Use of Alloy Steels in Rock Drilling, and Their Treatment
MR. C. R. WHITTEMORE: It is interesting to note that the mining industry is making increased use of alloy steels for drilling. They will undoubtedly lead to greater footage at lesser cost. Mr. Kemsley states that, for use in hard ground, the shanks are brought to a hardness of 435 to 440 Brinell by heating them to approximately l,800°F. It seems to me that this temperature is excessively high- it is considerably above the critical point of the steel. The only effect of such a high temperature is to lessen considerably the impact resistance of the steel.
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