US2360633A - Method and apparatus for annealing - Google Patents

Description

Oct. 17, 1944. E. ALLEN ET AL 2,360,633

METHOD AND APPARATUS FOR ANNEALING Filed Aug. 23, 1943 v INVENTORS 145. 14M? and d L W/I/fffl Patented Oct. 17, 1944 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR ANNEALING Application August 23, 1943, Serial No. 499,660

Claims. Cl- 26344) This invention relates to the art of annealing and, in particularly, to the annealing of flatrolled material such as strip or sheets.

In recent years, the use of cover-type annealing furnaces has become very widespread. Generally speaking, such furnaces comprise a base adapted to receive the charge to be annealed, i. e., strip in coils or sheets in a pile, an inner or protective cover disposed over the charge and a heating cover adapted to be lowered over the inner cover and provided with heating means. In some furnaces the heating means are mounted inside the inner cover. In the usual operation a single outer cover cooperates successively with a plurality of bases, being disposed thereon in turn during the heating portion of the annealing cycle. Heretofore, it has been the practice after the charge has been raised to the desired temperature, to permit the cooling thereof by loss of heat to the atmosphere. While this resulted in a slow cooling which is desirable, the time required for the charge to cool to a temperature at which the inner cover may be safely removed in such as to impose a serious limitation upon the amount of material it is possible to process with a given number of bases and a single outer cover.

As a mattter of fact, the charge may be cooled at rates considerably higher than that at which it cools by loss of heat to the atmosphere, without impairing the quality of the product. Attempts have accordingly been made to apply artificial cooling to reduce the over-all annealing time. So'far as we are aware, all such expedients have been of the makeshift variety and have not been wholly successful from the standpoint of actual operations.

We have invented a novel method and apparatus for annealing whereby the length of the cooling stage of the annealing cycle is reduced to about half the time required for cooling of the charge by loss of heat to the atmosphere. In a preferred embodiment and practice of our invention, we provide a cooling jacket adapted to be disposed over the inner cover. after removal' of the outer cover therefrom. By means of the jacket, we create a descending shower or curtain of liquid surrounding the cover but maintained out of contact therewith. We also blow air repeatedly through the descending curtain of liquid thereby causing partial evaporation thereof with the result that the inner cover and the charge enclosed thereby are subjected to a pronounced cooling effect.

Further details, novel features and advantages of the invention will be madeapparent by the following detailed description and explanation which refer to the accompanying drawing illustrating preferred embodiments of the apparatus contemplated by our invention. In the drawing,

Figure 1 is a central vertical section through one formv of base for a cover-type furnace, the inner cover thereon with built-in heating elements, and the cooling jacket of our invention disposed thereover;

Figure 2 is a portion of Figure 1 to enlarged scale; and

Figure 3 is a partial section similar to Figure 1 showing a form of cooling jacket adapted to cooperate with a slightly different type of base.

Referring now in detail to the drawing and, for the present, to Figures 1 and 2 our invention, in one form, comprises a coolingjacket ID adapted to be disposed over an inner cover ll resting on a charge-supporting base l2 and enclosing a charge 13 disposed on the base, in the illustrated example, a coil ofstrip. The inner cover H and base l2 are illustrated and described in detail in'Woodson Patent No. 2,249,- 411 and .it is therefore unnecessary to explain their construction further than to state that the base is composed of refractory brick laid on an enclosure fabricated from plate and structural members, and having a'charge-receiving casting l4 thereon while the inner cover is formed largely of metal plate, having the lower portion of its wall lined with refractory brick l5 and provided with radiant heating tubes l 6 mounted interiorly thereof. In horizontal section, the cover II is circular, to conform with the-shape of the charge and the base is of similar shape in plan. Both may be rectangular, however, if annealing sheets in piles.

The furnace cover adapted to cooperate With the inner cover II and base l2,'as shown in the Woodson patent, comprises simply an open-bottomed enclosure lined with refractory brick. The furnace cover is supported on a sealing flange depending from the bottom edge thereof adapted to be received in a channel I! extending around the inner cover I l.

The cooling jacket I!) is also an open-bottomed enclosure the lower edge of which is adapted to rest on the bottom of the channel [1. The jacket Ill comprisesa generally cylindrical outer wall 18 having a top H! thereon-provided with a central hole 2!]. The jacket also includes a partial inner wall 2| of generally frusto-conical shape, the lower edge of which is secured to the bottom edge of the outer wall I 8. Above the bottom edge, the inner wall is spaced inwardly from the outer wall. Posts Zla secured to the wall 2| support a distributor cone 22 the outer edge of which overhangs the upper edge of the wall. A substantially cylindrical bafile wall 23 is spaced inwardly from the outer wall and extends downwardly from the top l9, terminating above the junction of the inner and outer walls.

the posts 2|a to the baffle wall. Frusto- conical baffles 25 and 26 are mounted, respectively, on the baflie wall 23 and the post 2|a in vertically spaced relation, the two types of baffles being oppositely inclined and disposed in alternating relation in order to cause cascading of a curtain of liquid descending from the cone 22 within the baffle Wall 23, and into the space between the inner wall 2| and the outer wall l8. The inner wall 2| has notches 21 spaced circumferentially thereof through which liquid discharged downwardly of the cooling jacket may flow into the channel H. An overflow pipe or other equivalent means (not shown) is provided for conducting the water to a. cooling sump or to the sewer.

