METAL COMPOSITE AND METAL JOINING METHOD

Abstract

A metal composite and a metal joining method that are capable of suppressing an influence on joining strength of a friction stir welded section due to a tool hole formed when a tool is extracted, in the case in which two metals are joined through friction stir welding. In an overlapping section in an axial direction in which a first shaft and a second shaft overlap in the axial direction, an inscribed section in which the first shaft and the second shaft come in contact with each other and an non-inscribed section in which the first shaft and the second shaft do not come in contact with each other are formed. In the non-inscribed section, a plate thickness of the second shaft is decreased. Then, a starting point of a friction stir welded section is formed in the inscribed section, and an endpoint is formed in the non-inscribed section.

Claims

1. A metal composite having a friction stir welded section in which a second metal is friction stir-welded under a first metal, wherein the first metal comprises an inscribed section inscribed in the second metal and a non-inscribed section separated from the second metal, and a starting point of the friction stir welded section is formed in the inscribed section and an endpoint of the friction stir welded section is formed in the non-inscribed section.

2. The metal composite according to claim 1, wherein both of the first metal and the second metal are formed in a cylindrical shape, and the friction stir welded section is formed in a circumferential direction of an outer circumferential surface of the first metal.

3. The metal composite according to claim 1, wherein the friction stir welded section has a first linear section extending from the starting point along the outer circumferential surface of the first metal, and a second linear section bent at a bending angle of 45° or less in a direction away from the starting point with respect to the first linear section and reaching the endpoint along the outer circumferential surface of the first metal.

4. The metal composite according to claim 1, wherein a plate thickness reduction section is formed at either the first metal or the second metal in the non-inscribed section.

5. The metal composite according to claim 4, wherein the plate thickness reduction section is formed at the second metal.

6. A metal joining method of friction stir-welding an overlapping section in which a first metal and a second metal overlap by inserting a tool into the first metal with respect to the overlapping section while pressurizing and rotating the tool, and extracting the tool from the first metal after the tool is moved in a predetermined tangential direction, the metal joining method comprising: forming a gap between the first metal and the second metal in the overlapping section; inserting the tool into the first metal related to an inscribed section in which the gap is not formed; and extracting the tool from the first metal related to a non-inscribed section in which the gap is formed.

7. The metal joining method according to claim 6, wherein the second metal having a cylindrical shape is inserted inside the first metal having a cylindrical shape, and the tool is moved in a circumferential direction of an outer circumferential surface of the first metal.

8. The metal joining method according to claim 6, wherein, when the tool is moved in the circumferential direction of the outer circumferential surface of the first metal, before extracting the tool, a motion of the tool is bent at a bending angle of 45° or less in a direction away from a starting point at which the tool is inserted.

9. The metal joining method according to claim 6, wherein a plate thickness of either the first metal or the second metal is partially reduced.

10. The metal joining method according to claim 9, wherein the plate thickness of the second metal is partially reduced.

11. The metal joining method according to claim 6, wherein a portion or the entirety of the non-inscribed section is removed from the first metal.

12. The metal composite according to claim 2, wherein the friction stir welded section has a first linear section extending from the starting point along the outer circumferential surface of the first metal, and a second linear section bent at a bending angle of 45° or less in a direction away from the starting point with respect to the first linear section and reaching the endpoint along the outer circumferential surface of the first metal.

13. The metal composite according to claim 2, wherein a plate thickness reduction section is formed at either the first metal or the second metal in the non-inscribed section.

14. The metal composite according to claim 3, wherein a plate thickness reduction section is formed at either the first metal or the second metal in the non-inscribed section.

15. The metal joining method according to claim 7, wherein, when the tool is moved in the circumferential direction of the outer circumferential surface of the first metal, before extracting the tool, a motion of the tool is bent at a bending angle of 45° or less in a direction away from a starting point at which the tool is inserted.

16. The metal joining method according to claim 7, wherein a plate thickness of either the first metal or the second metal is partially reduced.

17. The metal joining method according to claim 8, wherein a plate thickness of either the first metal or the second metal is partially reduced.

18. The metal joining method according to claim 7, wherein a portion or the entirety of the non-inscribed section is removed from the first metal.

19. The metal joining method according to claim 8, wherein a portion or the entirety of the non-inscribed section is removed from the first metal.

20. The metal joining method according to claim 9, wherein a portion or the entirety of the non-inscribed section is removed from the first metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1(a) to FIG. 1(c) is a view for describing a dissimilar metals shaftto which a friction stir welding method of the present invention is applied.

[0037] FIG. 2(a) to FIG. 2(c) is a view for describing another dissimilar metals shaft to which the friction stir welding method of the present invention is applied.

[0038] FIG. 3(a) to FIG. 3(f) is a view for describing the friction stir welding method of the present invention.

[0039] FIG. 4 is a view for describing a dissimilar metals shaft according to Variant 1 to which the friction stir welding method of the present invention is applied.

[0040] FIG. 5 is a view for describing a dissimilar metals shaft according to Variant 2 to which the friction stir welding method of the present invention is applied.

