JP5484147B2 - Pulse laser welding method of aluminum alloy material - Google Patents

Description

  The present invention relates to a pulse laser welding method for an aluminum alloy material in which a welding material made of an aluminum alloy is welded by irradiating a pulse laser beam.

  Conventionally, secondary batteries such as lithium-ion batteries have been used as power sources for mobile phones, electric vehicles, hybrid cars, and the like. These secondary batteries are lightweight, have excellent heat dissipation properties, and have high strength. As a battery case material or the like, an aluminum alloy material such as JIS A 3004 is used.

  In the production of the secondary battery, the aluminum alloy plate material is formed by, for example, deep drawing to form a secondary battery case material, and then the case material is filled with contents such as an electrode and an electrolytic solution, An aluminum alloy material serving as a lid is placed on the case material, and the lid material and the case material are joined by welding.

  Pulse laser welding is a welding method with excellent productivity, and is suitable for joining such members as a secondary battery. In particular, when the workpiece is thin, pulse laser welding is a suitable welding method.

  In pulse laser welding of an aluminum alloy material, various studies have been conducted in order to improve the quality of the weld joint. FIG. 7 is a diagram showing a waveform of a pulsed laser beam used for conventional pulsed laser welding. As shown in FIG. 7, in conventional pulse laser welding, a pulse laser beam having a rectangular wave (FIG. 7A) or triangular wave (FIG. 7B) waveform is used. However, there may be cases where organic matter such as an electrolytic solution adheres to the secondary battery case. When the waveform of the pulse laser beam is a conventional rectangular wave or triangular wave, the molten aluminum alloy and the organic matter are heated. In some cases, the reaction may occur, the organic substance may evaporate and a hole is formed in the welded portion, and the joint strength of the welded joint may decrease. In order to solve this problem, Patent Document 1 discloses an organic component on a surface of a material to be welded by a pulsed laser beam of a rectangular wave in a method of laser welding an aluminum alloy material used for a secondary battery or the like. Discloses a technique for joining materials to be welded by irradiating a triangular wave pulse laser beam having a pulse peak output larger than that of a rectangular wave after evaporating organic components under a condition that does not enter the molten pool.

  Patent Document 2 discloses that aluminum alloy plates used in aircraft, automobiles, electrical and electronic equipment parts, etc., are devised in terms of the composition of the aluminum alloy material, so that the aluminum alloy plates can be aluminum even when they are welded by pulse laser welding. A technique for increasing the strength of an alloy plate and preventing cracking of a welded portion is disclosed.

Japanese Patent Laid-Open No. 11-245066 JP 2006-104580 A

  However, the above-described conventional technology has the following problems. Recently, the demand for mobile phones, hybrid cars, and the like is increasing, and therefore, it is desired to improve the productivity in manufacturing parts made of these aluminum alloy materials. In the manufacture of such a component, in order to improve productivity, it is necessary to increase the welding heat input of, for example, pulsed laser light. In this case, when the pulsed laser light applied to the material to be welded is a rectangular wave or a triangular wave, there is a problem that a weld crack occurs in the welded portion. On the other hand, aluminum alloy materials are desired to be reduced in weight, and in order to reduce the thickness, it is necessary to contain a large amount of components such as Mg, Cu, Fe and Si, thereby increasing the pressure resistance strength of the aluminum alloy material. . However, in the case of containing such an alloy component that increases the pressure strength, there is a problem that the cracking sensitivity of the aluminum alloy material is increased and weld cracking is likely to occur during pulse laser welding. In particular, when an aluminum alloy material containing a large amount of Mg, such as an aluminum alloy such as JIS A 3004, is used, the occurrence of weld cracks becomes significant.

  The technique of patent document 1 is for solving the problem in the case where an organic substance such as an electrolytic solution adheres to a member to be welded, and combines pulsed laser light of a rectangular wave and a triangular wave. The pulse laser beam for joining the materials is substantially a triangular wave. Therefore, when the welding heat input of the pulse laser beam is increased to improve the productivity, cracks occur in the welded portion as in the case of using the conventional rectangular or triangular pulse laser beam. Moreover, even when the aluminum alloy material contains a large amount of components such as Mg for reducing the thickness, the aluminum alloy material is more susceptible to cracking and weld cracking occurs.

  Moreover, although the composition which suppresses the crack of a welding part is disclosed by patent document 2 at the time of the pulse laser welding of aluminum alloy material, the aluminum alloy material of patent document 2 depends on the welding conditions at the time of pulse laser welding. It is impossible to prevent cracks from occurring in the weld. In particular, when the welding heat input is increased in order to improve productivity, cracks in the welded portion are remarkably generated.

