16Mo3
EN 10028-2 · 1.5415
16Mo3 is a pressure-vessel steel (Alloy High-Temp family) to EN 10028-2 (1.5415). It has a specified 0.2 % proof stress of 275 MPa and a typical tensile strength of about 450 MPa, with a uniform elongation of 22 %. Nominal carbon content is around 0.20 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 808 MPa above it. It is a general-purpose wrought steel selected on strength, cost and availability.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 22.0% · conservative analysis limit ½εu = 11.0%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitygood
Weldable with low-hydrogen consumables; preheat for thicker sections and post-weld heat treatment (PWHT) to temper the molybdenum-bearing HAZ is normal practice.
Formabilitymoderate
Formed like a normalised low-alloy plate — shells, ends and pipe bends.
Machinabilitymoderate
Machines much like a plain C-Mn plate.
Corrosion resistancepoor
None inherent — protect and allow for corrosion per the code.
Hardenabilitylow
Supplied normalised; strengthening is by composition and grain size, not quench-hardening.
Toughnessgood
Good notch toughness; the real feature is retained strength (creep resistance) at temperature.
Expert notes
16Mo3 is where the pressure-vessel range steps up from “strong when cold” to “strong when hot”. The ~0.3 % molybdenum keeps meaningful strength — creep resistance — in the 450–500 °C band where plain C-Mn plate like P355GH begins to sag under long-term load. It is the default for superheater tubes, steam headers and hot process vessels in that window.
Because the molybdenum hardens the weld HAZ, weld it with low-hydrogen consumables, preheat the thicker sections, and PWHT to temper the joint — skipping the PWHT is a classic in-service cracking cause.
There is a historical caution with plain-Mo steels: prolonged exposure at high temperature can cause graphitisation (carbides breaking down to graphite, embrittling the steel). It is the reason the chromium-molybdenum grades (13CrMo4-5, 10CrMo9-10) largely superseded plain-Mo for the hottest duty — above ~530–550 °C, move to Cr-Mo.
For design, use the code’s elevated-temperature proof and creep-rupture allowables at your metal temperature, not the room-temperature numbers.
Mechanical properties
| Condition | Section | Yield (MPa) |
|---|---|---|
| 16Mo3 · normalised | t ≤ 16 mm | 275 |
| 16 < t ≤ 40 mm | 270 | |
| 40 < t ≤ 60 mm | 260 | |
| 60 < t ≤ 100 mm | 240 |
UTS 440–590 MPa · Impact ≥ 31 J (killed, fine grain) · Hardness ~150 HB
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 81 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.5 | ×10⁻⁶/°C |
| Thermal conductivity | 42 | W/(m·K) |
| Specific heat | 460 | J/(kg·K) |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| ASTM | A204 Gr. A/B (plate) | |
| ASTM | A335 P1 (tube) | |
| DIN 17155 | 15Mo3 | |
| EN 10028-2 | 1.5415 |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| DIN 17155 | 15Mo3 | The long-standing German Mo boiler steel — still a common name. |
Common applications
- Superheated-steam pipework and headers
- Boilers and pressure vessels operating ~450–500 °C
- Refinery and petrochemical hot process plant
- Heat-exchanger and reactor components
History
Adding ~0.3 % molybdenum to boiler steel raises its creep strength at temperature; 16Mo3 (formerly 15Mo3) has been the entry-level creep-resisting grade for decades.
- 1950Mo-alloyed boiler steels (15Mo3) adopted for higher-temperature service
- 1992EN 10028 harmonises the grade as 16Mo3 (1.5415)