US3305901A - Vacuum casting method of multiple ingot casting - Google Patents

Description

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING J. B. GERO l2 Shee tS-Sheet 1 Feb. 28, 1967 Filed June 12, 1963 m a 4 a B e llllll-Illllllll lllllllll 28, 1967 J. B. GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, ,1963 12 Sheets-Sheet 2 Feb, 28, 1967 J 5 GERO VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, l965 12 Sheets-Sheet 3 llllllll I 9O $51 .6. lh

J. B. GERO Feb. 28, 1967 12 Sheets-Sheet 4 Filed June 12 J. B. GERO Feb. 28, 1967- VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, 1963 12 Sheets-Sheet 5 J. B. GERO l2 Sheets-Sheet 6 Feb. 28, 1967 VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, 1963 1 0 v I G Feb. 28, 1967 GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE'INGOT CASTING Filed June 12, 1963 12 Sheets-Sheet '7 Feb. 28, 1967 J. B. GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, 1963 l2 Sheets-Sheet 8 J. B. GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Feb. 28, 1967 12 Sheets-Sheet 9 Filed June 12, 1963 1967 J. B. GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Filed June 12, 1965 12 Sheets$heet l0 J. B. GERO 3,305,901

VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING Feb. 28, 1967 12 Sheets-Sheet 11 Filed June 12, 1963 J. B. GERO Feb. 28, 1967 12 Sheets-Sheet 12 Filed June 12, 1965 3m $250 we m; a 8+ u ouwm Etm 233E mE 3352 E mE 9 m m w m w n m o i 09 00w 1.) E oom I m 0 9: c E U 260mm M T 9: E

United States Patent 3,305,901 VACUUM CASTING METHOD OF MULTIPLE INGOT CASTING John B. Gero, Manchester-by-the-Sea, Mass., assignor to Gero Metallurgical Corporation, Boston, Mass, a corporation of Delaware Filed June 12, 1963, Ser. No. 287,416 2 Claims. (Cl. 22-209) The present application is a continuation-in-part of application Serial No. 122,440 filed July 7, 1961, now abandoned, and application Serial No. 235,953 filed November 7, 1962, now Patent No. 3,182,359 dated May 11, 1965.

This invention relates to methods and apparatus for vacuum casting of molten metals and, especially to vacuum casting of heavy forging ingots and the mass production of rolling ingots wherein gaseous components of harmful nature are in part removed from the molten metal during the period that the molten metal is being poured into an ingot mold or ladle.

Removal of gaseous components of harmful nature from molten metal is commonly referred to by the term degassing. At the present time degassing is conventionally carried out by several different methods, including the stream droplet method and the lift or recirculating method. The present invention and the copending applications referred to are in general concerned with novel methods and apparatus for carrying out degassing by the stream droplet technique utilizing a casting mold and a degassing chamber which is required to be secured to the casting mold in tightly sealed relationship for casting under a high vacuum.

In conventional apparatus heretofore used in the stream droplet technique, problems are encountered in maintaining a satisfactory high vacuum. To evacuate gases rapidly from the mold and the degassing chamber to a satisfactory degree requires extremely efficient sealing means and large volume pumping equipment. Since the vacuum must be fully maintained throughout the metal pouring interval there is a period during which the sealing means may be exposed to temperatures which will affect the sealing means. Moreover, there arises a problem of dimensional instability on the part of those surfaces which support the sealing means. This dimensional instability is produced by thermal shock from hot molten metal flowing into the mold and causing differential expansion of parts. A still further consideration is seal replacement where successive ingots are being poured continuously in the steel foundry. This type of continuous operation may require pouring equipment of a construction such that it may be quickly assembled and sealed on any one of a series of relatively rough surfaced, non-uniform casting molds to facilitate production of either large forging ingots or small rolling ingots as may be required from time to time. Existing equipment, so far as I am aware, does not meet these requirements. The methods and apparatus presently employed are unsatisfactory in maintaining a seal which will provide for holding a suitable vacuum and do not provide any practical means of seal replacement.

It is a chief object of the invention to improve methods and apparatus for vacuum casting and to devise means for more effectively and quickly establishing and maintaining a degassing chamber vacuum in order to produce quality steels with desirable magnaflux and micro-cleanliness ratings and to make possible vacuum casting of multiple large or small ingots from one heat or ladle. In such objectives the provision of a vacuum casting system of relatively small volume and more efficient pumping characteristics is of importance.

Another object of the invention is to devise a new combination of sealing compound and casting apparatus for 3,305,901 Patented Feb. 28, 1967 vacuum casting whereby unusual sealing effects may be accomplished and also whereby the evacuation of air tc produce a vacuum may be carried out in a highly efficient and rapid manner.

A further object of the invention is to devise a method and means for dealing with the problem of dimensionaI instability and compensating for differential expansion 01 casting components during the pouring interval.

Still another object is to provide a method of high temperature vacuum sealing which is based on the concept of utilizing a disposable sealing body which is subject to decomposition at relatively high temperatures and which is readily replaced when desired.

A further object is to provide improved methods anc' apparatus for sequence casting of metal ingots into 2 series of ingot molds in predetermined successive time intervals from a pouring ladle.

The method and apparatus of the invention hereinaftei disclosed presents several unique techniques for dealing with the problems outlined and realizing the foregoing objectives. These techniques are based on the concept 0: producing an extremely high vacuum by means of at expansible heat resistant seal, that is a seal suflicientl; deformable so as to be expansible with the surfaces t( which it is adhered. Nevertheless, the seal is maintainer in effect for a relatively short period.

In the method of the invention, vacuum casting part. are arranged upon one another and held in sealed rela tionship for a limited period at least as long as an ingo pouring interval and usually for a little longer than thi: interval as a factor of safety. The method is furthei characterized by novel compensation for differential ex pansion of the components when subjected to therma shock.

In one preferred embodiment the method of the inven tion includes the steps of evacuating air from a degassing chamber which is mounted on a casting mold; then releas ing molten metal from a pouring ladle and conducting tht molten metal through the evacuated degassing chambe: into a casting mold body whereby a thermally inducer differential expansion of the degassing chamber and tht casting mold takes place; and simultaneously supporting yieldable heat resistant sealing body between the degassing chamber and the casting mold, and subjecting the sealing body to forces of deformation to provide a compensating expansion which maintains the sealing body in vacuum tight sealing relationship with both the degassing chambe' and the casting mold for a limited period approximately corresponding to the ingot pouring interval.