  The present invention has been made in view of such problems, and even when pulsed laser welding is performed on a high-strength aluminum alloy material that is used after being thinned, the occurrence of weld cracks is prevented, and the productivity is high. An object is to provide a pulse laser welding method of an aluminum alloy material.

In the pulse laser welding method of the aluminum alloy material according to the present invention, Mn is 0.1 to 1.8% by mass, Mg is 0.4 to 1.2% by mass, Cu is 0.1 to 3.0% by mass, A pair of materials to be welded made of an aluminum alloy containing less than 0.3% by mass of Si and less than 1.0% by mass of Fe, with the balance being composed of aluminum and inevitable impurities are irradiated with pulsed laser light. In the pulse laser welding method of the aluminum alloy material to be welded, the pulse laser beam includes a first pulse laser beam having a rectangular waveform, and a second pulse laser beam having a rectangular waveform following the first pulse laser beam, The peak output value of the first pulsed laser light is P ₁ , the irradiation time of the first pulsed laser light on the material to be welded is t ₁ , and the second pulsed laser light. Peak out When the force value is P ₂ and the irradiation time of the _second pulse laser beam on the workpiece is t ₂ , the _second pulse laser beam has a peak output value with respect to the peak output value of the first pulse laser beam. The ratio P ₂ / P _{1 of} peak output values is 0.3 to 0.6, and the ratio t ₂ / t ₁ of the irradiation time of the second pulse laser light to the irradiation time of the first pulse laser light is 1.5 or der is, the central portion of the top of the weld the first layer, wherein the first layer of the weld is formed weld the second layer crystal grain size and crystal orientation that Do different, weld weld the first layer to the periphery of the welded portion of the second layer in a plan view there is obtained, characterized in Rukoto.

  In the above-described pulse laser welding method for an aluminum alloy material, the aluminum alloy preferably further contains 0.05 to 0.25 mass% of Zr.

In the above-described pulse laser welding method for an aluminum alloy material, the P ₁ is, for example, 1.5 to 5 kW, and the t ₁ is, for example, 0.1 to 5 msec.

  In the pulse laser welding method for aluminum alloy material of the present invention, the composition of the aluminum alloy material constituting the material to be welded is properly defined, and the pulse laser light irradiated to the material to be welded is the first and second pulses. A two-stage waveform is formed by continuous pulses made of laser light, and for the first and second pulse laser lights, the ratio of the peak output value and the ratio of the irradiation time to the material to be welded are defined within an appropriate range. As a result, even when the material to be welded is used with a reduced thickness, it has a high pressure strength and can be produced without causing cracks in the welded portion by controlling the output of the pulse laser beam and the irradiation time. The material to be welded can be welded with good performance.

It is a figure which shows the waveform of the pulse laser beam of this invention. It is a figure which shows the waveform of the pulse laser beam in the case of performing line welding by pulse laser welding as an example. It is a schematic diagram which shows a spot weld part and a line weld part. It is a figure which shows the waveform of a pulse laser beam as an example. It is the figure which observed macroscopically the welding part formed by the welding method of this invention. It is a macro observation figure which shows the case where a welding part is formed in one layer and a crack arises. It is a figure which shows the waveform of the pulse laser beam in the conventional pulse laser welding.

  Hereinafter, a pulse laser welding method for an aluminum alloy material according to an embodiment of the present invention will be described. First, the structure of the workpieces to be welded by the pulse laser welding method of the present invention will be described. The welded material in the present invention is made of an aluminum alloy, Mn is 0.1 to 1.8% by mass, Mg is 0.4 to 1.2% by mass, Cu is 0.1 to 3.0% by mass, Si Is less than 0.3% by mass and Fe is less than 1.0% by mass with the balance being composed of aluminum and inevitable impurities.

  As mentioned above, when thinning the aluminum alloy material as a material for the purpose of reducing the weight of the battery case, etc., the strength of the aluminum alloy material is increased, and the strength as a structural member such as a secondary battery, particularly the pressure resistance strength. Need to be increased. In order to increase the pressure strength of the aluminum alloy material, generally, Mg, Cu, Fe, Si, or the like is added as an alloy component of the aluminum alloy material. However, when the aluminum alloy material contains these components, the susceptibility of the aluminum alloy material to cracking increases, and when the aluminum alloy material is subjected to pulse laser welding, a weld crack occurs in the weld.

