US3606279A

US3606279A - Apparatus for heat treating a sheet

Info

Publication number: US3606279A
Application number: US864680A
Authority: US
Inventors: Robert G Auger
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1969-10-08
Filing date: 1969-10-08
Publication date: 1971-09-20
Anticipated expiration: 1988-09-20

Abstract

APPARATUS FOR HEAT TREATING A SHEET WHILE DISPOSED AT A SUBSTANTIALLY VERTICAL PLANE WITHOUT CONTACTING OPPOSI TE TREATED SIDES OF THE SHEET IS DISCLOSED. THE APPARATUS HAS A FURNACE FOR HEAT TREATING THE SHEET, POSITIONING MEANS ADJACENT THE FURNACE IN ENGAGEMENT WITH THE SHEET FOR POSITIONING THE SHEET IN THE SUBSTANTIALLY VERTICAL PLANE, SUPPORTING MEANS IN THE FURNACE IN ENGAGEMENT WITH THE BOTTOM OF THE SHEET FOR GUIDING THE SHEET THROUGH THE FURNACE AND DRIVE MEANS CONNECTED TO ONE OF THE POSITIONING MEANS AND THE SUPPORTING MEANS FOR MOVING THE SHEET THROUGH THE FURNACE.

Description

Sept. 20, 1971 R. G. AUGER 3,606,279

APPARATUS FOR HEAT TREATING A SHEET med oct. e, 196s 2 sheets-sheet 1 .S mi

Af forney Sept. 20, 1971 R. G. AUGER APPARATUS FOR HEAT TREATING A SHEET 2 Sheets-Sheet 2 F IG. `6.

Filed Oct. 8. 1969 FIG. 5A.

F/G. 5B.

INI/EN TOR.

n a n U n l.. l W l a r, T Rl r 0 n( United States Patent Office Patented Sept. 20, 1971 ABSTRACT OF THE DISCLOSURE Apparatus for heat treating a sheet while disposed at a substantially vertical plane without contacting opposite treated sides of the sheet is disclosed. The apparatus has a furnace for heat treating the sheet, positioning means adjacent the furnace in engagement with the sheet for positioning the sheet in the substantially vertical plane, supporting means in the furnace in engagement with the bottom of the sheet for guiding the sheet through the furnace and drive means connected to one of the positioning means and the supporting means for moving the sheet through the furnace.

BACKGROUND OFk THE INVENTION Heretofore, in the production of vitreous enameled steel, the cleaned metal sheet is coated with a water suspension of finely-ground enameling material commonly known as frit. The enamel coating is then treated and fired at temperatures often exceeding about 1400 F. For the purpose of preventing marring of the enameled surface, it is necessary to prevent contact with the coated enameled surface from the time of its application to the metal sheet until such enameled surface is fired and cooled to a solid state. Conventional continuous enameling lines maintain the strip unsupported between the rolls which feed the strip to the enameling application area and those rolls which carry the tired and cooled strip from the cooler. Utilizing a minimum time of about two minutes for the heating, firing, and cooling of the strip, a strip moving through the furnace at a speed of about l feet per minute will require a '20 foot length of furnace for the firing and cooling of the strip plus additional length of about fifteen feet for the application of the frit and the drying thereof. This more than 20 foot length of unsupported catenary of the treated sheet tends to stretch and permanently deform the sheet, especially at the high furnace temperatures. As a result, conventional continuous enameling lines are limited to strip speeds at less than about feet per minute.

I am aware of the conventional furnaces shown in the following U.S. Patents:

Issued 2,037,421, Little Apr. 14, 1936 3,241,735, Ranney Mar. 22, 1966 3,310,255, Sendzimir Mar. 2l, 1967 OBJECTS OF THE INVENTION It is the general object of this invention to avoid and overcome the foregoing and other difficulties of and objections to prior art practices by the provision of an improved apparatus for heat treating a sheet in a substantially vertical plane without contacting opposite treated sides of the sheet, which apparatus:

(a) Permits the construction of sheet enameling furnaces up to about several hundred feet in length with substantial elimination of the deformation of the steel sheet;

(b) Permits the use of strip speeds through the furnace Well in excess of conventional strip speeds of about 10 feet per minute thereby resulting in higher production rates of enameled sheet steel strip and attendant lower production costs;

(c) Permits the simultaneous coating of both sides of the steel sheet with an enameling frit;

(d) Substantially eliminates contact with the opposite treated sides of the enameled sheet during the heating, firing, and cooling of the enameled sheet; and

(e) Prevents wandering of the vertically aligned sheet through the furnace.

