US3099437A - Temperature controlled forge furnace or the like and method of operating same - Google Patents

Description

July 30, 1963 F. s. BLOOM :099,437

TEMPERATURE coNTRoLLED FORGE FURNACE 0R THE LIKE AND METHOD oF OPERATING SAME Filed Feb. 21, 1961 United States Patent O TEMPERATURE CNTRLLED FRGE FURNACE R THE LiKE AND METHGD 0F UPERA'HNG SAME Frederick S. Bloom, Mount Lebanon Township, Allegheny County, Pa. Filed Feb. 21, 1961, Ser. No. 99,766 6 Claims. (Cl. 263-43) This invention -relates to temperature-controlled fo'nge furnaces or the like and to a method for heating work therein to a predetermined temperature without overheating such work. More particularly, this invention pertains to ibatch type forge furnaces or the like having time-controlled radiant burner mechanism Ifor zonal heating control of a plurality of workpieces to be heated therein and removed therefrom at various regular or random times.

`In the heating of workpieces of steel or other rnetal in forge furnaces of lthe box type for subsequent forging or other processing, a problem has existed in controlling furnace temperature for the optimum heating of material and has been intensified by a kgeneral inability to control heating relatively well for respective workpieces in different stages of their heating cycle. Moreover, unless workpieces reaching shaping temperature were removed relatively promptly, they ran the risk of becoming overheated, or spoiled, particularly in furnaces having a high thermal head to minimize scaling.

Temperature-controlled forge furnace or like practices in accordance with this invention provide plural zone temperature control respectively whereby relatively cold workpieces can be rapidly brought up to temperature and the working temperature thereof maintained without overheating, or spoiling. Moreover, radiant heating provided by cooperating radiant burner mechanism is utilized in respective heat radiation zones within a single furnace enclosure to take care of -workpieces in different stages of heating in the respective progression thereof toward achievement of working temperature, maintenance of such temperature and removal at such temperature for use. Further, `a practice of this invention lprovides `automatic means for the discontinuance of rapid heating by time control means when the period has elapsed which was selected as suitable to bring workpieces in the zone so timed up to selected working temperature; and, thereafter, material remaining in s-uch zone will have such working temperature maintained without `likelihood of overheating and spoiling until each respective workpiece in that zone is remo-ved. Still further, each furnace or the like provides a plurality of zones for work in different stages of heating which may vary from relatively cold newly inserted work to heated work ready to be removed, selected so as to be consisten-t with the rate that Work heated Ito working temperature is needed.

Other objects, features and advantages of .this invention will be apparent from the lfollowing description and the accompanying drawings, which are illustrative of one embodiment only, in which lFIGURE 1 is a view in front elevation of a batch type forge furnace portion of one embodiment of this invention, the furnace being in section taken along line I-I of FIGURE 2 and the respective pairs of downwardly diverging dotted lines indicating respective areas more intensively heated by radiation;

FIGURE 2 is a view of the furnace shown in FIGURE l, in section taken along line ll-lI of FIGURE 1, the diverging dotted lines indicating an area more intensively heated by radiation;

FIGURE 3 is a `schematic view of the control mechyanism portion in the embodiment illustrated in the preceding iigures; and

3,099,437 Patented July 30, 1963 ice FIGURE 4 is one schematic electrical circuit utilizable in the illustrated embodiment of the invention.

