JPH09239546A - Method and device for ac plasma welding of aluminum roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of a joint, to reduce blow holes, to unify the depth of penetration, and to smooth the bead surface in the welding of an aluminum roller. SOLUTION: A ring-shaped boundary part between a flange and an aluminum hollow cylindrical body of an aluminum roller in which a flanged shaft member is inserted in an end part of an aluminum hollow cylindrical body is welded by the AC plasma welding while at least one of the roller and a plasma torch is relatively turned. In this welding, turning is continued at least two times, the plasma by the arc current is jetted to the boundary part by the plasma torch during that time, and the AC plasma welding is performed during at least one latter turn. That means, the boundary part to be welded is preheated at least one turn by the plasma torch, and then, welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to manufacturing of aluminum rollers, and more particularly, to AC plasma arc welding between a hollow cylindrical body forming an aluminum roller and a flanged shaft member. Although not intended to be limited to this, the aluminum roller is used as, for example, a paper feed roller used for feeding and conveying recording paper in a copying machine, a printer, or the like, or a core thereof.

[0002]

2. Description of the Related Art For example, in the case of manufacturing the roller for feeding the paper, as shown in FIG. 8, when manufacturing the roller Rn, aluminum is formed at both ends of a cylindrical aluminum pipe (hollow cylinder) Pn. Flange joint (shaft member with flange)
Put on Pnf. At that time, methods such as fixation by press fitting, fixation by pressure welding, or welding by welding are used. However, when the flange joint is fixed by press fitting, the aluminum pipe P is heated by the heat of the coating when the peripheral surface is coated after the flange joint is fixed.
n and the flange joint Pnf have a difference in coefficient of thermal expansion,
The flange joint Pnf comes off from the aluminum pipe, resulting in poor yield. Furthermore, the product life is short.

On the other hand, in the pressure welding method, one of the aluminum pipe Pn and the flange joint Pnf is fixed and the other is driven to rotate at a high speed to drive the aluminum pipe Pn and the flange joint Pn.
Press in f. The friction heat between the two causes the aluminum pipe Pn to reach a high temperature and adheres closely to the flange joint Pnf, but the opening edge that receives the flange joint Pnf bulges outwards. It is necessary to prepare an aluminum pipe that has been bulged or deformed, and processing costs and material costs are required.

Therefore, in order to manufacture the roller with high durability and at low cost, it is desirable to weld the flange joint by arc welding. However, since molten aluminum easily takes in hydrogen, has high thermal conductivity, and has a fast solidification rate, when welding is performed, hydrogen gas bubbles (blowholes) are generated in the molten aluminum and the bubbles are released into the outside air. Before it escapes, it cools and hardens, and blowholes BF are likely to occur in the welded portion. Also, while the melting point of aluminum is about 700 degrees, the melting point of alumina, which is an oxide of aluminum, is 3000.
Since the temperature is as high as about 100 degrees, if the surface of aluminum is oxidized to form a layer of alumina oxide film at the time of welding, the melting of aluminum is not smoothly performed, which causes cracking or welding failure. Also, during welding, the welding part is preheated by the heat of welding in advance, but since the starting point of welding does not change from the temperature of the surrounding air, this temperature difference causes a difference in the penetration depth of the starting point of welding, Problems such as width changes occur.

In order to solve these problems, Japanese Patent Laid-Open No. 52-52
JP-A-26334 discloses a TIG welding in which an arc is started at a current lower than a welding current in front of a welding line starting point at the time of welding an aluminum plate, moves to a starting point and is preheated, and welding is performed at the welding current from the starting point. Method, a method for preventing welding defects at the starting end has been proposed. According to this, the bead width and the penetration depth at the welding start end are made uniform by preheating the vicinity of the welding start end.

[0006]

However, Japanese Patent Application Laid-Open No.
In the method disclosed in Japanese Patent No. 26334, it is assumed that the welding surface is a flat surface, and it is difficult to apply it to welding in the circumferential direction of a pipe or the like. That is, in the circumferential welding of pipes, etc., the starting point and the ending point of the welding are the same, so preheating only the starting end of the welding may cause burn-through at the ending point (contacting the starting end) of the welding. Yes, it is difficult to make the penetration depth uniform over the entire circumference. In the case of AC TIG welding, the directivity of the arc (especially the directivity when the polarity is opposite) is weak, and if the moving speed of the torch with respect to the welding object is high, the arc will move relative to the relative movement. When trying to stand still, the arc is easily pulled, and it is easy for the arc to jump and break.

