US3581810A

US3581810A - Metallurgical furnace

Info

Publication number: US3581810A
Application number: US857253A
Authority: US
Inventors: Calvin C Blackman
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-07-16
Filing date: 1969-07-16
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01

Abstract

A furnace for heat-treating coiled strip material. The furnace has at least one plate in heat conductive relationship with the coil, and preferably there are a pair of such plates at opposite ends of the coil. The plates are directly heated and directly cooled to provide rapid heat transfer to and from the coil. In one embodiment intermediate sections are provided for disposition between stacked coils. The intermediate sections have directly heated top and bottom plates in conductive relationship of the edges of the coils directly above and below.

Description

United States Patent Inventor Calvin C. Blaekman 24272 W. Lake Road, Bay Village, Ohio 44140 Appl. No. 857,253 Filed July 16, 1969 Patented June 1, 1971 Continuation-impart of application Ser. No. 750,830, Aug. 7, 1968, now abandoned.

METALLURGICAL FURNACE 30 Claims, 14 Drawing Figs.

US. Cl 165/2, 165/48, 263/40, 266/5 Int. Cl F25b 29/00 FieldofSearch 165/12,48,

[56] References Cited UNITED STATES PATENTS 2,201,308 5/1940 Edge 263/43 2,228,088 1/1941 Roth 165/48 1,952,402 3/1934 Wilson 165/61 Primary Examiner-Charles Sukalo Attorney-William N. Hogg ABSTRACT: A furnace for heat-treating coiled strip material. The furnace hasat least one plate in heat conductive relationship with the coil, and preferably there are a pair of such plates at opposite ends of the coil. The plates are directly heated and directly cooled to provide rapid heat transfer to and from the coil. In one embodiment intermediate sections are provided for disposition between stacked coils. The intermediate sections have directly heated top and bottom plates in conductive relationship of the edges of the coils directly above and below.

PATENTED JUN 1 I97! SHEET t 0F 7 l /ll/l/l/ INS/ENTER BY a. 1). M1

ATTURNEY PATENTEDJUN nan 358L810 SHEET 5 [1F 7 cm m/ c. BLACK/VAN JNVENTUR A TTUHNEY PATENTED JUN 1 197i 3581.810

sum 5 or 7 CAL V/A/ c. BLACK/VAN 1N VEN7 UR ATTUHNE Y METALLURGICAL FURNACE This application is a continuationin-part application of my application Ser. No. 750,830, filed Aug. 7, I968, and now abandoned.

This invention relates generally to metallurgical furnaces, and more particularly to heat-treating furnaces adapted to heat treat-coiled strip material.

In the past there have been many proposals for heat-treating furnaces for treating coiled strip material. The most common form that these furnaces have taken is the so-called bell-type annealing furnaces. In these bell-type furnaces, one or more bases are provided on which the coiled strip material is placed. Normally, several coils are piled one on top of the other with separator or convector plates interposed between the various coils. Then a generally bell-shaped inner cover is placed over each stack of coils and sealed around the base.

An outer cover or furnace member is then placed over the inner cover or covers, which furnace is provided with some type of heating means such as electrical elements or radiant tubes. The heating of the coils is accomplished by heating the furnace. The furnace heats the inner covers which in turn radiate heat to the coils and also heat the atmosphere sealed within these inner covers. The atmosphere within these inner covers then convectively heats the coiled material therein in conjunction with the radiant heat from the inner covers.

The heating continues until the desired heat treating temperature is reached which temperature is held for the desired period of time. Heating is then stopped and the furnace member is removed.

Cooling within the inner covers takes place by convection flow to the inner cover then radiates the heat to the surrounding atmosphere. Cooled gases are supplied within the inner cover and circulated therein. Also, in some furnaces certain types of cooling devices are placed within the base structure of the furnace to cool the gases as they are circulated therein.

In some cases the cooling rate can be increased by removing the inner covers. However, this is not always possible since it is often necessary to provide a protective atmosphere around the coils to prevent scaling.

These bell-type furnaces have proved quite adequate for many years and have found widespread acceptance. However, they do have the very serious limitation of requiring a great deal of time for heating and cooling because of the use of convective heat transfer to and through gases and indirect radiation through the inner covers. In fact, in many instances a period of several days is required to complete a heating and cooling cycle for the heat treatment for certain types of material. This slowness in some cases is partially offset by the use of multipedestal base furnaces wherein coils are stacked on several bases. However, this is not an entirely effective solution because of the complexity of the installations and the expense of the furnaces for a somewhat limited increase in production rate.

Accordingly, one of the features of the present invention is the provision of an annealing furnace which provides at least one plate directly in contact with the coil and which plate is directly heated and directly cooled to thereby provide contact or conduction heat transfer to and from the coil thereby greatly decreasing the heating and cooling cycle time necessary to heat treat a coil.

Still another feature of this invention is the provision of an annealing furnace having directly heated and cooled plates contacting the coiled material at both ends thereof, and which is adaptable for varying sizes of coils.

