US2823641A

US2823641A - Apparatus for fluxing and coating metal strip

Info

Publication number: US2823641A
Application number: US412265A
Authority: US
Inventors: Nelson E Cook; Samuel L Norteman
Original assignee: Wheeling Steel Corp
Current assignee: Wheeling Steel Corp
Priority date: 1954-02-24
Filing date: 1954-02-24
Publication date: 1958-02-18
Anticipated expiration: 1975-02-18

Description

Feb. 18, 1958 N. E. COOK ET AL 2,823,641

APPARATUS FOR FLUXING AND COATING METAL STRIP Filed Feb. 24, 1954 2 Sheets-Sheet 1 lN/L-WTUA'S Mason E coox.

Feb. 18, 1958 N. E. COOK ET AL APPARATUS FOR FLUXING AND COATING METAL STRIP Filed Feb. 24. 1954 2 Sheets-Sheet 2 INVENTORS NELSON E. COOK & SAMUEL. L. NORTEMAN a; m4

United States Patent APPARATUS FOR FLUXING AND COATING METAL STRIP Nelson E. Cook. and Samuel L. Norteman, Wheeling,

W. Va., assignors to Wheeling Steel Corporation, Wheeling, W. Va., a corporation of Delaware Application February 24, 1954, Serial No. 412,265 13 Claims. '(Cl. 118-74) This invention; relates. to; apparatus, for fluxing and coating metal strip. In: its broader aspects the invention relatesto apparatus, for fluxing and coating wire as, well as to .apparatus for fluxing and coating flat strip and. we hereby define; the wordstrip as used herein to comprehend, metal in elongated'form and flexible so as to be adapted to be guided in a circuitous path asv it advances in the direct-ion of its length, irrespective of whether the metal is of fiat, round or other cross section, unless in particular instances the context requires otherwise.

The invention isv concerned with, apparatus for fiuxing and coating metal; strip when flux is applied to the strip in preparationforcoating. In certain of its aspects the invention may beconsidered as relating to apparatus for applying; flux to metal stripv in preparation for coating while. in. other, of its aspects the invention may be considered as. relating to, apparatus for coating metal strip including in, combination means for applying flux to the strip and means for subsequently coating the strip.

More particularly the invention is concerned with ap,.- paratns, for applying to metal strip to be coated. flux which reacts with the molten coating metal at. the temperature-of, the mol-tencoating metal so, that the flux can.- not, be floated uponthe molten coating metal The, invention is-applicablebroadly in the metal coating art, examples of specific, branches of the. metalv coating art in which thei-nventiqnzis applicable being galvanizing, terne coating: and. aluminizing. For purposes of explanation and, illustration we shal-lydescribe theinvention as applied specifically to the art of, tight coat hot dip galvanizing, i. e., coating strip withspelter which: contains, aluminum by passing, the strip. through the molten spelter.

Our:Pa t,entNo., 2,647,305, covers a tight coat galvanizing methodand' a product produced by that method; The apparatus; of the present invention is especially well adapted for employment in connection withspractice of the, method covered by our said patent and to produce the product covered; thereby, although it is emphasized that the presentinvention is of broad. scope. and not limited to such application.

Oneof the objects-of; thepresent invention. is to pro; vide; apparatusv making possible considerably increased stripspeed, in a continuous. metal-coating process utilizinga flux which reacts, with the molten coating. metal at; the temperature oflthe molten coating metal. The flux inappliedto:thestnip in gadvanceofrentry of the strip into the, molten coating metala in the. coating-pot. The fiuxed strip,- enters vthe molten'coating metal in a vertically'downward; direction, being. thereafter guided by guide rolls in; the pot submerged in: the molten coating metal to emerge from the bath of molten coating metal at another point-.- When' the fluxed strip entersthe molten coating metal the flux reacts with the molten coating metal; and it isimpor-tant to; the production of coated metal of -high quality and optimum surface characteristies that: the reaction between the flux and the molten coating metal becotnpletebefore the strip engagesthe Z,8Z3,b4l Patented Feb. 18, 1%58 first guide. roll. in the coating pot- Inother words, the speed of advance of the strip is limited to such a speed as, willpermit substantial completion of the reaction between the, flux and. the moltencoating metal before the zone. ofv engagement-of the strip with the first guide roll in. the coatingpot is reached.

