某机床球墨铸铁台架铸造工艺分析及优化

Analysis and Optimization of the Casting Process for a Ductile Iron Stand of Machine Tool

某机床球墨铸铁台架采用呋喃树脂自硬砂手工造型和阶梯浇注系统成形。原工艺采用冒口对铸件顶部厚大轴孔支撑架处补缩,但实际生产过程中发现冒口根部有轻微缩松,导致铸件不合格。经过多种方案分析及数值模拟,在其余铸造参数不变条件下,尝试无冒口铸造工艺:把原冒口改成楔形出气口,内浇道厚度减薄,在轴孔处附近设置外冷铁或内冷铁以提高轴孔处组织性能,同时,设计了轴孔铸出或后续机加工几种方案,进行对比生产,发现均可获得合格铸件。生产实践证明了台架铸件采用无冒口铸造工艺的可行性,简化了造型工艺,提高了铸件工艺出品率。

A ductile iron stand of machine tool is formed by using of manual molding of furan resin-bonded selfhardening sand and step gating system.In the original process,two risers were used to feed the shrinkages of support frame positions of the thick shaft holes at the top of the casting,but in actual production,it was found that there were slight shrinkage porosities at the roots of the risers,resulting in the casting being unqualified.After analysises of multiple schemes and numerical simulations,under the condition of keeping the other casting parameters unchanged,a riser-free casting process was attempted:the original risers were changed to wedge-shaped vent holes,the thicknesses of ingates were reduced,and external or internal chills were set near the shaft holes in order to improve the microstructure and performance of the shaft holes.At the same time,several schemes of the shaft holes being cast out or subsequently machined out were also designed and compared in production,and it was found that qualified castings could be obtained.Production practice had proven the feasibility of application of riser-free casting process in the stand castings,the molding process was simplified and the overall yield of casting was increased.