US2504810A - Apparatus for annealing - Google Patents

Description

April 18, 1950 w. H. BAILEY, JR

APPARATUS FOR ANNEALING Original Filed June 2, 1945 Patented Apr. I8, 1950 OFFICE i APPARATUS ron ANNI-:Auna

William n. Dailey, Jr., Library, Pa., assigner to Carnegie-Illinois Steel CQl'lwration, a corporation of New Jersey ai application June 2, 1945, Serial No. 597,323. Divided and tlm application May 17, 1947, Serial No. 748,733

l Claim.

The present invention relates to an improved apparatus ior annealing which, while not limited thereto. is well suited for annealing relatively wide coils of rolled steel strip. The applicaton is a division of my prior application Serial No. 597,323, flied June 2, 1945, for Method and apparatus for annealing. y.

It is well known to those skilled in the art that heretofore the annealing o1' coiled steel strip has been frequently carried out by enclosing the coils within bell-like gas-tight inner covers whose lower edges are sealed in sand or other suitable sealing material, the annealing heat having been applied externally by a bell-type radiant tube annealing furnace. In such conventional practice a protective deoxidizng gas is introduced into the inner covers so as to force out air and maintain a deoxidizing atmosphere within the inside cover. The gas forming the non-oxidizing atmosphere is usually exhausted through the sand Iseal at the base of the inner cover or through suitable outlets, the 'rate of iiow of the deoxidizing gas being controlled by maintaining a uniform gas pressure inside the inner covers or by maintaining a uniform gas pressure in the non-oxidizing. gas supply by manipulation of an adjustable pressure-regulating valve.

The above described conventional method of distributing deoxidizing gas to the inner covers is ineiilcient and objectionable for the reason that the iiow of gas through the inner covers decreases as the temperature inside the cover increases, and said gas flow, on the other hand, increases when the temperature inside the cover decreases. My invention is based on the recognitionA of the fact that contaminating gases are evolved from oil and water accretions on the surfvacesof the steel coils duringA the heating periodV Aprovided with suitable raised portions!! to retain which should be purged from the inner covers by the maximum rate of i'low oi deoxidizing gas dur- 40 y source oi' deoxidizing gas which is connected by a ing this heating stage of the annealing treatmentl but that after the heating stage, that is to say. during the cooling period after the application of heat to the furnace has been discontinued, the purging action is no longernecessary and the rate of ow of the deozliidizing gas can be reduced to the minimum necessary to prevent outside air from entering the inner cover, thus effecting a great saving in deoxidizing gas consumption.

One object of the present invention is to provide a means involving controlling the ow of gas to the inner covers at a substantially constant rate regardless of pressure variations inside the inner covers or pressure variations of gas emanating from the inlet pipes.

Another object of the invention is to provide means for maintaining the rate of iiow oi.' deoxidizing gas at the maximum necessary to obtain the desired purging action during the heating stage and for maintaining the rate oi ilow of deoxidizing gas during the cooling stage, at the minimum necessary to prevent entrance of air into the inner covers.

The invention will be more fully apparent from consideration of the following specitlcation, the accompanying drawings, and the appended claims.

In the drawings: l

Figure 1 is a somewhat diagrammatic plan view of the novel combination of annealing apparatus of my invention.

Figure 2 is a cross-sectional view on line II--II of Figure 1.

Referring more particularly to the drawings. reference numerals I0 and I2 represent suitable frame members secured to a plate Il on which is mounted a refractory lbase I6. Retained between the members I0 and I2 is a body of sand, indicated at I8, forming a gas seal. An outer vannealing furnace hood 2n is seated at the bottom of this sand seal. This furnace may be of any conventional form such as the well known type havingk radiant heater tubes 2|. The refractory base IB is formed with a plurality of raised platforms 22 each adapted to accommodate a stack of coiled material such as the coils C of strip steel indicated in the drawings.

Each` stack of coilsC is adapted to be enclosed by an inner bell-like cover 2l of generally circular form, closed at the top, the bottom of the cover resting in a body of sand or other sealing material such as indicated at 26, the base being the sand or other sealing material.

As shown in the drawings, 30 represents 'a supply pipe 32 having a control valve 34 and a flow indicator 36 therein which is adapted to deliver a deoxidizing gas at a uniform pressure and substantially constant rate to a gas header 3l extending lengthwise below the base I8. A plurality of branch pipes l0 lead from the main 3l, and each branch pipe contains a tting 42 having an orifice Q therein of predetermined diameter, and between each iltting 42 and the main each branch carries a. shut-0H valve Il.

