JP2022017972A - Tig welding head of galvanized steel pipe and welding method - Google Patents

Abstract

To provide a TIG welding head of galvanized steel pipe which permits automatic TIG welding of galvanized steel pipe without requiring manual welding of a skilled worker.SOLUTION: A TIG welding head 1 for galvanized steel pipe includes a driving mechanism which is used for moving a welding torch 2 along a circumference of the steel pipe, an arm 15 which holds the welding torch coupled with the driving mechanism, a copying part which keeps a distance between the welding torch 2 and the steel pipe at a constant length and a wire supplying part 25. Therein, the copying part is composed of a rod 3 which performs contact movement on a steel pipe welding part and a rod holding part 16 which holds the rod, the rod 3 is held so that a tip 19 is brought into contact with the galvanized steel pipe on the close front side of the welding torch, and the wire 4 is supplied from the rear side of a welding line along which the welding torch 2 moves from the wire supply part 25 to the welding part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a TIG welding head and a welding method for galvanized steel pipes. More specifically, the present invention relates to a TIG welding head, a TIG welder, and a welding method that enable automatic welding of zinc-plated steel pipes.

Conventionally, a large amount of zinc-plated steel pipes for water pipes (JIS G 3442 (SGPW)) have been used for equipment pipes and water pipes in building buildings, factory buildings, and the like. Due to the nature of these pipe configurations, high quality welding is required. As a welding method for these pipes, it is considered desirable to use TIG welding, which is efficient and does not generate spatter. However, if TIG welding is to be performed, the zinc film on the surface is vaporized into metal and becomes on the surface of the tungsten electrode. It cannot be welded because it adheres. However, even if the zinc film is removed in advance, there is a problem with the material, sufficient welding quality cannot be obtained, and TIG welding cannot be performed. Therefore, although it is inefficient at present, manual welding is performed by a skilled welder.

Specifically, using a shielded metal arc welding rod, the entire posture is required, and welding must be repeated many passes with respect to the groove, and the time and cost required for welding become extremely enormous. In addition, such welding of zinc steel pipes requires considerable skill and requires a welder with WES, but due to recent changes in the industrial structure and population decline, well-skilled and qualified welding. It is extremely difficult to secure work, creating a vicious cycle in which productivity declines and costs increase.

Therefore, it is an object of the present invention to enable automatic TIG welding of galvanized steel pipes without the need for manual welding by skilled workers.

In order to solve the above problems, the present invention is a TIG welding head for a zinc-plated steel pipe, which is connected to a drive mechanism for moving the welding torch along the circumference of the steel pipe and the drive mechanism. An arm portion for holding a weld torch, a copying portion for maintaining a constant distance between the welding torch and a steel pipe, and a wire supply portion are provided. The rod is held so that the tip of the rod is in contact with the zinc-plated steel pipe in the near front of the welding torch, and the wire is from the wire supply portion to the rear side of the welding line to which the welding torch moves. It consists of being supplied to the welded part from.

Further, it is preferable that the rod holding portion is located in front of the welding torch, the rod is made of tungsten, the tip is spherical, and the rod is held at an oblique angle with respect to the welding torch axis. Is.
Further, it is preferable that the wire supply unit is located behind the welding torch with respect to the welding torch, and the approach angle of the wire with respect to the welding position is 45 degrees or more.
Further, it is preferable that one end is connected to the copying portion side of the arm portion and the other end is provided with a pressing member connected to the driving portion, and the pressing member presses the copying portion against the steel pipe.

Further, the present invention is a method for welding a zinc-plated steel pipe, in which a zinc film is removed from the welded ends of a pair of steel pipes with a width of 3 to 10 mm, the groove accuracy is set to zero, and the butt gap is eliminated. It comprises a step of applying an active flux to the surface of a welding wire and a step of performing TIG welding by a TIG welding machine equipped with the above-mentioned TIG welding head.

Further, it is preferable that the tip of the rod is in contact with the welding line at the portion where the zinc film has been removed and within 20 mm in front of the welding torch traveling direction.
Further, the active flux may be composed of silicon dioxide (SiO2), iron metasilicate (Fe2SiO4), iron orthotitanium (Fe2TiO4), iron metatitanium (FeTiO3), and iron dititanium (FeTi2O5). Suitable.
Further, it is preferable that the wire entry accuracy is 45 degrees or more.

