Steel 94B15 CARB-QT
Heat-treated state
EN 94B15 · UNS G94151
CARB-QT = carburized, quenched and tempered
The intended service condition: hard wear-resistant case over a strong boron-hardened core for gears and pins.
Values for the CARB-QT condition
Other 94B15 tempers and conditions
94B15 is listed in 8 conditions; see the grade overview at 94B15.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose when parts (pins, bolts, gear blanks) are cold formed before carburizing. | 300 | 470 | 30 | 131 HB | 8 % IACS |
ANNDefault Annealed | Default supply condition for machining of blanks before carburizing. | 330 | 510 | 26 | 143 HB | — |
Hot rolled | Lowest-cost mill bar condition for parts that will be fully heat treated later. | 360 | 545 | 24 | 156 HB | 8 % IACS |
Normalized | Use to refine forging/rolling structure and give uniform response to later carburizing. | 400 | 590 | 24 | 174 HB | 8 % IACS |
Cold drawn | Pick for close-tolerance, straight bright bar with higher as-supplied strength. | 545 | 640 | 15 | 11 HRC | 8 % IACS |
quenched and tempered ~500 °C | Tough medium-hardness core condition for shafts and machined components. | 790 | 950 | 17 | 30 HRC | 8 % IACS |
CARB-QTThis page Carburized, quenched and tempered | The intended service condition: hard wear-resistant case over a strong boron-hardened core for gears and pins. | 830 | 1,100 | 12 | 60 HRC | — |
Q&T | Direct-hardened condition for small boron-steel parts needing maximum core strength without carburizing. | 970 | 1,240 | 13 | 42 HRC | — |
What is 94B15 CARB-QT?
94B15 CARB-QT is 94B15 heat treated to CARB-QT — the intended service condition: hard wear-resistant case over a strong boron-hardened core for gears and pins. 94B15 CARB-QT has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). 94B15 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). ANN is the default condition FabDigit quotes; CARB-QT is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Easy to machine — 62/100, better than 89% of steel grades
- High strength — 830 MPa (120 ksi), better than 87% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
Limitations
- 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 — 12%, worse than 84% of steel grades
94B15 CARB-QT properties
Typical room-temperature values for 94B15 CARB-QT; 11 are specific to this condition. Other listed values are 94B15 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
94B15 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).
Mechanical14
94B15 CARB-QT has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
94B15 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 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
94B15 CARB-QT conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 94B15 CARB-QT takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
94B15 CARB-QT's machinability is good (62/100, better than 89% of steel grades); weldability poor (15/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 94B15 CARB-QT
Is 94B15 easy to machine?
Machine in the annealed or normalized state (≈60–70 % of 1212) with sharp carbide tooling and generous coolant; leave grinding stock for post-carburizing distortion.
Can 94B15 be welded?
Weldable with low-hydrogen consumables, 150–250 °C preheat and post-weld temper; avoid welding after carburizing and expect hard HAZ from the boron hardenability.
Can 94B15 be formed, bent or molded?
Cold heading and upsetting are practical in the spheroidize-annealed condition; hot forge 1050–1200 °C but keep austenitizing below ~1050 °C to preserve boron hardenability.
What surface finishes work on 94B15?
No inherent corrosion resistance — protect by oiling, phosphating, black oxide, zinc or nitrocarburizing; carburized surfaces are usually ground and shot peened for fatigue.
94B15 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 | 0.13 – 0.18 | 0.16 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.3 – 0.6 | 0.45 |
| Cr | 0.3 – 0.5 | 0.4 |
| Mo | 0.08 – 0.15 | 0.12 |
| Bboron-treated (B-suffix grade); effective boron requires N-fixing with Ti/Al | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
94B15 CARB-QT — frequently asked
What is 94B15 CARB-QT used for?
94B15 CARB-QT is typically used for carburized gears, pins and case-hardened components. In short: low-cost carburizing steel; boron-boosted hardenability; deep case, tough core.
What is the yield strength of 94B15 CARB-QT?
94B15 CARB-QT has a typical yield strength of 830 MPa (120 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 94B15 CARB-QT easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machine in the annealed or normalized state (≈60–70 % of 1212) with sharp carbide tooling and generous coolant; leave grinding stock for post-carburizing distortion.
Can 94B15 CARB-QT be welded?
Not readily — weldability is rated poor (15/100). Weldable with low-hydrogen consumables, 150–250 °C preheat and post-weld temper; avoid welding after carburizing and expect hard HAZ from the boron hardenability.
What surface finishes work on 94B15 CARB-QT?
No inherent corrosion resistance — protect by oiling, phosphating, black oxide, zinc or nitrocarburizing; carburized surfaces are usually ground and shot peened for fatigue.
Can 94B15 CARB-QT be formed, bent or molded?
Cold heading and upsetting are practical in the spheroidize-annealed condition; hot forge 1050–1200 °C but keep austenitizing below ~1050 °C to preserve boron hardenability.
What is the maximum service temperature of 94B15 CARB-QT?
94B15 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.
What is the difference between 94B15-ANN and 94B15 QT-200?
ANN is the default condition — default supply condition for machining of blanks before carburizing. QT-200: direct-hardened condition for small boron-steel parts needing maximum core strength without carburizing. Yield strength is 330 MPa in ANN versus 970 MPa in QT-200.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Boron H-Steels — SAE International (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing and boron steels) — ASM International (1991)
- 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.