Continuous in-line processing to produce hot-dip zinc-spelter coated flat-rolled mild-steel strip

Abstract

Methods and apparatus for continuous in-line processing of flat-rolled mild steel substrate, by correlating in-line operations for surface cleansing and substrate heating in preparation for hot-dip zinc-spelter coating of flat-rolled mild steel, pneumatically controlling hot-dip zinc-spelter coating weight on each surface, selective surface solidification of said zinc-spelter coating, and in-line refined-surface-finishing of said solidified zinc-spelter, in a manner which enables in-line adjustment of mechanical-properties, and level presentation, carried out without darkening of such zinc-spelter color or detriment to said uniformly-smooth refined zinc-spelter finish; and, capable of added protective coating free of chemical-treatment of a refined-finish surface.

Description

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser. No. 60/497,734 filed on Aug. 25, 2003.

INTRODUCTION

This invention relates to continuous-line methods and apparatus for hot-dip zinc-spelter coating and finish-processing of flat-rolled mild-steel as continuous-strip; and, more particularly, to correlating continuous-in-line processing including surface-profiling refinement of solidified hot-dip zinc-spelter and enabling modification of characteristics of the mild-steel substrate free of detriment to the refined-surface finish of the zinc-spelter coating.

OBJECTS OF THE INVENTION

An important object is to provide method steps and apparatus which correlate surface preparation of continuous-strip flat-rolled mild-steel substrate for hot-dip zinc-spelter coating and in-line surface-finishing in a manner enabling subsequent in-line adjustment of steel substrate characteristics, including mechanical properties of the steel as well as a selective level presentation, to be carried-out free of detriment to surface appearance-characteristics of the finish-processed zinc spelter coating.

A related object improves the topography of the solidified zinc-spelter coating so as to provide a uniformly-smooth profiled surface, and to eliminate surface defects if any, carried-out in a manner which enables in-line adjustment of desired mechanical properties and/or tension-leveling of the flat-rolled steel substrate while eliminating prior chemical treatments by providing a smooth-profile refined-surface product capable of directly-added protective or decorative coating.

An integral object of the refined-finish processing of solidified hot-dip coated zinc-spelter is the capability for improvement of the flat-rolled mild-steel mechanical-properties and presentation, free from detriment to the refined-finish, enabling directly-added protective or decorative coating for fabricating products for the construction, transportation-equipment, household appliance, and like flat-rolled mild-steel fabricating industries.

The above objects, and other advantages and contributions of the invention, are considered in more detail in describing the invention as shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a box-diagram general-arrangement view for describing correlating flat-rolled mild-steel processing and finishing operations in a continuous-strip hot-dip zinc-spelter coating line in accordance with the invention;

FIG. 2 is a schematic general-arrangement view, partially in cross section, for describing continuous in-line apparatus for correlating preparation of flat-rolled mild-steel strip for hot-dip zinc-spelter coating, for selectively controlling hot-dipped coating weight, for controlling surface-properties of solidified hot-dip zinc-spelter, and for refinement-surface-finishing of the hot-dip zinc-spelter solidified coating in accordance with the invention;

FIGS. 2A and 2B are schematic views, partially in cross-section, of apparatus for selective optional in-line utilization in FIG. 2 for control of solidified hot-dip zinc-spelter surface properties in accordance with the invention;

FIG. 3 is an enlarged schematic view for describing apparatus for surface-finishing refinement of solidified hot-dip zinc-spelter in a continuous-line, as shown in FIG. 2, and in-line substrate adjustment apparatus of the zinc-spelter coated flat-rolled mild-steel substrate, in accordance with the invention;

FIG. 4 is a perspective partial view for describing construction of, dimensional configurational aspects of, and operational components of an elongated flapper-wiper surface-finishing structure used to smoothen a solidified zinc-spelter coated topography uniformly across strip width, in accordance with the invention;

FIGS. 5A and 5B are schematic expanded cross-sectional partial views of a single solidified surface of hot-dip zinc-spelter coated steel substrate shown, respectively, before and after refinement-surface-finishing, for describing results of flapper-wiper surface-profiling of the invention;

FIG. 6 is an expanded cross-sectional view for describing surface-profiled solidified uniform-thickness zinc-spelter coating, on each continuous-strip zinc-spelter coated mild-steel substrate surface, in accordance with the invention;

FIG. 7 is an enlarged cross-sectional view for describing solidified differential-thickness-coated hot-dip zinc-spelter flat-rolled mild-steel substrate, with each profile-refined solidified zinc-spelter surface provide for direct adherence of additional protective coating, and

FIG. 8 is an enlarged cross-sectional profile-view for describing solidified hot-dip zinc-spelter selectively differential-thickness-coated continuous-strip flat-rolled mild-steel with a single surface including directly-applied additional protective coating, free of intermediate steps, in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Continuous-strip flat-rolled mild-steel substrate is supplied at station 10 of FIG. 1 and unwound at uncoiling station 11, for feeding continuous-strip in-line. In preparing for surface-refinement of solidified zinc-spelter coating, surface-cleansing of the flat-rolled steel substrate is carried-out before initiating steps for hot-dip coating with zinc spelter.

