US2603470A - Method and apparatus for heating - Google Patents

Description

July 15., 1952 F50 HEss 2,603,470

METHOD AND APPARATUS FOR HEATING FEGE y 3N w f INVENTOR.

n FREDEmc o. Hass ATTORNEY.

July 15, 1952 F, 0, HESS 2,603,470

METl-iOD AND APPARATUS FOR HEATING Filed April 26, 1949 3 Sheets-Sheet 2 INVENTOR. FREDERIC O. HESS .AT TOR N'EY. l

July 15, 1952 F, o, H555 2,603,470 V METHOD AND APPARATUS FOB HEATING Filed April 26, 1949 5 Sheets-Sheet 5 O 0*1 mi INVENTOR. FREDERIC O.HESS

` ATTORNEY.

required for rolling.

Patent-ed July 15, 1952 METHOD AND APPARATUS FOR HEATING Frederic O. Hess, Germantown, Pa., assignor to Selas Corporation of America, Philadelphia, Pa., a corporation of Pennsylvania Application April 26, 1949, Serial No. 89,606

3 Claims.

The present invention relates to the heating of metal, and more particularly to the method of and apparatus for heating slabs or other large bodies'of metal'from ambient lto hot working temperatures such as the elevated temperatures In accordance with the present invention there is provided a furnace system including a plurality of aligned furnace units through which the slab or other metal piece is moved. The furnace units are each provided with a high temperature heating chamber and a preheating chamber that are in direct communication with each other. The furnace units on the charge end of the systemv have their preheating chambers open at the top through which charging takes place, while those in the main heating portion of the system have their preheating chambers closed. Conveying means is provided between each of the furnace units to vmove the work through the system with the work in the preheating chambers moving in one direction and the work in the heating chambers moving in the opposite direction.` At the end of the system opposite the charging and discharging end there is provided a transfer mechanism to shift the work vfrom the upper preheating level to the lower heating level.

It is an object of the present invention to provide apparatus forA heating rapidly and evenly slabs, billets, blooms" and other shapes of metal. The apparatus isl so designed that the work 'is heated evenly throughout its area from end to end. With the arrangement of the furnace units in the present invention a large portion of the heat normally lost is utilized to raise the temperature of the work to a relatively high value prior to the time the work passes into the actual heatingchamber.-

Y It is a further object of the inventionv to provide' apparatus for preheating work in which the Ahot products of combustion from the heating chamber pass directly tothe preheating chamber lwhile still at substantially their highest tempera- 'of the present invention work is moved by mechanical means, which may be automatic in operation, directly frorn the point of loading through the furnace system to the. mill, and is supplied to the mill at mill speed.

It is a further object of the invention to provide a method of heating metallic objects which comprises passing themxin opposite directions and at different levels through preheating and heating chambers of a furnace system.

In the following description of the invention the work being heated will be referred to as slabs. It will be understood, however, that the work being heated could be billets or blooms or any large pieces or shapes as desired. o

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with itsv use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention. Y

In the drawings: Y

Figure l is amore or less diagrammatic view showing the furnace line andthe apparatus used to transfer the billets from one level to another;

Figure 2 is a section of one of the furnace units onv theloading end of the system;

Figure 3 is a section of one of theffurnace units in the main heating portion of the system;

Figure 4 is a section of the transfer mechanism;

Figure 5 is a section of an alternative form in which the furnace units may be supplied; and

Figures 6 to 8 inclusive are diagrams showing the manner in which the system operates.

Referring to Figure 1 there is shown more or less diagrammatically the entire heating system to be used for heating slabs, billets, or other large bodies. In this system the furnace includesa plurality of furnace units forming the loading zone, which units are indicated at A. There are 3 Y alsoY a plurality of furnace units B forming the main heating section of the system, and a transfer section C which is used to transfer the pref heated billets to the high temperature heating chambers of the furnace units.

The furnace units of the loading section are identical as are the furnace units of the main heating section.V The furnace units of these sections differ from each other only in that the units ofthe loading section are provided with means for'loading the billets to be heated from above, while the units of the `main heating section do not have this provision.

