What are the mechanical properties of 15Mo3?
The mechanical properties of 15Mo3 steel generally include a tensile strength of 450-600 MPa, a minimum yield strength of approximately 270 MPa (varying with thickness), and a minimum elongation of 22%.
15Mo3 is a chromium-molybdenum low-alloy steel used in pressure vessels, superheater tubes, and piping exposed to high temperatures. It is commonly used in European power and chemical plants, with excellent thermal and mechanical stability.
Key characteristics
Maintains strength under medium-temperature steam conditions.
Good oxidation and creep resistance.
Compatible with standard welding and fabrication practices.
Decoding the name
"15" represents carbon content of ~0.15%,
"Mo" indicates molybdenum alloying, enhancing high-temperature performance,
"3" identifies the steel grade under DIN 17155.
Comparison
Compared to 13CrMo4-5, 15Mo3 is slightly less strong at high temperatures but easier to weld.
Performs better than S235JR at elevated temperatures.
Less creep-resistant than 12Cr1MoV steels but more cost-effective for medium-temperature applications.
Application
Superheaters and reheaters in boilers.
Pressure vessels and piping.
Chemical, petrochemical, and power generation equipment.
Does 15Mo3 resist corrosion?
15Mo3 has moderate corrosion resistance due to chromium, which protects against oxidation in steam and flue gas environments. However, it is not stainless steel, and additional surface protection, coatings, or linings may be required in highly corrosive or sulfur-rich conditions to prevent scaling, pitting, or long-term degradation during service.
What is the tensile strength of 15Mo3?
15Mo3 has a tensile strength typically ranging from 440–590 MPa, depending on thickness and heat treatment. Combined with yield strength around 220–275 MPa, it provides excellent mechanical performance for pressure vessels and industrial boilers. These properties ensure that components withstand both static and thermal stresses while maintaining structural integrity over time.
How good is the ductility of 15Mo3?
15Mo3 steel has good ductility and plasticity, typical for boiler steels, with elongation values around 20-22% (longitudinal/transverse) and excellent high-temperature performance, making it suitable for pressure vessels and heat exchangers despite its strength, offering a good balance for demanding environments. Its molybdenum content enhances its creep resistance and strength at high temperatures, while maintaining formability.
DIN 17155 15Mo3 Chemical Composition
| Grade | C% | SI% | Mn% | P%, max | S%, max | Al% | Cr% | Cu%, max | Mo% | Nb%, max | Ni%, max | Ti%, max | V%, max |
| 15Mo3 | 0.12-0.20 | 0.1-0.35 | 0.4-0.9 | 0.035 | 0.03 | ≤O.25 | 0.3 | 0.25-0.35 | 0.01 | 0.3 |
DIN 17155 15Mo3 Mechanical Property
| Steel Grade | Thickness, in mm | Yield Strength, min | Tensile Strength | Elongation, %, min |
| 15Mo3 | T≤16 | 275 | 440-590 | 20 |
| 16<T≤40 | 270 | |||
| 40<T≤60 | 260 | |||
| 60<T≤100 | 240 | 430-580 | 19 | |
| 100<T≤150 | 220 | 420-570 |
1. What applications is 15Mo3 used for?
15Mo3 is widely applied in industrial boilers, pressure vessels, superheater and reheater tubes, and heat exchangers. Its combination of medium-temperature strength, ductility, and creep resistance ensures reliability under thermal and pressure stress. It is commonly used in oil, gas, chemical, and power generation industries where safe, long-term high-temperature operation is required.
2. How does 15Mo3 plate thickness affect properties?
Mechanical properties of 15Mo3, such as yield and tensile strength, may slightly decrease with increasing plate thickness. Thicker sections also require more careful preheating and post-weld heat treatment to prevent residual stresses and cracking. Designers must account for thickness-dependent variations when specifying 15Mo3 to ensure proper performance in pressure vessels and heat-resistant components.
3. Is 15Mo3 suitable for welding without preheat?
No, preheating is recommended for 15Mo3, typically between 150–250°C, especially for thick sections. Without preheat, the risk of hydrogen-induced cracking increases. Controlled preheating, suitable low-hydrogen electrodes, and proper welding parameters ensure structural integrity, prevent weld defects, and maintain high-temperature strength and creep resistance in boilers, heat exchangers, and pressure vessels.
4. How does 15Mo3 improve vessel design efficiency?
15Mo3 allows designers to reduce wall thickness while maintaining strength at elevated temperatures. Thinner walls reduce material usage, lower weight, and simplify transportation and installation. Its excellent creep resistance and mechanical properties enable safer pressure vessel design, longer service life, and improved thermal efficiency in boilers, superheaters, and chemical process equipment, ultimately reducing lifecycle costs.
5.What is the European equivalent of 15Mo3?
15Mo3 corresponds to EN 10028‑2 grade 16Mo3 for pressure purposes. Both grades have similar chemical composition, mechanical properties, and heat treatment requirements, making them effectively interchangeable in most industrial applications. This equivalence allows international sourcing, design standardization, and consistent quality for pressure vessels, boilers, and heat-resistant components across Europe and beyond.
6. Can 15Mo3 be used under low-temperature conditions?
No, 15Mo3 steel is primarily designed for high-temperature service in boilers and pressure vessels, not low-temperature (cryogenic) applications, as its strength and properties are optimized for heat resistance, though it does have good weldability and resistance to moderate pressure. While it's excellent at elevated temperatures (up to around 450-600°C), its suitability for truly low-temperature conditions (like cryogenic) is generally not its intended use, with other alloys being preferred for those extreme cold applications.
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