JP7385194B2 - Dissimilar materials joining methods and composite members - Google Patents

Description

The present invention relates to a method for joining dissimilar materials and a composite member using friction stir molding.

In recent years, in order to reduce the weight of automobiles and aircraft, for example, it is expected that the use of multi-material parts will rapidly progress over the next 10 to 20 years. Research and development of bonding technology (dissimilar metals) is being actively conducted.

Regarding the joining of dissimilar materials, mechanical joining methods that can be used regardless of the materials to be joined, and metallurgical joining methods such as resistance spot welding are conventionally known.

Mechanical joining methods include screws, conventional rivets, self-piercing rivets, blind rivets, etc., but there is a problem in that the fasteners (rivets) add weight.

In addition, as a metallurgical joining method, in recent years, research has been conducted on the use of friction stir welding (FSW) and friction stir spot welding (FSSW) to join dissimilar materials. There is a problem in that there are restrictions on thermal conditions for controlling the thickness of the intermetallic compound layer.

On the other hand, the present inventor has proposed a method for joining dissimilar materials using friction stir forming (FSF) (Patent Document 1). Specifically, the welding method of Patent Document 1 uses a friction stir tool having a protrusion on the flat end portion of a cylindrical shape to (a) attach a plate-shaped material to the upper surface of a plate-shaped material to be welded with a pilot hole drilled therein. (b) A friction stir tool is rotated and lowered against the welding material, and the material is press-fitted while being fed in a predetermined horizontal direction to create friction. Stir. As a result, the fluidized joining material deforms and fills the cavity of the molding die to form a rivet-like joint bulge, and mechanically joins the joining material to the plate-shaped materials to be joined. ing.

Japanese Patent Application Publication No. 2018-51606

Mechanical behavior and fracture of easily-decomposable dissimilar-materials-joint fabricated by friction stir forming (Japan Society of Mechanical Engineers) Mechanical Engineering Journal Volume 5, No. 2 23 March, 2018 Paper No.17-00496

However, in the case of the joining method of Patent Document 1, a rivet-like joint is formed using the fluidized joining material, so the flatness of the joint is impaired by the protruding head of the joint, which is an issue that should be improved. It was considered as In addition, in the case of the joining method of Patent Document 1, in order to form the head of the rivet-like joint part, it is necessary to align the cavity of the mold and the pilot hole of the material to be joined, which increases the work load. It was thought that there were areas that needed improvement.

The present invention has been made in view of the above circumstances, and it is possible to join dissimilar materials with excellent bonding strength while ensuring the flatness of the joint with a relatively simple work process. The object of the present invention is to provide a method for joining materials and a composite member using the method.

In order to solve the above-mentioned problems, the dissimilar material joining method of the present invention is a dissimilar material joining method that joins a material to be joined and a joining material using a friction stir tool, the method comprising:
The following steps:
(1) forming a through hole in the material to be joined by punching using a punch and a die;
(2) A joining material is brought into contact with the first surface of the material to be joined located at one end of the through hole, and a patch plate is brought into contact with the second surface of the material to be joined located at the other end. Process;
(3) By pressing the friction stirring tool into the welding material while rotating and friction stirring, a part of the fluidized welding material is filled into the through hole of the welded material. and (4) a step of removing the caul plate from the material to be joined,
In the step (1), a groove or an inclined fracture surface is formed on the inner surface of the through hole of the material to be joined, and in the step (3), the joining material is formed through the groove or the fracture surface. It is characterized by fitting into the through hole.

The composite member of the present invention is a composite member in which a joining material is joined to one side of a material to be joined by friction stir molding,
The material to be joined is provided with a through hole in which a drooping or inclined fracture surface is formed on the inner surface,
The through-hole is filled with the joining material, the joining material is fitted into the through-hole via the bulge or the fractured surface, and the other surface of the material to be joined is connected to the through-hole. It is characterized in that the bonding material filling the hole is formed flush with the bonding material.

The method for joining dissimilar materials of the present invention can join dissimilar materials with excellent joint strength while ensuring the flatness of the joint through relatively simple work steps. Further, the composite member of the present invention has a flat joint portion and excellent joint strength.