In Figure 2 there is shown a furnace .unit A which is provided with a lower high temperature heating chamber 3 and an upper preheating chamber 4 that are directly connected by a passage 5' extending between the two chambers. Each end of the furnace unit is provided-with openings 6 through which the slab to be heated may be passed into and out of chamber 3. Openvings 1 are also providedin the preheating cham- .ber 4 through'which the slabs may be passed. It will be Vnoted that Yeach of these openings is `considerably smallerthan the size of the chamber and Vis only slightlylarger than the dimensionsV of the maximum size slab that is to be heated. -V f y The walls of the, 'chamber' 3 have in 'them burner blocks 8 which are properly located for the heating pattern desired and which are separated by suitable high temperature refractory blocks 9. The entire furnace unit is builtY up of the refractory and the .burner blocksand is vsupported by sheet metal backing Il in accordance with ordinaryjfurnace practice. The furnaces are providedV with braces l2 and rest upon a platform I3. Y'There are also provided supports YIii Vwhich extend throughout the length of the system and upon which each of the furnace units is mounted so that they may be positioned with the openings and 1 in axial alignment.V The beams M are mounted upon a'suit- Yable floor or 'foundation 15.

Each of the burners` 8 that is used may be of any'desired type that has suitable combustion characteristics for the size of furnace chamber 6 being used. The burnerY disclosed herein are similar to those-described and claimed in Hess vPatent No. 2,215,079, .issued September 17, 1940. Each of these burners consists of the refractory block 8 that-has a cup IS formedin its face.

lFuel, whichV consists of a combustibleV mixture Aof gas and air is-suppliedthrougha distributor l'! into the c-up in a plurality of small jets where it is completely burned in the cup. The fuel in burners of this type is burned in the cup to heat Vthe latter to incandescence thereby supplying radiant -heatto thework.V` Heatis also supplied by Vthe .hot gases of combustion as will be explained more fully below. The distributors I6 are connected-by Apipes i 8 with suitable manifolds and each pipe |-8 has -a valve I9 in it so that the amount of fuel supplied to each burner can be regulated individually. Y y

Between'each of the furnace units in both the loadingrr section as well as the main heating section there .is provided conveying mechanism to move the VVslabs that are to be heated through the system.l .Asshown in the drawings there is an upper conveyor roller -2l located between `rolls.

4 There is also provided alower conveyor roll 23 mounted on a shaft 24 between each of the furnace units at a level so that slabs can be moved through the high temperature furnace chambers. The lower conveyor rollers are so positioned that they will forward slabs to be heated through the high temperature chambers 3. It is notedV that in actual ,practice these conveyor rolls and their supportingshafts lwill be water cooled in order to prevent overheating of the Since, however, provision for water cooling rolls of this type is Well known, it is deemed unnecessary to describe such provisions in detail herein. The conveyor rolls are driven positively tomove the slabs being heated in the two furnace' chambers in opposite directions. To this end there is provided a gear 25 on shaft 22 and a gear 2t on shaft 2d. These gears are connected for rotation together by a pair of idler gears 2l and are positively driven by a pinion V28d-.on the shaft of a motorx29. While it would be possible todrive fthe-,various conveyor rollsV from a single motor and drive shaftit rhas'V been found preferableto drive each set of conveyor rolls individually :by its own motor and hook these motors together electrically so that they will rotate inunison. It is Y"noted that at the exit end of the. high temperature heating chambers, asshown at ythe .right `of Figure 1 of the drawing/thereis a pair-of pinch rollers 3| which areused to feedY positivelyV the vheated slabs into some mechanism for Voperating `upon them such as, forvexample, a .rolling mill.Y

As noted above the 4'furnace units in the main heating section are similar to those in the loading section, with the exception thatthe upper preheating chainberll in wthese units is closed so that a higherV degree of preheating maybe obtained. Such larfurnace is shown'in section in Figure 3 of the` drawings. The'high temperature heating chamber-of the furnace shown in Figure v3 is circular in shape rather than polygonal in shapeas'wasV the furnace disclosed in Figure 2. This is-amatter of design however, since the shape-the furnace chamber will take will be determined Yby the size and type of work being heated. In Figure 2 the lower high temperature chamber is shown at 32 andy integral part ofthe furnace unit and is built each of the furnace units and on a level so that y slabs can be moved through the preheating chambers. This roller is supported on a shaft 22 that is journalled'in any suitable manner.

