METHOD OF IMPROVING LIFE OF DIE FOR HOT OR WARM FORGING

摘要

A method of improving the life of a die for use in the hot or warm forging of a steel. The surface of the die which has been used for hot or warm forging is peened at least to such a degree that the compressive residual set of that part of the die which is weakest in forging is elevated to 150 MPa or higher as measured at a depth of 0.4 mm from the die surface. In the case of a high-hardness die, the peening thereof is desirably conducted while heating the die at a temperature not higher than the die tempering temperature, and is preferably conducted especially at 150-400°C.