As mentioned above, at present, TIG welding cannot be applied due to the presence of zinc plating. Therefore, it is possible after cutting and removing the galvanized steel pipe, but as a result of investigating the material of the steel pipe by the present inventor, Si, Mn, etc. due to the peculiarity of the galvanized steel pipe in the JIS standard, etc. It was found that there are many products that contain almost no alloy components and are not of good quality. Furthermore, it was also found that the thickness of the zinc plating was not uniform, and there was a permissible range in the JIS standard, so that many of them lacked roundness. Due to these conditions, sufficient conditions and environment for welding such as material, copying characteristics, and meltability cannot be given, and various welding defects and defects occur with known mechanisms, so TIG welding cannot be adopted. Therefore, as a result of research, automatic TIG welding was made possible for the first time by adopting it as the above configuration and process.

The TIG welding head of the present invention includes a drive unit for moving the welding torch along the circumference of the steel pipe. The drive unit typically and preferably holds the steel pipe in cooperation with a rotary drive roller that is driven while rotating along the circumference of the steel pipe, a drive motor that rotates the roller, and the rotary drive roller. , A pair of auxiliary rollers provided so as to sandwich the welding torch, and a connecting bar for connecting to an arm portion holding the welding torch. The connecting bars are provided in pairs so as to sandwich the rollers from both sides, and by providing at least one adjusting shaft for adjusting the distance between the steel pipes in the radial direction, the steel pipes are provided at three points by a pair of auxiliary rollers and a rotary drive roller. The weld torch can be rotated along the weld line around the steel pipe while clamping and holding. However, the configuration of the drive unit is not limited to the configuration as long as the object of the present invention is achieved.

The arm portion that holds the weld torch is held by the connecting bar and is installed parallel to the steel pipe shaft. On one end side thereof, it extends from the connecting bar to hold the welding torch, the copying portion, and the wire supply portion. Preferably, the arm portion is made of aluminum, preferably having a gas pipe, a water cooling pipe, or the like inside, and cools itself while providing water and gas to the welding torch. Further, on the other end side, an adjustment mechanism by a screw mechanism for adjusting the welding position in the axial direction of the steel pipe is provided. The nozzle, tungsten electrode, etc. provided on the welding torch have the same mechanism as known. Further, various other required mechanisms such as other wiring, a gas pipe, a power supply, and a control device can adopt the same configuration as the known TIG welding head.

The copying portion includes a tungsten rod that comes into contact with the steel pipe and a rod holding portion that holds the rod. Preferably, the rod holder is parallel to the weld torch shaft, which holds the rod at its end while allowing the vertical distance to the steel pipe to be adjusted by the housing and a fixing mechanism such as a screw mechanism or pin in the housing. A rod-shaped rod holding member arranged in is provided. The rod holding member is provided with a cavity for holding the rod and a fixing mechanism such as a screw, and the rod is inserted into the cavity and fixed. The cavity is provided at an oblique angle with respect to the axis of the rod holding member and the weld torch so that the tip of the rod can be closer to the weld.

The rod is made of tungsten, and in the zinc film peeling area on the weld line where the tungsten electrode of the weld torch moves, it is slanted toward the front in the direction of travel on the weld line so that it comes into contact with the steel pipe part near the weld position. To hold. A roller is not used as a copying configuration, and the tip of the rod is spherical in order to make contact while avoiding friction. The tip of the rod is preferably in contact with the rod tip 10 mm to 20 mm in front of the welding position due to the influence of welding heat. With these configurations, the tip of the electrode is closely traced and the distance between the electrode and the steel pipe is kept constant while avoiding the adverse effect of welding heat and enabling contact movement. Therefore, the distance between the electrode and the welding position in TIG welding, that is, the distance between the welding torch and the steel pipe is accurately maintained. The tip of the rod may be copied within a few millimeters, not the weld line itself, as long as the zinc-peeled portion is copied near the front in parallel with the weld line.

For urging, one end is connected to the lower part of the arm portion on the copying portion side, and the other end is provided with a pressing member connected to the connecting bar near the steel pipe axis from the one end and at a position opposite to the welding position. , The pressing member urges the arm portion toward the steel pipe side. Typically, since the spring member is provided between the connecting bar and the arm portion, the welding torch, the copying portion, and the wire supply portion are slightly urged to the other end side of the arm portion, which is advantageous in terms of space and stability. To urge the steel pipe side.

