| 摘要 |
PROBLEM TO BE SOLVED: To prevent corrosion of a mold by applying the surface treatment using a Cr compound on a metal surface whose surface hardness is increased by heat treatment, and providing a specified surface hardness. SOLUTION: As a metal for forming a base of an injection molding die, a material which increases the surface hardness by heat treatment is used. The surface hardness after the heat treatment is set as approximately 50 or more based on the Rockwell hardness. As the heat treatment conditions, for instance, a process of hardening for 1-5 hours at 700-1300 deg.C and a process of tempering for 1-5 hours at 400-600 deg.C are repeated respectively approximately 1-3 times. Also a metal surface forming a base surface is treated by using a Cr compound. At that time, the micro-Vickers hardness of a surface treated film is set in the range of 1,200-2,600. As the Cr compound, for example, CrN, CrC or the like is used. The thickness of the surface treated film is set approximately as 1-10μm. The corrosion of a mold composed of sulfuric gas, chlorine gas or the like can be prevented by the arrangement. |