Many fiuxes employed for'application to strip to be -etal-coaterl are stable in air only up to limited temperatures. We prefer to employ a flux which is stable up: to. a temperature relatively closely approaching the temperaturev of the molten coating metal and to preheat the fluxed strip, before introducing it into the bath of molten, coating metal, to a. temperature approaching the maximum temperature at. which the flux is stable in air and consequently to a temperature relatively closely approaching; the temperature of the molten coating metal.

The lower the temperature differential between the fluxed strip as-it; enters; the. bath of molten coating metal and the; metal of the bath the faster will be the reaction betweenthefluxandthe, coating metal and consequently the faster can-.be the speedof advance of the strip for a given position-in thecoating-potof the first guide roll.

It is alsoimportant that the flux be applied smoothly and uniformlytQ-the strip and that the thickness of the coating ofiflux; onvthe. strip becontrolled. An unnecessarily thick coating of flux shouldbe avoided. The flux is preferably-applied, to'ithe'strip in liquid form, and we find it desirable, and convenient to apply the flux in a Water solution. This; maybe done in various ways, our preference being to pass the strip through a bath of flux in water solution. When the. strip is passed through such a" bath it should be withdrawn from the bath substantially vertically upwardly to insure a uniform coating of flux on the strip. The strippasses about guide rolls, one-guide roll being positioned to change the vertically upward movement of the strip to'movement' in another direction as the strip moves generally toward the coat.- ing pot, The flux should be dry beforethe fluxed strip engagcsthat roll as if the flux is not dry it will be ad. verselyaffected by contact with the; guide roll with a consequent adverse effect upon the; ultimate product.

Consequently the fluxed strip should be; substantially completely dried between the time when it emerges from the bath of flux and the time whenv it, engages the first guide roll. We preferably control the thicknessof the flux on the strip by engaging the strip at a zone above the bath of flux solution. Such engagement: reduces the thickness of flux solution on the strip and insures an even coating. The strip is then heated. to evaporatethe water in the fiux solution so that the wateris substantially entirely evaporated when the fiuxed strip engages the first guide roll.v

We prefer to heat the fluxed strip in two stages, the first heating stage being to evaporate the water in the flux solution and being between the bath of the flux solution and the first guide roll thereafter and the second stage following the first stage and further heating the dried fluxed strip before it enters the bath of. molten coating metal.

By way of example, we may employ a flux comprising ammonium, chloride and zinc chloride in liquid solution in. such relative proportions that the mixture: has the property when evaporated to a dry coating on the stripof being substantially stable up to a temperature of the. order of 500 F. We have used with success a flux comprising 45% ammonium chloride and 55% zinc chloride, although the proportions may be. varied. After passing the strip through a bath of theflux in water solution and the the strip moves upwardly from the bathwe engage the strip, preferably between rolls and/or brushes, to remove excess flux and insure asmooth uniform coating of flux on the strip. As the strip continues its upward movement and before it engages the first guide roll after emerging from the flux bath We apply heat to the strip to evaporate the water in the flux, leaving a uniform dry coating of controlled thickness of flux upon the strip. This may bring the temperature of the fluxed strip to in the neighborhood of 250 F. As the dried fiuxed strip continues its advance toward the metal-coating pot it is further heated to bring it to a temperature approaching the maximum temperature at which the flux is stable. In this stage the temperature of the fiuxed strip may be raised to 450500 F. Such raising of the temperature of the fluxed strip before it enters the metal coating bath accelerates the reaction between the flux and the molten coating metal so that such reaction is complete before the strip is engaged by the guide means in the bath. This is true even at strip speeds as high as 300 feet per minute or more. The reaction between the fiux and the molten coating metal is complete in the first few inches of passage of the strip through the molten coating metal.

Consequently our invention enables the operation at unprecedentedly high speeds of strip coating lines in which a flux is used which reacts with the molten coating metal at the temperature of the molten coating metal. Also, the quality of the product is enhanced by reason of the application of the flux to the strip as a uniform coating of controlled thickness. The controlling of the thick- 7 ness of the coating is a feature of importance. The method is claimed in our copending application Serial No. 412,266, filed of even date herewith.

