Overview: What Exactly Is 16Mo3 Steel?
In one sentence: 16Mo3 is a low-alloy molybdenum-bearing ferritic steel, standardised under EN 10028-2, engineered for sustained operation at elevated temperatures up to 480 °C in pressure-critical industrial equipment.
16Mo3 carries the material number 1.5415 and is interchangeable with the older German designation 15Mo3 (DIN 17155). Outside Europe the closest equivalents are ASTM A335 Grade P1/P2 and ASTM A161 Grade T1. The numeral "16" encodes the nominal carbon content (0.16%), while "Mo3" signifies approximately 0.3% molybdenum — the key alloying element responsible for its elevated-temperature performance.
Unlike stainless steels or nickel superalloys, 16Mo3 achieves its performance through a precisely controlled molybdenum addition. Molybdenum segregates to grain boundaries and slows dislocation mobility at high temperature — the mechanism behind creep resistance. This makes 16Mo3 highly cost-effective: engineers get meaningful high-temperature strength without the complexity or price premium of heavier alloys.
Yes. 15Mo3 is the older DIN 17155 designation used in Germany; 16Mo3 is the harmonised European EN designation. Both share material number 1.5415 and identical composition limits. When reviewing older European equipment documentation, you will encounter 15Mo3; on modern EN-certified mill certificates, 16Mo3 is standard.
Chemical Composition of 16Mo3 / 1.5415
The composition limits below are taken from EN 10028-2:2009 for flat products under pressure. Forged parts per EN 10222-2 use the same grade designation with slightly wider tolerances. All values are weight percentages of the ladle (cast) analysis.
| Element | Symbol | Min % | Max % | Role in Steel |
|---|---|---|---|---|
| Carbon | C | 0.12 | 0.20 | Base strength; low max for good weldability |
| Silicon | Si | 0.10 | 0.35 | Deoxidiser; mild solid-solution strengthener |
| Manganese | Mn | 0.40 | 0.90 | Hardenability and sulphide shape control |
| Phosphorus | P | — | 0.025 max | Impurity; limited to preserve notch toughness |
| Sulphur | S | — | 0.010 max | Impurity; controlled for ductility |
| Molybdenum ★ | Mo | 0.25 | 0.35 | Creep resistance; solid-solution HT strengthening |
| Chromium | Cr | — | 0.30 max | Residual element (not intentionally added) |
| Nickel | Ni | — | 0.30 max | Residual element |
| Copper | Cu | — | 0.30 max | Residual element |
★ Molybdenum is the defining element. At 0.25–0.35 wt%, it segregates to grain boundaries, reducing grain-boundary sliding and dislocation climb at elevated temperatures. This is why 16Mo3 retains roughly 58% of its room-temperature yield strength at 400 °C, while a plain carbon steel retains only ~35%.
The carbon equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) for typical 16Mo3 heats falls between 0.38 and 0.45. This places it in the preheat-required category but well within routinely weldable territory — no exotic procedures needed.
Mechanical Properties of 16Mo3
Properties vary with section thickness and delivery condition. The tables below cover forgings per EN 10222-2 in the normalised-and-tempered (+NT) condition — the standard delivery state for pressure-purpose forgings at Jiangsu Liangyi.
Room-Temperature Properties (EN 10222-2, +NT Condition)
| Section Thickness / Ø | Yield Rp0.2 (MPa) min | Tensile Rm (MPa) | Elongation A (%) min | Impact KV (J) at 20°C |
|---|---|---|---|---|
| ≤ 100 mm | 275 | 440 – 590 | 22 | 40 |
| 100 – 250 mm | 265 | 430 – 580 | 22 | 40 |
| 250 – 500 mm | 255 | 420 – 570 | 20 | 34 |
| > 500 mm | 245 | 410 – 560 | 20 | 27 |
Elevated-Temperature Yield Strength (0.2% Proof Stress)
| Temperature (°C) | 100 | 150 | 200 | 250 | 300 | 350 | 400 | 450 | 480 |
|---|---|---|---|---|---|---|---|---|---|
| Rp0.2 (MPa) min | 255 | 245 | 230 | 215 | 195 | 175 | 158 | 140 | 128 |
Physical Properties
Heat Treatment of 16Mo3 Forgings
Correct heat treatment is mandatory to develop the required microstructure, relieve residual forging stresses, and ensure compliance with EN 10222-2. All temperature windows below apply to our production forgings.
