Steel 20CrMnMo QT-HT
Hardness band
GB 20CrMnMo
QT-HT = q&T high temper
Tough, machinable condition for shafts, connecting parts and pre-treatment of large forgings before finish machining and nitriding.
Values for the QT-HT condition
Other 20CrMnMo tempers and conditions
20CrMnMo is listed in 8 conditions; see the grade overview at 20CrMnMo.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Isothermal Annealed | Preferred pre-carburizing treatment for gear steel: uniform ferrite–pearlite banding-free structure giving stable hobbing/shaving and low distortion. | 400 | 630 | 21 | 11 HRC | 8 % IACS |
ADefault Solution annealed | Standard delivery condition for gear-blank bar and forgings — softest, most uniform structure for rough machining before carburizing. | 420 | 650 | 20 | 197 HB | — |
Hot rolled | Cheapest mill-supplied condition for parts that will be fully re-heat-treated; hardness scatter is high and machining is uneven. | 500 | 780 | 16 | 19 HRC | 7.8 % IACS |
Normalized | Grain refinement and structure homogenisation after forging; harder than annealed but more consistent for medium-size parts. | 550 | 820 | 15 | 22 HRC | 7.8 % IACS |
Cold drawn | Bright, close-tolerance bar for small shafts and pins machined without further sizing; residual stress can cause bow after machining. | 650 | 820 | 10 | 24 HRC | 7.8 % IACS |
QT-HTThis page Q&T high temper | Tough, machinable condition for shafts, connecting parts and pre-treatment of large forgings before finish machining and nitriding. | 800 | 980 | 15 | 31 HRC | — |
Carburized and hardened | The service condition for gears: hard wear-resistant case (0.6–2.0 mm typical) over a strong 30–45 HRC core, giving high bending and contact fatigue life. | 900 | 1,150 | 11 | 60 HRC | — |
Q&T | The standard test-blank condition defining the grade's strength class (≥1180 MPa); used for through-hardened shafts and highly loaded non-carburized parts. | 950 | 1,230 | 11 | 40 HRC | — |
What is 20CrMnMo QT-HT?
20CrMnMo QT-HT is 20CrMnMo heat treated to QT-HT — tough, machinable condition for shafts, connecting parts and pre-treatment of large forgings before finish machining and nitriding. 20CrMnMo QT-HT has a yield strength of 800 MPa (116 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi). 20CrMnMo QT-HT 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-HT is available on request or by drawing note.
Advantages
- High strength — 800 MPa (116 ksi), better than 86% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Difficult to machine — 40/100, worse than 77% of steel grades
20CrMnMo QT-HT properties
Typical room-temperature values for 20CrMnMo QT-HT; 12 are specific to this condition. Other listed values are 20CrMnMo reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20CrMnMo QT-HT 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).
Mechanical14
20CrMnMo QT-HT has a yield strength of 800 MPa (116 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20CrMnMo QT-HT is rated for continuous service to 450°C (842 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
20CrMnMo QT-HT 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 20CrMnMo QT-HT takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
20CrMnMo QT-HT's machinability is fair (40/100, worse than 77% of steel grades); weldability fair (35/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20CrMnMo QT-HT
Is 20CrMnMo easy to machine?
Rough machine in the annealed/isothermally annealed state (≤217 HB) with coated carbide; after carburizing and hardening only grinding or CBN hard-turning is practical.
Can 20CrMnMo be welded?
Poor weldability — carbon equivalent ~0.8; use low-hydrogen consumables with 200–300 °C preheat, interpass control and immediate stress-relief, and never weld carburized surfaces.
Can 20CrMnMo be formed, bent or molded?
Excellent hot forgeability at 1150–850 °C (gear blanks, ring rolling); cold forming limited to light coining or straightening after anneal.
What surface finishes work on 20CrMnMo?
Shot peening after case hardening markedly raises bending fatigue; protect with phosphating + oil, black oxide, zinc or manganese phosphate — the steel has no inherent corrosion resistance.
20CrMnMo 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 |
|---|---|---|
| CGB/T 3077-2015 | 0.17 – 0.23 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.9 – 1.2 | 1.05 |
| Cr | 1.1 – 1.4 | 1.25 |
| Mo | 0.2 – 0.3 | 0.25 |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.25 | — |
| P≤0.025 for high-grade quality steel | ≤ 0.03 | — |
| S≤0.025 for high-grade quality steel | ≤ 0.03 | — |
| Fe | balance | — |
20CrMnMo QT-HT — frequently asked
What is 20CrMnMo QT-HT used for?
20CrMnMo QT-HT is typically used for gears, shafts and gearbox parts. In short: mo-boosted hardenability; heavy-gear carburizing grade; poorest weldability in family.
What is the yield strength of 20CrMnMo QT-HT?
20CrMnMo QT-HT has a typical yield strength of 800 MPa (116 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 20CrMnMo QT-HT easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Rough machine in the annealed/isothermally annealed state (≤217 HB) with coated carbide; after carburizing and hardening only grinding or CBN hard-turning is practical.
Can 20CrMnMo QT-HT be welded?
With care — weldability is rated fair (35/100). Poor weldability — carbon equivalent ~0.8; use low-hydrogen consumables with 200–300 °C preheat, interpass control and immediate stress-relief, and never weld carburized surfaces.
What surface finishes work on 20CrMnMo QT-HT?
Shot peening after case hardening markedly raises bending fatigue; protect with phosphating + oil, black oxide, zinc or manganese phosphate — the steel has no inherent corrosion resistance.
Can 20CrMnMo QT-HT be formed, bent or molded?
Excellent hot forgeability at 1150–850 °C (gear blanks, ring rolling); cold forming limited to light coining or straightening after anneal.
What is the maximum service temperature of 20CrMnMo QT-HT?
20CrMnMo QT-HT is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20CrMnMo-A and 20CrMnMo-QT200?
A is the default condition — standard delivery condition for gear-blank bar and forgings — softest, most uniform structure for rough machining before carburizing. QT200: the standard test-blank condition defining the grade's strength class (≥1180 MPa); used for through-hardened shafts and highly loaded non-carburized parts. Yield strength is 420 MPa in A versus 950 MPa in QT200.
Sources
- JIS G 4053 (SCM420H) Low-alloyed structural steels — JSA (2016)
- SAE J404 Chemical Compositions of SAE Alloy Steels (4118/8622 comparison) — SAE International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
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.