EP0550667B1

EP0550667B1 - Method and apparatus for processing continuous strip sheet metal

Info

Publication number: EP0550667B1
Application number: EP91918772A
Authority: EP
Inventors: John W. Neumann; J. Scott Neumann
Original assignee: Bw- Vortex Inc; B W Vortex Inc
Current assignee: Bw- Vortex Inc
Priority date: 1990-09-28
Filing date: 1991-09-18
Publication date: 1997-05-07
Anticipated expiration: 2011-09-18
Also published as: WO1992005886A1; DE69126031D1; AU8764691A; EP0550667A4; EP0550667A1; DE69126031T2

Abstract

An apparatus and method for performing processing operations such as cleaning, rinsing, pickling, and plating or moving continuous sheet metal (49a) utilizing pressurized liquid vortex diffuser units (68). Each vortex diffuser unit is formed of vortex rails (71, 72) including liquid plenums (77) feeding pressurized liquid to vortex cups (78).

Description

BACKGROUND OF THE INVENTION

The invention relates to a moving continuous sheet metal processing station and a method for processing continuous sheet metal surfaces passing through a stationary enclosure.
Pretreatment processing in a continuous steel strip plating line, e.g., for chrome plating or tin plating, involves removing the soil and preparing the surface in order to assure dependable adherance of the plating. In a typical line processing stages including electrocleaning in or alkaline electrolyte tank; brush scrubbing to remove the loosened soil; in some cases, such as double reduced batch annealed strip steel, a second stage of electrolytic cleaning in an alkaline electrolyte tank, followed by further brush scrubbing; pickling in an acid solution tank; again followed by brush scrubbing before entering an electroplating tank.
In electrocleaning, the current electrolizes the water to form hydrogen gas at the negatively charged cathode and oxygen at the positively charged anode. The large columns of these gases generated at or near the strip surface provide the mechanical energy for cleaning in the form of bubbles which loosen the surface soil. Dispersion and replenishment of the surface bubbles on passing continuous steel strip enhances the cleaning process which in conventional practice is somewhat curtailed by liquid drag at the boundary layer which tends to carry a layer of bubbles rather than to disperse them. Such boundary layer also insulates the surface to impede the chemical action of the cleaner. Such drag and the tendency for progressive boundary layer buildup may cause overflowing of a tank which, in some cases, necessitates successive cleaning tanks rather than elongation of a single tank. This in turn requires a brush scrubbing unit after each cleaning tank. Deflection rolls are required for leading the continuous steel strip into and out of the cleaning tanks as well as wringer rolls at the exit to limit cleaning liquid drag out. The potential of surface defects and soil buildup on such rolls provides a maintenance problem for quality control. Likewise, the brush scrubbers and their associated wringer rolls for liquid containment involve serious maintenance problems and frequent expensive brush replacement. In a typical plating line, two days of maintenance including brush replacement may be involved in every week of operation.
In comparison, vortex diffuser substitutions of the present invention overcome certain limitations and defects of convention cleaning, scrubbing and pickling units. Vortex diffuser prior art includes a fluid bearing device disclosed in U. S. Patent 3,782,791 as a fluid bearing load supporting system having unidirection and omnidirectional capabilities which embody means for forming one or a plurality of fluid vortices for separating a body from a supporting surface by an intervening cushion of fluid, providing therewith an extremely low coefficient of friction that facilitates a conveyance of the body for the purposes of transportation, processing, treatment and the like. When such device is employed solely for the purposes of conveyance and/or transportation of articles, the fluid substance discharged conventionally comprises air; however, the patent discloses that alternative fluids can be used including fluids and fluid mixtures, and that