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以低碳复合添加微合金元素铌和钛为成分设计思路,综合运用细晶强化、相变强化和析出强化三种强化机制,在国内某厂1750 mm半连续热连轧机组进行了780 MPa级大梁钢的工业试制。结果表明,终轧温度需控制在780~860℃,卷取温度需控制在450~550℃。大梁钢的显微组织为贝氏体和少量的细晶铁素体,并获得了大量弥散的尺度为10 nm以下的(Nb,Ti)C析出物。大梁钢的屈服强度为700 MPa,抗拉强度为780 MPa,伸长率为19%。大梁钢具有良好的低温冲击韧性、冷弯成形性及焊接性能。
Low-carbon composite addition of niobium and titanium microalloying elements for the design ideas, the comprehensive use of fine-grain strengthening, phase transformation strengthening and precipitation strengthening three strengthening mechanism in a domestic plant 1750 mm semi-continuous hot strip mill 780 MPa class Industrial trial of girder steel. The results showed that the finishing temperature should be controlled at 780 ~ 860 ℃ and the coiling temperature should be controlled at 450 ~ 550 ℃. The microstructure of the beam steel is bainite and a small amount of fine-grained ferrite, and a large amount of (Nb, Ti) C precipitates with a scale of 10 nm or less are obtained. The yield strength of the girder is 700 MPa, the tensile strength is 780 MPa and the elongation is 19%. Big beam steel has good low temperature impact toughness, cold bend formability and weldability.