Angle steel is the most widely consumed hot-rolled long product after rebar and flat bar, and it remains the default choice wherever a light L-shaped member must carry tension, compression or shear in two perpendicular planes. It is rolled at high temperature from carbon steel or high-strength low-alloy steel, so the section is produced in one pass through the mill with no welding or forming operation, giving a predictable metallurgical structure and a cost per tonne that fabricated alternatives cannot match.
What Defines a Structural Angle Section
An angle section consists of two legs meeting at 90 degrees and forming an L-shaped cross-section. Legs may be equal or unequal in length, and the thickness is constant through the section. Two geometric features govern its structural behaviour: the centroid lies outside the section near the corner, so loading produces biaxial bending, and the principal axes are inclined to the legs. Designers therefore check bending about both axes, or connect angles back-to-back and toe-to-toe to create a more efficient built-up member.
Standard Dimensions and Nominal Mass
Equal and unequal angle dimensions are specified in EN 10056-1, with dimensional tolerances in EN 10056-2. Selection in the common range is normally driven by mass per metre:
| Size | Leg thickness (mm) | Nominal mass (kg/m) | Typical use |
|---|---|---|---|
| L 50 x 50 | 5 | 3.77 | Gratings, light brackets, edge trim |
| L 75 x 75 | 8 | 9.03 | Bracing, purlins, frame stiffeners |
| L 100 x 100 | 10 | 15.0 | Tower legs, truss chords, base frames |
| L 150 x 150 | 12 | 27.3 | Heavy braced frames, crane rail supports |
Longer leg and heavier thickness combinations are rolled to order, and unequal angles are used where one leg must be bolted to a wide face while the other carries the primary load.
Material Grades and Mechanical Requirements
European practice specifies EN 10025-2 grades, most commonly S235JR and S275JR, with minimum yield strengths of 235 MPa and 275 MPa respectively for material up to 16 mm thick. North American projects frequently call for ASTM A36, which requires a minimum yield strength of 250 MPa and a tensile strength of 400-550 MPa. Chinese production commonly uses Q235B to GB/T 706, and JIS G3192 covers hot-rolled sections for the Japanese market. The grade choice is usually driven by weldability and by the lowest service temperature, not by the section itself.
Fabrication: Cutting, Punching, Welding and Galvanizing
Angles are cut with band saws, abrasive discs or plasma, with shearing acceptable where edge deformation does not affect the connection. Punching is the most economical hole-making method, but hole clearance should be checked against the bolt diameter where slip-critical joints are used. Welding follows the same procedures as for other carbon steel sections, with weld acceptance to EN ISO 5817 and execution to EN 1090-2 where the work is structural. For outdoor exposure, hot-dip galvanizing to EN ISO 1461 provides an average coating thickness of 85 micrometres and a local minimum of 70 micrometres on steel 6 mm and thicker, which is normally sufficient for 20 years or more in rural and urban atmospheres.
Where Angle Sections Are Used
The dominant applications are wind and communication tower legs and bracing, transmission line structures, industrial shelving and racking, conveyor supports, transformer and switchgear frames, and light roof trusses. In building work they appear as lintels over small openings, stair stringers, secondary framing around penetrations, and as the edge members of composite decking. The common thread is a member whose load path changes direction, where an L-section resolves the geometry in a single rolled piece.
Buying and Inspection Points
Confirm the leg sizes and thickness against the design drawing, check that the mass per metre matches the standard table rather than the theoretical steel density only, and verify that the certificate states the grade, heat number and mechanical results. For galvanized material, check coating thickness on the inside of the leg as well as on the outer face, since the inner face is the first to fail in aggressive environments.
Frequently Asked Questions
Q: What is the difference between an equal angle and an unequal angle?
A: An equal angle has two legs of the same length, while an unequal angle has legs of different lengths. Unequal angles are used where one leg bolts to a wide surface and the other carries the main load.
Q: Which standard defines angle steel dimensions?
A: EN 10056-1 defines the dimensions and section properties, and EN 10056-2 covers the dimensional tolerances for hot-rolled angles.
Q: Is angle steel stronger than flat bar of the same weight?
A: Yes, for bending and compression. The two perpendicular legs raise the second moment of area and resistance to buckling far above a flat bar of identical mass.
Q: What minimum yield strength does ASTM A36 provide for angles?
A: ASTM A36 requires a minimum yield strength of 250 MPa and a tensile strength of 400-550 MPa, which suits most non-critical light framing.
Q: How thick is a hot-dip galvanized coating on angle steel?
A: To EN ISO 1461, steel 6 mm and thicker receives an average coating of 85 micrometres with a local minimum of 70 micrometres.