MS Angles, Channels and Structural Sections

The letters say what the section is; the numbers say how big. "IS" means Indian Standard. ISA is an angle, and the numbers give leg, leg and thickness in millimetres, so ISA 50 × 50 × 6 is an equal angle with 50 mm legs, 6 mm thick. An unequal angle reads the same way with two different legs, such as ISA 75 × 50 × 6.

Channels and beams are named by their depth. ISMC 100 is a medium-weight channel 100 mm deep; ISMB 200 is a medium-weight I-beam 200 mm deep. The flange width and web thickness for each depth are fixed by IS 808, so you only need to quote the depth. Other prefixes you may see are ISLC and ISJC for light and junior channels, which are lighter for the same depth.

These standard sections are hot rolled to the dimensions in IS 808, while the steel itself is normally to IS 2062.

An angle is the most versatile section: bracing, light frames, edge trims, supports for chequered plate floors, cleats and brackets. It is easy to bolt and weld, but it twists under load if used as a long beam.

A channel has a web and two flanges, so it is much stiffer in bending for its weight. Channels make good purlins, machine bases, trailer chassis members, stair stringers and back-to-back columns. For heavier beams and columns, an I-section such as ISMB carries more load again because its flanges are symmetrical about the web.

If you are pairing sections with plate floors, our chequered plates are usually welded straight onto angle or channel frames.

Section tables in IS 808 give the weight per metre for each size, and that is the figure to use. You can also estimate an equal angle yourself: thickness × (2 × leg − thickness) gives the cross-section area in mm², and multiplying by 0.00785 gives kg per metre.

For ISA 50 × 50 × 6 that is 6 × (100 − 6) = 564 mm², or about 4.4 kg/m, close to the table figure of about 4.5 kg/m (the table includes the root radius). Since steel sections are priced by the kilogram, multiply weight per metre by total length to compare quotes.

For most fabrication, IS 2062 E250 is the standard choice: 250 MPa minimum yield, good weldability, and widely rolled. Structural consultants sometimes specify impact-tested sub-grades (BR, B0 or C) or higher-strength grades such as E350 for heavier structures; follow the drawing. Our MS plates and flats page gives the E250 composition and properties.

Long sections can bow or twist in transport and storage. Store them flat on bearers spaced closely enough to stop sagging, and keep them off wet ground to limit rusting before fabrication. If a section is bent, it can usually be straightened in a press, but a twisted channel is harder to correct.

Mild steel sections rust if left bare, so they are primed and painted after fabrication, or hot-dip galvanised for outdoor structures. For enclosed frames, square hollow sections are an alternative; see our square pipes.

To quote, we need the designation of each section, the grade, and the quantity in metres, lengths or tonnes. Sizes are confirmed at enquiry, and each supply comes with a test certificate.