JPH08300164A - Device for shielding weld zone of resistance welded tube - Google Patents

Abstract

PURPOSE: To improve productivity, to detect forming defects of tube stock and to simplify correction by providing a shield cover for covering only a local part between the welding equipment around the weld zone and a tube stock minimizing the shielded space around the weld zone and decreasing the concentration of oxygen inside the space in a short time. CONSTITUTION: In this shielding device 20, a shield cover 22 is attached to the roll stand 100 of a squeeze roll 12, and only a local part (around a contactor 11 and the squeeze roll 12A) between the welding equipment 10 around the weld zone and a tube stock A is covered with the cover. Incidentally, 101 is the roll chock of an upper roll 12A. In addition, the device is provided with a shield rubber 102A in the part that comes into contact with the tube stock 1A and also a shield rubber 102B in the part with the welding equipment 10. Furthermore, the welding equipment 10 is capable of moving vertically between the lowered position with welding and the raised position without welding by means of an elevating part 13, and the contactor 11 is brought into contact with the tube stock 1A at the lowered position, thereby covering it with the shield cover 22 at this position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded portion shield device for an electric resistance welded pipe.

[0002]

2. Description of the Related Art In upset welding of an electric resistance welded pipe, when the material of the electric resistance welded pipe is a high Mn material or a high Cr content material, an oxide inclusion called a penetrator remains in the welded portion and It significantly deteriorates the quality. The cause of the penetrator is that while heating both edges of the seam of the raw tube with a high-frequency current, Mn, Cr, etc. in the raw tube combine with oxygen in the atmosphere to form an oxide, and both edges are squeezed. It is considered that the above oxides remain in the welded portion without being discharged to the outside when upset.

Conventionally, as a measure for preventing the occurrence of a penetrator,
As described in Japanese Patent Publication No. 59-32237, there is a technique of sealing the periphery of a welded portion and shielding the atmosphere of the welded portion with an inert gas or a reducing gas for welding (shield pipe forming technology). The shield pipe forming technology reduces the oxygen concentration around the welded portion and prevents the occurrence of penetrators.

[0004]

By the way, there are roughly two types of welding methods for electric resistance welded pipes, a high frequency induction welding type and a high frequency resistance welding type. The resistance welding method is the mainstream. In this high-frequency resistance welding method, a welding device such as a contactor (contact tip) for applying a current to both edges of the raw pipe or a large coil for generating a high-frequency current is arranged around the welded portion, so that the shield The device had to be a large one that enclosed the welding device from the outside.

However, when the shield device becomes large and the shield space around the welded part becomes large, it takes a long time to reduce the oxygen concentration around the welded part from the atmospheric state, and there is a problem that the operating rate is lowered. It was

Further, even if only a local portion around the welded portion is sealed, the shield device is fixed, so that there is a drawback that it is not possible to confirm and repair the occurrence of molding defects such as laps and wrinkles at the tip of the raw pipe, and the actual operation Would be unsuitable for.

It is an object of the present invention to make it possible to reduce the oxygen concentration around a welded part in a short time in a welded part shield device for an electric resistance welded pipe by setting a closed space around the welded part as a minimum volume.

It is another object of the present invention to make it possible to easily confirm and correct the occurrence of defective molding of a raw pipe in a welded portion shield device for an electric resistance welded pipe.

[0009]

According to the present invention as set forth in claim 1, when both edge portions of a seam of a raw pipe are heated by a high frequency resistance welding device, and both heated edge portions are upset welded by a squeeze roll, In a welded portion shield device for an electric resistance welded pipe that shields this welded portion with a shield gas, a roll cover of the squeeze roll is equipped with a shield cover that covers only a local portion between the welder around the welded portion and the raw pipe. It was made to do so.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the shield cover is provided with a seal rubber at a contact portion with a raw pipe and a contact portion with a welding device. It is the one.

According to a third aspect of the present invention, in addition to the first or second aspect of the present invention, the welding device can move up and down between a descending position during welding and an ascending position during non-welding. The shield cover is provided so as to cover only a local portion between the welding device in the lowered position and the raw pipe, and a space for confirming the forming state of the raw pipe is formed between the shield cover and the welding device in the raised position. It is the one.

