US3196504A - Cast nozzle inserts - Google Patents

Description

July 27, 1965 R. W. LIMES CAST NOZZLE INSERTS Filed Feb. 27, 1962 rllllllllllllm INVENTOR. ROBE/P7 W [/4455 AM/MM/ ATTORNEY United States Patent 3,196,504 CAST NGZZLE INSERTS Robert W. Limes, Cleveland, Ohio, assiguor to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey Filed Feb. 27, 1962, Ser. No. 175,956 5 Claims. (Cl. 22-85) This invention relates to refractory coatings, particularly unfired refractory coatings for use in contact with flowing streams of molten steel. In accordance with one embodiment, this invention relates to an improved bottom pouring steel ladle useful for pouring molten steel into molds and the like. In accordance with another embodiment this invention relates to an improved nozzle assembly useful in connection with a bottom pouring steel ladle to provide the orifice therethrough for use in a steel pouring operation. In accordance with yet another embodiment, this invention is directed to a method of protecting materials from contact with a flowing stream of molten steel. In accordance with still another embodiment, this invention is directed to an improved nozzle assembly, and method of producing same, useful in a steel pouring operation.

In steel production, molten steel is produced and flowed into a ladle, such as a bottom pouring ladle, for subsequent pouring into molds and the like. The pouring operation from the ladle to the mold is critical. The flow of molten steel must be controlled so as not to endanger personnel or damage equipment. Also poor pouring practice in the assembly and adjustment of the pouring equipment and in carrying out the pouring operation may seriously and adversely affect the surface quality of the poured steel product.

One of the most important factors affecting the surface quality of steel ingots and steel products made therefrom is the rate of flow of the steel during the pouring operation and the rate of rise of molten steel in the mold. This rate of rise is determined primarily by nozzle size, mold size, temperature and fluidity of the steel and the ferrostatic head or height of' metal in the steel pouring ladle.

In the pouring of steel from a bottom pouring ladle provided with a nozzle located in the bottom of the ladle, the nozzle defines the opening or orifice through which the molten steel pours from the ladle during the pouring operation. For the most part, nozzles have been made from low refractory clay which, like the refractory material employed to line the ladle, expands at high temperatures and thereby seals cracks which may develop in service. A nozzle made of low refractory clay experiences considerable erosion during the pouring operation. Enlargement of the nozzle bore due to erosion tends to compensate for the loss of ferrostatic head in the ladle so that desired pouring rates can be maintained even at the end of the pouring operation. However, the eroded material enters the mold with the steel and must free itself from the steel by levitation or become an entrapped inclusion. With certain grades of steel, such as leaded heats, it is necessary to control closely the rate of pour and this cannot be done with a clay nozzle the bore size of which varies during the pouring operation due to erosion.

It has been the practice heretofore to provide nozzles with a fired refractory insert to protect the nozzle from erosion during the steel pouring operation and/or to control the erosion of the nozzle bore or opening. Nozzle inserts may be in the form of cylinders which are inserted in the nozzle bore, either in the top, bottom or full bore length. Other insert designs make use of a split nozzle with a do-nut shaped insert cemented in the bore. The inserts which have been employed heretofore to protect the nozzle against the erosive effect of the flowing stream of molten steel have been fired refractory. products and, as indicated, have usually required a specially made nozzle body into which the insert can be fitted. Firing is a time-consuming operation which oftentimes results in an unsatisfactory insert which must be discarded and which adds considerably to the cost of the nozzle.

Firing of inserts often leads to problems arising from dimensional instability and tendency of the insert during firing to crack or warp. Cracks developed in the insert during firing result in a leaky, unsatisfactory insert. Warping of the insert during firing results in an insert which does not properly fit the nozzle body. The warped insert must often be discarded as unsatisfactory. When the insert is fired While inserted within the nozzle body diiferential shrinkage during firing results in the insert pulling away from the nozzle body. This condition gives rise to breakage during handling or a leaky, unsatisfactory nozzle assembly during use.

