Before you purchase the P20 steel products, it is better to know more about it. This article will break down the P20 steel material with its definition, specification standard, equivalents, composition, properties, applications, and a detailed comparison between P20 and 4140 steel.
What Is P20 Steel?
P20, also known as AISI P20, is a tool steel that is widely used in the manufacturing of plastic molds and die casting molds. P20 steel is usually supplied in a pre-hardened state with a hardness range of HRC28-33, which allows it to be directly used for mold making without further heat treatment. P20 mold steel has good machinability and can be processed through cutting, forging, heat treatment, and machining while maintaining good dimensional stability and surface quality, also suitable for polishing and etching.
P20 material is available in round or square bars and flat plates.
P20 Steel Equivalents
The steel grades are specified in different ways in each standard. AISI P20 (USA) tool steel is equivalent to DIN 1.2311 (German) and GB/T 3Cr2Mo (China).
P20 Steel Machinability
Assuming 1 percent carbon tool steel comes with a rating of 100, the pre-hardened P20 steel has a machinability rating of 65.
P20 Steel Heat Treatment
– Pre-hardening: When used as a material for large molds, the pre-hardening heat treatment system for P20 steel is heating and quenching at 830-860 ℃.
– Quenching: The quenching temperature range is roughly between 820~890 ℃, with 850~880 ℃ being commonly recommended.
– Tempering: The tempering temperature range is roughly between 500~640 ℃, with 540~640 ℃ being commonly recommended.
– Annealing: The annealing temperature is 850 ℃, with a holding time of 2-4 hours. The isothermal temperature is 720 ℃, with a holding time of 4-6 hours. The furnace is cooled to 500 ℃, and the furnace is then air-cooled.
P20 Steel Chemical Composition
The composition of P20 steel varies slightly among different standards.
- P20/3Cr2Mo
| Element |
Content (%) |
| Fe | 95.2-98.5 |
| C | 0.28-0.40 |
| Si | 0.20-0.80 |
| Mn | 0.60-1.00 |
| Cr | 1.40-2.00 |
| Mo | 0.30-0.55 |
| P | 0.03 |
| S | 0.03 |
- DIN 1.2311
| Element | Content (%) |
| Fe | Remainder |
| C | 0.35-0.45 |
| Si | 0.20-0.40 |
| Mn | 1.30-1.60 |
| Cr | 1.80-2.10 |
| Mo | 0.15-0.25 |
| P | 0.03 |
| S | 0.03 |
P20 Steel Material Properties (Physical, Thermal & Mechanical Properties)
P20 is a chrome-moly alloy and it has long been the steel of choice for pre-hardened mold steels. Below are the properties of P20 tool steel.
| Properties | Values |
| Density | 7.85 g/cc (0.284 lb/in) |
| Hardness | 300 Brinell (30 Rockwell C) |
| Ultimate Tensile Strength | 965-1030 MPa (140000-150000 psi) |
| Yield Tensile Strength | 827-862 MPa (120000-125000 psi) |
| Elongation at Break | 20 % |
| Modulus of Elasticity | 205 GPa (29700 ksi) |
| Compressive Strength | 862 MPa (125000 psi) |
| Thermal Conductivity | 29.0-34.0 W/m-K (201-236 BTU-in/hr-ft²-°F) |
| Thermal Expansion (20 ºC) | 12.8 x 10^-6/ºC |
P20 Steel vs 4140, What’s the Difference?
A basic comparison between 4140 steel and P20 clearly shows their differences.
1. Chemical Composition
| Elements | 4140 | P20 |
| Fe | 96.8-97.8 | 95.2-98.5 |
| C | 0.38-0.43 | 0.28-0.40 |
| Mn | 0.75-1.00 | 0.60-1.00 |
| P | 0.035 | 0.03 |
| S | 0.040 | 0.03 |
| Si | 0.15-0.35 | 0.20-0.80 |
| Cr | 0.8-1.10 | 1.40-2.00 |
| Mo | 0.15-0.25 | 0.30-0.55 |
| Cu | 0 | 0-0.25 |
2. Standard
P20 Steel is indicated in the ASTM A681 specification, which is applied for tool steels, while 4140 steel is covered in the ASTM A29 standard for Steel Bars, Carbon and Alloy, and Hot-Wrought.
3. Properties
| Properties | 4140 | P20 |
| Ultimate Tensile Strength (MPa) | 690 to 1080 | 540 to 1050 |
| Latent Heat of Fusion (J/g) | 250 | 260 |
| Thermal Conductivity (W/m-K) | 43 | 45 |
| Thermal Expansion (µm/m-K) | 13 | 12 |
| Electrical Conductivity (Equal Volume, % IACS) | 7.3 | 7.4 |
| Electrical Conductivity (Equal Weight, % IACS) | 8.4 | 8.5 |
| Thermal Shock Resistance (points) | 20 to 32 | 18 to 35 |
4. Cost
4140 steel is generally cheaper than P20 steel.
5. Applications
– P20 steel is mainly used for plastic molding and zinc die casting mold and can be quenched and tempered to achieve a good balance between hardness and toughness, which is beneficial for mold manufacturing.
– 4140 steel is best suited for various mechanical applications that require high strength and toughness. It is usually used for components such as gears, shafts, and bolts where hardness and wear resistance are crucial.
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