US2852246A

US2852246A - Vacuum degassing apparatus

Info

Publication number: US2852246A
Application number: US567969A
Authority: US
Inventors: Janco Nathan
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-02-27
Filing date: 1956-02-27
Publication date: 1958-09-16
Anticipated expiration: 1975-09-16

Description

United States Patent F VACUUM DEGASSING APPARATUS Nathan Janco, Tulsa, Okla. Application February 27, 1956, Serial No. 567,969

4 Claims. (Cl. 266-34) This invention relates to vacuum degassing apparatus for molten metals and more particularly to vacuum degassing equipment for degassing melts in the ladles or crucibles in which the molten metal is poured or melted respectively.

Many different apparatus for degassing metals have heretofore been devised but there has not been provided an apparatus for degassing in bucket type ladles using the ladle itself as a part of the vacuum chamber. Thus, if it is desired to degas a melt from an open hearth, the furnace must be tapped into a ladle, the melt then poured into degassing apparatus, and after degassing is completed the melt must be returned to the ladle for pouring the molds. The additional handling steps and equipment for such a procedure have caused the industry to generally omit this step not withstanding its obvious advantages.

It is an object of this invention to provide vacuum degassing apparatus for degassing melts in bucket type ladles using the ladle as part of the degassing chamber.

Another object is to provide degassing apparatus employing a bucket type ladle as a part of the vacuum chamber in which a cover for the ladle is connected to pumping and filtering apparatus through a flexible hose to permit the cover to be readily removed and replaced on the ladle.

Another object is to provide degassing apparatus employing a bucket type ladle as a part of the vacuum chamher in which an interference type seal is used and the seal is protected against overheating.

In the degassing of crucibles in vacuum chambers the top portion of the chamber usually includes most of the side wall of the chamber. This permits the crucible to be removed from the chamber without lifting the crucible an appreciable distance. These top portions of the chambers are difiicult to handle and position on the bottom portion of the chamber in the exact position desired with overhead cranes and the like.

Another object of this invention is to provide a vacuum degassing apparatus in which there is provided a means for easily handling the top portion of the degassing chamber and positioning it in the exact position desired.

Another objectis to provide a degassing apparatus in embodiments of this invention and wherein like reference numerals indicate like parts:

Fig. 1- illustrates a degassing apparatus utilizing a ladle as part of the degassing chamber with the ladle and cover shown in vertical cross-section and the remainder of the apparatus in elevation with the shell of the condenserfilter broken away to illustrate its interior;

Fig. 2 is a view in vertical elevation of the ladle and cover of Fig. 1;

Fig. 3 illustrates a degassing chamber for crucibles and a mast for handling the top of the chamber With the mast shown in vertical cross-section and the remainder of the apparatus in vertical elevation with parts broken away to illustrate certain parts of the apparatus; and

Fig. 4 is a view on an enlarged scale through a fragment of a hinge illustrating the manner of disengagement of'hinge parts to insure complete contact between the sealing surfaces of the two sections of the chamber.

Referring first to Fig. 1, the ladle indicated generally at 10 is provided with a cover indicated generally at 11 and air and gases are Withdrawn from the ladle through a flexible conduit 12 into a condenser-filter unit 13 where metallic particles and vapors are removed. A vacuum is pulled on the ladle by a vacuum pump indicated generally at 14.

Ladle 10 is of the bucket type and includes an outer metallic shell 15 which is lined with refractory material 16. The

usual trunnions

17 and 18 are provided for engagement by the bail, a portion of which is shown at 19. The bail may be of any desired form such as the square or triangular forms as generally used, and is omitted in part here for clarity of disclosure. Adjacent the upper end of the ladle there is provided as an integral part of the outer metallic wall 15 a radially extending annular flange 20. The upwardly facing surface 21 provided by the flange 20 provides a support for the cover 11. Surface 21 also cooperates with the cover 11 to provide a seal as will hereinafter more fully appear. For purposes of providing such seal, the surface 21 should be fairly smooth and kept free of splattered metal.

During the degassing process, the molten metal boils rather violently and to prevent splattering of metal onto the cover and to shield the cover from heat, a shield 22 which rests upon the top rim of the ladle is provided. The shield is made from refractory material and has a hole 23 through Which the molten metal may be visually inspected to determine if it has quit boiling.

