JPH0513678U - Gas shield device for pipe welding - Google Patents

Abstract

(57) [Abstract] [Purpose] In the production of ERW steel pipe by high frequency welding,
Prevents atmospheric air adhering to the inside and outside surfaces of the open pipe from entering the vicinity of the V junction. [Structure] An inner cylinder 8 having a large number of gas ejection ports 3 and an outer cylinder 1 having a plurality of gas supply ports 9 and inscribed in a work coil 2.
A hood having a double pipe seal box 1 made of 0 and having a shield gas passage formed between the inner cylinder 8 and the outer cylinder 11 and covering the V junction on the squeeze roll side of the seal box 1. In the gas shield device in which the gas injection nozzle 12 facing the V junction point of the open pipe 5 is provided in 7, the gas supply port 9 of the outer cylinder 10 is within a range of ± 30 ° with respect to the vertical line X passing through the V-shaped portion. To install. [Effect] It is possible to prevent the invasion of the air into the vicinity of the V-joint, to prevent the generation of the penetrator without deteriorating the shield atmosphere, and to manufacture a high-quality ERW steel pipe with high productivity and high yield.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gas shield device for continuously forming a raw material steel strip into a cylindrical shape by a group of forming rolls, and then joining the joints by an electric resistance welding method to form an electric resistance welded steel pipe.

[0002]

[Prior Art]

 Welding methods for welded steel pipe include electric resistance welding and arc welding. Of these, the electric resistance welded steel pipes that are joined by the electric resistance welding method are formed into open pipes by continuously forming the material strip steel into a cylindrical shape by a group of forming rolls, and the joints are formed by the electric resistance welding method. Manufactured by joining. The electric resistance welding method is classified into a direct current method, a low frequency method and a high frequency method according to the frequency of the current used. Among them, the high frequency welding method has many advantages in terms of quality and efficiency, and thus has become the majority of the electric resistance welding method.

In the joining of open pipes by the high frequency welding method, the V-shaped portion formed by the edges of the open pipes is heated by a high frequency current and immediately pressed and joined by a squeeze roll. In this high-frequency welding method, a high-frequency current is passed through the work coil placed immediately before the welding point, and a heating current is induced in the open pipe passing through the work coil, and contact tips are placed on both edges of the open pipe. There is a resistance method that directly supplies high frequency current, and the induction method is often used in Japan.

A problem in the production of electric resistance welded steel pipe by the above high frequency welding method is an oxide defect represented by a penetrator. Among oxides generated during heating, those having a high melting point are not discharged and remain on the joint surface. This defect is mainly due to high temperature oxidation by the atmosphere. Therefore, conventionally, a method of shielding the weld with a non-oxidizing gas such as argon gas or nitrogen gas has been adopted. This shield method is roughly classified into a box-type overall encapsulation type (JP-A-52-21237, etc.) and a local type (JP-A-56-23289, JP-B-59-27983, etc.). In both cases, a method is used in which the sliding part between the squeeze roll or open pipe and the shield device is sealed with an elastic body such as sponge or rubber.

However, in the method in which the sliding portion between the open pipe and the shield device is sealed with an elastic body or the like, the elastic body is liable to wear due to sliding, and it is necessary to replace it regularly, resulting in a lower operating rate. .. Also, since the open pipe moves at high speed, the air adhering to the pipe surface cannot be completely removed, and the shield atmosphere is slightly deteriorated by the air entering the shield device. Furthermore, the oil attached to the surface of the open pipe may turn into white smoke due to the welding heat, obstructing the field of view of the welding thermometer, and the temperature cannot be measured.In this case, it is difficult to weld the open pipe at the proper temperature. ..

As a method of solving the drawback of the method of sealing the sliding portion between the open pipe and the shield device with an elastic body or the like, the present applicant has an inner diameter larger than the outer diameter of the open pipe, and We have developed a method that uses a shield box consisting of an inner cylinder with a gas jet outlet and an outer cylinder with a plurality of gas supply ports that is installed inside a welding work coil. No. 62-109259, Japanese application 63-42635, Japanese application 63-237820). In this method, the shield box is externally fitted to the open pipe behind the V joint, and the shield gas is injected into the gap between the work coil and the inner cylinder, and the front, rear, and open pipes are formed along the outer surface of the open pipe. This is a method of shielding the V-junction by flowing out in three directions on the inner surface side of the pipe.

[0007]

[Problems to be solved by the device]

 However, the above-mentioned method is effective against the invasion of the atmosphere from the outer surface of the open pipe, but has a problem that the sealing property on the inner surface side is insufficient. That is, since the open pipe moves to the V-joint side at a welding speed, the air near the inner and outer surfaces of the open pipe will try to enter the shield box, but the shield gas ejected from the inner cylinder of the shield box is piped. Since it is directly injected to the outer surface, even if the flow rate of the shield gas is low, it is possible to sufficiently prevent atmospheric air from entering the outer surface of the pipe. On the other hand, since the shield gas is ejected to the inner surface of the open pipe through a small gap in the open portion of the pipe, the amount of the shield gas is smaller than that of the outer surface, and air cannot be sufficiently prevented from entering the inner surface. Can not. This phenomenon becomes more remarkable as the inner diameter of the open pipe increases.