  In order to prevent weld cracking during pulse laser welding of an aluminum alloy material, the inventors of the present application examined various amounts of components added to increase the pressure strength of the thinned aluminum alloy material while performing pulse laser welding. We investigated various welding conditions. In order to prevent the occurrence of weld cracking even when the welding heat input is high during pulse laser welding while increasing the pressure resistance strength of the aluminum alloy material, Mg is added to the aluminum alloy constituting the material to be welded in an amount of 0.4 to 0.4. It has been found that 1.2 mass%, Cu 0.1 to 3.0 mass%, Si less than 0.3 mass%, and Fe less than 1.0 mass% may be contained.

  In the present invention, a pair of materials to be welded made of an aluminum alloy having the above composition is subjected to pulse laser welding. For example, one of a pair of materials to be welded is placed with the other material to be welded superimposed, and the overlapped portion is subjected to pulse laser welding. Alternatively, a pair of materials to be welded are butted together, and the butted portion is pulsed laser welded. In the present invention, in addition to lap welding and butt welding, aluminum alloy materials having the above composition are used in various welding methods in which a pair of materials to be welded, such as fillet welding and worship welding.

  Hereinafter, the reason for limiting the numerical values of the composition of the aluminum alloy constituting the material to be welded according to the present invention will be described.

“Mn: 0.1 to 1.8% by mass”
Mn has the effect | action which solid-dissolves in the mother phase of an aluminum alloy, raises the intensity | strength of an aluminum alloy, and improves the pressure strength of an aluminum alloy material. When the content of Mn in the aluminum alloy is less than 0.1% by mass, the effect of increasing the pressure strength of the aluminum alloy material cannot be sufficiently obtained. On the other hand, when the content of Mn exceeds 1.8 mass%, the cracking sensitivity of the aluminum alloy becomes high, and when the aluminum alloy material is subjected to pulse laser welding, a weld crack is likely to occur. Therefore, the aluminum alloy constituting the material to be welded of the present invention contains 0.1 to 1.8% by mass of Mn.

“Mg: 0.4 to 1.2% by mass”
Similarly to Mn, Mg also has the effect of increasing the strength of the aluminum alloy by being dissolved in the matrix of the aluminum alloy and improving the pressure resistance of the aluminum alloy material. If the Mg content in the aluminum alloy is less than 0.4% by mass, the effect of increasing the pressure strength of the aluminum alloy material cannot be sufficiently obtained. If the Mg content exceeds 1.2% by mass, aluminum The cracking susceptibility of the alloy increases and weld cracking is likely to occur. Therefore, the aluminum alloy constituting the material to be welded of the present invention contains 0.4 to 1.2% by mass of Mn.

“Cu: 0.1 to 3.0 mass%”
Cu, like Mn and Mg, has the effect of being dissolved in the matrix of the aluminum alloy to increase the strength of the aluminum alloy and to improve the pressure resistance of the aluminum alloy material. And if the Cu content in the aluminum alloy is less than 0.1% by mass, the effect of increasing the pressure strength of the aluminum alloy material cannot be sufficiently obtained, and the Cu content is 3.0% by mass. If it exceeds, the cracking susceptibility of the aluminum alloy is increased, and weld cracking is likely to occur. Therefore, the aluminum alloy constituting the material to be welded of the present invention contains 0.1 to 3.0% by mass of Cu. Therefore, in the aluminum alloy of the present invention, the pressure resistance strength of the aluminum alloy material is effectively increased by containing more Cu than other alloy components that increase the pressure strength.

“Si: Less than 0.3% by mass”
Si, like Mn, Mg and Cu, contributes to the improvement of the pressure strength of the aluminum alloy material. However, Si tends to increase the weld cracking susceptibility of the aluminum alloy, and if it is contained in a large amount exceeding 0.3% by mass, weld cracking is likely to occur. Therefore, in the present invention, the aluminum alloy contains less than 0.3% by mass of Si.

“Fe: less than 1.0 mass%”
Fe also improves the pressure resistance of the aluminum alloy material, similar to the above alloy components, but it is easy to increase the weld cracking susceptibility of the aluminum alloy material, similar to Si. If Fe is contained in an aluminum alloy in a large amount exceeding 1.0 mass%, welding cracks are likely to occur, and welding workability during pulse laser welding is reduced. Therefore, in the present invention, the aluminum alloy contains less than 1.0% by mass of Si.

