Source: https://insight.rpxcorp.com/pat/US7473864B2
Timestamp: 2020-08-13 17:23:43
Document Index: 107015123

Matched Legal Cases: ['art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3']

Patent US 7,473,864 B2
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.
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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.
In this embodiment, the aluminum-coated steel sheet 1 is joined on the aluminum sheet 2 by resistance spot welding. Aluminum-coated layers 1b and 1c are formed on both surfaces of a steel substrate 1a of the aluminum-coated steel sheet 1. Intermetallic compound layers consisted of an Al—Fe composition and the like (not shown) exist on interfaces between the coated layer 1b and the steel sheet 1a, and between the coated layer 1c and the steel sheet layer 1a before the aluminum-coated steel sheet 1 is joined with the aluminum sheet 2.
A joined part 3 of the aluminum-coated steel sheet 1 and the aluminum sheet 2 includes an intermetallic compound layer 3a and an aluminum melted and solidified part 3b. The intermetallic compound layer 3a is formed on a part of the coated layer 1b before joining. The aluminum melted and solidified part 3b is formed within the aluminum sheet 2, and surrounds the intermetallic compound layer 3a. The atoms existing on the surface of the aluminum melted and solidified part 3b are metallic-bonded with atoms which exist on the surface of the steel sheet 1 except in the region in which the intermetallic compound layer 3a exists seen in the plan view. In other words, the intermetallic compound consisted of the Al—Fe composition and the like that exists before the joining disappears in the region where the aluminum melted and solidified part 3b and the steel sheet 1 are directly contacted. The intermetallic compound layer 3a is the intermetallic compound that exists before the joining or is newly developed upon the joining.
In this embodiment, the area of the intermetallic compound layer 3a at the interface between the aluminum-coated steel sheet 1 and the aluminum sheet 2 is limited to 60% or less of the total area of the joined part 3 constituting of the intermetallic compound layer 3a and the aluminum melted and solidified part 3b. Accordingly, the area of the aluminum melted and solidified part 3b exceeds 40% of the total area of the joined part 3.
A method of resistance spot welding the weldment of different materials described above will be described. The present inventor found that positive charges flow into the joining material from an electrode chip to produce deviations of the heat generations on the joining material in the resistance spot welding, and that when the deviations of the heat generations on the aluminum sheet 2 is produced at one welding point, the aluminum sheet 2 is molten intensively to produce a large amount of the intermetallic compound, whereby the percentage of the area of the intermetallic compound layer 3a that occupies the joining part 3 is increased. It is therefore required to avoid excessive heating of the aluminum sheet 2. In the resistance spot welding method, any of an AC, DC or capacitor type welding machine can be used.
In the three-phase low frequency type welding machine, a positive current flows at a positive electrode on welding points in odd numbers as shown in FIG. 3b, and a positive current flows at a negative electrode on welding points in even numbers (not shown). If the negative electrode chip is pressed against the aluminum-coated steel sheet 1 on the welding points in odd numbers and the positive electrode chip is pressed against the aluminum sheet 2 using the three-phase low frequency type welding machine, the deviations of the heat generations are produced on the aluminum sheet 2, as described above. As a result, no desired weldment can be provided. The same applies to the case that the positive electrode chip is pressed against the aluminum-coated steel sheet 1 on the welding points in even numbers and the negative electrode chip is pressed against the aluminum sheet 2. Accordingly, the polarity of the electrode chip should be changed per one welding point, when the three-phase low frequency type welding machine is used.
Al Coated Layer N Content in Polarity at Area
Si Content Thickness Steel Substrate Welding Steel Sheet Percentage No (% by mass) (μm) (% by mass) Machine Side (%)
Example 1 10 40 0.012 DC + 20 2 10 40 0.012 DC + 35 3 10 40 0.012 DC + 45 4 10 40 0.012 DC + 60 5 13 40 0.012 DC + 24 6 10 40 0.012 DC + 24 7 7 40 0.012 DC + 50 8 4 40 0.012 DC + 60 9 12 40 0.012 DC + 28 10 10 32 0.012 DC + 35 11 9 25 0.012 AC None 47 12 9 15 0.012 DC + 55 13 9 13 0.012 DC + 58 14 10 40 0.012 DC + 59 15 10 40 0.001 DC + 59 Comparative 16 10 40 0.012 DC + 70 Example 17 10 40 0.012 DC + 65 18 10 40 0.012 DC + 75
TABLE 2 Ductile Fracture No. Broken Part Energy
Example 1 Base Material Excellent Broken 2 Base Material Excellent Broken 3 Base Material Good Broken 4 Base Material Fair Broken 5 Base Material Excellent Broken 6 Base Material Excellent Broken 7 Base Material Good Broken 8 Base Material Fair Broken 9 Base Material Excellent Broken 10 Base Material Good Broken 11 Base Material Good Broken 12 Base Material Good Broken 13 Base Material Fair Broken 14 Base Material Good Broken 15 Base Material Fair Broken Comparative 16 Base Material Not Good Example Broken 17 Interface Broken Not Good 18 Interface Broken Not Good
Kobe Steel Limited, Nisshin Steel Company Limited (Nippon Steel Corporation)
Hashimoto, Shunichi, Sato, Fumihiro, Takeda, Hiroyuki, Iwase, Tetsu, Sasabe, Seiji, Katoh, Jun, Hino, Mitsuo, Tsubota, Kensuke
US 20050258145A1
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
Sponsoring Entity: Kobe Steel Limited, Nisshin Steel Company Limited (Nippon Steel Corporation)