低碳Mn-Nb钢和低碳Mn-Nb-Ti钢的显微组织

MICROSTRUCTURES IN LOW CARBON Mn-Nb STEEL AND LOW CARBON Mn-Nb-Ti STEEL

对低碳Mn-Nb钢和低碳Mn-Nb-Ti钢经不同温度加热奥氏体化后空冷和等温处理条件下的显微组织进行了研究。结果表明:当加热温度低于晶粒粗化临界温度(T_c)时,不论是空冷还是等温处理,两种钢均获得铁素体-珠光体组织。当加热温度高于T_c时,低碳Mn-Nb钢中易出现魏氏组织,而低碳Mn-Nb-Fi钢中则易于出现粒状贝氏体,这可能是因为微合金化元素溶入奥氏体中后影响了钢的转变动力学所致。

Microstructures in low carbon Mn-Nb steel and low carbon Mn-Nb-Ti steel after reheating, air cooling, and isothermal treatment have been investigated. The results show that ferrite- pearlite structure are formed in both tested steels whether the specimen are air cooled or isothermally treated as long as the austenitizing temperature is lower than T_c which is a critical temperature for grains to coarsen. When the reheating temperature is higher than T_c, Widmanstatten structure is liable to appear in the low carbon Mn-Nb steel, and granular bainite in the low carbon Mn-Nb-Ti steel. This may be the effects of microalloying elements dissolved in the austenites on the transformation dynamics of the steels.