The appropriate specification of steel is dependent on usage. For structural applications the strength is clearly an important factor and is specified by grade. The grade of steel is related to the minimum tensile strength expected for that grade.
The British Standard 4360: 1986 Weldable Structural Steels has been replaced by European standards EN 10 113 and EN 10 025 (1990). Section 4 of the former British Standard covered the specification of four grades of steel, with grade 43A and 50B being the most commonly used steel grades in construction in the UK. These numbers are related to the ultimate tensile strength of the steel, i.e. 430 and 500 N/mm² respectively. Generally, the higher yield steels are 10% more expensive than mild steel. Stainless steel is approximately seven times the price of ordinary steel.
The equivalent steel grades defined by the Eurocodes are S275 and S350 which have yield strengths of 275 and 350 N/mm² respectively.
Advice will be needed for specialist applications.
Standard grades and specifications are suitable for normal conditions. For special cases, particularly where high strength is required, for instance for cables and their connections, or where there is a high level of exposure, specialist advice is needed. It is common for architects and engineers to work directly with the steel manufacturers in these situations.