An object of the present invention is to improve the joint quality of the welding of the end portion of the hollow cylindrical body of the aluminum roller and the flanged shaft member. Specifically, reduce the blow holes,
Welding is performed for the purpose of making the penetration depth uniform over the entire circumference and smoothing the bead surface.

[0008]

SUMMARY OF THE INVENTION In the present invention, an aluminum roller having a shaft member inserted into an end portion of an aluminum hollow cylinder,
The ring-shaped boundary between the shaft member and the aluminum hollow cylinder is welded by AC plasma welding while rotating at least one of the roller and the plasma torch relative to the other. In addition, in this welding, the rotation is continued for at least 2 revolutions or more, during which the plasma due to the arc current is injected from the plasma torch to the boundary portion, and the AC plasma welding is performed for at least one half of the latter half of the rotation. . That is, welding is performed after preheating the boundary portion to be welded by the plasma torch for one rotation or more.

This preheating is preheating by an alternating-current plasma arc, but the pilot arc is maintained in the plasma torch and the main arc flies through this pilot arc, so even at high speed rotation. The jumping of the arc and breakage of the arc are unlikely to occur, the main arc is stable, and therefore the entire circumference is preheated uniformly. Due to this preheating, welding failure does not occur at the welding start end in the subsequent AC plasma welding. In addition, there is no burn through at the end. Moreover, the penetration depth becomes uniform over the entire circumference, and the bead surface becomes smooth. Further, the bead width at the welding start position is also the same as the bead width at the welding position after the welding start point, so that the bead width becomes uniform. Since the welding is performed while automatically removing the oxide film with a high melting point by AC plasma welding, aluminum is smoothly melted and welding defects do not occur.

AC plasma welding is suitable for welding aluminum because the oxide film is melted in the reverse polarity section and the aluminum is melted in the positive polarity section. Therefore, the oxide film on the surface of aluminum contains crystal water, which is welded. Sometimes it is one of the causes of hydrogen generation. Since aluminum has a high thermal conductivity, there is a high possibility that the molten portion will solidify while containing hydrogen. However, in the present invention, the entire circumference is preheated by the preheating for one rotation or more, which results in the blower. -Less. This is because the water of crystallization is reduced by partial destruction of the oxide film on the aluminum surface in the reverse polarity section of the AC plasma arc during preheating, or by preheating the entire circumference (heat storage). However, it is not certain whether it is due to the fact that the solidification of the molten portion during welding is delayed and the probability that hydrogen escapes is high, or it is due to the interaction between the two, but the welding method of the present invention ensures that the blow hole Reduce.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION During the rotation before AC plasma welding, the rotation speed is set higher than that during welding and / or the plasma arc current is set lower than that during welding. Thereby, the outer peripheral surface of the aluminum roller is not overheated before welding, and the temperature at the planned welding position can be uniformly increased.

The groove shape of the ring-shaped boundary has a groove depth of 0.
1-0.5 mm, groove angle 70-88 °
140-176 ° V-shaped groove. According to this, the convex bead does not appear due to the groove provided at the ring-shaped boundary,
You can get a beautiful bead that is smoothly continuous with the circumferential surface.

The aluminum roller is preheated by a heating means separate from the plasma torch just before the rotation for AC plasma welding. As a result, the preheating time (preheating rotation amount) by the plasma torch can be reduced.

