16Mo3
1.5415
Molybdenum-alloyed ferritic steel for pressure purposes with specified elevated-temperature properties · EN 10028-2:2017 — flat products for pressure purposes · EN 10216-2:2024 — seamless pressure tubes · EN 10217-2:2019 and EN 10217-5:2019 — welded pressure tubes · EN 10222-2:2017+A1:2021 — pressure-purpose forgings · EN 10273:2016 — hot-rolled pressure-purpose bars · EN 10253-2:2021 — butt-welding fittings
16Mo3 is a weldable, approximately 0.3% molybdenum ferritic pressure-equipment steel used where carbon steels no longer provide sufficient strength or creep resistance at elevated temperature. Its requirements are product-standard, dimension and condition dependent: EN 10028-2 defines flat products, while tubes, forgings, bars and fittings must be ordered to their own standards and must not be assumed to share the plate property table.
- Mo 0.25–0.35%Principal alloying addition · Molybdenum improves elevated-temperature strength and creep resistance relative to ordinary carbon pressure steels.
- +N is usualPlate delivery condition · Normalizing rolling may replace normalizing; +NT or untreated supply is possible only under the provisions of EN 10028-2.
- ReH ≥275 MPa; Rm 440–590 MPa at t ≤16 mmRoom-temperature plate strength · Both yield and tensile requirements decrease in specified steps as plate thickness increases.
- Rp0.2 ≥141 MPa at 500°C for plate t ≤16 mmElevated-temperature proof strength · This is a material-standard minimum, not a design allowable stress.
- KV2 ≥31 J at +20°CStandard plate toughness · For 16Mo3 plate, values at 0°C and −20°C are not automatic requirements and must be agreed when needed.
- Reference data, not guaranteed propertiesCreep data status · EN 10028-2 Annex C gives mean creep and rupture values with stated scatter; the applicable pressure design code governs allowable stress and service assessment.
Overview
- Designation system
- EN steel name according to EN 10027-1; steel number according to EN 10027-2
- Product forms
- Plate, sheet and strip, Seamless tube and pipe, Electric-welded and submerged-arc-welded tube, Forgings, Hot-rolled bars, Butt-welding fittings
- Condition
- Normalized (+N), Normalized and tempered (+NT), permitted for some flat products at the manufacturer's discretion, Normalizing rolled where permitted by the governing product standard, Untreated only by agreement, with properties verified on appropriately heat-treated test pieces
- Density
- 7.85 g/cm³ (Representative room-temperature value; not a grade acceptance requirement.)
What the designation covers
16Mo3 is an alloy special steel whose name is based on chemical composition rather than minimum yield strength. The leading number indicates an approximate carbon level of 0.16%, while Mo identifies the intentional molybdenum addition. The combination of moderate carbon and approximately 0.3% Mo produces a normalized ferrite-pearlite structure with better elevated-temperature strength and creep behaviour than common P…GH carbon-manganese pressure steels.
| Product form | Relevant specification | Practical consequence |
|---|---|---|
| Plate, sheet and strip | EN 10028-2:2017 together with EN 10028-1 | Plate chemistry, transverse mechanical properties, delivery condition and options are defined here. |
| Seamless tube | EN 10216-2:2024 | Tube properties depend on wall thickness, test category, orientation, manufacture and heat treatment; plate values do not apply. |
| Electric-welded tube | EN 10217-2:2019 | Includes requirements specific to the tube body and longitudinal weld. |
| Submerged-arc-welded tube | EN 10217-5:2019 | Includes manufacturing-route, weld and inspection requirements not covered by the plate standard. |
| Forgings | EN 10222-2:2017+A1:2021 | Mechanical properties and testing depend on the forging standard, ruling section and heat treatment. |
| Hot-rolled bar | EN 10273:2016 | Used for pressure-purpose components such as machined parts and some flange applications; bar requirements apply. |
| Butt-welding fittings | EN 10253-2:2021 | Component manufacture, geometry, heat treatment and testing are controlled by the fitting standard. |
A purchase order stating only “16Mo3” is incomplete. It should identify the product standard, dimensions, delivery condition, inspection document, required options and the applicable equipment or piping code.
Composition and metallurgical significance
| Element | Requirement, mass % | Significance |
|---|---|---|
| C | 0.12–0.20 | Balances strength, heat-treatment response, formability and weldability. |
| Si | ≤0.35 | Deoxidizing residual; excessive silicon is restricted. |
| Mn | 0.40–0.90 | Contributes to strength and hardenability. |
| P | ≤0.025 | Restricted for toughness and fabrication quality. |
| S | ≤0.010 | Low maximum supports toughness and weld quality. |
| N | ≤0.012 | Controlled interstitial content. |
| Cr | ≤0.30 | Residual limit rather than a defining chromium addition. |
| Cu | ≤0.30 | A lower Cu limit or a Cu-plus-Sn restriction can be agreed where hot formability is important. |
| Mo | 0.25–0.35 | Defining alloy addition for elevated-temperature and creep performance. |
| Ni | ≤0.30 | Residual limit. |
| Al | Report cast value | The aluminium content must be determined and stated in the inspection document; EN 10028-2 does not give a normal composition range for this grade. |
The standard limits are cast-analysis requirements. Product analysis is subject to separate permissible deviations and should not be compared directly with cast limits without applying those tolerances. EN 10028-2 does not specify a general maximum carbon-equivalent requirement for 16Mo3 plate; weldability assessment must therefore use the actual certified composition, product thickness, restraint, heat input and applicable fabrication standard.
