US2145074A

US2145074A - Metal treating fuknace and methob

Info

Publication number: US2145074A
Authority: US
Publication date: 1939-01-24
Anticipated expiration: 1956-01-24

Description

METAL TREATING FURNACE AND METHOD Filed Feb. ll, 1936 5 Sheets-Sheet 2.

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5m. 24, 1939, H. A, DREFFEN 2,145,074

METAL TREATING FURNACE AND METHOD Filed Feb. ll, 1936 3 Sheets-Sheet 3 Patented Jan. 24, 1939 UNITED STATES FATENT OFFICE 7 Claims.

This invention relates to annealing furnaces and has more particular reference to a furnace for heat treating metal sheets, strips, coils, plates, and similar members under desired atmospheric conditions in the furnace and to a novel method of annealing.

An important object of the invention is the provision of a novel and an improved furnace of the movable bell type.

Another important object of the invention is the pro-vision of a movable work enclosing shield or shell within such a furnace, so constructed and arranged that desired atmospheric conditions may be established and maintained therein.

A further important object of the invention is to provide a pressure stabilizing or compensating seal for preventing, or at least minimizing, the infiltration of air or other undesirable gases or mixtures thereof into the work enclosing shell if or when, during the operation of the furnace, a pressure differential occurs between the inside and the outside of the shell.

An additional important object of the invention is to provide such a seal for minimizing interference between convection currents in the work enclosing shell by the occurrence of a pressure differential between the inside and the outside of the shell, whereby to promote the efficient heat distribution and circulation within the shell.

Another important object of the invention is to provide work supporting means constructed and arranged to promote a uniform distribution of heat by convection in the work enclosing shell, whereby work on the supporting means in the shell will be heat treated on all sides.

Further important objects of the invention include the provision of a direct-fired annealing furnace of the movable bell type; a movable work enclosing shell within and spaced from the fur- 40 nace to provide a combustion chamber therebetween; a base for accommodating the furnace and the work enclosing shell; a seal between the base and the furnace; a pressure regulating seal between the base and the work enclosing shell; work supporting means on the base in the shell providing heat passages under the work for uniformly distributing the heat about the work; burner means arranged in the combustion chamber to direct the flame downwardly, and at such a level that the discharge pressure of the burner means will project the ame to adjacent the base for supplying maximum heat at the bottom of the combustion chamber and permitting the heat then to circulate about the work enclosing shell; such burner means in the combustion chamber (Cl. 26S-5) being adjustable for providing the proper amounts of heat in the furnace at the beginning, during, and at the end of the heat treatment operation; and a novel method of annealing in a movable furnace with a work enclosing shell therein by establishing desired atmospheric conditions in the annealing chamber, sealing that chamber to maintain such conditions, and directly firing the furnace.

Other objects of the invention will be apparent from the following description, and from the accompanying drawings, in which similar characters of reference refer to similar parts throughout the several views.

In the drawings,

Fig. 1 is a plan view, partially in section, of a furnace embodying the features of the invention;

Fig. 2 is a side elevational vie'w partially in cross section, of the furnace shown in Fig. 1;

Fig. 3 is an end elevation, partially in section, of the novel furnace;

Fig. 4 is a diagrammatic sectional view of the furnace shown in the preceding figures, and illustrates the assembly of the novel furnace;

Fig. 5 is a fragmentary detail of a slightly different form of seal from that shown in Fig. 2;

Fig. 6 is an elevational view partially in section, of one of the burners employed in the novel furnace, and showing certain details of construction and assembly;

Fig. 7 is an elevational View of the inlet end of the burner shown in Fig. 6;

Fig. 8 is a cross section taken substantially along the lines 8 8 of Fig. 6;

Fig. 9 is a cross section taken substantially along the lines 9-9 of Fig. 6; and

Fig. 10 is a fragmentary cross section taken substantially along the lines Ill- Hl of Fig. 8.

Illustrative of the invention, the novel furnace of the invention as shown in Figs. l to 3, may be briefly and generally described as comprising a base l5, work supporting means i6, on the base for supporting, for example, metal sheets l1 to be treated, a work enclosing shell or shield I8 for providing a treating chamber i9 about the work, and a movable furnace 2| of the bell type, arrangeable on the base l5 about, and in spaced relation with, the shell I8 for providing a combustion chamber 272 about the shell.

