USES material not qualified. Such as sand, stone, aggregate quality unqualified; In addition, mostly because cement volume expansion rate is too large (stability serious adverse).
Reducing expansion stress of the moulding sand and increasing wet tensile strength of moulding sand are the main measures to prevent scab defect.
防止夹砂缺陷的主要措施是降低型砂的膨胀应力和提高型砂的热湿拉强度。
3
Research has believed that veining in admission and exhaust passage of diesel engine cylinder head may mainly be caused by crack of sand core occurring in high temperature phase change expansion.