- I have discovered that it is possible to start with fluid tr wet parts to be sealed, then heat to form deformable solir sealingly adhered to the surfaces it contacts, thereafter tr set up on a mold surface an expansible sealing body which although decomposable in the upper range of tem peratures induced in a casting mold during an ingot pour ing interval, may nevertheless resist thermal attack sufii ciently long to yieldably maintain a seal for the periot roughly corresponding to the ingot pouring interval After the pouring interval a rapid increase in the tempera ture of the casting mold results in burning off the seal ing body to leave a powdery residue which is readily brushed away and replaced by a new sealing body for tht next ingot pouring operation. In thus setting up an ex pansible sealing body which is to be subjected to force: of deformation, I find that I may also employ means f0: supporting and reinforcing the sealing body as well as f0] controlling the degree of differential expansion to whicl the sealing body may be exposed.

As an example of a sealing material which is suitablt for this purpose, I may employ a new composition 0. matter comprising a mixture of three essential compo 'nents(I) a low molecular weight glycidyl polyether [1) a condensation product of a low molecular weight .ycidyl polyether and ethylene glycol and; (III) a curing gent composed of pyromellitic dianhydride mixed with re anhydride of a dicarboxylic acid. When these comments are combined in the hereinafter described proartions a resinous mixture is obtained which upOn ex- Jsure to moderate heat changes from fluid to solid and .ereafter at elevated temperatures resists melting and lres to a solidified adherent elastic body. In addition 1 the above ingredients it may be desirable to include IIiOllS fillers and a cure accelerating agent.

The composition of matter noted above is intended to be :presentative of sealing compound means which is sufiiently fluid to adhere to metal surfaces of casting mem ers; which is characterized by the ability to cure when rought into contact with metal surfaces heated to tem- :ratures of from room temperature 70 F. to 400 F. F form a tough deformable solid flexible adhesive tenaously secured to said surfaces; and which in this cured ate is capable of resisting flowing or decomposition in re presence of a range of temperatures of from 70 F. p to at least 600 F. for a limited period of time corre- IOHCllIlg approximately to an ingot pouring interval, and .ereafter to be decomposed at elevated temperatures to dry powdery mass which may be readily removed from re mold.

I find that by employing a sealing compound of the ass described as an externally located sealing body he veen the degassing chamber and casting mold, I am en- 716d to provide for unusually high vacuum as compared ith vacuum results obtained with conventional equip- .ent.

As an example of unusually high vacuum, there may cited absolute pressure readings of an order of magnilde of less than one micron before pouring in the deissing chamber. It should be understood that when Juring starts absolute pressures as defined by micron :adings temporarily rise from the one micron reading oted above, to micron readings of as high as 300 to 500 llCl'OIlS, for example. Then, as pouring continues rroughout a pouring interval which may range from one tinute to ten minutes, the micron reading rapidly deeases, in accordance with the invention, to values well slow the 300 to 500 range, for example, down to values E from 200 microns all the way to readings as low as 50 llCIODS or even less. In one typical pouring operation irried out in accordance with the method of the invenon there has been observed pressures as low as 45 mions. It must be borne in mind that the precise micron alue in any given pouring operation, however, depends n the grade of metal which it may be desired to make and :her related conditions. This latter micron reading is in )ntrast to optimum micron readings obtained with con- :ntional equipment of from 700 to 2,000 microns. It iould be understood that very low absolute pressure :adings of from 500 microns to microns or less are :cessary for efiicient pouring of highly alloyed metals. I have also determined that by thus producing and alding extremely low pressure readings at the degassing iamber through which the stream of molten metal is )nducted, I am able to produce very desirable results t that there is accomplished a greatly increased removal E harmful gases. Also, I am able to prevent the reridation and reabsorption of gases such as may occur hen ladle degassed metal is rcpoured into ingot molds posed to the open atmosphere.

I have further devised a method of vacuum casting a umber of metal ingots in which molten metal is released ltO a series of ingot molds in predetermined successive me intervals and in which a vacuum pump apparatus moved from one sealing position to another on suc- :ssive molds in a controlled sequence.

The nature of the invention and other objects and ovel features will be more apparent from the following :scription of preferred embodiments selected for pur- 75 poses of illustration and shown in the accompanying drawings, in which:

FIGURE 1 is a vertical cross sectional view of one simplified form of vacuum casting apparatus of the invention and indicates diagrammatically the operation of pouring molten metal while a vacuum is being exerted;

FIGURE 2 is an enlarged fragmentary view of the vacuum casting components and sealing means of FIG- URE 1 including a heating device for inducing selective expansion of the sealing means;

FIGURE 3 is a vertical cross sectional view of another form of vacuum casting apparatus particularly suited for casting a number of ingots from one pouring ladle and also illustrating another form of expansion device;

FIGURE 4 is a fragmentary perspective view broken away at one point to illustrate more clearly the sealing means shown in FIGURE 3;

FIGURE 5 is a perspective view of the casting mold construction of FIGURE 3 and shown separated from the degassing chamber portion of the apparatus to indicate a special channel construction;

FIGURE 6 is a cross sectional view illustrating vacuum pump and control valve mechanism of the invention as employed at the left hand side of FIGURE 3;

FIGURE 7 is a perspective view illustrating the vacuum casting equipment combined with apparatus for carrying out a number of pourings from a single ladle member;

FIGURE 8 is a fragmentary plan view further illustrating the expansible sealing means employed in FIG URES 3 to 7 inclusive; 7

FIGURE 9 is a cross sectional view taken approximately on the line 55 of FIGURE 8;

FIGURE 10 is a fragmentary view illustrating a modified form of casting mold formed with an upstanding flange portion with which the sealing means of the invention may be associated;

FIGUR E 10a is a fragmentary detail view of a portion of the mold structure shown in FIGURE 10* and illustrating sealing means in a position assumed before a vacuum is produced;

FIGURE 10]) is another view similar to FIGURE 10a, but showing the position of a sealing member after a vacuum has been produced;

FIGURE 10c is a view similar to FIGURES 10a and 10b, but further illustrating the casting mold and sealing means under vacuum and expanded by heat resulting from a pouring operation;

FIGURE 11 is a fragmentary perspective view of casting mold means and another desirable arrangement of sealing means mounted thereon;

FIGURE 12 is an elevational view partly in cross section illustrating another modified casting mold means having the sealing means of the invention associated therewith;

FIGURE 13 is a cross sectional view illustrating vacuum casting apparatus of the invention;

FIGURE 14 is a plan view illustrating diagrammatically another type of vacuum pumping apparatus for use in teeming metal in successive ingot molds;

FIGURE 15 is a cross sectional view further illustrating the vacuum pumping apparatus of FIGURE 14 on a larger scale and indicating sealing components of the apparatus in a closed position;

FIGURE 16 is a diagrammatic view illustrating in graph form a time curve for ingot pouring intervals; and

FIGURE 17 is a cross section taken on the line 1717 of FIGURE 13.

