JP2021013954A - Welding method and welding system - Google Patents

Abstract

To provide a welding method and a welding system which control a joint interface so as to uniformly disperse a material softened at a temperature lower than a melting point of the material and generate an intermetallic compound having a larger mechanical strength by stirring the material.SOLUTION: A welding method that welds a first member 62A composed of a first material having a first melting point and a second member 62B composed of a second material having a second melting point includes: a heating step of irradiating a first region 64A adjacent to the second member in the first member and a second region 64B adjacent to the first member in the second member with a first laser 44A and a second laser 44B in a state where the first member and the second member are butted, and softening the first material and the second material; and a stirring step of stirring the first material softened in the heating step, mixing the first material with the second material softened in the heating step, and producing an intermetallic compound.SELECTED DRAWING: Figure 3

Description

The present invention relates to welding methods and welding systems.

Parts made from metal materials with low mechanical strength may require reinforcement. To meet this demand, laser welding is used. Laser welding performs reinforcement by joining a material with high mechanical strength to a material with low mechanical strength. As for metal materials, it is necessary to select materials according to their functions, such as aluminum, which is known as a lightweight material, in order to optimally use them according to their functions. By arranging the right materials in the right places, automobiles are lightweight. It is possible to achieve both standardization and safety performance.

However, depending on the combination of materials, brittle intermetallic compounds may be formed at the bonding interface. To solve this problem, a method has been proposed in which heat is applied only to a high melting point material and the amount of heat given is controlled so that only the low melting point material is melted and joined (see Patent Document 1). According to this proposed method, the formation of fragile intermetallic compounds can be suppressed.

Japanese Unexamined Patent Publication No. 2005-279744

However, when the metal materials to be joined are iron and aluminum, once the melting of aluminum starts, the melting of aluminum quickly spreads from the place where the heat is applied to the surroundings. Further, as shown in FIG. 9, when the amount of melted aluminum increases and the concentration of aluminum at the bonding interface increases to around 75%, a fragile intermetallic compound containing a large amount of aluminum such as Fe ₂ Al ₅ or Fe Al ₂ is generated. May be done. This problem occurs in the region of the bonding interface near aluminum. In addition, the region containing more fragile intermetallic compounds becomes a portion having inferior mechanical strength and may be deformed by the assumed load.

On the other hand, when the molten iron and aluminum are stirred at the bonding interface, the intermetallic compounds at the bonding interface are uniformly dispersed, and the mechanical strength is improved. However, when aluminum is heated at a temperature corresponding to the melting point of iron, bumping occurs and it is difficult to stir stably.

Therefore, in the present invention, the bonding interface is controlled so as to uniformly diffuse the material and produce an intermetallic compound having a higher mechanical strength by stirring the softened material at a temperature lower than the melting point of the material. Welding methods and welding systems are provided.

In order to achieve this purpose, a welding method of welding a first member made of a first material having a first melting point and a second member made of a second material having a second melting point is used.
In a state where the first member and the second member are butted against each other, the first region adjacent to the second member in the first member and the first member in the second member. A heating step of irradiating the adjacent second region with the first laser and the second laser, respectively, to soften the first material and the second material, respectively.
It comprises a stirring step of stirring the first material softened in the heating step and mixing it with the second material softened in the heating step to produce an intermetallic compound.

According to the present invention, by stirring the softened first material and the second material, it is possible to provide a welding method for producing an intermetallic compound having a higher mechanical strength and uniformly diffusing it. The member formed by this method has excellent toughness.

It is a front view which shows the schematic structure of the welding system which concerns on Embodiment 1. FIG. It is a block diagram of the welding system shown in FIG. It is a perspective view which shows the schematic structure of the welding system shown in FIG. It is sectional drawing which shows the molten pool of 1st member and 2nd member. It is a perspective view which shows the schematic structure of the welding system which concerns on Embodiment 2. FIG. It is a perspective view which shows the schematic structure of the welding system which concerns on Embodiment 3. It is a phase diagram of iron-carbon. It is a phase diagram of aluminum-magnesium. It is a phase diagram of iron-aluminum.

Hereinafter, embodiments of the welding method according to the present invention will be described with reference to the accompanying drawings.

[Welding system]
FIG. 1 shows an outline of a welding system for carrying out the welding method according to the first embodiment. The illustrated welding system 10 has a lower structure 14 that supports the welding target 12, and an upper structure 16 that irradiates the welding target 12 composed of two metal members with a laser.

