Steel 20Cr4 CARB+QT
Heat-treated state
EN 20Cr4
CARB+QT = carburized, quenched and low-temperature tempered
The in-service condition: hard wear/rolling-contact surface over a tough ~30–40 HRC core for gears, pins and bearing races.
Values for the CARB+QT condition
Other 20Cr4 tempers and conditions
20Cr4 is listed in 8 conditions; see the grade overview at 20Cr4.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick when the part is cold extruded, headed or deep-drawn before carburizing — lowest hardness and best cold formability. | 310 | 500 | 28 | 155 HB | — |
Treated to a ferrite-pearlite structure within a specified hardness… | Choose for consistent, repeatable machining (uniform F-P microstructure) on automatic lathes and gear hobbing lines. | 345 | 560 | 24 | 165 HB | 7.8 % IACS |
+ADefault Annealed | Standard stock condition for bar and tube: soft, machinable, ready for carburizing after part machining. | 350 | 560 | 25 | 170 HB | — |
Supplied to specified hardenability (Jominy) band | Specify for carburized gears and races where case/core hardness after quench must be predictable (Jominy end-quench limits guaranteed). | 360 | 580 | 23 | 42 HRC | 7.8 % IACS |
Treated to a specified hardness range | Order when the mill must guarantee a narrow delivery hardness band for automated machining or cold drawing. | 380 | 590 | 22 | 180 HB | 7.8 % IACS |
Normalized | Use for grain refinement and uniform machining response on hot-rolled or forged blanks prior to carburizing. | 400 | 620 | 22 | 12 HRC | 7.8 % IACS |
Cold drawn | Cold-drawn bright bar for close tolerance and better surface finish where only light machining follows. | 570 | 700 | 10 | 215 HB | — |
CARB+QTThis page Carburized, quenched and low-temperature tempered | The in-service condition: hard wear/rolling-contact surface over a tough ~30–40 HRC core for gears, pins and bearing races. | 640 | 900 | 11 | 60 HRC | — |
What is 20Cr4 CARB+QT?
20Cr4 CARB+QT is 20Cr4 heat treated to CARB+QT — the in-service condition: hard wear/rolling-contact surface over a tough ~30–40 HRC core for gears, pins and bearing races. 20Cr4 CARB+QT has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Elongation at break is 11% and the elastic modulus is 210 GPa (30.5 Msi). 20Cr4 CARB+QT 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). +A is the default condition FabDigit quotes; CARB+QT is available on request or by drawing note.
Advantages
- High strength — 640 MPa (92.8 ksi), better than 79% of steel grades
Limitations
- Difficult to machine — 12/100, 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
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
20Cr4 CARB+QT properties
Typical room-temperature values for 20Cr4 CARB+QT; 14 are specific to this condition. Other listed values are 20Cr4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20Cr4 CARB+QT 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).
Mechanical16
20Cr4 CARB+QT has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Elongation at break is 11% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20Cr4 CARB+QT 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 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
20Cr4 CARB+QT 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 20Cr4 CARB+QT takes about 31 MJ of energy and emits 2.1 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 35%.
Manufacturability8
20Cr4 CARB+QT's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (15/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Cr4 CARB+QT
Is 20Cr4 easy to machine?
Machine in +A/+FP/+TH before carburizing; carbide or coated HSS, generous coolant, ~60 % of 1212 rating — after case hardening only grinding/EDM is practical.
Can 20Cr4 be welded?
Weldable in the soft condition with low-hydrogen consumables and 150–250 °C preheat plus post-weld stress relief; do not weld carburized surfaces.
Can 20Cr4 be formed, bent or molded?
Cold heading, extrusion and bending are good in +AC (spheroidized); hot forge 1100–1200 °C and normalize afterwards to restore grain size.
What surface finishes work on 20Cr4?
No anodizing (ferrous): protect with oil, phosphate, black oxide, zinc or hard chrome; grind/lap case-hardened surfaces to final size and allow 0.1–0.3 mm stock for distortion.
20Cr4 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 – 0.22 | 0.2 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| Slower S range available for cleanliness-critical bearing use | ≤ 0.04 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Fe | balance | — |
20Cr4 CARB+QT — frequently asked
What is 20Cr4 CARB+QT used for?
20Cr4 CARB+QT is typically used for bearing rings, gears and case-hardened shafts. In short: bearing-race case-hardening grade; good rolling-contact fatigue; cold-heads in spheroidized condition.
What is the yield strength of 20Cr4 CARB+QT?
20Cr4 CARB+QT has a typical yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 20Cr4 CARB+QT easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine in +A/+FP/+TH before carburizing; carbide or coated HSS, generous coolant, ~60 % of 1212 rating — after case hardening only grinding/EDM is practical.
Can 20Cr4 CARB+QT be welded?
Not readily — weldability is rated poor (15/100). Weldable in the soft condition with low-hydrogen consumables and 150–250 °C preheat plus post-weld stress relief; do not weld carburized surfaces.
What surface finishes work on 20Cr4 CARB+QT?
No anodizing (ferrous): protect with oil, phosphate, black oxide, zinc or hard chrome; grind/lap case-hardened surfaces to final size and allow 0.1–0.3 mm stock for distortion.
Can 20Cr4 CARB+QT be formed, bent or molded?
Cold heading, extrusion and bending are good in +AC (spheroidized); hot forge 1100–1200 °C and normalize afterwards to restore grain size.
What is the maximum service temperature of 20Cr4 CARB+QT?
20Cr4 CARB+QT 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.
Sources
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- GB/T 3077 — Alloy structural steels (20Cr) — SAC (2015)
- SAE J404 / J1268 — Chemical compositions and hardenability of alloy steels (5120/5120H) — SAE International (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing) — ASM International (1991)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
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.