The cover 11 includes a top section 24 which is of slightly greater radial dimension than the outer periphery of shell 15 of the ladle. The top section 24- is joined to a downwardly extending annular wall section 25 which telescopes over'the upper section of the ladle and rests upon which the upper section of the chamber is lifted from one side by a mast and in which the mast is disengaged from the upper section of the chamber when it is lowered into its rest position on the low section of the chamber so that the mast will not interfere with full abutment of the sealing surfaces of the upper and lower sections of surface 21 of shoulder 20. The end extremity of wall 25 is provided with a radially outwardly extending flange portion 26 which provides for rigidity of the cover at this point and whose under surface 27 engages surface 21;. The flange portion 26 is provided with an annular groove. 28 which opens into surface 27. An annular seal member 29 of the interference type is carried in groove 28 and engages surface 21 on flange 2t) to seal between the underside of the cover and the ladle.

The interference type seal 29 may be an O-ring fabricated of suitable material such as silicone rubber or other substances which will form the desired seal and withstand elevated temperatures. It has been found that with the structure illustrated, the area about seal 29can be mainthan that of the molten metal within the ladle 10, propermit visual inspection of the boiling metal.

vision is made for water cooling and includes a water jeeket in the top brewer 11 andacoil 30a, preferably of copper tubing, wrapped about the wall 25. Flexible conduit 31 introduces water from a suitable source to the water jacket 30 and a bianchfieirible conduit 3:1a lntroduces water tocoil 30a. Flexible outlet conduit 32 provides rmre moval of the water from the-jacket and coiland discharges the used water into discharged water mainfold 33 from which it maybe conducted to a suitable drain. The coil 30a may be silver soldered or welded to wall 25. Waterpassing through coil 3811 both cools the side walls and flange 26. In this manner; the tem perature'of seal 29 will be held to a low enough value toprotect the seal. This protection for the seal is very important for large ladles. While this protection is not absolutely necessary for small ladles, it is desirable. In either case, cooling of the cover with the water jacket is desirable. v

Thecover '11 is provided with a sight glass indicated generally at 34 in register with hole 23 through the ladle cover so that by visual inspection the state of the molten liquid may be determined. The sight glass is protected by a shield 35 which-is movable into a position beneath the sight glass 34 to protect it from the boiling metal and metallic vapors and into an out-of-the-way position to Shield 35 is carried by a shaft 36 suitably journaledandpacked in'cover 11 as shown. An arm 37 provides for manipulation of the sight glass cover 35.

Apassageway 33 is provided through the cover; preferably through side Wall 35 for establishing communication between the interior and exterior of the cover. A flexible hose 1-2 is secured to passageway 38 through suitable connecting means indicated at 39 and conveys air and gases withdrawn from ladle 1G to the condensertilter 13. The hose 12 will have a considerable length dimension so that the condenser-filter and pump will be located some distance from the ladle to permit free movement of the ladle, and the flexibility of hose 12 is such that the ladle cover 11 may be easily and quickly removed from or placed on a ladle 10. The

water conduits

31 and 32 are also flexible so as to not interfere with free movement of the ladle cover to and from the ladle. Water is delivered to coils 40 within the condenser-"filter 13 through a conduit-41 which together with the conduit 31 for supplying water to the cover, is connected to a'suit' able source of supply 42; The condenser-filter 13 is packed with steel wool 43 upon which the metallic particles and vapors passing through the condenser may con dense out and deposit as the temperature of the vapors are reduced due to the action of the condenser. Water from coil 40 is discharged through line 44 to discharge manifold 33.

Air is pulled from the condenser-filter through the vacuum control valve 45 by the vacuum pump 14.

In operation the cover 11 will be placed on a suitable stand adjacent the working area and water started through the condenser-filter and the cover manifold. A ladle of molten metal from a furnace will be brought into the degassing area with conventional overhead equipment. The shield is first positioned on the rim of the ladle. The cover 11 may then be picked up in any desired manner and placed over the ladle in the position shown in Fig. 1. In this connection, it is pointed out that the inverted cup shape cover is preferred as it telescopes over a ladle with a substantial clearance between the outer periphery of the ladle and the inner periphery of the wall section 25 of the cover to permit ease of placement of the cover over aladle. This form of cover also permits the use of a shield separate from the cover. Pumplmay now be started and the vacuum valve 45 opened to impose a vac uum on the interior of ladles 10. From time to time, the sight glass cover 35 is moved aside and the condition of the molten metal inspected.

