Laser welding method

Abstract

A laser welding method involves welding a first metal component (11) and a second metal component (12), and performing a first micro-oscillation process (ST1) along the butt joint (13) by irradiating a first laser beam with a first scanning pattern (P1) to form a first weld portion (21). Next, along the surface of the first weld portion (21) formed by the first micro-oscillation process (ST1), a second laser beam is irradiated with a second scanning pattern (P2), and a second micro-oscillation process (ST2) is performed over the first weld portion (21) to form a second weld portion (22) that is wider and shallower than the first weld portion (21). This forms a weld portion (20) that can prevent or suppress aging cracks.

Description

Technical Field

[0001] This invention relates to a laser welding method for joining difficult-to-weld materials by means of laser welding with micro-oscillation. Prior Technology

[0002] Laser welding, as is known, uses an optical system to irradiate a laser beam along the weld area and melt the base material in a short time, enabling welding with minimal heat-affected zones. As a laser welding method, to extend the weld bead width, it is known to use a scanning galvanometer to perform micro-oscillation machining, where the laser beam is irradiated in a circular motion along the weld area. This micro-oscillation machining allows for the welding of difficult-to-weld materials and dissimilar metals, which are challenging to laser weld.

[0003] Patent document 1 discloses a method for lap fillet welding of aluminum alloy plates using micro-oscillation processing. The welding method described therein alternates between periods of laser irradiation and periods of irradiation interruption, thereby preventing the formation of cracks in the lap fillet weld. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-078819 Summary of the Invention

[0005] [The problem that the invention aims to solve] In cases where micro-oscillating machining is used to join difficult-to-weld materials with laser welding, cracks may appear at the weld joint after a predetermined number of days, a problem known as aging cracks.

[0006] The purpose of this invention is to propose a laser welding method using micro-oscillation processing to join difficult-to-weld materials, etc., without producing welding cracks known as aging cracks. [Methods used to solve problems]

[0007] To solve the above-mentioned problems, the laser welding method of the present invention involves irradiating a laser beam along the mating line of the first metal component and the second metal component with a predetermined scanning pattern to weld the first and second metal components. Its characteristic is that: Along the aforementioned mating line, a first laser beam is irradiated with a first scanning pattern, and a first micro-oscillation process is performed along the aforementioned mating line to form a first weld portion of predetermined width and depth. Along the surface of the first weld portion formed by the first micro-oscillation process, a second laser beam is irradiated with a second scanning pattern, and a second micro-oscillation process is performed on the first weld portion to form a second weld portion that is wider and shallower than the first weld portion.

[0008] For example, by increasing the output of the first laser beam and decreasing the amplitude of the first scan pattern, a first weld portion is formed on the mating surface between metals in a narrow and deep area. Conversely, by decreasing the output of the second laser beam and increasing the amplitude of the second scan pattern, a second weld portion is formed on the mating surface in a wide area including the first weld portion and shallower than the first weld portion. [Invention Effects]

[0009] As mentioned above, the weld joint is formed by micro-oscillation processing across two metal mating surfaces, thereby confirming that aging cracks in the weld joint can be prevented or suppressed. Simple Explanation of the Diagram

[0010] [Figure 1] is an explanatory diagram showing a laser welding apparatus. [Figure 2] is a flowchart illustrating the laser welding method of the present invention. Implementation

[0011] The following describes an embodiment of the laser welding method of the present invention with reference to the illustrations.

[0012] First, the laser welding apparatus 1 used has a general configuration. As shown in Figure 1, the laser welding apparatus 1 is configured to irradiate the first metal member 11 and the second metal member 12 of the welding object with a laser beam L emitted from the laser beam generating unit 3 equipped with a laser light source 2 through the scanning mirrors 4a and 5a of a pair of scanning galvanometers 4 and 5 via the scanning mirrors 4a and 5a. The scanning mirrors 4a and 5a, which rotate around orthogonal axes, rotate synchronously to perform micro-oscillation processing by scanning the irradiation position of the laser beam L along the scanning pattern P of the scanning mirror 13.

[0013] Figure 2 is a schematic flowchart of the laser welding method in this example. In this example, the welding method involves setting the laser welding apparatus 1 so that the first metal component 11 and the second metal component 12 are joined together, and performing a first micro-oscillation process (ST1) along the mating line 13. Next, using the first micro-oscillation process, a second micro-oscillation process is performed along the first weld portion 21 formed by the mating line 13, overlapping the first weld portion 21 to form a second weld portion 22 (ST2).

[0014] In the first micro-oscillation processing (ST1), the laser beam L is a first output laser beam that irradiates along the mating line 13 with a first scan pattern, forming a first weld portion 21 of predetermined width and depth along the mating line 13. In this example, the first scan pattern P1 is a pattern drawn on the mating line 13 by moving the irradiation position of the first laser beam at a certain speed along the direction of the mating line 13 while drawing a circle with a first radius centered on it. Various patterns can be used for the first scan pattern P1.