Referring -to the drawings, the illustrated embodiment comprises a forge `furnace 10 having refractory end walls 11, a refractory back wall 12, and -a front wall 13` with a slot 14 therein to provide ingress and egress for workpieces relative to a refractory hearth 15 in base 16 of furnace 10. A refractory roof 17 is provided with laterally spaced burner mechanism openings 18, each of which has a refractory port block 19 therein for a radiant burner 2th which, as shown, is .a type C HTR radiant burner manufactured by Bloom Engineering Company, Inc., of Pittsburgh, Pennsylvania. Each port 21 in each block 19 has a widely flaring, downwardly .facing portion 22 which becomes radiant when its burner 20 burns sufficient iuel and radiates heat toward the portion of hearth 15 which it sees. Thereby the burner and its block transmit heat to workpieces on the por-tion of the hearth underlying them, respectively. As illustrated in FIGURE l, Ifor example, the spacing of the respective burner mechanisms 19`20 ldivides the furnace space, within the furnace enclosure comprising the walls, hearth and noof, into zones respectively designated as A, B and C and indicated, simply -for the purposes of general illustration, by respective pairs of diverging dotted lines proceeding from each flaring port portion 22 to the hearth portion bene-ath to indicate the general direction in which more intense portions ofthe respective radiant heat sources Iare beamed toward the hearth and workpieces thereon in the respective zones. After the furnace has been started up `and is soaked out, there will tbe a relatively high temperature in the entire furnace space, subject, however, to a thermal head increase or decrease in the respective zones in accordance with the operation of the respective burner mechanisms in the particular zone or zones for optimum heating of workpieces, or temperature holding thereof, as desired. For example, in a forge furnace in a particular operation heating steel billets, the furnace temperature within the enclosure space rnay always tbe kept lat a temperature in excess of 23 F., irrespective of whether one or more, or all, of the zones is in a working temperature maintaining or holding condition to keep any workpieces therein at workin-g temperature until withdrawn from the Ifurnace for use. On the other hand, in respect of a zone in which steel workpieces are being heated, the radiant burner mechanism in that zone will be on high-tire to produce a furnace temperature in that zone of a somewhat zonally localized character, which illustratively may 'be upwards of 2600 Fi, to |bring the workpieces in that zone up to selected working temperature, usually las rapidly =as possible where the furnace is being pushed for production.

It will tbe recognized although the illustrated embodiment shows la `single burner mechanism per zone, furnaces or the like may be constructed under this invention with zones whichv openate with more than oneI burner per zone positioned laterally or longitudinally, or a cluster of relatively small burner mechanisms may be utilized in one or more of the respective zones. Further, although in the present preferred embodiment shown, the burners are located in the roof, it will be recognized that work to be heated may be positioned in or moved through the furnace otherwise than in relation to a horizontal hearth and the burners` and blocks positioned in opposed fashion in some other part of the furnace enclosure in order to direct radiant heat against such work. Still further, work may be heated in `a hatch fashion as shown in the illustrated embodiment, or the work may travel within its respective zone and/ or furnace, as desired.

4Furnace 10 may :be used to heat a .wide variety 0f materials inclusive, for example, of groups of ste-el billets 3 23a, 23b and 23C shown in `outline form on hearth l5 within the respective zones A, B and C. Such billets may be utilized for forging or `other shaping or use and after being received brought to selected working temperature in furnace 10, the workpieces being inserted through slot 14 when being placed on hearth 15, and withdrawn through the same .slot when the workpiece has reached working temperature and a handler is ready -to remove it for shaping. By means orf this invention, the zones A, `B and C may be operated in any desired condition sequence by the handler or furnace operator with relative :assurance that the Work placed in a particular zone will be heated to working temperature at a selected rate with the burner 20` for that Zone operating at la selected work heating level and, further, that when work reaches working temperature due to the completion of a work heating cycle in that Zone, the further heating thereof will be arrested as the bur-ner yoperation level is automatically reduced to a low-tire condition to maintain the working temperature in the work in that zone even though the fwork is not Withdrawn as soon as such selected working temperature is attained. Thereby overheating or burning of the workpieces is avoided, even should the person attending have failed to turn `down the burner, or to remove the work, once it had attained its working temperature as determined by the selected timed work heating cycle. Moreover, the semi-automatic and automatic elements in the control portion of the illustrated embodiment provide for the relative independence of the respective zones, irrespective of number, and their use in -a program schedule suited to` the particular plant and service in lwhich this invention may be employed.

