US2495561A - Method of and apparatus for heating coiled strip metal - Google Patents

Description

HEATING COILED STRIP METAL Patented Jan. 2.4, 1950 ME'rHn oF AND APPARATUS Fon HEA'rmG 1 coman s'rmr METAL /f Lee Wilson, Rocky River, Ollio Application December s1, 1946, serial Nin-"nasse This invention relates to heating coiled strip metal, and more particularly to an improved' method of and apparatus for annealing or otherwise heat treating strip steel or the like in coils while protecting the surfaces of the strip from corrosion, scaling, de-carburization, or other vundesirable effects. I

Itis a usual practice to anneal strip'steel in coils and frequently, such as in brightf'annealev ing, it is desirable to protect the coil from contact with atmospheres which may harmfully affect the strip surfaces during the annealing operation, Furnaces of the Well-known bell orco'ver type are particularly well adapted for this type of heat treating and various means have been proposed for protecting the coils by maintaining an atmosphere of a protective gas around the coil while it is being raised to the desired temperature and cooled. One arrangement which has been successfully and extensively used for this purpose in cover type furnaces includes an inner shell or cover of relatively light gauge metal which is placed over a coil, or stack of coils, as the coil rests upon the furnace base with its axis vertically disposed. These protective covers fit loosely over and are spaced from vthe coil and means are provided for directing a protective atmosphere up through the furnace base into the hollow center of the coil and permitting it to ll the space within the cover and escape around its bottom edge. However, although' such protective covers achieve excellent results they constitute an item of continuing expense as they are relatively short lived because of the repeated handling in normal use and continued exposure to high temperatures for long periods of time in direct contact with the furnace atmosphere with resulting warping and corrosion.

It is, therefore, among the objects of my present invention to provide a method of and appara- 9 Claims, (CL 26H3).

a volume of protective gas is required: the provision of a furnace and coil support combination for heating coiled strip metal which obtains high heating efficiency at lowrst cost and operating expense, permits rapid heating` and cooling of the coils, and produces a uniform high quality product: the provision of a simple and rugged structure vfor supporting and protecting coils against harmful atmospheres which may be employed eithegjn direct or indirectly heated furnaces; and the provision of heating apparatus tus for heating -coiled strip metal in a furnace,

while protecting the strip from contact with harmful atmosphere, in which the use of the usual coil covers is eliminated and in which heat may effectively be applied to'th'eridsof coil for most emcient heating thereof. ',15'5 l,

Other objects of my invention include; thezprovision of heating apparatus for coiledstrp metal in which the outer layer of the coil itself serves as a protective sheath for the inner coil layers ;or convolutions; the provision of a coil heating apof the type described which reduces to a minimum the time and labor involved in setting up a coil prior to placing a furnace bell thereover.

The above and other objects of my invention will appear from the following description of several embodiments thereof, reference being had to the accompanying drawings in which:

Figure 1 is a vertical cross sectional view through a bell type furnace in which my improved coil supporting and protecting arrangement is incorporated.

Figure 2 is a detached side elevation of a coil of strip metal, the free outer end of the coll being secured to the adjacent surface of the coil in a somewhat modified manner from that shown in Figure 1.

Figure 3 is an enlarged fragmentary top view of the coil shown in Figure 1, taken on line 3 3 of Figure 1. Figure 4 is a horizontal cross sectional view taken on line -t of Figure 1.

Figure 5 is a view generally similar to Figure 2 but illustrating another modified arrangement for maintaining the outer end of the strip in close engagement with the adjacent surface of the coil.

Figure 6 is a view generally similar to Figure 5 but illustrating a third modification of the means for closing or sealing the outer free end of the coil.

Figure 'I is a fragmentary top view of a coil with the outer end of the strip free.

