or a computer (not shown) executing a program. The control system 141 of the welding power source 140 includes a current setting unit 36. In this embodiment, the current setting unit 36 has a function of setting various current values that define the welding current flowing through the welding wire 100. The current setting unit 36 has a function of setting the start and end times of each current control period. The current setting unit 36 has a target current setting unit 36A, a wire tip position conversion unit 36B, and a voltage setting unit 36C. The target current setting unit 36A has a function of setting the start and end times of each of the peak period Dap, fall period Ddwn, base period Db, and rise period Dup related to the current control. The wire tip position conversion unit 36B has a function of obtaining information on the tip position of the welding wire 100.

The various condition settings may be determined based on, for example, setting values entered in advance by the operator, a waveform control table prepared in advance, or a database of welding conditions. The setting values, tables, databases, etc. may be stored in any of the components of welding system 50. The setting values, tables, databases, etc. may be stored in welding control device 120, welding power source 140, etc., for example.

The various condition settings for the peak period Dap, fall period Ddwn, base period Db, and rise period Dup associated with the high current period TIP (in this embodiment, the sum of the Dup and Dp periods) and the low current period TIB (in this embodiment, the sum of the Ddwn and Db periods) can be determined by the waveform control table linear calculation unit 37 based on a waveform control table prepared in advance. In this embodiment, the various condition settings refer to the setting of conditions such as current value, time, or phase.

The welding current exhibits a pulse waveform that alternates between high-current periods TIP and low-current periods TIB based on the phase related to the wire tip position (hereinafter referred to as the "wire position phase" or "position phase"). In this embodiment, the timing of the peak period Dap, fall period Ddwn, base period Db, and rise period Dup is controlled based on the wire position phase of 0 to 360° (0 to 2π), with 0° being the angle when the wire tip position is closest to the tip side and 180° being the angle when it is closest to the base material side. The above wire position phase can also be expressed as the case where the wire position phase is set to 0°, based on the tip position of the welding wire when switching from the reverse feed period to the forward feed period.

Based on the set value of the average feed rate Favg in the welding condition information stored by the control system 141, a set current value Iap (hereinafter also referred to as "peak current Iap") for a peak period Dap in the high current period TIP and a set current value Ib (hereinafter also referred to as "base current Ib") for a base period Db in the low current period TIB, which are calculated by the waveform control table linear calculation unit 37, are set in the current setting unit 36. In the present invention, at least the set current value Iap and the wire position _phases at the start and end of the high current period, which will be described later, are set to optimal values in advance so that the value of the average welding current ITP _AVE during the forward feed period is higher than a predetermined current value (average welding current I AVE in this embodiment). This makes it possible to perform welding current control that provides good tip wear resistance.

In this embodiment, the welding current is basically controlled by two values: peak current Iap and base current Ib. Therefore, the start time of the low current period TIB, the time when the current transitions to base current Ib, i.e., the start time of the fall period Ddwn, may be expressed as the low current start time. The end time of the low current period TIB may also be expressed as the time when the base current Ib ends, i.e., the low current end time. The duration (time) of the fall period Ddwn and the duration (time) of the base period Db, which relate to the start and end times of the low current period TIB, are calculated by the waveform control table linear calculation unit 37. The time when the high current period TIP starts, i.e., the start time of the rise period Dup, may be expressed as the high current start time, and the time when the high current period TIP ends may be expressed as the high current end time.

As shown in Figure 7, the timing of the high current end time is determined by the set period d1 when the wire position phase starts at 0°, and the timing of the high current start time is determined by the set period d2 when the high current end time starts. This set period can be set by phase. For example, if d1 is set to 190° and d2 is set to 120°, the high current period ends when the wire position phase is 190° (d1) and starts when the wire position phase is 310° (d1 + d2). While the setting method uses d1 and d2 as described above, it can also be set by the value of d1 and the value of d1 + d2. In this embodiment, d1 is preferably set in the range of 100° to 200°, and d2 is preferably set so that d1 + d2 (the wire position phase at which the high current period starts) is in the range of 280° to 350°. For example, if you want to set d1 to 180° and d1 + d2 to 340°, you can set d2 to 160°. By setting d1 and d2 as above, you can achieve good tip wear resistance.

