ABS is widely used in home appliances, automotive interiors, and electronics due to its good toughness, rigidity, and processability. Mold steel selection directly affects mold life, part surface quality, dimensional stability, and production efficiency. The goal is to balance performance, polishability, corrosion resistance, wear resistance, and cost based on part requirements and production volume.
1 Key Requirements for Mold Steel
ABS has a wide melting range and is processed at mold temperatures of 25–70°C with injection pressures of 500–1000 bar, requiring stable heat resistance and pressure resistance. Its shrinkage is relatively stable, enabling tight tolerances, so the cavity needs good polishability. Flame-retardant or modified ABS may generate mild corrosive gases, requiring corrosion resistance or appropriate surface treatment.
2 Common Mold Steels and Applications
Pre-hardened steels (cost-effective mainstream)P20 (28–32 HRC) suits medium–low volume production with typical life of 100,000–300,000 shots. 718H (33–38 HRC) offers better polishability and uniformity, suitable for higher-precision parts and 300,000–800,000 shots.
Mirror steels (high-gloss parts)NAK80 (38–42 HRC) provides excellent mirror polishing (to Ra ≤ 0.01 μm) without post-heat treatment, ideal for high-end panels and cosmetic packaging, with typical life of 500,000–1,000,000 shots.
Corrosion-resistant steels (modified ABS)S136 (48–52 HRC after heat treatment) resists corrosive gases from flame-retardant additives and offers good polishability, suitable for medical and food-contact related applications with >500,000 shots. For cost-sensitive cases, chrome plating (0.01–0.03 mm) can provide basic corrosion protection.
Wear-resistant steels (reinforced ABS)H13 (52–56 HRC after heat treatment) provides high wear resistance and heat resistance, suitable for glass-fiber reinforced ABS and high-volume production (>1,000,000 shots).
3 Selection Principles
Match steel to production volume: low volume → P20; medium volume/higher precision → 718H; high volume/reinforced → H13. Match surface requirements: high-gloss → NAK80; corrosive modified ABS → S136 or plated steel. Balance cost: steel typically accounts for 15–30% of total mold cost; avoid over-specifying.
4 Conclusion
Mold steel selection for ABS should be demand-driven, considering material properties, surface finish, dimensional accuracy, production volume, and cost. Proper steel choice ensures stable molding, consistent part quality, and longer mold life while optimizing overall manufacturing costs.
