Method of resistance welding

• US 4,273,983 A
• Filed: 07/17/1979
• Issued: 06/16/1981
• Est. Priority Date: 07/14/1973
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Ogawa, Masahiro, Mizobe, Tugio
• Primary Examiner(s): Kucia, Richard R.
• Application Number:
  US06/058,172
• Time in Patent Office: 700 Days
• Field of Search: 219/93, 219/101, 219/104, 219/107, 219/118, 428/583, 428/934, 428/653, 428/660, 428/677, 428/684
• US Class Current: 219/93
• CPC Class Codes: B23K 11/04 Flash butt welding
• CPC Class Codes: B23K 11/20 of different metals
• CPC Class Codes: B23K 33/00 Specially-profiled edge portions of workpieces for making soldering or welding connections; Filling the seams formed thereby B23K11/14 takes precedence
• CPC Class Codes: Y10S 428/934 Electrical process
• CPC Class Codes: Y10T 428/12271 having discrete fastener, marginal fastening, taper, or end structure

Abstract

An improved method for resistance welding two metallic articles, made of dissimilar metals which form brittle intermetallic compounds when melted together. A first one of the metallic articles is provided with a tapered, flat-topped projection which is pressed against the other metallic article. The first article preferably is composed of the metal most difficult to melt, as determined by the four parameters of melting point, electrical resistance, heat conductivity and specific heat. The projection is formed with a predetermined relation between height, top width, and angle of taper such that a preselected extremely high welding current passed for a very short time will establish a maximum temperature near the top of the projection sufficient to melt the contacting surfaces of the two metallic articles and a temperature gradient such that an intermediate portion of the projection becomes markedly plastic while the adjacent base portion of the projection remains undeformable under extremely high welding pressure. Impurities and intermetallic compounds in the molten metal at the top of the projection are squeezed out to the periphery of the surfaces to be welded, and the weld joint is made between plastic but unmelted metal of the projection and the other article.

Claims

1. A method for resistance welding two members made of dissimilar metals that includes the steps of placing a surface of a first member made of one metallic material into electrically conductive contact with a surface of a second member made of another metallic material different from the first material, passing an electrical welding current across the contact area between the two members for a time sufficient to render plastic a portion of the metallic material of one of the members, and pressing the first and second members together with sufficient force to squeeze any surface impurities and intermetallic compounds to the edges of the contact area, wherein the improvement comprises:

forming at least one small, integral, tapered, flattopped projection of trapezoidal cross section on the first member, the projection having a predetermined height, divided into a top portion, an intermediate portion and a base portion, and a predetermined width of the flat-topped surface, and opposite sides of the tapered projection each making a predetermined angle with a line perpendicular to the flat-topped surface such that passage of a welding current through the projection will generate a temperature distribution that decreases continuously from the top portion to the base portion, and further, that the projection radially spreads in a plastic flow;

pressing the top surface of the at least one projection of the first member against the surface of the second member with a high welding pressure selected to be approximately in the range of 15-100 kg/mm² of top surface area of the projection, but which does not exceed a force that will deform the projection prior to the application of welding current, and;

passing a predetermined high welding current density approximately in the range of 0.75 to 3.4 KA/mm² to top surface area of the projection for a short time period approximately in the range of 0.5 to 10 cycles at 60 Hz, such that the contacting surfaces of the two members are melted, said intermediate portion of the projection flows plastically under said welding pressure and the base portion of the projection does not plastically flow, and due to said plastic flow, obtaining welded surfaces having no intermetallic compound of said dissimilar metals remaining at said welded surfaces.

2. The method of claim 1 wherein the metallic material of the first member is the more difficult of the two metallic materials to melt by passage of an electric current therethrough.

3. The method of claim 1 wherein the predetermined height of the projection is about two millimeters, and the predetermined width of the top surface of the projection is about one-half millimeter.

4. The method of claim 1 wherein the projection has a predetermined height of approximately 2 mm, a predetermined to width of approximately 0.5 mm, and a predetermined side angle of between approximately 7 to approximately 35 degrees.

5. The method of claim 4 wherein the predetermined welding current density is approximately in the range of 1.10 to 3.3 KA/mm² of top surface area of the projection;

and the predetermined welding pressure is approximately in the range of 28 to 83 kg/mm² of top surface area of the projection.

6. The method of claim 1 wherein the one metallic material of the first member is steel, and the other metallic material of the second member is aluminum.

7. The method of claim 6 wherein said predetermined side angle of the projection is approximately 12 degrees to 30 degrees.

8. The method of claim 7, wherein said predetermined height and width of the projection are approximately 2 mm and 0.5 mm, respectively.