In general, as a method for improving the sealing performance on the inner surface side of an open pipe, a method of filling the gap between the inner surface bead cutting tool and the inner surface side of the pipe with an elastic body to prevent atmospheric air from entering the inner surface side is known. However, even with this method, the open pipe moves at a high speed, so it is not possible to completely prevent the invasion of the atmosphere adhering to the inner surface, and the welding due to the accumulation of scale on the sliding parts. There was a problem such as scale biting into the part. Further, the applicant of the present invention, as a method of solving the problem of the sealing property on the inner surface side of the open pipe, has a gas injection port of the inner cylinder of the shield box at a predetermined angle so that the shield gas is ejected to the forming roll side. A method using a shield box tilted to the side (Japanese Patent Application No. 63-308526) was proposed. However, even if the seal box of Japanese Patent Application No. 63-308 526 is used, if the position of the gas supply port connected to the outer cylinder is improper, it is necessary to sufficiently prevent atmospheric air from entering the inner surface of the open pipe. I can't.

An object of the present invention is to provide a shield device capable of preventing the invasion of air into the inner and outer surfaces of an open pipe in the production of an electric resistance welded steel pipe by a high frequency welding method.

[0010]

[Means for Solving the Problems]

 The present inventors conducted various test studies in order to achieve the above object. As a result, there is a close relationship between the position of the gas supply port connected to the outer cylinder that supplies non-oxidizing gas to the shield box and the invasion of the atmosphere into the inner surface of the open pipe, and the open pipe to be welded If the gas supply port is installed within a range of ± 30 ° with respect to the vertical line passing between the end faces, the gas flow velocity flowing between the end faces to be joined into the inner face will cause the invasion of the atmosphere from the forming roll side to the inner face side. It was clarified that a sufficient flow velocity could be obtained to prevent this, and the inventors arrived at this invention.

That is, according to the present invention, the V-shaped portion formed by the edge of the open pipe is heated by a high-frequency current, and is immediately pressurized and joined by a squeeze roll to have an inner diameter larger than the outer diameter of the open pipe for high-frequency welding of the electric resistance welded steel pipe. It has an inner cylinder that has a large number of gas outlets, and an outer cylinder that has a plurality of gas supply ports and is inscribed in the high-frequency work coil. A shield gas passage is formed between the inner cylinder and the outer cylinder. A gas shield device comprising a double-pipe shield box and a hood provided on the squeeze roll side of the shield box so as to cover the V junction, and a gas ejection nozzle facing the V junction, wherein Is a gas shield device for pipe welding, in which a plurality of gas supply ports are installed within a range of ± 30 ° with respect to a vertical line passing through the V-shaped portion.

[0012]

[Action]

 In this invention, a plurality of gas supply ports of the outer cylinder of the seal box are installed within a range of ± 30 ° with respect to the vertical line passing through the V-shaped portion of the open pipe. As shown, the shield gas is supplied from near the V-shaped portion of the open pipe. Therefore, compared to the case where the gas supply port of the outer cylinder is installed at 90 ° to the vertical line passing through the V-shaped portion of the open pipe shown in Fig. 3 (b), the V-shaped portion to the inner surface The flow velocity of the shielding gas flowing into the pipe is high, and it is possible to prevent the invasion of the atmosphere into the inner surface of the pipe.

[0013]

【Example】

 The details of this invention will be described below with reference to FIGS. 1 is a vertical side view of the gas shield device of the present invention, FIG. 2 (a) is a vertical front view taken along the line AA of FIG. 1, and FIG. 1 (b) is a vertical front view taken along the line BB of FIG. Is. In FIGS. 1 and 2, reference numeral 1 denotes a double-tube structure seal box which is inscribed in the work coil 2 and has a large number of gas ejection openings 3 on the entire circumference of the work coil 2 on the forming roll side. On the squeeze roll 4 side, a hood 7 that covers the V-joint 6 side of the open pipe 5 is provided in a protruding manner, and an outer cylinder 10 having a plurality of gas supply ports 9 on the outer circumference. As shown in FIG. 2A, the plurality of gas supply ports 9 of the outer cylinder 10 are installed within a range of ± 30 ° with respect to the vertical line X passing through the V-shaped portion of the open pipe 5. There is. The shield gas supplied from the gas supply port 9 into the space 11 formed between the outer cylinder 10 and the inner cylinder 8 is configured to be ejected from the numerous gas ejection ports 3 to the open pipe 5. Further, the gas ejection nozzle 12 provided in the hood 7 is configured to inject gas toward the V junction point 6. In addition, 13 is an impeder.