Surface debris from hot-rolling and/or cold-rolling thickness reduction of the flat-rolled mild-steel is removed at surface cleansing station 12 at FIG. 1. Surface debris includes particulate iron, particulate iron oxide, and rolling solution. Apparatus provided for separation of such debris from the cleansing solution during in-line usage is described in more detail in relation to FIG. 2.

Surface cleansing of the steel substrate is carried out prior to heat-treatment of the substrate at station 14 of FIG. 1. Preferably, a heat-treatment temperature of the strip is carried-out at approximately hot-dip zinc-spelter bath temperature in a controlled-reducing atmosphere so as to prevent, and/or to eliminate, surface oxidation. The temperature of the reducing atmosphere is controlled such that the mild-steel strip helps to maintain melt temperature for the molten zinc-spelter bath. Such temperatures also decrease stress in the flat-rolled mild-steel from cold-rolling thickness reduction. However, such controlled heating causes stress relief in the mild-steel substrate which can decrease temper of the steel substrate more than desired for market-usage fabrication of hot-dip zinc-spelter coated product.

Mild-steel and “low-carbon steel” as used herein refer to flat-rolled steel having a carbon content of about 0.2% to about 0.35%, minor percentages of manganese and silicon, and some residual sulfur and phosphorous. The surface-refinement of the invention subsequent to hot-dip zinc-spelter coating and solidification, enables adjustment of the temper of such low-carbon steel substrate so as to provide desired mechanical properties for market-product fabrication and/or also enables tension-leveling of the steel substrate. Further, such adjustments can now be accomplished in-line, free of darkening, or other detriment, to the solidified zinc-spelter-refined-finish produced by the correlated operations of the invention.

Use of reducing atmosphere in station 14 of FIG. 1 removes iron oxide, if any, prevents surface oxidation of the recently cleansed steel substrate surfaces. Those steps present substantially-pristine mild-steel surfaces for enhanced adhesion of molten hot-dip zinc-spelter coating; and such heated strip as directly immersed in a hot-dip molten zinc-spelter bath, helps to maintain desired molten bath temperature. Both planar surfaces are coated at station 15 of FIG. 1, followed by controlling the coating-weight of the molten zinc-spelter coating on each surface at station 16 of FIG. 1; that coating weight control is carried-out pneumatically as described in more detail in relation to FIG. 2.

Contributions which increase diversity for market-usage products, provided by the invention include selective coating weight control for each respective surface during that coating control; enabling selectively providing for uniform coating weight on both surfaces or differential-coating weights on opposite planar surfaces of the steel substrate.

In addition to increasing product selections by coating weight; methods and means are provided which enable selecting characteristics for zinc-spelter surfaces prior to solidification of such controlled-weight zinc-spelter. One such measure is to produce a minimized-spangle surface by impinging atomized water spray, or wet steam, on each surface. Such water-bearing impingement promptly produces numerous solidifying nuclei for molten zinc-spelter crystals preventing formation of large-crystal spangles. Minimized-spangle control of zinc-spelter solidification is carried out at station 17 of FIG. 1; that minimized spangle contribution facilitates achieving the desired refined-surface-finishing of the invention; its selection and advantages are described in more detail in relation to later-presented FIGS.

A further step contributing to achieving the desired surface finish comprises alloying, containing zinc-spelter of varying aluminum content, with the steel substrate. Alloying of the zinc-spelter with the iron of the steel substrate can eliminate spangle formation; which contributes to desired uniformity of the distinctive silvery refined-surface finish of the zinc-spelter of the invention. Alloying of the zinc-spelter with substrate iron, at station 18 of FIG. 1, utilizes a correlated in-line heating; such as: (i) high frequency induction heating of the steel substrate, or (ii) gas-fired surface heating, or (iii) a combination of (i) and (ii). Such alloyed zinc-spelter-iron refined-surface-finish of the invention facilitates direct additional protective and/or decorative coatings, which augment opportunities to provide desired coloration for industrial uses, as described later herein.

In addition to the selective in-line travel paths for stations 17 and 18 of FIG. 1, travel path 19 provides for processing after solidification of other hot-dip zinc-spelter coatings. For example, large-crystal zinc-spelter spangles present a relatively-large proportion of mirror-like reflective areas with rougher-surface boundaries for those mirror-like portions; such large-crystal spangled surfaces have required chemical treatment, such as “bonderizing”, in which a zinc phosphate film is formed, so as to facilitate painting. Any such requirement is eliminated by the present invention.

Another example for processing along path 19, comprises zinc-spelter utilizing about five (5) percent aluminum by weight, and small quantities of “misch-metal” containing about 50% cerium, with the remainder lanthanum and neodymium; hot-dip coated at station 15 is followed by coating weight controlled at station 16. Such misch-metal zinc-spelter coated strip can be solidified substantially free of spangles, so as to facilitate later refined-surface-processing of the invention which can also enhance adhesion of added protective coating.

Optional selections of constituents for the zinc-spelter, and the spelter-solidification-modifications, as described above, are disclosed in greater detail in relation to later-presented FIGS and data. Accommodating differing zinc-spelter compositions, which respond differently to correlated in-line steps and refined-finish-surface processing of the invention, increases the diversity of market-usage products available for the construction and the sheet-metal fabricating industries. It should also be noted that each embodiment described here has the high productivity advantages provided by correlating continuous-line hot-dip zinc-spelter coating operations and finish-processing of the invention are carried-out by correlating in-line operational steps. Said finishing operations, as taught herein, also facilitate adherence of directly-applied added coatings, applied for appearance and/or longer-range protective purposes, as later described in more detail, in accordance with the invention.

