MULTIPLEX-WOUND STEEL PIPE

摘要

A proper amount of copper can be supplied for brazing in a multiwall steel tube manufacturing process such that copper does not resolidify on the surface of a steel tube and a satisfactory fillet is formed along a seam in the steel tube. A steel sheet has first and second surfaces coated respectively with a copper film of a thickness t1 and a copper film of a thickness t2 greater than the thickness t1 by plating. The steel sheet is formed in a multiwall steel tube with the first surface facing outside.