JP6975743B2 - Welding method using semi-automatic welding equipment and semi-automatic welding equipment - Google Patents

Description

The present invention relates to a semi-automatic welding apparatus and a welding method using the semi-automatic welding apparatus.

In the semi-automatic welding apparatus, welding can be performed using the welding wire that is automatically fed and supplied. Generally, in welding by a semi-automatic welding device, a shield gas is ejected so as to surround the welding wire to shut off the arc from the outside air. By blocking the arc from the outside air, it is possible to prevent the metal portion heated during welding from reacting with the air. When the environmental temperature of the place to be welded is low, the gas supply pipe that supplies the shield gas is cooled by the outside air, and the temperature of the shield gas also drops. When the temperature of the shield gas decreases, the volume decreases, so that the volumetric flow rate of the supplied shield gas decreases, and the arc may not be sufficiently shielded from the outside air.

When welding is performed in a freezer warehouse, a gas cylinder placed in a normal temperature environment outside the freezer warehouse and a welding torch placed at a low temperature in the freezer warehouse are connected by a gas supply pipe. If the gas supply pipe has a long extension in the freezer warehouse, or if the gas supply pipe is placed in the freezer warehouse for a long period of time, the gas supply pipe in the freezer warehouse may be included in the gas supply pipe. The temperature of the shield gas supplied from the gas cylinder drops significantly. Therefore, the volumetric flow rate of the shield gas ejected from the welding torch may be insufficient to block the arc from the outside air. In such a case, the metal portion heated by welding is oxidized, so that a good welded portion cannot be formed.

Although it is not a countermeasure when the environmental temperature of the place where welding is performed is low, as a technology to prevent cracking during welding, there is a technology to heat the entire object to be welded in the enclosure with an inert gas atmosphere and then weld in the enclosure. Yes (see Patent Document 1). However, when welding is performed using the technique described in Patent Document 1 in a facility that needs to be maintained at a low temperature, such as in a freezer warehouse, the periphery of the welding target is also surrounded by an enclosure and heated. Therefore, the cargo stored frozen in the area surrounded by the enclosure needs to be moved to another freezing warehouse before welding so that it will not be thawed. Along with this, there is a problem that it is costly to secure a freezing warehouse at the destination and to move the cargo, and the peripheral area to be welded cannot be used as a freezing warehouse during welding.

Japanese Unexamined Patent Publication No. 2009-0287888

An object of the present invention is to provide a semi-automatic welding apparatus and a welding method capable of suppressing a decrease in the volumetric flow rate of a shield gas and suppressing a temperature rise in the ambient environment to be welded even when the welding location is below freezing temperature. To do.

The semi-automatic welding apparatus of the present invention has a welding torch that holds a welding wire that is automatically fed and supplied and ejects a shield gas so as to surround the welding wire, and a welding torch that is connected to the welding torch and is connected to the welding torch. In a semi-automatic welding device equipped with a gas supply pipe for supplying the shield gas, the welding torch has a wire feeding mechanism for automatically feeding the welding wire, and is arranged at a temperature lower than -5 ° C. Within the range of the gas supply pipe, at least, it is arranged on the outer peripheral surface of the target range including the torch side supply pipe extending between the supply pipe in the feeding mechanism of the wire feeding mechanism and the welding torch. It is characterized by being provided with a temperature maintenance mechanism having a heater for heating the target range of the gas supply pipe so as to maintain the temperature of the target range of the gas supply pipe in a predetermined temperature range of -5 ° C or higher. do.

In the welding method using the semi-automatic welding apparatus of the present invention, a shield gas is ejected so as to surround the welding wire that is automatically fed and fed while being held by the welding torch, and the member to be welded. In a welding method using a semi-automatic welding device that generates an arc between the welding wires to perform welding, the welding wire is automatically fed to the welding torch by a wire feeding mechanism, and the temperature is lower than -5 ° C. Within the range of the gas supply pipe that is arranged in and supplies the shield gas toward the welding torch, it extends at least between the supply pipe in the feeding mechanism of the wire feeding mechanism and the welding torch. A heater is arranged on the outer peripheral surface of the target range including the torch side supply pipe, and the gas is supplied so that the temperature of the target range of the gas supply pipe is maintained in a predetermined temperature range of -5 ° C or higher by the heater. It is characterized in that welding is performed while heating the target range of the pipe.

