JX4D24缸体外表面气孔缺陷的成因分析

Formation Reason Analysis of Outer Surface Blowhole Defects of JX4D24 Cylinder Block

介绍了JX4D24发动机缸体的铸件结构及生产工艺,为鉴别生产中出现的外观孔眼缺陷的性质,进行试验分析,最后确定该缺陷是气孔,并采取了如下改进措施：将耐高温覆膜砂的粒度由60±4 mm调整为45±4 mm,发气量由14~18 m L/g调整为11~16 m L/g;将铸型排气通道截面积增加20%,保留帽芯原排气通道,取消薄片小油道芯人工钻孔工序,增加砂芯及铸造工艺的排气能力。生产结果显示：JX4D24缸体的外观孔眼缺陷可以一直稳定在0.9%以下,与原工艺相比,孔眼缺陷引起的废品率大大降低,每年可降低废品损失约65.8万元。

The casting configuration of JX4D24 engine cylinder block and production process were introduced. In order to distinguish the sort of the holes defects occurring on the outer surface of castings,test and analysis was conducted. It was confirmed finally that the defects were blowholes,and the following improving measures were adopted：the gain size of the high temperature resistant coated sand was changed from former 60±4 mm into 45±4 mm,its gas evolution was changed from 14~18 m L/g into 11~16 m L/g,the venting hole section area of the mould was increased by 20% and kept the former venting hole of the cap core,cancelled manually drilling procedure of the thin slice core for the small oil canal to increase the venting ability of the cores and casting method. Production results showed that outer surface holes defects of JX4D24 cylinder block could be stabilized at all times less than 0.9%,the rejection rate caused due to the hole defects has been decreased greatly,the rejection loss could be reduced about 658 000 yuan RMB/year.