,lindrical Vfur-nace chamber.

of vrefractory materials .as is the rest of the furnace unitnln this case the furnace units B are mounted on a-pair of Supports 31, the upper part of which is-semi-circular in shape to support the furnace and thelower part of which is flat to be received on platform I 3.- As noted v above, the burners used in this chamberare exactly the same as those used in the heating` chamber described iii-connection with Figure 2. The only difference in these burners'is that their outer; contour has to be changed to fit the cy.-

The conveyors are placed between each of these furnace units as they were between each of thev units in the loading zone and the conveyors are driven in the sam-e manner.

In the operationV of the system, asvwill be pointed out more indetail below, slabs are loaded into the preheating chamber Vand are moved to the left in Figure .1. After passing through all -of the furnace units they are moved vertically downward in alignment with` theopenings inthe high temperature chambers and are then moved to the right to the exit of the system. A transl fer mechanism C is used for I lowering/the slabs from the preheating to the jhigh temperature chambers.` This transfer mechanism includes a trans'ferduct 38 that is, in effect, a tunnelclosed at its left end andl open at itsfrightend so that the'slabs may be inserted and removed'therefrom.'

not driven since the slab is moved into and out of the transfer duct by a pair of pinch rollers 46 and 41 that are mounted on shafts 48 and 49 respectively. These shafts are journalled for rotation in bearings 50 which are attached to the bracing 42 for the duct and may be driven in opposite directions by means of gearing I from a suitable electric motor 52 that is mounted on platform 43.

In order to raise and lower the transfer duct a plurality of plates 53 are attached suitably to the beams `44 at various points along the length of the duct. These plates have pivoted to them a pair of levers 54 and 55, the other ends o f which are pivoted'to a rigid support 56. Thus by rotating the levers the entire duct can be moved vertically. The raising and lowering movement of the duct is accomplished by a lever 51 thatis attached for movement withV lever 55 to form a bell crank. The lower end of the lever 51 is connected by a link 58 to a piston rod 59 that has on its'end a piston received in a cylinder 6|. Fluid under pressure can be admitted in any suitable manner main `66 would extend from one end of the furnace system to the other tol supply fuel to all of vthe units of which it is comprised. n'

. In order to fire the furnace a combustible mixture of gas and air is supplied through the main 66 and suitablemanifolds to the various burners of theindividual `furnace units where it is dis- 'chargedin a'plurality of small jets to lbe completely burned' in the-cups 16,; of the burners. ,The cupsare heated to a lhigh-degree of incan- Adescence and radiate theirheat to allportions of the furnace chamber which isalsowheated to incandesence. In effect, the high4 temperature chambers 3, 32 and 62 are radiant tunnels through which the slabs are moved so that they may be evenly heated aroundvtheir entire surface. The hot products of combustion which are vproduced as a result of the combustion,` and which would normally be wasted, risev through passages'between the high temperature chambers and the 'preheater chambers where they circulate around a second slab to preheatl the same. Some of these gases also ow through the openings 6 and 1 to protect the slabsl from;` the atmosphere as theyv are. moved from vone furnace unitjto the other.

. Thus the slabs are'heated in a series of steps as theypass from o ne of the; furnace'units to the other and they are protected'from oxidation as theylmovevbetwee'n the furnace units by means .to opposite ends of the cylinder lin order to lower and raise the transfer duct to move slabs from the upper preheating chambers to a position in which they can be fed to the lower. high temperal ture chambers.

Each of the furnace units that were described above shows the slabs to be heated mounted on their sides.- The furnace units, however, could be constructed so that the slabs are mounted on edge rather than on their sides if it is so desired. The controlling factor in this case would be the type of working apparatus to which the slabs are supplied. There is shown in Figure 5 a furnace unit in which the slabs are mounted on edge as they are being moved through the system. It will be seen that high temperature chamber'62 and preheating chamber 63 in this case are rectangular in shape with their narrow sides at the top and bottom thereof. These chambers are connected by a passage 64. The furnace unit is constructed, as were the previously described units, in accordance with ordinary furnace practice and similar parts are given similar reference numerals. The burners used in this type of furnace are also similar to those described above. It is noted. however, that the placement of the burners is slightly different in that the burners are located in the vertical sides of the high temperature chamber and are directed toward the slab which would be passing between them. In this case, each of the pipes that supply the burners is shown as being connected to a manifold 65, and the manifolds in turn connected to a main 66. In a system of the type described the of a blanket of exhaust gaseswhich blows through thel entrance and exit openings of each unit.

