Steel 20Cr
GB 20Cr · AISI/SAE 5120 · JIS SCr420
20Cr is a low-alloy chromium carburizing steel in the GB alloy steel family, equivalent to SAE 5120, JIS SCr420 and 20Cr4; strength comes from a carburized case over a tough low-carbon core.
Reference datasheet — 20Cr 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 HR condition
20Cr tempers and conditions
20Cr 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 |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition; choose for deep cold forming, cold heading or heavy pre-machining before carburizing. | 300 | 520 | 27 | 156 HB | — |
HRDefault Hot rolled | Standard mill stock condition for 20Cr bar; rough-machine then carburize and harden. | 380 | 600 | 22 | 170 HB | — |
Normalized | Uniform fine-grained structure with good chip control; standard pre-treatment before carburizing. | 400 | 620 | 22 | 179 HB | — |
Quenched + high tempered 500–600 °C | Tough, machinable through-hardened condition for shafts and fasteners that will not be carburized. | 550 | 750 | 18 | 20 HRC | — |
Cold drawn | Bright, close-tolerance bar for small shafts and pins machined to near-net size before case hardening. | 570 | 700 | 12 | 200 HB | — |
Quenched 880 °C (water/oil) + tempered 200 °C | The condition in which GB/T 3077 mechanical properties are certified; direct hardening for small high-strength parts. | 620 | 900 | 13 | 30 HRC | — |
Carburized 900–930 °C, quenched + 180–200 °C temper | Service condition for gears, pins and splines: hard wear-resistant case over a tough low-carbon core. | 720 | 1,000 | 10 | 60 HRC | — |
What is 20Cr?
20Cr is a low-alloy chromium carburizing steel in the GB alloy steel family, equivalent to SAE 5120, JIS SCr420 and 20Cr4; strength comes from a carburized case over a tough low-carbon core. It is chosen for gears, shafts and pins and is stocked as hot-rolled and cold-drawn bar in annealed, normalized, quenched-and-tempered (QT200, QT550) or carburized conditions, with core values near 380 MPa yield, 600 MPa tensile, 22 % elongation and 170 HB. Service is limited to about 400 °C, carburized surfaces must not be welded, and hardenability is lower than 20CrMnTi, which is the usual step up for heavier gearing. 20Cr 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). 20Cr has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 68% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
What is 20Cr used for?
- gears
- shafts
- pins
- small carburized parts
20Cr properties
Typical room-temperature values for 20Cr-HR; bars are the position among steel grades.
Physical3
20Cr 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).
Mechanical15
20Cr has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 68% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20Cr is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
20Cr 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 20Cr takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
20Cr's machinability is good (60/100, better than 83% of steel grades); weldability good (55/100); formability good (60/100).
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. 20Cr is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 20Cr
Is 20Cr easy to machine?
Best machined normalized or annealed (≈65 % of AISI 1212) with carbide tooling; leave 0.2–0.4 mm grinding stock because carburize-quench distortion must be corrected after heat treatment.
Can 20Cr be welded?
Weldable with low-hydrogen electrodes at 150–250 °C preheat plus post-weld stress relief; do not weld carburized surfaces — the high-carbon case cracks.
Can 20Cr be formed, bent or molded?
Good cold heading and upsetting in the spheroidize-annealed state; hot forge at 1150–1200 °C and finish above 850 °C, then normalize to restore grain size.
20Cr 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 | 0.18 – 0.24 | 0.21 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.7 – 1 | 0.85 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| Moresidual | ≤ 0.1 | |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 20Cr?
No passive film — protect with phosphate + oil, black oxide, Zn or Zn-Ni plating (bake to avoid hydrogen embrittlement after case hardening); case-hardened surfaces are finished by grinding or honing.
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 20Cr in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 20Cr cost?
20Cr 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.
20Cr — frequently asked
What is 20Cr used for?
20Cr is typically used for gears, shafts, pins and small carburized parts. In short: entry-level carburizing steel; hard case, tough core; cheaper than 20CrMnTi.
What is the yield strength of 20Cr?
20Cr has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20Cr easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Best machined normalized or annealed (≈65 % of AISI 1212) with carbide tooling; leave 0.2–0.4 mm grinding stock because carburize-quench distortion must be corrected after heat treatment.
Can 20Cr be welded?
Yes — weldability is rated good (55/100). Weldable with low-hydrogen electrodes at 150–250 °C preheat plus post-weld stress relief; do not weld carburized surfaces — the high-carbon case cracks.
What surface finishes work on 20Cr?
No passive film — protect with phosphate + oil, black oxide, Zn or Zn-Ni plating (bake to avoid hydrogen embrittlement after case hardening); case-hardened surfaces are finished by grinding or honing.
Can 20Cr be formed, bent or molded?
Good cold heading and upsetting in the spheroidize-annealed state; hot forge at 1150–1200 °C and finish above 850 °C, then normalize to restore grain size.
What is the maximum service temperature of 20Cr?
20Cr 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.
What is the difference between 20Cr-HR and 20Cr CARB?
HR is the default condition — standard mill stock condition for 20Cr bar; rough-machine then carburize and harden. CARB: service condition for gears, pins and splines: hard wear-resistant case over a tough low-carbon core. Yield strength is 380 MPa in HR versus 720 MPa in CARB.
How much does 20Cr cost?
20Cr 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 (SCr420) Low-alloyed steels for machine structural use — JISC (2016)
- EN 10084 Case hardening steels (20Cr4 / 1.7027) — CEN (2008)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook (machinability ratings) — Industrial Press (2020)
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.