低Mn高Nb耐酸管线钢热处理工艺研究

对高Nb管线钢在500～680 ℃回火工艺处理后的性能与组织进行了研究。试验结果表明，与轧态相比，600 ℃回火后，材料力学性能达到最优值，其屈服强度提高105～130 MPa,抗拉强度提高50～70 MPa；韧性、伸长率变化较小；回火前后的组织类型保持不变，仍以针状铁素体为主；随回火温度的升高，铁素体板条逐渐合并，M/A组元和碳化物明显分解，出现准多边形铁素体；600 ℃回火后，析出物钉扎位错的现象比较明显；细小析出物的增加是强度增加、塑性改善的主要原因。

Research on Heat Treatment Process of Low Mn High Nb Sour Resistance Pipeline Steel

The mechanical properties and microstructure of high Nb pipeline steel after tempering at 500～680 ℃were studied. The results indicated that the mechanical properties achieved the optimal value after tempering at 600 ℃，compared with the steel at rolled status. The yield strength was increased by 105~130 MPa and tensile strength was enhanced about 50~70 MPa. The toughness and elongation varied slightly. The microstructure type before and after tempering keep the same, which were mainly acicular ferrite；With tempering temperature increased, the ferrite lath gradually was merged，M/A islands and carbides were obviously decomposed, and polygonal ferrite was evolved. After 600 ℃ tempering，the pinning dislocation phenomenon was obvious，and the increase of fine precipitates are the main reason for strength increase and plasticity improvement.