Continuous-strip flat-rolled mild-steel, with solidified hot-dip zinc-spelter coating, can be further cooled to about ambient temperature, as indicated at station 20, during subsequent in-line travel of FIG. 1. If required, air cooling of the coated substrate is carried out at cooling station 20; use of quench liquid, if any, is removed prior to spelter surface refinement processing at station 22.

Surface-refinement-processing of the invention at station 22 enables adjustment of mechanical properties and/or tension-leveling of the substrate to be carried out, in-line, at station 24 of FIG. 1. Such adjustment of characteristics at station 24 are accomplished without darkening a desired uniform color appearance, or any detriment to the zinc-spelter finish. Such combination of surface-refinement-processing at station 22, and adjustment of substrate characteristics 24 of FIG. 1, supplement other previously-identified selections of zinc-spelter characteristics; adding to the quantity and diversity of market-usage products; which are contributed by “on-line” production as taught herein.

Minimized-spangle, alloyed iron/zinc spelter, and the misch-metal zinc-spelter coating for flat-rolled mild-steel each facilitate achievement of a refined uniform surface-finishing; and, also, contribute to direct application, and adherence, of added protective and/or decorative coatings. The latter can include organic lacquer or polymeric formulations at station 26 of FIG. 1; or, solvent-based paints at station 31. Selecting from methods available for applying organic coatings enables in-line coiling at station 27; or, directing the refined-surface-finish-processed with added organic coating for fabricating, or preparation for that use, at station 28.

In an optional selective path, any of the hot-dip zinc-spelter coated embodiments, as finished processed at station 22, including aluminized zinc-spelter, can be directed for temper-rolling and/or tension leveling at 24; then, for direct coiling in-line at station 30 of FIG. 1. Any of the refined-surface-processed coated products including refined-surface painting of processed full-crystal spangled zinc-spelter coated flat-rolled mild-steel, can be directed for painting at station 31; free of any bonderizing or other chemical treatment requirement, before continuing on for fabricating or coiling.

Organic coatings, as referred to herein, include natural organic lacquers, which can be applied directly free of bonderizing or the like; that is, fabrication is available directly at station 32 of FIG. 1; or, for coiling free of any bonderizing or any chemical treatment requirement, at station 33. Organic coatings also include selective combinations of polymers; specifically, thermoplastic polymeric-formulations are useful for fabricating building panels, doors, door and window framing, or, similar types of forming for hot-dip zinc-spelter coated flat-rolled mild-steel; and, are available based on the above-described continuous-line production of the invention.

Hardness, temper, and ductility of flat-rolled mild-steel substrate are considered when testing suitability for market-usage product fabrication. Adjusting mechanical properties, as described herein, can restore desired temper to the steel substrate and, also, avoid so-called “luder lines” experienced in certain forming or stamping types of fabrication. Tension-leveling enables production of desired planar characteristics for added protective coating of market-usage zinc-spelter flat-rolled steel product. Such procedures can be carried-out with no detriment to the desired uniform glare-free silvery appearance by applying the refined-surface-finishing to both surfaces.

In-line apparatus for carrying out the invention is shown schematically in the general arrangement view of FIG. 2. Coil 34 and/or 35 direct flat-rolled mild-steel so as to enable forming of continuous-strip at lap-welder 37; strip 38 is then directed at a selected line speed, into surface cleansing unit 40. The contribution of separator apparatus 41, is to permanently remove iron, iron oxide and other particulate debris, from a caustic cleansing solution, heated to about 180° F. in unit 40, by magnetic-assisted separation and retention; as described in U.S. Pat. No. 5,599,395, entitled “Apparatus for Continuous Flat-rolled Steel Strip Cleansing and Finishing Operations”, which is included herein by reference.

Looping pit 42, of FIG. 2, maintains line speed while interconnecting flat-rolled steel from the separate coils (34, 35) to form continuous-strip 38. Prevention of iron-oxide formulation and/or removal of such oxide, if any, can be achieved, in addition to desired heating of the strip, to a selected temperature in heat-treatment unit 44. A reducing atmosphere is maintained in heat-treatment unit 44 to remove oxide, and prevent oxidation of the mild-steel; and, the strip is heated to a temperature which can facilitate maintaining desired molten zinc-spelter coating temperature; which is selected between about 850° F. to about 900° F. The reducing atmosphere of unit 44 is continued within snout 45 which enables direct immersion of the cleansed strip, free of iron oxide, into molten zinc-spelter bath 47 for submersed travel as shown; and, for enhanced adhesion of the zinc-spelter.

Strip, with adhering molten zinc-spelter coating, exits bath 47 substantially vertically, passing between pneumatic nozzles 48, 49, used for controlling the zinc-spelter coating weight on each respective surface; such pneumatic control is described in U.S. Pat. No. 5,614,266 “Continuous-Strip Coating Control Methods” which is incorporated herein by reference. Pneumatic control of coating weight is carried out as the strip travels substantively-vertically upwardly toward cooling-tower roll 50; supplemental movement of cooling air can be used; and, other controls of coating solidification are described in relation to FIGS. 2A and 2B.

