US2120319A

US2120319A - Method of annealing

Info

Publication number: US2120319A
Application number: US26853A
Authority: US
Inventors: Wilson Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-06-15
Filing date: 1935-06-15
Publication date: 1938-06-14
Anticipated expiration: 1955-06-14

Description

June 14, 1938. L. wlLsoN METHOD OF ANNEALING Filed June l5, 1935 MM. QM.

Patented June 14,1938

` UNrrEzo` STATES 2,120,319 METHOD F ANNEALING Lee Wilson,` Cleveland. Ohio Application June 15, 1935, ASerial No. 26,853

1 Claim.

' My invention relates to the art of treating metal and, in particular, to the annealing of thin gauge metal in strip form. The annealing of strip has always been attended with considerable diiilculty heretofore. About the best procedure evolved so far is the annealing of-strip in coils in which it is reeled after cold rolling, either in conventional annealing boxes or in boxes particularly designed to receive round coils. The

boxes may be heated by heating means mounted therein, or may be bodily movable into a heating furnace. In either case, the annealing process is very slow and the efficiency is not very high, particularly as to the stacking of coils in conventional annealing boxes. A large amount of equipment is necessary because of the slowness of the process. and this makes the operation very expensive.

My invention overcomes the aforementioned objectionsto the present practice of annealing strip and provides, for the ilrst time, so far as I am aware, a practical, inexpensive and rapid method of annealing strip. In accordance with my invention, I anneal strip by heating it to the required temperature while in strand form. I coil the strip while still hot and cool it slowly in the coiled form. The heating, coilingand cooling operations are preferably conducted in the absence of atmospheric oxygen. I stitch togather successive strips being annealed and sever the strip when a suillcient amount thereof has been coiled fromthe strand I also'prefer to cool the strip slightly before coiling to prevent stick.

vice and a cooling chamber; and i Figure 2 is a sectional view taken along the line II II oi' Figure 1. .f

Referring now in detail to the drawing. 'ah annealing furnace I0 of the so-called tunnelf type. i has side walls il, a roof I2 and a hearth i2 comeVy My invention. also includes a.

Figure 1A is a similar view of the coiling de posed of refractory material assembled within a structural framework (not shown). The entrance end of the furnace has a restricted port or opening I4 normally closed by flexible flaps I5 which arel displaceable by strip material in- 5 dicated at I8 moving into the furnace. The discharge end of the furnace is-provided with an opening or port I1.

. The interior of the furnace is divided by a transverse partition wall I8 into a heating cham- 10, ber I8 and a cooling chamber 2B. Pinch roll stands 2i and 22 located at the entrance end of the furnace\,and adjacent the discharge opening i1, respectively, serve to feed the strip through the furnace in the directionof the arrow 15.

23. Conveyor'rollers 24 are mounted at intervals along the length of the furnace to support vthe material being passed therethrough.

The heating chamber i9 is provided with a plurality of heat exchange tubes 25. In the particular formv of the invention illustrated, the tubes extend transversely ofv the furnace chamber and penetrate the side walls Il' thereof at points above the rolls 24. Any otherv suitable arrange- `ment of the tubes may, however, be employed. 25

Burners 28 extend into the tubes adjacent one end, the other e'nd of each tube bein'g open for vdischarging combustion gases. A damper 21 is mounted adjacent' the discharge end of ,each tube for controlling.the flow of gases therethrough. Fuel is supplied tothe burners 26 from headers 2l'and air for combustion is induced throughthe open ends of the tubes in which the burners are mounted.

The cooling chamber l20 is also provided with conveyor rolls 24. Heat exchangeltubes 20a extend transversely ofthe furnace above the conveyor rolls and are Yconnected to any suitable source of cooling medium, such as air. The function of the tubes 20a is to cool` the material I6 40 slightly before it emerges from the furnace.

A portable coller 2l comprises a frame 30 preferably provided with wheels 3i for easy movement, and an enclosure 22 of any suitable construction. A .coller 23 is mounted on the 45 frame 3l within the enclosure 22. The construction of coilersis well known and requires no detailed disclosure.

At one side, the enclosure I2 is providedwith la` tubular projection 24 adapted to enter the port 50 I1 and make a substantially gas-tight connection therewith The enclosure 321s also provided with a door 2l which may be hinged or slidably mounted for opening.

