US3072392A

US3072392A - Vacuum furnace

Info

Publication number: US3072392A
Application number: US118039A
Authority: US
Inventors: Howard R Palmer
Original assignee: Titanium Metals Corp
Current assignee: Titanium Metals Corp
Priority date: 1961-06-19
Filing date: 1961-06-19
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08
Also published as: DE1172050B

Description

H. R. PALMER VACUUM FURNACE Jan. 8, 1963 2 Sheets-Sheet 1 Filed June 19, 1961 INVENTOR. Howard R. Palmer Jan. 8, 1963 H. R. PALMER VACUUM FURNACE 2 Sheets-Sheet 2 Filed June 19, 1961 INVENTOR. Howard R. Palmer United States Patent ()fliice Patented Jan. 8, 1963 3,072,392 VACUUM FURNACE Howard R. Palmer, Henderson, Nev., asslgnor to Titanium Metals Corporation of America, New York, N.Y., a corporation of Delaware Filed June 19, 1961, Ser. No. 118,039 Claims. (Cl. 263--3) This invention relates to a furnace and more particularly to a furnace for heating metallic strip in vacuo.

Metallic strip is generally produced in the form of a coil for convenience in handling during processing, and later transportation and sale. Such a coil may consist of a long length of strip and be correspondingly heavy and bulky. Heating such as coil is a long procedure since heat transfer to the central portion is extremely slow. Therefore such strip is often heated by unwinding a coil, heating the strip progressively as it is unwound and then rewinding it into another coil. Conditions often require this operation to be conducted in vacuo, for example, when heating titanium, zirconium or other reactive metals, and also certain steels. The design and construction of a furnace" for heating coiled strip in vacuo has heretofore. been diflicult to accomplish since mechanical problems of handling the heavy coils, of keeping the structure vacuum tight and applying suitable heat to providethe proper heat treatment, are diflicult to solve.

:A principal object of this invention is to provide an improved furnace for heating metal strip in vacuo. An-

' other object of this invention is to provide a furnace for heating metal strip in vacuo which is simple and convenient to load and unload with heavy coils of metal strip. Another object of this invention is to provide a furnace which is readily loaded and unloaded and which is capable of being evacuated to low pressure. These and other objects of this invention will be apparent from the following description thereof and from the annexed drawings in which:

FIG. 1 shows a vertical, longitudinal sectional view of a furnace embodying features of this invention.

FIG. 2 shows a vertical cross-section of the furnace of FIG. 1 taken along the line 2--2.

' FIG. 3 shows-'a vertical cross-section of the furnace of'FIG. 1 taken along the line 33.

FIG. 4 shows a vertical cross-section of the furnace of FIG. 1 taken along the line 44.

. FIG. 5 shows in some detail one of the heater elements as seen from 55 in FIG. 1.

Referring now particularly to FIGS. 1 and 2, the fur- I nace comprises a generally cylindrical, closed-end shell having a horizontal axis, the said shell 10 being divided or sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at an angle between and 50 degrees to the vertical, and preferably about 30 degrees, to form a cover section 12 and a base section 14, which are hingedly attached to each other at the juncture of their top edges as at 16. The complete shell 10 may be suitably supported along its length by legs 18.

Horizontally and rotatably mounted in shell 10 and attached to the base section 14 are spools 20a and 20b. These are mounted so that their shafts projecting through thewall of base section 14 are sealed to preserve low pressure conditions inside shell 10. The details of this construction will be described with particular reference to spool 20a and will be apparent from FIG. 2 in which spool 20a is fixedly attached to a shaft 22 which is supported and journaled in a pair of spaced-apart bearings 24. These bearings 24 are in turn supported in place by tub member 26 which transfixes the wall of base section 14 and is attached and sealed thereto at its passage therethrough as by welding as at 28. Spool 20a is thus rotatably mounted in horizontal position and, by bearing tube 26, attached to base section 14. Flange 30 is attached and sealed, as by welding at 32 to the exteriorly projecting end of bearing tube 26.

