370 MPa级纵向变厚度耐候桥梁钢板性能及组织演变研究

为了开发桥梁用减量化、节约型绿色纵向变厚度(LP)钢板,通过合理的化学成分设计,结合鞍钢集团鲅鱼圈5 500 mm厚板生产线工艺路线,设计了合理的加热及轧制规程,成功试制出370 MPa级纵向变厚度桥梁钢板,其最大变厚度尺寸25 mm;通过拉伸、冲击、弯曲、OM、TEM等试验,检测了其组织性能。结果表明:纵向变厚度桥梁钢板具有优良的综合力学性能,随着轧制方向钢板厚度的增加,总变形量减小、终轧温度升高、冷却速率减小,钢板屈服强度有所降低,伸长率提高,抗拉强度较为稳定,-40 ℃冲击功有所波动。不同厚度处钢板金相组织分布有所不同,钢板薄端和中部为铁素体+少量珠光体及贝氏体组织,晶粒尺寸细小;而厚端位置贝氏体组织消失,晶粒较为粗大。钢板轧后空冷的析出相主要为(Nb,Ti)C,薄端析出相尺寸小、数量多,厚端析出相尺寸大、数量少。试制的LP钢板整板组织性能均匀性较好。

Research on properties and microstructure evolution of 370 MPa grade longitudinal profiled weathering bridge plate

In order to develop a reduced and economical green longitudinal profiled plate for bridges, through reasonable chemical composition design, combined with the process route of the Bayuquan 5 500 mm heavy plate production line of Anshan Iron and Steel Group, a reasonable heating and rolling schemes were designed, and a 370 MPa grade longitudinal profiled weathering bridge plate was successfully trial-produced.The plate had a maximum variable thickness size of 25 mm, its microstructure and properties were tested through tensile, impact, bending, OM, TEM and other tests.The results show that the longitudinal profiled weathering bridge plate has excellent comprehensive mechanical properties.With the thickness increase of the plate in the rolling direction, the total deformation decreases, the finishing temperature increases, the cooling rate decreases, the yield strength and the elongation of the plate decreases, the tensile strength is relatively stable, and the impact energy at -40 ℃ fluctuates.The distribution of the microstructure of the plate is different at different thicknesses.The thin end and the middle of the plate are ferrite+a small amount of pearlite and bainite, and the grain size is small, while the bainite structure at the thick end disappears, and the grains are relatively coarse.The precipitates of air cooled plate after rolling are mainly (Nb, Ti)C, the thin end precipitates are small in size and large in number, and the thick endprecipitates are large in size and small in number.The microstructure and properties of the trial-produced LP plate are well uniform.