Accordingly, it is an object of this invention to provide an improved nozzle or nozzle assembly, and method of producing same, useful in association with a bottom pouring steel ladle.

Another object of this invention is to provide a simple, relatively inexpensive nozzle useful in a steel pouring operation.

Still another object of this invention is to provide a nozzle insert which does not have to be fired and which has good adherence to the nozzle body.

Yet another object of this invention is to provide an unfired nozzle coating which can readily be made to coat or fit substantially any nozzle bore configuration.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure made with reference to the accompanying drawings wherein:

FIG. 1 somewhat schematically illustrates in side view a steel pouring ladle provided with a bottom nozzle;

FIG. 2 is a fragmentary cross-sectional view taken along lines 22 of FIG. 1; and wherein FIG. 3 is a cross-sectional view of a nozzle body in accordance with one embodiment of this invention.

It has been discovered that a layer or coating of refractory, phosphate-bonded material is useful for protecting the surface of a refractory body against contactwith a flowing stream of molten steel. In accordance with one embodiment of this invention an improved nozzle or nozzle assembly is provided by forming or coating the surface of the nozzle defining the nozzle opening or bore therethrough with a layer of unfired refractory, phosphate-bonded ceramic material. In accordance with a very particular embodiment of this invention an improved bottom pouring steel ladle is obtained by, forming a layer or coating of unfired, refractory,

phosphate bonded, ceramic material on the surface of the nozzle defining the opening or bore therethrough;

Phosphate-bonded, ceramic materials are particularly useful since such materials exhibit satisfactory high tem-v perature strength and do not require the time-consuming, expensive and oftentimes fault-producing firing opv The refractory, phosphate-bonded, ceramic material, V

such as phosphate-bonded alumina, employedas a coating material in the practices of this invention is prepared as follows: Material, such as alumina, e.g. tabular alu-- mina, i.e. alumina converted to the corundum form by calcining at a temperature below the fusion point, or other ceramic material capable of undergoing phosphate bondsurface in some instances may be desirable, the presence of spodumene, a lithium aluminum silicate added as a vitrifying agent is also useful.

Specific examples of phosphate-bonded, refractory coat-' ing materials which have been found to be satisfactory are set forth in the accompanying Table I.'

Table I Coating Composition, 1 Percent by Weight Material Alumina V 100 76 95 20 Zircon 19 70 Graphite- 5 5 'Spndnmmw l0 All'the coating compositions set forth in Table I'were prepared by admixing the solid materialsjto casting coning is admixed with aqueous phosphoric acid and .;the resulting admixture or slip is applied to the surface to be coated. .Depending upon the consistency of the coating admixture, whether paste form or fluent, itmay be applied by mechanic'ally uniformly spreading the admixture onto the surface to be coated or by centrifugal casting or by placing the body to be coated in association with'a form or mold and adding the fluent} admixture thereinto to form a coating on the surface.

The following is illustrative ,of a method of providing I a coating of phosphate-bonded material onto a refractory surface. A-solids admixture comprising %by weight zircon sand (zirconium silicate ZrO SiO 40% by weight zircon having a' particle-size smaller than 400' mesh and 20% by weight tabular alumina having a particle size less than 320 inesh is mixed or tempered with 'a 10% aqueous phosphoric acid solution. Sufficient 10% phosphoric acid solution is employed to make a casting" slip or slurry. of creamy consistency. 'A nozzle of conventional design, i.e. a'refractory clay body having a bore.

sistency with 10% aqueous phosphoric acid: Nozzles coatedwith these phosphate-bonded compositions were prepared by introducing these solid admixtures as a casting slip with'10% aqueous phosphoric acid into the nozzle bore fitted with a wooden dowel insert plug or by centrifugal casting. Although there is substantially no limitation on the: thickness of the;phosphate-bondedcoating material employed, very thin" or very thick' layers should be avoided; Layers of phosphate-bonded, ceramic material having a thickness of about A inch have yielded satisfactoryresults.

