中文摘要：

采用热模拟技术、力学性能测试手段及显微分析方法，研究了三种X80管线钢焊接粗晶区在不同焊接热输入（E）下冲击韧性和断裂韧性的变化规律。结果表明，当E〉30kJ／cm时，由于粗晶区中多边形铁素体和珠光体的形成，致使其韧性严重恶化；在E〈15kJ／cm条件下，由于马氏体的过饱和固溶作用以及较高冷却速度所形成的高应力状态，使得粗晶区的韧性受到损害；而在E=15-20kJ／cm条件下，试验钢焊接粗晶区的主要组织为多位向分布的针状铁素体，表现出较好的韧性值。

英文摘要：

The effect of welding heat input on the toughness and microstructure of CGHAZ in X80 pipeline steels was studied by means of thermal simulation technology, mechanical property tests and microstructure analysis. The results show that the formation of polygonal ferrite and pearlite results in the deterioration of the toughness of CGHAZ in experimental steels when the welding heat input is above 30kJ/crrt When the welding heat input is lower 15 kJ/em,the toughness of CGHAZ in experimental steels decreases as the solid solution effect of super-saturated martensite and the high stress state formed at higher cooling rate appear. The good toughness can be obtained at 15-20kJ/cm of welding heat input because microstructure of CGHAZ in experimental steels is mainly acicular ferrite with high dislocation density and multidirectional distribution.