Heat treatment of plastic mold steel
The characteristics of steel for plastic mold forming parts are:
1) steel is widely used. In the primary stage, there is no special steel for plastic mold parts, but other steel types are used, such as structural steel, tool steel, stainless steel, spring steel and so on. Now has become more and more formal, special steel has its own system, in our country that is in the steel number before the top SM(plastic mold two characters of the first letter of the Chinese pinyin). Its chemical composition and alloy tool steel steel number (not crown SM) is basically the same, but the metallurgical quality is high, sophisticated processing, so favorable for heat treatment.
2) some plastic mold parts of the surface quality requirements are particularly high, requires a good polishing and mirror quality, so the purity of steel, the number of carbides, size, shape to be strictly controlled; For example, the carburized steel used in the manufacturing of plastic mold parts by cold extrusion forming method is comparable to ordinary carburized steel (structural steel) and specially designed special steel, such as P2, P4 and P6 steel of the United States. Sweden's 8416; Our country code for LJ steel. The carbon content is extremely low, the plastic deformation ability is extremely strong, the carburizing quality request is higher than the ordinary structure part, must adopt the effective carbon potential control, therefore increased the heat treatment difficulty and the cost;
3) in order to avoid deformation or other heat treatment defects in the process of hardening and tempering of mold parts, it is common for plastic mold steel to be supplied in the form of pre-hardening steel. In this way, it is easy to manufacture high precision plastic mold and reduce the manufacturing cost. At the same time, micro - alloy non - quenched and tempered steel has been widely used in plastic mold manufacturing.
4) petrochemical products as raw materials of plastic products, have different degrees of corrosion, so corrosion resistant steel (stainless steel) application is more. In the past with coating method, due to high cost, poor quality, pollution and gradually eliminated.
5) with the application of pre-hardened steel, non-quenched and tempered steel, cutting is also the characteristics of plastic mold steel, the progress of cutting technology and promote the promotion of pre-hardened steel, non-quenched and tempered steel application.
6) good thermal conductivity and weldability.
In order to meet the various performance requirements of plastic mold parts, plastic mold steel often has a variety of characteristics, such as both corrosion resistance and pre-hard type, with free cutting and high mirror. The following classification of the narrative is only to emphasize or highlight a particular feature, to facilitate the introduction of it.