Furthermore, it is preferable to set the peak current Iap value in the range of 300 to 650 A. It is also possible to set the peak current Iap value in stages so that the current increases in the latter half of the high current period TIP. In this way, by selecting and setting at least one value from the range of 300 to 650 A for the peak current Iap, a liquid lubricant film can be generated stably, and good tip wear resistance can be achieved.

Note that the various start times, end times, etc. mentioned above are explained based on time. However, processing may also be performed by converting the value from wire position phase to time or cycle cyc using the value of wire position phase as the reference. In other words, since the values of wire position phase, time, and cycle cyc are mutually convertible, control may be performed based on any of these values.

Furthermore, the wire tip position conversion unit 36B determines the wire tip position based on the phase synchronization signal and phase delay correction amount signal from the servo amplifier 160. Note that in this embodiment, the wire tip position may be expressed using an angle (0 to 2π) as the wire position phase, as described above.

The phase delay correction amount signal is output from the phase delay correction unit 38. The phase delay correction unit 38 has a database (not shown). This database stores data that has been calculated in advance for each welding condition, which is the difference between periodic setting information and the operating signal for the actual forward and reverse feed operation of the servo motor 170. For example, if the welding condition is the forward and reverse wire frequency, the phase delay correction amount is determined based on the above database in accordance with the value of the forward and reverse wire frequency used, and is output from the phase delay correction unit 38 as a phase delay correction amount signal.

The main power supply circuit of the welding power supply 140 is composed of a three-phase AC power supply (hereinafter also referred to as the "AC power supply") 1, a primary rectifier 2, a smoothing capacitor 3, a switching element 4, a transformer 5, a secondary rectifier 6, and a reactor 7.

The AC power input from the AC power source 1 is full-wave rectified by the primary rectifier 2, and then smoothed by the smoothing capacitor 3 before being converted into DC power. The DC power is then converted into high-frequency AC power by inverter control using the switching element 4, and then converted into secondary power via the transformer 5. The AC output of the transformer 5 is full-wave rectified by the secondary rectifier 6, and then smoothed by the reactor 7. The output current of the reactor 7 is provided to the contact tip as output from the main power supply circuit, and is passed through the welding wire 100, which serves as a consumable electrode.

The welding wire 100 is fed by the push motor 180 and the servo motor 170, generating an arc between the welding wire 100 and the base material 200. The forward feed period during which the tip of the welding wire 100 moves toward the base material 200 is referred to as the forward feed period TP. The reverse feed period during which the tip of the welding wire 100 moves in the opposite direction to the direction in which the base material 200 is located is referred to as the reverse feed period TN. In this embodiment, the feed motor periodically feeds the welding wire 100, with the forward feed period TP and the reverse feed period TN combined forming one cycle. Note that the tip of the welding wire normally refers to the tip of the wire when ignoring the presence of droplets hanging from the wire tip. In other words, the wire melted by the arc is considered to have immediately transferred to the base material 200.

The feeding of the welding wire 100 by the push motor 180 is controlled by a control signal based on the push feeder control unit 39. The average value of the feeding speed is approximately the same as the melting speed. In this embodiment, the feeding of the welding wire 100 by the push motor 180 is also controlled by the welding power source 140.

The push feeder control unit 39 also performs control according to the state of the wire buffer 190. In this embodiment, the wire buffer 190 is provided with a wire slack portion (a gap into which the wire can escape if it becomes loose due to feeding between the motors) to prevent a large load from being placed on the wire in the feeding path between the push motor 180 and the servo motor 170, and the amount of wire buffered is detected as a rotation angle by an absolute encoder, which is a sensor built into the wire buffer 190. The detected value is converted into an analog signal by a serial-to-analog converter 191, and the electrical angle is calculated by an electrical angle calculation unit. The calculated electrical angle is input to the A/D input unit 40 of the welding power source.

