Journal of Northeastern University(Natural Science) ›› 2013, Vol. 34 ›› Issue (12): 1725-1728.DOI: 10.12068/j.issn.1005-3026.2013.12.013

• Materials & Metallurgy • Previous Articles     Next Articles

Effects of Tempering Temperatures on Microstructure and Properties of Low Carbon High Strength Bainitic Steels

SUN Mingxue, WANG Meng, YI Hailong, LIU Zhenyu   

  1. The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China.
  • Published:2013-07-09
  • Contact: SUN Mingxue
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Abstract: The variations of microstructure, mechanical properties of a low carbon highstrength bainitic steel tempered at different temperatures were investigated with optical microscopy(OM), SEM and TEM. The results showed that the appearance of variations of the dislocation density, morphology of the precipitates, merging and coarsening of lath bainite, and decomposition of M/A islands after tempring were the main reasons for the variations of mechanical properties. Compared with the asrolled steel, after tempered at 600℃, the yield strength of the tempered steel increased 35MPa, meanwhile, the impact absorbing energy at -40℃ enhanced 49J, thus the test steel obtained the best combination of the strength and toughness. The improvement of the low temperature impact toughness after tempering mainly relied on the decomposition of the bulk M/A islands. Fine and evenly dispersed M/A islands effectively prevented the propagation of cracks, thus improved the low temperature impact toughness.

Key words: tempering temperature, bainite, precipitation, M/A islands, dislocation

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