JPH08257776A - Method for butt-welding steel plate by laser beam welding machine - Google Patents

Abstract

PURPOSE: To provide a method for butt-welding a steel plate by a laser beam welding machine. CONSTITUTION: In butt welding by converging a laser beam and irradiating the abutting part of steel plates 4 with the laser beam, the shape of the reinforcement of weld at the abutting part is detected by an image sensor 12, the dimension of such shape is determined by an arithmetic and control unit 14, and the stress concentration factor is computed at the toe of the reinforcement of weld so that the welding conditions are controlled with the factor brought close to 1.0, thereby enabling a uniform and satisfactory shape to be obtained for the reinforcement of weld over the entire welding line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a butt welding method for steel plates by a laser beam welding machine.

[0002]

2. Description of the Related Art Conventionally, in the welding method using a laser beam welding machine, the focal point of the laser beam is aligned with the gap between the abutted steel plates, the laser beam is penetrated from one side of the abutted steel plates, and the both sides of the steel plate are exposed. By controlling the shapes of the extra and back extras, these extras are smoothed,
Methods have been taken to ensure the strength of butt welded joints of steel plates.

An outline of the structure of the laser beam welding machine will be described with reference to FIG. 5. In the drawing, 1 is a laser beam, 2 is a condenser lens, 3 is a working head, 4 is a steel plate, 5 is a filler wire, and 6 is a wire. Is a filler wire feeder, 7
Is a filler wire feeding speed control panel, 8 is a wire tube,
Reference numeral 9 is a support for supporting the wire tube 8. The laser beam 1 is condensed by the condenser lens 2 and irradiated onto the welding line of the steel plate 4. At that time, the filler wire 5 is inserted into the molten pool in the gap between the welding lines, and the filler wire 5 is melted by the laser beam 1 to replenish the molten material.
As shown in FIG. 5, a front sill 10a or a back sill 10b is formed at the abutting portion of the steel plate 4.

At this time, the size of the gap g at the abutting portion of the steel plate 4 is measured in advance, and the feed rate of the filler wire 5 is set so that a substantially good weld surplus shape can be obtained along the entire welding line. Then, the filler wire 5 is fed from the drum 6a inside the filler wire feeder 6 through the wire tube 8 to the molten pool of the butt welded portion of the steel plate 4 according to the feeding speed. The feeding speed of the filler wire 5 is controlled by the filler wire feeding speed control board 7.

[0005]

By the way, as described above, the feeding speed of the filler wire 5 at the time of butt welding the steel plates by the laser beam welding machine is constant, but the gap g of the butted portions of the steel plates 4 is actually Change in the welding line direction of the steel plate 4, and in this case, the shape of the bulge due to the welding of the butt portion of the steel plate 4 may become non-uniform in the direction of the welding line. There was a problem that the strength was reduced.

As one of means for solving such a problem, there is a laser processing apparatus disclosed in, for example, Japanese Patent Laid-Open No. 61-212496. As shown in FIG. 7, this device connects an image signal from an image sensor 12 attached to a processing head 3 by a support 11 to a filler wire feed speed control board 7 via an image control device 13 so as to perform welding. The size of the gap of the welding line is measured in advance, and the feeding speed of the filler wire 5 is controlled according to the size of the gap.

However, in the apparatus disclosed in Japanese Patent Laid-Open No. 61-212496, the size of the butt gap on the front surface side of the steel plate 4 can be detected by the image sensor 12, but the butt gap in the plate thickness direction of the steel plate 4 can be detected. The size cannot be detected. Therefore, when the gap between the butted portions of the steel sheet 4 in the plate thickness direction varies in the welding line direction, even if the feeding speed of the filler wire 5 is controlled, the extra-height shape in the welding line direction can be improved. However, there is a problem that the strength of the welded joint varies due to the non-uniform excess shape, and sufficient strength cannot be obtained.

It is an object of the present invention to provide a butt welding method for steel plates by a laser beam welding machine, which solves the problems of the prior art as described above.

[0009]

SUMMARY OF THE INVENTION The present invention is a method of irradiating a butt portion of a steel plate which is a laser beam output from a laser beam oscillator and abutting the radiated laser beam to butt weld the butt portion together. And a step of calculating a surplus shape dimension from the surplus shape, calculating a stress concentration coefficient at the toe of the surplus, and calculating welding parameters such that the stress concentration coefficient is minimized. A butt welding method for a steel plate by a laser beam welding machine, which comprises a step of continuously controlling the extra-height shape of the butt portion based on the obtained welding parameters.

