US3271000A

US3271000A - Disposable hot top

Info

Publication number: US3271000A
Application number: US301723A
Authority: US
Inventors: Darold W Thiem; Gordon W Gottschalk
Original assignee: Universal Refractories Corp
Current assignee: Universal Refractories Corp
Priority date: 1963-08-13
Filing date: 1963-08-13
Publication date: 1966-09-06
Anticipated expiration: 1983-09-06

Description

Sept. 6, 1966 Filed Aug. 13, 1963 D. W. THIEM ETAL DISPOSABLE HOT TOP 2 Sheets-Sheet l INVENTORS Gordon W. Goflschulk BY Dorold W. Thuem L020 8:. Barry Attorneys Sept. 6, 1966 0. w. THIEM ETAL 3,271,000

DISPOSABLE HOT TOP Filed Aug. 13, 1963 2 SheetsSheet 2 v INVENTORS Gordon W. Goflschulk Darold W. Thiem L020 8 Ba rry Attorneys United States Patent 3,271,000 DISPOSABLE HOT TOP Darold W. Thiem, Elm Grove, and Gordon W. Gottschalk, Hales Qorners, Wis., assignors to Universal Refractories Corporation Filed Aug. 13, 1963, Ser. No. 301,723 6 Claims. (Cl. 249-197) This invention rel-ates to an improved hot top for an ingot mold. More particularly, it relates to disposable, single-use, hot tops of a novel design and to methods of fabricating and using such hot tops.

In broad outline the instant invention provides a lightweight disposable hot top for an ingot mold which comprises, in combination, a sinkhead casing consisting essentially of a formed shell of refractory composition material adapted to extend downwardly into the opening of an ingot mold, and exposed chill means on the lower end of the casing (adapted to facilitate rapid chilling of molten metal coming in contact with such chill means and tofreeze-in to the molten met-a1 when it solidifies. Thereby, the molten metal coming in contact with the chill means freezes around the exposed portion to anchor the hot tops against upward displacement by the buoyant (ferrostatic) force of the molten metal in the mold.

In the casting of various cast parts and more particularly metal ingots, it is common practice to maintain the head of the ingot in a molten condition so that the molten metal will feed the body of the ingot as the latter shrinks during solidification. By prolongation of the liquid state in the head of the ingot, it is possible to confine the shrinkage cavity to a sinkhead, sometimes called shrinkhead, at the top of the ingot, thus minimizing the amount of steel that must be cropped in the rolling mill to obtain a product free from pipe and excessive chemical segregation.

With many grades of steel, it has been found necessary that the mold have special provision at its top to retard chilling and to retain a fluid reservoir of molten metal to feed into the space being formed by shrinkage. The most suitable device for this purpose is the hot top which consists principally of a shaped or formed shell inserted into the top of the ingot mold. In the steel industry such a hot top may receive as much as 10% to 25% by volume of the molten metal in the entire ingot.

Heret-ofore, types of hot tops commonly in use have been formed in whole or in part of fire clay molded to the desired shape and then burned or fired, or fire brick laid up as a lining in a suitable metal casing. Specific types of conventional hot tops are (1) the semi-perma nent type consisting of a heavy metal housing lined with fire brick, and (2) single-use fire clay shells which may be one piece or sectional types formed of slabs or the like which must be fastened together by means of wire.

As is well known the semi-permanent hot top is costly to fabricate and its use requires a considerable inventory of expensive metal casings of different sizes and shapes. Such hot tops are heavy and necessitate mechanical equipment and several men to facilitate the placement of the hot tops with reference to the ingot mold. Moreover, when such hot top is stripped or broken away from the ingot, portions of the burned brick will adhere to it due to the metal of the ingot freezing to the fire brick. Here again, manual labor with its attendant expense is essential.

Another problem is the necessary exposure of the outer metal casing, especially the bottom portion when molten metal is poured through this type of hot top. After a series of operations this exposed metal is adversely affected and, in the course of time, becomes pitted and cracked and interferes considerably with the operation 3,271,0fl0 Patented Sept. 6, 1966 "ice of stripping the hot top from the ingot, finally making a new casing necessary. In order to increase the lifetime of the casing, it has become common practice to employ bottom rings of baked refractory composition material which are removable and replaceable after each pour. Generally, however, it has been impossible to remove all of the bottom ring material from an ingot so that such adherent portions are carried by the ingot into the blooming mill where they have a deleterious effect upon the ingot and likewise cause roll trouble and contamination of the roll scale.

