P355NH is a normalized, weldable fine-grain structural steel produced according to the European standard EN 10028-3. It is specifically designed for manufacturing pressure vessels, boilers, and pipes that operate in elevated temperature environments, typically up to 400 °C.
Key Specifications
Standard: EN 10028-3 (Steels for pressure purposes).
Material Number: 1.0565.
Designation: "P" stands for Pressure, "355" indicates a minimum yield strength of 355 MPa (for thickness ≤ 16mm), and "NH" signifies it is normalized and intended for high-temperature service.
Delivery Condition: Normalized (heated to 900–950 °C and air-cooled) to achieve a uniform fine-grain structure
Chemical composition
| Variant | Cast | Weldability | C % | Si % | Mn % | P % | S % | Cr % | Ni % | Mo % | V % | Ti % | Cu % | Al % | Nb % | N % | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2714 | CC | CEV 0.43max | Min | 0.01 | 0.01 | 1.10 | 0.000 | 0.000 | 0.00 | 0.00 | 0.00 | 0.000 | 0.000 | 0.00 | 0.020 | 0.000 | 0.0000 |
| Pcm 0.27max | Max | 0.18 | 0.50 | 1.70 | 0.025 | 0.010 | 0.30 | 0.50 | 0.08 | 0.100 | 0.030 | 0.30 | - | 0.050 | 0.0120 |
Mechanical Properties
| Variant | Condition | Format | Dimension [mm] | Yield strength min [MPa] | Tensile strength [MPa] | Elongation A5 [%] | Impact (ISO-V) strengthmin |
|---|---|---|---|---|---|---|---|
| Rp0.2 * Reh, ** Rel | |||||||
| 2714 | +AR | Round bar | 25 < 35 | 355* | 490-630 | 22 | -20 °C 40 J (long) |
| Round bar | 35 < 50 | 345* | 490-630 | 22 | -20 °C 40 J (long) | ||
| Round bar | 50 < 70 | 325* | 490-630 | 22 | -20 °C 40 J (long) | ||
| Round bar | 70 < 100 | 315* | 470-610 | 21 | -20 °C 40 J (long) | ||
| Round bar | 100 < 150 | 295* | 450-590 | 21 | -20 °C 40 J (long) | ||
Transformation temperatures
| Temperature °C | |
|---|---|
| MS | 432 |
| AC1 | 717 |
| AC3 | 847 |
P355NH Advantages
Outstanding high-temperature and pressure resistance: It maintains stable mechanical properties at operating temperatures up to 400℃, with a minimum yield strength of 355MPa. It can withstand high pressure up to 10MPa and resist thermal fatigue under alternating temperature conditions, making it suitable for high-pressure and high-temperature pressure vessel operations in petrochemical and power generation industries.
Excellent low-temperature toughness: With a Charpy V-notch impact energy of ≥30J at -20℃, it has strong resistance to low-temperature impact and brittle fracture. This advantage ensures safe operation in alpine regions, low-temperature storage and transportation equipment, and marine low-temperature environments without structural damage.
Superior processability: It features good hot workability (850–1150℃) with low deformation resistance, facilitating forging, rolling and bending. It also supports cold forming and stamping without preheating for most cases. The material is easy to weld with common methods, requiring no complex pre-weld heat treatment for thin and medium plates, improving production efficiency.
Stable material performance and durability: As a fine-grained structural steel with strictly controlled impurity content (S≤0.035%, P≤0.035%), it has uniform chemical composition and microstructure. It has good corrosion resistance to general industrial media and offshore salt spray, reducing equipment maintenance costs and extending service life. It also meets international standards (EN 10028) for reliable quality.
Core Applications
Petrochemical and chemical equipment: Core material for pressure-bearing components including reactors (crude oil cracking, chemical synthesis), heat exchangers (medium heat transfer), separators (material separation and purification) and spherical tanks (high-pressure medium storage).