Further features of the invention provide for direct heating and cooling of the ends sectional coils attacked in a furnace.

These and other features of the invention together with a fuller understanding thereof may be had by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. I is a longitudinal sectional view of one embodiment of heat-treating furnace according to this invention;

FIG. 2 is a plan view of the baseplate ofa furnace with a coil resting thereon, with a portion of the coil and baseplate broken away;

FIG. 3 is a plan view of the furnace with the cover thereon with parts broken away for clarity;

FIG. 4 is a sectional view taken substantially on the plane designated by line 4-4 of FIG. 1;

FIG. 5 is another embodiment of a cover member of the device of this invention incorporating a circulating fan;

FIG. 6 is a longitudinal sectional view of another embodiment ofa furnace according to this invention;

FIG. 7 is a sectional view taken substantially along the plane designated by the line 7-7 of FIG. 6;

FIG. 8 is a sectional view taken substantially along the plane designated by the line 8-8 of FIG. 7;

FIG. 9 is a longitudinal sectional view ofa modification of a furnace adapted to provide intermediate heating and cooling of stacked coils;

FIG. 10 is a sectional view taken substantially along the plane designated by the line 10-10 of FIG. 9;

FIG. 11 is a sectional view of a portion of the cover section of an embodiment where the contact plate itself forms a portion of the firing chamber;

FIG. 12 is a partial plan view partially in section with parts broken away for clarity of an electrically heated contact plate;

FIG. 13 is a sectional view taken substantially along the plane designated by the line 1343 of FIG. 12; and

FIG. 14 is a partial plan view partially in section with parts broken away for clarity of another form of electrical heating ofa contact plate.

Briefly the present invention contemplates a contact type annealing furnace for heat-treating coiled material. The furnace includes a baseplate upon which the coiled strip material rests and a cover member having a top plate which preferably is in contact with the opposite end of the coil. Both the top plate and baseplate are directly heated and directly cooled to thereby provide conductive heat transfer to and from the coil for rapid and efficient heating and cooling of the coil.

Also, in one form intermediate sections are provided between coils stacked in the furnace, which intermediate sections have directly heated and cooled plates in contact with the coils.

Referring now to the drawings, and for the present to FIGS. 1 and 2, one embodiment ofa heat-treating furnace according to this invention is shown. The furnace has a base structure generally designated as 10, which includes a baseplate l2, supported by underlying beams 14.

Beneath the baseplate 12, are a plurality of longitudinally extending radiant burner tubes 16. The inlet ends of the tubes 16 are connected to a manifold burner 18, which in turn is connected to a source of air and a source of fuel gas. The radiant tubes l6, are spaced from the baseplate l2 and are adapted to radiate heat thereto upon heating of the tubes. Support brackets (not shown) may be used to support the tubes 16. The discharge ends of the burner tubes 16 are connected to an exhaust header 20 which is provided with a vertical exhaust pipe 22 to raise the exhaust fumes above head level and prevent any danger to workmen.

A plurality of water tubes or pipes 24 are secured to the underside of the baseplate 12 by metal collars 26 welded to the bottom of the plate 12. A water inlet manifold 28 is provided which attaches to each of the water pipes 24 and to a supply source of water. The outlet ends of the water tubes 24 are connected to a water collection pipe 30 which in turn is connected to a drain.

A forced air fan 31 is provided and is disposed to blow air across the bottom of plate 12.

The baseplate 12 is adapted to support a coiled strip of material designated generally as C. In order to provide for gas circulation around the edges of the coil C, a central opening 32 is provided in the plate 12 and extending radially therefrom are a plurality of channels 34. A gas supply pipe 36 is provided which is connected to the central opening 32 and to a source of atmosphere gas. This will provide for the desired gas atmosphere within the furnace.

Referring now to FIGS. l and 3, a removable cover structure generally designated as 38 is provided. The cover structure 38 includes an end wall 40 which has depending therefrom an annular sidewall 42. A cover plate 44 is secured to the sidewall 42 in spaced relationship from the end wall 40. The cover plate 44 has a plurality of radially extending channels 46 extending from the center thereof. These channels, as the channels in the baseplate, are to provide for circulation of gases to the edges of the coil.

A plurality of burner tubes 48 are provided in the space between the end wall 40 and the cover plate 44 and spaced from the cover plate 44. As in the case of the tubes 16, support brackets (not shown) may be used to support the tubes 48. The burner tubes 48 are connected at their inlet ends to a burner manifold 50. The manifold 50 is connected by

quick disconnect couplings

52 and 54 to sources of air and gas respectively. The exhaust ends of the burner tubes 48 are connected to an exhaust manifold 56 which is provided with an exhaust pipe 58 extending above head height.

