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根据大型筒节的轧制和轧后冷却模型,模拟大型筒节轧制截面的应变率和轧后冷却速度曲线;结合Gleeble-3800对金属小试样2.25Cr-1Mo-0.25V钢进行了热压缩模拟实验,得出了多道次压缩的流变应力曲线;分析了小试样热变形后不同冷却方式对其组织形貌的影响和对后期正火晶粒细化的作用。结果表明,2.25Cr-1Mo-0.25V钢轧制过程心部大部分区域温度不变;轧制压下率低,心部应变率不足10%;道次间歇时间长,静态软化率高达95%,奥氏体晶粒回复长大;轧后空冷过程心部冷却速度缓慢,冷却后基体主要为粒状珠光体组织,经后期热处理晶粒不易细化,是造成组织遗传的主要原因;增大轧后冷却速度和降低冷却转变温度有利于后期热处理晶粒细化,采用喷淋-空冷联合冷却能充分利用大型筒节的轧后余热,冷却过程热应力较小,有利于促进后期热处理组织细化。
According to the rolling and rolling cooling model of the large tubular section, the strain rate and the cooling rate curve after the rolling of the large tubular section are simulated. The hot metal small sample 2.25Cr-1Mo-0.25V is heated with Gleeble-3800 Compression experiments were carried out to obtain the multi-pass flow stress curves. The effect of different cooling methods on the microstructure and the grain refinement of the late-stage nodules were analyzed. The results show that the temperature in most of the 2.25Cr-1Mo-0.25V steel rolling process is constant, the rolling reduction rate is low, the strain rate of the heart is less than 10%, the intermittent time is long, the static softening rate is as high as 95% , The austenite grains grow back up. After cooling, the core cooling rate is slow. After cooling, the matrix is mainly composed of granular pearlite, which is not easy to be refined after the heat treatment. It is the main reason that causes the heredity of the tissues. The post-cooling rate and the cooling-reduction transition temperature are favorable for the grain refinement in the later stage. Spraying-air-cooling combined cooling can make full use of the post-rolling residual heat of the large tubular section. The thermal stress during the cooling process is small, .