Journal of Northeastern University Natural Science ›› 2017, Vol. 38 ›› Issue (9): 1251-1256.DOI: 10.12068/j.issn.1005-3026.2017.09.009

• Materials & Metallurgy • Previous Articles     Next Articles

Effects of Welding Speed on Microstructure and Properties of Laser Welded Joints of Dual-Phase Steel

DONG Dan-yang, JIANG Di, YANG Run-chen   

  1. School of Sciences, Northeastern University, Shenyang 110819, China.
  • Received:2016-04-18 Revised:2016-04-18 Online:2017-09-15 Published:2017-09-08
  • Contact: DONG Dan-yang
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Abstract: In order to improve the service reliability of the welded component for auto-body under the dynamic load, the effects of laser welding speed on the microstructure and tensile properties at various strain rates of the pulsed laser welded joints of 1.4mm thick DP780 steel were studied. The results showed that the DP780 welded joints exhibit the hardening in the fusion zone and the softening in the outer heat-affected zone under various welding speeds. The softening degree of the welded joints decreases with increasing welding speed. The strength of the welded joints increases with increasing strain rate, and the ultimate tensile strength and fracture elongation increase first and then decrease with increasing welding speed. The welded joints with good surface morphology, moderate weld width and penetration, no weld defect are fabricated when the welding speed is 400mm/min. And the softening degree of the outer heat-affected zone is the lowest with the softening fraction of 9% and the hardness in the fusion zone is moderate. The overall strength and ductility of the DP780 welded joint reach an optimum value under the welding speed of 400mm/min.

Key words: dual-phase steel, laser welding, welding speed, mechanical properties, strain rate

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