1. Application
- Plastic Molds and Dies
- Die-Casting Dies (for low-melting alloys)
- Hot Extrusion (specifically for Aluminum and Magnesium)
2. Chemical composition
| Element | Carbon (C) | Manganese (Mn) | Silicon (Si) | Chromium (Cr) | Molybdenum (Mo) | Phosphorus (P) | Sulfur (S) |
| Content (%) | 0.28 – 0.40 | 0.60 – 1.00 | 0.20 – 0.80 | 1.40 – 2.00 | 0.30 – 0.55 | ≤ 0.030 | ≤ 0.030 |
3. P20 Steel Properties
- Pre-hardened hardness: 32 HRC.
- Hardness of P20 filler wire: 40 HRC.
- Yield Strength: 950 MPa after prehardening.
- Elastic Modulus: 210 GPa (30 × 10^6 psi) at room temperature. This decreases to about 185 GPa (27 × 10^6 psi) at 260 °C (500 °F) and to about 150 GPa (22 × 10^6 psi) at 540 °C (1000 °F).
- Poisson’s Ratio: 0.287.
- Machinability: Good machinability. It is readily machined in its pre-hardened condition. Machinability can be further improved by adding sulfur to the P20 grade. Machining prior to final P20 tool steel heat treatment results in better machinability.
- Polishability: Excellent polishability. Higher hardness (e.g., 40 HRC) can improve polished quality.
- Dimensional Stability: Good dimensional stability. It has fewer dimensional changes on hardening compared to water-hardening steel grades.
- Toughness: Medium to high toughness. Carburized P20 material provides good toughness. If higher toughness than P20 is needed (e.g., for large dies subject to severe shock), we suggest P4 and P6 mold steels.
- Wear Resistance: It has low to medium wear resistance in its general condition. Wear resistance is improved by carburizing.
- Weldability: Medium weldability.
- Other Processing: P20 material is also suitable for photo-etching (texturing) and Electrical Discharge Machining (EDM).
[Reference: ASM International. (2000). ASM Handbook, Volume 8: Mechanical Testing and Evaluation. ASM International.]
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4. Heat Treatment
P20 steel is commonly supplied in a pre-hardened state, with a hardness of 28-40 HRC. It can be directly machined into complex mold cavities and put into use without further high-temperature heat treating. The pre-hardened state helps to avoid deformation and dimensional changes that may occur during subsequent heat treatment.
Although P20 material is always used directly in a pre-hardened state, its surface properties can be enhanced through further heat treatment (particularly carburizing) to meet specific application requirements, such as plastic molding.
4.1 Carburization
For plastic molding applications, P20 material is frequently carburized and then hardened after the mold impression has been machined. The as-quenched surface hardness of carburized P20 molds can reach up to 65 HRC, with the core hardness typically around 45 HRC. Case depths can be controlled, generally varying from 0.030 inches for smaller molds to 0.065 inches for large molds. We would like to remind you that the resistance of carburized P20 material to softening during tempering is relatively low, similar to that of plain carbon steel.
The carburizing temperature should NOT exceed 870°C (1600°F). Exceeding this temperature will adversely affect its polishing performance. For instance, carburizing at 845°C (1550°F) resulted in a surface hardness of 65.6 HRC and a case depth of 0.36 mm, whereas at 900°C (1650°F), the surface hardness was slightly lower at 62.5 HRC with a case depth of 0.41 mm.
Carburized P20 steel has a good combination of wear resistance, toughness, and polishability.
4.2 Preheating
We strongly recommend preheating P20 tool steel to a temperature of 1200°F (650°C).
The purpose of preheating is to precondition the molecules within the part for transformation and to relieve stresses caused by machining. It also helps to equalize heat within the part, allowing stresses to dissipate before the metal becomes too soft at higher temperatures.