As pressure within the ladle reduces, gases and the metal are continuously evolved until substantially all of the gases'within the marten nietaih'ave been released'and the surface of the metal will stop boiling. When this condition is noted to prevail through sight glass 34, the pump 14 is stopped and pressure within and without the ladle equalized either through vacuum valve 45 or through the provision of a special air inlet valve 58 as shown in Fig. 3. As soon as pressure is equalized within and without the ladle, the cover and shield may be lifted tree from the ladle and moved into an out-of-the-way position to permit the overhead equipment to pick up the ladle and proceed to the mold. It will be noted that the weight of the coveris relied uponto hold the cover in place and permit seal 29to seal between the ladle and cover and thus the ladle cover may be lifted free without the necessity of removing any clamping device.

Referring now to Figs. 3 and 4, there is shown a degassing chamber for crucibles which is made up of top portion 46 and bottom portion 47. 7 The vacuum is, drawn on the chamber by a pump 4la with the air and gases from the chamber being first passed through a condenser filter 49. The top half of the chamber is raised and lowered and moved into an out-of-the-way position by a hoisting mast and hinge ar angement indicated generally at 50. h s The chamber proper is substantially tubular in shape and theupper and lower halvesare provided with radially,- outwardly extending abutting flanges 51 and 5 2 respec tively at their-juncture. The

flanges

51 and 52 impart strength to the halves and provide a sealing area [or the employment of an interference type seal. Preferably, the under face 53 of flange 51 is provided with an annular groovej i and an interference type seal, preferably an O-ring 55, is carried in groove 54. The O-ring, of course; engages the upper face or flange 52 and forms a seal between the upper and lower halves.

A sight glass 34 is provided in the top of the chamber together with the sight glass cover 35 and actuator han dle therefor. An air inlet valve 58 is provided. to equalize the pressure Within and without the chamber after degassing has been completed. A reflective shield 80 of stainless steel or aluminum coated steel, covers substantially the entire side wall of upper section 46 of the chamber. The lower end of the shield terminates just above the bottom face 53 of the flange 51*to prevent it being damaged in handling the top section of the chamber.

The upper half 46 of the chamber includes most of the vertical wall portion of the chamber so that upon removal of the upper half the crucible 56 may be removed from the chamber with only slight vertical lifting of the crucible. In this regard, it is pointed out that a stool 57 is provided in the chamber for supporting the crucible which raises the crucible almost to the level of the top of the lower portion of the chamber. The stool 57 has a diameter substantially less than the tubular wall 47a to provide an annular space therebetween for the condenser-filter. I

By positioning the condenser-filter within the chamber, a separate'unit need not be built to stand pressure differential and the bottom and sidewall of the chamber may be utilized as a portion of the filter, In this instance, the condensepfilter comprises acoil 59 arranged circumferentially about the steel 57 and a filter side 60 and filter. top 61; A plurality of inlets 79 to provide an inlet into condenser-filter 49. The filter is again filled with steel wool as at 62. It will be noted that the, condenser-filter incl des a wall which is immediately adjacent to flange 5 2. Thus, the condenser-filter will tend to remove heat from the area of seal 54 and prevent temperatureri's} ing to an undesirable amount. While this is" desirableas' it prolongs" the life of seal 55, the problemis not as critical as with the ladle of Fig. 1 due to both the reflective shield 80 and the fact that the crucible is not in direct contactwith the's'eal surface and therefore the space between the crucible and side walls provides an insulator which space has very good insulation properties upon evacuation of air therefrom.

The air and gases are drawn from the condenser-filter unit through a conduit 63 and the vacuum control valve 64 by the vacuum pump 48.

The handling apparatus for the top half 46 of the chamber includes a telescoping mast in which the exterior section 64 telescopes over an interior section 65. The lower end of the exterior section is provided with a guide 66 which slidably engages the interior section of the mast to position the lower end of the mast. The upper end of the mast is positioned by a guide 67 carried by the innersection 65 of the mast and slidably engaging the exterior section 64 of the mast. With this arrangement, the telescoping section 64 of the mast is raised and lowered along a fixed path.

