US2890878A

US2890878A - Apparatus for annealing in a high vacuum

Info

Publication number: US2890878A
Application number: US631083A
Authority: US
Inventors: Hans A Steinherz; Edward S Candidus
Original assignee: Nat Res Corp
Current assignee: National Research Corp
Priority date: 1956-12-28
Filing date: 1956-12-28
Publication date: 1959-06-16
Anticipated expiration: 1976-06-16

Description

- H. A. STEINHERZ ETAL 2,890,878

APPARATUS FOR ANNEALING 1N A HIGH VACUUM Filed Dec. 2s, 195e AJune 1s, 1959 2 Sheets-Sheet 1 June 16, 1959 i H. A. STEINHERZ ETAL 2,890,878

y APPARATUS FUR ANNEALING 1N A HIGH VACUUM Filed Dec. 28, 1956 2 sheets-sheet 2 INVENTOR-S #am SHK erz BY gela/@mf S- Candida;

United States Patent APPARATUS FOR ANNEALING 1N A HIGH t VACUUM 'Application December 28, 1956, Serial No. 631,083 z Claims; (C1. 26a- 3) This invention relates to apparatus for treating sheet material under vacuum. For convenience the invention will be primarily described in connection with its use for treating metal strip under vacuum. This treatment can be, for example, the vacuum annealing of a strip of a reactive metal such as titanium. In prior art attempts to achieve this result, a coil of the strip to be vacuum annealed is placed in a batch-type high vacuum furnace. TheV long heating, cooling and pump-down cycles attendant to a batch-type annealing operation, are economically unattractive. Furthermore, control of quality and uniformity is difficult to maintain because many of the factors such as the rate of evolution of gasses which affect the properties of the coiled strip materials are very dicult' to control in a batchtype process.

Another procedure for vacuum annealing metal strip which has been described in the prior art comprises placing a coil of the strip metal in a high vacuum system, unwinding the coil within the vacuum system, and then treating and recoiling the strip. This procedure also has the disadvantage of the long time necessary to bring the whole furnace structure up to temperature and then to cool the whole structure after annealing.

An often suggested alternative to the above-described batch-type operations comprises a continuous process wherein the coiled strip material is unwound outside of the vacuum system and subsequently passed through vacuum seals into the Vacuum system for treatment. However, this type of operation is subject to the many diliculties and the great expense involved in the production of a unit that is flexible enough to handle metal strip of various widths and thicknesses. In the past this problem has been solved by mercury seals. However, this solution is unsuitable when it is desired -to treat paper and metals which dissolve in mercury.

In the instant invention, the problems and disadvantages of prior art vacuum annealing techniques have been either solved or circumvented.

.Accordingly, it is a principal object of the present invention to provide improved apparatus for treating sheet material under vacuum.

Another object of the invention is to provide vacuum treating apparatus which is flexible enough to be utilized in treating metal strip of a wide range of thicknesses and widths.

Still another object of the invention is to provide apparatus which is capable of vacuum annealing strip metal under a vacuum at a high over-all production rate.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus possessingthe construction,` combination of elements and arrangements of parts which are exemplified in the following detailed description and the scope of the application'of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the` invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings wherein:

'2,890,878 Patented June 16, 1959 lceN Fig. 1 is a diagrammatic, schematic illustration of one preferred embodiment of the invention.

Fig. 2 is an enlarged View of one of the vacuum seals of Fig. 1.

