S136 is a high-quality martensitic stainless mold steel with excellent corrosion resistance, polishability, and wear resistance, widely used in plastic injection molds, especially for processing corrosive plastics and high-gloss plastic products. Unlike ordinary plastic mold steel (such as P20, 718H), S136 has strong corrosion resistance, which can avoid mold rust caused by corrosive plastics, and its excellent polishability can achieve a mirror surface effect, improving the grade of plastic products. This article will detail the performance characteristics, chemical composition, application scenarios, heat treatment, and selection tips of S136 mold steel, helping you fully utilize its advantages in production.
Core Performance Characteristics of S136 Mold Steel
S136 mold steel’s outstanding advantages lie in its corrosion resistance and polishability, while also having good toughness and wear resistance, making it suitable for high-end plastic injection scenarios:
- Excellent Corrosion Resistance: S136 contains high chromium content (13-15%), which can form a dense chromium oxide film on the surface, effectively resisting the corrosion of corrosive plastics (such as PVC, PC, flame-retardant plastics) and mold release agents, avoiding mold rust and extending mold service life.
- Superior Polishability: S136 has high purity, uniform structure, and no obvious impurities, which can be polished to a mirror surface (Ra ≤ 0.02 μm) without obvious streaks or defects, suitable for high-gloss plastic products.
- Good Wear Resistance: After heat treatment, S136 has high hardness (50-54 HRC), good wear resistance, which can resist the wear caused by plastic flow during injection molding, ensuring stable mold size.
- High Toughness: S136 has good toughness, which is not easy to crack during processing or use, suitable for complex structure molds (such as thin-walled parts, multi-cavity molds).
- Stable Dimensional Accuracy: After proper heat treatment, S136 has small deformation, stable structure, and can ensure the dimensional accuracy of the mold, meeting the requirements of high-precision plastic products.
Chemical Composition of S136 Mold Steel
The excellent performance of S136 is closely related to its reasonable chemical composition. The following is the detailed chemical composition (mass fraction) of S136 mold steel:
| Element | Content Range | Function |
| C (Carbon) | 0.38-0.45% | Improve hardness, wear resistance and strength |
| Cr (Chromium) | 13.00-15.00% | Form passive film, enhance corrosion resistance and wear resistance |
| Mo (Molybdenum) | 0.40-0.60% | Improve corrosion resistance and toughness, refine grain |
| V (Vanadium) | 0.10-0.30% | Refine grain, improve wear resistance and dimensional stability |
| Si (Silicon) | 0.80-1.20% | Improve oxidation resistance and strength |
| Mn (Manganese) | ≤ 0.50% | Improve machinability, avoid harmful impurities |
Applications of S136 Mold Steel
Due to its excellent corrosion resistance and polishability, S136 is mainly used in high-end plastic injection molds, especially for processing corrosive plastics and high-gloss plastic products. The main application scenarios are as follows:
1. Corrosive Plastic Injection Molds
S136 is the first choice for molds processing corrosive plastics, which can effectively avoid mold rust and ensure product quality:
- PVC plastic molds: PVC pipes, PVC profiles, PVC fittings injection molds (PVC will release corrosive gas during injection molding, which is easy to rust ordinary mold steel).
- PC plastic molds: PC lenses, PC optical parts, PC electronic shells injection molds (PC has certain corrosiveness and high surface requirements).
- Flame-retardant plastic molds: Flame-retardant electronic shells, flame-retardant plastic parts injection molds (flame-retardant additives have strong corrosiveness).
- Medical plastic molds: Medical catheters, medical syringes, and other medical plastic products injection molds (require corrosion resistance and high cleanliness).
2. High-Gloss Plastic Injection Molds
S136’s excellent polishability makes it suitable for molds of high-gloss plastic products, which can achieve a mirror surface effect and improve product grade:
- Cosmetic packaging molds: Cosmetic bottles, cosmetic boxes, and other high-gloss packaging molds.
- Electronic product shells: High-end mobile phone cases, tablet shells, TV shells injection molds.
- Automotive parts: Automotive lamp covers, instrument panels, and other high-gloss automotive interior and exterior parts molds.
3. High-Precision Complex Molds
S136 has good toughness and dimensional stability, suitable for high-precision and complex structure molds:
- Thin-walled plastic molds: Thin-walled electronic parts, thin-walled packaging molds (require high toughness to avoid cracking).
- Multi-cavity molds: Multi-cavity injection molds for small plastic parts (require stable dimensional accuracy to ensure consistent product size).
Heat Treatment Guide for S136 Mold Steel
S136 is a martensitic stainless steel, and its heat treatment process directly affects its corrosion resistance and polishability. The following is the recommended heat treatment process and specifications:
1. Annealing (Before Processing)
Purpose: Reduce hardness, eliminate internal stress, improve machinability, and ensure uniform structure.
- Annealing Temperature: 800-850℃
- Holding Time: 2-3 hours
- Cooling Method: Slow cooling (furnace cooling) to 500℃, then air cooling to room temperature
- Annealed Hardness: ≤ 248 HB
2. Preheating (Before Quenching)
Purpose: Avoid uneven heating, reduce internal stress, and prevent mold cracking.
- Preheating Temperature: 600-700℃
- Holding Time: 1-2 hours
3. Quenching (To Improve Hardness and Corrosion Resistance)
Purpose: Form a martensitic structure, improve hardness and wear resistance, and enhance corrosion resistance.
- Quenching Temperature: 1000-1050℃
- Holding Time: 1-1.5 hours
- Cooling Method: Oil cooling (cool to 150-200℃, then air cooling to room temperature); avoid water cooling to prevent cracking.
- Quenched Hardness: 56-60 HRC
4. Tempering (To Improve Toughness and Stabilize Structure)
Purpose: Eliminate the brittleness caused by quenching, improve toughness, stabilize the structure and size, and adjust the hardness to meet the working requirements.
- Tempering Temperature: 200-250℃ (for high hardness and wear resistance); 450-500℃ (for better toughness and corrosion resistance)
- Holding Time: 2-3 hours per time, twice tempering is recommended
- Cooling Method: Air cooling to room temperature
- Tempered Hardness: 50-54 HRC (common for plastic molds)
Selection Tips & Common Mistakes to Avoid
Selection Tips
- If you process corrosive plastics (PVC, PC, flame-retardant plastics) → Choose S136 (excellent corrosion resistance, avoid mold rust).
- If you need high-gloss plastic products (mirror surface) → Choose S136 (superior polishability, reduce polishing time and costs).
- If you have high requirements on mold precision and dimensional stability → Choose S136 (stable structure, small deformation).
- If you have a limited budget but need corrosion resistance → Choose 2083 (cost-effective alternative to S136, but polishability is slightly worse).
Common Mistakes
- Using S136 for ordinary non-corrosive plastics (such as ABS, PP) → Waste of cost, P20 or 718H is sufficient.
- Neglecting tempering after quenching → S136 has high brittleness after quenching, which is easy to crack; twice tempering is necessary.
- Using water cooling during quenching → Leading to internal stress increase, mold cracking, oil cooling is recommended.
- Ignoring mold maintenance → After use, failure to clean and apply anti-rust oil will reduce the corrosion resistance of S136 and shorten mold service life.
We provide high-quality S136 mold steel, with complete quality certificates and corrosion resistance test reports, and free custom cutting, polishing, and heat treatment services. Our professional engineer team can provide you with free selection advice according to your plastic material and product requirements. Contact us now to get a free quote and detailed material data sheet!
S136 / S136H (Premium ESR Grade) Corrosion Resistant Stainless Plastic Mold Steel Plate – KUTU