The Idod Trust

Charles A Willetts

John J Borzym

Theodore H Krengel

Edward Wiesenthal, Iii

Curtis R Brown

The method of forming a seamed metal tube having a metal coating of this invention includes applying a metal coating to the upper face of a metal strip prior to welding. The strip is then formed into an open seam tube and welded, preferably in a non-oxidizing atmosphere with the seam preferably located in the lower portion of the tube. Finally, at least a lower portion of said tube is reheated with the seam located in the lower portion of the tube, thereby causing the metal coating to flow downwardly over the seam, coating the seam. In one embodiment, the strip is preformed into an arcuate shape and coated, wherein the metal coating increases in thickness toward the lateral strip edges, such that the coating will flow over the seam following welding. The inside coated seamed tube may also be immersed in a galvanizing or metal coating bath to coat the outside of the tube. In a preferred embodiment, the inside and outside coatings comprise substantially the same metal and a single galvanizing bath apparatus is used to coat the inside and outside surfaces of the seamed tube. In another embodiment, the coating on the inner surface of the seamed tube has a melting temperature substantially below the melting temperature of the metal strip, but higher than the melting temperature of the outside metal coating. In another embodiment, a lance is provided having a free end which extends through the adjacent lateral edges of a tube-shaped strip and a nozzle which applies metal coating material over the seam. A control loop is also disclosed for improved reflow of the metal coating over the seam.

Method of forming seamed metal tube

The method of forming a seamed metal tube having a metal coating of this invention includes applying a metal coating to the upper face of a metal strip prior to welding. The strip is then formed into an open seam tube and welded, preferably in a non-oxidizing atmosphere with the seam preferably located in the lower portion of the tube. Finally, at least a lower portion of said tube is reheated with the seam located in the lower portion of the tube, thereby causing the metal coating to flow downwardly over the seam, coating the seam. In one embodiment, the strip is preformed into an arcuate shape and coated, wherein the metal coating increases in thickness toward the lateral strip edges, such that the coating will flow over the seam following welding. The inside coated seamed tube may also be immersed in a galvanizing or metal coating bath to coat the outside of the tube. In a preferred embodiment, the inside and outside coatings comprise substantially the same metal and a single galvanizing bath apparatus is used to coat the inside and outside surfaces of the seamed tube. In another embodiment, the coating on the inner surface of the seamed tube has a melting temperature substantially below the melting temperature of the metal strip, but higher than the melting temperature of the outside metal coating.

The method of forming a seamed metal tube having a metal coating of this invention includes galvanizing the strip prior to welding. The strip is then formed into an open seam tube and welded in an inert atmosphere with the seam located in the lower portion of the tube. Finally, the metal coating is caused to flow downwardly over the seam, coating the seam by several means. In one embodiment, the strip is preformed into an arcuate shape and galvanized, wherein the zinc coating increases in thickness toward the lateral strip edges, such that the coating will flow over the seam following welding. The tube may also be reheated following welding, preferably in an enclosure containing an inert atmosphere which includes the weld apparatus. In another embodiment, an inert gas is directed over the inner and outer surfaces of the tube, adjacent the seam, driving the molten metal downwardly over the seam to coat the seam. In another embodiment, the lateral edges of the strip are formed with indentions or grooves directed toward the lateral edges which direct the molten metal downwardly over the seam.

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Stourbridge, United Kingdom

Charles A Willetts