JPH0369637B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of butt welding thin plate welded members using a laser beam.

[Prior Art] Laser beams can concentrate energy in a narrow range, so they can be suitably used for butt welding of thin plate members. However, when butt welding thin metal plates with a laser beam, it is necessary to increase the energy density of the laser beam as the welding speed increases, and the following phenomenon occurs during such high-speed welding. That is, bump-like projections called humping appear discontinuously along the weld bead surface. Also, depending on the welding conditions, the central portion of the welded portion may bulge continuously, resulting in an undercut on the back side. Furthermore, if the above condition becomes severe, pitting may occur. For example, this phenomenon occurs when welding a surface-treated steel plate with a thickness of 0.2 mm at a speed of 30 m/s.
It appears noticeably when welding at a temperature higher than min.

A technology to improve the above phenomenon was developed in JP-A-62-
61786. According to the method proposed in JP-A-62-61786, as shown in FIG. 7, the welding members are inclined at an angle α and abutted against each other with their upper ends opened by a distance d. The welding member is pressed by force in the directions shown by C and D, and the lower ends are in line contact, and the laser beam is irradiated from the direction of the upper part B to the abutting portion. The method proposed in the above-mentioned Japanese Patent Application Laid-open No. 62-61786 had the following problems.

That is, when abutting is performed at an opening angle of α, the contact between the end faces is linear, so misalignment is likely to occur, making it difficult to stably form the butt shape shown in FIG. 7. Furthermore, since the butt is performed at an opening angle of α, the shape of the butt surface after welding is not flat but has an irregular shape with bends.

Japanese Patent Application No. 62-61786 filed by the present applicant for a technique for improving the drawbacks of the above-mentioned Japanese Patent Application Laid-Open No. 62-61786
Suggested in 244365. According to the method proposed in Japanese Patent Application No. 62-244365, the abutting end faces of the welding members are processed to form a recess, and a laser beam is irradiated to perform welding with a gap existing in the abutting state. The gap may penetrate through the plate at the same depth in the thickness direction, or it may appear in a portion of the entire plate thickness.

[Problems to be Solved by the Invention] The method proposed in the above patent application No. 62-244365 is effective in preventing humping and drilling, but it is difficult for the laser beam to enter the inside of the abutting portion, and energy is lost. There was a problem that it was difficult to efficiently transmit the information to the welding parts. In other words, if the gap is the same depth and penetrates the entire plate thickness, a considerable portion of the laser beam energy will pass through the gap. In addition, if a gap appears in a part of the total plate thickness, the laser beam will be blocked by the welding member and will be difficult to directly reach the inside of the butt part. The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a butt welding method using a laser beam that is less likely to cause humping or pitting, has good energy transmission efficiency, and can obtain a flat joint. shall be.

[Means for Solving the Problems] In order to achieve the above object, in the laser beam butt welding method according to the present invention, thin plate welding members are butted and a laser beam is irradiated along the butted end surfaces. In the method of butt welding, a recess is provided on at least one of the butt end surfaces of the welding member, the gap on the upper surface side being larger than the gap on the lower surface side, and this recess penetrating through the entire plate thickness, The welding process is characterized in that the welding members are abutted straightly and a gap is created between the abutted end faces.

