The Idod Trust

Allied Tube & Conduit Corporation

Theodore H Krengel

John J Borzym

Charles A Willetts

Edward Wiesenthal, Iii

Curtis R Brown

Curt Brown

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.

Method and apparatus for coating the seams of welded tubes

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. Where the method of this invention is utilized to apply a protective metal coating over the exterior surface of the welded seam, the protective metal coating is preferably applied by thermally spraying molten metal coating material over the seam and the coating material metallurgically bonds with the seam during the final heating step. In the preferred method, a flux is applied to the exterior surface of the seam prior to applying the coating material. In the method of applying a protective metal coating to the interior surface of the seam, the protective metal coating material is preferably applied by spraying the interior surface with metal coating material in the form of a fine metal powder and liquid flux and the entire tube is heated with the seam located in a lower portion of the tube.

Method of coating the seams of a welded 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. 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.

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. An improved galvanizing apparatus is also disclosed having a sealed galvanizing tank which receives the seamed tube below the level of the molten zinc and which is enclosed within a sealed housing and wherein the inert gas pressure in the galvanizing tank is greater than the inert gas pressure in the housing. The galvanizing apparatus includes improved inert gas seals which may be also used to shape the molten zinc on the tube leaving the housing.

Continuous tube forming and 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.

A tubing mill for roll forming a strip of metal into a fluted tube having alternating longitudinally extending high and low portions on its outside surface. The mill includes feed means for supplying a generally planar strip of metal and embossing means for forming the high and low portions on the surface of the strip to be formed into the outside surface of the tube. The mill also includes breakdown means for sequentially transversely bending the strip from its planar condition. The breakdown means includes roller means having a gripping surface for engaging the strip and having alternating high and low portions shaped to mate with those of the strip. Additionally, the mill includes closure means for bringing into abutment the lateral ends of the bent portions of the strip, and welding means for seam welding the ends together.

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Flossmoor, IL, United States of America

Theodore H Krengel