US2254891A

US2254891A - Heat-treating furnace

Info

Publication number: US2254891A
Application number: US348725A
Authority: US
Inventors: James H Germany
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1940-07-31
Filing date: 1940-07-31
Publication date: 1941-09-02
Anticipated expiration: 1958-09-02

Description

p 1941- J. H. GERMANY 2,254,891

HEAT- TREATING FURNACE Filed July 31, 1940 2 Sheets-Sheet 1' Ja'mea H Germany MK ATTORNEY p 1941- J. H. GERMANY 2,254,891

HEAT-TREATING FURNACE gl/Z INVENTOR 4 5%; Jamej H, Germany Jaguar 24.

ATTORNEY be further processed for such purposes Patented Sept. 2, 1941 UNITED STATES PAT ENT OFFICE nEAr-raEA'rmc-mmoa James H. Germany, Edgewood, 2a., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh Pa, a corporation of Pennsylvania Application'July 31, 1940, Serial N- 348,725

' 8 Claims. -(Cl. 268-) the gas inlets and gas outlets along the length heat-treating processesrequire a large number of diflerent types of furnaces, each, as a rule, designed to carry out] most efllciently the particular heat-treating process involved; and the furnace in which one particular charge can be heattreated may not be-useful for a different heattreatment of the same or a similar charge. As an example of such a condition, a furnace for annealing a high carbon alloy or tool steel may not be particularly useful for tempering or drawing the same or a similar charge at a relatively low temperature because the former process usually requires heating the charge to temperatures at which heat is transferred predominantly by radiation, while the latter may require heating the charge to temperatures at which heat is ing, the heating and cooling being controllableof the furnace, and by controlling the gas-flow through each or some of them, the furnace can be generally utilized to effect a controlled heating, as, for example, in tempering, or to effect acontrolled cooling, as, for example, in annealso as to uniformly heat-treat the charge.

The recirculation of the gas can be :used during low-temperature heating processes as a convection heat-transferring means for more speedily-and more uniformly heat-treating the charge. In order to use the same conduit system for heattreating processes .in which controlled cooling is required. the gas circulation conduits maybe provided with selectablev branch-passages, one of which includes a'cooler and, if desired, a drier,

so that by suitablemanipulation of valves the recirculating gas'es may be caused to pass through the cooler for-certain cooling steps of annealing processes, or the cooler may be by-passed durtransferred most efficiently and effectively by primary object of my invention to provide a single furnace of more general utility than prior 7 furnaces of the same general type.

It is a more specific object of my invention to provide a furnace in which aplurality of controlled'heat-treating processes can be carried out for the heat-treatment of steeior the like, which processes include, for example, annealing, normalizing and tempering.

It is a general object of my invention to include in cheat-treating furnace, provisions for recirculating a gas, or air, or an atmosphere of controlled composition through the heat-treat-. ing chamber of the furnace in such-manner that the gas flows in paths substantially transverse to the length of the heat-treating chamber.

Preferably the gas is recirculated by a blower parts omitted for clarity outside of the furnace proper-and by distributing 5 5 ing heating steps of a heat-treating process.

It is an additional object of my invention to provide a bell furnace of the type having a separable base and bell, th bell being provided with a gas circulating system entirely supported by it so that duct-connecting and duct-disconnecting are not required during the raising or lowering of the bell, the gas circulating conduit system being raised or lowered with the bell as a unit.

The objects, advantages andapplications of my invention are numerous and generally embrace those indicated as well as others not speciflcally mentioned, which will be apparent from the following descriptionwhich is to be taken in conJunctionwith the accompanying drawings, in which:

Figurel is an elevational view, partly in vertical section, of the essential features of a furnace embodying my invention;

Fig. 2 is a top plan view of the furnace 3 is a transverse vertical sectional view of thefurnace: I Fig. 4 is a fragmentary top plan view of a modifled form of furnace embodying my invention with parts omitted for clarity of illustration; and Fig. 5 iso. sectional vlewsimilar to Fig. 3 of a furnace embodying my invention, the furnace having provisions for transmitting a controlled atmosphere to, and bleeding it from, the heattreating chamber of the furnace.

