【摘要】 利用Gleeble-3500热模拟试验机对18CrNiMo7-6齿轮钢进行了等温单道次压缩试验，研究了变形温度为900～1150℃,应变速率为0.01～5 s^-1,应变为0.76的条件下材料的热变形行为；并且通过光学显微镜对热变形后的微观组织进行了分析。建立了唯象型Arrhenius本构方程，预测的峰值应力与试验数据具有很好的一致性。高温热变形过程是加工硬化与动态回复以及动态再结晶的竞争过程，在热变形的过程中会形成变形晶粒、再结晶晶粒、等轴晶和晶粒长大等4种类型的微观组织。当应变速率为0.01 s^-1时，动态再结晶程度与变形温度成正比，当变形温度超过1050℃时，变形能转变成晶粒长大的驱动能，使得晶粒粗大；当应变温度一定（1050℃）时，随着应变速率的增大，动态再结晶发生不完全，导致晶粒组织出现细化、畸变、不完全再结晶共存的现象。变形程度越大，晶粒越细小。更多还原

【Abstract】 Isothermal single-pass compression test of the 18CrNiMo7-6 gear steel was carried out by Gleeble-3500 thermal simulation testing machine. The hot deformation behavior of the tested steel was studied under the conditions of deformation temperature of 900-1150 ℃, strain rate of 0.01-5 s^-1 and strain of 0.76, and the microstructure after hot deformation was analyzed by optical microscope. The Arrhenius constitutive equation is established, and the predicted peak stress is in good agreement with the experimental data. The hot deformation process at high temperature is a competitive process between work hardening and dynamic recovery and dynamic recrystallization. In the process of hot deformation, four types of microstructure including deformed grains, recrystallized grains, equiaxed grains and grown grains are observed. When the strain rate is 0.01 s^-1, the higher the temperature, the more sufficient the dynamic recrystallization. However, when the deformation temperature exceeds 1050 ℃, the deformation energy transforms into the driving energy of grain growth, which makes the grains coarsen. When the deformation temperature is constant（1050 ℃）, with the increase of strain rate, the dynamic recrystallization occurs incompletely, the resulted grains are mixed of refined, distorted and incompletely recrystallized ones. The larger the deformation degree, the smaller the grain size.更多还原