How to Select Mold Steel for PA6 Products
2026-03-05 14:53:48
Plastic Molds
PA6, namely nylon 6, has the characteristics of low melting point, easy water absorption, certain glass fiber reinforcement, strong corrosiveness and high requirements for mold wear resistance. Mold steel selection directly affects mold life, product appearance, dimensional accuracy and maintenance cost.
Influence of Pure PA6 and Glass Fiber Reinforced PA6 on Mold Steel
Pure PA6 material has low wear and weak corrosion, and the requirements for mold steel are mainly polishability, toughness and stability. Glass fiber reinforced PA6 has high hardness and strong fluidity, which will cause strong scouring and wear on cavity, core, runner and gate. At the same time, it will release acid gas in high-temperature melting state with certain corrosion. Mold steel must meet the conditions of high hardness, high wear resistance and corrosion resistance at the same time, otherwise the mold will quickly appear strain, erosion, rust and dimensional deviation. Generally speaking, the higher the glass fiber content, the higher the requirements for mold steel hardness and wear resistance.
Mold Steel Selection According to Product Type and OutputFor small-batch, non-appearance requirement and pure PA6 products, P20 and 718H pre-hardened steel can be selected. These materials do not need heat treatment and can be directly used after processing, with low cost and short cycle, suitable for products with simple structure and output less than 300,000 molds. For medium-batch, general appearance and slight glass fiber PA6 products, NAK80 is suitable, with uniform hardness, good polishing performance, mirror effect, better corrosion resistance and wear resistance than 718H, suitable for products of 500,000 to 1,000,000 molds. For large-batch, high glass fiber reinforced and high life requirement PA6 products, quenched and tempered steel such as S136, S136H, SKD61 and H13 must be selected. After heat treatment, they have high hardness, wear resistance and corrosion resistance, and can meet production requirements of more than 1,000,000 molds.
Mold Steel Selection According to Appearance RequirementsFor high-appearance, mirror, transparent or matte PA6 products, S136, S136H and NAK80 are preferred. These materials have high purity and uniform structure, can achieve high mirror effect after polishing, without material lines and pits, suitable for shells, decorative parts and appearance parts. For ordinary appearance, structural parts and internal parts, 718H, 718 and P20 can be selected to meet basic gloss requirements with higher cost performance, suitable for structural functional parts without high surface requirements.
Mold Steel Selection According to Mold Cavity StructureFor thin-walled, deep-cavity and complex structure PA6 products, mold steel needs good toughness and processability to avoid cracking and deformation. 718H, NAK80 and S136H with good toughness and high stability are preferred. Runners, gates, inserts and other parts most seriously scoured, even if the mold base uses ordinary steel, these parts are recommended to use high hardness and wear-resistant materials such as SKD61 and S136 to prevent erosion, shrinkage and flash after long-term production.
Corrosion Resistance and Rust Resistance SelectionPA6 will release trace acid gas during high-temperature injection molding, and the mold is easy to rust and corrode especially in humid environment. For long-term use, humid environment and unattended production molds, S136 and S136H stainless steel are recommended directly, with good rust resistance, no frequent rust prevention treatment and low maintenance cost. For short-term production, dry environment and timely maintenance molds, 718H and NAK80 can be used with daily anti-rust oil to control cost.
Application Summary of Common Mold Steels for PA6P20 is suitable for low requirement, low output, pure PA6 and non-appearance parts with the lowest cost.718H is suitable for medium output, general appearance, pure PA6 or low glass fiber products with strong universality.NAK80 is suitable for medium and high output, polishing required, non-high glass fiber appearance parts, easy to process and polish.S136H is suitable for high output, high mirror, corrosion resistant and glass fiber PA6 products with strong comprehensive performance.SKD61 and H13 are suitable for high glass fiber reinforced, high wear and high life molds with outstanding wear resistance.
Quenched S136 is suitable for ultra-large batch, high mirror, high corrosion and high-end PA6 products with the longest life.
Final Selection SuggestionSelect 718H for pure PA6, general appearance and output less than 500,000 molds.Select NAK80 for PA6 appearance parts, polishing required and output of 500,000 to 1,000,000 molds.Select S136H for PA6 with glass fiber, high life and high rust prevention requirement.Select SKD61 or quenched S136 for high glass fiber reinforced, long-term mass production and high wear products.As long as you select according to the four key points of whether the product contains glass fiber, output, appearance requirement and rust prevention, you can ensure stable and durable mold, consistent product quality and lowest maintenance cost.
