Overview
S355J2H is a high-quality, non-alloy structural steel grade defined by the European standard EN 10210. The "H" specifically indicates that it is supplied as a Hollow Section (pipe or structural tubing). It is known for its excellent combination of strength, toughness, and weldability.
Breakdown of the Designation
The name "S355J2H" can be broken down to understand its properties:
S: Stands for "Structural Steel".
355: Indicates the minimum yield strength (ReH) at room temperature for thicknesses ≤ 16 mm. The value is 355 MPa (or 355 N/mm²). This is the key indicator of its strength.
J2: Denotes the impact toughness (Charpy V-notch test) at -20°C.
J: Means the steel is impact tested.
2: Specifies the test temperature of -20°C and a minimum energy absorption of 27 Joules.
H: Signifies that the product is a Hollow Section (e.g., circular, square, or rectangular pipes/tubes).
Key Characteristics & Mechanical Properties
The properties are specified in EN 10210-1. The following are typical minimum values for common thicknesses:
| Property | Value (for thickness ≤ 16 mm) | Notes |
|---|---|---|
| Minimum Yield Strength (ReH) | 355 MPa | This is the stress at which the material begins to deform plastically. It's the primary design criterion for structural components. |
| Tensile Strength (Rm) | 470 - 630 MPa | The maximum stress the material can withstand while being stretched. |
| Elongation at Break | ~22% (varies by thickness) | A measure of ductility (how much it can stretch before breaking). |
| Impact Energy (KV) | ≥ 27 J at -20°C | This ensures good toughness for use in cold or dynamic loading environments. |
Note: Mechanical properties, especially yield and tensile strength, decrease slightly as the material thickness increases.
Chemical Composition
The chemical composition (by weight %) is tightly controlled in EN 10210-1. A typical range is:
Carbon (C): ≤ 0.22% (Relatively low carbon content improves weldability)
Manganese (Mn): ≤ 1.60%
Silicon (Si): ≤ 0.55%
Phosphorus (P): ≤ 0.035% (Impurity, kept low)
Sulfur (S): ≤ 0.035% (Impurity, kept low)
This balanced composition provides the desired strength while maintaining good weldability and formability.
Comparison with Similar Grades
It's common to compare S355J2H with other similar structural steels:
vs. S355J2H vs. S355J2H:
S355J2H is for hot-finished hollow sections (EN 10210).
S355J2H is for cold-formed hollow sections (EN 10219). The chemical composition and mechanical properties are very similar, but the manufacturing process is different, which can lead to slight variations in residual stresses and dimensional tolerances.
vs. S355JR:
S355JR is a general structural steel plate/section grade. Its impact toughness is tested at +20°C (room temperature), making it unsuitable for low-temperature applications where S355J2H (-20°C toughness) would be required.
vs. ASTM A500 Grade C:
A500 Gr. C is a common American standard for structural tubing. Its specified minimum yield strength is 50 ksi (~345 MPa), which is very close to S355J2H's 355 MPa. They are often considered comparable grades for many structural applications, though the exact chemical and toughness requirements differ.
Common Applications
S355J2H pipes and hollow sections are widely used in heavy-duty structural applications where high strength and good toughness are critical:
Building and Construction: Structural columns, beams, and trusses in commercial buildings, industrial halls, and stadiums.
Bridges: As primary load-bearing members.
Heavy Equipment: Frames and booms for cranes, excavators, and other machinery.
Offshore and Marine Structures: Supports and frameworks that require resistance to dynamic loads and cold temperatures.
General Mechanical Engineering: For frames, supports, and chassis that require high strength-to-weight ratio.
Summary
In short, S355J2H carbon steel pipe is a high-strength, low-alloy structural steel tube characterized by:
Minimum Yield Strength: 355 MPa
Good Impact Toughness: 27 J at -20°C
Excellent Weldability and formability.
Primary Standard: EN 10210 (for hot-finished hollow sections).
It is a premium choice for engineers and designers working on critical structures that must withstand significant loads and potentially low environmental temperatures.
