8. Materials used

Please refer to Numerical data on unalloyed and low-alloyed structural steels in the Metallic materials volume.

As a general rule, the steel used is a basic grade of standard NF EN 10025. However, there are a few exceptions to this rule:

• collars and fasteners in contact with the tube wall are of the same grade or of a grade close to that of the tube, when the latter has been chosen for reasons of resistance under temperature;

• Tie rods and hangers must be structurally resistant to brittle fracture. Impact tests are sometimes required for tie rods and hangers that have to take up heavy loads (use of Creuselso 38 type carbon steel).