One of the most serious disadvantages of the steel casing-fire brick lining hot tops has been the requirement for extensive manual and mechanical operations to prepare, maintain and recondition the units. The fire brick linings must be fabricated by hand and periodically replaced. The bottom rings can be used only once, have to be manually attached to the casing by wire clips or clamps, and are often dislodged during the handling of the hot top attendent its positioning atop the ingot mold. Even with the use of costly modern mechanical methods for stripping, cleaning, repairing and relining this cumbersome and complex type of hot top, it has been impossible to overcome major problems connected with its use.

It is apparent that many of the difficulties connected with the semi-permanent style of hot top can be avoided by utilization of the single-use shell of fire clay either in the form of a one-piece molded structure or an assembly of slab side-walls. Such hot tops require no heavy metal casing or bottom ring, and are easily handled and mounted in place in the opening of an ingot mold. Used only once, they require no costly repairs after the ingot has been poured. Unfortunately, however, fire clay hot tops generally are extremely difficult to remove when portions of them adhere to the ingot. This entails substantial labor costs in the removal and when, as is often the case, the removal is not complete, the adhering material is harmful to the ingot and to the mill scale produced during rolling. Further, such debris can contaminate the soaking pits.

One of the most serious problems which has kept the industry from giving more attention to the use of lightweight hot tops, results from the fact that heretofore hot tops fabricated without heavy metal housings have generally required complicated auxiliary bindings to hold them in place on the mold and resist the buoyant ferrostatic force of the molten metal as it rises in the mold. When a hot top floats off with subsequent loss of the shrinkhead, the ingot usually is lost because the ingot body is piped and must be scrapped. Attempts to avoid such losses with back-pouring techniques have not been altogether successful and result in loss of time and efficiency. Further, the possibility of a running stopper is always present in which case there is no opportunity of waiting for a hot top seal to form become completing the pour. While many of these problems might be substantially eliminated by the use of auxiliary fastenings of various types, practical considerations involved in the complex pouring operations of a present day steel mill, dictate that the need for such additional fastenings and the extra labor involved in applying them simply cannot be tolerated.

Accordingly, one of the objects of the present invention is the provision of an improved disposable hot top which is both easy and inexpensive to manufacture and use. Another object is to facilitate the handling and positioning of hot tops preparatory to the {pouring operation and to provide a -single-use refractory type hot top which requires no auxiliary fastenings or bindings to secure it to the ingot mold and yet is not subject to dislocation and floating-off when the mold and hot top are filled at one pouring. A further object is provision \of means of the character stated which may be applied to a hot top casing of heat-degradable refractory composition material having the characteristic of partially disintegrating at temperatures of molten steel with the result that the casing is transformed into a friable skeleton consisting principally of loosely-bound, finely-divided particles which can be readily removed from the ingot and its sinkhead.

Still another object of the present invention is to provide a new and improved method of fabricating .and using a disposable hot top in a casting operation, which method does not require the user of the hot top to maintain an inventory of metal casings or bottom rings, thereby eliminating problems in storing, shipping and handling. Hot tops of the instant invention are received by the mill complete and ready for use. Moreover, they can be readily fabricated at the steel mill itself using conventional foundry techniques with direct production economies.

The above and other objects of the invention are attained in accordance with aspects of this invention which are broadly directed to ingot mold hot tops and methods of their fabrication which obviate the disadvantageous limitations of the prior art as outlined above. In brief abstract the instant invention contemplates a disposable hot top comprising, in combination, a shrinkhead casing consisting essentially of a formed or shaped shell of refractory composition material adapted to extend downwardly into the opening of an ingot mold, and chill means, such as a chill-iron member or a chill ring or channel on the lower end of the casing adapted to facilitate rapid chilling of molten metal coming in contact therewith and to freeze-in and lock to the molten metal as it solidifies.

In a preferred embodiment of the invention, the sinkhead casing comprises a formed one-piece or slab assembly structure of heat degradable refractory composition material having suflicient structural strength to withstand necessary handling during shipping and at the mill and to contain molten metal when the ingot is poured, but capable, under the influence of the heat of molten steel, of transformation into a friable skeleton of loosely-bound, finely-divided particles, whereby the now frangible casing can be collapsed readily, as with light blows or a jet of air, and the entire hot top stripped cleanly and easily from the sinkhead of the ingot when the ingot is ready for removal from the mold.

