Technical Summary
Mold steel is the core material of a mold. It directly affects mold service life, processing efficiency, and the quality of molded parts. The selection should be based on four key factors: molded material properties, part precision requirements, production volume, and processing technology.
Selection Based on Molded Material Properties
Different molded materials, such as metal, plastic, and rubber, place different demands on mold steel in terms of wear resistance, corrosion resistance, and heat resistance.
| Molded Material Type | Core Requirements | Recommended Mold Steel Type | Application Scenario |
|---|---|---|---|
| Metal (stamping/forging) | High hardness, high wear resistance, impact resistance | Cold work mold steel (e.g. Cr12MoV, D2); Hot work mold steel (e.g. H13, 5CrNiMo) | Forming of metal stamping parts and forging parts |
| Plastic (injection molding/extrusion) | Polishing performance, corrosion resistance for corrosive plastics, wear resistance | Pre-hardened mold steel (e.g. P20, 718); Corrosion-resistant mold steel (e.g. S136, 420) | Injection molding and extrusion molding of plastic parts |
| Rubber (vulcanization molding) | Aging resistance, anti-adhesion | Alloy tool steel (e.g. Cr12, 9CrSi) | Forming of rubber seals and rubber products |
Selection Combined with Production Volume and Precision Requirements
For small-batch trial production or low-precision parts, pre-hardened mold steel such as P20 is a practical choice. It does not require additional heat treatment, which helps reduce processing cost and shorten the production cycle.
For mass production or high-precision parts, quenched and tempered mold steel such as Cr12MoV and S136 is more suitable. After heat treatment, the hardness can reach HRC58–62, providing excellent wear resistance and helping maintain mold precision over a long service life.
Matching with Mold Processing Technology Requirements
For complex cavity processing, such as CNC and EDM, it is better to choose steel with good machinability and strong EDM performance, such as 718 or S136. This helps reduce deformation during processing.
For high-polish surface requirements, such as transparent plastic parts, mirror-finish mold steel with high purity and low impurity content should be selected, such as S136 or NAK80. These materials can be polished to below Ra0.01μm.
Core Selection Principle
Cost-effectiveness should always come first. Avoid choosing high-grade steel without a clear need. For small-batch production, standard mold steel is often enough. For mass production or high-demand applications, high-performance specialty mold steel is the better choice.