. ary supporting base. Preferably supported above paratus in which the contact of undesirable gas atmospheres with the surfaces of the strip in the .mil :nay effectively be prevented without the use oi special coil enclosures or the like and which the furnace base structure, and in spaced ,relationthereto, I provide a coil carrying plate having a generally iiat upper surface of slightly larger area than the end area of the largest coil to be supported thereon. Means are provided for directing a protective atmosphere up through a centrally located inlet port in this plate. The

coil to be heated is placed on this supporting plate "i afieatci or carrier in up-ended position with its axis extending vertically and substantially aligned with the center of the plate so that the outer edge of the plate extends beyond the outer edge of the end of the coil. Next an upper cover plate ls placed on the top of the coil. This plate extends beyond the outer edge of the top end of the coil and the outer end of the metal strip is preferably substantially sealed against the adjacent outer layer of the coil to prevent circumferential ilow of the outside atmosphere into the coil convolutions. Thus, when the coil is supported as described and a protective gas is discharged into the center of the coil and permitted to escape between the top and bottom end surfaces of the coil and their respective cover plates, access of harmful gases to all parts of the coil is prevented except to the outer side surface thereof. After the annealing orother heat treating operation is completed the outer convolution of the coil may, ofcourse, be oxidized but the remaining strip in the coil will be in the desired condition having been protected during the heating operation and it is only necessary to cut oif and discard from the outer end of the coil a length equal substantially to the outer circumference of the coil.

Referring to the accompanying drawings, a furnace bell or cover is indicated at F and includes a supporting frame structure I and a refractory lining 2. It will be understood that the furnace is diagrammatically illustrated and that, although a relatively small unit adapted to heat only a single coil is illustrated, the furnace might be enlarged to accomodate any desired and practical number of coils in a single charge. Fuel burners 3 and 4 .discharge downwardly through the top of the furnace bell structure toward the top of the coil C and are supplied with fuel from the feed lines and 6 respectively. Although the illustrated furnace is provided with three top burners arranged symmetrically around the vertical center line of the bell (the third burner not being shown in the drawings) it will be understood that any desired number of burners may be employed and that the location of the burners in the furnace may be varied to achieve the most efficient heating results.

Supported above the foundation line 1 on suitable structural members 8 is the stationary furnace base generally indicated at B. In the apparatus illustrated this base is circular in form and is provided with a refractory section 9 and an annular sealing trough III. A corresponding annular sealing flange II is carried by the bottom of the furnace bell F and a suitable sealing material I2, such as sand or water, is disposed in the trough I0 in well-known manner. When the bell is in operating position as shown in Figure 1 the flange II, in cooperation with the trough I0 and sealing material I2, provides a substantially gas tight seal between the furnace base B and the bell F while permitting the bell F readily to be lifted fro-m and replaced onto the base, `An eye or lifting ring I3 secured to the top of the frame structure I facilitates handling of the furnace bell.

The bottom coil supporting and end covering plate I4 is supported on stanchions I5, I6, and

I1 which, as is best seen in Figure l, preferably have their lower ends mounted in socket members I8. Bottom burners I9, and 2| extend upwardly through the base B and are supplied with fuel through suitable pipes as indicated at I9' and 20'. These burners are preferably 4/ symmetrically spaced around' the vertical center line of the base B in the same manner as the top burners previously described and the discharge with the bottom burners I9, 20 and 2I is directed upwardly against the under side of the coil supporting plate I4.

A suitable source of supply of protective gas is connected to the supply pipe 22 which extends up through packing gland 23 and the base B into the center gas inlet port 24 in the plate I4. It will be observed that the plate I4 is recessed on its under side to provide sockets for the upper ends of the stanchions I5, I6 and I1 and that the bottom coil supporting plate can be removed by merely lifting it off of the supporting stanchions. Although the pipe 22 has a substantially gas tight connection with the plate I4 it is not securely attached thereto.

The coil being annealed, generally indicated at C, is positioned on the bottom plate I4 with its central axis substantially aligned with the center of the plate I4. Thus, as is clearly seen in Figure 1,' the hollow center 25 of the coil C will receive the protective gas discharged through the port 24. To control and restrict the flow of protective gas through the port 24 and to protect the strip edge surfaces which make up the upper end 26 of the coil C, I provide a top cover plate 21 which is preferably substantially the same size and shape as the bottom plate I4 except that it is imperforate and may be provided with lifting rings 28 and 29 to facilitate handling. Top and bottom plates I4 and 21 are preferably made of a suitable high temperature alloy and are sufficiently thick to prevent excessive and undesirable warping when repeatedly subjected to furnace temperatures.

In operating the apparatus described above the desired protective gas is discharged through the pipe 22 and the port 24 into the hollow center 25 of the coil C. This gas is maintained under greater pressure than that which exists outside of the coil C. Due to normal variations in strip width and in winding the coil, a completely gas tight fit between the bottom end of the coil C and the substantially flat upper face of plate I4 and between the upper end of coil C and the substantially flat bottom face of plate 21 is not practicable. Thus the protective gas is permitted to escape across the ends of the coil, as indicated by the small arrows in Figure 1, and effectively prevents the entry of undesirable atmosphere between the cover plates and the ends of the coil.