The method of sealing of the invention may be employed with various forms of casting components and may be designed to provide very low pressure. For example, FIGURES 1 and 2 illustrate a relatively small volume degassing chamber structure mounted on a casting mold, and a sealing body arranged externally of the line of junction of these members to provide for one type of vacuum casting. FIGURES 3 to 9 illustrate a somewhat difierent arrangement in which the sealing body is protectively arranged around an expansion device to provide very low pressure micron readings for vacuum casting operations where a series of casting molds are used. FIGURES 10, a, 10b, 10c, 11, 12, 13, 14 and illustrate still further modifications of the sealing means of the invention.

Considering first the form of invention illustrated in FIGURES 1 and 2, numeral 2 denotes an ingot casting mold 2 having an ingot cavity 4. One type of conventional mold now commonly used may have a cavity volume of approximately 16 cubic feet, for example. This mold member is preferably seated on a heavy flat bottom stool 6. At its upper side the ingot mold is formed with a generally flat but rough and non-uniform seat surface 8 which extends around the ingot cavity 4 to provide a support for a degassing chamber member generally indicated by the arrow 10. The degassing chamber and casting mold are sealed together by the sealing means of the invention as noted below. Conventional existing cast iron molds of the type used in the foundry can be economically used in the method of the invention.

In one suitable form the degassing chamber 10 includes an upper container section 10a, and a lower conduit section 1%. These sections are separated by a transverse wall 10:: through the center of which is formed a pouring aperture 12 which is normally closed by a fusible closure cap '14 of aluminum or other suitable material. The cap 14 is secured by bolts 16 and 18. In the presence of hot metal discharged from transporting ladle 22, for example, shown at the upper side of FIGURE 1, the closure member 14 becomes fused and will then allow the hot metal to flow through the aperture 12 and down through the conduit section 10b to finally be received in the mold cavity 4.

A novel feature of the combination of degassing chamber section and mold member resides in providing the degassing chamber with a volume which is less than the volume of the mold. For example, with a mold cavity of 16 cubic feet, as noted above, I find I may employ a degassing chamber volume of approximately 5 cubic feet and I find that by thus employing a degassing chamber volume less than the volume of the mold cavity, I am enabled to obtain unexpectedly rapid pump-down to a degree such that micron readings as low as 200 microns in a time interval of 15 seconds may be obtained. This has not been accomplished in the art before in vacuum casting.

In the lower conduit section 10b is also supported an annular refractory hot top 19, which is necessary on all deoxidized steels.

I further construct the degassing chamber 10 with means for evacuating gases from the conduit section 10b as indicated in FIGURE 1. The evacuating means includes a passageway formed through the sidewall portion of the conduit section as shown and into which is tightly fitted a tubular member 26. Attached at some convenient point to the outer end of the tubular member 26 is a conventional vacuum pump unit which is not shown in the drawings.

When a casting operation is to be carried out, the degassing chamber is located on the relatively rough and non-uniform upper surface of the casting mold and these parts are sealed in accordance with the invention. In forming a seal a body of special sealing compound 30 is located externally around the junction of the degassing chamber 10, and the casting mold 2. This sealing compound is applied in a sufficiently fiuid condition so that when placed in contact with the metal surfaces of the degassing chamber and a casting mold, it will adhere to the surfaces of the casting components, and in spite of the unequalities of the rough and uneven noted surface. After the compound has been applied, it is cured by heating. It will be understood that the sealing compound may be applied either before or after the degassing chamber is placed on the mold surface 8. In ordinary working cor ditions the degassing chamber and casting mold undt usual melt shop conditions may be at temperatures from F. to 400 F., at which temperatures, for e: ample, satisfactory curing will take place. The sealir compound 30 cures to form an expansible solid bod tenaciously secured to the metal parts in contact with i Before pouring takes place, air is evacuated from the dl gassing chamber and casting mold to produce a desire vacuum. Normally I find that in this period before pou ing takes place an absolute pressure of approximately 1( microns or less may be reached in about thirty second Pressures as low as 10 microns and below are consistent attained by continuing evacuation of air for a period approximately one minute or less. Speed of pump dow is highly critical in successive pourings, especially in pou ing from a single ladle into a series of prearranged IIlOk since temperature losses in the molten metal in the pou ing tend to occur and produce undesirable solidificatic of metal in the casting components of the pouring ladl It is not uncommon with existing processes to have solid fied metal left in the ladle after pour, or to have t1 nozzle and stopper rod freeze together if too much tirr is wasted and the temperature loss of the molten metal i the ladle is sufliciently great.

The release of pressure on the molten metal as it 163W the nozzle and enters the degassing chamber causes violent evolution of gases such as hydrogen, nitrogen an oxygen in the form of carbon monoxide. These gases a1 drawn off by the vacuum pump. At the same time tl molten metal as it collects in the ingot mold is cause to continuously ebbulate and in the course of this actic a further removal of gases takes place.

The percent-age of gases in the molten metal may, find, be very significantly reduced in both of these way i.e., from the dispersed material and the collected mat rial. Especially significant is a reduction in carbon co. tent where the initial carbon content is low. This remov of carbon monoxide serves both as a deoxidation trea merit for high carbon steels and a decarburization trea ment and deoxidation treatment for low carbon conte. steel.

As the body of molten metal M collects in the ca: ing mold 2, intense heat of the molten metal is conduct through the body portion of the casting mold at a muc greater rate than occurs with respect to the degassii chamber section 1012. As a result the surface 8 of ca: ing mold 2, undergoes in effect a thermal shock and e pands differentially with respect to expansion of the d gassing chamber section 10b.

However, in accordance with the method of the i vention I find I may compensate for this differential e pansion by utilizing a sealing material which is capab of deforming under stress to provide for a compens-atii expansion without splitting or separation taking plac Furthermore, the compensating expansion is accor plished with a compound whose unusual heat resista characteristics enable it to withstand relatively high te-r peratures for a limited period of time, yet to thereaft decompose for ready removal from its mold and chamb surfaces.

As illustrative of temperatures to which the seal exposed I may start, for'example, with a mold which at room temperature, or the mold may occur in a ran, of temperatures of from F. to 400 F. The latt temperatures may occur as a result of an earlier used mo having cooled to these temperatures subsequent to remov of a steel ingot, or may be heated to these temperatur by any means such as a gas flame. The pouring intt val may take anywhere from one to ten minutes to I completed and in this pouring interval temperatures from 100 F. up to 400 F. and possibly higher m. occur, depending on the relative distance of the cor pound from the molten metal interface. The compoui of the invention, for a short period after pouring, co.

ues to maintain itself in a vacuum-tight sealing conion and then starts to decompose as initially evidenced the smoking. The temperatures in the mold, after uring is completed, rise very quickly above 400 all way up to 1,500 E, and higher. At these temperaes the sealing body 30 almost completely burns off leave a very thin powdery residue which can be readibrushed away and replaced by new compound when sired.

