Key Points for Low-Cost Steel Selection in Plastic Molds

Using low-cost mold steels reasonably is an effective way to reduce mold cost without sacrificing basic service life and product quality. Low-cost steels do not mean inferior materials, but accurate matching with product structure, output, appearance requirements, and plastic materials.

Applicable Scenarios for Low-Cost Mold Steels

Low-cost steels are suitable for small-to-medium batch production, generally within 500,000 shots. They apply to common plastic products with ordinary appearance requirements, simple structures, and non-appearance structural parts. They are also ideal for prototype molds, testing molds, and low-volume production molds using standard plastics such as PP, PE, PS, and ABS.

Common Low-Cost Mold Steels

45# steel is the lowest-cost option, easy to machine but low in hardness and wear resistance, suitable for prototype molds and simple internal structures. Domestic P20 is the most cost-effective pre-hardened steel, with hardness 28–33 HRC, suitable for general production molds. Domestic 718H offers better purity and polishability, suitable for textured surfaces and general appearance parts. Economic NAK80 provides better polishing performance for products with moderate surface requirements.

Core Matching Principles

Match hardness and service life according to production volume. Lower volumes can use softer steels, while higher volumes require better wear resistance. Match material properties according to plastics: glass-filled materials require higher wear resistance, and corrosive materials require better anti-corrosion treatment. 

Match polishability according to appearance requirements: non-appearance parts can use lower-grade steels, while high-gloss surfaces need improved materials. Use graded material allocation: use better steels for cavity and core, and low-cost steels for non-forming structural parts.

Avoiding Common Pitfalls

Do not use 45# steel for all parts, as it causes frequent wear and high repair costs. Do not ignore surface treatment for low-cost molds, as proper nitriding or coating greatly extends life. Do not use overly inferior steels for high-appearance or transparent parts, as they cause surface defects. Choose reliable suppliers to ensure stable material hardness and quality.