Overview
P20 Mold Steel is one of the world’s most widely used pre-hardened plastic mold steels, valued for its excellent combination of machinability, polishability, toughness, dimensional stability, weldability, and cost-effectiveness.
Unlike many tool steels that require final heat treatment after machining, P20 is typically supplied in a pre-hardened condition (28–34 HRC), allowing mold manufacturers to machine molds directly without additional hardening processes.
P20 is widely used in:
- Plastic Injection Molds
- Blow Molds
- Compression Molds
- Die Casting Support Components
- Mold Bases
- Automotive Mold Tools
- Consumer Product Molds
- Prototype Tooling
Because of its ease of machining and reliable performance, P20 has become the industry standard material for medium-volume plastic mold manufacturing.
Material Specification
| Property | Value |
|---|---|
| Material Designation | P20 Mold Steel |
| Standard | ASTM A681 |
| UNS Number | T51620 |
| Material Family | Pre-Hardened Plastic Mold Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Pre-Hardened |
| Standard Hardness | 28–34 HRC |
| Standard Forms | Plate, Block, Round Bar, Mold Base Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.28–0.40 |
| Chromium (Cr) | 1.40–2.00 |
| Manganese (Mn) | 0.60–1.00 |
| Molybdenum (Mo) | 0.30–0.55 |
| Silicon (Si) | 0.20–0.80 |
| Phosphorus (P) | ≤0.030 |
| Sulfur (S) | ≤0.030 |
Chromium and molybdenum improve hardenability, toughness, and wear resistance while maintaining excellent machinability.
Mechanical Properties
Pre-Hardened Condition
| Property | Value |
|---|---|
| Tensile Strength | 900–1100 MPa |
| Yield Strength | 750–950 MPa |
| Elongation | 12–18% |
| Hardness | 28–34 HRC |
| Elastic Modulus | 210 GPa |
Nitrided Condition
| Property | Value |
|---|---|
| Surface Hardness | 55–65 HRC |
| Wear Resistance | Excellent |
| Mold Life | Significantly Improved |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1460°C |
| Thermal Conductivity | 29 W/m·K |
| Electrical Resistivity | 0.23 μΩ·m |
| Thermal Expansion Coefficient | 12.0 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Good |
| Dry Atmosphere | Good |
| Humid Environment | Moderate |
| Outdoor Environment | Moderate |
| Marine Environment | Poor |
| Chemical Environment | Moderate |
P20 is not stainless steel and may require protection in humid environments.
Recommended surface treatments:
- Nitriding
- Hard Chrome Plating
- Electroless Nickel Plating
- PVD Coating
- QPQ Treatment
- Polishing
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Excellent |
| MIG Welding | Good |
| Arc Welding | Good |
| Laser Repair Welding | Excellent |
| Mold Repair Welding | Excellent |
P20 is widely used in mold repair applications due to its excellent weldability.
Recommended:
- Preheat: 200–300°C
- Controlled Cooling
- Stress Relief After Repair
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Drilling | Excellent |
| Grinding | Excellent |
| EDM Machining | Excellent |
| Wire EDM | Excellent |
Machinability Comparison
| Material | Machinability |
|---|---|
| P20 | Excellent |
| 4140 | Good |
| H13 | Good |
| D2 | Fair |
| S136 | Good |
P20 is specifically developed for high-efficiency mold machining.
Heat Treatment
Typical Supply Condition
| Property | Value |
|---|---|
| Hardness | 28–34 HRC |
| Heat Treatment Required | No |
Re-Hardening (Optional)
| Parameter | Value |
|---|---|
| Austenitizing Temperature | 830–870°C |
| Cooling Medium | Oil |
| Tempering Temperature | 540–650°C |
Nitriding
| Property | Value |
|---|---|
| Surface Hardness | 55–65 HRC |
| Case Depth | 0.10–0.50 mm |
| Wear Resistance | Excellent |
Stress Relieving
| Parameter | Value |
|---|---|
| Temperature | 500–600°C |
| Purpose | Reduce Machining Stress |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | P20 |
| UNS | T51620 |
| GB/T (China) | 3Cr2Mo |
| EN (Europe) | 35CrMo7 |
| DIN (Germany) | 1.2311 |
| DIN Modified | 1.2738 (P20+Ni) |
| JIS (Japan) | PDS-3 |
| ISO | 35CrMo7 |
Common P20 Variants
| Grade | Description |
|---|---|
| P20 | Standard Pre-Hardened Mold Steel |
| P20+Ni | Improved Toughness & Uniform Hardness |
| 1.2738 | Nickel-Modified P20 |
| 3Cr2Mo | Chinese Equivalent |
Available Forms
| Product Type | Availability |
|---|---|
| Mold Plates | Yes |
| Mold Blocks | Yes |
| Round Bar | Yes |
| Pre-Hardened Stock | Yes |
| Forgings | Yes |
| Precision Ground Blocks | Yes |
Typical Applications
Plastic Injection Molds
- Automotive Components
- Consumer Products
- Appliance Parts
- Industrial Plastic Components
Blow Molding Industry
- Bottle Molds
- Packaging Molds
- Container Molds
Compression Molding
- Thermoset Components
- Industrial Parts
Mold Base Manufacturing
- Mold Bases
- Support Plates
- Structural Mold Components
Die Casting Support Components
- Holders
- Backing Plates
- Structural Inserts
Prototype Tooling
- Low-to-Medium Production Molds
- Development Tooling
- Prototype Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Machining | Outstanding |
| EDM Machining | Outstanding |
| Wire EDM | Outstanding |
| Polishing | Excellent |
| Mold Texturing | Excellent |
| Nitriding | Excellent |
| Weld Repair | Outstanding |
Advantages
Pre-Hardened Condition
No additional hardening required for most mold applications.