With the shield cover, the shield gas gas sprayed by the plasma torch onto the ring-shaped boundary of the aluminum roller is forced to flow in the circumferential direction of the ring-shaped boundary.
As a result, not only just under the torch but also most of the ring-shaped boundary part is shielded from the outside air by the inert gas, the ring-shaped boundary part has a high shielding effect, and water vapor (hydrogen) in the outside air can be taken in. No blowholes are easily generated.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0016]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, the x-arrow direction is the right, the y-arrow direction is the rear, and the direction z from the back of FIG. 1 to the front is the top. In the cylindrical aluminum pipe Pn, aluminum flange joints Pnf are press-fitted at both ends thereof in a press-fitting process (not shown), so that the roller Rn
Becomes The flange joints Pnf at the two ends of the roller Rn and the mating portion (ring-shaped boundary portion) of the roller Rn are circumferentially welded by AC plasma welding using the apparatus shown in FIG. As a welding process, an operator uses a flange joint P
When the nf press-fitted aluminum roller Rn is set by the set lever 28 between the rotary drive shaft 25 and the roller receiving shaft 26 of FIG. 1 and the start switch 30 is turned on, the torch 1
Moves to the welding position and performs automatic welding. The torch 1 returns to the original position after the welding is completed. The operator once operates the set lever 28 to release the set, reverses the right and left of the roller Rn, and sets the roller Rn between the rotary drive shaft 25 and the roller receiving shaft 26 again. Then, when the start switch 30 is turned on, welding is performed by the torch 1 in the same process as described above, and the aluminum roller Rn is completed. Depending on the material and shape of the aluminum roller, the welding may be performed after preheating to a predetermined temperature by the electric furnace 50 before welding.

Next, the structure of the apparatus will be described. To the right of the upper surface of the workbench 3 of the apparatus, the rollers Rn
There is a receiving shaft 26 that rotatably receives the right flange joint Pnf at its left end portion, and is supported by a support member 27 so as to be slidable in the left-right direction. A set lever 28 extending in the front-rear direction is provided at the right end of the workbench 3 further to the right of the receiving shaft 26. Base of the set lever 28 (rear end)
Are rotatably supported by a shaft portion 28a extending in the z direction. The shaft portion 28a is fixed to the workbench 3 via a supporting member, and the set lever 28 pivots the tip (front end portion) in the left-right direction about the shaft portion 28a. However, the tip of the shaft portion 28a is always pulled leftward by the spring 29 stretched between the shaft portion 28a and the support member 27. An elongated hole is formed in the middle of the set lever 28 so as to engage with a pin 26a protruding above the receiving shaft 26. The receiving shaft 26 slides leftward and rightward (in the direction of the arrow 3x) by the turning motion of the set lever 28 about the shaft portion 28a.

On the left side of the upper surface of the workbench 3, there is a rotary drive shaft 25 whose front end faces the receiving shaft 26. The rotary drive shaft 25 is rotatably supported by the support member 24. When the lever 28 is turned in the unclamping direction (rightward), the receiving shaft 26 retracts to the right. A worker inserts a flange joint Pn between the rotary drive shaft 25 and the receiving shaft 26.
When the roller Rn in which f is pressed is set and the lever 28 is returned to the clamping direction (leftward) again, the roller Rn is clamped between the rotary drive shaft 25 and the receiving shaft 26 by the force of the spring 29. A motor 2 for rotating and driving the roller is mounted on the rear side of the support member 24. A pulley 21 is fixed to the rotation shaft of the motor 2, and the pulley 21 and
The timing belt 22 is stretched between the pulley 23 fixed to the tail end of the rotary drive shaft 25 protruding from the left side surface of the support member 24. When the motor 2 rotates in the normal direction, the rotation of the rotation shaft is transmitted to the pulley 23 via the pulley 21 and the timing belt 22, and the pulley 23
The rotary drive shaft 25 integrated with the shaft rotates in the direction of the rotation arrow r in FIG. A one-rotation detection switch 12 is provided at the tail end of the rotary drive shaft 25, and one detection pulse is generated for each rotation of the rotary drive shaft 25.

FIG. 7 (a) shows a flange joint Pnf at the right end of one roller. The flange joint at the left end also has the same shape as the flange joint Pnf at the right end. The circumferential surface of the flange of the flange joint Pnf near the end of the pipe Pn is cut into a conical shape so as to form a groove.
The groove angle is θ1 (70 ° to 88 °), and the groove depth L1 is 0.1 to 0.5 mm. Flange joint Pn
A circular hole pf for receiving the tip of the receiving shaft 26 is provided at the center of the end surface of the rotating shaft portion of f. The left end flange joint also has a round hole for receiving the tip of the rotary drive shaft 25.

