How H-Beam Grades Are Chosen
There is no single steel grade for an H-beam. The grade is selected from mechanical properties, chemical composition and the demands of the application, and the same section can be rolled in several grades. Because grades are named and controlled under different regional standards, the first step is always to fix the standard system the project follows, whether that is GB/T, ASTM, EN or JIS.
Chinese Grades to GB/T 11263 and GB/T 1591
Hot-rolled H-beams in China are dimensioned to GB/T 11263-2017, which also defines the HW, HM and HN series. The steel itself is normally ordered to GB/T 1591-2018 for low-alloy high-strength structural steel, or to GB/T 700 for the plain carbon grade Q235B.
| Grade | Yield strength | Impact test | Typical use |
| Q235B | 235 MPa min | +20 °C | General building frames, light industrial sheds, low-load members |
| Q355B | 355 MPa min | +20 °C | Standard high-rise and industrial steelwork |
| Q355C | 355 MPa min | 0 °C | Cooler climates, moderate dynamic load |
| Q355D | 355 MPa min | -20 °C | Long-span bridges, low-temperature service |
| Q355E | 355 MPa min | -40 °C | Severe cold, heavy dynamic load |
| Q390, Q420, Q460 | 390-460 MPa min | By grade | Special heavy structures and seismic design |
The B, C, D and E suffixes denote the impact test temperature, not the strength: B is tested at +20 °C, C at 0 °C, D at -20 °C and E at -40 °C. Q355B, Q355C and Q355D require a minimum absorbed energy of 34 J, while Q355E requires 27 J at -40 °C. Q355 is the current designation for the grade that was previously called Q345.
American Grades to ASTM
ASTM A36 - 250 MPa minimum yield, the general-purpose carbon structural steel and the closest equivalent to Q235.
ASTM A572 Gr.50 - 345 MPa minimum yield with higher tensile strength, broadly comparable to Q355.
ASTM A992 - the standard grade for hot-rolled W-shapes, with 345-450 MPa yield and 450 MPa minimum tensile plus limits on the yield-to-tensile ratio for seismic framing.
ASTM A588/A588M - weathering steel with added copper, chromium and nickel for unpainted outdoor service.
European Grades to EN 10025-2
| Grade | Yield strength | Charpy impact |
| S235JR | 235 MPa min | 27 J at +20 °C |
| S275JR | 275 MPa min | 27 J at +20 °C |
| S355JR | 355 MPa min | 27 J at +20 °C |
| S355J2 | 355 MPa min | 27 J at -20 °C |
| S355K2 | 355 MPa min | 40 J at -20 °C |
| S460M | 460 MPa min | By grade |
The suffix letters matter as much as the number. JR denotes room-temperature impact testing, J0 and J2 denote 0 °C and -20 °C testing at 27 J, and K2 demands 40 J at -20 °C. The N and M designations indicate normalized or thermomechanically rolled delivery. S355J2 is the usual European substitute for Q355D in cold-climate work, and S355JR is the direct counterpart of Q355B.
Japanese Grades and Selection Factors
Japanese sections are supplied to JIS G3101 for general structural steel, which covers SS400, and to JIS G3106 for welded structural steel, which covers SM400, SM490, SM520 and SM570. SS400 corresponds broadly to Q235, and SM490 corresponds broadly to Q355. Once the standard system is fixed, five factors drive the final grade choice.
Load: heavy static or dynamic loading such as bridge girders calls for 345-355 MPa and above.
Ambient temperature: for cold service select a grade impact tested at or below the minimum design metal temperature, such as Q355D, S355J2 or A572 Gr.50.
Welding: low-alloy grades need matching electrodes, controlled heat input and preheat in thick sections.
Corrosion: coastal or humid sites justify a weathering grade such as Q355NH or ASTM A588/A588M.
Availability: not every grade is rolled in every HW, HM or HN size, so the section list constrains the grade list.
Frequently Asked Questions
Q: Which steel grade is most common in H-beams?
Q235B and Q355B dominate Chinese production, while ASTM A992 and ASTM A572 Gr.50 are standard for American W-shapes.
Q: What is the difference between Q355B, Q355C and Q355D?
Yield strength is the same; the letters set the impact test temperature at +20 °C, 0 °C and -20 °C respectively.
Q: Is Q355 the same as S355?
They are close equivalents. Q355D aligns with S355J2, and Q355B aligns with S355JR, but tolerance and testing requirements differ.
Q: Which grade should be used for a bridge in a cold region?
A grade with impact testing at or below the design temperature, such as Q355D, Q355E or S355J2, rather than a basic room-temperature grade.
Q: What is Q355NH used for?
It is a weathering grade for coastal or humid environments where an unpainted surface with a stable protective rust layer is acceptable.
Q: Can Q235B and Q355B be welded together?
Yes, but the filler metal and procedure must match the higher-strength grade, and the weld is then qualified against that grade.