The strip, with solidified coating, then travels in-line from top-roll 50 toward guide-roll 51, for guidance into an at-least partially enclosed-space 52 for surface-refinement travel of the invention, including a plurality of the flapper-wiper structures and back up rolls. Those flapper-wiper structures are shown subsequently in an enlarged view of FIG. 3 and, also, are described in greater detail. The number of flapper-wiper stations is selected based on line-speed. In FIG. 2, flapper-wiper structure 53 utilizes back-up roll 54 at the entry station of partially-confined space 52. At similar in-line stations flapper-wipers 55, 57 and 59 are shown in conjunction with a back-up roll at each station. Flapper-wiper-filaments are water-cooled at each station, without detriment to the desired finish of the zinc-spelter coating; both refined-finish surfaces are rinsed at station 60 upon exit from confined-space 52.

Refined-surface-finishing also enables adjusting of the temper of the steel-substrate at station 61; and, also provides the strip travel, in-line, through station 62 for tension-leveling of the strip, as may be required; both are carried-out free of detriment to the refined-finish. The strip is moved in-line partially by the bridle-rolls, as shown, toward recoiling station 63. A looping pit or looping tower can be used in approaching coiling station 63 to maintain continuous in-line speed during change of coils for recoiling purposes of the treated flat-rolled steel continuous-strip.

FIGS. 2(A) and 2(B) are concerned with controlling the surface of the solidifying zinc-spelter, in-line, upon exit from the pneumatic coating weight control nozzles (48, 49) of FIG. 2. In FIG. 2(A) atomized water, or wet steam, is directed against each surface within housings 64 and 65. The resulting fine moisture particulate each solidify a nucleus for solidifying a zinc-spelter crystal. The concentrated distribution of numerous moisture-particulate crystal-nuclei per unit surface area, inhibits the growth of large-crystal spangles. The result is a minimized-spangle surface, as described in U.S. Pat. No. 3,148,080 entitled “Metal Coating Process and Apparatus” which is incorporated herein by reference. Such minimized-spangle surface, free of the large-crystal-spangles, facilitates flapper-wiping refinement-finishing; that is, minimized-spangle presents a smoother-surface entering the refined-finish-processing station 52 of FIG. 2, which contributes-in-part to the pronounced refined-surface results.

A separate surface treatment is carried out in FIG. 2 (B), with a low-aluminum-content (about 0.1 to 0.15% by weight aluminum) zinc-spelter, coating both surfaces in the molten zinc-spelter bath. The strip travels vertically through the coating weight-control station which provides a light coating on each surface; prior to passage through a heating unit for each surface, 66 and 67, respectively. High-frequency electromagnetic-induction units heat the steel substrate surface rapidly; and, are preferred; however, gas produced open-flame units can be substituted, or used to implement the high-frequency induction heating so as to help to provide for more uniform distribution of heating throughout coating thickness; that is, by raising the temperature of the coating both internally and externally of the zinc-spelter coating.

The heating units cause alloying of the low-percentage aluminum zinc-spelter with iron of the steel substrate; that produces a matte-finish alloy on each surface which is free of crystalized spangle formation. That alloyed surface has been found to respond to flapper-wiper finishing, as disclosed herein, by more-readily producing uniform silvery reflectance, free of glare. That result supplants the prior darkened matte-finish experienced when using liquids to cool such a surface, when attempting to adjust the substrate mechanical properties or tension leveling of the zinc-iron-alloy-coated flat-rolled mild-steel.

FIG. 3 is an enlarged schematic cross-sectional view of the confined-space 52 of FIG. 2 housing multiple-stations, with a single flapper-wiper structure acting against a solidified zinc-spelter finish, while being supported from the opposite side of the strip by a single back-up roll at each station. Rotation of each flapper-wiper structure is at a selected RPM; the direction of rotation of each is such that the circumferential rate of movement of the flattened wiper portions, at each flapper-wiper location, is added to the rate of linear movement of the strip at the selected line-speed. Line-speed can be selected between about three hundred to about six hundred (300 to 600) feet per minute. Line speed is selected, in large measure, based on line-handling-capacity for the thickness gauge of the substrate.

At each flapper-wiper station a coolant inlet arrangement with a control valve for each, is provided; for example, as shown schematically at valve 64 for cooling the initial in-line flapper-wiper structure; and, as represented by a single angled-line at each remaining flapper-wiper station. The flapper-wiper structures are mounted and supported so as to be capable of controlled movement toward and away from the in-line travel path of the strip; such controlled movement is in the directions indicated at 68. The pressure of the contact, against the strip, causes the filaments of each flapper to be angled with respect to an original strictly-radial orientation for the filaments.

That is, movement of a wiper structure toward the strip causes increased-angled-wiping contact of the filaments which increases the wiping action on the zinc-spelter surface. That is, the wiping-force of abrasive-grit, carried near the distal ends of the elongated polymeric filaments, against the strip surface is increased; and, in accordance with present teachings such increase in force can be measured by the electrical power required to rotate each flapper-wiper structure.

