JP5193462B2 - Metal joining method - Google Patents

Description

  The present invention relates to a method for joining metal materials, and more particularly to a method for joining metal materials in which a joint portion is covered with a backing material and friction stir welding is performed.

In a conventional method for joining metal materials, a technique for joining metal materials by friction stir welding (FSW = Friction Stir Welding) is known. In friction stir welding, the metal materials to be joined are made to face each other at the joint, a probe provided at the tip of the rotary tool is inserted into the joint, and the rotary tool is rotated and moved along the longitudinal direction of the joint. Then, the two metal materials are joined by causing the metal material to plastically flow by frictional heat. Friction stir welding, as a general rule, can obtain good joint strength, but the part on the opposite side (front side) to the side where the probe is inserted (rear side) becomes insufficient due to insufficient heat input. There is a risk of insufficient strength. Therefore, Patent Document 1 describes a technique for performing friction stir welding by disposing a heat shielding member (backing material) made of ceramics or the like having low thermal conductivity on the back side of the joint. Patent Document 2 describes a technique in which an anvil containing a metal and a nitride is disposed on the back side of a joint and friction stir welding is performed.
JP 2001-121274 A JP-T-2004-528990

  However, even if the backing material is arranged on the back side of the joint as in the above technique, the joint strength of the joint may be insufficient. Moreover, since a big load is applied to the back surface side of a junction part via a to-be-joined material from the rotary tool inserted in the junction part, the intensity | strength of backing material may be insufficient. In particular, when the material to be joined is a material having a high hardness and a high melting point such as stainless steel, the joining strength tends to be insufficient on the back side of the joining portion, and a large load is applied, so that the strength of the backing material tends to be insufficient.

  In view of such circumstances, the present invention intends to provide a metal material joining method capable of performing friction stir welding even when joining materials to be joined having high hardness and high melting point. Is.

  In the present invention, two metal materials are opposed to each other at the joint, and one side of the joint is covered with a backing material having a thermal conductivity of 15 W / mK or less and a bending strength at 900 ° C. of 500 MPa or more. This is a metal material joining method in which a rod-shaped rotating tool is inserted from the other side of the part and the rotating tool is rotated to join two metal materials.

  According to this configuration, since the joint portion is covered with the backing material having a thermal conductivity of 15 W / mK or less and low thermal conductivity, it is possible to further prevent the diffusion of heat from the back side of the joint portion. Heat is uniformly applied to the entire surface, and good bonding can be obtained in the entire region from the front surface side to the back surface side of the bonding portion. Moreover, since the backing material has a bending strength at 900 ° C. of 500 MPa or more, the backing material has sufficient strength even when a large load is applied from the rotating tool through the material to be joined during friction stir welding. For this reason, according to the said structure, even if it is a to-be-joined material which has high hardness and high melting | fusing point, friction stir welding can be performed more favorably.

  In the metal material joining method of the present invention, (1) the end portions of the plate-like metal material are brought into contact with each other to form a joint portion, and the rotary tool is moved while being rotated along the longitudinal direction of the joint portion. Friction stir welding that joins metal materials, (2) Spot friction stir welding where the ends of plate-shaped metal materials are butted together to form a joint, and the rotary tool is rotated without moving at the joint ( (Spot FSW), (3) Spot friction stir welding where metal materials are overlapped at the joint, a rotating tool is inserted into the joint, and the rotating tool is rotated without moving at that location to join the metal materials together. (4) Friction stir welding in which metal materials are overlapped at the joint, a rotary tool is inserted into the joint, and the rotary tool is moved while rotating along the longitudinal direction of the joint to join the metal materials together. 1) includes four aspects and combinations of these - (4).

  In this case, the backing material may be formed by coating a base material having a bending strength at 900 ° C. of 500 MPa or more with a coating material having a thermal conductivity of 15 W / mK or less.

Alternatively, the backing material is preferably a material containing Si ₃ N ₄ .

When such is backing strip and with those containing _Si 3 _{N 4,} for _Si 3 _{N 4} is the thermal conductivity is as low as approximately 13W / mK, and 800MPa or more in bending strength at 1000 ° C., high Even when joining materials to be joined having hardness and high melting point, friction stir welding can be performed more satisfactorily.

  In this case, the metal material preferably has a melting point of 1000 ° C. or higher.

  In the present invention, the thermal conductivity of the backing material is low and the strength of the backing material is high, so that the present invention is more effective particularly when joining a metal material having a melting point of 1000 ° C. or higher and a high joining temperature.

  In this case, the metal material preferably contains Fe.

