抄録
In high speed steel generally grain growth occurs owing to high quenching temperature; the temperature causing abnormal grain growth varies due to heat treatment before quenching. If the temperature giving strain before quenching rises to more than 1200°, the abnormal grain growth occurs when the quenching temperature is equal to or higher than the above temperature, but this steel becomes of smaller grain and is more superior in the cutting durability than the larger one; but the cutting durability cannot be conceived only by the grain size; the history of the heating works must be considered.