Referring more particularly to the drawings,

the furnace shown is of the bell type comprising a raisable and lowerable bell indicated in its enwith operating position resting on a car base indicated in its entirety by the reference character 4; the bell being provided with suitable eye-bolts or the like by means of which it may be lifted to enable the, car base to be rolled inposition below it or removed after the heat-treating process for the reception of another car base or the same car base after reloading with a second charge.

The car base 4 comprises a metallic base plate 6 around the periphery of which is gas tightly secured a sealing trough 8. The base plate supports refractory and insulating tile l8 constructed and arranged to contain troughs l2 in which may be disposed base heating elements H. The refractory tile also supports a plurality of heat-resistant alloy hearth sections I8 each being provided with side legs l8 and an upright between the legs, the upright having suitable reinforcing ribs 22 between enlarged holes 24 in the upright. Each hearth section has a horizontal hearth plate 28 between the legs and on top of the upright, and as may be observed from Figs. 1 and 3, the arrangement of the hearth sections is such that the hearth can support bars of various lengths. The car base includes spaced trucks 28, each having wheels 30 adapted to ride on rails 32 for movement into and out of position beneath the raisable bell 2.

The refractory tile of the car base is stepped along its edges for the reception of the walls of the bell 20 which is provided with a heavy supporting peripheral base-frame 34. The bell 2 further comprises end walls 36, side walls 38 and a top wall 39, the walls being constructed of insulating and refractory tile in a customary, manner and defining a heat-treating or heattreatment chamber 4| in conjunction with the car base. The walls are encased in an outer metallic casing or shell 40, and suitable structural steel channels 42, secured to the.supporting base-frame 84, extend upwardly above the top of the bell walls. A sufllcient number of these channels are provided along the outside of the bell to provide, in conjunction with transverse top channels 44, a strong and rigid bell structure, the top channels 44 also serving to support the gas circulating system to be later described. Depending from the base-frame 34 is a sealing flange 48 cooperating with the trough 8 to provide a gas-seal between the car base and the bell when the trough is filled with a suitable sealing means such as oil 48.

The furnace is heated by means of the bottom heating units l4 and additional heating units 5|! mounted along the length of the inside of the side walls and 52 on the end walls. In Figs l, 3

and 5, Heating elements have been omitted forclarity of the illustration. The heating units are preferably divided into separate controllable zones along the length of the furnace selectively energizable to controllable. degrees.

Gas is circulated in substantially transverse orbits in the heat-treating chamber 4| by forced drafts created by a blower 54 driven by a motor 56. The blower discharges into a distribution manifold 58 which extends longitudinally across the top of the bell. A plurality of discharge ducts 80 branch from this manifold at spaced distances along its length and extend downwardly through the top wall 38 to provide a discharge of gas at the top of theheat-treating chamber 4|. Attached to the gas discharge opening of each of these ducts is a flow-distributing device 82 comprising a bottom spreader tirety by the reference character 2, the bell in plate 84 spaced from the end of the associated duct 60 and secured thereto by a plurality of small supporting members 68. The gas is discharged at the top of the chamber 4| at 'a plurality of points along its longitudinal center by the spaced discharge ducts 60, and is withdrawn from along the bottom of the chamber by means of a plurality of outlet ducts 68 and. 10, the outlet ducts 68 being associated with one of the side walls 38 and the outlet ducts 18 being associated with the other side wall.

The alternate outlet ducts 68 and 10 are staggered with respect to each other and with respect to the discharge ducts 60, and it is obvious that the gas discharged ,by the discharge ducts will be spread by the spreaders 64 and will flow downward to the outlet ducts 68 and 10, the holes 24 in the hearth sections facilitating the distribution and flow of the gas about the charge. The outlet ducts 68 and I0 extend through the side walls and upwardly along the walls to connect to a suitable exhausting system leading to the intake of the blower- 54. This exhausting system comprises an exhaust collector pipe 12 substantially paralleling the intake distribution manifold 58 and receiving the gas flowing through the outlet ducts 68 and 10.

