Mn含量对高强度耐候钢连续冷却过程中组织和性能的影响

Effect of Mn Content on Microstructure and Properties of High Strength Weathering Steel During Continuous Cooling

采用Gleeble-2000型热模拟试验机及DT-1000膨胀仪研究了两种不同Mn含量（1号含1.42%Mn和2号含0.90%Mn）高强度耐候钢的连续冷却转变过程,分析了不同冷速下两种钢的组织转变和力学性能。结果表明,Mn元素可显著增加高强度耐候钢过冷奥氏体的稳定性,在0.1-60℃/s的冷速范围内1号钢先共析铁素体析出温度比2号钢低约30-50℃。当冷速vNo.1〈0.5℃/s、vNo.2〈1℃/s时,得到F＋P组织。在整个冷却转变过程中,随着冷速的提高,1号钢逐渐得到以岛状马氏体、粒状贝氏体和板条马氏体为主的组织,而2号钢始终是以铁素体为主的组织。同时,随着冷速的提高,两种钢的硬度、抗拉强度随之提高,其中1号钢明显高于2号钢。

CCT curves of No. 1（ 1.42% Mn） and No. 2（0.9% Mn） high strength weathering steels containing ditterent weight percent of Mn were studied by Gleeble-2000 hot simulation test machine and DT-1000 dilatometer. Microstructures and mechanical properties of both steel No. 1 and steel No. 2 at different cooling rates were analyzed. The results show that Mn element obviously improves the stability of supercooled austenite and transformation temperature of proeutectoid ferrite of steel No. 1 is about 30 -50 ℃ lower than that of steel No. 2 at the cooling rate ranges of 0. 1 -60 ℃/s. At the cooling rate ranges of 〈0.5 ℃/s for steel No. 1 and of 〈 1℃/s for steel No. 2 ,the transformation microstructures of these two steels are F ＋ P. With increasing the cooling rate, the microstructure of steel No. 1 gradually becomes to mixture of predominant island-shape martensite, granular bainite and lath martensite;while steel No. 2 is still predominant ferrite. Simultaneously,it is also found that the Vickers-hardness and tensile strength of steel No. 1 and steel No. 2 increase with increasing the cooling rate, and steel No. 1 more dramatically than steel No. 2.