In the case yof the illustrated embodiment, if it is assumed that workpieces 23h in zone B have reached worktng temperature and are being withdrawn, then the burners for that zone would have gone on low-lire to provide la maintenance or holding condition at the end of the high-tire heating period. At the same time zone A, for example, may be in maximum work heating condition to heat relatively cold billets 23a which have just been placed on the hearth 15, while zone C may be in an intermediate portion of la timed maximum work heating condition needed to cause the `workpieces 23C in that zone to reach `a selected working temperature `desired sooner than the workpieces in zone A without substantial adverse effect upon the work temperature maintenance condition of zone B. In an operation such as that being described, the Zonal scheduling and timing is correlated so that when `the workpieces 23b have all been withdrawn for use, Ithe workpieces 23e will have just attained working temperature. When the latter happens, the burner mechanism 19-20 `of Zone C will automatically shift to hold condition to maintain the working temperature of the work 23e to avoid subjecting such work to conditions which would overheat or burn the metal. At this stage, the handler would place relatively cold billets on the hearth in zone B `and press the `starting button to initiate the heating of a fresh set of workpieces 23b at the timed maximum radiant heat transfer rate selected `for that zone, which would continue until the new set of Workpieces 23h have been exposed to the selected radiant heating condition in zone B during its work heating time cycle, at the end of which, the fuel flow to the burner for zone lB will automatically be reduced to shift zone B into a working temperature holding or low-tire condition. Thus, in the exemplary operation, the heating of workpieces in Zones A, C and B may follow one `another in endless succession and selected order lfor as long as required.

FIGURES 3 and 4 illustrate schematically one control t-o achieve the temperature controlled zonal heating and holding action of the illustrated embodiment; the circuit in FIGURE 3 being shown in maximum work heating position; while FIGURE 4 is shown before any operation is begun. Therein, a control panel 24 is provided 'with three identical ventical sets `of instrumentalities arranged side-by-side and utilizable respectively in the operation of the burner mechanisms lil-Ztl regulating the heating conditions in the respective zones A, B and C. Considering the right hand set on panel 24 as allOcat-\ able to pont block 19C and burner 20c to operate zone C in furnace 10, there is :a cycle timer 25 `of conventional make, a signal light 26, which normally is lighted when burner Zlc is operating at work heating condition, a timer start `switch 27, a timer emergency stop switch 28, an air pressure regulating valve 3G .and an air pressure gauge 29 to show the -air pressure as so` regulated by valve 30. Compressed air is supplied to panel 24 through a pipe 3l, a branch `of which behind panel 24 leads to valve 3i? to provide a second source of instrument air at a selected lower pressure in accordance Iwith the :regulation o-f valve 30, deliverable through a pipe 32 indicated in FIGURE 4. in the illustration of FIGURE 3, higher pressure air from pipe 3l passes through a 3-way solenoid A.valve 65a on panel 24 to impulse pipe 33 and la diaphragm operator 34, which correspondingly affects the position of butterlly valve 35 in a combustion air branch pipe 36 leading to the combustion air opening 37 lin burner 20c. As shown, Iburner 20c is operating in `a high fire condition to heat the port surface Z2 and the workpieces 23C by radiant heating and convection until the workpieces 23C achieve the desired working temperature so that they may be withdrawn from Zone C of furnace l() through slot 14, suitably heated or reheated, `as the case may be.

Combustion air is supplied by a motor-driven blower 38 to a pipe 3S and combustion air header 39 from' which each branch header 36 supplies one of the burners Ztl, respectively. A takeoff pipe 4@ leads into a mixer 41 which also receives fuel gas through a pilot fuel pipe 42, the resulting combustible mix-ture from mixer 4l being 4discharged into a pilot burner manifold 43 from whence through a branch 44 it passes to `a pilot burner 45 which usually is left burning, the flame therefrom passing through a pilot burner opening 46 in port block 19C ready `for the igniting of a combustible mixture produced by burner 20c and discharged into the outer end of the port 21 of port block 19C. Fuel gas for the pilot burner is supplied through a pipe 47, which is tapped into a main fuel gas line 48. A safety valve 47' is interposed in the pilot fuel line and normally kept open by a diaphragm 49 so long as there is sufficient air pressure exerted thereon through a pipe 50 communicating through mixer 41 with pipe 40.

The combustion air line 38 is provided with a safety pressure switch 51 which, in the event that the combustion air pressure drops below the switch setting, will open an electrical circuit through a solenoid 52 in the fuel gas line and automatically shut off fuel gas passing to the burners 30 by closing valve 53. An orice meter 54 in the combustion air branch and an oriiice meter 55 in the fuel gas branch indicate the respective quantities of combustion air and fuel gas used by burner 20c. Moreover, a pressure tap 56 in branch 36 regulates a pressure ratio control valve 57 in the fuel gas branch 58 leading to the fuel gas inlet on burner 20c, the tap 56 being on the downstream side of butterfly valve 35. Hence, the fuel gascombustion air ratio supplies burner 20c with those respective fluids in respective volumes suitable for the formation of |a combustible mixture which burns in port 21 of block 19C.

