US2201308A - Metal strip coil heating - Google Patents

Description

May 21, 1940. D, EDGE 2,201,308

` METAL STRIP COIL HEATING Filed Aug. 24, 1938 l 3 Sheets-Sheet 1 [mei/502:-

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May 2l, 1940. D. EDGE METAL STRIP COIL HEATING Filed Aug. 24, 1938 I5 Sheets-Sheet 2 bww/dar:

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Patented 4May 21, 1940 UNITED STATES PATENT ori-ics METAL snm con. HEATING Dexter Edge. om. ma. x Appummn August 24, 193s, sein1 No. 220,534

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'This invention is concerned with the heating of coiled metal strip, an example being the heat treatment of coils of cold rolled steel.

One of the objects is to more emciently heat treat such material, but other objects may be inferred from the following description.

One example of the invention is illustrated by the accompanying drawings, in which:

Figure 1 is a horizontal section oi' a bell-type u) furnace embodying the principles of the invention;

Figures 2 and 3 are vertical sections taken from the lines II--lI and III-III, respectively, in Figure 1; and,

Figure 4 is an enlargement of a. detail shown by Figure 1.

More specifically, the furnace shown by these drawings includes a base I on which coils 2 of c'old rolled steel arerposltioned on end. These coils are enclosed on the base by a metal cover 3 in a gas-tight manner by reason of the lower edge of this cover 3 resting in a sand seal 3, Figure 2 shows this cover 3 of less than actual height for illustrative purposes, the cover usually being suiiiciently high to permit other coils of strip to be placed concentrically on. top of those shown.

Heating is effected by means of la bell l provided with suitable heating elements 5, this bell being lowered over the charged base during the heating period. A plurality of bases and covers similar to those illustrated are provided so that the charges can be cooled to a non-oxidizing temperature before the covers 3 are removed, it being understood that a non-oxidizing atmosphere is maintained within the shield during the heating and cooling periods The bell may be used with any of the bases and so functions continuously, except while being raised and lowered during base changes.

According to the present invention each of the bases I is provided with a plurality of cylindrical hea-ting elements in the form of gas iired heat radiators 6. These heat radiators have diameters substantially equaling the diameter of the coiled strip and are arranged in groups with the respective radiators relatively adjacent. 'Ihe coils are registered with these radiators and are therefore also close to one another; 'and since they stand on end, the coils are parallel each other.

Each heat radiator is in the form. of two concentric interconnecting tubes, the inner tube 6 receiving the ame from a gas burner 'land exhausting into the outer tube 6b which, in turn, 55 exhausts through a suitable outlet 8. Due to this (Cl. 263-52) v arrangement, the inner tube 8* attains a higher temperature than the outer tube 6b. These heat radiators do not directly heat the coils but serve to heat iiat metal plates 9 interposed between the radiators and the coils of strip, the latter therefore receiving heat by conduction through their bottom edges. Strip is normally coiled with its edges flush, and, since the plates 9 are dat, the bottom edges of the strips are in substantially continuous contact with these heated plates. l v

The operation of these heated bases involvesv the grouping of a plurality of the coils of metal on end and in parallel arrangement, the coils being so placed on the metal plates 9. The cover 3 is then placed over the coils and flushed in the usual manner with a suitable atmosphere. The heat radiators 6 are thenplaced in operation so as to preheat the charge to prepare it for ultimate heating by means of the furnace bell.

In the case of the present invention, heat radiation losses are reduced to a practical value during preheatzlng. One reason for this is that the closeness of the various coils to one another causes heat radiation to become largely a matter of heat exchange from one coil to another. Furthermore, the heat radiation from each coil is relatively small due to the fact that the greatest amount of heat is being applied the inner convolutions of the coils. Another factor promoting general efliciency is the heating of coils by way of their bottom edges by reason o1' the latr directly connecting the heated metal plates. It is to be understood that after the charge on one of the bases is preheated to a point where radiation losses become extreme in spite of the various preventative factors, that the heating 4bell is placed over the charge.v

In addition to speeding operations materially, a better metallurgical eect is obtained when this invention is practiced, due to the even heating of the coils which results. Other advantages follow from this even heating, namely, that the total time required to preheat the charge on the base and then further heat it by means of the iurnace bell, is less than the total time required to produce proper results by the use of the furnace bell without the preheating procedure.