Power generation equipment: Key components for thermal power, nuclear power and hydropower stations, such as boiler drums, nuclear reactor pressure shells, hydropower high-pressure water pipes and turbine volutes.
Energy storage and marine components: Applied to hydrogen energy storage and transportation containers, air separation equipment low-temperature adsorbers, offshore platform structural parts and ship pressure pipelines.
Pharmaceutical and food equipment: Sanitary pressure vessels, raw material storage tanks and transportation pipelines that meet hygiene standards for pharmaceutical and food processing.
Typical Application Scenarios
Petrochemical field: Oil refineries, chemical plants and natural gas processing stations, adapting to high-pressure (up to 10MPa) and alternating temperature (-20℃ to 400℃) working conditions.
Power generation field: Thermal power plant boiler rooms, nuclear power plant reactor buildings and alpine hydropower stations, resisting temperature changes to ensure stable power supply.
Energy storage and marine field: Hydrogen refueling stations, air separation plants, offshore oil and gas platforms and ocean-going ships, withstanding low-temperature impact and salt spray corrosion.
Pharmaceutical and food field: Pharmaceutical raw material workshops, food and beverage processing plants and sterile packaging workshops, meeting FDA and other hygiene standards to avoid product pollution.
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What heat treatment is required for P355NH?
P355NH is usually supplied in the normalized condition (heating to 890-950℃, holding for a certain time, then air cooling). Normalization improves its microstructure, enhances toughness and ensures uniform mechanical properties across the material.
What is the difference between P355NH and P355N?
The main difference lies in the impact test temperature. P355NH requires impact testing at -20℃, while P355N is tested at 20℃. Both meet the same yield and tensile strength requirements, but P355NH has better low-temperature toughness.
What is the tensile strength range of P355NH?
The tensile strength of P355NH ranges from 470 MPa to 630 MPa, as specified in EN 10028-2. This strength level ensures it can withstand high pressure and load in pressure vessel and boiler applications without deformation or failure.
What is the yield strength of P355NH?
P355NH has a minimum yield strength of 355 MPa at room temperature. This means it can resist permanent deformation when subjected to a stress below 355 MPa, which is crucial for maintaining the structural integrity of pressure-bearing components.
Can P355NH be used in pressure vessels?
Absolutely. P355NH is specially designed for pressure vessel manufacturing. Its high strength, good toughness and resistance to moderate temperatures make it suitable for storing and transporting gases, liquids and other media under pressure in various industries.
What industries commonly use P355NH?
P355NH is widely used in petrochemical, power generation (thermal power plants), chemical, oil and gas, and boiler manufacturing industries. It is used to make pressure vessels, boilers, heat exchangers and pipelines for high-pressure and high-temperature media.
What is the maximum thickness of P355NH plates?
The maximum thickness of P355NH plates specified in EN 10028-2 is usually 200 mm, but it can be customized according to specific requirements. Thicker plates may need stricter heat treatment and testing to ensure uniform performance through the thickness.
What is the density of P355NH?
The density of P355NH is approximately 7.85 g/cm³, the same as most carbon and low-alloy steels. This value is used for weight calculation in engineering design, material procurement and structural analysis of pressure vessels and other components.
Can P355NH be used at low temperatures?
Yes, P355NH can be used at low temperatures down to -20℃. Its minimum impact energy of 30 J at -20℃ ensures it has good toughness and avoids brittle fracture in low-temperature pressure-bearing scenarios, such as cold regions or low-temperature media storage.
What testing methods are used for P355NH?
Common testing methods for P355NH include chemical composition analysis (spectrometry), mechanical tests (tensile, yield, elongation), impact test (Charpy V-notch) at -20℃, and non-destructive testing (ultrasonic, radiographic) to check for internal defects.
Does P355NH have corrosion resistance?
P355NH has basic corrosion resistance in atmospheric and mild corrosive environments. However, in harsh environments (e.g., acidic, alkaline or saltwater), it needs additional protection like painting, galvanizing or coating to prevent corrosion and extend service life.