In order to prevent or limit the entry of outside atmosphere into the covolutions of the coil C at the outer end 30 of the strip I preferably provide means for maintaining the outer end of `the strip sealed to or in close engagement with the adjacent surface of the coil. I have illustrated several ways in which the end of the strip may be maintained in the desired position, Figures 1 and 3 showing a' continuous Weld 30 between the end 30 of the coil and the adjacent outer layer 32. In Figure 2 a series of spot welds 33 secure the outer end of the strip in place during the heating operation while Figure 5 illustrates a coil which has been bound by metal bands or straps 34, 35, and 36 which hold the end 31 of the coil in close engagement with the coil body. A modification of the arrangement shown in Figure 5 is illustrated in Figure 6 in which a pressure distributing bar 38 extends bestantial entry of outside atmosphere between the outer layer of the coil and the next adjacent inner layer.

When welding is employed to seal the end of the strip against the body of the coil, as shown in Figures l, 2 and 3, it is necessary to cut through the outer layer of the coil in order to permit it to be unwound and cut off after the heating operation is completed. With the banding arrangement shown in Figures 5 and 6, it is only necessary to cut the bands and then unwind and cut ofi7 the exposed outer layer of the strip. By securing the outer end of the strip against the body of the coil, entry of harmful gases into the coil convolutions is substantially prevented and the amount of protective atmosphere which is required to prevent oxidation of the coil is maintained at a minimum. However` it will be understood that in some cases it may be practical to leave the outer end of the strip free as iis-indicated in Figure 7 and to depend entirely on supplying enough protective gas to the interior of the coil to prevent damage to the strip surfaces during heating. When the outer end of the strip is left free it is possible `that the outside atmosphere will work into the coil for a limited distance, butwith some types of material the outer layer will hug the body of the coil suf- `application the con is assemmed with top and bottom cover plates and placed on suitable sup portsln the furnace and connections made to a source of protective gas.

i'lciently tightly to restrict the entry of outside B to the header 46 which in turn connects with a discharge ue tl. The top burners 3 and 4 and the third burner of the top' set (not shown) discharge downwardly against the top plate 21 and thus this plate is heated directly by convection as well as by radiation from the furnace walls, etc. The products of combustion from the top burners move downwardly around the outer surface of the coil C and, together with the By 'providing top and bottom end covers for the coil and maintaining a. `iiow of inert or protective gasinto the center of the coil and out between the ends of the coil and the covers, I have completely eliminated the necessity for separately enclosing the coils in a separate sheath or cover in' which. the protective atmosphere is maintained. My arrangement not only substantially reduces operating costs by saving the expense of maintaining and renewing the coil covers but also reduces the time required for loading and unloading the furnace and, by improving the heating emciency by more direct application of heat to the coil, reduces the heating time cycle and substantially increases the possible output of a given furnace installation.

Although I have described the illustrated embodiments of my invention in considerable detail, it will be understood by those skilled in the art that variations and modifications may be made in the arrangement and proportions of the ,parts making up my improved apparatus and in the procedure employed in carrying out my method without departing from the spirit of my invention. I do not, therefore, wish to be limited to the method and apparatus herein particularly disclosed but claim as my invention all embodiments thereof comingwithin the scope of the appended claims.

I claim:

1. Apparatus for protecting coils of strip metal during annealing or other heat treatment comprising two end covers, each having a substantially fiat coil engaging face, said faces having greater area than the ends of the coil to which they are to be applied whereby they will completely cover said ends, means for substantially sealing the outer free end portion of saidv coil against the next below layer of said coil, and means for discharging gas under pressure into the hollow center of said coil.

2. In combination with a coil of strip metal having its outer free end portion held in close engagement with the next below layer of said coil, a cover plate in engagement with and subproducts of combustion from the bottom burners id, 2d and 2i, flow out through the nues 42, I3, it and t5.

