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自从苏联九片密集式、双排十二片密集式硬合金钻头被介绍到我国之后,曾引起许多勘探队的重视,并在使用中取得了良好的效果,其中尤以湖南黄沙坪
Since the Soviet Union nine dense, double row of twelve hard alloy drill bit introduced to our country, has attracted the attention of many exploration teams and achieved good results in use, especially in Hunan Huangshaping