ASSAB 718 plastic mold steel | P20+Ni | 3Cr2NiMo | 1.2738 | M238
Characteristics of 718 Plastic Mold Steel
718 mold steel (also known as 718 plastic mold steel) is a widely utilized pre-hardened alloy renowned for its balanced mechanical properties, excellent polishability, and adaptability to complex manufacturing requirements. Below is a detailed analysis of its key characteristics:
1,Chemical Composition and Equivalent Grade.
The optimized composition of 718 mold steel includes:
- Carbon (C): 0.32–0.40% (enhances hardness and wear resistance).
- Nickel (Ni): 0.85–1.10% (improves toughness, corrosion resistance, and hardenability).
- Chromium (Cr): 1.70–2.00% (boosts hardness and oxidation resistance).
- Molybdenum (Mo): 0.25–0.40% (strengthens high-temperature stability and fatigue resistance).
- Manganese (Mn): 1.10–1.50% (enhances hardenability and machinability).
ASSAB 718 plastic mold steel | AISI P20+Ni | GB 3Cr2NiMo | DIN 1.2738 | M238
This formulation ensures uniform hardness distribution in large cross-sections and superior performance under prolonged stress.
2. Mechanical Properties
718 mold steel exhibits exceptional mechanical characteristics:
- Hardness: Pre-hardened to 28–47 HRC (depending on processing), eliminating the need for additional heat treatment in most applications.
- Tensile Strength: ~1,100 MPa; Yield Strength: ~980 MPa (ensures structural integrity under high loads).
- Toughness: Impact toughness exceeds 20 J/cm², minimizing brittle fracture risks.
- Wear Resistance: Enhanced surface durability through optimized alloying and heat treatment.
3. Thermal Processing
718 mold steel achieves optimal performance through controlled heat treatment:
- Normalizing: 880°C followed by air cooling to refine grain structure.
- Tempering: 580°C to stabilize hardness and relieve internal stresses.
- Forging: Performed at 1,050–1,140°C start temperature and ≥850°C end temperature, with slow cooling to prevent cracking.
4. Applications
The versatility of 718 mold steel makes it ideal for:
- Large Plastic Injection Molds: For automotive parts, electronics housings, and household appliances.
- High-Precision Tools: Optical lens molds and components requiring low surface roughness (Ra < 0.05 μm)
- Die-Casting Molds: Suitable for low-melting-point alloys (e.g., zinc, aluminum).
5. Advantages
- Pre-Hardened State: Reduces post-machining distortion and production costs.
- Machinability: Excellent cutting and polishing performance in pre-hardened conditions.
- Weldability: Repairable via welding with proper preheating and post-treatment.
Conclusion
718 mold steel stands out as a cost-effective, high-performance material for demanding mold applications. Its combination of pre-hardened convenience, mechanical robustness, and surface quality makes it a preferred choice in global manufacturing industries