TWI529025B - Method and apparatus for welding of a pipe which passes through a tunnel in a die - Google Patents

Description

Tunnel tube forming welding method and device

The invention relates to a process for manufacturing a cylinder in which a flat plate is bent into a cylindrical shape, and the butt joints (grooves) of the sides of the original flat plate which are bent into a cylindrical shape are welded, in particular, with respect to the C-type jig, that is, One part of the peripheral surface of the thick-walled cylinder is formed into a groove-like opening extending through the inner space, and the cylindrical workpiece is clamped in the radial direction, and the cylindrical end of the cylindrical workpiece is pressed against the rear end of the cylindrical workpiece to move the cylindrical space inside the C-shaped jig. A fusion torch inserted into the opening of the C-shaped jig, and a tunnel tube formed by welding a groove of a cylindrical workpiece inside the C-shaped jig.

Patent Document 1 describes one of such tube forming and welding devices. A fusion torch is connected to one of the positive (+) and negative (-) poles of the fusion power supply, and a C-type fixture is connected to the other pole, and the welding power supply - C type fixture - cylindrical workpiece - welding torch - welding There is a spliced current flowing in the loop of the power supply (splicing current loop). Between the C-shaped jig and the cylindrical workpiece, the C-shaped jig clamps the cylindrical workpiece in the radial direction, and is electrically connected by crimping between the two.

In the welding, since the cylindrical workpiece moves in the cylindrical space inside the C-shaped jig, the contact area of the cylindrical workpiece to the C-shaped jig becomes larger as the front end of the cylindrical workpiece enters the inside of the C-shaped jig. When the front end of the cylindrical workpiece reaches the exit of the C-shaped jig, it becomes the largest. Therefore, it does not change before the end of the cylindrical workpiece reaches the entrance of the C-shaped jig. After reaching the inlet, it gradually becomes smaller, and when the rear end of the cylindrical workpiece reaches When the C-type jig is exported, the contact area becomes zero (non-contact). Through the change of the contact area, the current is produced from the C-shaped fixture through the cylindrical workpiece to the cylindrical workpiece of the fusion torch. Change. On the other hand, in the fusion of the rear end of the cylindrical workpiece close to the end region of the fusion torch, an arc current is generated, and the magnetic flux immediately below the arc becomes higher in density between the rear end of the cylindrical workpiece and the welding torch, and the magnetic flux The effect on the arc current, that is, magnetic blowing (parallel magnetic blowing) becomes stronger. This magnetic blow is to push the welding arc at the front end of the welding torch to the rear in the direction in which the slot line extends. When the displacement of the welding arc toward the rear becomes larger, the molten metal pool flows into the rear side, and excessive bulging occurs in the center portion of the rear welded bead. With this bulging, the metal amount pushed to the rear is at the end portion of the plate. , causing insufficient metal to produce concave beads or depressions and other welded beads.

On the other hand, in the position where the opening of the welding torch is inserted into the C-shaped jig, since the welding current flows from the C-shaped jig into the cylindrical workpiece, there is a grooved orthogonal component in the welding current, and the groove is orthogonal The component is that the welding current flows from the inside of the cylindrical workpiece into the circumferential direction (the direction orthogonal to the slotted line) and reaches the front end of the welding torch. This is a magnetic field that affects the welding arc in the direction of the slotting line, and pushes the welding arc toward The direction orthogonal to the slotted line. In the present specification, it is represented by orthogonal magnetic blowing. The current component in the cylindrical workpiece orthogonal to the slotted line becomes larger after the magnetic flux density (parallel magnetic blowing) of the cylindrical workpiece gradually becomes higher, and in this region, the power is supplied from the C-type fixture to the cylindrical workpiece. The changes in the electrical contacts (contact points/contact areas) are large. That is, in the end welding region of the cylindrical workpiece, the variation of the orthogonal magnetic blowing is large. Thereby, the position of the welding arc is biased in a direction orthogonal to the groove line, so that the deflection range changes. Due to the parallel magnetic blowing and the orthogonal magnetic blowing in the rear end welding region, the shape and position of the welding arc are easily unstable, and in the welded beads in the rear end region, welding beads such as pits and depressions are sometimes generated. bad.