  In the present invention, since the thermal conductivity of the backing material is low and the bending strength is high, particularly when joining objects to be joined that have a high melting point and need to apply a large load from a rotating tool during friction stir welding, such as Fe. It is effective.

  In this case, the metal material is preferably a plate-like material having a thickness of 13 mm or less.

  When a thin plate-like material is friction stir welded, the heat applied from the rotary tool easily escapes from the joined portion, so that the joining strength on the back surface side of the joined portion tends to decrease. However, in the present invention, heat is more evenly applied from the front surface side to the back surface side of the joint portion. Therefore, even when a thin plate material having a thickness of 13 mm or less is joined, the joint strength on the back surface side of the joint portion is reduced. Hateful.

  According to the method for joining metal materials of the present invention, even when joining materials to be joined having high hardness and high melting point, friction stir welding can be performed more satisfactorily.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing an embodiment of a method for joining metal materials according to the present invention. In the present embodiment, as shown in FIG. 1, the end portions of the plate-like metal materials 1 and 2 are butted together at the joint portion 3, and the back surface side of the joint portion 3 is covered with the plate-like backing material 4. 3, the probe 6 of the rotary tool 5 is inserted from the surface side of the metal 3, and the metal materials 1 and 2 are joined together.

  In this embodiment, a light alloy material containing Al or the like can be applied as the metal materials 1 and 2, but in this embodiment, heat is applied more uniformly from the front surface side to the back surface side of the joint. Therefore, it is preferable to apply a high melting point material having a melting point of 1000 ° C. or higher, or a steel material containing Fe or the like. Specifically, for example, carbon steel, alloy steel, austenitic stainless steel such as SUS304, SUS301L, and SUS316L, ferritic stainless steel such as SUS430, or duplex stainless steel can be applied. Alternatively, different materials can be applied as the metal materials 1 and 2 instead of the same material. Specifically, for example, joining of carbon steels such as joining of SS400 and S45C, joining of carbon steel and stainless steel such as joining of SS400 and SUS304, joining of light alloys such as joining of A5083 and AZ41, etc. The joining method of the present embodiment can perform joining, joining of aluminum alloys, which are non-heat treated materials such as A5083 having a large plate thickness, and joining of non-heat treated materials and heat treated materials such as joining of A5083 and A6N01. .

  Further, in the present embodiment, it is possible to uniformly apply heat from the front surface side to the back surface side of the joint portion, and even when a thin plate-shaped material that easily escapes heat is joined, Since a temperature gradient is unlikely to occur between the rear surface side and the metal materials 1 and 2, it is preferable to apply a plate-like material having a thickness of 13 mm or less. When the metal materials 1 and 2 are aluminum alloy extruded shapes such as 6N01 and 7N01, it is preferable to apply a plate-like material having a thickness of 13.0 mm or less. Further, when the metal materials 1 and 2 are stainless steel, it is preferable to apply a plate-like material having a thickness of 4.5 mm or less, and more preferably a plate-like material having a thickness of 1.5 mm or less. It is more preferable to apply.

The backing material 4 may be made of a material having a thermal conductivity of 15 W / mK or less and a bending strength at 900 ° C. (more preferably 1000 ° C.) of 500 MPa or more, particularly preferably 800 MPa or more. possible, this embodiment applies the backing material 4 consisting of _Si 3 _{N 4.} As the backing material 4, any material having a thermal conductivity of 15 W / mK or less and a bending strength at 900 ° C. (more preferably 1000 ° C.) of 500 MPa or more, particularly preferably 800 MPa or more can be applied. For example, zirconia, silicon carbide, hafnia (HfO ₂ ), or the like can also be applied. The backing material 4 can be formed by coating a base material having a bending strength at 900 ° C. of 500 MPa or more with a coating material having a thermal conductivity of 15 W / mK or less. For example, carbon steel A material obtained by coating a base material with a coating material such as hafnia, Al ₂ O ₃ , Si ₃ N ₄ , or zirconia can be used.

As shown in FIG. 1, the rotary tool 5 has a substantially cylindrical shape, and includes a substantially columnar probe 6 having a smaller diameter than the main body at the tip. Note that a probe is not necessarily required, and in some cases, a substantially cylindrical rotating tool having no probe may be used. The material of the rotary tool 5 is, for example, a tool steel such as SKD61 steel standardized by JIS, a cemented carbide made of tungsten carbide (WC) or cobalt (Co), or a ceramic such as Si ₃ N ₄ , or It can be made of a refractory metal such as W or Mo. The distance between the backing material 4 and the tip of the probe 6 of the rotary tool 5 inserted into the joint portion 3 is preferably as short as possible so as not to cause an unjoined portion, and is 0.3 to 0.05 mm. Preferably, it is less than 0.01 mm, ideally 0 mm.

