Patent Publication Number: US-3877975-A

Title: Metallic coating of metal tubes and similar work pieces

Description:
United States Patent Raymond Apr. 15, 1975 [22] Filed:  
 [5 METALLIC COATING OF METAL TUBES AND SIMILAR WORK PIECES [76] Inventor: Anthony John Raymond, 20429 Attica Rd., Olympia Fields, 111. 60461 Apr. 12, 1973 [21] App], N0.: 350,535  
 [52] US. Cl. 427/345; 118/405; 118/419; 427/367; 427/420; 427/433 [51] Int. Cl. C23c l/00 [58] Field of Search 117/102 A, 114 A, 94; 118/404, 405, 419, 420  
 [56] References Cited UNITED STATES PATENTS 6/1968 Burch 118/405 2/1968 3,533,761 Pierson 117/114 A Primary Examiner-Mayer Weinblatt Assistant Examiner-Edith L. Rollins Attorney, Agent, or FirmKinzer, Plyer, Dorn &amp; McEachran [5 7 ABSTRACT A method and means of continuously applying molten coating metal, as in galvanising of tubes or members which must pass through the galvanising bath in a straight line, in which the molten metal is passed through a zone beneath a reservoir for the molten metal from which molten metal is discharged onto the tube or rod and the flow around the tube or rod is controlled by a splash plate, and from which the excess coating material flows back to a kettle or the like from which it was originally pumped to the reservoir.  
 10 Claims, 6 Drawing Figures METALLIC COATING OF METAL TUBES AND SIMILAR WORK PIECES BACKGROUND OF INVENTION In the art of galvanising steel tubes by the application of molten zinc thereto, one of the problems which exists is the surrounding of the tube with the galvanising material without the tube being bent to pass through a trough or the like as has been customary when galvanising continuous lengths of wire or strip.  
  It will be realised that in the galvanising of wires or strips no problem exists as the wire or strip can be bent by passing it over guide rollers to extend down into the galvanising bath and can then be guided along the bath and taken out of the bath at the other end by again passing around appropriately positioned guide rollers, but when it is necessary to galvanise tubing or larger rods or members which can not be bent, and which have a length such that they cannot be submerged in the bath, the method used for galvanising is to pass the products through a trough which had closed ends and sides and into which the galvanising liquid is pumped, the trough having apertures in its end so that the tube can pass into the trough at one end and out at the other with a minimal spill of galvanising through the apertures.  
  Processes of the type described are used particularly in the continuous formation of tubes which are then galvanised and cut into length, the forming of the tubes being usually effected from flat strip which is passed through forming guides and bent to tubular form and the joint is then welded to give a continuous tube, means being used to cutoff any projecting metal at the weld. the tube being then usually heated by induction in an inert atmosphere and is passed into the galvanising section in which the trough is positioned above the level of the molten zinc in the kettle, this section usually also being maintained in an inert atmosphere by enclosing the top of the kettle and the trough. On leaving the trough excess zinc is removed from the tube by means of an air knife or the like surrounding the tube, the excess zinc flowing back into the kettle, the tube passing out of this zone to a flying shear which then cuts the formed and galvanised tubing to length.  
  The present invention relates generally to this type of process but is not necessarily limited thereto as it can be applied anywhere where tube or conduit or rod or the like, which will generally be referred to as a work piece&#34; requires to be continuously passed through a metal coating zone while maintaining linear alignment of the work piece being coated.  
  Certain objections exist to the use of a trough which has ends and sides and has sealed apertures through which the work piece to be treated must pass, one of these being to obtain optimum size of the apertures in relation to the tubing to ensure that especially at the I exit end the coat of galvanising material which has been to ensure that the level will be maintained and also to ensure that there will be a correct temperature gradient over all parts of the trough for most effective galvanis- These and other problems are overcome by the present invention which is preferably applied to the galvanising of tubes or similar work pieces of a rigid nature such that they must be fed through the galvanising bath without disturbing the linear alignment, but it is to be clear that the invention need not necessarily be limited to the galvanising of tubing formed by wrapping and welding strip which eventually, after galvanising, is cut into lengths.  
 SUMMARY OF INVENTION The process according to the present invention consists of flowing the molten metal (e.g. galvanising material) over the work piece from a reservoir while using a splash plate to direct the flow around the work piece in the most effective manner.  
  The splash plate is open ended and can be in the form of a tube, either open at the top or closed but connected to the reservoir to receive the molten galvanising material from slots or apertures in the reservoir. The space between the splash plate and the work piece can be relatively narrow as the supply of the galvanising fluid is constantly replenished from the reservoir, and because of this the ends of the splash plate can be open as flow control can be regulated by dimensions of the space and the length of the splash plate.  
