Steel H-Beam vs I-Beam Buying Guide: Sizes, Grades (A36, S275, Q235/Q355), and How to Specify Structural Beams for Buildings and Bridges
When a steel frame must carry floors, roofs, or bridge decks, the members doing the work are almost always steel H-beams and I-beams — hot-rolled sections shaped so the two flanges resist bending while the web resists shear. Pick the wrong section family, grade, or length tolerance and the beam arrives short, drills badly, or needs costly substitution after the steelwork is already fabricated.
This guide compares the beam families buyers actually quote, the size and grade options, the standards inspectors check, and exactly what to put on your RFQ.
H-Beam vs I-Beam vs Wide-Flange: What’s the Difference
The three names overlap, and regional usage differs, so confirm by section drawing:
| Section | Shape | Flange Width | Best For |
|---|---|---|---|
| H-beam (H-section, UC/UB) | H — wide parallel flanges | Wide (≈ depth for columns) | Columns, heavy frames, bridges |
| I-beam (INP / S-beam) | I — tapered inner flange faces | Narrow | Lifting, trolleys, light joists |
| Wide-flange (W-shape) | W — parallel flanges | Wide | US beams, general framing |
Modern construction uses mostly H and wide-flange sections because their parallel flange faces make bolting simple; classic tapered I-beams survive mainly as runway and monorail track.
Sizes Buyers Specify Most Often
- H-beam (metric): 100×100 to 400×400 mm columns; beams 150–900 mm deep.
- W-shape (US): W8–W36; state the weight per foot (e.g., W18×76).
- I-beam (European/Japanese): INP 80–600; IPN/JIS equivalents.
- Length: 6 m, 9 m, 12 m standard; cut-to-length on request.
Always send the section designation plus mass per metre — two beams with the same depth can differ 30% in weight.
Grades Compared
| Grade | Standard | Yield (MPa) | Use |
|---|---|---|---|
| Q235B | GB/T 700 | 235 | General Chinese projects |
| Q355B | GB/T 1591 | 355 | Heavier Chinese frames |
| A36 | ASTM A36 | 250 | US general structures |
| A572 Gr 50 | ASTM A572 | 345 | US high-strength |
| S275JR / S355JR | EN 10025 | 275 / 355 | European / CE projects |
Standards and Tolerances
- ASTM A6: US dimensional tolerances for rolled shapes.
- EN 10034 / 10024: European I/H tolerances.
- JIS G3101 / G3192: Japanese sections and dimensions.
- EN 1090: fabrication / CE marking rules for structural work.
State the tolerance standard so camber, sweep, and end-squareness are judged correctly at inspection.
Surface, Primer, and Coating
- As-rolled (mill scale): cheapest; for indoor primer-coated frames.
- Shot-blasted + shop primer: standard for fabricated steelwork.
- Hot-dip galvanized: outdoor, corrosive sites (check section size limits).
- Fireproof coating base: confirm adhesion class if intumescent paint follows.
Common Applications
- Building frames: columns, girders, joists.
- Bridges: plate-built and rolled girders.
- Industrial plants: crane girders, platforms.
- Solar / infrastructure mounting frames.
RFQ Checklist
- Section: H / I / W with designation + kg/m
- Grade and standard (Q355B / A36 / S355JR…)
- Lengths (fixed or random) and cutting tolerance
- Surface: as-rolled / shot-blast+primer / HDG
- Quantity (tonnes, per size) and piece marks
- MTC, inspection, and destination / Incoterm
FAQ
H or I for my columns? H (wide flange square-ish) for columns; I for monorail trolleys where the taper helps.
Can Q355B replace S355JR? Often mechanically yes, but confirm impact testing and CE documentation with your engineer.
What lengths ship? 6/9/12 m are standard; over-length needs flat-rack or break-bulk booking.
Why Source Beams from Yihang Metal
Yihang Metal supplies H-beams, I-beams, and wide-flange sections in Q235/Q355, A36/A572 Gr 50, and S275/S355 to ASTM, EN, and JIS tolerances, as-rolled or shop-primed, with mill test certificates and third-party inspection. Standard sizes typically ship in 20–30 days for full containers.
Ready to specify your beams? Send us the section designation, grade, lengths, and tonnage, and we will confirm availability and lead time with a fixed-price quote and MTC. Email [email protected] or use the quote form on this page — our team replies within one business day.