Choosing between 1.2311, 1.2312, and 1.2738 is one of the most common decisions for mold manufacturers, buyers, and engineers. These three steels all belong to the P20 family, but they are designed for different applications, performance levels, and budgets.
So how do you choose the right one?
This guide will help you understand the real differences, avoid common mistakes, and reduce your mold manufacturing cost.
What Are 1.2311, 1.2312, and 1.2738 Steel?
These three grades are pre-hardened plastic mold steels, typically supplied at 28–34 HRC, and widely used for plastic injection molds and mold bases.
Basic Overview
| Grade | Type | Key Feature |
|---|---|---|
| 1.2311 | Standard P20 | General-purpose mold steel |
| 1.2312 | Free-machining P20 | Better machinability |
| 1.2738 | Ni-added P20 | Better toughness & uniform hardness |
Chemical Composition Comparison
The biggest differences lie in sulfur and nickel content.
Typical Chemical Composition
| Grade | C (%) | Mn (%) | Cr (%) | Mo (%) | Ni (%) | S (%) |
|---|---|---|---|---|---|---|
| 1.2311 | 0.35–0.45 | 1.30–1.60 | 1.80–2.10 | 0.15–0.25 | — | Low |
| 1.2312 | 0.35–0.45 | 1.30–1.60 | 1.80–2.10 | 0.15–0.25 | — | 0.05–0.10 |
| 1.2738 | 0.35–0.45 | 1.30–1.60 | 1.80–2.10 | 0.15–0.25 | 0.80–1.20 | Low |
Why This Matters
- Sulfur (1.2312) → Better machinability
- Nickel (1.2738) → Better toughness and uniform hardness
Common Buyer Mistakes
Mistake 1: Choosing 1.2312 for Mirror Finish
Result:
- Poor surface quality
- Customer complaints
Mistake 2: Using 1.2311 for Very Large Molds
Result:
- Hardness variation
- Deformation risk
Mistake 3: Using 1.2738 for Low-End Applications
Result:
- Unnecessary cost increase
Why Quality Matters More Than Grade
Even the right steel can fail if quality is poor.
Always check:
✔ Steelmaking process (EAF + LF + VD)
✔ ESR (for high-end molds)
✔ UT testing
✔ Hardness uniformity
📩 Need help selecting the right steel?
Contact us:
Email: rika@otaisteel.com
WhatsApp: +8613642825398
