50crmnva钢静态连续冷却相变研究大学生毕业论文（设计）.doc

摘 要 随着经济的快速发展，市场对的需求量越来越大。钢是典型的高技术含量和高附加值产品它的自主供应和是一种需求量很大的高潜力钢。本文以中国第一汽车公司为研究对象，在Formastor-F型全自动相变膨胀仪上进行了不同冷却速度的态热模拟实验，采用热膨胀法与金相组织观察法相结合手段，利用orgin软件绘制了的连续冷却转变曲线，即CCT曲线，研究了在连续冷却相变过程中的显微组织演变规律。研究结果表明：随着冷却速度的，铁素体。改变。当冷却速度小于℃/s时，0.5℃/s冷却速率下，显微组织为珠光体、贝氏体和极少量的铁素体。当冷却速率达到0.75℃/s时，相变组织为珠光体和贝氏体。当冷却速率为1~2℃/s时，相变组织为贝氏体和马氏体。当冷却速度超过5℃/s时，相变组织为单一的马氏体组织。随着冷却速度的提高，实验钢的相变组织由铁素体+珠光体，逐渐过渡为体+贝氏体，最后为马氏体，与此同时，其维氏硬度数值逐渐由升高到。 关键词： thermal simulation analysis on continuous cooling phase transformation of the 50CrMnVA steel Abstract With the rapid economic development, market demand for high-quality flat steel spring growing. 50CrMnVA technical requirements in the mechanical properties of steel, gas content, inclusions, and other aspects of decarbonization are higher than conventional spring steel, is typical of high-tech and high value-added products, and both high and ultra high strength plastic, in automotive, chemical containers, heavy industry has a lot of applications [1,2]. It is independent of supply and demand a great spring steel, so that it is particularly important in the existing national spring steel and is a great demand for high potential spring steel.  In this paper, the first Chinese car company provides 50CrMnVA steel for the study, in Formastor-FII-automatic instrument for the expansion phase change on a static thermal simulation experiment with different cooling rates, the use of thermal expansion of the law and observe the microstructure and hardness measurements wears combined means of using software to draw the experimental steel orgin static continuous cooling transformation curve, namely static CCT curves of steel in static experiments studied the continuous cooling transformation process of microstructure evolution. The results show that: (1) CCT curve of the steel high-temperature phase transition region including the transition region, the temperature in the transition region and low transition region into three parts. Mainly transformation products of fer