[0012]

According to the present invention described in claim 1, the following effects are obtained. Since the shield cover covers only the local area around the welded part (for example, the welding contactor and the upper roll periphery of the squeeze roll), it shields only the minimum necessary range that prevents the occurrence of penetrators. The oxygen concentration around the parts can be lowered in a short time, and the operating rate can be improved.

Since the shield cover is fixed to the roll stand of the squeeze roll, the sudden vibration transmitted from the raw pipe to the shield cover and the frictional force acting on the shield cover from the raw pipe are supported by the roll stand of the squeeze roll. . The roll stand of the squeeze roll has a high-strength structure so that it can withstand the plastic deformation resistance force acting on the squeeze roll from the raw pipe, so it has sufficient strength against the above-mentioned vibration and frictional force, and is not damaged. You can continue shielded pipe making without fear. In addition, when the shield cover is fixed to the welding device, the welding device is damaged by the above-mentioned vibration or frictional force acting on the shield cover,
There is a possibility that the shield pipe manufacturing cannot be continued.

The present invention according to claim 2 has the following effects. Since the shield cover is provided with the seal rubber, it is possible to improve the above-mentioned shield performance and obtain a cushioning action against vibration.

The present invention according to claim 3 has the following effects. When the welding device is raised, a space for confirming the state of forming the raw pipe is formed between the shield cover and the welding device. Therefore, it is possible to easily confirm and repair the occurrence of molding defects at the tip of the raw pipe by using this raw pipe molding state confirmation space.

[0016]

1 is a schematic view showing an embodiment of the present invention, FIG.
Is a view taken along the line II-II in FIG. 1, FIG. 3 is a diagram showing the oxygen concentration lowering time, and FIG. 4 is a schematic diagram showing a shield gas blowing nozzle.

As shown in FIGS. 1 and 2, the electric resistance welded pipe 1 is heated by heating both edges of the seam of the raw pipe 1A by high-frequency energization from a contact (contact tip) 11 of a high-frequency resistance welding apparatus 10. Both edge portions are upset welded by the squeeze roll 12 and continuously manufactured.

At this time, the shield device 20 is installed around the welded portion of the raw pipe 1A, and the shield gas blowing nozzle 2 is provided.
A shield gas (inert gas or reducing gas) blown out by 1 (FIG. 4) shields the periphery of the welded part, and as a result, the above-mentioned penetrator is prevented from being generated.

The shield device 20 includes a squeeze roll 12
The shield cover 22 is attached to the roll stand 100, and the shield cover 22 locally covers the welding unit 10 and the base pipe 1A (around the contact 11 and the upper rolls 12A and 12A of the squeeze roll 12). Cover only. In FIG. 1, 101 is a roll chock of the upper roll 12A.

Further, the shield device 20 is provided with a seal rubber 102 at a contact portion with the base pipe 1A and a seal rubber 102B at a contact portion with the welding device 10.

In addition, the welding device 10 can
It is possible to move up and down between the descending position during welding and the ascending position during non-welding, and in the descending position, the contactor 11 is brought into contact with the base pipe 1A,
At the raised position, the contactor 11 is separated from the raw tube 1A.
Then, the shield cover 22 is provided so as to cover only a local portion between the welding device 10 in the lowered position and the raw pipe 1A,
Between the shield cover 22 and the welding device 10 in the raised position, a space for confirming the state of forming the raw pipe is formed.

Therefore, the welding device 10 operates as follows. (1) Since it is not necessary to energize the surface of the raw pipe 1A during non-welding, the elevating part 13 of the welding device 10 sets the welding device 10 to the raised position and separates the contact 11 from the surface of the raw pipe 1A. There is. Therefore, the shield cover 22 and the welding device 10
A space for confirming the state of forming the raw pipe is formed between the base pipe 1A and the end edge portion of the raw pipe 1A is correctly abutted, and whether or not molding defects such as wrinkles have occurred. It can be easily confirmed, and the defective molding can be easily repaired.

(2) After the defective molding of the raw pipe 1A is repaired, the elevating part 13 of the welding device 10 is lowered to move the contact 11 to the raw pipe 1.
The nozzle 21 is brought into contact with both edge portions and the nozzle 21 supplies the shield gas into the shield cover 22.

