Effect of Controlled Cooling on Microstructure and Tensile Properties of Low C Nb-Ti-Containing HSLA Steel for Construction

Author： Fan Yi Wang Qian Liu Hongwu Wang Tongliang Wang Qingfeng Zhang Fucheng

Publisher： MDPI

E-ISSN： 2075-4701|7|1|23-23

ISSN： 2075-4701

Source： Metals, Vol.7, Iss.1, 2017-01, pp. : 23-23

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Abstract

The thermo-mechanical control processing (TMCP) of low carbon (C) Nb-Ti-containing HSLA steel with different cooling rates from 5 to 20 °C/s was simulated using a Gleeble 3500 system. The samples’ microstructure was characterized and the tensile properties measured. The results show that a microstructure mainly consisting of quasi-polygonal ferrite (QPF), granular bainitic ferrite (GBF), and martensite/austenite (M/A) constituent formed in each sample. Furthermore, the accelerated cooling led to a significant grain refinement of the QPF and GBF, and an increase in the density of dislocations, as well as suppressed the precipitation of nanoscale particles; however, the overall yield strength (YS) still increased obviously. The accelerated cooling also brought about a decrease in amount of M/A constituent acting as a mixed hard phase, which weakened the overall strain-hardening capacity of the QPF + GBF + M/A multiphase steel and simultaneously elevated yield-to-tensile strength ratio (YR). In addition, the mechanisms in dominating the influence of controlled cooling on the final microstructure and tensile properties were discussed.