JP2021122829A - Laser joining method and junction structure - Google Patents

Abstract

To provide a laser joining method for joining a first joint material made of a stainless-steel material to a second joint material made of a zinc alloy material using a laser beam.SOLUTION: A laser joining method includes: a first step of arranging a second joint material on a first surface of a first joint material so as to expose a part of the first surface to an outside; a second step of melting a part of the second joint material by emitting a laser beam to the second joint material from an opposite side to the first joint material in an end part of the second joint material and a first region including a part of the first surface which is exposed to the outside from the end part; and a third step of joining the partially melted second joint material to the first joint material of which first surface is heated by a laser beam.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laser bonding method and a bonding structure.

Patent Document 1 below discloses a technique for joining dissimilar metals with a laser.

Japanese Unexamined Patent Publication No. 2001-252777

However, in the laser bonding method of Patent Document 1, for example, when a zinc alloy material having a significantly different melting point from each other and a stainless steel material are melted and bonded, the zinc alloy volatilizes when heated to a temperature at which the stainless steel is melted. Therefore, there is a problem that the zinc alloy material and the stainless steel material cannot be melted by a laser and joined.

In view of the above circumstances, one of the objects of the present invention is to provide a laser bonding method and a bonding structure capable of bonding a zinc alloy material and a stainless steel material.

According to the first aspect of the present invention, it is a method of joining a first joining material made of a stainless steel material and a second joining material made of a zinc alloy material by using a laser, and the first surface of the first joining material. A first step of arranging a second joining material so as to expose a part of the first surface, and an end portion of the second joining material and a part of the first surface exposed from the end portion. The second step of melting a part of the second joining material by irradiating the first region including the second joining material with a laser from the side opposite to the first joining material, and the said that a part of the second joining material is melted. Provided is a laser joining method comprising a third step of joining the second joining material and the first joining material whose first surface is heated by the laser.

According to the second aspect of the present invention, a second bonding material made of a zinc alloy material is bonded onto the first surface of the first bonding material made of a stainless steel material so as to expose a part of the first surface. Provided is a bonded structure in which the first bonding material and the second bonding material are bonded by the laser bonding method of the first aspect.

According to one aspect of the present invention, it is possible to provide a laser bonding method and a bonding structure capable of bonding a zinc alloy material and a stainless steel material.

FIG. 1 is a diagram showing a configuration of a joining device. FIG. 2 is a flowchart showing a part of the procedure of the laser joining method. FIG. 3 is a diagram showing a part of the procedure of the laser joining method. FIG. 4 is a diagram showing the configuration of the joined structure.

In the following description, the direction parallel to the Z axis shown in each figure is referred to as a vertical direction, the direction parallel to the X axis is referred to as a front-back direction, and the direction parallel to the Y axis is referred to as a left-right direction. The front-back direction and the left-right direction are orthogonal to each other and orthogonal to the vertical direction. The positive side of the Z-axis in the vertical direction is the upper side, and the negative side of the Z-axis in the vertical direction is the lower side. The positive side of the X-axis in the front-rear direction is the front side, and the negative side of the X-axis in the front-rear direction is the rear side. The positive side of the Y-axis in the left-right direction is the right side, and the negative side of the Y-axis in the left-right direction is the left side.

In the present embodiment, the vertical direction, the front-rear direction, the horizontal direction, etc. are names for simply explaining the arrangement relationship of each part, and the actual arrangement relationship, etc. are the arrangement relationships, etc. indicated by these names. The arrangement relationship may be other than the above.

FIG. 1 is a diagram showing a configuration of a joining device used in the laser joining method of the present embodiment.
As shown in FIG. 1, the joining device 100 of the present embodiment includes a chamber 1, a holding unit 2, a laser irradiation unit 3, and a gas supply unit 4. The chamber 1 closes the work space for laser bonding. The holding unit 2 holds the object 10 to be laser-bonded in the chamber 1.

The holding portion 2 includes a pressing plate 2b that restrains the object 10 by sandwiching the object 10 from above between the base portion 2a and the base portion 2a. The base portion 2a and the pressing plate 2b are made of a metal having excellent heat dissipation, such as copper. The holding portion 2 also functions as a cooling member that cools the object 10 at the time of laser joining.

The laser irradiation unit 3 irradiates an object with a predetermined laser L. The laser irradiation unit 3 includes a laser light emitting unit 3a that emits a YAG laser and an optical lens 3b that converges the laser emitted from the laser light emitting unit 3a. The laser irradiation unit 3 can change the convergence position of the laser by moving the optical lens 3b by an actuator (not shown).

