Tool Steel P20

Tool Steel P20 (AISI P20, also known as 1.2311 or 1.2312 in European standards) is a pre-hardened plastic mold steel that revolutionized injection mold manufacturing when it was introduced. Supplied in the pre-hardened condition at HRC 28–36, P20 requires no heat treatment before machining, EDM, or polishing, eliminating the risk of distortion, cracking, or dimensional change associated with quenching and tempering. This combination of ready-to-machine hardness, excellent machinability, good wear resistance, and superior polishability makes P20 the industry-standard material for injection mold bases, mold frames, and medium-duty mold cavities. Its balanced chromium-nickel-molybdenum composition (Cr 1.9%, Ni 0.9%, Mo 0.2%) provides good through-hardening, dimensional stability in service, and moderate corrosion resistance in humid mold environments. P20 is the workhorse steel of the injection molding industry worldwide.

Mechanical Properties

• Density: 7.85 g/cm³
• Tensile Strength: 1100 MPa
• Yield Strength: 950 MPa
• Elongation at Break: 14%
• Reduction of Area: 38%
• Hardness: HRC 28–36 (pre-hardened, as-supplied)
• Modulus of Elasticity: 205 GPa
• Thermal Conductivity: 32 W/m·K
• Melting Point: 1427 °C
• Coefficient of Thermal Expansion: 12.0 × 10⁻⁶ /°C

Advantages

✔Pre-hardened to HRC 28–36 — ready to machine without heat treatment, eliminating heat treatment risk, cost, and lead time

✔ Excellent machinability at working hardness — machines readily with standard carbide tooling; superior to hardened tool steels

✔ Good polishability — achieves high-luster Class A surface finishes (Ra < 0.2 μm) required for cosmetic product molds

✔ Good through-hardening and dimensional stability — uniform hardness in large cross-sections; minimal dimensional change in service

✔ Good wear resistance — suitable for moderate-production injection molds and die-cast bases (50,000–500,000 shots)

✔ Nitriding capability — can be nitrided to HRC 65+ for mold inserts requiring extra wear resistance

Machining & Manufacturing

Common Applications