1. The Standard Section Range
Standard rolled H-beams and I-beams are catalogued by nominal height, flange width, web thickness and flange thickness. Heights commonly run from around one hundred millimetres up to several hundred millimetres, and each height is offered in a range of weights per metre. The catalogue values are nominal, and the applicable standard sets the permissible deviations.
2. ASTM A36 and Q235B Compared
ASTM A36 specifies a minimum yield strength of about 250 megapascals and a tensile range that suits welded and bolted construction. Q235B to GB/T 700 has a similar yield level but its own chemistry limits and impact requirements. Both weld readily and are used for general structural framing, so the choice is normally made by the project specification and the design code in force.
3. Dimensional Tolerances
Standards such as ASTM A6, EN 10034 and GB/T 11263 set tolerances on height, flange width, web and flange thickness, out-of-square and straightness. These tolerances matter for automated welding and for connections that rely on parallel flange faces. A dimensional inspection record with the shipment avoids disputes when sections are assembled on site.
4. How to Specify a Standard Beam
A complete specification gives the standard, the grade, the section designation, the length and the quantity. The buyer should also state the surface condition, whether mill certificates are required and any tolerance on length. Where the beam is to be galvanized or welded into a fabricated girder, the relevant process requirements should be named at the enquiry stage.
5. Quality Evidence
A mill test certificate is the basic quality document, showing heat number, chemical composition and mechanical properties for the cast. For larger projects, third-party inspection and dimension checks against the ordered standard are commonly added. Keeping the certificate linked to the heat number marked on each bundle makes traceability straightforward.
Frequently Asked Questions
Q: Are A36 and Q235B interchangeable?
They are close in yield level and both weld well, but the governing design code and the project specification decide which one may be used.
Q: What heights are available as standard?
Standard rolled sections cover a wide range of heights, and the exact availability depends on the mill and the section family.
Q: How are beam dimensions checked?
Against the tolerances of the applicable standard, using measurements of height, flange width, thickness and straightness.
Q: Can beams be ordered cut to length?
Yes, cut-to-length supply is routine, and the buyer should state the tolerance on the finished length.
Q: What certificate comes with the steel?
A mill test certificate stating heat number, chemistry and mechanical properties is standard for structural beams.