The gas supply unit 4 keeps the inside of the chamber 1 in an inert atmosphere by supplying the inert gas G such as nitrogen or argon gas into the chamber 1. By keeping the inside of the chamber 1 in an inert atmosphere, the joining device 100 of the present embodiment can improve the joining reliability by laser joining the object 10 in a cleaning environment.

The object 10 to be joined by the joining device 100 of the present embodiment is a laminate in which a first joining material 11 made of a stainless steel material and a second joining material 12 made of a zinc alloy material are laminated. Austenitic stainless steel (SUS304) was used as the stainless steel material constituting the first bonding material 11, and a zinc die-cast material (ZDC2) was used as the zinc alloy material constituting the second bonding material 12.

In the present embodiment, a case where the first bonding material 11 and the second bonding material 12 constituting the object 10 to be laser-bonded have a plate shape will be described. The shapes of the first joining material 11 and the second joining material 12 are not particularly limited.

Here, the melting point of SUS304 constituting the first bonding material 11 is about 1370 degrees, and the melting point of ZDC2 constituting the second bonding material 12 is about 470 degrees. That is, the difference in melting point between the first bonding material 11 and the second bonding material 12 is about 900 degrees.
Conventionally, it has not been possible to melt and join dissimilar materials having greatly different melting points with a laser. This is because when the SUS304 having a high melting point is heated to a temperature at which it is melted, ZDC2 is volatilized and both materials cannot be in a melted state.

On the other hand, the joining device 100 of the present embodiment can join the first joining material 11 (SUS304) and the second joining material 12 (ZDC2), which are different materials having significantly different melting points, as described later. ..

FIG. 2 is a flowchart showing a part of the procedure of the laser joining method using the joining device 100 of the present embodiment. FIG. 3 is a diagram showing a part of the procedure of the laser joining method. FIG. 3 is an enlarged view of the inside of the chamber 1 of the joining device 100. FIG. 4 is a diagram showing a configuration of a bonded structure bonded by the laser bonding method of the present embodiment.

As shown in FIG. 2, the laser joining method using the joining device 100 of the present embodiment includes an arrangement step (first step) S1, a melting step (second step) S2, and a joining step (third step) S3. And, including. In the joining device 100 of the present embodiment, the arrangement step S1, the melting step S2, and the joining step S3 are performed in the chamber 1. That is, in the laser joining method of the present embodiment, the placement step S1, the melting step S2, and the joining step S3 are performed in an inert atmosphere in the chamber 1, respectively.

The arrangement step S1 is a step of arranging the object 10 for laser bonding in the chamber 1 of the bonding device 100 as shown in FIG. The melting step S2 is a step of melting a part of the second bonding material 12 by irradiating the second bonding material 12 with a laser. The joining step S3 is a step of joining the second joining material 12 whose part is melted and the first joining material 11 whose first surface 11a is heated by a laser.

Specifically, in the arrangement step S1, as shown in FIG. 3, an object in which the second bonding material 12 is arranged on the first surface 11a of the first bonding material 11 so as to expose a part of the first surface 11a. 10 is held in the chamber 1 by the holding portion 2.

In the arranging step S1 of the present embodiment, the object 10 is arranged in the chamber 1 so that the second joining member 12 is located above the first joining member 11. The holding portion 2 holds the object 10 in a pressurized state by sandwiching the object 10 between the base portion 2a and the pressing plate 2b. That is, the first joining material 11 and the second joining material 12 are held in a state of being pressurized in the vertical direction.

In the joining device 100 of the present embodiment, in addition to the arranging step S1, the object 10 is held in a state of being pressurized by the holding portion 2 during the melting step S2 and the joining step S3. That is, in the laser joining method of the present embodiment, in the arrangement step S1, the melting step S2, and the joining step S3, the first joining material 11 and the second joining material 12 are held in a pressurized state.

In the joining device 100 of the present embodiment, as shown in FIG. 3, in the melting step S2, the laser irradiation unit 3 is a part of the end portion 15 of the second bonding material 12 and a part of the first surface 11a exposed from the end portion 15. A part of the second bonding material 12 is melted by irradiating the light irradiation region (first region) SA including the above with the laser L. In the present embodiment, the laser irradiation unit 3 irradiates the laser L from the side opposite to the first bonding material 11 of the second bonding material 12, that is, from the upper side to the lower side.

In the melting step S2, laser irradiation is performed so that the optical axis L1 of the laser L irradiated to the light irradiation region SA is located on the end portion 15 of the second bonding material 12. That is, in the melting step S2, the laser irradiation unit 3 lasers so that the ratio of the second bonding material 12 contained in the light irradiation region SA is larger than the ratio of the first surface 11a contained in the light irradiation region SA. Irradiate.

