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How to Choose Mold Steel For Plastic Molds?

In plastic mold manufacturing, the selection of mold steel is one of the key factors determining the service life of the mold. Whether it is high-end molds that require millions of injection cycles or ordinary molds that only require 100000 injection cycles, choosing the right steel can significantly improve production efficiency and product quality. This article will provide a detailed analysis on how to choose suitable mold steel according to different needs, helping your product stand out in market competition.

The service life of molds is usually divided according to the number of injection molding cycles, such as over one million cycles, 500000 to 1 million cycles, 300000 to 500000 cycles, 100000 to 300000 cycles, and below 100000 cycles. Different levels of molds have vastly different requirements for steel. The first and second level molds require steel to have excellent wear resistance and high hardness, in order to maintain accuracy and stability under long-term high load work.

For high-end molds that need to withstand millions of injection molding cycles, the following steel materials are recommended:

1.H13 (4Cr5MoSiV1) and 2344: After quenching and hardening, these two types of steel can achieve a hardness of around HRC50, with good wear resistance and thermal stability, making them ideal choices for manufacturing long-life molds. However, for specific high-strength or corrosive materials, further consideration may be needed for their corrosion resistance.

2.S136 and 2316: These steels are known for their excellent corrosion resistance and are particularly suitable for handling strong acids or corrosive plastics. For transparent parts with high appearance requirements, S136 is the preferred choice, as its excellent polishing performance can ensure the smoothness of the product surface.

3.LG mold steel: For molds with complex structures, including slender sloping tops and inserts, LG mold steel is an ideal choice due to its high toughness (8-9 times that of DC53) and high hardness (HRC54-58). Its wear resistance and fracture resistance are far superior to traditional steel, which can significantly extend the service life of molds.  

For molds that need to inject 100000 injection molding times, although the requirements for steel are relatively low, economy and practicality still need to be considered. The following steels can be used as references:

1.P20 and 718: These two types of steel are widely used in mold manufacturing, with moderate costs, and are suitable for molds with general requirements. Among them, 718H, as a pre hardened plastic mold steel, does not require quenching and tempering treatment, making it easy to process and has a relatively long service life.

2.45 # steel and S50C: For molds with low requirements, these low-cost steels can be directly used to process the cavity on the mold base. Although its wear resistance and service life are limited, it is sufficient to meet short-term production needs.

In addition to selecting appropriate steel, surface treatment of mold steel is also an important means of extending the life of molds. Nitriding treatment can enhance the surface hardness of steel, while electroplating can effectively modify steel, improve corrosion resistance and brightness. For special requirements such as molds with high smoothness or high corrosion resistance, it is recommended to use corresponding surface treatment techniques.