A plurality of water tubes or pipes 60 are provided within the space between the end wall 40 and the cover plate 44. The pipes 60 are secured to the cover plate 44 by a plurality of collars 62 welded thereto in a manner similar to the securing of the water pipes 24 to the baseplate 12. An intake manifold 64 is connected to the pipes 60 and to a supply of water by a disconnect coupling 66. The exhaust ends of the water pipe 60 are connected to an outlet water collector pipe 68 which in turn is connected through a disconnect coupling 70 to a drain. In place of the coupling 70, a sight drain could be provided if desired.

A second forced air fan 71 is provided which is disposed to force air into the space between the

plates

40 and 44. A plurality of vents 72 are provided to exhaust the air from the space between the

plates

40 and 44.

The end wall 40 of the cover structure 38 is provided with a lifting eye 73 welded thereto. This allows a crane to lift and move the cover structure as required. The movement of the cover structure, of course, will take place only when the

couplings

52, 54, 66 and 70 are disconnected.

In order to provide for a gastight interior within the furnace, a dual sealing device is provided. This sealing device also allows for different height of coils to be utilized and still provide adequate sealing. The sealing device includes an annular wall structure 74 extending upwardly from the base 10. An annular radiation shield 76 is provided around the wall 74. This sealing ring 76 operates against the inner face of the sidewall 42. The sidewall 42 is also provided with a downwardly extending annular flange 78 which is adapted to extend into an annular trough 80 supported by the base 10, which trough is filled with a sealing liquid. This sealing liquid may take the form of oil, or woods metal or other suitable sealing liquid.

The cover structure 38 is also provided with a gas atmosphere exhaust device in the form of a tube 82 extending through the sidewall 42. This tube 82 has a coupling 84, which is adapted to connect with a gas exhaust system.

In operation, the furnace is charged by placing a coil C on the baseplate with the cover section removed. The cover section is then lowered into place until the cover plate 44 comes to rest on the opposite end of the coil C. In this position, the flange 78 will be extending into the sealing liquid in the trough 80, and the sealing ring 76 will be abutting against the inner surface of the sidewall 42. The couplings S2, 54, 66, 70 and 84 are then connected to their respective supply and exhaust systems. The coil is now ready to be heated to a heat-treating temperature.

Before heating starts, normally, gas atmosphere will be supplied through the gas pipe 36 and allowed to run a sufficient time to purge the interior of the furnace. The heating of the coil is then begun by heating the radiant tubes 16 (in the base section) and 48 (in the cover section).

These

tubes

16 and 48 when heated will radiate heat directly to the baseplate l2 and cover plate 44 which in turn are directly in contact with the opposite ends of the coil C. Because of this direct contact, the baseplate l2 and cover plate 44 will supply heat to the opposite ends of the coil by direct conduction heat transfer which is an extremely efficient type of heat transfer. Thus, the heating of the coil can be accomplished at as rapid a rate as the coil is able to conduct the heat from the

plates

12 and 44. (In the preferred embodiment the

radiant tubes

16 and 48 are spaced from their respective plates in order to prevent any hot spots from developing on the plates and to provide a more uniform distribution of the heat to the plates).

The heating of the coil continues until the coil has reached the desired heat-treating temperature, and it is maintained at this temperature by controlling the rate of firing of the radiant tubes for the desired length of time. When the coil has been maintained at the temperature for the desired length of time, the firing of the tubes is discontinued.

To cool the coils, water is supplied to the water tubes 24 (in the base) and 60 (in the cover). The water tubes are directly in contact with the

respective plates

12 and 14 and hence they directly cool these plates. Also, the fans 31 (in the base) and 71 (in the cover) are started which causes air to flow across the surface of the plates. This flowing air acts as a cooling medium to remove heat from the plates. This direct cooling of the

plates

12 and 44 by the air and water will provide direct cooling to the coil, removing heat by conductive heat transfer. Hence, the coils can be cooled as rapidly as the coil can conduct heat to the baseplate l2 and the cover 44. (It is to be understood that either the water tubes alone or the forced air alone would provide direct cooling of the plates. In some situations either alone might be used; but normally the use of both together is desired, since the two together will usually provide a faster cooling rate than either alone).

The principal heating and cooling mechanism of the coil is by direct heating and cooling of a pair of plates which are in conductive heat transfer relationship with the coil, thus causing a relatively rapid heat exchange by conductive heat transfer. It is true that some additional heat transfer will take place by convection, both in heating and cooling, by virtue of the gaseous atmosphere circulating within the furnace. However, the principal heat transfer mechanism is by conductive heat transfer by virtue of directly heating and cooling plates which are in contact with the coils. This is more efficient heat transfer than convection and radiation heat transfer, which are the principal methods of heating and cooling of the coils in prior art bell-type furnaces. This conduction heat transfer is limited only by the rate at which the coil itself can take on or give up the heat from the directly heated cover and baseplates.

If greater gas atmosphere circulation within the furnace is desired than it is obtainable with a natural flow, then a fan may be incorporated within the furnace as shown in FIG. 5. This greater gas flow may be desired to perform certain metallurgical reactions, such as in open coil treating, or it may be desired simply to remove the effects of any atmosphere or combustion products that may find their way within the furnace and which can be removed by a rapid gas flow.

