中文摘要：

研究了600，550，500和450℃等温处理对中碳含钒微合金钢晶内铁素体形成的影响，及530℃下钢的组织随等温时间的转变规律。同时测量了不同等温温度处理后钢的维氏硬度，分析了钢中诱导晶内铁素体析出的夹杂物的成分。结果表明：由600℃逐渐降低至500℃进行等温处理，晶内铁素体的含量随之增加，其形状由等轴状变为针状，钢的硬度逐渐降低；但是等温温度降至450℃时，钢中出现了贝氏体，钢的硬度亦随之升高。实验中发现，在远离原奥氏体晶界处，晶内铁素体先于珠光体发生形核长大；由Si、Mn、Ti和V等元素构成的及Mn、Ti和S等元素构成的复合夹杂物可以诱导晶内铁素体形核析出。

英文摘要：

Effect of isothermal treatment temperature in the range of 600, 550, 500 and 450℃, and that of isothermal holding time at 530℃ on formation of intragranular ferrite （IGF） in a medium-carbon vanadium-microalloyed steel were studied. Vickers hardness test was also carried out for the steel isothermally treated at different temperatures, and the constituent of the inclusions that enhance the formation of intragranular ferrite was analyzed by EDAX. The results show that the amount of IGF increases, the shape of IGF changes from equiaxed to acicular, and the hardness decreases, when the isothermal temperature decreases from 600℃ to 500℃. However, bainite forms and the hardness increases when the isothermal temperature decreases to 450℃. It is found that IGF nucleated prior to pearlite in the regions apart from the austenite grain boundary. The further analysis indicates that inclusions consisting of Si, Mn, Ti and V, or of Mn, Ti and S, could induce the IGF nucleation.