In actual tests wherein phosphate-bonded coatings having theabove compositions were employed with amachined'carbon nozzle body in a pouring operation, after use the coating material came away cleanly from '7 the, carbon nozzle body and a second coating was'cast in the samenozzle body. These operations werejrepeatted therethr-ough larger than that desired for use'in pouring is provided. A wooden templet having the desired bore diameter is'centered in the nozzle bore and the casting slip poured into the space between the templet and the V nozzle bore. Since the nozzle body is somewhat porous,

' the liquid in the slip. slowly'drains thereinto. After a relatively'short period of time bonding, i.e. phosphate bonding, takes place between the alumina and the phos-, phoric acid and the resulting formation of the complexalumina-phosphate bond and the cast material solidifies and hardens onto the. nozzle-bore. The templet is. re-- for a total of four'times. In viewof these tests it is possib'le by following the practices of this invention, to leave 7 the nozzle body in the ladle itself, if desired, and only replace the coating layer after each pour instead of removing theentire nozzle assembly and replacing it with a newnozzle assembly as is now done. a

Phosphate-bonded, ceramic coatings have alsobeen prepared by admixingx40 parts 'by weight zircon having a weight of 10% aqueous phosphoric acid to form a creamy vibrator during the 'castingtoperationis sometimes de-p sirable so as to produce a more dense casting, thereby producing stronger. phosphate-bonded coating material.

In general, as indicated hereinabove any coating com'r' position can be employed which, reacts with the phosphoric acid to form a phosphate'bond. Raw clays, such as alumina-containing clays, may be employed but shrinkage of these materials during casting and curing must. be controlled by the addition of a suitable grog or cal-1* cine thereto. Suchmaterials, although not usually preferred in the practices of this invention, are useful and than is now practical with conventional fired inserts.

In the preparation of the refractory phosphate-bonded,

coating materials of this invention since zircon and car bon, e.g. graphite, are not wet by'moltensteeLthese ma.- 1

terials are particularly useful as, components of the phosphate-bonded coating materials. Also, since a glazed" nozzles having substantially any surface bore configura- I the nozzleflrolled on a set of rolls.

slurry. The' amount of phosphoric acid iu the resulting slurry amounts to about 2% by weight. The resulting creamy slurry is preferably applied to the nozzle bore by centrifugal casting. In the centrifugal casting technique the creamy slurry is introduced into the nozzle bore, the bore beingcylindrical, and both ends thereof capped and During the rolling operation the slurry uniformly distributes itself over the nozzle bore. Since the nozzle is porous and withdraws water from the slurry, the slurry solids are deposited on the nozzle bore as a coating closely conforming to the surface configurations. In general, the'unfired coating composltions of this invention can be applied as inserts to having substantially any comsize less th anj3 25 mesh, bonded by the addition of 20% by weight of 10% aqueous phosphoric acid, have also been prepared. Larger amounts of phosphoric acid in the casting slip i.e. an amount of phosphoric acid greater than about 2% by weight, as much as 4% by weight and higher, may be employed. When the coating composition contains graphite as a component larger amounts of phosphoric acid in the initial coating composition are desirable since graphite is hard to wet and tends to weaken the coating composition.

In the practices of this invention it is preferred that the phosphate-bonded coating composition contain at least 20% by weight phosphate-bonded alumina. The incorporation of substantially pure alumina, such as tabular alumina, in the coating composition is not necessary but is desirable. Satisfactory phosphate-bonded alumina is obtainable by admixing alumina-containing fire clay and phosphoric acid. Also the remaining 80% material may be any suitable refractory aggregate, such as a material which does not react violently with the phosphoric acid. Particularly suitable are such refractory materials as zirconia, graphite and the like.

Referring now to the drawings, FIG. 1 shows in side view a steel pouring ladle provided with trunnion 11. The bottom of ladle 10 is provided with outlet or nozzle assembly 12. The bottom of ladle 10 is sloped in a direction of nozzle outlet 12 so that the molten steel content of ladle 10 completely drains through nozzle outlet 12. Ladle 10 is made of an outer steel shell and a heavy inner lining of refractory material, such as refractory brick. The refractory material lining the inside of ladle 10 may be of uniform thickness or be thickest at the bottom with the thickness of the refractory material lining the side wall of ladle 10 diminishing from the bottom to the top, since the bottom and the lower side wall of the ladle receives more severe service than the top portion of the interior side Wall.