The wire supply unit provides the wire from the rear side on the weld line to which the weld torch moves at an oblique angle toward the weld torch in order to enable continuous wire supply to the weld point at a constant angle. In the present invention, the molten pool is invaded from the rear, but the intrusion angle is different from the normal angle, and it is preferable to enter at 45 degrees or more. With this configuration, in the present invention in which the welding pool is narrow and deep (for example, a thickness of 3.5 mm and a surface width of about 4.0 mm, a thickness of 5.8 mm and a surface width of about 5.9 mm), a sufficient amount of penetration to the back wave is secured. It can enable one-pass automatic welding of thick steel pipes.

As a welding method, an automatic welding machine equipped with a TIG welding head having the above configuration is used to automatically weld a steel pipe. First, the zinc film is removed from the welded ends of the pair of steel pipes to be welded along the weld line with a width of 3 to 10 mm. These can be removed by a known method such as cutting a tool with an automatic cutting machine. Then, at each end, if necessary, polishing or the like is performed, the groove accuracy is set to zero, the butt gap is eliminated, the steel pipe is connected, and temporary attachment or polishing is performed as necessary. The steps of removing the zinc film and adjusting the groove accuracy are not limited to the above method.

Then, the active flux is applied along the welding line. The active flux needs to be for TIG welding, which contains oxides such as SiO2, TiO2, SiO2, or Cr2O3 and is effective for deep penetration, but is particularly preferably the flux disclosed in Patent No. 5560504. Is desirable. The products according to the disclosure include silicon dioxide (SiO2), iron metasilicate (Fe2SiO4), iron orthotitanium (Fe2TiO4), iron metatitanium (FeTiO3), iron dititanium (FeTi2O5), and silicon dioxide (SiO2). Is a flux having a composition ratio of about 2% and the rest of about 98%. The composition does not contain toxic substances, and the melting points of the main composition elements occupying 98% of the flux are relatively low melting points, and the specific gravity values are close to each other. The configuration has sufficient alloy components required for deep penetration in all postures, creates a narrow and deep molten pool with a thickness of 6 mm even upwards, enabling one-pass welding with zero grooves.

Then, TIG welding is performed by the automatic TIG welding head provided with the above TIG welding head. At this time, the welding torch moves on the welding line due to the rotation of the rotary drive roller, but the tip of the copying rod directly precedes and nears the welding line, and the distance between the welding position and the electrode is always kept constant. It will be possible. Then, the welding wire is introduced at an angle of 45 degrees or more from the rear of the welding line in the cross-sectional view of the steel pipe. With these configurations, even with a steel pipe having a thickness of more than 5 mm, sufficient melting and stirring can always be obtained with a constant amount of heat input, and high-quality back wave automatic welding can be performed in one pass.

According to the present invention, automatic TIG welding of a galvanized steel pipe becomes possible, and welding can be advantageously performed not only in terms of quality and safety, but also in terms of time, manpower, and cost.

It is a figure which shows an example of the TIG welding head of this invention. It is a figure which shows an example of the TIG welding head of this invention. It is an enlarged view which shows the welding torch part and the like of the TIG welding head of this invention. It is an enlarged view which shows the welding torch part and the like of the TIG welding head of this invention. It is a photograph which shows the steel pipe welded using the TIG welding head of this invention.

Hereinafter, an example of carrying out the present invention will be described with reference to the drawings.
1 and 2 are views showing an example of the TIG welding head 1 of the present invention. FIG. 1 is a view seen from the cross-sectional side (opening side) of the steel pipe 100. FIG. 2 is a view seen from the side surface side of the steel pipe 100, and is shown through the steel pipe to show an arm and the like. 3 and 4 are enlarged views showing the welding torch 2, the rod holding portion 16, and the wire supply portion 24 of the TIG welding head of the present invention. FIG. 3 is from the cross-sectional side (opening side) of the steel pipe 100, and FIG. 4 is. It is a figure seen from the side surface side of a steel pipe 100.

The TIG welding head 1 (total length 240 mm) includes a welding torch 2, a rod 3, and a wire 4. The motor 5 coaxially drives the rotary drive roller 6. A pair of auxiliary rollers 7 and 8 are provided so as to sandwich the welding torch 2 from the front and rear, and both ends of the rotary drive roller 6 and the pair of auxiliary rollers 7 and 8 are held by a pair of connecting bars 9 and 9'. The handle 17 controls the transmission of power to the rotary drive roller 6 of the motor 5.