Housing 34 is provided at one end with plate 36 through which the exterior end of shaft 22 passes with sufiicient clearance for rotation. At the other end of housing 34 is provided flange 38 which is attached thereto as by welding at 40 and is of dimension to generally correspond with bearing tube flange 30. Between

flanges

38 and 30, and sealed to each by provision of O-ring gaskets 42, is plate 44 through which passes shaft 22.

Rotating vacuum seal 46 is arranged to seal shaft 22 to plate 44 during rotation thereof, being biased in sealing engagement by spring 48 bearing against collar 50. Shaft 22 is connected by coupling 52 to shaft 54 of electric fotor 56.

Spool 20a is arranged as the spool on which the strip is wound during processing, while spool 2012, similar in mounting and shaft sealing details, is the spool holding the original coil and from which the strip is unwound.

Therefore a motor 56 is not always essential for powering of its shaft 22 although it may be useful for back winding if necessary.

, Also rotatably mounted in horizontal positionin shell 10 and attached to the base section 14 are a pair of lower cooling rolls 58. As will be seen more clearly in FIG( 3, each'of these is mounted on a shaft 60 which is journaled at its inner end in bearing 62 which is supported by upright member 64 and brace member 66. Shaft 60 passes through plate 68 which is attached at the inner end of tubular member 70 which pierces the wall of base section 14 and whose projecting end carries outer shaft bearing 72. Passage of shaft 60 through plate 68 is sealed as in the case of shaft 22 by provision of another rotating seal 46 biased by a similar spring 48 bearing against collar 50. Shaft 60 is preferably hollow as is also roller 58 to allow circulation therethrough of cooling fluid such' as water introduced by axial tube 74.

Also mounted in shell 10 on base section 14 are means for heating the underside of a strip being treated in the furnace, and comprising an open-top box-like heat shield 76 supported by uprights 78. Inside heat shield 76 are placed electric heater units 80 which are bent as shown more clearly in FIG. 5. They are fabricated of high resistance alloy and are connected by lead wires 82 which pass through the wall of base section 14 being insulated and sealed at such passage by bushings 84.

Also mounted in shell 10 and attached to the base section 14 is rotatably mounted guide roll 86. This guide roll is attached to a horizontal shaft 88 which is journaled into bearings 90 which are in turn supported by pedestal 92.

Communicating with the interior of shell 10 is vacuum pipe 94 which is connected through line valve 96 to vacuum pump 98. Motor 100 operates pump 98 through belt 102. Vacuum pipe 94 is provided with bleed line 104 controlled by bleed valve 106.

The above describes elements which are attached to or associated with the base section 14 of shell 10. The elements which are attached to or associated with the cover section 12 of shell 10 will now be considered.

Upper cooling roll 108 is rotatably mounted inside shell 10 and attached to cover section 12. It is mounted on shaft 110 which is supported at its inner end in bearin 11?. whi h is in turn supported by hanging bracket 114. Tubular element 116 transflxes the wall of cover section 12, through which the outer end of shaft 110 passes and is provided with flange 118 to which is adjustably attached in sealing engagement bearing plate 120 and outer plate 122. Enclosed within housing 124, and rotatably sealing shaft 110 to plate 122, is rotating seal 46, similar to those previously described biased by spring 48 against collar 59. Shaft 110 is hollow, communicating with the hollow interior of roll 1G8, cooling fluid, such as water, being supplied thereto through internal pipe 126. Cooling roll 108 is located so that it is laterally spaced midway between lower cooling rolls 58 and arranged so that when cover section 12'is closed, its lower edge is somewhat lower than the upper edges of cooling rolls 58.

Means for heating the upper surface of a strip being treated are also mounted in shell and attached to the cover section 12. An open bottom heat shield 128 is supported from cover section 12 by brackets 130. Inside heat shield 128 are placed electric heater elements 132' which are bent to shape as shown. They are, like elements 80, fabricated of high resistance alloy and are connected by lead wires 134 which pass through the wall of cover section 12 being insulated and sealed at such passage by bushings 136.

The corresponding edges of cover section 1'2 and base section 14 of shell 10 are provided with

mating flanges

138 and 140 respectively. One of these, for example, flange 140'as shown is provided with a continuous groove 142 which is fitted with continuous O-ring gasket 144 preferably of rubber or other resilient material.