FIG. 1 is a cross-sectional view illustrating an embodiment of the dissimilar material joining method of the present invention. (A) is a diagram showing a form in which spot friction stir forming (FSF) is performed without sending the friction stir tool in the horizontal direction. (B) is a diagram showing a form in which friction stir forming (FSF) is performed by press-fitting a friction stir tool while feeding it in a horizontal direction. (A) is a schematic diagram showing a mechanism in which a through hole is formed by punching (press shearing) using a punch and a die. (B) is a schematic diagram showing the sag and fracture surface formed on the inner surface of the through hole. FIG. 2 is a schematic diagram illustrating a form in which a curved surface (R), a step, or an inclination is provided on the outer edge of a punch or the inner edge of a hole in a die. 1 is a front view showing a friction stir tool used in Example 1. FIG. FIG. 3 is a diagram showing the volume of a bonding material filled in a hole formed by friction stir molding. This is a photograph of the joining material and the parts to be joined after friction stir forming (FSF). FIG. 2 is a front view (A) and a side view (B) of a cross tensile test piece used in Example 2. FIG. FIG. 3 is a diagram showing the relationship between the clearance between the punch and the die in step (1) and the cross tensile strength of the bond between the bonding material and the bonded material.

An embodiment of the dissimilar material joining method of the present invention will be described. FIGS. 1A and 1B are cross-sectional views illustrating an embodiment of the dissimilar material joining method of the present invention, respectively. FIG. 1(A) is a diagram showing a form in which spot friction stir forming (FSF) is performed without sending the friction stir tool in the horizontal direction. FIG. 1(B) is a diagram showing a form in which friction stir forming (FSF) is performed by press-fitting a friction stir tool while feeding it in a horizontal direction.

The dissimilar material welding method of the present invention uses a friction stir tool 1 to join a welded material 2 and a welding material 3.

The friction stir tool 1 may be one that is used for friction stir forming (FSF), and its specific form is not limited, but for example, the friction stir tool 1 described in Patent Document 1 can be exemplified. Specifically, as illustrated in FIGS. 1A and 1B, the friction stirring tool 1 includes a substantially cylindrical main body and a protrusion provided on a flat end portion 12 located at the lower end of the main body 11. It is preferable to include a section 13. Moreover, it is preferable that the friction stir tool 1 is formed of a hard and highly heat-resistant heat-resistant alloy or the like.

The shape of the protrusion 13 is not particularly limited, and examples thereof include a disk shape, a cylindrical shape, a conical shape, a hemispherical shape, a screw shape, and the like. Further, the flat end portion 12 on which the protrusion 13 is provided can be provided with an inclination angle θ of, for example, within 5°, as a whole or in part, if necessary. The magnitude of the inclination angle θ is preferably determined by taking into account the horizontal feeding force of the friction stirring tool 1, the occurrence of burrs, the aesthetic condition of the movement marks (tool marks) 31 of the friction stirring tool 11, etc. . Note that if the volume of the void in the through hole 21 of the material to be joined 2, which will be described later, is small, the protrusion 13 can be omitted. Further, as the volume of the protrusion 13 of the friction stir tool 1 becomes larger, it is possible to fill a portion of the welding material 3 into the through hole 21 having a larger volume.

Although the shape of the material to be joined 2 is not particularly limited, it is preferably plate-shaped, for example. Further, the material of the material to be joined 2 is not particularly limited, and examples thereof include hard steel plates, titanium, glass, CFRP, and the like. When the material to be welded 2 is plate-shaped, the thickness of the material to be welded 2 is not particularly limited, and may vary depending on the cross-sectional area of the through hole 21, the conditions for fluidizing the welding material 3, and the design of the friction stir tool 1, which will be described later. It can be designed taking into consideration the operating conditions and other factors. Specifically, for example, the thickness of the material 2 to be joined can be up to 10 times the thickness of the material 3 for joining. Further, regarding the design of the material to be joined 2, the description in Non-Patent Document 1 can be considered, for example.

Although the shape of the joining material 3 is not particularly limited, it is preferably plate-shaped, for example. Further, the material of the joining material 3 is not particularly limited, but examples thereof include aluminum and its alloys, magnesium alloys, copper and its alloys, titanium and its alloys, steel, and the like. In addition, when the joining material 3 is plate-shaped, its thickness can be increased depending on the depth at which the friction stir tool can be press-fitted within the range of the processing equipment power and the overall length and strength of the friction stir tool. It is possible. Therefore, the thickness of the welding material 3 is not particularly limited as long as it is larger than the height of the protrusion 13, but for example, from the practical range of power of the processing equipment and the practical strength range of the friction stir tool, The thickness of the material 3 is preferably less than 30 mm. As a rough guide, in the case of friction stir forming (FSF), in which a friction stir tool is fed horizontally and press-fitted, a thin plate with a thickness of less than 3 mm, and a medium plate with a thickness of 3 mm or more and less than 6 mm are preferred joining materials 3. In addition to the above example, in the case of spot friction stir forming (FSF) in which the friction stir tool is only press-fitted without sending it horizontally, thick plates with a thickness of 6 mm or more and less than 30 mm are preferably joined. This can be exemplified as the material 3 for use.

