Specification for structural steels

Weldable structural steels are defined by British Standards BS EN 10

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113, and BS EN 10 025, which are now the UK issues of European standards for steel as a structural material. These standards replace BS 4360, in which the most common grades were 43A and 50B, referring to the ultimate tensile strength of the steel, i.e. 430 and 500 N/mm respectively. A and B refer to the toughness characteristics of the steel, which are relevant to the limit temperature at which the steel is used in service.

New designations S275 and S355JR to BS EN 10 025 replace grades 43A and 50B respectively, and refer to the minimum guaranteed yield strength of the material in N/mm . Apart from the change in designation, the properties of S275 and Grade 43 steel are the same. The yield strength of steel is approximately 70% of its ultimate tensile strength. Design resistances are based on the yield strength of steel rather than its ultimate tensile strength.

For hot-rolled tubular sections, the new standard is BS EN 10 210 and the most common grades are S275J2H and S355J2H, which replace the previous grades 43D and 50D respectively. J2H refers to the toughness characteristic.

For cold-rolled tubular sections, the new standard is BS EN 10

219, which designates steel in the same way as for hot-rolled sections. Cold-rolled sections should not be used as a direct substitute for hot-rolled hollow sections and it is important that the standard is referred to in the designation, i.e. BS EN 10 210 - S275 J2H, or BS EN 10 219 - S275J2H.

For so-called 'weathering steels', the new standard is BS EN 10 155 and the common designations are S355JOWP and S355JOW, replacing grades WR50A and WR50B in the previous standard.

Technical information on the comparisons between the B and BS EN standards is available from the Corus Advisory Service (see Chapter 16 for contact details).

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