Patent Document 2 describes an arc welding method for preventing welding failure due to magnetic blowing, and the groove portion of the cylindrical workpiece is over the entire length of the grooved line for abutting against the resistance of the cylindrical workpiece. Conductive member for power supply of 1/5 or less resistor. In this welding method, the diameter of the cylindrical workpiece is large and fixed, and the multi-electrode welding torch opens the inner space of the cylindrical workpiece along the grooved line. Since the conductive member for power supply is over the entire length of the slotted line and is located directly under the slot Since the welding current is lower than that of the cylindrical workpiece, the welding current flows directly under the welding torch, and flows from the welding torch into the cylindrical workpiece and the conductive member for power supply. Actually, the groove is orthogonal to the circumferential direction of the cylindrical workpiece. ingredient. Therefore, although parallel magnetic blowing is generated, since the orthogonal magnetic blowing is not generated, the shape and position of the welding arc are relatively stable, and the welding beads on the rear end region are less likely to be depressed. However, in the above-described tunnel tube forming welding (for example, Patent Document 1), since the cylindrical workpiece moves in the space inside the C-shaped jig, it is impossible for the C-type jig to abut the individual power supply conductive members to the barrel. The groove of the workpiece is directly below.

Patent Document 3 discloses a welding device in which a welding is performed from a fixed point to a welding of a butt groove (annular groove) at a rear end of a welded steel pipe and a welded end of another welded steel pipe. In the conventional example of the object steel pipe, if the fixing point is separated from the welding torch, stray current is generated in the steel pipe to be welded, so that the welding arc becomes unstable, and therefore, in order to improve the instability, the welding torch is maintained. The carrier is equipped with a graphite sliding member crimped to the welded steel pipe, and the graphite sliding member supplies power to the welded steel pipe. In the case of the annular groove, from the start of welding to the end of the welding, since the graphite sliding member is pressed against the steel pipe at any time, the flow path of the welding current from the graphite sliding member to the steel pipe directly under the welding torch is stable and the welding arc is stabilized. However, in the above-described tunnel tube forming welding (for example, Patent Document 1), since the cylindrical workpiece moves in the space inside the C-shaped jig, even if the graphite sliding member is provided, the graphite sliding member cannot be brought into contact with the cylindrical workpiece at any time. .

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-141033

Patent Document 2: Japanese Patent Laid-Open Publication No. 2003-25069

Patent Document 3: Japanese Laid-Open Patent Publication No. Hei 8-155643

[Abstract of invention]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the shape of a welded bead of a back end welded region by tunnel tube forming welding.

(1) A tunnel-type tube forming welding method, in which a C-shaped jig (2) is used, that is, a part of the peripheral surface of the thick-walled cylinder is made into a groove-shaped opening (23) extending through the inner space, and the flat plate is bent into a cylindrical shape. The cylindrical workpiece (1) is clamped in the radial direction, and while the rear end is pressed to move the cylindrical space inside the C-shaped jig, the welding torch (4L, 4T/4) inserted into the opening is used for the aforementioned The butted groove (11) between the side faces of the original flat plate of the cylindrical workpiece (1) inside the C-shaped jig is welded, and the moving direction of the cylindrical workpiece (1) is from the aforementioned C-type. The power supply sliding member (6r, 6s) is fixedly disposed at the front end position (D) of the cylindrical workpiece (1) at the exit of the jig (2) to the back welding region (the front end is DE). a surface of the original plate portion adjacent to the welded bead of the cylindrical workpiece (1) extruded from the outlet (22) of the C-type jig (2), when the cylindrical workpiece (1) is in contact with the power supply sliding In the case of the pieces (6r, 6s), the welding main current path of the welding torch (4L, 4T/4) is switched from the C-type jig (2) to the feeding sliders (6r, 6s).

In addition, for the sake of easy understanding, the symbols of the corresponding elements or corresponding items of the embodiments described later in the drawings are attached to the parentheses for reference. The same applies to the following.

In the welding, since the cylindrical workpiece (1) moves in the cylindrical space inside the C-type jig (2), the contact area of the cylindrical workpiece (1) to the C-shaped jig (2) follows the cylindrical workpiece ( 1) The front end becomes larger inside the C-type jig, and becomes the largest when the front end of the cylindrical workpiece (1) reaches the exit of the C-type jig (2). Therefore, it does not change until the end of the cylindrical workpiece (1) reaches the inlet (21) of the C-type jig (2). The inlet (21) gradually becomes smaller, but before the front end of the cylindrical workpiece (1) reaches the position (C) of the aforementioned power supply sliding member (6r, 6s), the cylindrical workpiece (1) is opposed to the C-shaped fixture (2). Since the contact area is large, the change of the current path in the cylindrical workpiece from the C-shaped jig (2) through the cylindrical workpiece (1) to the welding torch (4L, 4T/4) is small, so the orthogonal magnetic blowing Smaller, the welding arc is more stable.

