US2479814A

US2479814A - Annealing furnace

Info

Publication number: US2479814A
Application number: US637012A
Authority: US
Inventors: Cone Carroll
Original assignee: Surface Combustion Corp
Current assignee: Surface Combustion Corp
Priority date: 1945-12-22
Filing date: 1945-12-22
Publication date: 1949-08-23
Anticipated expiration: 1966-08-23

Description

Aug. 23, 1949. c. CONE I 2,479,814

' ANNEALING FURNACE Filed Dec. 22, 1945 g Maw; $41M Patented Aug. 23, 1949 2,473,814 smmauno runmca CarrollCone, near Toledo, Ohio, assignor to Surface Combustion Corporation, Toledo, Ohio, a

corporation of Ohio v Application December 22, 1945, Serial No. 637,012

The present invention relates to the annealing of metal strip in coils and has for its object to provide a furnace which shall be particularly well adapted for annealing such material.

For a consideration of what I believe to be novel and my invention, attentign is directed to the following specification and the claims appended thereto.

In the drawings- Fig. 1 is a vertical section through the improved furnace.

Fig. 2 is a vertical section on line 2-2 of Fig. 1.

Fig. 3 shows certain parts of Fig. 2 in a different operating position.

Fig. 4 is a plan view (with a portion broken away) of a spacer plate adapted to be positioned between the coils.

Fig. 5 is an enlarged fragmentary sectional view of the said spacer plate.

Fig. 6 is a plan view of an orifice plate adapte to be placed on top of the coil stack.

The improved furnace comprises a relatively tall heat insulated bell-type cover or hood i adapted to be disposed over a stack 2 of coils 3 of metal strip to be annealed, such as cold rolled steel strip, five of such coils being shown, the said hood and stack bein supp rted on a furnace base 4 above the floor level i by a structural steel work generally indicated at 6.

The hood i is a relatively light-weight affair comprised of an inner metal lining II, a layer of heat insulating material It and an outer steel casing it which gives rigidity to the hood. At the top of the hood is a handle or fixture 8 by which the hood may be lifted by a crane. The seat between the hood and furnace base is made gas-tight by a liquid holding trough l'l around the base for receiving a depending peripheral blade 20 carried by the hood.

The coils 3 are separated from each other by heat-conductingannular spacers 2i, each having a circumferential series of radially extending open-ended channels 22, so that the core 23 of the coil stack and the annular space 24 between the stack and hood are in open although restricted communication by way of the said gas channels 22. On top of the coil stack there is placed a cover plate 25 having a relatively restricted central aperture 26 whereby to produce a back pressure in the core 23 of the stack when a gaseous medium is introduced thereinto through a central gas port 21 at the bottom of the stack. Consequently, exit of the gaseous medium from the core of the coil stack will be primarily by way of the spacer channels 22 with resultant heat 4 Claims. (Cl. 233-42) exchange between the gaseous medium and the edges of the coiled strip through the intermediary of the top and bottomwalls of the spacers. The use of channeled spacers between the coils does not per se constitute part of the present invent on.

The primary object of the present invention is to provide improvements in apparatus for the heating and cooling and forcible circulation of a gaseous medium into and out of the space encompassed by the hood to the end that a given load of strip coils 3 may be processed more rapidly than has heretofore been possible with conventional equipment.

In the present invention the central gas port 21 constitutes the upper end of an upcomer gas passage 30 in a sub-structure generally indicated at II, the passage leading from a chamber 32 to which the gaseous medium is delivered by a power-driven centrifugal fan 33 arranged in a downcomer g s pas age whose gas intake end is a gas port 34 at one side of the foot of the coil stack 2 and whose lower or discharge end opens on said chamber 32 as indicated at 38. To encompass the gas port 34 the hood i has a laterally extending bulge 36.

A plurality of hair-pin type combustion tubes 31 project into the said chamber 32 from one end wall 38 thereof, each tube being fired by a burner-33'. The tubes are preferably arranged in laterally spaced sets of two tubes each, one tube above the other with their exhaustless 40 adjacent each other and with their exhaust ends connected to a suction exhaust manifold ii, the said sets of tubes being separated from each other by vertical partition walls 42 which divide the chamber," in a plurality of parallelly extending'gas channels 43 for the said gaseous medium. Transverse vertical bailies 44 may be provided in each of said channels to cause the gaseous medium to flow in a zig-zag course over the tubes. Because the gases are heated after leaving said fan it will be readily appreciated that the gases handled by the fan are relatively cool, thereby insuring the optimum operating efllciency of the fan.

