JPS6284889A - Method and device for laser welding - Google Patents

Abstract

PURPOSE:To execute exactly welding and to improve the efficiency by providing a mirror system which is constituted of a convex mirror, and an integral mirror consisting of plural concave mirrors, on the optical path of a laser beam, and controlling the shape of the laser beam and its intensity distribution. CONSTITUTION:In the inside of a beam shape converter 7, an optical axis converting mirror Ma, a convex mirror Mb, and an integral mirror Mc are provided in order from a light source direction non the optical axis of the laser beam. The integral mirror Mc is constituted by juxtaposing in parallel plural concave mirrors in the lateral and longitudinal directions. A laser beam LB from a laser oscillator 5 is projected to the butting part of end parts 2, 2 of a tubular body 1 through a converter 7, a mirror 8 and beam duct 9. In this case the angle of each concave mirror of the integral mirror Mc is adjusted so that a focal light spot has an energy distribution. According to this method, the shape of the laser beam and its intensity distribution can be controlled, therefore, welding is executed exactly, and also its efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for welding objects using a laser beam as an energy source.

[Conventional technology]

Welding using a laser beam as an energy source
For example, "3rd Edition Steel Handbook Volume VI Secondary Processing 1 Surface Treatment,
It is applied to various uses as shown in "Heat Treatment, Welding" edited by Welding Society of Japan, pp. 446-481. The present applicant has also proposed a method of welding by first forming a welding part into a wedge shape and irradiating the wedge-shaped part with a laser beam (Japanese Patent Publication No. 6).
0-32553).

A method of combining the method with electric resistance welding (Japanese Patent Application Laid-open No. 1983-
No. 100985, Japanese Unexamined Patent Publication No. 191577/1983), etc., and filed a patent application. However, in these methods, the laser beam diameter, output, etc. are controlled.

Performing welding under optimal conditions has never been easier.

Further, the above-mentioned electric resistance welding method (hereinafter abbreviated as ERv) is one of the most commonly used welding techniques. For example, in the field of manufacturing welded steel pipes, a method for manufacturing pipes generally called electric resistance welded pipes is widely used as a welding method with high welding speed, that is, with high productivity.

Fig. 6 shows an example of pipe making using the conventional high frequency contact electric resistance welding method, in which a copper strip is formed into a tubular shape by a group of forming rolls (not shown), and then the steel pipe (hereinafter referred to as The ends 2, 2 of a tubular body (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. In addition, squeeze roll 3,3
A high frequency voltage is applied from the high frequency power supply 4 to the contacts 4a and 4b provided upstream of the contacts 4a and 4b (or 4b).
A high frequency current circuit is formed from to 4a) to heat the wedge-shaped ends 2, 2. As a result, the steel strip reaches the welding temperature at the apex of the wedge shape, and the squeeze roll 3
It is pressure welded and becomes a steel pipe. However, this ER
W 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, as shown in FIG. 7, 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 center portion 2c of the plate thickness, and as a result, the temperature distribution becomes as shown in Ha2. As a result, a low-temperature zone occurs in the center of the plate thickness, resulting in welding defects. Also,
When a high heat input state is created to eliminate cold welding, the temperature distribution becomes as shown by Hal in FIG. 7, and a penetrator defect occurs.

Therefore, the present inventors first applied a laser beam to the ERW, that is, introduced the laser beam horizontally into the wedge-shaped part of the tubular body as described above, and heated the part. (Japanese Unexamined Patent Publication No. 58-100985, No. 59)
-191577).

C Problems to be Solved by the Invention] The present invention makes welding more reliable by controlling the shape of the laser beam in welding using a laser beam as an energy source or in welding using a laser beam and other energy sources in combination. The purpose is to do so efficiently.

[Means for solving problems]

When welding by irradiating a workpiece with a laser beam, the present invention disposes a mirror system constituted by an integrating mirror consisting of a convex mirror and a plurality of concave mirrors in the optical path of the laser beam, and positions the mirror system. The shape and intensity distribution of the laser beam are controlled by controlling the distance between the welding point and the welding point, the distance between the convex mirror and the integrating mirror, and the focusing direction of each concave mirror that makes up the integrating mirror. In addition, in order to carry out this advantageously, a mirror system consisting of an optical axis changing mirror, a convex mirror, and an integrating mirror having a large number of concave mirrors is provided in the optical path connecting the laser light source and the welding point. The individual directions of the constituent concave mirrors are adjustable, and the distance between the convex mirror and the integrating mirror is movable.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the mirror system used in the present invention.
7 is a beam shape converter, and inside thereof, on the optical axis of the laser beam, in order from the light source direction, an optical axis converting mirror Ma;
A convex mirror Mb, an integrating mirror Mc, etc. are arranged.