“Zr: 0.05 to less than 0.25% by mass”
Zr, when added, has the effect of refining the structure of the aluminum alloy, and has the effect of suppressing weld cracks in the aluminum alloy. Further, when Zr is added, the formability of the aluminum alloy material is improved. If the content of Zr in the aluminum alloy is less than 0.05% by mass, the effect of improving the strength due to the formation of the microstructure and the effect of improving the formability of the aluminum alloy material cannot be sufficiently obtained. When the content exceeds 0.25% by mass, a giant crystallized product of Zr is formed during melting / casting, which adversely affects the rolling and drawing of the plate. Therefore, in the present invention, the aluminum alloy preferably contains 0.05 to 0.25% by mass of Zr.

  In the present invention, the aluminum alloy may contain, for example, Cr as less than 0.05% by mass, Ti as less than 0.5% by mass, and B as less than 0.005% by mass as inevitable impurities. In general, when an aluminum alloy contains Mn, unavoidable impurities in the aluminum alloy increase, but in the present invention, for example, a large amount of Ti and B are included by defining the content of the unavoidable impurity components. The occurrence of bead irregularities caused by the above can be suppressed. It is preferable to adjust the content of these impurity components as appropriate in accordance with the dimensions and required strength of the structure.

  Next, the configuration of the pulse laser beam in the pulse laser welding method of the present invention will be described. In the conventional pulse laser welding, a rectangular wave and a triangular wave pulse laser beam as shown in FIG. 7 or a rectangular wave and a triangular wave as in Patent Document 1 are combined, and a peak output value of the rectangular wave pulse laser beam is obtained. The peak output value of triangular pulse laser light has been made smaller. However, in these prior arts, in recent aluminum alloy materials that have been thinned and used, the cracking susceptibility is increased, and the occurrence of weld cracks cannot be prevented.

  The inventors of the present application have studied various welding conditions for preventing the occurrence of weld cracks during pulsed laser welding while maintaining high pressure resistance when the aluminum alloy material is used after being thinned. Then, the pulse laser beam is constituted by a two-stage waveform composed of a continuous pulse of a first pulse laser beam and a second pulse laser beam having a rectangular waveform, and the peak output value of the first pulse laser beam is set to the second pulse. It has been found that if the laser beam is larger than the peak output value, the molten pool is solidified in two stages and the weld is formed in two layers. That is, the pulse laser beam is constituted by a continuous two-stage waveform of a rectangular waveform, and the peak output value is controlled as described above, so that the first layer weld is solidified when the first layer weld is formed. Since the molten metal is replenished from the molten pool, for example, the molten metal is interpolated to the defective portion such as the shrinkage nest of the welded portion. It has been found that welds with different crystal grain sizes and crystal orientations are formed, and further that the welds of the first layer absorb the shrinkage force acting on the welds of the second layer, thus preventing the occurrence of weld cracks. .

  Further, the inventors of the present application allow the solidification of the molten pool to proceed at an appropriate speed by setting the irradiation time of the pulsed laser light to an appropriate range, thereby preventing the welded material from being generated without generating a weld crack. It was found that welding was possible. As a result, even when the aluminum alloy material contains a component that increases the pressure strength, it has been found that a sound weld can be obtained by pulse laser welding without causing weld cracks in the weld. Invented.

  In the present invention, as shown in FIG. 1, the pulse laser beam is configured in two stages composed of continuous pulses of a first pulse laser beam 1 and a second pulse laser beam 2 each having a rectangular waveform. Note that the pulse laser beam shown in FIG. 1 is a pulse waveform when a pair of materials to be welded are welded at one point during pulse laser welding. That is, as shown in FIG. 3, a pair of materials to be welded 3 are welded to each other in a dot shape by irradiation of one pulse laser beam, a welded portion 4 is formed, and the materials to be welded 3 are joined together. The In the case of performing line welding by pulse laser welding, as shown in FIG. 2, the pulse laser beam is irradiated to the workpiece 3 a plurality of times. As a result, the welded materials are welded to each other with a single pulse laser beam, and the irradiation position of the pulse laser beam is moved so as to slightly wrap around the already welded portion, and then another pulse laser beam. As a result, the materials to be welded 3 are newly welded in the form of dots. By repeating this a plurality of times, the welded portion 5 is formed in a linear shape by the plurality of spot-like welded portions, and the workpieces 3 are joined to each other.