When the front end of the cylindrical workpiece (1) reaches the position (C) of the power supply sliding member (6r, 6s), the welding main current path of the welding torch (4L, 4T/4) is from the aforementioned C-type jig (2) Switching to the aforementioned power supply sliding member (6r, 6s), so that the welding main current path does not change from the position (C) of the power supply sliding member (6r, 6s) to immediately below the welding torch, in the cylindrical workpiece (1) The rear end is kept in this state until it is welded directly under the torch (4L, 4T/4). Since the flow of this current flows from the welding side (the side where the welding bead is formed) from the start line on the groove line to the welding torch, the force in the direction opposite to the direction of the current flowing into the arc (Fleming's left-hand rule) (Loolez force) It acts and blows toward the side of the welding traveling direction. This action acts in the direction in which the slot line of the rear end region extends in the opposite direction to the force pushed rearward, thereby preventing the molten metal pool from flowing backward. That is, in the welding of the back-end welding region, the welding main current path does not change, the orthogonal magnetic blowing becomes small, and the welding arc is relatively stable, so that no pits, depressions, etc. are generated in the welded beads in the rear end region. Poor welding beads.

(2) The tunnel-type tube forming and welding method according to the above (1), wherein the welding in the rear end welding region is a flow in which the welding current is substantially parallel to the welding bead from the front end position of the workpiece. This can reduce parallel magnetic blowing in the direction of the molten metal pool. According to this method, since the parallel magnetic blowing of the welding of the rear end welding region can be reduced, the displacement toward the rear becomes smaller in the direction in which the groove of the welding arc is extended, and the magnetic metal pool of the welded metal pool at the rear end is blown toward the rear. When the size is small, excessive bulging occurs in the central portion of the welded bead in the rear end welding region. With this bulging, the metal portion end portion which is pushed rearward is insufficient in metal, and the welded beads which are less likely to form concave beads or depressions are defective. .

(3) A tunnel tube forming welding device comprising: The C-type jig (2) has: an inlet (21) for receiving a cylindrical workpiece (1) for bending a flat plate, an outlet (22) for discharging the cylindrical workpiece (1), and a groove-shaped opening (23) of a space in which a part of the circumferential surface is opened; the cylindrical workpiece (1) pressed into the inner space from the inlet (22) is clamped in a radial direction, and the cylindrical workpiece is formed ( 1) a welding current path; a workpiece driving means (3) for pressing the cylindrical workpiece (1) from the inlet (21) of the C-shaped jig (2), and from the outlet (22), Extrusion of the cylindrical workpiece (1); welding torch (4L, 4T/4), through the aforementioned opening (23) of the C-type jig (2), aligning and driving by the workpiece driving means (3) The grooved surface (11) of the original flat surface of the cylindrical workpiece (1) is welded to each other, and is welded; in the direction of the pressing and pressing of the cylindrical workpiece (1), from the welding torch to the rear welding region At the front end position (D) of the cylindrical workpiece (1) at the start of welding, the power supply sliding members (6r, 6s) are fixedly disposed at the position (C) for sliding the welding of the cylindrical workpiece (1). The original board table next to the bead And a flow path switching means (7/8, 9), when the front end of the cylindrical workpiece (1) contacts the power supply sliding member (6r, 6s), the welding current of the welding torch (1) is fused The road is switched from the aforementioned C-type jig (2) to the aforementioned power supply sliding member (6r, 6s).

According to this device, in the welding, since the cylindrical workpiece (1) moves in the cylindrical space inside the C-type jig (2), the contact area of the cylindrical workpiece (1) to the C-shaped jig (2) It becomes larger as the front end of the cylindrical workpiece (1) enters the inside of the C-type jig (2), and becomes the largest when the front end of the cylindrical workpiece (1) reaches the exit of the C-type jig (2). Therefore, it does not change before the end of the cylindrical workpiece (1) reaches the inlet (21) of the C-shaped jig (2), and gradually becomes smaller after reaching the inlet (21), but reaches the foregoing at the front end of the cylindrical workpiece (1). Before the position (C) of the power supply sliding member (6r, 6s), since the contact area of the cylindrical workpiece (1) to the C-shaped jig (2) is large, the C-shaped jig (2) passes through the cylindrical workpiece ( 1) The change in the current path in the cylindrical workpiece (1) reaching the fusion torch (4L, 4T/4) is small, so the orthogonal magnetic blow is small, and the welding arc is relatively stable. set.

When the front end of the cylindrical workpiece (1) reaches the position (C) of the power supply sliding member (6r, 6s), the welding main current path of the welding torch (4L, 4T/4) is from the aforementioned C-type jig (2) Switching to the aforementioned power supply sliding member (6r, 6s), so that the welding main current path does not change from the position (C) of the power supply sliding member (6r, 6s) to immediately below the welding torch, in the cylindrical workpiece (1) The rear end is kept in this state until it is welded directly under the torch (4L, 4T/4). That is, the welding defects caused by the parallel magnetic blowing are likely to occur, and in the welding of the rear end welding region, the main current path of the welding does not change, and the orthogonal magnetic blowing becomes small, so that the parallel magnetic blowing disappears in the opposite direction. The Lorentz force acts and the welding arc is relatively stable, so that no weld beads, such as pits or depressions, are formed on the welded beads in the rear end region.

