US2550735A - Cartridge for below-surface treatment of molten metals - Google Patents

Description

May 1, 1951 s, T 2,550,735

CARTRIDGE FOR BELOW-SURFACE TREATMENT OF MOLTEN METALS Filed Aug. 2, 1947 2 Sheets-Sheet 1 fly-:36

Patented May 1, 1951 CARTRIDGE FOR BELOW-SURFACE TREAT- MENT OF MOLTEN METALS Sam Tour, New York, N. Y., assignor to Julius S. W. Bates, Phoenix, Ariz.

Application August 2, 1947, Serial No. 765,751

3 Claims. (01. 75--93) This invention relates to new and useful improvements in the below-surface treatment of molten metals.

In the conventional purification of molten metals such as degasification (elimination of oxygen, carbon oxides, hydrogen and nitrogen),

the elimination of stable oxides, and desulfurizaand up to now efficient ways of adding these additives have not been found.

One of the difiiculties resides, inter alia, in the fact that the additive material, being lighter (at the bath temperature) than the molten metal to be treated will remain on the surface of the bath and will thus not reach the bulk of the material to be treated. Attempts have been made to remedy this by securing the additive to the end of a rod and plunging the same into the molten metal, thus pushing it underneath the surface thereof. This is extremely hazardous, particularly when the addition agent is one of high reactivity.

Alternatively, cored solid pieces of metal basically of the composition of the molten metal bath, and in which the cores are composed of the addition or treating agent, have been used. In this case, the composite is selected sufficiently heavy so that it initially will sink below the surface of the metal bath with the hope that it will there release the treating agent. This desideratum, however, is not achieved. If the cored piece is open to the outside, such as an open ended tube, the major portion of the charge will have been released by the time the piece has sunk an appreciable depth. If the cored piece is substantially closed, such as a tube with crimped or plugged ends, in which case dissolution of the body of the piece by the molten metal bath is relied upon for release of the charge, such release is effected substantially at the surface of the bath. This is by reason of the fact that, as the body of the composite is dissolved away by the molten metal bath, the ratio of core cavity to body of the composite reaches a point at which sinking takesplace no longer. As some of the body is dissolved away, the composite will begin to rise towards the surface of the molten metal bath. When sufficient of the body material has been dissolved away to expose the additive in the corecavity or release the same to the metal bath, such part of the composite as then remains will have risen to substantially the bath surface.

One object of the instant invention comprises inter alia an improved cartridge capable of discharging or exposing an additive at an effective treating level below the surface of a molten metal bath.

Another object of the invention comprises such a cartridge with a time-fuse capable of dissolvv ing away, thereby exposing or releasing the additive to the metal bath, in advance of excessive dissolution of the body of the cartridge.

The foregoing and still further objects of the invention will be apparent from the following description'read in conjunction with the drawings representing preferred embodiments of the invention in which:

Fig. 1 represents a cross-sectional cut through an open treating cartridge;

Fig. 2 is a cross-section through a loaded, hermetically closed cartridge in accordance with the invention;

Figs. 3 and 319 show cross-sections through indented sealing discs for a treating cartridge;

Fig. 4 is a top view of the construction shown in Fig. 1;

Figs. 5 and 5b are fragmentary cross-sections illustrating alternative forms of cartridge construction;

Fig. 6 shows a cross-sectional view of part of a further alternative form of construction;

Fig. '7 is a bottom view of the cartridge illustrated in Fig. 6;

Fig. 8 represents a bottom view of an alternative indented body construction of a cartridge, and

Fig. 9 is a cross-sectional view illustrating the sealing of a preferred form of cartridge.

The treating cartridge in accordance with the invention is provided with a time-fuse arrangement defined by a mass of dissolvable material extending between the core cavity and the outer surface of the cartridge and having a predetermined thickness to be substantially dissolved away in advance of the body of the cartridge. The predetermined thickness of the mass of dissolvable material is so selected for-a given bath and combination of materials that it will not have dissolved away substantially earlier than the point at which the cartridge has sunk to an effective treating level within the molten metal bath and not later than the point at which the body of the cartridge has been dissolved to an extent which will cause it to rise towards the surface of the molten metal bath.

