讨论了X65、X70管线钢铸坯不同温度区间高温延塑性的差异。根据Gleeble1500热/力模拟机得到的数据绘出X65、X70钢铸坯断面收缩率-温度曲线，利用扫描电镜、金相显微镜对断口形貌及组织进行分析，得出两钢种在各温度区间塑性差别的主要原因：①高温脆性区(tl~1 300 ℃)X70塑性较好，碳含量越高，硫、磷在奥氏体晶界的偏析量越多；②高温高塑性区(1 100~1 300 ℃)X65延塑性较好，钛含量越高，使得TiN析出物越粗大，分布越随机；③在塑性槽高温端(900~1 100 ℃)，低熔点硫化物等析出，动态再结晶发生温度不同，导致两个钢种塑性明显有差别；④在塑性槽两相区(700~900 ℃)，先共析铁素体的出现是两个钢种塑性低的共同原因，钛可以促进铁素体在晶内和晶界同时生成，最后X65塑性恢复较好。
The difference of the hot ductility of X65 and X70 pipeline casting blank is mainly discussed. The RA changes with temperature were got by means of Gleeble1500 machine. Then their fracture surface and metallic phase tissue were analyzed by SEM and optical microscope. The difference in the two kinds of steel ductility in different temperature zone is as follows: ① Within the scope of high temperature brittle zone (tl-1 300 ℃), X70 is better, the more the carbon content, the more is the sulphur at γ grain boundary; ② In high temperature high ductility zone, X65 is better, the higher the Ti content, the thinker is the TiN and the more is the TiN random distribution in and out of grain boundary; ③ At upper side of ductility trough (900-1 100 ℃), X70 was better than X65, low melting point materials emerged which weakened grain boundary and dynamic recrystallization temperature differed, which result in different ductility; ④ In low temperature brittle zone (700-900 ℃), ductility decreased because of precipitated proeutectoid ferrite emerged, strain induced ferrite was urged by Ti formed at grain boundary and crystal interior simultaneously. The plasticity of X65 steel was restored better in the end.
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