4.3 Hardening (Austenitizing)
The hardening temperature is 1525°F (830°C). The soaking time is 45–60 minutes per inch of thickness. For parts under 1 inch in thickness, we recommend a minimum soaking time of 45–60 minutes. [For information about austenite, please refer to the explanation of austenite on Wikipedia.]
4.4 Quenching
Material P20 steel is oil quenched. Oil quenching from a relatively low temperature results in less dimensional change compared to water-hardening steels. After quenching, parts should be cooled to a minimum of 150°F (66°C) if air-hardened, or 150-200°F (66-93°C) if liquid-quenched, and then tempered immediately.
4.5 Tempering
P20 tool steel usually requires double tempering. The standard tempering temperature is 400°F (205°C).
For a P20 steel that has been oil quenched from 845°C (1550°F) and tempered for 2 hours at 205°C (400°F), the resulting hardness is 36-38 HRC, with a tensile strength of 1310 MPa, a yield strength of 1172 MPa, 13% elongation, and 51% reduction of area. If the as-quenched microstructure is bainitic, the hardness after tempering may be 4 HRC lower than standard tempering diagrams.
4.6 Forging
P20 should be slowly preheated to 815°C (1500°F). The forging temperature is 1065 to 1230°C (1950 to 2250°F). For larger sections or when heavy and rapid reductions are planned, it is advisable to use the higher end of this temperature range. For smaller sections or lighter reductions, the lower end of the range is more suitable. Do NOT forge P20 below 815 °C (1500 °F).
After forging, the steel is cooled slowly by cooling it inside the furnace or burying it in heat-insulating media such as lime, mica, or diatomaceous earth.
[Reference: Roberts, G., Krauss, G., & Kennedy, R. (1998). Tool Steels: 5th Edition. ASM International.]
5. Supply forms and dimensions
The P20 tool steel we supply is available in various shapes, including round bars, sheet plates, slabs, flat bars, square bars, and blocks. The dimensions of the flat bar range from: width 20–600 mm × thickness 20–400 mm × length 1,000–5,500 mm. The dimensions of the round bar range from a diameter of 20–400 mm × a length of 1,000–5,500 mm. The block dimensions are obtained by cutting the flat bar.
UT testing: Sep 1921-84 D/d, E/e.
Surface Treatment: original black, peeled, machined/turned, polished, grounded, or milled surface finishes.
Inventory Status: We do not maintain a stock. We arrange production based on customer orders.
Delivery time: Electric Arc Furnace (EAF) materials are 30-45 days.
FAQ
1. What is P20 tool steel?
P20 tool steel is a versatile, low-alloy tool steel known for its good toughness at moderate strength levels, excellent dimensional stability during heat treatment, and good polishability. It is typically sold in a pre-hardened condition.
2. What are the key properties of P20 steel?
Key properties of P20 steel include excellent dimensional stability during heat treatment, good polishability, and good toughness at moderate strength levels. It has a density of 0.284 lb/in³ (7861 kg/m³) and a machinability rating of 60-65% of a 1% carbon steel.
3. What is the hardness of P20 steel?
P20 steel is typically supplied with a Brinell hardness (HBW) of approximately 300, which is roughly equivalent to 30 Rockwell C (HRC). It can be tempered to achieve a Rockwell C hardness between 28 and 37.
4. Is P20 tool steel pre-hardened?
Yes, P20 steel is typically supplied in a pre-hardened condition with a hardness of approximately 300 HBW. This allows for direct use in mold making without further hardening or heat treatment, cutting down on the running period and improving efficiency.
5. What are the common applications for P20 mold steel?
P20 mold steel is extensively used for plastic injection mold cavities and tooling, and for die casting dies for zinc. It is also ideal for large plastic molds. Other applications include die holders, backers, bolsters, hydroforming tools, and various components in automotive, mechanical engineering, and tool manufacturing (e.g., punches, milling cutters, turning tools).