[0041] FIG. 6 is a view for describing a dissimilar metals shaft according to Variant 3 to which the friction stir welding method of the present invention is applied.

[0042] FIG. 7 is a view for describing a dissimilar metals shaft according to Variant 4 to which the friction stir welding method of the present invention is applied.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0044] FIG. 1(a) to FIG. 1(c) is a view for describing a dissimilar metals shaft 100 to which a friction stir welding method of the present invention is applied. Further, FIG. 1(a) is a plan view of the dissimilar metals shaft 100 and FIG. 1(b) is a cross-sectional view taken along line A-A of FIG. 1(a). In addition, FIG. 1(c) is an enlarged view of a portion B of FIG. 1(b).

[0045] The dissimilar metals shaft 100 is constituted by a first shaft 11 and a second shaft 12 press-fitted to an inner circumferential surface of the first shaft 11. The first shaft 11 is a cylindrical hollow shaft formed of a light metal, for example, aluminum or an alloy thereof, as a whole. The second shaft 12 is a cylindrical hollow shaft formed of an iron-based metal, for example, stainless steel and in concentric with the first shaft 11.

[0046] As shown in FIG. 1(a), the first shaft 11 and the second shaft 12 are joined, for example, in a spiral shape over two laps through friction stir welding by pressing and rotating an axially overlapping section 40 in which an inner circumferential surface of the first shaft 11 and an outer circumferential surface of the second shaft 12 overlap in an axial direction using a friction stir welding tool 20 (hereinafter, referred to as “a tool”) (FIG. 3). Accordingly, a friction stir welded section 40FSW configured to couple the first shaft 11 and the second shaft 12 is formed in a spiral shape at an outer circumferential surface of the first shaft 11.

[0047] In addition, as shown in FIG. 1(b), the axially overlapping section 40 is constituted by an inscribed section 41 in which the inner circumferential surface of the first shaft 11 comes in contact with the outer circumferential surface of the second shaft 12, and a non-inscribed section 42 in which the inner circumferential surface of the first shaft 11 does not come in contact with the outer circumferential surface of the second shaft 12. In addition, the second shaft 12 has a plate thickness reduction section 12a, and a plate thickness t2 of the non-inscribed section 42 is smaller than a plate thickness t1 of the inscribed section 41. For this reason, a gap d is formed between the first shaft 11 and the second shaft 12 in the non-inscribed section 42.

[0048] In the dissimilar metals shaft 100, a starting point (hereinafter, also simply referred to as “a starting point”) 43 of the friction stir welded section 40FSW is formed in the inscribed section 41, and an endpoint (hereinafter, also simply referred to as “an endpoint”) 44 of the friction stir welded section 40FSW is formed in the non-inscribed section 42.

[0049] Accordingly, the first shaft 11 and the second shaft 12 are not friction stir-welded in the non-inscribed section 42, and the gap d is filled with only a stirred member which is the first shaft 11 softened and stirred by the tool 20. The non-inscribed section 42 including the endpoint 44 is in a state in which the non-inscribed section 42 does not contribute to a joining strength of the friction stir welded section 40FSW. Accordingly, as will be described later with reference to FIG. 2(a) to FIG. 2(c) and FIG. 3(a) to FIG. 3(f), the non-inscribed section 42 of a tool hole 44a can be cut away from the first shaft 11.

[0050] In addition, as shown in FIG. 1(c), a boundary line between the inscribed section 41 and the non-inscribed section 42 has a step difference with an inclination θ (for example, 30° or less).

[0051] FIG. 2(a) to FIG. 2(c) is a view showing another dissimilar metals shaft 200 to which the friction stir welding method of the present invention is applied. Further, FIG. 2(a) is a plan view of the dissimilar metals shaft 200, and FIG. 2(b) is a cross-sectional view taken along line A-A of FIG. 2(a). In addition, FIG. 2(c) is an enlarged view of a portion B of FIG. 2(b).

[0052] The dissimilar metals shaft 200 corresponds to a member in which an area of the first shaft 11 related to the non-inscribed section 42 including the tool hole 44a is removed (cut away) from the dissimilar metals shaft 100. Accordingly, the endpoint 44 is not present in the friction stir welded section 40FSW formed at the outer circumferential surface of the first shaft 11. Since the friction stir welded section 40FSW related to the non-inscribed section 42 is not a section configured to join the first shaft 11 and the second shaft 12 through friction stir welding, even when the area is removed, the joining strength of the friction stir welded section 40FSW is not decreased. Hereinafter, the friction stir welding method of the present invention of manufacturing the dissimilar metals shaft 200 from the dissimilar metals shaft 100 will be described.

[0053] FIG. 3(a) to FIG. 3(f) is a view for describing the friction stir welding method of the present invention. Further, processes are presented in a plan view and a cross-sectional view. In addition, FIG. 3(a) to FIG. 3(c) show processes related to the dissimilar metals shaft 100 and FIG. 3(d) to FIG. 3(f) show processes related to the dissimilar metals shaft 200.