After the completion of the heating operation, the gaseous medium which is being circulated by the fan 33 must be cooled in order that the coils 3 may be cooled with the least possible delay to below oxidizing temperature before the hood I is removed. The fuel to the burners 30 is, of course, shut off but not the air, thereby insuring initial quick cooling of the tubes by air passing therethrough. Cooling of the said gaseous me- 3 dium is accomplished by routing the same through water-cooled means comprising two

radiators

50 and 5| located at opposite sides of the downcomer passage 3l35 wherein the fan is positioned.

The water pipes leading to and from the radiators are indicated at 49. The radiator 50 is separated from said passage by a plate valve 53 and the radiator 5| is separated from said passage by a similar plate valve 54. The plate valve 53 is mounted on a horizontal shaft 55 to turn therewith and the valve plate 54 is mounted on a similar shaft 56 to turn therewith, the two shafts being interconnected by appropriate gearing I! to turn in unison in opposite directions. When said plate valves are in upright position (as in Fig. 2) the return gaseous medium flows directly to the fan but when they are in horizontal position (as in Fig. 3) the said medium must flow laterally as two streams to and through said radiators to reach the fan as will now be readily understood. The downcomer duct has a vertical side wall 60 which has an orifice 6| coaxial with the fan to constitute the inlet to the fan.

It will be understood that the gaseous medium which is being circulated by the fan will be of such composition as to provide a protective atmosphere for the metal strip which makes up the coils 3. A typical gaseous mixture for this purpose will contain about 70.7% nitrogen, 12.5% hydrogen, 10.5% carbon monoxide, 5% carbon dioxide, 0.5% methane, and 0.8% water vapor. Fresh gas to compensate for leakage and reduction in volume of the atmosphere on being cooled may be supplied to the circuit at any suitable point as through an inlet 63 at the upper end 34 of the downcomer gas passage.

A removable closure 64 in the end wall of chamber 32 permits ready access to the combustion tubes 31 for removal in case of repairs and a removable closure 65 in the downcomer duct wall permits ready removal of the fan for inspection and repairs.

From the foregoing description it will be understood that there are no fuel supply pipes for burners or electric conductors for heating elements leading to the hood or cover I and, therefore, there need be no loss of time in removing the hood from the furnace base at the end of the annealing cycle nor in starting the heating operation once the hood has been placed on the base. The use of cooling water for removing the heat of the charge during the cooling cycle permits a drastic reduction in the total length of the cycle, especially with large coils of thin gauge material.

What I claim as new is:

1. A heat treating furnace comprising, in com-. bination, an enclosure for the workto be treated and comprising a base whereon the work is supported, means forming an entrance passage for 4 the admission of circulated gas to said enclosure and means forming a return passage for the withdrawal of the gas, a blower having an inlet connected to the return passage and having an outlet connected to the entrance passage for circulating the gas to and from said enclosure, a tubular element extending within said entrance passage with its inlet and outlet ends therewithout, means for producing a flow of cooling medium through the tube when the circulated gas is required to be cooled. and means comprising a burner at the inlet end of the tube for producing -a flow of hot gas through the tube when the circulated gas is required to be heated.

2. A furnace according to claim 1, wherein said return passage comprises first and second flow paths leading to the blower, means for directing the circulated gas through the first flow path when said gas requires to be heated by said tube, and means in the second flow path for precooling the circulated gas before it reaches said tube.

3. A heat treating furnace comprising, in combination, an enclosure for the work to be treated and comprising a base whereon the work is supported, means forming an entrance passage for the admission of circulated gas to said enclosure and means forming a return passage for the withdrawal of the gas. a blower having an inlet connected to the return passage and having an outlet connected to the entrance passage for circulating the gas to and from said enclosure, a tubular element extending within said entrance passage with its inlet and outlet ends therewithout and with the inlet end open to the inflow of atmospheric air, means comprising a suction producing means coupled to the outlet end of the tube to draw said air through the tube to cool the tube when the circulated gas is required to be cooled, and means comprising a burner at the inlet end of the tube for producing a flow of hot gases through the tube when the circulated gas is required to be heated.

4. A furnace according to claim 3, comprising means in the return passage for precooling the air when it requires to be cooled by the tube in the entrance passage.

CARROLL CONE.

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

UNITED STATES PATENTS Date