The base i5 is constructed to provide a foundation 23 of suitable construction, a foundation covering 24 of any suitable insulating or refractory material. and a retaining structure preferably of metal sheets 25, channels 26, and corner or angle members 2l, arranged about the sides of the base and extending to a level above that of the insulating base covering 24. Such a base may, as .shown in Figs. l to 3, be rectangular in top plan View and is adapted to carry thereon, if desired, furnace aligning pins or studs 23 fixed in diagonally opposite corners of the base i5 and extending upwardly therefrom for engaging in apertured brackets 29 correspondingly positioned on the movable furnace 2l during the assembly of the furnace on the base.

The work supporting means it may be generally rectangular in plan, of smaller plane dimensions than the base, and is constructed and arranged centrally thereof. t comprises a mounting layer 3! of insulating or refractory material carrying thereon a metal pan 32 with upstanding sides 33 spaced inwardly of the metal sheets 25 and providing or dening therewith a trough or channel 3d circumscribing the sides 3S of the pan 32 for carrying an appropriate sealing agent 35. In and centrally of the pan 32 a plurality of spaced upstanding members of insulating or refractory material carry a work supporting metal plate El. The members Sii are arranged to extend Itransversely of the 32 beginning and ending at positions respectively spaced inwardly from the end sides 33 of the pan and are 0f such length that their opposite ends are spaced inwardly from the longitudinal sides of the pan. Thus a trough or channel 35 is provided between the sides of the pan and spaced members 36 for carrying a suitable sealing agent 3*.

The work enclosing shell I8 is of metal construction With side walls di, end walls LZ2, and a top or roof 43, and is provided with eyelet means lil to facilitate positioning the shell on the base and removing it therefrom. The dimensions and configuration of the shell iii are such that the side walls are receivable in the channel 35 between the sides of the pan 32 and the members 36.

For cooperating with the sealing agent 39 to provide a seal about the lower edges of the shell i3 between the treating chamber i9 and the combustion chamber 2 2, the lower marginal portions of the side and end walls 4i and 42 are constructed to provide one (see Figs. l to fi) or more (Fig. 5) sealing spaces or passages 45 receivable in 'the channel 3B. Such a passage or such passages may be provided at the lower peripheral margin of the shell i8 by a flange-like member conforming to the configuration of the shell and connecting therewith above the lower edges of the side and end walls. Such iiange-like member is provided with an outwardly extending portion 46 and, connecting therewith, a depending portion 47 spaced from the walls of the shell i8 to provide one passage iii or, if desired, a plurality of spaced depending portions 4S (Fig. 5) connecting with the outwardly extending portions 6 and spaced from the walls of the shell i8 to provide a plurality of the passages 4E.

The movable furnace 2i comprises two side walls fle, two end walls 5l, and a roof or crown constructed of a suitable refractory material in a metal casing that is reinforced by a suitable frame or superstructure Eil. In the roof or crown are provided a plurality of flue openings 55, and suitable eyelet means is constructed on the superstructure or frame 54 to facilitate positioning the furnace on the base and removing it therefrom. The dimensions and configuration of the movable furnace 2l are such that the walls 49 and 5i thereof are adapted to seat in the trough or channel 34 for cooperating with the sealing agent 35 to provide a seal about the bottom of the movable furnace between the inside and the outside of the combustion chamber 22.

A plurality of individual burners 5l' are arranged in the combustion chamber 2 above the bottom thereof and project through the side walls i9 of the furnace 2i. At their outer ends the burners 5l are provided with suitable connections liil communicating with a fuel supply mann fold 5S' and with connections Si communicating With a supply pipe 62 for supplying air for combustion to tie burners. Those burners El' are respectively associated at their ends in the combustion chamber 22 with individual hoods 63 of suitable refractory material and secured in any desired manner over the burners along the walls 49 in the combustion chamber to provide a downwardly extending passage iid for each burner, communicating at its lower end with the com.- bustion chamber.

In determining the position of the burners 5': above the bottom of the combustion chamber 22 in the direct-fired, movable furna the burner discharge pressure is considered and. the burners are arranged at such a height that the pressure employed will carry the flame to adjacent the bottom of the combustion chamber for supplying the maximum heat where it is most needed. If the burners are too near the bottom for the pressure employed, the sealing agent 3S may be disturbed with the result that combustion products or gases may pass from the combustion chamber into the treating chamber and deleteriously affect the work. If, on the other the burners are too high, the heat at the bottom of the coinbust'ion chamber may be considerably less than the heat at the top thereof with the result that all of the work is not uniformly heated. i have .found that the best results are obtained when the burners are arranged, with reference to the discharge pressure thereof, at such a distance above the bottom of the combustion chamber 22 that the burner flames will just barely reach thc bottorn of the combustion chamber.

