US3580331A

US3580331A - Apparatus for annealing with accelerated cooling

Info

Publication number: US3580331A
Application number: US839761*A
Authority: US
Inventors: William Wargo
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1969-05-23
Filing date: 1969-05-23
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

Apparatus for cooling stacked coils of steel sheet from an annealing temperature at an accelerated rate. A hood is provided for sealing the coils from the oxidizing ambient atmosphere during the period when the coils are heated. Within the hood means, cooling separator structures are placed in contact with the planar coil surfaces. These separators include weight bearing members used to support the coils and provide space for closed fluid conduits. These conduits are interposed between, under and atop the coils in intimate contact with the planar surfaces of the coils. This arrangement provides for conductive heat transfer from the coils to coolant circulated in the fluid conduits without causing oxidation of the coils.

Description

United States Patent inventor William Wargo Dearborn, Mich.

App]. No. 839,761

Filed May 23,1969

Patented May 25, 1971 Assignee Ford Motor Company Dearborn, Mich.

APPARATUS FOR ANNEALING WITH ACCELERATED COOLING 11 Claims, 6 Drawing Figs.

US. Cl 165/48, 263/40 Int. Cl F25b 29/00 Field ot'Search... 165/12, 48, 7l, 73,108,134, 6l;263/40, 46, 42 (R); 266/1 References Cited UNITED STATES PATENTS 3/1934 Wilson 263/42 2,201,308 5/1940 Edge Primary Examiner-Charles Sukalo Attorneys-John R. Faulkner, Thomas H. Oster and E. Dennis OConnor ABSTRACT: Apparatus for cooling stacked coils of steel sheet from an annealing temperature at an accelerated rate. A hood is provided for sealing the coils from the oxidizing ambient atmosphere during the period when the coils are heated. Within the hood means, cooling separator structures are placed in contact with the planar coil surfaces. These separators include weight bearing members used to support the coils and provide space for closed fluid conduits. These conduits are interposed between, under and atop the coils in intimate contact with the planar surfaces of the coils. This arrangement v provides for conductive heat transfer from the coils to coolant circulated in the fluid conduits without causing oxidation of the coils.

P ATENTED IAYE 519?:

SHEET 1 OF 2 W/ L 1. MM WARGO INVENBORJ /41w W571i ATTORN EYS APPARATUS FOR ANNEALING WITH ACCELERATED COOLING BACKGROUND OF THE INVENTION Conventional steel mill practice for the production of high quality surface finished steel sheet includes the rolling of slabs in roughing mills and hot and cold finishing mills to produce sheets within a few thousandths of an inch of the final thickness dimension required. The sheet then is pickled to remove the oxide coating generated in the hot rolling previously accomplished. The sheet then in annealed to produce a sheet of the requisite drawability by reducing the stresses and hardness introduced by cold reduction. Subsequent to annealing, a final finishing or skin pass in made in a finishing mill to improve the surface quality of the sheet and reduce the sheet to the final dimension desired.

The normal time to process a coil of sheet steel from melt to finished product is 23% days. Twenty-five percent of this time is consumed before the annealing step, while 55 percent of the time is spent in annealing and finishing the sheet. Cooling temperature alone accounts for 38 percent of the manufacturing time. It thus can be seen that a reduction in the time required to anneal the sheet would reduce greatly the total length of time required to produce the finished product and would yield a substantial savings in cost.

The annealing step in the production of finished sheet is important because, as mentioned above, annealing removes stresses and hardness introduced by cold reduction by relieving the ferrite grains present in the sheet and returning the grain structure to the equilibrium condition. Conventional annealing temperatures range in the vicinity of 1,300 F. These temperatures are obtained by stacking massive coils of sheet vertically and placing a bell furnace about them. The elevated temperatures induced in the furnace would lead to the deleterious formation of oxide scale upon the sheet if the normal atmosphere was not purged from about the coils and replaced by a nonoxidizing atmosphere. This is accomplished under normal practice by covering the coils with a hood under which the nonoxidizing atmosphere is circulated prior to the positioning of the bell furnace about the coils.

Cooling of the coils prior to this invention was accomplished by removing the bell furnace from about the hood and allowing the stacked coils to sit in the protective atmosphere under the hood until their temperature had decreased from the annealing temperature of about l,300 F. to 250 F. This cooling took approximately 60 hours. The hood then was removed and the coils exposed to ambient air until their ternperature reached 100 F. This temperature decrease took approximately 48 hours.

