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Hardness Distribution and Microstructures of Electric Resistance Spot Welded 1GPa Grade Dual Phase Steel

1GPa급 DP강 전기저항점용접부의 경도분포와 미세조직의 상관관계

  • Na, Hye-Sung (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kong, Jong-Pan (Dept. of Material Science and Engineering, Pusan National University) ;
  • Han, Tae-Kyo (POSCO Technical Research Laboratories) ;
  • Chin, Kwang-Geun (POSCO Technical Research Laboratories) ;
  • Kang, Chung-Yun (Dept. of Material Science and Engineering, Pusan National University)
  • Received : 2012.04.16
  • Accepted : 2012.04.30
  • Published : 2012.04.30

Abstract

In this study, the effect of the welding current on the hardness characteristics and microstructure in the resistance spot welding of 1GPa grade cold-rolled DP steel was investigated, Also, correlation between the hardness and microstructure was discussed. In spite of the change in the welding current, the hardness distributions near weld was similar. the hardness in the HAZ and the fusion zone was higher than that of the base metal and the hardness in the fusion zone was variated with the location. Especially, the hardness of HAZ adjacent to the base metal showed maximum value, and softening zone in the base metal adjacent to HAZ was found. With the increasing of welding current, there were no difference in maximum hardness and average hardness in the fusion zone were, but the hardness of the softening zone reduced. The difference in the hardness in each location of weld due to grain size of prior austenite. The softening of the base metal occurred by tempering of the martensite.

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