Referring to Figs. 1 to 4 of the drawings, I represents the body of a treating cartridge which may be of any desired form or configuration. It ispreferred, however, to have a substantially cylindrical cartridge. cavity 2 is provided opening onto recessed portion 3. The conical base 2a of the core ca vitymay constitute as much as of the volume of the cavity. The quantity of core. material charged.

or placed into the core cavity does not fill it com.- pletely. Since many treating materials used have higher coefficients of expansion than the solid material of which the cartridge is made, it has been found necessary to allow spacefor some expansion to take place. This method of providing the expansion space by way of the conical base is a convenient one when the cavities are produced by machining. Any other methods to provide for core material expansion may be used, such as leaving the expansion space above or around the charge of core material. The car tridge body illustrated in the drawings can be made into the desired shape and to the required dimensions by hobbing, hot forging or machining. The additive agent is placed into the depression or core cavity 2. After this addition a pressure retaining disc of suitable material and thickness such as disc 4 (Fig. 2) is placed into the recessed portion 3. The latter defines a seat 5 upon which the disc 4 rests. The recessed por tion 3 is preferably annular and when sealing the cartridge with the core of additive agent 6 in position, a suitable tool, such as a punch 8 (Fig. 9) of an outside diameter larger than the diameter of the recessed portion 3 is then forced into the top of the container, thereby forming from the sides of the recess the sealing ring of displaced metal portion la over and onto disc 4 to press the same against seat 5 and thereby establishing a seal. The punch is designed of such size and the depth to which it is pressed in is such that the displaced metal I (Fig. 2) above the disc 4 is of sufiicient thickness and has sufficient overlap to give the desired pressure retaining strength to the assembly. The relation of the original recess to the ultimatelyjformed substantially annular metal portion, displaced by the punch from the sides of the recess, is for instance illustrated by the broken outline of Fig. 1 indicating the disc 41) and the overlyingsealing ring 12).

The disc 4 is pressed against the seat 5 by the displaced metal portion 1 with aforce suficient to obtain andmaintain a hermetical seal of the.

core opening. The displaced metal 1 acts as a sealing ring to hold the disc 4 upon seat 5 and against any internal pressure created in the core cavity 2 by the additive treating material in that cavity.

In lieu of the disc and sealing ring construction illustrated in Fig. 2, any other suitable closure construction may be used. Thus, for instance, a threaded plug as shown in Fig. 6 may serve as a closure for the cartridge to effect a substantially hermetical seal thereof against such internal pressure as may be created by the treating charge in the core cavity. As there shown, plug 9- is A centrally located core.

threaded into the recessed portion of the car tridge body l2 and bears substantially tightly against the shoulder H. The upper portion of plug 9 projecting beyond the body 12 of the cartridge is prefereably constituted in the form of a hex nut 53 to permit appropriate tightening of the plug.

In the illustration of Fig. 2, the time-fuse in accordance with the invention is constituted by the mass of material underlying the exposed area 4a of disc 4. When submerged in a molten metal bath the exposed mass of disc material will progressively dissolve in the manner as for instance indicated in the dotted outlines. It will finally dissolve to an extent where a sufiicient mass has been completely dissolved away to substantially open the core cavity. The core material 6 can then react with the molten metal of the bath. To the extent that internal pressure has built up within the core cavity, and particularly when using a material vaporized at the treating temperature, rupture will occur of the thinned disc portion before complete dissolution of any area thereof.

In lieu of the solid disc 4 an indented disc such as shown in Fig. 3 and carrying indent I4 may be used. In this case the mass of dissolvable material defining the time-fuse is the portion overlying the indent. Only a relatively small amount of dissolution of the disc material is necessary for effective opening of the core material by way of the indent ill. The use of an indent has the additional advantage that it is possible to better control thetype. and size of injector orifice. This is especially of advantage when using additives vaporizable at the treating temperature of the moltenmetal. In such case controlled gradual release. of treating material vapors (normally under relatively high pressure) is desirable. In such cases it is preferred to provide an indent defining a jet opening upon the dissolution of the overlying material andto choose an indent of sufficient depth. to assure that the jet opening will not become unduly distorted by the dissolving action of the molten metal bath and/ or the vapor pressure within the cartridge cavity.

of the core cavity. This indent leaves a relatively.

small overlying mass of dissolvable material. When the body 4 Sci this cartridge commences to dissolve the mass of dissolvable material overlying. the indent i5 will rapidly thin to a point where it will open the indent defined aperture to the core cavity considerably in advance'of any appreciable dissolution of the. body of the cartridge.

