S355K2H rectangular hollow section Description
S355K2H structural hollow section (material number 1.0512) is a European structural grade carrying a minimum yield strength of 355 MPa and a guaranteed Charpy impact energy of 40 J at −20 °C - the highest toughness rating in the S355 class. It is supplied hot-finished as EN 10210 S355K2H or cold-formed as EN 10219 S355K2H, in round, square and rectangular shapes. The K2 impact rating, not the yield number, is what decides whether this grade is specified for fracture-critical, thick-walled or cold-climate structures.
S355K2H hollow section belongs to the family of welded structural hollow sections used as load-bearing members - columns, braces, truss chords and crane booms - rather than as pressure pipe. The same chemistry and strength are delivered through two manufacturing routes, and the route changes the residual stress, corner geometry and cost, but not the grade's mechanical minimums.
GNEE supplies S355K2H HSS in CHS, SHS and RHS with EN 10204 3.1 certificates and third-party inspection on request. Send your section type, dimensions and quantity for a quotation with lead time.
Technical Specifications
| Parameter | Capability |
|---|---|
| Standard | EN 10210-1 (hot finished) or EN 10219-1 (cold formed) |
| Grade / material number | S355K2H / 1.0512 |
| Section shape | CHS (round), SHS (square), RHS (rectangular) |
| Dimensional range | CHS OD ≈ 21.3–660 mm; SHS 20×20 to 400×400 mm; RHS 40×20 to 500×300 mm |
| Wall thickness | 1.0–25 mm (heavier walls available on request) |
| Length | 6 m, 12 m, or cut to length |
| Tolerance | Per EN 10219-2 / EN 10210-2: OD ±1% (min ±0.5 mm, max ±10 mm); wall per standard |
| Ends | Square cut, or bevelled for butt welding |
| Surface | Black (as-welded), oiled, shot-blasted and primed, painted, or galvanized on request |
| Delivery condition | Hot finished, or cold formed (normalizing/controlled rolling for S355 series where required) |
| Certification | EN 10204 3.1; third-party inspection (e.g. SGS, BV, TÜV) available |
Chemical Composition
The S355K2H chemical composition is controlled to the ladle-analysis limits below (maximum % unless noted). Each element manages a specific risk for weld toughness and the fine-grain structure behind the K2 rating.
| Element | S355K2H (max %) | Note |
|---|---|---|
| Carbon (C) | 0.22 | For nominal wall ≤ 40 mm (0.22 also for >40–65 mm) |
| Silicon (Si) | 0.55 | - |
| Manganese (Mn) | 1.60 | - |
| Phosphorus (P) | 0.030 | K2H tighter than J0H (0.035) |
| Sulfur (S) | 0.030 | K2H tighter than J0H (0.035) |
| Nitrogen (N) | 0.012 | Not applicable if Al total ≥ 0.020 % with Al/N ≥ 2:1 |
| CEV (max) | 0.45 | For wall ≤ 16 mm; rises with thickness |
Each controlled element manages a specific risk: low P and S protect weld toughness and through-thickness ductility, and nitrogen is bound by aluminum or other nitride-formers to preserve the fine-grain structure that the K2 impact rating depends on.
Mechanical Properties
The S355K2H mechanical properties below are the EN 10219-1 / EN 10210-1 minimum requirements. Note that the guaranteed yield steps down as the wall thickens.
| Property | S355K2H |
|---|---|
| Yield strength ReH (≤ 16 mm) | ≥ 355 MPa (≈51,500 psi) |
| Yield strength (16–40 mm) | ≥ 345 MPa |
| Yield strength (40–65 mm) | ≥ 335 MPa |
| Tensile strength Rm | 470–630 MPa (510–680 MPa for thin walls ≤ 3 mm) |
| Elongation A | ≥ 20 % (EN 10219, transverse); ≥ 22 % hot finished (EN 10210) |
| Impact (Charpy V, K2) | 40 J at −20 °C (average) |
| CEV (max) | 0.45 (≤ 16 mm), increasing with thickness |
| Test standards | Tensile EN 10002-1; impact EN 10045-1 / ISO 148 |
The S355K2H yield strength is 355 MPa for walls up to 16 mm, and a common pitfall is applying that thin-wall value to a 20 mm wall, which over-estimates capacity. Confirm the value for your actual wall thickness from the certificate.
S355J0H vs S355J2H vs S355K2H
| Grade | Test temp. | Min. impact (KV) | Typical use |
|---|---|---|---|
| S355J0H | 0 °C | 27 J | General structures, mild climates |
| S355J2H | −20 °C | 27 J | Cold-climate and heavier structures |
| S355K2H | −20 °C | 40 J | Fracture-critical, thick-wall, dynamic or low-temp structures |
All three share the 355 MPa yield and 470–630 MPa tensile band. The only engineering difference is impact energy, so the choice is a toughness-and-risk decision, not a strength upgrade.