(4) The tunnel-type tube forming and welding apparatus according to the above (3), wherein the power supply sliding members (6r, 6s) are a pair, the slots of the cylindrical workpiece (1) are vacated, and the slots are opened. Stride in the direction of the week. According to this device, the power supply to the welding torch (4L, 4T/4) is ensured and stabilized by the power supply sliding members (6r, 6s) and the cylindrical workpiece (1).

(5) The tunnel tube forming and welding device according to the above aspect (3), wherein the flow path switching means includes a resistor (7), the resistor is inserted in the first current path, and the first current path is The first current path of the splicing current path between the first pole (+) of the splicing power source (5L, 5T/5) and the C-type fixture (2) of the welding torch is set to be larger than the first pole and the power supply The welding current path between the sliders (6r, 6s) is the first current path in which the second current path is relatively high impedance. According to this device, when the cylindrical workpiece (1) reaches the power supply slider (6r, 6s), since the welding main current is automatically switched from the first current path to the second current path, the switching of the welding main current path is confirmed. And stable.

(6) The tunnel tube forming and welding apparatus according to the above (3) or (4), wherein the flow path switching means includes: a front end position detecting means (8) for detecting a front end of the cylindrical workpiece (1) Arriving at the position of the aforementioned power supply sliding member (6r, 6s); and an electrical switch (9) according to the front end position The detection means (8) of the detection, the first current (s) which is supplied to the welding power source (5L, 5T/5) of the welding torch (5L, 5T/5) and the welding current path between the C-type fixture (2) The circuit is cut off; if the resistor (7) is inserted in the first current path according to the device, power loss due to the resistor (7) does not occur.

(7) The tunnel-type tube forming and welding device according to the above (5), wherein the flow path switching means further includes: a front end position detecting means (8) for detecting the cylindrical workpiece ( 1) the front end reaches the position of the power supply sliding member (6r, 6s); and the normally open type electrical switch (12) is inserted into the second current path, according to the detection of the front end position detecting means (8), The second current path is switched from non-energized to energized.

(8) The tunnel tube forming and welding device according to the above aspect, wherein the flow path switching means further includes: a normally open type electrical switch (12) inserted in the second current path, the second current path a welding current path between the first pole (+) of the welding power source (5L, 5T/5) and the power supply sliding member (6r, 6s), and the foregoing detection according to the front end position detecting means (8) 2 The current path is switched from non-energized to energized.

(9) The tunnel-type tube forming and welding apparatus according to the above aspect, wherein the flow path switching means further includes: a normally-closed type electrical switch (9) connected in parallel with the resistor inserted in the first current path ( 7) The first current path can be switched from energized to non-energized according to the detection by the front end position detecting means (8).

1‧‧‧Cylinder workpiece

2‧‧‧C type fixture

3‧‧‧Workpiece driving means

4‧‧‧welding torch

4L‧‧‧ first welding torch

4T‧‧‧ After welding torch

5‧‧‧Splicing power supply

5L‧‧‧First torch welding power supply

5T‧‧‧After the welding of the torch

6r, 6s‧‧‧ power supply sliding parts

7‧‧‧Resistance as a means of switching the flow path

8‧‧‧ as the end of the flow path switching means position detection means limit switch

9‧‧‧Electrical switch as a means of switching the flow path

10‧‧‧Resistance as a means of switching the flow path

11‧‧‧ slotting

12‧‧‧Normally open electrical switch

21‧‧‧ entrance

22‧‧‧Export

23‧‧‧ openings

A‧‧‧First welding torch 4L position

After B‧‧‧ welding torch 4T position

C‧‧‧Location of power supply slides 6r, 6s

D‧‧‧The position of the front end of the cylindrical workpiece 1 when the rear end region starts to be welded

E‧‧‧The rear end position of the cylindrical workpiece 1 at the end of the welding end

I ₁ ‧‧‧1st splicing current

I ₂ ‧‧‧2nd welding current

I _L ‧‧‧ first welding torch 4L welding current

I _T ‧‧‧ After welding the welding torch 4T welding current

Fig. 1 (a) is a schematic block diagram showing a tunnel-type tube forming and welding apparatus according to a first embodiment of the present invention, and Fig. 1(b) is a view of a hollow arrow b in Fig. 1(a). The right side view of the jig 2, Figure 1 (c) shows the current level map, which flows along the first current path (ie, the positive (+) pole and the C type of the fusion power source 5L, 5T The first welding current I ₁ of the welding current path of the jig and the welding current path between the positive (+) poles of the welding power sources 5L, 5T and the power supply sliding members 6r, 6s flowing through the second current path The movement of the tubular workpiece 1 of the second welding current I ₂ is changed.