In the embodiment shown in FIG. 5, the base structure is the same as that shown in the previous embodiment. Also, as in the previous embodiment, the cover structure includes an end wall 40, a sidewall 42, and an end cover plate 44; burner tubes 48 and water tubes 60 are provided to heat and cool the end cover plate 44 in the same manner, and preferably fans 31 and 7] also.

However, in this embodiment a circulation fan 86 is provided which is journaled by bearings 88 provided in the sidewall 42 and driven by a motor 90 externally mounted on the sidewall. A plenum structure 92 is interposed between the cover plate 44 and the end of the coil C. This plenum structure includes a hollow central annular column member 94, having a passage 96 into a chamber 98.

An annular ring 100 is slidably mounted on the central column 94. The ring 100 has secured thereto a lower plate 102 having gas passages formed therein which may be similar to the channels 34 formed in the baseplate 12. The ring 100 is frictionally engaged on the column 96 but is moveable thereon by virtue of the weight of the cover member pressing thereon when it is placed on the coil. A retainer ring 103 prevents the ring from falling off the column member 94. A baffle wall 104 is provided which provides a passage for the gas between the chamber 98 and the fan 86. The gas flow will be generally as designated by the arrows in the figure. This particular construction, as indicated above, promotes increased circulation of the gases within the furnace structure.

If desired, the structure shown in FIG. 5 can be modified to place the plenum structure 92 above the cover plate 44 and thus allow the cover plate 44 to be in direct contact with the top of the coil as in the previously described embodiment.

This has the advantage of allowing direct conductive type heat transfer, both at the top and the bottom of the furnace; where maximum efficiency of heat transfer is required this is a very desirable structure.

Referring now to FIG. 6, another embodiment of the metallurgical furnace according to this invention is shown, incorporating certain additional features.

The furnace includes a base structure 110. This base structure 110 includes a metal shell 111 supported on underlying beams 114. A baseplate 112 is disposed within the shell 111 and rests on mounting brackets 113. In some cases, a coil-centering device may be desired which is shown as a projection 115 extending upwardly from the plate 112. Beneath the baseplate 112, and supported by the mounting brackets 113, are a plurality of longitudinally extending radiant burner tubes 116 similar to the type shown in the previous embodiment. The burner tubes 116 are provided with appropriate gas and air burner nozzles and outlet manifolds, not shown, which allow combustion. to take place within the tubes to radiantly heat the baseplate 112. The support brackets 113 also support water pipes 120 in contact with the plate 112 which, as in the previously described embodiment, provided for the supplying of cooling water to cool the baseplate 112. In order to increase cooling of the baseplate, a plurality of studs 121 are end welded thereto. This will increase the surface area for increased heating and cooling rates.

The plate 112 is welded to a downwardly extending leg portion 122 of the shell 111 and is supported on the support brackets 113, but it is not secured thereto.

This peripheral weld is the only fixed connection of the baseplate to shell containing the other parts of the base structure. Thus, if the baseplate 112 needs repair or replacement, it can easily be removed by merely breaking this weld and lifting the baseplate out and supplying a new or reworked plate. The whole base structure 110 need not be tied up during repair of the plate, nor is it necessary to replace the whole base structure if the plate only needs replacement.

The metal shell 122 is provided with thermal insulating material to minimize heat loss. The thermal insulating material is supplied in two layers. There is a backing layer 124 and a facing layer 126. The backing layer 124 is made of a rigid material, while the facing layer 126 is made of a flexible resilient material. The flexible material is easy to install and form to shape, while the rigid material maintains the shape and distribution of the insulation during use.

The base structure 110 is also provided with at least one air inlet opening 128 and a fan 130 disposed to blow air through the opening 128. An air exhaust opening 132 is also provided. This allows for the blowing of air directly across the baseplate 112 to directly cool the baseplate. This can be used to supplement the cooling of the water tubes 120 or, in some cases, it can be used in place of the cooling of the water tubes 120.

In order to improve the efliciency of the cooling air, a plurality of baffle walls 133 are provided which extend from the bottom insulation 126 to the plate 112. As can best be seen in FIGS. 7 and 8,'the baffle walls are each formed of corrugated strip of metal, and each has a plurality of openings 134 adjacent the plate 112. The walls 133 with their openings 134 direct the airflow across the plate, and also increase the velocity of the airflow to improve the cooling efficiency. The air flow is shown by arrows in FIG. 6.

A thermocouple 135 is provided which is imbedded in the baseplate 112 and has leads 136 extending therefrom through the walls of the base structure 110. These leads may be connected to the appropriate control equipment or recording equipment or both.