I claim: v 1. A method of heating 4metal stripcoils by 50 means of heating equipment including a plurality of bases for carrying said coils with shields for covering said coils 4when on said bases and a heating bell adapted to be lowered onto said bases one at a time, said shields being inadequate to as thermally insulate said coils to any practical degree, said method comprising arranging a plurality of said coils on end on one of saidbases with said coils in mutually adjacent parallel relation to form a compact group, heating said group of said coils on said base through their bottom portions only by means other than said bell to effect a preheating of said group while permitting said bell to be used with other of said bases and with the mutually adjacent parallel relation of said coils keeping heat radiation losses to a practical rninimum, subsequently lowering said bell onto said base over said group of said coils while they are covered by one of said shields and while they retain the heat of said preheating, and heating said group of said coils to higher temperaturesI by means of said bell.

2. A method of heating metal strip coils by means of heating equipment including a plurality of bases for carrying said coils with shields for covering said coils when on said bases and a heating bell adapted to be lowered onto said bases one at a time, said shields being inadequate contacting substantially the entire bottom edge of said coil on said base with a iiat metal plate, heating said coil on said base by heating said plate so that heat travels by conduction from said plate into said bottom edge of said e011 whereby appreciable heat losses can occur only by radiaf tion from the outer convolution and top edges of said coil, said heating being eiected by means other than saidv heating bell to eiect a preheating of said coil while permitting said bell to be used with other of said bases, subsequently lowering said bell onto said base over said coil while it is covered by one of said shields and while it retains the heat of said preheating, and heating said coil to higher temperatures by means of said' bell.

3. A method of heating metal strip coils by means of heating equipment including a. plurality of bases for carrying said coils with shields covering said coils when on said bases and a heating bell adapted to be lowered onto said bases one at a time, said shields being inadequate to thermally insulate said coils to any practical degree, said method comprising arranging at least one of said `coils on end on one of said bases, said base having a circular heating element of substantially the same diameter as said coil and pro` viding inner and outer circular heating zones, said coil being registered with said element and the latter being operatedkso that said inner zone provides a greater heat output and said outer zone provides a lesser heat output, said element being so operated While said base is free rfrom said heating bell as to effect a preheating of said coil while permitting said bell to be used with other of said bases, subsequently lowering said bell onto said base while said coil is covered by one of said shields and while it retains the heat of said preheating, and heating said coil to higher temperatures by means of said'bell, said inner zone of `said element imparting a greater heat input to the inner convolutions of said coil so that this heat must largely travel through the outermost convolutions of said coil receiving a lesser heat input from said outer zone, before it can' be lost by radiation.

4. A method of heating metal strip coils by means of heating equipment including a plurality of bases for carrying said coils with shields for covering said coils when on said bases and a heating bell adapted to be lowered onto said bases one at a time, `said shields being inadequate to thermally insulate said coils to any practical degree, said method comprising arranging a plurality of said coils on end on one of said bases with said coils in mutually adjacent parallel i relation to form a compact group, heating said group of said coils on said base by means other than said bell to effect a preheating of said group while permittingsaid bell to be used with other of said bases and with` the mutually adjacent parallel relation of said coils keeping heat radiation losses to a practical minimum, subsequently lowering said bell onto said base over said group of said coils while they are covered by one of said shields and while they retain the heat of said preheating, and heating said group of said coils to higher temperatures by means of said bell, said group of said coils on said base being arranged on a iiat metal plate contacting substantially the entire bottom edge of each of said coils and said base being provided with a plurality of heating elements grouped beneath said plate as required for individual registration with said coils, said elements being circular with diameters similar to those of said coils and each providing inner and outer heating zones, each of said elements being operated so that said inner zone produces a greater heat output andsaid outer zone produces a lesser heat output to effect said preheating by conduction from said plate heated by said elements into said coils by way of their loweredges whereby appreciable heat losses can occur only by radiation from the outer convolutions and top edges of said coils, said inner zones of said elements imparting greater heat inputs to the inner convolutions of said coils so that this heat must largely travel through the outermost convoiutions of said coils receiving lesser heat inputs from said outer zones before said heat from said inner zones can be lost by radiation.

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