S136 is a martensitic stainless mold steel with excellent corrosion resistance, high polishability and good dimensional stability, which is widely used in high-gloss, corrosion-resistant plastic injection molds. It is a high-end stainless mold steel, and its corrosion resistance and polishability are better than 4Cr13 and 2083, which can meet the high requirements of high-gloss plastic products (such as automotive interior parts, electronic product shells, medical plastic products). S136 has good machinability and toughness, and can be processed into complex structure molds, which is the preferred material for high-end plastic mold manufacturers. This article will detail the performance characteristics, chemical composition, application scenarios, heat treatment specifications and selection tips of S136 mold steel, helping you fully understand and use S136 mold steel.

Core Performance Characteristics of S136 Mold Steel

S136 mold steel is mainly characterized by high gloss, excellent corrosion resistance and good dimensional stability, which is especially suitable for high-end plastic mold scenarios requiring high surface quality and corrosion resistance:

• Excellent Corrosion Resistance: S136 contains high content of chromium (13-15%) and nickel (0.8-1.2%), which can form a dense and stable chromium oxide passive film on the surface, effectively resisting the corrosion of strong corrosive plastics (such as PVC, PC/ABS alloy plastics) and mold release agents. It can work stably in humid and corrosive environments, avoiding mold rust and ensuring the service life of the mold.
• High Polishability: S136 has high purity, low impurity content, and uniform structure, which can be polished to a high-gloss surface (mirror finish, Ra ≤ 0.02μm). It is suitable for plastic molds that require high surface quality of products, such as high-gloss automotive interior parts, electronic product shells.
• Good Dimensional Stability: S136 has small deformation during heat treatment and plastic injection molding, stable structure, and can ensure the dimensional accuracy of the mold and products. It is suitable for high-precision plastic molds (such as precision electronic product molds).
• High Toughness: S136 contains nickel and molybdenum elements, which can refine the grain and improve the toughness of the steel. It can withstand the impact during mold processing and use, and is not easy to crack, suitable for complex structure molds.
• Good Machinability: S136 has good machinability in the annealed state, which is easy to cut, drill, mill and polish, reducing tool wear and processing costs, and improving processing efficiency.
• Good Wear Resistance: After proper heat treatment, the hardness of S136 can reach 48-52 HRC, which has good wear resistance, can resist the wear caused by plastic flow during injection molding, and ensure the service life of the mold.

Chemical Composition of S136 Mold Steel

The excellent performance of S136 is determined by its scientific chemical composition, and its detailed chemical composition (mass fraction) is as follows. The reasonable ratio of chromium, nickel and molybdenum ensures its corrosion resistance and polishability:

Applications of S136 Mold Steel

S136 is mainly used in high-end plastic injection molds requiring high gloss, corrosion resistance and high precision, and its application scenarios are concentrated in the following fields, especially in automotive, electronic and medical industries:

1. High-Gloss Plastic Injection Molds

S136 has excellent polishability, which is suitable for high-gloss plastic product molds that require high surface quality:

• Automotive interior parts molds: Molds for high-gloss automotive dashboards, door panels, center consoles (require high gloss and corrosion resistance to resist the corrosion of automotive interior cleaning agents).
• Electronic product shell molds: Molds for high-gloss mobile phone shells, tablet shells, computer casings (require high precision and high surface finish).
• Home appliance shell molds: Molds for high-gloss TV shells, refrigerator panels, air conditioner casings (require high gloss and wear resistance).

2. Corrosive Plastic Injection Molds

S136 has excellent corrosion resistance, which is suitable for molds processing strong corrosive plastics:

• PVC plastic molds: Molds for PVC pipes, PVC profiles, PVC plastic products (PVC will release corrosive gases during processing, and S136 can resist corrosion).
• PC/ABS alloy plastic molds: Molds for PC/ABS alloy electronic parts, automotive parts (PC/ABS alloy has certain corrosiveness, and S136 can ensure stable mold performance).
• Flame-retardant plastic molds: Molds for flame-retardant electronic accessories, flame-retardant plastic shells (flame-retardant plastics will release corrosive substances during processing).

3. High-Precision Plastic Molds

S136 has good dimensional stability, which is suitable for high-precision plastic molds:

• Precision electronic product molds: Molds for precision electronic components, connectors, sensors (require high dimensional accuracy and surface quality).
• Medical plastic molds: Molds for medical syringes, medical catheters, medical plastic parts (require high precision, corrosion resistance and cleanliness).
• Complex structure plastic molds: Molds for plastic parts with complex structures (such as multi-cavity molds, sliding block molds) require good toughness and machinability of S136.

Heat Treatment Guide for S136 Mold Steel

The heat treatment of S136 is the key to exerting its corrosion resistance, polishability and dimensional stability. The core is to control the quenching and tempering temperature to balance hardness, toughness and corrosion resistance. The recommended heat treatment process is as follows:

1. Annealing (Before Processing)

Purpose: Reduce hardness, eliminate internal stress, improve machinability and polishability, and lay the foundation for subsequent processing and heat treatment.

• Annealing Temperature: 800-850℃
• Holding Time: 2-3 hours (depending on the size of the mold blank, ensure uniform heating)
• 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 of the mold during quenching, reduce internal stress, and prevent mold cracking. Preheating can also improve the uniformity of the structure and enhance polishability.

