1.5662 Carbon Steel Boiler Steel Pipe – Technical Overview
1. Introduction
1.5662 is a German (DIN/EN) material number designating a molybdenum-alloyed heat-resistant carbon steel. It is primarily used for manufacturing seamless tubes and pipes for boilers, superheaters, heat exchangers, and high-temperature pressure vessels. Its key characteristic is enhanced creep resistance and strength at elevated temperatures compared to plain carbon steels.
2. Material Specifications & Standard Equivalents
This grade is governed by European standards for seamless pressure pipes.
| Standard | Designation | Product Form | Key Application |
|---|---|---|---|
| EN 10216-2 | P235GH | Seamless Tubes | Pressure & temperature purposes |
| DIN 17175 | 15Mo3 | Seamless Tubes | Boilers, heat exchangers, piping |
| Material Number (Werkstoff Nr.) | 1.5662 | - | Universal identifier in German system |
| Common UNS Approx. | K31509 | - | Similar to ASTM A204 Gr. B / A335 P1 |
3. Chemical Composition (Typical, %)
The molybdenum addition (approx. 0.25-0.35%) provides solid solution strengthening.
| Element | Carbon (C) | Silicon (Si) | Manganese (Mn) | Phosphorus (P) max | Sulfur (S) max | Molybdenum (Mo) |
|---|---|---|---|---|---|---|
| Content | 0.10 - 0.20 | 0.10 - 0.35 | 0.40 - 0.80 | 0.025 | 0.020 | 0.25 - 0.35 |
4. Mechanical Properties (at room temperature)
Properties are specified for the normalized or normalized & tempered condition.
| Property | Yield Strength (Rp0.2) min | Tensile Strength (Rm) | Elongation (A) min | Impact Energy (KV) min* |
|---|---|---|---|---|
| Value | ≥ 255 MPa | 450 - 600 MPa | ≥ 24% | ≥ 40 J (at +20°C) |
| Note: Impact testing is typically required for wall thicknesses >16mm or as specified by the order. |
5. Key Characteristics & Applications
High-Temperature Performance: Designed for long-term service at temperatures typically up to ~500°C (930°F). Offers good resistance to creep (slow deformation under stress and heat).
Weldability: Good weldability using common methods (SMAW, GTAW, SAW). Preheating and post-weld heat treatment (PWHT) may be required for thicker sections to relieve stresses.
Main Applications:
Seamless boiler tubes and superheater tubes
High-temperature and high-pressure piping systems in power plants
Heat exchanger tubing
Components for petrochemical and process industries
6. Important Notes for Procurement
Testing & Certification: Pipes are supplied with a 3.1 or 3.2 material certificate according to EN 10204, verifying compliance with chemical and mechanical properties.
Non-Destructive Testing (NDT): Mandatory per standards (e.g., ultrasonic or hydrostatic testing) to ensure integrity.
Material Condition: Typically supplied in normalized (+N) or normalized and tempered (+NT) condition to achieve the specified microstructure and properties.
Not for Low-Temperature Use: This grade is not intended for low-temperature or cryogenic service due to its ferritic-pearlitic microstructure.
In summary, 1.5662 (15Mo3 / P235GH) is a reliable, standardized, and widely used molybdenum steel for critical high-temperature pressure equipment, offering an optimal balance of strength, manufacturability, and cost for its intended temperature range.
