IS 4923 is the Bureau of Indian Standards (BIS) specification for cold-formed square hollow sections (SHS) and rectangular hollow sections (RHS) used in structural steelwork. Buyers use it when the section must carry structural load as a closed profile rather than convey water or gas. The 2017 revision is the common commercial reference for size tables, dimensional tolerances, mechanical properties, and routine mill tests. Yield-strength grades commonly stocked and ordered under this family are YSt 210, YSt 240, and YSt 310; later amendments to IS 4923 also define higher-strength grades (YSt 355 and above) that appear in PEB and industrial projects. Order the higher grades only when the drawing, design note, and mill capability explicitly support them — do not assume every IS 4923 stock line automatically includes them. IS 4923 is not a pipe standard for fluid service: circular structural tubes fall under IS 1161, and water/gas conveyance tubes fall under IS 1239. A complete purchase line states outside dimensions × wall thickness × grade × length × finish (black or galvanized), plus MTC and inspection requirements.
What IS 4923 covers — and what it does not
IS 4923 governs cold-formed square and rectangular hollow steel sections for structural applications. It addresses dimensions, mass, tolerances, mechanical properties, and testing for sections that designers treat as structural members — columns, beams, purlins, bracings, and fabricated frames.
It does not govern circular structural tubes (use IS 1161) or water/gas/sewage conveyance pipes (use IS 1239 for small-bore and IS 3589 for large-diameter mains). Ordering “MS pipe as per IS 4923” without stating SHS/RHS size is a common RFQ error and delays quote turnaround.
Grades — YSt 210, YSt 240, YSt 310 (and YSt 355 practice)
- YSt 210 — 210 MPa minimum yield; common for light fabrication, secondary members, and general structural frames
- YSt 240 — 240 MPa minimum yield; frequent mid-range choice for industrial structures and mezzanines
- YSt 310 — 310 MPa minimum yield; used where higher design stress or weight reduction is specified
- YSt 355 — used on some PEB and high-strength structural scopes; confirm design approval and mill supply before treating it as default IS 4923 stock
- Always write grade explicitly on the PO; “IS 4923 only” is incomplete
Dimensions, tolerances, and testing buyers should expect
Commercial RFQs specify SHS as side × side × thickness (for example 50 × 50 × 3.2 mm) and RHS as long side × short side × thickness (for example 100 × 50 × 3.6 mm). Mass per metre should align with the size table for the ordered wall; large mass variance is a red flag on receipt inspection.
Expect dimensional checks on outside dimensions, wall thickness, squareness/out-of-square, twist, and length. Mechanical testing typically includes tensile properties (yield, tensile strength, elongation). For welded hollow sections, flattening or equivalent formability checks are part of the mill’s quality regime under the standard — call out any extra NDT or third-party hold points in the tender if the structure is critical.
Typical applications in Indian projects
- Pre-engineered building (PEB) columns, rafters, purlins, and bracing
- Mezzanine floors, walkways, and equipment platforms
- Solar module mounting structures and tracker frames
- Warehouse racking, storage systems, and conveyor supports
- General structural fabrication — trusses, portals, and machine frames
How to specify and what MTC should show
Write the order as: size (SHS/RHS) × thickness × grade × length × quantity × finish. Example: “IS 4923 RHS 100 × 50 × 3.6 mm, YSt 310, 6 m, black, MTC 3.1.” If zinc-coated supply is required, state the galvanizing route on the PO — hot-dip galvanizing is commonly referenced to IS 4736 for tubes, with zinc coating mass tested per IS 6745.
Mill Test Certificates should identify heat/cast number, chemical composition, mechanical results for the ordered grade, dimensions/size, and reference to IS 4923. For project sites, retain heat-wise traceability so cut lengths still link to the certificate.
RP Sales supplies structural hollow sections for fabrication and project offtake. For current size and grade availability, see Structural Hollow Sections (/products/structural-hollow-sections) and send size × thickness × grade on the RFQ.
IS 4923 vs IS 1161 vs IS 1239 — quick distinction
Use IS 4923 when the member is a square or rectangular hollow section for structural load. Use IS 1161 when the member is a circular structural tube graded by yield strength. Use IS 1239 when the tube is for water, gas, or similar conveyance with Light/Medium/Heavy wall classes and hydrostatic testing as the primary pressure proof.
Do not substitute these standards by outside diameter alone. A circular tube ordered for a handrail or column should cite IS 1161; a water riser should cite IS 1239; a SHS column should cite IS 4923.