There are m integrating mirrors Mc in the horizontal direction as shown in FIG.

It is constructed by arranging n concave mirrors in parallel in the vertical direction.

Note that each concave mirror has a curvature R.

Further, FIG. 3 is an explanatory diagram showing a manufacturing mode of an electric resistance welded pipe in which the present invention is carried out by using a combination of laser and electric resistance welding, in which 1 is a tubular body made of a copper strip formed into a tubular shape, and 2 is a wedge-shaped portion thereof. It is. 4 is a high frequency power supply, 4a.

4b is a contact. 5 is a laser oscillator, 7 is a beam shape converter, 8 is an objective mirror, and 9 is a beam duct through which the laser beam LB passes. 10 is an antioxidant gas supply pipe, 10a is a nozzle portion at its tip, 2a is an upper end of the joint end, and 2b is a lower end.

2c is the central portion. Note that 51 and 52 are oscillation mirrors.

The present invention irradiates a welding part with a laser beam LB from a laser oscillator 5 via a beam shape converter 7, and at this time controls the beam shape by adjusting a mirror system built into the beam shape converter 7. It is characterized by:

The actual situation will be explained by taking as an example a case where laser welding and electric resistance welding are used together to manufacture an electric resistance welded pipe as shown in FIG.

As in the case of FIG. 6 described above, a steel strip is formed into a tubular shape using forming rolls (not shown), and a laser beam LB is emitted from a laser oscillator 5, a beam shape converter 7, an objective mirror 8, and a beam duct 9. The light is projected onto the abutting portion of the ends 2, 2 of the tubular body 1 through the tube. on the other hand.

The high frequency current from the high frequency power supply 4 is transferred to the contacts 4a and 4b.
The liquid is poured into the wedge-shaped end of the tubular body l through the tube and heated. As a result, the wedge-shaped end 2.2 (referred to as the V-groove) can be heat-welded. At this time, in the present invention, a beam shape converter 7 is arranged in the optical path of the laser beam LB,
The converter includes an optical axis conversion mirror Ma, a convex mirror Mb, and a curvature R.
Since a mirror system consisting of an integrating mirror Mc with a large number of concave mirrors arranged in parallel is provided, the focal length and condensing diameter are determined by changing the respective distances between the convex mirror Mb, integrating mirror Mc, and the welding part. can do.

That is, the divergence angle of the laser beam LB from the laser oscillator 5 is O1, the focal length of the convex mirror Mb is fb, the focal length of the concave mirror Min constituting the integrating mirror Mc is fc, and the mirror opening distance between the convex mirror Mb and the integrating mirror Mc is When Dx is assumed, the condensing pressure 1illQx and the condensing diameter dx are as follows.

Q x = f c (Dx - f b) (Dx - f b
−f c) −”d x= A f b−f c(D
x −f b −f c)-' where A is a constant determined by the mode of the laser beam, the transmission distance, etc.

Therefore, as shown in FIG. 4a, the angle of each concave mirror Min constituting the multilayer iMc is adjusted to set the focal point P+on to a required energy density distribution. 4th b
The figure shows the laser energy density distribution in the setting state of FIG. 4a. As a result, the laser beam LB is focused at a focusing distance Qx of the integrating mirror Mc in the beam traveling direction X-axis.

Figure 5a shows each concave surface ja on the vertical plane at the focal position.
FIG. 5b shows the intensity distribution of Mmn light condensing state. Further, the condensing diameter dx is also determined by the above relationship.

Therefore, depending on the thickness t of the welded steel plate, the welding speed V, and the high-frequency power EPIP, the distance between the mirrors Dx and the focusing position fi of the concave mirror Mmn! Pn+n and laser power P. etc., and
Weldability can be improved by controlling the welded shape to be flat.