As contributing to the uniformity of the coating of flux on the strip we also prefer to flow flux in liquid solution into the crotch between the last guide roll in the bath of flux solution and the strip as the strip emerges from the bath of flux solution. That guide roll preferably has its lower portion immersed in the flux solution and its upper portion above the surface of the fiux solution. The roll axis may be slightly above the surface of the fiux solution. The flowing of flux in liquid solution into the crotch between the roll and the strip compensates for a tendency which exists for more liquid flux solution to cling to the surface of the strip disposed away from the guide roll than to the surface of the strip disposed next the guide roll.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings we have shown a present preferred embodiment of the invention in which Figure l is a diagrammatic elevational view of tip paratus for fluxing and coating metal strip;

Figure 2 is a view to enlarged scale, partly in elevation and partly in axial cross section, of one of the rubber surfaced rolls for controlling the coating of flux on the strip;

Figure 3 is a view to enlarged scale, partly in elevation and partly in axial cross section, of one of the brushes for controlling the coating of flux on the strip;

Figure 4 is a fragmentary axial cross-sectional view to enlarged scale of the roll shown in Figure 2; and

Figure 5 is a fragmentary axial cross-sectional view to enlarged scale of the brush shown in Figure 3.

In the drawing the strip 1, which may, for example, be steel strip to be galvanized, is shown as passing in the direction of the arrows first about a guide roll 2 and then about guide rolls 4, 10 and 13 as shown. being performed will be considered by way of example to be a tight coat galvanizing method employing spelter containing aluminum. The method may be that of our Patent No. 2,647,305. The power for advancing the strip may be applied by a reel (not shown) which coils up the coated strip and which may, if desired, be supplemented by other driving rolls in the line.

The method The guide rolls 4 are mounted with their lower portions immersed in a bath of flux in water solution in a receptacle 3. The guide rolls 4 are shown as having their axes slightly above the surface of the flux solution. The flux solution will for purposes of example be deemed to be a water solution of 45% ammonium chloride and 55% zinc chloride. The strip 1 moves vertically upwardly from the flux bath as shown. There is a tendency in the flux bath for more flux to adhere to the surface of the strip disposed away from the guide rolls 4 than to the surface of the strip disposed against the guide rolls, and to compensate for that tendency flux solution is introduced through a pipe 5 and flowed into the crotch t; between the right-hand guide roll 4 and the strip as shown in the drawing. This insures the application of a relatively uniform coating of flux to the respective faces of the strip. The bath of flux is replenished to compensate for the flux removed on the strip. The flux solution may have a specific gravity of 10-20 Baum and a temperature of l50-200 F. The flux solution may, if desired, be continuously recirculated and filtered.

As the strip moves upwardly from the crotch 6 it carries on both faces a relatively heavy layer of flux solution. The strip passes between rubber surfaced metering rolls 7 and levelling brushes 8 which may. for example, be nylon bristle brushes. The rolls and brushes are for the purpose of removing part of the fiux solution and insuring that the unremoved flux solution is in a smooth uniform coating on the strip. The rolls and brushes may all be used'at the same time or only selected ones thereof may be used, depending on conditions. Those of the metering rolls 7 which are in use at any given time preferably turn in the direction in which the strip tends by friction to rotate them and at the same surface speed as the strip. They are preferably rotated by frictional engagement with the strip, although they may be independently driven. The metering rolls 7 are preferably grooved. The portions of the metering rolls 7 which engage the strip squeeze off the flux solution and the grooves meter the amount of flux solution which can pass through, later to be smoothed out or levelled by the levelling brushes 8. The levelling brushes 8 may be rotated or not, and if they are rotated they may be rotated in either direction at selected speeds. Normally the levelling brushes 8 will be rotated slowly in the direction opposite the direction in which the strip tends by friction to rotate them.

Figure 2 shows one of the rubber surfaced metering rolls 7. The left-hand half of the roll is shown in elevation and the right-hand half in cross section. A fragment of the roll is shown in cross section to enlarged scale in Figure 4. The roll comprises a cylindrical body 16 having integral reduced ends 15 on which the roll is mounted for rotation and having disposed thereabout a hollow rubber cylinder 17 having therein spiral grooves 18. Preferably. opposed rolls 7 are alike with respect to the spacing, pitch and cross section of the spiral groove, but the'upper set of rolls 7 may differ from the lower set of rolls 7 by having the grooves thereof of different pitch and/or different spacing and/or different cross section. The rolls of each pair engage the strip at opposite faces. They reduce in controlled manner the thickness of the coating of flux solution on the strip. For a particular strip'speed only one of the sets of rolls 7 may be used, for a different strip speed only the other of the sets of rolls 7 may be used and for a still different strip speed both sets of rolls 7 may be used simul taneously. Under certain conditions the brushes 8 may alone be adequate so that neither set of rolls 7 may be used. a

Figure 3 shows one of the levelling brushes 8. A shaft 19 carries the brush. The left-hand half of the brush is shown in elevation and the right-hand half in cross section. A fragment of the brush is shown in cross section to enlarged scale in Figure 5. The brush brushes are operative they actagainst the opposite faces of the strip and are preferably rotated slowly in the direction opposite the direction in which the strip tends, by friction to rotate them. They tend. to smooth and distribute the coating of flux solution .on the stripto produce a very uniform even coating. By :selectionofdesired rolls 7 and/or brushes Sand rotation .of the brushes at desired speed the thickness of the coating on the strip may be closely controlled.