The ends oi. this pipe 12 are closed but substantially centrally thereof a pair of paralleled branch duct-passages is provided which ultimately come together and lead to the intakeof the blower 54. One of these branch passages includes an air-conditioning means, while the other lay-passes this air-conditioning means so that the gas flowing in the exhaust collectorpipe 12 may be directly led to the blower without air-conditioning treatment or may be led to the blower after traversing the air-conditioning branch wherein the gas may be treated in any desired manner. To this end a duct 14 leads from the exhaust collector pipe 12, the duct 14 being connected to two branch duct-passages 16 and 18, the duct-passage 18 including a heatexchange unit in the form of a cooler 80. The two duct-passages rejoin near the blower intake. Valves 82 are provided at the gas intake and gas outlet of the cooler for controlling the gas-flow through the branch duct-passage l8, and a similar valve 84 controls the gas-flow through the branch duct-passage 18; the valves being suitably controlled through suitable mechanical

connections including handwheels

86 and 88 on the sides of'the bell, the adjustment of the valves being indicated by an indicating means including stationary indicating scales 80 behind the handwheels and suitable indicating pointers on the handwheels.

The discharge ducts 60 are each provided with gas-flow control means in the nature of handoperated valves controlled by handwheels 82 provided with pointers cooperating with scales on stationary back plates 84 for indicating the adjustment of the gas-flow through the associated discharge duct.

1 A furnace such as described has general utility I for heat-treatment of metals or the like, and in operation a charge is loaded on the car base by any suitable means, the charge-supporting hearth being particularly adapted in this case within the trough 8 and as soon as the bell is in position, oil may be pumped into the trough to seal the heat-treatingchamber. The furnace is then ready for heat-treatment and can be utilized for any one of the number of different heattreatment purposes. For example, in the event a charge having a length substantially equal to the length of the heat-treating chamber 4I is to be annealed, a process usually involving heating to ranges about 1700-1900" F. and subsequent controlled cooling, the heating elements are suitin the branch duct-passage 16 for the purpose of drying a controlled atmosphere fed to the furnace by a plurality of pipes I02 distributed alongthe bell ably energized, and-zone-controlled 9 bring the temperature up to the-proper point.

For cooling a heated charge, or subsequent cooling of a preheated charge, the valves 02 and 84 may be manipulated so that recirculation of the atmosphere may be utilized to cool the charge,

it being understood that energization of the blower motor is suitably controlled in the discussion of these processes, a switch 99 being shown in Fig. 4 in the energizing leads of the motor, as representative of motor-controlling means.

By controlling the operation of the blower motor, or the relative open and closed positions of the

valves

82 and 84, or the flow of the refrigerant or cold water through the cooler 80, or

any combination of these, the degree of cooling.

. the chamber can b'e'controlled as desired, the temperatures being indicated by any suitable thermal-responsive means in the customary manner. Such thermal responsive means may also be utilized, if desired, to automatically control the heating elements or the position of the valves in the various ducts as is known to one skilled in the art.

A furnace such as described can be utilized for annealing with controlled cooling, or for normalizing or for tempering various products. Incase the furnace is used for tempering, which involves temperatures generally in the range of approximately 900 to 250 F., the cooling duct-passage I6 is closed, and duct-passage I8 opened so that the atmosphere in the chamber 4| is continuously recirculated for effecting a rapid and uniform transfer of heat to the charge by convection.