The lower structure 14 has a base 18 fixed to the floor of a building or the like, a moving table 20 arranged on the base 18, and a support table 22 arranged on the moving table 20. The support table 22 includes a horizontal support surface 24 that supports the welding target 12. The support table 22 also includes a jig 26 for fixing the welding target 12 supported on the horizontal support surface 24. The moving table 20 is connected to the table moving motor 28, and the support table 22 can be moved in the direction extending in the left-right direction (x direction) parallel to the horizontal support surface 24 based on the drive of the motor 28. It is configured so that it can be done.

In the embodiment, the support table 22 is formed with a refrigerant transport path 30 in a space for transporting the refrigerant. The refrigerant may be either air or a suitable liquid. The refrigerant transport path 30 is connected to the cooler 34 via the refrigerant circulation path (pipe line) 32. The cooler 34 transports the refrigerant to the refrigerant transport path 30 via the refrigerant circulation path 32, and also has a pump 36 for recovering the refrigerant from the refrigerant transport path 30 via the refrigerant circulation path 32, and the recovered refrigerant. Is provided with a heat exchanger 38 that cools the air again.

The superstructure 16 has two heating devices arranged side by side in the direction (y direction) from the front side to the back side of FIG. 1. The heating device has laser processing machines 40A and 40B, respectively. The laser processing machines 40A and 40B have processing laser oscillators 42A and 42B, respectively. The lasers 44A and 44B output from the laser oscillators 42A and 42B may be any of a YAG laser, a CO2 laser, and other lasers. The laser processing machine 40B and its related configurations are shown only in FIG.

The superstructure 16 has a stirring device 46 for friction stir welding of a welding object 12 including two metal members. The stirring device 46 has a rod-shaped stirring rotary tool 48 that extends downward (in the z direction) from above. The stirring rotary tool 48 is made of, for example, SKD (alloy tool steel), nickel alloy, cobalt alloy, or tungsten carbide, and is connected to the tool rotary motor 50 so as to rotate about an axis extending in the z direction. The tool rotation motor 50 is connected to the tool movement motor 52 together with the stirring rotation tool 48 so that it can move in the z direction. Therefore, the stirring rotary tool 48 is inserted from above into the welding target 12 softened by the above-mentioned laser irradiation, and is configured to rotate in the welding target 12.

In the embodiment, the moving table 20 is configured to move in the + x direction (right side in FIG. 1). Therefore, the welding system 10 moves the welding target 12 from the right side to the left side in the drawing with respect to the lasers 44A and 44B and the stirring rotary tool 48 based on the drive of the table moving motor 28, whereby the lasers 44A and 44B The irradiation position and the stirring position of the stirring rotary tool 48 are configured to be moved with respect to the welding target 12.

The table moving motor 28, the pump 36, the laser oscillators 42A and 42B, the tool rotating motor 50, and the tool moving motor 52 described above are connected to the controller 54. The controller 54 is also connected to the storage unit 56 (see FIG. 2). Therefore, the controller 54 can drive the above-mentioned equipment based on the program or data stored in the storage unit 56 to perform a predetermined welding process. Specifically, various welding processes that can be performed by the welding system 10 will be described.

[Embodiment 1]
In the first embodiment, the welding target 12 includes two members butted in the y direction, that is, a first member 62A and a second member 62B, as shown in FIG. In the drawings, the first member 62A and the second member 62B are both quadrangular plate-shaped members, but the combination thereof is not limited.

In the first embodiment, the first member 62A is made of carbon steel (iron). The second member 62B is made of an aluminum magnesium alloy (aluminum).

In the first member 62A and the second member 62B, the first member 62A is arranged on the right and the second member 62B is arranged on the left, and the linear end surface (first end surface) and the second member 62A of the first member 62A are arranged. The linear end faces (second end faces) of the member 62B of the member 62B are butted against each other, and the butted straight end faces are arranged along the x direction and fixed by an appropriate jig 26 (see FIG. 1).

The first member 62A and the second member 62B have a first laser irradiation region 64A and a second laser irradiation region 64B that are adjacent to and extend along the abutted end faces. The first and second laser irradiation regions 64A and 64B are regions where the lasers 44A and 44B are irradiated, respectively.

