16Mo3 and 15Mo3 are essentially the same chromium-molybdenum (Cr-Mo) boiler/pressure vessel steel, with 16Mo3 being the modern European (EN 10028-2) designation replacing the older German (DIN 17155) 15Mo3, sharing the same material number (1.5415) and nearly identical composition and properties, though 16Mo3 often features tighter control on impurities like Phosphorus (P) and Sulfur (S) for slightly better performance at high temps, making it the preferred standard for new builds.
Chemical composition:
| Grade | C | Si | Mn | P | S | Cr | Cu | Mo | Ni | N |
| 15Mo3 | 0.12-0.20 | 0.10-0.35 | 0.40-0.90 | ≦0.035 | ≦0.030 | ≦0.25 | ≦0.30 | ≦0.30 | ||
| 16Mo3 | 0.12-0.20 | ≦0.35 | 0.40-0.90 | ≦0.025 | ≦0.010 | ≦0.30 | ≦0.30 | 0.25-0.35 | ≦0.30 | ≦0.012 |
Mechanical properties:
| Grade | Yield Strength | Tensile Strength | Elongation |
| (Mpa) | (MPa) | (%) | |
| 15Mo3 | ≧275 | 440-590 | ≧20 |
| 16Mo3 | ≧275 | 440-590 | ≧22 |
16Mo3 pressure vessel steel, designated with steel number 1.5415, is an European (DIN EN) steel grade for alloy steels. 16Mo3 pressure vessel steel plate is Cr-Mo alloy steel. The addition of molybdenum (Mo) not only improves the resistance of 16Mo3 pressure vessel steel plate to pitting corrosion, but also significantly enhances creep strength of 16Mo3 pressure vessel steel plate at elevated temperatures. The chromium(Cr) improves the resistance of 16Mo3 pressure vessel steel plate to high-temperature hydrogen attack and graphitization.
Key Differences & Relationship
Standard: 15Mo3 is from DIN 17155; 16Mo3 is from EN 10028-2.
Superseded: EN 10028-2 (16Mo3) replaced DIN 17155 (15Mo3) around the 1990s/2000s.
Equivalency: They are considered equivalent grades, often interchangeable in design, but 16Mo3 is the current standard.
Chemical Composition: 16Mo3 generally has stricter limits on elements like Phosphorus (P) and Sulfur (S), leading to slightly improved mechanical properties, especially creep resistance at high temperatures (up to ~500°C).
Summary of Properties (Similarities)
Type: Low-alloy Mo-steel for pressure vessels/boilers.
Heat Treatment: Both typically supplied normalized.
Usage: Power plants, petrochemicals, high-temp service.
Weldability: Good weldability.
In essence, if a drawing specifies 15Mo3, you can generally use 16Mo3 as its direct, modernized replacement, offering potentially better quality due to tighter impurity controls.
