JPS5816781A - Production of welded pipe - Google Patents

Abstract

PURPOSE:To prevent the oxidation of alloy components in a blank material and the generation of penetrators in the stage of producing a welded pipe by irradiating a laser beam near the welding point and welding the blank material while allowing the metal in the irradiated part to evaporate. CONSTITUTION:A steel strip is fed and is formed to a U shape; further, it is formed approximately to a circular shape to form an open pipe OP. Both opposed edges of the open pipe are accurately guided and the pipe is fed into an induction heating coil 1. High frequency current is supplied to the coil 1 to heat the opposed side edge parts. The open pipe OP heated at said parts is pressurized with squeeze rolls 3l, 3r and are welded at a welding point A, by which a pipe P is formed. A laser beam generator 7 is installed above the point A, and irradiates a laser beam to the area near the point A. The metallic surface near the point A evaporates and the metallic surface is shielded from the atmospheric air by the vapor pressure thereof, whereby a non-oxidative atmosphere is maintained around the heated parts.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing welded pipes such as electric resistance welded steel pipes using welding techniques such as high frequency welding, which effectively prevents the generation of penetrators and improves welding quality. This paper proposes a method for manufacturing pipes.

In general, in the method of manufacturing ERW steel pipes, a steel strip is continuously fed to a group of forming rolls consisting of a plurality of breakdown rolls, side rolls, fin bath rolls, etc., and is first formed into a U-shape, and then approximately It is bent into a circular open pipe, then fed to the inoculation, and after heating and melting that part by passing high-frequency current to the opposite end face of the open pipe using an induction coil method or thermage tool method, the part is pressed by a squeeze roll. By doing this, ERW steel pipes are manufactured.

The major advantage of this method is that it is highly efficient compared to other pipe manufacturing methods, and it can reduce the cost of oil country tubular goods, steel pipes for line pipes, steel pipes for boilers, steel pipes for machine structures, etc. .

However, when the opposite end face of the open pipe is heated and melted, the alloy components in the material are oxidized by oxygen in the atmosphere, and among the oxides that are produced, there is one with a high melting point (Mn* Sip C).
(oxidants such as R) may remain inside the weld without being discharged, causing a welding defect called penetration. significantly deteriorate the physical properties of
Since it reduces the reliability of the ERW steel pipe, it becomes a factor that limits its uses.

For this reason, various methods have been developed to prevent the occurrence of penetrators, the main ones being a method of stabilizing the welding phenomenon and a method of shielding the area around the heated part with nitrogen gas or the like. The former method focuses on the fact that penetrators are likely to occur when excessive welding heat input is applied, and by controlling changes in plate thickness, shape, power supply voltage, etc., so that an appropriate heat input is always obtained. This is a method to prevent the occurrence of oxidation, but even if control is possible to obtain an appropriate temperature, as long as Benetrator is caused by the oxidation phenomenon of alloy components such as Mn*SitCr in the material, the oxidation will be prevented. Unless the phenomenon is fundamentally prevented, the occurrence of penetrators cannot be completely eliminated, and in reality, minute penetrators remain if only the welding heat input is controlled.

The latter method is a method in which the area around the heating part is shielded from the atmosphere using nitrogen gas, etc. to prevent oxidation, and it is already known that the generation of penetrators is considerably reduced. Due to the complicated structure of the coil or contact feeder, it is not possible to completely shield the area around the heating part from the atmosphere to prevent oxidation of alloy components such as Cr, which inevitably generates minute penetrators, and the equipment is damaged. It is a large-scale project, and its maintenance is also typical.

The present invention has been made in view of the above circumstances, and it is possible to substantially completely prevent the oxidation of the material around the heated part when manufacturing welded pipes such as electric resistance welded steel pipes, and to significantly reduce the minute penetration torque. ,
The purpose is to improve the quality of welded pipes.

The method for manufacturing a welded pipe according to the present invention includes bending a metal strip so that its side end surfaces face each other to form an open pipe;
In the method of manufacturing a pipe by welding the opposite ends of the open pipe by passing electricity through the opposite ends and applying pressure from both sides, a Lede beam is irradiated near the welding point, and the metal at the irradiated part is It is characterized by welding while evaporating.

Hereinafter, the method of the present invention will be explained in detail based on the drawings showing its implementation state. FIG. 1 is a plan view schematically showing a main part of an ERW steel pipe manufacturing fin, and FIG. 2 is a perspective view schematically showing the vicinity of the welding point. The steel strip ST, whose both side edges have been finished with a surface suitable for welding by an edge side device (not shown), is fed in the direction of the white arrow ' to plate rolls 61a, 6.
1b and 62a.