According to the present invention, the gas supply pipe is heated so as to maintain the temperature of the gas supply pipe arranged at a temperature lower than -5 ° C within a predetermined temperature range of -5 ° C or higher, so that the arc can be sufficiently generated from the outside air. It is possible to secure the volumetric flow rate of the shield gas that can be shut off. Therefore, even if the place where welding is performed is at a low temperature, the decrease in the volumetric flow rate of the shield gas is suppressed, and a good welded portion can be formed in which oxidation of the heated metal portion is prevented. Further, in the present invention, since the gas supply pipe is heated by the heater arranged on the outer peripheral surface of the gas supply pipe, it is possible to suppress the temperature rise of the ambient environment to be welded at the time of welding.

It is explanatory drawing which illustrates the outline of the semi-automatic welding apparatus of this embodiment. It is an enlarged view of the welding torch and the torch side supply pipe of FIG. It is explanatory drawing which illustrates the torch side supply pipe and the cylinder side supply pipe of FIG. 1 from the side view. It is explanatory drawing which illustrates the state which omitted the heat insulating material of FIG. It is explanatory drawing which illustrates the torch side supply pipe and the cylinder side supply pipe of FIG. 3 in the vertical cross-sectional view. It is explanatory drawing which shows the modification of the electric heating heater of FIG. 4 from the side view of a gas supply pipe. It is explanatory drawing which shows another modification of the electric heating heater of FIG. 4 from the side view of a gas supply pipe. It is explanatory drawing which shows the further modification of the electric heater of FIG. 4 from the side view of a gas supply pipe.

Hereinafter, the semi-automatic welding apparatus and the welding method of the present invention will be described based on the embodiment shown in the figure.

The embodiment of the semi-automatic welding apparatus 1 of the present invention exemplified in FIG. 1 is used when welding is performed under a temperature condition lower than -5 ° C. This semi-automatic welding device 1 is used when a member Bb, which is a steel frame for seismic retrofitting, is welded to a member Ba, which is an existing steel frame which is a structural member of a freezer warehouse. The area A surrounded by the broken line in FIG. 1 is inside the freezer warehouse, and the room temperature thereof is, for example, 18 ° C. or lower below the freezing point. In a general freezer warehouse, the room temperature of region A is about 18 ° C below freezing point to 25 ° C below freezing point. The area outside the area A is outside the freezer warehouse and is at room temperature.

The semi-automatic welding device 1 includes a welding torch 2, a gas supply pipe 3, and a temperature maintenance mechanism 4, and further includes a member-side electrode 5, a power supply 6, and a wire feeding mechanism 7. The gas supply pipe 3 connected to the welding torch 2 is connected to the gas cylinder 13. The shield gas S stored in the gas cylinder 13 is supplied to the welding torch 2 through the gas supply pipe 3. As will be described later, the gas supply pipe 3 of this embodiment is composed of a torch side supply pipe 3a, a supply pipe in the feeding mechanism 3b, and a cylinder side supply pipe 3c. The welding wire W is supplied to the welding torch 2 by the wire feeding mechanism 7.

As the gas supply pipe 3, a flexible pipe such as a rubber hose is used. As the shield gas S, an inert gas is used, and for example, carbon dioxide, argon, or a mixed gas thereof may be used. In this embodiment, the pressure adjustment section 14 is interposed between the gas supply pipe 3 and the gas cylinder 13. The pressure adjusting unit 14 has a valve for shutting off and releasing the supply of the shield gas S through the gas supply pipe 3.

