Effects of Ultra-Fast Cooling Technology on Microstructure and Properties of Low Carbon Steel

Abstract

The cooling technology after hot-rolling influences the microstructure and mechanical properties of steels. Combined with dynamic continuous cooling transformation (CCT) curve by the thermal simulation experiments of Q235B steel, the effects of ultra-fast cooling technology on microstructure and properties of Q235B steel were investigated by optical microscope, scanning electron microscope, tensile and impact tests. Also, the fracture morphology analysis was conducted by scanning electron microscope. The results show that both yield and tensile strength are enhanced by ultra-fast cooling technology. Moreover, the yield and tensile strength increase with the increase of cooling rate of ultra-fast cooling process, while the ductility has no significant change. Furthermore, the yield and tensile strength increase with the decrease of final cooling temperature of ultra-fast cooling process with a little reduction in ductility. The impact tests show that all samples possess excellent impact toughness varying within a small range. The yield strength, tensile strength, and impact toughness of Q235B steel could increase to 395, 516 MPa, and 143 J, respectively, using ultra-fast cooling technology. The study provides theoretical guidance for industrial application of ultra-fast cooling technology.