In the present invention, the pulse laser beam is configured in two stages consisting of continuous pulses of the first pulse laser beam 1 and the second pulse laser beam 2, and the peak output value P ₁ of the _first pulse laser beam is set to the second level. By making it larger than the peak output value P ₂ of the pulse laser beam 2, a welded portion having a two-layer structure is formed, and the workpieces 3 are joined together. That is, a molten pool is formed on the workpiece 3 by irradiation with the first pulse laser beam 1 having a large peak output value, and the molten pool is solidified from the peripheral region by irradiation with the second pulse laser beam 2. As a result, the first-layer weld is formed. In the present invention, the second pulsed laser beam 2 is irradiated to the molten pool even when the molten pool is solidified. As a result, the molten pool is rapidly solidified to prevent welding cracks due to the occurrence of welding defects such as shrinkage. Thereafter, the portion irradiated with the second pulse laser beam 2 is solidified, and a second layer weld is formed at the center of the molten pool, for example.

In the present invention, irradiating the first pulsed laser beam pulsed laser light so becomes longer irradiation time t ₂ of the second pulse laser beam from the irradiation time t ₁ of the. Thereby, a sufficiently long period of solidification of the first-layer welded portion is ensured, and then the second-layer welded portion is formed by stopping the irradiation of the second pulse laser beam 2. By configuring the irradiation time of the first and second pulse laser beams in this way, the molten metal is interpolated in the defect portion such as the shrinkage of the welded portion that solidifies in forming the welded portion of the first layer. Therefore, it is possible to prevent the occurrence of weld cracks due to the occurrence of weld defects such as shrinkage.

In the present invention, the peak output value of the pulse laser beam and the irradiation time of the pulse laser beam at the time of pulse laser welding are handled as important parameters for determining the formation state of the molten pool and determining the quality of the weld. That is, in the present invention, the ratio P ₂ / P ₁ of the peak output value P ₂ of the second pulse laser beam to the peak output value P ₁ of the first pulse laser beam is 0.3 to 0.6. . When the ratio P ₂ / P ₁ is less than 0.3, the effect obtained by configuring the pulse laser beam with continuous two-stage pulses is reduced, and the weld is formed in one layer as in the conventional case. Therefore, it becomes easy to generate | occur | produce the crack of a welding part. On the other hand, even when the ratio P ₂ / P ₁ exceeds 0.6, the high-power second pulse laser beam 2 is irradiated during solidification of the weld of the first layer. The formation of the welded portion does not proceed smoothly, and the welded portion is constituted by one layer, so that a weld crack is likely to occur.

The peak output value P1 of the _first pulse laser beam is preferably 1.5 to 5 kW. When the peak output value P1 of the _first pulse laser beam is less than 1.5 kW, the overall output of the pulse laser beam irradiated to the material to be welded 3 is reduced, and the amount of heat input to the welded portion is reduced. It becomes difficult to form a molten pool with a sufficient size, and the welding strength slightly decreases. On the other hand, when the peak output value P1 of the _first pulse laser beam exceeds 5 kW, the output value of the pulse laser beam becomes excessive, and the solidification of the welded portion is difficult to proceed smoothly even when the solidification time is lengthened. .

In the present invention, the ratio t ₂ / t ₁ of the irradiation time t ₂ of the second pulse laser light to the irradiation time t ₁ of the first pulse laser light is 1.5 or more. When the ratio t ₂ / t ₁ is less than 1.5, it is difficult to sufficiently obtain the solidification time of the first layer welded portion and form the welded portion in two layers. Therefore, it becomes easy to generate a weld crack at the time of forming a welded portion.

The irradiation time t ₁ of the first pulse laser beam is preferably 0.1 to 5 msec. When the irradiation time t1 of the _first pulse laser beam is less than 0.1 msec, it is difficult to obtain a sufficient solidification time when forming the welded portion, and it is difficult to form a sound welded portion. On the other hand, if the irradiation time t1 of the _first pulse laser beam exceeds 5 msec, the irradiation time of the pulse laser beam becomes longer and the welding time becomes longer. For example, the productivity of an aluminum alloy material for a secondary battery or the like is increased. It tends to decrease.

  Next, the operation | movement of the pulse laser welding method of the aluminum alloy material of this invention is demonstrated. In the present invention, as shown in FIG. 2, a pair of materials to be welded 3 made of an aluminum alloy are arranged, for example, so as to overlap each other, and the overlapped portion is irradiated with a pulse laser beam so that the materials to be welded 3 are aligned. Join by pulse laser welding. In addition, in the case of butt welding a pair of materials to be welded 3, the materials to be welded 3 are butted and arranged, and the butt portion is irradiated with a pulse laser beam. Also in other welding methods, a pair of materials to be welded 3 are appropriately arranged in accordance with each welding method, pulsed laser light is irradiated, and the materials to be welded 3 are joined by pulse laser welding. When the pulse laser beam is irradiated to one point, a spot-like welded portion 4 is formed. When the pulse laser beam is irradiated a plurality of times while slightly wrapping the irradiation position, a plurality of spot welds are formed. A linear welded portion 5 is formed by the portion.