The dissimilar material joining method of the present invention includes the following steps (1) to (4):
(1) A step of forming a through hole 21 in the material to be joined 2 by punching using a punch and a die,
(2) The joining material 3 is brought into contact with the first surface portion 2A of the material to be welded 2 located on one end side of the through hole 21, and the patch plate 6 is brought into contact with the second surface portion 2B of the material to be joined 2 located on the other end side. The process of bringing the two into contact;
(3) By pressing the friction stirring tool 1 into the welding material 3 while rotating it and friction stirring, a part of the fluidized welding material 3 fills the through hole 21 of the welded material 2. The process of making
(4) Includes the step of removing the backing plate 6 from the material 2 to be joined.

Each step will be explained below.

In step (1), a through hole 21 is formed in the material to be joined 2 by punching (press shearing) using a punch and a die.

FIG. 2 is a schematic diagram showing a mechanism in which the through hole 21 is formed by punching (press shearing) using a punch and die.

As illustrated in FIG. 2, in the punching process, shear cracks are generated in the material from the part where the shoulder 41 of the die 4 and the edge 51 of the punch 5 come into contact, and when these cracks are connected, the through hole 21 is formed. be done. Therefore, an inclined fracture surface 21a is formed on the inner surface of the through hole 21 in the shear direction due to the difference (clearance) between the outer diameter of the punch 5 and the inner diameter of the die 4. Furthermore, depending on the clearance conditions, a droop 21b is also formed. In step (1), a droop 21b or an inclined fracture surface 21a is formed on the inner surface of the through hole 21 of the material to be joined 2 by punching. Therefore, in step (1) of the method for joining dissimilar materials of the present invention, it is preferable to set the material, thickness, clearance, etc. of the materials to be joined 2 so that the droop 21b or the fracture surface 21a is formed.

FIG. 3 is a schematic diagram illustrating another form of the punch and die. For example, in order to obtain a larger droop 21b, the outer edge of the punch 5 and the inner edge of the hole of the die 4 may be provided with a curved surface (R), a step, or an inclination, as shown in FIG.

The clearance at which a preferable bond strength is generated is preferably 10% or more of the thickness of the weld materials 2, for example, when the material of the weld materials 2 is mild steel. is more preferably 30% or more. Similarly, as a guideline for generating a preferable bonding strength, the clearance is 15% or more of the thickness of the welded materials 2 in the case of hard steel, 12% or more of the thickness of the welded materials 2 in the case of silicon steel, In the case of stainless steel, 12% or more of the thickness of the material to be joined 2, in the case of copper, 7% or more of the thickness of the material to be joined 2, in the case of brass, 10% or more of the thickness of the material to be joined 2, phosphorus In the case of bronze, 10% or more of the thickness of the material 2 to be joined, in the case of nickel silver, 10% or more of the thickness of the material 2 to be joined, in the case of aluminum, 8% or more of the thickness of the material 2 to be joined, Burmalloy In this case, a range of 8% or more of the thickness of the material to be joined 2 can be exemplified.

Further, the number of through holes 21 formed in the material to be joined 2 may be one or more than two, and in the case of two or more, the size of each through hole 21 may be the same diameter or different diameters. good. Further, the cross-sectional shape of the through hole is not limited to a circular shape, and may be, for example, a substantially elongated hole shape, a slit shape, a curved hole shape, or the like.

In step (2), the joining material 3 is brought into contact with the first surface 2A of the materials 2 to be joined located at one end of the through hole 21, and the material 3 for joining is brought into contact with the second surface 2B of the materials 2 to be joined located at the other end. The backing plate 6 is brought into contact.

In the embodiment illustrated in FIGS. 1A and 1B, the joining material 3 is in contact with the first surface portion 2A on the upper side of the materials 2 to be joined, and the backing plate is in contact with the second surface portion 2B on the lower side of the materials 2 to be joined. 6 are in contact with each other, and the top and bottom of the through hole 21 are closed. The backing plate 6 only needs to be able to close the lower side of the through hole 21, and its material, thickness, etc. can be designed as appropriate.

In step (3), a part of the fluidized welding material 3 is inserted into the welding material 3 through the through hole of the welded material 2 by pressing the friction stirring tool 1 into the welding material 3 while rotating and performing friction stirring. Fill it to 21.