It is an object of this invention to provide apparatus for accelerating the cooling of stacked coils of steel sheet from an annealing temperature in order to reduce greatly the total time required for the manufacture of such steel. This apparatus allows the use of water as a coolant and yet provides for the protection of the surface of the steel sheet from deleterious chemical attack while the sheet is at elevated temperatures.

SUMMARY OF THE INVENTION Apparatus constructed in accordance with this invention is separator to accomplish accelerated cooling from an annealing temperature of massive cylindrical coils of steel sheet that are stacked vertically with the planar surfaces of each coil lying in horizontal planes. This apparatus includes hood means surrounding the coils and capable of sealing the coils against the oxidizing ambient atmosphere during the period when the coils are heated to an elevated temperature. This hood means allow a nonoxidizing atmosphere to be circulated about the coils to the exclusion of ambient air. Cooling separator means are placed in contact with the planar coil surfaces. These separator means include weight-bearing members used to support the coils and to provide space for closed fluid circuits that are interposed between, under and atop the coils in intimate contact with the planar surfaces of the coils.

The separator structure adapted to be placed beneath the bottom coil of the stacked coils comprises a plate having grooves formed in the top surface thereof. A fluid conduit is positioned in these grooves and is in intimate contact with the bottom planar surface of the bottom coil of the stack. The separator means adapted to be placed between adjacent coils comprises individual weight-bearing segments oriented is spaced-apart relationship and maintaining the coils a spaced distance apart. A fluid circuit is placed between the separator segments such that it is in contact with the adjacent planar surfaces of the proximate coils. A fluid circuit adapted to be placed upon the top planar surface of the uppermost of the stacked coils comprises a length of fluid tubing wound into a spiral that substantially is coextensive with the planar surface of the coil upon which it is placed.

DESCRIPTION OF THE DRAWINGS FIG. I is an exploded view of stacked metal coils and ap paratus for accelerating the cooling of these coils from the annealing temperature and arranged in accordance with this invention;

FIG. 2 is a top view of cooling apparatus particularly adapted to be placed on the top planar surface of the uppermost of the stacked coils;

FIG. 3 is an enlarged sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a top view of modified cooling apparatus particularly adapted to be placed beneath the stack of coils or between adjacent stacked coils;

FIG. 5 is a sectional view taken along the line 55 of FIG. 4; and

FIG. 6 is a partial sectional view taken along the line 6-6 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION Referring now in detail to the drawings and in particular to FIG. 1, three coils ofsteel sheet, ll, 12 and 13, coils 11 and 13 being illustrated schematically, are shown in a vertically stacked arrangement for annealing and cooling. Cooling separators, including closed liquid circuits, are indicated generally at l4, l5 and 16 and are shown below the stack of coils and between the individual coils.

The stack of coils and cooling separators is covered by a hood 17 that allows an inert atmosphere to be circulated about the stack of coils when a bell furnace (not shown) is positioned about the coils for heating the coils to the annealing temperature. Hood 17 has means, not illustrated, for the introduction and exhaustion of an inert atmosphere about the coils.

Cooling separator 14 particularly is adapted to bear a great deal of weight and, therefore, is shown positioned at the bottom of the composite stack. Separator 14 consists of plate 18 having a central aperture 19 and channels 21 machined in its top surface of the form of a cross. Positioned within channels 21 is a liquid circuit 22 constructed of flexible tubing and connected to inlet and outlet conduits as later will be described in detail. The top surface 20 of plate 18 is adapted to bear the weight of coils ll, 12 and 13, as well as the weight of cooling separators l5 and 16. The formation of channels 21 to a depth approximately equal to the diameter of the tubing forming liquid circuit 22 allows the tubing of liquid circuit 22 to remain in intimate contact with the bottom planar surface of coil 11 without being crushed by the weight of the composite stack.

Positioned on the top planar surface of coil 11 is a liquid circuit 23 identical to liquid circuit 22 and also adapted for the circulation of water. The formation of liquid circuit 23 is the form of a cross allows for the positioning of separator segments 25 peripherally around liquid circuit 23 to bear the weight of coils l2 and 13 and cooling separators 16. Liquid circuit 23 also is connected to inlet and outlet circuits as will be described in detail below. Liquid circuit 23 is in intimate contact with both the top planar surface of coil 11 and the bottom planar surface of coil 12.

Cooling separator 16, comprising a liquid circuit 24 and separator segments 25, is identical to cooling separator and bears a like relationship to coils 12 and 13 as separator 15 bears to coils 11 and 12.

