CN102642070A - Narrow-gap GMAW (gas metal arc welding) method for band electrode - Google Patents

Abstract

The invention relates to a strip electrode narrow gap GMAW method, relating to a strip electrode narrow gap GMAW method. The invention aims to solve the problem of poor fusion of side walls in the existing narrow gap welding process. Method: 1. Use a strip-shaped electrode with a rectangular cross-section as the melting electrode. The strip-feeding mechanism guides the strip-shaped electrode into the electrode holder in the welding torch, and then puts the welding torch into the gap between the workpieces to be welded so that the width direction of the strip-shaped electrode is in line with the The welding direction is vertical; 2. Enter the shielding gas, adjust the voltage, start the welding power supply, feed the belt, ignite the arc, and carry out welding, that is, the narrow gap GMAW of the strip electrode is completed. The method of the invention has good fusion to the side wall, and there are no defects such as pores and inclusions. The welding process parameters are few, the method is simple, the operation is convenient, the equipment is simple, and the cost is low. It is used in the field of MIG shielded welding.

Description

Narrow Gap GMAW Method for Strip Electrodes

technical field

The invention relates to a strip electrode narrow gap GMAW method.

Background technique

Narrow-gap GMAW (gas metal arc welding) is a common welding technique for components thicker than 20mm. In practical applications, this method generally adopts a unilateral groove angle of 0° to 3°, and a width of 9 to 12mm at the bottom of the groove. Since the narrow-gap groove greatly reduces the filling amount of weld metal and improves welding efficiency and joint performance, narrow-gap GMAW is an efficient, high-quality, and energy-saving welding method, which has become the focus of practical application and research.

However, due to the small opening angle of the GMAW arc, the arc concentrates on the bottom of the groove, and under low heat input, it is easy to produce sidewall unfused, which is the most critical problem of the narrow gap GMAW technology. Therefore, the core idea of narrow-gap GMAW is to enhance the heating effect of the arc on the two side walls, ensure the fusion of the side walls, improve the weld formation, and prevent welding cracks. The fundamental measure to solve this problem is to make the arc burn close to the side wall of the gap and enhance the heat input to the side wall.

Contents of the invention

The invention aims to solve the problem of poor side wall fusion in the existing narrow gap welding process, and provides a narrow gap GMAW method for strip electrodes.

The belt-shaped electrode narrow-gap GMAW method of the present invention is carried out according to the following steps: 1. Use a belt-shaped electrode with a rectangular cross-section as the melting electrode, the width of the belt-shaped electrode cross-section is 6-8 mm, and the thickness is 0.2-0.4 mm. Lead the strip electrode into the electrode holder in the welding torch, and then put the welding torch into the gap of the workpiece to be welded. The size of the gap is 8-10mm, so that the width direction of the strip electrode is perpendicular to the welding direction, and the extension length of the strip electrode is 10-20mm; 2. Put in the protective gas, adjust the voltage to 20-30V, start the welding power supply, feed the belt at a speed of 7-18m/min, ignite the arc, and carry out welding, that is, the narrow gap GMAW of the strip electrode is completed .

The flow rate of the protective gas introduced in step 2 is 15-30 L/min.

In the second step, the welding speed is 20-30 cm/min.

The present invention replaces the round welding wire in the traditional melting electrode welding process with a strip electrode with a rectangular cross section. The width direction of the strip electrode is perpendicular to the welding direction during welding, and the size of the gap is properly matched with the width of the strip electrode, so that the two sides of the strip electrode The distance between the side of the gap and the side wall of the gap is not greater than the arc length when the arc is free to burn, so that the arc cannot always burn between the strip electrode and the bottom of the gap, but burns sequentially on the two side walls and the bottom of the gap, which leads to a strip The distance between the end of the electrode and the two side walls and the bottom of the gap changes periodically; with the continuous feeding of the strip electrode, the arc burns alternately at the end of the electrode, the two side walls and the bottom of the gap, and a vertical arc is formed in the gap. The welding direction has a transverse swinging arc with a certain swing frequency, so as to enhance the fusion to the side wall and realize narrow gap welding.

The method of the present invention adopts a strip-shaped electrode with a rectangular cross-section as the melting electrode to generate a swinging arc in the gap, without additional complicated arc swinging/rotating mechanism and control measures, and does not require a special welding power source, and uses the self-generated swinging arc It can achieve good heating and melting of the two side walls of the gap, good fusion of the side walls, and no defects such as pores and inclusions. The welding process parameters of the invention are few, the method is simple, the operation is convenient, the equipment is simple, and the cost is low.