A cooling chamber' It of any suitableconstruction and preferably having a door 31, is disposed in any desired location, preferably adjacent the furnace l 0. 'I'he function o'f the cooling chamber is to receive coils of strip for slow cooling after they have been heated to the annealing temperature and, so long as it performs its function, the specific construction thereof 'is not of great moment.

The method of my invention will now be explained referring to the apparatus already described.l Strip metal is usually rolled in relatively long lengths and coiled when the rolling is completed. It may be assumed, therefore, that the material I6 entering the furnace I0 is unwound from a. coil mounted on an uncoiler. Alternatively, the strip may be fed directly from the mill to the furnace. The first length of strip may be fed through the furnace by means of a rigid leader in a manner Well known to the art, and successive lengths of strip may be attached by spot welding or otherwise, to the trailing end of the preceding length, so as to form a continuous movement of successive strips through the furnace. The heating chamber of the furnace is preferably maintained at a temperature of 1500 F. to 1800 F. The strip is heated to this temperature gradually as it passes through the furnace, and the length of the furnace and therate oftravel of 'the material therethrough may be coordinated to insure the desired heating of the strip. As the strip enters the cooling chamber 20, it is cooled rapidly to about 1250 F. or any other desired temperature. I preferably maintain a non-oxidizing atmosphere within the chambers I9 and 20 of the furnace to prevent oxidation of the strip by atmospheric oxygen. .This deoxidizing atmosphere also illls the enclosure 32 of the coiler 29 by virtue of the connection 34 between the enclosure and the cooling chamber 20. 'I'he strip on emerging from the furnace passes through the tubular connection 34 and on to the coiler 33. The strip is thus coiled at a temperature of substantially 1250 F., in a non-oxidizing atmosphere. When a sumcient amount of strip has been coiled, the coiler 29 is pulled away from the furnace and the strip severed adjacent the port I1. 'I'he coiler is then moved to the cooling chamber 36, the door 31 of which is opened, to permit the coil formed by the coiler 33 to be removed therefrom through the door 35 and deposited in the cooling chamber. If desired, the open end of the tubular projection 34 may be temporarily closed by any suitable cover while the coiler is being removed to the cooling chamber 36. When the hot coil has been placed in the cooling chamber, the coiler is returned to the position shown in Figure 1 and a new coil is started.

After a period of slow cooling in the chamber 36, the annealing is completed and the coils may be removed therefrom for further manufacturing operations.

The rapid cooling step of the process is not necessary when annealing certain material, such as silicon steel or corrosion-resistant steel alloys, because such materials are not subject to sticking of adjacent turns of the coil at the normalizing temperature above mentioned, viz., around 1500 to 1800 F.

It will be apparent that the invention described in the foregoing constitutes a marked improvement over present processes of annealing. The rate of performing the annealing operation is greatly increased and only a relatively small amount of equipment is necessary. Since the material passes through the furnace rather rapidly, the tonnage output is high. The chamber in which the coils are slowly cooled may be of relatively inexpensive construction and easily designed for almost any desired capacity. The invention also lends itself admirably to bright annealing, since all the operations can be conducted in the absence of atmospheric oxygen.

The portable coiler makes it possible to conduct the coolingoperation in a non-oxidizing atmosphere and thereby protect the strip being coiled from atmospheric oxidation. The coiler also serves as a convenient means for transporting coils from the furnace to the cooling chamber.

The indirect heating of the annealing furnace is advantageous in that it insures a substantially uniform temperature throughout the furnace and prevents overheating of or injury to the material being treated, which might result from direct contact of the hot combustion gases therewith.

Although I have illustrated and described herein but one preferred form and practice of the invention, it will be apparent that any changes in the apparatus and method disclosed may be made Without departing from the spirit of the invention or the scope of the appended claim.

I claim:

A method of annealing a steel strip including the steps of heating the strip in strand form to a temperature of about'1300" F. or above, cooling the strip rapidly to a lesser elevated temperature but sufficiently below 1300 F. to prevent sticking of turns when coiled, coiling the strip at said temperature, and thereafter cooling the coiled strip slowly to room temperature.

LEE WILSON.