The main control valve 34 is adapted to be manually manipulated to regulate the gas'iiow, and the gas passes through the ilow indicator 38' which has an oriiice ot predetermined size and is equipped with conventional means for indicating the rate of gas ilow. The oriilces in the ttings 42 of the branch pipes are so designed that they provide suicient pressure drop to give substantially'uniform distribution of deoxidizing gas under all conditions.

By using the apparatus and distributing system illustrated, the rate of gas iiow is shown at all times by means of the rate-of-ow indicator 35, and this rate of iiow can be set at the will of the operator at any desired value by manipulation of the control valve 34. It is thus apparent that during the heating period of the annealing treatment, a substantially constant amountof gas per unit of time can be delivered to each of the inner covers 24. By'way of example, during this period when heat is being applied by the radiant heat supplied by the annealing furnace bell 20, the operator may so set the control valve 34 as to provideapproximately 50 cubic feet of deoxidizing gas per hour to the interior of each inner cover 24. 'I'his amount, of course, willv vary with the tonnage of steel being treated, and in this example it is assumed that approximately tons of steel strip are contained within each inner cover 24. And during the cooling period, after the outer cover has beenremoved and the radiant heat is no longer being applied to the coils C, the control valve 34 will be operated so as to supply a lower rate of input of deoxidizing gas,

yet this input will be maintained substantially v constant so as to adequately maintain a superatmospheric pressure within the inner covers to thus exclude the entrance of air. During this cooling stage valve 34 may, for example, be set so as to admit approximately 20 cubic feet of nonoxidizing gas per hour, at a uniform pressure.

From the foregoing it is apparent that the layout of the deoxidizing gas distribution system is such that the branch lines are equipped with orices designed with suilicient pressure drop to provide substantially uniform distribution of deoxidizing gas under -all conditions and that because of the inclusion of the ow indicator 33 and the control valve 34 the rate of gas iiow is made known to the operator at all times.` Such rateof flow can be set at any desired value by manipulation of the control valve 34. Thus it is apparent that during the heating step, when gases are evolved from oil and water accretions on the surfaces of the coil C, resulting from normal steel rolling practice, a constant maximum supply of deoxidizing gas can be supplied at a uniform pressure so as to exert a purging action. Thereafter, during the cooling stage, upon cutting oiT ci.' the heat by removal of the outer hood 20, the supply of deoxidizing gas will be reduced to the minimum necessary to prevent outside air from entering under the inner cover.

Since gas is being constantly supplied, namely, at a uniform high rate during the heating stage and at a uniform low rate during the cooling stage. during both stages the excess gas escapes or illters out through the sand seais 26 surrounding the inner covers 24. If desired, escape ports can be used. The equipment will usually include a oonventional motor-driven Ian 46 for circulating the gas within each inner cover -24.

Although an actual reduction to practice shows that the above described embodiment of the invention is highly desirable, it is not to be construed that I am limited thereto, since various modications may be made by those skilled in the ing means associated with the base and outerv hood: a plurality of inner covers each adapted to enclose a stack of coils of rolled steel strip carryingv accretions of oil and water resulting from normal steel rolling operations; and means for supplying a constant maximum amount of nonoxidizing gas at a uniform pressure to each ot said inner covers during the heating period and a minimum amount of non-oxidizing gas during the cooling period; said last named means comprising a. supply pipe connected to a source of nonoxidizing gas, a device for indicating the rate of gas iiow. a control valve between said device and said gas source adapted to vary the rate of ilow to said device, a main leading from the indicating device to a plurality of branch pipes each communicatin'g with said main and with the interior of one of said covers, each branch pipe having therein a cut-oi valve and an orice controlling the rate of flow of non-oxidizing gas from said main to the interior of said cover.

WILLIAM H. DAILEY, Jn.

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

UNITED STATES PATENTS Number Name Date 1,903,909 Cope et al Apr. 18, 1933 2,003,226 Weller May 28, 1935 2,003,970 Machlet June 4. 1935 2,201,308 Edge May 21, 194i)l 2,254,891 Germany Sept. 2, 1941 2,414,130 Wilson Jan. 14, 1947 2,417,063 Cooper Mar. ll, 1947

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