US2359088A

US2359088A - Treating metal strip

Info

Publication number: US2359088A
Application number: US319475A
Authority: US
Inventors: George M Croft
Original assignee: Blaw Knox Co
Current assignee: Blaw Knox Co
Priority date: 1940-02-17
Filing date: 1940-02-17
Publication date: 1944-09-26
Anticipated expiration: 1961-09-26

Description

Sept. 26, 1944. e. M. CROFT TREATING METAL STRIP Fiied Feb. 17, 1940 4 Sheets-Sheet 1 NIT- INVENTOR Sept. 26, 1944. G. M. CROFT TREATING METAL STRIP V Filed Feb. 17, 1940 4 Sheets-Sheet 2 FiglB.

INVENTOR Sept. 26, 1944. cs. M. CROFT TREATING METAL STRIP Filed Feb. 17, 1940 4 Sheets-Sheet 3 R O m w m m v .1 n U Sept. 26, 1944. G. M. CROFT 2,359,033

TREATING METAL STRIP Filed Feb. 17, 1940 v 4 Sheets-Sheet 4 Fig. 2A.

INVENTOR Patented Sept. 26, 1944 2,359,088 TREATING METAL sum 7 George M. Croft, Pittsburgh, Pa, assignor to Blaw-Knox Company, Pittsburgh, Pa., a corporation of New Jersey Application February 1'7, 1940, Serial No. 319,475

8 Claims. (Cl. 134-9) This invention relates to procedui'e and apparatus for cleaning moving metal sheets, strip, or wire to remove grit, dirt, grease, scale, and other impurities.

Such cleaning is usual as a treatment preparatory to enameling, lacquering, galvanizing or otherwise plating, or other use that requires clean sheets. The invention i particularly concerned with the conservation of chemicals used in cleaning solutions and of heat applied during the cleaning processes. The invention also aims to secure an arrangement of apparatus by which strip or other articles undergoing treatment may be moved at higher speeds than have been practicable hitherto. This is accomplished by avoid ing bendsor turns in the direction of motion of the strip. Heretofore the practice has been'to d flect the strip downwardly into, beneath the surface level of, and upwardly out of the cleaning solution; this tends to limit the speed or rate of movement of the strip.

makes it commercially practicable to employ more expensive ingredients than could otherwise be used.

These and many other objects of my invention will appear to those skilled in the art from the drawings, the specification, and the claims.

In the drawings chosen for illustrating the principles and idea of my invention:

Figures 1A, 1B, and 1C, considered in their respective order from left to right, are vertical views in elevation and in partial section of acomplete layout or arrangement for treating continuous strip;

I have determined that the strip delivered to i the cleaning apparatus commonly has not only non-uniformly distributed grease and oil on its surface, but also grit and dirt. The practice has been to pass the strip directly to the hot caustic cleaning solution; thus, the caustic or other solution must be supplied in suflicient quantity to remove all loose as well as adhering grease and oil. Some grit and dirt tends to adhere so strongly that the solution fails to remove it, and the strip passes through imperfectly cleaned. In accordance with the present invention, I lessen the burden on and increase the efiectiveness of the cleaning solution by preliminarily removing a large part of the dirt and grit and much of the grease and oil before the strip is introduced into the caustic solution. .Although a preliminary water wash per se is not new, the applicant employ a previously used dilute cleaning solution preliminary wash and other new features which will be fully described herein.

When the strip emerges from the cleaning solution, it carries with it on both sides a film of the solution that may be several thousandths of an inch in thickness. Since the strips are often three feet or more in width and move very fast, the solution carry-over becomes large, and thus, carry-over p esents an important problem. Heretofore the carry-over film has been removed by washing andthe cleaning chemicals wasted, with a consequent depletion of the cleaning solution; as a result, new chemicals were required to compensate for the loss or waste.

By reducing waste of chemicals, the invention Figures 2A and 2B, likewise considered respectively from left to right, are reduced top plan views somewhat diagrammatically showing the apparatus arrangement or layout of Figur 1A, B, and C.

Although for the purposes of illustration, I have shown'a layout utilizing and providing strip in coil form, it will appear that the invention is not limited in employment to interrupted lengths of strip, as the apparatus is laid out for continuous treatment. In the arrangement shown, metal strip 5 is moved to the right from an uncoiler 6, and is initially threaded through cleaning ap-, paratus by endless cable means l0. When the end of the first coil is reached, to continue the operation, after trimming with a down-cut shear 8, the leading end of a new coil is welded to the trailing end of a used coil by apparatus 9, thereby providing a. continuous succession of strip lengths.

