Steel 20Cr CARB
Heat-treated state
GB 20Cr · AISI/SAE 5120 · JIS SCr420
CARB = 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.
Values for the CARB condition
Other 20Cr tempers and conditions
20Cr is listed in 7 conditions; see the grade overview at 20Cr.
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 | — |
CARBThis page 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 CARB?
20Cr CARB is 20Cr heat treated to CARB — service condition for gears, pins and splines: hard wear-resistant case over a tough low-carbon core. 20Cr CARB has a yield strength of 720 MPa (104 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 20Cr CARB 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). HR is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- High strength — 720 MPa (104 ksi), better than 82% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
20Cr CARB properties
Typical room-temperature values for 20Cr CARB; 13 are specific to this condition. Other listed values are 20Cr reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20Cr CARB 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 CARB has a yield strength of 720 MPa (104 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20Cr CARB is rated for continuous service to 180°C (356 °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 CARB 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 CARB 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 CARB's machinability is not recommended (12/100, worse than 99% of steel grades); weldability not recommended (10/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Cr CARB
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.
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.
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 | — |
20Cr CARB — frequently asked
What is 20Cr CARB used for?
20Cr CARB 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 CARB?
20Cr CARB has a typical yield strength of 720 MPa (104 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 82% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20Cr CARB easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% 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 CARB be welded?
Not readily — weldability is rated not recommended (10/100). 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 CARB?
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 CARB 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 CARB?
20Cr CARB is rated for continuous use to about 180°C (356 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.