As the strip carrying a controlled coating .of liquid flux solution passesupwardly' from 'thei brushes'8-it enters a heating chamber 9 in which the strip is heated to evaporate the water in the flux solution. The heat may be supplied by any appropriate means, such as electric heating elements, heated air, products of combustion, etc.

The strip is free from engagement by any portion of,

the apparatus after it leaves the brushes 8 until it reaches the left-hand guide roll 10. As a consequence the flux is dried on the strip uniformly and smoothly. The uniformity and smoothness of the coating of flux on the strip might be impaired if the strip were engaged by any portion of the apparatus during the drying operation and before that operation had been substantially completed.

The strip reaching the left-hand guide roll 10 therefore has on both faces a substantially dry uniform coating of flux at a temperature of the order of 250 F. The strip passes over the guide rolls 10 and thence downwardly toward the galvanizing pot 12 which contains molten spelter containing aluminum. In its downward passage the strip passes through a further heating chamber 11 wherein its temperature is raised to a temperature approaching the maximum temperature of stability of the dry flux coating on the strip. That temperature in the case of flux containing 45% of ammonium chloride and 55% of zinc chloride is 450500 F. The heat in the heating chamber 11 may be applied by any of the methods mentioned in connection with applying heat in the heating chamber 9.

Thus as the strip enters the bath ofspelter in the galvanizing pot 12 its temperature relatively closely approaches the temperature of the molten spelter with the result that the dry flux coating on the strip reacts wih relatively great rapidity with the spelter. The reaction is so rapid that it is substantially complete by the time the strip reaches the left-hand guide roll 13 in the galvanizing pot. Thus we provide for the formation of coated strip of controlled high quality and at the same time make possible material increase in the speed of advance of the strip in the coating line. The coated strip emerges from the galvanizing pot 12 between the rolls 14 which may be the conventional exit rolls of the galvanizing rig.

While we have shown and described a present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

We claim:

1. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, a guide roll mounted for rotation the lower portion of which is immersed in liquid flux in the container and the upper portion of which is disposed above the liquid flux, means for advancing the strip in the direction of its length about a portion of the periphery of the guide roll so that the strip is immerced in the liquid. flux and is delivered generally vertically upwardly 6 therefrom tangent to the guide roll, means flowing liquid Jinx into the upwardly open crotch between the strip and the guide roll to compensate for the tendency of the strip to pick up in the liquid'flux container a heavier coating of fluxon' the surface-of the strip disposed away from "the guide roll than 'on the surface of the strip disposed next theguide rolland opposed'means disposed generally above the liquid flux container engaging the strip .at both of the surfaces thereofto promote uniformity of 10 and limit the thickness of the-coating of ,flux thereon. -2. Apparatus=for applying fiux to metal strip in preparation for metal-coatingthemetaistrip-comprising aliquid flux container, means for advancing strip in the, direc- -tion of its length through liquid flux *inthe liquid flux 15 container and thence generally vertically upwardly and rolls having rubber-like surfaces disposed generally above theliquid-flux container engaging the strip at its opposite faces-to promote uniformity of and limit the thickness v,.of---'the coating of "-flux thereon.

3. Apparatus for applying flux to metal strip in preparation r'or metal-coating the metal strip comprising a liquid flux container, means for-advancing strip in the direction of..=its length through liquid flux in the liquid flux container-and thence generally vertically upwardly and rolls having rubber-like surfaces with spiral grooves thereinengaging the strip at its opposite faces above the ,surface of the l quidflux to promote uniformity of and limit the thickness of thecoating of flux thereon.

4. Apparatus for applying flux to metal strip in preparation tor metal-coating the metal strip comprising. a

liquid flux container, means for advancing strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and directly opposed rotary bristle brushes engaging the strip atits opposite faces above-the surface of the liquid flux to promote uniformity of and limit the thickness of thecoating of flux thereon.