Delivery condition and heat treatment
For EN 10028-2 flat products, the usual condition is normalized (+N). Normalizing rolling may replace furnace normalizing at the manufacturer's discretion. Additional testing after simulated normalizing can be agreed when the purchaser needs confirmation that the properties will survive a later normalizing operation. The grade may also be supplied normalized and tempered (+NT) at the manufacturer's discretion.
| Operation | Guidance | Important qualification |
|---|---|---|
| Normalizing | 890–950°C | After the temperature has been attained throughout the cross-section, further holding is generally unnecessary and should be avoided. |
| Tempering after normalizing | 590–650°C in certain cases | Not the routine delivery treatment for every product; use only under an approved manufacturing or fabrication procedure. |
| Untreated delivery | Possible by agreement | Testing is performed on test pieces in the usual heat-treated condition, so as-delivered properties must not be inferred from the certificate without checking the stated delivery condition. |
| Post-fabrication heat treatment | Controlled by the fabrication and pressure-equipment code | The accumulated time-temperature exposure can reduce strength; all intended heat-treatment cycles should be communicated to the material producer. |
EN 10028-2 plate properties at room temperature
| Nominal thickness t, mm | Minimum ReH, MPa | Rm, MPa | Minimum elongation A, % |
|---|---|---|---|
| ≤16 | 275 | 440–590 | 22 |
| >16 to 40 | 270 | 440–590 | 22 |
| >40 to 60 | 260 | 440–590 | 22 |
| >60 to 100 | 240 | 430–580 | 22 |
| >100 to 150 | 220 | 420–570 | 22 |
| >150 to 250 | 210 | 410–570 | 22 |
| Test temperature | Minimum average KV2 | Status |
|---|---|---|
| +20°C | 31 J | Standard requirement; 40 J may be agreed at enquiry and order. |
| 0°C | By agreement | No automatic value for 16Mo3. |
| −20°C | By agreement | No automatic value for 16Mo3. |
The tabulated EN 10028-2 properties apply to transverse test pieces. Impact-test location, specimen size and any requirement for mid-thickness specimens must be specified and assessed in accordance with the standard and the governing construction code.
Elevated-temperature behaviour
| 0.2% proof strength (MPa) | 50°C | 100°C | 150°C | 200°C | 250°C | 300°C | 350°C | 400°C | 450°C | 500°C |
|---|---|---|---|---|---|---|---|---|---|---|
| Minimum Rp0.2 for EN 10028-2 plate with t ≤16 mm | 273 | 264 | 250 | 233 | 213 | 194 | 175 | 159 | 147 | 141 |
Specified minimum material properties; not allowable design stresses.
| Nominal thickness t, mm | Rp0.2 at 400°C, MPa min. | Rp0.2 at 450°C, MPa min. | Rp0.2 at 500°C, MPa min. |
|---|---|---|---|
| ≤16 | 159 | 147 | 141 |
| >16 to 40 | 156 | 145 | 139 |
| >40 to 60 | 150 | 139 | 134 |
| >60 to 100 | 139 | 129 | 123 |
| >100 to 150 | 127 | 118 | 113 |
| >150 to 250 | 121 | 113 | 108 |
The elevated-temperature proof-strength table explains the grade's value in boilers, pressure vessels, heat exchangers and pressure piping: it retains specified strength through 500°C under EN 10028-2. It does not establish a universal maximum service temperature. Design temperature is controlled by the construction code, design life, allowable stress, creep regime, oxidation or corrosion environment, weldments, cyclic loading and the actual product specification.
| Temperature | 1% creep strain, 10,000 h | 1% creep strain, 100,000 h | Rupture, 10,000 h | Rupture, 100,000 h | Rupture, 200,000 h |
|---|---|---|---|---|---|
| 450°C | 216 MPa | 167 MPa | 298 MPa | 239 MPa | 217 MPa |
| 500°C | 132 MPa | 73 MPa | 171 MPa | 101 MPa | 84 MPa |
| 530°C | 84 MPa | 36 MPa | 102 MPa | 53 MPa | 45 MPa |
Informative mean values derived with an indicated scatter band of approximately ±20%. They are not guaranteed acceptance properties and do not authorize continuous service at the listed temperatures.