  In the present invention, the aluminum alloy constituting the material to be welded 3 has Mn of 0.1 to 1.8 mass%, Mg of 0.4 to 1.2 mass%, and Cu of 0.1 to 3.0 mass%. %, Less than 0.3% by mass of Si, and less than 1.0% by mass of Fe, thereby increasing the pressure strength of the aluminum alloy material.

The workpiece 3 is subjected to pulsed laser welding by irradiating the workpiece 3 with pulsed laser light. In the present invention, as shown in FIG. 1, the pulse laser beam irradiated to one point is configured in two stages composed of continuous pulses of a first pulse laser beam 1 and a second pulse laser beam 2 each having a rectangular waveform. Has been. First, the first pulsed laser beam 1 having a rectangular waveform is irradiated onto the workpiece 3. At this time, the peak output value P ₁ of the first pulse laser beam 1 is set to, for example, 1.5 to 5 kW, and the irradiation time t _{1 is set} to, for example, 0.1 to 5 msec. Thereby, a circular molten pool is formed in the part to which the pulse laser beam of the to-be-welded material 3 was irradiated, for example in planar view.

After t ₁ elapses, the second pulse laser beam 2 is continuously applied to the workpiece 3. The peak output value P2 of the _second pulse laser beam ₂ is 0.3 to 0.6 times the peak output value P1 of the _first pulse laser beam. By making the peak output value of the second pulse laser beam 2 smaller than that of the first pulse laser beam, the molten pool is gradually solidified, for example, from the peripheral edge thereof. The irradiation time of the second pulse laser beam 2 is 1.5 times or longer than the irradiation time of the second pulse laser beam 1. Thereby, the solidification of the molten pool proceeds while the second pulse laser beam 2 is irradiated, and the first layer weld is formed in an annular shape in plan view, for example. At this time, a weld defect such as a shrinkage nest may be formed in a solidified portion in the first layer welded portion, and the molten metal is interpolated from the molten pool as needed to this defective portion. . Therefore, no weld cracking due to a weld defect such as a sinkhole occurs in the first layer weld. Thereafter, the irradiation with the second pulse laser beam 2 is stopped.

  By stopping the irradiation of the second pulse laser beam 2, the molten pool remaining in the center of the annular first layer welded portion is gradually cooled, for example, from the periphery thereof, and the second layer welded portion. Will be formed. Thereby, the spot-like welded part 4 as shown in FIG. 3 is formed. In this way, by forming the welded part in two layers, the welded part having the crystal grain size and crystal orientation different from the welded part of the first layer is formed in the second layered welded part. This absorbs the shrinkage force acting on the second layer weld. Accordingly, no weld cracks are generated in the welded portion even when the second layer welded portion is formed.

  As shown in FIG. 3, in the case where the workpiece 3 is welded linearly to form the linear welded portion 5, the irradiation of the pulse laser beam is performed after the irradiation of the second pulsed laser beam 2 is stopped. The position is moved so as to slightly wrap around the welded portion, and the first and second pulse laser beams 1 and 2 are irradiated again. As a result, the workpiece 3 is irradiated with the intermittent pulse laser beam as shown in FIG. 2 while moving the irradiation position of the pulse laser beam on the workpiece 3. Thereby, the welding part 5 is formed in the to-be-welded material 3 in the shape of a line by a some point welding part. Thus, even when the workpiece 3 is welded linearly, weld cracks do not occur in the one-by-one welded portions constituting the welded portion 5. Therefore, according to the pulse laser welding method of the aluminum alloy material of the present invention, the material 3 to be welded has a high pressure strength, and the welded portion is cracked by controlling the output of the pulse laser beam and the irradiation time. The welded material 3 can be welded with high productivity.

  Note that the formation state of the molten pool and the quality of the welded portion can be determined by observing the cross section of the weld bead after solidification. That is, after the weld bead has solidified, the material to be welded is cut so as to include the weld bead, the cross section is immersed in, for example, Keller's solution, and the cross section is etched. Can do. FIGS. 5 and 6 are macroscopic observations of a cross-section etched with Keller's solution using a microscope (50 × magnification). FIG. 5 shows a sound weld by welding using the pulse laser welding method of the present invention. FIG. 6 is a diagram showing a case where a crack occurs in the welded portion. In FIGS. 5 and 6, the composition of the aluminum alloy constituting the material to be welded satisfies the scope of the present invention. Keller's solution is an etching solution produced by mixing nitric acid: 2.5% by volume, hydrofluoric acid: 1.0% by volume, hydrochloric acid: 1.5% by volume and distilled water 95.0% by volume. .

