Steel 4012 CARB-QT
Heat-treated state
AISI/SAE 4012 · UNS G40120
CARB-QT = carburized, quenched and tempered
Final service condition: hard wear-resistant case over a tough low-carbon core, for gears and pins.
Values for the CARB-QT condition
Other 4012 tempers and conditions
4012 is listed in 7 conditions; see the grade overview at 4012.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition; pick for deep machining, cold forming or before carburizing. | 295 | 440 | 32 | 126 HB | — |
Hot rolled | Cheapest stock form for parts that will be machined and then carburized. | 320 | 480 | 27 | 143 HB | 7.8 % IACS |
NDefault Normalized | Standard stock condition — uniform fine-grain structure for machining and subsequent case hardening. | 330 | 470 | 28 | 137 HB | — |
Stress relieved | Cold drawn bar with residual stress removed for dimensionally stable machining. | 420 | 520 | 20 | 156 HB | 7.7 % IACS |
Cold drawn | Tighter tolerance and better surface with a strength boost; choose for turned parts and shafts. | 470 | 550 | 16 | 163 HB | — |
Q&T | Used only where a tough medium-strength core is needed without carburizing; low carbon limits attainable hardness. | 480 | 620 | 22 | 11 HRC | 7.7 % IACS |
CARB-QTThis page Carburized, quenched and tempered | Final service condition: hard wear-resistant case over a tough low-carbon core, for gears and pins. | 520 | 700 | 18 | 60 HRC | — |
What is 4012 CARB-QT?
4012 CARB-QT is 4012 heat treated to CARB-QT — final service condition: hard wear-resistant case over a tough low-carbon core, for gears and pins. 4012 CARB-QT has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 67% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). 4012 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). N is the default condition FabDigit quotes; CARB-QT is available on request or by drawing note.
Limitations
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
4012 CARB-QT properties
Typical room-temperature values for 4012 CARB-QT; 14 are specific to this condition. Other listed values are 4012 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4012 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
4012 CARB-QT has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 67% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4012 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
4012 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 4012 CARB-QT takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability7
4012 CARB-QT's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (25/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4012 CARB-QT
Is 4012 easy to machine?
Machines like a gummy low-carbon steel — use sharp positive-rake tooling, high speed and generous coolant; normalizing before turning improves surface finish and chip control.
Can 4012 be welded?
Readily weldable (CE ≈ 0.35) by SMAW/GMAW with low-hydrogen consumables; preheat 100–150 °C on heavy sections and never weld after carburizing.
Can 4012 be formed, bent or molded?
Good cold formability in the annealed condition (bending, upsetting, cold heading); hot forge at 1100–1200 °C and normalize afterwards.
What surface finishes work on 4012?
No anodizing — protect with zinc or manganese phosphate, black oxide, zinc/nickel plating or paint; carburized surfaces should be finish-ground after hardening.
4012 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 |
|---|---|---|
| CSAE J404 heat analysis | 0.09 – 0.14 | 0.12 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Mo | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
4012 CARB-QT — frequently asked
What is 4012 CARB-QT used for?
4012 CARB-QT is typically used for carburized gears, small shafts, camshafts and pins. In short: tough carburizing core steel; most weldable 40xx grade; low-carbon moly case grade.
What is the yield strength of 4012 CARB-QT?
4012 CARB-QT has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 67% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 4012 CARB-QT easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machines like a gummy low-carbon steel — use sharp positive-rake tooling, high speed and generous coolant; normalizing before turning improves surface finish and chip control.
Can 4012 CARB-QT be welded?
Not readily — weldability is rated poor (25/100). Readily weldable (CE ≈ 0.35) by SMAW/GMAW with low-hydrogen consumables; preheat 100–150 °C on heavy sections and never weld after carburizing.
What surface finishes work on 4012 CARB-QT?
No anodizing — protect with zinc or manganese phosphate, black oxide, zinc/nickel plating or paint; carburized surfaces should be finish-ground after hardening.
Can 4012 CARB-QT be formed, bent or molded?
Good cold formability in the annealed condition (bending, upsetting, cold heading); hot forge at 1100–1200 °C and normalize afterwards.
What is the maximum service temperature of 4012 CARB-QT?
4012 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 4012-N and 4012 CARB-QT?
N is the default condition — standard stock condition — uniform fine-grain structure for machining and subsequent case hardening. CARB-QT: final service condition: hard wear-resistant case over a tough low-carbon core, for gears and pins. Yield strength is 330 MPa in N versus 520 MPa in CARB-QT.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM International (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes (carburizing) — ASM International (2013)
- 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.