Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling ...Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature （Ar3）, phase microstructures, and hardness were studied. The results show that, in the ease of the deformation with the true strain of 0. 4, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on At3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.展开更多
The design of high-strength steel has long been discussed in the field of metal structural materials.To further increase the strength of common high-strength steel and further decrease the cost for production,three di...The design of high-strength steel has long been discussed in the field of metal structural materials.To further increase the strength of common high-strength steel and further decrease the cost for production,three direct-quench hot rolled steels were designed and fabricated.The rolling and coiling processes were set based on continuous cooling transformation curves.In addition,the effect of the coiling temperature on the tensile properties was discussed to further guide the optimization of the process.It was found that compared with granular bainite,lower bainite probably has more advantages for both the strength and low temperature impact toughness of direct-quench hot rolled steels.Through a process of tailoring the morphology of bainite and controlling the grain boundary precipitation,the newly designed direct-quench hot rolled steels showed greatly improved strength and acceptable ductility/toughness compared with traditional quenched and tempered steels.展开更多
基金Item Sponsored by National Natural Science Foundation of China (50527402)
文摘Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature （Ar3）, phase microstructures, and hardness were studied. The results show that, in the ease of the deformation with the true strain of 0. 4, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on At3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51722101 and U1808208)National Key Research and Development Program(Grant Nos.2017YFB0304402 and 2017YFB0703001)the financial support provided by the Joint Project of Benxi Iron and Steel Group Co.,(KJB2016004).
文摘The design of high-strength steel has long been discussed in the field of metal structural materials.To further increase the strength of common high-strength steel and further decrease the cost for production,three direct-quench hot rolled steels were designed and fabricated.The rolling and coiling processes were set based on continuous cooling transformation curves.In addition,the effect of the coiling temperature on the tensile properties was discussed to further guide the optimization of the process.It was found that compared with granular bainite,lower bainite probably has more advantages for both the strength and low temperature impact toughness of direct-quench hot rolled steels.Through a process of tailoring the morphology of bainite and controlling the grain boundary precipitation,the newly designed direct-quench hot rolled steels showed greatly improved strength and acceptable ductility/toughness compared with traditional quenched and tempered steels.