Therefore, the shield gas supplied from the plurality of gas supply ports 9 of the outer cylinder 10 flows through the space 11 formed between the outer cylinder 10 and the inner cylinder 8, and a large number of gas ejection ports 3 Through the inner cylinder 8 and the open pipe 5, and between the V-joint 6 and the V-shaped gap on the forming roll side, and between the inner surface of the open pipe 5 and the impeder 13 to flow in the axial direction of the pipe. It flows out to the side of the squeeze roll 4 and the forming roll (not shown). Of these, the gas flow flowing to the side of the forming roll opposite to the V-joint 6 removes the atmospheric layer adhering to the inner and outer surfaces of the open pipe 5 and prevents the atmospheric air from entering the vicinity of the V-joint 6. To do. On the other hand, on the V joint point 6 side, the end face of the shield box 1 and the V joint point 6 are shielded by the gas flow flowing out to the squeeze roll 4 side and the gas flow ejected from the gas ejection nozzle 12.

FIG. 4 shows an outer diameter of 34.0 mm containing 1.0% by weight of Cr and 0.2% by weight of Mo, and a wall thickness of 1. This is a measurement of the relationship between the oxygen concentration and the number of penetrators at the V junction at the time of manufacturing a 6 mm ERW steel pipe. As is clear from FIG. 4, the oxygen concentration at the V junction was set to 0. By setting the content to 2% or less, the penetrator can be eliminated altogether. Fig. 5 shows the case where the outer diameter is 89.1 mm, the wall thickness is 5.0 mm, the gap value between the shield box inner cylinder and the open pipe is 9 mm, the nitrogen gas as the shield gas is ³ Nm ³ / min, and the angle of the gas ejection nozzle 12 is 15 °. The pipe making speed (maximum 80 m / min) and the V joint point when the angle α with respect to the vertical line X passing through the V-shaped portion of the open pipe 5 of the gas supply port 9 of the outer cylinder 10 in FIG. 1 is changed. 6 is a graph showing the relationship of oxygen concentration in No. 6; As is apparent from FIG. 5, in order to eliminate the penetrator, the angle α with respect to the vertical line X passing through the V-shaped portion of the open pipe 5 of the gas supply port 9 of the outer cylinder 10 is set to 0 to 30 °. It is necessary.

As described above, according to the present invention, by optimizing the position of the shield gas supply port to the shield box, it is possible to reliably prevent atmospheric air from entering the inner surface of the open pipe and deteriorate the shield atmosphere. It is possible to eliminate the occurrence of penetrators without causing any problems. In addition, since shield materials such as elastic bodies on the inner and outer surfaces are not required, the operating rate is significantly improved, and high-quality electric resistance welded steel pipes can be manufactured with high productivity and high yield.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a gas shield device of the present invention.

2 is a sectional view taken along line AA and BB in FIG. 1, where FIG. 2 (a) is a vertical sectional front view on the line AA, and FIG. 2 (b) is a vertical sectional front view on the line BB.

FIG. 3 shows the relationship between the gas supply position of the outer cylinder of the shield box and the ejection speed of the shield gas. FIG. 3 (a) shows the case where the angle α with respect to the vertical line X passing through the V-shaped portion of the open pipe is 0. , (B) shows the case where the angle α with respect to the vertical line X passing through the V-shaped portion of the open pipe is 90 °.

FIG. 4 is a graph showing the relationship between the oxygen concentration at the V junction and the number of penetrators.

FIG. 5 is a graph showing the relationship between the pipe manufacturing speed and the oxygen concentration at the V junction when the angle α with respect to the vertical line X passing through the V-shaped portion of the open pipe is changed.

[Explanation of symbols]

 1 Shield Box 2 Work Coil 3 Gas Jet 4 Squeeze Roll 5 Open Pipe 6 V Joint 7 Hood 8 Inner Tube 9 Gas Supply Port 10 Outer Tube 11 Space 12 Gas Jet Nozzle 13 Impeder

Claims (1)

[Scope of utility model registration request] 1. A V-shaped portion formed by the edge of the open pipe is heated with a high frequency current and immediately pressed / joined with a squeeze roll to have an inner diameter larger than the outer diameter of the open pipe at the time of manufacturing the electric resistance welded steel pipe, and A double pipe having an inner cylinder having a large number of gas ejection ports and an outer cylinder having a plurality of gas supply ports and inscribed in the high-frequency work coil, and forming a shield gas passage between the inner cylinder and the outer cylinder. In a gas shield device in which a shield box is provided, and a hood provided on the squeeze roll side of the shield box so as to cover the V joint point is provided with a gas ejection nozzle facing the V joint point, a plurality of gases of the outer cylinder are provided. ± from the vertical line passing through the V-shaped part
Gas shield device for welding pipes installed in the range of 30 °.