​15Mo3​​ is a ​low-alloy steel grade​​ standardized under the European norm ​EN 10028-2:2017 (Flat products made of steels for pressure purposes - Part 2: Non-alloy and alloy steels with specified elevated temperature properties).​​

Here's a breakdown of its key characteristics:

​Composition:​​ The name "15Mo3" reveals its composition:

​15:​​ Indicates approximately ​0.15% Carbon​​ (C).

​Mo3:​​ Indicates approximately ​0.25% - 0.35% Molybdenum​​ (Mo).

Other key elements include Manganese (Mn) around 0.40% - 1.00%, and traces of Silicon (Si), Phosphorus (P), Sulfur (S), and sometimes small amounts of Chromium (Cr), Nickel (Ni), or others within specified limits.

​Key Alloying Element:​​ ​Molybdenum (Mo)​​ is the primary alloying element responsible for its enhanced properties. Molybdenum significantly improves:

​High-Temperature Strength​​

​Creep Resistance​​ (resistance to slow deformation under stress at high temperatures)

​Primary Application:​​ It's specifically designed for use in ​elevated temperature service​​, particularly in ​welded pressure vessels, boilers, and heat exchangers​​. Common applications include:

Power plant components (boiler drums, headers, superheater tubes/headers)

Chemical processing equipment

Refinery equipment

​Key Properties:​​

​Good Elevated Temperature Strength:​​ Maintains strength better than plain carbon steels at temperatures typically ranging from 350°C (660°F) to around 550°C (1020°F). Useful maximum service temperatures are often cited around 500-525°C (930-975°F), depending on stress levels and design codes.

​Good Creep Resistance:​​ Essential for components under constant stress at high temperatures.

​Good Weldability:​​ Weldable using standard methods suitable for low-alloy steels, though preheating and Post-Weld Heat Treatment (PWHT) are usually required to avoid cracking and ensure long-term integrity, especially in thicker sections or critical applications.

​Good Formability:​​ Can be formed using standard methods like hot forming.

​Standards & Specifications:​​

Primary Standard: EN 10028-2:2017.

Commonly supplied in plate and tube forms (e.g., pipes and tubes would be covered under standards like EN 10216).

​ASTM Equivalent:​​ The closest comparable grade in the ASTM system is often considered ​ASTM A204 Grade A​​ (for plate) or ​ASTM A335 P1​​ (for pipe). ASTM A387 Grade 1 is also similar (though the Cr content differs slightly). ​Important:​​ Equivalency is approximate; always consult the relevant design code and material specifications.

​In Summary:​​

15Mo3 is a ​molybdenum-alloyed creep-resistant steel​​ standardized for ​high-temperature pressure equipment​​ (e.g., boilers, pressure vessels, heat exchangers), offering significantly better performance at temperatures ranging from ~350°C to 550°C than plain carbon steel due to the addition of around 0.30% Molybdenum. Its primary standards are European (EN), with approximate equivalents in ASTM standards like A204 A or A335 P1.