METHOD OF PRODUCTION OF WELDED METAL PIPE Russian patent published in 1998 - IPC

FIELD: production of welded metal pipes with antirust coating, applicable in pipe industry. SUBSTANCE: prior to welding, zinc coating is applied onto strip 20. Then strip 20 is formed into an unwelded pipe and welded in inert atmosphere, with weld 71 positioned in the lower part of the pipe. Conditions are provided for running-off of metal coating 56 down over weld 71 covering weld 71 with the aid of various means. In one of the variants of realization of the method strip 20 is preliminarily formed into arched shape 20a and subjected to zinc-coating. Thickness of zinc coat 56 increases in the direction to strip lateral edges 48 so that coat 56 would run off over weld 71 after welding. Besides, pipe 20c may be heated after welding, preferably in shell 78, containing inert atmosphere and accommodating welding unit 62. According to another variant of realization, inert gas is fed to the inner and outer surfaces of pipe 20c near weld 71; as a result, molten metal moves downwards towards weld 71 and closes weld 71. In one more variant of realization recesses or grooves 118 are made on lateral edges 48 of strip 20, directed towards lateral edges 48, through which molten metal moves downwards towards weld 71. EFFECT: guaranteed production of completely closed weld without additional expenditures. 19 cl, 21 dwg