As shown in FIG. 1, in this embodiment, the metal material 1 is inserted by inserting the probe 6 of the rotary tool 5 into the joint 3 and moving the rotary tool 5 along the longitudinal direction of the joint 3 while rotating the rotary tool 5. , 2 can be joined. In the present embodiment, since the backing material 4 made of Si ₃ N ₄ having a low thermal conductivity is applied, even when stainless steel having a high melting point is joined, the heat from the rotary tool 5 is joined. 3 is difficult to diffuse, the heat distribution is uniform from the front surface side to the back surface side of the joint portion 3, and uniform stirring is obtained, so that more stable joining is obtained and the joining strength is improved.

Moreover, in this embodiment, since the backing material 4 made of Si ₃ N ₄ having excellent strength at the temperature at the time of joining is applied, 1000 kg or more is applied from the rotary tool 5 to the backing material 4 at the time of joining in order to have high hardness. Even when joining the stainless steel to which a load of 1 mm is applied, it is possible to perform the joining without causing the strength of the backing material 4 to be insufficient.

  Moreover, in this embodiment, since the heat | fever can be efficiently given to the junction part 4 by the function of the backing material 4, even if it makes a joining speed faster than the conventional method, it can give sufficient heat input, As a result, the joining speed can be improved.

  Further, in the present embodiment, the temperature of the joint portion is further increased by the action of the backing material 4, and the heat distribution is uniform from the front surface side to the back surface side of the joint portion 3. And the burden on the rotary tool 5 is reduced, so that the life of the rotary tool 5 can be improved.

  Moreover, in this embodiment, even if the metal materials 1 and 2 are plate-shaped materials with a thickness of 13 mm or less, heat is given more uniformly from the front surface side to the back surface side of the joint portion by the action of the backing material 4. For this reason, even when a thin plate material having a thickness of 13 mm or less in which heat is easily diffused is bonded, the bonding strength on the back surface side of the bonded portion is unlikely to decrease. In the present embodiment, even when a thin plate-like material having a thickness of 13 mm or less is joined, the temperature gradient at the joined portion 3 is reduced, so that the life of the rotary tool 5 can be improved.

  Further, in the present embodiment, when friction stir welding is performed as in stainless steel, even when a metal material that is likely to be corroded due to distortion of the joint or an intermetallic compound is joined, the backing material 4 works. Since the degree of stirring of the joint portion 3 is increased and the distortion of the joint portion 3 is reduced, corrosion of the joint portion 3 can be prevented.

  In addition, in this embodiment, the metal materials 1 and 2 are easily softened by the action of the backing material 4 and the plastic flow of the metal materials 1 and 2 is promoted. A good dissimilar joint with few defects can be obtained.

  FIG. 2 is a diagram showing a method for joining metal materials according to another embodiment of the present invention. As shown in FIG. 2, in the present embodiment, the metal materials 1 and 2 are overlapped at the joint 3, the rotary tool 5 is inserted into the joint 3 through one metal material 1, and the rotary tool 5 is rotated. Metal materials 1 and 2 are joined together. Similarly, the friction stir welding can be performed even in the wide joint portion 3 by sequentially inserting and rotating the rotary tool 18 in other locations.

  In addition, the joining method of the metal material of this invention is not limited to above-described embodiment, Of course, various changes can be added within the range which does not deviate from the summary of this invention.

  Next, an experimental result in which the inventor actually joined a metal material by the metal material joining method of the present invention will be described.

Experimental example 1
A SUS304 plate material and a SUS301L-DLT plate material having a thickness of 1.5 mm were prepared. The prepared SUS304 board | plate material and the SUS301L-DLT board | plate material were joined by the method shown in FIG. 1, and the test piece was created. A plate material made of Si ₃ N ₄ was used for the backing material 4, and a rotating tool made of Si ₃ N ₄ was also used as the rotating tool 5. The rotating speed of the rotating tool 5 was 600 rpm, and the joining speed was changed to create a test piece. Three test pieces were prepared for each joining speed, and a tensile strength test was performed for each. For comparison, a plate material made of stainless steel was applied as the backing material 4 to prepare test pieces in the same manner, and a tensile strength test was performed.

3 and 4 are graphs each showing a joining result when a SUS304 material and a SUS301L-DLT material are joined by the above-described method. In addition, the rotational pitch in FIGS. 3 and 4 means a joining speed (mm / min) / rotational speed (rpm). 3 and 4, it is understood that when a plate material made of Si ₃ N ₄ is used for the backing material 4, high tensile strength can be obtained at any joining speed. Also, from FIGS. 3 and 4, when a plate material made of Si ₃ N ₄ is used for the backing material 4, almost the same stable tensile strength is obtained for the three test pieces at most joining speeds. It can be seen that the value is also high.

