Steel P20 Prehard
Heat-treated state
AISI/SAE P20 · UNS T51620 · EN 1.2311, 40CrMnMo7 · GB 3Cr2Mo
Prehard = pre-hardened
Default stock condition: machine the cavity directly, no post-machining heat treatment or distortion risk.
Values for the Prehard condition
Other P20 tempers and conditions
P20 is listed in 4 conditions; see the grade overview at P20.
- Annealed
- Prehard
- Prehard-Nitrided
- Q&T
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 | — |
PrehardThis page 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 Prehard?
P20 Prehard is P20 heat treated to Prehard — default stock condition: machine the cavity directly, no post-machining heat treatment or distortion risk. P20 Prehard has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). P20 Prehard 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). Annealed is the default condition FabDigit quotes; Prehard is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- High strength — 860 MPa (125 ksi), better than 89% 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 Prehard properties
Typical room-temperature values for P20 Prehard; 14 are specific to this condition. Other listed values are P20 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P20 Prehard 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 Prehard has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
P20 Prehard 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 Prehard 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 Prehard 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 Prehard's machinability is good (55/100, better than 62% of steel grades); weldability fair (50/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P20 Prehard
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.
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.
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 |
P20 Prehard — frequently asked
What is P20 Prehard used for?
P20 Prehard 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 Prehard?
P20 Prehard has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is P20 Prehard easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% 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 Prehard 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 Prehard?
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 Prehard 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 Prehard?
P20 Prehard 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.
Can FabDigit make parts in P20 Prehard?
Yes — P20 Prehard 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.