焊接热输入对Q690高强度桥梁钢焊接热影响区粗晶区组织与力学性能的影响

Effect of welding heat input on microstructure and mechanical properties of coarse-grained welding heat-affected zone of Q690 high strength bridge steel

采用Gleeble-3500热模拟试验机研究了16 mm厚Q690高强度桥梁钢不同焊接热输入(E)条件下焊接热影响区粗晶区(CGHAZ)的组织演变规律,研究了焊接热输入、组织和力学性能之间的关系。结果表明:Q690高强度桥梁钢CGHAZ的组织主要为板条马氏体(LM)、板条贝氏体(LB)和粒状贝氏体(GB)。随着焊接热输入的增大,LM含量逐渐减少,LB和GB含量逐渐增多,组织逐渐粗化;CGHAZ的显微硬度和-40℃冲击吸收能量均逐渐减小;当15 kJ/cm≤E≤30 kJ/cm时,CGHAZ组织为细小的LM和LB,大角度晶界(HAGB)含量较高而GB和M-A组元含量较少,显微硬度较高且冲击韧性较好。

Microstructure evolution of coarse-grained heat-affected zone(CGHAZ) of 16 mm thick Q690 high strength bridge steel under different welding heat input(E) conditions was studied by a Gleeble-3500 thermal simulation testing machine, and the relationships among the heat input, the microstructure and the mechanical properties of the CGHAZ were studied. The results show that the microstructure of CGHAZ of the Q690 high-strength bridge steel is mainly composed of lath martensite(LM), lath bainite(LB) and granular bainite(GB). With the increase of the welding heat input, the content of the LM is gradually reduced, the content of the LB and GB is gradually increased, the microstructure is gradually coarsened, the microhardness and the impact absorption energy at-40 ℃ of the CGHAZ are gradually reduced. When the welding heat input is in the range of 15-30 kJ/cm, the microstructure of the CGHAZ is fine LM and LB, and the high angle grain boundary(HAGB) content is high and the content of GB and M-A components is small, the microhardness is high and the impact toughness is good.