灰铸铁件裂隙状气孔的成因分析与防止措施

Cause Analysis and Prevention Measures of Slit-like Porosity in Gray Iron Castings

介绍了大批量生产灰铸铁壳体铸件出现的裂隙状皮下气孔缺陷的原因和防止措施。采用扫描电镜和能谱分析仪分析了缺陷的类型、产生条件与原因。分析认为:在高温铁液作用下砂芯产生了大量的N2或H2,从而形成混合性裂隙状气孔。通过将树脂加入量降低至1.5%~1.7%,尤其是将聚乙氰酸脂加入量控制在0.7%~0.85%,降低冷芯盒砂芯的烘干速度,保证冷芯盒砂芯的烘干时间在60 min以上,减少了铁液中的w(N)、w(H)量。生产结果显示:壳体铸件再也没有出现同类气孔缺陷。

The reasons and prevention measures of slit-like substomatal porosity defects appearing in mass production of gray cast iron shell castings were introduced. Scanning electron microscopy and energy spectrum analyzer were used to analyze the types of defects,conditions and causes. The analysis shows that：the sand core produces a large amount of N2 or H2 under the high temperature molten iron. That caused the generation of mixed slit-like porosity. By reducing the amount of resin to 1.5%~1.7%,in particular,controlling the amount of polycyanic acid to 0.7% ~0.85%,reduce drying speed of the cold core sand core,and ensure the cold core sand core baking drying time above 60 min,the amount of w（N）,w（H）in the molten iron were reduced. Production results showed that shell castings no longer have the same kind of pore defects.