What Angle Iron Is
Angle iron is the common name for a hot rolled L-shaped steel section with two legs meeting at a right angle. The profile is efficient in bending and simple to connect, which makes it the default section for building supports, brackets and bracing. Angle iron is supplied as equal or unequal legs, in lengths from 6 m to 12 m.
The section is called angle iron because it was traditionally rolled in iron before steel became universal; today the material is always carbon steel.
Grade Q235
Q235 per GB/T 700 is a carbon structural steel with a minimum yield strength of 235 MPa up to 16 mm thickness and a tensile range of 370 to 500 MPa. The grade is cheap, weldable and formable, which is why it covers most building support applications.
Minimum yield: 235 MPa up to 16 mm.
Tensile strength: 370 to 500 MPa.
Impact: 27 J at 20 degrees Celsius for grade B.
Weldability: excellent with all standard processes.
Standard Sizes
Building supports typically use angles from 40 x 40 x 4 mm to 100 x 100 x 10 mm, with heavier sections up to 200 x 200 x 24 mm for large structures. Equal angles dominate building work, and unequal angles are used where one direction carries more load.
Roles in Building Structures
Angle iron serves as bracing in roof trusses, lintels over openings, supports for beams and slabs, door frames, stair stringers, handrail posts and equipment brackets. Bolted or welded to the main frame, angle members transfer loads and stiffen the structure against wind and seismic action.
Processing and Protection
Angles are cut, drilled, punched and notched to the shop drawing. For outdoor and humid service, hot dip galvanizing or painting is applied; indoor members are often used black. Mill certificates document the chemistry and mechanical properties of each heat.
Frequently Asked Questions
Q: What is the difference between angle iron and angle steel?
The names describe the same L-shaped section; angle iron is the traditional trade term, and angle steel reflects the carbon steel material used today.
Q: What size angle is used for window lintels?
Lintels commonly use angles of 50 x 50 x 5 mm to 75 x 75 x 6 mm depending on the opening width and load.
Q: Is Q235 angle iron strong enough for building bracing?
Yes, Q235 covers standard bracing duties; higher grades are only needed for large spans and heavy loads.
Q: Can angle iron be welded to H-beams?
Yes, angle-to-H-beam connections are welded or bolted with standard details.
Q: How is angle iron protected against rust?
Galvanizing or a paint system is applied for outdoor exposure, while indoor members can be used with a primer or black finish.