Each of the connecting bars 9 and 9'consists of a first bar 10 for holding the rotary drive roller 6 and a second bar 11 for holding the pair of auxiliary rollers 7 and 8. The presence of the shaft 12 connecting the first bar 10 and the second bar 11 makes it possible to adjust the opening degree between the two bars (see the dotted line in FIG. 1). Therefore, the steel pipe 100 can be stably clamped by the rotary drive roller 6 and the pair of auxiliary rollers 7 and 8. The clamp knob 31 controls holding / opening of the clamped state. At the time of installation on the steel pipe 100, the opening degree of the connecting bars 9 and 9'is adjusted via the shaft 12 in the clamp open state, and the steel pipe 100 is clamped by the rotary drive roller 6 and the pair of auxiliary rollers 7 and 8. By driving the motor 5 and rotating the rotary drive roller 6, the TIG welding head 1 rotates and moves along the circumference of the steel pipe.

The welding torch 2 has a mechanism similar to that of a known welding torch, such as a tungsten electrode 13, a torch nozzle, and a collet, and enables welding to an object. The vertical adjustment handle 14 is provided so that the distance between the torch 2 and the steel pipe 100 can be adjusted (up and down 5 mm width).

The welding torch 2 is connected to the arm 15. The arm 15 has a prismatic shape and is held by the connecting bar 9 in parallel with the axis of the steel pipe 100. Inside, pipes necessary for welding such as gas pipes, water pipes, and wiring are provided and supplied to the welding torch 2. Further, since the arm 15 is made of aluminum, it cools itself while supplying water to the welding torch 2. Water and gas are injected from the inlet 32 by a supply pipe (not shown). Further, the arm adjusting handle 18 using the screw mechanism enables the position adjustment (5 mm width) of the arm 15 in the direction parallel to the axis of the steel pipe 100.

The rod holding portion 16 is connected to the arm 15 and holds the tungsten rod 3. The rod 3 is a 3.2 mm system, and the tip 19 is formed in a spherical shape. The rod holding portion 16 enables the vertical position adjustment of the housing 20 connected to the arm 15, the cage 22 provided with the rod holding cavity and the fixing screw 21 installed in the housing 20, and the cage 22 via the screw mechanism. It is composed of a handle 23. In the side view of the pipe (FIG. 2), the shaft of the rod 3 is arranged parallel to the welding line 102 which is the abutting portion of the steel pipes 100 and 101. In the cross-sectional view of the pipe, the rod 3 is arranged from the cage 22 toward the tip of the tungsten electrode 13, that is, a position closer to the welding position, and in this embodiment, the rod tip 19 is in contact with the steel pipe 10 mm in front of the welding position. ing. Further, although the steel pipes 100 and 101 are galvanized 103, each end has a zinc-cut peeling portion 104, and the tip 19 is located on the peeling portion 104 at a position 3 mm away from the weld line. I'm in contact. Further, the rod 3 is urged by a spring 24 provided between the arm 15 and the connecting bar 9, and the rod 3 moves in advance in contact with the weld line 102 without separating from the steel pipe. Therefore, the distance between the tip of the tungsten electrode 13 and the steel pipe can always be maintained and moved at 1.5 mm, which is the most effective.

The wire supply unit 24 includes a first housing 26, a second housing 27, and a wire cage 25 connected to the arm 15. The first housing 26 is provided on the arm 15 and the handle 28 enables the axial position adjustment of the steel pipe 100. The second housing 27 is provided with a handle 29, which enables the vertical position adjustment of the wire cage 25. In the side view of the pipe (FIG. 2), the axis of the wire cage 25 is parallel to the welding electrode, and the wire 4 is arranged from the rear at 45 degrees or more toward the welding position and 50 degrees with respect to the welding position tangent in this embodiment. Will be done. Further, the wire supply motor 30 is connected to the connecting bar 9 to enable continuous supply.

Welding Example SGP galvanized steel pipes were welded using a TIG welding machine equipped with the TIG welding head of the above embodiment of the present invention. Each steel pipe has an outer diameter of 114.3 mm and a plate thickness of 4.5 mm. First, for both steel pipes, using WACHS SDB series (grooving machine), zinc plating in the range of 7 mm width on the end surface is cut to make a gap zero, and both pipes are butted to form four circumferences. Temporarily attached by TIG welding.