A differential signal obtained by calculating the difference between the electrical angle from the A/D input unit 40 and a reference value for the electrical angle preset in the electrical angle adjustment unit 41 is input to the push feeder control unit 39. Based on this differential signal, the push feeder control unit 39 controls the push motor 180 to ensure an appropriate amount of wire is buffered, thereby performing interference control to prevent a heavy load from being placed on the feeding system. Note that while interference control is performed as described above in this embodiment, this is not limited to this. Also, while an absolute encoder built into the wire buffer 190 is used in this embodiment, this is not limited to this. For example, a rotation angle sensor may be used, in which case the serial-to-analog conversion unit 191 may not be provided.

The current setting unit 36 receives a voltage setting signal Vap from the voltage setting unit 36C, which is the target value of the voltage to be applied between the welding tip and the base material 200.

On the other hand, the voltage detection signal Vo is an actual measured value. In this embodiment, the voltage detection signal Vo passes through a low-pass filter LPF, passes through a separation detection unit 33 (described below), and is input to the current setting unit 36 together with a separation detection signal DTR (described below). Note that a voltage comparison unit may be provided to amplify the difference between the voltage setting signal Vap and the voltage detection signal Vo, and output it to the current setting unit 36 as a voltage error amplified signal.

The current setting unit 36 controls the welding current during the peak period Dap so that the length of the arc (hereinafter also referred to as "arc length") remains constant. The current setting unit 36 determines and sets at least the peak period, rise period, base period, and rising period based on the voltage setting signal Vap and the voltage detection signal Vo. The values of the peak current Ip and base current Ib may also be reset. A current setting signal CCset corresponding to the set period or value is output to the current error amplifier (PWM) 34.

The current error amplifier 34 amplifies the difference between the current setting signal CCset provided as the target value and the current detection signal Io detected by the current detection unit 31, and outputs this as a current error amplified signal Ed to the inverter driver 30. The inverter driver 30 corrects the drive signal Ec of the switching element 4 using the current error amplified signal Ed.

The current setting unit 36 also receives a detachment detection signal DTR, which is a signal that detects the detachment of a droplet from the tip of the welding wire 100. The detachment detection signal DTR is output from the detachment detection unit 33. The detachment detection unit 33 monitors changes in the voltage detection signal Vo output by the voltage detection unit 32, and detects the detachment of a droplet from the welding wire 100 from these changes. The detachment detection unit 33 is an example of a detection means.

The detachment detection unit 33 detects droplet detachment by, for example, comparing the differentiated or second-order differentiated value of the voltage detection signal Vo passed through an LPF with a predetermined detection threshold. The detection threshold is pre-stored in a memory unit (not shown). The detachment detection unit 33 may also generate the detachment detection signal DTR based on changes in resistance calculated from the voltage detection signal Vo and current detection signal Io, which are actual measured values.

The waveform control table linear calculation unit 37 is provided with the average feed speed Favg of the welding wire 100 being fed. The average feed speed Favg is pre-stored in the feed setting data unit 35. In this embodiment, the feed setting data unit 35 is located within the welding power source 140, but various information related to the feed settings may be stored within the welding control device 120, and the various information may be output from the welding control device 120 to the welding power source 140.

The waveform control table linear calculation unit 37 determines values such as the peak current Ip, base current Ib, the time when the base current Ib starts, and the time when the base current Ib ends based on the given average feed speed Favg, and outputs these to the current setting unit 36. As mentioned above, the values of the wire position phase, time, and cycle cyc are mutually convertible, so the setting value of the base start phase, etc. may be converted into a time or cycle cyc value, and the converted value may be output to the current setting unit 36.