  As shown in FIG. 5, when an aluminum alloy material is welded by the pulse laser welding method of the present invention, the weld bead is formed in a dome shape so as to rise from the surface of the material to be welded. The welded portion and the second-layer welded portion at the center are configured in two layers. And the crack has not generate | occur | produced in the welding part, but the healthy welding part is obtained. On the other hand, FIG. 6 shows a welded portion in the case where the waveform of the pulsed laser light is a rectangular wave or a triangular wave as in the conventional case, the welded portion is formed in one layer, It can be seen that a large weld crack occurs in the center.

  In addition, in the case of macro-observing the formation state of the molten pool and the quality of the welded portion, after immersing the cross section of the weld bead with, for example, emery paper (preferably 200 series) before dipping in the Keller solution It can be determined by etching and observing with a microscope.

In the present invention, the pulse laser beam applied to the material to be welded 3 has a two-stage configuration composed of continuous pulses of the first and second pulse laser beams 1 and 2 having a rectangular waveform, and the peak of the first pulse laser beam 1 is obtained. to be greater than the output value P ₁ of the second peak output value P ₂ of the pulse laser beam 2, while preventing the occurrence of weld cracking, for example, as shown in FIG. 4 (a), if the pulse In the case where the laser beam 13 is configured in three stages, the temperature of the molten pool is changed in three stages, and the welded portion to be formed also has three layers, but the waveform of the pulse laser beam becomes a triangular wave in FIG. By becoming close, the temperature gradient of the molten pool gradually decreases, for example, from the peripheral portion to the central portion. Therefore, in this case, the crystal grains gradually become coarser from the peripheral portion to the center portion of the welded portion, and a weld crack occurs. In addition, even when the pulse laser beam has a slope-like waveform 14 as shown in FIG. 4B, the welded portion is exposed to the welded portion in the same manner as when the conventional rectangular and triangular pulse laser beams are irradiated. Weld cracking occurs. That is, as in the present invention, the pulse laser beam has a two-stage configuration including continuous pulses of the first and second pulse laser beams 1 and 2 having a rectangular waveform, and the peak output value P ₁ of the first pulse laser beam ₁ is By making it larger than the peak output value P _{2 of} the second pulse laser beam 2 and setting the irradiation time of each pulse laser beam to an appropriate range, an effect of preventing the occurrence of weld cracks can be obtained.

  Hereinafter, the effect of the embodiment of the present invention will be described in comparison with a comparative example. In this example, a test piece having a width of 30 mm and a length of 100 mm was cut from a plate material having a thickness of 0.8 mm made of an aluminum alloy having the composition shown in Table 1, and used as a co-test material for each example and comparative example. And the pulse laser welding was performed on the test piece of each Example and the comparative example with the pulse YAG welding machine (The product name: M802E by the OMRON laser front company). Welding methods were spot-on welding and line welding of bead-on-plate, and welding conditions were pulse wave frequency: 10 to 200 Hz, welding speed: 100 to 800 mm / min, and shielding gas: Ar (20 L / min). In the wire welding of the workpiece, the bead length was constant at 90 mm for each test piece.

Then, when the pulse wave of the pulse laser beam is a rectangular wave (conventional), a two-stage waveform, a three-stage waveform, and a slope waveform, the peak output value and irradiation time of the laser pulse wave are changed, and welding after pulse laser welding is performed. A partial cross section was observed. At this time, in the case of irradiating laser light having a rectangular wave and a two-stage waveform, the peak output value P1 of the first-stage laser pulse wave is ₁ to 10 kW, and the first-stage laser pulse wave is also emitted. Time t ₁ was set to 0.2 to 5 milliseconds. And the number of layers of the weld and the presence or absence of weld cracks were confirmed. When the pulse wave of the pulse laser beam has a three-stage waveform, the peak output value of the first-stage laser pulse wave is 3 kW, the irradiation time is 1.5 msec, and the peak output value of the second-stage laser pulse wave is The peak output value of the third-stage laser pulse wave was 1 kW and the irradiation time was 2 msec. The number of layers of the welded part was confirmed by observing the welded part macroscopically after cutting the test piece so as to include the beads when spot-welded and etching with Keller solution. The presence or absence of weld cracks was confirmed by macro-observing the surface of the welded part by wire welding. For weld cracking, ○ when no cracks occurred in the welded part, △ when cracks occurred even in part of the welded part, and x when cracks occurred throughout the length of the welded part. Judged. Table 2 below shows the application conditions of the pulse wave, the number of welded layers, and the results of determination of weld cracks for each example and comparative example.

