Method of welding overlapped portion, method of manufacturing overlap-welded member, overlap-welded member, and automotive part

A method of welding an overlapped portion in which a plurality of steel sheet members including a galvanized steel sheet having a hot-dip galvanneal coating or a hot-dip galvanizing coating formed thereon are joined at the overlapped portion, the method including:

• forming a spot-welded portion having a nugget in the overlapped portion;
• and
• emitting a laser beam to form a melted and solidified portion crossing an end of the nugget and located between the nugget and a position outside of the nugget, the melted and solidified portion being formed in a manner such that a depth of the melted and solidified portion at a portion corresponding to a contacting surface of the spot-welded portion is shallower than a contacting surface having the hot-dip galvanneal coating or the hot-dip galvanizing coating formed thereon.

An overlap-welded member in which a plurality of steel sheet members are joined at an overlapped portion, and at least one of the plurality of steel sheet members contains martensite, wherein

• a spot-welded portion having a nugget is formed in the overlapped portion, and
• a melted and solidified portion is formed through emission of a laser beam between the nugget and a position externally spaced apart from an end of the nugget by not less than 3 mm, the melted and solidified portion crossing an end of the nugget and having a depth of not less than 50% of a thickness of the steel sheet member containing the martensite at a position externally spaced apart from the end of the nugget by 1 mm.

An overlap-welded member in which a plurality of steel sheet members including a galvanized steel sheet having a hot-dip galvanneal coating or a hot-dip galvanizing coating formed thereon are joined at an overlapped portion, wherein

• a spot-welded portion having a nugget is formed in the overlapped portion;
• and
• a melted and solidified portion is formed through emission of a laser beam between the nugget and a position outside the nugget so as to cross an end of the nugget and have a depth at a portion corresponding to a contacting surface of the spot-welded portion shallower than a contacting surface having the hot-dip galvanneal coating or the hot-dip galvanizing coating formed thereon.