the use of such alternative fluid substances is desirable when the vortex diffuser fluid bearing device is employed for effecting a simultaneous conveyance and processing of work pieces supported thereby. Also, that such selected treatments can be achieved in a prescribed sequentially-phased manner by changing the type of fluid substance discharged from selected sections of the air rail assembly such that each work piece is subjected to a prescribed treatment during its travel along each section; and by selecting the appropriate gaseous substance, work pieces such as a container can be subjected to treatments including cleaning, etching, conversion coating, surface coating or painting, electrostatic coating applications, electrocoating or painting, heat treating, baking, drying, cooling, quenching, lubricating, etc. However, such suggestion of various potential treatments of discrete work pieces by vortex diffusion by the appropriate gaseous substance has failed to anticipate the present discovery of the application of vortex diffusion of liquids as substitute for conventional cleaning, with brush scrubbing in blank washers; or as a substitute for conventional cleaning, brush scrubbing and pickling operations in a continuous steel strip plating mill, which substitutions have not been discovered, tested and proven viable during approximately fifteen years since the issuance of said prior art patent.
US-A-4 270 317 discloses an apparatus for the treatment of sheet metal wherein a sheet of metal is guided in a horizontal pathway between successive treatment tanks or units having horizontally elongated chambers with two rows of oppositely disposed and horizontally aligned nozzles between which the sheet of metal travels on a liquid bed that is created by the nozzles which are designed to direct streams of liquid, under pressure, against the travelling metal sheet at angles that are substantially less than 90° relative to the plane in which the metal sheet travels. The individual units are free of conventional sprays and flooding nozzles and of brushes and other such devices which are normally used to aid in the cleaning of the sheet of metal.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention and further developments of the invention are defined in the claims.
Electrolytic alkaline cleaning may be performed, without submersion in a liquid alkaline bath, by passing continuous steel strip between opposed liquid alkaline vortex diffusers in close fractional inch proximity to the strip and including a series of transverse longitudinally spaced vortex rails having alternately oppositely charged metal vortex cups which electrolyze the liquid alkaline vortex discharge to create successive hydrogen and oxygen bubbling at the strip surface with immediate removal by the vortex action. Conductivity in the metal strip between vortex rails completes the electrolytic circuit, as in the case of conventional tank cleaning, with a major difference of continuous bubble dispersion more effectively removing the soil rather than merely loosening it for brush removal as in conventional electrolytic cleaning. Enhanced chemical action at the surface is also realized. Liquid drag at the boundary layers is avoided and liquid containment at the cleaning station is effected by liquid knives directed inwardly at the entrance and exit of enclosures for the cleaning station. Such knives take the place of conventional wringer rolls, which together with deflection rolls have been dispensed with.
In place of conventional brush scrubbers following the conventional cleaning tank, the present invention employs vortex diffuser hot water rinsing to remove any alkaline solution from the strip surface.
Successive pickling and rinse stations are similarly isolated preferably by liquid knives which confine the liquid within the enclosure at each of the individual stations. Air knives or wringer rollers are optionally available for such purpose. Such stations, preferably employ a "Strip Tech Module" which may be the same or similar for all successive stations. Such module has a fixed lower set of vortex rails with manifolds supplied by manifold headers and pumps, together with entrance and exit liquid knives for liquid containment. A hinged top unit of the module contains upper vortex diffuser rails, manifolds and liquid knives supplied by connections with the lower manifold supply which are completed by closing of the upper unit so as to dispense with any need for flexible hose connections. The upper unit is opened by hydraulic motors adapted to actuate through the hinge opening and closing of the upper unit for strip threading and servicing purposes.