Description of drawings

Fig. 1 is a schematic diagram of the working principle of establishing an arc between the strip electrode and the left wall of the gap in Embodiment 4; Fig. 2 is a schematic diagram of the arc transitioning from the left side wall to burning with the bottom of the gap in Embodiment 4; Fig. 3 is a schematic diagram of the embodiment Figure 4 is a schematic diagram of the working principle of the strip electrode and the right side wall to establish an arc; Figure 5 is a macroscopic photo of the weld section obtained in Embodiment 4; Figure 6 is a weld obtained in Embodiment 5 macro photo of seam section.

Detailed ways

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Specific Embodiment 1: The strip-shaped electrode narrow-gap GMAW method in this embodiment is carried out according to the following steps: 1. Use a strip-shaped electrode with a rectangular cross-section as the melting electrode. The width of the strip-shaped electrode cross-section is 6-8mm, and the thickness is 0.2- 0.4mm, the belt feeding mechanism guides the strip electrode into the electrode holder in the welding torch, and then puts the welding torch into the gap of the workpiece to be welded. The gap size is 8-10mm, so that the width direction of the strip electrode is perpendicular to the welding direction. The protruding length of the strip electrode is 10-20mm; 2. Introduce the protective gas, adjust the voltage to 20-30V, start the welding power supply, feed the tape at a speed of 7-18m/min, ignite the arc, and perform welding, which is completed Strip electrode narrow gap GMAW.

The material and thickness of the workpiece to be welded that are suitable for the traditional narrow-gap GMAW method are applicable to the method of this embodiment. The material of the strip electrode used should match the workpiece to be welded. In particular, it should be pointed out that the parameters involved in this method include gap width, strip width, strip extension length, strip feeding speed (ie welding current), arc voltage, welding speed, shielding gas composition and flow rate, and should be based on the actual material. Type, size, joint form, gap size, etc. are systematically optimized for these main process parameters, and the reasonable matching of these parameters is comprehensively considered, so as to ensure high-quality joints. Among them, the gap width, strip pole width, strip pole extension length and strip feeding speed play a decisive role in the welding effect of this method. The general selection principle is to ensure that the arc forms an automatic swing in the gap, and at the same time, it can also restrain the arc along the side. Wall climbing, specifically: the larger the gap width, the wider the matching strip pole and the greater the thickness; the greater the belt feeding speed, the higher the matching arc voltage.

Embodiment 2: This embodiment differs from Embodiment 1 in that: the flow rate of the protective gas introduced in step 2 is 15-30 L/min. Others are the same as in the first embodiment.

Embodiment 3: This embodiment differs from Embodiment 1 or Embodiment 2 in that: the welding speed in step 2 is 20-30 cm/min. Others are the same as in the first or second embodiment.

Specific embodiment four: the strip electrode narrow gap GMAW method of this embodiment is carried out according to the following steps: one, the workpiece to be welded is two 304 stainless steel plates, and the plate thickness is 25mm, that is, the gap depth is 25mm, using a strip with a rectangular cross section As the melting electrode, the two side walls of the steel plate to be welded are processed into a 3° U-shaped groove surface. The material of the strip electrode is 304 stainless steel. The width of the section of the strip electrode is 6mm and the thickness is 0.2mm. Insert the conductive tip in the welding torch, then put the welding torch into the gap to be welded, the size of the gap is 9mm, make the width direction of the strip electrode perpendicular to the welding direction, and the extension length of the strip electrode is 15mm; 2. Introduce the shielding gas , the flow rate is 20L/min, the voltage is adjusted to 23.5V, the welding power supply is turned on, and the belt is fed at a speed of 9m/min, the arc is ignited, and the welding speed is set to 20cm/min for welding, that is, the narrow gap of the strip electrode is completed GMAW.

The protective gas in the second step is Ar95%+CO ₂ 5% argon-rich gas.