Means are provided, not shown in FIG. 1 but illustrated in FIG. 2, for use in cooperation with nozzle outlet 12 to control the flow of molten steel from ladle 10. FIG. 2 of the drawings is a fragmentary, partial cross-sectional view taken along line 22 of FIG. 1 and serves to illustrate the construction of the nozzle assembly and the flow control means associated therewith. As illustrated in FIG. 2 the outer steel shell 14 of the ladle is provided with an inner refractory lining 15, the refractory lining extending along the side wall and the bottom of the ladle. At the nozzle, generally indicated by reference numeral 16, there is provided a refractory nozzle body 18 which may be of any suitable cross section, e.g. square, round, oval With a circular opening or bore 19 therethrough. The nozzle body 18 is fitted in the bottom of the ladle and supported therein by means of steel base plate 20 and washer 20a. The upper end of nozzle 18 is located in sump or well 21 made of suitable refractory material. As illustrated, the nozzle bore is lined with phosphate-bonded refractory material 22 in accordance with this invention, and the top surface of nozzle 18 is contoured so as to present a substantially continuous profile with the surface of well 21.

The flow of molen steel through nozzle bore 19 is controlled by means of stopper head 24 made of suitable refractory material, proferably harder at the pouring temperature than the refractory material comprising the top surface of nozzle body 18. Stopper 24 is fixed to pin 25 which is fixed to rod 23. Rod 23 i provided with an outer coating or sleeve 26 of suitable refractory material to protect it from contact with the molten steel. Refrac tory filler material 24a fills the assembly cavity of stopper 24 and key 25a fixes rod 23 to pin 25. Means are provided, not illustrated, for lifting rod 23 and stopper head 24 from contact with the top surface of nozzle 18 to permit the flow of molten steel through nozzle bore 19. Means are also provided for moving rod 23 and stopper head 24 downwardly into contact with the top surface of nozzle 18 to shut off the flow of molten steel through nozzle bore 19.

FIG. 3 shows in cross section a nozzle body prepared in accordance with this invention wherein the nozzle body 30 made of suitable refractory material has the opening or bore 32 therethrough coated with a lining 31 of phosphate-bonded, alumina-containing material as described hereinabove. Lining 31 of phosphate-bonded material completely covers the nozzle bore 31 and the top surface of nozzle body 30 so that substantially no portion of the nozzle body comes into direct contact with the molten steel. This embodiment of the nozzle differs from the nozzle shown in FIG. 2 in that the nozzle illustrated in FIG. 2 is provided with a lining or coating of phosphatebonded alumina only along the bore or opening through the nozzle and not on the top surface thereof which is exposed to contact with the molten steel.

The following is further illustrative of the practices of this invention. Phosphate-bonded, alumina-containing ceramic materials having the composition set forth in accompanying Table II were employed to coat nozzle bores and the resulting coated nozzles were employed in steel pouring operations.

In one pouring operation, an exceptionally hot grinder dust heat, so hot that the metal was boiling in the molds, was successfully poured through a refractory nozzle lined with a coating of phosphate-bonded, ceramic material having the composition of No. 3. Eleven ingots were poured using 16 shut-offs, all good. Nozzles lined with the compositions of Table II were satisfactorily employed in steel pouring operations. Some of the nozzles employed had the phosphate-bonded, ceramic material coating the seat or top surface of the nozzle body. In the pouring operations with heats as large as 200 tons successful pours and shut-offs were obtained.

Further illustrative of the versatility of the practices of this invention, phosphate-bonded, ceramic materials having the compositions set forth in accompanying Table III were employed as nozzle coatings.

These coated nozzles performed satisfactorily during steel pouring operations.

