Building Construction Handbook, Eighth Edition

Material ~ Mild steel or high yield steel. Both contain about 99%

iron, the remaining constituents are manganese, carbon, sulphur

and phosphorus. The proportion of carbon determines the quality

and grade of steel; mild steel has 0„25% carbon, high yield steel

0„40%. High yield steel may also be produced by cold working or

deforming mild steel until it is strain hardened. Mild steel has the

letter R preceding the bar diameter in mm, e.g. R20, and high yield

steel the letter T or Y.

Standard bar diameters ~ 6, 8, 10, 12, 16, 20, 25, 32 and 40 mm.

Grade notation ~

• Mild steel † grade 250 or 250 N/mm^2 characteristic tensile
  strength (0„25% carbon, 0„06% sulphur and 0„06% phosphorus).


• High yield steel † grade 460/425 (0„40% carbon, 0„05% sulphur
  and 0„05% phosphorus).
  460 N/mm^2 characteristic tensile strength: 6, 8, 10, 12 and 16 mm
  diameter.
  425 N/mm^2 characteristic tensile strength: 20, 25, 32 and 40 mm
  diameter.

Ref. BS 4449: Steel for the reinforcement of concrete, weldable

reinforcing steel. Bar, coil and decoiled product. Specification.

Types of Reinforcement---Steel Bars