JP7400233B2 - Welding method and welding system - Google Patents

Description

The present invention relates to a welding method and a welding system.

Components made from metal materials with low mechanical strength may require reinforcement. Laser welding is used to meet this demand. Laser welding performs reinforcement by joining a material with high mechanical strength to a material with low mechanical strength. In order to use metal materials optimally according to their functions, such as aluminum, which is known as a lightweight material, it is necessary to select materials according to their functions. It is possible to achieve both safety and safety performance.

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

Japanese Patent Application Publication No. 2005-279744

However, when the metal materials to be joined are iron and aluminum, once the aluminum begins to melt, the melting of the aluminum quickly spreads from the point where the heat is input to the surrounding area. Additionally, as shown in Figure 9, when the amount of melted aluminum increases and the concentration of aluminum at the bonding interface increases to around 75%, fragile intermetallic compounds containing a large amount of aluminum such as Fe ₂ Al ₅ or FeAl ₂ are formed. There is a risk that This problem occurs in the region of the bonding interface that is close to the aluminum. Further, a region containing a larger amount of brittle intermetallic compounds becomes a region with poor mechanical strength, and there is a possibility that it will deform under an assumed load.

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

Therefore, the present invention aims to control the bonding interface by stirring the softened material at a temperature lower than the melting point of the material to uniformly diffuse the material and generate an intermetallic compound with greater mechanical strength. A welding method and a welding system are provided.

To achieve this objective, 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 is as follows:
When the first member and the second member are butted together, a first region of the first member adjacent to the second member, and a region of the second member adjacent to the first member. a heating step of softening the first material and the second material by respectively irradiating a first laser and a second laser to an adjacent second region;
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 generate an intermetallic compound;
The irradiation area of the first laser on the first member is formed by an obliquely beveled slope,
The end portion of the second member is characterized in that it is constituted by a vertical plane orthogonal to the opposing direction.

According to the present invention, it is possible to provide a welding method in which an intermetallic compound with higher mechanical strength is generated and uniformly diffused by stirring the softened first material and second material. Components formed by this method have excellent toughness.

1 is a front view showing a schematic configuration of a welding system according to Embodiment 1. FIG. 2 is a block diagram of the welding system shown in FIG. 1. FIG. 2 is a perspective view showing a schematic configuration of the welding system shown in FIG. 1. FIG. FIG. 3 is a cross-sectional view showing a molten pool of a first member and a second member. FIG. 2 is a perspective view showing a schematic configuration of a welding system according to a second embodiment. FIG. 3 is a perspective view showing a schematic configuration of a welding system according to a third embodiment. It is an iron-carbon phase diagram. FIG. 2 is a phase diagram of aluminum-magnesium. It is a phase diagram of iron-aluminum.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a 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 a welding object 12 and an upper structure 16 that irradiates a laser beam onto the welding object 12 made of two metal members.

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

In the embodiment, the support table 22 has a refrigerant transport path 30 formed therein as a space for transporting refrigerant. The coolant may be either air or a suitable liquid. The refrigerant transport path 30 is connected to a cooler 34 via a refrigerant circulation path (pipe) 32. The cooler 34 includes a pump 36 for transporting the refrigerant to the refrigerant transport path 30 via the refrigerant circulation path 32, and a pump 36 for recovering the refrigerant from the refrigerant transport path 30 via the refrigerant circulation path 32, and a pump 36 for transporting the refrigerant to the refrigerant transport path 30 via the refrigerant circulation path 32, and a pump 36 for transporting the refrigerant to the refrigerant transport path 30 via the refrigerant circulation path 32. A heat exchanger 38 is provided to cool the water again.

The upper structure 16 has two heating devices arranged side by side in the direction from the front side to the back side (y direction) in FIG. The heating devices each have laser processing machines 40A and 40B. The laser processing machines 40A and 40B have processing laser oscillators 42A and 42B, respectively. Lasers 44A and 44B output from laser oscillators 42A and 42B may be YAG lasers, CO2 lasers, or other lasers. Laser processing machine 40B and its related configuration are shown only in FIG.

The superstructure 16 has a stirring device 46 for performing friction stir welding on the 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 rotation motor 50 so as to rotate about an axis extending in the z direction. The tool rotation motor 50 is coupled to a tool movement motor 52 so as to be able to move in the z direction together with the stirring rotation tool 48 . Therefore, the stirring rotary tool 48 is inserted from above into the welding object 12 that is softened by the above-described laser irradiation, and is configured to rotate within the welding object 12.

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

The table moving motor 28, pump 36, laser oscillators 42A, 42B, tool rotating motor 50, and tool moving motor 52 described above are connected to a controller 54. The controller 54 is also connected to a 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 with the welding system 10 will be explained.

[Embodiment 1]
In Embodiment 1, the welding target 12 includes two members abutted against each other in the y direction, ie, a first member 62A and a second member 62B, as shown in FIG. In the drawings, both the first member 62A and the second member 62B are rectangular plate-like members, but the combination is not limited to this.