In the present embodiment, in the laser irradiation unit 3, the ratio of the second bonding material 12 (end portion 15) included in the light irradiation region SA is made larger than the ratio of the first surface 11a included in the light irradiation region SA. In addition, the irradiation position of the laser L and the size of the irradiation spot of the laser L are adjusted.

In the laser L irradiated from the laser irradiation unit 3 of the present embodiment in this way, the irradiation area of the end portion 15 of the second bonding material 12 is larger than the irradiation area of the first surface 11a.

In the present embodiment, the laser irradiation unit 3 emits the laser L from the laser light emitting unit 3a by pulse oscillation. That is, in the melting step S2, the laser L is irradiated in a pulse shape. In the present embodiment, the power of the laser L radiated in a pulse shape from the laser irradiation unit 3 is set to, for example, 0.7 kW, and one pulse time is set to 5 μsec. By irradiating the laser L in a pulse shape in this way, the energy of the laser L can be easily transmitted to the lower side in the thickness direction of the second bonding material 12.

In the melting step S2, the laser irradiation unit 3 performs laser irradiation so that the laser L is converged on the first surface 11a side of the thickness of the second bonding material 12. Here, the energy of the laser L has the highest focal point.

The laser irradiation unit 3 of the present embodiment performs laser irradiation so that the laser L is converged on the first surface 11a of the first bonding material 11. As a result, the laser L connects the focal point La on the first surface 11a. As described above, since the energy of the laser L has the highest focal point La, the temperature of the end portion 15 of the second bonding material 12 irradiated with the laser L is in the vicinity of the first surface 11a where the focal point La of the laser L is located. Is the highest. At this time, a portion of the end portion 15 of the second joining material 12 that comes into contact with the first surface 11a of the first joining material 11, that is, a part of the lower surface 12a of the second joining material 12 is melted to form the molten portion 13. Generate. In this way, the melting step S2 produces a molten portion 13 in which a part of the second bonding material 12 is melted.

In the present embodiment, the laser irradiation unit 3 sets the power of the laser L so that the second bonding material 12 can be melted at the focal point La portion where the energy is highest. As a result, the portion near the focal point La, that is, the portion near the first surface 11a of the second bonding material 12 can be selectively melted to generate the molten portion 13.

Further, in the present embodiment, the first surface 11a of the first bonding material 11 located in the light irradiation region SA is efficiently heated by the laser L connecting the focal points La on the first surface 11a. In the laser bonding method of the present embodiment, the first surface 11a is heated by the laser L in the melting step S2. As described above, since the melting point of the first joining material 11 is sufficiently higher than the melting point of the second joining material 12, the first surface 11a of the first joining material 11 does not melt.

Further, the laser irradiation unit 3 of the present embodiment irradiates the object 10 with the laser L from the upper side to the lower side. Specifically, the laser irradiation unit 3 irradiates the laser L from the direction perpendicular to the first surface 11a of the first bonding material 11 (Z-axis direction). According to this configuration, it is possible to make it difficult for the laser L to be reflected by the surface of the object 10, that is, the surface 12b of the second bonding material 12. Therefore, since the laser L is efficiently incident on the lower side in the thickness direction of the second joining material 12, the end portion 15 of the second joining material 12 can be efficiently heated by the laser L. That is, according to the laser bonding method of the present embodiment, in the melting step S2, the heat of the laser L can be efficiently used to melt the second bonding material 12.

In the laser joining method of the present embodiment, during the melting step S2, the first joining material 11 and the second joining material 12 are held in a state of being pressurized by the holding portion 2, so that the first joining material 11 is held. The first surface 11a and the lower surface 12a of the second joining member 12 are held in close contact with each other. As a result, the molten portion 13 formed on the lower surface 12a of the second joining material 12 adheres well to the first surface 11a of the first joining material 11.

In the joining step S3, the first surface 11a of the first joining material 11 and the lower surface 12a of the second joining material 12 are held in close contact with each other, and the laser irradiation from the laser irradiation unit 3 is stopped. As a result, the molten portion 13 solidifies as the temperature decreases, and forms a bonding layer 14 that joins the first surface 11a of the first bonding material 11 and the second bonding material 12.

In the laser bonding method of the present embodiment, when the bonding step S3 is performed, the temperature of the first surface 11a located in the light irradiation region SA is raised in advance. Specifically, the temperature of the portion of the first surface 11a close to the melting portion 13 is substantially equal to that of the melting portion 13. That is, in the laser joining method of the present embodiment, when the joining step S3 is performed, the temperature difference between the temperature of the first surface 11a close to the melting portion 13 and the melting point of the melting portion 13 can be reduced.

When the joining step S3 is performed, the present inventors have a joining layer 14 formed by solidifying the melting portion 13 when the temperature difference between the first surface 11a close to the melting portion 13 and the melting portion 13 is relatively large. It was found that the adhesion between the surface and the first surface 11a is lowered.