A removable cover structure 138 is provided which is formed of an enclosure section 140 and a heat transfer section 142. The heat transfer section 142 includes a top plate member 144 which has secured thereto a plurality of support brackets 146 which support thereon burner tubes 148. The burner tubes are provided with burner and air nozzles and exhaust manifolds, not shown, to allow burning to take place in the tubes to radiantly heat the top plate 144. A plurality of water tubes 150 are also secured to the top plate which are adapted to be supplied with water for cooling. Also, cooling studs 15] similar to those used in the baseplate are employed.

Also, baffle walls 151A with openings 1518, similar to those in the base section, are secured to the top plate 144 to increase the airflow and velocity around the plate.

The enclosure section 140 of the cover section 138 includes a metal shell 152 having an upturned leg 153 which is secured by welding to the top plate 144. The plate 144 is not attached to any other portion of the shell 152. This construction allows for the greater thermal expansion of the plate 144 than the main part of the shell 152 to prevent differential stresses from cracking the shell or plate. As in the case of the base section, the shell 152 has dual layer refractory material comprised of a high density-backing layer 154, and low density-facing layer 156. The top of the shell152 has welded thereon a lifting lug 158. This allows a crane to remove and replace the cover section as desired.

The two part construction of the cover section 138 allows for facile repair and replacement of the heat transfer section 142 without the necessity of completely replacing the entire cover structure as in the case of the base structure. If the top plate 144 becomes warped, worn, or in some way damaged or needs repair, the heat transfer section 142 can be easily removed from the remainder of the cover section merely by breaking the single weld between the plate 144 and the shell 152. A new heat transfer section 142 with burner tubes and cooling pipes can be quickly and easily secured to the enclosure section 140 and the cover member be placed back into service rapidly. The removed heat transfer section 142 can then be repaired without having the entire cover section tied up during this repair period.

The cover structure 138 is also provided with an air inlet opening 160, at which is disposed a fan 162 to supply cooling air directly to the top plate, and an air exhaust opening 164.

In the embodiment shown in FIG. 6, a positioning guide structure is shown which includes a vertically extending post 166 upwardly adjacent to the base section which post is rounded at the end thereof as shown at 168. The cover structure 138 has secured thereto annular collar 170 which is disposed to slidingly engage the post 168. When the cover section is to be emplaced, the collar 170 is slipped over the post 166 which gives an initial alignment to the cover structure and the cover is lowered into place on the coil.

The embodiment of FIG. 6 also incorporates an improved labyrinth seal configuration which will not only provide an effective seal, but also help in reducing the temperature at the extreme outside of the furnace at the sealing area.

The sealing structure includes an internal wall 172 and an intermediate wall 174, and an external wall 176, all formed as a part of the base structure. Both the internal wall 172 and intermediate wall 174 incorporate the dual insulating structure whereas the external wall 176 is of a sheet metal material. An annular interior chamber 178 is defined between the internal wall 172 and the intermediate wall 174, and an annular exterior chamber 180 is defined between the intermediate wall 174 and the external wall 176.

The enclosure section 140 of the cover structure 138 includes an interior depending wall 182, and an external depending wall 184 which define therebetween a chamber 186. The interior wall 182 incorporates the dual layer insulation and the external wall 184 is formed of sheet material. The walls and chambers of the base and cover are so positioned that the interior chamber 178 and the external wall 184 of the cover section extends into the exterior chamber 180. Similarly, the intermediate wall 174 of the base extends into the chamber 186 formed from the cover member. Thus, there is a labyrinth configuration provided in the relationship between the walls and the chambers ofthe cover structure 138 and the base structure 110.

In addition to the labyrinth structure, a radiation heat shield 188 is secured to the top of the internal wall 172 and disposed to project into contact with the internal wall 182 of the cover structure. This radiation heat shield is preferably formed of a woven fibrous refractory material such as asbestos fiber, glass wool, or other ceramic wool fiber. This is essentially a radiation barrier, and will not serve to provide much sealing of gas within the interior of the furnace. Hence, a gastight seal is also provided. In the embodiment shown in FIG. 6, this takes the form of an annular fluid inflatable flexible seal 190 positioned on the outside of the intermediate wall 174. Preferably, this seal is of the type described in my copending application, Ser. No. 842,208 entitled Fluid Inflatable Seal filed July 16, I969. Essentially, this seal is an endless fluid impervious annular flexible member, having a valve provided thereto (not shown), which allows the seal 190 to be inflated, which will cause the seal 190 to expand tightly into contact with the external wall 184 of the enclosure section 140. This will prevent the leakage of gas from the interior of the furnace to the surrounding ambient atmosphere. (As in the previously disclosed embodiments, the furnace interior may be provided with means to deliver a protective atmosphere to the interior thereto and so the plates may be configured to allow gas circulation passage around the edges of the coil). By providing a labyrinth seal and a radiation shield on the inside thereof, it is possible to use this type of sealing member at the location shown due to the relatively low temperature which can be maintained at this point, compared to the internal temperature of the heat-treating furnace. Previously, the materials forming the seal have been limited to materials which will withstand relatively high temperatures, and due to the present construction, this seal can serve effectively at this location.