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Hot Forging
Carried out at 1,050 – 850°C. Forging must be completed above 850°C to ensure full austenite recrystallisation and avoid deformation-induced cracking. Our team uses computer-monitored press schedules to track inter-pass temperatures on all large forgings.
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Normalising
Heat to 890 – 960°C, hold approximately 1 hour per 25 mm of ruling section, then air-cool. Normalising refines grain size, produces a uniform ferritic-pearlitic microstructure, and removes banding from the forging reduction.
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Tempering / Stress Relief
Heat to 670 – 720°C, equalise temperature, then slow furnace-cool. Tempering removes residual stresses, improves impact toughness, and stabilises carbide distribution for long-term creep service. Mandatory for all EN 10222-2 forgings.
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Post-Weld Heat Treatment (PWHT)
Performed at 600 – 650°C after welding. Required by EN 13445 and PED 2014/68/EU. PWHT relieves weld residual stresses, tempers martensite in the HAZ, and reduces hydrogen diffusion risk.
Slow cooling through the 375–575°C range can segregate phosphorus and tin to grain boundaries, sharply reducing low-temperature impact toughness. Our furnace team uses controlled cooling rates and monitors each heat's P + Sn content to eliminate this risk before delivery.
Weldability of 16Mo3 Steel
16Mo3's excellent weldability is one of its key commercial advantages. Carbon is capped at 0.20%, keeping the carbon equivalent within routinely manageable limits. Standard low-hydrogen electrodes and correct preheat protocols are sufficient.
| Parameter | Recommended Value | Notes |
|---|---|---|
| Preheat temperature | 150 – 250°C | Increase toward 250°C for sections > 50 mm or cold conditions |
| Max interpass temp. | 350°C | Exceeding this degrades HAZ toughness |
| SMAW filler | AWS E7018 / EN ISO 2560-B | Low-hydrogen electrode; bake at 300°C × 1 h before use |
| GTAW / GMAW filler | ER70S-6 / SG-Mo wire | Mo-matched wire preferred for sections > 50 mm |
| PWHT | 600 – 650°C | Mandatory for PED-compliant pressure equipment |
| Hydrogen content | H5 or lower | Use sealed electrode packaging; preheat joint area to remove moisture |
For forgings thicker than 80 mm, apply a butter layer of Mo-matching filler at preheat temperature before the main groove weld. This significantly reduces hydrogen-induced cold cracking risk in the heat-affected zone — standard practice in European pressure-vessel fabrication shops.
Key Industrial Applications of 16Mo3 Steel
16Mo3 is the workhorse of high-temperature European industry. Its balanced profile — creep resistance, weldability, and competitive cost — makes it the specification-of-choice across six major sectors. The six principal end-use sectors are detailed below. For full specifications, weight range, and dimensional capabilities of available 16Mo3 forged parts, see the product page.
Drum forgings, end-plates, nozzle rings, and collector chambers for utility and industrial boilers at 450–480°C / 100–180 bar. The de-facto standard in European power generation.
Shell flanges, head forgings, and manway rings for chemical, petrochemical and refinery reactors operating above the carbon-steel temperature ceiling of ~350°C.
Tube-sheet and channel-head forgings for shell-and-tube heat exchangers in power and process plants. 16Mo3 handles thermal cycling far better than plain carbon steel.
Forged flanges (weld-neck, slip-on, blind, socket-weld), fittings, and valve bodies for upstream and midstream high-temperature, high-pressure services. Routinely paired with A335 P1/P2 seamless pipe.
