Welding in the World

, Volume 61, Issue 1, pp 57–67 | Cite as

Displaced hardness peak phenomenon in heat-affected zone of welded quenched and tempered EM812 steel

  • D.P. Dunne
  • W. Pang
Research Paper


Investigations of microstructural and hardness gradients in the heat-affected zone (HAZ) of quenched and tempered (Q&T) steels have indicated that peak hardness does not occur in the grain-coarsened heat-affected zone (GCHAZ) adjacent to the fusion boundary, which is typical of ferritic steels, but corresponds more closely to the grain-refined region (GRHAZ). This phenomenon, the displaced hardness peak (DHP) effect, is considered to arise when the hardenability of the steel is high enough to result in the same microstructure in the GC and GR heat-affected zones, except for significant refinement of the microstructure of the GRHAZ, which increases the hardness and strength above those of the GCHAZ. The current paper concentrates on the effect of grain size on hardness in the HAZ of a boron-containing low-carbon martensitic steel subjected to bead-on-plate welding. Thermal simulation experiments were used to clarify the relationship between prior austenite grain size and the hardness gradients in the actual HAZ. The simulation work demonstrated that peak hardness in simulation samples occurred in regions of lower austenite grain size, supporting the proposed origin of the DHP effect in actual welds. Implications regarding hydrogen-induced cold cracking (HICC) susceptibility of the GRHAZ are discussed.

Keywords (IIW Thesaurus)

Heat-affected zone Hardness Low-carbon steels Grain size Microstructure Hydrogen embrittlement Cold cracking 



The authors are grateful for the contributions of research students of the University of Wollongong, in particular, Alan Giumelli, Sanjay Dani, Liam Bell and Wayne Staff. We also gratefully acknowledge CSIRO MT, Adelaide, for providing the welded samples and Bisalloy Steels Pty Ltd. for the steel plate.


  1. 1.
    (1964) The making, shaping and treating of steel: 8th Ed, USS Corp., Pitts., PA, 1092–3Google Scholar
  2. 2.
    Pang W, Ahmed N, Dunne D (2011) Hardness and microstructural gradients in the heat affected zone of welded low-carbon quenched and tempered steels. Australasian Weld J - WRS 56(2):36–48Google Scholar
  3. 3.
    (1967) International Institute of Welding, IIW Doc. IX-535-67Google Scholar
  4. 4.
    Dunne DP (1995) “Weldable copper strengthened low carbon steels”, Proceedings of HSLA’95 Conference, Beijing, Oct., 90–98Google Scholar
  5. 5.
    Pang W (1995) “The structure and properties of the heat affected zone of structural plate steels welded by high productivity processes”, Ph.D Thesis, University of WollongongGoogle Scholar
  6. 6.
    Dunne DP, Pang W (2013) Structural and hardness gradients in the heat affected zone of welded low carbon martensitic steels. Mater Sci Forum 738-739:206–211CrossRefGoogle Scholar
  7. 7.
    Dani SG (1993) “The effect of pre-heat on the structure and properties of the HAZ of a welded quenched and tempered steel plate”, Master of Engineering (Hons) Thesis, University of WollongongGoogle Scholar
  8. 8.
    Guimelli A, Pang W, Hamilton G, Dunne D (1992) “Weld thermal cycle simulation using computer controlled resistance heating”, Pacrim Weldcon ‘92, Proc. 40th National Conf. of Welding Technology Institute of Australia, Vol. 2, WTIA, Darwin, Paper 45Google Scholar
  9. 9.
    (1992) Atlas for Bainitic Microstructures: Vol. 1, Bainite Committee of Iron and Steel Inst. of JapanGoogle Scholar
  10. 10.
    Liang Chen (2000) “Characterisation of transverse cold cracking in weld metal of a high strength quenched and tempered steel”, Ph.D Thesis, The University of WollongongGoogle Scholar
  11. 11.
    Rosenthal D (1946) Trans ASME 68:167Google Scholar
  12. 12.
    Easterling K (1983) Introduction to the physical metallurgy of welding. Butterworths, LondonGoogle Scholar
  13. 13.
    Widgery DJ (1972) “The design and use of a resistance heated weld simulator”, Seminar Handbook, The Welding Institute, 15Google Scholar
  14. 14.
    Dunne D (1999) Ferrite morphology and residual phases in continuously cooled low carbon steels. Materials Forum 23:63–76Google Scholar
  15. 15.
    Pickering FB (1978) Physical metallurgy and the Design of Steels. App. Sci. Publishers Ltd, LondonGoogle Scholar
  16. 16.
    Grange RA (1966) Trans Q. ASM, 59 26Google Scholar
  17. 17.
    Honeycombe RWK, Bhadeshia HKDH (1995) Steels—microstructure and properties, 2nd edition. Edward Arnold, LondonGoogle Scholar
  18. 18.
    Pavlina EJ, Van Tyne CJ (2008) J Mater Eng Perform 17:888–893CrossRefGoogle Scholar
  19. 19.
    Beachem CD (1972) Metallurgical Transactions 3(2):437CrossRefGoogle Scholar
  20. 20.
    Zimmer P, Bollinghaus Th, Kannengiesser Th (2004) “Effects of hydrogen on weld microstructure and mechanical properties of high strength steels S690Q and S1100SQ”, IIW Document III-A-141-04Google Scholar

Copyright information

© International Institute of Welding 2016

Authors and Affiliations

  1. 1.Faculty of Engineering and Information SciencesUniversity of WollongongWollongongAustralia
  2. 2.Export and Armour ManagerBisalloy SteelsUnanderraAustralia

Personalised recommendations