微合金元素Nb对高碳合金钢动态再结晶行为的影响

Effect of microalloying element niobium on dynamic recrystallizationbehavior of high carbon alloy steel

为研究微合金元素Nb对高碳合金钢动态再结晶行为的影响,利用Gleeble-3500热模拟试验机进行单道次压缩试验,测定了高碳合金钢在变形温度为950~1150℃、应变速率为0.01~5 s^(-1)的流变应力曲线,利用Zeiss光学显微镜观察了奥氏体动态再结晶晶粒形态,通过回归计算获得了相应的再结晶激活能,建立了热变形方程。结果表明:较高的变形温度和较低的应变速率有利于含铌高碳合金钢发生动态再结晶;含铌高碳合金钢的动态再结晶晶粒尺寸随着变形温度的升高而增大,当变形温度为1050℃时,含铌高碳合金钢已大量出现动态再结晶晶粒;0.040%铌加入到高碳合金钢中,在应变速率为0.1 s^(-1),变形温度为1150℃时推迟了钢的动态再结晶开始时间约2.23 s,动态再结晶形变激活能增加了52.26 k J/mol。

In order to study the effect of microalloying element Nb on dynamic recrystallization behavior of the high carbon alloy steel,a single pass compression test was carried out by using Gleeble-3500 thermal simulation tester,and the flow stress curve of the high carbon alloy steel at the deformation temperature of 950-1150℃and the strain rate of 0.01-5 s^(-1) was measured.The dynamic recrystallization grain morphology of austenite was observed by means of Zeiss optical microscope,the corresponding activation energy of recrystallization was obtained through regression calculation,and the thermal deformation equation was established.The results show that the dynamic recrystallization is easier to occur at higher deformation temperature and lower strain rate.The grain size of dynamic recrystallization of the high carbon alloy steel containing Nb increases with the increase of deformation temperature.When the deformation temperature is 1050℃,a large number of dynamic recrystallization grains in the high carbon alloy steel containing Nb can be obtained.The addition of 0.040%niobium to the high carbon alloy steel delays the onset of dynamic recrystallization of the steel by about 2.23 s when the strain rate is 0.1 s^(-1) and the deformation temperature is 1150℃,and increases the activation energy of dynamic recrystallization deformation by 52.26 kJ/mol.