A pinch roll unit I I grips the strip after it has been treated by the cleaning apparatus of the present invention and pulls it with sufllclent force to draw it through apparatus located beyond the uncoiler 6, overcoming resistance offered by guide rolls, friction, scrubbers, cleaning jets, and other retarding influences. The strip is moved in a lon-' gitudinal, substantially straight-line, horizontal path or plane, and subjected to only enough deflection to insure its proper guidance, to provide uniform stresses within any transverse sectional portion, and to support it during scrubbing operations.

The strip then passes, as shown, with slack into a drag roll unit I2, is severed at the splice or weld by a down-cut shear l3 and is coiled by unit H, see Figure 10.

The specific apparatus represented by numerals '5' to H, inclusive, has been shown somewhat diagrammatically, as the uncoiling, shearing, wlding. motivating, pulling, and recoiling apparatus illustrated is conventional. It is shown for the purpose of making clear the positionof the parts embodying the invention with relation to these parts in the cleaning stand as a whole, and as no details of these parts are claimed further description of them is unnecessary. Applicant also contemplates employing suitable conventional brushing devices, rollers, blowers, and other apparatus well known to the art, though the general arrangement thereof is new.

For convenience of illustration, the cleaning or treating apparatus is indicated generally by letters A to E, inclusive. In accordance. with the present invention, the strip is moved, while being subjected to successive treating applications, in continuous progression through treatin chambers A, B, C, D, and E. I

In accordance with a preferred procedure, the strip 5 is cleaned and scrubbed on both sides with a previously-used hot water wash solution, applied in any suitable manner, as through jets 34. The scrubbing may be done by metal brushes 32 backed by rollers 30. After being scrubbed the sheet is rinsed by a high pressure spray applied through jets 36. This rinse water also has been previously used as rinse water at the other end of the line. After passing jets 36 the strip passes between hot air blast nozzles 38, which remove most of the film of rinse water (all in chamber A) before the strip is subjected to chemical treatment in chamber B. ,In this manner, the amount of cleaning load required in chamber B is lessened and a carry-over of water from chamber A is prevented. The solution may be applied under a lower pressure at 34 than at 36. The purposeoi' jets 34 is to wet the strip being scrubbed, that I of jets 3G to rinse as thoroughly as practicable. After the hot water washing operation, if used (for it may be optional), the strip is subjected to a chemical cleaning operation. The nature of the chemical reactions which take place during space confined above and below by casings 45 and "a, the strip emerging through constricted slot- I like openings 46. After this treatment the strip may be scrubbed by brushes 52 that cooperate with rolls 5! while covered by concentrated solution supplied by jets 54. Before leaving chamber B, the strip is washed off with a high pressure spray 56 of a diluted solution to lessen the carryover of the expensive cleaning solution into chamber Cl Drying by'evaporation is inadvisable as the chemicals employed. will be left on the strip. vThe film of concentrated solution is replaced by a film of dilute solution before the strip 5 leaves chamber 13; provision is also made for collecting and employing the washed off solution to replenish concentrated solution lost by evaporation, etc.

' In chamber C, a pair of rolls 6!! cause the major portion of the solution film remaining to fiow oif sideways; provision is made for returning this solution to the concentrated solution. The liquid film that passes the rolls is further diluted and washed off by applications at 56a. of dilute solu-' tion, then with clean hot water (see jets 56b) a aasaoss solution remaining as a film before the strip enters chamber D.

In chamber D the strip is again subjected to a series of clean hot water applications 56c; thence. a pair of rolls "6 removes a large part of the liquid film, having the consistency of practically pure water, before the strip enters chamber E.

In E, the clean strip is passed between hot air blasts 81a, 61b, and roll pairs lllc to blow 01! all possible of the remaining water and to finally dry the strip.