Fig. 2 (a) is a schematic block diagram showing a tunnel type tube forming and welding apparatus according to a second embodiment of the present invention, and Fig. 2(b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 3 (a) is a schematic block diagram showing a tunnel-type tube forming and welding device according to a third embodiment of the present invention, and Fig. 3(b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 4 (a) is a schematic block diagram showing a tunnel type tube forming and welding apparatus according to a fourth embodiment of the present invention, and Fig. 4 (b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 5 (a) is a schematic block diagram showing a tunnel-type tube forming and welding apparatus according to a fifth embodiment of the present invention, and Fig. 5(b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 6 (a) is a schematic block diagram showing a tunnel-type tube forming and welding apparatus according to a sixth embodiment of the present invention, and Fig. 6(b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 7 (a) is a schematic block diagram showing a tunnel type tube forming and welding apparatus according to a seventh embodiment of the present invention, and Fig. 7(b) is a current level diagram showing the current level as it flows through The movement of the first welding current I _{1 of the} current path and the movement of the cylindrical workpiece 1 flowing through the second welding current I ₂ of the second current path are changed.

Fig. 8 is a plan view showing the distribution of the surrounding magnetic flux at the time of welding of the cylindrical workpiece. Fig. 8(a) shows the welding of the central portion of the cylindrical workpiece, and Fig. 8(b) shows the welding of the terminal region.

The invention can be further understood by the following description of the embodiments with reference to the drawings Other purposes and characteristics.

[Examples] -First Embodiment -

The cylindrical workpiece 1 shown in Fig. 1(a) is a side surface of an original flat steel plate in which a flat steel is bent into a cylindrical shape, and the cylindrical workpiece 1 is pressed into the C-shaped jig 2 by a workpiece driving means 3. Inside the inlet 21, the C-shaped jig 2 is clamped in the radial direction and moved toward the outlet 22. As shown in Fig. 1(b), the C-type jig 2 has a portion of the peripheral surface of the thick-walled cylinder as a groove-like opening 23 extending through the inner space. The welding torches 4L and 4T are inserted into the opening 23, and the slits 11 formed by the abutting faces of the cylindrical workpiece 1 are welded. In this embodiment, both of the fusion torches 4L, 4T are plasma arc welding torches. The welding power source 5L supplies the keyhole welding power to the preceding welding torch 4L, and the welding power source 5T supplies the smoothing power to the subsequent welding torch 4T. Smoothing refers to smoothing the surface of the welded beads. Further, since the slots are welded by the two welding torches 4L and 4T, the welding speed can be increased. Moreover, since the other fusion torch is used for the keyhole welding and the smooth welding, high-quality welded beads can be obtained.

In order to implement the present invention, a pair of power supply sliders 6r, 6s are directly connected to the positive (+) output ends of the fusion power sources 5L, 5T, and the C-type fixture 2 is connected by a low resistance resistor 7 as a flow path switching means. The pair of power supply sliding members 6r, 6s are erected in the slot 11 as shown in Fig. 1(b), and are symmetrically disposed in the slot so as to be surely slidably attached to the plate portion of the cylindrical workpiece 1 (grooving 11) The circumferential side of the side). The symbols A to E shown in Fig. 1(a) indicate the positions shown below:

A: First weld the position of the torch 4L

B: Position of the welding torch 4T

C: Position of the power supply slides 6r, 6s

D: the front end position of the cylindrical workpiece 1 when the rear end region starts to be welded

E: the position of the front end of the cylindrical workpiece 1 when the rear end region ends the welding

The work drive means 3 is connected to a reciprocating drive mechanism (not shown). Round trip drive The prime mover of the mechanism is a servo motor equipped with: a mechanical component for generating position data indicating the position of the work drive means 3; and a circuit for transmitting the position data to a welding controller of a control panel not shown. According to the positional data, the welding controller transmits a command for controlling the welding current to the welding power sources 5L, 5T as shown in Fig. 1(c).