In this embodiment, the average feed speed Favg is input to the waveform control table linear calculation unit 37, but a value related to the average feed speed Favg may be input as a set value to the waveform control table linear calculation unit 37, and the waveform control table linear calculation unit 37 may use this set value as the average feed speed Favg. For example, if a database of average feed speeds Favg and average current values that enable optimal welding for that average feed speed Favg is stored in a memory unit (not shown), the average current value may be used as the set value, and the set value may be used as the average feed speed Favg.

The feed setting data unit 35 may store setting values such as the average feed speed Favg, wire amplitude Wf, wire forward/reverse frequency Hf, and wire forward/reverse cycle Tf. The wire amplitude Wf, wire forward/reverse frequency Hf, and wire forward/reverse cycle Tf may be determined based on the input average feed speed Favg. The feed setting data unit 35 may also store setting values other than these as feed setting data. In this embodiment, the value of the wire amplitude Wf refers to the wave height Wh shown in Figure 7. In other words, the set value of the wire amplitude Wf is set to the same value as the wave height Wh.

In this embodiment, the period when the feed speed is higher than the average feed speed Favg is defined as the forward feed period, and the period when the feed speed is lower than the average feed speed Favg is defined as the reverse feed period, resulting in feed in which forward feed periods and reverse feed periods alternate (hereinafter referred to as "amplitude feed" for short). Note that a period when the feed speed is lower than the average feed speed Favg refers to a period less than the average feed speed Favg, and includes a negative feed speed, i.e., a speed at which the wire tip moves in the opposite direction from the position of the base material 200. The wire amplitude Wf gives the range of change relative to the average feed speed Favg, and the wire forward/reverse cycle Tf gives the time for change in the wire amplitude, which is the repetition unit. The wire forward/reverse frequency Hf is the reciprocal of the wire forward/reverse cycle Tf. In this embodiment, the set values for the wire amplitude Wf and wire forward/reverse frequency Hf are not particularly important, but from the perspective of welding workability, it is preferable to select and set, for example, the wire forward/reverse frequency from the range of 50 Hz to 150 Hz, and the wire amplitude represented by the wave height Wh from the range of 3.3 mm to 6.3 mm.

The average feed speed Favg, wire amplitude Wf, wire forward/reverse frequency Hf, and wire forward/reverse cycle Tf stored in the feed setting data unit 35 are input from the digital communication unit 42 to the digital communication unit 122 of the welding control device 120. In this embodiment, this feed setting data is communicated via CAN communication.

The welding sequence unit 43 processes each task in the following order based on the teaching data: idle, gas flow, arc start, welding in progress, and anti-stick. For convenience, in Figure 6, the welding condition information held by the welding control device 120 is also shown enclosed within the welding power source 140 by a dashed line.

(Functional configuration of welding control device)
As described above, feed setting data such as average feed rate Favg, wire amplitude Wf, wire forward/reverse frequency Hf, and wire forward/reverse cycle Tf are input to digital communication unit 122 of welding control device 120 via CAN communication from feed setting data unit 35 of welding power source 140. Welding control device 120 has digital communication unit 123 for outputting this feed setting data to digital communication unit 162 of servo amplifier 160. In this embodiment, digital communication unit 123 of welding control device 120 and digital communication unit 162 of servo amplifier 160 are connected via EtherCAT (registered trademark) communication.

(Servo amplifier functional configuration)
Feed setting data such as average feed speed Favg, wire amplitude Wf, wire forward/reverse frequency Hf, and wire forward/reverse cycle Tf are input to digital communication unit 162 of servo amplifier 160 via EtherCAT (registered trademark) communication. Forward/reverse feed command generation unit 161 of servo amplifier 160 generates a feed command for forward feed or reverse feed based on the setting information input via digital communication, i.e., the feed setting data. Forward/reverse feed command generation unit 161 calculates an amplitude feed speed Ff from the wire amplitude Wf and the wire forward/reverse cycle Tf, and outputs a feed speed command signal Fw to servo motor 170 based on the amplitude feed speed Ff and average feed speed Favg.

