S355H Overview
S355H is a structural steel grade used for hollow sections such as circular, square, or rectangular profiles, specified per EN 10210 for hot-finished structural hollow sections or EN 10219 for cold-formed welded sections. The H denotes hollow sections, and variants such as S355J2H or S355K2H indicate specific impact toughness requirements. The minimum yield strength is 355 MPa with tensile strength typically 470 to 630 MPa.
S355NH Overview
S355NH is specified under the same hollow section standards with additional requirements for normalization or normalization rolling per EN 10025-3 for normalized fine-grain steels. The N indicates that the steel is normalized or normalized rolled, which refines the grain structure and improves toughness and weldability, especially at low temperatures. S355NH requires guaranteed impact toughness, typically 40 J at minus 20 degrees C for the NH grade.
Key Differences
The primary difference is the normalized condition: S355H is a general hollow section grade with optional impact requirements, while S355NH is the normalized fine-grain version with guaranteed low-temperature toughness and better weldability. S355NH is more suitable for demanding applications in cold climates, offshore structures, or where improved weldability is needed.
Mechanical Properties
Both have a minimum yield strength of 355 MPa and similar tensile strength, but S355NH has guaranteed impact toughness of 40 J at minus 20 degrees C due to the fine-grain normalized structure, while S355H's impact requirements depend on the specific variant specified, such as J2H at 27 J or K2H at 40 J at minus 20 degrees C.
Applications
S355H is used for general structural columns, beams, and hollow profiles in construction. S355NH is used for structural applications requiring higher toughness such as cold-climate structures, offshore platforms, and critical welded components where guaranteed low-temperature performance is required.
Frequently Asked Questions
Q: What is the difference between S355H and S355NH?
A: S355NH is the normalized fine-grain version with guaranteed low-temperature toughness; S355H is the general grade with optional impact requirements.
Q: What does the N in S355NH mean?
A: Normalized or normalized rolled delivery, refining the grain for better toughness and weldability.
Q: What impact energy does S355NH require?
A: Typically 40 J at minus 20 degrees C per EN 10210 or EN 10219.
Q: Which standard governs these grades?
A: EN 10210 for hot-finished and EN 10219 for cold-formed structural hollow sections, with EN 10025-3 for normalized fine-grain steels.
Q: Where is S355NH preferred?
A: In cold climates, offshore structures, and critical welded components requiring guaranteed toughness.
Q: What is the yield strength of both?
A: 355 MPa minimum, with tensile strength typically 470 to 630 MPa.
For S355H and S355NH hollow section and plate quotations, contact our sales team.
