Abstract: The method for coating the seam of a welded tube of this invention includes applying a mixture of the desired protective metal coating in powdered form and a liquid flux over the internal surface of the welded seam with the welded seam located in a lower portion of the tube, then heating the welded seam to the melting temperature of the protective metal coating, melting the metal coating which flows over the seam forming an adherent metallurgical bond. The preferred apparatus includes a wand which extends between the opposed edges of the open seam tube in the welding apparatus and extends axially through the tube to overlie the welded seam spaced from the welding apparatus. The wand includes three conduits transmitting the powdered protective metal coating, liquid flux and nonoxidizing gas to the applicator which includes a nozzle which atomizes and sprays the liquid flux over the internal surface of the seam and which combines with the powdered protective metal coating to form a paste.

Abstract: An improved method of coating the welded seam of a metal tube comprising heating the weld area only of the metal tube to a first temperature which is less than the melting temperature of the protective metal coating, applying the protective metal coating over the seam and heating the entire tube preferably with a full body induction coil to a second temperature which is at least equal to the difference between the first temperature and the melting temperature of the metal coating, such that the temperature of the seam area is heated to a temperature equal to or greater than the melting temperature of the metal coating, whereby the metal coating firmly adheres to the welded seam.

Abstract: 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.

Abstract: 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.

Abstract: An improved continuous tube forming and coating process and apparatus, wherein the tube is preferably formed and welded with the seam located at the bottom of the tube. One surface of the strip is coated with a paint or other protective coating and the open seam tube is formed with the painted surface on the inside of the tube. An improved coating applicator and impeder is disclosed which coats the inner surface of the seam following welding preferably in an inert atmosphere. The improved impeder includes an outer annular chamber adjacent the casing which includes one or more ferrite rods and circulating coolant and an inner axial paint applicator tube having a free end which extends through the impeder casing having a nozzle which applies a protective coating over the seam, preferably located in the lower portion of the tube. In one preferred embodiment of the impeder, an inert gas passage surrounds the paint applicator tube.

Abstract: 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.

Abstract: An improved continuous tube forming and coating process and apparatus, wherein the tube is preferably formed and welded with the seam located at the bottom of the tube. One surface of the strip is coated with a paint or other protective coating and the open seam tube is formed with the painted surface on the inside of the tube. An improved coating applicator and impeder is disclosed which coats the inner surface of the seam following welding preferably in an inert atmosphere. The improved impeder includes an outer annular chamber adjacent the casing which includes one or more ferrite rods and circulating coolant and an inner axial paint applicator tube having a free end which extends through the impeder casing having a nozzle which applies a protective coating over the seam, preferably located in the lower portion of the tube. In one preferred embodiment of the impeder, an inert gas passage surrounds the paint applicator tube.

Abstract: The method of forming a coated seamed metal tube of this invention is particularly, but not exclusively adapted to existing continuous tube forming mills, wherein the tube is formed from a metal strip and welded with the seam located in an upper portion of the tube. In the process of this invention, at least one surface of the strip is coated with a metal coating prior to forming and welding. The tube is then turned to relocate the welded seam in a lower portion of the tube and the lower portion of the tube is then reheated to melt the metal coating and the metal coating then flows downwardly over and coating the welded seam. In the most preferred continuous or in line process of this invention, the tube is continuously spirally twisted following welding to locate the seam in a lower portion of the tube adjacent a heater and the tube is then heated by the heater to the melting temperature of the metal coating, causing the coating to coat the seam.

Abstract: 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.

Abstract: 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 in creases 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 an other 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.