In a specific embodiment, with seven (7) inch diameter flapper-wiper structures; each flapper-wiper structure is rotatably driven by an electric motor. The electrical-current, when there is no contact of the grit-ladened distal-end filaments with the coated surface of the substrate, is a half ampere. With increased wiping-action contact with the coated strip, the electrical current, for rotation of a flapper-wiping structure, can increase to about nine (9) amps; providing a significant range for the force of angled-filament flapper-wiper action by controlled movement of the wiper structure(s) toward the coated surface. That is, increasing wiping force of the angled-filaments measurably increases the power demand for each flapper-wiper structure; and, enables accurate electrical measurement, and control, of wiping-action for surface-refinement of the described products.

Cooling water inlets, with control at each structure, are for cooling the grit-ladened filaments during wiping; and, are not for cooling the strip. As a result of that filament-cooling action, service life of the filaments is increased. Such cooling and wiping action enables passage of the substrate, between working rolls at subsequent station 61, for changing mechanical properties of the substrate. The rolls at station 61 can be water quenched, for their protection, free of any detriment to the desired glare-free, uniform silver-reflectance of the refined-finish-surface.

FIG. 4 is an enlarged photographic perspective partial view of a flapper-wiper structure. A centrally-located metal core 70 facilitates assembly of a longitudinally-elongated roller configuration and enables control of rotation about an axis of rotation centrally-located within core 70. Each flapper-wiper structure is assembled with an elongated longitudinal-dimension which exceeds the width of the strip. That elongated dimension extends beyond each lateral edge of the strip, so as to compensate for strip tracking-irregularities, of a particular line, which may cause the travel path of the strip to move laterally.

The flapper-wiper structure at FIG. 4, preferably constructed with a solid metal core 70; and, with elongated non-woven nylon filaments 72; with abrasive materials embedded contiguous to filament distal ends, presenting a cylindrical-roll configuration when radially extended. Such flapper-wiper structures are available from:

• • USA Lippert, Inc. 6915 Americana Parkway Reynoldsburg, Ohio 43068, U.S.A.,
    and at other locations in other nations.

Abrasive materials can include particulate grit, such as aluminum oxide, having sizes from extra-coarse grit 80 to ultra fine grit 800; or, silicon carbide grit, with sizes from coarse through ultra fine. The nylon-plastic for the filaments is selected for toughness and flexibility.

In the practice taught herein, the coarser sizes of grit are used at the entry location of the zinc-spelter coated steel strip surface-refinement travel in space 52 (FIGS. 2, 3). In continuing travel during surface-refinement, progressively finer grit can be used on the coated substrate. In addition to grit size, the rigidity and density of the filaments can also be selected for the surface-refinement travel within such space 52.

Several of the solidified-surface embodiments of the zinc-spelter, for example: minimized spangle, the described zinc-spelter with misch-metal, and the zinc-spelter/iron alloy, with varying percentages of aluminum, are more responsive to the wiper-action finishing-processing of the invention. Those solidified embodiments augment surface-finishing by more readily producing the desired refined-finish; those examples can also enable use of finer grit sizes, softer medium-density filaments, and/or lighter wiping force.

To visualize one effect of the embedded abrasive-grit-flapper-wiper action on a zinc-spelter coated surface, it should be noted that casual observation of a zinc-spelter coated surface, free of magnification, may convey the impression of a somewhat smooth surface. However, an enlarged cross-sectional view of hot-dip zinc-spelter-coated surfaces will generally show an irregular topography; as indicated at 74 in FIG. 5A which presents a cross-sectional view of a single zinc-spelter coated surface before flapper-wiper treatment of the solidified zinc-spelter coating on steel substrate 75. Flapper-wiper finishing of such roughed topography produces a smooth profile for the surface as shown at 76 in FIG. 5B.

A silvery surface appearance and uniform glare-free reflectivity comprise visually-improved characteristics of the wiper-action finishing-processing of the invention. Also, as previously mentioned, flapper-wiper finishing of the zinc-spelter surface enables temper-rolling of the coated substrate, to restore desired mechanical properties for the low-carbon steel while permitting use of quench water, free of darkening or detriment to the desired glare-free silvery finish-surface appearance. In addition, as described in relation to later figures, such flapper-wiper finished surface can be painted or otherwise coated directly; that is, free of any requirement for chemical treatment or other such preparation. Such wiper-action refined-surface-finish also enhances adhesion for polymeric formulations applied directly upon completing the refined-surface finishing.

FIG. 6 is an expanded cross-sectional view of mild-steel substrate 78, which includes a uniform thickness zinc-spelter coating (79, 80) on each respective planar surface; and, each presents a smooth-surface topography due to refinement flapper-wiping, as disclosed above.

In another embodiment, a differential coating-weight is established for the zinc-spelter as hot-dip coated, as shown on steel substrate 81 of FIG. 7. A greater-thickness, heavier zinc-spelter coating weight is shown at 82; and, a lesser-thickness lighter-coating weight is located at 83 of FIG. 7. Refined-surface-finishing as disclosed herein, enables adherence of added paint, or organic coating, as indicated at 84 and 85, respectively; such added coating can be protective and/or decorative; and, can be directly applied, free of any added pretreatment to enable protective or decorative coating, for utilization on either, or both, of the finished surfaces of FIG. 7.

