mold parts without special requirements can be manufactured from carbon structure steel( such as Japan’s S45C, S50C, and S55C) or carbon tool steel(such as Japan’s SK series), which are cheap, easily accessible, and good in processing property and with the carbon content of 0.45%–0.6%. to ensure low surface hardness of the plastic molds, some special requirements, such as the content of harmful impurities and microstructure of steel, have been proposed for the metallurgical quality of carbon steel.
For mold parts with high requirements, better mold materials should be used.