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利用Gleeble-3500D热模拟试验机,在变形温度为870~1170℃,应变速率为0.05~3 s-1,最大变形量为60%的条件下,对LZ50钢进行等温恒应变速率的热压缩实验,研究应变速率和变形温度对流变应力的影响,建立LZ50钢热变形时的本构方程和热加工图。结果表明:LZ50钢的流变应力随变形温度的升高和应变速率的降低而减小,其动态再结晶型流变应力曲线可表述为加工硬化、过渡、软化和稳态流变4个阶段;热变形激活能为304.265 k J/mol,根据双曲正弦方程建立包含Z参数的峰值流变应力本构方程;将LZ50钢的热加工图与快锻液压机的技术参数及通过Deform模拟获得的优化工艺参数相结合可得,当压下量为15%~20%,在开始锻造的高温阶段1050~1150℃,可采用较高的应变速率0.5~3 s-1,随着锻件温度降低至870~1050℃,应适当降低应变速率至0.5~1.5 s-1以避开失稳区,整个变形过程的微观组织演变机制为动态回复。
Using the Gleeble-3500D thermal simulation tester, the isothermal compression test of isothermal constant strain rate of LZ50 steel was carried out under the conditions of deformation temperature of 870 ~ 1170 ℃, strain rate of 0.05 ~ 3 s-1 and maximum deformation of 60% The effect of strain rate and deformation temperature on the flow stress was studied. The constitutive equation and the hot working diagram of LZ50 steel were established. The results show that the flow stress of LZ50 steel decreases with the increase of deformation temperature and the decrease of strain rate. The dynamic recrystallization flow stress curves can be expressed as four stages of work hardening, transition, softening and steady flow ; The thermal deformation activation energy is 304.265 kJ / mol, the peak flow stress constitutive equation including Z parameter is established based on the hyperbolic sine equation; the thermal processing diagram of LZ50 steel and the technical parameters of the fast forging hydraulic press are obtained by Deform simulation Optimum process parameters can be obtained when the reduction of 15% to 20%, at the beginning of forging high temperature 1050 ~ 1150 ℃, the higher strain rate can be 0.5 ~ 3 s-1, as the forging temperature decreases to 870 ~ 1050 ℃, the strain rate should be properly reduced to 0.5 ~ 1.5 s-1 to avoid the instability zone. The microstructure evolution mechanism of the whole deformation process is a dynamic response.