Overlap-welded member, automobile part, method of welding overlapped portion, and method of manufacturing overlap-welded member

Abstract

The present invention provides an overlap-welded member in which an overlapped portion including plural steel sheet members is joined at a spot-welded portion, in which at least one of the plural steel sheet members contains martensite, and the spot-welded portion includes: a nugget formed through spot welding; a heat-affected zone formed in the vicinity of the nugget; the softest zone having the lowest Vickers hardness in the heat-affected zone; and a tempered area formed between a central portion of the nugget and the softest zone and made out of tempered martensite having Vickers hardness of not more than 120% in the case where Vickers hardness of the softest zone is 100%.

1 . An overlap-welded member in which an overlapped portion including a plurality of steel sheet members is joined at a spot-welded portion, wherein
 at least one of the plurality of steel sheet members contains martensite; and   the spot-welded portion includes:
 a nugget formed through spot welding; 
 a heat-affected zone formed in the vicinity of the nugget; 
 a softest zone having the lowest Vickers hardness in the heat-affected zone; and 
 a tempered area formed between a central portion of the nugget and the softest zone and made out of tempered martensite having Vickers hardness of not more than 120% in a case where Vickers hardness of the softest zone is 100%. 
   
     
     
         2 . The overlap-welded member according to  claim 1 , wherein
 the plurality of steel sheet members include a hot-stamped member.   
     
     
         3 . An automobile part including the overlap-welded member according to  claim 1 .