While the burners 5l may be of any suitable construction, the ends of the invention are best served by employing multi-nozzle, adjustable burners of the type illustrated in Figs. 6 to i0. Such burners have the additional advantage of facilitating the bringing of the furnace up to proper heat conditions after which the heat sup- Y plied may be adjusted to a value for maintaining such conditions. Each such burner 5l, accordingly, comprises an outer an` supply fixture 65, an inner fuel supply xture and an assembly head or fixture 61 provided with a closure meinber 63 at its outer end. That assembly head 61 serv-es as a mounting for the air supply fixture 65 and the fuel supply fixture G5. For that purpose the assembly head has adapter fixture Eil connectible in communication with one of the connections Sill and extending through the closure member $8 for connection at its other end to the fuel fixture Sii; and communicating connecting portions 'il and i2. The connecting portion 'ii of each assembly head is connectible to one of the connections 6l. and the connecting portion 'l2 is connected to the air xture 65.

The air xture 55 is provided near its inner or discharge end with a plurality of discharge apertures or orifices i3 of the same or different sizes and, respectively aligned therewith are a plurality of fuel discharge apertures or orifices 74 of the same or different sizes in the fuel fixture 66. By such a construction, fuel supplied to the fuel xture 66 may be discharged through one or more of the orifices 14, mixed with air supplied to the air fixture B5, and the combustible mixture discharged through one or more of the orifices 73. For adjusting the fuel and air supplied by the novel burner, a slidable valve member 'I5 is arranged in the air fixture 65 between the inner wall thereof and the outer wall of the fuel fixture 65. That valve member 'I5 is constructed to provide a surface I6 for closing an orifice 'I3 in the air fixture 65 and a surface 'I'I for closing an orifice 'I4 in the fuel fixture 85 when the valve member is moved longitudinally of the burner in one direction, and to open those orifices when the valve member is moved in the opposite direction.

Valve operating means in the form of a reciproca-ble rod 'I8 is secured as at 'I9 to the valve member 'I5 and extends outwardly therefrom, longitudinally of and between the coaxial fixtures 65 and G6, through the closure member 88, outside of which the rod 'I8 is guidably supported in a bracket 8| suitably secured tothe assembly head 61 and is provided with means 82, for limiting the reciprocable movement of the rod. Each hood 63 may be provided with a bayonet slot 83 for cooperation with a lug 84 on each burner for holding the hood in position.

For establishing the desired atmospheric conditions in the treating chamber IB, I provide means, diagrammatically illustrated at 85 in Figs. 1 to 4, which provides communication between the inside and the outside of the chamber. Means, diagrammatically illustrated at 85, provides communication between the inside and outside of the sealing spaces or chambers 45 for establishing the proper atmospheric conditions therein for maintaining the atmospheric conditions in the treating chamber.

In operation, the sheets I'I or other work to be treat-ed is placed on the work supporting plate 37 of the work supporting means I6, and an overhead crane is employed to lower the work enclosing shell I8 and the movable furnace 2I to their respective positions on the base I with the shell I8 inwardly of and spaced from the furnace 2l, thus forming the treating chamber I9 inside of the shell and the combustion chamber 22 between the shell and the furnace. In thus assembling the novel furnace, the sealing chambers about the lower marginal portions of the shell I8 are positioned in communication with the means 86 for establishing the proper atmospheric conditions in the sealing chambers, and the sealing agent 38, for example, sand, may be tamped in the channel 39 about the outer depending walls of the sealing chambers. The lower edges of the furnace 2| seat in the channel 34, and the sealing agent 35 is employed to seal between those edges and the bottom of the channel.

After the furnace has been assembled on the base I5, the

means

85 and 86 may be employed for providing the desired atmosphere in the treating chamber I9 and in the sealing chamber 4.5 thereabout, for example, a suitable gas such as coke producer gas, deoxidized natural gas, or any atmosphere for protecting or desirably aecting the work, may be supplied to or established in the treating and sealing chambers by the

means

85 and 86. When the desired atmospheric conditions have been reached in the treating chamber, the means 85 may be adjusted in any well known manner to: reduce or to terminate its action in supplying'gas to or establishing other desirable atmospheric conditions in the treating chamber, whereupon the means 86, cooperating with the sealing chamber 45 and the sealing agent 39, effectively seals off the treating chamber for maintaining the atmospheric conditions established therein.