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

The first member 62A and the second member 62B are arranged such that the first member 62A is arranged on the right and the second member 62B is arranged on the left. The linear end surfaces (second end surfaces) of the members 62B are butted against each other, and the abutted linear end surfaces are fixed by an appropriate jig 26 with the abutted linear end surfaces arranged along the x direction (see FIG. 1).

The first member 62A and the second member 62B have a first laser irradiation area 64A and a second laser irradiation area 64B adjacent to and extending along the abutted end surfaces. The first and second laser irradiation areas 64A and 64B are areas that are irradiated with lasers 44A and 44B, respectively.

During welding, the controller 54 reads the welding program stored in the storage section 56, and drives the table movement motor 28, laser oscillators 42A, 42B, tool rotation motor 50, and tool movement motor 52 according to the program. Thereby, the lasers 44A and 44B output from the laser oscillators 42A and 42B are irradiated from the z direction onto the first laser irradiation area 64A and the second laser irradiation area 64B, respectively. The irradiation positions 66A and 66B of the lasers 44A and 44B are set to the welding target 12 by moving the welding target 12 including the first member 62A and the second member 62B in the +x direction based on the drive of the table moving motor 28. It moves in the −x direction relative to the object.

The light intensity of the lasers 44A and 44B emitted by the laser oscillators 42A and 42B is determined depending on the materials of the first member 62A and the second member 62B, and the laser irradiation areas 64A and 44B of the first member 62A and the second member 62B are 64B are each heated to a predetermined temperature. This temperature is the temperature at which the material in each laser irradiation area softens as atoms constituting the member diffuse through a thermal activation process.

For example, if the first member 62A is made of iron (the melting point of iron is 1538 degrees Celsius), the first member 62 is heated to about 900 degrees Celsius. Further, when the second member 62B is made of 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. Carbon steel is known to take forms such as ferrite (α iron) and austenite (γ iron) depending on the temperature and carbon ratio. 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 spacing between iron atoms in austenite is wider than that in ferrite, other atoms (for example, carbon atoms) are likely to penetrate into the austenite. In other words, the first member 62A that has changed to austenite easily mixes with the aluminum-magnesium alloy that is the material of the second member 62B.

Region 72 shown in FIG. 7 indicates that the carbon steel becomes austenitic. On the other hand, region 74 shows a mixture of ferrite and austenite. As an example, when the carbon content of the carbon steel that 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 being heated, and completely changes to austenite. The temperature of change (at which austenitic transformation begins) is approximately 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 can be easily mixed with the second member 62B.

FIG. 8 is a state diagram of the aluminum magnesium alloy that is the material of the second member 62B. It is known that aluminum-magnesium alloys become solid solutions of aluminum depending on the temperature and magnesium ratio. At this time, other atoms (for example, magnesium atoms) are likely to enter. That is, the second member 62B that has changed into a solid solution of aluminum easily mixes with the carbon steel that is the material of the first member 62A.

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 that 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 300-550°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 is 500° C., the second member 62B can be easily mixed with the first member 62A.

When the first member 62A and the second member 62B are heated to the above-mentioned temperatures, they become easier to mix, that is, are in a softened state.

In this state, the stirring rotary tool 48 of the stirring device 46 rotates based on the drive of the tool rotation motor 50 and, based on the drive of the tool moving motor 52, irradiates the softened first member 62A with the first laser. 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 stirred, and the stirred first member 62A is mixed with the softened adjacent second member 62B, thereby forming the first member 62A and the second member 62B. A molten pool 78 shown in FIG. 4 is formed at the boundary.

As described above, the stirring rotary tool 48 is inserted into the first laser irradiation area 64A and stirs 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, resulting in an intermetallic structure in which the proportion of iron atoms is higher than the proportion of aluminum atoms. Compounds (eg, FeAl, FeAl ₂ , Fe ₃ Al, etc. shown in FIG. 9) are produced. As known to those skilled in the art, intermetallic compounds such as FeAl, _FeAl2 , _Fe3Al have greater mechanical _strength compared to intermetallic compounds such as _Fe2Al5 , _FeAl3 . Furthermore, even if intermetallic compounds Fe ₂ Al ₅ and FeAl ₃ with low mechanical strength are partially generated, the stirring rotary tool 48 stirs the molten pool 78, so that these intermetallic compounds are uniformly dispersed. Therefore, no brittle region is created at the bonding interface.

During the laser welding described above, the pump 36 of the cooler 34 is continuously driven and coolant is supplied to the coolant transport path 30 via the coolant circulation path 32 (see FIG. 1). Thereby, the welding target 12 is cooled from its lower surface 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 a substantially cylindrical first member 162A and a second member having the same or almost the same outer diameter. It is 162B. The materials of the first member 162A and the second member 162B are carbon steel and aluminum magnesium alloy, respectively, which are the same as the first member and the second member of the first embodiment.