1 to 3 are schematic diagrams of the working principle of this embodiment. In the figure, 1 is the strip electrode, 2 is the belt feeding wheel, 3 is the contact tip, 4 is the arc, 5 and 7 are the workpieces to be welded, 6 and 8 are the U-shaped groove surface processed by the workpieces to be welded, and 9 is the welding power source . The belt-feeding pulley 2 sends the strip-shaped electrode 1 into the conductive tip 3, extends its width direction into the gap in a manner perpendicular to the welding direction, starts the welding arc, and the welding power source 9 delivers the welding current to the arc 4 to start welding. When the arc is ignited, since the distance between the side of the strip electrode and the side wall of the groove of the workpiece is less than the arc length, according to the principle of minimum voltage, the welding arc cannot keep burning at the end of the strip electrode and the bottom of the gap, and turns to establish with the side wall of the gap. arc. The strip electrode 1 establishes an arc with the left side wall of the gap, as shown in Figure 1, the left part of the strip electrode 1 melts more and the right part melts less or basically does not melt; as the strip electrode 1 continues The distance between the right part and the bottom of the gap and the right wall of the gap gradually decreases, and when it is reduced to less than the arc length of the left side wall, the arc 4 transitions from the left side wall to the bottom of the gap, as shown in Fig. As shown in Figure 2, and then transferred to the right wall to establish an arc, as shown in Figure 3; then, the left part of the strip electrode 1 melts less or basically does not melt while the right part melts more, and its left part is in contact with the gap bottom and The distance from the left side wall of the gap gradually decreases, and when it is reduced to less than the arc length of the burning arc on the right side wall, the arc transitions from the right side to the bottom of the gap and turns to the left side for combustion, and so on. As the welding process progresses, the arc 4 swings back and forth in the gap perpendicular to the welding direction, forming a swing arc. The swinging arc stays longer on both sides of the gap and shorter at the bottom, so the heating effect on the side walls is significant and good fusion can be achieved.

FIG. 4 is a schematic diagram showing the shape of a strip electrode used in this embodiment. The section of the strip electrode is rectangular, the section width is W, and the thickness is T.

The macroscopic photo of the weld section obtained by the narrow gap GMAW method of the strip electrode in this embodiment is shown in Figure 5. From the macroscopic metallography of the joint, it can be seen that the bottom of the gap, the side wall and the interlayer are completely fused, and there are no defects such as pores and inclusions. . The results show that the strip electrode is directly inserted into the gap, and with proper parameter matching, the heating of the sidewall of the gap is improved by relying on the swinging arc formed automatically at the end of the strip electrode in the gap, thereby promoting the fusion of the sidewall without additional The unique arc swing or arc rotation mechanism can realize narrow gap welding.

Specific embodiment five: the narrow gap GMAW method of the shape electrode of this embodiment is carried out according to the following steps: one, the workpiece to be welded is two pieces of Q235 low-carbon steel, and the plate thickness is 25mm, that is, the gap depth is 25mm, using a strip with a rectangular cross-section As the melting electrode, the two side walls of the steel plate to be welded are processed into a 3° U-shaped groove surface. The material of the strip electrode is Q235 low-carbon steel. The electrode is connected to the conductive tip in the welding torch, and then the welding torch is put into the gap to be welded. The size of the gap is 9mm, so that the width direction of the strip electrode is perpendicular to the welding direction, and the extension length of the strip electrode is 15mm; Shielding gas, the flow rate is 20L/min, the voltage is adjusted to 24V, the welding power supply is started, the belt is fed at a speed of 10m/min, the arc is ignited, and the welding speed is set to 20cm/min for welding, that is, the narrow strip electrode is completed. Clearance GMAW.

The protective gas in the second step is Ar95%+CO ₂ 5% argon-rich gas.

The macroscopic photo of the weld cross section obtained by the strip electrode narrow gap GMAW method in this embodiment is shown in Figure 6. From the macroscopic metallography of the joint, it can be seen that the bottom of the gap, the side wall and the interlayer are completely fused, and there are no defects such as pores and inclusions. . The results show that the strip electrode is directly inserted into the gap, and with proper parameter matching, the heating of the sidewall of the gap is improved by relying on the swinging arc formed automatically at the end of the strip electrode in the gap, thereby promoting the fusion of the sidewall without additional The unique arc swing or arc rotation mechanism can realize narrow gap welding.

Claims (3)

1. the narrow clearance G MAW method of band electrode; It is characterized in that the narrow clearance G MAW method of band electrode, carry out according to the following steps: one, use the band electrode with square-section as consumable electrode, the width in band electrode cross section is 6～8mm; Thickness is 0.2～0.4mm; Tape-feed imports the electrode holder in the welding gun with band electrode, then welding gun is put into the gap of workpiece to be welded, and said gap length is 8～10mm; Make the width of band electrode vertical, band electrode extension elongation 10～20mm with welding direction; Two, feed protective gas, regulation voltage is 20～30V, starts the source of welding current, send band, and sending tape speed is 7～18m/min, and the electric arc that ignites welds, and promptly accomplishes the narrow clearance G MAW of band electrode.

2. the narrow clearance G MAW method of band electrode according to claim 1 is characterized in that the flow of feeding protection gas in the step 2 is 15～30L/min.

3. the narrow clearance G MAW method of band electrode according to claim 1 and 2 is characterized in that speed of welding is 20～30cm/min in the step 2.

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