At the time of welding, the controller 54 reads out the welding program stored in the storage unit 56, and drives the table moving motor 28, the laser oscillators 42A and 42B, the tool rotating motor 50, and the tool moving motor 52 according to the program. As a result, the lasers 44A and 44B output from the laser oscillators 42A and 42B are irradiated to the first laser irradiation region 64A and the second laser irradiation region 64B from the z direction, respectively. The irradiation positions 66A and 66B of the lasers 44A and 44B are moved to the welding target 12 by the welding target 12 including the first member 62A and the second member 62B moving in the + x direction based on the drive of the table moving motor 28. On the other hand, it moves relatively in the -x direction.

The light intensity of the lasers 44A and 44B emitted by the laser oscillators 42A and 42B is determined according to the materials of the first member 62A and the second member 62B, and the laser irradiation region 64A of the first member 62A and the second member 62B, Each of the 64B is heated to a predetermined temperature. This temperature is a temperature at which the material in each laser irradiation region is softened by diffusing the atoms constituting the member by the thermal activation process.

For example, if the first member 62A is iron (iron has a melting point of 1538 degrees Celsius), the first member 62 is heated to about 900 degrees Celsius. When the second member 62B is aluminum (the melting point of aluminum is 660 degrees Celsius), the second member 62B is heated to about 500 degrees Celsius.

FIG. 7 is a state diagram of carbon steel, which is the material of the first member 62A. It is known that carbon steel takes the form of ferrite (α-iron), austenite (γ-iron), etc., depending on the temperature and the ratio of carbon. Ferrite has a body-centered cubic lattice structure formed of iron atoms. On the other hand, austenite has a face-centered cubic lattice structure formed by iron atoms. Since the distance between iron atoms in austenite is wider than that in ferrite, invasion of other atoms (for example, carbon atom) is likely to occur. That is, the first member 62A changed to austenite is easily mixed with the aluminum magnesium alloy which is the material of the second member 62B.

The region 72 shown in FIG. 7 indicates that the carbon steel becomes austenite. On the other hand, region 74 indicates that ferrite and austenite are mixed. As an example, when the carbon content of the carbon steel which is the material of the first member 62A is about 0.2%, the carbon steel moves from the region 74 to the region 72 by heating and is completely austenite. The changing temperature (where the austenite transformation begins) is about 900 ° C. Therefore, by determining the light intensity of the laser 44A emitted by the laser oscillator 42A according to this temperature, the first member 62A is likely to be mixed with the second member 62B.

FIG. 8 is a state diagram of the aluminum magnesium alloy which is the material of the second member 62B. It is known that an aluminum-magnesium alloy becomes a solid solution of aluminum depending on the temperature and the ratio of magnesium. At this time, invasion of other atoms (for example, magnesium atom) is likely to occur. That is, the second member 62B, which has been transformed into a solid solution of aluminum, is easily mixed with carbon steel, which is the material of the first member 62A.

The region 76 shown in FIG. 8 indicates that the aluminum magnesium alloy becomes a solid solution. As an example, when the magnesium content of the aluminum magnesium alloy which is the material of the second member 62B is about 5.6%, the aluminum magnesium alloy is a solid solution as long as the temperature is about 300 to 550 ° C. Therefore, for example, by determining the light intensity of the laser 44B emitted by the laser oscillator 42B so that the temperature of the aluminum magnesium alloy becomes 500 ° C., the second member 62B can be easily mixed with the first member 62A.

The first member 62A and the second member 62B are easily mixed by being heated to the above-mentioned temperatures, that is, they are in a softened state.

In this state, the stirring rotary tool 48 of the stirring device 46 rotates based on the driving of the tool rotating motor 50, and the first laser irradiation of the softened first member 62A based on the driving of the tool moving motor 52. It is inserted into the region 64A from above. The rotation speed is preferably about 2000 rpm. As a result, the softened first member 62A is agitated, and the agitated first member 62A is mixed with the softened adjacent second member 62B, so that the first member 62A and the second member 62B are mixed. The molten pool 78 shown in FIG. 4 is formed at the boundary between the two.