BRIEF SUMMARY OF THE INVENTION The aforesaid objects of this invention, and other objects which will become apparent as the description proceeds are achieved by providing an improved apparatus for heat treating a sheet in a substantially vertical plane without contacting opposite treated sides of the sheet. This apparatus has a furnace for heat treating the sheet, positioning means adjacent the furnace in engagement with the sheet for positioning the sheet in the substantially vertical plane, supporting means in the furnace in engagement with the bottom of the sheet for guiding the sheet through the furnace and drive means connected to one of the positioning means and the supporting means for moving the sheet through the furnace.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS VOF THE DRAWINGS For a better understanding of this invention, reference should be had to the accompanying drawings wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIG. la is a diagrammatic side elevational view of the cleaning and flashing apparatus utilized to prepare a steel sheet for the enameling operation;

FIG. lb is a View similar to FIG. 1a and a continuation of FIG. la showing the frit application apparatus, the dryer and the furnace for heating, ring and cooling the enameled sheet;

FIG. 1c is a vertical sectional View taken along the line lc-lc of FIG. 1b in the direction of the arrows;

FIG. 2 is a fragmentary enlarged side elevational view of the sheet disposed in the vertical plane and supported by the slotted pockets carried by the continuous chain of the supporting means shown in FIG. 1b;

FIG. 3 is an end elevational view taken along the line 3-3 of FIG. 2 in the direction of the arrows;

FIG. 4 is a view similar to FIG. 3 of an alternative embodiment of the supporting means showing a grooved supported roller;

,'FIGS. 5a and 5b are side elevational views taken along the lines Sa-Sa of FIG. 4 in the direction of the arrows and showing respectively a corrugated and serrated contact surface; and

FIG. 6 is a view similar to FIG. 1c showing an alternative embodiment of the apparatus and utilizing a top guide member.

Although the principles of this invention are broadly applicable to apparatus for the treating of a sheet in a substantially vertical plane without contacting opposite treated sides of the sheet, this invention is particularly adapted for use in conjunction with apparatus for enameling a sheet and hence it has been so illustrated and will be so descirbed.

DETAILED DESCRIPTION With specific reference to `the form of this invention illustrated in the drawings, and referring particularly to FIGS. la, 1b, apparatus for enameling a steel sheet 10 is indicated generally by the reference numeral 12. An enamel is a vitreous, inorganic coating fused to a metal.

In this apparatus 12 the sheet 10 is fed from a feed roll \14 successively into an alkali and soap solution tank 16a for removing the grease and dirt from thev sheet, 10, into an acid solution tank 16b for removing oxidized metal from the sheet 10, into a water rinse tank 16C containing water at about 180-200" F. and into a pickling solution tank 16d containing about 68% sulfuric acid maintained at a. temperature of about 140-150 F. A flash nickel plating tank 16e then plates a thin film of nickel on the iron sheet 10. The tank 16e contains a solution of about v1.0 toI 1.5 ounces of nickel salts, such as nickel sulfate per gallon of Water. The pH of such solution is controlled between about I3.0 and 3.5 and the temperature between about 16S-170 F. An aiverage emersion time is about 4-6 minutes thereby producing a neutralized ash deposit of about .04 to .l2 gram per square foot.

lo After removal of the plated sheet 10 from the tank 16e the sheet 10 enters a water rinse tank 16]" at room temperature, and a neutralizing tank 16g containing a cyanide bath of about 0.2 ounce of sodium cyanide per gallon plus substantial sodium hydroxide to provide about 20 0.'3-0.5% Na2O. After the neutralizing solution, the sheet 10 enters a conventional dryer 18 of the horizontal drying oven type manufactured by Young Brothers Co., Cleveland, Ohio, which dryer .118 is maintained at a temperature of about 23S-250 F. and is provided with good 25 zontal tension rolls 20a and vertical tension rolls 20b 30 cooperate to turn the dried sheet 10 90 preparatory for the enamel frit application and the enameling operation shown in FIGS. 1b and 1c.

