Abstract: A method for manufacturing of steel tube from a long steel strip, including providing a length of steel strip material to the process, forming a tube of the steel strip material, welding the formed tube in longitudinal direction, giving the tube a heat treatment wherein the mentioned steps are performed in one continuous in-line manufacturing line and the heat treatment includes a heating regime such that in successive cross-sections of the tube a microstructure is achieved which holds at least 50 vol % austenite and a cooling trajectory to re-introduce ferrite, and/or bainite in desired volume fractions.

Abstract: A method for manufacturing of steel tube from a long steel strip, including providing a length of steel strip material to the process, forming a tube of the steel strip material, welding the formed tube in longitudinal direction, giving the tube a heat treatment wherein the mentioned steps are performed in one continuous in-line manufacturing line and the heat treatment includes a heating regime such that in successive cross-sections of the tube a microstructure is achieved which holds at least 50 vol % austenite and a cooling trajectory to re-introduce ferrite, and/or bainite in desired volume fractions.