In this embodiment, the feeding speed command signal Fw is expressed by the following equation.
Fw=Ff+Favg...Formula (A)

Furthermore, the forward/reverse feed command generation unit 161 may detect at which wire position phase of the amplitude feed the detachment occurred, based on the detachment detection signal DTR provided by the detachment detection unit 33. However, the feed speed command signal Fw expressed by equation (A) is valid only when the detachment of a droplet from the tip of the welding wire 100 is detected within an expected period. If the detachment of a droplet is not detected within the expected period, the forward/reverse feed command generation unit 161 may switch the feed speed command signal Fw to feed control at a constant speed. For example, the forward/reverse feed command generation unit 161 switches the feed speed command signal Fw to feeding at an average feed speed Favg. The switch from feeding at the average feed speed Favg to feed control expressed by equation (A) is determined depending on the timing at which the detachment of a droplet is detected.

Servo amplifier 160 performs inverter control of servo motor 170 based on the feed speed command signal Fw. In addition, synchronization signal generator 163 of servo amplifier 160 outputs a phase synchronization signal to welding power source 140. This phase synchronization signal is generated based on the feed speed command signal Fw.

The present invention will be described in more detail below, but it should be understood that the present invention is not limited to these examples and can be implemented with modifications within the scope of the present invention, all of which are within the technical scope of the present invention. Furthermore, the welding conditions described here are merely examples, and the present embodiment is not limited to the following welding conditions.

[Gas-shielded arc welding]
Gas-shielded arc welding was performed using welding wires with various compositions using a feed control method, and the amount of tip wear was evaluated. The compositions of the welding wires used are shown in Figure 8, and the feed control conditions are shown in Figure 9. Other welding conditions are also shown below. Figure 8 is a diagram showing the compositions of the welding wires used in this embodiment. Figure 9 is a diagram showing the feed control conditions in this embodiment.

[Other welding conditions]
Base material: SS400
Welding position: Downward Shielding gas: 100% _CO2 gas Average current: 280-320A
Average voltage: 34-40V
Tip-to-base metal distance: 25 mm
Wire feeding rate: 14-16m/min
Welding speed: 30 cm/min
Welding time: 1 hour

[Evaluation test]
(Tip wear test)
10 is a diagram showing the results of the evaluation test in this embodiment. The difference between the weight of the contact tip before welding and the weight of the contact tip after welding was measured as the amount of wear. A wear amount of 2.0 mg or less was rated as pass (rating D), less than 1.4 mg was rated as preferable (rating C), less than 1.0 mg was rated as more preferable (rating B), and less than 0.5 mg was rated as even more preferable (rating A). On the other hand, a wear amount of more than 2.0 mg was rated as failing (rating E) because the amount of wear was too large. Note that a result in which the amount of wear is negative (the weight after welding is greater) is a phenomenon that occurs when Fe or Cu from the welding wire side is transferred to the contact tip side, and indicates that wear of the contact tip is suppressed.

[(amount of solid lubricant/square of current during positive feeding period)×10 ⁸ ]
FIG. 11 is a diagram showing the relationship between the amount of solid lubricant, the square of the current during the normal feeding period, and the amount of wear.

The average current during the forward feed period that enables stable production of a liquid lubricant film is better, as it is necessary to stably melt the Fe and plated Cu of the wire, and is preferably 420 A or more, more preferably 450 A or more, and even more preferably 480 A or more. Furthermore, the production of a liquid lubricant film also depends on the amount of sulfide, which is a solid lubricant, and in this embodiment, the value of Equation 1 derived from the amount of sulfide and the average current during the forward feed period was used as an index of tip wear. It is preferable for the value of Equation (B) to be 45 or more, and more preferably 50 or more.

(amount of solid lubricant/square of current during positive feeding period)×10 ⁸ ≧45 Equation (B)

Furthermore, if the average current during the forward feed period is low, the Fe and plated Cu of the wire will not melt stably, so this parameter is preferably used when the current is 420 A or higher. Here, Test Nos. T13 and T14 of this example shown in Figure 10 are within the range of the parameters of formula (B), but because they are outside the range of the present invention, the amount of tip wear is large.