As mentioned previously the invention will be particularly described at least initially, in connection with its use in the vacuum annealing of a highly reactive metal strip such as titanium or the like. To accomplish this objective the apparatus includes a vacuum-tight heat treating chamber, a vacuum-tight loading chamber and an intermediate vacuum chamber between the treating` and loading chamber. The various chambers are provided with evacuating means to permit evacuation of these chambers to a predetermined low pressure. In one preferred embodiment, the loading chamber operates at a pressure on the order of 0.l-0.5 mm. Hg abs.; the intermediate chamber has a pressure on the order of microns Hg abs. and the heat treating chamber has an operating pressure of 0.1 microns Hg abs. Between the vacuum treating chamber and the intermediate chamber, there is provided a low friction seal through which the strip can be passed with only a small transfer of gases from the intermediate chamber to the vacuum treating chamber under the relatively small (e.g. a few hundred microns) driving force existing between these chambers. In a preferred embodiment, the seal comprises a pair of closely spaced rolls between which the strip passes. Between the intermediate chamber and the loading chamber, there is provided another vacuum seal. This second vacuum seal preferably comprises a pair of surfaces between which the strip normally passes with only slight frictional contact. During the annealing operation this seal is not intended to constitute a vacuum seal with the metal strip moving therethrough. However, this seal is arranged so that its two surfaces can be pressed tightly together to provide very tight contact with both surfaces of the strip when the strip is stationary in order to thereby form a seal which effectively prevents transfer of any appreciable quantity of gases through the seal even though one side of the seal is exposed to full atmospheric pressure when the door to the loading chamber is open.

In a preferred embodiment of the invention a treated strip material preferably passes from the treating chamber into a second intermediate chamber and thence into a second unloading chamber. For the purposes of simplicity of construction, these chambers are positioned along a long tubular vacuum tank.

With this arrangement of elements, when a strip has been vacuum annealed for example, and the end of the roll has been approached, travel of the strip is stopped, and the seal between the loading chamber and the intermediate C'nambers is closed so as to seal oi'f the inter-` mediate chamber from the loading chamber. Air is then admitted to the loading chamber and the door of the loading chamber is opened to permit the positioning of the next roll of material to be treated. This roll is suitably fastened onto the end of the preceding roll so that it will beautomatically threaded through the apparatus as the preceding roll is completely wound up. All this takes place without disturbing the high vacuum within the heat ltreating portion of the furnace and without the necessity for cooling olf the furnace.

Referring now to the drawings, the apparatus comprises in one preferred embodiment a long cylindrical chamber 10 such as, for example, a long section of pipe. Suitable partitions are provided inside of the overall chamber 10 so as to provide a number of subchambers including a loading chamber M, an intermediate chamber 16, a heat treating chamber 12, another intermediate chamber 20, a cooling chamber 22 and an unloading chamber 18. A coil of the strip to be vacuum annealed is indicated at l 24. As shown the strip 24 passes from the loading cham:

ber 14, through a first seal 26 into the intermediate chamber 16, then passes through a second seal 28 into the vacuum treating chamber 12 where it is subjected to annealingy temperatures by suitable means such as radiant heaters 30 positioned on both sides of the sheet. Heat shields 32 are provided to preserve the heat in the heat treating chamber. The strip next passes into the cooling chamber where it is contacted by a plurality of water-cooled rolls 34; thence the strip passes through another seal similar to that shown at 28 into an intermediate pumping chamber 20 and thence through seal 38 to the unloading chamber 1S where it is suitably coiled up for removal as a coil. The loading and unloading chambers are provided with

doors

40 and 42 respectively and all of the chambers are provided with pumping ports. The loading and unloading chambers 14 and 1S are preferably evacuated by mechanical booster pumps.

Intermediate chambers

16 and 20 are preferably evacuated by means of small mechanical pumps. The heat treating chamber 12 and the cooling chamber 22 are preferably evacuated to low pressures on the order of 0.1 microns Hg abs. by means of oil diffusion pumps.