A high re condition for radiant heating to 4working temperature is produced in any of the zones A, B and C by the pushing of the timer start button 27 momentarily for that zone respectively. Pushing button 27 closes switch 27a and thereby a circuit between power lines 59 and 60 which have a voltage difference therebetween. A solenoid 61 in the momentarily completed starting circuit is thereupon energized and closes a multiple motor energizing switch 61a and 61h. The closing of switch 61a establishes a circuit through conductor 62, switch 61a,

cycle timer motor 63 and conductor 64, which circuit remains closed even though the operator removes his finger from button 27, opening switch 27a. The closing of switch 61b completes a circuit through lamp 26 and energizes a solenoid 65 which controls a 3-way valve 65a and moves it to connect the higher pneumatic pressure in pipe 31 directly to pipe 33, simultaneously shutting off communication between the lower pressure air in pipe 32 and pipe 33. In starting, also, -a lever 53a is manually swung to the position shown in FIGURE 3 to open the fuel gas shut-off valve 53 which, when opened, remains held in open position by the energization of the coil in the solenoid 52 upon ow occurring in mains 38 and 48 closing safety switches 51 and 68 respectively to complete the circuit lthrough solenoid 52 and conductor 69. Solenoid 52 Ias shown has insufficient strength itself to open shut-off valve 53 upon energization unless .and until the lever 53a is first moved as above stated, but when energized it will hold valve 53 open.

Fuel gas is admitted to the main Igas line 4S by the opening of a main valve 66 which once opened normally is left open, the fuel gas passing through an automatic pressure regulator 67 before flowing past safety pressure swtich 68 and valve 53. So long as there is pressure in the main 48 and in air main 38', the respective pressure switches 68 and 51 remain closed completing an electrical circuit through conductor 69 and the coil of solenoid 52 as shown in FIGURE 4. On the other hand, `should the pressure in main 48 or air main 38', respectively, drop below a preselected safe pressure, the respective switch 65 or 51 will open, deenergizing `solenoid 52 and automatically closing the `gas shut-off valve 53. Further, should anything require the early stopping of the work heating firing of any one of the lburners in furnace 10, the respective stop button 28 pertaining to that burner and Zone is pushed breaking the circuit through the respective conductor 62. In its circuit, the opening of such switch Z8 deenergizes solenoid 61, opens the switches 61a and 61b deenergizing the respective timer motor 63 so that the timer resets itself to initial position by spring action as shown by the dial to await the initiation of a new timing period. Further, the opening of switch 61b shifts 3-way valve 65a so that it automatically shuts olf direct communication between pipe 31 and impulse pipe 33 by deenergizing solenoid 65, and simultaneously restorescommunication between lower pressure air from pipe 32, indicated by an arrow in FIGURE 4, and the impulse line 33 to place the respective burner 20 affected in low lire condition to place the zone in question into a condition for holding the temperature of work therein at the then attained temperature. Access of lower pressure air to pipe 33 moves valve 35 to a selected position which is but partly open and correspondingly reduces the quantity of fuel lgas fed to the lburner through valve 57 to achieve such low-lire condition.

In a normal operation, however, it would not be necessary usually to actuate any stop button 28. In that case, `assuming that the control elements of FIGURES 3 and 4 apply to burner mechanism 20c regulating the heating condition of zone C primarily, the timer 25 for that Zone will continue burner 20c on a selected high lire condition, such as the maximum ring rate indicated, until the end of the selected period preset on the time dial, at the end of which the workpieces 23e normally Iwill have reached a desired working temperature. At the conclusion of that lselected preset period, the timer, which is conventional, has mechanism which will trip and open swicth 63a, which will deenergize coil 61 and open switch 61a and 61b. Such will have the same effect as pointed out above in connection with the pressing of the stop button 28l for the particular zone involved, except that in a normal operation there is no curtailment of the heating period. When the timing period has ended and switch 63a has opened, that switch will normally reclose immediately but not before the deenergizing of solenoid 61. Further, burner 20c will move from high tire condition selected for the heating of the workpieces on the hearth 15 in zone C to low tire condition selected to maintain such workpieces at selected working temperature until the handler thereof removes them from furnace 10. When all of the readied workpieces 23C have been removed, then button 27 is repus'hed to start a new selected timing high ire period 4for working temperature radiant heating to heat the newly inserted relatively colder workpieces placed in zone C for that purpose. The burner mechanisms for zones A and B respectively lare connected and operated in the same manner.