The present invention is not limited to the above-described embodiments, and the invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the disclosures in the specification and well-known technology, and these modifications and applications are within the scope of the protection sought.

As described above, this specification discloses the following:

(1) A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire,
In the step of controlling at least the welding current,
the welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP _AVE during the forward feed period is higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding method.

This gas-shielded arc welding method provides excellent tip wear resistance regardless of the current range.

(2) The gas-shielded arc welding method described in (1), characterized in that the feed control method is a method of feeding the welding wire at the average wire feed speed while periodically repeating forward and reverse feed in accordance with a wire forward/reverse frequency, with a forward feed period and a reverse feed period forming one cycle.

This gas-shielded arc welding method, which applies a short-circuit suppression feed control method, can achieve excellent tip wear resistance regardless of the current range.

(3) The gas-shielded arc welding method described in (2), wherein, in the step of controlling at least the welding current, the high current period is switched to the low current period at wire position phase d1, which is set in the range of 100° to 200°.

This gas-shielded arc welding method can further reduce abrasive wear on the contact surface of the contact tip.

(4) The gas-shielded arc welding method described in (1), characterized in that the solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide.

With this gas-shielded arc welding method, sulfides act as solid lubricants to stabilize feedability up to the contact tip, and act to generate a liquid lubricant film on the contact surface within the contact tip, suppressing adhesive wear.

(5) A gas-shielded arc welding method as described in (1), characterized in that oil is applied to the surface of the welding wire, and the solid lubricant is contained in the oil.

In this gas-shielded arc welding method, sulfide is mixed with lubricating oil and applied to the plated surface of the welding wire, and the amount of adhesion can be controlled by adjusting the mixture ratio.

(6) The gas-shielded arc welding method described in (1), characterized in that the solid lubricant is 0.05 to 0.40 g per 10 kg of wire.

This gas-shielded arc welding method allows for the appropriate generation of a liquid lubricating film.

(7) A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
a welding wire feed control device;
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
the feed control device controls at least the welding current in accordance with the tip position of the welding wire;
the welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the feed control device controls the welding current so that an average welding current ITP _AVE during the forward feed period becomes a current higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding system.

This gas-shielded arc welding system provides excellent tip wear resistance regardless of the current range.

(8) A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, controls an average welding current at least during a period of forward feed to be higher than a predetermined current value depending on a tip position of the welding wire, and feeds the welding wire at a predetermined average wire feed speed,
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface.
Welding wire.

When these welding wires are used in gas-shielded arc welding using the feed control method described above, excellent tip wear resistance can be achieved regardless of the current range.

(9) The welding wire is
With respect to the total mass of the welding wire,
Fe: 90% by mass or more,
C: 0.15% by mass or less,
Si: 1.10% by mass or less,
Mn: 2.30% by mass or less,
Ti: 0.30% by mass or less,
Al: 0.30% by mass or less,
Zr: 0.30% by mass or less,
Mg: 0.30% by mass or less,
Ni: 4.75% by mass or less,
Cr: 0.60% by mass or less,
Mo: 0.90% by mass or less,
Cu: 0.50% by mass or less,
Nb: 0.50% by mass or less,
V: 0.50% by mass or less,
B: 0.0050% by mass or less,
P: 0.050% by mass or less,
S: 0.050% by mass or less,
The welding wire according to (8), characterized in that it contains

When these welding wires are used in gas-shielded arc welding using the feed control method described above, excellent tip wear resistance can be achieved regardless of the current range.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. Those skilled in the art will clearly be able to come up with various modifications or alterations within the scope of the claims, and it will be understood that these naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

This application is based on a Japanese patent application (patent application No. 2024-053556) filed on March 28, 2024, the contents of which are incorporated herein by reference.