Thus it will be observed that the compound exhibits Ieral desirable characteristics and performs a number of portant functions. First, there is a sealing with resistce to heat; secondly, there is a limited degree of derma-tion to compensate for differential expansion of a casting components during the short pouring interl; third, there is the ability to decompose and thus nstitute a disposable sealing member which can be ickly replaced by a new sealing body without special :aning operations.

The sealing compound 30, as noted above, may be of a class of compounds containing, in general, polyoxide mate-rials. Epoxy resins are prepared by the action of a dihydric phenol and epichlorohydrin in the esence of sufficient alkli to maintain the reaction mixre substantially neutral.

The predominant constituent of the reaction product represented by the formula:

lerein R represents a divalent aromatic hydrocarbon dical and n is an integer. By varying the ratio of ichlorohydrin to the dihydric phenol, compositions of rying molecular weight (varying 11) may be obtained, a value of n decreasing as the quantity of epichlorohyin is increased.

Considering for purposes of illustration the most widely iployed dihydric phenol, bis(4-hydroxy phenyl) diethyl methane (hereinafter termed Bisphenol A) the glycidyl ether has the formula:

lere n of Formula 1 is zero. By employing a mole tio of epichlorohydrin to Bisphenol A of 10:1 the divci-dyl ether is produced in a fairly pure state. As the ole ratio is decreased the proportion of higher molecular :ight polyethers increases. In general, mole ratios of 1 to 1011 give average molecular weights of about to 450. In practice it is found that though the size the major portion of the polyether molecules may be ntrolled, some small proportion of longer and shorter igth molecules will be present. In addition side reacvns may occur with some formation of intermediates, .t the quantity of these side products does not noticely influence the properties of the resin.

In preparing the sealing compound 30, I produce comnen-t 1, the low molecular weight glycidyl ether by ing a dihydric phenol, bis(4-hydroxy phenyl) dimethyl ethane, having an average molecular weight of from 0 to 450. With other dihydric phenols this range will ry slightly. Referring to Formula 1 the average molule of the ether will contain between 1 and 1.5 Rs romatic radicals) and n will vary from 0 to 1. The oxide equivalent (weight of resin in grams containing gram equivalent of epoxy) should be between about 5 .-an-d 225. Assuming the resin chains to be substanlly linear with an epoxy group terminating each end, en the epoxide equivalent is one-half the average mo- :ular weight. The viscosity of the polyether will vary )m 5,000 to 20,000 cps. as measured with a Brookld LVT-5X viscometer with No. 5 spindle at 6 r.p.m.

at 25 C. Many commercially avail-able epoxy resins with suitable properties may be used. Among these are Bakelite ERL-2774 and Bakelite ERL3794, Epi- Rez 510, Epon 820 and Epon 828. Bakelite is the trade-mark of Union Carbide Corp; Epi-Rez is the trade-mark of the Jones-Dabney Co., Div. of Devoe & Reynolds Co.; Epon is the trademark of the Shell Chemical Corp.

Component II is the reaction product of Component I with a glycol, for example, ethylene glycol. The ratio of epoxy to hydroxy can be varied from 1/0.5 to 1/2 with little effect on the finished compound. The reaction may be carried out by mixing the desired quantities of epoxy and ethylene glycol and heating to -150 to 185 C. for one hour or until the mixture becomes homogeneous.

The product has a molecular weight of 385 to 485 and is believed to consist primarily of the product resulting from the reaction of one epoxide ring with an hydroxyl group of the glycol. Since Component I can be considered to contain an average of two epoxy groups per molecule, it is quite certain that the primary condensation product resulting from such controlled conditions may be represented by the formula:

For convenience I shall refer to the condensation product as the 50% condensate of Component I with a glycol.

Component II lends flexibility to my resin composition, but must be used in controlled amounts. I have found empirically that the ratio of Component I to Component II may vary from 20/80 to 12/88 with good results. When the quantity of Component II is more than 88 parts, the resin after curing is gel-like and weak. When the amount of Component II is less than parts, the composition cures to a brittle, easily cracked material.

The third Component III of my composition is a curing agent which acts to cross-link the epoxy compounds. The curing agent which I prefer to use is a mixture of a primary curing agent, pyromellitic dianhydride, and a secondary curing agent selected from the group of organic acid anhydrides. The anhydride mixture is used in stoichiometric quantities based on the amount of epoxy and hydroxyl groups present in the resin mixture. A slight excess, about 5%, is employed in the case of solid acid anhydrides to allow for uneven dispersion of the anhydride powders in the resin.

Anhydrides of dicarboxylic acids are well known in the art as curing agents and include phthalic anhydride, maleic anhydride, succinic anhydride, dodecenylsuccinic anhydride, and hexahydrophthalic anhydride.

Depending upon the particular anhydride curing agent used, the proportions of primary and secondary curing agents in Component III may be varied within certain well-defined limits. I have found that 2 to 15 parts of pyromellitic dianhydride and 43 to 17 parts of secondary anhydride for every parts of resin give satisfactory sealing materials for high temperature uses.

The manner in which Component III is added to the epoxy composition will depend upon the particular anhydrides in Component III. Phthalic anhydride must ordinarily be passed with the resin through a colloid mill to get a good dispersion. Maleic anhydride, on the other hand, is sufficiently fine to be mixed in by hand.

When it is desired to shorten the curing time, various well-known cure accelerators may be added to the composition. Among these are alphamethylbenzyl dimethyl amine, n-butyl amine, pyridine and n-methyl pyridine. These are used in catalytic amounts, from 0.5 to 3% of the weight of the resins in the composition.

In addition to the above basic ingredients it is advantageous to add various fillers to the composition to add .and counteract differences in thermal expansion between the resin and the bonded metal. The quantity of filler may be varied from a few percent to three or four times the weight of the resin. The compounding manipulations are well-known to those skilled in the art.

The following examples illustrate the preparation of the compositions of my invention:

EXAMPLE I A commercial epoxy resin, Epi-Rez 510 with the following properties was employed as Component I:

Viscosity, cps. at 25 C 12,000 Specific gravity 1.15 Color (Gardner scale) 3 Epoxide equivalent 185 Hydrolyzable Cl, percent 0.1

Component II is also a commercial epoxy resin, Epi- Rez 507 which is the condensation product of Component I and ethylene glycol in the previously described ratios. It has the following properties:

Viscosity, cps. at 25 C 550 Specific gravity 1.14 Color (Gardner scale) 2 Epoxide equivalent 385 Hydrolyzable Cl, percent 0.15

Twelve parts of Component I was blended with 88 parts of Component II and 43 parts of phthalic anhydride and passed through a colloid mill to reduce the particle size of the phthalic anhydride to 0.025 mm. or less. Care must be maintained to keep the temperature below about 50 C. during passage through the mill. After cooling to room temperature 2.5 parts of pyromellitic dianhydride was added together with 55 parts of micronized silica, 35 parts of atomized aluminum, and 350 parts of short fiber asbestos. The mixture was thoroughly blended while maintaining the temperature of the mix below about 25 C. and 0.3 parts of pyridine were added to the mixture to act as a cure accelerator. The composition was applied to two steel rods about 2.5 cm. by 1.25 cm. by 30 cm. and the steel rods were pressed together end to end. These rods were heated to 205 C. for minutes to cure the composition. The rods were then raised to 315 C., allowed to cool to room temperature and heated again to 345 C. The resin bond remained strong with no cracks or thermal decomposition noticeable.

