铬钒系微合金车轴钢晶粒粗化与变形抗力研究

【作者】 李英；

【导师】 刘建雄； 柯晓涛；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2010， 硕士

【摘要】 金属材料的变形抗力是指金属在一定的变形条件下进行塑性变形时,单位横截面积上抵抗此变形的能力,是表征金属和合金压力加工性能的一个基本量,是轧制力计算过程中的一个重要参数,也是制定合理的轧制工艺、设备能力校核的参数。晶粒粗化是车轴失效的主要原因之一,在热处理过程中,应当注意并防止奥氏体晶粒粗化。铬钒系微合金车轴钢是攀枝花钢铁研究院根据铁道部科学研究院最新提出的铁路货车车轴技术条件研发的一种性能优于LZ50车轴钢的新材质车轴钢。论文针对于晶粒粗化是造成车轴失效的主要原因之一设计了晶粒粗化实验；针对攀铬钒系微合金车轴钢连铸坯中存在的中心疏松、偏析等缺陷,必须在轧制过程中采用大的压下量使中心得到充分变形以消除铸坯中存在的缺陷问题以及采用大的压下量后是否影响轧制设备的正常运行问题设计了变形抗力实验。通过微合金车轴钢晶粒粗化试验,确定了微合金车轴钢的晶粒粗化温度,对于制订合理的车轴钢热处理工艺、防止车轴钢在热处理过程中发生晶粒粗化引起的性能恶化有重要意义。本文利用Gleeble-3500热模拟实验机进行的微合金车轴钢的变形抗力实验研究,对于了解新材质车轴钢的变形抗力特征、优化现场轧制工艺具有重要的参考意义。晶粒粗化实验结果表明微合金车轴钢奥氏体晶粒粗化温度在1150℃左右,比普通碳钢高约200℃,微合金元素钒形成的稳定的第二相粒子阻碍晶界的迁移,阻止奥氏体晶粒的长大,是晶粒粗化温度升高的主要原因。变形抗力热模拟实验结果表明,变形抗力随着变形速率、变形程度的增加而升高,随着变形温度的升高而下降；变形温度与变形抗力遵循在半对数坐标中的线性关系；变形速率与变形抗力遵循在双对数坐标中的线性关系。根据测试的变形抗力曲线特征,分析了变形温度和变形程度对再结晶行为的影响,结果表明高温低速变形条件下容易发生再结晶行为,而低温高速下不易发生；采用Mat lab软件进行了多元非线性模拟,得到的微合金车轴钢变形抗力数学模型。论文对铬钒系微合金车轴钢与40SiMn2、30MnTiB和42CrMo的变形抗力进行了对比分析,结果表明,在常用轧制温度范围内,相同变形条件下微合金车轴钢的变形抗力略低于对比钢种,能够满足轧制工艺和正常生产的要求。更多还原

【Abstract】 Metal materials’deformation resistance, an elementary quatity of their plastic properties, is the capability to resist plastic deformation per unit cross-sectional area under certain deformation conditions. It is an important parameter of rolling force calculating, reasonable rolling process establishing and equipment checking. As a main cause of axle failure, austenitic grain coarsening should be paid enough attention during heat treatment.Cr-V micro-alloy axle steel, a new kind of axle steel, is developed by Panzhihua Iron & Steel Research Institute according to the axle technology of railway freight cars proposed by Ministry of Railways. Its mechanical properties are superior to those of axle steel LZ50. In this thesis, the grain coarsening experiment was designed based on its influence on axle failure. And the deformation resistance experiment was prepared to study whether heavy rolling reduction, able to eliminate center porosity, segregation and other defects of Cr-V micro-alloy axle steel casting billet, has negative effects on rolling equipment’s normal operation. Appropriate coarsening temperature was determined through grain coarsening experiment, which is important to make reasonable heat treatment process and prevent performance degradation caused by grain coarsening during heat treatment. In this subject, the study on deformation resistance of micro-alloy axle steel, conducted on Gleeble-3500, has a reference significance for understanding the stress-strain curves’characteristics of new axle steel and optimizing onsite rolling process.The grain coarsening results show that austenite grain coarsening temperature of new axle steel is about 1150℃,200℃higher than ordinary steel. The stable second phase formed by Vanadium and other elements is the main reason for the increase of grain coarsening temperature.The deformation resistance results show that deformation resistance increases with the increase of deformation rate and extent, and decreases with the increase of deformation temperature; the deformation temperature and resistance follow a linear relationship in semi-logarithmic coordinate, so do the deformation rate and resistance in double logarithmic coordinate. Based on the characteristics of stress-strain curves, the effects of deformation temperature and extent on recrystallization were analyzed. It is found that recrystallization happens easily under high temperature and low deformation rate, but not under low temperature and high deformation rate. With mat lab software, multivariate non-linear simulation was carried out, and the mathematical model of Cr-V micro-alloy axle steel was obtained.A further study on deformation resistance was made among Cr-V micro-alloy axle steel,40SiMn2,30MnTiB and 42CrMo. The results show that under common rolling temperature and same deformation conditions, micro-alloy axle steel, whose deformation resistance is slightly lower than other steels’, can completely meet the needs of rolling process and normal production.更多还原