Hot Finished vs Cold Formed
| Aspect | Hot finished (EN 10210-1) | Cold formed (EN 10219-1) |
|---|---|---|
| Residual stress | Low | Higher (corner strain hardening) |
| Corner radius | Larger, more uniform | Sharper |
| As-formed tolerance | Generally wider | Tighter |
| Size / wall limit | Larger and heavier sections | Mid-range, cost-efficient |
| Relative cost | Higher | Lower within its range |
Both routes satisfy the same product requirements, but only one removes a specific variable - hot finishing eliminates most residual stress, while cold forming gives tighter as-formed dimensions at lower cost. The design code and tolerance target decide the route.
S355K2H CS Hot Finished Rectangular Pipes
Quality Control and Testing
Chemical analysis - ladle analysis verified against EN 10219-1 / EN 10210-1 limits, reported on the 3.1 certificate.
Tensile and Charpy impact testing - one tensile and impact set per tested batch; the −20 °C / 40 J K2 value is confirmed, not assumed.
Dimensional verification - outside dimension, wall thickness, straightness, corner profile and mass per EN 10219-2 / EN 10210-2.
Weld integrity - longitudinal seam NDT (e.g. ultrasonic) to detect discontinuities; hydrostatic testing is not a hollow-section requirement (it is a pressure-pipe test).
Visual inspection and marking - steel designation, manufacturer, and (for specific inspection) order/heat number per EN 10219 / EN 10210.
Why Source S355K2H from GNEE
Supply across both routes - hot finished (EN 10210-1) and cold formed (EN 10219-1) - with the grade, route and tolerance confirmed at quotation.
EN 10204 3.1 certificates as standard; third-party inspection (SGS, BV, TÜV) arranged on request.
Section types CHS / SHS / RHS, with cutting, bevelling, blasting and coating handled in-house.
Technical support on grade selection, impact requirement and welding input data.
Test and inspection
Packaging and shipping
Send your section type, dimensions, grade route (EN 10210 or EN 10219) and quantity - our technical team will confirm the specification and return a quotation with lead time. Contact GNEE today.
FAQ
What does S355K2H mean?
S355K2H is a European grade for structural hollow sections. S means structural steel, 355 is the minimum yield strength in MPa (≥355 MPa for wall thickness up to 16 mm), K2 means a guaranteed Charpy impact energy of 40 J at −20 °C, and H identifies the grade as a hollow section (EN 10210 / EN 10219) rather than a flat or long product. Its material number is 1.0512.
What is the difference between S355J0H, S355J2H and S355K2H?
All three share the same 355 MPa yield and 470–630 MPa tensile band; they differ only in impact toughness. S355J0H is tested at 0 °C with a 27 J minimum, S355J2H at −20 °C with 27 J, and S355K2H at −20 °C with a higher 40 J minimum. For fracture-critical members, thick walls, dynamic loads or cold-climate sites, specify S355K2H.
Is S355K2H hot finished or cold formed?
S355K2H is available under both EN 10210-1 (hot finished) and EN 10219-1 (cold formed). Hot finished sections have lower residual stress, larger corner radii and better through-thickness uniformity; cold formed sections are produced from strip at ambient temperature with sharper corners and are generally more economical within their size range. The choice follows your design code and tolerance/cost targets.
What yield and tensile strength does S355K2H have?
Minimum yield strength is 355 MPa for wall thickness up to 16 mm, stepping down to 345 MPa (16–40 mm) and 335 MPa (40–65 mm). Tensile strength is 470–630 MPa for walls above 3 mm; some mill certificates for thin walls (≤3 mm) quote 510–680 MPa. Verify the exact band on the EN 10204 3.1 certificate.
Can S355K2H be used for pressure piping?
No. S355K2H is a structural hollow section designed to carry axial, bending and shear loads in framed structures - it is not a pressure-containment pipe. For internal-pressure service use linepipe (API 5L, EN ISO 3183) or pressure-vessel standards, which carry their own design, hydrostatic-test and NDT requirements.
What is the carbon equivalent and preheat for welding S355K2H?
Maximum CEV is 0.45 for thickness up to 16 mm, rising with wall thickness per EN 10210 / EN 10219. Preheat and interpass temperatures follow your qualified WPS and EN 1011-2, driven by CEV, thickness and hydrogen level. The certificate rarely prints CEV automatically - request it as a reported value on the 3.1 MTC.
What sizes and wall thicknesses are available?
Cold-formed ranges run CHS outside diameter about 21.3–660 mm, SHS 20×20 to 400×400 mm, RHS 40×20 to 500×300 mm, wall 1.0–25 mm (heavier on request), lengths 6 m / 12 m or cut to length. Hot-finished sections cover similar and often larger/heavier sizes. Exact stock depends on the mill - request a current size and grade availability list before specifying.
Should I specify EN 10210 or EN 10219?
Specify EN 10210-1 (hot finished) when the design code calls for low residual stress, larger corner radii or heavier walls beyond the cold-forming comfort range. Specify EN 10219-1 (cold formed) for general construction where cost and tighter as-formed tolerances matter. If your drawing names a standard, quote that standard; otherwise we will confirm the route at quotation.
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