Excellent Machinability
Reduces machining time and tooling costs.
Good Polishability
Suitable for consumer and automotive molds.
Excellent Weldability
Easy to repair and modify.
Good Toughness
Resists cracking and chipping.
Cost Effective
One of the most economical mold steels available.
Limitations
Lower Hardness Than H13
Not ideal for high-wear tooling.
Limited Corrosion Resistance
Unsuitable for corrosive plastic molding without coatings.
Lower Mirror Polish Performance Than S136
Not recommended for optical-grade molds.
Moderate Wear Resistance
May require nitriding for long production runs.
Comparison with Other Mold Steels
| Property | P20 | H13 | S136 | NAK80 | 1.2738 |
|---|---|---|---|---|---|
| Hardness | 28–34 HRC | 44–54 HRC | 48–52 HRC | 37–43 HRC | 30–36 HRC |
| Machinability | Excellent | Good | Good | Excellent | Excellent |
| Polishability | Good | Excellent | Outstanding | Outstanding | Good |
| Corrosion Resistance | Moderate | Moderate | Excellent | Good | Moderate |
| Cost | Moderate | Higher | Higher | Higher | Moderate |
Comparison with Mold Materials
| Material | Hardness | Polishability | Mold Life |
|---|---|---|---|
| P20 | 28–34 HRC | Good | Good |
| H13 | 44–54 HRC | Excellent | Excellent |
| S136 | 48–52 HRC | Outstanding | Excellent |
| NAK80 | 37–43 HRC | Outstanding | Excellent |
| 1.2738 | 30–36 HRC | Good | Excellent |
Available Surface Finishes
Raw Finishes
- Pre-Hardened Finish
- Ground Finish
- Precision Machined Finish
Functional Finishes
- Nitrided Finish
- Polished Finish
- EDM Finish
- Mold Texture Finish
Protective Finishes
- Hard Chrome Plating
- Electroless Nickel Plating
- PVD Coating
- QPQ Treatment
Frequently Asked Questions (FAQ)
What is P20 mold steel?
P20 is a pre-hardened plastic mold steel widely used for injection molds, mold bases, and tooling applications.
What is P20 steel used for?
Typical applications include:
- Plastic Injection Molds
- Blow Molds
- Mold Bases
- Automotive Molds
- Consumer Product Molds
What is the equivalent material to P20?
Common equivalents include:
- 3Cr2Mo
- DIN 1.2311
- DIN 1.2738
- PDS-3
What hardness does P20 have?
Typically supplied at:
- 28–34 HRC
without additional heat treatment.
Can P20 be nitrided?
Yes. Nitriding can increase surface hardness to approximately 55–65 HRC.
What is the difference between P20 and H13?
| Property | P20 | H13 |
|---|---|---|
| Hardness | Lower | Higher |
| Machinability | Better | Good |
| Wear Resistance | Lower | Higher |
| Mold Cost | Lower | Higher |
Is P20 suitable for injection molds?
Yes. P20 is one of the most commonly used materials for medium-volume injection molds.
Is P20 suitable for mirror polishing?
For standard polishing, yes. For optical-grade mirror finishes, S136 or NAK80 are usually preferred.
Why is P20 widely used in mold manufacturing?
Because it combines:
- Pre-Hardened Condition
- Excellent Machinability
- Good Weldability
- Cost Efficiency
- Reliable Mold Performance
Does GCNOV provide custom manufacturing services for P20 steel?
Yes. GCNOV provides:
- CNC Machining
- Mold Manufacturing
- EDM Processing
- Wire EDM
- Mold Polishing
- Nitriding
- Mold Repair Welding
- Prototype Development
- Low-Volume Production
- Mass Production