How to Select Mold Steel Materials: Hardness, Wear Resistance, And Polishability of Different Materials

In the injection molding industry, building a highly efficient tool begins with a critical engineering question: How to select mold steel materials? Choosing the wrong steel can lead to premature mold wear, poor surface finishes, or costly production downtime.

To achieve optimal results, SHD manufacturing teams select tool steels based on a balance of product precision, mass production volume, plastic raw materials, and specific product appearance requirements.

Core Four: Factors Influencing Tool Steel Selection

Before ordering a tool, manufacturing engineers evaluate four primary project constraints to determine the exact steel grade required:

• Product Precision: High-tolerance components require stable steels that maintain their shape during long production runs.
• Mass Production Volume: Prototype or low-volume runs can utilize pre-hardened, economical steels, while millions of cycles demand premium hard-wearing alloys.
• Plastic Raw Materials: Corrosive plastics (like PVC) or abrasive materials (like glass-filled nylon) require special rust-resistant or high-wear steel grades.
• Appearance Requirements: High-gloss or optical parts dictate the use of ultra-pure steels capable of uniform finishes.

Comparing Popular Mold Steel Grades: S136, H13, 718H, and Beyond

To meet diverse manufacturing demands, choose from several industry-standard tool steels, including P20, 718H, H13, S136, and STAVAX. Each material brings unique physical properties to the tool room.

S136 & STAVAX: The Mirror Finish Champions

When cosmetic perfection is mandatory, engineers frequently turn to S136 and STAVAX. S136 has excellent polishability and can reach a flawless mirror finish. Because it offers superb corrosion resistance, it is highly recommended for medical devices, optical lenses, and transparent plastic parts.

H13: Built for High-Temperature Durability

For heavy-duty industrial applications, H13 stands out as a premier hot-work tool steel. H13 has good high-temperature performance and wear resistance. This makes it the go-to choice for demanding injection molds or die-casting components subjected to intense heat and mechanical stress.

718H & P20: Cost-Effective High Performance

For mid-to-high volume production where extreme corrosion resistance isn’t required, 718H and P20 offer a highly reliable balance. Specifically, 718H is easy to cut and has high cost performance. It comes pre-hardened, allowing faster machining times while offering better core hardness than standard P20.

Critical Role of Heat Treatment:

Understanding raw chemical compositions is only half the battle. Tooling specialists emphasize that the hardness and wear resistance vary significantly depending on the material and heat treatment.

While pre-hardened steels like 718H or P20 save machining time, through-hardening steels like H13 and S136 must undergo precise vacuum quenching and tempering processes. Proper heat treatment optimizes the steel’s microstructure, ensuring the mold can withstand the rigorous clamping forces and abrasive pressures of a high-speed injection molding machine over its intended lifespan.

FAQ:

Q1: How do I select mold steel materials for a high-volume project?

A: To select the best material, analyze your target production volume, part aesthetics, and plastic resin. For high-volume, high-gloss parts, opt for high-grade through-hardened steels like S136 or STAVAX. For standard industrial parts requiring high durability, choose H13. For cost-effective, medium-volume production, 718H or P20 is usually ideal.

Q1: Why is S136 preferred for transparent or cosmetic plastic parts?

A: S136 is an exceptionally pure stainless steel alloy with an ultra-fine grain structure. Because S136 has excellent polishability and can reach a mirror finish, it allows manufacturers to produce perfectly clear, defect-free plastic parts with minimal tool wear over time.

Q1: How does heat treatment impact mold longevity?

A: Heat treatment alters the internal crystalline structure of the metal. Because mold hardness and wear resistance vary significantly depending on the material and heat treatment, selecting the right hardening cycle ensures the steel reaches its peak mechanical performance, preventing premature cracking or deformation.

Why choose SHD?

• Over 20 years of Industry expertise
• ISO 9001 & ISO 14001
• Multi-industry precision mold & molding experience, including automotive, medical devices, water purification systems, 3C, etc., to meet all your requirements.
• Years of cooperation with multinational companies & global export experience, ensuring your peace of mind.
• Full-chain precision equipment: high-precision CNC, EDM, WEDM, injection molding and measuring machines to meet your highest standards.
• Integrated mold & molding solutions streamline your supply chain, delivering final products directly to you.

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