Steel 20MnVB-QT400
Heat-treated state
GB 20MnVB
QT400 = oil quench + 400 °C temper
Medium-high strength with better ductility than low-temper for shafts and connecting parts.
Values for the QT400 condition
Other 20MnVB tempers and conditions
20MnVB is listed in 8 conditions; see the grade overview at 20MnVB.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Soft condition for cold forming, machining of blanks and prior to carburizing. | 360 | 580 | 24 | 180 HB | — |
Hot rolled | Cheapest mill delivery form for forging, hot upsetting or subsequent heat treatment. | 430 | 680 | 20 | 200 HB | — |
Normalized | Uniform fine-grained structure for machining and as a pre-treatment before carburizing or Q&T. | 470 | 720 | 19 | 215 HB | — |
Cold drawn | Bright bar with close tolerance for shafts and fastener blanks needing no further sizing. | 620 | 750 | 12 | 20 HRC | 8 % IACS |
Oil quench + 550–600 °C temper | Tough quenched-and-tempered condition for machined shafts and structural parts where impact matters. | 680 | 830 | 18 | 26 HRC | — |
QT400This page Oil quench + 400 °C temper | Medium-high strength with better ductility than low-temper for shafts and connecting parts. | 820 | 980 | 14 | 32 HRC | — |
Carburized and hardened | Primary gear condition: hard wear-resistant case (0.6–1.4 mm effective depth) over a tough 30–40 HRC core. | 900 | 1,150 | 10 | 60 HRC | — |
QT200Default 860 °C oil quench + 200 °C temper | Standard spec heat treatment giving maximum strength (Rm ≥1080 MPa) for highly loaded shafts and fasteners. | 950 | 1,150 | 12 | 38 HRC | — |
What is 20MnVB-QT400?
20MnVB-QT400 is 20MnVB heat treated to QT400 — medium-high strength with better ductility than low-temper for shafts and connecting parts. 20MnVB-QT400 has a yield strength of 820 MPa (119 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 87% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi). 20MnVB-QT400 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). QT200 is the default condition FabDigit quotes; QT400 is available on request or by drawing note.
Advantages
- High strength — 820 MPa (119 ksi), better than 87% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
20MnVB-QT400 properties
Typical room-temperature values for 20MnVB-QT400; 11 are specific to this condition. Other listed values are 20MnVB reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20MnVB-QT400 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).
Mechanical16
20MnVB-QT400 has a yield strength of 820 MPa (119 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 87% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20MnVB-QT400 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 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
20MnVB-QT400 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 20MnVB-QT400 takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 30%.
Manufacturability8
20MnVB-QT400's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20MnVB-QT400
Is 20MnVB easy to machine?
Machine in the annealed or normalized state (≤207 HB) with coated carbide; after carburizing or low-temper Q&T only grinding/hard turning is practical.
Can 20MnVB be welded?
Weldable with care (CE ≈0.4): preheat 150–250 °C, low-hydrogen consumables and post-weld temper; boron increases hardenability so HAZ cracking risk is real — avoid welding carburized parts.
Can 20MnVB be formed, bent or molded?
Hot forge 1150–1200 °C, finish above 850 °C, slow cool then normalize/anneal; cold heading of fasteners requires spheroidize-annealed wire.
What surface finishes work on 20MnVB?
No corrosion resistance as-machined — use phosphating + oil, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 1000 MPa); polishes well after hardening.
20MnVB 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 | 1.05 – 1.35 | 1.2 |
| Vgrain refiner / carbide former | 0.05 – 0.1 | 0.08 |
| Bhardenability booster; needs Ti/Al-fixed nitrogen | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Crresidual max | ≤ 0.3 | — |
| Niresidual max | ≤ 0.3 | — |
| Curesidual max | ≤ 0.25 | — |
| Fe | balance | — |
20MnVB-QT400 — frequently asked
What is 20MnVB-QT400 used for?
20MnVB-QT400 is typically used for automotive gears, shafts and gear rings. In short: low-cost boron gear steel; high hardenability, low alloy; poor weldability, hard case.
What is the yield strength of 20MnVB-QT400?
20MnVB-QT400 has a typical yield strength of 820 MPa (119 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 20MnVB-QT400 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed or normalized state (≤207 HB) with coated carbide; after carburizing or low-temper Q&T only grinding/hard turning is practical.
Can 20MnVB-QT400 be welded?
With care — weldability is rated fair (35/100). Weldable with care (CE ≈0.4): preheat 150–250 °C, low-hydrogen consumables and post-weld temper; boron increases hardenability so HAZ cracking risk is real — avoid welding carburized parts.
What surface finishes work on 20MnVB-QT400?
No corrosion resistance as-machined — use phosphating + oil, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 1000 MPa); polishes well after hardening.
Can 20MnVB-QT400 be formed, bent or molded?
Hot forge 1150–1200 °C, finish above 850 °C, slow cool then normalize/anneal; cold heading of fasteners requires spheroidize-annealed wire.
What is the maximum service temperature of 20MnVB-QT400?
20MnVB-QT400 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 20MnVB-QT200 and 20MnVB-A?
QT200 is the default condition — standard spec heat treatment giving maximum strength (Rm ≥1080 MPa) for highly loaded shafts and fasteners. A: soft condition for cold forming, machining of blanks and prior to carburizing. Yield strength is 950 MPa in QT200 versus 360 MPa in A.
Sources
- GB/T 3077 (Alloy structural steels) (2015)
- GB/T 699 / GB/T 702 bar dimensions and delivery conditions — SAC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. (machinability and heat-treatment data) — Industrial Press (2020)
- (20MnVB/20CrMnTi ) — Mysteel / 1688 (2025)
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.