1. Product Overview
S275NH is a non-alloy structural steel grade designated for hollow sections (tubes/pipes) and other structural components. The designation breaks down as follows:
S: Structural Steel
275: Minimum specified yield strength (ReH) of 275 MPa (Megapascals) at room temperature.
N: Normalized rolled (meaning the steel has been normalized, a heat treatment process that improves toughness and refines the grain structure).
H: Hollow sections (specifically for products like pipes, tubes, hollow sections).
This grade is specified under the European standard EN 10210-1:2006 for hot-finished seamless and welded structural hollow sections. It is a common and versatile steel used extensively in construction and engineering.
2. Key Features and Applications
Good Weldability and Machinability: As a non-alloy, low-carbon steel, it is easy to weld and fabricate.
Improved Toughness: The "N" (Normalized) condition ensures better impact toughness, making it suitable for structures subjected to dynamic loads or lower temperatures.
Common Applications:
Building frames and structures (commercial and industrial)
Bridges
Machinery frames
Support columns and beams
General structural applications requiring good strength and toughness.
3. Chemical Composition (By Weight %)
The chemical composition is specified in EN 10210-1. The values are maximum percentages unless a range is indicated.
| Element | Standard Requirement (Max %) | Typical Value / Note |
|---|---|---|
| Carbon (C) | 0.20% | Low carbon for good weldability. |
| Silicon (Si) | 0.55% | - |
| Manganese (Mn) | 1.50% | - |
| Phosphorus (P) | 0.035% | Impurity control. |
| Sulfur (S) | 0.035% | Impurity control. |
| Nitrogen (N) | 0.015% | - |
Note: The steel must be fully killed (deoxidized).
4. Mechanical Properties
The following table outlines the minimum required mechanical properties as per EN 10210-1.
| Property | Symbol | Value | Notes / Conditions |
|---|---|---|---|
| Yield Strength | ReH | ≥ 275 MPa | This is the key parameter. Measured at a thickness (t) ≤ 16 mm. For thicker sections, the min. yield strength decreases (see below). |
| Tensile Strength | Rm | 370 - 530 MPa | The range the ultimate strength must fall within. |
| Elongation at Fracture | A | ≥ 22% (Longitudinal) | For a proportional gauge length of 5.65√So. Indicates good ductility. |
| Impact Energy (Charpy V-Notch) | KV | ≥ 27 Joules (J) | Tested at -20°C. This is a key benefit of the "NH" grade over non-normalized grades. |
Yield Strength vs. Thickness
The minimum yield strength value depends on the product's thickness (t):
| Thickness (t) | Minimum Yield Strength (ReH) |
|---|---|
| t ≤ 16 mm | 275 MPa |
| 16 mm < t ≤ 40 mm | 265 MPa |
| 40 mm < t ≤ 63 mm | 255 MPa |
| 63 mm < t ≤ 80 mm | 245 MPa |
| 80 mm < t ≤ 100 mm | 235 MPa |
5. Technical Data Table Summary
| Parameter | Specification / Value | Governing Standard |
|---|---|---|
| Product Standard | Hot-finished structural hollow sections (seamless and welded) | EN 10210-1:2006 |
| Material Grade | S275NH | EN 10210-1 / EN 10025-3 |
| Delivery Condition | Normalized (N) | - |
| Main Application | Load-bearing structural components | - |
| Yield Strength (t≤16mm) | ≥ 275 MPa | EN 10210-1 |
| Tensile Strength | 370 - 530 MPa | EN 10210-1 |
| Elongation (A) | ≥ 22% | EN 10210-1 |
| Impact Energy (at -20°C) | ≥ 27 J | EN 10210-1 |
| Density | Approximately 7.85 g/cm³ | - |
6. Important Notes for Engineers and Buyers
Equivalent Grades: S275NH is very similar to S275J2H (from EN 10219 for cold-formed hollow sections). The main difference often lies in the impact test temperature.
Comparison with S355NH: S355NH has a higher minimum yield strength (≥ 355 MPa) but may have slightly different chemical composition limits (e.g., higher Carbon Equivalent Value - CEV) which can affect weldability. The choice depends on the design strength requirements.
Certification: Always request a Mill Test Certificate (MTC) / EN 10204 3.1 Certificate from the supplier. This document verifies that the material complies with the standard's chemical and mechanical requirements.
Design Standards: When designing structures with S275NH, engineers should refer to relevant standards like the Eurocode 3 (EN 1993-1-1).
In summary, S275NH is a reliable, normalized structural steel pipe offering an excellent balance of strength, toughness, and weldability, making it a fundamental choice for a wide range of construction projects in Europe and internationally.