〔Example〕

The shape of the beam and its intensity distribution can be adjusted by adjusting the aperture ratio @Dx to set the focusing diameter dx and focusing position Pmn of the laser beam, and by adjusting the angle of each concave mirror Mmn that constitutes the integrating mirror Mc. was controlled in the desired manner. That is, by adjusting the angle of each concave mirror, the 8th a.
It was possible to obtain beams with intensity distributions as shown in Figures 8b and 8c.

For example, the aperture ratio is Dx of 1000 to 1500 nuu, f
b=730++u++, f c=1300m+m
, the unit focusing diameter is 2 to 6 mrnφ, and the energy density distribution can be set based on this. As a result, a smooth energy density distribution of 10 mrnφ (the energy density shown in Figure 8a) distribution).

On the other hand, for example, “La5er Focus” Nov,
1979 68 pages rA Convex Beam In
tegraIl, orJ discloses a means for controlling a laser beam using a convex mirror and a concave mirror as shown in FIG. 9, but with this method it is not possible to obtain the intensity distribution as in the present invention.

〔Effect of the invention〕

As described above, according to the present invention, a laser beam from a laser oscillator is matched to an intensity distribution.

Also, depending on the shape of the object to be welded, heating conditions, etc.
By controlling the distance of the opening of the integrating mirror and the focusing position of the concave mirror inside the integrating mirror, the shape and intensity distribution of the laser beam can be optimized, making it possible to perform welding more reliably, which is extremely effective. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a mirror system in a laser beam converter embodying the present invention, FIG. 2 is a front view showing the configuration of an integrating mirror in the mirror system used in the present invention, and FIG. It is a perspective view showing an embodiment. FIG. 4a is a sectional view showing the relationship between the optical axis and focal point of the integrating mirror used in the present invention, and FIG. 4b is a graph showing the laser energy density distribution according to the focal point distribution shown in FIG. 4a. Fifth
Fig. 5a is a front view showing the condensing state of the integrating mirror used in the present invention, and Fig. 5b is a graph showing the laser energy density distribution in the condensing state. FIG. 6 is a perspective view showing the manufacturing process of an electric resistance welded pipe by conventionally known high-frequency contact electric resistance welding, and FIG. 7 is a partial sectional view showing the temperature distribution in the pipe thickness direction in the manufacturing process. Figures 8a, 8b, and 8c are graphs showing examples of the shape and intensity distribution of the laser beam in the present invention, where the vertical axis represents the intensity of the laser beam, and the horizontal axis represents the amount of deviation from the optical axis (X). y-axis position). FIG. 9 is an explanatory diagram showing the relationship between the intensity adjustment mode of a laser beam and the energy density distribution according to the prior art. ■ = Tubular body 2: End portion 3 squeeze roll 4: High frequency power source 4a, 4b:
Contactor 5: Laser oscillator 7: Beam shape converter 8: Objective mirror LB: Laser beam 9
: Beam duct lO: Gas supply pipe 10a: Nozzle part Ma: Mirror for optical axis conversion Mb: Convex mirror Mc: Multilayer i Man: Concave mirror Pan: Focusing position of concave mirror Dx: Mirror opening distance between convex mirror and integrating mirror Qx= Integrating mirror focusing distance

Claims (4)

[Claims] (1) When performing welding by irradiating a workpiece with a laser beam, a mirror system consisting of a convex mirror and an integrating mirror consisting of a plurality of concave mirrors is placed in the optical path of the laser beam, and the position of the mirror system is A laser welding method characterized by controlling the shape and intensity distribution of a laser beam by controlling the distance to a point to be welded, the distance between a convex mirror and an integrating mirror, and the focusing direction of each concave mirror constituting the integrating mirror. (2) The laser welding method according to claim (1), wherein electrical energy is supplied to the workpiece, the welded area is heated by the generated Joule heat, and the welded area is irradiated with a laser beam. (3) The opposing welding surfaces are wedge-shaped with asymptotic approaches to each other with the welding point as the apex, and the wedge-shaped surface is irradiated with a laser beam. Laser welding method. (4) An integrating mirror that includes an optical axis changing mirror, a convex mirror, and a large number of concave mirrors in the optical path connecting the laser light source and the welding point;
What is claimed is: 1. A laser welding device comprising: a mirror system comprising: a mirror system; the individual directions of the concave mirrors constituting the integrating mirror can be adjusted; and the distance between the convex mirror and the integrating mirror can be moved.