P235GH Carbon Steel: Pressure Vessel Steels (EN 10028-2)
P235GH carbon steel, designated under the EN 10028-2 standard for non-alloy and alloy steels used in elevated temperature pressure vessels, is a normalized or normalized formed and tempered low-carbon steel grade (equivalent to ASTM A516 Grade 55 or BS 3059 Grade 161). With its controlled chemistry and robust mechanical properties, it offers excellent weldability, moderate strength, and good formability, making it ideal for fabricating boilers, pressure vessels, and high-temperature piping systems in power generation, petrochemical, and industrial heating applications. This article explores its chemical composition, mechanical characteristics, manufacturing processes, typical uses, and comparisons with similar grades.
1. Core Chemical Composition (EN 10028-2 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.16% | Provides basic strength; low level enhances weldability and ductility |
| Manganese (Mn) | 0.10 – 0.50% | Improves hot workability and toughness; aids in deoxidation |
| Silicon (Si) | ≤ 0.35% | Acts as a deoxidizer; enhances high-temperature strength and scale resistance |
| Phosphorus (P) | ≤ 0.025% | Controlled impurity; minimizes brittleness in welded joints |
| Sulfur (S) | ≤ 0.015% | Restricted to prevent hot shortness and ensure good ductility |
| Chromium (Cr) | ≤ 0.30% | Trace element for minor corrosion resistance in mild environments |
| Molybdenum (Mo) | ≤ 0.08% | Improves creep resistance at elevated temperatures |
2. Key Mechanical Properties (Room Temperature)
- Tensile Strength (Rm): 360 – 480 MPa (EN 10028-2 requirement for structural integrity under pressure)
- Yield Strength (ReH): ≥ 235 MPa (minimum for thicknesses up to 16mm; supports load-bearing in vessels)
- Elongation (A): ≥ 25% (longitudinal; indicates good ductility for forming and expansion)
- Impact Toughness (KV): ≥ 27 J at 20°C (ensures fracture resistance; optional Charpy V-notch testing)
- Hardness (HB): 120 – 170 (suitable for machining and welding without excessive hardness buildup)
3. Manufacturing Process Characteristics
- Steelmaking: Basic oxygen furnace (BOF) or electric arc furnace (EAF) followed by ladle refining to achieve low impurity levels and precise chemistry for pressure service.
- Hot Rolling: Rolled at 850-1100°C to produce plates or sheets (thicknesses 6-200mm), with controlled cooling to normalize the microstructure and refine grain size.
- Heat Treatment: Normalization at 880-950°C followed by air cooling; optional stress-relieving at 550-650°C to minimize residual stresses post-welding.
- Surface Preparation: Shot blasting or pickling to remove mill scale; protected with oil coating for storage and transport to prevent corrosion during handling.
4. Typical Application Fields
Power Generation
Boiler drums, steam headers, and superheater tubes — withstands moderate pressures and temperatures up to 450°C in fossil fuel plants.
Petrochemical Industry
Pressure vessels for distillation columns, reactors, and storage tanks handling non-corrosive hydrocarbons and gases.
Oil & Gas Sector
Piping systems, heat exchangers, and separators for upstream and midstream operations under elevated pressures.
Industrial Heating Equipment
Furnace components, hot water tanks, and autoclaves — reliable for thermal cycling and steam generation processes.
5. Difference from Similar Grades (P235GH vs P265GH vs P355GH)
| Grade | Yield Strength (MPa) | Key Advantage | Suitable Scenario |
|---|---|---|---|
| P235GH | ≥ 235 | Superior weldability; cost-effective for low-to-medium pressure | General boilers and vessels up to 16 bar and 400°C |
| P265GH | ≥ 265 | Higher strength for thicker sections; improved impact resistance | Medium-pressure applications like steam lines and larger tanks |
| P355GH | ≥ 355 | Enhanced tensile properties for high-stress environments | High-pressure vessels and elevated temperature piping systems |
6. Selection & Usage Precautions
- Temperature Limits: Suitable for service up to 450°C; avoid prolonged exposure above 500°C to prevent graphitization and loss of strength — opt for alloyed grades like 16Mo3 for higher temperatures.
- Welding Guidelines: Preheat to 150-200°C for thicknesses >20mm; use low-hydrogen electrodes (e.g., E7018) and post-weld heat treatment if required to avoid hydrogen cracking.
- Corrosion Considerations: Provides basic atmospheric protection; apply protective coatings (e.g., epoxy) in humid or mildly corrosive environments; not ideal for acidic or chloride-laden conditions.
- Quality Assurance: Verify compliance with EN 10028-2 via material certificates (EN 10204 3.1/3.2); conduct hydrostatic testing per ASME Section VIII for pressure vessels.
7. Get a Carbon Steel Quote
If you need customized P235GH carbon steel products (plates, sheets, pipes, fittings) or want to get a detailed price quote, please contact our team directly. Our specialists will provide professional technical support and competitive pricing based on your requirements.