As a further test of the ability of the composition of Example I to withstand high temperatures, a sample of the composition which had been cured at 205 C. for 15 minutes was placed in contact with a surface at 315 C. for a period of eight hours. There was no evidence of serious charring or decomposition, and the sample re-. tained its normal compressibility.

EXAMPLE II Component I was prepared in the manner described in US. Patent No. 2,682,515, column 6, under the heading Polyether A.

Component II was prepared by adding 46.5 grams of ethylene glycol to 180 grams of Component I. The reaction mixture was maintained at 150 C. for one hour. Upon cooling there resulted a clear, low viscosity monofunctional-epoxy flexibilizer.

Sixteen parts of Component I was mixed with 84 parts of Component II and blended well at 25 C. To the mix was added 13.8 parts of pyromellitic dianhydride, 19.4 parts of maleic anhydride, 75 parts of micronized silica, 25 parts of atomized iron, and 150 parts of short fiber asbestos. After mixing well a homogeneous blend 0 milk-like consistency was produced. To this Was adder 0.4 part of N-methyl pyridine to act as a cure accelerator The composition was spread on steel rods and baked fo 20 minutes at C. After carrying out the heating ant cooling steps of Example I, the bond was found to retai: its strength.

Though in the foregoing examples Component II wa in each case a condensate of Component I and ethylen glycol, this need not be the case. Component II of Ex ample I could have been substituted for Component II 0 Example 11 and vice versa. It is only necessary that Com ponent II be approximately a 50% condensate of a glycc and a glycidyl polyether epoxy resin having a molecula weight between about 350 and 450, an epoxide equivalen of 175225, between 1 and 1.5 aromatic radicals per poly ether chain and a viscosity between 5,000 and 20,000 cps Also, though I have shown Component 1 to be mad from Bisphenol A and epichlorohydrin for purposes 0 illustration, other dihydric phenols are suitable. Thes include resorcinol; 1,1-bis (4-hydroxyphenyl) ethane 1.1-bis (d-hydroxyphenyl) propane; 1,1-bis (4-hydroxy phenyl) butane; 2,2-bis (4-hydroxyphenyl) butane an 1,1-bis (4-hydroxyphenyl) Z-methyl propane.

In thus providing a method of vacuum sealing in whicl the sealing body is expanded or otherwise deformed, may desire to control the expansion of the degassin chamber relative to the expansion of the casting mold i' such a way as to further compensate for the differentia expansion between these members. For example, in FIG URES 1 and 2, I have disclosed a heating coil 32 which i contained in a protective annular housing 34 mounte around the degassing chamber section 10b at a point im mediately above the sealing body 30. Energizing the heat ing coil 32 by means of an electrical current operates t heat and expand the degassing chamber section 10b. Thi expansion may be controlled to compensate for the ex pansion of the casting mold 2, and by timing the electrica current with a rise in temperature in the casting mold 2 I may prevent or substantially reduce differential ex pansion.

It is pointed out that by thus controlling expansion 0 the degassing chamber, a lesser amount of flexing or de formation of the sealing compound is required to tak place and, therefore, the operation of holding the severe parts in substantially constant relationship to one anothe is made easier. This is illustrated in FIGURE 2, for ex ample, by the broken line showings of the component part 10b, 2 and 30 where the broken lines illustrate diagram matically the controlled expansion of both the castin mold and the degassing chamber in very nearly the sam degree.

In controlling the expansion of one casting componer with respect to another, it will be apparent that compound of lesser yieldability characteristics may be employed fo sealing purposes and it is intended that this method c compensatory expansion may be practiced with variou sealing compounds which are capable of resisting thermz attack during the ingot pouring interval. It is also cor templated that mechanically induced expansion of on casting component relative to the other may be carrie out by means of other devices such as hydraulically cor trolled expansion devices and the like.

In FIGURES 3 to 9 inclusive, I have illustrated anothe desirable form of method and apparatus for carrying'ot a degassing operation which is particularly suited to pou] ing a series of casting molds.

It will be understood that in steel foundries as presentl equipped, there is provided a crane mechanism which i arranged to pick up a ladle filled with molten metal 311% carry the ladle to a pouring section of the melt shop wher a series of casting molds are set up. Ordinarily, in typical operation there is an operator station which er ables an operator to control the pouring of molten met:

.to the casting molds one after another in rapid succeson. Here it is very important to deal with a small volne and to employ a rapid pump down in providing for icuum casting into a plurality of molds.

The apparatus illustrated in FIGURES 3 to 9 inclusive, concerned especially with this type of operation and as lOWH includes a platform P (FIGURE 7) along one side i which extends rail'si R, R1, on which is supported a old truck T. Mounted in truck T are a series of casting lOldS C, C1, C2, C3.

The casting molds have secured thereto in sealed relaonship respective degassing chamber units D, D1, D2 1d D3. Located above the platform P is a travelling 'ane structure including an operator control unit movale along elevated rails R2 and R3 on suitable pulleys. he crane structure further includes transversely suported rails R4 and RS on which is received a travelling Dist H from which is suspended a pouring ladle L. Also ipported on rail R3, and another rail R6, is a movable icuum pump V and carriage V1.

In FIGURE 3, I have illustrated a pouring ladle and :gassing chamber unit similar to those shown in FIG- RE 7 and indicated on a somewhat larger scale. The ructure of FIGURE 3 comprises the same type of castig mold already described in FIGURES 1 and 2, together ith a suitable degassing chamber. In addition, however, IGURE 3 illustrates a special compound containing roove and a flexible sealing skirt component. The skirt located at the bottom section of the degassing chamber hereinafter described in greater detail.

Referring first to the ladle components of FIGURE 3, 1 comprises a conventional type pouring ladle which is :ted with a bottom discharge nozzle 60 having an adjust- Jle stopper rod 62. Molten metal M1 is conducted from re ladle L1 into a degassing chamber 10' which is sup- Jrted in sealed relationship on a casting mold 2'. Inuded in the degassing chamber structure is a bottom auring ladle L2 which is fitted with a refractory lining Z. A nozzle 22a provides an outlet for molten metal to :ave the ladle L2 as suggested diagrammatically in FIG- "RE 3.