As described above, the stirring rotary tool 48 is inserted into the first laser irradiation region 64A to stir the first member 62A. Therefore, the first member 62A softened in the first laser irradiation region 64A is mixed with the second member 62B softened in the second laser irradiation region 64B, and the ratio of iron atoms is larger than the ratio of aluminum atoms between the metals. Compounds (eg, FeAl, FeAl ₂ , Fe ₃ Al, etc. shown in FIG. 9) are produced. As known to those skilled in the art, _FeAl, intermetallic compounds such as FeAl 2, _Fe 3 Al has _a larger mechanical strength than intermetallic compounds such as Fe ₂ Al 5, FeAl _3. Further, even if the intermetallic compound mechanical strength is small Fe 2 _{Al 5,} FeAl ₃ was generated in part, by the stirring rotation tool 48 to stir the molten pool 78, their intermetallic compounds uniformly dispersed Therefore, no brittle region is formed at the bonding interface.

During the laser welding described above, the pump 36 of the cooler 34 is continuously driven, and the refrigerant is supplied to the refrigerant transport path 30 via the refrigerant circulation path 32 (see FIG. 1). As a result, the welding target 12 is cooled from the lower surface thereof via the support table 22, and in particular, the second member 62B is controlled so as not to be excessively heated.

[Embodiment 2]
In the welding system 110 of the second embodiment shown in FIG. 5, the first member and the second member to be welded are substantially cylindrical first members 162A and second members having the same or substantially the same outer diameter. It is 162B. The materials of the first member 162A and the second member 162B are the same carbon steel and aluminum magnesium alloy as the first member and the second member of the first embodiment, respectively.

Each of the first member 162A and the second member 162B is rotatably supported around the central axis by an appropriate means in a state where the central axes are aligned on the same straight line and the end faces are aligned. The first member 162A and the second member 162B are also connected to the first motor 168A and the second motor 168B, respectively, in the same direction at the same speed, in the same direction at different speeds, or in different directions. It is designed to rotate at the same speed or at different speeds.

The laser machines 140A and 140B are arranged on both sides of the butt surface of the first member 162A and the second member 162B, and are emitted from the laser oscillators 142A and 142B of the laser machines 140A and 140B. The lasers 144A and 144B are the first laser irradiation position 166A in the region (first laser irradiation region 164A) adjacent to the second member 162B in the first member 162A and the first in the second member 162B, respectively. The second laser irradiation position 166B in the region (second laser irradiation region 164B) adjacent to the member 162A of the member 162A is set to be irradiated.

The stirring device 146 includes a stirring rotary tool 148 and a tool rotary motor 150 connected to the stirring rotary tool 148, and is supported in a state where the tip of the stirring rotary tool 148 faces the first laser irradiation region 164A. The stirring device 146 also includes a tool moving motor 152 that moves the stirring rotary tool 148 forward and backward toward the first laser irradiation region 164A.

In the second embodiment configured as described above, at the time of welding, the first member 162A and the second member 162B are centered on their central axes based on the drive of the first motor 168A and the second motor 168B. Is rotated in the same direction or in different directions. In this state, the laser machines 140A and 140B have the first laser 144A and the second laser in the first laser irradiation region 164A and the second laser irradiation region 164B of the first member 162A and the second member 162B. Each of 144B is irradiated, and the materials of the first laser irradiation region 164A and the second laser irradiation region 164B are heated and softened. In this state, the tool rotating motor 150 and the tool moving motor 152 are driven, and the tip of the rotating stirring rotary tool 148 is inserted into the softened material of the first laser irradiation region 164A to rotate and stir. Further, the material of the softened second member 162B is drawn into the rotational stirring of the material of the first member 162A, whereby the first member 162A in the boundary region between the first member 162A and the second member 162B. The material of the second member 162B is mixed with the material of the above, and an intermetallic compound (for example, FeAl, FeAl ₂ , Fe ₃ Al, etc.) having a ratio of iron atoms higher than that of aluminum atoms is produced.

As described above, according to the second embodiment, the first laser 144A and the second laser 144B have the first laser irradiation region 164A and the second laser irradiation region of the first member 162A and the second member 162B. 164B is repeatedly heated, and the repeatedly heated material is stirred by the stirring rotary tool 148. Therefore, the first member 162A and the second member 162B are quickly and efficiently heated and stirred. Further, by changing the rotation speeds of the first member 162A and the second member 162B, and by rotating both members in opposite directions, the softened first member 162A and the second member 162B are efficiently agitated. Will be done.

