JPH046474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite welding method that uses both electric resistance welding and a laser beam.

The electrical resistance well method (hereinafter abbreviated as ERW) is
This is one of the most commonly used welding techniques. For example, in the field of manufacturing welded steel pipes,
2. Description of the Related Art A method of manufacturing a pipe generally called an electric resistance welded pipe is widely used as a welding method with a high welding speed, that is, with high productivity.

Figure 1 shows an example of pipe making using the conventional high frequency contact electric resistance welding method, in which a steel strip is formed into a tubular shape by a group of forming rolls (not shown), and then the steel End portions 2, 2 of a band (hereinafter referred to as a tubular body) 1 are butted against each other by squeeze rolls 3, 3 to form a wedge shape with the abutted portion as the apex. Furthermore, a high frequency voltage is applied from the high frequency power supply 4 to the contacts 4a and 4b provided upstream of the squeeze rolls 3 and 3, and a high frequency current circuit is connected from the contacts 4a to 4b (or from 4b to 4a) at the wedge-shaped end. The end portions 2, 2 are heated by this high frequency current. As a result, the welding temperature is reached at the apex of the wedge shape,
Pressure welding is performed by the squeeze roll 3.

However, this ERW also has problems when the welded material becomes thick or when an attempt is made to increase the welding speed. For example, when the wall thickness becomes thicker, the high frequency current density at the corner portions 2a and 2b of the end portion 2 becomes higher than the high frequency current density at the central portion 2c of the plate thickness, as shown in Fig. 2a, and as a result, the temperature distribution becomes as shown in Ha ₂ . As a result, a low-temperature area occurs in the center of the plate thickness, and cold welding defects occur. Furthermore, if a high heat input state is created to eliminate cold welding, the temperature distribution will become as shown in Ha ₁ , and penetrator defects will occur.

Therefore, the present inventors first used a laser beam in conjunction with ERW, that is, introduced the laser beam horizontally into the wedge-shaped part of the tubular body as described above, and heated the part. proposed to solve such problems.

The present invention was made for the purpose of performing welding more reliably and efficiently by controlling the shape of the laser beam in a welding method that uses a laser beam in combination with ERW. In an electric resistance welding method in which electrical energy is supplied to a workpiece having a wedge shape whose surface is asymptotic and the welding point is the apex, the temperature of the apex of the wedge shape is heated to the melting temperature by the generated Joule heat and welded; A laser beam is projected onto the welding point from the open side of the wedge shape to heat the wedge-shaped inner surface, and an astigmatism mirror is placed in the optical path of the laser beam to change the distance between the mirror and the object to be welded. This controls the shape of the laser beam.

The present invention will be described in detail below with reference to the drawings.
FIG. 3 is an explanatory diagram showing an example in which the present invention is applied to manufacturing an electric resistance welded pipe. In the figure, 1 is a tubular body formed from a steel strip, and 2 is a wedge-shaped end thereof. 4 is a high frequency power source, and 4a and 4b are contacts. 5 is a laser oscillator, 6 and 7 are beam shape converters, 8 is an objective mirror, and 9 is a beam duct through which the laser beam LB passes. 10
10a is the nozzle portion at the tip of the anti-oxidation gas supply pipe, 2a is the upper end of the joint end, 2b is the lower end, and 2c is the center portion.

FIG. 4 is an explanatory diagram showing the action of the astigmatism mirror placed in the beam shape converter 7, and shows Ma,
Mb and Md are bending mirrors for changing the optical axis direction, and Mc is an astigmatism mirror (concave condensing mirror).

To perform welding according to the present invention, a steel strip is formed into a tubular shape using forming rolls (not shown) as in the case of FIG. It flows through the wedge-shaped ends 2, 2 of the tubular body 1 and heats these parts.

On the other hand, the laser beam from the laser oscillator 5
The LB is projected onto the abutting portion of the ends 2, 2 of the tubular body 1 via the beam shape converters 6 and 7, the objective mirror 8 and the beam duct 9. As a result, the wedge-shaped ends 2, 2 (hereinafter referred to as V-grooves) can be heat-welded together with the high-frequency current.

At this time, in the present invention, the laser beam
The shape of the laser beam LB can be controlled by changing the distance between the astigmatism mirror placed in the optical path of the LB and the irradiated area (V groove).
FIGS. 4 to 6 show the details. As shown in FIG.
Further, a bending mirror Mb is provided at a position opposite to the bending mirror Ma in the beam shape converter 7, an astigmatism mirror Mc is provided at the opposite position, and an exit side of the beam shape converter 7 is provided. A bending mirror Md is provided at the bent portion of the beam duct 9.