As shown, the-treating chambers are provided with enclosfng hood portions 2| having inspection doors 2i, and vents". 4

The chambers A to E have suitable liquid collector tanks positioned therebeneath, into which liquid from the strip drains, the strip as a whole never being submerged below the liquid level in any tank. 'Tank 42 is under chamber A; tank 58 isunder chamber B; tank 82 is under a lefthand portion and tank 63 is under the remainder of chamber C; and, tank 64 is under chamber D. I have also shown a hot water container 12 hav ing a settling compartment H and a concentrated solution container ll having a settling.

compartment Ila. Heat exchangers HI to H4 and motor driven pump units Ml, Pl to MD, PC are employed to circulate and heat-condition the cleaning fiuids or liquids. Valves for adjusting and closing 0t! llquidsprays or jets are indicated by the general designation (1, and valves in liquid lines for the most part have been given the general designation b.

The circulation system is connected to effect maximum utilization of chemicals involved, and of heat applied to the treating solutions. A steam supply line it receives steam from any suitable'soln'ce such as a boiler, not shown. It will be noted that this line 03 which'enters the system as shown in drawings IB and IC, is connected to heat exchangers HI. H2, and H3. Steam from the same or other source (through connections not shown) is preferably used as a heating means in the air heaters u and .8. Condensate from these heaters as well as heat ex-' changers HI, H2 and H3 is delivered to condensate line 8|. Connections from the heat exchangers Hi, H2 and III to this line only are shown at "II, M, and in Figure 1B. As shown particularly in Figure 1A, condensate in line 9! is delivered beneath the liquid level in containers II and I2 through suitable'noules or outlets d. I utilize condensate from the air heaters such as 39 and II which are connected by branch lines Sla and Nb, see Figures 2A and 28, to a main line 8| which, in turn, is connected by line to heat exchanger Hland by line 94 to heat exchanger H2. The addition of this hot condensate to the preliminary wash water keeps the supply thereof hot and compensates for heat lost after the first use 'of the same water in unit D. I

.Clean plant supply water is introduced through the piplng I. This water is continuously used for rinsing the strip in unit I), and occasionally,

whenever desired to wash down the empty tanks H, Ila, I2 and I3. as a spray against the sides of these tanks. As shown in Figure 1A, 88 is provided with suitable outlets or nozzles c that introduce washdown water as needed in spray form against the walls of hot water container 12 and concentrating, solution supply container 13 through open top portions thereof; the line 86 second'pair of rolls 60a removes most of the dilute has a branch line it that supplies water to the sametanks and to tanks II and Ila at a lower level through nozzles or outlets e.

-Wash water for the upper and lower spray units 34 in the chamber A is supplied through branch 35 and line 15 by pump PI under a suitable relatively low pressure which takes the water fromthe hot water container I2 through a line 98. Line I5 is provided with a branch line I6 that opens into collector tank 42 at a point representing a desired level of fluid therein. Thus, a suitable amount of wash water may be bled off from the supply line I5 to keep the liquid in tank 42 at a desired level.

The wash water (preferably hot) contains some of the chemical solution for reasons which will hereinafter be apparent; and, is collected in tank 42, drains by gravity through line I1 into settling container 'II that is separated by a baffle f from the wash water supply container I2. Grease and dirt carried by the liquid from the strip are removed by employing a conventional skimming and settling means well known to the art and thus not shown. It will be apparent that the water collected in container 1| after it has been skimmed, etc., falls over the bafllej into the hot water supply container I2.

To prevent overflow and to maintain suitable liquid levels within compartments I2 and I3, I have provided an overflow pipe 99 adjacent partition g that discharges into a sewer and that is provided with two branches 99a and 9912 that are connected to the compartments I2 and 13 at a point representing the desired liquid level.

The hot water supplied to the jets 34 of compartment A is supplied by line I04 from tank 64 that is positioned beneath compartment D and collects wash water that has been applied to the strip therein through nozzles 560. It is also apparent that the actual water that is used in compartment A by nozzles 34 may have been used several times by the same nozzles, losses, of

course, being made up by the supply from the line I04.

As previously pointed out, relatively pure hot wash water is supplied under relatively high pressure to nozzles 36 in compartment A through line I8 by pump P5 that is directly supplied with once-used wash water of compartment D through gravity flow line 88. a

The concentrated cleaning solution, which may consist of an alkali, is supplied by container I3.