In FIG. 8, steel substrate 86 utilizes a differential zinc-spelter coating weight. Each surface has been finished to present a smoother profile and uniform reflectivity, with the greater-thickness, heavier-weight, zinc-spelter coating located at 87; and, the lesser-thickness lighter zinc-spelter coating weight located at 88. Solely the greater-thickness refined-surface-finish zinc-spelter coating 87 can be selected for added protective or decorative coating, as indicated at 90. Such an embodiment, and the selective combination at embodiments of FIGS. 5 through 8, increase the diversity of market-usage product.

For example, a selected color for the added coating of FIG. 8 can be located on the exterior surfaces of the greater thickness zinc-spelter coating on commercial buildings, such as equipment storage sheds, including open-front pole-type structures, and the like. Those exterior surfaces can be matched in color to the choice of a State Road Commission, farm operator, or other business entity while the interior silvery refined-finish surfaces are free of coloration as disclosed herein; providing an appearance with desired reflectivity for increasing and improving interior visibility, or improved electrical illumination.

Zinc-spelter, as referred to herein, includes combinations of zinc and aluminum (Al); for example:

• • (i) from less than about 0.03% to about 0.05% by weight Al for alloying zinc-spelters;
  • (ii) about 1.2% to 1.5% by weight Al for minimized-spangle or full-crystal spangle;
  • (iii) about 5% by weight Al, with minor percentage of the misch-metals, for substantially spangle-free zinc-spelter coating, and
  • (iv) about forty to sixty (40 to 60) percent Al by weight for an aluminized zinc-spelter in which spangle-formation, especially large-crystal spangle formation, can be decreased.

In carrying out the refined-surface-finishing operations of the invention, each flapper-wiper structure is positioned to co-act with its respective back-up roll. Coolant is directed onto flapper-wiping filaments as shown in FIG. 3, so as to help to prevent undesirable increases in temperature of the filaments during the flapper-wiping action. Coolant water flow for each flapper-wiper station is selected in the range of about four to five gallons per minute for each foot of strip width. The confined-housing space for flapper-wiper stations has openings for entrance and exit of coated strip, for access of coolant supplies, and for escape of coolant vapors. The number of flapper-wiper stations in a “confined-space”, such as 52 of FIGS. 2, 3, is dependent on line-speed; which can be determined, in part, by in-line substrate cleansing, heat-treatment of heavier thickness gauges, and hot-dip zinc-spelter coating operations. As taught herein, the number of flapper wiper stations within a confined-space (52 FIGS. 2,3), is selected to provide at least one flapper-wiper station, for each surface, for each one hundred feet per minute (100 fpm) of line-speed.

The elongated longitudinal dimension of a flapper-wiper structure is selected in a range of about fifteen to twenty percent (15-20%) greater than strip width. The purpose of that dimensional elongation is to provide for strip tracking; which may present an irregular travel path with lateral movements, during strip travel in a particular line. That increased longitudinally elongated-dimension assures flapper-wiper-finishing across full strip width. Further, flapper-wiper structures with such increased longitudinally elongated dimension can be gradually oscillated in a lateral direction; that lateral movement can help to provide more uniform flapper-wiper wear; and, can increase service life of the flapper-wipers.

It has been found in tests that the flapper-wiper action, as disclosed herein, while providing a smoother profile, does not decrease coating weight; no measurable change in coating weight could be detected after the described flapper-wiper finishing.

While specific operational processing data and coating materials have been disclosed which enable achieving stated objectives of the invention, it should be recognized that in light of the above teachings, those skilled in the art may attempt to modify certain such specified steps or data, while continuing to utilize innovative concepts combined by the invention; therefore, for purposes of determining the scope of protection for the subject matter disclosed, reference should be made to the appended claims, the language of which should be construed relying on the above described principles of operation.

Claims

1. Continuous in-line processing of flat-rolled steel substrate, providing for

i. substrate surface preparation for hot-dip zinc-spelter coating of flat-rolled mild steel,

ii. selective hot-dip zinc-spelter coating weight of said substrate,

iii. selective in-line solidification of said molten zinc-spelter coating,

iv. in-line refinement-surface-finishing of said solidified zinc-spelter, and

v. in-line adjustment of characteristics of said steel substrate, free of detriment to said refined zinc-spelter finish, comprising the steps of

(A) supplying flat-rolled mild steel substrate of selected thickness gauge;

(B) delivering said steel substrate as continuous-strip establishing an in-line travel path for carrying out zinc-spelter hot-dip coating operations;

(C) cleansing planar surfaces of said flat-rolled substrate by removing surface debris;

(D) heat-treating said continuous-strip substrate in-line in preparation for entry at a selected temperature into a molten hot-dip zinc-spelter coating bath;

(E) pre-selecting molten zinc-spelter composition for said hot-dip coating bath;

(F) controlling submersed travel and substantially-vertical in-line exit travel from said molten zinc-spelter coating bath;

(G) pneumatically controlling molten zinc-spelter coating weight remaining on each planar surface of the substrate while traveling substantially-vertically in-line above said molten hot-dip coating bath;

