US2534973A - Cooling apparatus - Google Patents

Description

De@ 3199 E950 c. v :Psi-:N ErAL COOLING APPARATUS Filed March 2, 1949 Smc. rem WJ OO n 17W @LBW mmh t Iaa A Cm r .V .l

Faiented Bec., i9, 1950 CGOLING APPARATUS Carl L. Ipsen. Schenectady, and Norman B. Jones, Ballston Lake, N. Y., assignors to General Electric Company, a corporation of New York Application March z, 1949, serial No. 79,256

(ci. 26o- 3) 1 claim. l

Our invention relates to cooling apparatus for hot metals and more particularly to apparatus of the type adaptable for location at the exit of a continuous strip annealing furnace to provide controlled cooling of the continuous metal strip.

The primary object of our invention is the provision of a simple and readily controlled cooling apparatus of this character which provides uniiorm cooling of hot strip material.

Another object of the invention is. the pro-A vision oi' a cooling apparatus for location at the outlet of a continuous strip annealing furnace which is economical to construct and economical to maintain and operate.

In the annealing of continuous strip material auch as steel strip, for example, it is necessary to control the rate of cooling of the strip after it emerges from the furnace in order to provide the strip material with the desired physical properties. To accomplish such cooling it'is customary to pass the hot strip through one or more enclosed cooling chambers immediately after it leaves the furnace. In these cooling chambers the strip material is cooled usually by radiation from the hot strip to the outer enclosures of the cooling chambers or to water-filled cooling coils within the chambers. In some cases, the strip material is cooled b v a combination of radiation and convection, with fans being provided for internal circulation of the atmosphere in the cooling chambers. The method of removing at least a part of the heat externally is also known, in which case the atmosphere in the coollng chambers is removed. passed through external coolers and then returned to the cooling chambers.

.All oi the foregoing methods of removing heat from the strip material have disadvantages. In the iirst two cases of cooling by radiation only or by a combination of radiation and convection, the principal disadvantage is the large size of the cooling apparatus which is required to properly cool rapidly moving strip material. A further disadvantage of these two methods is the difiiculty of accurately controlling the cooling, particularly under abnormal conditions. The chief disadvantage of the third or atmosphere removal method of cooling is the possibility of warping the hot strip material by bringing the incoming cold atmosphere in contact with the strip, while a further disadvantage of this method is the high cost of the external atmosphere handling equipment.

It is an object of our invention to provide a cooling apparatus for hot strip material which is relatively small in size in comparison with equipments previously used for the same purpose.

A still further object of the invention is the provision of a cooling apparatus which provides accurately controllable cooling in order to minimize the possibility of strip warpage.

Additional objects of our invention, together with the features and advantages thereof will become apparent from the reading of the subsequent detailed description in conjunction with the accompanying drawing.

In' carrying out our invention in one form, we provide a cooling apparatus for continuous steel strip which has six vertical chambers arranged in a continuous row. Alternate chambers are interconnected at the top and at the bottom and each interconnecting space between two chambers is provided with a roller. The steel strip enters the apparatus through an inlet opening in one endmost chamber, passes longitudinally through successive cooling chambers as it is supported vertically in each chamber by said rollers, and leaves the apparatus through an outlet opening in the other endmost chamber. The cooling apparatus is provided with an artificial non-oxidizing atmosphere which is circulated through successive cooling chambers in a direction opposite to the movement of the steel strip material through the chambers. The atmosphere is removed from thechamber containing the steel inlet opening and is reintroduced into the chamber containing the steel outlet opening to provide this circulation. At a point near the inlet opening for the steel strip a controllable portion of the atmosphere is extracted and after being cooled is mixed again with the main portion of the atmosphere before the latter is reintroduced into the outlet chamber. the atmosphere is continuously circulated through the apparatus in a direction opposite to the movement of the steel strip therethrough, with a portion of the atmosphere being cooled during each cycle.

For a more complete understanding of our invention, reference should be had to the accompanying drawing, Fig. 1 of which is a sectional view of a cooling apparatus embodying our invention; Fig. 2 is a partial end view in outline of the lower portion of the apparatus illustrated in Fig. l; and Fig. 3 is a side outline view of the same portion of the apparatus which is shown in Fig. 2.

Referring to Fig. 1 of the drawing, a cooling apparatus embodying our invention is designated Thus, all

generally by the numeral I. The cooling apparatus I has an outer enclosure on all tour sides and top and bottom composed of an outer layer 2 of metal and an inner layer 3 o! heat insulating material. The upper part of enclosure 2, 3 is divided into six vertical cooling chambers or passages consisting of end chambers 4 and 5 and four intermediate chambers 6. The enclosure 2, 3 is supported laterally by vertical structural steel members II and horizontal cross members I2, which are best seen in Fig. 2.

