Steel P20
AISI/SAE P20 · UNS T51620 · EN 1.2311, 40CrMnMo7 · GB 3Cr2Mo
P20 (EN 1.2311 / 1.2312 / GB 3Cr2Mo / T51620) is a medium-carbon Cr-Mo plastic mould steel supplied pre-hardened to about 28–34 HRC, so cavities can be cut directly with no further heat treatment and no quench distortion.
Values for the Annealed condition
P20 tempers and conditions
P20 is supplied in 4 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft annealed, ~180–220 HB | Choose when the part will be rough-machined and then through-hardened, or for deep hot-work/EDM-free forming of blocks. | 440 | 700 | 20 | 200 HB | — |
Pre-hardened | Default stock condition: machine the cavity directly, no post-machining heat treatment or distortion risk. | 860 | 1,000 | 15 | 31 HRC | — |
pre-hardened core with gas/plasma nitrided case | Use for abrasive or glass-filled resins: hard nitrided case (0.1–0.3 mm) on the 28–34 HRC core improves wear and corrosion slightly. | 860 | 1,000 | 13 | 31 HRC | 7.8 % IACS |
Quenched and tempered | Pick when higher wear resistance and cavity-face hardness than pre-hardened stock is needed; accept quench distortion and finish-grinding. | 1,150 | 1,350 | 11 | 42 HRC | — |
What is P20?
P20 (EN 1.2311 / 1.2312 / GB 3Cr2Mo / T51620) is a medium-carbon Cr-Mo plastic mould steel supplied pre-hardened to about 28–34 HRC, so cavities can be cut directly with no further heat treatment and no quench distortion. It polishes well, accepts hard chrome plating and nitriding, and offers better toughness and through-hardening in thick sections than plain carbon structural steel, which makes it the workhorse for injection moulds, mould bases and extrusion plates; the 1.2312 variant adds sulphur for easier machining. Limits are poor corrosion resistance (needs oil or plating), a hardness ceiling with less wear resistance than H13 or 420-type stainless mould steels, and service temperature that should stay about 150 °C below the tempering temperature. P20 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). P20 has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is P20 used for?
- Plastic injection mould cavities and cores
- Mould bases and bolster plates
- Die-cast mould frames
- Extrusion dies and die plates
- Blow-mould bodies
- Large textured automotive trim cavities
- Machine fixture and jig plates
Advantages
- Easy to machine — 65/100, better than 93% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Poor heat conductor — 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
P20 properties
Typical room-temperature values for P20-Annealed; bars are the position among steel grades.
Physical3
P20 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical17
P20 has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
P20 is rated for continuous service to 450°C (842 °F). It conducts heat at 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades. Thermal expansion is 12.4 µm/m·K (6.89 µin/in·°F).
Electrical2
P20 has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of P20 takes about 32 MJ of energy and emits 2.2 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 40%.
Manufacturability7
P20's machinability is good (65/100, better than 93% of steel grades); weldability fair (50/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. P20 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with P20
Is P20 easy to machine?
Machines predictably at 28–34 HRC with coated carbide (vc ≈ 120–180 m/min milling); rigid setups and positive rake reduce work-hardened burr, and stress-relieve at 550 °C after heavy roughing of deep cavities.
Can P20 be welded?
Repair-weldable with matching low-alloy or 1.2311-type filler using 300–350 °C preheat, low heat input and immediate 500–550 °C post-weld temper to avoid HAZ cracking.
Can P20 be formed, bent or molded?
Not a cold-forming steel; shape by hot forging at 1050–850 °C followed by slow cooling and soft annealing, or by machining/EDM in the pre-hardened state.
Manufacturability
The process limits FabDigit's quote engine applies to P20. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Good65 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
P20 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C1.2311 typically 0.35–0.45 | 0.28 – 0.4 | 0.35 |
| Si | 0.2 – 0.8 | 0.4 |
| Mn | 0.6 – 1 | 0.8 |
| Cr | 1.4 – 2 | 1.7 |
| Mo | 0.3 – 0.55 | 0.4 |
| P | ≤ 0.03 | |
| Smax; free-machining variant 1.2312 has S 0.05–0.10 | ≤ 0.03 | |
| Niresidual; P20+Ni (1.2738) adds ~1.0 Ni for large blocks | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on P20?
Polishes to mirror finish (best from ESR/VAR remelted plate); typically hard-chrome plated, electroless-nickel plated or nitrided/texture-etched for mold cavities, and must be oiled to prevent rust.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel P20 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does P20 cost?
P20 is a specialty-cost steel ($$$$$), pricier than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
P20 — frequently asked
What is P20 used for?
P20 is typically used for plastic injection mould cavities and cores, mould bases and bolster plates, die-cast mould frames, extrusion dies and die plates, blow-mould bodies and large textured automotive trim cavities. In short: pre-hardened plastic mold.
What is the yield strength of P20?
P20 has a typical yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is P20 easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Machines predictably at 28–34 HRC with coated carbide (vc ≈ 120–180 m/min milling); rigid setups and positive rake reduce work-hardened burr, and stress-relieve at 550 °C after heavy roughing of deep cavities.
Can P20 be welded?
With care — weldability is rated fair (50/100). Repair-weldable with matching low-alloy or 1.2311-type filler using 300–350 °C preheat, low heat input and immediate 500–550 °C post-weld temper to avoid HAZ cracking.
What surface finishes work on P20?
Polishes to mirror finish (best from ESR/VAR remelted plate); typically hard-chrome plated, electroless-nickel plated or nitrided/texture-etched for mold cavities, and must be oiled to prevent rust.
Can P20 be formed, bent or molded?
Not a cold-forming steel; shape by hot forging at 1050–850 °C followed by slow cooling and soft annealing, or by machining/EDM in the pre-hardened state.
What is the maximum service temperature of P20?
P20 is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between P20 Annealed and P20 Prehard?
Annealed is the default condition — choose when the part will be rough-machined and then through-hardened, or for deep hot-work/EDM-free forming of blocks. Prehard: default stock condition: machine the cavity directly, no post-machining heat treatment or distortion risk. Yield strength is 440 MPa in Annealed versus 860 MPa in Prehard.
How much does P20 cost?
P20 is a specialty-cost steel ($$$$$), pricier than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in P20?
Yes — P20 is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A681 – Alloy Tool Steels (Type P20) — ASTM International (2015)
- GB/T 1299 (3Cr2Mo) — SAC (2014)
- EN ISO 4957 Tool steels (40CrMnMo7 / 1.2311) — CEN (2018)
- ASM Handbook Vol.1 – Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 – Machining — ASM International (1989)
- Mold steel 1.2311 / P20 datasheet (physical & mechanical data, prehardened) — European tool-steel producers (Böhler / Buderus-type data) (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.