As shown in FIG. 7B, the groove angle of the left and right flange joints is θ2 (140 ° to 176).
The groove may be a V-shaped groove. Even in this case, the groove depth L1 is 0.1 to 0.5 mm.

Please refer to FIG. 1 again. The receiving shaft 26 and the rotary drive shaft 25 are opposed to each other at their tips, and each has a conical shape, and the tips are spherical surfaces that match the above-described round holes pf. When the roller Rn is set by the operator, the tip of the receiving shaft 26 enters the round hole Pnf of the flange joint press-fitted on the right side of the roller Rn and hits the bottom thereof, and the shaft center of the roller Rn and the receiving shaft 26 rotate. The roller Rn is pressed leftward while being aligned with the center of the drive shaft 25. In this way, the roller Rn is rotated by the pulling force of the spring 29 in the left direction with the center of the roller Rn being the same as the center of the rotational drive shaft 25 and the receiving shaft 26.
It is fixed between the tip of the and the receiving shaft 26. In this state, when the rotation drive shaft 25 is driven to rotate in the direction of the rotation arrow r by the motor 2, the roller Rn and the receiving shaft 26 rotate integrally with the rotation drive shaft 25 in the same direction.

A torch front-rear mechanism 11 for supporting the welding torch 1 and driving it in the y direction (arrow 11y direction) is provided at the right rear of the fixed position of the roller Rn. The welding torch 1 is driven in the forward direction by the torch front-rear mechanism 11, and when the driving limit is reached, it stops at the boundary between the pipe Pn and the flange joint Pnf of the fixed roller Rn, that is, immediately above the weld. It is located in. The torch front-back mechanism 11 is further provided with an up-down mechanism 14, and when the welding torch 1 reaches the drive limit in the front direction, the welding torch 1 is driven downward. The torch front-rear mechanism 11 is a solenoid SOL described later.
The welding torch 1 is driven in the forward direction by energizing 1 and retracted to the rear when the energization is lost. Torch up / down mechanism 14
Drives the welding torch 1 downward by energizing the solenoid SOL2, and retracts upward when the energization is stopped. When performing welding, the torch front-rear mechanism 11 drives the welding torch 1 in the front direction and stops it at the welding position on the roller Rn (shown by the two-dot chain line in FIG. 1), and the torch up-and-down mechanism 14 further moves the welding torch. 1 is driven downward to start welding.

FIG. 2 shows a view of the right end portion of the roller Rn at this time as seen from the direction indicated by the one-dot chain line arrow 2A in FIG. A shield cover 1c having a substantially cylindrical shape and a U-shaped side opening across which a roller Rn traverses at the lower end is attached to the tip of the welding torch 1, and the welding torch 1 is driven downward by a torch front-rear mechanism 11. , U of shield cover 1c
The roller Rn is in the side opening of the mold. Therefore, the welded portion of the roller Rn is covered with the shield cover 1c, and the shield gas is injected from the torch centering on the plasma arc into the inside of the shield cover 1c, and from the lower opening of the cover-1c,
Exit below the roller Rn. The shield gas flow shields the welded portion (ring-shaped boundary portion) over the entire circumference and prevents air (especially water) from contacting the welded portion. A similar shield cover is also attached to the welding torch 1b.

The subsequent welding process is performed by the AC plasma welding machine 40 shown in FIG. 3 and the motor controller Mc shown in FIG. The operation timing of the operation up to this point and the welding process by the AC plasma welder 40 and the motor controller Mc is controlled by the sequence control circuit CS shown in FIG. FIG. 6 shows the operation timing (operation sequence) of each element of the apparatus of this embodiment.