  According to this invention therefore the hot molten metal which may be zinc, or zinc with an additive such as aluminum. flows from the reservoir where it is maintained at the correct temperature by heating means, and into which it is pumped from thevkettle in regulated quantities, flows from the bottom of the reservoir over the work piece as it moves in a straight line beneath the reservoir, but to control the flow around the work piece, the splash plate is used to ensure that the work piece is completely surrounded by the galvanising fluid and also because the splash plate can have relatively small dimensions between the splash plate and the work piece, longitudinal flow can be induced of the galvanising medium which can be controlled in its direction by shaping of the splash plate or by inclining the splash plate, so that a much better form of control of the galvanising can be achieved by the present invention.  
  It will be obvious that the apertures in the reservoir through which the flow takes places on to the work piece, can be variously positioned and can be of any selected shape from perhaps a long slit in the bottom of the reservoir corresponding to the medial line of the tube which is disposed to move beneath the slit, to a series of apertures along the reservoir to control the amount of galvanising liquid at any particular part of the work piece as it moves through the splash plate.  
  Because excess liquid can flow from the ends of the splash plate, which are not obstructed, and flow can also take place over the walls of the splash plate if these are relatively low in relation to the top of the work piece, advantages in control will be obvious as opposed to a work piece simply passing through a bath of the molten galvanising fluid by entering the bath through an aperture in one end and leaving the bath through an aperture in the other end.  
  Further details of the invention will be appreciated from a description which will be made of preferred forms illustrated in the accompanying drawings.  
 BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic sectional side elevation of a tube galvanising plant showing the tube passing through an area below a reservoir and with a splash plate to regulate the flow, the kettle from which the galvanising fluid is pumped to the reservoir being shown below the reservoir so that surplus galvanising fluid passes back to the kettle.  
  FIG. 2 is a section of the reservoir and tube and splash plate on line 2-2 of FIG. 1.  
  FIG. 3 shows a modified form of the invention utilising a long slit to discharge into a tubular splash plate.  
  FIG. 4 is a section of the unit shown in FIG. 3 as on line 44 of FIG. 3;  
  FIG. 5 is a view similar to FIG. 3 but showing a further modified form of the device in which a tiltable splash plate is used to further regulate the flow of the galvanising fluid; and  
  FIG. 6 is a view similar to FIG. 4 showing a modified form of splash plate.  
 DESCRIPTION OF PREFERRED EMBODIMENT In the embodiment shown in FIG. 1 a kettle I has in it the molten galvanising fluid 2 which is pumped by any convenient pumping device to the reservoir 3 through the pipe 4.  
  The reservoir comprises walls 5 at the sides and ends and a bottom 6 which has in it a series of apertures 7 through which molten material pumped into the reservoir flows onto the tube 8 which forms the work piece in this case, the tube 8 being however surrounded on its underside and sides by the splash plate 10 which is open at the top so that the fluid from the reservoir can flow onto the tube and is then guided around the tube by the splash plate 10.  
  It will be noted that the splash plate has open ends as fluid control can be effected by the size and positioning of the apertures 7 and also by the proximity of the splash plate to the tube 8 being treated.  
  As shown in FIG. 1, the level of molten coating metal should be as close as practical to the underside of the splash plate to maintain the splash plate hot thereby to prevent chilling and freezing of the molten metal in contact with the splash plate. In this same connection, heat exchangers as the plates 9, extend from the splash plate into the body of molten metal in the kettle.  
  As shown in the illustration. the galvanising fluid 2 flows back into the kettle 1 through the open ends of the splash plate I0, but depending on the height of the walls of the splash plate 10, it could also flow over the walls back into the kettle.  
  A preheating induction coil 11 is shown surrounding the tube 8 as it enters the galvanising area, this being general practice as it is necessary to raise the tube 8 to a selected temperature to ensure correct galvanising.  
  As the galvanising is preferably carried out in an inert atmosphere, a cover 12 is illustrated which encloses the space above the kettle l and includes the reservoir and complete galvanising area.  
  Excess galvanising fluid can be removed from the tube 8 by any of the known means, but in the illustra-&#39; tion an air knife 14 is shown which removes the excess galvanising material which returns to the kettle.  
 tle.  
 Guides 15 and 16 are shown for the tube 8.  
  Heater elements 17 surround the reservoir maintain the molten galvanising fluid at the required temperature.  
  In the modification shown in FIGS. 3 and 4, the reservoir 20 is again provided with heating means 21 but in this case has a slit 22 along its bottom, coinciding with the axis of the tube which passes beneath the reservoir.  
  The tube is designated 23 and as will be seen particularly from FIG. 4 the splash plate 24 is in this case in the form of a tube with direct communication at its top through the aperture 22 with the reservoir 20 so that in this case the molten galvanising fluid flows along the tube as the tube moves through the splash plate 24 to discharge at the open ends of the splash plate 24 and it will be noted that in such a case there is a flow both in the direction of movement of the tubular work piece 23 and against the direction of movement of the work piece 23 and by for instance regulating the size of the slit or opening 22 the volume of flow can be controlled so that instead of the tubular work piece moving through a reservoir as in the prior art embodiments where it moves through what is virtually a static supply of molten fluid, galvanising according to this present system is by regulating flow along the tubular work piece by discharging onto the work piece and then&#39; guiding flow by means of the splash plate.  
