GH4169大型铸坯加热过程温度场与晶粒度演变研究

Research on Temperature Field and Grain Size Evolution During Heating of GH4169 Large Casting Billet

摘要:

基于DEFORM-3D有限元软件,针对GH4169合金大型铸坯加热过程中表面至芯部传热不均匀问题,建立了大型铸坯温度场模型,研究了加热工艺参数对合金内部传热特性和温度场分布规律的影响。模拟结果表明,不同表面综合换热系数对传热效率具有显著影响,对于不同固定值表面综合换热系数,随着表面综合换热系数的升高,表面至芯部的传热效率明显提升;而对于变化值表面综合换热系数,截面温差相对较小,表面至芯部的传热效率相对较低,但传热过程相对较为均匀。为了研究GH4169合金加热过程中晶粒度变化规律,制备了GH4169合金试样,并系统实施多组热处理试验,通过金相观测法对热处理后的组织及晶粒结构演变规律展开分析,试验结果显示,经多组热处理后,材料表面组织的晶粒出现显著粗化现象,具体表现为:在1 000 ℃以下热处理时,晶粒呈现缓慢长大趋势,保温时间越长,晶粒长大越为明显,尺寸为3~8 μm;而在1 100 ℃以上热处理时,晶粒呈现显著粗化趋势,尺寸增长到75~100 μm,随着保温时间的加长,晶粒长大逐渐缓慢。

Abstract:

Based on the DEFORM-3D finite element software, a temperature field model of the large casting billet was established for the problem of uneven heat transfer from the surface to the core during the heating process of the large casting billet of GH4169 alloy. The influence of heating process parameters on the internal heat transfer characteristics and temperature field distribution law of the alloy was studied. The simulation results show that the comprehensive heat transfer coefficients of different surfaces have a significant impact on the heat transfer efficiency. For the comprehensive heat transfer coefficients of surfaces with different fixed values, as the comprehensive heat transfer coefficients of the surfaces increase, the heat transfer efficiency from the surface to the core is significantly improved. For the variable surface comprehensive heat transfer coefficients, the cross-sectional temperature difference is relatively small, the heat transfer efficiency from the surface to the core is relatively low, but the heat transfer process is relatively uniform. In order to study the variation law of grain size of GH4169 alloy during the heating process, GH4169 alloy samples were prepared, and multiple sets of heat treatment tests were systematically carried out. The microstructure and the evolution law of grain structure after heat treatment were analyzed through metallographic observation. The test results showed that after multiple sets of heat treatment, the grains of the surface microstructure of the material showed a significant coarsening phenomenon. The specific manifestations are as follows: When heat-treated below 1 000 ℃, the grains show a slow growth trend. The longer the holding time, the more obvious the grain growth, with a size range of 3~8 μm. When heat-treated above 1 100 ℃, the grains show a significant coarsening trend, and the size increases to 75~100 μm. With the extension of the holding time, the growth of the grain structure gradually slows down.