A further alternative form of providing a suitable time-fuse is illustrated in Figs. 6 and '7. As there shown the bottom of the cartridge I1 is provided with a substantially annular inent I8 in substantial alignment with the lower portion of the core cavity l9. Also in this case a comparatively small amount of dissolution ofthe body l2 of the cartridge will cause an open-' ing to be established through the indent lB-to -In all cases care should be taken that the cartridge or any part thereof including the dissolvable material defining the time-fuse is basically substantially the same as the metal of the bath to be treated, i. e., compatible with and nondeleterious to the bath metal. a

In order to assure substantially self-submergence of the treating cartridge the percent volume of its core cavity should be less than substantially progressive dissolution of the body of the cartridge in the metal bath being treated, the percent volume of the core cavity reaches a value greater than the one just mentioned, the cartridge will commence to rise. The dissolvable material therefore should substantially dissolve for effective cavity or core exposure substantially in advance of this point. On the other hand, the thickness of the dissolvable material should be such that the same is not substantially dissolved away prior to the time required for the sinking of the cartridge to an effective belowsurface treatment level within the molten metal bath.

The maximum 'mass of dissolvable material defining the time-fuse, and which will dissolve away for exposure of the core cavity, should be such in relation to the core that the combined weight of the core material and of such dissolvable material is not greater than the difference in weight between the cartridge and the volume of the molten metal of the bath displaceable by the cartridge. If such combined weight were less than said weight difference the dissolving material would be sufilciently large to offset the maximum percentage volume of the core cavity as expressed in the above formula to a point where the cartridge would commence to rise before satisfactory exposure of the core material has been obtained.

Little is known about the strength and ductility of many of the common metals at temperatures just below their melting points. Little is known about the rate of dissolution for soild pieces of metal in molten metal of basically similar composition at various temperatures above their melting points. For this reason, it is not possible to calculate in advance for any given combination the thickness of the dissolvable material defining the time-fuse. The same, however, may beempirically determined for each given combination. Such empirical determination may be carried out for instance by preparing a number of cartridges loaded with a desired treating charge and identical in all respects except as to thickness of the dissolvable material defining the time-fuse which is selected different in each case.

The different cartridges are then each tested by addition to a test bath of the molten metal to be treated. If a turbulent, spattering or localized. reaction is observed by way of ebullition of the surface the release of the core material has taken place at or near the surface. If on the other hand the surface ebullition is of a controlled gradual well distributed nature the release of thecore material has taken place at a depth satis-- factory for the desired treatment, i. e., at the effective treating level for said bath. The thick-- ness of the dissolvable material, which produced. the last mentioned surface ebullition is the correct thickness for that combination.

When using in the preparation of a treating cartridge in accordance with the invention a seal-- ing disc and a sealing ring as for instance illustrated in Figs. 2 and 9, it is important that thedisc is held by the sealing ring onto the seat with. sufficient force to overcome any internal pressure that may be created in the core cavity by the: additive treating material in the cavity before exposure of the cavity by the dissolution of the meltable material constituting the time-fuse in accordance with the invention.

Broadly speaking, the invention thus embraces, in combination with a treating cartridge of the hermetically closed, self-submerging type for the treatment of molten metals and having a core cavity containing a charge of treating material, at least one time-fuse defined by a part of said cartridge and comprising a mass of dissolvable material extendin between said core cavity and the outer surface of said cartridge and of a predetermined thickness to be substantially dissolved away, by the molten metal bath to be treated, within a period of time not less than that required for the sinking of said cartridge to an effective treating level within said bath and not substantially more than that required for the percent volume of said cavity to have increased to the point where the entire cartridge rises.

In all cases, the hermetical seal should outlast the time required for dissolution of the meltable material to the extent necessary to open the core cavity within the limiting conditions herein stated. A satisfactory seal, therefore has a thicker section than the time fuse section.

The expression dissolve away or similar term used herein in connection with the removal of dissolvable material to effectively expose the core cavity of a cartridge in accordance with the invention, includes the limiting case in which at least part of the meltable material is ejected into the molten metal of the bath in substantially molten or at least heat softened condition by any pressure created by the core material at the temperature of the molten metal bath. Such ejection may particularly occur in connection with the use of a core material which will substantially vaporize at or below the temperature of the metal bath to be treated.