It is preferred as will be seen from the drawings that the tops of guide roll 86, the means for heating the under side of strip and lower cooling rolls 58 lie in the same general horizontal plane.

In operation, the cover section 12 of shell 16 is first.

raised as shown in FIG. 2; suitable mechanical hoisting means (not shown) may be employed if necessary. Then a coil of metal strip to be heat treated is placed on spool 21% and the free end of the strip 146 is unwound for a sufiicient length so that it may be laid on top of guide roll 86, then across the top of lower heat shield 76, then over the two cooling rolls 58 and finally temporarily attached to the surface of spool 20a. Cover section 12 is then lowered so that cover section flange 138 mates with base section flange 140, with gasket 144 compressed in groove 142 to form a seal. lowers the top heat shield 128 onto the bottom heat shield 76 (suitable apertures being arranged in their ends to allow for passage therethrough of strip 146) and upper heating elements 132 will be in position to heat the upper surface of strip 146, and bottom heating elements 80 will be in position to heat its under side. At the same time upper cooling roll 108 will be lowered into position to contact and depress sheet 146 thereby providing good contact area for sheet 146 over the three cooling rolls. Bleed valve 106 is closed and vacuum line valve 96 is opened and the interior of shell 10 evacuated by operation of motor 100 actuating vacuum pump 98.

After suitably reduced pressure has been attained in shell 10,

heating element connectors

82 and 134 are connected exteriorly of shell 10 to a suitable source of electric power (not shown). When these elements have reached the desired temperature motor 56 is operated to rotate spool 20:: to rewind the coil onto this roll. It will be understood that the rate of travel of the strip between the heating elements and the temperature to which it is subjected during such passage will be adjusted to provide the desired heat treatment. Cooling rolls 108 and 58 have been found effective to cool the heat treated strip so that it may be recoiled without sticking or welding between turns. The heat treatment is continuously applied to the strip as the coil is unwound from spool 20/) and rewound on spool 20a, with vacuum being maintained inside shell 10. When the coil has been completely heat treated and rewound on spool 20 motor 56 is stopped,

heater elements

132 and 80 are disconnected or switched off and vacuum line valve 96 is closed. Then bleed valve 106 is opened allowing the atmosphere to enter shell 10 and cover section 12 is raised. The heat treated and refound coil on spool 25):: is then removed; if additional strip is to be procesed another coil may be placed on Closing of cover sect on 12 d spool 20b laid across the heaters and coil and the heat treating operation repeated.

The furnace of this invention is particularly designed for vacuum heat treatment of metallic strip handled in the form of coils, and its unique features provide for proper maintenance of high vacuum, ease of loading and unloading coils, and eificient and continuous progressive heat treatment. The angle of the juncture between the cover section 14 and the base section 12 is important. This angle, between 20 and 50 degrees to the vertical, provides adequate horizontal opening for coils to be loaded onto spool 26b and unloaded from spool 20a. While loading andunloading opening is adequate, at the same time the weight of the cover will provide good contact between it and gasket 144 so that when the vacuum pumping equipment is turned on suflicient initial seal will be obtained so that reduced pressure inside shell 10 will tend to pull the cover secton 12 and base section 14 together and thus perfect the seal. If the angle of the intersection of cover section 14 and base section 12 is less than 20 degrees to the vertical, the free weight component will generally be insufficient to initiate the seal. If the angle is greater than 50 degrees then, while efficient sealing can be obtained, the horizontal section of the opening is too much restricted for ready handling of the bulky and heavy coils in and out of the furnace.

The location of the various elementsinside the furnace,

with respect to their attachment to the cover section 14- or' the base section 12 is also important. With the upper cooling roll 58 and the upper part of the heating means attached to cover section 12 when this is raised then both these elements are raised clear of the lower cooling rolls and the lower part of the heating means. This arrangement provides for easy location of the strip end when it is originally placed in starting position spanning the furnace interior from spool 20]) to 20a. Metallic strip of the type readily handled by furnaces of the type described is often stiff and difficult to handle if it has to be threaded through a tortuous path. However, with the furnace of this invention, the starting end is s mply laid over the guide roll, the lower part of the heating means and the lower cooling rolls 58 to wind-up roll 20a; When the strip end is in place lowering the cover section 14 automatically lowers the upper cooling roll 108 and heat shield 128 (with its heating elements) in their proper places on top of the strip.