5. Apparatus for applying flux to metal strip in preparation for metal-coatingthe metal strip comprising a liquid flux container, means for advancing strip in the direction of its length through liquid fiux in the liquid flux container and thence generally vertically upwardly, a plurality of means in series at least one of which has a rubber-like-surface disposed generally above the liquid flux'container mounted in position to successively engage the strip to promote uniformity of and limit the thickness of the coating of flux thereon, a drying chamber through which the upwardly moving strip passes but which is out of contact with the strip and heating means for applying heat to the strip in the drying chamber to dry the flux during the upward movement of the strip.

6. Apparatus for coating metal strip with coating metal having a lower melting point than the metal of the strip comprising a molten metal coating receptacle, means ,for

advancing the strip in the direction of its length, means guiding the advancing strip in a path having a generally vertical reach in which the strip moves upwardly and at least one subsequent reach in which the strip moves to and into the molten coating metal, means for applying 6O flux to the strip adjacent the bottom of the first mentionedreach, a drying chamber'through which the strip passes in the first mentioned reach but which is out of contact with the strip, heating means for applying heat to the strip in the drying chamber to dry the flux before it reaches the top of the first mentioned reach, a heating chamber through which the strip passes subsequent to the first mentioned reach and heating means separate from the first mentioned heating means for applying heat to the strip in the heating chamber to raise the temperature of the fiuxed strip to a temperature relatively closely approaching that of the molten coating metal.

7. Apparatus for coating metal strip with coating metal having a lower melting point than the metal of the strip comprising a molten metal coating receptacle, means for advancing the strip in the direction of its length, means guiding the advancing strip in a path having a generally vertical reach in which the strip moves upwardly and at least one subsequent reach in which the strip moves to and into the molten coating metal, means for applying flux to the strip adjacent the bottom of the first mentioned reach, means engaging the strip above the flux applying means to promote uniformity of and limit the thickness of the coating of flux thereon, a drying chamber through which the strip passes in the first mentioned reach but which is out of contact with the strip, heating means for applying heat to the strip in the drying chamher to dry the flux before it reaches the top of the first mentioned reach, a heating chamber separate from the drying chamber through which the strip passes subsequent to the first mentioned reach and heating means for applying heat to the strip in the heating chamber to raise the temperature of the fluxed strip to a temperature relatively closely approaching that of the molten coating metal.

8. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, means for advancing strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and rolls disposed generally above the liquid flux container having rubber-like surfaces which are axially straight, which surfaces engage the strip at its opposite faces to promote uniformity and limit the thickness of the coating of flux thereon.

' 9. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, means for advancing the strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and a plurality of means in series at least one of which has a rubber-like surface disposed generally above the liquid flux container mounted in position to successively engage the strip at its opposite faces to promote uniformity and limit the thickness of the coating of flux thereon, at least one of said means being disposable selectively in operative position in engagement with the strip and in inoperative position out of engagement with the strip so that a coating of flux of desired thickness may be applied to the strip at different speeds of advance of the strip.

10. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, means for advancing the strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and a plurality of means in series disposed generally above the liquid flux container engaging the strip at its opposite faces to promote uniformity and limit the thickness of the coating of flux thereon, said means including at least one set of rolls and at least one set of bristle brushes.

11. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid fiux container, means for advancing the strip in the direction of its length through liquid flux in the vposable selectively in operative position in engagement with the strip and in inoperative position out of engagement with the strip so that a coating of flux of desired thickness may be applied to the strip at different speeds of advance of the strip.

12. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, means for advancing the strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and a plurality of means in series disposed generally above the liquid flux container engaging the strip at its opposite faces to promote uniformity and limit the thickness of the coating of flux thereon, at least one of said means comprising rolls having rubber-like surfaces which are axially straight with spiral grooves therein,

-which surfaces engage the strip at its opposite faces.

13. Apparatus for applying flux to metal strip in preparation for metal-coating the metal strip comprising a liquid flux container, means for advancing the strip in the direction of its length through liquid flux in the liquid flux container and thence generally vertically upwardly and a plurality of means in series disposed generally above the liquid flux container engaging the strip at its opposite faces to promote uniformity and limit the thickness of the coating of flux thereon, at least one of said means being disposable selectively in operative position in engagement with, the strip and in inoperative position out of engagement with the strip so that a coating of flux of desired thickness may be applied to the strip at different speeds of advance of the strip, at least one of said means comprising rolls having resilient surfaces which are axially straight with spiral grooves therein, and at least one of said means comprising rotary bristle brushes.

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