(H) solidifying said controlled coating-weight hot-dip zinc-spelter coating while traveling in-line above said bath;

(I) delivering approximately ambient-temperature zinc-spelter-coated substrate traveling in-line, in preparing for refinement-surface-finishing of said solidified zinc-spelter coating;

(J) providing elongated flapper-wiping structures with elongated flexible polymer filaments presenting an elongated exterior configuration which is symmetrically-disposed relative to an elongated centrally-located axis of rotation;

(K) arranging a plurality of said flapper-wiping structures within an at-least partially-enclosed space establishing a longitudinally-elongated in-line travel path for surface refinement of said solidified zinc-spelter coating;

(L) orienting said individual wiping structures to extend width-wise of said coated strip during said surface-refinement travel, with each said flapper-wiping structure (i) presenting radially-oriented elongated polymer filaments, characterized by polymeric toughness and flexibility, which filaments are arranged in contiguous-contacting-relationship both radially and along said elongated roll-dimension of said individual wiper structure, (ii) presenting, when free of contact with coated substrate, a substantially-continuous cylindrical exterior configuration, in which (iii) distal ends of said filaments are embedded with abrasive-particulate-grit, establishing a working surface for each said wiper-structure when said filaments are contacting zinc-spelter coated substrate;

(M) selecting abrasive particulate grit size for distal ends of said filaments, of each said flapper-wiper structure, as said structures are distributed longitudinally along said elongated surface-refinement travel path;

(N) refining said zinc-spelter coating on contacted substrate, by: (i) powered rotational driving of each said flapper-wiper-structure, about its respective centrally-located axis of rotation, (ii) positioning each said rotatably driven flapper-wiper structure, to selectively establish embedded-grit-distal-ends of wiping-filaments, in contact with solidified zinc-spelter coated surface of said substrate during said surface-finishing travel, and (iii) controlling-pressure exerted by each said roller-configuration flapper-wiper structure to control wiping action force exerted by each said longitudinally-elongated working structure, providing for smoothening and producing a glare-free silvery finish for said contacted zinc-spelter surface; followed, in-line, by

(P) adjusting said steel substrate characteristics, by selecting from the group consisting of (i) adjusting temper of said steel substrate (ii) tension-leveling said steel substrate, and (iii) a combination of (i) and (ii); while

(P) enabling liquid quenching of said finish-surface zinc-spelter coated substrate, during said selected adjusting of characteristics of said substrate, free of detriment to said refined-surface-finish of said zinc-spelter coating.

2. The process of claim 1, further including

(Q) selecting axial-length and axial orientation of said longitudinally-elongated cylindrical-roll-configuration flapper-wiper structures, so as to extend across strip width and beyond each respective lateral-edge of said elongated strip, during said surface-finishing in-line travel; while

(R) providing for rotating each cylindrical-roll wiper structure about its respective centrally-located longitudinal axis, (i) contacting zinc-spelter coated surface across full width of said strip with a selected force, during said surface-finishing travel, (ii) selectively establishing the number of flapper-wiping-structures operating during said surface-refining travel, and (iii) increasing the number of flapper-wiping structures during said surface-refining travel with increasing surface-refining in-line travel speed for said zinc-spelter coated mild-steel substrate.

3. The process of claim 2, further including

(S) selecting particle size of embedded grit contiguous to distal ends of said radially-oriented flapper wiping filaments, while (i) correlating location of said selected grit rotatable flapper-wiper structures along said travel path for surface-refinement, by: (ii) establishing larger particulate-size embedded grit for more aggressive wiping by filaments of a flapper-wiping-structure as located for first contacting said zinc-spelter coated substrate during in-line surface-finishing travel, and (iii) establishing smaller particulate-size embedded grit and less-aggressive wiping, by said structures at locations subsequent to said entrance location during said surface-refining travel.

4. The process of claim 1, in which a selected adjustment of steel substrate temper is carried-out, by

limiting percentage elongation of said steel substrate to be within a range from less than about 0.5% and extending to about 3.0%.

5. The process of claim 4, further including

(T) applying a protective coating to a refined-zinc-spelter finish-surface, by

selecting said protective coating from the group consisting of (i) paint, (ii) organic lacquer, and (iii) a thermoplastic polymeric formulation; including

(U) applying said protective coating by selecting from the group consisting of (i) both said zinc-spelter refined-surfaces of said substrate, and (ii) solely a single zinc-spelter refined surface of said substrate.

6. Hot-dip zinc-spelter coated flat-rolled mild-steel substrate with refined-surface-finish having

a uniformly-smooth zinc-spelter finish surface produced in accordance with the process of claim 1.

7. Hot-dip zinc-spelter coated flat-rolled mild-steel substrate, with refined-surface-finish, having

a uniformly smooth zinc-spelter finish surface produced in accordance with the process of claim 3.

8. Hot-dip zinc-spelter refined-surface-finish flat-rolled mild-steel substrate, having

an added protective coating produced in accordance with claim 5.