The embodiment illustrated shows the furnace equipped with cooling rolls 108' and 58 to cool the heated strip sufficiently so that it may readily be coiled onto wind-up spool 200. In applications wherein the heating temperature is low, or where the characteristics of the metal being treated permit hot coiing, then, as will be apparent, the cooling rolls may not be used. The advantages of the invention with respect to the ease of loading and unloading, the initial sealing of the cover section 14 to base section 12 and the benefits occuring from attachment of the upper heating means to cover section 14, will however, be obtained as otherwise.

The furnace of this invention is useful for annealing strip of reactive metals such as titanium or zirconium and may also be employed for annea ing strip of other metals that may be affected by atmospheric exposure at annealing temperature.

I claim:

1. Apparatus for heating a metal strip in vacuo comprising; a generally cylindrical closed-end shell, having a horizontal axis and being sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at an angle between 20 and 50 degrees to the vertical to form a cover section and a base section thereof, said cover section being hingedly attached to said base section at the juncture of the top edges of said base and cover sections, a pair of spaced apart spools horizontally and rotatably mounted in said she l and attached to the base section thereof, means for rotating at least one of said spools, a guide roll mounted in said shell and rotatably attached to the base section thereof, means mounted in said shell and attached to the cover section thereof for heating the upper surface of a metal strip disposed between and coiled on said spools, means mounted in said shell and attached to the base section thereof for heating the under surface of said strip, a resilient gasket adapted to seal the edges of said shell at the juncture of the cover and base sections thereof, and means for evacuating said shell.

,2. Apparatus for heating a metal strip in vacuo comprising; a generally cylindrical closed-end shell, having a horizontal axis and being sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at an angle of about 30 degrees to the vertical to form a cover section and a base section thereof, said cover section being hingedly attached to said base section at the juncture of the top edges of said base and cover sections, a pair of spaced apart spools horizontally and rotatably mounted in said shell and attached to the base section thereof, means for rotating at least one of said spools, a guide roll mounted in said shell and rotatably attached to the base section thereof, means mounted in said shell and attached to the cover section thereof for heating the upper surface of a metal strip disposed between and coiled on said spools, means mounted in said shell and attached to the base section thereof for heating the under surface of said strip, a resilient gasket adapted to seal the edges of said shell at the juncture of the cover and base sections thereof, and means for evacuating said shell.

3. Apparatus for heating a metal strip in vacuo comprising; a generally cylindrical closed-end shell, having a horizontal axis and being sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at an angle between 20 and 50 degrees to the vertical to form a cover section and a base section thereof, said cover section being hingedly attached to said base section at the juncture of the top edges of said baseand cover sections, a pair of spaced apart spools horizontally and rotatably mounted in said shell and attached to the base section thereof, means for rotating at least one of said spools, a cooling roll mounted in said shell rotatably attached to the cover section thereof and a cooling roll mounted in said shell rotatably attached to the base section thereof, a guide roll mounted in said shell and rotatably attached to the base section thereof, means mounted in said shell and attached to the cover section thereof for heating the upper surface of a metal strip disposed between and coiled on said spools, means mounted in said shell and attached to the base section thereof for heating the under surface of said strip, a resilient gasket adapted to seal the edges of said shell at the juncture of the cover and base sections thereof, and means for evacuating said shell,