One feature of the present invention is the facilitation with which projections to aid in lifting the ingot out of the mold can be cast on the surfaces of the sinkhead. Shaped transversely extending projections or beads which can be straight, curved or angular as desired, are formed easily on at least two opposed sides of the sinkhead simply by utilizing appropriately shaped cavities on the inner walls of the disposable hot top casing. H-eretofore, with conventional re-usable hot tops, formation of such projections has been extremely troublesome owing to the difiiculty in stripping the metal casing and the attendant damage to the fire brick lining caused by the projections themselves.

It is an additional feature of the instant invention that the refractory composition material which becomes collapsible during the solidification of the ingot can be reclaimed so that a substantial proportion of it can be recovered for reuse in the fabrication of new hot tops.

The novel featuresivhich are believed to be characteristic of the invention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will be understood more clearly and fully from the following detailed description considered in connection with the accompanying drawings in which:

FIG. 1 is a perspective view, partially broken and sectioned, of a one-piece hot top exemplifying, for illustrative purposes, one embodiment 'of the subject invenlion;

FIG. 2 is a bottom view of the disposable hot top shown in FIG. '1 illustrating a corner chill-iron member projecting into a shaped cavity positioned on the periphery of the lower portion of the casing. A pair of exposed cavities in the inner wall of the casing used to form projections on the sinkhead of the ingot are also illustrated;

FIG. 3 is a perspective view of a hot top formed of an assembly of blocks or slabs having interengaging surfaces exernplifying, for illustrative purposes, another embodiment of the subject invention;

FIG. 4 is a perspective view of one side wall of a slab wall hot top similar to the hot top shown in FIG. 3;

FIG. 5 is a cross-sectional view of a portion of the hot top shown in FIG. 3 showing the close fitting spaced relationship with the walls of an ingot mold and the exposed chill channels frozen-in to the skin formed by the molten metal poured into the ingot mold;

FIG. 6 is a cross-sectional view of a portion of wall, taken along line 6-6 of FIG. 4 of the disposable hot top; and

FIG. 7 is a cross-sectional view of a portion of wall of a hot top similar to the hot top shown in FIG. 1 illustrating another embodiment of the subject invention in which gate-metal chill means are employed.

Referring to the drawings in detail, FIG, 1 shows a disposable hot top comprising a sinkhead casing designated generally at 2, adapted to extend downwardly into an ingot mold (not shown). In the embodiment illustrated, the casing 2 comprises a formed structure of heatdegradable refractory material 4 having sufficient structural strength to withstand necessary handling and to contain molten metal when in use on an ingot mold, but capable, under the influence of the heat of the molten steel poured therein, of transformation into a friable skeleton of loosely-bound, finely-divided particles. As the description proceeds, it will be appreciated that the composition of the refractory material employed in the construction of the disposable hot top is an important element in the preferred mode of this invention, but for convenience at this stage in the description, the composition will be described only in terms of the results which it achieves in conjunction with the configuration of the disposable hot top itself.

The hot top casing can be formed from a single molding as shown in FIG. 1 and FIG. 2 or it can be formed by assembling a plurality of separate slabs 31, four in the case of a square or rectangular configuration as shown in FIG. 3 and FIG. 4. The individual slabs 31 are molded to shape and subsequently interfitted at their edges and banded, for example, by a steel strapping 33, or other wrapping means generally known in the art. In fabrication, a bead of suitable compressible sealant 47 is employed to prevent metal run out through the joints. In some instances, banding on the exterior or outer wall of the disposable hot top may be desirable, even if the casing is formed as a single piece structure as shown in FIG. 1. Such banding, depending upon the particular refractory composition employed, can increase the strength of the casing markedly so that it can better resist breakage, cracking, and the like during the jostling which occurs in the course of its manufacture, subsequent handling and use in a steel mill. Further, steel strapping 33 can be used to supply additional temporary lateral support to the casing after it has been transformed into a friable skeleton of heat-degraded material, and until it is stripped from the sinkhead of the ingot. Four of such reinforcing bands or straps 33 are shown in FIGS. 1 and 3 disposed in band grooves 5 of sunk fillet configuration. Preferably, the grooves for receiving the reinforcing bands are molded into the casing during manufacture.