  In FIG. 5 is shown reservoir 30 again with heating means 31 but in this case apertures 32 are shown in the bottom of the reservoir and these feed the molten liquid through a slit or opening 34 in the tubular splash plate 35, but in this case the tubular work piece 36 is not concentrically disposed within the splash plate as for instance in FIGS. 3 and 4 but the splash plate 35 is inclined so that at the entry end of the tubular work piece 36 it is lower than at the exit end of the work piece 36, this then encouraging a greater flow in counter direction to the movement of the tubular work piece 36 and again giving enhanced control over the galvanising action.  
  In FIG. 6 is shown a still further modification and in this case the reservoir 40 which again has heating elements 41 within it, is simply provided with a longitudinal slit 42 through which the molten galvanising fluid flows onto the travelling tubular work piece 43, but in this case a pair of splash plates 44 and 45 are shown which serve to guide the molten material around the tube and these splash plates can discharge through an opening 46 between their lower ends, back into the ket- Thus it will be seen from the various embodiments just described that the mode of practice can be varied quite considerably, but the basic principle is maintained under which the tubular or other work piece does not pass through a trough containing the molten coating metal, and which under the prior art conditions is required to be maintained beneath the fluid level therein.  
  According to the present invention the reservoir merely serves as a means of supply of molten metal flowing through apertures or slits in the reservoir downward onto the work piece which passes beneath the reservoir and thus has a flow over the work piece for the purposes of effecting galvanising. It will be realised that the splash plate form can be greatly varied because the purpose of this is to regulate the flow around the tubular work piece. Thus the splash plate or splash plates can obviously take various forms and could be of relatively small dimensions; also the splash plates need not necessarily be continuous but could be longitudinally sectioned and be associated with outlets from the reservoir, all such modifications falling within the spirit of the present invention which resides as stated, in the principle of flowing the molten galvanising fluid from a reservoir onto the work piece to be galvanised and using a splash plate of any required form, or multiple splash plates to ensure that the galvanising fluid is correctly guided in relation to the work pieces as it passes through the galvanising zone.  
 I claim:  
  1. The method of continuously applying a molten metal galvanising coating to a metal tube or other work piece which must pass through the coating metal in a straight line inside a housing, said housing having an entrance opening and an exit opening equipped with a guide for the work piece, comprising heating the metal in a kettle to provide a body of liquid metal, pumping the molten metal into a reservoir located within the housing and above said kettle, allowing a controlled stream of molten metal to flow from said reservoir, passing the work piece through the housing along a path beneath said reservoir to allow the molten metal to flow over said work piece, disposing a splash plate beneath said work piece to control the flow of molten metal around the said work piece, allowing free flow of the molten metal outward of the end of the splash plate adjacent the exit opening and positioning the guide at the exit opening forward of the adjacent end of the splash plate so that the work piece will unobstructedly drag molten metal from the splash plate during its transit from the splash plate to the exit opening guide.  
  2. The method of claim 1 wherein said splash plate is an open ended tube at least partly surrounding the lower part of said work piece, but opening to said reservoir to guide molten metal around said work piece and back to said kettle, and wherein heat exchange is effected between the splash plate and the molten metal in the kettle.  
  3. The method of claim 2 wherein said splash plate is tilted in relation to the direction of movement of the work piece to control flow of the molten metal along and around said work piece.  
  4. The method of claim 1 wherein a splash plate is used on each side of said work piece to guide molten metal around said work piece.  
  5. The method of claim 4 wherein the arrangement of said splash plates leaves an elongated opening beneath said work piece to allow return of molten metal to said kettle through said opening.  
  6. The method of claim 1 wherein a heat exchange is effected between the reservoir and the body of molten metal in the kettle.  
  7. The method of claim 6 wherein the reservoir is heated independently of the kettle.  
  8. The method of continuously galvanising steel tubes or other work pieces which must pass through the galvanising bath in a straight line inside a housing which has an entrance opening and an exit opening for the work piece, comprising heating the galvanising bath in a kettle to form a molten mass, pumping the molten galvanising medium into a reservoir disposed above the said kettle and extending along the line of movement of the work piece, heating the molten galvanising medium in said reservoir to maintain galvanising temperature, allowing a controlled stream of galvanising medium to flow downward from the said reservoir through an opening in said reservoir, passing the work piece beneath the said reservoir to have the galvanising medium flow over the said work piece as it passes progressively beneath said reservoir, disposing at-least one splash plate adjacent to said work piece to control the flow of the galvanising medium around and along the said work piece and back to said kettle, allowing free flow of the molten metal outward of the end of the splash plate which is adjacent the exit opening in the housing, and positioning the guide at the exit opening forward of the adjacent end of the splash plate so that the work piece will unobstructedly drag molten metal from the splash plate during its transit from the splash plate toward the exit opening guide.  
  9. The method of claim 8 wherein a heat exchange is effected between the molten medium in the reservoir and in the kettle.  
 10. The method of claim 9 wherein the reservoir is heated independently of the kettle. t