US2173586A - Twin annealing oven - Google Patents

Description

Sept. 19, 1939.. c. F. HERINGTQN 1 5 TWIN ANNEALING OVEN Filed Nov. 18, 1956 5 Sheets-Sheet l Sept. 19, 1939. c. F. HERINGTON ;I'WIN ANNEALING OVEN Filed Nov. s, 1936 5 Sheets-Sheet 2 sept. 19, 1939.

c. F. HERINGTON 2,173,586

TWIN ANNEALING OVEN Filed Nov. 18, 1936 5 Sheets-Sheet 4 INVE NTOR Sept. 19, 1939. c. F. HERINGTON TWIN ANNEALING OVEN Filed Nov. 18, 1936 5 Sheets-Sheet 5 Patented Sept. 9, 1939 PATENT OFFICE &173586 TWIN ANNEALING OVEN Cecil F. Herington, Bellevue,

Amco,

Incorporated, Pittsburgh, Pa.,

Pa., assignor to a. coi-poration of Pennsylvania Application November 18, 1936, Serial No. 111,369

2 Claims.

This invention relates to new and useful improvements in apparatus and method of annealing castings, and it is among the objects thereof to obtain a relatively short annealing cycle in the production of maleable iron with the advantages of prompt shipments, reduction in inventories, saving in equipment and increased production Capacity of the annealing equipment.

That the reduction of the malleableizing cycle may be accomplished through better furnace design and atmosphere control to reduce the time for bringing the charge to heat and for cooling, and by the elimination of use of packing materials has been generally recognized, but seemingly ignored in commercial practice.

In accordance with the present invention, a short annealing cycle for' malleable iron is attainable by a twin annealing oven unit, one of which is operated at greater temperature than the other, and both of which are fired from a common heating source, thereby conserving heat and fuel. By transferring the charge from one of the twin oven units to the other without necessitating cooling of the high temperature furnace to the lower temperature desired, the annealing capacity of such furnace is greatly increased and there is little or no time lost in generating the necessary temperature condition in either of the twin oven units.

The invention further contemplates the provision of a system of transfer cars and tracks to facilitate handling of the charges in and around the furnaces.

A commercial form of apparatus for reducing the malleableizing cycle in accordance with the above stated objects is shown in the accompanying drawings constituting a part hereof in which:

Fig. 1 is a half front elevational and half-cross sectional View of a furnace unit embodying the principles of this invention;

Fig. 2 is a horizontal cross-section of the high temperature furnace taken along the line 2-2, Fig. 1;

Fig. 3 a horizontal cross-sectional view of the low temperature furnace;

Fig. 4 a longitudinal vertical cross-sectional View of the high temperature furnace shown in Fig. 2;

Fig. 5 a longitudinal Vertical cross-sectional view of the low temperature furnace shown in Fig. 3;

Fig. 6 a diagram illustrating the annealing cycle; and

Fig. '7 a diagrammatic view of a factory layout showing the arrangement of furnace and track.

While the apparatus shown in the drawings is suitable for annealing in malleable iron or steel foundry practice, the temperature figures hereinafter referred to as illustrating an embodiment of the invention are the annealing temperatures for malleable iron.

With reference to Fig. 1 of the drawings, the furnace unit comprises a suitable base or founda- 10 tion l of concrete upon which is mounted a pair of rails 2 for supporting a. truck 3 constituting the furnace hearth, the truck being mounted on wheeled axles 4 which traverse the rails 2 and the sides of the trucks are provided with a de- 15 pending fiange 5 carrying sand 6, which seals the upper furnace chamber by engagement with a depending fiange element 1.

The furnace chamber is constituted by arched side walls and a roof 9 as shown in the half cross 20 section, which constitutes a mufile chamber heated by the products of combustion which are produced by a gaseous flame introduced through a series of firing ports ID at the sides of the furnace adjacent the top thereof, and a roof 25 structure ll forming a heating chamber with the roof tile 9 of the mufiie into which the products of combustion are delivered. A series of vertical flues l2 constitutes waste gas passages for the products of combustion which are exited through bottom openings l3 in the side walls of the furnace into a waste gas passage M, dampers l5 being provided to control the distribution of heat longitudinally of the furnace by regulating the Volumes of the waste gases withdrawn at any portion of the furnace throughout its longitudinal extent. Control of temperature is also obtainable by the regulation and number of the firing ports o, of which four are shown in Fig. 2 of the drawings in staggered relation to efiect a blanketing of the mufile by a heat fiame extending transversely of the muflie wall.

Both the front and rear of the furnace walls are provided with relatively large openings controlled by doors 16 which are suspended and provided with counter-weights IT to facilitate opening and closing of the furnace doors. The doors are suitably insulated to reduce loss of heat by radiation. The outer furnace wall is reinforced by the usual buck stays !8 and channels 50 |9 to provide a rigid Construction and heavy wall insulation 20 is employed to minimize the fuel input to the furnace.