Before starting the work, the worker first turns on the plasma power supply 40 to ignite the pilot arc (see fire) and puts the welding arc in the ON / OFF standby state. Next, the aluminum roller Rn is held by hand, and the set lever 28 is pushed rightward to retract the receiving shaft 26 rightward. When the aluminum roller Rn is arranged on the axis line between the rotary drive shaft 25 and the receiving shaft 26 and the set lever 28 is returned to the left, the aluminum roller Rn causes the rotary drive shaft 25 and the receiving shaft 26 to move by the pulling force of the spring 29. Set in between,
The welding standby state is reached after the loading is completed. Here, the end of loading means
This is the time when the seat sensor 15 detects that the roller Rn has been carried in between the receiving shaft 26 and the rotary drive shaft 25 and is turned on.

When the seat sensor 15 is turned on, the switch LS1 is closed in conjunction with it. As a result, the solenoid 1 and the relay coil R1 are turned on via the normally closed relay contact R7a. Contact R1 of relay coil R1
a, R1b are closed, and relay coil R1 has contact R1a
The self-holding of the energization is carried out. Also, the solenoid S
OL1 is energized and turned on. Solenoid SOL1
Interlocks with the torch front-rear mechanism 11, projects the plasma welding torch 1 supported by the torch front-rear mechanism 11 toward the front, and in conjunction with this, the limit switch LS2 is closed. When the limit switch LS2 is closed, the solenoid SOL2 is turned on via the normally closed timer contact T1a. The solenoid SOL2 is interlocked with the torch up / down mechanism 14 and drives the torch 1 downward. When the plasma welding torch 1a reaches the welding position, the limit switch LS4 is closed in conjunction with it. When the limit switch LS4 is closed, the relay coil R2 is turned on. When the relay coil R2 is turned on, its contacts R2a (FIG. 5), R2b
(FIG. 3) and R2c (FIG. 4) are closed.

Contact R2b of relay coil R2 shown in FIG.
Is a power contact of the AC plasma welding machine 40, and a contact R
When 2b is closed, the AC plasma welding machine 40 outputs an instruction to the external gas supply device to start supplying the shield gas to the plasma welding torch 1.

On the other hand, the contact R2c of the relay coil R2 shown in FIG. 4 is a power supply contact of the motor controller Mc, and when the contact is closed, the controller Mc starts energizing the motor 2. Here, the contact point R5e in FIG.
Is closed, the voltage supplied to the motor 2 is as shown in FIG.
The high voltage V1 as shown in FIG. This allows the motor 2
Rotates at high speed, and the roller Rn rotates at high speed accordingly. The one-rotation detection sensor 12 and the limit switch LS10 shown in FIG. 1 generate an electric pulse indicating each rotation of the roller Rn.

Please refer to FIG. 5 again. When the roller Rn makes one rotation, the limit switch LS10 is momentarily closed. Since the contact R2a is already closed, this turns on the relay coil R3, and the contacts R3a, R3b, R
3c is closed. Energization of the relay coil R3 is maintained by its self-holding contact R3a. When the contact R3b is closed, the relay coil R4 is energized via the normally closed contact Sa1 in the arc detection circuit Sa. On the other hand, contact point R3
When c is closed, the two-stage preset counter C1 starts counting the number of times the limit switch LS10 is closed.

By energizing the relay coil R4, the arc O of the AC plasma welding machine 40 shown in FIG.
The arc contact R4a connected to the N / OFF terminal is closed, and the welding machine 40 causes the plasma welding torch 1 and the roller Rn.
AC voltage is applied between them. As a result, a plasma arc is generated between the plasma welding torch 1 and the roller Rn, and an alternating arc current flows. Here, the contacts R5a,
Since R5c is closed, the arc current flowing between the plasma welding torch 1 and the roller Rn has a positive electrode current I shown in FIG.
p1 and the negative electrode current is In1. The arc detection circuit Sa shown in FIG. 5 detects the generation of a plasma arc by the flow of the arc current, and opens the internal contact Sa1 and closes the contact Sa2. As a result, the energization of the relay coil R4 is cut off and the contact R4a is once opened, but the welding machine 40 uses the plasma welding torch 1 and the roller Rn.
The plasma arc is maintained until the contact R4a is closed again. In this state, the arc current is low and the rotation speed of the roller is high, so even if the welded portion is warmed, it does not interfere with welding. This is the preheating of the rollers by the welding torch.