The hot top includes means provided on the outer wall of the molded casing for use in supporting the hot top on an ingot mold. As shown in FIGS. 1 and 3, such means, for example, can be a plurality of staggered support slots 6 cast into the lower portion of the outer wall of the casing, each proportioned to receive suitable support tabs 7 such as metal bars or the like, which, in use, rest upon the upper surface of the ingot mold as best shown in FIG. 5. These support tabs effectively control the depth of insertion of the hot top into the mouth of the ingot mold. They can be preset in the walls of the hot top in accordance with the particular conditions to be encountered in the steel mill. Usually, however, they will be positioned so that a set of slots can be chosen which will hold the hot top with fromabout l" to 6" of the bottom portion inserted into the mold. By staggering the support slots unusual strength is obtained in the sidewall construction.

In order to easily handle the disposable hot top in the factory where it is made, and in the course of use in the mill, suitable lifting means can be provided on the outer wall of the sinkhead casing during manufacture thereof. Shaped pockets 10, as shown in FIG. 1, adapted to re ceive the ends of lifting hooks, are cast into the walls of the casing when it is molded. In the embodiment shown in FIGS. 3 and 4, a pair of right triangle configured pockets 35 are provided in each side face. It will be observed in this embodiment that the hypotenuse of the right triangle angles upwardly and toward the corner in each position. When hooks of a crane or a fork lift truck are employed, they will automatically slide along this hypotenuse wall into the corners thereby spreading laterally the suspension points and increasing the stability of the carry.

To reduce any tendency to crack by reason of the load hooks, reinforcing means such as reinforcing rods or crimped wires can be cast interiorly of the disposable hot top positioned in the manner well known in the art to relieve stress and strain at critical points of the structure. It is particularly advantageous to embed reinforcing wires (or the like (not shown) in hot tops of heat degradable refractory material to aid in holding the friable skeleton together after pouring, especially in the case of large hot tops on a side or more. Internal reinforcing means are generally not required in smaller hot tops but can be employed, if desired, without detrimental effect.

In accordance with the present invention, the refractory casing of the novel hot top is provided with chill means on the lower end of the casing adapted to facilitate rapid chilling of the molten metal coming in contact with the chill means and to freeze-in to said metal as it solidifies. By means of this discovery the hot top is anchored against upward displacement by the buoyant force of the metal poured into the mold and will not float away during the pour with resultant leaking of the molten metal and loss of the ingot due to extensive piping.

Regardless of size, all shapes of ingot molds are of necessity provided with thick metal walls having great heat absorbing capacity. When liquid steel,,for example, is poured into an ingot mold, it immediately loses heat at a rapid rate adjacent the walls of the molds and forms a shell or skin of fine grained metal encasing the ingot along its entire length. The ingot being formed is then confined within its own shell and the metal solidifies inwardly at a slowly decreasing rate as heat is absorbed and carried off by the side walls of the mold.

It has now been discovered that if suitable chill means are provided on the lower end of the hot top adjacent the mold walls but out of contact therewith, that even a relatively lightweight, disposable hot top can be anchored-in to the skin of the ingot in the first fraction of a minute, for example, about 10 seconds, after pouring to resist the buoyant force of the molten metal rising in the mold.

In the embodiment shown, the unique design utilizes a chill channel section 12 along the bottom edge of the disposable hot top to prevent leakage and float-away, and to minimize the clearance between the ingot mold walls and the hot top casing. This consists of a series of chill channels 14 and chill channel da'ms 16 vertically disposed on the lower outer wall of casing 2. In addition, the entire chill channel section 12 tapers outwardly from bottom to top at an angle of approximately 5-30, to permit easy insertion of the hot top into the ingot mold. The half-round configuration of each darn 16 provides maximum strength so that chipping and the like during placement of the hot top is minimized.