The annular chamber 180 can also serve the function of a trough to catch water if the seal 190 uses water for inflation. Also, liquid in the trough can be used for additional sealing if for any reason the inflatable seal would not prove efficient. Ifa gas is used to inflate the seal or a supplemental water seal is not required, the external wall 176 can be omitted.

One of the advantages of this type of seal is that it allows sealing with different size coils within the furnace. Both wide and narrow coils can be heat treated in the furnace.

Also, it it to be understood that the various connections of gas, air, water, etc., are required the same as is the previously described embodiments, but the showing of these is omitted for simplicity of illustration. Of course, other features shown in the previously disclosed embodiments can be incorporated in the embodiment of FIG. 6, such as circulating fans, etc.

In FIG. 9, a metallurgical furnace having a base structure 110 and a cover structure 138 identical to the base and cover structures shown in FIG. 6 is shown. However, in this embodiment, one or more intermediate sections are employed in order to increase the number of coils which can be stacked and heat treated in the furnace at a given time and at a rapid rate. For depicting this embodiment, the basic cover and base sections of FIG. 6 have been chosen as the basis of the description and showing. However, it is to be understood that this principle of multiple coil heating and cooling can be used with other structures within the scope of this invention, including the structures shown in FIGS. 1 through 5.

As in the case of FIG. 6, a coil is layed on edge in the base section on the baseplate 112. However, on top ofthis coil, an intermediate section 200 is placed. The intermediate section has upper and

lower contact plates

202 and 204 respectively. The lower plate 204 rests directly on the top of the coil in the lower section. The

plates

202 and 204 are maintained in spaced relationship by a plurality of load-bearing members 206, extending between the upper plate 202 and lower plate 204. The load bearing members 206 also serve to support burner tubes 208 which are similar in construction to the burner tubes of the base and cover sections. Also, the upper plate has secured to the inner side thereof water pipes 210, and a lower plate 204 has water pipes 212 secured to the upper surface thereof. Thus, the burner tubes 208 directly heat both the upper plate 202 and the lower plate 204. The water pipes 210 directly cool plate 202 and water pipes 212 directly cool plate 204. Also, if desired, air inlet and air outlet openings can be provided and a fan utilized to provide cooling air between the plates in a manner similar to how cooling air is provided in the base section and cover section.

Baffle walls 213 are provided which extend between the

plates

202 and 204. The plates are preferably corrugated, similar to those shown and in the top and bottom sections. As can best be seen in FIG. 10, the plates have upper openings 213a and lower openings 213!) to increase the air volume and velocity flow in contact with the

plates

202 and 204.

The upper plate 202 is also provided with an upwardly projecting coil-centering device 214 similar to that provided in the base section. Both

plates

202 and 204 are also shown with cooling studs 215.

The intermediate section 200 includes a depending wall structure 216 which is adapted to mate with the walls and chambers of the base to form a seal in a manner similar to the forming of a seal by the cover section therewith. The depending wall structure 216 includes an internal wall 218 and an external wall 220. As in the case of the cover section, the internal wall 218 is preferably incorporated with a double layer of insulation, the external wall 220 preferably being of sheet metal material. The

wall walls

218 and 220 define between them an annular chamber 221, and these walls and chamber mate with the walls and chamber of the base section to seal in a manner similar to the sealing arrangement provided by the cover section.

In addition to the depending wall structure 216, the intermediate section also has an upwardly extending wall structure 222. This upwardly extending wall structure 222 includes an interior wall 224 and intermediate wall 226 and exterior wall 228. These walls are similar in construction to the interior wall, intermediate wall and exterior wall of the base section. These walls define the same type of chambers as defined by the walls of the base section and seal in conjunction with another superimposed intermediate section or the top section. Preferably, a heat shield 230, similar to the heat shield of the base section is provided, and a sealing member 232 similar to the seal of the base member is also provided. Also, a locating collar 234 is also provided similar to the collar on the cover member. Necessary water, gas and air connections are not shown for simplicity of illustration.

To use the intermediate section 200, the section is picked up by a crane, and for this purpose-lifting lugs (not shown) are provided. The intermediate section is raised so that the collar 234 can be slipped over the post 166 and is then lowered into place, so that the lower plate 204 rests on top of the coil of the base section. An additional coil can then be placed in the intermediate section 200 on the upper plate 202. The stacking of the coils can then continue using intermediate plates until the desired height is reached, at which time the cover section 138 is placed on. During the cooling and heating cycles, the plates of the intermediate sections, as well as the plates of the base and cover sections, are directly heated and cooled to provide direct conductive heat transfer relationship to the tops and the bottoms of the coils intermediate of the furnace. This directly heats and cools the plates, as opposed to conductive heat transfer which is slow and time consuming, which can take place to some extent by the use of convector plates between coils caused by flowing gasses within the furnace.