The first member 162A and the second member 162B are each rotatably supported around the central axis by appropriate means with their central axes aligned on the same straight line and their end surfaces aligned. The first member 162A and the second member 162B are also coupled to a first motor 168A and a second motor 168B, respectively, and may be coupled in the same direction and at the same speed, or in the same direction and at different speeds, or in different directions. They are designed to rotate at the same speed or at different speeds.

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

The stirring device 146 includes a stirring rotary tool 148 and a tool rotation motor 150 connected thereto, and is supported with the tip of the stirring rotary tool 148 facing the first laser irradiation area 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 area 164A.

In the second embodiment configured in this way, during welding, the first member 162A and the second member 162B are rotated about their central axes based on the driving of the first motor 168A and the second motor 168B. rotated in the same direction or in different directions. In this state, the laser processing machines 140A and 140B apply the first laser 144A and the second laser to the first laser irradiation area 164A and the second laser irradiation area 164B of the first member 162A and the second member 162B. 144B, and the materials of the first laser irradiation area 164A and the second laser irradiation area 164B are heated and softened. In this state, the tool rotation motor 150 and the tool movement motor 152 are driven, and the tip of the rotating stirring rotary tool 148 is inserted into the softened material in the first laser irradiation area 164A to rotationally stir it. Furthermore, the softened material of the second member 162B is drawn into the rotational agitation of the material of the first member 162A, so that the material of the first member 162A in the boundary area between the first member 162A and the second member 162B The material of the second member 162B is mixed with the material of the second member 162B, and an intermetallic compound in which the proportion of iron atoms is higher than the proportion of aluminum atoms (for example, FeAl, FeAl ₂ , Fe ₃ Al, etc.) is generated.

Thus, according to the second embodiment, the first laser 144A and the second laser 144B are applied to the first laser irradiation area 164A and the second laser irradiation area 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. Furthermore, by changing the rotational speed of the first member 162A and the second member 162B, or by rotating them in opposite directions, the softened first member 162A and second member 162B can be efficiently stirred. be done.

[Embodiment 3]
Welding system 210 of Embodiment 3 shown in FIG. 6 is a modification of the welding system of Embodiment 1. The opposing portion) is formed by an obliquely beveled slope 280A, and the end of the second member 262B (the end facing the first member 262A) is formed by a vertical surface 280B orthogonal to the opposing direction. It is configured. The other configurations are the same as in the first embodiment. Therefore, devices or locations that are the same as or correspond to the devices or locations in Embodiment 1 are given the reference numerals with "200" added to the reference numerals in Embodiment 1, and their descriptions are omitted.

According to the third embodiment configured in this way, the laser 244A irradiated to the first laser irradiation area 264A (slope 280A) of the first member 262A is The reflected light is incident on the second laser irradiation area 264B (vertical surface 280B) of the second member 262B facing thereto, thereby heating the second laser irradiation area 264B. Further, the laser 244A reflected by the second laser irradiation area 264B (vertical surface 280B) enters the first laser irradiation area 264A (slope 280A) again and heats the first laser irradiation area 264A. Therefore, according to the third embodiment, both the first laser irradiation area 264A and the second laser irradiation area 264B are efficiently heated. Therefore, the inclination angle of the slope 280A of the first member is preferably an angle (for example, 45 degrees) at which the laser irradiated thereon is reflected toward the second member.

Embodiment 3 described above may be applied to Embodiment 1, and the first laser irradiation area of the first member in Embodiment 1 may be formed by a slope, and the first laser may be irradiated onto this slope. In this case as well, the same effects as in the third embodiment can be obtained.

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

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

Claims (12)

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, the welding method comprising:
When the first member and the second member are butted together, a first region of the first member adjacent to the second member, and a region of the second member adjacent to the first member. a heating step of softening the first material and the second material by respectively irradiating a first laser and a second laser to an adjacent second region;
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 generate an intermetallic compound;
The irradiation area of the first laser on the first member is formed by an obliquely beveled slope,
A welding method, characterized in that the end of the second member is constituted by a vertical plane orthogonal to the opposing direction. 2. The welding method according to claim 1, wherein in the stirring step, a tool is inserted only into the softened first material, and the tool is rotated 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 coaxially arranged with their central axes aligned on the same straight line,
an end surface of the first cylindrical member and an end surface of the second cylindrical member are butted against each other,
3. The welding method according to claim 1, 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. 4. 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 surface,
The second member has a linear second end surface,
3. The welding method according to claim 1, wherein the first end surface and the second end surface are butted against each other. 6. The welding method according to claim 1, wherein the first melting point of the first material is the same as the second melting point of the second material. 6. The welding method according to claim 1, wherein the first melting point of the first material is higher than the second melting point of the second material. 6. The welding method according to claim 1, 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 the first member and the second member are both made of iron. The welding method according to any one of claims 1 to 5, wherein the first member and the second member are both made of aluminum. 10. The welding method according to claim 8, wherein in the heating step, the iron is heated to a temperature at which austenite transformation begins. The welding method according to claim 8 or 10, wherein in the heating step, the aluminum is heated to a state where it becomes a solid solution.

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