ENAM'ELING IRON The enameling iron employed for the sheet 10 should be a substantially pure grade of commercial iron. The sum of the elements carbon, silicon, sulfur, phosphorus and magnesium should not be greater than about 0.10%

by weight on ladle samples nor greater than 0.14% on 40 stock samples. Mild steels, such as 10/ 10 and 10/20; cast iron containing an analysis of about 2.50% silicon, 0.70% phosphorus, 0.60% magnesium, 0.08i% sulfur, 3.00% free carbon, and 0.40% combined carbon; stainless steels of various types; zinc-copper alloys; gold, sil'ver 45 and platinum may be satisfactorily enameled.

PREPARATION OF THE ENAMEL The batch ingredients for the preparation of the frit are carefully weighed and thoroughly mixed as shown Thepenarnel raw batch` is lcomposed as shown in the following Table B:

TABLE B Approximate Typical Mill Formulas for Sheet-Steel Coats The enamel raw batch is weighed, mixed, and melted in a suitable furnace (not shown), quenched and dried, and milled in a roll mill (not shown) until approximately of the solid material will pass through about a 200 mesh screen. The enamel slip is then stored and aged for a period of time to dissipate heat and air. Before being applied to the sheet 10 the enamel slip is adjusted to a ground coat dipping and spraying specific gravity from about 1.55 to 1.70, where the weight of the ground coat would be about 40 grams i.e. 20 grams on each square foot of area. The spraying gravity for a sheet steel cover -coat ranges from about 1.8 to 1.9 and the weight from about 15 to 50 grams.

ENAMELING OPERATION The enamel slip may be applied to the sheet 10 by dipping, slushing, spraying, or dredging and, as shown in FIG. 1b, by the spray guns 22 to both sides of the sheet 10. Thereafter, the now sprayed sheet 10 enters a dryer 24 of the gas infra-red dryer type manufactured by enameled sheet 10 to a temperature of about 40G-450 F. to remove the Water from the enamel coating on opposite sides of the sheet 10. The sheet 10 then enters a furnace 26 for heat treating the sheet 10; in a heating zone of such furnace 26 to the temperature of about 1000 F.; and in a firing zone of such furnace 26 to a temptrature of about 1450-15 00 F. The sheet 10 is then subjected to air cooling in a cooling zone of the furnace 26 to an exit temperature of about 70 F.

As shown in FIGS. 1b and 1c the furnace 26 has an inlet 26a and exit 26h. Radiant heat is applied to the sheet 10 from radiant burners 26e` (FIG. lc) Which burners 26C are fed by lines 26d from a suitable gas manifold 26e. Cooling means in the cooling zone comprise nozzles 27a (only one pair of which is shown in in the following Table A: FIG. 2) connected to a cooling fluid manifold 27 b TABLE A Approximate Percentage Batch Weights oi Typical Enamel Frits Sheet-steel cover coat Cast-iron ground coat Cast-iron cover coat Sheet-iron Acid- Wet Dry Wet Dry Copper Component ground coat Regular Opaque resisting process process process process enamel Potash feldspar 32.0 31. 5 17. 5 9. 5 33. 0 28.0 33. 0 B 3l. 0 24. 5 23.0 18.0 20.0 29.0 21. 0

Fluorspar Cobalt oxide (00304)-:

Nickel oxide (NiO).

Manganese dioxide- Cryolite Sodium uosilicate. Sodium antimonate Bone ash Tin oxide Zinc oxide Barium carbonate Arsenic oxide Potassium nitrate After melting the mixture in a furnace (not shown), the molten frit is tapped into a water-filled tank (not shown) ywhere it is quenched, shattered, dried, crushed and placed in storage.

( FIG. 2) by lines 27e. Positioning means such as powerdriven tension rolls or first positioning assembly 20b and second positioning assembly 20c (FIG. 1b) are disposed adjacent the furnace 26 in engagement with the Ferro Corporation, Cleveland, Ohio, for heating thev sheet for positioning the sheet 10 in such substantially vertical plane. Supporting means, such as slotted lugs 28 (FIGS. 1b, 1c, 2, 3, 6) mounted on a continuous conveyor or chain (FIGS. 1b, lc, 2, 3, 6) engage the bottom of the sheet 10 during the path of movement of the sheet 10 through the furnace 26. For the purpose of supporting the continuous conveyor 3() between the sprockets 30a and 3tlb (FIG. lb), a support member 32 (FIGS. 1b, 1c, 3, 6) is mounted on the furnace 26 as by welding or the like.

Drive means are connected to one means of the positioning means and to supporting means for moving the sheet 10 through the furnace 26. This drive means 34 may comprise either a motor 34a (FIG. 1b) connected to one of the sprockets 30a, 30h, 30C, 30a', such as the sprocket 30e or either the motor 34b (FIG. 1b) connected to the tension rolls 2Gb or the motor 34e (FIG. 1b) associated with the tension rolls 20c.

