S136 is a martensitic stainless mold steel widely used for plastic injection molds that require excellent corrosion resistance, high surface quality, and long service life. Thanks to its high chromium content and excellent hardenability, S136 is suitable for molds processing corrosive plastics, transparent materials, and products with demanding surface finish requirements.
Supplied in the annealed condition, S136 is typically hardened and tempered to 48–52 HRC before use. After proper heat treatment, it offers an excellent combination of corrosion resistance, wear resistance, polishability, and dimensional stability, making it one of the most popular stainless mold steels for high-quality plastic molds.
Why Choose S136 Mold Steel?
S136 is widely selected when mold durability and surface quality are equally important.
Key benefits include:
- Excellent corrosion resistance
- High mirror polishing capability
- Good wear resistance after heat treatment
- Stable dimensional accuracy
- Excellent texture etching performance
- Low maintenance requirements
- Suitable for humid production environments
- Long mold service life
These characteristics help reduce maintenance while maintaining consistent molding quality throughout long production runs.
Chemical Composition
| Element | Typical Content |
|---|---|
| Carbon (C) | 0.33–0.43% |
| Chromium (Cr) | 13.5–14.5% |
| Molybdenum (Mo) | 0.40–0.60% |
| Silicon (Si) | 0.20–0.40% |
| Manganese (Mn) | 0.30–0.50% |
The high chromium content forms a passive oxide layer that protects the mold against rust and corrosion, even in humid environments or when processing corrosive plastics.
Typical Applications
Medical Plastic Molds
S136 is commonly used for precision molds requiring excellent cleanliness and corrosion resistance.
Typical products include:
- Syringes
- Medical containers
- Diagnostic components
- Laboratory consumables
Food Packaging Molds
Its corrosion resistance makes S136 suitable for molds used to manufacture:
- Food containers
- Beverage closures
- Kitchen products
- Baby care products
Material selection should always comply with local regulatory requirements for food-contact applications.
Optical and Transparent Plastic Molds
The excellent polishing performance of S136 makes it suitable for:
- Optical lenses
- Light guides
- Transparent covers
- Automotive lighting components
Proper polishing techniques are essential to achieve optical-grade surfaces.
Corrosion-Resistant Plastic Molds
S136 performs well when molding plastics that may release corrosive gases during processing, including:
- PVC
- Flame-retardant engineering plastics
- Some halogen-containing materials
Its corrosion resistance helps reduce rust, pitting, and maintenance downtime.
Heat Treatment
Proper heat treatment is essential for maximizing the performance of S136.
Typical process:
Hardening
- Austenitizing: 1030–1050°C
- Vacuum hardening
- Gas quenching
Tempering
- Double tempering
- 520–540°C
- Final hardness: 48–52 HRC
Vacuum heat treatment helps minimize distortion while maintaining corrosion resistance and dimensional stability.
Machining and Polishing
S136 is generally machined in the annealed condition before heat treatment.
Recommended practices include:
- Complete rough machining before hardening.
- Use carbide cutting tools with adequate cooling.
- Remove the EDM recast layer before polishing.
- Follow a progressive polishing sequence for high-gloss applications.
Proper machining and polishing procedures are essential for achieving the best surface quality.
S136 vs. NAK80 vs. 2316
| Property | S136 | NAK80 | 2316 |
|---|---|---|---|
| Corrosion Resistance | Excellent | Moderate | Good |
| Delivery Condition | Annealed | Pre-Hardened | Pre-Hardened |
| Mirror Polish | Excellent | Excellent | Good |
| Heat Treatment Required | Yes | No | No |
| Best Application | Corrosion-Resistant Molds | High-Gloss Molds | General Stainless Molds |
S136 is generally preferred when corrosion resistance and mirror polishing are the primary requirements. NAK80 is often selected to shorten manufacturing time because it is supplied pre-hardened, while 2316 offers a practical balance between corrosion resistance and production efficiency.
How to Choose S136
S136 is recommended for molds that require:
- High corrosion resistance
- Excellent polishing performance
- Long service life
- Transparent plastic products
- Medical and laboratory applications
- Food packaging components
- High-humidity production environments
For general-purpose plastic molds where corrosion resistance is less critical, pre-hardened steels such as 2316 or 718H may offer a more economical solution.
Frequently Asked Questions
What is S136 mold steel used for?
S136 is widely used for plastic injection molds requiring corrosion resistance, high surface quality, and long-term dimensional stability.
What hardness does S136 reach?
After proper heat treatment, the recommended working hardness is typically 48–52 HRC.
Is S136 suitable for mirror polishing?
Yes. S136 offers excellent polishing performance and is commonly used for transparent plastic products and high-gloss mold cavities.
Does S136 require heat treatment?
Yes. S136 is normally supplied in the annealed condition and requires hardening and tempering before use.
How does S136 compare with 2316?
Both are stainless mold steels, but S136 generally provides higher hardness and better polishing performance after heat treatment, while 2316 is supplied pre-hardened for faster mold manufacturing.
Why Choose KUTU S136 Mold Steel?
KUTU supplies premium S136 stainless mold steel for demanding plastic injection mold applications.
Our services include:
- Custom cutting
- Rough machining
- Vacuum heat treatment
- Material certification
- Technical support
- Fast global delivery
Whether you are producing medical components, transparent plastic products, or corrosion-resistant molds, KUTU provides reliable S136 mold steel to help improve mold performance, extend service life, and maintain consistent production quality.
NAK80 (Pre-Hardened 40 HRC) Mirror Polishing Plastic Mold Steel Plate for Precision Molds – KUTU
S136 / S136H (Premium ESR Grade) Corrosion Resistant Stainless Plastic Mold Steel Plate – KUTU