Introduction

P20+Ni (also known as DIN 1.2738 or 40CrMnNiMo8-6-4) is a high-quality, nickel-alloyed mold steel developed as an upgrade over standard P20 steel. It is delivered in a pre-hardened condition and is specifically designed to offer excellent through-hardening capabilities, improved toughness, enhanced machinability, and better polishability.

The addition of approximately 1% Nickel allows the material to achieve uniform hardness even in large cross-sections, making P20+Ni highly suitable for high-performance plastic molds, die-casting dies, and various tooling components requiring durability, wear resistance, and dimensional stability.

Properties of P20+Ni Steel:

  • Pre-Hardened: Delivered in pre-hardened condition around 30–36 HRC.
  • Excellent Through Hardening: Uniform hardness even in large sections.
  • High Toughness: Improved impact strength due to nickel content.
  • Superior Machinability: Good machinability compared to conventional steels.
  • Excellent Polishability and Texturing: Suitable for mirror-finished molds.
  • Dimensional Stability: Reduced risk of distortion during machining and service.
  • Good Wear Resistance: Ideal for heavy-duty tooling operations.
  • Surface Treatment Capability: Can be nitrided or chromed for enhanced performance.

Uses/Applications of the Grade:

P20+Ni finds widespread applications across several industries, including:

  • Plastic Injection Molds: Ideal for large and complex molds requiring high surface finish.
  • Die Casting Dies: Primarily for low melting alloys like zinc and magnesium.
  • Blow Molding Dies: For manufacturing plastic bottles and hollow products.
  • Mold Frames and Bases: For multi-cavity and large injection molds.
  • Automotive Parts: Molds for headlights, bumpers, and dashboards.
  • Tooling Components: Shafts, sleeves, bushings requiring wear and impact resistance.

Chemical Composition:

Element Content (%)
Carbon (C) 0.35 – 0.45
Silicon (Si) 0.20 – 0.40
Manganese (Mn) 1.30 – 1.60
Chromium (Cr) 1.80 – 2.10
Molybdenum (Mo) 0.15 – 0.25
Nickel (Ni) 0.80 – 1.20
Phosphorus (P) ≤ 0.025
Sulfur (S) ≤ 0.005

The nickel addition improves toughness and uniformity in hardness across sections.

Mechanical Properties:

Property Typical Value
Hardness (as delivered) 30 – 36 HRC
Tensile Strength ~1100 MPa
Yield Strength ~900 MPa
Elongation at Break ~12%
Impact Toughness High

These properties ensure the material’s robustness under mechanical and thermal stresses.

Physical Properties:

Property Typical Value
Density 7.85 g/cm³
Modulus of Elasticity 205 GPa
Thermal Conductivity ~29 W/m·K at 20°C
Coefficient of Thermal Expansion 12.3 × 10⁻⁶ /°C (20–100°C)
Specific Heat Capacity ~460 J/kg·K

Forging:

  • Forging Temperature Range: 1050°C – 850°C.
  • Cooling Method: Slow cooling in furnace or dry ash to prevent cracking.
  • Precautions: Avoid overheating and rapid cooling to maintain microstructural integrity.

Proper forging practices ensure enhanced mechanical performance.

The thermal properties allow P20+Ni to perform reliably in dynamic and high-temperature environments.

Heat Treatment:

P20+Ni is supplied pre-hardened but can undergo further treatments for improved surface properties:

  • Stress Relieving: After rough machining, heat to ~550–650°C, hold for 1–2 hours, then cool slowly.
  • Nitriding: Achieves a surface hardness up to 60–65 HRC, enhancing wear resistance while preserving core toughness.
  • Tempering: If re-hardening is performed, appropriate tempering is required to achieve balanced mechanical properties.

Heat treatment enhances the material’s durability for critical mold-making applications.

Dimensional Tolerances:

Bright bars and forged forms are available in precise dimensional tolerances:

  • Round Bars: h9 or h11 tolerance class.
  • Plates: Thickness tolerance typically ±0.30 mm.
  • Customized Sizes: Available on request as per customer drawings.

Tight tolerances ensure reduced machining time and higher mold accuracy.

Machinability:

  • P20+Ni offers good machinability (around 75% relative to free-machining steels).
  • Suitable for high-speed cutting, milling, drilling, and turning.
  • Proper coolant application is recommended to enhance tool life and surface quality.
  • Minimal tool wear and high-quality surface finishes are achievable.

Its superior machinability makes it ideal for complex molds and tooling parts.

Weldability:

  • P20+Ni exhibits good weldability with proper preheating (~250–300°C) before welding.
  • Post-weld stress relieving (at ~600°C) is strongly advised to prevent cracking.
  • Low-carbon consumables matching the base hardness should be used.

Good welding practice ensures the retention of toughness and dimensional stability.

Corrosion Resistance:

  • P20+Ni has moderate corrosion resistance but is not stainless.
  • Suitable for molds used in dry or controlled environments.
  • Surface protection methods such as nitriding, chrome plating, or coatings are recommended for applications exposed to moisture.
  • Regular maintenance extends service life.

Available Form:

P20+Ni Steel is commercially available in various standard forms:

  • Bright Bars (Round, Hexagonal, Square)
  • Forged Bars (Rounds)
  • Flat Bars and Blocks
  • Plates and Die Steel Sheets
  • Customized Pre-machined Mold Blocks

This versatility meets a broad range of manufacturing and tooling needs.

Conclusion:

P20+Ni is a premium mold steel offering significant advantages over conventional P20 steel. Its nickel content improves toughness, hardness uniformity, and machinability, making it the material of choice for high-performance mold-making applications, especially large, complex molds requiring fine surface finishes and dimensional stability.

With excellent through-hardening ability, good polishability, reliable machinability, and moderate corrosion resistance, P20+Ni is a comprehensive solution for mold makers and tooling engineers striving for superior performance and durability. Proper processing and surface treatment further enhance the steel’s life span and functionality.

Related Products :   D2, DB6, DIN 1.2714, DIN 1.2080, DIN 1.2379, DIN 1.2343, DIN 1.2344, EN31, H11, H13, OHNS, HCHCR, M2, P20+S, P20, P20+Ni, K310, Maps