In addition to liquid constantly being supplied to this container I3 from settling container 'IIa over bafiie h after suitable conventional means, not shown, has been utilized for settling and skimming ofi impurities which are carried by the solution from the treated strip, make-up solution is taken from tank 63 (under compartment C) through line I03; a valve 860 connected in this line is provided with a float 81 which automatically supplies liquid make-up in accordance with the demand. Concentrated solution applying apparatus 43 and 54 of compartment B are supplied with liquid through

branch lines

44 and 55 and trunk line I9. Liquid falling by gravity from the strip into collector tank 58 is pumped by pump P2 through line 88 and heat exchanger HI to this trunk line I9. The liquid in tank 58 is maintained-at a desired level by a take-01f line I00 connected to 'a concentrating solution container I3 and pumped therefrom by pump P3 through line IIlIf the supply through line IOI is automatically controlled by a valve 86a that is operated by a float 81a operably positioned within the tank 58.

Concentrated solution liquid collected in tank 58 also flows by gravity through line I82 into settling container Ila, and from the lefthand tank 62 of compartment C, into the same line I82 and thence, into the same settling container.

The high pressure spray 56- of compartment B and sprays 56a of compartment C are supplied with solution which has drained from strip 5 into collecting tank 63 of compartment C, through gravity line 84, by a pump P4 which moves the liquid through line 83 into a heat exchanger H2 and thence into supply line 82. The tank 63 is provided with an outlet connection I05 entering the tank at a point representing the desired liquid level and having a valve controlled branch I86 connected at a lower point to the tank .for discharging surplus or overflow material to the sewer as indicated. The level in tank 63 is further maintained by a float 8Ib'that operates valve 86b which controls the liquid supply to the righthand'spray units 56?) of compartment C.

Clean rinse water is supplied to the last set of nozzles 560 in compartment D by a line 85 which is connected to heat exchanger H3. The steam line 93 is connected to heat exchanger H3 to suitably heat the rinse water supplied to 85. Water is supplied to line 85 directly from the clean water supply line 86 through line 81 by pump P6 which forces the water through line 88 into the first heat exchanger H4 and from there through line 89, into the heat exchanger H3. The condensate from heat exchanger H3 drains through connection 90 and line 9| to the preliminary hot wash-water tanks as previously described.

From the above detailed outline of the operative connections of the liquid flow circuit employed, it will be apparent that I have been able to effect a maximumutilization of heat applied to any portion of the liquid, of the liquid itself, and of chemicals utilized in forming a suitable solution with such liquid. The first treatment unit to the left of compartment A employs wash water that may contain some solution and that has been used and reused. The second or high pressure spray 36 of the same compartment employs once used wash water which is .taken from the last compartment D. This compartment D is supplied with fresh cleaning water and thus the water supplied by nozzles 36 is, in effect, once used wash water. "Concentrated treatin cleaning solution is then applied to the strip in compartment B. This solution is used and reused and supplied with make-up water and chemicals as needed to take care of any losses.

The make-up water is supplied'continuously by sprays 56b, to the dilute solution tank 63, and thence, after picking up chemicals rinsed from the strip, to the concentrated solution tank 58 by sprays 56. That is, maximum utilization is made of the principle of collectin and reusing the stronger portions of the treating solution for revitalizing the original solution.

The main or initial fluid supply to compartment C is eifected through the righthand nozzles 56b which are supplied directly from the fresh water plant supplyline 86 after being suitably heated by heat exchangers H3 and H4, in the same manner as the nozzles 560 of compartment D. The water supplied by nozzles 56b in compartment C is collected in tank 63, reheated by heat exchanger H2 and reused again and again by nozzles 56a. As will be noted particularly in Figure 1B, the heat exchanger HI is employed to maintain the temperature" of the'chemical treating solution in compartment B at a suitable value. Pumps are used throughout for supplying the various spray or nozzle units with cleaning or treating fiuid under suitable pressure while gravity flow is used wherever possible for return lines.

The plant layout chosen for the purpose of illustrating my invention does not limit the scope of the invention which is believed to involve many novel features such as those early enumerated herein, in that the present arrangement is subwith a concentrated cleaning solution, removing I the concentrated cleaning solution by an application of a dilute cleaning solution, and conserving the dilute cleaning solution and using it in the make-up of concentrated cleaning solution.

2. In a'method of treating metal strip, the steps of subjecting bothsides of a moving strip to chemical action of a strong cleaning solution; removing the film of strong cleaning solution that adheres to the moving strip by an application of and a replacement with a film of dilute cleaning solution, and returning said removed strong solution to its source of suppl for re-use; replacing the film of dilute cleaning solution by an application of and a replacement with a film of wash-water, and conserving said replaced dilute solution for re-use and for replenishment of said strong solution.