When the treating cartridge in accordance with the invention is added to a molten metal bath for the treatment thereof, it will sink below the surface due to the predetermined greater specific gravity of the composite. In View, however, of the chilling effect of the cartridge, a certain amount of crust formation occurs which is undesirable. I have found that it is possible to alleviate such crust formation to a large extent by providing the cartridge in accordance with the invention with a heat retarding or insulating material such as a coating of ceramic or similar matter. I have found that the use of such an insulating material reduces the rate of dissolution of the container in the molten metal ass t-es a lbwj it mt-re. t me to is s ifallyi advantageous. when treating large deep baths of moltenmetal,

When, using a cartridge or the substantially self-submerging type described in accordance with the invention, though the same will initially sink, the specific gravityof the composite'chang'es at times so rapidly by the partial melting of cartridge exterior, that the same may soonstart to: rise towards the surface without having re maimed at the desired effective bathle'vel afsuflicient time for sa'tis'factory release of charging material. overcome this condition by the use oia cartridge having a' core cavitynot exceeding substantially (l -d; 13d;

v lume of the body f a Cart dselds in th specific gravity of the metal, ofthe cartridjge body when ome at its melting point and'd'e. being the.

specific gravity of the metal of thebody' 9f the cartridge at its freezing point when molten. Such a cartridge equipped with a suitable closure such as a disc of proper thickness irrespective of the material constituting the core will always sink' and remain at a sufiicient' depth below the surfac up to the time at which the release of charging material as 'iorinstance controlled by the disc thickness, is efiected, For most pur-- poses I find that a core cavity corresponding substantially to -7% by volume of the body of the cartridgewill substantially satisfy this for.-

mula and will constitute a universally usable car tridge for the majority of the conventional molten metal bath treating materials of the kind and type herein mentioned.

V'IThe' foregoing description is for purposes of illustration and not of limitation and it is my intention therefore that the invention be limited only by the appended claims or their equivalents wherein'I have endeavored to claim broadly all inherent novelty.

I claim:

1. A cartridge for the treatment of aniolten metal with a relativelysmall amountof a treating agent of lower specific. gravity than said metal, consisting'o'f a'metal container defining and completely enveloping a cavity, a charge of said treating agent within said cavity, a minor section of the wall of said cavity being relatively I have found that I can satisfactorily thin n'n dboi atq teem-net the r' m ide f;- se d. al be n 'r ti qly thick. and hea y. the e ifghtf oithe container and charge exceeding the weightoi a, ,corresponding volume in liquid state; ofthe metal of which the container is composed.

2 ,A. ca rtridg:e for the treatmentota molten metal with av relatively small amount of a treat- ,ing agent of lower specific gravity than-said. 10

metal, consisting of a metal container defining and-, om let ly en l ping a y. said cavity having a volume equal to 5, 7% of the volume of the, body of the cartrid e, a charge of said treating agent within said cavity a minorsection of the wall of the container being relatively thin in, proportionto the. remainder, the remainder of. said. wall being'relatively thick and heavy, the. weight Off the container; and charge exceeding the'weight of a corresponding volume in liquid state of the metal of which the container is composed.

3. A cartridge for the treatment of a, molten metal with a relatively small amount. of a treat-. ,ing-"agent'of lower specific gravity than said metal, consisting of a cylindrical metal container defining and co'mpletely enveloping a centrally located cylindrical cavity, a charge of said treating agent within said cavity, a minor section of .the wa ll'of said ccntainerbeing relatively thin in proportion to, the remainder, the remainder o'fjsaid Wall being relatively thick and heayy the weight of the container and charge exceeding the, e h of es olnd n volume. in liquid state ;of the metal of which the container is composed.

SAM TOUR.

7 REFERENCES CITED" 'iheLfollowing references are of record in the

Claims (1)

1. A CARTRIDGE FOR THE TREATMENT OF A MOLTEN METAL WITH A RELATIVELY SMALL AMOUNT OF A TREATING AGENT OF LOWER SPECIFIC GRAVITY THAN SAID METAL, CONSISTING OF A METAL CONTAINER DEFINING AND COMPLETELY ENVELOPING A CAVITY, A CHARGE OF SAID TREATING AGENT WITHIN SAID CAVITY, A MINOR SECTION OF THE WALL OF SAID CAVITY BEING RELATIVELY THIN IN PROPORTION TO THE REMAINDER, THE REMAINDER OF SAID WALL BEING RELATIVELY THICK AND HEAVY, THE WEIGHT OF THE CONTAINER AND CHARGE EXCEEDING THE WEIGHT OF A CORRESPONDING VOLUME IN LIQUID STATE OF THE METAL OF WHICH THE COSNTAINER IS COMPOSED.

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