Proceedings of the Third International Conference on Metals & Hydrogen P64

Delayed fracture in quenching and partitioning steels for automotive applications

Z. Wang (1)1(2)2 , Z.C. Luo (1)1(2)2 , M.X. Huang (1)1(2)2

  • (1) 1

    Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China

  • (2) 2

    Shenzhen Institute of Research and Innovation, The University of Hong Kong, Shenzhen 518000, China


Hydrogen induced delayed fracture has recently become a more severe problem for automotive steels, especially for newly developed advanced high strength steels, such as quenching and partitioning (Q&P) steels. In this work, hydrogen induced delayed fracture of two industrial-grade Q&P steels, Q&P 980 and Q&P 1180, was studied by deep drawn cup tests and slow strain rate tensile tests. The results showed that Q&P 980 steel has better delayed fracture resistance than Q&P 1180. It is demonstrated that in Q&P steels, hydrogen induced cracks can nucleate in sensitive regions like retained austenite islands, and tend to propagate along prior austenite grain boundaries and martensite boundaries. In Q&P 980 steel, ferrite can effectively isolate the sensitive regions and interrupt the continuity of prior austenite grain boundaries, which accounts for the blunting of cracks and thus better hydrogen induced delayed fracture resistance.


  • Q&P steels
  • Hydrogen embrittlement
  • Deep drawn cups
  • Slow strain rate tests
  • Retained austenite