The temperature maintenance mechanism 4 maintains the gas supply pipe 3 arranged at a temperature lower than −5 ° C. in a predetermined temperature range Z of −5 ° C. or higher. The predetermined temperature range Z is, for example, 0 ° C. or higher and 40 ° C. or lower, more preferably 10 ° C. or higher and 30 ° C. or lower, and further preferably about room temperature (15 ° C. or higher and 25 ° C. or lower). When the temperature of the gas supply pipe 3 becomes low, the volumetric flow rate of the shield gas S flowing through the gas supply pipe 3 becomes insufficient, and the arc cannot be sufficiently shut off from the outside air during welding. In this case, since the metal portion heated by welding reacts with air, a good welded portion cannot be formed. On the other hand, if the gas supply pipe 3 is overheated, problems such as deformation and deterioration of the gas supply pipe 3 occur. Therefore, this semi-automatic welding device 1 also includes a temperature maintenance mechanism 4.

The temperature maintenance mechanism 4 of this embodiment includes a torch side temperature maintenance unit 4a, a feeding mechanism temperature maintenance unit 4b, a cylinder side temperature maintenance unit 4c, a power adjustment unit 21, a temperature sensor 22, and a control unit 23. The torch side temperature maintenance unit 4a, the feeding mechanism temperature maintenance unit 4b, and the cylinder side temperature maintenance unit 4c maintain the torch side supply pipe 3a, the supply mechanism internal supply pipe 3b, and the cylinder side supply pipe 3c in the target temperature range, respectively. Has the function of The details of the temperature maintenance mechanism 4 will be described later.

The member-side electrode 5 is electrically connected to the members Ba and Bb to be welded. As the member-side electrode 5, for example, a conductive clip or clamp that sandwiches and holds the member Bb is used.

A control cable 16, a power cable 17, a member-side cable 18, and a remote control cable 20 are connected to the power supply 6. The control cable 16 connects the wire feeding mechanism 7 to the power supply 6. The power cable 17 connects the welding tip 11 to the power source 6. The member-side cable 18 connects the member-side electrode 5 to the power supply 6. The remote control cable 20 connects the remote control 19 to the power supply 6. Using the remote controller 19, operations such as adjusting the voltage and current supplied from the power supply 6 to the member-side electrode 5 and the welding tip 11 are performed.

Further, a control unit 23 is connected to the power supply 6, and a pressure adjustment unit 14 and a power adjustment unit 21 are connected to the control unit 23. Further, a temperature sensor 22 arranged on the outer peripheral surface of the gas supply pipe 3 is connected to the control unit 23 via a lead wire. As the temperature sensor 22, for example, a thermocouple is used. The temperature sensors 22 may be provided at a plurality of locations at intervals in the longitudinal direction of the gas supply pipe 3. The electric heating heaters 24 and 27 constituting the temperature maintenance mechanism 4 are connected to the power adjusting unit 21.

The operation of the pressure adjusting unit 14 and the power adjusting unit 21 is controlled by the control unit 23, and the temperature data detected by the temperature sensor 22 is input to the control unit 23. The power adjustment unit 21 is controlled by the control unit 23 based on the temperature detected by the temperature sensor 22. The power supply 6, the gas cylinder 13, the control unit 23, the pressure adjusting unit 14, and the power adjusting unit 21 are arranged in an area outside the area A.

As illustrated in FIG. 2, the welding torch 2 includes a torch body 8, a grip 9, a nozzle 10, a welding tip 11, and a start switch 12. The torch body 8 is a tubular member to which a nozzle 10 is connected to the tip end and a gas supply pipe 3 (torch side supply pipe 3a) is connected to the rear end. A grip 9 is fitted on the torch body 8. A connector 15 is attached to the torch side supply pipe 3a connected to the rear end of the torch body 8. In this embodiment, coil springs are externally fitted to the front end and the rear end of the torch side supply pipe 3a.

The welded wire W supplied by the wire feeding mechanism 7 passes through the inside of the torch body 8, and the shield gas S supplied through the gas supply pipe 3 passes through the inside of the torch body 8. The grip 9 is a tubular member that holds the welding torch 2 by being gripped by an operator.