6. What is the typical mold life expectancy for P20 steel?
For pre-hardened P20 steel (1.2311), the die life can reach 500,000 “mode times” (shots). Some vendors guarantee 100,000 shots, and P20 molds are known to run for thousands of parts.
7. Is P20 steel suitable for polishing?
Yes, P20 steel is known for its good polishability. It is capable of achieving a good polished finish and offers an excellent polished finish, which is crucial for mold applications.
8. Can P20 steel be nitrided or carburized?
Yes, P20 tool steels are capable of being nitrided or carburized. Case hardening or nitriding is an option to achieve maximum surface hardness, for applications such as compression molding plastic dies.
9. Is P20 steel used for high-temperature applications?
P20 tool steels are typically used for low-temperature applications, including injection molds. However, in the field of die-casting molds, P20’s excellent thermal conductivity and thermal expansion coefficient allow it to resist the impact of high pressure and high temperature in mold manufacturing, ensuring precision and quality.
10. How does P20 steel compare to 4140 steel for mold applications?
P20 steel offers excellent dimensional stability during heat treatment and good polishability, making it ideal for mold applications. In contrast, 4140 steel is renowned for its strength and impact resistance. While 4140 steel is generally used for high-stress parts like shafts and gears, it can sometimes replace P20 steel plate in certain mold industry applications.
11. How does P20 steel compare to S50C steel for injection molding?
P20 is generally considered better than S50C for mold steel. For prototyping molds needing only thousands of pieces, S50C is acceptable, but for more than 10,000 pieces, P20 is preferable. P20 offers better machinability and mirror grinding performance and is more frequently recommended for plastic molds compared to S50C, which has low cold deformation plasticity and poor welding performance.
12. Is P20 steel more expensive than 4140 steel?
Yes, P20 steel is generally more expensive than 4140 steel. This is attributed to its specialized applications and chemical composition.
13. Can 4140 steel be used for mold applications?
Yes, 4140 steel can be used for some mold applications, particularly those that require high strength and resistance to wear and tear. However, P20 is more commonly selected for molds due to its superior dimensional stability under heat treatment.
14. What are the different types or equivalents of P20 steel?
Besides the standard AISI P20, it is known by international equivalents such as DIN 1.2311 and GB/T 3Cr2Mo. There are also variants like P20+Ni (1.2738), which has added nickel for consistent hardness in larger sections and is easy to polish, and P20+S (1.2312), which has higher sulfur for improved machinability but is less suitable for polishing.
15. What standards apply to P20 steel?
In the USA, P20 steel generally adheres to the ASTM A681 standard. In Europe, it’s recognized by the DIN EN ISO 4957 standard (e.g., 1.2311 and 1.2312), and in China, the equivalent grade is 3Cr2Mo under the GB/T 1299 standard.
16. What is the machinability of P20 steel?
P20 steel has a machinability rating of 60-65% when compared to a 1% carbon steel. It is noted for its excellent cutting performance and overall good machinability.
17. Does P20 steel have good weldability?
Yes, P20 tool steel is stated to benefit from good weldability.
18. What is similar to P20 material?
When looking for materials similar to P20, you’ll primarily find a range of P20-modified steels, such as DIN 1.2738, 1.2311, 1.2312, and various branded versions, that build upon its properties, as well as other tool steels and stainless steels such as H13, P21, A2, D2, and 420, that serve similar purposes in mold making but offer different balances of properties such as wear resistance, toughness, or corrosion resistance.
19. Is P20 weldable?
Yes, P20 steel is weldable, particularly for repair and fabrication, though specific precautions and techniques are recommended to ensure good results.
20. Is P20 similar to 4140?
No, they are not similar in their fundamental design, typical processing, and intended applications.
21. Is P20 a high-carbon steel?
P20 steel is not high-carbon steel. Its carbon content generally falls within the range of medium-carbon steels.
22. How do you stress relieve P20?
Stress relieving for P20 steel is typically recommended at temperatures between 705 and 730 °C (1300 and 1350 °F)
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