Performance Comparison and Material Selection Guide Between Mold Steel S136 and NAK80

Mold steel selection directly affects mold machining performance, surface effect, wear resistance and service life. Wrong steel selection will cause cavity wear, rust spots, unqualified polishing effect and insufficient mold life. S136 and NAK80 are two high‑polish mold steels widely used in plastic molds. Many mold engineers will hesitate in the selection process. Through the comparison of hardness, corrosion resistance, polishing performance, machining performance and applicable scenarios, it can provide reference for reasonable material selection of mold projects.

1. Basic material performance overview

NAK80 is pre‑hardened nickel‑alloy mold steel, with delivery hardness of 38‑42HRC. It can be directly milled, drilled and polished without quenching and tempering heat treatment. The internal structure of steel is uniform, with excellent mirror polishing performance and stable etching texture effect. Its anti‑rust performance is general, and it cannot resist long‑term erosion of corrosive gas decomposed by some plastics.

S136 is martensitic stainless mold steel. After quenching and tempering, the hardness can reach 48‑52HRC. High chromium content brings excellent anti‑rust and anti‑corrosion ability, and can achieve ultra‑high‑gloss mirror effect. Quenching heat treatment is required in the processing process, and attention should be paid to controlling heat‑treatment deformation. The pre‑hardened version S136H can skip quenching process, which is suitable for projects with tight construction period, but its hardness is lower than quenched S136.

2. Comparison of polishing, corrosion resistance and wear resistance

Both steels can achieve high‑mirror surface finish. NAK80 reaches good mirror effect with simpler polishing steps, and texture etching performance is more stable, which is suitable for products with strict texture requirements. S136 needs more careful polishing operation to avoid surface pinholes caused by material structure. In terms of corrosion resistance, S136 has obvious advantages. When molding PVC, POM and other materials that produce corrosive gas, S136 can effectively prevent mold cavity rust. NAK80 is easy to generate rust spots under such working conditions, requiring frequent anti‑rust maintenance. For wear resistance, quenched S136 has higher hardness and performs better for glass‑filled modified plastics. NAK80 is suitable for non‑abrasive raw materials, and the cavity is prone to wear under long‑term production of glass‑filled materials.

3. Machining cost and delivery cycle difference

NAK80 is supplied in pre‑hardened state. Mold factories can start CNC processing directly after material arrival, without heat treatment procedure, the whole processing cycle is short. Its cutting performance is stable, and the loss of cutting tool is relatively low. S136 needs quenching and tempering heat treatment for high‑hardness state. Heat‑treatment procedure will increase production cycle and produce small deformation, so subsequent finish machining allowance should be reserved. S136H pre‑hardened material cancels quenching step, but its wear‑resistant and anti‑corrosion performance cannot reach the level of quenched S136. The material cost of S136 series is higher than NAK80, and post‑processing cost also increases accordingly.

4. Practical project selection suggestions

Choose NAK80 when the product requires fine texture etching, non‑corrosive plastic raw material, medium and low output, and the project pursues short mold delivery cycle. It is widely used in household appliance shell, consumer electronics appearance parts and daily‑use plastic products. Choose quenched S136 when molding corrosive plastics, high‑gloss mirror appearance requirements, mass‑production with glass‑filled material and long‑life mold requirements. S136H can be selected as a compromise scheme for projects with tight time limit but certain anti‑corrosion demands. In actual project evaluation, balance appearance demand, raw material corrosiveness, production volume, delivery time and budget to select appropriate mold steel.

Conclusion

S136 and NAK80 are both classic high‑polish mold steels, neither of which can completely replace each other. NAK80 wins in convenient processing, stable etching texture and short cycle. S136 takes advantages in corrosion resistance, hardness and wear resistance. Clarify product material characteristics, surface requirements and production target before ordering mold steel. Correct steel selection can reduce mold maintenance frequency, stabilize product surface quality and extend the comprehensive service life of injection molds.