In the drilling process, should be kept clean hole soil, encountered hole collapse, shrinkage and other abnormal situations, timely solution.
在钻进过程中，应随时清理孔口积土，遇到塌孔、缩孔等异常情况，应及时研究解决。
There is abnormal bottom shrinkage in Zn Al alloy castings and top riser has little effect on them.
锌铝系合金铸造时出现反常的底部缩孔，而用一般上置式冒口对此类缩孔的补缩效果甚微。
There is abnormal bottom shrinkage in Zn Al alloy castings and top riser has little effect on them.
锌铝系合金铸造时出现反常的底部缩孔，而用一般上置式冒口对此类缩孔的补缩效果甚微。
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