[Operation] The reason why the presence of a minute gap in the butt portion produces a favorable effect on welding is presumed to be as follows. In other words, it is known that in laser beam welding, a laser beam hole called a keyhole is formed, but during high-speed welding, the direction in which this keyhole extends is not straight downward, but the welding It is thought that the welded part is lifted up and the back side is notched, or a humping phenomenon occurs. This phenomenon is called bead-on-plate, and is more pronounced when a laser beam is simply irradiated onto a flat plate. For example, in the case of a bead-on plate made of a surface-treated steel plate with a thickness of 0.2 mm, the above phenomenon becomes noticeable when the laser beam movement speed is 20 m/min or more. The reason why phenomena such as lifting or humping of the weld occur more significantly with bead-on-plate than with butt welding is because the keyhole bends significantly in the downstream direction of welding.In other words, the gap between the butt and the keyhole It is thought that it has the effect of correcting the bending. It is considered that by proactively providing a minute gap in the abutting portion, it becomes possible to direct the keyhole downward. Furthermore, the metal vapor generated by the application of laser beam energy does not flow out from the gap and the vapor pressure increases, so that the molten metal is not lifted up. In any case, it has been found that due to the effect of the minute gap existing in the butt portion, welding can be performed with almost no lifting or humping of the welded portion. In this application, the gap between the abutting parts is deep at the top and shallow at the bottom, so the laser beam is directly irradiated onto the oblique end face of the welding member that forms the gap, and the energy is absorbed there, resulting in high energy transmission efficiency. , the welding speed can be increased compared to the method disclosed in Japanese Patent Application No. 62-244365 with the same output laser beam. Further, since the welded parts are butted straight, the resulting welded joint does not have an irregular shape as in the method of JP-A-62-61786. Furthermore, since the recess penetrates the entire thickness of the welding member and welding is performed with a gap created between the abutting end faces, the vapor pressure within the keyhole is reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention. In the figure, 1 and 2 are welded parts of thin metal plates. Welded part 1 is formed into a bay shape with both ends protruding and the middle part receding, and the upper retraction distance d ₁ is the lower retraction distance.
d greater than ₂ . and when the welded parts are butted together
d ₁ and d ₂ are the gaps above and below the abutting portion. Such processing of the welded member 1 can be achieved by slightly changing the shape of a cutting tool such as a shear or a punching press for cutting a thin plate material from a straight line. As shown in the figure, the welding members 1 and 2 which have been butted together are given relative movement with the laser beam B by a conventionally known feeding device, so that a welded part without humping or the like can be obtained.

A second embodiment of the invention is shown in FIG. In this embodiment, the gaps 3, 3, . . . in the abutting portions are formed intermittently in the welding direction, making it easier to control the size of the gaps compared to the first embodiment. The welding members 1 and 2 which are abutted in this manner are welded by the laser beam B in the same manner as in the first embodiment. As shown in the figure, the upper gap d ₁ of the gap is larger than the lower gap d ₂ . The value of d ₂ is preferably 3 μm or more and 25 μm or less, and more preferably 3 μm or more and 15 μm or less. If d ₂ is less than 3 μm, the laser light will not penetrate into the lower side of the butt.
If d ₂ exceeds 25 μm, the laser beam may penetrate through the gap, resulting in poor energy transfer efficiency, and the molten metal on both sides may become separated and not melt together. The length _l1 of the upper gap is greater than the length _l2 of the lower gap, but the difference is not particularly necessary and the lengths may be the same. Compared to the first embodiment, even if the width of the gap is increased somewhat, the total volume of the gap can be made smaller.
The thickness of the welded part is reduced or holes become less likely to occur. By increasing the width of the gap in this way, the effect of the gap increases and a more preferable welding condition can be obtained. Further, in order to maintain the effect of the gap over the entire welding area, the length of the abutting part between the gaps that are substantially in contact with each other is preferably equal to or less than twice the diameter of the laser beam, It is particularly preferable that the diameter be less than or equal to the diameter of the laser beam. As described above, since there is a contact portion for butt between the gaps, it is possible to easily butt at an accurate position. The shape of the end face of the welding member 1 shown in FIG. 2 can be obtained, for example, by machining with knurling 6 as shown in FIG. That is, the welding member 1 moves between the table 4 and the upper pressing roller 5 while being pushed by the pickers 7, 7, is pressed by the side rollers 8 and the knurling 6, and the irregularities on the surface of the knurling 6 are transferred. Since the knurling 6 is inclined and pressurized by the spring 9, the recess on the end face of the welding member 1 is deep at the top and shallow at the bottom, as shown in FIG. As another method of processing, it is also possible to shave off a portion of the abutting end faces by cutting such as milling or grinding to create irregularities on the end faces. Specific data of this example will be shown below. The end face of a thin steel plate with a thickness of 0.21 mm was provided with sawtooth-like irregularities using the apparatus shown in Fig. 3. The depth of the dent is approximately 0.04mm at the top and approximately 0.04mm at the bottom.
The pitch of the teeth was 0.10mm. The end face of the welded member 1 thus made is matched with the end face of the welded member 2, which has no unevenness, and the output
Welding speed 60 while irradiating 1.8kw laser beam
Butt welding was performed at m/min. A cross section of the obtained welded part is shown in FIG. As shown in the figure,
The molten solidified portion 11 in the welded portion is in a normal state with no defects such as lifting on the irradiated side or notches on the back side. Next, welding members 1 and 2
Butt welding was carried out under the same conditions as in this example except that the end face of the specimen was not roughened and the opening angle α was set to 17°. That is, butt welding was performed by the method disclosed in Japanese Patent Application Laid-Open No. 62-61786, and the cross section of the welded part obtained by this method is shown in FIG. The molten solidified portion 11 has a recess on its upper surface, and the welding members 1 and 2 are butted against each other in an inclined state. Furthermore, butt welding was performed by straightly butting the end surfaces of the welding members 1 and 2 without making any irregularities, and under the same conditions as in this example. That is, butt welding was performed by a conventional method, and the cross section of the welded part obtained by this method is shown in FIG. The upper part of the melt-solidified part 11 is raised and the lower part is notched.

