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).
所用材料不合格。如砂、石、集料质量不合格；除此之外，大多数是因为水泥体积膨胀率太大(安定性严重不良)。
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。
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.
研究认为，柴油机气缸盖进、排气道脉纹的产生主要是由硅砂高温发生相变膨胀导致砂芯开裂引起的。
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