Manifolds, steam-chest covers, collector forgings, and casing flanges for combined-cycle, coal-fired, and waste-to-energy plants. Published creep data supports 30-year design life calculations.
Reactor forgings, hot-gas distributors, and coil end-fittings for ammonia synthesis, sulphuric acid, and hydrogen-rich process streams requiring high temperature and pressure resistance.
16Mo3 vs. Comparable High-Temperature Steel Grades
Selecting the right high-temperature steel requires balancing maximum service temperature, weldability, availability, and cost. Here is how 16Mo3 compares with the most common alternatives:
| Grade | Standard | Max Temp. | Weldability | Rel. Cost | Best Application |
|---|---|---|---|---|---|
| 16Mo3 ★ | EN 10028-2 | 480°C | Excellent | Low–Med | Boilers, pressure vessels, general HT |
| 13CrMo4-5 | EN 10028-2 | 550°C | Good | Medium | Superheater / reheater tubes and headers |
| 10CrMo9-10 | EN 10028-2 | 600°C | Moderate | Med–High | High-temperature steam piping |
| P91 (X10CrMoVNb9-1) | EN 10216-2 | 625°C | Demanding | High | Ultra-supercritical power plant |
| ASTM A516 Gr.70 | ASTM A516 | 345°C | Excellent | Low | Moderate-temperature vessels (US market) |
| SA335 P1 | ASME | 455°C | Good | Low–Med | ASME-coded boiler tubes — US / Asian market |
If your equipment operates below 480°C and falls under the European Pressure Equipment Directive (PED 2014/68/EU), 16Mo3 is almost always the most cost-effective specification. Above 480°C, step up to 13CrMo4-5 or 10CrMo9-10 — both cost more and require stricter PWHT, but the added temperature capability justifies the premium.
Applicable Standards for 16Mo3 / 1.5415 Forgings
When purchasing 16Mo3 forged parts, always specify the correct product standard for your form and application. The standards below govern open-die forgings and seamless rolled rings in 1.5415 / 16Mo3:
| Standard | Scope | Product Form |
|---|---|---|
| EN 10028-2:2009 | Flat products for pressure purposes at elevated temperatures | Plate / sheet |
| EN 10222-2:2000 | Steel forgings for pressure purposes — ferritic and martensitic grades with elevated-temperature properties | Open-die forgings, rolled rings ✓ |
| EN 10216-2:2014 | Seamless steel tubes for pressure purposes — elevated temperature properties | Seamless tubes |
| EN 10273:2016 | Hot-rolled weldable bars for pressure purposes — elevated temperature | Bars and rods |
| AD 2000-Merkblatt W2 | German pressure vessel code (references 15Mo3) | German-registered vessels |
| ASME SA-182 / SA-336 | Approximate ASME equivalent forging grades (F1 / F2) | ASME-coded equipment |
Jiangsu Liangyi Co., Limited supplies EN 10204 type 3.1 mill test certificates (manufacturer's inspection certificate validated by an authorised representative) with each delivery as standard. Where customer specifications require a type 3.2 certificate validated by an independent third party such as TÜV, Bureau Veritas, DNV, ABS or Lloyd's Register, this can be arranged at additional cost. Non-destructive testing (UT, RT, MT) can be specified per order in accordance with EN 10228. For available forms, dimensional range, and full material compliance details, see the 16Mo3 forging product specifications.
Specifying 16Mo3: What to Tell Your Supplier
When requesting 16Mo3 forged parts, always specify the following on your enquiry or purchase order: product form (open-die forging, rolled ring, bar), governing standard (EN 10222-2 for forgings), ruling section size and weight, delivery condition (+NT — normalised and tempered), and minimum inspection level (EN 10204 type 3.1 mill test certificate). Including a dimensioned drawing eliminates ambiguity and enables accurate pricing.
