Steel 3Cr2Mo
GB 3Cr2Mo · AISI/SAE P20
3Cr2Mo is the P20-type Cr-Mo pre-hardened plastic mold steel, supplied at 300 HB (30 HRC) with 830 MPa yield, 1000 MPa tensile and 15% elongation, and also available annealed, normalized, at 33–38 HRC, quenched and tempered to 40–44 or 48–52 HRC, nitrided, or as ESR quality.
Reference datasheet — 3Cr2Mo is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the PH 28-32 HRC condition
3Cr2Mo tempers and conditions
3Cr2Mo is supplied in 8 conditions, soft to hard. PH 28-32 HRC is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
soft annealed for deep machining/EDM before hardening | Pick when the mould will be through-hardened after roughing, or for maximum machinability. | 450 | 700 | 22 | 210 HB | — |
air cooled from austenitizing, intermediate strength | Used for bar stock and for grain refinement before final quench and temper. | 570 | 860 | 18 | 24 HRC | 8 % IACS |
PH 28-32 HRCDefault Pre-hardened 28–32 HRC | Default stock condition: machine the cavity directly, no further heat treatment or distortion risk. | 830 | 1,000 | 15 | 30 HRC | — |
Pre-hardened then gas/plasma nitrided surface | Pick for abrasive glass-filled resins: hard nitrided case on a 30 HRC tough core, minimal distortion. | 830 | 1,000 | 13 | 30 HRC | 8 % IACS |
Electroslag-remelted, pre-hardened 28–32 HRC | Choose when optical or high-gloss polish and low inclusion content are required in large cavities. | 850 | 1,020 | 17 | 30 HRC | 8 % IACS |
Pre-hardened 33–38 HRC | Choose for higher wear resistance and better texture/polish on large moulds where machining power allows. | 1,000 | 1,180 | 13 | 36 HRC | — |
Quenched and tempered to 40–44 HRC | For inserts and small cores needing extra wear resistance; machine soft, then harden and finish-grind/EDM. | 1,150 | 1,350 | 11 | 42 HRC | — |
Quenched and low-tempered to 48–52 HRC | Maximum attainable hardness for small sections; toughness and machinability drop sharply, EDM/grinding only. | 1,450 | 1,700 | 8 | 50 HRC | — |
What is 3Cr2Mo?
3Cr2Mo is the P20-type Cr-Mo pre-hardened plastic mold steel, supplied at 300 HB (30 HRC) with 830 MPa yield, 1000 MPa tensile and 15% elongation, and also available annealed, normalized, at 33–38 HRC, quenched and tempered to 40–44 or 48–52 HRC, nitrided, or as ESR quality. Engineers use it as the default block and plate material for injection mold cavities, cores and bases because it machines and EDMs readily (machinability 55) in the pre-hardened state with no post-machining heat treatment. It is not stainless, so corrosive resins and humid storage call for chrome or nickel plating, and service temperature is limited to about 400 °C; use S136/HPM38 where corrosion resistance or mirror polish is critical. 3Cr2Mo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). 3Cr2Mo has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
What is 3Cr2Mo used for?
- Injection mold cavities
- Mold bases
- Die-casting dies
Advantages
- High strength — 830 MPa (120 ksi), better than 87% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Limited formability — 15/100, worse than 87% of steel grades
- Poor heat conductor — 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades
3Cr2Mo properties
Typical room-temperature values for 3Cr2Mo-PH 28-32 HRC; bars are the position among steel grades.
Physical3
3Cr2Mo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
3Cr2Mo has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
3Cr2Mo is rated for continuous service to 400°C (752 °F). It conducts heat at 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
3Cr2Mo conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 3Cr2Mo takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 35%.
Manufacturability6
3Cr2Mo's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability poor (15/100).
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. 3Cr2Mo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 3Cr2Mo
Is 3Cr2Mo easy to machine?
Cuts well at 28–32 HRC with coated carbide (roughing ~120–180 m/min); use rigid setups and avoid dwell to prevent work-hardened glazing, EDM finishing is routine.
Can 3Cr2Mo be welded?
Weldable for mould repair with matching low-alloy or 420-type filler at 200–300 °C preheat plus post-weld temper 20–30 °C below the original tempering temperature.
Can 3Cr2Mo be formed, bent or molded?
Not a cold-forming steel; hot forge 1050–850 °C followed by slow cool and annealing, then quench from 850–880 °C in oil and temper 550–650 °C for the pre-hardened level.
3Cr2Mo 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 |
|---|---|---|
| C | 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 | 0.45 |
| P | ≤ 0.03 | |
| Smax; free-machining variants (3Cr2MnNiMo/718S) add S ~0.05-0.10 | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 3Cr2Mo?
Takes a good but not mirror polish (ESR quality is better), responds well to photo-etch texturing, and is commonly hard-chrome or nickel plated for corrosive resins and gloss surfaces.
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 3Cr2Mo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- AISI / SAE
- P20
How much does 3Cr2Mo cost?
3Cr2Mo is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
3Cr2Mo — frequently asked
What is 3Cr2Mo used for?
3Cr2Mo is typically used for injection mold cavities, mold bases and die-casting dies. In short: industry-standard mold block steel; pre-hardened, no heat treatment; cheaper than stainless mold steels.
What is the yield strength of 3Cr2Mo?
3Cr2Mo has a typical yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 3Cr2Mo easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Cuts well at 28–32 HRC with coated carbide (roughing ~120–180 m/min); use rigid setups and avoid dwell to prevent work-hardened glazing, EDM finishing is routine.
Can 3Cr2Mo be welded?
With care — weldability is rated fair (40/100). Weldable for mould repair with matching low-alloy or 420-type filler at 200–300 °C preheat plus post-weld temper 20–30 °C below the original tempering temperature.
What surface finishes work on 3Cr2Mo?
Takes a good but not mirror polish (ESR quality is better), responds well to photo-etch texturing, and is commonly hard-chrome or nickel plated for corrosive resins and gloss surfaces.
Can 3Cr2Mo be formed, bent or molded?
Not a cold-forming steel; hot forge 1050–850 °C followed by slow cool and annealing, then quench from 850–880 °C in oil and temper 550–650 °C for the pre-hardened level.
What is the maximum service temperature of 3Cr2Mo?
3Cr2Mo is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 3Cr2Mo cost?
3Cr2Mo is a standard-cost steel ($$), cheaper than about 71% 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.
Sources
- ASTM A681 Standard Specification for Tool Steels Alloy (P20) — ASTM (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Tool Materials — ASM International (1995)
- Pre-hardened plastic mould steel (P20/718 class) datasheet — Uddeholm / ASSAB (2021)
- P20/3Cr2Mo — Mysteel / 1688 (2025)
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.