When the front end of the cylindrical workpiece 1 which is pressed by the working driving means 3 and pushed into the C-shaped jig 2 reaches the starting welding position A of the preceding welding torch 4L, the welding torch 4L is first started to activate the locking hole welding arc, when the front end arrives When the welding torch 4T is started to be welded to the position B, the rear welding torch 4T starts the smooth welding arc. When the front end of the cylindrical workpiece 1 reaches the C position, that is, when the power supply sliding members 6r, 6s are contacted, most of the welding of the cylindrical workpiece 1 flows from the positive electrode of the welding power source 5L, 5T through the C-type jig 2 The current (welding main current) flows into the cylindrical workpiece 1 through the power supply sliders 6r, 6s. This is because the resistor 7 as the flow path switching means is inserted into the current path between the positive electrode of the fusion power sources 5L, 5T and the C-type jig 2. However, a small amount of current passes through the resistor 7 and then flows into the cylindrical workpiece 1 via the C-type jig 2 .

Before the front end of the cylindrical workpiece 1 contacts the power supply sliding members 6r, 6s, since the cylindrical workpiece 1 contacts the C-shaped jig 2 in a large area (long), at the position away from the opening 23, from the C-type treatment The welding current flowing into the cylindrical workpiece 1 has a flow in the circumferential direction of the cylindrical workpiece 1 (the direction orthogonal to the slotted line), and the orthogonal component of the slot immediately below the front end of the welding torch is reduced, so that the welding arc is biased and The orthogonal magnetic blow in the orthogonal direction of the slotted line is small.

Conventionally, the rear end of the cylindrical workpiece 1 is welded to the end portion near the welding torch (the front end reaches the D position), and since the cylindrical workpiece 1 contacts the C-shaped jig 2 with a small (shorter) area, the cylindrical workpiece is removed from the cylindrical workpiece. In the inner circumferential direction (the direction orthogonal to the slotted line), the orthogonal component of the slot immediately below the front end of the welding torch is increased, and the welding arc is deflected to the orthogonal magnetic flux in the direction orthogonal to the slotted line. . Further, in the welding, as shown in FIG. 8(a), the surrounding magnetic flux is generated centering on the arcs of the welding torches 4L and 4T, and the circumferential magnetic flux of the intermediate portion of the cylindrical workpiece is the welding torch 4L in the direction of the groove line. The magnetic flux in the front and rear directions of 4T is substantially the same, and is substantially the same as the Lorentz force acting on the welding arc, so the arc is relatively stable. However, as shown in FIG. 8(b), when the cylindrical workpiece 1 is adjacent to the rear end welding region, the surrounding magnetic flux is out of balance, so that the magnetic flux density at the rear end portion of the workpiece is sharply increased, between the magnetic flux and the arc current. The Lorentz force acts, the arc blows (parallel magnetic blow) on the side of the molten metal pool, and the molten metal is pushed backward, so that the molten metal becomes large at the end portion of the workpiece to produce a thickened bead. In particular, the Lorentz force of a large current such as a double torch becomes larger, and the amount of the recess is also increased in proportion to the Lorentz force.

However, in the present embodiment, in the rear end welding region, since most of the welding current is in parallel with the groove (welding bead) 11 between the power supply sliding members 6r, 6s of the cylindrical workpiece 1 and the welding torches 4L, 4T The short interval flows, and since the slotted orthogonal component disappears, orthogonal magnetic blowing does not occur. Further, by flowing the current from the side of the fusion bead to the welding torches 4L, 4T, the welding arc is blown to the opposite direction of the inflow current (the direction opposite to the molten pool) according to Fleming's left-hand rule (eliminating The force of the parallel magnetic blowing works, so the molten pool is not pushed rearward. Therefore, since the conventional welding beads which are caused by the orthogonal magnetic blowing and the parallel magnetic blowing disappear, the welding beads are not defective.

- Second embodiment -

In the second embodiment shown in Fig. 2, the normally open type limit switch 8 and the normally closed type electrical switch 9 are used as the flow path switching means instead of the resistor 7 of the first embodiment. The other configuration is the same as that of the first embodiment shown in Fig. 1. When the normally open type limit switch 8 hits the front end of the cylindrical workpiece 1, it is switched to the ON state, and the electric coil of the normally closed type electrical switch 9 is energized. By this energization, a magnetic field is generated in the electric coil, and the electrical tab inside the electrical switch 9 is switched from the ON position to the OFF position. By this switching, the power from the welding 5L, 5T of the positive (+) by electrical shutter 9 and C-2 and flows into the fixture cylindrical workpiece fusing current I ₁ of the first cut 11, thus welding current becomes The second welding current I ₂ flows into the cylindrical workpiece 1 through the power supply sliders 6r and 6s.

