| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for regenerating a used tool for piercing, by which service life can be made longer.SOLUTION: A used tool for piercing whose durability has been deteriorated is, as scale regeneration heat treatment, heated and held to a heating temperature in the range of 850 to 1,000°C, is temporarily cooled to a temperature in the range of 600 to 700°C at a cooling rate of ≥30°C/h, thereafter is reciprocated to a temperature of 750 to 800°C and is further cooled to a temperature of ≤700°C at a cooling rate in the range of 3 to 20°C/h, thus a scale layer with a proper thickness is regenerated to make longer the service life of the tool for piercing. The tool for piercing is composed of a base material having a composition including, by mass, 0.05 to 0.5% C, 0.1 to 1.5% Si, 0.1 to 1.5% Mn, 0.1 to 1.5% Cr, 0.6 to 3.5% Mo, 0.5 to 3.5% W and 0.1 to 1.0% Nb and further including 0.5 to 3.5% Co and 0.5 to 4.0% Ni so as to satisfy 1.0≤Ni+Co≤4.0. |
