Views: 0 Author: Site Editor Publish Time: 2026-09-08 Origin: Site
Food-contact plastic products require the highest standards of hygiene, stability, and compliance. Unlike ordinary consumer plastic parts, food-grade components such as food containers, water cups, packaging shells, and tableware must pass strict FDA 21CFR and GB 4806 migration tests. For manufacturers running multi-million-shot mass production, choosing the right injection mold steel is not just a quality decision—it is a critical factor for long-term compliance, stable surface finish, and lowest overall production cost.
Many standard mold steels like P20, 718H, and NAK80 are widely used for general plastic parts, but they are not qualified for food-contact molding surfaces. These carbon-alloy steels lack reliable corrosion resistance. In long-term mass production, cooling water condensation, humid workshop environments, and tiny thermal decomposed plastic residues will cause surface rust, pitting, and oxidation.
Rust spots and metal precipitation on mold cavities will directly lead to heavy metal migration failures, black spots, and contamination on finished food-grade products. For multi-million-shot orders, such continuous hidden risks will result in batch rejections, compliance audit failures, and costly production downtime.
S136-ESR contains high chromium content, delivering excellent resistance against cooling water condensation, workshop moisture, and weak acidic gas decomposed from plastics. It effectively prevents cavity rust, metal precipitation, and surface oxidation during long-cycle mass production. This stable performance ensures consistent food contact compliance (FDA & GB 4806) throughout millions of molding shots, eliminating contamination risks.
S136-ESR supports SPI A1 mirror polishing (Ra ≤ 0.4μm), far exceeding the surface finish of ordinary pre-hardened steels. The ultra-smooth cavity surface leaves no tiny gaps for plastic residues, dust, or bacteria to accumulate, achieving easy mold cleaning and meeting strict food hygiene requirements. Unlike regular steel that develops foggy surfaces and pitting after hundreds of thousands of shots, S136-ESR maintains stable gloss and flatness for multi-million-shot production.
After professional quenching and tempering to HRC 48–52, S136-ESR features high hardness and uniform internal structure. It perfectly adapts to long-term continuous molding of pure food-grade plastics, supporting 5–10 million stable shots without obvious wear or deformation. It avoids frequent mold repair, repolishing, and downtime, greatly improving production efficiency and reducing long-term mold maintenance costs.
The electroslag remelting (ESR) process minimizes internal impurities and inclusions, ensuring uniform steel texture and stable molding performance. It effectively prevents defective issues like black spots, silver streaks, and uneven surface gloss on food-grade products, guaranteeing consistent quality for every batch of mass-produced parts.
-P20 / 718H / NAK80: No anti-rust capability. Prone to rust and oxidation in humid production environments, completely unqualified for food-contact molding surfaces.
- Acidic plastic (POM, food-grade PA): S136-ESR is applicable for conventional mass production. For ultra-long-cycle production, food-grade hard chrome plating is recommended to enhance acid corrosion resistance.
Optimal Solution: S136-ESR (HRC48-52) + Semi-Hot Runner
For ultra-high-budget and extreme material-saving demands, S136-ESR matched with full hot runners achieves nearly zero scrap and maximum production benefits.
Food-grade injection molding is a compliance-driven industry. For multi-million-shot mass production, mold steel performance directly determines product qualification rate, audit pass rate, and long-term production costs. Heat-treated S136-ESR stainless steel (HRC48-52) is the undisputed best choice for mainstream food-grade PP, PE, PS, PET, and PC products, with unbeatable advantages in corrosion resistance, polishing performance, production stability, and service life.