[0015] Using the first micro-oscillation process, a first welding part 21 with a width of W1 and a depth of H1 is formed on the surface of the first and second metal components 11 and 12 along the butt joint 13, with the butt joint 13 as the center.

[0016] The second micro-oscillation process (ST2) involves irradiating a second laser beam (smaller than the first output) along the first weld section 21 using a second scan pattern P2 as the laser beam L, and overlapping it with the first weld section 21 along the mating line 13 to form a second weld section 22. For example, the scanning speed of the second laser beam is the same as the scanning speed of the first laser beam. In this example, the second scan pattern P2 is a pattern drawn on the mating line 13, depicting a circle with a second radius centered on the line while moving the irradiation position of the second laser beam at a certain speed along the direction of the mating line 13. The second radius is larger than the first radius. Various patterns can also be used for the second scan pattern P2.

[0017] By means of the second micro-oscillation processing, a second weld portion 22 is formed on the first and second metal components 11 and 12, which is wider than the width W1 on the surface of the component and shallower than the depth H1 in the direction from the surface of the component along the mating surface 15.

[0018] As described above, a narrow but deep first weld portion 21 is formed between the first and second metal components 11 and 12 using a high-output first laser beam. Overlapping with this first weld portion 21, a wide but shallow second weld portion 22 is formed using a low-output second laser beam. As described above, the weld portion 20 formed by micro-oscillation processing across two steps has been shown to prevent or suppress the generation of aging cracks in the weld portion.

[0019] To confirm the effectiveness of the laser welding method of the present invention, the inventors conducted welding experiments as follows. Bearing steel (SUJ2) was used as the first metal component 11, and mechanical construction alloy steel (SNCM439) was used as the second metal component 12. The output of the first laser beam in the first micro-oscillation processing was set to 800W, and the first radius (micro-oscillation radius) of the circle in the first scan pattern P1 was set to 0.2mm. The output of the second laser beam in the second micro-oscillation processing was set to 150W, and the second radius (micro-oscillation radius) of the circle in the second scan pattern P2 was set to 0.8mm. As a result, a first weld portion 21 with a depth H1 of approximately 2.3mm was formed along the mating surface 15, and a second weld portion 22 with a width W2 of approximately 2.3mm was formed by overlapping the first weld portion 21. Upon observation of this weld portion 20, no aging cracks were observed, confirming the formation of a good weld portion.

[0020] In addition to welding experiments on SUJ2 alloy steel and SNCM439 alloy steel for mechanical structures, the inventors have also conducted welding experiments on combinations of various metallic materials. For example, welding experiments on SCM415 or SNCM439 materials, and welding experiments on carbon steel (S45C) and spheroidal graphite cast iron (FCD). In welding of ferrometallic materials (carbon steel, alloy steel, cast iron), the output of the first and second laser beams was appropriately set to within a range of 1000W, and the micro-oscillation radius (amplitude) of the scanning pattern was set to within a range of 1.0mm, thereby confirming the formation of a good weld without aging cracks.

[0021] 1: Laser welding equipment 2: Laser light source 3: Laser beam generation section 4: Scanning galvanometer 4a: Scanning mirror 5: Scanning galvanometer 5a: Scanning mirror 11: First metal component 12: Second metal component 13: Connecting wire 15: Dating Surface 20: Welding Section 21: Welding Section 1 22: Second Welding Section L: Laser Beam P: Scanned image P1: First scan image P2: Second scan image W1, W2: Width H1, H2: Depth

Claims

1. A laser welding method comprising irradiating a laser beam along a mating line of a first metal component and a second metal component with a predetermined scanning pattern, wherein the first and second metal components are welded, characterized in that: a first laser beam is irradiated along the mating line with a first scanning pattern, and a first micro-oscillation process is performed along the mating line to form a first weld portion of predetermined width and depth; a second laser beam is irradiated along the surface of the first weld portion formed by the first micro-oscillation process with a second scanning pattern, and a second micro-oscillation process is performed over the first weld portion to form a second weld portion that is wider and shallower than the first weld portion; the scanning speed of the first laser beam in the first micro-oscillation process is the same as the scanning speed of the second laser beam in the second micro-oscillation process; and the output of the first laser beam in the first micro-oscillation process is greater than the output of the second laser beam in the second micro-oscillation process. The amplitude of the first scan pattern of the first laser beam in the first micro-oscillation process, which is orthogonal to the mating line, is smaller than the amplitude of the second scan pattern of the second laser beam in the second micro-oscillation process, which is orthogonal to the mating line. The first scan pattern is a pattern that moves along the mating line while depicting a circle with a first radius centered on a point on the mating line, representing the irradiation position of the first laser beam. The second scan pattern is a pattern that moves along the mating line while depicting a circle with a second radius larger than the first radius centered on a point on the mating line, representing the irradiation position of the second laser beam. The first metal component is made of SUJ2 material, and the second metal component is made of SNCM material. The output of the first laser beam in the first micro-oscillation process is 800W, and the first radius of the first scan pattern is 0.2mm. The output of the second laser beam in the second micro-oscillation process is 150W, and the second radius of the second scan pattern is 0.8mm.

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