含铜低碳硅锰钢的连续冷却转变曲线及显微组织

摘要

通过 Gleeble-3800型热模拟试验机测出含铜低碳硅锰钢在不同冷却速率(1~150℃·s－1)下连续冷却的热膨胀曲线，绘制出该钢的连续冷却转变(CCT)曲线；结合金相观察及显微硬度测试分析了冷却速率对相变组织及硬度的影响。结果表明：冷却速率在1~5℃·s－1时，显微组织主要为铁素体＋珠光体；当冷速为10℃·s－1时组织中出现马氏体，随着冷速增大，马氏体含量增多，珠光体发生退化并逐渐减少，铁素体总量减少，其中针状铁素体增加而多边形铁素体减少并消失；冷却速率超过120℃·s－1后，针状铁素体基本消失，显微组织为马氏体＋少量残余奥氏体；试验钢显微硬度随冷却速率的增大而增加。%The dilatometric curves of the copper bearing low-carbon Si-Mn steel at different cooling rates (1-1 50 ℃·s-1 )were determined by Gleeble-3800 thermal mechanical simulator.And the continuous cooling transformation (CCT)curves of the steel were obtained.The effects of the cooling rates on the microstructure evolution and microhardness were also analyzed with the microstructure observation and hardness measurement.The results show that at the cooling rate between 1 - 5 ℃·s-1 ,the microstructure mainly consisted of ferrite and pearlite.The martensite appeared at the cooling rate of 10 ℃·s-1 and the content increased with the increase of cooling rate,meanwhile the pearlite degenerated and decreased and the content of ferrite also decreased,among which the acicular ferrite increased and polygonal ferrite decreased then disappeared.The acicular ferrite disappeared and the microstructure consisted of martensite and retained austenite when the cooling rate was higher than 120 ℃·s-1 .The microhardness of the steel increased with the cooling rate increase.