It is desirable for the general utility of my furnace to lag or heat-insulate the distributing manifold 58, the distributing duct 60, the outlet ducts 68 and 10,- the exhaust pipe 1.2, and the duct-passage 78 to make the furnace more efficient. during tempering operations. This might entail a slightly larger cooler than would be the case if these pipes were not heat insulated as is the present practice, but the slightly larger cooler represents an insignificantly increased fraction of the cost of theextra furnace for tempering, which my invention makes unnecessary. 7

in Figs. 4 and 5, I show modified forms of furnaces in which the air-conditioning means includes, in addition to the cooler 80, a drier I00 and leading from along amanifoldl04 fed with protective atmosphere by a flexible connection I06 connected to suitable atmosphere producing equipment. A bleeder arrangement comprising a few pipes I08 extends from'the top of the chamber M to a manifold IIO from which extends a pipe terminating in a burner tip or in proximity to avacuum exhaust system H2. A valve'f'll 4 controls the supply of the controlled atmosphere to the furnace and a valve I16 controls the amount of atmosphere bled from the furnace since in usual practice it is desirable to continu ally feed a small amount of atmosphere to the heat-treating chamber 4| in order to maintain the atmosphere pure and clean. However, it must be understood that the amount of controlled atmosphere fed to the furnace is very small com- .pared to the rate at which the atmosphere is circulated by the blower 54. Thus, for one particular design during a controlled cooling operation, the blower recirculated the gas at the rate of approximately 1000 cubic feet per minute, whereas the controlled atmosphere supplied was at the .rate of approximately 10 cubic feet per minute.

It should be understood, of course, that in preparing the furnace for heat-treatment with a controlled atmosphere in the heating chamber, it is first necessary to purgethe furnace and conduit systems.

The drier I00 in the furnace modification shown in Fig. 4 is especially useful with certain furnaces employing non-decarburizing gases as protective or controlled atmospheres since it is desirable in such cases to remove watervapor from the atmosphere in order to maintain a low dew point.

In accordance with the objects of my invention, I have described a furnace of general utility in which charges of various lengths can be uni formly heat-treated in accordance with a selected number of different heat-treatment processes, and while I have shown preferred forms of fur-. naces'embodying my invention, it is obvious that;

many changes may be made and equivalents subg,

, substantially surrounded by a recirculating gas comprising a base including a charge-supporting hearth; a removable insulated heating bell for said base cooperating therewith to provide a heat-treating chamber; heating means for heating said heat-treating chamber, said heating means having surfaces for emitting heat and being of the type which does not introduce combustion gases into said chamber for heating, said heating means being supported by said bell; a blower secured to the outside of said .bell; conduit means secured to the outside of said bell for providing gas-flow paths to and from said blower for' recirculating gas from and to said heattreating chamber with said gas passing in direct contact with said surfaces of said heating means, said conduit means including gas-conditioning means comprising a cooler, said conduit means including by-pass ducts for said cooler and valve means for causing the gas to flow through said cooler or said by-pass ducts, said conduit means being supported by said bell, and having gasinlet and gas-outlet openings in said bell at said heat-treating chamber, whereby said bell. with said conduit means may be raised from and lowered on said base as a unit.

2. A heat-treating bell furnace adapted for heat-treating a charge while substantially enveloped by a recirculating gas, comprising an elongated base including an elongated substantially rectangular charge-supporting hearth, an elongated substantially rectangular heating bell cooperating with said base to provide a heattreating chamber, said base and said bell being.

separable, heating means for heating said heattreating chamber, gas-conduit means including a blower, for providing gas-flow paths to and from said blower for recirculating gas from and to said heat-treating chamber, said gas-conduit means including a branch passage having therein a gas-conditioning means comprising a cooler, valve means for controlling the flow of gas through said branch passage, said gas-conduit means including a plurality of ducts having a series of gas-inlet openings and a series of gasoutlet openings at said heat-treating chamber,

the openings of one of said series of openings being spaced along the length of said bell at the top thereof, and the openings of the other of said series being spaced along the length of said bell near the bottom of the sides thereof, the last said series of openings being staggered with respect to the said one series of openings, and means to control the flow of gas through said ducts.