[0010]

[Operation] According to the present invention, the surplus shape dimension of butt welding is measured, and the stress concentration coefficient at the toe end of the extra weld is calculated from the surplus shape dimension so that the stress concentration coefficient approaches 1.0 as much as possible. Since various welding parameters are obtained and the bulge shape of the butt portion is continuously controlled based on this welding parameter, a uniform and favorable bulge shape can be obtained over the entire welding line of the butt weld portion.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention. In the figure, the same parts as those in the conventional example are designated by the same reference numerals and the description thereof will be omitted. As shown in the drawing,
The arithmetic and control unit 14 is connected between the image control unit 13 and the filler wire feed speed control panel 7, and the image control unit 13 inputs information on the extra-shape shape obtained from the image signal from the image sensor 12. In addition to calculating the stress concentration factor at the extra toe, the optimum filler wire feeding speed is calculated and output to the filler wire feeding speed control board 7 to continuously control the extra shape of the butted portion. Have.

The arithmetic control procedure in the arithmetic and control unit 14 will be described in detail below. Calculation of the stress concentration coefficient α of the excess toe portion: Now, as shown in FIG. 2, the excess shape shape dimension in the butt welding portion input from the image control device 13 has an excess width L (mm), a steel plate. The plate thickness of 4 is 2 t (mm), the height of the front sill 10a is h (mm),
The height from the top of the front sill 10a to the top of the back sill 10b is 2
If T (mm) and the radius of curvature of the extra toe are r (mm),
Calculate the stress concentration factor α at the extra toe by the following equation (1).

[0013]

[Equation 1]

Calculation and setting of optimum value of welding parameter β; FIG. 3 shows repeated bending strength (number of times) and excess toe of welded joint when repetitive force is applied to both sides of welded joint in the direction of arrow M. 3 shows the relationship with the stress concentration coefficient α of. As can be seen from this figure, the stress concentration factor α takes a value of 1.0 or more.The larger the stress concentration factor α, the greater the stress value acting on the extra toe and the repeated bending strength decreases. Become. Therefore, it is desirable that the stress concentration coefficient α of the extra toe portion is as close to 1.0 as possible, and particularly preferably 1.5 or less.

For that purpose, it is necessary to control the extra-filling shape dimension. For example, it is preferable to reduce the extra-filling height h and increase the radius of curvature r of the extra-filling toe. Therefore, in order to control the surplus shape dimension concretely, the welding parameter β defined by the following equation (2) is set to the optimum value so that the stress concentration coefficient α of the surplus toe is as close to 1.0 as possible. Must be set to.

Β = v _W / (v _T · G _SV ) (2) Where, v _W : Filler wire feeding speed (mpm), v _T ; Welding speed (mpm), G _SV ; It is the root gap of the steel plate butted part. An example of the relationship between the welding parameter β and the stress concentration coefficient α obtained by the experiment is shown in FIG. As can be seen from this figure, when the welding parameter β is around 8.0, the stress concentration factor α can approach 1.0.

Calculation of the optimum value of the filler wire feeding speed v _W : By setting the welding speed v _T and the root gap G _SV under constant conditions, the filler wire feeding speed v _W of the filler wire feeding speed v _W for making the stress concentration factor α close to 1.0 is set. Find the optimum value. Control of the filler wire feeding speed v _W ; the optimum value of the filler wire feeding speed v _W obtained in the step is output to the filler wire feeding speed control board 7 to
The feeding speed of the filler wire 5 from the filler wire feeding device 6 is controlled so as to optimize _W.

[0018]

As described above, according to the present invention,
Measure the surplus shape dimension of butt welding, calculate the stress concentration factor at the toe end of the extra weld from the surplus shape dimension, and find the optimum welding parameter values so that this stress concentration factor approaches 1.0 as much as possible. Since the bulge shape of the butt joint is controlled continuously based on the welding parameters, it is possible to obtain a uniform and good bulge shape over the entire weld line of the butt weld, which has uniform strength. Welded joints can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram of a surplus shape.

FIG. 3 is a characteristic diagram showing a relationship between a stress concentration factor and repeated bending strength.

FIG. 4 is a characteristic diagram showing the relationship between welding parameters and stress concentration factors.

FIG. 5 is a schematic diagram showing a configuration of a conventional example.

FIG. 6 is a cross-sectional view showing a surplus shape.

FIG. 7 is a schematic diagram showing the configuration of another conventional example.

[Explanation of symbols]

 1 Laser Beam 2 Condensing Lens 3 Processing Head 4 Steel Plate 5 Filler Wire 6 Filler Wire Feeding Device 7 Filler Wire Feeding Speed Control Panel 10a Front Extent 10b Back Extent 11 Support 12 Image Sensor 13 Image Control Device 14 Arithmetic Control Device

Claims (1)

[Claims] 1. A method of irradiating a butt portion of a steel plate, which collects and abuts a laser beam output from a laser beam oscillator, to butt-weld the butt portion, the step of detecting an extra-height shape of the butt portion, The process of calculating the extra-filling shape dimension from the fill-up shape, calculating the stress concentration factor of the extra toe and calculating the welding parameters that minimize the stress concentration factor, and the matching based on the obtained welding parameters. A butt welding method for a steel sheet by a laser beam welding machine, which comprises a step of continuously controlling the extra-height shape of the portion.