  Example No. shown in Table 2 In Nos. 1 to 8, the composition of the aluminum alloy material satisfies the scope of the present invention, and the irradiation condition of the pulse laser beam is also within the scope of the present invention. A two-layer bead as shown in FIG. Neither occurred.

Comparative Example No. 1 is that the ratio P ₂ / P ₁ of the peak output values of the first and second pulsed laser beams is less than the range of the present invention, so that one layer of bead as shown in FIG. Cracks occurred throughout the entire length direction. Comparative Example No. 2, the ratio P ₂ / P ₁ of the peak output values of the first and second pulse laser beams exceeds the range of the present invention, and a single-layer bead as shown in FIG. 6 is formed. Cracks occurred.

  Comparative Example No. 3, since the pulse wave of the pulse laser beam applied to the aluminum alloy material was a rectangular wave similar to the conventional one, a single-layer bead as shown in FIG. 6 was formed, and the entire length of the welded portion was extended. Cracks occurred. Comparative Example No. 4, since the aluminum alloy material was irradiated with a pulse laser beam having a three-stage waveform as shown in FIG. 4A, the number of layers of the formed welded portion was three, but the crystal grains were of the welded portion. It gradually increased in size from the peripheral part to the central part, and cracks occurred throughout the length of the weld. Comparative Example No. 5, since the aluminum alloy material was irradiated with a pulse laser beam having a slope waveform as shown in FIG. 4B, as shown in FIG. A single layer of beads was formed, and cracks occurred throughout the length of the weld.

  Comparative Example No. 6 and 7, the irradiation conditions of the pulsed laser light applied to the aluminum alloy material satisfy the scope of the present invention, and the welded portion was formed in two layers, but the content of Mg in the aluminum alloy material was that of the present invention. Beyond the range, the cracking sensitivity increased, and cracking occurred throughout the length of the weld. Comparative Example No. In Nos. 8 and 9, although the irradiation condition of the pulse laser beam applied to the aluminum alloy material satisfies the scope of the present invention and the welded portion is formed in two layers, the content of Si in the aluminum alloy material is the present invention. Exceeding the range, the crack sensitivity increased, and cracks occurred in some of the welds.

  1: 1st pulse laser beam, 2: 2nd pulse laser beam, 3: material to be welded, 4: (dot) weld, 5: linear weld, 11: rectangular wave, 12: triangular wave , 13: 3-stage wave, 14: slope wave

Claims (4)

0.1 to 1.8% by mass of Mn, 0.4 to 1.2% by mass of Mg, 0.1 to 3.0% by mass of Cu, less than 0.3% by mass of Si, and 1. In a pulse laser welding method of an aluminum alloy material, comprising less than 0% by mass, the balance being irradiated with pulsed laser light on a pair of materials to be welded made of an aluminum alloy having a composition composed of aluminum and inevitable impurities,
The pulse laser beam is a two-stage waveform composed of a first pulse laser beam having a rectangular waveform and a second pulse laser beam having a rectangular waveform following the first pulse laser beam,
P ₁ is a peak output value of the first pulse laser beam, t ₁ is an irradiation time of the first pulse laser beam to the welding material, P ₂ is a peak output value of the second pulse laser beam, The ratio P of the peak output value of the second pulse laser beam to the peak output value of the first pulse laser beam, where t ₂ is the irradiation time of the _second pulse laser beam to the workpiece. ₂ / P ₁ is 0.3 to 0.6, and the ratio t ₂ / t ₁ of the irradiation time of the second pulse laser light to the irradiation time of the first pulse laser light is 1.5 or more. The
The central portion of the top of the weld the first layer, wherein the first layer of the weld is formed weld the second layer crystal grain size and crystal orientation that Do different, welding the second layer in a plan view pulse laser welding method of an aluminum alloy welds weld the first layer is present in the peripheral portion, characterized in Rukoto obtained parts. 2. The pulse laser welding method for an aluminum alloy material according to claim 1, wherein the aluminum alloy further contains 0.05 to 0.25% by mass of Zr. Wherein P ₁ is a pulse laser welding method of an aluminum alloy material according to claim 1 or 2, characterized in that 1.5 to 5 kW. Wherein t _1, a pulse laser welding method of an aluminum alloy material according to any one of claims 1 to 3, characterized in that 0.1 to 5 msec.

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