The vertical cooling chambers `are interconnected alternately at the top and at the bottom. In cach interconnecting opening and located substantially half in each chamber is a transverse roller 1. End chamber 4 has an entrance roller 3 at the bottom thereof, while end chamber 5 has an exit roller 9 positioned in an outward extension I II of enclosure 2, 3.

Positioned immediately adjacent to the` entrance to cooling apparatus I in a typical apparatus embodying our invention is a high temperature electric annealing furnace I3. Furnace I3 may, for example, be of the type disclosed in copending application Serial No. 79,252 of Albert N. Otis, now Patent No. 2,491,828. which is assigned to the assignee of the present invention and which was led concurrently herewith. This furnace comprises a plurality of vertically disposed heating chambers I4 with electric heating velements I5 positioned on the side walls of chambers I4 to provide a source of heat. A continuous strip I6 of steel, which is to be annealed, is passed vertically through the heating chambers I4 of furnace I3 by means of rollers I1 located at the top and bottom of each heating chamber.

After the strip material I6 leaves the annealing furnace, it enters cooling apparatus I through an entrance opening I8, after which it passes beneath roller 8. From roller 8 it passes consecutively around upper and lower rollers 'I until it reaches exit roller 9 following which it leaves the cooling apparatus through an outlet opening I9.

From opening I9, the strip I6 passes into a conduit which takes it to the next process (not shown) in the treatment of steel strip.

Cooling apparatus I is constructed to operate with an artificial non-oxidizing atmosphere which may, for example, be of hydrogen or a mixture of hydrogen and nitrogen. A suillcient quantity oi.' the gas which is used to provide the artificial atmosphere is continuously put into the cooling chambers 4 and 5 through pipes 2| to maintain the pressure in apparatus I above the surrounding atmospheric pressure. The atmosphere is circulated through the end cooling chambers 4, 5 and intermediate cooling chamber 5 in a direction opposite to the movement of steel strip IB through these chambers. This circulation is provided by a blower 22 which may be driven by an electric motor 23 through a belt drive mechanism composed of driving pulley 4I, belt 24 and driven pulley 42. Blower 22 forces the atmosphere upward in chamber 5 in the direction indicated by the arrows in Fig. l, after which the atmosphere moves alternately downward and upward through intermediate chambers l and ilnally downward through chamber 4.

A From chamber 4 the atmosphere is drawn by blower 22 through an opening 25 in the bottom of chamber 4 which may be equipped with a ilap valve 26 into chamber 21 which occupies all of the lower portion of the cooling apparatus enclosure.. From chamber 21 the atmosphere is again picked up by blower 22 and recirculated up through chamber 5 and thence through the intermediate chambers Ii and end chamber 4 back to bottom chamber 21. On the side walls of interconnecting passage or chamber 21 are located a plurality of heating elements 28 which may be of the electrical resistance type, with the heating elements being surrounded by vertical and horizontal projections 29 of heat refractory material for mechanical protection.

On each side of entrance chamber 4 is located an opening 30 which is connected by means of a duct 3| to an atmosphere cooler 32. Cooler 32 may be of the shell and tube type with the cooling water entering through a pipe connection 33 and leaving the cooler through a connection 34. A duct 35 .connects the atmosphere outlet 'connection of cooler 32 to a blower 36 which may be driven by an electric motor 31 through a belt drive mechanism composed of a driving pulley 43, a belt 38, and a driven pulley 44. The atmosphere outlet of the blower 36 is connected to an opening 39 in chamber 5 by means of a variable opening valve 4II.

In the operation of cooling apparatus I, steel strip I6 enters the apparatus through opening I8. The strip I6 passes ilrst around roller 8. then alternately around upper and lower rollers 1, thence around roller s and out of the cooling apparatus through opening i9. The atmosphere is circulated upward through chamber 5, alternately downward and upward through chambers 6 and downward through chamber 4 1n the opposite direction to the motion of steel strip I6. As the steel strip and the atmosphere move counter to each other, the former is cooled and the latter is heated. The point of highest atmosphere temperature in the cooling apparatus, for usual operation, is at the bottom of chamber 4 and the point of lowest atmosphere temperature is in chamber 5, above atmosphere inlet 39, with an approximately uniform atmosphere temperature gradient between these two points along the path of atmosphere flow through the series of cooling chambers. Thus, the temperature of the steel strip is reduced gradually and at approximately a uniform rate as it moves from inlet opening I8 to outlet opening I9.