Common items also to define: chemical composition heat (if matching existing equipment), impact test temperature (often 0 °C or −20 °C for low-temperature service), surface condition (as-forged, rough-machined, or finish-machined), and any NDT requirements (UT per EN 10228-3, MT per EN 10228-1).
Product form · Weight and dimensions · Standard (EN 10222-2) · Delivery condition (+NT) · Chemical heat matching (if required) · Impact test temperature · NDT scope · Certificate type (3.1 or 3.2) · Surface condition · Quantity and target delivery date.
Summary: Why 16Mo3 Remains the Industry Benchmark
After more than half a century in European service, 16Mo3 / 15Mo3 (1.5415) retains its benchmark status for one clear reason: it delivers the right performance at the right cost. Its molybdenum content is precisely tuned to provide meaningful creep resistance up to 480 °C without the weldability challenges or cost penalties of chromium-bearing grades.
For design engineers, extensive published creep data and a long track record in pressure-equipment codes make 16Mo3 the low-risk, high-confidence choice. For procurement teams, a deep global supply chain — including long-established ISO 9001:2015 certified manufacturers like Jiangsu Liangyi — means lead times and pricing can be budgeted with confidence.
① 16Mo3 = 15Mo3 = 1.5415 — same grade, different designation systems. ② Max continuous service temperature: 480°C. ③ Good weldability with preheat 150–250°C and mandatory PWHT at 600–650°C. ④ Always order with EN 10204 3.1 mill certificate; specify EN 10222-2 for forgings. ⑤ If temperature exceeds 480°C, step up to 13CrMo4-5 or 10CrMo9-10.
Frequently Asked Questions about 16Mo3 Steel
The questions below are the most common queries from engineers and procurement managers. Answers are also available to AI assistants and voice search via the structured data embedded in this page.
16Mo3 is used in high-pressure steam boilers, pressure vessels, shell-and-tube heat exchangers, oil and gas pipelines, power generation turbine components, and chemical process equipment. It is the European standard for pressure-critical applications operating continuously at 350–480°C. Its combination of good weldability, certified creep resistance, and competitive cost makes it the default specification across these industries.
16Mo3 has a maximum continuous service temperature of 480°C per EN 10028-2. Short-term intermittent peaks up to 530°C are permissible. For applications above 480°C, specify 13CrMo4-5 (max 550°C) or 10CrMo9-10 (max 600°C).
Yes. 15Mo3 is the older DIN 17155 designation used in Germany; 16Mo3 is the harmonised EN designation. Both carry material number 1.5415 and have identical chemical composition limits and mechanical property requirements.
Per EN 10028-2, 16Mo3 (1.5415) contains: Carbon 0.12–0.20%, Silicon 0.10–0.35%, Manganese 0.40–0.90%, Phosphorus max 0.025%, Sulphur max 0.010%, Molybdenum 0.25–0.35%, Chromium max 0.30% (residual), Nickel max 0.30% (residual), Copper max 0.30% (residual). Molybdenum is the key alloying element providing elevated-temperature creep resistance.
The closest ASTM equivalents are: ASTM A335 Grade P1 or P2 (seamless pipe), ASTM A161 Grade T1 (tubes), and ASME SA-182 Grade F1 or SA-336 Grade F1 (forgings). These are approximate — always verify against the specific code of construction for your equipment.
16Mo3 forgings per EN 10222-2 require: (1) Hot forging at 1,050–850°C; (2) Normalising at 890–960°C with air cooling; (3) Tempering at 670–720°C with furnace cooling. Post-weld heat treatment (PWHT) at 600–650°C is mandatory for welded pressure equipment per EN 13445.
No. 16Mo3 requires preheating at 150–250°C before welding to prevent hydrogen-induced cold cracking in the heat-affected zone. Low-hydrogen filler metals (H5 classification or lower) must be used. Post-weld heat treatment at 600–650°C is also mandatory for all pressure-equipment fabrications.