Patent ID: 8487206

Claim:
A method for spot-welding a steel product and an aluminum material, said method comprising: forming a joint product of the steel product and the aluminum material by spot welding a steel product having a sheet thickness t 1 of 0.3 to 3.0 mm with an aluminum material having a sheet thickness t 2 of 0.5 to 4.0 mm, wherein a nugget area in a joint part is from 20×t 2 0.5 to 100×t 2 0.5 mm 2 , wherein an area of a portion where a thickness of an interface reaction layer is from 0.5 to 3 μm is 10×t 2 0.5 mm 2 or more, wherein a difference between the thickness of the interface reaction layer at a joint part center and the thickness of the interface reaction layer at a point distant from the joint part center by a distance of one-fourth of a joint diameter is 5 μm or less, wherein the aluminum material is either a pure aluminum or an aluminum alloy material, and wherein the spot welding is performed while cooling at least one of the steel product and the aluminum material to 5° C. or less.