Steel 18MnMoNi5-5 QT+SPWHT
Heat-treated state
EN 18MnMoNi5-5
QT+SPWHT = qT + simulated post-weld heat treatment
Test condition/delivery for plate that will see long PWHT soaks; slight strength loss, used for design allowables of welded thick shells.
Values for the QT+SPWHT condition
Other 18MnMoNi5-5 tempers and conditions
18MnMoNi5-5 is listed in 5 conditions; see the grade overview at 18MnMoNi5-5.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest supply state for deep machining or subsequent hot work; requires re-heat-treatment to reach code properties. | 320 | 520 | 26 | 160 HB | 8 % IACS |
Normalized and tempered | Alternative for sections where full quench is impractical; lower strength and toughness than QT, sometimes used for tube/pipe and smaller forgings. | 400 | 570 | 23 | 175 HB | 7.9 % IACS |
Normalized | Intermediate mill condition for plate/forging stock before final QT; not a normal service condition. | 430 | 640 | 20 | 14 HRC | 7.8 % IACS |
QT+SPWHTThis page QT + simulated post-weld heat treatment | Test condition/delivery for plate that will see long PWHT soaks; slight strength loss, used for design allowables of welded thick shells. | 440 | 590 | 23 | 185 HB | 7.8 % IACS |
QTDefault Quenched and tempered | Standard EN 10028-2 delivery condition for heavy pressure-vessel plate and forgings; best strength/toughness balance. | 470 | 620 | 22 | 195 HB | — |
What is 18MnMoNi5-5 QT+SPWHT?
18MnMoNi5-5 QT+SPWHT is 18MnMoNi5-5 heat treated to QT+SPWHT — test condition/delivery for plate that will see long PWHT soaks; slight strength loss, used for design allowables of welded thick shells. 18MnMoNi5-5 QT+SPWHT has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 50% of steel grades. Elongation at break is 23% and the elastic modulus is 206 GPa (29.9 Msi). 18MnMoNi5-5 QT+SPWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F). QT is the default condition FabDigit quotes; QT+SPWHT is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 190 MPa·√m (172.9 ksi·√in), better than 99% of steel grades
18MnMoNi5-5 QT+SPWHT properties
Typical room-temperature values for 18MnMoNi5-5 QT+SPWHT; 22 are specific to this condition. Other listed values are 18MnMoNi5-5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18MnMoNi5-5 QT+SPWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F).
Mechanical15
18MnMoNi5-5 QT+SPWHT has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 50% of steel grades. Elongation at break is 23% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
18MnMoNi5-5 QT+SPWHT is rated for continuous service to 400°C (752 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical2
18MnMoNi5-5 QT+SPWHT has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 18MnMoNi5-5 QT+SPWHT takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 20%.
Manufacturability7
18MnMoNi5-5 QT+SPWHT's machinability is good (58/100, better than 75% of steel grades); weldability good (65/100); formability fair (48/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18MnMoNi5-5 QT+SPWHT
Is 18MnMoNi5-5 easy to machine?
Machines like Q&T 4130/A508 at ~190 HB — carbide tooling, rigid setups, moderate speeds with flood coolant; stress-relieve before final passes on thick shells.
Can 18MnMoNi5-5 be welded?
Weldable by SAW/SMAW/GTAW with matching Mn-Mo-Ni consumables; preheat 150–200 °C, control hydrogen, and PWHT 600–620 °C to restore HAZ toughness.
Can 18MnMoNi5-5 be formed, bent or molded?
Hot-form or hot-roll heavy shells at 900–1150 °C then re-quench and temper; cold forming limited by high yield strength and section thickness.
What surface finishes work on 18MnMoNi5-5?
Not anodizable — protect by shot blasting plus epoxy paint, or clad the process side with 308L/309L stainless weld overlay for corrosive service.
18MnMoNi5-5 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 |
|---|---|---|
| Cheat analysis | 0.15 – 0.21 | 0.18 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 1.15 – 1.5 | 1.35 |
| Prestricted to limit temper/irradiation embrittlement | ≤ 0.01 | 0.01 |
| S | ≤ 0.01 | 0 |
| Ni | 0.5 – 0.8 | 0.65 |
| Mo | 0.4 – 0.6 | 0.5 |
| Crresidual | ≤ 0.2 | 0.1 |
| Curesidual; low Cu for irradiation resistance | ≤ 0.12 | 0.06 |
| Vresidual | ≤ 0.02 | 0.01 |
| Altotal Al, grain refining | ≤ 0.04 | 0.03 |
| N | ≤ 0.01 | 0.01 |
| Fe | balance | — |
18MnMoNi5-5 QT+SPWHT — frequently asked
What is 18MnMoNi5-5 QT+SPWHT used for?
18MnMoNi5-5 QT+SPWHT is typically used for nuclear/chemical reactor vessels, heavy-wall pressure vessels and power plant boiler components. In short: heavy-section reactor steel; 470 MPa yield class; thick-wall toughness.
What is the yield strength of 18MnMoNi5-5 QT+SPWHT?
18MnMoNi5-5 QT+SPWHT has a typical yield strength of 440 MPa (63.8 ksi) and a tensile strength of 590 MPa (85.6 ksi) — stronger than 50% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 18MnMoNi5-5 QT+SPWHT easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like Q&T 4130/A508 at ~190 HB — carbide tooling, rigid setups, moderate speeds with flood coolant; stress-relieve before final passes on thick shells.
Can 18MnMoNi5-5 QT+SPWHT be welded?
Yes — weldability is rated good (65/100). Weldable by SAW/SMAW/GTAW with matching Mn-Mo-Ni consumables; preheat 150–200 °C, control hydrogen, and PWHT 600–620 °C to restore HAZ toughness.
What surface finishes work on 18MnMoNi5-5 QT+SPWHT?
Not anodizable — protect by shot blasting plus epoxy paint, or clad the process side with 308L/309L stainless weld overlay for corrosive service.
Can 18MnMoNi5-5 QT+SPWHT be formed, bent or molded?
Hot-form or hot-roll heavy shells at 900–1150 °C then re-quench and temper; cold forming limited by high yield strength and section thickness.
What is the maximum service temperature of 18MnMoNi5-5 QT+SPWHT?
18MnMoNi5-5 QT+SPWHT 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.
What is the difference between 18MnMoNi5-5-QT and 18MnMoNi5-5-A?
QT is the default condition — standard EN 10028-2 delivery condition for heavy pressure-vessel plate and forgings; best strength/toughness balance. A: softest supply state for deep machining or subsequent hot work; requires re-heat-treatment to reach code properties. Yield strength is 470 MPa in QT versus 320 MPa in A.
Sources
- EN 10028-2 — Flat products of steels for pressure purposes, Part 2: Alloy steels with specified elevated temperature properties — CEN (2017)
- ASME BPVC Section II, Part D — Properties (Metric) — ASME (2023)
- ASTM A533/A533M — Pressure Vessel Plates, Alloy Steel, Quenched and Tempered, Mn-Mo and Mn-Mo-Ni — ASTM (2022)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 19 — Fatigue and Fracture — ASM International (1996)
- Heavy pressure-vessel plate / forging datasheets for 1.6308 (18MnMoNi5-5) — Dillinger / JSW / Böhler (2022)
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.