The method and apparatus of the present invention include a sheet feeder for developing the processing parameters for particular metal condition and processing requirements thereby minimizing the need for experimental testing of variables on a complete continuous strip line. Such sheet feeder conveys a single sheet of sample material over a succession of processing stations adapted to selectively clean, rinse, pickle and plate at conveyance speeds equal to and exceeding continuous strip mill speeds. Removal and inspection of each individual piece of sheet metal accommodates advance process testing of such parameters as vortex diffuser to sheet gap; effective relative speeds; effective variations in cleaner liquid chemistry; electrocleaning voltage; vortex diffuser design variations; vortex pressure variations; different soil conditions on metal surface; different pickling solutions; different vortex cup configurations and spacing etc., in order to both minimize test requirements on a complete line and optimize vortex diffuser results.
In a like manner, an enclosure with a continuous metal belt driven at controlled variable speeds in an enclosure with superimposed vortex diffuser rails supplied with liquid under variable pressure, together with air or liquid knives at the entrance and/or exit of the enclosure accommodates simulation of continuous strip operation for visually observed pretesting of the effective pressure variations, vortex cup design and spacing, gap variations and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a prior art chrome plating line;
FIG. 2 is a schematic view of a comparable vortex diffuser line;
FIG. 3 is a perspective view of a typical vortex diffuser Strip Tech Module with its top section closed;
FIG. 4 is a perspective view of the FIG. 3 module with the top section open;
FIG. 5 is a phantom view of the FIG. 3 module illustrating the internal piping;
FIG. 5A is an enlarged sectional view illustrating a typical connection between upper and lower vortex or liquid knife manifolds taken through the center line of such connection in an area such as identified by circled FIG. 5A in FIG. 5;
FIG. 5B is a further enlarged fragmentary view of the sectional area identified by circled 5B in FIG. 5A illustrating O-ring seals for providing liquid containment;
FIG. 5C is a fragmentary sectional view of a typical liquid knife manifold;
FIG. 5D is a sectional fragmentary view of a typical vortex manifold;
FIG. 5E is an enlarged perspective view of a single vortex cup;
FIG. 6 is a perspective view of a "sheet feeder" high speed continuous strip simulator;
FIG. 6A is an enlarged perspective broken view illustrating the internal arrangement at a typical location such as indicated at A in FIG. 6; and
FIG. 7 is a perspective view of an endless sheet metal or plastic belt continuous strip simulator.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to FIG. 1, a typical prior art chrome plating line is schematically illustrated showing cleaning, scrubber and pickling stations for which vortex diffuser substitutions of the present invention have been developed, tested and successfully reduced to practice. The additional operations performed at the chrome plater, reclaim tank, spray rinse, hot rinse tank, dryer and electrostatic oiler are believed capable of similar vortex diffuser substitution, e.g, as an extension of the technology described in U.S. Patent No. 3,957,599, Process for Electrowinning with regard to plating stationary sheet metal. Starting at the left-end of FIG. 1, strip steel 49 from the looping tower is fed through drag bridle rollers 50 and deflection roller 51 into liquid bath 52 of the cleaning tank passing between pairs of alternately charged plus and minus grids 53 and 54 which produce current electrolizing the water in the electrolytic alkaline cleaning liquid to form oxygen at the positively charged anode grids and hydrogen gas at the negatively charged cathode grids, the bubbling of which near the strip surface provides the mechanical energy for cleaning. At the exit of the cleaning tank, deflection roller 55 and wringer rollers 56 lead strip 49 to scrubber unit 57 including a pair of entrance wringer rollers 58, a series of four brush scrubbers 59, alternately upper and lower with backup rollers on the opposite side, and exit wringer rollers 60.