An external spray head 28 in the form of a circular pipe having holes therein is mounted on brackets 29 centrally of the cone 22. Liquid such as water, when supplied to the head 28 from a suitable source through a pipe 30, runs down the distributor cone and over the edge thereof forming a descending shower or curtain distributed substantially uniformly around the circumference of the jacket ID. The liquid strikes the top retarder plate 24 and on passing through the holes thereof, comes in contact with the baffles 25 and 26 successively and thus cascades downwardly. This sequence is repeated as the liquid continues to fall toward the bottom of the jacket. 7

An internal spray head 3| similar to the head 28 connected to the source of liquid by pipe 3| may be employed to direct a uniformly distributed spray on top of the inner cover during the final portion of the cooling stage of the cycle, if desired.

A cage 32 mounted on the top I9 is composed of posts 33 and annular bars 34 secured thereto in vertically spaced relation. A top 35 surmounts the cage and is provided with a lifting eye 36. Diagonal braces 31 spaced circumferentially of the jacket extend from the top 35 to the-outer edge of the top IS.

A motor 38 is disposed centrally of the cage 32, being carried on any suitable form of suspension such as a hanger 39 depending from the top 35, and is provided with a fan 39 adapted to drive air downwardly through the opening 20 in the top I9. A conical b aille 40 is mounted on brackets 4| extending upwardly from the spray head 28. The bafile 40 and the distributor cone 22 guide the air entering the jacket downwardly within the baffle wall 23. The air delivered by the fan is drawn into the cage 32 between the bars thereof. The air descending through the jacket strikes the retarder plate 24 and the bafiies 25 and 26. The latter cause the air to pass repeatedly through the descending curtain or cascade of liquid, thereby evaporating a substantial portion of the liquid and exerting a strong cooling action. On reaching the bottom edge of the baflie wall 23, the air passes upwardly through the space between the baffle wall and the outer wall IB through outlet ports 4| spaced circumferentially of the latter near the upper edge thereof.

While the normal functioning of the apparatus described above and the method of our invention will doubtless be understood from what has already been said, a complete annealing cycle will now be described for the sake of completeness.

When the base I2 is ready to receive a change to be annealed, i. e., when the cooling jacket, inner cover and previous charge have been removed, the next charge is placed on the base, the inner cover lowered thereover and the outer cover placed on the inner cover. The radiant tubes l6 are then fired for the period of time necessary to bring the charge up to the desired annealing temperature, e. g., 1100 F. When the charge has been raised to this temperature, the outer cover is removed and firing of the tube I6 is discontinued. The cooling jacket I0 is then lowered over the inner cover and the supply of liquid for the spray head 28 is turned on. While we prefer to use Water as the liquid to be evaporated, any other suitable liquid may be used instead. The motor 38 is then started to cause air to be blown downwardly through the jacket. It will be apparent that the air descending through the jacket in an annular curtain has intimate contact with the descending cascade of liquid and passes repeatedly therethrough. This causes evaporation of a portion of the liquid and the resulting cooling effect causes heat to be removed rapidly from the inner cover and the charge enclosed thereby. Neither the liquid nor the air have direct contact with the inner cover proper. This avoids excessive oxidation of the inner cover which would otherwise occur because of its high initial temperature. The inner cover, nevertheless, is directly subject to the cooling effect resulting from evaporation of the liquid.

After the charge has been reduced to a temperature of say 500 F., the water supply for the spray head 3| may be turned on to deliver a cooling spray in direct contact with the inner cover I The inner cover, however, will have a longer life if the cooling jacket alone is relied on to abstract heat from the charge, instead of apply.- ing cooling liquid directly to the inner cover. After the charge has been sufficiently cooled, the cooling jacket and inner cover are removed and then the charge itself.

Our invention contemplates the delivery of a large volume of air through the jacket and the supply of sufiicient cooling liquid to make the descending shower or curtain substantially continuous, circumferentially of the jacket. A cooling jacket for an inner cover adapted to accommodate strip from 60" to wide should have a motor and fan capable of delivering approximately 100,000 cubic feet of ai per hour.

