Steel 20CrMnMo
GB 20CrMnMo
20CrMnMo is a Cr-Mn-Mo case-hardening steel close to SAE 4118 and JIS SCM420H, in which molybdenum raises hardenability and core strength so larger sections can be carburized.
Reference datasheet — 20CrMnMo 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 A condition
20CrMnMo tempers and conditions
20CrMnMo is supplied in 8 conditions, soft to hard. A 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 |
|---|---|---|---|---|---|---|
Isothermal Annealed | Preferred pre-carburizing treatment for gear steel: uniform ferrite–pearlite banding-free structure giving stable hobbing/shaving and low distortion. | 400 | 630 | 21 | 11 HRC | 8 % IACS |
ADefault Solution annealed | Standard delivery condition for gear-blank bar and forgings — softest, most uniform structure for rough machining before carburizing. | 420 | 650 | 20 | 197 HB | — |
Hot rolled | Cheapest mill-supplied condition for parts that will be fully re-heat-treated; hardness scatter is high and machining is uneven. | 500 | 780 | 16 | 19 HRC | 7.8 % IACS |
Normalized | Grain refinement and structure homogenisation after forging; harder than annealed but more consistent for medium-size parts. | 550 | 820 | 15 | 22 HRC | 7.8 % IACS |
Cold drawn | Bright, close-tolerance bar for small shafts and pins machined without further sizing; residual stress can cause bow after machining. | 650 | 820 | 10 | 24 HRC | 7.8 % IACS |
Q&T high temper | Tough, machinable condition for shafts, connecting parts and pre-treatment of large forgings before finish machining and nitriding. | 800 | 980 | 15 | 31 HRC | — |
Carburized and hardened | The service condition for gears: hard wear-resistant case (0.6–2.0 mm typical) over a strong 30–45 HRC core, giving high bending and contact fatigue life. | 900 | 1,150 | 11 | 60 HRC | — |
Q&T | The standard test-blank condition defining the grade's strength class (≥1180 MPa); used for through-hardened shafts and highly loaded non-carburized parts. | 950 | 1,230 | 11 | 40 HRC | — |
What is 20CrMnMo?
20CrMnMo is a Cr-Mn-Mo case-hardening steel close to SAE 4118 and JIS SCM420H, in which molybdenum raises hardenability and core strength so larger sections can be carburized. It is a standard grade for heavy machinery gears, forged gear blanks and gearbox shafts, available as hot-rolled, annealed, isothermally annealed, normalized and cold-drawn bar. Annealed core values are about 420 MPa yield, 650 MPa tensile, 20% elongation and 197 HB (92 HRB), with service to roughly 450 °C. Weldability is poor (carbon equivalent ~0.8) and cold formability is limited; 20CrNiMo (8620) is the more weldable option. 20CrMnMo 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). 20CrMnMo has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 650 MPa (94.3 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
What is 20CrMnMo used for?
- gears
- shafts
- gearbox parts
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
20CrMnMo properties
Typical room-temperature values for 20CrMnMo-A; bars are the position among steel grades.
Physical3
20CrMnMo 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).
Mechanical14
20CrMnMo has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 650 MPa (94.3 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20CrMnMo is rated for continuous service to 450°C (842 °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 µm/m·K (6.67 µin/in·°F).
Electrical3
20CrMnMo conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 20CrMnMo takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
20CrMnMo's machinability is good (58/100, better than 75% of steel grades); weldability fair (35/100); formability fair (45/100).
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. 20CrMnMo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 20CrMnMo
Is 20CrMnMo easy to machine?
Rough machine in the annealed/isothermally annealed state (≤217 HB) with coated carbide; after carburizing and hardening only grinding or CBN hard-turning is practical.
Can 20CrMnMo be welded?
Poor weldability — carbon equivalent ~0.8; use low-hydrogen consumables with 200–300 °C preheat, interpass control and immediate stress-relief, and never weld carburized surfaces.
Can 20CrMnMo be formed, bent or molded?
Excellent hot forgeability at 1150–850 °C (gear blanks, ring rolling); cold forming limited to light coining or straightening after anneal.
20CrMnMo 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 |
|---|---|---|
| CGB/T 3077-2015 | 0.17 – 0.23 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.9 – 1.2 | 1.05 |
| Cr | 1.1 – 1.4 | 1.25 |
| Mo | 0.2 – 0.3 | 0.25 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| P≤0.025 for high-grade quality steel | ≤ 0.03 | |
| S≤0.025 for high-grade quality steel | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 20CrMnMo?
Shot peening after case hardening markedly raises bending fatigue; protect with phosphating + oil, black oxide, zinc or manganese phosphate — the steel has no inherent corrosion resistance.
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 20CrMnMo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 4118SCM420H
How much does 20CrMnMo cost?
20CrMnMo is a budget-cost steel ($), cheaper than about 90% 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.
20CrMnMo — frequently asked
What is 20CrMnMo used for?
20CrMnMo is typically used for gears, shafts and gearbox parts. In short: mo-boosted hardenability; heavy-gear carburizing grade; poorest weldability in family.
What is the yield strength of 20CrMnMo?
20CrMnMo has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 650 MPa (94.3 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 20CrMnMo easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Rough machine in the annealed/isothermally annealed state (≤217 HB) with coated carbide; after carburizing and hardening only grinding or CBN hard-turning is practical.
Can 20CrMnMo be welded?
With care — weldability is rated fair (35/100). Poor weldability — carbon equivalent ~0.8; use low-hydrogen consumables with 200–300 °C preheat, interpass control and immediate stress-relief, and never weld carburized surfaces.
What surface finishes work on 20CrMnMo?
Shot peening after case hardening markedly raises bending fatigue; protect with phosphating + oil, black oxide, zinc or manganese phosphate — the steel has no inherent corrosion resistance.
Can 20CrMnMo be formed, bent or molded?
Excellent hot forgeability at 1150–850 °C (gear blanks, ring rolling); cold forming limited to light coining or straightening after anneal.
What is the maximum service temperature of 20CrMnMo?
20CrMnMo 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 20CrMnMo-A and 20CrMnMo-QT200?
A is the default condition — standard delivery condition for gear-blank bar and forgings — softest, most uniform structure for rough machining before carburizing. QT200: the standard test-blank condition defining the grade's strength class (≥1180 MPa); used for through-hardened shafts and highly loaded non-carburized parts. Yield strength is 420 MPa in A versus 950 MPa in QT200.
How much does 20CrMnMo cost?
20CrMnMo is a budget-cost steel ($), cheaper than about 90% 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
- JIS G 4053 (SCM420H) Low-alloyed structural steels — JSA (2016)
- SAE J404 Chemical Compositions of SAE Alloy Steels (4118/8622 comparison) — SAE International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
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.