Steel 18MnMo4-5 +A (Annealed)
Heat-treated state
EN 18MnMo4-5
Soft condition for heavy machining or cold work before the final NT/QT heat treatment.
Values for the +A condition
Other 18MnMo4-5 tempers and conditions
18MnMo4-5 is listed in 4 conditions; see the grade overview at 18MnMo4-5.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+AThis page Annealed | Soft condition for heavy machining or cold work before the final NT/QT heat treatment. | 300 | 520 | 26 | 155 HB | — |
Normalized | Normalized only — used for thinner bar/tube sections where tempering is not required by the order. | 390 | 620 | 20 | 190 HB | 7.8 % IACS |
+NTDefault Normalized and tempered | Standard delivery condition for EN 10222-2 / EN 10273 pressure forgings and bars up to moderate wall thickness. | 400 | 610 | 21 | 185 HB | — |
Quenched and tempered | Choose for heavy-wall forgings needing uniform through-thickness strength and better low-temperature toughness. | 470 | 660 | 19 | 20 HRC | — |
What is 18MnMo4-5 +A?
18MnMo4-5 +A is 18MnMo4-5 heat treated to +A — soft condition for heavy machining or cold work before the final NT/QT heat treatment. 18MnMo4-5 +A has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). 18MnMo4-5 +A 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). +NT is the default condition FabDigit quotes; +A is available on request or by drawing note.
Advantages
- Easy to machine — 62/100, better than 89% of steel grades
- High service temperature — 480°C (896 °F), better than 88% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
Limitations
- Low strength — 300 MPa (43.5 ksi), worse than 86% of steel grades
18MnMo4-5 +A properties
Typical room-temperature values for 18MnMo4-5 +A; 11 are specific to this condition. Other listed values are 18MnMo4-5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18MnMo4-5 +A 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).
Mechanical16
18MnMo4-5 +A has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18MnMo4-5 +A is rated for continuous service to 480°C (896 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
18MnMo4-5 +A 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 18MnMo4-5 +A takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
18MnMo4-5 +A's machinability is good (62/100, better than 89% of steel grades); weldability very good (70/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18MnMo4-5 +A
Is 18MnMo4-5 easy to machine?
Machines like a 0.2 %C low-alloy steel at ~180–210 HB; carbide inserts at 120–180 m/min, rigid setups, coolant to avoid built-up edge on the tough tempered structure.
Can 18MnMo4-5 be welded?
Weldable with matching 1Mn-0.5Mo consumables (SMAW/SAW/GTAW); preheat 150–250 °C for thick sections, control hydrogen, and apply PWHT ~620–680 °C as required by the pressure code.
Can 18MnMo4-5 be formed, bent or molded?
Forge/hot form at 1150–850 °C followed by normalizing or re-austenitizing; cold bending is limited — allow generous bend radii and re-heat-treat afterwards.
What surface finishes work on 18MnMo4-5?
No self-passivation: shot blast then prime/paint, aluminise or weld-overlay with stainless/Inconel for corrosive or wet service; phosphating suits temporary protection.
18MnMo4-5 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 |
|---|---|---|
| C18 in designation = 0.18 % C | 0.15 – 0.22 | 0.18 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.8 – 1.2 | 1 |
| P | ≤ 0.03 | — |
| S | ≤ 0.02 | — |
| Mo | 0.45 – 0.6 | 0.5 |
| Crresidual | ≤ 0.3 | 0.15 |
| Niresidual | ≤ 0.4 | 0.2 |
| Curesidual | ≤ 0.3 | — |
| Algrain refinement (total Al) | 0.02 – 0.06 | 0.03 |
| Fe | balance | — |
18MnMo4-5 +A — frequently asked
What is 18MnMo4-5 +A used for?
18MnMo4-5 +A is typically used for pressure vessels, boiler drums and piping. In short: higher strength than 16Mo3; elevated-temperature vessel steel; PWHT required after welding.
What is the yield strength of 18MnMo4-5 +A?
18MnMo4-5 +A has a typical yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is 18MnMo4-5 +A easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machines like a 0.2 %C low-alloy steel at ~180–210 HB; carbide inserts at 120–180 m/min, rigid setups, coolant to avoid built-up edge on the tough tempered structure.
Can 18MnMo4-5 +A be welded?
Yes — weldability is rated very good (70/100). Weldable with matching 1Mn-0.5Mo consumables (SMAW/SAW/GTAW); preheat 150–250 °C for thick sections, control hydrogen, and apply PWHT ~620–680 °C as required by the pressure code.
What surface finishes work on 18MnMo4-5 +A?
No self-passivation: shot blast then prime/paint, aluminise or weld-overlay with stainless/Inconel for corrosive or wet service; phosphating suits temporary protection.
Can 18MnMo4-5 +A be formed, bent or molded?
Forge/hot form at 1150–850 °C followed by normalizing or re-austenitizing; cold bending is limited — allow generous bend radii and re-heat-treat afterwards.
What is the maximum service temperature of 18MnMo4-5 +A?
18MnMo4-5 +A is rated for continuous use to about 480°C (896 °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 elevated temperature properties — CEN (2017)
- EN 10273 — Hot rolled weldable steel bars for pressure purposes with specified elevated temperature properties — CEN (2016)
- EN 10028-2 — Flat products for pressure purposes: weldable fine grain / elevated temperature steels — CEN (2017)
- ASTM A204/A204M — Pressure Vessel Plates, Alloy Steel, Molybdenum — ASTM International (2019)
- 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)
- EN 13445-3 Annex O — Physical properties of steels — CEN (2021)
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.