The nozzle 10 is a tubular member that communicates with the torch body 8, and the supplied shield gas S is ejected from the tip thereof. The welding tip 11 is attached to the tip of the torch body 8 so as to be surrounded by the nozzle 10 on the outside. The welding tip 11 is a cylindrical electrode that holds the fed welding wire W in a inserted state, and is electrically connected to the holding welding wire W.

The start switch 12 is used when starting and ending the welding operation. When the operator presses the start switch 12, a signal instructing the start or end of welding is transmitted to the control unit 23 via the wiring. Based on this signal, the device such as the wire feeding mechanism 7 is operated or the operation thereof is stopped, and the voltage application from the power supply 6 or the voltage application thereof is stopped to the member side electrode 5 and the welding tip 11.

In this embodiment, the gas supply pipe 3 is connected to the welding torch 2 through the wire feeding mechanism 7. The wire feeding mechanism 7 includes a reel 7a for winding and holding the welded wire W and a reel drive motor 7b. By rotating the reel 7a by the reel drive motor 7b, the welding wire W is unwound from the reel 7a and supplied to the welding torch 2 along the gas supply pipe 3.

The wire feeding mechanism 7 is built in the heat-insulating box body 26. Therefore, in this embodiment, the gas supply pipe 3 is inserted into the box body 26 by inserting the torch side supply pipe 3a extending between the welding torch 2 and the wire feeding mechanism 7 and the wire feeding mechanism 7. The extending supply pipe 3b in the feeding mechanism and the cylinder side supply pipe 3c extending between the box body 26 and the gas cylinder 13 are continuously configured. The torch side supply pipe 3a and the supply pipe 3b in the feeding mechanism are detachably connected via the connector 15. The supply pipe 3b in the feeding mechanism and the supply pipe 3c on the cylinder side are seamlessly continuous, but can be detachably connected via a connector.

An electric heater 27 is provided in the box body 26. The box body 26 and the electric heater 27 constitute a feeding mechanism temperature maintaining unit 4b. The box body 26 has a heat insulating property capable of insulating the inside thereof from the outside. For example, the structure is such that a heat insulating material (glass wool, urethane foam, etc.) is attached as a wall to the frame that is the skeleton. The electric heater 27 prevents the atmosphere temperature in the box body 26 from dropping, thereby preventing the supply pipe 3b in the feeding mechanism, which is inserted into the wire feeding mechanism 7, from being cooled.

As illustrated in FIGS. 3 to 5, the torch side temperature maintenance unit 4a and the cylinder side temperature maintenance unit 4c are the electric heater 24 arranged on the outer peripheral surface of the gas supply pipe 3 (3a, 3c), respectively, and the electric heater 24 thereof. It has a heat insulating material 25 that covers the electric heater 24 and is wound around the gas supply pipe 3. As illustrated in FIG. 1, for the cylinder side supply pipe 3c, the cylinder side temperature maintenance unit 4c (electric heater 24) is arranged only in the range arranged in the region A. As the heat insulating material 25, it is preferable to use a glass cloth tape, urethane foam tape, or the like that does not hinder the flexibility of the gas supply pipe 3.

A flexible strip-shaped electric heater 24 is spirally wound around the outer peripheral surfaces of the gas supply pipes 3a and 3c. In this embodiment, the electric heater 24 is spirally wound in the longitudinal direction of the gas supply pipes 3a and 3c. It is also possible to arrange a plurality of (2, 3 or the like) electric heaters 24 in parallel and wind them in a spiral shape. When a plurality of electric heaters 24 are used, the gas supply pipes 3 (3a, 3c) can be heated by the other electric heaters 24 even if some of the electric heaters 24 cannot be heated for some reason.

A heat insulating material 25 is spirally wound around the outer peripheral surface of the electric heater 24 in the longitudinal direction of the gas supply pipes 3a and 3c. The heat insulating material 25 protects the electric heater 24 from external impacts and the like, and functions so that heat generated by the electric heater 24 does not escape into the air surrounding the gas supply pipes 3 (3a, 3c) and raise the temperature inside the warehouse. .. In this embodiment, the winding directions of the electric heater 24 and the heat insulating material 25 are opposite to each other, but the winding directions of the electric heater 24 and the heat insulating material 25 can be the same.