At its upper side the degassing chamber 10' is formed ith a tubular section 11' having a flange 13 on which is rceived a ladle liner 18'. The latter member is formed ith a flange 20b on which is mounted another flange artion 20a of the bottom pouring ladle L2. Numeral [)d indicates a sealing gasket. The ladle liner 18 is also tted with a fusible aluminum or magnesium disc 26' iaintained in sealed relationship with ladle liner 18' by ange member 24 and bolts as 24a and 24b. Suspended the underside of the flange member 24' is a refractory )ray shield 28 for confining the molten metal droplets l the line of travel indicated in FIGURE 3.

The degassing chamber 10 may be of any desired shape s, for example, the outer housing portion shown in FIG 'RE 4 which terminates at its lower side in a bearing :ction 10c, having a box shape chosen to coincide with re rectilinear shape of the top of the casting mold 2 FIGURE The lower edge of bearing section c is lpported on a top surface 8 of casting mold 2'.

In accordance with the invention, I combine with the :gassing chamber a sealing member comprising a flexible all or skirt 12 which is preferably constructed of metal 1d which is secured to the underside of the degassing iamber as best shown in FIGURE 3. The flexible wall 2' may, in the preferred form shown, be constructed ith corrugations or pleats extending perpendicularly to l6 circumference of the skirt as is more clearly inditted in FIGURES 8 and 9, and also shown in FIGURE This flexible skirt 12 has its lower edge embedded l a sealing compound 30 located in a groove 31 formed l the surface 8 of the mold 2'. The skirt extends all t6 way around the mold and constitutes a yieldable seallg wall which is especially designed to be extended perimetrically. It will be observed that the bearing section occurs inside of this sealing skirt in a position to shield it from high temperatures occurring within the casting mold and degassing chamber when a pour is taking place.

It is further pointed out that the separated relationship of sealing wall 12' with respect to bearing section 100 provides a substantially enclosed space which in the presence of high vacuum, exerted by vacuum pumping means hereinafter described, constitutes an evacuated volume of high heat insulating character capable of retarding flow of heat from molten metal through the bearing section 10c towards the sealing wall 12'. Thus the sealing wall and also the portion of the sealing mass 30' occurring between the sealing wall 12 and the bearing section 10c, are protected by the evacuated volume of heat insulating character and there is avoided a flow of heat of sufficient intensity to effect the sealing capabilities of either the sealing wall 12 or the portion of the sealing mass 30' occurring between the sealing wall and the bearing section 100 during such periods as the sealing wall is being flexed as noted below. a

In FIGURES 8 and 9, the flexible skirt 12 is shown on a somewhat larger scale and the broken line showings are intended to indicate diagrammatically changes in position of the groove, sealing body, and skirt occurring during differential expansion of the casting mold 2' during an ingot pouring interval.

As noted above the skirt 12' is preferably constructed of a flexible steel sheet which is corrugated along vertical lines of folding, as viewed in FIGURES 3 and 4. By reason of this corrugated construction and the type of steel used, the skirt is adapted to flex in two directions. It may flex in such a way that is increases in perimetrical dimension with increase in perimeter of the casting mold groove 31. Also, the bottom edge of the skirt may flex in or out relative to the top edge. Both of these changes are represented by the broken line showings in addition to the expansion which the compound itself undergoes.

I have found that under some conditions of differential thermal expansion, the combination of the compound, groove, and skirt provides optimum sealing results. It is believed that the corrugated skirt becomes extended with expansion of the mold groove. As the skirt expands it continues to maintain an anchored relationship in the bottom of the sealing compound in the groove while acting as a reinforcing medium for the sealing compound and materially reducing the stresses induced in the sealing compound itself.

It should be understood that as soon as a vacuum is established in the degassing chamber, atmospheric pressure tends to exert forces against the outer side of the skirt and that portion of the sealing compound which lies between the skirt and the outer edge of the groove. This occurs concurrently with the mold expanding and tending to stretch the sealing body at a time when the scaling is subjected to increasingly high temperatures. Thus there are various forces of deformation acting on the sealing body and the corrugated skirt exercises both a stabilizing and compensation action. Anchoring of the lower extremity of the skirt becomes especially important in view of the atmospheric pressure condition. In some cases the lower edge of the skirt may be supported at the bottom of the groove and in other cases I may desire to have the skirt occur in slightly spaced relation to the bottom of the groove.

For more clearly illustrating the positive sealing action between the bottom marginal portion of the skirt 12 which is of flexible steel and which may flex in two directions as stated, attention is called to FIGURES 10, 10a, 10b and 10c in which disclosures the skirt 12' is shown associated with a mold 2 formed with an upstanding flange having an outer face 12a providing an outwardly facing abutment against which the sealing compound or material 30a is positioned. The inner face of the skirt 12 is normally 13 positioned outwardly of the abutment and in sealing engagement with the sealing material 30a prior to the application of vacuum and the pouring operation, as shown in FIGURE a.

In FIGURE 10 there is illustrated the positioning of the skirt 12 when vacuum has been applied to the mold 2" at the initiation of the pouring operation. When vacuum is established in the degassing chamber, atmospheric pressure exerts force against the outer side of the flexible skirt and deflects the skirt inwardly so that pressure is applied by the inner bottom portion of the skirt to the sealing compound a to compress the same to insure and provide a positive seal against the outer face 122 of the abutment about the upper mold structure.

In FIGURE 10:: there is illustrated in dotted lines at 2a the position of the mold 2" before it receives the molten metal. In the full line position the mold is shown after heating during the pouring operation and as indicated, the mold body 2" has been expanded outwardly so that the outer face 12a applies pressure to the sealing compound 30a against the adjacent inner face of the flexible skirt 12. Thus as the pouring proceeds and as the temperature of the mold increases, an additional force is applied to the sealing compound due to the expansion of the mold and an ever increasing sealing effect is present as the pouring progresses and as the temperature of the mold increases. As a result of the foregoing, any disadvantages which might occur in the effectiveness of the sealing compound due to its curing by the heat of the mold is positively overcome by ever increasing pressure to the sealing compound by the continuous expansion of the mold structure.

The advantage of this new and novel concept is twofold. In the first instance an effective seal is provided between the mold and the skirt instantly upon the application of vacuum due to the atmospheric pressure which positively deflects the flexible skirt inwardly against the sealing compound, and secondly, the sealing effect is grad ually increased by the pressure applied by the mold structure during its expansion resulting from the absorption of heat from the molten metal being poured therein. Thus a gradual and ever increasing pressure is applied to the material forming the seal between the skirt and the out wardly facing abutment of the mold structure and while the sealing effect is continuous and gradually increased to provide maximum sealing, no damaging or excessive force is possible as the flexible skirt is capable of outward deflection should a condition occur in which maximum sealing effect and hardness of the sealing compound is approximated. In other words, every possible advantage occurs by the use of both inward and outward pressure against the sealing compound with the pressure on the compound gradually increasing during the pouring and in addition a safety factor is present which would prevent any hazards which might occur should the skirt be of such a character that it was incapable of necessary outward expansion. Obviously the operator of the invention is basically dependent upon the use of the depending, yieldable and extensible skirt portion, the use of which re sults in a positive initial sealing by atmospheric pressure against the fixed abutment 12a and a gradual continuous controlled increase in the sealing pressure between the flexible steel skirt and its applied pressure and the expanding fixed abutment during the pouring of the metal in the mold. This skirt portion is shown as formed of a plurality of wall portions disposed in angular relation to each other and angularly movable relative to each other.