4. Apparatus for heating a metal strip in vacuo comprising; a generally cylindrical closed-end shell, having a horizontal axis and being sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at an angle between 20 and 50 degrees to the vertical to form a cover section and a base section thereof, said cover section being hingedly attached to said 6. base section at the juncture of the top edges of said base and cover sections, a pair of spaced apart spools horizontally and rotatably mounted in said shell and attached to the base section thereof, means for rotating at least one of said spools, a cooling roll mounted in said shell rotatably attached to the cover section thereof and a pair of cooling rolls mounted in said shell and rotatably attached to the base section thereof with the cooling roll attached to the cover section positioned laterally mid-way between the pair of cooling rolls attached to the base section and when the cover section is closed its lower edge will be lower than the upper edges of the cooling rolls attached to the base section, a guide roll mounted in said shell and rotatably attached to the base section thereof, means mounted in said shell and attached to the cover section thereof for heating the upper surface of a metal strip disposed between and coiled on said spools, means mounted in said shell and attached to the base section thereof for heating the under surface of said strip, a resilient gasket adapted to seal the edges of said shell at the juncture of the cover and base sections thereof, and means for evacuating said shell.

5. Apparatus for heating a metal strip in vacuo comprising; a generally cylindrical closed-end shell, having a horizontal axis and being sectioned on a longitudinal plane extending axially and inclined upwardly and rearwardly at a angle between 20 and 50 degrees to the vertical to form a cover section .and a base section thereof, said cover section being hingedly attached to said base section at the juncture of the top edges of said base and cover sections, a pair of spaced apartspools horizontally and rotatably mounted in said shell and attached to the base section thereof, means for rotating at least one of said spools, a cooling roll mounted in said shell rotatably attached to the cover section thereof and a pair of cooling rolls mounted in said shell and rotatably attached to the base section thereof with the cooling roll attached to the cover section positioned laterally mid-way between the pair of cooling rolls attached to the base section and when the cover section is closed its lower edge will be lower than the upper edges of the cooling rolls attached to the base section, a guide roll mounted in said shell and rotatably attached to the base section thereof, means mounted in said shell and attached to the cover section thereof for heating the upper surface of a metal strip disposed between and coiled on said spools, means mounted in said shell and attached to the base section thereof for heating the under surface of said strip, the tops of said guide roll, said means for heating the underside of said strip and said lower cooling rolls lying in the same general horizontal plane, a resilient gasket adapted to seal the edges of said shell at the juncture of the cover and base sections thereof, and means for evacuating said shell.

References Cited in the file of this patent UNITED STATES PATENTS 1,732,244 Salzman Oct. 22, 1929 2,203,241 Waldron June 4, 1940 2,812,270 Alexander Nov. 5, 1957

Claims

1. APPARATUS FOR HEATING A METAL STRIP IN VACUO COMPRISING; A GENERALLY CYLINDRICAL CLOSED-END SHELL, HAVING A HORIZONTAL AXIS AND BEING SECTIONED ON A LONGITUDINAL PLANE EXTENDING AXIALLY AND INCLUDED UPWARDLY AND REARWARDLY AT AN ANGLE BETWEEN 20 AND 50 DEGREES TO THE VERTICAL TO FORM A COVER SECTION AND A BASE SECTION THEREOF, SAID COVER SECTION BEING HINGEDLY ATTACHED TO SAID BASE SECTION AT THE JUNCTURE OF THE TOP EDGES OF SAID BASE AND COVER SECTIONS, A PAIR OF SPACED APART SPOOLS HORIZONTALLY AND ROTATABLY MOUNTED IN SAID SHELL AND ATTACHED TO THE BASE SECTION THEREOF, MEANS FOR ROTATING AT LEAST ONE OF SAID SPOOLS, A GUIDE ROLL MOUNTED IN SAID SHELL AND ROTATABLY ATTACHED TO THE BASE SECTION THEREOF, MEANS MOUNTED IN SAID SHELL AND ATTACHED TO THE COVER SECTION THEREOF FOR HEATING THE UPPER SURFACE OF A METAL STRIP DISPOSED BETWEEN AND COILED ON SAID SPOOLS, MEANS MOUNTED IN SAID SHELL AND ATTACHED TO THE BASE SECTION THEREOF FOR HEATING THE UNDER SURFACE OF SAID STRIP, A RESILIENT GASKET ADAPTED TO SEAL THE EDGES OF SAID SHELL AT THE JUNCTURE OF THE COVER AND BASE SECTIONS THEREOF, AND MEANS FOR EVACUATING SAID SHELL.