9. The method of claim 6 wherein the projection has a predetermined height of approximately 2 mm, a predetermined top width of approximately 0.5 mm, and a predetermined side angle of approximately 12 to 30 degrees;

the predetermined welding current density is approximately in the range of 1.5 to 2.6 KA/mm² of top surface area of the projection; and

the predetermined welding pressure is approximately in the range of 30 to 100 kg/mm² of top surface area of the projection.

10. The method of claim 9, wherein said welding current density is in the range from 1.8 to 2.3 KA/mm², and said welding pressure is in the range from 48 to 83 kg/mm².

11. The method of claim 1 wherein the one metallic material of the first member is steel, and the other metallic material of the second member is cast iron.

12. The method of claim 11 wherein said predetermined side angle of the projection is approximately 12 degrees to 35 degrees.

13. The method of claim 12 wherein said predetermined height and width of the projection are approximately 2 mm and 0.5 mm, respectively.

14. The method of claim 11 wherein the projection has a predetermined height of approximately 2 mm, a predetermined top width of approximately 0.5 mm, and a predetermined side angle of approximately 12 to 35 degrees;

the predetermined welding current density is approximately in the range of 0.75 to 2 KA/mm² of top surface area of the projection; and

the predetermined welding pressure is approximately in the range of 15 to 90 kg/mm² of top surface area of the projection.

15. The method of claim 14 wherein said welding current density is in the range from 1.1 to 1.7 KA/mm², and said welding pressure is in the range from 34 to 71 kg/mm².

16. The method of claim 1 wherein the one metallic material of the first member is copper, and the other metallic material of the second member is aluminum.

17. The method of claim 16 wherein said predetermined side angle of the projection is approximately 12 degrees to 30 degrees.

18. The method of claim 17 wherein said predetermined height and width of the projection are approximately 2 mm and 0.5 mm, respectively.

19. The method of claim 16 wherein the projection has a predetermined height of approximately 2 mm, a predetermined top width of approximately 0.5 mm, and a predetermined side angle of approximately 12 to 30 degrees;

the predetermined welding current density is approximately in the range of 2.9 to 3.4 KA/mm² of top surface area of the projection;

the predetermined welding pressure is approximately in the range of 20 to 50 kg/mm² of top surface area of the projection; and

the predetermined welding time is in the range of approximately 0.5 to 3 cycles at 60 Hz.

20. The method of claim 19 wherein said welding current is in the range from 3.0 to 3.3 KA/mm², and said welding pressure is in the range from 28 to 32 kg/mm².

21. The method of claim 1 wherein the one metallic material of the first member is steel, and the other metallic material of the second member is copper.

22. The method of claim 21 wherein said predetermined side angle of the projection is approximately 15 degrees to 25 degrees.

23. The method of claim 22 wherein said predetermined height and width of the projection are approximately 2 mm and 0.5 mm, respectively.

24. The method of claim 21 wherein the projection has a predetermined height of approximately 2 mm, a predetermined top width of approximately 0.5 mm, and a predetermined side angle of approximately 15 to 25 degrees;

the predetermined welding current density is approximately in the range of 2.3 to 2.9 KA/mm² of top surface area of the projection;

the predetermined welding pressure is approximately in the range of 20 to 80 kg/mm² of top surface area of the projection; and

the predetermined welding time is in the range of approximately 1 to 5 cycles at 60 Hz.

25. The method of claim 24 wherein said welding current is in the range from 2.5 to 2.7 KA/mm², and said welding pressure is in the range from 35 to 65 kg/mm².

26. The method of claim 1 wherein the one metallic material of the first member is steel, and the other metallic material of the second member is titanium.

27. The method of claim 26 wherein said predetermined angle of the projection is approximately 7 degrees to 25 degrees.

28. The method of claim 27 wherein said predetermined height and width of the projection are approximately 2 mm and 0.5 mm, respectively.

29. The method of claim 26 wherein the projection has a predetermined height of approximately 2 mm, a predetermined top width of approximately 0.5 mm, and a predetermined side angle of approximately 7 to 25 degrees;

the predetermined welding current density is approximately in the range of 1.4 to 2.0 KA/mm² of top surface area of the projection;

the predetermined welding pressure is approximately in the range of 30 to 100 kg/mm² of top surface area of the projection; and

the predetermined welding time is in the range of approximately 0.5 to 3 cycles at 60 Hz.

30. The method of claim 29 wherein said welding current is in the range from 1.6 to 1.8 KA/mm², and said welding pressure is in the range from 48 to 83 kg/mm².