响应曲面法优化各向同性石墨的冷等静压成型工艺

Cold Isostatic Pressing Optimization of Isotropic Graphite by Response Surface Methodology

以成型压力、保压时间、升压速率和降压速率为考察因素,通过单因素条件实验确定各向同性石墨的成型工艺参数为:成型压力300MPa、保压时间10min以及升/降压速率都为1MPa/s。然后采用Box-Behnken的中心组合实验设计及响应曲面分析法对冷等静压成型工艺进行研究,得到体积密度的预测模型。结果表明:体积密度=1.30+0.011A-5.333×10-4 B-1.558×10-3 C-7.750×10-4 D-1.650×10-3 AB-1.350×10-3 AC+4.000×10-4 AD-9.500×10-4 BC+5.000×10-5 BD+1.725×10-3 CD-3.601×10-3 A2-1.001×10-3 B2-9.883×10-4 C2-7.383×10-4 D2,优化得到最佳成型工艺条件为:成型压力349 MPa、保压时间13min、升压速率0.5 MPa/s、降压速率0.6 MPa/s。因素分析表明,成型压力和保压时间对压坯体积密度的影响显著;在最佳成型工艺参数下进行实验,压坯体积密度的实验值与理论值吻合较好,二者相差0.3%,且能有效消除拱桥效应。

With molding pressure, dwell time, pressure rise rate and pressure release rate as inspection factors. Firstly, affecting factor and level by single factor experiment were selected, which determine the molding process parameters of isotropic graphite as follows：pressure 300 MPa, dwell time 10 min, pressure rise rate 1 MPa/s and pressure release rate 1 MPa/s. Then the cold isostatic molding process was studied through Box-Benhnken design and response surface methodology （RSM）,and consequently prediction model of bulk density can be derived. The results show that bulk density =1.30＋0.011A-5.333×10^-4B-1.558×10^-3C-7.750×10^-4D-1.650×10^-3AB-1.350×10^-3AC＋4.000×10^-4AD-9.500×10^-4BC＋5.000×10^-5BD＋1.725×10^-3CD-3.601×10^-3A2-1.001×10^-3B2-9.883×10^-4C2-7.383×10^-4D2.The optimized conditions for the molding process are：pressure 349 MPa, dwell time 13 min, pressure rise rate 0.5 MPa/s and pressure release rate 0.6 MPa/s.Factor analysis shows that molding pressure and dwell time influence the compact′s bulk density obviously.Experiment under optimum molding process parameters was conducted,whose value of compact′s bulk density is in good agreement with the theoretical value,with a difference of 0.3%, and the arch effect can be effectively eliminated.