镍基高温合金调压铸造非线性压力曲线设计与验证

目的 针对变截面铸件在调压铸造充型阶段出现充型不稳定这一问题，结合数值模拟分析，提出非线性压力曲线的设计方法。方法 基于Pro CAST软件对不同壁厚和不同截面比的模型进行模拟，研究在不同加压速度和不同型壳预热温度下不同壁厚模型浇口速度的变化情况，以及在不同加压速度下不同截面比模型浇口速度的变化情况。针对数值模拟结果提出变截面模型工艺优化方法，设计特征模型进行数值模拟验证；推导在实际调压铸造充型过程中加压速度与充型速度的关系，并利用水力学模拟进行验证。结果 用非线性加压进行数值模拟，相对于线性加压充型过程，其浇口速度普遍呈下降趋势，其中最大浇口速度由0.29 m/s下降到0.2m/s，降幅为45%；在变截面前后，浇口速度呈周期性波动，说明非线性加压充型较为稳定；对推导出的加压速度计算公式进行了水力学模拟实验，从充型形态可以看出，在变截面处水流波动平稳，验证了加压速度计算公式的正确性。结论 通过研究变截面突变浇口速度的变化情况，提出了非线性加压方法，有效解决了调压铸造过程中出现的金属液飞溅、振荡、充型不稳定等问题，不仅提高了铸件的成品率，而且优化了调压设备的精准控压。

Design and Verification of Nonlinear Pressure Curve for Pressure Regulation Casting of Nickel Base Super-alloy

The work aims to propose a design method of nonlinear pressure curve by combining numerical simulation analysis to solve the problem of unstable filling of variable section castings in the filling stage of pressure regulation casting. The model with different wall thickness and different section ratio was simulated based on ProCAST software, and the gate velocity changes under different pressure rates and different shell preheating temperatures were studied under different wall thickness, and the gate velocity changes under different section ratio models under different pressure rates. According to the numerical simulation results, the process optimization method of variable cross section model was proposed, and a characteristic model was designed for numerical simulation verification. The relationship between the pressure rate and the filling velocity in the actual pressure regulation casting process was deduced and verified by hydraulic simulation. The numerical simulation with nonlinear pressure curve showed that compared with the linear pressure filling process, the gate velocity generally decreased, and the maximum gate velocity decreased from 0.29 m/s to 0.2 m/s, with a decrease of 45%. The gate velocity fluctuated periodically before and after the variable section, indicating that the nonlinear pressure filling was stable. The hydraulic simulation experiment was carried out on the deduced formula of pressure rate. It can be seen from the filling shape that the water flow fluctuated smoothly at the variable section, which verified the correctness of the formula. The nonlinear pressure method proposed by studying the change of the velocity of the variable section gate effectively solves the problems of metal liquid spatter, shock and filling instability in pressure regulation casting. It not only improves the yield of castings, but also optimizes the precise pressure control of the pressure regulation equipment.