The

seals

26 and 38 are preferably arranged as shown in Fig. 2 schematically in enlarged detail so that they I can be clamped tightly shut to prevent any substantial leakage of air even though the loading and unloading chambers are open to atmosphere. The partition between the loading chamber 14 and the intermediate chamber 16 is indicated at 5t). An opening in this partition is defined by a rst surface 52, which preferably comprises a compressible element such as a block of rubber, and a second element 54 which can also be a compressible element such as another block of rubber. Element S4 is preferably movably supported by means of a door member 56 arranged to slide in a channel 58 carried by the upper half of the partition 5t). This door is arranged to be pushed downwardly by suitable means such as `a cam schematically indicated at 6i). A sealing ring 62 is provided between the door and the facing surface of the partition 50. This sealing ring 62 forms a complete seal around the opening in the partition Sii. In a preferred embodiment, channel 58 provides =a somewhat loose t so that the door 56 can be raised and lowered easily Vwith only slight bearing force on the sealing ring 62. However, when the door 56 has been pushed downwardly into place andthe pressure in loading chamber 14 is raised to atmospheric, the pressure difference existing across the door 56 pushes the door tightly against the seal 62, thereby forming a vacuum-tight seal.

Referring again to Fig. 1 the seal between the intermediate chamber 16 and the high vacuum treating chamber 12 is preferably formed by a pair of rolls 70 which preferably rotate with the sheet. Another seal is provided between rolls 70 and the wall 74 by means of sealing lips, such as those illustrated at 72. Similar arrangements are preferably provided for the seal between the cooling chamber and the intermediate chamber 20. These sealing rolls. 70 are preferably spring mounted so as to accommodate strips of different thickness. Even though the resultant seal 28 is not very tight it is adequate to prevent the transfer of any substantial quantity of gas therethrough because of the extremely small pressure gradient (only a few microns Hg abs.) thereacross.

While one preferred embodiment of the invention has been described above, numerous modifications thereof can be made. For example, the heat treating chamber 12 can be modified to provide a vacuum coating operation instead of, or in addition to, thel heat treating operation. Thus, for example, if it is desired to manufacture a tin plate substitute, a strip of black plate can be run through the apparatus and can be provided with a thin corrosion resistant layer of aluminum by vapor deposition techniques. When vacuumv evaporation is to be provided, it is preferred that the aluminum vapor source be-of the type shownl in U.S. Patent 2,665,320.

Since certain changes may be made in the above described process without departing from the scope of the invention herein involved, itf is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In apparatus for vacuum-annealing a strip of reactive metal such as titanium, which includes a Vacuumannealing chamber, means for evacuating said annealing chamber, and heating means in said annealing chamber for heating said strip to annealing temperature Ewhile said strip moves through said chamber and Wherein the annealing chamber requires a long time for reaching annealing temperature, the improvement which comprises a vacuum-tight loading chamber, -a vacuum-tight door for said loading chamber, an intermediate vacuum chamber, means for evacuating said loading chamber,4 separate means for evacuating said intermediate chamber, means defining a first opening through which the strip can be passed between said loading and intermediate chambers, means for positioning a coil of the strip to be annealed within said loading chamber, a second opening through which said strip is passed into said vacuum-annealing chamber, at least one low-friction seal in said second opening, a pair of sealing surfaces between which the strip passes associated with the iirst opening, said sealing surfaces being formed of compressible material attached in fixed relation to non-com pressible support members, one of the support members being movably mounted for movement towards the other support member so that the compressibley surface carried by the movable support member can be suiciently tightly compressed towards the other sealing surface t0 permit maintenance of a high vacuum of less than about l micron Hg abs. in said annealing chamber While said loading chamber is opened to the atmosphere, mechanical means for moving said moveable sealing surface to relax the grip of said seal on the strip so as to permit the strip to be moved -with no more than slight frictional contact between the strip and the sealing' surfaces during movement of the strip, whereby successive rolls of strip can be sequentially annealed without the necessity of opening the annealing chamber to the atmosphere.

2. The apparatus of claim 1, wherein there is provided a third opening through which said strip is passed from said vacuum-annealing chamber, at least one lowfriction seal in said third opening, means for cooling said strip after annealing and before said strip passes through the third opening, a fourth opening communicating with an unloading chamber, a pair of sealing surfaces associated with the fourth opening, one of the sealing surfaces being moveably supported so that it can be suiiiciently tightly compressed towards the other sealing surface to permit maintenance of a high vacuum of less than about l micron Hg abs. in said annealing chamber while said unloading chamber is opened to the atmosphere, mechanical means for moving said moveable seal to relax the grip of said seal on the strip so as to permit the strip to be moved with no more than slight frictional contact between the sheet andthe sealing surfaces during movement of the strip.