With such sealing means about the treating chamber, if a pressure differential between the outside and the inside of the treating chamber is caused by, for example, temperature variations, variations of pressure in the combustion chamber 22 due toy combusti-on conditions therein, or to changes in the air and/or fuel supply pressures, or whatever the cause, that pressure differential will not produce the objectionable pressure oscillations about the lower edges of the shell I8, or if such pressure oscillations are produced, they will not result in a transfer of combustion gases or atmosphere from the combustion chamber into the treating chamber because the atmosphere in the sealing chamber 45, being under pressure, acts first to oppose the infiltration of gas from the combustion chamber into the sealing chamber, and secondly to provide an atmosphere that protects or otherwise desirably affects the work if any gas from the sealing chamber should be, by displacement from gas seeping therein from the combustion chamber, transferred into the treating chamber.

During the first step of the heat treatment, the burners 5'1 along opposite sides of the movable furnace ZI may be operated with all of the discharge orifices 'I3 and 'I4 open until the furnace is brought up to the desired temperature, whereupon the reciprocable rods 'I8 may be pushed inwardly to the position shown in Fig. 6 to move the slidable valve members 'I5 to a position for closing a sufficient number of the aligned orifices I3 and I4 for adjusting the heat supply to a value suicient to maintain the desired heat conditions in the furnace.

It will be seen that the flames from the burners 51 will be directed downwardly toward the bottom of the combustion chamber for supplying heat where it is most needed, and the heat thus supplied may circulate in the combustion chamber about the shell I8 for heating the work therein. As the atmosphere in the treating chamber within the shell I8 is thus heated by the directfired furnace 2 I, heat distribution may be effect? ed by convection under the work between succeeding spaced members 36 andy on all sides of the work for effective and eicient heat treatment thereof.

Thus, by directly firing the furnace, heat transfer losses are minimized. 'Ihat desirable result is made possible by the novel and effective seal between the combustion and treating chambers, which insures the maintenance of proper atmospheric conditions in the treating chamber without, or at least with only a minimum of, contamination by gases having a deleterious effect upon the work seeping into the treating chamber. The sealing means and the direct firing thus cooperate with the n-ovel burner and the means for permitting a uniform circulation of heat in the treating chamber for efiiciently heat-treating the work therein.

While I have illustrated and described a preferred embodiment of my invention, many modications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details set forth but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A furnace comprising a base, a work enclosing shell mounted on said base and providing a treating chamber in the shell, a shell enclosing bell removably mounted on said base about and in spaced relation with said shell for providing a combustion chamber in said bell about said shell, a burner in a side wall of said bell and having adjustable outlet means in said com- 'bustion chamber and having inlet means outside of said bell, and means extending outside of said bell for adjusting said adjustable outlet means.

2. A furnace comprising a base, a movable work enclosing shell thereon providing a treating chamber about the Work and having a sealing chamber adjacent the base and surrounding the shell, a movable shell enclosing bell on the base about and in spaced relation with the shell for providing a combustion chamber in the bell about the shell, and a plurality of multi-nozzle burners in the combustion chamber.

3. A furnace comprising a base, a movable work enclosing shell thereon providing a treating chamber about the work and having a sealing chamber adjacent the base and surrounding the shell, a removable shell enclosing bell on the base about and in spaced relation with the shell for providing a combustion chamber in the bell about the shell, a plurality of burners in said combustion chamber, adjustable means in said combustion chamber for adjusting each said burner, and means outside of said combustion chamber for adjusting said adjustable means.

4. In a furnace of the movable bell type, a treating chamber, a combustion chamber around said treating chamber and separated therefrom, burner means having a plurality of burner outlets in said combustion chamber to direct flames, and burner outlet control means in said combustion chamber andy operable from outside thereof for controlling said burners.

5. In a furnace, a base, a movable outer bell, an inner bell spaced from said outer bell to provide a combustion chamber therebetween, and burner means in said combustion chamber above said base and directed downwardly for providing a plane that extends barely to the bottom of said combustion chamber.

6. In a furnace of the movable bell type, a treating chamber, a combustion chamber separated therefrom and surrounding said treating chamber, and downwardly directed burner means arranged in said combustion chamber so that with reference to the discharge pressure of said burner means the flames therefrom will barely reach the bottom of the combustion chamber.

7. In a furnace of the movable bell type, a method of heat treatment which comprises providing a treating chamber in and separated from a combustion chamber, forming a sealing chamber around the bottom of the treating chamber and between it and the combustion chamber, establishing a work affecting atmosphere in the sealing chamber, directly firing the combustion chamber, and extending the flame downwardly barely to the bottom of the combustion chamber.

HENRY A. DREFFEIN.