As both the bottom and top coil cover plates iii and 2li are subjected to direct heat from the burners and are in direct contact with the coil ends, the coil is most advantageously heated because the major heat input is through the ends of the coil. It is now recognized that such application of heat to a coil provides more efclent heating than the application of heat through the outer side surface of the coil. It will be understood that, although I have illustrated and described a direct red furnace in which my top and bottom coilA cover plates and the outer surface of the coil are exposed directly to the products of combustion, my invention is Vequally applicable to use with furnaces employing radiant tubes, electrical heating ele'-, ments, or muiiie arrangements in which the products of combustion are prevented from directly contacting the coil. Furthermore, my coil protecting apparatus may be used with box type'.

furnaces in which the coil is moved into and out' of the furnace heating chamber. In such an stantially completely covering one end of said coil, a second cover plate in engagement with and substantially completely covering the other end of said coil, and means for discharging gas under pressure into the hollow center of said coil, said cover plates preventing the escape of said gas from said hollow center except between said coil endsl and the inner coil engaging surfaces of said cover plates.

3. Apparatus for protecting a coil of strip metal during annealing or other heat treatment thereof comprising a pair of end cover plates for said coil, one of' said plates being adapted to support said coil in `up-ended -position and cover the bottom end thereof and the other of said plates being adapted to'rest upon and cover the top end of said coil,` one'of said plates having an aperture therethrough, and means for discharging gas under pressurethrough said aperture into the hollow center of said coil, said plates having nonsealing engagement with the ends of said coil -wherebyigasdischarged into thecenter of said coil may iescape'between the ends of said coil and said plates th" "by preventing the entry of outside atm(Vis-.pli re etween said plates and the ends .of .I i

aaeaei 4. In combination in apparatus for heating coils of strip metal, a bottom coil supporting and end covering plate, a top end cover plate adapted to rest upon and cover the top end of a coil when said coil is supported on its bottom end on said bottom plate, said bottom plate having a gas port extending therethrough, said plates having non-sealing engagement with the ends of said coil, means for discharging a protective gas through said port into the hollow center of a coil disposed on said bottom plate, and furnace means for heating saidv plates and a coil disposed therebetween.

5. In apparatus for heating coils of strip metal, the combination of a furnace base, a bottom coil supporting and end covering plate having a substantially horizontal top surface of larger area than the coil supported thereon, said bottom plate having a gas port extending therethrough, means -for supporting said plate above and in spaced relation to said furnace base, means for conducting gas under pressure to said gas port, a top coil covering plate adapted to rest upon and cover the top end of a coil when said coil is supported by said bottom plate, a removable furnace bell adapted to be positioned on said furnace base over said coil covering plates and a coil disposed therebetween, and means for heating the interior of said furnace bell.

6. The method of protecting a coil of strip metal against contact with an undesirable atmosphere which includes the steps of substantially sealing the outer free end portion of the strip against the next below layer of the coil. covering the ends of said coil and leaving the side surface thereof exposed, maintaining a desired atmosphere within the hollow center of said coil under greater pressure than that which exists outside of said coil, and permitting said desired atmosphere to escape across the ends of said coil.

7. The method of heating a coil of strip metal which includes the stepsv of substantially sealing the outer free end portion of the strip against the next below layer of the coil, covering the ends ol the coil and leaving the side surface thereof exposed, directing protective gas into the hollow center of said coil at greater pressure than that which exists outside of said coil, and heating said coil in a furnace while maintaining said protective gas within said coil at greater pressure than that which exists outside of said coil.

8. The method of heating a coil of strip metal which includes the steps of substantially sealing the outer free end portion of the strip against the next below layer of the coil, supporting the coil on a base plate with the coil axis vertical, covering the upper end of the coil by a top plate in direct contact therewith, enclosing the coil and plates within a furnace, applying heat to said plates and to the side surface of said coil, and

maintaining a gaseous atmosphere within the hollow center of the coil at greater pressure than that which exists within the furnace outside of the coil whereby said gaseous atmosphere is caused to escape into the furnace between said plates and the top and bottom ends of said coil.

9. In combination an apparatus for heating coils of strip metal, a bottom coil supporting and end covering plate adapted to support and cover the bottom end of a coil, a top end cover plate adapted to rest upon and cover the top end of a coll supported by said bottom plate, said bottom plate having a gas port extending therethrough, said plates having non-sealing engagement with said coil ends, and means for discharging protective gas through said port into the hollow center of the coil disposed on said bottom plate.

' LEE WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 138,060 Waters Apr. 22, 1873 1,960,808 Cope May 29, 1934.

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