Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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Effects of Phosphorus and in-situ Post-heat Pulse Conditions on Resistance Spot Weldability of High Si DP980 Steel Sheet

고Si DP980강 스폿 용접 특성에 미치는 Phosphorus (P) 및 in-situ 후열처리 펄스 조건의 영향

  • 최두열 (포스코 제품이용연구센터(PAC))
  • Received : 2015.11.12
  • Accepted : 2015.12.17
  • Published : 2015.12.30
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Abstract

Recently, application of UHSS(Ultra High Strength Steels) whose tensile strength is over 1000MPa to car body structure are growing due to great needs for light weighting and improved crash worthiness. However, their poor weldability is one of obstacles to expand selecting to car body. In this study, effect of Phosphorus contents on resistance spot weldability of high elongation DP980 steel whose Si content is over 1% was investigated. The cross tension strength (CTS) was decreased showing partial interface fracture as Phosphorus content increase because of solidification segregation of Phosphorus. In order to improve resistance spot weldability by modification of welding condition, in-situ post-weld heating pulse was introduced after main pulse. The optimum cooling time between main and post pulse and post-pulse current condtion were determined through FEM welding simulation and DOE tests. The CTS was increased about 1.5 time showing plug fracture. The decrease of Phosphorus segregation was found to be a major reason for weld ductility and CTS improvement.

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References

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