Plastic Mold Steels Comparison: 1.2311 vs 1.2312 vs 1.2738

As representatives of pre-hardened plastic mold steel, we will conduct a comprehensive comparison of 1.2311 steel, 1.2312 steel and 1.2738 steel in terms of chemical composition, mechanical properties, heat treatment process, processing performance, application areas, etc. The following is their precise comparative analysis based on the latest revised composition data and performance characteristics:

1. Chemical Composition Comparison

Grade	C	Cr	Mn	Mo	S
1.2311	0.35-0.45	1.8-2.1	1.3-1.6	0.15-0.25	≤0.03
1.2312	0.35-0.45	1.8-2.1	1.4-1.6	0.15-0.25	0.05-0.1
1.2738	0.35-0.45	1.8-2.1	1.3-1.6	0.2-0.4	≤0.035

Key summary:
– 1.2311 and 1.2312: The composition is almost the same, 1.2312 has a slightly higher sulfur content (better machinability), and both do not contain nickel.
– 1.2738: Unique nickel (Ni) and higher molybdenum (Mo), and extremely low sulfur, suitable for high polishing and high hardenability requirements.

2. Mechanical Properties Comparison

Grade	Pre-hardening hardness (HRC)	Tensile strength (MPa)	Toughness	Hardenability	Polishability
1.2311	30-35	1000-1100	Medium	General	Good
1.2312	28-32	950-1050	Medium	General	Excellent(sulfur microspheroidization)
1.2738	30-34	1100-1200	High	Excellent (for thick sections)	Excellent (low sulfur)

Performance analysis:

– 1.2311/1.2312: Similar hardness, 1.2312 has slightly better polishing performance due to more uniform sulfur distribution, but no significant difference in toughness.

– 1.2738: High nickel-molybdenum significantly improves hardenability and toughness, and low sulfur ensures that polishing can achieve a mirror effect (Ra < 0.01μm).

3. Comparison of Processing Characteristics

Characteristics	1.2311	1.2312	1.2738
Machinability	Excellent (good chip breaking performance with high sulfur)	Better (higher sulfur content)	General (low sulfur requires wear-resistant tools)
Weldability	Medium (preheating required)	Medium (preheating required)	Poor (professional process required)
Heat treatment	Direct processing in pre-hardened state	Direct processing in pre-hardened state	High temperature quenching + tempering required (high cost)
Cost	Low	Slightly higher than 1.2311	High (complex alloy composition)

4. Application Field Comparison

Grade	Typical application scenarios	Industry cases
1.2311	Highly overlapped with 1.2311, more suitable for mass production requiring fast cutting (such as multi-cavity molds)	Consumer electronics accessories, plastic containers
1.2312	Medium (preheating required)	Medium (preheating required)
1.2738	Large and complex molds, high-finish parts (such as automotive interior and exterior decoration, optical lenses), scenarios requiring high dimensional stability	Automotive bumpers, medical instruments, camera lens molds

5. Selection Recommendations

1.2311:
– Advantages: low cost, easy processing, suitable for short-term projects or small batch production.
– Limitations: general toughness, not suitable for high impact or high precision polishing requirements.
1.2312:
– Advantages: high surface finish, suitable for transparent parts and optical products.
– Limitations: slightly lower tensile strength, not suitable for ultra-high load scenarios.
1.2738:
– Advantages: excellent hardenability, suitable for large molds and complex structures, strong long-term stability.
– Limitations: high cost, difficult processing, professional heat treatment support required.

6. Common Misunderstandings Clarified

Myth 1: 1.2312 contains nickel → Wrong! Both 1.2312 and 1.2311 do not contain nickel, the only difference is the sulfur content.
Myth 2: 1.2738 has poor polishability → Wrong! Its low sulfur and high purity can achieve top polishing effects.

7. Summary

1.2311: Economical and practical, suitable for conventional plastic molds.
1.2312: Cutting efficiency is prioritized, suitable for rapid production.
1.2738: High-end and versatile, designed for large and high-demand molds.

Choose according to specific needs (size, surface requirements, budget). If you have further questions (such as heat treatment details), please continue to discuss!