1 AC power supply 2 Primary side rectifier 3 Smoothing capacitor 4 Switching element 5 Transformer 6 Secondary side rectifier 7 Reactor 30 Inverter drive unit 31 Current detection unit 32 Voltage detection unit 33 Separation detection unit 34 Current error amplification unit 35 Feed setting data unit 36 Current setting unit 37 Waveform control table linear calculation unit 38 Phase delay correction unit 39 Push feeder control unit 40 A/D input unit 41 Electrical angle adjustment unit 42 Digital communication unit 43 Welding sequence unit 50 Welding system 100 Welding wire 110 Welding robot 111 Welding torch 120 Welding control device 122, 123 Digital communication unit 140 Welding power source 141 Control system unit 150 Controller 160 Servo amplifier 161 Forward/reverse feed command generation unit 162 Digital communication unit 163 Synchronization signal generation unit 170 Servo motor 180 Push motor 190 Wire buffer 191 Serial analog conversion unit 200 Work

Claims (9)

A gas-shielded arc welding method employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
The feed control method includes a step of controlling at least a welding current in accordance with a tip position of the welding wire,
In the step of controlling at least the welding current,
the welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and an average welding current ITP _AVE during the forward feed period is higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding method. The gas-shielded arc welding method according to claim 1, characterized in that the feed control method feeds the welding wire at the average wire feed speed while periodically repeating forward and reverse feed in accordance with a wire forward/reverse frequency, with a forward feed period and a reverse feed period forming one cycle. In the step of controlling at least the welding current,
3. The gas-shielded arc welding method according to claim 2, wherein the high current period is switched to the low current period at a wire position phase d1 set in a range of 100° to 200°. The gas-shielded arc welding method described in claim 1, characterized in that the solid lubricant contains at least one of molybdenum disulfide and tungsten disulfide. The gas-shielded arc welding method described in claim 1, characterized in that oil is applied to the surface of the welding wire and the solid lubricant is contained in the oil. The gas-shielded arc welding method described in claim 1, characterized in that the solid lubricant is 0.05 to 0.40 g per 10 kg of wire. A gas-shielded arc welding system employing a feed control method for feeding a welding wire at a predetermined average wire feed speed while alternately repeating forward feed and reverse feed,
a welding wire feed control device;
The welding wire is
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface,
the feed control device controls at least the welding current in accordance with the tip position of the welding wire;
the welding current has at least a high current period in which the welding current is higher than a predetermined current value and a low current period in which the welding current is lower than the predetermined current value, and the feed control device controls the welding current so that an average welding current ITP _AVE during the forward feed period becomes a current higher than the predetermined current value;
When a wire position phase based on a tip position of the welding wire at the time of switching from the reverse feeding period to the forward feeding period is set to 0 deg, a wire position phase at which the low current period is switched to the high current period is set in a range of 280° to 350°.
Gas shielded arc welding system. 1. A welding wire for use in a feed control method that alternately repeats forward feed and reverse feed, and controls an average welding current at least during a period of forward feed to be higher than a predetermined current value according to a tip position of the welding wire, and feeds the welding wire at a predetermined average wire feed speed,
Fe or an Fe-based alloy;
plating with Cu or a Cu-based alloy;
and a solid lubricant having at least a layered crystal structure and a sulfide on the plating surface.
Welding wire. The welding wire is
With respect to the total mass of the welding wire,
Fe: 90% by mass or more,
C: 0.15% by mass or less,
Si: 1.10% by mass or less,
Mn: 2.30% by mass or less,
Ti: 0.30% by mass or less,
Al: 0.30% by mass or less,
Zr: 0.30% by mass or less,
Mg: 0.30% by mass or less,
Ni: 4.75% by mass or less,
Cr: 0.60% by mass or less,
Mo: 0.90% by mass or less,
Cu: 0.50% by mass or less,
Nb: 0.50% by mass or less,
V: 0.50% by mass or less,
B: 0.0050% by mass or less,
P: 0.050% by mass or less,
S: 0.050% by mass or less,
The welding wire according to claim 8, characterized in that it contains