What Is P20 Steel - P20 Tool Steel Material Properties, Composition, Equivalent & P20 Steel vs 4140

Before you purchase the P20 steel products, it is better to know more about this alloy. This article will break down the P20 tool steel material with its definition, specification standard, equivalents, composition, properties, applications, and comparisons of P20 with 4140 steel and H13 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, and is also suitable for polishing and etching.

P20 material is available in round or square bars, flat plates, and metal sheets.

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), GB/T 3Cr2Mo (China), and UNS T51620 (North America).

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 involves 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 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 Hardness

Tempering will change the hardness of P20 steel, and it does so in a very predictable way: every 100 °C increase in tempering temperature drops hardness by roughly 2–4 HRC points. The higher the tempering temperature, the softer the steel becomes.

Tempering Temperature (°C)	Hardness (HRC)
100 °C	51
200 °C	50
300 °C	48
400 °C	46
500 °C	42
600 °C	36

P20 Steel vs 4140: What Are the Differences?

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 molds 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 needed.

P20 vs H13 Tool Steel: What Are the Differences?

H13 is another tool steel. Below is a chart comparing the differences between P20 and H13.

Difference	P20 Tool Steel	H13 Tool Steel
Type	Low-alloy, pre-hardened plastic mold steel	Chromium-molybdenum hot-work tool steel
Hardness	28-34 HRC (pre-hardened)	44-52 HRC (after heat treatment)
Primary Applications	Injection molds, blow molds, die-casting molds (low-temp alloys), extrusion tooling	Hot-working tools such as die-casting molds (high-temp alloys), forging dies, extrusion dies
Machinability	Excellent machinability, can be machined easily without further heat treatment	More difficult to machine due to high hardness, requires specialized tooling
Heat Resistance	Moderate, not suited for high-temperature applications	Superior heat resistance, maintains hardness and toughness at elevated temperatures
Wear Resistance	Moderate wear resistance	High wear resistance and thermal fatigue resistance
Toughness & Ductility	Good toughness, elongation ~20%, easier to shape	Very high toughness, elongation ~10-15%, more resistant to cracking under thermal stress
Thermal Properties	Higher thermal conductivity and thermal expansion (~11.7 µm/m°C)	Lower thermal conductivity but excellent resistance to thermal fatigue and heat checking
Composition	Lower alloy content: ~1.4-2% Cr, 0.3-0.55% Mo, no Vanadium, contains 0.85-1.15% Ni for toughness	Higher alloy content: ~5% Cr, 1.1-1.75% Mo, 0.8-1.2% V, providing enhanced hardness, wear, and heat resistance
Heat Treatment	Supplied pre-hardened, usually no need for further heat treatment	Requires air hardening or quenching and tempering to develop properties
Surface Finish	Highly polishable, ideal for detailed molds and aesthetic parts	Good polishability, but priority is on durability under thermal cycling
Cost & Production	More economical due to easier machining and no post-machining heat treatment	Higher initial costs due to complex heat treatment and machining challenges, but longer tool life in demanding environments
Corrosion Resistance	Moderate; requires maintenance to prevent rust	Better resistance due to higher chromium content
Suitability for Cold Work	Used mainly for plastic molds and low-temp die casting	Not ideal for cold work; designed for hot work
Typical Industries	Plastics, automotive interiors, consumer electronics molds	Aerospace, die casting of aluminum and steel, forging, and extrusion

When it comes to the selection between H13 and P20 mold steels, H13 steel significantly outperforms P20 in high-temperature environments, so it is more suitable for hot work, including die casting, forging, and extrusion. Because P20 is easier and cheaper to machine, it is often used to make plastic injection molds and cold working molds.

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