It will thus be seen that by means of this invention, relatively independent firing action can be obtained in a furnace having a common furnace space and a variety of work constantly being put into the furnace can be heated and taken out at selected working temperatures Zonally controlled for substantially continuous rotational operation, utilizing time as a regulator.

Various changes and modifications may be made in the illustrated embodiment and other embodiments provided without departing from the spirit of this invention or the scope of the appended claims.

I claim:

1. A temperature controlled forge furnace or the like, comprising, in combination, a common furnace enclosure having a common hearth and an opening for ingress and egress of workpieces placed on and removed from said hearth, a plurality of laterally spaced radiant bur-ners in corresponding heating Zones of said hearth principally overlying correspondingly laterally spaced areas of said hearth, laterally adjacent radiant burners regulating laterally adjoining areas of hearth respectively to provide corresponding heating Zones of said hearth principally controlled by said burners respectively, each said burner during operation at any level supplying radiant heat with its greatest intensity to its corresponding heating zone, timer mechanism for the radiant burners of said zones respectively to provide a selected period for a higher rate of radiant heating of workpieces on said hearth in each respective Zone to raise the temperature of workpieces therein, and means associated with said timer mechanism for automatically ending said higher rate of radiant heat-. ing in a particular zone to maintain the working temperature of such workpieces upon the expiration of said period in that particular zone.

2. A temperature controlled forage furnace or the like, comprising, in combination a furnace enclosure having a hearth and an opening for movement of workpieces in an ingress and egress direction to be placed on and removed from said hearth, a plurality of radiant burners in the roof of said furnace directed toward and overlying laterally spaced areas on said hearth respectively, adjoining said radiant burners regulating adjoining said areas of said hearth respectively to provide corresponding` heating zones principally controlled by said burners respectively, each said burner during operation at any level supplying radiant heat with its greatest intensity to its corresponding heating zone, a timer for the respective burners of said zones to provide a selected period for a higher rate of radiant heating of work-pieces on said hearth in each respective zone to raise the temperature of workpieces therein, means for automatically reducing `said higher rate of radiant heating in a particular zone to a relatively lower rate of radiant heating to maintain the working temperature of such workpieces upon the expination of said period in that particular zone, a higher pressure instrument air source, a lower pressure instrument air source, and an air-gas ratio controller alternatively connectilble to said sources for said higher heating and lower heating operation of said burners respectively.

3. A temperature controlled forge furnace or the like comprising, in combination, a common furnace enclosure having a common hearth for workpieces, a plurality of laterally spaced radiant burners in said furnace directed toward and overlying said hearth with laterally adjacent burners principally determining the respective temperatures of laterally adjoining areas of said hearth to provide corresponding heating zones controlled by said burners respectively, each said burner during operation at any level supplying radiant heat with its greatest intensity to its corresponding heating zone, timer mechanism for respective burners of `said zones to provide a selected period for relatively higher radiant heating of workpieces on said hearth in said respective zone during said period, each said period for cach Zone being individually predeterminable, and means for automatically reducing said radiant heating in each Zone to provide a lower work temperature maintenance radiant heating for workpieces upon the expiration of said period in the respective zone concerned.

4. A temperature controlled furnace or the likey comprising, in combination, a cornrnon furnace enclosure having a common hearth for workpieces, a plurality of laterally spaced radiant burners to burn fluid fuel and combustion air supplied under pressure, said burners being mounted in said furnace and directed toward and overlying said hearth with laterally adjacent burners regulating adjoining areas of said hearth to provide corresponding heating zones controlled by said burners respectively, each said -burner during 'operation at any level supplying radiant heat with its greatest intensity to its corresponding heating zone, a timer for each of said zones operatively connected to its corresponding burner to provide a selected period for relatively higher radiant heating of workpieces on said hearth in said respective zone during said period, each said period for each zone being individually predeterminable, means for automatically reducing said radiant heating in each Zone to provide a lower Work temperature maintenance radiant heating for workpieces upon the expiration of said period in the respective Zone concerned, means for automatically proportioning the ratio of combustion air and iluid fuel fed to said burners, and safety means to shut oi at least said fluid fuel responsive to a predetermined reduction in said pressure.

