球铁油缸浇注系统补缩无冒口工艺设计

球铁油缸,材质QT500-7,铸件重101 kg,外径φ270 mm,内径φ220 mm,壁厚25 mm,高750 mm,一端球面封口。采用立浇工艺,封口向上。原工艺为阶梯浇注系统,在铸件上部安放1个φ120 mm×200 mm冒口,因冒口下缩孔、浇口引入处缩松,缸壁气孔、夹渣,渗漏废品率54%。为了消除铸造缺陷,新工艺根据均衡凝固原理,采用以顶注为主的浇注系统补缩无冒口工艺,用收缩模数法设计直浇道、横浇道、内浇道尺寸,经批量生产验证,消除了缩孔、缩松、气孔、夹渣缺陷。机加工后经250 MPa×5 min水压试验无渗漏。工艺出品率从77%提高到88%。表明采用收缩模数法计算浇注系统尺寸,用浇注系统补缩的无冒口工艺是可靠的。

Design of Gating and Feeding System without Riser to Produce the Oil Cylinder of Ductile Iron

The oil cylinder with an end spherical surface seal was made of QT500-7,which has(101 kg) weight,270 mm external diameter,220 mm internal diameter,25 mm thickness and 750 mm height.The vertical gating system was adopted,and the seal was upward.The step gating system was adopted by the original design,in which a riser with a size of 120 mm diameter and 200 mm height was put on the top of oil cylinder.As there are the shrinkage below the riser and dispersed shrinkage in the junction of gate and casing,thus result in blowhole,inclusion,and rejection ratio of leakage was up to 54%.In order to eliminate casting defects,the final gating system was designed using proportional solidification technology,in which the top pouring system without a riser was adopted,the sizes of sprue,runner and ingate were designed by moduli calculation method.It is verified after a batch of production that these casting defects,such as shrinkage,dispersed shrinkage,blowhole and inclusion,were eliminated.After machining,the oil cylinder has no leakage at water pressure 250 MPa for 5 mins.The overall yield of casting is improved from 77% to 88%.The results show that the gating and feeding system without riser is reliable through calculating the sizes of gating system by moduli calculation method.