Impact Tensile Strength of Laser Welded Butt Joint of Steel Sheets for Vehicles
Hiroshi TSUDA, Masashi DAIMARUYA and Hidetoshi KOBAYASHI
Abstract:The present study is concerned with the static and dynamic characteristics of laser welded joints related to the tailored blanks technique for vehicles. Three kinds of laser welded butt joints made of different steel sheets for vehicles, a mild steel HR270, high tensile strength steels HR590 and HR780, were used in the static and impact tensile tests. In the static test, all welded butt joint specimens showed that the tensile strength was similar to that of the base metal specimens corresponding to them, but the strain at fracture decreased. The measurement of the impact tensile strength of laser welded butt joints was performed by means of the modified split Hopkinson bar method for impact tensile test. The impact tensile strength of the laser welded butt joint of mild steel HR270 tended to increase comparing with the static one due to the effect of strain rate. On the other hand, regarding the high tensile strength steels of HR590 and HR780, the effect of strain rate was not recognized at about 320 s-1. Thus the impact tensile strength and the fracture strain were almost same as the results in the static tests. Key Words:Impact test, Impact tensile strength, Split Hopkinson bar, Laser welded butt joint, High tensile strength steel, Vehicles