加热温度对钛铌复合微合金化高强钢析出和性能的影响

在实验室冶炼了一种低碳高强度微合金钢,进行了轧制和回溶试验,对轧制试样进行了拉伸试验﹑检验了金相组织,并用TEM对比分析了不同加热温度下试样的析出物形貌、成分、尺寸。结果表明,1 280℃加热保温后轧制产品的性能优于1 180℃加热轧制后产品的性能;两种加热温度下轧制试样的组织都由铁素体和珠光体组成,晶粒尺寸基本相同;轧制试样的析出物均为(Ti,Nb)(C,N)复合析出,但1 280℃加热温度的试样析出更加细小、数量更多。析出强化理论计算表明,加热温度高的试样析出强化要比加热温度低的试样高131 MPa。回溶试验表明,铸坯在1 280℃保温1.5 h后,析出物基本回溶,而1 180℃保温1.5 h后,析出物不能充分溶解,证明了加热温度对钛铌微合金化高强钢析出强化有较大的影响。

Effect of Heating Temperature on Precipitation and Property of Ti-Nb Composite Microalloyed High-strength Steel

A low-carbon high-strength microalloyed steel was smelted in laboratory.Rolling,redissolving and tensile tests were performed.In addition,microstructure of the rolled steels was observed and the morphology,type and size of precipitates at different reheating temperature were analyzed.The results show that property of the sample heated at the temperature of 1 280 ℃ is superior to that of sample heated at 1 180 ℃;the microstructures of these steels under the two temperature schemes consist of ferrite and pearlite with basically the same grain size;and the(Ti,Nb)(C,N) composite precipitates,but the precipitates of the sample heated at 1 280 ℃ are smaller and more in quantity.The calculation based on precipitation hardening theory indicates that the precipitation hardening of the sample heated at high temperature is 131 MPa higher than that of low temperature-heated specimen.Furthermore,redissolving experiment shows that the precipitates virtually dissolve in steel as the sample is heated to 1 280 ℃ and kept at the temperature for 1.5 hours,while the precipitates cannot fully dissolve in steel as the sample is heated to 1 280 ℃ and kept at the temperature for 1.5 hours,which proves that heating temperature has a strong influence on the precipitation hardening of Ti-Nb composite microalloyed steel.