铸辗复合成形法兰坯高温变形行为及加工图

Deformation Behavior at Elevated Temperature and Processing Maps of Flange Blanks on Casting-rolling Compound Forming Technology

环件铸辗复合成形工艺具有缩短工艺流程、高效和节能节材等优点,研究铸态环坯在铸辗复合成形工艺下的高温变形行为,揭示其组织演变机理,是实现材料在该成形工艺中成形与成性的关键。在不同变形条件下对砂型铸造和离心铸造Q235B法兰坯进行高温压缩试验,分析其流变应力的变化,推导出二者的本构方程。综合变形温度和应变速率对材料微观结构与性能的影响,建立基于动态材料模型的加工图。试验结果表明:二者的流变应力随着应变速率的增加和变形温度的降低而增大。离心铸造法兰坯的流变应力较低,动态再结晶易于发生,且功耗效率值及其变化幅度都要大于砂型铸造,表明了其显微组织变化剧烈,演变更加充分。结合二者的热加工图及其识别出的典型区域显微组织,获得了适合该法兰坯辗扩工艺的热力参数范围,离心铸造可为法兰坯铸辗复合成形工艺提供高质量的铸坯。

Casting-rolling compound forming technology of ring-shaped parts has significant advantages such as shortening production process,efficient,saving materials and energy.The deformation behavior and microstructure evolution mechanism are studied for as-cast ring billet during casting-rolling compound forming,and has becoming the key to realize forming and performance of the materials.The compression tests of Q235 B flange blanks from sand casting and centrifugal casting are conducted under different conditions.The variation of flow stresses is analyzed and the constitutive equations are derived.The processing maps are constructed by considering the effects of temperature and strain rate on microstructure and performance based on dynamic materials model.The experimental results show that the flow stress of these two materials increases with increasing strain rate and decreasing temperature.The level of the stress of flange billet for centrifugal casting is low and the dynamic recrystallization is easy to occur.Both the value and the variation of efficiency of power dissipation for centrifugal casting are higher than that of sand casting.It indicates the severe microstructure change and sufficient evolution in centrifugal casting billet.The rolling parameters are achieved by combined with the processing maps and the microstructure of typical areas identified from these maps.The centrifugal casting can provide high-quality materials for casting-rolling compound forming technology.