Image Number 13 for United States Patent #5968380.
In case of producing a welded tube from a metal band by using laser welding, edges of the metal band are preheated so that the temperature at the edges of the metal band before laser welding is not less than a predetermined temperature, the preheated abutting edges of the metal band are laser-welded to form a welded tube and welding beads generated on the outer and/or inner surfaces of the welded tube having been produced are eliminated by cutting. The predetermined temperature is determined depending on the thickness of the metal band and the time from the start of laser welding to the cutting of the welding beads. The edges of the metal band are preheated before welding to prevent the welding beads from being hardened by quick cooling at the welded section after laser welding.
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