What material is equivalent to P275NH Steel Plate?

P275NH (Material No. 1.0487) is a non-alloy, fine-grain pressure vessel steel specified in EN 10028-3.

It is primarily used for the manufacture of pressure vessels, boilers, and welded pressure-retaining structures operating under elevated temperature and moderate pressure conditions.

The steel is supplied in the normalized (+N) condition, ensuring uniform mechanical properties, good weldability, and reliable performance in pressure equipment.

According to EN 10028-3

The chemical composition of P275NH is strictly controlled to guarantee strength, toughness, weldability, and structural stability.

Chemical Composition Limits (wt.%)

Controlled micro-alloying elements (Nb, Ti, V) refine grain size

Tensile Strength (Rm) – Normalized (+N)

Minimum Yield Strength (ReH) – Normalized (+N)

Impact Energy (Charpy V-Notch) – Normalized (+N)

P275NH is a weldable pressure vessel steel, and several international grades are considered equivalent or comparable depending on application and code requirements.

Equivalent Grades of Steel P275NH (1.0487)

*Chinese grades are approximate equivalents; engineering verification is required for code compliance.

P275NL1 and P275NL2

These grades belong to EN 10028-3, with NL1 and NL2 indicating enhanced low-temperature notch toughness.
They are preferred where impact resistance at −40℃ or −50℃ is required.

P265GH and P295GH

P265GH (EN 10028-2): Commonly used for general pressure vessel and boiler applications

P295GH: Higher yield strength, suitable for more demanding pressure conditions

Compared with these grades, P275NH offers a balanced combination of strength, weldability, and elevated-temperature performance.

P275NH (1.0487) is a normalized, fine-grain pressure vessel steel with controlled chemical composition and stable mechanical properties.

It is widely used in boilers, pressure vessels, and welded pressure equipment, and is comparable to A516 Gr.60, WSt E285, and other EN pressure vessel steels.

Its versatility, availability, and compliance with EN standards make P275NH a reliable and cost-effective choice for pressure equipment manufacturing.

1. Q: What is the fundamental difference between P275N, P275NH, P275NL1, and P275NL2?
A: The core distinction lies in their guaranteed impact toughness temperatures and application temperature ranges, which result from differences in chemical composition control and delivery condition requirements.
* P275N: Guarantees impact toughness at room temperature and down to -20℃. Suitable for general pressure vessels and boilers (-20℃ to +350℃).
* P275NH: Builds upon P275N with stricter chemical controls (e.g., lower S, P content) to ensure mechanical property stability at elevated temperatures. Suitable for higher temperature service (up to +400℃), such as steam headers and high-temperature vessels.
* P275NL1: Guarantees impact toughness down to -50℃ (longitudinal specimens). Designed for low-temperature environments (e.g., -40℃ to +350℃).
* P275NL2: Guarantees impact toughness down to -60℃ (longitudinal specimens) with even tighter control of S and P. Intended for more severe cryogenic applications (e.g., -50℃ to +350℃), such as LNG-related equipment.

2. Q: Why is controlling heat input and performing PWHT particularly important when welding P275NH plate?
A: P275NH is designed for high-temperature service.
* Controlling Heat Input (typically recommended <=35 kJ/cm): Prevents excessive grain growth in the Heat-
* Mandatory PWHT Requirement: Primarily aims to eliminate welding residual stresses. Under high-temperature and high-pressure conditions, residual stresses can promote stress corrosion cracking or creep damage. PWHT significantly reduces these stresses, enhancing the long-term safety and dimensional stability of the structure at high temperatures.

3. Q: How is the allowable stress for P275N steel plate determined at different design temperatures?
A: The room temperature yield strength cannot be used directly. It is essential to consult the allowable stress values at the design temperature provided in the relevant pressure vessel design codes (e.g., ASME BPVC Section II-D, EN 13445-2). These values are derived from the material's strength properties at elevated temperatures, considering factors like creep and oxidation, and then divided by a safety factor. For example, the allowable stress for P275N at 350℃ is significantly lower than its value at room temperature.

4. Q: When purchasing P275NL1/NL2 plate, what is the most critical acceptance test besides room temperature mechanical properties?
A: The most critical test is the Low-Temperature Impact Toughness (Charpy V-notch, CVN). Strict adherence to contract and standard (EN 10028-3) requirements is necessary:
* Verify Test Temperature: Is it -40℃, -50℃, or another specified temperature?
* **Verify SpecVerify Specimen Orientation: Transverse (T) or Longitudinal (L). Standard requirements for longitudinal specimens are typically higher than for transverse. The guaranteed values for NL1 and NL2 primarily apply to longitudinal specimens.
* Verify Acceptance Value: Confirm that the minimum impact energy (J) meets the requirement. This is the key indicator to prevent brittle fracture at low temperatures.

5. Q: What does the "Normalized" condition of P275N steel plate imply, and how does it affect fabrication?
A: "Normalized" is the standard delivery condition. It means the plate is reheated above its austenitizing temperature after rolling and then cooled uniformly in air.
* Purpose: To refine grain structure, homogenize the microstructure, improve mechanical properties and toughness, and relieve internal stresses.
* Impact on Fabrication: Subsequent hot forming (e.g., hot rolling into shells) or welding (equivalent to localized reheating and cooling) alters the material's condition. If the hot working temperature enters the normalizing range and is followed by air cooling, it may have a "normalizing effect." However, excessive temperatures or improper cooling can degrade properties. Therefore, for critical pressure parts subjected to significant hot work, re-normalizing heat treatment may be required to restore the specified properties.

6. Q: The yield strength of P275N plate varies with thickness. How is this considered in design?
A: EN 10028-3 clearly specifies the minimum yield strength (ReH) values for different thickness ranges (e.g., decreasing from 275 MPa for ≤16mm to 235 MPa for >100mm). This reflects the "thickness effect" where thicker sections cool slower, leading to a slight reduction in strength.
* In Design: The corresponding minimum yield strength value for the actual thickness range of the plate being used must be selected for calculations.
* In Procurement and Certification: The manufacturer's test certificate must provide the actual measured yield strength for the batch, corresponding to its thickness. This value must be >= the standard's specified minimum for that thickness.

7. Q: Can P275N be used interchangeably with common carbon steels (e.g., Q235B, Q345R) or American standard materials (e.g., SA516 Gr.60)?
A: They are not directly interchangeable. So-called "equivalent" grades are for approximate reference only.
* Different Standard Systems: P275N conforms to the European standard (EN). Its chemical composition, mechanical properties, test methods, and acceptance criteria differ from Chinese (GB) or American (ASTM/ASME) standards.
* Differences in Key Properties: Even if the strength levels are similar, there can be variations in the alloying system, impact toughness requirements, and applicable temperature ranges.
* Correct Procedure: Any material substitution must be re-calculated and approved by the design authority, ensuring the new material fully complies with all requirements of the original design code. Compatibility with the welding procedure must also be re-evaluated.