j A description of the operation'of vthe system will now be made with particular reference to Figures 6, 7 and 8. It is intendedthat the slabs will by supplied to the system at ambient temperature and discharged into larolling mill for hot rolling, -for example,v at a temperature of about 2250 F. Inorder toattain this temperature the lower chambers of the furnace units are fired at a rate sufficient to maintain the burner cups I6 at substantially 2700 F., and the interior of the chambers Vat the slightly lower temperature of from ,2 400" Atol 2500o F. The time the slabs mustbe kept in the furnace units will vary with their analysis and their dimensions, with smaller slabs vrequiring less time to heat than thosethat are larger. 'I he number of furnace units A and B that are used will vary with the length of the slabs being heated. As shown herein each slab is of such a length that five furnace units A are required'to receive it, and there are provided ten furnace units B. A smaller or larger numberof units B could be used, but there should be the samefnumber as there are units A or a multiple thereof. Enough furnace units'are disclosed herein to handle six slabs at once. Y I f In Figure 6 slabs D and E are shown in the lower chambers and slab F is shown in the transfer section C,l which is in its lower position, ready to be fed to the lower-heating chambers. Slabs G and H are shown in the" upperA preheating chamber of furnace units'B and a slab I is about to be placed in the preheating chambers of furnace units A. This may be accomplished by any suitable'slab handling mechanism, such as an overhead crane. During this time the conveying mechanism is'being operated to move slabs D, E,

Gand H back and forth for a distance at least n .duc to' the exhaust gases encircling the slabs .at .these points, the gases-are notas hot as theinte'ror of the heating .chambers'of the furnace units.r Pinch rolls i6 and di are operated to feed slab F into the.heatingqchambers belowslab G whileslab I is being placed imposition in the preheatingrchambers of furnace units A.'

While all six -slabs are in their respective chambers: ofthe, furnace units `las shown inA Figure 7; f

sirable to move the slabs .back and forth to insure veven Vheating throughout their` length. When slab D is upto temperature it .will be moved to the left far .enough to be received by pinch rolls 3|. The pinchrolls will feed the slab rto a rolling millor other mechanism to .perform'work upon-them. ,Thesamef operation .of the conveyingrolls-which `moves slab Dto pinch rolls 3l will 'move .slab .Cf intolpinch r- olls 46, 41 in thev transfer .mechanism'Q YThese latter .rolls will then move the .slab .G .into the transfer duct, as

Y shown in Figure .8 by the'time slab F leaves the heating chamber .of the furnace unit A on vthe right end of theline..

The transfer mechanism c win then be moved to its lower position of Figure 6 carrying the slab F with it. VThe parts are thenin position to start the heating cycle on a new slab that is to be placedin furnace units A, y

With the arrangement shown .the slabs will be Y i8 Y value. One suggestcdsystem is a soecalled interlock system in which the fuel supply is controlled inresponse to the work `temperature and the furnace temperature is used .as a high limit control. The details of -such a control system form Yno part of the present invention so-for that reason haveA not .been illustrated, One form that the con-trol systemmay take is disclosed in Hess et z al. vappli-cation Serial NumberV 761,602, filedJu'ly k from one Vlevel to the other, however, it is 4de- Y heated to approximately 30.0" F. by the time they` Y .leave'the preheating chambers to pass into the transfer duct. YDuring their passage through `the lower heating chambers the slabs areraised to a temperature -of 2250'L7 F. for hot working. In order to obtain these temperatures a combustible mixture of gas Iand airis burned the cups I8 of the'burners `to heat them to a temperature of 2700" F. The radiation from the cups assisted by .the hot products of vcombustion will heat the entirev lower chamber of each furnace unit to a temperature in the neighborhood of 2400 F. to 2.500" F. Therefore each chamber comprises a radiant wall entirely .surrounding that portion of the slab received thereby to heat therentire Yarea of the slab evenly. This heating is, of course, assisted by the high temperature products of combustion that are moving through the hightem- .perature .chamberrto the preheating chamber.-