After applying the flux disclosed in Patent No. 5560504 to the welded portion, the TIG welding head of the present invention is used to fix the distance from the weld electrode tip to the steel pipe welding position at 1.5 mm, and the rod tip is the electrode tip ( Welding position) was contacted at the leading position of 10 mm, and one-pass welding was performed.

The comparison target was a groove processing of 30 degrees with a thickness of 1.5 mm remaining, and a temporary welding was performed by manual welding in accordance with the conventional enforcement method. In this welding, it took 35 minutes to perform in 3 passes while requiring all postures.

The following is a table comparing with the conventional enforcement law.

As is clear from the above table, conventionally, it took about 10 minutes to process the incision, but in the present invention, the groove angle is not required, and the zinc film can be removed in 5 minutes. Furthermore, since the temporary attachment has no gap and the TIG welder of the present invention can be used, it can be completed in 5 minutes. Since one-pass automatic welding is possible, the main welding takes only 5 minutes, which is one-seventh of the time required by the conventional welding method (three passes are required in this comparative example). Compared with the time from groove processing, it is only one-third, which is a remarkable effect.

A photograph of the welded steel pipe is shown in FIG. As shown in the photograph, the weld bead was also good, withstood a pressure resistance test of 1.5 MPa, and good automatic TIG welding could be performed.

1 TIG welding head 1
2 Welding torch 3 Rod 4 Wire 5 Motor 6 Rotary drive roller 7, 8 Auxiliary roller 7, 8
9,9'Connecting bar 10 First bar 11 Second bar 11
12 Axis 13 Tungsten Electrode 14 Handle 15 Arm 16 Rod Holder 17 Handle 18 Handle 19 Tip 20 Housing 21 Screw 22 Cage 23 Handle 24 Wire Supply 25 Wire Clamp 26 1st Housing 27 2nd Housing 28, 29 Handle 30 Wire Supply motor 31 Clamp knob 32 Injection port 100, 101 Steel pipe 102 Welding wire 103 Galvanized 104 Peeling part

Claims (9)

A TIG welding head for galvanized steel pipes
A drive mechanism for moving the weld torch along the circumference of the steel pipe,
An arm portion that holds the welding torch connected to the drive mechanism and
It is provided with a copying section that keeps the distance between the welding torch and the steel pipe at a constant length, and a wire supply section.
The copying portion includes a rod that moves in contact with the welded portion of the steel pipe and a rod holding portion that holds the rod.
The rod is held so that the tip is in contact with the galvanized steel pipe in the near front of the welding torch.
A TIG welding head for a galvanized steel pipe, characterized in that the wire is supplied from the wire supply portion to the weld portion from the rear side of the weld line to which the weld torch moves. The rod holding portion is located in front of the welding torch.
The TIG welding head according to claim 1, wherein the rod is made of tungsten, has a spherical tip, and is held at an oblique angle with respect to the welding torch shaft. The wire supply section is located behind the weld torch with respect to the weld torch.
The TIG welding head according to claim 1 or 2, wherein the approach angle with respect to the welding position of the wire is maintained at 45 degrees or more. One of claims 1 to 3, wherein one end is connected to the copying portion side of the arm portion and the other end is provided with a pressing member connected to the driving portion, and the pressing member presses the copying portion against the steel pipe. The TIG welding head according to item 1. A TIG welding machine equipped with the TIG welding head according to claims 1 to 4. It is a welding method for galvanized steel pipes.
Remove the zinc film from the welded ends of the pair of steel pipes with a width of 3 to 10 mm.
Set groove accuracy to zero, eliminate butt gaps,
The process of applying active flux to the surface of the weld wire,
A method comprising the steps of performing TIG welding by the TIG welding machine according to claim 5. The method according to claim 6, wherein the tip of the rod is in contact with the welding line at a portion where the zinc film has been removed and within 20 mm in front of the welding torch in the traveling direction. The active flux is characterized by containing silicon dioxide (SiO2), iron metasilicate (Fe2SiO4), iron orthotitanium (Fe2TiO4), iron metatitanium (FeTiO3), and iron dititanium (FeTi2O5). The method according to claim 6 or 7. The method according to any one of claims 6 to 8, wherein the approach angle of the wire is 45 degrees or more.

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