During the heating to and soaking at the annealing temperature of

coils

11, 12 and 13, no water is circulated through

liquid circuits

22, 23 and 24. At the termination of the soaking at the annealing temperature, however, water is circulated through

liquid circuits

22, 23 and 24 to accelerate the cooling of coils l1, l2 and 13. This is accomplished by the introduction of water through inlet pipe 30. Pipe 30 is attached to a conventional apparatus for developing high water pressure such as a pump (not shown). Water then is pumped to the top of liquid circuit 24 through inlet pipe 30 that is attached to liquid circuit 24 by means of couplings 29. After circulation through liquid circuit 24, the water travels through pipe section 26 to liquid circuit 23 and thereafter through exhaust or outlet pipe 28 to a low-pressure sink. The liquid circuits are connected to the pipe sections by conventional couplings 29 or may be joined as by welding.

Liquid circuits may be arranged between the coils of steel strip and, if greater cooling is desired, beneath the bottom coil and the stack as illustrated in FIG. 1 and also on the top planar surface of the uppermost coil of the stack. A particular embodiment of a liquid circuit adapted to be placed on the top planar surface of the uppermost coil of the stack, or to be used whenever the weight to be borne by the liquid circuit is insufficient to crush the tubing of the circuit, is illustrated in FIGS. 2 and 3.

This cooling separator 31, since it need bear little weight, may be constructed of a continuous tube 32 wound in an alternate spiral and having a central aperture 37 through which a crossover section 36 of tube 32 extends. The ends of tube 32 are connected, by means of suitable couplings 29 through inlet and outlet pipes 33 and 34 respectively, so that water may be circulated through the central passage 33 of tubes 32. To add rigidity to the tube spiral, the individual windings of tube 32 are joined as at 35 by soldering, brazing, or other conventional joining techniques.

FIGS. 4 through 6 illustrate another embodiment of liquid circuit that also functions as a coil separator, as it is capable of acting as a structural member to bear the weight of a portion of all of a composite stack of coils and separators, and that may be positioned at the bottom of a coil stack. This liquid circuit is indicated generally at 41 and includes a plate 42 having formed therethrough an internal bore 43 arranged generally in an alternate spiral. Within bore 43 may be positioned a tube 45 through which water may be circulated entering by inlet pipe 46 and exiting through exit or outlet pipe 47. Inlet pipe 46 and outlet pipe 47 are connected to tube 45 by means of suitable couplings 29.

It readily may be appreciated, however, that tube 45 is not a requisite element to enable fluid circuit 41 to perform satisfactorily to cool the stacked coils. Inlet pipe 46 and outlet pipe 47 may be connected directly to spiral bore 43, and water circulated directly through this bore. Also, it should be noted that it tube 45 is utilized for reasons such as facilitating maintenance, it will not diminish the cooling capability of liquid circuit 41 as tube 45 and plate 42, because of their intimate relationship, will conduct heat as though these elements were integral. It is important, however, as noted in regard to the cooling separators illustrated in FIGS. 1 to 4, that liquid circuit separator 41 be substantially planar along its outer surfaces so that it may be maintained in intimate contact with contiguous coils during the entire period of water circulation.

An aperture 48, in which is mounted a locating bushing 49, may be formed in plate 42 to accommodate a thermocouple or other temperature measuring device, thereby facilitating the determination of the temperature of the coils being annealed. Projections 51 may be fabricated on the surface of plate 42 as locating devices to aid in the positioning of plate 42 on a shop floor.

The use of water as the coolant made possible by the apparatus of this invention is dictated by the ready availability and low cost of this liquid as well as its capability of conducting large amounts of heat from the stacked coils to be cooled.

The dramatic advantages of cooling stacked coils of sheet by the use of the apparatus of this invention as compared to conventional air cooling may be seen from the following data. The cooling runs detailed were accomplished from an annealing temperature of 1,300" F. to a final temperature of 250 F. utilizing liquid circuits as illustrated in FIGS. 4 and 5 at the bottom of the coil stack and between individual coils. Water at A similar percentage time saving has been experienced in the cooling period during which the stacked coils are reduced from 250 F. to F. preparatory to the final rolling mill finishing path.

It thus may be seen that by circulating water through the liquid circuits that are in intimate contact with the planar surfaces of the stacked coils, of which there may be any number without departing from the scope of the invention, a greatly accelerated rate of cooling is promoted with subsequent savings in time and expense for the production of finished steel sheet. Also, the use of water as a coolant assures a plentiful and inexpensive supply of a coolant capable of transmitting large amounts of heat without the risk of the coolant chemically attacking the surface of the steel coil.

