Steel 15Kh CARB
Heat-treated state
GOST 15Kh (15Х)
CARB = carburized + quenched + 180 °C temper
Final service condition for gears and pins: hard wear-resistant case (0.5–1.2 mm) over a tough medium-strength core.
Values for the CARB condition
Other 15Kh tempers and conditions
15Kh is listed in 6 conditions; see the grade overview at 15Kh.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for deep machining, cold heading or cold extrusion before carburizing. | 300 | 490 | 28 | 160 HB | — |
Hot rolled | Mill delivery condition for bar and billet that will be machined and then carburized. | 330 | 540 | 24 | 170 HB | — |
Normalized | Uniform fine-grain structure with better machined-surface finish than annealed; standard pre-carburizing condition. | 350 | 560 | 22 | 11 HRC | 9 % IACS |
Cold drawn | Bright, close-tolerance bar for pins, bushings and shafts machined with minimal stock removal. | 520 | 640 | 12 | 200 HB | — |
Q&TDefault Quenched and tempered | The GOST 4543 acceptance condition — use these numbers for the core of small hardened parts and for through-hardened pins. | 540 | 750 | 14 | 20 HRC | — |
CARBThis page Carburized + quenched + 180 °C temper | Final service condition for gears and pins: hard wear-resistant case (0.5–1.2 mm) over a tough medium-strength core. | 590 | 800 | 12 | 58 HRC | — |
What is 15Kh CARB?
15Kh CARB is 15Kh heat treated to CARB — final service condition for gears and pins: hard wear-resistant case (0.5–1.2 mm) over a tough medium-strength core. 15Kh CARB has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 76% of steel grades. Elongation at break is 12% and the elastic modulus is 212 GPa (30.7 Msi). 15Kh CARB has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F). Q&T is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 590 MPa (85.6 ksi), better than 76% of steel grades
Limitations
- Difficult to machine — 10/100, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
15Kh CARB properties
Typical room-temperature values for 15Kh CARB; 12 are specific to this condition. Other listed values are 15Kh reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15Kh CARB has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
15Kh CARB has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 76% of steel grades. Elongation at break is 12% and the elastic modulus is 212 GPa (30.7 Msi).
Thermal6
15Kh CARB is rated for continuous service to 180°C (356 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
15Kh CARB conducts electricity at 8.2 % IACS, better than 61% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 15Kh CARB takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
15Kh CARB's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (10/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15Kh CARB
Is 15Kh easy to machine?
Machine in the annealed or normalized state (≈60–65 % of AISI 1212); leave 0.1–0.3 mm grinding stock for post-carburizing finishing.
Can 15Kh be welded?
Weldable with low-hydrogen electrodes at 150–250 °C preheat plus post-weld stress relief; do not weld carburized surfaces.
Can 15Kh be formed, bent or molded?
Good hot forgeability at 1150–850 °C and acceptable cold upsetting when spheroidize annealed; normalize after forging.
What surface finishes work on 15Kh?
No anodizing — protect with phosphating and oil, black oxide, or zinc/nickel plating; ground and honed case surfaces give best fatigue life.
15Kh 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 | 0.12 – 0.18 | 0.15 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.4 – 0.7 | 0.55 |
| Cr | 0.7 – 1 | 0.85 |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.3 | — |
| Simpurity | ≤ 0.04 | — |
| Pimpurity | ≤ 0.04 | — |
| Fe | balance | — |
15Kh CARB — frequently asked
What is 15Kh CARB used for?
15Kh CARB is typically used for lightly loaded small gears, pins and pivot pins, small shafts and spindles, bushings, cams and levers and sprockets. In short: entry-level chromium case steel; low-cost carburizing grade; weldable before carburizing.
What is the yield strength of 15Kh CARB?
15Kh CARB has a typical yield strength of 590 MPa (85.6 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 76% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 15Kh CARB easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine in the annealed or normalized state (≈60–65 % of AISI 1212); leave 0.1–0.3 mm grinding stock for post-carburizing finishing.
Can 15Kh 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.
What surface finishes work on 15Kh CARB?
No anodizing — protect with phosphating and oil, black oxide, or zinc/nickel plating; ground and honed case surfaces give best fatigue life.
Can 15Kh CARB be formed, bent or molded?
Good hot forgeability at 1150–850 °C and acceptable cold upsetting when spheroidize annealed; normalize after forging.
What is the maximum service temperature of 15Kh CARB?
15Kh 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 15Kh Q&T and 15Kh-A?
Q&T is the default condition — the GOST 4543 acceptance condition — use these numbers for the core of small hardened parts and for through-hardened pins. A: softest condition — choose for deep machining, cold heading or cold extrusion before carburizing. Yield strength is 540 MPa in Q&T versus 300 MPa in A.
Sources
- GOST 4543 — Alloyed structural steel bars — Gosstandart / Rosstandart (2016)
- GB/T 3077 (15Cr equivalent) — SAC (2015)
- Marochnik Stali i Splavov — grade 15Kh property tables — Marochnik (2020)
- ASM Handbook Vol.1 & Vol.4 — carburizing low-alloy steels — ASM International (1991)
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.