The national standard angle iron, commonly known as angle bar, is a long strip of steel with two perpendicular sides. The dimensional deviation must be controlled within 0.25 millimeters according to national standards. It is classified into equal-leg angle iron and unequal-leg angle iron based on shape. The specifications of equal-leg angle iron are denoted by "width × width × thickness" (e.g., ∠30×3) or model number (e.g., ∠3#). The specifications of hot-rolled products cover sizes from 2# to 20#. The main material is carbon structural steel (such as Q235B), which is hot-rolled from low-carbon square billets and is usually delivered in a hot-rolled or normalized state.

This steel is widely used in structural fields such as construction, bridges, and machinery, and must meet requirements for weldability, plastic deformation capacity, and mechanical strength. The production process performs tensile tests (GB/T228-87) and bending tests (GB/T232-88), with key indicators including yield point, tensile strength, elongation, and bending qualification rate. The weight and inspection standards for products of different specifications strictly follow national technical specifications.