The preset counter C1 shown in FIG. 5 counts the number of times the detection switch LS10 is closed, and when the count reaches 3, the contact C1a is closed (SET1: end of preheating, start of main welding). As a result, the relay coil R5 is energized. By turning on the relay coil R5, FIG. 3 and FIG.
The contacts R5a, R5b, R5c shown in are opened and the contacts R5d, R5e, R5f are closed. Then, by closing the contacts R5d and R5e shown in FIG. 3, the current value of the alternating current flowing between the plasma welding torch 1 and the roller Rn becomes the positive electrode current value Ip2 as shown in FIG. 6, and the negative electrode current value becomes It becomes In2. That is, the current level increases, and this is the main welding current. On the other hand, by closing the contact R5f shown in FIG. 4, the voltage applied to the motor 2 drops to V2 shown in FIG. 6, and the rotation speed of the roller Rn becomes slow. By increasing the arc current in this way, the roller R
The state where the rotation speed of n is slow is the main welding state.

After that, the preset counter C1 shown in FIG.
Causes the contact point C1b to be further closed when the count reaches 4 (the roller Rn makes one rotation after starting the main welding) (SET2: end of main welding, start of crater processing). As a result, the relay coil R6 is energized, its contact R6a is closed, and the timer T1 starts counting. By closing the contact R6a, the relay coil R4 is energized again and the contact R4a shown in FIG. 3 is closed. The welding machine 40 gradually decreases the arc current value flowing between the plasma welding torch 1 and the roller Rn by closing the contact R4a for the second time. During this time, the motor controller Mc continues to energize the motor 2, and the motor 2 continues to rotate the roller Rn. As the arc current decreases, the plasma arc decreases, and the roller Rn continues to rotate while gradually reducing its molten pool. This is crater processing.

When the timer T1 finishes counting, the contacts T1a and T1c are opened and the contact T1b is closed. When the contact T1c is opened, the relay coil R6 is de-energized, the contact R6a is opened, and the relay coil R4 is opened.
With the switch off, the contact R4a shown in FIG. 3 is opened, and the welding machine 40 returns to the welding standby state. Further, the opening of the contact T1a cuts off the energization of the solenoid SOL2 to raise the welding torch 1, and in conjunction with this, the limit switch LS5
Is closed, the relay coil R7 is energized through the already closed timer T1b, the contact R7a is opened, and the relay coil R1 and the solenoid SOL1 are turned off. When the solenoid SOL1 is turned off, the welding torch 1 is returned to the rear. Further, when the relay coil R1 is turned off at the same time, the contacts R1a and R1b of the relay coil R1 are opened, the self-holding of the relay coil R1 is released, and all the relay coils, timers, solenoids and counters are released and activated. Return to the state before. The operator operates the set lever 28
Is driven to the right and the receiving shaft 26 is moved to the right, the aluminum roller Rn is released from the restraint and can be taken out. When the other unwelded portion of this aluminum roller Rn is placed on the right side and the same work setting operation as described above is performed again, and the start switch 30 is turned on again, the apparatus performs welding by the same welding operation as described above, Welding is completed.

When it is necessary to preheat the aluminum roller Rn such as when it has a large diameter, it is preheated to a predetermined temperature in the electric furnace 50 before welding, taken out of the electric furnace 50 immediately before welding, and subjected to the same welding operation as described above. Weld.

Table 1 shows the results of welding performed by changing the conditions using the apparatus of this embodiment. Further, FIG. 9 shows a graph showing the number of blowholes generated when the preheating rotation speed is changed. In Table 1 and FIG. 9, common conditions are as follows.

1) Material Material Pipe diameter φ14 mm Thickness 1.5 mm A6063 Flange joint φ14 mm A5056 2) Construction conditions Welding machine used: Double inverter type AC plasma welding machine Nozzle diameter: φ2.4 mm Advance angle: 15 ° Pilot gas: Ar 0.35 L / min Shield gas: Ar 10 L / min Standoff: 2 mm Crater time: 1.5 sec AC positive electrode ratio: 75% AC frequency: 250 Hz Reverse polarity current: 100 A

[0037]

[Table 1]

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a perspective view of a right end portion of a roller Rn shown in FIG.