- In providing a vacuum with the sealing skirt arrangement described, I may also desire to add materials to the pour and I may wish to use special pumping equipment. At one side of the degassing chamber. 10 is provided a sight port 40 having a removable high temperature optical glass 42 maintained in sealed relationship by means of a rubber gasket 44'. At an opposite side 14 of the degassing chamber 10' is a vacuum exhaust man fold 10d which is shown fragmentarily in FIGURE 3 an also indicated in FIGURE 6. The vacuum exhaust man fold communicates with a vacuum pump 7 8' and locate between the manifold and the pump 78' is a valve mecha nism including a pneumatically operated three-Way hig vacuum valve mechanism 74).

The valve mechanism 70 includes an air release valw 72', a by-pass valve 74' and a main valve structure 91 The valve structure has a valve shaft 92' supported i a shaft seal 98 to the lower end of which is fixed closure disc 94' which is adapted to engage a valv seat 70a. This three-way valve mechanism is connected t the exhaust manifold in some convenient manner as, fc example, by a flexible connection 50' and I may als employ a filter screen 76' located in a position to prr tect the valve mechanism from particles of molten met: and dirt in operation.

I may desire to add materials to the molten metal du: ing the degassing operation in which case such additior may be made directly into the bottom pour ladle at th time of pouring, or I may provide an alloy additior mechanism as suggested at the right hand side of FIC URE 3. This alloy additions mechanism may includt for example, a segmented barrel 32 mounted on a sha 36a which is sealed at 36' in a suitable bearing membe Numeral 34 indicates a turning knob for rotating t-h segmented barrel at a point directly below a funnel 3304 Material to be added to the pour is indicated at A in th container structure A' and passes through the funnel 230 down through a chute structure 300. The container 1 is normally closed by a cover A. The cover A is pr vided with a sealing means A.

In setting up the apparatus shown in FIGURE 3 pr paratory to casting an ingot, I first provide a hot to; 19' consisting of a body of refractory material which positioned in the upper portion of the mold 2' as show in FIGURE 3 and which is sealed by tamping steel WOt into a narrow space provided between the inner surface the mold 2 and the outer surface of the hot top 19 The steel wool is denoted by the numeral 5'. It will t observed that the refractory body 19 comprises a sul stantial thickness of material which extends well belo the top surface 8' of the casting mold 2, and thus tl member 19' may function to provide heat insu-latic and to protectively shield the extreme upper surface the casting mold 2 where the sealing compound 30 located.

In applying the sealing compound 38, a quantity of ti compound is provided in a liquid condition and intrt duced all around the casting mold groove 31' to substai tially fill this space. While the compound is still in soft fluid condition, the sealing skirt 12' is located 1' the sealing material with the section 100 of the degassir chamber coming to rest on the top surface 8 of the cas ing mold. It will be observed that the lower edge the sealing skirt 12' becomes thoroughly embedded in tl compound and extends below the surface 8' 0f the mo] for an appreciable distance. However, the hot top 1! projects well below the bottom of the groove 31' so th: the heat insulating and protective effect above referre to is maintained all the way around the top of the cas ing. I have found that by thus employing a heat bafl and insulating medium in the manner described, I am e1 abled to retard the flow of heat from the molten met: into that part of the casting top where the groove an its compound occur. This is helpful in dealing with compound which has limited resistance to thermal a tack and insures that a premature decomposition of ti sealing compound will not take place where a sealir mass of more limited heat resistance may be desired 4 be employed.

As earlier disclosed the preferred sealing compour is cured at temperatures of 100 F. to 400 F. and suc temperatures may, in many cases, be present in a castir mold which has been used and allowed to cool. If tl 31d is not in this partly heated condition as a result of ving cooled from standing for an extended period of me, then I may heat the mold. For example, I may l-ploy a conventional gas burner which may be applied ound the outer side of the mold or accelerator may be ded to the compound. As soon as the compound is lly cured the apparatus is ready to receive molten etal. I In pouring a single ingot, the fusible aluminum or agnesium disc 26" may be maintained in sealed relation th ladle L2. In pouring a series of molds, however, the sible disc 26' is attached to liner 18 by flange 24 and vnge bolts 24a in the manner already described. It .11 be observed that ladle L2, without the fusible disc ay be inserted in a liner at any time and therefore may transferred from mold to mold. This allows greater xibility, fewer ladles L2, and less maintenance, skull moval, refractory repair, etc. Refractory lining 22 of ile L2 may be heated, with a conventional gas burner, a dull red color before pour to prevent the formation of skull, or solidification of meta-l in the lower section ladle L2. If additions to the pour is desired, carefully weighed loy additions are placed in the alloy container and vered and sealed by flange 30a and O ring 30'. Sight ass 42 is positioned over sealing ring 44. Filter screen i is placed in valve inlet and sleeve 78' moved into sition and secured. The assembly is now ready for leration and the vacuum pumps 50' are started. The pumps 50, run continuously, blank-off at less than le micron against valve 70'. Three-way valve 76' is opated 'by a portable, three step, spring-loaded push butn switch of conventional type and not shown in the 'awings. The switch button is depressed to the first poiion and, normally open, air release valve 72, which is 2" valve, is closed. The push button is then depressed a second position and, normally closed, by-pass valve l, which is a 1" valve, is opened and air is removed from e mold cavity and manifold 10d until the pressure is duced to below 200' millimeters. The push button is rally depressed to a third position and valve disc 94', hich is a 16" valve, is opened and the pressure quickly ops below 200 microns in a matter of seconds. If .fficient time is available, pressures of less than 1 micron e consistently obtained with degassing chambers and olds that have been used time after time without mainnance or machining.

By-pass valve 74' serves a dual purpose. To open a 5" disc against atmospheric pressure would require 000 lbs. of pressure. To open a 1 valve against atospheric pressure requires 12 lbs. of pressure. By re- Jcing the pressure differential across valve 94 to less an 2,000 microns, a small air cylinder may be employed r its operation. The by-pass valve also serves as a )w control valve for the blowers by allowing a limited )w of air to the pumps initially. A controlled flow of I through by-pass valve 74 minimizes the load on the Jmps. I may, for example, employ a 25 hp. motor on large Roots blower booster pump. This size motor will mdle pressure differentials of 10 mm. across the blower hereas a pressure differential of 1 atmos. would require )ssibly a 150 hp. motor.