In addition, after the front end of the cylindrical workpiece 1 contacts the power supply sliding member 6r, 6s, From the point of view, the limit switch 8 is moved from the C position to the slightly downstream position in advance. The limit switch 8 is closed. In order to avoid this, the low resistance resistor 10 is previously connected in parallel to the electrical shutter 9 as shown by the broken line in Fig. 2(a). In this way, before the front end of the cylindrical workpiece 1 contacts the power supply sliding members 6r, 6s, the limit switch 8 is closed, and even if the electrical shutter 9 is opened, the welding current is supplied to the cylinder through the resistor 10 and the C-type fixture 2. Shape workpiece 1. At this time, before the limit switch 8 is switched to be closed (the electric switch 9 is opened), in fact, since the welding current does not flow into the resistor 10, it mainly flows into the C-type jig 2 through the electric shutter 9, so that no electric power is generated. Loss (Joule heat due to electrical resistance).

- Third embodiment -

In the third embodiment shown in Fig. 3, the torch 4 is welded by one plasma arc, and the slit 11 of the cylindrical workpiece 1 is subjected to keyhole welding. Similarly to the first embodiment, a pair of power supply sliding members 6r and 6s are directly connected to the positive (+) output end of the welding torch 5, and a C-type jig is connected via a low-resistance resistor 7 as a flow path switching means. 2. The other configuration is the same as that of the first embodiment.

- Fourth embodiment -

In the fourth embodiment shown in Fig. 4, the torch 4 is welded by one plasma arc, and the slit 11 of the cylindrical workpiece 1 is subjected to keyhole welding. Similarly to the second embodiment, the normally open type limit switch 8 and the normally closed type electric switch 9 are used. The other configuration is the same as that of the second embodiment shown in Fig. 2 .

- Fifth embodiment -

In the fifth embodiment shown in Fig. 5, the resistor 7 of the first embodiment is added, and the normally open type limit switch 8 and the normally open type electric switch 12 are used. The normally open type electrical switch 12 is inserted into the second current path (I ₂ ), and when the limit switch 8 is closed by the cylindrical workpiece 1, it is switched to be closed, so that the second current path (I ₂ ) is off. The power is switched to power. The other configuration is the same as that of the first embodiment shown in Fig. 1.

- Sixth embodiment -

In the sixth embodiment shown in Fig. 6, the torch 5 is welded by one plasma arc, and the slit 11 of the cylindrical workpiece 1 is subjected to keyhole welding. In the same manner as in the fifth embodiment, the normally open type limit switch 8 and the normally open are used. Type of electrical shutter 12 . The other configuration is the same as that of the fifth embodiment shown in Fig. 5.

- Seventh embodiment -

In the seventh embodiment shown in Fig. 7, the normally-closed type electrical switch 9 of the second embodiment is incorporated, and the normally open type electrical switch 12 is used. The normally open type electrical switch 12 is inserted into the second current path, and when the limit switch 8 is closed by the cylindrical workpiece 1, it is switched to be closed, so that the second current path is switched from non-energized to energized. The other configuration is the same as that of the second embodiment shown in Fig. 2 . Similarly to the second embodiment, the low-resistance resistor 10 is previously connected in parallel to the electrical switch 9, and is switched between the opening and closing of the electrical switches 9 and 12, and the electrical switch is closed even before the electrical switch 12 is closed. 9 is turned on, and the welding current also flows into the cylindrical workpiece through the resistor 10 and the C-type jig 2 . The other configuration is the same as that of the second embodiment shown in Fig. 2 . Further, the electric switches 9 and 12 can be changed to one electric switch.

Further, in the second and fourth to seventh embodiments, the limit switch 8 is used as a part of the flow path switching means, but the following mode is also adopted, that is, the limit switch 8 is omitted, and the electric switch 9 is used and electrically insulated. The circuit for energizing the coil (coil driver), according to the position data of the work drive means 3 generated by the servo motor for driving the work drive means 3 by the reciprocating drive mechanism, the fusion controller determines that the cylindrical workpiece 1 reaches the C position, and the coil driver The cutoff command is transmitted to drive the electric shutter 9 to OFF.

In the above embodiments, although a plasma arc welding torch is used, a TIG (Tungsten Insert Gas) welding torch or a CO ₂ or MIG (Metal Insert Gas) welding torch may be used. Furthermore, when using a dual torch, different types of torches can be combined.