FIG. 3 is an electric circuit diagram showing the connection of the AC plasma welding machine 40 shown in FIG. 1 with peripheral circuits.

4 is an electric circuit diagram showing a connection with a peripheral circuit of a motor controller Mc that rotationally drives the motor 2 shown in FIG.

5 is a moving mechanism 11, 1 of the welding torch 1 shown in FIG.
4 is an electric circuit diagram showing an AC plasma welder 40 and a sequence circuit CS that controls the operation of the motor controller Mc shown in FIG. 4.

6 is a time chart showing the operation timing of each control element by the sequence circuit shown in FIG.

FIG. 7 (a) is a flange joint Pnf having a concave groove.
FIG. 4B is an enlarged plan view of the flange joint Pnf having a V-shaped groove.

FIG. 8 is a vertical cross-sectional view of a welded portion in conventional roller welding.

FIG. 9 shows a roller Rn before main welding using this example.
3 is a graph showing changes in the number of blowholes generated when welding is performed while changing the rotation speed of the.

[Explanation of symbols]

21, 23: Pulley 22: Timing belt 24: Support member 25: Rotating drive shaft 26: Receiving shaft Pn: Pipe Pnf: Flange joint pf: Round hole Rn: Roller C1: Two-stage preset counter R1 to R7: Relay coil Sa: Arc detection circuit SOL1 to SOL2: Solenoid T1: Timer LS1: Switch LS2: Limit switch LS4: Limit switch LS5: Limit switch LS10: Limit switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Hoshino 7-6-1, Higashi Narashino, Narashino City, Chiba Prefecture Nittetsu Welding Industry Co., Ltd.

Claims (7)

[Claims] 1. A ring-shaped boundary between the shaft member and the aluminum hollow cylinder of an aluminum roller in which a shaft member is inserted at the end of the aluminum hollow cylinder is at least the roller and the plasma torch. In welding by alternating-current plasma welding while rotating one relative to the other, the rotation is continued for at least two revolutions during which the plasma
A method for AC plasma welding of an aluminum roller, characterized in that plasma from an arc current is jetted to the boundary portion from a groove and AC plasma welding is performed during at least one half of the latter half of the rotation. 2. A low rotation speed and / or a low arc current during the AC plasma welding rotation, and a high rotation speed and a low arc current during the previous rotation. On the other hand, the method of AC plasma welding of an aluminum roller according to claim 1. 3. The groove shape of the ring-shaped boundary portion is a groove groove having a groove depth of 0.1 to 0.5 mm and a groove angle of 70 to 88 ° or a V groove having a groove angle of 140 to 176 °. First, claim 1, claim 2
Alternatively, the method of AC plasma welding of an aluminum roller according to claim 3. 4. The aluminum roller according to claim 1, wherein the aluminum roller is preheated by a heating means separate from the plasma torch just before the rotation for performing the AC plasma welding. AC plasma welding method. 5. A means for rotationally driving an aluminum roller having a shaft member inserted at the end of an aluminum hollow cylinder; for welding a ring-shaped boundary between the shaft member and the aluminum hollow cylinder of the aluminum roller. Plasma welding torch; AC power source for supplying AC arc current to the plasma welding torch with variable current level; Means for detecting rotation amount of aluminum roller; and aluminum roller via the rotation driving means To drive the AC power supply to supply a low level current, and when the rotation amount detecting means detects a set rotation amount, instructs the AC power supply to supply a high level current, and supplies the high level current to the rotation. An aluminum roller AC plasma welding apparatus, comprising: control means for continuing to supply a high level current until the quantity detecting means detects a set rotation speed. 6. The AC plasma welding apparatus for an aluminum roller according to claim 5, wherein the control means drives the aluminum roller to rotate at high speed, and switches to low speed rotation when the rotation amount detecting means detects the set rotation amount. 7. The apparatus further comprises a shield cover for forcing the gas injected by the plasma torch onto the ring-shaped boundary portion of the aluminum roller in a flow along the circumferential direction of the ring-shaped boundary portion. An AC plasma welding apparatus for an aluminum roller according to claim 6.