The above tests illustrate not only the versatility of this invention with respect to the materials which may be employed in the phosphate-bonded, ceramic coatings but also the effectiveness of the phosphate-bonded material as a protective coating for the nozzle body during a steel pouring operation.

The cast, unfired, refractory, phosphate-bonded, ceramic material can also be used to coat a permanent nozzle body, such as a nozzle body made substantially only of carbon or other equivalent refractory material so that after use only the coating material need be replaced. In accordance with this aspect of the invention carbon nozzles were prepared and a zircon-containing, phosphatebonded coating material prepared by admixing 40 parts by weight 400 mesh zircon flour, 40 parts by weight 7 1 -60 mesh granular zircon, 20 parts, by Weight --325 mesh tabular alumina and 15 parts byweightof 10% "aqueous phosphoric acid, This material was cast into the bore and over the seat of the carbon nozzles. Two such carbon nozzles were used three times eachiin a small arc,

furnace ladle and good pours and shut-offs were obtained. After use the phosphate-bonded coating material came away cleanly from the carbon nozzle body.

As will be apparent tozthose skilled in the ,art'init'he A 'through and a coatingof refractory material deposited on the surface of said nozzle body defining said opening for the flow of molten steel therethrough, said coating being an unfired, refractory, phosphate-bonded, ceramic material, consisting essentially of alumina component, at

least ab out 20%, and phosphoric acid component alford-,

ing between about 2 and 10 parts by weight of acid per 100 parts of alumina, said alumina-acid reaction produc being the sole bondingmaterial insaid coating. r 2. A nozzle assembly "comprising a body of refractory material provided with an opening extending therethrough and a coatingof unfired refractory, phosphate-bonded ceramic material deposited uponthe'surface of said re- 30 j made of carbon.

fractory material defining said opening, where said coating consists essentially of alumina component, at least about 20%,and phosphoric acid component affording between about 2 and 10 parts by Weight of acid per -100 parts of alumina, said alumina-acid reaction product be- 7 ing the sole bonding material in said coating.

3.'The nozzle assembly of claim12 wherein said alumina is particulatetabular alumina. v a 7 4. Thenozzle'assembly of claim 2 wherein said coating includes at least one member of the class consisting of zircon, zirconia, silica, graphite and, sp odumene. f 5. Theindzzle assembly of claim z wherein said body is References-Cited by the Examiner UNITED STATES PATENTS 1,325,725

12/19 Kohler et, al. 106-38.27 2,268,482 12/41 Harvey 2284 2,282,349 5/42 Wellings et a1 l0638.26 2,534,652 12/50 'Allison et a1. 2285 2,702,425 2 /55" Thompson"; l()6286 2,995,453 8/61 'Noble 106286 7 FOREIGN PATENTS 1,137,454 '1/5'7 France.

WILLIAM I. SiTEPI- IENSON, Primary 'Exarniner;

7 ROBERT F. WHITE, MICHAEL V; BRINDISI,

Examiners.

Claims (1)

1. A STEEL POURING LADLE COMPRISING A CONTAINER LINED WITH REFRACTORY MATERIAL, THE BOTTOM OF SAID CONTAINER PROVIDED WITH A NOZZLE BODY HAVING AN OPENING THERETHROUGH AND A COATING OF REFRACTORY MATERIAL DEPOSITED ON THE SURFACE OF SAID NOZZLE BODY DEFINING SAID OPENING FOR THE FLOW OF MOLTEN STEEL THERETHROUGH, SAID COATING BEING AN UNFIRED, REFRACTORY, PHOSPHATE-BONDED, CERAMIC MATERIAL, CONSISTING ESSENTIALLY OF ALUMINA COMPONENT, AT LEAST ABOUT 20%, AND PHOSPHORIC ACID COMPONENT AFFORDING BETWEEN ABOUT 2 AND 10 PARTS BY WEIGHT OF ACID PER 100 PARTS OF ALUMINA, SAID ALUMINA-ACID REACTION PRODUCT BEING THE SOLE BONDING MATERIAL IN SAID COATING.

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