The construction of the lower temperature furnace of Figs. 3 and 5 is similar to the high temperature furnac described in connection with Figs. 1, 2 and 4 excepting for the absence of the burner ports ID, the heat being supplied through the waste gas conduits !4 which extend from the high temperature furnace to the low temperature furnace and communicate with the heating chamber of the furnace through the 'passages l3a and vertical fiues Iza. combustion chambers 2! may be provided in the space intermediate the high and low temperature urnaces to generate an auxiliary source of heat which is communicated direct to the conduits 14 for delivery to the low temperature furnace through the openings" I3a at the bottom of the furnace, the aggregate waste gases of the two furnaces being removed through a stack 22 which is controlled by a damper 23. The conduits Id are provided with dampers 24 at their respective ends to-regulate the air supply to the low temperature furnace as desiredl- In the factory lay-out diagram of Fig. 7, the arrangement of furnaces and track is shown to be such that the car supporting the castings is moved from a transfer track into' the high temperature oven, thence into the intervening space between the high and low temperature ovens, then to the low temperature oven from which it travels to a transfer track and then a return track to be recharged and again moved through the furnace. The dotted portion of the diagram illustrates an additional installation of a twin furnace unit to provide for increased annealing Capacity with economy of space.

In utilizing the above described apparatus for short malleableizing annealing cycles, the castings loaded on the truck 3 are delivered to the furnace of Fig. 2 of the twin annealing oven unit, wherein it is subjected to temperatures of 1700 F. for ordinary malleableizing, although for some malleable foundries, temperatures as low as 1500 F. may be used and 900 F. is the normal temperature at which the furnace is operated for steel castings. v

By controlling the fuel delivered through the firing ports o and the distribution of the products of combustion by manipulation of dampers !5, a uniform temperature is maintained throughout the furnace chamber, thereby subjecting the charge to uniform heat and the waste gases from the high temperature furnace are withdrawn through passages I 3 into the waste gas Conduit from which they are conveyed into the furnace shown in Fig. 3 which is operated at a temperature of about 1350 F. or otherwise as desired.

The charge is maintained at a uniform temperature of substantially 1700 F. in the first furnace unit, Fig. 2, for a period of about 24 hours after which the car is removed into the intervening space between the two furnaces, and the charge allowed to cool to a temperature of substantially 1250 F. The car with its charge of castings is then moved into the second furnace shown in Fig. 3 and sub-jected to the 1350 F.' temperature for a period of about twenty-eight hours or as desired. The furnaces are thus continually operated since a new charge is placed into the high temperature furnace immediately when the first charge has been removed.

Very little heat is required to bring the charge up to the critical temperature in the second furnace as the charge and supporting truck is already at a temperature of 1250 F. when they are charged into the second furnace.

If the products of combustion from the high temperature furnace have dropped in temperature below the temperature of 1350 F.- required with reference to the diagram of the annealing cycle of Fig. 6 which is for a week of one hundred and sixty-eight hours employing a cycle of sixtyseven hours for each car containing ten to twelve tons of castings. The cycle shows plainly that every thirty-four hours a new load is placed in the first oven and a car removed from the second d oven for unloading. This gives an annealing capacity of two hundred tons of castings a month.

The fuel economy obtainable is dependent on the cost of fuel, oil or gas at the point of use, but by the use of the mufe type oven the manner of firing and control of heat application a saving of more than thirty percent over conventional forms of annealing ovens is possible.

Annealing pots are unnecessary, thus requiring less initial investment in equipment and a reduction in the heat absorption of the mass passing through the furnace. If, however, circumstances require the use of pots, they may obviously be employed with a resultant lengthening of the annealing cycle but with less erosive effect on the pots, which will last indefinitely. If the castings to be annealed are of a kind in which oxidation should be prevented, a cover may be provided for the truck or charge when it is moved to the air cooling space between the twin oven unit.

From the foregoing description of the invention, it will be apparent that substantial saving in time and fuel are available over the conventional type of long cycle annealing ovens in which, after firing has been stopped, cooling is accelerated by opening dampers to drop the temperature to the critical point, which ties-up such furnaces for the entire annealing cycle, and requires reheating of a substantial temperature range when recharged for a subsequent annealing of castings. r

Although one embodiment of the invention has been herein illustrated and described, it will be apparent to those skilled in the art that various modifications may be made in the details of construction without departing from the principles hereinset forth.

I claim:

1. A twin oven unit for annealing castings comprising a pair of heating ovens in tandem having a space therebetween, said ovens having muffle chambers for receiving the charge to be annealed and having outer walls forming a combusticn spacewith the muffie wall, means for introducing a gaseous fuel into the firing chamber of one of said ovens and means for withdrawing the products of combustion through vertical flues at the bottom of said oven, a waste gas condut for delivering the products of combustion to the second of said ovens, said conduit constituting a manifold having a plurality of passages leading to vertical fiues of the second named oven to direct the products of combustion around the mufile of said oven and to a stack at the top of said oven, and means for regulating the distribution of the products of combustion in said ovens to obtain uniform temperatures throughout the heating chambers.

2. A tw'n oven annealing unit comprising a pair of ovens in tandem having a track extending therethrough and being spaced apart to permit exposing the charges to the atmosphere in their travel on said track from one to the other of said ovens, trucks movable on said track and constituting a hearth for said ovens transfer-' able from one oven to the other and having seals for prevention of heat loss through the bottom of the ovens, said ovens comprising a muflie Wall cooperating with the movable trucks to constitute heating chambers, one of said ovens having burner ports above the muffie Wall, and both ovens having an outer wall and roo structure forming a combustion space having vertical ues extending downwardly on the sides of the ovens provided With dampers for regulating the Volume of the gases passing through said flues, and a manifold on the respective sides of said ovens having passages connecting With said fiues at the bottom thereof to remove the products of combustion in regulable quantities from the longitudinal extent of one side of one of said ovens and deliver said gases through the manifold passages to the same side on the other of said ovens.

CECIL F. HERINGTON.

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