Steel 12CrNi3A-QT (Quenched and tempered)
Heat-treated state · default condition
EN 12CrNi3A
Standard property-verification condition of GB/T 3077 and the usual through-hardened state for un-carburized shafts and fasteners in this grade.
Values for the QT condition
Other 12CrNi3A tempers and conditions
12CrNi3A is listed in 8 conditions; see the grade overview at 12CrNi3A.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for maximum machinability and cold workability before carburizing; the standard stocked bar condition under GB/T 3077. | 390 | 620 | 22 | 190 HB | — |
Normalized + high-temperature temper | Common mill delivery route for Ni-Cr carburizing bar: gives uniform, easily machined structure with ≤269 HBW. | 450 | 680 | 20 | 14 HRC | 5.9 % IACS |
Hot rolled | Raw mill condition of round bar; usually re-annealed or normalized before machining because as-rolled Ni-Cr steel is already fairly hard. | 500 | 780 | 16 | 21 HRC | 6.2 % IACS |
Normalized | Grain refinement and structure homogenisation before carburizing or final Q&T; harder than annealed. | 540 | 800 | 18 | 22 HRC | 6.2 % IACS |
Cold drawn | Choose for close-tolerance bright bar and small carburized pins/shafts machined with minimal stock removal. | 640 | 780 | 10 | 20 HRC | 6 % IACS |
Quenched and high-temperature tempered ~600 °C | Use when maximum core toughness and dimensional stability matter more than hardness, e.g. un-carburized heavy shafts. | 700 | 850 | 17 | 25 HRC | — |
QTDefaultThis page Quenched and tempered | Standard property-verification condition of GB/T 3077 and the usual through-hardened state for un-carburized shafts and fasteners in this grade. | 785 | 980 | 13 | 31 HRC | — |
Carburized + hardened + 180–200 °C temper | The service condition for gears and pins: 0.6–1.5 mm hard wear-resistant case over a tough ~3%Ni core. | 800 | 1,050 | 11 | 60 HRC | — |
What is 12CrNi3A-QT?
12CrNi3A-QT is 12CrNi3A heat treated to QT — standard property-verification condition of GB/T 3077 and the usual through-hardened state for un-carburized shafts and fasteners in this grade. 12CrNi3A-QT has a yield strength of 785 MPa (114 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 86% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi). 12CrNi3A-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- High strength — 785 MPa (114 ksi), better than 86% of steel grades
- Polishes to a fine finish — 68/100, better than 83% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low electrical conductivity — 5.7 % IACS, worse than 80% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
- Difficult to machine — 40/100, worse than 77% of steel grades
12CrNi3A-QT properties
Typical room-temperature values for 12CrNi3A-QT; 16 are specific to this condition. Other listed values are 12CrNi3A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
12CrNi3A-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
12CrNi3A-QT has a yield strength of 785 MPa (114 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 86% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
12CrNi3A-QT is rated for continuous service to 200°C (392 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
12CrNi3A-QT conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 12CrNi3A-QT takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
12CrNi3A-QT's machinability is fair (40/100, worse than 77% of steel grades); weldability fair (35/100); formability poor (22/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 12CrNi3A-QT
Is 12CrNi3A easy to machine?
Machine in the annealed or high-temper condition (≤269 HBW); the 3%Ni matrix is gummy, so use sharp positive-rake carbide, rigid setups and generous coolant, and finish-grind after carburizing.
Can 12CrNi3A be welded?
Weldable with low-hydrogen consumables but requires 150–250 °C preheat and prompt stress relief/tempering; never weld a carburized surface.
Can 12CrNi3A be formed, bent or molded?
Hot forge at 1150–850 °C followed by slow cooling and normalizing; cold forming only in the annealed state and limited to modest deformation.
What surface finishes work on 12CrNi3A?
Not anodizable — protect with oil, phosphate/black oxide, zinc or nickel plating; masking with copper plate or paste is standard for selectively carburized areas.
12CrNi3A 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 | 0.1 – 0.17 | 0.13 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.3 – 0.6 | 0.45 |
| Cr | 0.6 – 0.9 | 0.75 |
| Ni | 2.75 – 3.25 | 3 |
| Curesidual | ≤ 0.25 | — |
| Phigh-grade quality (A) limit | ≤ 0.03 | — |
| Shigh-grade quality (A) limit | ≤ 0.03 | — |
| Fe | balance | — |
12CrNi3A-QT — frequently asked
What is 12CrNi3A-QT used for?
12CrNi3A-QT is typically used for gear shafts, carburized pins and small gears. In short: medium-duty carburizing steel; tough 3 % Ni core; lighter-duty 9310 alternative.
What is the yield strength of 12CrNi3A-QT?
12CrNi3A-QT has a typical yield strength of 785 MPa (114 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 86% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 12CrNi3A-QT easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine in the annealed or high-temper condition (≤269 HBW); the 3%Ni matrix is gummy, so use sharp positive-rake carbide, rigid setups and generous coolant, and finish-grind after carburizing.
Can 12CrNi3A-QT be welded?
With care — weldability is rated fair (35/100). Weldable with low-hydrogen consumables but requires 150–250 °C preheat and prompt stress relief/tempering; never weld a carburized surface.
What surface finishes work on 12CrNi3A-QT?
Not anodizable — protect with oil, phosphate/black oxide, zinc or nickel plating; masking with copper plate or paste is standard for selectively carburized areas.
Can 12CrNi3A-QT be formed, bent or molded?
Hot forge at 1150–850 °C followed by slow cooling and normalizing; cold forming only in the annealed state and limited to modest deformation.
What is the maximum service temperature of 12CrNi3A-QT?
12CrNi3A-QT is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 12CrNi3A-QT and 12CrNi3A-A?
QT is the default condition — standard property-verification condition of GB/T 3077 and the usual through-hardened state for un-carburized shafts and fasteners in this grade. A: pick for maximum machinability and cold workability before carburizing; the standard stocked bar condition under GB/T 3077. Yield strength is 785 MPa in QT versus 390 MPa in A.
Sources
- SAE J404 Chemical Compositions of SAE Alloy Steels (3310 comparison) — SAE International (2009)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing of Ni-Cr 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.