Strong steels are usually difficult to resistance spot weld because of the tendency to form hard phases. This applies particularly to the transformation induced plasticity (TRIP) assisted steels with relatively high carbon equivalents. A new development in this context is the δ-TRIP steel, designed to retain δ-ferrite as a stable phase at all temperatures below melting. Fully martensitic regions are therefore avoided, making it possible to weld in spite of the high carbon concentration. The authors present here the first spot welding tests on the novel alloy system.
MatsumuraO., SakumaY. and TakechiH.: ‘Enhancement of elongation by retained austenite in intercritical annealed 0·4C–1·5Si–0·8Mn steel’, Trans. ISIJ, 1987, 27, 570–579.
2.
MatsumuraO., SakumaY. and TakechiH.: ‘TRIP and its kinetic aspects in austempered 0·4C–1·5Si-0·8Mn steel’, Scr. Metall., 1987, 27, 1301–1306.
3.
DeCoomanB. C.: ‘Structure–properties relationship in TRIP steels containing carbide-free bainite’, Curr. Opin. Solid State Mater. Sci., 2004, 8, 285–303.
4.
JacquesP. J.: ‘Transformation-induced plasticity for high strength formable steels’, Curr. Opin. Solid State Mater. Sci., 2004, 8, 259–265.
5.
SugimotoK., KobayashiM. and HashimotoS.: ‘Ductility and strain-induced transformation in a high-strength trip aided dual phase steel’Metall. Trans. A, 1992, 23A, 3085–3091.
6.
SherifM., Garcia-MateoC., SourmailT. and BhadeshiaH. K. D. H.: ‘Stability of retained austenite in TRIP-assisted steels’, Mater. Sci. Technol., 2004, 20, 319–322.
7.
KhanM. I., KuntzM. L., SuP., GerlichA., NorthT. and ZhouY.: ‘Resistance and friction stir spot welding of DP600: a comparative study’, Sci. Technol. Weld. Join., 2007, 12, 175–182.
8.
KhanM. I., KuntzM. L. and ZhouY.: ‘Effects of weld microstructure on static and impact performance of resistance spot welded joints in advanced high strength steels’, Sci. Technol. Weld. Join., 2008, 13, 294–304.
9.
DaneshpourS., RiekehrS., KocakM., VentzkeV. and KorkukA. I.: ‘Failure behaviour of laser spot welds of TRIP800 steel sheets under coach-peel loading’, Sci. Technol. Weld. Join., 2007, 12, 508–515.
10.
PouranvariM. and MarashiS. P. H.: ‘Key factors influencing mechanical performance of dual phase steel resistance spot welds’, Sci. Technol. Weld. Join., 2010, 15, 149–155.
11.
KhanM. S., BholeS. D., ChenD. L., BiroE., BoudreauG. and van DeventerJ.: ‘Welding behaviour, microstructure and mechanical properties of dissimilar resistance spot welds between galvannealed HSLA350 and DP600 steels’, Sci. Technol Weld. Join., 2010, 14, 616–625.
12.
OroszC., PalotásB. and DobránszkyB.: ‘Welding investigations of modern high strength dual phase and TRIP-steel for automotive industry application’, Mater. Sci. Forum, 2007, 537–538, 431–438.
13.
DaneshpourS., RiekehrS., KocakM. and GerritsenC. H. J.: ‘Mechanical and fatigue behaviour of laser and resistance spot welds in advanced high strength steels’, Sci. Technol. Weld. Join., 2009, 14, 20–25.
14.
CretteurL., KorkukA. I. and Tosal-MartínezL.: ‘Improvement of weldability of trip steels by use of in-situ pre- and post-heat treatments’, Steel Res., 2002, 73, 314–319.
15.
CretteurL. and KorukA. I.: ‘Heat treatments to improve weldability of new multiphase high strength steels’, Mater. Sci. Forum, 2003, 426–432, 1225–1230.
16.
MimerM., SvenssonL. E. and JohanssonR.: ‘Process adjustments to improve fracture behaviour in resistance spot welds of AHSS and UHSS’, Weld. World, 2004, 48, 14–18.
17.
ChatterjeeS., MurugananthM. and BhadeshiaH. K. D. H.: ‘δ-TRIP steel’, Mater. Sci. Technol., 2007, 23, 819–827.
18.
YiH. L., GhoshS. K., LiuW. J., LeeK. Y. and BhadeshiaH. K. D. H.: ‘Nonequilibrium solidification and ferrite in δ-TRIP steel’Mater. Sci. Technol., 2010, 26, 817–823.
19.
YiH. L., LeeK. Y. and BhadeshiaH. K. D. H.: ‘Extraordinary ductility in Al-bearing δ-TRIP steel’, Proc. R. Soc. A, 2010, DOI: 10.1098/rspa.2010.0127.
20.
BhadeshiaH. K. D. H.: ‘Bainite in steels’, 2nd edn; 2001, London, Institute of Materials.
21.
‘Specimen dimensions and procedure for shear testing resistance spot and embossed projection welded joints’, JIS Z 3136, Japanese Standards Association, Tokyo, Japan, 1999.
22.
‘Specimen dimensions and procedure for cross testing resistance spot and embossed projection welded joints’, JIS Z 3137, Japanese Standards Association, Tokyo, Japan, 1999.
23.
‘Method of macro test for section of spot welded joint’, JIS Z 3139, Japanese Standards Association, Tokyo, Japan, 1978.
24.
‘Method of inspection for spot weld’, JIS Z 3140, Japanese Standards Association, Tokyo, Japan, 1989.
25.
‘Resistance welding – Weldability – Part 2: Alternative procedures for the assessment of sheet steels for spot welding’, ISO 18278–2:2004E, ISO, Geneva, Switzerland, 2004.
26.
SakumaY. and OikawaH.: ‘Factors to determine static strengths of spot-welds for high strength steel sheets and developments of high-strength steel sheets with strong and stable welding characterisitics’, Nippon Steel Corp. Tech. Rep., 2003, (88), 34–38.
27.
YiH. L., LeeK. Y. and BhadeshiaH. K. D. H.: ‘Stabilisation of ferrite in hot-rolled in d-TRIP steel’, Mater. Sci. Technol., 2010, 26, DOI: 10.1179/026708309X12506934374001.
28.
ChukoW. L. and GouldJ. E.: ‘Development of appropriate resistance spot welding practice for transformation-hardened steels’, Weld. J., Res. Suppl., 2002, 81, 1S–7S.
29.
SantellaM., BabuS. S., RiemerB. W. and FangZ.: ‘Influence of microstructure on the properties of resistance spot welds’, in ‘Trends in welding research’, (ed. S. A. David et al.), 605–609; 1999, Materials Park, OH, ASM International.
