Abstract: The structure and mechanical properties of 15 mm plate of bridge steel Q690q (/% : 0. 05C, 0. 30Si, 1. 40Mn, 1. lOCu, 0. 50Cr, 0. 80Ni, 0. 07V, 0. 55Mo, weld cold-cracking sensitivity index P_cm ≤0. 267) processed by both technology i. e. the thermal-mechanical control rolling process (TMCP) - finishing rolling at 920 ℃ , cooling at finishing temperature 830 T with 12℃ /s to 590 Y , air cooling, and the process of TMCP + quenching at 940 ℃ , tempering at 630 ℃. have been studied. Results show that the main structure of bridge steel Q690q produced by TMCP process consists of granular bainite and minor ferrite, and the structure of steel Q690q produced by TMCP + quenching-tempering treatment is polygonal ferrite and minor cement with yield strength R_{P0. 2}- 845 〜870 MPa, tensile strength R_m-895 ~900 MPa, impact energy at -20 ℃ 153 〜186 J, at -40℃ 141 〜155 J. Due to quenching and tempering treatment the M/A island size and the dislocation density in structure of steel products decrease thereby to get higher strength and better impact toughness of steel Q690q.

摘要： 研究了920℃精轧,830℃终轧以12℃/s冷至590℃,空冷的TMCP控制轧制工艺和TMCP+940℃淬火-630℃回火两工艺的桥梁钢Q690q(/%:0.05C、0.30Si、1.40Mn、1.10Cu、0.50Cr、0.80Ni、0.07V、0.55Mo,焊接冷裂纹敏感指数P_cm≤0.267)15mm板组织和力学性能。结果表明,TMCP工艺生产的桥梁钢Q690q组织主要由粒状贝氏体和少量铁素体组成,TMCP+调质处理后的组织为多边形铁素体和少量渗碳体,其屈服强度R_p0.2为845～870MPa,抗拉强度Rm895～900MPa,-20℃冲击功153～186J, -40℃为141～155 J。调质处理减小了钢材的M/A岛尺寸和位错密度,使Q690_q钢保持高强度的同时也具有较好的冲击韧性。