On the other hand, in the laser bonding method of the present embodiment, the first surface 11a and the second bonding material 12 of the first bonding material 11 are heated by directly heating the first surface 11a close to the molten portion 13 with the laser L. The joining step S3 can be performed in a state where the temperature difference from the melting portion 13 is reduced. As a result, the joining reliability of the joining layer 14 that joins the first joining member 11 and the second joining member 12 is improved.

Further, in the laser bonding method of the present embodiment, gas is generated when the above-mentioned molten portion 13 is generated. Examples of such a gas include a gas generated from the molten second bonding material 12, a gas contained in the zinc material constituting the second bonding material 12, and the like.

In the laser bonding method of the present embodiment, in the melting step S2, a part of the first surface 11a of the first bonding material 11 is formed on the end portion 15 of the second bonding material 12 in the light irradiation region SA irradiated with the laser L. It is in a state of being exposed from. Therefore, according to the laser joining method of the present embodiment, the gas generated at the time of forming the molten portion 13 can be released from the gap between the first surface 11a and the end portion 15 of the second joining member 12. As a result, the gas remaining in the joining layer 14 that joins the first joining material 11 and the second joining material 12 can be reduced, so that the joining reliability of the first joining material 11 and the second joining material 12 by the joining layer 14 can be improved. It can be improved further.

As described above, according to the laser joining method of the present embodiment, as shown in FIG. 4, the joining structure 20 in which the first joining member 11 and the second joining member 12 are joined by the joining layer 14 is formed by the joining step S3. Obtainable. Since the joint structure 20 has high joint reliability between the first joint material 11 and the second joint material 12 due to the joint layer 14, it is possible to provide a joint structure having excellent reliability.

As described above, according to the laser bonding method of the present embodiment, it is possible to generate a bonding structure 20 in which the first bonding material 11 and the second bonding material 12 having significantly different melting points are bonded by laser bonding. Since the bonding structure 20 of the present embodiment is formed by laser bonding a first bonding material 11 made of a stainless steel material and a second bonding material 12 made of a zinc alloy material, an inexpensive bonding structure is provided. ..

As described above, the configurations described in the present specification can be appropriately combined within a range that does not contradict each other.

For example, in the above embodiment, the laser irradiation unit 3 irradiates the object 10 with the laser L from the vertical direction as an example, but the irradiation direction of the laser L is not particularly limited. That is, the laser irradiation unit 3 may irradiate the laser L from diagonally above.

11 ... 1st bonding material, 11a ... 1st surface, 12 ... 2nd bonding material, 15 ... end, 20 ... bonding structure, L ... laser, S1 ... placement process (1st process), S2 ... melting process ( Second step), S3 ... Joining step (third step), SA ... Light irradiation region (first region).

Claims (10)

It is a method of joining a first joining material made of a stainless steel material and a second joining material made of a zinc alloy material using a laser.
The first step of arranging the second joining material on the first surface of the first joining material so as to expose a part of the first surface, and
Irradiating the first region including the end portion of the second joining material and a part of the first surface exposed from the end portion with a laser from the side opposite to the first joining material of the second joining material. In the second step of melting a part of the second bonding material in
A laser joining method comprising a third step of joining the second joining material, which is partially melted, and the first joining material whose first surface is heated by the laser. The second step is characterized in that laser irradiation is performed so that the ratio of the second bonding material contained in the first region is larger than the ratio of the first surface contained in the first region. The laser bonding method according to claim 1. The laser joining method according to claim 1 or 2, wherein in the second step, laser irradiation is performed from a direction perpendicular to the first surface of the first joining material. Any of claims 1 to 3, wherein in the second step, laser irradiation is performed so that the laser is converged on the first surface side of the thickness of the second bonding material. The laser bonding method according to the first paragraph. The laser joining method according to claim 4, wherein in the second step, laser irradiation is performed so that the laser is converged on the first surface of the first joining material. The laser joining method according to any one of claims 1 to 5, wherein in the second step, the laser is irradiated in a pulse shape. The invention according to any one of claims 1 to 6, wherein in the first step to the third step, the first joining material and the second joining material are held in a pressurized state. Laser bonding method. The laser bonding method according to any one of claims 1 to 7, wherein a YAG laser is used as the laser. The laser bonding method according to any one of claims 1 to 8, wherein the first step to the third step are performed in an inert atmosphere. A bonding structure in which a second bonding material made of a zinc alloy material is bonded so as to expose a part of the first surface on the first surface of the first bonding material made of a stainless steel material.
A bonding structure characterized in that the first bonding material and the second bonding material are bonded by the laser bonding method according to any one of claims 1 to 9.

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