Steel 20Mn5 +QT (Quenched and tempered)
Heat-treated state
EN 20Mn5
Choose for thicker sections or when higher proof stress and the best low-temperature Charpy values (e.g. −46 °C service) are required.
Values for the +QT condition
Other 20Mn5 tempers and conditions
20Mn5 is listed in 4 conditions; see the grade overview at 20Mn5.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition, used for heavy machining or cold working of forging blanks before final heat treatment. | 260 | 460 | 30 | 135 HB | — |
Normalized | Standard low-cost delivery condition for pressure forgings up to moderate wall thickness; uniform fine ferrite-pearlite structure. | 310 | 520 | 25 | 152 HB | — |
+NTDefault Normalized and tempered | Most commonly stocked pressure-forging condition (flanges, fittings, A350 LF2 equivalent): normalizing plus a tempering/stress-relief cycle for stable properties and good low-temperature toughness. | 320 | 530 | 25 | 155 HB | — |
+QTThis page Quenched and tempered | Choose for thicker sections or when higher proof stress and the best low-temperature Charpy values (e.g. −46 °C service) are required. | 370 | 570 | 24 | 12 HRC | — |
What is 20Mn5 +QT?
20Mn5 +QT is 20Mn5 heat treated to +QT — choose for thicker sections or when higher proof stress and the best low-temperature Charpy values (e.g. −46 °C service) are required. 20Mn5 +QT has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi). 20Mn5 +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). +NT is the default condition FabDigit quotes; +QT is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 135 MPa·√m (122.9 ksi·√in), better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- Readily welded — 75/100, better than 76% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
20Mn5 +QT properties
Typical room-temperature values for 20Mn5 +QT; 19 are specific to this condition. Other listed values are 20Mn5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20Mn5 +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).
Mechanical16
20Mn5 +QT has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20Mn5 +QT is rated for continuous service to 400°C (752 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
20Mn5 +QT conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 20Mn5 +QT takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
20Mn5 +QT's machinability is good (56/100, better than 71% of steel grades); weldability very good (75/100); formability fair (52/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Mn5 +QT
Is 20Mn5 easy to machine?
Machines like a normalized 1021/1330-class steel — use carbide at 120–180 m/min with generous feed; the gummy ferrite-pearlite structure needs sharp tooling and chip breakers to avoid built-up edge.
Can 20Mn5 be welded?
Readily weldable by SMAW/GMAW/SAW with matching low-hydrogen consumables; CEV ≈ 0.45 so preheat 100–150 °C for sections above ~30 mm, and PWHT 580–620 °C is usual for pressure-code work.
Can 20Mn5 be formed, bent or molded?
Designed for hot forging at 1100–1250 °C with finishing above 850 °C, followed by normalizing; cold bending is limited by the ~25 % elongation and should use generous radii.
What surface finishes work on 20Mn5?
No native corrosion protection — specify shot blast plus epoxy/zinc primer, hot-dip galvanizing or PTFE/rubber lining; phosphating suits bolted and threaded features.
20Mn5 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 |
|---|---|---|
| CEN 10222-2 heat analysis | 0.17 – 0.23 | 0.2 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 1 – 1.5 | 1.25 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.02 | 0.01 |
| CrCr+Cu+Mo+Ni total ≤ 0.80 | ≤ 0.3 | 0.1 |
| Cu | ≤ 0.3 | 0.1 |
| Mo | ≤ 0.08 | 0.03 |
| Ni | ≤ 0.3 | 0.1 |
| Nb | ≤ 0.01 | 0.01 |
| V | ≤ 0.02 | 0.01 |
| AlAl total, grain refinement | ≥ 0.02 | 0.03 |
| Fe | balance | — |
20Mn5 +QT — frequently asked
What is 20Mn5 +QT used for?
20Mn5 +QT is typically used for flanges, valve bodies, pressure vessel forgings and pipe fittings. In short: pressure-purpose forging grade; A350 Gr. LF2 equivalent; weldable to pressure codes.
What is the yield strength of 20Mn5 +QT?
20Mn5 +QT has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 570 MPa (82.7 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is 20Mn5 +QT easy to machine?
Reasonably — machinability is rated good (56/100, better than 71% of steel grades). Machines like a normalized 1021/1330-class steel — use carbide at 120–180 m/min with generous feed; the gummy ferrite-pearlite structure needs sharp tooling and chip breakers to avoid built-up edge.
Can 20Mn5 +QT be welded?
Yes — weldability is rated very good (75/100). Readily weldable by SMAW/GMAW/SAW with matching low-hydrogen consumables; CEV ≈ 0.45 so preheat 100–150 °C for sections above ~30 mm, and PWHT 580–620 °C is usual for pressure-code work.
What surface finishes work on 20Mn5 +QT?
No native corrosion protection — specify shot blast plus epoxy/zinc primer, hot-dip galvanizing or PTFE/rubber lining; phosphating suits bolted and threaded features.
Can 20Mn5 +QT be formed, bent or molded?
Designed for hot forging at 1100–1250 °C with finishing above 850 °C, followed by normalizing; cold bending is limited by the ~25 % elongation and should use generous radii.
What is the maximum service temperature of 20Mn5 +QT?
20Mn5 +QT is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10222-2 — Steel forgings for pressure purposes, ferritic and martensitic steels with specified elevated temperature properties — CEN (2017)
- ASTM A350/A350M — Carbon and Low-Alloy Steel Forgings for Piping Components with Notch Toughness Testing — ASTM International (2023)
- EN 10027 / Stahlschlüssel material 1.1133 designation data — Verlag Stahlschlüssel (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, machinability ratings for carbon steels — 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.