In order to reduce the temperature of the atmosphere which is drawn from the bottom of chamber 4 by blower 22 and reintroduced into chamber 5, a portion of the hot atmosphere is extracted through openings 30 in chamber 4. This portion of the atmosphere is drawn through coolers 32 by blowers 36, after which it is injected back into the atmosphere circulating system through openings 39 in chamber 5. It will be noted that openings 39 are well below the point at which the recirculated atmosphere rst comes in contact with the steel strip I5. This permits the cooled atmosphere from openings 39 to be thoroughly mixed with the hotter portion of tha. atmosphere being blown upward through chamber 5 by blower 22. Thus, the atmosphere is at a uniform temperature when it comes in contact with strip I6 and the possibility that the steel strip I6 may be warped by the cooler atmosphere is minimized.

Another advantage of our invention is that a relatively small volume of atmosphere is circulated externaliy through the shell and tube type coolers, whereas a relatively high volume is recirculated through the strip cooling chambers by the internal fan 22. This reduces both the size and cost of the equipment required for handling atmosphere externally to the main cooler enclosure 2, 3. At the same time, the advantages of convection cooling are retained by cooling a portion of the furnace atmosphere and mixing the cooled portion with the balance of the atmosphere before it is recirculated through the furnace. A large volume of circulating atmosphere is necessary for satisfactory convection cooling, and a large volume is achieved by our invention without the necessity of removing all the atmosphere from the cooling apparatus and reintroducing it again.

The heating units 28, which are located in lower chamber 21, are for the purpose of adding heat to the atmosphere under abnormal conditions of operation. Such a condition may occur, for example, when it is necessary to move the strip i6 through the cooling apparatus at lower than the normal speed. In such a case, it may be necessary to raise the temperature of the circulating atmosphere in order to prevent the strip from cooling too rapidly. In this event, valves 40 are closed to stop the operation of coolers 32 and heating units 28 are energized from a source of electrical current to add heat to the atmosphere. Automatic means (not shown) are provided for controlling valves 40 and heating units 28 responsively to the temperature of the strip in chamber 5.

Although heating units 28 are located in chamber 21 in this embodiment of our invention, they may be located instead in the lower portion of chamber if desired, with equal eilect.

This method of adding heat to the atmosphere when necessary, together with variable opening valves 40 which make it possible to regulate the portion of the atmosphere which is cooled, makes possible the accurate control of the temperature oi' strip material I6 over a wide range of operating conditions. Furthermore, the counterflow arrangement of our invention which makes it possible to utilize heat removed from the strip being cooled to retard the cooling rate of another portion of the same strip, allows the use of fewer heating units 28 than would be the case if it were necessary to provide in this way all the heat required to accurately control the strip temperature under abnormal conditions.

While we have illustrated and described one preferred embodiment of our invention, many modications thereof will occur to those skilled in the art and, therefore, it should be understood that we intend to cover by the appended claim anv such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

Apparatus for coolingr continuously moving strip material at a predetermined rate, said apsupporting said strip material in said chambers and providing for the passage of said material longitudinally through `consecutive interconnected chambers, an entrance opening for said strip material in one endmost chamber, an exit opening for said strip material in the other endmost chamber, means including an atmosphere outlet opening in the strip entrance chamber, an atmosphere inlet opening in the strip exit chamber. an interconnecting passage between said atmosphere outlet and inlet openings, and a blower, for recirculating said atmosphere through consecutive interconnected chambers in a direction opposite to the movement of said strip 'material therethrough, whereby a part of the heat removed by convection from said strip material in the portion of the apparatus nearer the strip entrance is returned to the strip material in the portion nearer the strip exit, selective hgating means for adding heat to said atmosphere after it has left the cooling chambers and before it is returned for recirculation through them, and selective means for extracting a variable portion of said atmosphere from the circulating system, cooling said portion, and returning said portion to said system to aiect the temperature of all of the atmosphere, said last-named means comprising an extraction opening in said strip entrance chamber, a controllable opening in said strip exit chamber, an linterconnecting duct between said extraction opening and said controllable opening, an atmosphere cooler, and a second blower, whereby the temperature of said strip material is reduced substantially uniformly and at a predetermined rate irrespective of the speed of movement of the strip material through the cooling apparatus.

CARL L. IPSEN. NORMAN B. JONES.

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

UNITED STATES PATENTS Number Name Date 2,023,285 Otis Dec. 3, 1935 2,199,472 Wean May 7, 1940 2,232,391 Keller Feb. 18, 1941 2,345,181 Cooper et al. Mar. 28, 1944 2,441,500 Miess May 11, 1948

Images