ALTERNATIVE EMBODIMENTS It will be understood by those skilled in the art that alternatively, as shown in FIG. 4, the supporting means may comprise a plurality of grooved support rollers 36 one or more of which are driven by a motor 34d. The motor 34d is operable by a switch 35. The rollers 36 are journaled by bearings 36a in the wall 26j of the furnace 26.

As shown in FIGS. 5a and 5b, the slot 36h in the roller 36 may have a corrugated surface 36b' (FIG. 5a) or a serrated surface 36b (FIG. 5b). It will be further understood that the surface 28a (FIG. lb) of the lugs 28 in engagement with the bottom of the sheet 10 may be roughened, i.e, such as serrated 28a (FIG. 2) or corrugated 28a (FIG. 2). In FIG. 6, the furnace 266 is provided with a guide for engaging the top of the sheet 10.

SUMMA'RY OF THE ACHIEVEMENTS OF THE OBJECTS OF THE INVENTION It will recognized by those skilled in the art that the objects of this invention have been achieved by providing an apparatus 12 for heat treating a sheet 10 while the sheet 10 is in a substantially vertical plane without contacting opposite treated sides of the sheet 10. This apparatus 12 permits the construction of sheet enameling furnaces 26 up to about several hundred feet in length with substantial elimination of the deformation of the steel sheet 10; permits the use of strip speeds through the furnace 26 well in excess of conventional strip speeds of about l0 feet per second thereby resulting in higher production rates of enameled sheet steel strip 10 and attendant lower production costs; permits the simultaneous coating of both sides of the steel sheet 10 with an enameling frit; substantially eliminates Contact with the opposite treated sides of the enameled sheet 10 during the heating, tiring, and cooling of the enameled sheet 10; and prevents wandering of the vertically aligned sheet 10 through the furnace 26.

While in accordance with the patent statutes, preferred and alternative embodiments of this invention have been illustrated and described in detail, it is to be particularly understood that the information is not limited thereto or thereby.

I claim:

1. Apparatus for heat treating a sheet in a substantially vertical plane without contacting opposite treated sides of said sheet, said apparatus having:

(a) a furnace for heat treating said sheet;

(b) positioning means disposed on each side of said furnace in gripping engagement with said sheet for maintaining a predetermined tension on said sheet to position in said substantially Vertical plane while said sheet is passing through said furnace and to prevent any sagging or deformation of said sheet;

(c) supporting means in said furnace in engagement with the bottom of said sheet for guiding said sheet through said furnace; and

(d) drive means connected to one means of said positioning means and said supporting means for moving said sheet through said furnace.

2. The apparatus recited in claim 1 wherein said -furnace has an entrance land said positioning means has a rst positioning assembly adjacent said entrance.

3. The apparatus recited in claim 2 wherein said furnace has an exit and said positioning means has a second positioning assembly adjacent said exit.

4. The apparatus recited in claim 1 wherein said supporting means has a longitudinal groove.

5. The apparatus recited in claim 1 wherein said supporting means has a roller and said roller has a roller groove.

6. The apparatus recited in claim 1 wherein said supporting means has a continuous conveyor and a support on said continuous conveyor is provided with a support groove.

7. The apparatus recited in claim 1 wherein said positioning means is serrated.

8. The apparatus recited in claim 1 wherein said positioning means is corrugated.

9. The apparatus recited in claim 1 wherein said supporting means is serrated.

10. The apparatus recited in claim 1 wherein said supporting means is corrugated.

11. The apparatus recited in claim 6 and having a support member on said furnace adjacent said continuous conveyor for supporting said continuous conveyor.

12. The apparatus recited in claim 1 and having a guide member on said furnace in engagement with the top of said sheet.

13. The apparatus recited in claim 1 wherein said drive means is connected to said positioning means.

14. The apparatus recited in claim 1 wherein said drive means is connected to said supporting means.

y References Cited UNITED STATES PATENTS 1,751,712 3/1930 Owen 34--150X 1,827,079 10/1931 Fahrenwald 263-3X 3,062,520 1l/1962 Frey et al. 34-150X 3,267,902 8/1966 Pritchard et al. 34-15OX JOHN l. CAMBY, Primary Examiner U.S. Cl. X.R. 34-150