Steel 6120 QT-32
Hardness band
AISI/SAE 6120 · UNS G61200
QT-32 = q&T 30–35 HRC
Highest practical through-hardened strength for this 0.20 % C grade; use in small sections only.
Values for the QT-32 condition
Other 6120 tempers and conditions
6120 is listed in 9 conditions; see the grade overview at 6120.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Choose for severe cold heading/upsetting of fastener and gear blanks. | 340 | 530 | 32 | 150 HB | 7.8 % IACS |
ADefault Solution annealed | Standard soft stocking condition for machining, cold forming and carburizing blanks. | 370 | 570 | 29 | 163 HB | — |
Hot rolled | Cheapest mill condition for bar and forging stock that will be re-heat-treated anyway. | 400 | 620 | 24 | 179 HB | 7.5 % IACS |
Normalized and tempered | Stress-relieved normalized bar for structural parts needing dimensional stability and impact toughness. | 420 | 620 | 27 | 180 HB | 7.5 % IACS |
Normalized | Uniform fine-grain structure and better toughness than as-rolled; usual pre-treatment before carburizing or machining of forgings. | 440 | 655 | 25 | 190 HB | 7.5 % IACS |
Cold drawn | Pick for tight-tolerance bright bar with higher yield strength and better surface without heat treatment. | 600 | 700 | 13 | 207 HB | — |
Q&T 22–28 HRC | Through-hardened condition for tough shafts and structural fasteners where a moderate strength level is enough. | 650 | 830 | 20 | 25 HRC | — |
Carburized, Quenched and Tempered | The intended service condition for gears, pinions and cams — hard wear-resistant case over a tough Cr-V core. | 750 | 1,000 | 12 | 60 HRC | — |
QT-32This page Q&T 30–35 HRC | Highest practical through-hardened strength for this 0.20 % C grade; use in small sections only. | 820 | 1,000 | 16 | 32 HRC | — |
What is 6120 QT-32?
6120 QT-32 is 6120 heat treated to QT-32 — highest practical through-hardened strength for this 0.20 % C grade; use in small sections only. 6120 QT-32 has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi). 6120 QT-32 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). A is the default condition FabDigit quotes; QT-32 is available on request or by drawing note.
Advantages
- High strength — 820 MPa (119 ksi), better than 87% of steel grades
6120 QT-32 properties
Typical room-temperature values for 6120 QT-32; 11 are specific to this condition. Other listed values are 6120 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
6120 QT-32 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).
Mechanical13
6120 QT-32 has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
6120 QT-32 is rated for continuous service to 350°C (662 °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
6120 QT-32 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 6120 QT-32 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
6120 QT-32's machinability is fair (52/100, better than 52% of steel grades); weldability good (55/100); formability good (58/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 6120 QT-32
Is 6120 easy to machine?
Machines well annealed or normalized (~60 % of 1212) with carbide tooling and flood coolant; finish-grind after carburizing since the case is essentially unmachinable.
Can 6120 be welded?
Weldable with low-hydrogen consumables; preheat 150–250 °C and post-weld temper, and never weld carburized surfaces.
Can 6120 be formed, bent or molded?
Cold head and bend in the annealed or spheroidized condition; hot forge 1150–1200 °C and finish above ~900 °C, then normalize to restore grain size.
What surface finishes work on 6120?
No corrosion resistance bare — use black oxide, phosphate-and-oil, zinc or hard chrome; shot-peen carburized gear roots for fatigue life and bake after plating to avoid hydrogen embrittlement.
6120 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 – 0.22 | 0.2 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.7 – 0.9 | 0.8 |
| V0.10 % min per SAE J404 | ≥ 0.1 | 0.15 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
6120 QT-32 — frequently asked
What is 6120 QT-32 used for?
6120 QT-32 is typically used for gears, structural fasteners and shafts. In short: fine-grain carburizing grade; tough Cr-V gear core; moderate hardenability only.
What is the yield strength of 6120 QT-32?
6120 QT-32 has a typical yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 6120 QT-32 easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machines well annealed or normalized (~60 % of 1212) with carbide tooling and flood coolant; finish-grind after carburizing since the case is essentially unmachinable.
Can 6120 QT-32 be welded?
Yes — weldability is rated good (55/100). Weldable with low-hydrogen consumables; preheat 150–250 °C and post-weld temper, and never weld carburized surfaces.
What surface finishes work on 6120 QT-32?
No corrosion resistance bare — use black oxide, phosphate-and-oil, zinc or hard chrome; shot-peen carburized gear roots for fatigue life and bake after plating to avoid hydrogen embrittlement.
Can 6120 QT-32 be formed, bent or molded?
Cold head and bend in the annealed or spheroidized condition; hot forge 1150–1200 °C and finish above ~900 °C, then normalize to restore grain size.
What is the maximum service temperature of 6120 QT-32?
6120 QT-32 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 6120-A and 6120 QT-32?
A is the default condition — standard soft stocking condition for machining, cold forming and carburizing blanks. QT-32: highest practical through-hardened strength for this 0.20 % C grade; use in small sections only. Yield strength is 370 MPa in A versus 820 MPa in QT-32.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 / ASTM A304 — Hardenability requirements for alloy steel bars — SAE / ASTM (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing of Cr-V steels) — ASM International (1991)
- Machinery's Handbook, 31st ed. (machinability ratings, alloy steel heat treatment) — Industrial Press (2020)
- GB/T 3077 (20CrV comparison grade) — SAC (2015)
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.