5 and 6 are graphs showing the joining results when a SUS304 material and a SUS301L-DLT material are joined using a stainless steel backing material. 5 and 6, when a plate made of stainless steel is used for the backing material 4, the tensile strength is higher than that when a plate made of Si ₃ N ₄ is used for the backing material at any joining speed. It can be seen that the variation in tensile strength among the three test pieces is large. In addition, when a stainless steel backing material is used, a defect occurs in the bonded portion at a bonding speed of 600 mm / min for the SUS304 material and at a bonding speed of 540 mm / min for the SUS301L-DLT material, which makes it impossible to create a test piece. It was possible.

In order to confirm the effect of the backing material 4, a thermocouple was inserted into the joint portion 3 from below, and the temperatures of the back surfaces of the metal materials 1 and 2 were measured. FIG. 7 is a graph obtained by measuring the temperature of the back surface of the joint 3 in Experimental Example 1. FIG. 7 shows time on the horizontal axis and temperature on the vertical axis, and the rotating tool adds a portion where a thermocouple is arranged, and shows how the measured temperature rises and then falls. As shown in FIG. 7, when the Si ₃ N ₄ backing material 4 and the stainless steel backing material were used, the joining speed was 60 mm / min or 420 mm / min. However, it can be seen that the case where the backing material ₄ of Si ₃ N ₄ is used is kept at a higher temperature.

Further, in the case where the plate material made of Si ₃ N ₄ is used for the backing material 4 and the case where a stainless steel plate material is used, the SUS304 material is bonded nine times each using one rotating tool 5. And the degree of wear of the rotating tool was measured. In each case, the rotational speed of the rotary tool 5 was 600 rpm, and the joining speed was 420 mm / min. Further, in each case, the diameter of the main body (shoulder) of the rotary tool was 15 mm, and the diameter of the probe 6 was 5 mm. As shown in FIG. 8, when a stainless steel plate was used for the backing material 4, the probe diameter was worn from 5.00 mm to 4.80 mm after 9 times of joining. On the other hand, when the plate material made of Si ₃ N ₄ was used for the backing material 4, the probe 5 was only slightly reduced to 4.95 mm after 9 times of joining.

Further, in the case of using the above-mentioned backing material composed of Si ₃ N ₄ and the case of using the backing material of stainless steel, a salt spray test for 1000 hours was performed on the test pieces joined in each case. As a result, compared with the amount of rust generated on the test piece made of the stainless steel backing material, the amount of rust produced on the test piece made of the Si ₃ N ₄ backing material was drastically reduced to at least 1/10 or less.

It is a perspective view which shows one Embodiment of the joining method of the metal material which concerns on this invention. It is a perspective view which shows another embodiment of the joining method of the metal material which concerns on this invention. It is a graph which shows the joining result at the time of joining SUS304 material by the method of this embodiment. It is a graph which shows the joining result at the time of joining SUS301L-DLT material by the method of this embodiment. It is a graph which shows the joining result at the time of joining SUS304 material using the backing material of stainless steel. It is a graph which shows the joining result at the time of joining a SUS301L-DLT material using the backing material of stainless steel. 6 is a graph showing the temperature of the back surface of a joint part 3 in Experimental Example 1. FIG. It is a figure which shows the degree to which a rotary tool is worn out in Experimental Example 1.

Explanation of symbols

1, 2 ... Stainless steel material, 3 ... Joint, 4 ... Backing material, 5 ... Rotating tool, 6 ... Probe.

Claims (5)

When the metal material is SUS301L-DLT material, the two metal materials which are plate-like materials having a thickness of 1.5 mm are opposed to each other at the joint, and the thermal conductivity is 15 W / mK or less and bending at 900 ° C. Cover one side of the joint with a backing material having a strength of 500 MPa or more, insert a rod-shaped rotary tool from the other side of the joint, rotate the rotary tool, and Method of joining metal materials to be joined.   2. The metal material joining method according to claim 1, wherein the backing material is formed by coating a base material having a bending strength at 900 ° C. of 500 MPa or more with a coating material having a thermal conductivity of 15 W / mK or less. The metal material joining method according to claim 1, wherein the backing material includes Si ₃ N ₄ .   The metal material joining method according to claim 1, wherein the metal material has a melting point of 1000 ° C. or higher.   The metal material joining method according to claim 1, wherein the metal material contains Fe.

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