In addition, the beam shape converter 7 is connected to the beam duct 9
On the other hand, the astigmatism mirror Mc is configured to be movable within a distance range of lx ₁ - lx ₂ within the beam shape converter 7. .

In Fig. 4, P ₀ is the position of bending mirror Mb, P ₁ and P ₂ are the positions of astigmatism mirror Mc, P ₃ is the position of bending mirror Md, and l ₁ is the position of bending mirror Mb and P. ₁ is the distance at the horizontal position of the astigmatism mirror Mc, l ₂ is the distance at the same P ₂ point, l ₃ is the distance between the bending mirrors Mb and Md at the horizontal position, l ₄ is the bending mirror Md
and the irradiated site 2c.

Therefore, as shown in Fig. 4, an astigmatism mirror is used.
When the position of Mc is moved from point P ₁ to point P ₂ (that is, when it is moved a distance lx ₂ − lx ₁ ), the angle of incidence of astigmatism mirror Mc changes continuously from θ ₁ to θ ₂ . Accordingly, the amount of aberration can be changed.

That is, as shown in Fig. 5a, as the incident angle increases, the aberration increases, and the shape of the laser beam LB increases in ellipticity [θ ₁
→θ ₂ , (c)→(a)].

That is, if the aspect ratio Rab=a/b, then Rab(a)<Rab(b)<Rab(c). Note that Rab(a) shows the state of (a) in FIG. 5a when the incident angle θ is small.

Furthermore, by moving the beam shape converter 7 along the beam duct 9, the degree of focus alignment of the laser beam LB at the irradiated site can be adjusted.

That is, the focal length of the astigmatism mirror Mc is l ₀
Then, the distance lt from the irradiated site caused by the movement of the mirror Mc is lt=lx+l ₃ +l ₄ and can be set as ltmax>l ₀ >ltmin.

Therefore, in Fig. 5b, when the aspect ratio Ra is about 1, lt=l ₀ [(c) in Fig. 5b] When Rab>1, lt<l ₀ [(a), (b) in Fig. 5b] ] When Rab<1, lt>l ₀ [(d), (e) in Figure 5b].

Note that FIG. 6 shows an example of the amount of change in beam diameter near the focal point due to astigmatism. According to the results, when the focal length of the astigmatism mirror is 1 m and the workpiece is irradiated with a laser beam, the beam diameter near the focal point is: when θ = 3°, a = 5.5 mm, b = 5.8 mm When θ=20°, a=6.7mm, b=7.0mm, and the beam diameter 100mm behind the focal point is a=6.5mm, b=6.8mm when θ=3°. Ta.

As explained above, according to the present invention, the shape of the laser beam can be controlled by changing the distance between the astigmatism mirror and the object to be welded, so the shape of the object to be welded, the heating state, etc. Accordingly, the laser beam can be shaped to the optimum shape, making welding more reliable, and the effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an overview of the pipe-making process using the conventional high-frequency contact electric resistance welding method, and FIGS. 2a, 2b, and 2c are
An explanatory diagram showing the temperature distribution at the end of the tube according to the conventional method, FIG. 3 is an explanatory diagram showing an example of the method of the present invention, and FIG. 4 is an explanatory diagram showing the action of the astigmatism mirror in the method of the present invention. FIGS. 5 and 6 are explanatory diagrams showing how the laser beam diameter changes in the present invention. 1: tubular body, 2: end, 3: squeeze roll,
4: High frequency power supply, 4a, 4b: Contact, 5: Laser oscillator, 6, 7: Beam shape converter, 8: Objective mirror, LB: Laser beam, 9: Beam duct, 10: Gas supply pipe, 10a: Nozzle Department,
Ma, Mb, Md: bending mirror, Mc: astigmatism mirror.

Claims (1)

[Scope of Claims] 1. Electrical energy is supplied to a workpiece in the shape of a wedge in which mutually opposing welding surfaces asymptotically approach and the welding point is the apex, and the temperature at the apex of the wedge shape is reduced by the generated Joule heat. In the electric resistance welding method of heating and welding to a temperature; heating the wedge-shaped inner surface by projecting a laser beam from the open side of the wedge shape to the welding point, and arranging an astigmatism mirror in the optical path of the laser beam, An electric resistance welding method using an energy beam, characterized in that the shape of the laser beam is controlled by changing the distance between the mirror and the object to be welded.