3. A heat-treating furnace device comprising, in combination, an elongated structure comprising walls defining a heat-treating chamber having an elongated charge-supporting means therein, gas-conduit means for recirculating gas in gas-flow paths including portions in said heattreating chamber, said gas-flow path portions being generally transverse to the length of said heat-treating chamber, said gas-conduit means including agas-propelling means, and gas-distributing ducts providing a series of spaced gas-inlet openings and an Tassociated series of spaced gas-outlet openings at said heat-treating chamber, the openings of one of said series of openings being spaced along th length of said chamber near the top thereof, and the openings of the other of, said series of openings being spaced along thelength of opposite walls of said chamber near the bottom thereof, for causing the gas-paths from said gas-inlet openings to include portions flowing directly from each gas-inlet opening to proximate gas-outlet openings.-

4. A heat-treating furnace adapted for various heat-treating processes involving heating or cooling a charge, or both, comprising an outer heatresistant structure including walls defining a heat-treating chamber having a charge-supportoutlet openingsdistributed in said walls along the length thereof, and means for distributing the flow of the gas through said openings.

5. A heat-treating furnace adapted for various heat-treating processes involving heating or cooling a charge, or both, comprising a heat-resistant structure including wallsdefining an elongated heat-treating chamber, a hearth in said heat-treating chamber upon which a charge is adapted to be supported, said hearth having substantially transverse passages for the flow of gas, heating means in said heat-treating chammeans comprising gas-propelling means outside said structure and gas-ducts providing a series of spaced gas-inlet openings and a series of spaced gas-outlet openings for said heat-treating chamber, one of said series being staggered with mg hearth; heating means in said'heat-treating chamber, said heating means having surfaces for emitting heat and being of the type which introduces no combustion gases into said heat-treating chamber for heating, said heating means being supported by said walls; a blower outside said structure; conduit means for providing gas-flow paths to and from said blower for recirculating gas to and from said chamber with the gas passing in contact with said surfaces of said'heating spaced gas-inlet and a plurality of spaced gasrespect to the other of said series.

6. A heat-treating furnace adapted for various heat-treating processes involving heating or in contact with said surfaces, said'gasconthiit means comprising gas-propelling means outside said structure and gas-ducts providing a series of spaced gas-inlet openings and a series of spaced gas-outlet openings for said heat-treating chamber, one of said series of openings being near the top of said structure and the other of said series being near the bottom of said structure.

'7. A heat-treating furnace adapted for various heat-treating processes involving heating or cooling a charge, or both, comprising a heat-resist- I ant structure including walls defining an elongated heat-treating chamber, a hearth in-said heat-treating chamber upon whicha charge is adapted to be supported, said hearth having substantially transverse intercommunicating passages for the flow ofgas, heating means in 'said heat-treating chamber having surfaces for emitting heat, said heating means being of the type which introduces no combustion gases in said heating chamber for heating, gas-conduit .means for recirculating a gas in gas-flow paths including said heat-treating chamber and said passages, the gas passing in contact with said surfaces, said gas-conduit means comprising gaspropelling means outside saidstructure and gasducts providing a series of spaced gas-inlet openings and a series of spaced gas-outlet openings for said heat-treating chamber, one of said series of openings being near the top of said structure and the other of saidseries being near the bottom of said structure, with one series in stag-' gered relation to the other series.

8. A heat-treatingfurnace adapted for various heat-treating processes involving heating or cooling a charge, or both, comprising a heatresistant structure including walls defining an ing chamber and said passages, the gas passing l5 in contact with said surfaces, said gas-conduit means comprising gas-propelling means outside said structure and gas-ducts providing a series of spaced gas-inlet openings and a series of spaced gas-outlet'openings for said heat-treating chamber, one of said series of openings being near the top of said structure and the other of said series being near the bottom 01 said structure, said gas-conduit means further comprising a gasconditioning means, by-pass ducts for by-passing' said gas-conditioning means, and valve means for controlling the flow of gas through said gasconditioriing means and said by-pass ducts.

JAMES GERMANY.