3. In the cleaning of strip metal, the steps of moving the strip in a substantially horizontal plane through an initial scrubbing, rinsing and drying operation, whereby to eliminate loose particles and more easily removed surface contaminations and leave the surface thereof rela-- tively free, of liquid, thereafter applying concentrated treating liquid to the surface, the freeing of {the strip from moisture by the preceding drying step conserving the treating liquid from dilution, removing most of the concentrated treating solution from the surface of the strip and diluting the residual film which remains on the strip with a second solution to conserve the chemical in the said residual film, collecting most of the weaker solution so used and which has been rendered more potent by reason of being so used for re-use, subsequently removing ,the residual film of dilute solution on the strip with water and conserving and reusing the water so employed.

4. In the cleaning of strip metal, the steps which comprise moving the metal in a substantially horizontal plane through a succession of treating stations, mechanically scrubbing the strip in the first of said stations, immediately thereafter rinsing the strip, drying the strip, applying a concentrated chemical solution to the dried surface of the strip and removing from the concentrated solution, thereafter rinsing the strip with water and utilizing some of the water so used for rinsing the strip in said first rinsing operation.

5. In the cleaning of strip metal, the steps which comprise moving the metal in a substantially horizontal plane through a succession of treating. stations, mechanically scrubbing the strip in the first of said stations, immediately thereafter rinsing the strip, drying the strip, applying a'concentrated chemical solution to the dried surface of the strip and removing from the surface of the strip most of the concentrated solution so used, thereafter spraying the strip with a'more dilute chemical solution to wash of! the residue of concentrated solution remaining on the strip, collecting the liquid that results from the application of the diluted solution to the strip and utilizing it for the preparation of the concentrated solution, thereafter rinsing the strip with water and utilizing some of the water so used for rinsing the strip in said first rinsing operation, and utilizing other of the rinse water so used for the preparation of the dilute solution.

6. In the cleaning of strip metal, the steps which comprise moving the metal in a substantially horizontal plane through a succession oi! treating stations, mechanically scrubbing the strip in the first of said stations, immediately thereafter rinsing the strip, drying the strip, 8pplying a concentrated chemical solution to the dried surface of the strip and removing from the surface of the strip most of the concentrated solution so used, thereafter spraying the strip with a more dilute chemical solution to wash of! the residue of concentrated solution remaining on the strip, collecting the liquid that results from the application of the dilute solution to the strip and utilizing it for the preparation of the concentrated solution, thereafter rinsing the strip with water and utilizing some of the water so used for rinsing the strip in said first rinsing operation, said rinse water and solutions being heated, the heat being also conserved through the said re-use of theliquids.

7. In the treatingof strip metal to prepare it for the reception of a coating, the steps which comprise moving the metal strip in a substantially horizontal plane, and subjecting the strip while moving in this manner to a succession of operations performed in sequence as follows: mechanically scrubbing the strip on both surfaces with hot water to remove solid particles and easily removed surface contaminations, drying the strip to prevent the carry-over of a film of water beyond the drier, applying a relatively strong chemical solution to both surfaces of the moving strip to remove impurities and surface contaminations not removed by the scrubbing, washing away the relatively strong solution which remains on the strip with a relatively weaker solution, and removing the relatively weaker solution-with rinsing sprays of water and thereafter drying the strip.

8. In the treating of strip metal to prepare it for the reception of a coating, the steps which comprise moving themetal strip in a substantially horizontal plane, and subjecting the strip while moving in this manner to a succession of operations performed in sequence as follows: mechanically scrubbing the strip on both surfaces with hot water to remove solid particles and easily removed surface contaminations, drying the strip to prevent .thecarry-over of a film of water beyond the drier, applying a relatively strong chemical solution to both surfaces of the moving strip to remove impurities and surface contaminations not removed by the scrubbing, washing away the relatively strong solution which remains onthe strip with a relatively weaker solution, and removing the relatively weaker solution with rinsing sprays ocf water and thereafter drying the strip, and heating and reusing the rinsing water, the dilute solution and the strong solution, some of the dilute solution being used in the preparation of the strong solution.

GEORGE M. CROFT.