Q235, A36, S235JR and S235J2H H Beams for Construction

Grade Portfolio and Standard Coverage

Hot rolled H beams for construction are normally ordered against one of three regional systems: GB/T 700-2006 for Q235, ASTM A36/A36M for the American market, and EN 10025-2 for S235JR and S235J2. The four grades sit in the same strength band, so selection usually turns on impact test temperature, chemical limits and the inspection document required, not on strength alone. The section geometry is produced to GB/T 706-2016 for hot rolled sections, with dimensional tolerances agreed to EN 10034 or ASTM A6/A6M when the project specification is European or American.

For S235 grades, yield falls as flange thickness grows: 225 MPa from 16 to 40 mm, 215 MPa from 40 to 63 mm and 215 MPa up to 80 mm, with tensile strength stepping down to 350-500 MPa above 100 mm. Buyers should therefore state the section size and test temperature, not only the grade name, when a thin-flange and a heavy-flange section are both in the same order.

Chemical Composition Limits

Carbon and manganese control both weldability and Charpy performance, so the chemical tables of the four grades are not interchangeable. Q235B permits slightly higher phosphorus and sulphur than the European J0 and J2 classes, while A36 fixes a manganese range rather than a maximum.

Note that the H suffix used with S235J2H denotes delivery as a hot finished hollow section under EN 10210-1 rather than a hot rolled open section; the impact class, however, is the same as for S235J2, that is 27 J at -20 °C on longitudinal Charpy V-notch specimens tested to EN ISO 148-1.

Section Range, Tolerances and Rolling Practice

Beams are rolled from continuously cast blooms and finished in a universal mill, which forms the parallel flanges and the central web without a separate welding step. Press or roller straightening follows cooling, and the finished piece is cut to ordered length, usually 6 to 12 m, or to a project cutting plan. Flange and web thickness tolerances are agreed at the ordering stage; the most common references are EN 10034 for I and H sections, ASTM A6/A6M general requirements for American practice and GB/T 706-2016 for domestic sections.

Mill test certificates are issued to EN 10204 type 3.1 in the European route and to the equivalent clause of ASTM A6/A6M in the American route. The certificate records heat number, chemical analysis, tensile and yield results, elongation and Charpy energy, and lets the fabricator trace each beam back to its cast.

Applications and Selection Logic

Q235 and A36 H beams are used for general building frames, mezzanine floors, plant structures and support frames where the design temperature stays above freezing. S235JR suits the same duties in European specifications. S235J2 is preferred for cold store frames, outdoor structures in cold regions and members that must pass a -20 °C impact requirement. When a project mixes grades, keep the grade and heat number marked on each section so that on-site traceability is not lost during fabrication.

Frequently Asked Questions

Q: Is Q235 equivalent to S235JR or to A36?
A: They are close but not identical. Q235B and S235JR both specify 235 MPa minimum yield, but S235JR limits phosphorus and sulphur to 0.035% and requires 27 J at +20 °C, while A36 specifies 250 MPa minimum yield with a 400-550 MPa tensile range. Substitution must be approved by the designer against the governing specification.

Q: What does the H in S235J2H mean?
A: It identifies hot finished hollow sections supplied under EN 10210-1. If the order is for an open hot rolled H beam, the correct designation is S235J2 to EN 10025-2, and the two should not be mixed on a single certificate.

Q: At what temperature are the impact tests carried out?
A: Q235B and S235JR are tested at +20 °C with 27 J minimum, S235J2 at -20 °C with 27 J minimum. A36 has no Charpy requirement unless a supplementary impact clause is added to the order.

Q: Which certificate type is supplied with the beams?
A: EN 10204 type 3.1 is supplied as standard for European grades, giving heat-by-heat chemical and mechanical results signed by the manufacturer's independent inspection representative. Type 3.2 is available when a third-party inspector must countersign.

Q: Can the beams be cut to length or drilled before delivery?
A: Yes. Beams can be cut to a project cutting plan, coped, punched or drilled on request. Holes are normally drilled rather than flame cut when the connection is bolted, and the grade and heat number are transferred to the cut piece to keep traceability.