Next, an example of a welding method using the semi-automatic welding apparatus 1 will be described.

As illustrated in FIG. 1, the semi-automatic welding device 1 is installed in a freezer warehouse. At least a part of the gas supply pipe 3 extends in the region A in which the member Ba exists. Next, the member Bb is combined with the member Ba in a desired posture and grounded. The members Ba and Bb are preheated as necessary in the same manner as in normal welding.

The member Ba and the member Bb are electrically connected to the member side electrode 5. After that, with the welding wire W held by the welding torch 2, the operator presses the start switch 12 to start welding. By this start operation, the shield gas S of the gas cylinder 13 is supplied toward the welding torch 2 through the gas supply pipe 3 and ejected from the nozzle 10. Further, a voltage is applied from the power supply 6 to the welding wire W held by the welding tip 11 and the member-side electrode 5, and a potential difference is generated between the two.

Therefore, the tip of the welding wire W is brought into contact with the member Ba or the member Bb and then separated to generate an arc. The shield gas S injected so as to surround the welding wire W shuts off the arc from the outside air. In this state, the welding wire W is melted by the heat of the arc, adheres to the member Ba and the member Bb, and both are welded.

During welding, the temperature of the gas supply pipe 3 is constantly detected using the temperature sensor 22. The control unit 23 controls the power adjustment unit 21 based on the temperature detected by the temperature sensor 22. By this control, the electric power supplied from the power source 6 to the electric heater 24 and the electric heater 27 is adjusted, and the temperature of the gas supply pipe 3 placed at a temperature lower than -5 ° C is set to a predetermined temperature range of -5 ° C or higher. Keep at Z. Therefore, the welding work can be continued while maintaining the temperature of the gas supply pipe 3 within this predetermined temperature range Z.

Even if the gas supply pipe 3 is arranged at a temperature lower than -5 ° C, the gas supply pipe 3 is heated by the electric heaters 24 and 27 so as to maintain the temperature within a predetermined temperature range Z of -5 ° C or higher. Therefore, it is possible to secure a shield gas S having a volumetric flow rate that can sufficiently shut off the arc from the outside air. Therefore, even when the place where welding is performed is at such a low temperature, the decrease in the volumetric flow rate of the shield gas S is suppressed, and the occurrence of welding defects caused by the contact of the weld metal portion heated by welding with air can be prevented. Therefore, even in the welding work in the freezer warehouse where the gas supply pipe 3 needs to be extended in the region A below the freezing point of 18 ° C., a sufficient volumetric flow rate of the shield gas S to be injected can be secured.

Further, in the present invention, since the gas supply pipe 3 is locally heated by using the electric heater 24 arranged on the outer peripheral surface of the gas supply pipe 3, the temperature rise of the ambient environment to be welded is slight at the time of welding. .. Therefore, when the welding work is performed in the freezing warehouse, it is not necessary to move the cargo stored frozen to another freezing warehouse before the welding work so as not to be thawed, or the amount to be moved can be small. As a result, it is possible to secure a freezing warehouse to which the cargo is to be moved and to reduce the cost required for moving the cargo, which is extremely advantageous.

When a plurality of electric heaters 24 are used, the electric heaters 24 may be arranged in parallel at intervals G and similarly spirally wound around the gas supply pipe 3. By spirally winding the electric heater 24 and the heat insulating material 25 with the interval G in this way, the flexibility of the gas supply pipe 3 can be ensured as compared with the case where there is no interval G. Further, when the electric heater 24 and the heat insulating material 25 are wound in the same direction, it becomes easier to secure the flexibility of the gas supply pipe 3 as compared with the case where the winding directions of the electric heater 24 and the heat insulating material 25 are opposite to each other. If the flexibility of the gas supply pipe 3 can be ensured, the gas supply pipe 3 can be easily handled, which also contributes to the efficiency of the welding work.