(3) Pipe forming (welding) is started when the oxygen concentration in the shield cover 22 drops to, for example, 1% or less.

The operation of this embodiment will be described below. The shield cover 22 covers only a local portion around the welded portion (for example, the periphery of the welding contactor 11 and the upper roll 12A of the squeeze roll 12), and shields only the minimum necessary range for preventing the occurrence of the penetrator. Therefore, the oxygen concentration around the welded portion can be reduced in a short time, and the operating rate can be improved.

The shield cover 22 is a squeeze roll 1.
Since it is fixed to the second roll stand 100, the sudden vibration transmitted from the raw pipe 1A to the shield cover 22 and the frictional force acting on the shield cover 22 from the raw pipe 1A are supported by the roll stand 100 of the squeeze roll 12. . Since the roll stand 100 of the squeeze roll 12 has a high-strength structure so as to withstand the plastic deformation resistance force acting on the squeeze roll 12 from the raw pipe 1A, it has sufficient strength against the above-mentioned vibration and frictional force. Therefore, shield pipe manufacturing can be continued without fear of damage. When the shield cover 22 is fixed to the welding device 10,
Due to the above-mentioned vibration and frictional force acting on the shield cover 22, the welding device 10 may be damaged and the shield pipe manufacturing may not be continued.

The shield cover 22 is a seal rubber 102.
Since A and 102B are provided, the above-mentioned shielding performance can be improved and a cushioning action against vibration can be obtained.

When the welding device 10 is moved up, a space for confirming the state of forming the raw pipe is formed between the shield cover 22 and the welding device 10. Therefore, it is possible to easily confirm and repair the occurrence of defective molding at the tip of the raw pipe 1A by using this raw pipe molding state confirmation space.

FIG. 3 shows a comparison of the oxygen concentration lowering times in the atmosphere of the welded portion in the case of the apparatus of the present invention and the conventional apparatus at the time of pipe making of size 24 inches × 14.88 mmt and grade API 5L × 65. is there. The device of the present invention is according to the above-described embodiment, and the conventional device is a large-sized device which encloses the entire welding device. According to the device of the present invention, it is recognized that the oxygen concentration lowering time can be significantly shortened.

In the practice of the present invention, when an inert gas such as Ar gas having a large specific gravity is used as the shield gas, the shield gas flows down from the outer surface of the tube to the inner surface of the tube and is covered with the shield cover 22. Can shield the entire thickness of both edges of the pipe. Therefore, the shield gas ejection nozzle 2
It suffices to provide 1 on the outer side of the raw tube 1A, and it is not necessary to provide a nozzle on the inner side of the raw tube 1A.

[0031]

As described above, according to the present invention, in the welded portion shield device for an electric resistance welded pipe, it is possible to reduce the oxygen concentration around the welded portion in a short time with the sealed space around the welded portion being the minimum volume.

Further, according to the present invention, in the welded portion shield device for an electric resistance welded pipe, it is possible to easily confirm and correct the occurrence of defective molding of the raw pipe.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

FIG. 3 is a diagram showing an oxygen concentration lowering time.

FIG. 4 is a schematic diagram showing a shield gas blowing nozzle.

[Explanation of symbols]

 1 ERW pipe 1A Element pipe 10 Welding device 12 Squeeze roll 13 Elevating part 20 Shield device 21 Nozzle 22 Shield cover 100 Roll stand 102A, 102B Seal rubber

Claims (3)

[Claims] 1. An electric resistance welded pipe in which both edges of a seam of a raw pipe are heated by a high frequency resistance welding device, and when the heated edges are upset welded by a squeeze roll, the welds are shielded by a shield gas. In the welded portion shield device, a roll cover of the squeeze roll is provided with a shield cover that covers only a local portion between the welding device around the welded portion and the raw pipe. Shield device. 2. The welded portion shield device for an electric resistance welded pipe according to claim 1, wherein the shield cover is provided with seal rubber at a contact portion with the raw pipe and a contact portion with the welding device. 3. The welding device can move up and down between a lowered position during welding and a raised position during non-welding, and the shield cover covers only a local portion between the welding device and the raw pipe in the lowered position. The welded portion shield device for an electric resistance welded pipe according to claim 1 or 2, wherein a shielded state of the raw pipe is formed between the shield cover and the welding device in the raised position.