[Embodiment 3]
The welding system 210 of the third embodiment shown in FIG. 6 is a modification of the welding system of the first embodiment, in which the end portion of the first laser irradiation region 264A in the first member 262A (to the second member 262B). The facing portion) is formed of an obliquely grooved slope 280A, and the end portion of the second member 262B (the end facing the first member 262A) is a vertical plane 280B orthogonal to the facing direction. It is configured. Other configurations are the same as those in the first embodiment. Therefore, the same or corresponding device or location as the device or location of the first embodiment is designated by adding "200" to the code of the first embodiment, and the description thereof will be omitted.

According to the third embodiment configured as described above, the laser 244A irradiated to the first laser irradiation region 264A (slope 280A) of the first member 262A is in the first laser irradiation region 264A (slope 280A). It reflects and is incident on the second laser irradiation region 264B (vertical plane 280B) of the second member 262B facing the second member 262B to heat the second laser irradiation region 264B. Further, the laser 244A reflected by the second laser irradiation region 264B (vertical plane 280B) is again incident on the first laser irradiation region 264A (slope 280A) to heat the first laser irradiation region 264A. Therefore, according to the third embodiment, both the first laser irradiation region 264A and the second laser irradiation region 264B are efficiently heated. Therefore, it is preferable that the inclination angle of the slope 280A of the first member is an angle (for example, 45 degrees) in which the laser irradiated there is reflected toward the second member.

The above-described third embodiment is applied to the first embodiment, and the first laser irradiation region of the first member in the first embodiment may be formed on a slope, and the slope may be irradiated with the first laser. In this case as well, the same effect as in the third embodiment can be obtained.

In the above-described first to third embodiments, the first member is carbon steel (iron) and the second member is an aluminum magnesium alloy (aluminum), but the application of the present invention is not limited to the combination thereof. For example, both the first member and the second member may be iron or aluminum, or may be other metals.

10: Welding system 40A, 40B: Heating device (laser processing machine)
44A, 44B: Laser 46: Stirrer 62A: First member 62B: Second member 64A: First laser irradiation area 64B: Second laser irradiation area

Claims (14)

A welding method for welding a first member made of a first material having a first melting point and a second member made of a second material having a second melting point.
In a state where the first member and the second member are butted against each other, the first region adjacent to the second member in the first member and the first member in the second member. A heating step of irradiating the adjacent second region with the first laser and the second laser, respectively, to soften the first material and the second material, respectively.
A welding method comprising a stirring step of stirring the first material softened in the heating step and mixing it with the second material softened in the heating step to produce an intermetallic compound. The welding method according to claim 1, wherein the stirring step is to insert a tool into the softened first material and rotate the tool about an axis in the tool insertion direction. The first member comprises a first cylindrical member.
The second member comprises a second cylindrical member.
The first cylindrical member and the second cylindrical member are arranged coaxially with their central axes aligned on the same straight line.
The end face of the first cylindrical member and the end face of the second cylindrical member are abutted against each other.
The welding method according to claim 1 or 2, wherein in the heating step and the stirring step, the first cylindrical member and the second cylindrical member are rotated in the same direction or in opposite directions. The welding method according to claim 3, wherein the first cylindrical member and the second cylindrical member are rotated at the same speed or different speeds. The first member has a linear first end face and has a linear first end face.
The second member has a linear second end face and
The welding method according to claim 1 or 2, wherein the first end face and the second end face are abutted against each other. The welding method according to any one of claims 1 to 5, wherein the first melting point of the first material is the same as the second melting point of the second material. The welding method according to any one of claims 1 to 5, wherein the first melting point of the first material is higher than the second melting point of the second material. The welding method according to any one of claims 1 to 5, wherein the first material is iron and the second material is aluminum. The welding method according to any one of claims 1 to 5, wherein both the first member and the second member are iron. The welding method according to any one of claims 1 to 5, wherein both the first member and the second member are made of aluminum. The welding method according to claim 8 or 9, wherein in the heating step, the iron is heated to a temperature at which austenite transformation starts. The welding method according to claim 8 or 10, wherein in the heating step, the aluminum is heated to a state of becoming a solid solution. A welding system in which a first member made of a first material and a second member made of a second material are butted and welded.
A first laser and a second laser are provided in a first region of the first member facing the second member and a second region of the second member facing the first member. A heating device that irradiates and heats and softens each
A welding system comprising a stirrer that stirs the softened first material and mixes it with the softened second material to produce an intermetallic compound. The welding system according to claim 13, wherein the stirring device includes a tool inserted into the softened first material and a rotating mechanism for rotating the tool about an axis in the tool insertion direction.

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