[0054] As shown in FIG. 3(a), the first shaft 11 is inserted into the axially overlapping section 40 in which the inner circumferential surface of the first shaft 11 and the outer circumferential surface of the second shaft 12 overlap in the axial direction while the tool 20 is pressurized and rotated, and the inscribed section 41 is moved in a spiral direction under predetermined joining conditions (a rotational speed and a tool moving speed of the tool 20) in a state in which an insertion depth D (a distance from the outer circumferential surface of the first shaft 11 to a pin tip 21 of the tool 20) is maintained. Further, in order to remove impurities (an oxide film) present between the first shaft 11 and the second shaft 12, the tool 20 grinds off the outer circumferential surface of the second shaft 12 to a predetermined depth K (=the insertion depth D—a plate thickness t11 of the first shaft).

[0055] As shown in FIG. 3(b), when the tool 20 moves on the non-inscribed section 42, an aluminum material softened and stirred by the tool 20 is filled into the gap d. In this case, the gap d (FIG. 1(b)) formed between the first shaft 11 and the second shaft 12 in the non-inscribed section 42 is set such that a depth (distance) thereof is equal to or larger than K. Accordingly, in the non-inscribed section 42, the tool 20 does not grind off the surface of the second shaft 12. As a result, the first shaft 11 and the second shaft 12 in the non-inscribed section 42 are in a state in which friction stir welding is not performed.

[0056] As shown in FIG. 3(c), when the tool 20 is extracted from the first shaft 11, the tool hole 44a is formed at the endpoint 44. The first shaft 11 and the second shaft 12 are not friction stir-welded at the endpoint 44. That is, the non-inscribed section 42 including the endpoint 44 is not contributing to the joining strength of the friction stir welded section 40FSW. Accordingly, the non-inscribed section 42 including the tool hole 44a is preferably removed (cut away).

[0057] The first shaft 11 and the second shaft 12 in the non-inscribed section 42 are in a state in which friction stir welding is not performed. Further, an aluminum material softened and stirred by the tool 20 is filled into the gap d. Accordingly, as shown in FIGS. 3(d) and 3(e), the non-inscribed section 42 including the tool hole 44a can be easily cut away from the first shaft 11 by a cut-off tool 50.

[0058] As shown in FIG. 3(f), as the non-inscribed section 42 is cut away from the first shaft 11, the dissimilar metals shaft 200 according to the present invention is obtained.

[0059] FIG. 4 is a view for describing a dissimilar metals shaft 300 according to Variant 1 to which the friction stir welding method of the present invention is applied.

[0060] In the dissimilar metals shaft 300, in order for the friction stir welded section 40FSW not to overlap, a moving direction (a tangential direction) of the tool 20 characterized by a first straight line 40L1 is bent at a bending angle δ in a direction away from the starting point 43 in front of the endpoint 44 and varied in the moving direction characterized by a second straight line 40L2. Further, the bending angle δ is defined as an angle formed between the first straight line 40L1 before variation and the second straight line 40L2 after variation, and an angle measured counterclockwise from the first straight line 40L1. Accordingly, the configuration is otherwise the same as in the above-mentioned dissimilar metals shaft 200.

[0061] FIG. 5 is a view for describing a dissimilar metals shaft 400 according to Variant 2 to which the friction stir welding method of the present invention is applied.

[0062] The dissimilar metals shaft 400 is a shaft obtained by cutting the non-inscribed section 42 including the tool hole 44a away from the dissimilar metals shaft 300. Accordingly, the configuration is otherwise the same as in the dissimilar metals shaft 300.

[0063] FIG. 6 is an explanatory view for describing a dissimilar metals shaft 500 according to Variant 3 to which the friction stir welding method of the present invention is applied.

[0064] Unlike the dissimilar metals shaft 300, in the dissimilar metals shaft 500, the friction stir welded section 40FSW is formed in the circumferential direction. Accordingly, the configuration is otherwise the same as in the dissimilar metals shaft 300. Accordingly, like the dissimilar metals shaft 300, in the dissimilar metals shaft 500, in order for the friction stir welded section 40FSW not to overlap, a moving direction (a tangential direction) of the tool 20 characterized by the first straight line 40L1 is bent at the bending angle δ in a direction away from the starting point 43 in front of the endpoint 44 and varied in the moving direction characterized by the second straight line 40L2.

[0065] FIG. 7 is a view for describing a dissimilar metals shaft 600 according to Variant 4 to which the friction stir welding method of the present invention is applied.

[0066] The dissimilar metals shaft 600 is a shaft obtained by cutting the non-inscribed section 42 including the tool hole 44a away from the dissimilar metals shaft 500. Accordingly, the configuration is otherwise the same as in the dissimilar metals shaft 500.

[0067] Hereinabove, the dissimilar metals shaft and the metal joining method according to the embodiment have been described with reference to the accompanying drawings. However, the embodiment of the present invention is not limited to the above-mentioned embodiment and various modifications and alterations may be made without departing from the technical spirit of the present invention. For example, the first shaft 11 and the second shaft 12 may be formed of similar metals. In addition, in the moving direction of the tool 20 according to the friction stir welded section 40FSW, in addition to a spiral shape and a circumferential shape, a zigzag shape or a combination thereof may be used. Further, the number of laps of the tool 20 may be two or more.