The mast is raised and lowered by a chain drive and a prime mover 68. The chain drive is provided by a chain 69 which runs over idler sprockets 7d and 71' in the bottom and top of the mast respectively and has its ends secured to the mast guide 66 at 67 and 69a. Upon rotation of the drive sprocket by the prime mover 68, the chain 69 will be taken in over idler sprocket 70 to raise the mast, and the chain from the drive sprocket will be prevented from becoming tangled by being drawn up with the mast due to its attachment to the mast at 69a. On the lowering of the mast, the chain is let out over idler sprocket 70 and the mast lowered while its weight is supported over idler sprocket 70 and the excess chain is fed into the drive sprocket as the telescoping section 64 of the mast lowers. W

The mast is secured to the upper section 46 of the chamber by a pair of vertically spaced hook and eye hinges which support the upper section of the chamber and permit 'it to be swung from a position over the bottom section of the chamber into an out-of-the-way position to permit handling of the crucible with overhead equipment. Each hinge includes an eye half 72 and a pin half 73 with the pin half supported by the eye half so that the telescoping mast section 64 may be lowered to a point at which the pin and eye will become disengaged and therefore the mast will not in any way hinder the complete engagement of the interference seal 54 to form a perfect seal. If the hinges were left connected, it is possible that on occasions the upper section of the chamber would not competely seat about its entire seal area and the O-ring would be driven by pressure through the crack between the two sealing

flanges

51 and 52 and possibly damaged.

Referring particularly to Fig. 4, the preferred construction of the hook and eye hinge is illustrated. The eye section of the hinge 72 is provided with a concave depression 74 which is preferably conical in shape and the pin section 73 is provided with a pin 75 having a.

convex nose section 76 preferably conical in shape and mating with the conical depression 74. In this type of arrangement, the eye section of the hinge need be lowered only a slight distance after the upper portion of the chamber has seated on the lower portion to separate the eye and the hook of the hinge and the conical pin and eye will hold the upper section of the chamber in true alignment even with wear so that it will descend with the sealing flange 51 in a horizontal plane.

In order that the weight of the upper section 46 of the chamber may be borne equally by the two hinges, the pin portion of the hinges are provided by hinge arms 81 through which the hinge pin in the form of a threaded bolt 75 extends and a pair of

lock nuts

77 and 78 are arranged above and below the arm 75. With this arrangement, the pin 75 may be locked in a selected vertical position to engage the eye portion of the hinge. It will be appreciated that with this arrangement the eye portions of the hinge may be secured to the mast at the approximate correct positions and the adjustment feature of the pin depended ber.

: upon for providing equal support of the chamber vtop by both hinges. I

From the above, it will be seen that all of the objects of this invention have been attained. There has been pro-' vided an apparatus for degassing which utilizes a ladle as a portion of the degassing chamber and provides for, rapid and easy handling of the degassing step. The degassing cover is flexibly attached to the condenser-filter and pump so that these portions of the apparatus may be arranged along the usual path of travel of the ladle from the furnace to the molds and the ladle stopped along its normal path and the degassing step carried out.

There has been provided a seal arrangement for adegassing apparatus which employs a ladle in which the seal is protected against excessive temperatures to permit it to seal with the body of the ladle itself.

There has also been provided a degassing chamber which has a handling arrangement for the upper half of the chamber which permits it to be readily removed from about a crucible and swung to an out-of-the-way position and in which the mast while supporting the top of the chamber from one side does so in .such a manner that when'the upper section of the chamber is seated on the lower section of the chamber the mast is entirely disengaged from the upper section of the chamber so as to not interfere with full seating of the upper section of the chamber on the lower section about its entire sealing surface.

There has also been provided a degassing chamber in which the condenser-filter is positioned within thecham- From the foregoing it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It .will be understood that certain features and subcombinations are of utility and may be'employed without reference to other features and'subc'ombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1s:

1. Vacuum degassing apparatus comprising, a sealed chamber divided into top and bottom portions, said portions having annular confronting surfaces at their juncture, seal means for sealing between said surfaces, a vacuum pump for evacuaitng gases from the chamber, a condenser-filter for removing metallic vapors from gases drawn from the chamber before it reaches the pump, a mast having a traveling portion for raising and lowering the chamber top, and a plurality of vertically spaced hinges for swinging the chamber top from the traveling portion of the mast to provide for raising and lowering the chamber top with the traveling portion of the mast and permitting the top of the chamber to be swung to and from a position over the lower portion of the chamber, each of said hinges separating into two disengaged parts upon further downward movement of the traveling portion of the mast after the top portion of the chamber is supported on the bottom of the chamber.