Particularly in the case of a line for double reduced batch annealed steel, a second duplicate cleaning operation 61 and scrubber operation 62 lead to pickling tank 63 where deflection rolls 64 lead strip 49 through a bath of acid pickling liquid with exit deflection rolls 65 leading to a third scrubber unit 66.
In comparison with the conventional prior art line thus far described, and with reference to FIG. 2, the corresponding line incorporating vortex diffuser technology of the present invention includes a series of vortex diffuser stations, each comprising one or more Strip Tech Modules, as later described in detail. Strip 49a leaving a conventional looping tower passes horizontally straight through a vortex precleaning heating unit, a series of three Strip Tech Modules 67 serving as a vortex electrolytic cleaner unit; a vortex rinse unit; a vortex pickler unit; a vortex rinse unit; and vortex dryer unit preceeding entrance to a chrome plater.
With reference to FIGS. 3-5, a typical Strip Tech Module is illustrated wherein strip 49a passes through vortex diffuser unit 68 comprising upper section 69 and lower section 70 each equipped respectively with four vortex diffuser upper rails 71 and 72; also with an entrance upper liquid knife rail 73 and lower 74, and an upper exit liquid knife rail 75 and lower 76. As illustrated in FIG. 5D, each vortex rail includes liquid plenum 77 feeding a plurality of electrically conductive metal vortex cups 78 seated in metal plate 79 retained by nonconductive cover 80. As shown in FIG. 5C, each liquid knife rail comprises plenum 81 feeding liquid knife slit 82 at the juncture of horizontal plate 83 and adjustable vertical angle plate 84 with the liquid knife exit directed inwardly at both entrance and exit of the module in order to provide liquid containment.
With reference to FIG. 5, six pipe lines 85 provide liquid under pressure through flexible isolators 86 to the six pairs of liquid knife and vortex plenums, which are in turn supplied by three pumps through three filters, three control valves and three manifold headers. Pump 87 supplies both pairs of liquid knives through filter 88, control valve 89 and header 90. The inboard manifolds are supplied by pump 91, filter and control valve not shown, and header 92; and outboard manifolds are supplied by pump 93, filter 94, control valve 95 and header 96.
With reference to FIGS. 5A and 5B, each of six supply passages 97 from a lower plenum 98 to an upper plenum 99 is sealed, when upper section 69 is closed over lower section 70, by a pair of O-rings 100 seated in annular grooves 101. Tapered shoulders 102 on inserts secured to the respective plenums serve to assure accurate alignment of each pair of plenums.
With reference to FIG. 5E, each vortex cup 78 is provided with four inlet holes 103 leading to tangential outlets at the interior perimeter 104 so as to create vortex swirling of the liquid discharged against passing strip 49a.
In the case of the vortex electrolytic cleaner station illustrated schematically in FIG. 2, following the vortex preclean strip heating station, each of the three adjacent modules 67 is provided with electrical connections, not shown, to the respective manifold plates 79 with alternate positive and negative electrical circuits in order to electrolize the water to form hydrogen gas at the negatively charged cathode and oxygen at the positvely charged anode. In the vortex rinse, pickling and dryer units, such electrical connections may be omitted, but the modules are otherwise standardized, to provide successive required surface treatment of the passing strip metal.