Referring now to FIGS. 11 to 14, modifications of devices for directly heating are shown. For simplicity of illustration of the principle in each instance, the cover section has been chosen. However, these principles are equally applicable to the base section or intermediate sections as will become apparent.

In FIG. 1], an upper plate 240 is shown which, with the refractory material 242 in the remainder of the cover structure, forms a combustion chamber 244 in which combustion of the gas-air mixture from a nozzle takes place. Hence, the upper plate 240 itself forms a portion of the combustion chamber and does not receive its heat from radiation, but directly from the combustion flame from burners 243. This will allow even more efficient and rapid heating, since the combustion is taking place directly against the upper plate 240. To control the distribution of the flames, deflectors, some of which are shown and designated as 245, are provided on the plate 24!}.

FIGS. 12 and 13 show electrical heating of a contact plate. In this embodiment, a contact plate is shown designated generally as 248. The plate 248 has an upper section 250 and a lower section 252'in direct contact with the coil. The lower section 252 has formed therein convolute-shaped element receiving spaces 254, and disposed within these spaces are electrical heating elements 256. The convoluted shape is desirable in order to distribute evenly the heat provided by the heating elements 256. The heating elements 256 are provided with the necessary plug outlets 258 for attachment to a source of electricity. A layer of insulating material 259 and outer shell 260 overlies the plate 248.

FIG. 14 shows a modification of electrically heated plate designated'generally as 262. In this case, upper and

lower plate sections

264 and 266 are provided. The lower section 264 has radially extending passages 268 in which heating elements 270 are provided. The elements in this case have one straight leg and one leg shaped generally as a damped sine wave. The purpose of this shape is to provide even distribution of the heat from the heating element through the plate.

The electrical heating of the contact plates may be desirable in cases where maximum heat input is required with a minimum of loss. In effect, by burying the heating elements within the contact plates, very little heat is wasted, the efficiency thereby being quite high in the use of the heat generated to heat the plate.

It is to be understood that there are many variations and modifications that can be made in the present design and still stay within the scope of the invention. For example, if greater gas flow is desired, a more elaborate channel structure may be devised to give different types of flow patterns for the gas. These channels may be formed directly in the top and bottom plates, or various types of convector or separator plates can be interposed between the coil and the top and bottom plates. One example of such convector plate is shown and described in U.S. Pat. No. 3,4l5,506, entitled Coil Spacer.

There are other types of convector plates also that are available on the market and which can be used for this purpose. The use of this plate still maintains the baseplate in conductive heat transfer relationship with the coils since the convector plate rests directly on the baseplate and the coil rests directly on the convector plate. Thus, for heat transfer purposes the convector plate can be considered a part of the baseplate or the top plate as the case may be. Other plates for other purposes may also be employed, such as plates with con toured surfaces which are beneficial for certain types of coils. Also, liquid metal may be employed in various ways to increase heat transfer characteristics. This metal may be permanently disposed in the cooling studs, or in the contact plates, or it may be circulated in contact with the contact plates.

Other modifications can include the use of other types of seals such as sand seals and the like, which are well known in the art.

Also, by providing proper valving, it is possible to utilize the combustion air for cooling of the plates by directing its flow to the spaces above the cover plates and below the baseplates instead of using additional fans.

Further, several narrower coils can be heat treated in the furnace by stacking them to required height. This stacking can be used when the total height is not sufficient to warrant the use of intermediate sections as shown in FIG. 9. This stacking can be either with or without convector plates separating the coils depending upon the degree of atmosphere gas flow required to the edge of each coil.

While several embodiments of this invention have been shown and described, various adaptations and modifications may be made without departing from the scope of the invention as defined in the appended claims.

I claim:

1. A furnace for annealing coiled strip material comprising, a base section, said base section including a baseplate adapted to support said coiled material, a cover section disposed to overlie said coil when supported on said plate, said cover section having atop plate, at least one of said plates being in conductive heat transfer relationship with said material, means disposed to directly heat at least one of said plates, and means for supplying cooling media in thermal contact with at least one of said plates, whereby to supply and remove heat to and from said material by conductive heat transfer.

2. The invention as defined in claim 1, further characterized by both of said plates being in conductive heat transfer relationship with the material and both of said plates being directly heated and cooled.

3. The invention as defined in claim 1, wherein said means to cool said plates includes means to cause fluid to flow in heat conductive relationship with said plates.

means to cool said plates includes water-cooled pipe means secured to said plates to provide the cooling thereof.

6. The invention as defined in claim I, wherein the means to heat said plates includes means disposed to radiantly heat each of said plate means;

7. The invention as defined in claim 6, wherein said means to radiantly heat said plates includes radiant tube means.

8. The invention as defined in claim 7, wherein said tube means are spaced from their respective plates.

9. The invention as defined in claim 1, further characterized by means providing for gas flow passages adjacent the ends of the coil.

10. The invention as defined in claim 5, further characterized by fan means within said cover disposed to cause gas circulation.