62b and side rolls 51/, 51r, 52/,
52r and 53/y It is formed into a U-shape by 53r. And fin bus roll 41 installed vertically
, 42 (only the upper row A/ is shown in the figure)
Furthermore, the final side roll 54/l 54r between the fin bath d-rules 41 and 42 forms the open pipe OP into a substantially circular shape, and the opposite edges are formed by the fin plate of the upper fin bath roll. is accurately guided and fed to the induction heating coil 1. 200 to 500 from high frequency power supply 2 to induction heating coil 1
A high frequency current of about kHz is supplied, and the open pipe O
An ij induced current is generated at the opposite end of P. Open pipe 0P whose opposite end is heated by this induced current
It is pressurized from both sides by the ti squeeze rolls 3/e3r and welded at the welding point A to form the pipe P. A radar beam generator 7 is installed above the welding point A as shown in FIG. 2, and irradiates the vicinity of the welding point A with a laser beam.

Here, the vicinity of the welding point A refers to the actual welding point where the heated and melted opposite end is joined by the squeeze roll 3/*3r, which is the so-called welding butt point and the heated and melted opposite end that is joined by The appearance where the side ends are close together and appear to be joined refers to the area up to the upper welding point, and further upstream of the welding point about 20w.

Further, as the laser beam generator 17, a solid laser such as ruby or YAG or a gas laser typified by CO3 is used, and the beam is continuously irradiated with an output of about 100 KW/csf. The opposite end is heated by a high frequency induced current, and this level is sufficient to vaporize the metal in the irradiated area.

In the example, the laser beam was irradiated directly from the laser beam generator 7 to the vicinity of the welding point A, but a mirror was placed at an appropriate position above the welding point A, and the laser beam generated at other positions was reflected by the mirror. It is also possible to irradiate the vicinity of the welding point A by placing the mirror at an appropriate position on the upstream side of the welding point, for example, in the gap created between the opposing ends of the open pipe OP, and to irradiate the vicinity of the welding point A. The Rede beam may be reflected by the mirror and irradiated to the vicinity of the welding point A as a horizontal beam.

According to one method of the present invention, the metal surface near the welding point A is rapidly heated by the laser beam, and the gold J
l! Fi evaporates, and its vapor pressure shields the gold surface from the atmosphere. Further, as the steam is oxidized, surrounding oxygen is consumed, and the oxygen partial pressure is significantly reduced. Also, most of the oxides from the insect repellent are scattered into the atmosphere and do not have any adverse effect on the welded parts. In this way, in the method of the present invention, the metal surface self-shields as the material metal evaporates by itself, so it is possible to effectively create a non-oxidizing atmosphere around the heated area, and the alloy components in the material in that area can be effectively created. This prevents oxidation and also prevents minute penetration marks. Furthermore, compared to the conventional shielding method using nitrogen gas or the like, the device is simple and can be easily applied to existing equipment.

Next, I will explain the implementation example for January with zero launches. Chemical components are C: 0.14%, Si: 0.30%, Mn: 0.5
Cr: 0%, Cr: 1.0% test material was made into a steel pipe with a plate thickness of 3.2 mm and an outer diameter of 48.6 steel at a pipe manufacturing speed of 2 minutes.

Table Xl51 compares the occurrence of penetrators between the conventional method and the method of the present invention.

Even if welding is carried out under welding heat input conditions that would cause many penetrators to occur when using the conventional method, the present invention can reduce the occurrence of penetrators to almost no, thereby preventing the occurrence of penetrators that occur in Method J, which generates zero penetrators. The effectiveness of this method was confirmed.

As detailed above, when using the IJ1 method of the present invention, when manufacturing a welded pipe, a laser beam is irradiated near the welding point, and the metal in the irradiated area is evaporated while welding is performed, so that the raw metal self-shields the metal surface from the atmosphere. do. - Therefore, it is possible to prevent the oxidation of the alloy components in the material, effectively preventing the generation of penetrators, and having a great effect on improving the quality of welded pipes such as electric resistance welded steel pipes.

[Brief explanation of the drawing]

Figure 1 is a plan view schematically showing the main parts of the electric resistance welded copper pipe manufacturing line, and Figure 2 is a perspective view schematically showing the vicinity of the welding point. P...Pipe OP...Open pipe ST...
・Strip steel A...Welding point 1...Induction heating coil 2
...High frequency power supply 3/+3r...Squeeze roll
7... Laser beam generator patent applicant: Sumitomo Metal Industries Co., Ltd. agent Patent attorney Noboru Kono Inu

Claims (1)

[Claims] 1. The side end surfaces of the metal strips are bent to form an open pipe so as to face each other, and the opposing ends of the open pipe are heated by passing an electric current through them and pressure is applied from both sides to weld the both ends. In a method of manufacturing a tube,
A method for manufacturing a welded pipe, characterized by irradiating a laser beam near the welding point and welding while vaporizing the metal in the irradiated area.