References Cited in the le of this patent UNITED STATES PATENTS 1,683,254 Minton Sept. 4, 1928 1,688,481 Austin Oct. 23', 1928 1,987,577 Moers Jan. 8, 1935 2,264,885 Mueller Dec. 2, 19.41 2,304,432 Wood Dec. 8, 1942 2,345,181 Cooper et al; Mar. 28, 1944 2,367,174 Renlrin Jan. 9 1945 2,562,182 Godley J'uly 31, 1951

Claims

1. IN APPARATUS FOR VACUUM-ANNEALING A STRIP OF REACTIVE METAL SUCH AS TITANIUM, WHICH INCLUDES A VACUUMANNEALING CHAMBER, MEANS FOR EVACUATING SAID ANNEALING CHAMBER, AND HEATING MEANS IN SAID ANNEALING CHAMBER FOR HEATING SAID STRIP TO ANNEALING TEMPERATURE WHILE SAID STRIP MOVES THROUGH SAID CHAMBER AND WHEREIN THE ANNEALING CHAMBER REQUIRES A LONG TIME FOR REACHING ANNEALING TEMPERATURE, THE IMPROVEMENT WHICH COMPRISES A VACUUM-TIGHT LOADING CHAMBER, A VACUUM-TIGHT DOOR FOR SAID LOADING CHAMBER, AN INTERMEDIATE VACUUM CHAMBER, MEANS FOR EVACUATING SAID LOADING CHAMBER, SEPARATE MEANS FOR EVACUATING SAID INTERMEDIATE CHAMBER, MEANS DEFINING A FIRST OPENING THROUGH WHICH THE STRIP CAN BE PASSED BETWEEN SAID LOADING AND INTERMEDIATE CHAMBERS, MEANS FOR POSITIONING A COIL OF THE STRIP TO BE ANNEALED WITHIN SAID LOADING CHAMBER, A SECOND OPENING THROUGH WHICH SAID STRIP IS PASSED INTO SAID VACUUM-ANNEALING CHAMBER, AT LEAST ONE LOW-FRICTION SEAL IN SAID SECOND OPENING, A PAIR OF SEALING SURFACES BETWEEN WHICH THE STRIP PASSES ASSOCIATED WITH THE FIRST OPENING SAID SEALING SURFACES BEING FORMED OF COMFIG 01 PRESSIBLE MATERIAL ATTACHED IN FIXED RELATION TO NON-COMPRESSIBLE SUPPORT MEMBERS, ONE OF THE SUPPORT MEMBERS BEING MOVABLY MOUNTED FOR MOVEMENT TOWARDS THE OTHER SUPPORT MEMBER SO THAT THE COMPRESSIBLE SURFACE CARRIED BY THE MOVABLE SUPPORT MEMBER CAN BE SUFFICIENTLY TIGHTLY COMPRESSED TOWARDS THE OTHER SEALING SURFACE TO PERMIT MAINTENANCE OF A HIGH VACUUM OF LESS THAN ABOUT I MICRON HG ABS. IN SAID ANNEALING CHAMBER WHILE SAID LOADING CHAMBER IS OPENED TO THE ATMOSPHERE, MECHANICAL MEANS FOR MOVING SAID MOVEABLE SEALING SURFACE TO RELAX THE GRIP OF SAID SEAL ON THE STRIP SO AS TO PERMIT THE STRIP TO BE MOVED WITH NO MORE THAN SLIGHT FRICTIONAL CONTACT BETWEEN THE STRIP AND THE SEALING SURFACES DURING MOVEMENT OF THE STRIP, WHEREBY SUCCESSIVE ROLLS OF STRIP CAN BE SEQUENTIALLY ANNEALED WITHOUT THE NECESSITY OF OPENING THE ANNEALING CHAMBER TO THE ATMOSPHERE.