Welding members used in the present invention include steel plates,
Surface-treated steel plates such as tin plate or teinfree tail, and thin metal plates such as aluminum and its alloys are used. It is also possible to apply the present invention to plastic materials. The plate thickness of the applied welding member is preferably about 0.15 to 0.4 mm, but the invention is not particularly limited thereto.

[Effects of the Invention] As explained above, according to the present invention, by providing a recess between the end faces of the welding member of the thin plate to be welded, the gap on the upper surface side is larger than the gap on the lower surface side. absorption efficiency can be improved.

Furthermore, since the welded members are butted straight, the shape of the joint after welding will not be distorted.

Furthermore, by welding with the recess penetrating the entire plate thickness and creating a gap between the butt end faces, the vapor pressure inside the keyhole is reduced, and even if the welding speed with the laser beam is increased, welding such as humping can occur. Defects are less likely to occur and good welding is possible.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show the first and second embodiments of the present invention.
FIG. 3 is a front view showing the processing state of a welded member used in the second embodiment of the present invention, and FIGS. 4 and 5 are welded parts as comparative examples. Fig. 6 is an enlarged cross-sectional view of the welded part obtained in the second embodiment of the present invention;
FIG. 7 is a sectional view showing a conventional technique. 1, 2... Welding member, 3... Gap, 4... Stand,
5... Presser roller, 6... Knurling, 7... Picker, 8... Side roller, 9... Spring, 11
...Melting and solidifying part.

Claims (1)

[Claims] 1. In a method of butt welding by butting thin plates of welding members and irradiating a laser beam along the butt end faces of the welding members, at least one of the butt end faces of the welding members has a lower surface between the upper surface side and the lower face. A laser beam characterized in that a recess is provided that is larger than the gap between the sides, and the recess penetrates the entire thickness of the plate, and the welding is performed in a state where the welding members are abutted straightly and a gap is created between the butt end faces. Butt welding method. 2. The butt welding method using a laser beam according to claim 1, wherein the recess is formed into a bay shape with both ends protruding and a middle part receding, and the both ends are pressed together between welding members. 3. The abutting method using a laser beam according to claim 1, wherein the recesses appear repeatedly in the longitudinal direction of the abutting end faces.