低锰管线钢的相变行为

PHASE TRANSFORMATION BEHAVIOR OF LOW MANGANESE LINEPIPE STEEL

低锰成分体系的管线钢因其优异的耐酸性能,在国际管线钢领域引发热烈关注。利用热力学软件Thermo-Calc计算了低锰和高锰成分钢在包晶反应和共析反应温度区间的相图,结果表明低锰钢的δ-Fe单相区温度跨度比高锰钢大,更有利于溶质原子均匀化扩散,在共析温度附近的α-Fe单相区中C的最大固溶度显著高于高锰钢。利用Thermecmastor-Z热模拟试验机对某低锰含量管线钢进行了形变奥氏体连续冷却转变热模拟试验,以冷速0.1~10℃/s连续冷却时,组织主要为多边形铁素体和很少量的珠光体,随冷速增加,铁素体和珠光体都更加细小;冷速超过15℃/s时,组织为铁素体和粒状贝氏体。

Steel of low manganese has attracted enthusiastic attention from the linepipe industry globally, owing to its excellent sour resistance. The phase diagrams in the peritectic and euteetoid temperature range of low-Mn and high-Mn steel were calculated by Thermo-Calc, respectively. In low-Mn steel, the temperature span of ^-Fe phase region and the maximum solubility of carbon in α-Fe phase were obviously larger than those in high-Mn steel. The thermo-simulator Thermecmastor-Z was used to investigate the continuous cooling transformation behavior of the tested low-Mn steel. While the cooling rate ranges from 0. 1 to 10 ℃/s, the deformed austenite transformed to polygonal ferrite and a little pearlite, which was refined by the increased cooling rate. While the cooling rate exceeds 15 ℃/s, the transformed microstructure was composed of polygonal ferrite and granular bainite.