A modified form of cooling jacket I0 shown in Figure 3 is adapted for cooperation with a furnace base such as that shown in Woodson Patent 2,137,869. In the construction shown in that patent, the radiant heating tubes are mounted on the inside of the outer cover, the inner cover I! comprising simply an enclosure fabricated from plate adapted to be disposed over the charge l3 resting on the base I2. The jacket I0 is generally similar to the jacket I0 except that the bottom of the inner wall 2| flares outwardly to form a generally horizontal flange 42. The outer wall l8 has a bottom annular flange 43. The flange 42 has a depending annular wall 44 adapted to enter a sealing channel 45 on the base and is provided with holes 46 for the escape of the liquid discharged downwardly through the jacket. The inner cover I! also has a depending annular wall 41 entering the channel 45 and an annular supporting wall 48 spaced inwardly therefrom adapted to rest on the bottom of a second channel 49. When the jacket I0 is in position over the inner cover, the flange 42 thereof rests on the upper edge of the outer wall of the sealing channel 45. Other parts of the modified construction are similar to corresponding parts of the jacket is and are designated by similar reference numerals with a prime afiixed. The jacket l functions in the same manner as the jacket IE! to produce rapid cooling of the charge within the inner cover I l.

The advantages of our method and apparatus for annealing have already been mentioned briefly. The strong cooling effect obtained by partial evaporation of the descending shower or curtain accelerates the cooling of the charge so that the time required for cooling it to a temperature at which the inner cover may be safely removed is only about half the time required for cooling by atmospheric convection. This saving of time is directly reflected in the over-all cost of annealing since it makes possible an increase in the production obtainable with a given number of furnace bases or permits the same production to be obtained With a smaller number of bases. The structure of the cooling jacket is simple and inexpensive and the use thereof does not require any special skill or training.

Although we have illustrated and described only a preferred practice and two embodiments of our invention, it will be understood that changes in the construction and operation disclosed may be made Without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base. said apparatus comprising an openbottomed jacket adapted to be disposed over said cover and including spaced inner and outer'walls. means delivering a curtain of cooling liquid downwardly within the outer wall into the space between said walls, and means for causing a flow of gas along the path of the liquid, thereby cooling said charge by evaporation of a portion of the liquid.

2. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an openbottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, means delivering a curtain of cooling liquid downwardly within the outer walls into the space between said walls, means for causing a flow of gas along the path of the liquid, and bafiies in said space effective to cause intermingling of the liquid and gas.

3. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an open-bottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, means delivering a curtain of cooling liquid downwardly within the outer wall into the space between said walls, means for causing a flow of gas along the path of'the liquid, a baffle wall intermediate said inner and outer walls terminating short of the bottom of the jacket and providing an annular passage for upflowing gas, and gas outlets in said outer wall.

4. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an open-bottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, frusto-conical bafiles spaced vertically of the outer wall, adjacent bafiies being oppositely disposed, and means for supplying cooling fluid to the upper region of said space for downward flow therethrough.

5. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an open-bottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, frusto-conical baffles spaced vertically of the outer wall, adjacent baffles being oppositely disposed, and means for supplying a cascade of cooling liquid descending over said baflies.

6. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an open-bottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, frusto-conical bafiies spaced vertically of the outer wall, adjacent baflies being oppositely disposed, means for supplying cooling fluid to the upper region of said space for downward flow therethrough, and means for blowing gas through the fluid repeatedly to evaporate a portion of the liquid.

'7. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover enclosing a charge on the base, said apparatus comprising an open-bottomed jacket adapted to be disposed over said cover and including spaced inner and outer walls, means delivering a cascade of cooling liquid downwardly into the space between said walls, and means for causing a flow of gas through said cascade, means carried by said jacket for delivering a cooling spray onto the top of the inner wall and means within the jacket for delivering a spray onto said cover.

8. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover adapted to enclose a charge on the base, said apparatus comprising an open-bottomed cooling jacket adapted to be disposed over the cover, a distributor cone adjacent the top of the jacket, means delivering cooling fluid onto said cone and means discharging a blast of air toward the vertex of said cone.

9. Cooling apparatus for use with a cover-type annealing furnace including a charge-supporting base and a protective cover adapted to enclose a charge on the base, said apparatus comprising an open-bottomed cooling jacket having spaced inner and outer walls and adapted to be disposed over said cover, a distributor cone extending over the upper edge of the inner wall, means delivering cooling fluid onto said cone and means for discharging a blast of air toward the vertex of the cone.

10. A cooling jacket for an annealing cover comprising an open-bottomed cylinder, a distributor cone in the cylinder near the top, a fan blowing air onto the cone and a cylindrical baffle spaced inwardly of the jacket cylinder and terminating above the lower edge thereof.

ALFRED E. ALLEN. JAMES L. WHITTEN.

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