As shown in FIGS. 1(A) and 1(B), the friction stirring tool 1 can be lowered while being rotated and, if necessary, fed in a predetermined horizontal direction, press-fitted and friction stirred.

For the design, operating conditions, etc. of the friction stir tool 1, the description in Patent Document 1 can be considered, for example.

Specifically, for example, the area of the flat end of the rotating friction stir tool 1, the volume of the protrusion, the rotation speed, the distance and speed of movement in the horizontal direction, the pressing force and amount of press-fitting when press-fitting, etc. ,
1) Type (softening temperature) and thickness of bonding material 3;
2) Thickness of the material to be joined 2, diameter of the through hole 21,
3) Conditions for fluidizing the welding material 3 can be determined in consideration of the formation of burrs at the contact portion between the outer edge of the friction stir tool 1 and the welding material 3.

In friction stir forming (FSF), the fluidized joining material 3 has excellent ability to fill the inside of the mold, so it can be filled into the through holes 21 of the materials 2 to be joined. Further, since one side (lower side) of the through hole 21 of the material to be joined 2 is closed by the backing plate 6, leakage of the fluidized joining material 3 from the through hole 21 is suppressed. Since the through hole 21 is formed with a recess 21b or an inclined fracture surface 21a, the fluidized joining material 3 penetrates through the recess 21b or the fracture surface 21a by utilizing this slight inclination. It can be mechanically interlocked and fitted into the hole 21 to form an interlock. Therefore, the material to be joined 2 and the joining material 3 can be joined and integrated with excellent joining strength.

Furthermore, since the volume of the void in the through hole 21 is determined by the thickness of the welded material 2 and the cross-sectional area of the through hole 21, the conditions for fluidizing the welding material 3, the design and operating conditions of the friction stir tool 1, etc. In consideration of this, for example, in step (1), adjustment can be made such that the thicker the material to be joined 2, the smaller the cross-sectional area of the through hole.

In step (4), the backing plate 6 is removed from the material 2 to be joined.

By removing the backing plate 6 from the material 2 to be joined, the lower surface of the material 2 to be joined is exposed. In step (3), since the fluidized joining material 3 is prevented from leaking from the through hole 21 by the backing plate 6, the joining material 3 filling the lower surface 2B of the welded material 2 and the through hole 21 is are formed flush with each other, ensuring the flatness of the joint.

As described above, in the method for joining dissimilar materials of the present invention, a droop 21b or an inclined fracture surface 21a is formed in the through hole 21 of the material to be joined 2, and by utilizing this inclination, the fluidized joining material 3 is Since it mechanically fits into the through hole 21, it has excellent bonding strength. Furthermore, as in Patent Document 1, for example, there is no need to align the cavity of the mold and the prepared hole of the material to be joined, and the work process is simple. Further, there is no need to form a protruding joint portion, and the flatness of the joint can be achieved.

Further, the composite member 7 of the present invention can be obtained by the above-described dissimilar material joining method. That is, in the composite member 7, the material to be joined 2 and the joining material 3 are joined by friction stir molding. The material to be joined 2 is provided with a through hole 21 in which a droop 21b or an inclined fracture surface 21a is formed on the inner surface. The joining material 3 is in contact with the first surface portion (upper surface in FIG. 1) 2A of the material to be joined 2 located on one end side of the through hole 21, and a part of the joining material 3 fills the through hole 21. However, the joining material 3 is fitted into the through hole 21 via the groove 21b or the broken surface 21a. The second surface portion (lower surface in FIG. 1) 2B of the material to be joined 2 located on the other end side of the through hole 21 and the joining material 3 filling the through hole 21 are formed flush with each other.

The dissimilar material joining method and composite member of the present invention are not limited to the above embodiments.

Hereinafter, the dissimilar material joining method and composite member of the present invention will be described in more detail along with examples, but the dissimilar material joining method and composite member of the present invention are not limited to the following examples.

<Example 1> Method for determining the through hole diameter of the welded material and the thickness of the welded material
A 3 mm thick A5083P-O aluminum alloy plate was used as the material for friction stir welding, and the welding material was flowed into a hole with an inner diameter of 2 to 9 mm by friction stir molding using a friction stir tool as shown in Figure 4. The volume of the filled bonding material was evaluated.

FIG. 5 shows the volume by hole diameter (Non-Patent Document 1). On the other hand, the diameter of the through hole and the thickness of the material to be joined were determined within a range in which the void volume of the through hole in the material to be joined did not exceed the volume.

<Example 2> Method of forming a joint
A demonstration test of a composite member was conducted using 3mm thick A5083P-O aluminum alloy plates as the material for friction stir welding and 1mm thick SPCE steel plates as the welded parts.

