Steel 20CrMo
GB 20CrMo · AISI/SAE 4118 · JIS SCM420
20CrMo is a low-carbon chromium-molybdenum case-hardening steel from the GB alloy family, equivalent to AISI 4118, JIS SCM420 and 20CrMo4 / 1.7218, and supplied hot-rolled, cold-rolled, cold-drawn, annealed, normalized, quenched-and-tempered or carburized.
Values for the HR condition
20CrMo tempers and conditions
20CrMo is supplied in 7 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize anneal (≈860–890 °C, slow cool) | Softest condition — use for deep machining, cold forming or before carburizing. | 350 | 540 | 25 | 170 HB | — |
≈880–900 °C, air cool (often + 600–680 °C temper) | Uniform fine grain and stable properties for weldments, pressure parts and forging stock. | 440 | 650 | 22 | 195 HB | — |
HRDefault Hot rolled | Most-stocked mill condition for bar, seamless tube and plate; machine then heat treat as required. | 450 | 680 | 20 | 200 HB | — |
Cold rolled | Choose for thin strip/sheet needing good surface and tight thickness before stamping and heat treatment. | 480 | 640 | 14 | 195 HB | 7.5 % IACS |
Cold drawn | Pick for precision-diameter shafting and screw-machine work where higher yield and better surface are wanted without heat treatment. | 620 | 780 | 11 | 230 HB | — |
Quenched and tempered | Standard high-strength condition for shafts, gears, bolts and high-pressure fittings; properties quoted on 15 mm test blank. | 760 | 950 | 14 | 30 HRC | — |
gas carburize 900–930 °C, quench + 180–200 °C temper | Use for gears, splines and pins needing a 0.6–1.2 mm hard case (58–62 HRC) on a tough Q&T core. | 800 | 1,050 | 11 | 60 HRC | — |
What is 20CrMo?
20CrMo is a low-carbon chromium-molybdenum case-hardening steel from the GB alloy family, equivalent to AISI 4118, JIS SCM420 and 20CrMo4 / 1.7218, and supplied hot-rolled, cold-rolled, cold-drawn, annealed, normalized, quenched-and-tempered or carburized. The low-carbon core keeps toughness while carburizing builds a hard wear surface, which makes it a standard choice for medium-duty gears, drive shafts and bolts at 450 MPa yield and 680 MPa tensile in the default condition. It has no corrosion resistance and must be coated; where higher through-hardened core strength is needed, 42CrMo / 4140 is the usual step up. 20CrMo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). 20CrMo has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 680 MPa (98.6 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
What is 20CrMo used for?
- Carburized gears and pinions
- Industrial drive shafts
- Bolts and studs
- Splined couplings and yokes
- Camshafts and rocker pins
- Pump and gearbox spindles
- Hydraulic and pneumatic fittings
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
20CrMo properties
Typical room-temperature values for 20CrMo-HR; bars are the position among steel grades.
Physical3
20CrMo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical13
20CrMo has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 680 MPa (98.6 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20CrMo is rated for continuous service to 500°C (932 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical2
20CrMo has an electrical resistivity of 2.3×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 20CrMo takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
20CrMo's machinability is good (58/100, better than 75% of steel grades); weldability good (62/100); formability fair (50/100).
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. 20CrMo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 20CrMo
Is 20CrMo easy to machine?
Machines like 4118/4130 — best in annealed or normalized state (~60 % of AISI 1212); carbide tooling, rigid setup and flood coolant above 280 HB.
Can 20CrMo be welded?
Weldable with low-hydrogen or matching Cr-Mo filler; preheat 150–250 °C for thick or Q&T parts and post-weld temper at 620–680 °C to avoid HAZ hardening/cracking.
Can 20CrMo be formed, bent or molded?
Cold form only in annealed condition with generous radii; hot forge 1150–850 °C followed by normalizing or annealing to restore grain size.
Manufacturability
The process limits FabDigit applies to 20CrMo. Every 20CrMo part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better58 / 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 |
Sheet metal
| Formability | Better50 / 100 |
|---|---|
| Weldability | Better62 / 100 |
20CrMo 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 | 0.17 – 0.24 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.4 – 0.7 | 0.55 |
| Cr | 0.8 – 1.1 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 20CrMo?
No natural corrosion resistance — specify phosphate+oil, black oxide, zinc, zinc-nickel or QPQ nitrocarburizing; takes a good polish after Q&T.
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 20CrMo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 20CrMo cost?
20CrMo 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.
20CrMo — frequently asked
What is 20CrMo used for?
20CrMo is typically used for carburized gears and pinions, industrial drive shafts, bolts and studs, splined couplings and yokes, camshafts and rocker pins and pump and gearbox spindles. In short: workhorse chrome-moly bar.
What is the yield strength of 20CrMo?
20CrMo has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 680 MPa (98.6 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20CrMo easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like 4118/4130 — best in annealed or normalized state (~60 % of AISI 1212); carbide tooling, rigid setup and flood coolant above 280 HB.
Can 20CrMo be welded?
Yes — weldability is rated good (62/100). Weldable with low-hydrogen or matching Cr-Mo filler; preheat 150–250 °C for thick or Q&T parts and post-weld temper at 620–680 °C to avoid HAZ hardening/cracking.
What surface finishes work on 20CrMo?
No natural corrosion resistance — specify phosphate+oil, black oxide, zinc, zinc-nickel or QPQ nitrocarburizing; takes a good polish after Q&T.
Can 20CrMo be formed, bent or molded?
Cold form only in annealed condition with generous radii; hot forge 1150–850 °C followed by normalizing or annealing to restore grain size.
What is the maximum service temperature of 20CrMo?
20CrMo is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20CrMo-HR and 20CrMo-CD?
HR is the default condition — most-stocked mill condition for bar, seamless tube and plate; machine then heat treat as required. CD: pick for precision-diameter shafting and screw-machine work where higher yield and better surface are wanted without heat treatment. Yield strength is 450 MPa in HR versus 620 MPa in CD.
How much does 20CrMo cost?
20CrMo 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.
Can FabDigit make parts in 20CrMo?
Yes — 20CrMo is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 3077 Alloy structural steels — SAC (China) (2015)
- GB/T 8162 Seamless steel tubes for structural purposes — SAC (China) (2018)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating — ASM International (1991)
- Chinese alloy structural steel property tables (20CrMo / 4118 equivalence) (2016)
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.