5. A method of temperature controlling a furnace heating operation or the like, comprising, in combination, respectively heating a plurality of zones in a common furnace enclosure by radiant heat at selectively varied times, positioning a plurality of workpieces at diiferent times in said zones respectively, initiating a selected automatically timed period for the radiant heating of a workpiece in a particular zone at a relatively rapid rate, relatively rapidly heating said workpiece directly by radiant burner heat during said period, automatically turning down said radiant burner heating at the conclusion of said period at least to a relatively lower heat maintaining rate, and continuing not to exceed said lower heat maintaining rate in said particular zone to inhibit excessive further heating of said workpiece.

6. A method of temperature controlling a forge furnace heating operation or the like, comprising, ,in combination, respectively heating a plurality of Zones in a conimon furnace enclosure by correspondingly spaced radiant burner heat, positioning a plurality of workpieces at different times in said zones respectively, initiating a selected automatically timed high-fire period for the radiant heating of a plurality of workpieces in said zones respectively at a relatively rapid rate at selectively varied times accordance with a furnace demand and workpiece Working temperature schedule, relatively rapidly heating said workpieces by radiant heat during said high-tire period, automatically turning down said radiant heat at the conclusion of said period in each said zone at least to a relatively lower heat maintaining rate, continuing not in excess of said lower` heat rate in said zones respectively to inhibit excessive further heating of said workpieces until said workpieces are removed and new time periods are begun respectively, replacing removed workpieces from a particular zone with further ones to be heated, and initiating a further high-tire period in said particular zone.

References Cited in the tile of this patent UNITED STATES PATENTS 1,321,098 Gray et al. Nov. 11, 1919 1,646,976 Norwood Oct. 25, 1927 2,261,904 McDermott Nov. 4, 1941 2,458,624 Morton et al. Jan. l1, 1949 2,693,952 Nesbit Nov. 9, 1954 2,869,845 Selvaggio et al Ian. 20, 1959 2,871,869 Howard Feb. 3, 1959

Claims (1)

1. A TEMPERATURE CONTROLLED FORGE FURNACE OR THE LIKE, COMPRISING, IN COMBINATION, A COMMON FURNACE ENCLOSURE HAVING A COMMON HEARTH AND AN OPENING FOR INGRESS AND EGRESS OF WORKPIECES PLACED ON AND REMOVED FROM SAID HEARTH, A PLURALITY OF LATERALLY SPACED RADIANT BURNERS IN CORRESPONDING HEATING ZONES OF SAID HEARTH PRINCIPALLY OVERLYING CORRESPONDINGLY LATERALLY SPACED AREAS OF SAID HEARTH, LATERALLY ADJACENT RADIANT BURNERS REGULATING LATERALLY ADJOINING AREAS OF HEARTH RESPECTIVELY TO PROVIDE CORRESPONDING HEATING ZONES OF SAID HEARTH PRINCIPALLY CONTROLLED BY SAID BURNERS RESPECTIVELY, EACH SAID BURNER DURING OPERATION AT ANY LEVEL SUPPLYING RADIANT HEAT WITH ITS GREATEST INTENSITY TO ITS CORRESPONDING HEATING ZONE, TIMER MECHANISM FOR THE RADIANT BURNERS OF SAID ZONES RESPECTIVELY TO PROVIDE A SELECTED PERIOD FOR A HIGHER RATE OF RADIANT HEATING OF WORKPIECES ON SAID HEARTH IN EACH RESPECTIVE ZONE TO RAISE THE TEMPERATURE OF WORKPIECES THEREIN, AND MEANS ASSOCIATED WITH SAID TIMER MECHANISM FOR AUTOMATICALLY ENDING SAID HIGHER RATE OF RADIANT HEATING IN A PARTICULAR ZONE TO MAINTAIN THE WORKING TEMPERATURE OF SUCH WORKPIECES UPON THE EXPIRATION OF SAID PERIOD IN THAT PARTICULAR ZONE.

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