• First Preheating Temperature: 600-650℃, holding time 1-2 hours
• Second Preheating Temperature: 800-850℃, holding time 1-1.5 hours

3. Quenching (Core Heat Treatment Step)

Purpose: Form a martensitic structure, improve the hardness, wear resistance and corrosion resistance of S136, and lay the foundation for subsequent tempering.

• Quenching Temperature: 1020-1050℃ (small molds use 1040-1050℃, large molds use 1020-1040℃ to avoid deformation)
• Holding Time: 1-1.5 hours (ensure the mold is fully austenitized, but avoid excessive holding time to prevent grain growth and affect polishability)
• Cooling Method: Oil cooling (cool to 150-200℃, then air cooling to room temperature); avoid water cooling to prevent mold cracking due to excessive internal stress.
• Quenched Hardness: 52-56 HRC

4. Tempering (Improve Toughness and Stabilize Structure)

Tempering is a key step for S136, which can eliminate the brittleness caused by quenching, improve toughness, stabilize the structure and size, and enhance corrosion resistance and polishability. Two times tempering is recommended to ensure stable performance:

• Tempering Temperature: 200-250℃ (for high hardness and wear resistance); 450-500℃ (for better corrosion resistance and toughness)
• Holding Time: 2-3 hours per time, twice tempering (the first tempering eliminates internal stress, the second tempering stabilizes the structure and improves corrosion resistance)
• Cooling Method: Air cooling to room temperature after each tempering
• Tempered Hardness: 48-52 HRC (common for high-gloss plastic molds)

S136 vs 4Cr13 vs 2083: Detailed Performance Comparison

S136, 4Cr13 and 2083 are all common stainless mold steels, but their performance and application scenarios are quite different. Understanding their differences can help you choose the most suitable material according to your product requirements and budget. The detailed comparison is as follows:

• Corrosion Resistance: S136 has the best corrosion resistance, which can resist strong corrosive plastics (such as PVC) and humid environments; 2083 is slightly inferior to S136, suitable for weak to medium corrosive scenarios; 4Cr13 has the weakest corrosion resistance, only suitable for weak corrosive plastics (such as ordinary PC, ABS) and general environments.
• Polishability: S136 has the highest polishability, which can be polished to a mirror finish (Ra ≤ 0.02μm), suitable for high-gloss products; 2083 has good polishability, which can meet the general high-gloss requirements; 4Cr13 has ordinary polishability, which is only suitable for products with general surface quality requirements.
• Dimensional Stability: S136 and 2083 have good dimensional stability, small deformation during heat treatment and injection molding, suitable for high-precision molds; 4Cr13 has slightly poor dimensional stability, which is suitable for ordinary precision molds.
• Toughness: S136 has the best toughness, which can be processed into complex structure molds and is not easy to crack; 2083 has good toughness, second only to S136; 4Cr13 has moderate toughness, suitable for simple and medium-complex structure molds.
• Cost: S136 is the most expensive, suitable for high-end high-demand scenarios; 2083 is moderately priced, suitable for medium-high-end scenarios; 4Cr13 is the cheapest, suitable for low-budget and general requirement scenarios.

Selection Tips & Common Mistakes for S136 Mold Steel

Selection Tips

• If you need high-gloss plastic molds (such as automotive interior parts, electronic product shells) → Choose S136 (excellent polishability, can achieve mirror finish).
• If you process strong corrosive plastics (such as PVC, PC/ABS alloy) → Choose S136 (excellent corrosion resistance, avoid mold rust).
• If you need high-precision, complex structure plastic molds (such as medical plastic molds, multi-cavity molds) → Choose S136 (good dimensional stability and toughness).
• If you have limited budget and only need general high-gloss and corrosion resistance → Choose 2083 (cost-effective, meet medium-high-end requirements).
• If you process weak corrosive plastics and have tight budget → Choose 4Cr13 (cheapest, meet basic requirements).

Common Mistakes

1. Using S136 for ordinary plastic molds with low surface requirements → Wasting cost; 4Cr13 or 2083 can meet the requirements and are more cost-effective.
2. Neglecting preheating before quenching → S136 is prone to uneven heating and internal stress without preheating, leading to mold cracking and affecting polishability.
3. Using only one tempering → One tempering cannot fully eliminate the quenching brittleness of S136, which will lead to poor toughness and easy cracking of the mold during use.
4. Confusing S136 with 4Cr13/2083 and using them interchangeably → S136’s corrosion resistance and polishability are much better than 4Cr13 and 2083; blind interchange will lead to unqualified product surface or shortened mold service life.
5. Pursuing high gloss and using excessive polishing without proper heat treatment → The polishability of S136 is based on reasonable heat treatment; insufficient heat treatment will lead to uneven structure and failure to achieve high-gloss effect.

We provide high-quality S136 mold steel, with complete chemical composition detection reports and professional heat treatment guidelines, and free custom cutting, forging, heat treatment and polishing services. Our team of engineers can provide personalized solutions according to your product surface requirements (high gloss, mirror finish), plastic material and mold structure, helping you maximize the performance of S136 mold steel and reduce production costs. 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