I claim:

1. Apparatus for cooling from an annealing temperature a massive cylindrical coil of steel sheet, said coil being positioned on one of its planar surfaces on supporting base means, said apparatus including: hood means surrounding said coil and capable of sealing said coil against the ambient atmosphere such that the coil may be surrounded by a nonoxidizing atmosphere; weight-bearing means interposed between said one planar surface of said coil and said base means and maintaining said planar surface at a predetermined distance from said base means; at least said weight-bearing means and said planar surface cooperating to define a space beneath said coil; and closed fluid circuit means capable of conducting fluid coolant, positioned in said space and in intimate contact with said planar surface.

2. Apparatus according to claim 1 wherein said weightbearing means comprises a plate having at least one groove formed in the top surface thereof, said fluid circuit being at least partially located in said groove.

3. Apparatus according to claim 1, said coil being one of a plurality of coils vertically stacked such that the planar surfaces of the coils are contiguous.

4. Apparatus according to claim 3, wherein said weightbearing means comprise plural plate segments positioned between adjacent coils is spaced-apart relationship and having a thickness corresponding to said predetermined distance, said circuit means being positioned between said segments and having a thickness substantially the same as said segments.

5. Apparatus according to claim 1 and further including a second closed fluid capable of conducting fluid coolant and resting in intimate engagement on the other planar surface of said coil.

6. Apparatus according to claim 5, wherein said second fluid circuit comprises a length of tubing arranged in the form of a spiral, said spiral being coextensive with said other planar surface.

7. Apparatus for cooling from annealing temperatures massive cylindrical coils of steel sheet, said coils being vertically stacked such that the planar surfaces of the cylindrical coils are contiguous, said apparatus including: hood means surrounding said coils and sealing said coils against the ambient atmosphere such that the coils may be surrounded by a nonoxidizing atmosphere; separator means interposed between adjacent coils and maintaining the adjacent coils a predetermined distance apart; closed fluid circuit means capable of conducting fluid coolant, interposed between adjacent stacked coils and of a size such that said conduit means simultaneously are in intimate contact with both of adjacent stacked coils.

8. Apparatus according to claim 7, wherein said separator means comprise plural, separator segments positioned between adjacent coils in spaced-apart relationship and having a thickness corresponding to said predetermined distance,

said circuit means being positioned between said segments and having a thickness substantially the same as said segments.

9. Apparatus according to claim 7 and further including weight-bearing means located beneath the bottom coil of said stacked coils, a portion of said weight-bearing means and the bottom planar surface of said bottom coil defining therebetween a cavity, and second closed fluid circuit means positioned in said cavity for facilitating cooling of said bottom coil.

10. Apparatus according to claim 7, wherein said separator means and said fluid circuit means are integrally formed.

ll. Apparatus according to claim 10, said separator means comprising a plate having a thickness corresponding to said predetermined distance, said fluid circuit means comprising at least one passageway formed in said plate.

Claims

1. Apparatus for cooling from an annealing temperature a massive cylindrical coil of steel sheet, said coil being positioned on one of its planar surfaces on supporting base means, said apparatus including: hood means surrounding said coil and capable of sealing said coil against the ambient atmosphere such that the coil may be surrounded by a nonoxidizing atmosphere; weightbearing means interposed between said one planar surface of said coil and said base means and maintaining said planar surface at a predetermined distance from said base means; at least said weight-bearing means and said planar surface cooperating to define a space beneath said coil; and closed fluid circuit means capable of conducting fluid coolant, positioned in said space and in intimate contact with said planar surface.

2. Apparatus according to claim 1 wherein said weight-bearing means comprises a plate having at least one groove formed in the top surface thereof, said fluid circuit being at least partially located in said groove.

4. Apparatus according to claim 3, wherein said weight-bearing means comprise plural plate segments positioned between adjacent coils is spaced-apart relationship and having a thickness corresponding to said predetermined distance, said circuit means being positioned between said segments and having a thickness substantially the same as said segments.

8. Apparatus according to claim 7, wherein said separator means comprise plural, separator segments positioned between adjacent coils in spaced-apart relationship and having a thickness corresponding to said predetermined distance, said circuit means being positioned between said segments and having a thickness substantially the same as said segments.

11. Apparatus according to claim 10, said separator means comprising a plate having a thickness corresponding to said predetermined distance, said fluid circuit means comprising at least one passageway formed in said plate.