11. The invention as defined in claim 1, further characterized by said cover means being configured for vertical removal from said base means and sealing means disposed to seal said cover means with respect to said base means when said cover means is in place.

12. The invention as defined in claim 2 wherein said cover section and said base section have wall means disposed in telescoping relationship.

13. The inventionas defined in claim 12 wherein sealing means are interposed between said telescoping wall means.

14. The invention as defined in claim 13 further characterized by said sealing means being configured and arranged to seal over a range of relative axial positions of said members.

15. The invention as defined in claim 12 further characterized by said telescoping wall means having space therebetween, and by heat shield means disposed between said interior of said cover section and the space between said wall means.

16. The invention as defined in claim 12 wherein at least one of said sections includes a pair of circumferentially spaced annular walls defining therebetween an annular space and the other of said sections having wall means disposed to project into said space.

17. The invention as defined in claim 16 wherein each of said sections has a pair of eircumferentially spaced wall means defining therebetween an annular space and one of said walls of each section is disposed to project into the annular space of the opposite section.

18. The invention as defined in claim 2 wherein electric heating elements are disposed in said plates.

19. The invention as defined in claim 18 wherein said electric heating elements are disposed in a convoluted pattern with respect to the plates.

20. The invention as defined in claim 2 further charactcrized by said means to heat said plate including a combustion chamber for heating the plates, and wherein the combustion chamber for each plate is defined in part by the plate.

2]. The invention as defined in claim 2 wherein said cover section includes insulated shell means mounting said top plate, and wherein said shell means and said top plate are facilely separable for replacement of said plate.

22. The invention as defined in claim 2 wherein said base section includes insulated support means mounting said bottom plates, and wherein said support means and said bottom plate are facilely separable for replacement of said plate.

23. The invention as defined in claim 2 wherein said cover member includes a metal shell with heat-insulating material disposed therein.

24. The invention as defined in claim 2 wherein the furnace is insulated at least in part by a double layer of insulation, one of said layers having substantially more flexibility than the other layer.

25. The invention as defined in claim 2 further characterized by at least one intermediate section configured and ar' ranged to be interposed between a pair of coils in vertically stacked relationship on said base section, said intermediate member including upper and lower plates in conductive heat transfer relationship with said coils, and means to directly heat and pass cooling media in thermal contact with both said upper and lower plates.

26. The invention as defined in claim 25 wherein each of said sections includes means to provide a seal in cooperation with the section thereabove and therebelow.

27. The invention as defined in claim 2 further characterized by guide means configured and arranged to engage and position said cover section 'when said cover section is in place.

28. The invention as defined in claim 27 wherein said guide means includes at least one vertical post adjacent said base section, and said cover section includes collar means adapted to slidingly engage said post.

29. The invention as defined in claim 1 further characterized by metal liquid at elevated temperatures disposed in heat conductive contact with at least said one plate.

30. The method of heat-treating coiled strip material comprising the steps of contacting opposite sides of said coiled strip with a pair of contact plates, and directly heating and passing cooling media in thermal contact with said contact plates to thereby heat and cool said material by conduction heat transfer.

Claims

1. A furnace for annealing coiled strip material comprising, a base section, said base section including a baseplate adapted to support said coiled material, a cover section disposed to overlie said coil when supported on said plate, said cover section having a top plate, at least one of said plates being in conductive heat transfer relationship with said material, means disposed to directly heat at least one of said plates, and means for supplying cooling media in thermal contact with at least one of said plates, whereby to supply and remove heat to and from said material by conductive heat transfer.

4. The invention as defined in claim 1, wherein said means to cool said plates includes means to cause air to flow across said plates.

5. The invention as described in claim 1, wherein said means to cool said plates includes water-cooled pipe means secured to said plates to provide the cooling thereof.

6. The invention as defined in claim 1, wherein the means to heat said plates includes means disposed to radiantly heat each of said plate means.

13. The invention as defined in claim 12 wherein sealing means are interposed between said telescoping wall means.

17. The invention as defined in claim 16 wherein each of said sections has a pair of circumferentially spaced wall means defining therebetween an annular space and one of said walls of each section is disposed to project into the annular space of the opposite section.

20. The invention as defined in claim 2 further characterized by said means to heat said plate including a combustion chamber for heating the plates, and wherein the combustion chamber for each plate is defined in part by the plate.

21. The invention as defined in claim 2 wherein said cover section includes insulated shell means mounting said top plate, and wherein said shell means and said top plate are facilely separable for replacement of said plate.

25. The invention as defined in claim 2 further characterized by at least one intermediate section configured and arranged to be interposed between a pair of coils in vertically stacked relationship on said base section, said intermediate member including upper and lower plates in conductive heat transfer relationship with said coils, and means to directly heat and pass cooling media in thermal contact with both said upper and lower plates.

27. The invention as defined in claim 2 further characterized by guide means configured and arranged to engage and position said cover section when said cover section is in place.