Tool Steel for Plastic Injection Moulds: Material Selection for Optimal Performance

Plastic injection moulds are widely used across various industrial scenarios, which also generates the requirement to obtain the right tool steel material. While you select the plastic mould steel, you will have to pay attention to certain key aspects to make sure the manufacturing process is not obstructed due to material incompatibility.

Comparing Key Grades of Tool Steel

Primarily, the preference is to select tool steel according to the production volume, but you should also consider the surface finish requirements and the plastic resin characteristics. Here is a brief list of common tool steel grades that are considered for this process.

1. H13 Tool Steel: This type is usually preferred for its capacity for mass production, as it can generate over 1 million cycles of moulding. It is a ‘hot work steel’ that has been hardened to 48-52 HRC, resulting in a high degree of material toughness. The superior thermal fatigue resistance exhibited by H13. It makes it the best option for high-temperature polymers and abrasive resins like glass-filled nylon.
2. S7 Tool Steel: This type is manufactured to exhibit extreme toughness. The powerful impact resistance is a part of it. The industrial situation requires the components to withstand repeated mechanical stress. It should be without cracking under pressure. S7 could be a suitable choice here. This tool steel is often used for moving components, such as lifters, slides, and ejector pins.  
3. S136 Tool Steel: In industrial processes where corrosion resistance is a paramount factor, factory managers generally prefer the S 136 tool steel. Especially in the moulding of PVC and foam, when corrosive gases are released, the martensitic tool steel holds up strong to achieve the intended output. Also, this grade is preferred in the manufacturing of medical devices and optical products, primarily because it can be polished to a mirror finish.
4. P20 Tool Steel: For low to medium production volumes (<100,000 cycles), the P20 is a popular choice for manufacturers. The semi-hardened steel in the range of 28-34 HRC is an ideal choice. It's the best choice for machining large industrial parts. It is also relatively cost-effective without extra heat treatment.
5. NAK 80 Tool Steel: Manufacturers looking for better polishability compared to P20 often prefer the NAK 80, which is pre-hardened to 37 – 43 HRC. This grade exhibits better dimensional stability, which makes it an automatic choice for moulding high-quality transparent parts.

Selecting Tool Steel According to the Surface Finish

Finding the right tool steel based on the surface finish can be tricky, as you will have to find a type that balances purity and material hardness. Generally speaking, harder steels exhibit higher degrees of polishing, while the types with lesser non-metallic inclusions (purity level) are ideal to prevent surface defects like the ‘orange peel’.

Best Supplier to Rely on

Manufacturers must insist on finding the best plastic mould steel supplier to make sure that the production process runs smoothly till the end. You should start by comparing the available information on different steel grades, so that you can compare the properties with your specific requirements.

Reputed suppliers like Kushal Metal can be instrumental in ensuring the continuity of the production process while minimising potential setbacks before and after. Backed by years of reputation, the major industrial steel supplier is recommended by industry experts for its astute service.