Weldment of different materials and resistance spot welding method

• US 7,473,864 B2
• Filed: 05/19/2004
• Issued: 01/06/2009
• Est. Priority Date: 05/19/2004
• Status: Expired due to Term

• Current Assignee: Klaus Schmidt, Nisshin Steel Company Limited (Nippon Steel Corporation)
• Original Assignee: Kobe Steel Limited, Nisshin Steel Company Limited (Nippon Steel Corporation)
• Inventors: Hashimoto, Shunichi, Sato, Fumihiro, Takeda, Hiroyuki, Iwase, Tetsu, Sasabe, Seiji, Katoh, Jun, Hino, Mitsuo, Tsubota, Kensuke
• Primary Examiner(s): Kerns; Kevin P
• Assistant Examiner(s): Aboagye; Michael
• Application Number:
  US10/848,165
• Publication Number:
  US 20050258145A1
• Time in Patent Office: 1,693 Days
• Field of Search: 219/118, 219/117.1, 219/119, 219/76.17, 219/85.16, 219/86.1, 219/86.25, 219/91.2, 427/318, 427/319, 428/653, 428/570, 428/659
• US Class Current: 219/118
• CPC Class Codes: B23K 11/20 of different metals
• CPC Class Codes: B23K 11/34 Preliminary treatment
• CPC Class Codes: Y10T 428/12757 Fe

Abstract

A joined part of an aluminum-coated steel sheet and an aluminum sheet is composed of an intermetallic compound layer which exists in a region in which a part of a coated layer exists before the joining and an aluminum melted and solidified part which also exists on the side of the aluminum sheet to enclose the intermetallic compound layer. The atoms existing on the surface of the aluminum melted and solidified part are intermetallic-bonded with atoms which exist on the surface of the steel sheet except in the region in which the intermetallic compound layer exists seen in the plan view. Further, the area of the intermetallic compound layer is limited to 60% or less of the total area of the joined part at the interface between the aluminum-coated steel sheet and the aluminum sheet. Thus, the area of the aluminum melted and solidified part exceeds 40% of the total area of the joined part. The strong joining having a high fracture energy can be provided at a high efficiency.

Claims

1. A weldment of different materials, the weldment having a ductile fracture energy of at least 7.5 Joules, comprising:

an aluminum or aluminum alloy sheet and an aluminum-coated steel sheet having an aluminum coated layer with a thickness of 15 μ

m or more, said aluminum or aluminum alloy sheet and said aluminum-coated steel sheet being resistance spot welded,

wherein a joined part exists on an interface between the aluminum or aluminum alloy sheet and the aluminum-coated steel sheet, and wherein the area of an intermetallic compound layer in the joined part is 60% or less of the total area of the joined part constituting the intermetallic compound layer and the melted and solidified region created by the resistance spot welding,

wherein the aluminum-coated steel sheet comprises a steel substrate containing 0.002% by mass or more of N.

2. A weldment of different materials according to claim 1, wherein the aluminum-coated steel sheet comprises an aluminum-coated layer containing 5% by mass or more of Si.

3. A method of resistance spot welding the weldment of different materials comprising an aluminum or aluminum alloy sheet and an aluminum-coated steel sheet according to claim 1, comprising the steps of pressing the aluminum-coated steel sheet against an electrode chip at an anode, and pressing the aluminum or aluminum alloy sheet against an electrode chip at a cathode side using a DC or capacitor type welding machine.