Reduction to practice in an operating plating mill for strip steel having a thickness of 0.152 - 0.635 mm (0.006-0.025") and a width up to 914 mm (36") traveling at a line speed up to 564 m/min (1850 feet per minute). Successful cleaning, was achieved with a non-foaming alkaline electrolytic liquid in the cleaning station having a trade designation NXP-116 formulated as follows:

NXP-116 CLEANER
Compound	Parts by Weight
Sodium Carbonate	10.86
Sodium Gluconate	2.72
Sodium Metasilicate (Pentahydrate)	40.73
Progasol COG * (Concentrate)	2.24
Sodium Hydroxide	43.45

* Progasol COG Surfactant - SP Gr 1.030 Obtained from: Lyndal Chemical Co. Dalton, Georgia

22 to 67 g/l (3 to 9 ounces per gallon) of water provided a suitable cleaning solution.

Vortex cups having one and 12.7 mm (one-half inch) cylindrical discharge opening were positioned in staggered relation across each rail in contiguous relation relative to area coverage of passing strip surface with a gap spacing in the range of 3.97 to 19.05 mm (5/32 to 3/4 inch) utilizing liquid vortex plenum pressure of 2.07 bar (30 psi) and liquid knife pressure of 1.1 bar (16 psi). With 67 g/l (nine ounces per gallon) cleaning solution at 82°C (180°F). and 50 volts, a current density of 304,8 Amp/m² (1000 amps/sq. ft). was achieved.
The same vortex diffuser configuration and pressures are employed at successive water rinsing and 5% sulfuric acid 60°C (140°F). pickling stations.
With further reference to FIG. 2, the illustrated five module vortex chrome plater has not been tested on line to date, but based on an extension of the technology of the vortex Process for Electrowinning disclosed in U. S. Patent 3,957,599 and the aforementioned successful results of vortex diffuser electrolyte cleaning of a moving strip, equally successful plating is foreseen. While such patent is limited in its disclosure to plating on a stationary sheet, which comprises the cathodic portion of an electrolytic couple, applicants believe that effective metal plating may be achieved on a cathodic moving strip using an appropriate electrolyte with electrical contact to the strip. Likewise, it is anticipated that the vortex rinse following plating will be effective for reclaiming the electrolyte solution.
Based on reduction to practice experience for cleaning, scrubbing and pickling stations, and reasonable assumptions for the balance of the line, applicants have determined that comparable metal plating can be effected in approximately one half the length of the FIG. 1 conventional line.
With reference to FIG. 6 and 6A, the sheet feeder high speed continuous strip simulator provides a series of ten separate liquid holding tanks over each of which transverse vortex manifolds 110 are mounted between a pair of Z rails 11 with vortex cups 112 adapted to discharge liquid from each individual tank pumped up through supply lines 113 to overpassing metal sheets 114 on the underside of carrier sled 115 supported by hangers 116 sliding on plastic rails 117 and driven by cable 118 in a forward direction through attachment 119 to carrier bracket 120 and driven in a return direction by attachment 121 at the other end of the cable.
As shown in FIG. 6, the drive cable extends around drive pulley 121 at the forward end of the sheet feeder and idler pulley 122 at the return end with each end on the underside attached to bracket 120. The drive pulley is threaded for helical cable engagement with a sufficient number of wraps on each side of center to equal the total length of the sheet feeder so that when the ends of the cable are attached to bracket 120 under tension, the underside will wind on the drive pulley while the sled advances from the idler end to the drive end and the upper side of the cable unwinds from the drive pulley. Upon reversal of the drive pulley, the sled is returned to the idler end with similar winding of the upper side and unwinding of the lower. In this manner, the hydraulic pump and drive motor are capable of rapidly accelerating the sled before reaching the first tank to a speed as high as 823,5 m/min (2700 feet per minute), which is in excess of the maximum plating line speeds.
A single steel sheet metal blank is held on the underside of the sled by a magnetic surface material which is adequate to hold it securely in passing over vortex diffusers selectively actuated by control panel 123 to energize individual station pumps, not shown, for individual liquid holding tanks. Sample sheets having typical soil conditions can thereby be passed over cleaning, scrubber, rinsing, pickling, plating and any other optional vortex diffuser processing tanks to simulate, on one side only, the processing typical of both sides in a continuous steel strip plating line.
As best shown in FIG. 6A, containment of liquid between individual tanks is accomplished by upper and lower containment brushes 124 on both sides of the sled, together with fixed containment shields 125 in lieu of exit and entrance liquid knives, preferably employed in the Strip Tech Modules.
With reference to FIG. 7, a moving belt test stand is also employed with a stainless steel or clear plastic endless belt 126 adapted to pass under a vortex manifold 127 and liquid knife 128 within a clear plastic enclosure 129 which enables a viewer to observe the vortex action and liquid knife action in a manner simulating a continuous steel strip plating line.