As shown in FIG. 7, a plurality of cylindrical electric heaters 24 may be wound and arranged on the outer peripheral surface of the gas supply pipe 3 at intervals G in the longitudinal direction. According to this embodiment, by independently controlling the temperature of each electric heater 24, it is advantageous to heat the portion of the gas supply pipe 3 that needs to be heated without excess or deficiency. Further, even if some of the electric heaters 24 cannot be heated for some reason, the gas supply pipe 3 can be heated by the other electric heaters 24.

Each of the tubular electric heaters 24 can be arranged without a gap in the longitudinal direction of the gas supply pipe 3. Further, it is also possible to form a notch 24a in the cylindrical axial direction of the cylindrical heat insulating heater 24 so that the cross-sectional shape is C-shaped. According to this specification, the notch 24a can be wide open to fit the electric heater 24 to a desired position on the outer peripheral surface of the gas supply pipe 3.

As shown in FIG. 8, a plurality of cylindrical electric heaters 24 may be arranged on the outer peripheral surface of the gas supply pipe 3 with different intervals G1 and G2 in the longitudinal direction. This form may be adopted, for example, when the gas supply pipe 3 is placed in an environment where the gas supply pipe 3 is in the longitudinal direction and the temperature is different. That is, since the portion requiring heating can be sufficiently heated and the portion not requiring heating can be omitted, energy-saving and efficient heating becomes possible. Even when the electric heater 24 illustrated in FIG. 6 is spirally wound, the same effect can be obtained with the form of FIG. 8 by making the winding pitch different at the position in the longitudinal direction of the gas supply pipe 3.

(Test 1)
Fillet welding of the T joint was performed in a freezing warehouse at 20 ° C. below freezing point using the semi-automatic welding apparatus illustrated in FIG. First, as members to be welded, a plate-shaped rolled material for general structure and a rolled steel material for welded structure were prepared. The dimensions were 200 mm in width, 500 mm in length, and 20 mm in thickness. The rolled material for general structure was placed flat, and the rolled steel material for welded structure was placed vertically in the center of the upper surface in the width direction so as to be parallel to each other in the longitudinal direction to form a T shape. Next, both edges of the contact surfaces of each other were preheated to 50 ° C., and then both edges were fillet welded from end to end in the longitudinal direction to form a T joint. At the time of welding, the temperature of the gas supply pipe arranged in the freezer warehouse was maintained at room temperature (about 20 ° C.) by using a temperature maintenance mechanism, and the shield gas (carbon dioxide) was ejected from the nozzle. As shown in FIGS. 3 and 5, an electric heater and a heat insulating material were wound on the outer peripheral surface of the gas supply pipe. Glass cloth tape was used as the heat insulating material. After the welding was completed, the T joint was left in the freezer warehouse until the temperature of the welded portion (bead portion) became the same as the room temperature in the freezer warehouse. Then, the T joint was moved to a normal temperature environment, left to stand until the temperature reached room temperature, and then a penetrant inspection was performed on the welded portion. As a result, no cracks or defects that seemed to be unwelded were found. If the welding work was started under the condition that the gas supply pipe was not heated, a sufficient amount of shield gas could not be ejected from the nozzle, and the welding could not be performed normally. ..

(Test 2)
The same rolled material for general structure and rolled steel material for welded structure as in Example 1 were placed flat, one end faces were butted against each other so that the longitudinal directions were parallel, and the butted portions were butt welded from end to end. Other conditions were the same as in Example 1. The penetrant inspection was performed on the welded portion under the same conditions as in Example 1, but no cracks or defects that seemed to be unwelded were found.

