Steel 18KhGT CARBONIT
Heat-treated state
GOST 18KhGT (18ХГТ)
Choose for thin-section, lightly loaded gears and small shafts where a shallow, low-distortion, wear-resistant case is enough.
Values for the CARBONIT condition
Other 18KhGT tempers and conditions
18KhGT is listed in 7 conditions; see the grade overview at 18KhGT.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick when heavy hobbing, broaching or cold forming of blanks is required before carburizing. | 400 | 640 | 23 | 170 HB | — |
HRDefault Hot rolled | Standard mill delivery condition for bar/forging stock — machine, then carburize and harden. | 500 | 760 | 18 | 197 HB | — |
Normalized | Use to homogenize forgings and refine grain before carburizing or final machining. | 560 | 820 | 16 | 18 HRC | 7.8 % IACS |
Cold drawn | Choose for small-diameter shafts and pins needing close tolerance and good surface before case hardening. | 700 | 850 | 9 | 22 HRC | 7.7 % IACS |
CARBONITThis page case 58–63 HRC, shallow case | Choose for thin-section, lightly loaded gears and small shafts where a shallow, low-distortion, wear-resistant case is enough. | 970 | 1,150 | 10 | 60 HRC | 7.5 % IACS |
Quenched (860–880 °C, oil) + tempered 200 °C | The GOST 4543 property-verification condition; also used for small through-hardened parts not needing a carburized case. | 980 | 1,150 | 11 | 38 HRC | — |
Carburized + quenched + tempered | The service condition for gears, splines and pinions: hard wear-resistant case on a tough core; grind after treatment. | 1,000 | 1,200 | 9 | 60 HRC | — |
What is 18KhGT CARBONIT?
18KhGT CARBONIT is 18KhGT heat treated to CARBONIT — choose for thin-section, lightly loaded gears and small shafts where a shallow, low-distortion, wear-resistant case is enough. 18KhGT CARBONIT has a yield strength of 970 MPa (141 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 18KhGT CARBONIT has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). HR is the default condition FabDigit quotes; CARBONIT is available on request or by drawing note.
Advantages
- High strength — 970 MPa (141 ksi), better than 91% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 3/100, 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
18KhGT CARBONIT properties
Typical room-temperature values for 18KhGT CARBONIT; 22 are specific to this condition. Other listed values are 18KhGT reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18KhGT CARBONIT has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical13
18KhGT CARBONIT has a yield strength of 970 MPa (141 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18KhGT CARBONIT is rated for continuous service to 180°C (356 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
18KhGT CARBONIT conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 18KhGT CARBONIT 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
18KhGT CARBONIT's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18KhGT CARBONIT
Is 18KhGT easy to machine?
Machine soft (≤217 HB, ideally isothermally annealed) with carbide at moderate speeds; after carburizing only grinding/EDM is practical, so leave 0.1–0.3 mm grind stock.
Can 18KhGT be welded?
Weldable only before case hardening — preheat 200–300 °C, low-hydrogen filler, post-weld temper; welding a carburized surface causes cracking.
Can 18KhGT be formed, bent or molded?
Excellent hot forgeability at 1150–1200 °C (stop ≥850 °C) followed by normalizing; cold forming limited, best done in the annealed state.
What surface finishes work on 18KhGT?
Not corrosion resistant — protect with oil, manganese/zinc phosphate, black oxide, or Zn/Ni plating (bake to avoid hydrogen embrittlement on hardened parts); shot peening boosts gear-tooth fatigue life.
18KhGT 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 – 0.23 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.8 – 1.1 | 0.95 |
| Cr | 1 – 1.3 | 1.15 |
| Tigrain-refining addition; GB/T 3077 20CrMnTi specifies 0.04–0.10 | 0.03 – 0.09 | 0.06 |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.3 | — |
| S | ≤ 0.04 | — |
| P | ≤ 0.04 | — |
| Fe | balance | — |
18KhGT CARBONIT — frequently asked
What is 18KhGT CARBONIT used for?
18KhGT CARBONIT is typically used for automotive transmission gears, gearbox shafts, differential ring gears and pinions, splined shafts, synchronizer hubs and sprockets. In short: standard automotive gear steel; titanium-refined fine grain; nickel-free carburizing grade.
What is the yield strength of 18KhGT CARBONIT?
18KhGT CARBONIT has a typical yield strength of 970 MPa (141 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 18KhGT CARBONIT easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine soft (≤217 HB, ideally isothermally annealed) with carbide at moderate speeds; after carburizing only grinding/EDM is practical, so leave 0.1–0.3 mm grind stock.
Can 18KhGT CARBONIT be welded?
Not readily — weldability is rated not recommended (5/100). Weldable only before case hardening — preheat 200–300 °C, low-hydrogen filler, post-weld temper; welding a carburized surface causes cracking.
What surface finishes work on 18KhGT CARBONIT?
Not corrosion resistant — protect with oil, manganese/zinc phosphate, black oxide, or Zn/Ni plating (bake to avoid hydrogen embrittlement on hardened parts); shot peening boosts gear-tooth fatigue life.
Can 18KhGT CARBONIT be formed, bent or molded?
Excellent hot forgeability at 1150–1200 °C (stop ≥850 °C) followed by normalizing; cold forming limited, best done in the annealed state.
What is the maximum service temperature of 18KhGT CARBONIT?
18KhGT CARBONIT 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 18KhGT-HR and 18KhGT CARB58?
HR is the default condition — standard mill delivery condition for bar/forging stock — machine, then carburize and harden. CARB58: the service condition for gears, splines and pinions: hard wear-resistant case on a tough core; grind after treatment. Yield strength is 500 MPa in HR versus 1,000 MPa in CARB58.
Sources
- GOST 4543-2016 Alloy structural steels — grades (18ХГТ) — Rosstandart (2016)
- GB/T 3077-2015 (20CrMnTi) — SAC/China (2015)
- Marochnik steel grade database — 18ХГТ — Marochnik (2023)
- ASM Handbook Vol.1: Properties and Selection — Carburizing Steels — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating (carburizing, case depth and hardness) — ASM International (1991)
- 20CrMnTi / — Mysteel / 1688 (2026)
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.