泡沫模密度对消失模-型壳铸造件表面质量的影响

Influence of foam pattern density on the surface roughness of expendable pattern-shell compound casting

综合考察泡沫模对消失模-型壳复合铸造的铸件表面质量和失模过程的影响,借助TGA和DSC等手段从失重、玻璃化转变、发气量和发气速度及体积变化等方面分析不同密度泡沫模的特性,研究泡沫模密度对泡沫模、型壳和铸件表面粗糙度以及失模过程的影响规律.结果表明:随着泡沫模密度的增大,泡沫模、型壳及最终铸件的表面粗糙度降低.高密度泡沫模的起始失重和玻璃化转变温度略有提高.随着泡沫模密度的增大,泡沫模的发气量、发气速度和体积变化不断增大,同时会大大增加型壳在失模过程中的开裂倾向.综合考虑泡沫模对铸件表面质量和失模过程的影响,泡沫模的密度应控制在0.050～0.065g/cm3之间.

Influences of foam pattern on surface roughness of castings and removing pattern process in the expendable pattern-shell compound casting were investigated, and the characteristic including loss weight, vitrification transition, producing-gas quantity, producing-gas velocity, and volume change for foam pattern with different densities were analyzed by using the thermogravimetric analysis （TGA）, and the differential scanning calorimetry （DSC） methods. Meanwhile, the influences of density of foam pattern on the surface roughness of foam, ceramic shell, and castings as well as removing pattern process were also studied. The results indicate that the surface roughness of foam, ceramic shell and castings with the increase of density of foam pattern decrease gradually. The temperatures of loss weight and vitrification transition increase a little for the foam pattern with higher density. With increasing of density of foam pattern, the producing-gas quantity, producing-gas velocity, and volume change of foam pattern increase gradually, and the foam pattern with higher density is prone to leading to cracking of ceramic shell. The density of foam pattern should be controlled at 0. 050-0. 065g/ cma based on the influences of foam pattern on surface roughness of castings and removing pattern process.