2. Vacuum degassing apparatus comprising, a sealed chamber divided into top and bottom portions, said portions having annular confronting surfaces at their juncture, seal means for sealing between said surfaces, a vacuum pump for evacuating gases from the chamber, a condenser-filter for removing metallic vapors from gas drawn from the chamber before it reaches the pump, a mast having a traveling portion for raising and lowering the chamber top, and a plurality of vertically spaced hook and eye hinges between the traveling portion of the mast and the top of the chamber for raising and lowering the chamber Up With the traveling portion of the liiast and permitting the top of the chamber to be swung" to "25m item we; "the Tower; portion of thecjhamber; 's ieti v e1- ing of the inast femovable from 'fifstfbitid it which the top of the chamber may be swung ahout'the hinges-to an qfit-of-the-way pastries; to' a secondpositibn where said top is supported-oh the libt'tom 'of thefchai'hher and the eye and hook "of the megeswm; be disengaged so that the mast wm'n tgprevefi ebutment of said conrrofiting surfaces about their en'tire'imular dim'ehsio'n. I

3. The degassing apparatus [of claiin'2 wherein theHQYe of each hinge is formed by concave depression see the pin is some by a member a cbnveir end which mates with such concave depressidrijand sag piri aiid eye need not be completely separated from each ether eut eh y the concave and convex i s paraf'edto prevent the'traveling portion of the mast from interfering with the fuli sealing of the surfaces of the top arid'bbtto'm portions of the sealing chamber. 7 e I, M:

4, Vacuum degassing apparatus comprisihg'a sealed chamber divided into top and bottom portions" said tions having annular confronting srirfaces at 111 are, seal means for sealing between said surfaces d bottom portion provided by ahottom platea'rid a hirlai upstanding l s h 9 fl iqi eie e d IL' M its upper end in a flange to provide the eonfiont1 face of the bottorn portion an annplar stool for s p V l i ms tl 'me n e nt bffiheib it em portion of the chamber and having" a lesser diameter th amet f. h ups an n W t P ov d an a a l space; therbe'twee'n, a condenser filter in said anfiularispace for removing metallic vapors from gas drawn from the chambeigj a vacuum pump for evacuating gas from the chamber through the condenser-filter, anannu lar shield of eemary material carried bythe top of the chamberand shielding substantially the entire side wan portion of 8 the top of the ehamber, a mast having a traveling portion for raising and lowering the chamber top, and a plurality of vertically spaced hook and eye hinges between the traveling portion of the mast and the top of the chamber for raising and lowering the chamber top with the travel ing portion of the mast and permitting the topof the chamber to be swung to and from over the lower portion of the chamber, said traveling portion of the mast being removable from a first position at which the top of the chamber may be swung about the hinges to an out-ofthe-way position to a second position Where said top is supported on the bottom of the chamber and the eye and hook 'of the hinges will be disengaged so that the mast will not prevent abutment of said confronting surfaces about their entire annular dimension.

References (sited in the file of this patent UNITED STATES PATENTS 287,273 Gordon Oct. 23, 1883 448,944 Durfee et a1. Mar. 24, 1891 828,142 Simpson Aug. 7, 1906 1,077,925 Baradue-Miller Nov. 4, 1913 1,131,488 Dolensky Mar. 9, 1915 1,301,374 Brown Apr. 22, 1919 2,181,092 Ness Nov, 21, 1939 2,196,003 Wood -Apr. 2, 1940 2,214,611 Greenberg Sept. 10, 1940 2,253,421 De Mare Aug. 19, 1941 2,587,793 Waldron Mar. 4, 1952 2,123,428 Chambers Nov. 15, 1955 2,766,110 Meister Oct. 9, 1956 2,781,260 Grandpierre Feb. 12, 1957 FOREIGNPATENTS p 426,573 Great Britain Apr. 5, 1935