P20 + Ni/1.2378 Tool steel
P20 + Ni / 1.2738 Steel is a nickel-alloyed plastic mold steel that is widely used for making large plastic injection molds and die-casting molds. It is an improved version of standard P20 steel, with the addition of nickel (Ni) to enhance its toughness, strength, and hardness uniformity. This steel is usually supplied in a pre-hardened condition (around 30–36 HRC), which means it can often be used directly without additional heat treatment. Because of its good machinability and stable mechanical properties, it is very popular in mold manufacturing.
P20 + Ni / 1.2738 steel contains alloying elements such as carbon, chromium, manganese, molybdenum, and nickel, which improve its wear resistance, polishability, and dimensional stability. The presence of nickel allows the steel to maintain consistent hardness even in large mold blocks, making it ideal for heavy-duty molds. Due to these properties, P20 + Ni / 1.2738 steel is commonly used in the production of plastic injection molds, blow molds, die-casting molds, automotive parts molds, and large industrial plastic components. It is widely used in industries such as automotive, consumer products, packaging, and plastic manufacturing, where durable and high-quality mold materials are required.
Main characteristics and applications
Pre-hardened plastic mould steel with excellent hardening penetration, good machinability, polishing and texturing properties.
This steel is used for plastic moulds of medium and big size. It can be subject to a nitriding or PVD treatment to improve its wear resistance.
Main applications: thermoplastic injections and extrusion moulds, rubber moulds, large moulds, frames, containers.
Critical points
- Ac1 720 °C
- Ac3 800 °C
- Ms 290 °C
Production technology
- EAF – LF – VD – Forging – Heat treatment QT
US specification
- In according to standard EN10228-3 Class 4 and standard SEP 1921 Class E/e
Delivery condition
- WW.NR. 1.2738 is delivered in quenched and tempered condition, with hardness range 300 – 340 HB (32 – 37 HRC).
| C | Si | Mn | P (Max) | S (Max) | Cr | Mo | Ni |
|---|---|---|---|---|---|---|---|
| 0.35 - 0.45 | 0.20 - 0.40 | 1.30 - 1.60 | 0.03 | 0.03 | 1.80 - 2.10 | 0.15 - 0.25 | 0.90 - 1.20 |
| Property | 20°C | 100°C | 200°C | 500°C |
|---|---|---|---|---|
| Thermal expansion coefficient (10⁻⁶/K) | 12.0 | 12.4 | — | 14.1 |
| Thermal conductivity (W/m·K) | 33.1 | 33.5 | — | 32.6 |
| Young's modulus (kN/mm²) | 212 | 205 | — | 175 |
| Treatment | Temperature (°C) | Holding Time | Cooling | Comments |
|---|---|---|---|---|
| Annealing | 680 – 700 | Min. 2 min/mm | Air or furnace | In order to obtain hardness lower than 250 HB (24 HRC) to improve machinability |
| Stress relieving | 560 – 600 (max 30°C below tempering temp) |
Min. 2 min/mm | Air or furnace | To be carried out after machining to eliminate residual stresses induced by mechanical working |
| Hardening | 860 – 880 | Min. 1 min/mm | Polymer / Oil | Heat uniformly to austenitizing temperature |
| Tempering | 550 – 620 | Min. 3 min/mm | Air or furnace | To be carried out after hardening. 2nd tempering must be performed to max 30°C below tempering temperature |
📌 Material Summary:
Type: Prehardened plastic mold steel
Delivery Condition: Prehardened to 280-325 HB (approx. 30-34 HRC)
Key Characteristics: Excellent polishability, good corrosion resistance, high toughness, good machinability
Typical Applications: Large plastic injection molds, die casting dies, extrusion tools, mold bases
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