9. Continuous in-line production apparatus for correlating coating and substrate processing of

(i) hot-dip zinc-spelter coated flat-rolled mild steel substrate, with

(ii) refined-finish-surface of solidified zinc-spelter, and

(iii) subsequent in-line adjustment of characteristics of said steel substrate, free of detriment to said refined-surface-finish zinc-spelter coating, comprising

(A) means supplying coils of flat-rolled mild steel substrate of selected thickness gauge for hot-dip zinc-spelter coating;

(B) continuous-line means for forming continuous-strip from said coils for in-line travel;

(C) means for preparing said continuous-strip steel substrate for hot-dip zinc-spelter coating, including: (i) cleansing means for planar surfaces of said flat-rolled steel substrate to remove manufacturing debris, and (ii) means for removing surface iron oxide;

(D) temperature-controlled molten zinc-spelter hot-dip coating-bath means for immersion of said cleansed strip and in-line travel;

(E) means for delivering said strip from said coating-bath means, with adhering molten zinc-spelter, for substantially-vertical upwardly-directed in-line travel;

(F) pneumatic means, located along said substantially-vertical in-line travel path, for controlling molten-spelter coating weight on each surface of said steel substrate,

(G) means for controlling solidification characteristics of said molten zinc-spelter coating, selected from the group consisting of: (i) means for minimizing spangle formation during solidification of said coating, (ii) heating means for alloying said zinc-spelter with iron of said mild steel substrate during solidification of said coating, and (iii) in-line means for cooling-solidification of said controlled-coating weight molten zinc-spelter and substrate;

(H) in-line means for refinement-surface-finishing of said solidified zinc-spelter, including (i) a plurality of longitudinally-elongated rotatably-mounted flapper-wiper-structures sequentially mounted in-line for surface-finishing travel with said coated strip, with each such wiper structure (ii) defining a longitudinally-elongated external cylindrical-roll-configuration, which is symmetrical with a central axis of rotation for said configuration, (iii) an inner longitudinally-elongated rigid core means, which is symmetrical with said axis of rotation, with (iv) flapper-wiper elongated flexible filaments contiguously-located longitudinally and radially of said cylindrical-configuration, extending radially from each said core means, with (a) distal-end portions of said filaments ladened with embedded grit of selected particulate size and hardness, (b) located for wiping contact with coated zinc-spelter; and (v) means for controlling wiping force exerted by contact of said distal ends of said flexible filaments, by controlling contact thereof during surface-refining travel of said zinc-spelter coated surface, by: (a) selective size of said abrasive particulate grit as embedded contiguous to such distal end portions of said filaments, for contacting said zinc-spelter coated surface, (b) selective rate of rotating longitudinally-elongated wiping structures, and (c) means for controlling contact of said embedded grit distal-end portions, which extend across full-strip width and beyond each lateral-edge during said surface finishing in-line travel, by controlling movement of said cylindrical-configuration flapper wiper structures toward and away from said zinc-coated substrate, to change the force exerted by said wiping contact;

(I) means for rotatably driving said flapper-wiper means with embedded abrasive-grit contiguous to said distal ends of said filaments contacting said zinc-spelter coating so as to produce a uniformly-smooth surface during said surface-finishing in-line contact, and

(J) means located in-line, subsequent to said refined-surface-finishing means, for adjusting characteristics of said mild-steel substrate, by selection from the group consisting of (i) changing mechanical-properties by limited elongation of said coated substrate, (ii) tension-leveling of said coated substrate, and (iii) combinations of (i) and (ii); in which (a) elongation of said coated substrate, if any, is limited to a range of length of less than 0.5% and extending to about 3.0%.

10. The apparatus of claim 9, in which

(i) said means for cleansing planar surfaces to remove manufacturing debris include heated caustic solution, from which

(ii) solid particulate is removed from said solution during said cleansing; and

(iii) means for removing surface oxide comprise heated-reducing gas located within a confined passageway leading into said hot-dip zinc-spelter coating bath,

(iv) pneumatic means provided for controlling zinc-spelter coating weight, on each respective mild-steel substrate surface, selected from group consisting of (a) uniform zinc-spelter coating weight on each surface, and (b) a differential zinc-spelter coating weight on each surface.

11. The apparatus of claim 10, in which

said uniform zinc-spelter coating weight for each surface is selected in the range of about four to about nine ounces per square foot, total for both surfaces.

12. The apparatus of claim 10, in which

said differential zinc-spelter coating weight is selected to comprise about point two (0.2) ounces per square foot on one surface, and about point seven (0.7) ounces per square foot on the remaining surface.

13. The apparatus of claim 9, in which

said hot-dip zinc-spelter bath is selected from the group consisting of

(i) about point five (0.5) to about one point two (1.2) percent aluminum with the balance substantially pure zinc,

(ii) about forty to about sixty percent aluminum with the balance substantially pure zinc, and

(iii) about five percent aluminum and misch-metal contents, with the balance substantially pure zinc.

14. The apparatus of claim 13, including

(a) selecting a zinc-spelter metal with about point five (0.5) to about point one point two (1.2) percent aluminum, and further including

(b) means for heating said substrate and coating to alloy said zinc-spelter with iron of said steel substrate.

15. The apparatus of claim 9, including

(O) means for delivering refined-surface-finish of said zinc-spelter coated steel strip, free of chemical treatment so as to enable direct application of a protective coating selected from the group consisting of (i) paint, (ii) organic lacquer, and (iii) a thermoplastic polymeric formulation.