CSA 350W Class H specifaction is the result of the heat treatment of CSA G40.21 350W / 50 w class C. These tubes will be heated up to 450ºC (850ºF) using large furnaces then cooled over a determined period of time. The purpose of the heat treatment is to reduce the stress in the alloy of the tubes created when they are manufactured.
Indeed, the method of manufacturing welded tubes is to continuously roll and weld a steel sheet to form a perfectly round tube. It will then be moulded to form a square or rectangular tube. This last step causes stress in the alloy of the HSS tubes, more precisely towards the corners.
Note that the heat treatment (Class H) does not change the chemical composition of the steel and is only available with grade CSA G40.21 50W / 350W.
|Yield strength||50 000 PSI|
|Tensile Strength||65 000 to 90 000 PSI to|
|Thickness tolerance||+ 10% to -5 % from the side|
|Mass tolerance||+ 10% to -3.5% from the theoretical weight|