When the mold has been evacuated to less than 200 icrons, metal M1 from ladle L1 is transferred from a elting furnace to a position so that nozzle 60 is directly ove ladle L2. This may be a distance of approximately inches. Stopper rod 62 is raised by an operator and etal M1 is discharged into preheated ladle L2. A liquid a1 is quickly formed in the lower extremity of L2 due I its conical shape and small volume. The conical shape 1d small volume combine to do away wit-h the necessity r a stopper rod. As the liquid seal is formed, metal 'ocee'ds through the nozzle 22a and melts fusible disc 26. On entering the vacuum chamber, the stream separates I 11 l i 1 Q1 QI P tS v l the manner earlier described.

Id The flaring of the stream at the nozzle may, for example, encompass an angle of approximately to 120. The design of the nozzle 22a is important in controlling the scatter of the metal stream by minimizing the tendency of certain viscous alloys to form a large bell-shaped icicle. This formation grows rapidly during pour until it welds to shield 28' and causes undue scatter and impingement of the stream on the hot top and mold wall.

As the stream falls through the degassing chamber, the scatter of droplets is minimized by collecting sleeve 28'. The sleeve 28' prevents the scatter of molten droplets from causing a buildup of solidified metal on the lower inside portions of the vacuum chamber, the hot top and the mold 'Walls.

Impingement and erosion of the refractory hot top affects the cleanliness of the poured ingot and a buildup of droplets on the mold wall produces seams and scabs on the rolled and forged surfaces. Normally with collecting sleeve 28 in place I find that the surfaces of my vacuum cast ingots are far superior to air cast ingots.

During pour there is a further evolution of gas evolved from metal M1 in the mold. The combination of high vacuum, and cold rough mold surface promotes a further evolution of gas. As the metal level rises into hot top 19, steel wool 5' prevents metal from leaking up through between the hot top and the mold 2' and entering the hood.

When the metal level in the hot top 19' reaches to within an inch or two of the top, stopper 62 is lowered and theflow of metal from ladle L1 stopped. The balance of metal in L2 drains into the vacuum chamber and just fills the hot top. At the instant metal from L1 is stopped, valve control push button on switch 70' is released and main valve 94 and bypass valve 74' are closed and air release valve 72 is opened in timed sequence. Thus as the last metal leaves nozzle 22a air release valve 72' floods the vacuum chamber and manifold with air.

Without the air release valve it may be noted that the vacuum chamber and manifold would be flooded with air entering through nozzle 22a after the last metal is discharged from ladle L2. The blast of atmosphere through, for example, a /3" or nozzle 22a, into a high vacuum chamber is sufiicient to blow molten metal from the hot top and spray it around the entire vacuum chamber and manifold. As soon as the air release valve floods the vacuum chamber and manifold to atmospheric pressure, sight glass 42 is removed and tubular member 46' is inserted through sight port 40.

After completion of the above procedure the manifold is removed. The mold and hood assembly are allowed to remain in position until such time as the poured metal in the mold is completely solidified. This may require an hour or more for a two to four ton ingot. During this period, heat from the solidifying metal raises the temperature of the mold to 1,000 F. to 1,500" F. :and decomposes the sealing compound 30' to a powder. By the time the ingot is stripped from the mold, the compound is completely decomposed. After stripping, the mold groove 31' may be blown out or brushed lightly and is then ready to receive sealant again when cool enough.

Before pour, as earlier described, the mold is consistently evacuated down to 20 microns in about 30 seconds and if additional time is allowed pressures as low as one micron are attained as the refractory hot top is outgassed. It may be noted that an absolute pressure of .76 micron is one millionth of an atmosphere :and during my pouring interval pressures of from microns down to as low as 45 microns have frequently been observed. This is far below the 750 to 2,000 microns obtained by conventional vacuum casting operations.

The flexible sealing wall 12 and its arrangement relative to the degassing chamber 10' and casting mold 2 may be modified in various ways. For example, in FIGURE 11, I have illustrated a flexible sealing wall 12" which is

Claims (1)

1. IN A METHOD OF SEQUENCE CASTING OF METAL INGOTS UNDER VACUUM IN WHICH VACUUM PUMP APPARATUS IS CONNECTED THROUGH A SERIES OF DEGASSING CHAMBERS CONNECTED IN SEALED RELATION TO A SERIES OF INGOT MOLDS IN PREDETERMINED SUCCESSIVE TIME INTERVALS AND PORTIONS OF MOLTEN METAL ARE PERIODICALLY RELEASED FROM A REMOVABL POURING LADLE, HAVING A NOZZLE AND AN ADJUSTABLE LADLE STOPPER FOR OPENING AND CLOSING THE NOZZLE, INTO A LOWER STATIONARY POURING LADLE WHICH IS CONNECTED TO THE DEGASSING CHAMBER, THE STEPS WHICH INCLUDE APPLYING A VACUUM IN ONE OF THE DEGASSING CHAMBERS AND ITS INGOT MOLD, OPENING THE LADLE STOPPER AFTER THE MOVABLE LADLE IS POSITIONED OVER THE STATIONARY LADLE CONNECTED TO THE DEGASSING CHAMBER, POURING MOLTEN METAL FROM THE MOVABLE LADLE INTO THE STATIONARY LADLE AND THROUGH THE DEGASSING CHAMBER INTO THE INGOT MOLD UNITL THE MOLD AND THE STATIONARY LADLE ARE SUBSTANTIALLY FULL, CLOSING THE LADLE STOPPER, CONTINUING THE APPLICATION OF VACUUM, CONTINUING THE POURING OF MOLTEN METAL FROM THE STATIONARY LADLE THROUGH THE DEGASSING CHAMBER AND INTO THE MOLD TO SUBSTANTIALLY FILL THE MOLD AND AS THE POURING FROM STATIONARY LADLE INTO THE DEGASSING CHAMBER SUBSTANTIALLY CEASES, DISCONTINUING THE APPLICATION OF VACUUM AND VENTING THE DEGASSING CHAMBER TO ATMOSPHERE, AND THEREAFTER SEQUENTIALLY REPEATING THE ABOVE STEPS IN CONNECTION WITH ANOTHER DEGASSING CHAMBER AND IT INGOT MOLD IN TIMED RELATION TO THE TEMPERATURE OF THE MOLTEN METAL ADJACENT THE LADLE STOPPER SO THAT THE STOPPER IS AGAIN OPENED TO POUR MOLTEN METAL FROM THE MOVABLE LADLE TO ANOTHER STATIONARY LADLE BEFORE THE MOLTEN METAL ADJACENT THE STOPPER HAS AN OPPORTUNITY TO FREEZE, THE TIME LAPSED BETWEEN EACH OF THE SEQUENTIAL OPENINGS OF THE LADLE STOPPER BEING IN THE RANGE OF 10 TO 300 SECONDS.

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