1‧‧‧Cylinder workpiece

2‧‧‧C type fixture

3‧‧‧Workpiece driving means

4L‧‧‧ first welding torch

4T‧‧‧ After welding torch

5L‧‧‧First torch welding power supply

5T‧‧‧After the welding of the torch

6r, 6s‧‧‧ power supply sliding parts

7‧‧‧Resistance as a means of switching the flow path

21‧‧‧ entrance

22‧‧‧Export

23‧‧‧ openings

A‧‧‧First welding torch 4L position

After B‧‧‧ welding torch 4T position

C‧‧‧Location of power supply slides 6r, 6s

D‧‧‧The position of the front end of the cylindrical workpiece 1 when the rear end region starts to be welded

E‧‧‧The rear end position of the cylindrical workpiece 1 at the end of the welding end

I ₁ ‧‧‧1st splicing current

I ₂ ‧‧‧2nd welding current

I _L ‧‧‧ first welding torch 4L welding current

I _T ‧‧‧ After welding the welding torch 4T welding current

Claims (9)

A tunnel-type tube forming welding method, in which a C-shaped fixture is used, that is, a part of the peripheral surface of the thick-walled cylinder is made into a groove-shaped opening extending through the inner space, and the cylindrical workpiece which is bent into a cylindrical shape is clamped in a radial direction. While pressing the rear end to move the cylindrical space inside the C-shaped jig, the original flat sides of the cylindrical workpiece inside the C-shaped jig are butted apart from each other by a welding torch inserted into the opening. The groove is welded, characterized in that, in the moving direction of the cylindrical workpiece, a power supply sliding member is fixedly disposed at a front end position of the cylindrical workpiece from the welding torch to the rear end region to be welded, for sliding the cylindrical shape The surface of the original plate portion beside the welded bead of the workpiece, when the cylindrical workpiece contacts the power supply sliding member, the welding main current path of the welding torch is switched from the C-shaped jig to the power supply sliding member. The tunnel tube forming welding method according to claim 1, wherein in the rear end region, the welding current flows in a direction substantially parallel to the welding beads from the front end position of the workpiece, thereby reducing the direction toward the molten metal pool. Parallel magnetic blowing. A tunnel type tube forming welding device, comprising: a C-type jig having: an inlet for receiving a cylindrical workpiece for bending a flat plate, an outlet for discharging the cylindrical workpiece, and a circumferential surface a slot-shaped opening of the inner space that is opened, the cylindrical workpiece that is pressed into the inner space from the inlet is clamped in a radial direction, and a welding current path of the cylindrical workpiece is formed; and the workpiece driving means is from the C The foregoing inlet of the jig, presses the cylindrical workpiece into the inside, and extrudes the cylindrical workpiece from the outlet; and fuses the torch through the aforementioned opening of the C-shaped jig, and is aligned with the workpiece driving means Abutting grooves between the sides of the original flat plates of the cylindrical workpieces driven to drive, and welding the power supply sliding members in the direction of the pressing of the cylindrical workpieces from the aforementioned welding torch The position of the front end of the cylindrical workpiece when the welding is started in the rear end region is fixedly disposed at a position of the surface of the original plate portion adjacent to the welded bead of the cylindrical workpiece; and the flow path switching means, when the cylindrical workpiece is When the front end contacts the power supply sliding member, the welding main current path of the welding torch is switched from the C-shaped jig to the power supply sliding member. The tunnel-type tube forming and welding apparatus according to the third aspect of the invention, wherein the power supply sliding member is a pair, and the slots of the cylindrical workpiece are vacated and spaced apart in the circumferential direction. The tunnel tube forming and welding device according to the third or fourth aspect of the invention, wherein the flow path switching means includes a resistor, the resistor is inserted in the first current path, and the first current path supplies power to The first current path of the welding current path between the first pole of the fusion welding power source of the welding torch and the C-type jig is set to be higher than the second current path of the welding current path between the one pole and the power supply sliding member. . The tunnel tube forming and welding device according to the third or fourth aspect of the invention, wherein the flow path switching means includes: a front end position detecting means for detecting that the front end of the cylindrical workpiece reaches the power supply sliding member And the electrical switch, according to the detection by the front end position detecting means, cuts off the first current path which is a welding current path between the first pole of the welding power source of the welding torch and the C-shaped jig. The tunnel tube forming and welding device according to claim 5, wherein the flow path switching means further comprises: a front end position detecting means for detecting a position at which the front end of the cylindrical workpiece reaches the power supply sliding member; The normally open type electrical switch switches the second current path from non-energized to energized in accordance with the detection of the distal end position detecting means inserted in the second current path. The tunnel tube forming and welding device according to claim 6, wherein the flow path switching means further comprises a normally open type electrical switch, according to the first pole inserted into the welding power source and the power supply sliding member The front end position of the second current path The detection of the detection means switches the second current path from non-energized to energized. The tunnel tube forming and welding device according to claim 7, wherein the flow path switching means further includes a normally closed type electrical switch that is connected in parallel to the resistor inserted in the first current path, according to the foregoing The detection of the front end position detecting means switches the first current path from energization to non-energization.