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Cr-Mo低合金钢在工业生产中有着重要的应用。CCT曲线是研究过冷奥氏体相转变的重要依据。通过Gleeble-3500热模拟试验机及DIL805A淬火变形膨胀仪模拟了Cr-Mo低合金钢的变形及冷却工艺,并利用超组元模型进行热力学计算分析。理论计算结果表明,形变通过提高了Cr-Mo低合金钢相变过程中的自由能进而影响了碳在奥氏体中的活度及相界面碳平衡摩尔分数,相界面碳平衡摩尔分数的变化带来了相变驱动力与形核驱动力的不同,进而影响相变的孕育期与过冷度。结果表明,相变孕育期与过冷度的变化与理论计算结果一致,热力学计算很好地解释了形变对相变的影响。同时表明形变可以提高铁素体相变临界冷速,当冷速为0.3℃/s时,Cr-Mo低合金钢可获得最为均匀细小的铁素体晶粒。适当的变形与冷却工艺对改善Cr-Mo低合金钢组织与性能有着重要的作用。
Cr-Mo low alloy steel in industrial production has an important application. CCT curve is an important basis for studying the phase transition of undercooled austenite. The deformation and cooling process of Cr-Mo low alloy steel were simulated by Gleeble-3500 thermal simulation tester and DIL805A quenching deformation dilatometer, and the thermodynamic calculation and analysis were performed by using the super element model. The theoretical calculation results show that the deformation of the Cr-Mo low-alloy steel during the phase transformation process can affect the carbon activity in the austenite and the change of the carbon equilibrium mole fraction at the phase interface and the carbon equilibrium mole fraction at the phase interface Brings about the difference between the driving force for phase transition and the nucleation driver, and then affects the incubation period and degree of undercooling of the phase transition. The results show that the change of phase transition temperature and degree of undercooling is consistent with the theoretical calculation. The thermodynamic calculation well explains the effect of deformation on phase transition. At the same time, it shows that the deformation can increase the critical cooling rate of ferrite transformation. When the cooling rate is 0.3 ℃ / s, the most uniform and fine ferrite grains can be obtained in the Cr-Mo low alloy steel. Appropriate deformation and cooling process to improve the microstructure and properties of Cr-Mo low alloy steel has an important role.