Claims

A continuous sheet metal (49) processing station (68) including a stationary enclosure (69, 70) and a means for moving said continuous sheet metal surface through said processing station, comprising an electrolytic cleaning liquid vortex diffuser means (71, 72) disposed within said enclosure (69, 70) with atmospheric clearance for vortex liquid discharge impingement on both surfaces of the continuous passing sheet metal (49), said diffuser means (71, 72) including adjacent alternating oppositely electrically charged vortex diffuser outlets (78) linearly spaced along the sheet metal path, said station serving as a means for performing typical electrolytic cleaning functions on the sheet metal passing submerged through electrolytic cleaning liquid.
Station of claim 1 including pickling liquid vortex diffuser means (71, 72) disposed within said enclosure (69, 70) with atmospheric clearance for vortex liquid discharge impingement on both surfaces of continuous passing sheet metal (49), said station serving as means for performing typical pickling functions on the sheet metal passing submerged through pickling liquid.
Station of claim 1 or 2, wherein said means for confining fluid within said enclosure (69, 70) comprises pressurized fluid knife means (73, 74) directed at both surfaces of said sheet metal (49) inwardly from an extremity of said enclosure (69, 70).
Station of claim 3, wherein said fluid knife means (73, 74) comprises pressurized liquid.
Station of any of the preceding claims incorporated in a continuous metal strip (49) surface processing line extending between metal strip coil unwind and wind-up reels with continuous travel of the strip metal (49) through said station.
Station of any of the preceding claims including modular vortex diffusion means (69, 70) having upper (69) and lower (70) vortex diffuser sections hinged for opening, and having piping connection means (85) for conducting pressurized liquid between lower (70) and upper sections (69) effected by closing the top section in operation position over the bottom.
Station of claim 1 incorporated in surface processing simulaton means for testing processing parameters comprising a plurality of said processing stations linearly spaced, each station having vortex diffuser means (71, 72) disposed for upward discharge impingement on the undersurface of overpassing flat metal sheet (114), a sheet carrier sled (115) and track means (117) for transporting an individual sheet over the vortex diffuser means (71, 72) of said successive stations, a drive means (118) for reciprocating said sled (115) between starting and finishing ends at a start-to-finish speed at least corresponding to continuous metal strip surface processing requirements, whereby individual metal sheets (114) having surface condition corresponding to production sheet metal may be subjected to simulated processing to establish parameters for subsequent implementation on production processing.
Station of claim 7 wherein reciprocation of said sled (115) is effected by flexible forward and return tow line means (118) coiled on a drive drum (121) at the finishing end with a sufficient number of convolutions to equal at least double the length between said starting and finishing ends and with said tow line (118) extending from said drive drum (121) over a pulley (122) at the starting end and back to said drive drum.
Station of claim 7 or 8 wherein the bottom of said sled (115) is provided with a magnetic surface for retaining a sheet of metal to be processed during transportation of said sled.
Station of claim 1 including an endless steel or plastic belt extending with a horizontal surface over drive (121) and idler (122) rollers in said enclosure (69, 70), including vortex diffuser means disposed above the upper surface of the belt whereby parameters for processing production sheet metal surfaces may be tested.
Station of claim 10 wherein said enclosure (69, 70) is constructed with transparent material (129) to provide means for observing operation of said station.
A method for processing continuous sheet metal surfaces passing through a stationary enclosure, comprising electrolytically processing said continuous strip sheet metal (49) passing through said enclosure (69, 70) by the impingement of pressurized electrolyte liquid including the step of oppositely electrically charging adjacent alternating linearly spaced vortexes (71, 72) along the sheet metal path.
Method of claim 12 for pickling continuous strip sheet metal passing through an enclosure (69, 70) including the impingement of pressurized pickling liquid on said surfaces.
Method of claim 12 for brushless rinsing continuous strip sheet metal passing through said enclosure (69, 70) including the impingement of pressurized liquid on said surfaces.
Method of claim 12 for cleaning continuous strip sheet metal passing through said enclosure (69, 70) including the impingement of pressurized electrolyte cleaning liquid, and including the step of oppositely electrically charging adjacent alternating linearly spaced vortexes (71) along the sheet metal path.
Method of claim 12 for brushless scrubbing continuous strip sheet metal (49) passing through said enclosure including the impingement of pressurized liquid on said surfaces.