1 Semi-automatic welding device 2 Welding torch 3 Gas supply pipe 3a Torch side supply pipe 3b Feeding mechanism internal supply pipe 3c Cylinder side supply pipe 4 Temperature maintenance mechanism 4a Torch side temperature maintenance part 4b Feeding mechanism temperature maintenance part 4c Cylinder side temperature maintenance Part 5 Member side electrode 6 Power supply 7 Wire feeding mechanism 7a Reel 7b Reel drive motor 8 Torch body 9 Grip 10 Nozzle 11 Welding tip 12 Start switch 13 Gas cylinder 14 Pressure adjustment section 15 Connector 16 Control cable 17 Power cable 18 Member side cable 19 Remote control 20 Remote control cable 21 Power adjustment unit 22 Temperature sensor 23 Control unit 24 Electric heat heater 24a Notch 25 Insulation material 26 Box body 27 Electric heat heater Ba, Bb Member W Welding wire A Area S Shield gas

Claims (9)

A welding torch that holds a welding wire that is automatically fed and supplied and ejects a shield gas so as to surround the welding wire, and a gas that is connected to the welding torch and supplies the shield gas to the welding torch. In a semi-automatic welding device equipped with a supply pipe
The welding torch has a wire feeding mechanism that automatically feeds the welding wire , and at least within the range of the gas supply pipe arranged at a temperature lower than -5 ° C., the wire feeding mechanism is fed. It is arranged on the outer peripheral surface of the target range including the torch side supply pipe extending between the supply pipe in the feeding mechanism and the welding torch, and the temperature of the target range of the gas supply pipe is set to -5 ° C or higher. A semi-automatic welding apparatus including a temperature maintenance mechanism having a heater for heating the target range of the gas supply pipe so as to maintain the temperature within a predetermined temperature range. The semi-automatic welding apparatus according to claim 1, wherein the heater is a strip-shaped electric heater wound around the target range of the gas supply pipe. The semi-automatic welding apparatus according to claim 2, wherein the strip-shaped electric heater is spirally arranged in the target range of the gas supply pipe at intervals in the longitudinal direction. The semi-automatic welding apparatus according to claim 2, wherein a plurality of strip-shaped electric heaters are wound around the gas supply pipe at intervals in the longitudinal direction in the target range of the gas supply pipe. The semi-automatic welding apparatus according to any one of claims 1 to 4, wherein the temperature maintaining mechanism has a heat insulating tape that covers the heater and is wrapped around the target range of the gas supply pipe. The gas supply pipe is connected to the welding torch through the wire feeding mechanism arranged at a temperature lower than -5 ° C. , and the temperature maintaining mechanism is internally provided with the wire feeding mechanism. The semi-automatic welding apparatus according to any one of claims 1 to 5, further comprising a heat-insulating box body and an electric heater provided in the box body. It is provided with a power adjusting unit that adjusts the electric power supplied to the heater, a temperature sensor that detects the temperature of the gas supply pipe, and a control unit that inputs the temperature detected by the temperature sensor.
Any of claims 1 to 6 in which the power adjustment unit is controlled by the control unit so that the temperature of the gas supply pipe is maintained within the predetermined temperature range based on the temperature detected by the temperature sensor. Semi-automatic welding equipment described in Crab. While the shield gas is ejected so as to surround the welding wire that is automatically fed and fed while being held by the welding torch, an arc is generated between the member to be welded and the welding wire to perform welding. In the welding method using a semi-automatic welding device
Feeding the welding wire to the welding torch by a wire feed mechanism automatically feeds out a range of the gas supply pipe for supplying toward said shield gas to the welding torch is positioned low temperature than minus 5 ° C. At least, a heater is arranged on the outer peripheral surface of the target range including the torch-side supply pipe extending between the supply pipe in the feeding mechanism of the wire feeding mechanism and the welding torch, and the gas is provided by the heater. Welding using a semi-automatic welding device, characterized in that welding is performed while heating the target range of the gas supply pipe so as to maintain the temperature of the target range of the supply pipe in a predetermined temperature range of -5 ° C or higher. Method. The welding method according to claim 8, wherein the member is a structural member of a freezing warehouse, and the target range of the gas supply pipe is extended to an environment of 18 ° C. or lower below the freezing point in the freezing warehouse.

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