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Microstructure and properties of spot welded joints of hot-stamped ultra-high strength steel used for automotive body structures

Journal Article


Abstract


  • Hot-stamped ultra-high strength steels have been widely used in automobile structural parts. Considering the high splash tendency in resistance spot welding due to their extremely high hardness, in this work, microstructural characteristics and mechanical performance of the resistance spot welded ultra-high strength steels are investigated. The results indicate that the interface between the nugget and heat-affected zone (HAZ) is the weakest zone where fractures initiate. In tensile shearing tests, a qualified spot welding joint failed with a button-shaped fracture. Welding defects would significantly decrease the load-carrying capacity and lead to interfacial fracture, except for a button-shaped fracture. In spot welding, it was found that a specific mid-frequency alternating current (AC) input mode, in which a 6 ms cooling cycle was inserted between every two neighboring current pulses, can avoid the splash in the spot welding of hot-stamped hardened steels.

UOW Authors


  •   Qiao, Zhixia (external author)
  •   Li, Hui Jun.
  •   Li, Lianjin (external author)
  •   Ran, Xiaoyu (external author)
  •   Feng, Liwen (external author)

Publication Date


  • 2019

Published In


Citation


  • Qiao, Z., Li, H., Li, L., Ran, X. & Feng, L. (2019). Microstructure and properties of spot welded joints of hot-stamped ultra-high strength steel used for automotive body structures. Metals, 9 (3), 285-1-285-13.

Scopus Eid


  • 2-s2.0-85063407924

Start Page


  • 285-1

End Page


  • 285-13

Volume


  • 9

Issue


  • 3

Place Of Publication


  • Switzerland

Abstract


  • Hot-stamped ultra-high strength steels have been widely used in automobile structural parts. Considering the high splash tendency in resistance spot welding due to their extremely high hardness, in this work, microstructural characteristics and mechanical performance of the resistance spot welded ultra-high strength steels are investigated. The results indicate that the interface between the nugget and heat-affected zone (HAZ) is the weakest zone where fractures initiate. In tensile shearing tests, a qualified spot welding joint failed with a button-shaped fracture. Welding defects would significantly decrease the load-carrying capacity and lead to interfacial fracture, except for a button-shaped fracture. In spot welding, it was found that a specific mid-frequency alternating current (AC) input mode, in which a 6 ms cooling cycle was inserted between every two neighboring current pulses, can avoid the splash in the spot welding of hot-stamped hardened steels.

UOW Authors


  •   Qiao, Zhixia (external author)
  •   Li, Hui Jun.
  •   Li, Lianjin (external author)
  •   Ran, Xiaoyu (external author)
  •   Feng, Liwen (external author)

Publication Date


  • 2019

Published In


Citation


  • Qiao, Z., Li, H., Li, L., Ran, X. & Feng, L. (2019). Microstructure and properties of spot welded joints of hot-stamped ultra-high strength steel used for automotive body structures. Metals, 9 (3), 285-1-285-13.

Scopus Eid


  • 2-s2.0-85063407924

Start Page


  • 285-1

End Page


  • 285-13

Volume


  • 9

Issue


  • 3

Place Of Publication


  • Switzerland