Using a punch with an outer diameter of 4 mm and a circular hole die with an inner diameter of 4.2 to 6 mm, a through hole was punched in the SPCE steel plate (part to be joined) (step (1)). This through hole has a droop and an inclined fracture surface. The members to be joined were placed on a stainless steel plate made of SUS304 (covering plate) and subjected to friction stir molding using a friction stir tool as shown in FIG. 4 (steps (2) and (3)).

In this experiment, the tool was not fed horizontally, and spot friction stir forming (FSF) was performed (Fig. 1 (A)), the spindle rotation speed was 1240 rpm, the press-in depth of the tool was 2.7 mm, and the bottom dead center of press-in was 30 mm. The tool was held in a rotating state for seconds. Thereafter, the caul plate was removed (step (4)).

Figure 6 shows a photograph of the joining material and the parts to be joined after friction stir forming (FSF).

The through-hole made by punching (press shearing) was filled with the bonding material, and no gaps were observed. In addition, although burnt due to frictional heat was observed on the members to be joined, no deformation such as bulges was observed near the through holes, and it was confirmed that the members were flat.

<Example 3> Cross tensile test Cross tensile strength was measured using a cross tensile test piece as shown in FIG. The test machine used was SHIMADZU AUTOGRAPH AG-10TB/AG-X/R, and the crosshead speed was 1 mm/min.

Figure 8 shows the results of the cross tension test.

It was confirmed that the joints formed in the through-holes with a punch-die clearance of up to 0.1mm, which is 10% of the plate thickness, exhibited joint strength, but the cross tensile strength (CTS) was less than 300N. there were. On the other hand, the joints formed by drilling through-holes with a punch-die clearance larger than 0.3 mm, which is more than 30%, exceeded 300 N on average, confirming that they had sufficient joint strength. In addition, since the cross tensile strength of this joint is thought to be proportional to the circumference of the through-hole, it is necessary to devise a prepared hole shape other than circular so that the circumference is longer, or to create a hole with a large number of small circles arranged in high density. It is thought that the strength can be further increased by making improvements such as using holes.

In addition, in many conventional methods of forming high-strength dissimilar material joints, the fasteners protrude outside of the plates to be joined, or the materials to be joined (steel plates) are greatly deformed, or the materials to be joined (steel plates) are brought into contact with tools. This is accompanied by deformation and destruction of the contact surface. On the other hand, the method of this example has no contact between the tool and the material to be joined (steel plate), and the surface of the joint on the material to be joined is flat, making it difficult to recycle due to mechanical joining. In addition to its superiority, it also has uniqueness and superiority in terms of tool life and joint appearance.

1 Friction stirring tool 2 Material to be joined 2A First surface portion 2B Second surface portion 21 Through hole 3 Welding material 4 Die 5 Punch 6 Backing plate 7 Composite member

Claims (4)

A dissimilar material joining method for joining materials to be joined and materials for joining using a friction stir tool, the method comprising:
The following steps:
(1) forming a through hole in the material to be joined by punching using a punch and a die;
(2) A joining material is brought into contact with the first surface of the material to be joined located at one end of the through hole, and a patch plate is brought into contact with the second surface of the material to be joined located at the other end. Process;
(3) By pressing the friction stirring tool into the welding material while rotating and friction stirring, a part of the fluidized welding material is filled into the through hole of the welded material. and (4) a step of removing the caul plate from the material to be joined,
In the step (1), a groove or an inclined fracture surface is formed on the inner surface of the through hole of the material to be joined, and in the step (3), the joining material is formed through the groove or the fracture surface. A method for joining dissimilar materials, characterized by fitting into the through hole. 2. The method for joining dissimilar materials according to claim 1, wherein in the step (1), a difference (clearance) between the outer diameter of the punch and the inner diameter of the die is 8% or more of the thickness of the materials to be joined. 3. The method for joining dissimilar materials according to claim 1, wherein in the step (1), at least one of an outer edge of the punch and an inner edge of the hole of the die is provided with a step or an inclination. A composite member in which a material to be joined and a material for joining are joined by friction stir molding,
The material to be joined is provided with a through hole in which a drooping or inclined fracture surface is formed on the inner surface,
The joining material is in contact with the first surface of the material to be joined located on one end side of the through hole, and a part of the joining material is filled in the through hole, causing the droop or the fractured surface to The welding material is fitted into the through hole through the through hole, and the second surface portion of the welded material located on the other end side of the through hole and the welding material filling the through hole. A composite member characterized by being formed flush with the material.

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