The Four Economy Structural Grades
ASTM A36, JIS SS400, St37, and GB Q235 are the most frequently ordered carbon steel grades for structure H-beams, and they are close relatives in the 235 to 250 MPa yield class. A36 to ASTM, with a minimum yield of 250 MPa and a tensile range of 400 to 550 MPa, is the standard American grade. SS400 to JIS G3101 guarantees a tensile range of 400 to 510 MPa with a minimum yield of 245 MPa. St37-2 to the former DIN 17100, equivalent to S235JR in EN 10025-2, provides a minimum yield of 235 MPa, and Q235B to GB/T 700 provides the same yield with a tensile range of 370 to 500 MPa.
How the Grades Compare in Practice
For most building frames, all four grades are interchangeable at the design level because the difference in yield strength, 235 to 250 MPa, is small compared with the safety factors in the design codes. The choice is normally driven by the design standard of the project and by stock availability in the local market. When a project is designed to Eurocode, S235JR or S275JR is specified; to American practice, A36; to Japanese practice, SS400; and to Chinese practice, Q235B.
Mechanical Properties and Weldability
All four grades are low-carbon structural steels with excellent weldability using ER70S-6 wire or E7018 electrodes, and none requires preheat in normal section sizes. The carbon content is similar, about 0.20 percent maximum in most cases, and the elongation is above 20 percent, which gives ductile behavior in bending and connection zones. Because the grades are so close, substitution between them is usually accepted by engineers provided the yield and tensile values meet the design assumptions.
Stock Availability and Lead Times
Common H-beam sizes such as HW 100 to HW 400, HM 300 to HM 600, and the European HEA, HEB, and IPE series are held in stock in 6 and 12 meter lengths, with delivery in days for standard quantities. Non-standard sizes, long lengths, and large tonnage are supplied against the rolling schedule, and the lead time should be confirmed at quotation. Stock beams are supplied with mill certificates, and surface condition can be checked before dispatch.
Ordering Advice for Structure Beams
When ordering structure H-beams, state the standard and grade, series and size, length, and quantity, and confirm whether the price includes cutting, drilling, or surface treatment. Request the mill test certificate with the delivery and verify that the heat number and mechanical results match the order. For projects that allow grade substitution, confirm the acceptable equivalents with the engineer in advance to avoid delays at material approval.
Frequently Asked Questions
Q: Is St37 the same as Q235?
St37-2 and Q235B are both 235 MPa yield grades, with St37 following the former DIN 17100 and Q235B following GB/T 700; S235JR is the modern EN equivalent.
Q: Which grade is cheapest for an H-beam frame?
Q235B and St37-equivalent S235JR are typically the lowest-priced grades, followed closely by SS400 and A36.
Q: Are these grades weldable without preheat?
Yes, all four grades weld without preheat in normal thicknesses using standard carbon steel consumables.
Q: What sizes are usually held in stock?
HW 100 to HW 400, HM and HN series, and HEA, HEB, and IPE sections in common sizes, in 6 and 12 meter lengths.
Q: Can stock beams be supplied cut to length?
Yes, beams are cut to the required lengths at the stockyard, with saw-cut ends prepared for fabrication.