Oxygen cutting Weathering steels can be cut with conventional oxygen-gas equipment using similar procedures to those used on structural steels of the same thickness. As for standard carbon steels, weathering steels should be preheated to between 120 and 150°C if: • The steel sheets have been stored in a cold environment (< 5°C) • Edges will undergo high stress or deformation in subsequent processes • An exact thickness is important Cold forming – Bending Weathering steels can be processed using conventional manufacturing methods. ArcelorMittal recommends a minimum inner radius for 90° bending which depends on the thickness of the metal: The radius can be reduced in the bending direction. Local surface grinding is advised before bending. Press settings must be adapted to the type of material. A normalisation phase might be necessary depending on the deformation level. Hot forming ArcelorMittal recommends hot forming for: • Plates above 20 mm • Sheets below 20 mm if the equipment does not have sufficient power for cold work Normalising heat treatment The reheating temperature should be set between 900 and 950°C and followed by air cooling. Annealing to restore the initial mechanical characteristics of the weathering steels is not required. Stress relieving Heat treatments can be applied to either relieve internal stress (after cold forming for example) or comply with regulations or other requirements. The recommended treatment is 580°C for two minutes per millimetre of thickness. Temperature speed is 80°C/hour (over 300°C). Slitting and machining operations The same processes are used for weathering steels and structural steels which have the same mechanical characteristics and thickness. Sandwich panels Weathering steels (with and without oil) are not compatible with foam. Pre-painted steels which provide a similar aesthetic finish must be used for the external skin of sandwich panels. Painting Post painting of weathering steels greatly improves resistance to corrosion. The effect is superior to that achieved by painting regular structural steels. On weathering steels, the paint creates a protective layer of oxides which stop the rust underneath swelling. The excellent corrosion resistance of post-painted weathering steel is enhanced by the self-healing effect where scratches occur.