The lproducts of combusti-on exhaust through the entrance and exit openings of each chamber and form a Vblanket of protective gases through which the slabs move from one of the furnace units to the next. The slabs are therefore protected from oxidation during the time they are being heated. As has `been noted-above, the time required for heating theslabs lwill varywiththeir dimensions and physical characteristics as well as the final temperature that is desired. ,In any event, the time required will be `a matter of minutes rather than the hour-s that are required for heating slabs in the lconventional typeof furnaces. Any suitable control system may be used to insure that the temperature of the Work will be at the desired '17, 1947.y -y f .Y

.Inthe operation of the system slabs. are moved in what is. in effect, 4a Acontinuous line through the furnace units. During their travel they are raised one after another from ambient temperature to the temperature required for hot working, land aredelivered directly .to the hot working mechanism before they have a chance to cool or become covered with an objectionable scale.- The arrangement is such that a minimum of space is required for the equipment. After theslabs are placed in the .preheatingchambers no further manual handling of them is required.

From the .above `description it will be seen. that I have provided apparatus bymeans of which slabs, billets .or other large pieces vof metal may be rapidly .heated 'one after another to a desired elevated temperature. The invention also Y,dis-

closes a novel method of heating and handling l large pieces o f metal. Y

While in accordance with the provisions of the statutes I have illustratedand described the best Y form of embodiment 4of my invention nowiin-ovvn to me ,it will be apparent to those 'skilledV in the art that changes may be made inthe form ofthe apparatus disclosed Without departingfrom the spirit Vand scope Yof the invention, as set forth'in the appended claims, and thatinfsome cases-certainfeatures of my invention :may be used toadvantage without a corresponding vuse of other features.

What is claimed is: Y

l. In apparatus for heating slabs and the like, the combination of a plurali-ty of Yfurnace units each having a pair of vertically displaced charnbers in open .communication with each other,

each of said chambers having axially aligned entrance land exit openings, means to mount said furnace units in axial alignment with each other, means located between eac-h unit and on a rlevel with said openings for forwarding slabs through Yone set of chambers in one'di-rect-ion and through the .other set of chambers in the Opposite'direction, means in the lowercham-ber of each 'unit to heat slabs in said chambers, a transfer device having an elongated chamber therein to receive a slab, means to mount said transfer device for movement from a position in which its chamber is aligned with the upper set of said openings :to receive slabs therefrom to a position inl which it is aligned with the lower set of said openingsto deliver slabs thereto, :and means to feed slabs into and out of the chamber of said transfer device.

2. In `apparatus for heating slabs and the like the combination of a row cf individual and axially aligned furnace units, each furnace .unit having a pair of vertically displaced and communicating chambers in which slabs .are heated, conveying means for slabs in each chamber located between the furnace units, drive means for said conveying means operative to move slabs in Y one direction throughV the upper chambers and chamber, said transfer device including means forming an elongated chamber in which a slab may be received, mechanism operative to shift said transfer device `from a position in which it is aligned with one of the rows of chambers of said furnace units to a position in which it is aligned with the other row of chambers of the.

furnace units, and means carried by said transfer device to move slabs into and out of the chamber thereof.

3. The method of heating slabs and the like in a row of separate heating units each comprising Aa heating chamber and a preheating chamber located vertically above the heating chamber and in direct communication therewith which comprises the steps of moving the slabs one after the other in one direction through the preheating chambers, receiving the slabs from the preheating chambers, moving them downward to a position aligned with said heating chambers, moving the slabs in the opposite direction through said heating chambers, protecting the slabs from substantial loss of heat from the time they leave v said 'preheating chambers until they enter said f heating chambers, heating the slabs in said heating chambers by radiant heat and hot products of combustion, and in said preheating chambers by hot products of combustion, and moving said slabs in each direction from points between said heating units.

FREDERIC O. HESS.

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

UNITED STATES PATENTS Number Name Date 1,788,977 Blockinger Jan. 13, 1931 1,946,971 Harter Feb. 13, 1934 2,214,157 rBannister Sept. 10, 1940 2,473,629 Andrews June 21, 1949 OTHER REFERENCES Pages 8 and 9 of Trinks Industrial Furnaces, vol. I, third edition, copyright 1944. Published by John Wiley and Sons, New York, N. Y.

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