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Effect of Al-Si Coating on Weldability of Press-Hardened Steels

  • RuiMing Chen
  • ChaoQun Zhang
  • Ming Lou
  • YongBing LiEmail author
  • Blair E. Carlson
Article
  • 41 Downloads

Abstract

Resistance spot welding (RSW) of Al-Si-coated PHS was undertaken, and the effect of Al-Si coating on nugget formation and mechanical properties was investigated. Press-hardened steel (PHS) has long been applied to automotive body structure construction to support mass and corresponding greenhouse gas emission reductions. PHS materials are often combined with an Al-Si coating applied as an oxidation barrier though unfortunately, the Al-Si coating poses a challenge to the resistance spot welding (RSW) of PHS containing stack-ups. As a newly developed coating for the hot stamping process, the property of Al-Si coating is different from base metal and traditional coatings, and the influence mechanism of Al-Si coating on the welding process is not clear. It would remain at nugget edge and might cause severe stress concentration. To investigate this problem, RSW of 1.5-mm Al-Si-coated PHS was undertaken, and the results indicate that a large portion of the Al-Si coating is extruded and forms a sharp notch close to the nugget edge during the welding process. During the post-weld cooling stage, a thin layer of residual coating is formed between the nugget and notch root. The mechanical performance of the welded joints is limited by the thin residual Al-Si layer which acts as a preexisting crack and supports the interfacial fracture. The presence of the Al-Si coating at the faying interface also significantly delays nugget formation, though it contributes to a larger nugget size by inhibiting expulsion events at the faying interface.

Keywords

Al-Si coating press-hardened steel resistance spot welding ultrahigh-strength steel 

Notes

Acknowledgments

The authors would like to acknowledge the supports of GM Research and Development Center. The authors gratefully acknowledge the supports of National Natural Science Foundation of China (Grant Nos. U1564204, U1764251, and 51805323).

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Copyright information

© ASM International 2020

Authors and Affiliations

  • RuiMing Chen
    • 1
  • ChaoQun Zhang
    • 1
  • Ming Lou
    • 1
  • YongBing Li
    • 1
    Email author
  • Blair E. Carlson
    • 2
  1. 1.Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, State Key Laboratory of Mechanical System and Vibration, School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghaiPeople’s Republic of China
  2. 2.Manufacturing Systems Research LabGeneral Motors Research & Development CenterWarrenUSA

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