Welding, forming and fabrication
16Mo3 is generally weldable by established fusion-welding processes, but it must not be treated as an ordinary structural carbon steel. The molybdenum addition and possible upper-range carbon content increase hardenability. Welding procedure qualification should address actual heat chemistry, combined thickness, restraint, heat input, hydrogen level, preheat, interpass control and any required post-weld heat treatment. EN 10028-2 refers welding practice to EN 1011-1 and EN 1011-2.
| Issue | Practical requirement |
|---|---|
| Filler selection | Use a consumable qualified for the required weld-metal chemistry, room-temperature strength, toughness and elevated-temperature or creep duty. A generic carbon-steel filler should not be assumed acceptable. |
| Hydrogen cracking | Apply low-hydrogen consumables and controlled storage, joint cleanliness and thermal practice appropriate to thickness and restraint. |
| PWHT | Determine from the governing construction code and qualified procedure. Account for every fabrication, repair and shop heat-treatment cycle in the accumulated thermal exposure. |
| Hot forming | Control finishing temperature and resulting condition. If forming changes or replaces normalizing, demonstrate the required final properties. |
| Cold forming | Consider strain ageing, local thinning and the code requirement for subsequent heat treatment or property verification. |
| Dissimilar joints | Base filler selection and heat treatment on both materials, service temperature, carbon migration, creep compatibility and the applicable design code. |
| Machining and cutting | Conventional methods are applicable, but flame-cut or heavily restrained edges should receive suitable thermal and quality control before welding. |
Service limitations and supplementary testing
16Mo3 is not a stainless or inherently corrosion-resistant steel. General corrosion, high-temperature oxidation, sulfidation, erosion-corrosion and process-specific degradation must be evaluated independently. Its molybdenum content improves elevated-temperature mechanical performance but does not by itself establish suitability for a corrosive process environment.
| Condition | What must be addressed |
|---|---|
| Sour H2S service | EN 10028-2 permits HIC testing to be specified at enquiry and order. Select the test solution, acceptance class and any additional hardness or SSC requirements required by the project specification. |
| Pressurized hydrogen or high-temperature hydrogen | Assess the material against the applicable hydrogen-service rules and operating envelope; designation 16Mo3 alone is not an approval for hydrogen service. |
| Low-temperature operation | Standard plate toughness is specified only at +20°C. Required minimum metal temperature and impact test temperature must be established by the construction code. |
| Long-term creep service | Use code-approved allowable stresses and weld-joint rules. Annex C creep data are informative and should not be inserted directly into a design calculation. |
| Multiple PWHT or repair cycles | Advise the steelmaker of the intended time-temperature exposure and consider simulated heat-treatment testing where the EN 10028-2 Pcrit threshold will be exceeded. |
| CrMo embrittlement concerns | Where relevant to the operating environment and alloy system, specify any required step-cooling or other embrittlement assessment rather than assuming it is included. |
Ordering and certification
| Item | What to state or verify |
|---|---|
| Product specification | The exact product standard and edition, not only 16Mo3 or 1.5415. |
| Dimensions and tolerances | Thickness or wall, diameter, width, length, dimensional standard and any restricted tolerance. |
| Delivery condition | For example +N, including whether normalizing rolling is acceptable and whether simulated heat-treatment testing is required. |
| Inspection document | Normally an EN 10204 document appropriate to the equipment code and purchaser requirements, commonly type 3.1 where specified. |
| Mechanical tests | Required test temperature, orientation, specimen location, impact energy and elevated-temperature tensile tests. |
| Nondestructive examination | Method, extent, acceptance level and whether it applies to parent material, welds or the finished component. |
| Supplementary service tests | HIC, step cooling, hardness, simulated PWHT or other project-specific tests. |
| Fabrication history | Intended forming, normalizing, stress relief and the number and duration of anticipated PWHT cycles. |
| Regulatory requirements | Applicable pressure-equipment legislation, construction code, material approval route, marking and certification. |
Check the certificate against the product standard actually ordered. A certificate showing 16Mo3 chemistry does not demonstrate compliance with a different product specification, delivery condition or construction code.
Substitution and cross-standard comparisons
Cross-reference tables frequently associate 16Mo3 with carbon-molybdenum ASTM or ASME materials. These comparisons are useful for identifying a similar application class, but they do not establish equivalence. The ASTM/ASME materials commonly compared with 16Mo3 can have higher molybdenum, different carbon limits, different thickness rules, different heat-treatment requirements and different mechanical-property or inspection bases.
A substitution review should compare the complete product specifications, dimensions, manufacturing route, chemistry, heat treatment, room- and elevated-temperature properties, toughness, creep data, weldability, certification and acceptance under the governing construction code.
Sources
- BS EN 10028-2:2017 — Flat products made of steels for pressure purposes, Part 2British Standards Institution
- DIN EN 10028-2:2017-10DIN Media
- EN 10028-2:2017 standard previewSlovenian Institute for Standardization / iTeh
- DIN EN 10216-2:2025-02 / EN 10216-2:2024DIN Media
- EN 10217-2:2019iTeh Standards
- DIN EN 10222-2:2021-08DIN Media
- DIN EN 10273:2016-10DIN Media
- 16Mo3 heat-resistant pressure-vessel steelsSalzgitter Flachstahl GmbH
- 1.5415 — 16Mo3 material dataWalzwerke Einsal GmbH
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