减少覆砂铁型曲轴表面脉纹的措施

Measures to Reduce Surface Veining Defect of Resin Sand-coated Iron Mold Cast Crankshaft

介绍了曲轴脉纹的缺陷形貌及位置,分析其原因为:分型面存在0.8 mm的间隙,小于覆膜砂受热膨胀所产生的位移,导致上、下型的覆膜砂会受到挤压而发生错层,从而在铸件表面上形成脉纹。采取了以下措施:(1)选用低膨胀系数的原砂生产覆膜砂可以降低覆膜砂的膨胀系数;(2)在铁型平衡块侧面增加凹槽,增加覆膜砂的附着力。生产结果显示:脉纹得到有效控制,存在比例由85%以上减少至10.29%,铸件表面质量合格,满足客户要求。

The veining defect morphology and its location of the crankshaft was introduced. The reason causing defect was analyzed as：there was gap of 0.8 rant in the mold parting surthee which less than the displacement caused by resin coated sand expansion due to being heated and therefore led the resin coated sand of cope mold and drag mold to be squeezed and thus the staggered layer produced that caused veining on casting surthee. Following measures were adopted：（ 1）Choosing raw sand with low eoeffieient of expansion to produce resin-coated sand could reduce the expansion eoeffieient of the resin-coated sand. （2）Setting concave grooves on the balance block side facee to increase adhesive foree of the coated sand. Production resuh showed,the veining defect had been effectively controlled,the defect rate had been reduced form more than 85% to 10.29%, surthee quality of castings had been qualified and met elien,s requirentent.