It is understood that a single c'hill channel or a plurality of same can be utilized in accordance with the present invention. Various shaped channels or the like can be used, e.g., Fillet and Fascia, Sunk Fillet, Quarter Round or Ovolo, Torus, Bead or Astragal, Reed or Reeding, Ovolo or Thumb, Cavetto, Scotia, Conge or Beak. Alternatively, a plurality of shaped pockets or cavities can be utilized as chill means in the outer wall of the easing. These are peripherally positioned on the lower portion of the casing so that when the casing is inserted into the opening of an ingot mold, the pockets or cavities will be spaced slightly from the inner surfaces of the mold walls and exposed, for filling, to molten metal poured into the mold. By means of the generally concave shape of the channels, pockets or cavities, the frozen metal therein will lock the hot top to the ingot being formed within its frozen skin. This effect is illustrated by FIG. 5 showing a portion of the outer wall 51 of the hot top casing having a plurality of spaced parallel channels 52 which encircle the lower portion of the casing, and are positioned adjacent but spaced slightly from the inner surface of the mold wall 54 so that they will be exposed to molten metal 55 poured into the mold. It is seen that the metal has frozen along the surface of the mold wall 54, and the wall of the casing 51 to form a skin of frozen metal 57 which by reason of the channels 52 has anchored the hot top against upward displacement by the ferrostatic forces of the molten metal.

In another embodiment of the present invention, also illustrated in FIG. 1, chill-iron members, designated generally at 20 are disposed in one or more of the shaped pockets 22 cast into the body of the casing 2. In the example shown the chill-iron member has a base plate 23 attached to a supporting member 24, the other end of which is embedded in the refractory material 4 of the casing wall. Reinforcing cross-bar members 25 serve to res-train the chill-iron member and prevent it from pulling out when the molten metal flows over and around the base plate 23 and freezes to it. When corner chills are used, preferably one is utilized at each corner of the hot top with the exposed base plates 23 extending flush with the bottom of the casing.

Another type of chill-iron is shown in FIGS. 3 and 6,

disposed in this instance in the side walls of the casing.

In the embodiment shown, chill-bar hangers 34 are embedded in the lower body portion of the casing so that the base of each projects into pockets 36 for exposure to molten metal. Each chill-iron consists of a base 37, two oppositely facing bar hangers 38 and anchor tabs 39 afiixed to the upper portion of each hanger 38.

It will be noted that the casing of the hot top has a frusto-pyramidal top portion 40 and a series of converging

inner walls

42 and 44 from the lower base 45 to the upper fiat 46. Such converging wall structure, coupled with the exothermic reaction caused by the decomposition of the heat degradable refractory material and/or the exothermic cake applied thereto, as will be described hereinafter, promotes a reduction in the amount of piping in the sinkhead. A pair of shaped cavities 62 in the inner wall 44 provides projections on the sinkhead useful to aid in lifting the ingot out of the mold. These cavities 62 can be formed, as by casting, when the hot top casing is molded.

The tapered inner surface 42 is adapted to produce an upwardly inclined tapered shoulder upon the ingot at the junction of the ingot proper and the sinkhead. This downwardly and outwardly inclined surface 42 can be formed during the casting operation whether the hot top is made in one piece or fabricated as a sectional unit. It is also beneficial in permitting dirt and debris to float past the ingot shoulder and up into the sinkhead. Preferably, a conventional refractory coating 63, for example, con- '-taining silica or zircon properly bound, is painted onto the inner surface of the hot top to prevent the sand composition from prematurely spalling into the ingot mold and causing debris in the mold.

FIG. 7 illustrates another embodiment of the invention in which metal chill means designed to cooperate with shaped chill cavities or channels are created in situ in the form of gate-metal members which transfix the lower end of the casing running from the inner wall thereof, through the casing, to the wall of the ingot mold. Molten metal rising in the hot top will run through the gates or pin holes 71 in the casing wall 51 and fill the spaces between the outer wall of the casing and the mold wall before freezing. Preferably a spaced series of pin-holes is cast into the casing around its entire perimeter positioned in the lower portion designed to be inserted into the ingot mold for example, in the lower 4 inches of the hot top. Generally, holes having a diameter in the range of A" to /4. are suitable. They can be tapered with the smaller end opening into the interior of the hot top to better control the flow of molten metal. A particular advantage of such gate-metal members is the fact that no foreign metal is used to anchor the hot top to the ingot, the chill-irons being formed of the same metal poured into the casting.

Preferably, disposable hot tops of the present invention are fabricated with suitable chill means of the novel type described above, in combination with the use of a refractory composition formulated to produce a heat-degradable refractory material. Such material should have sufiicient strength to withstand necessary handling and to contain molten metal when the ingot is poured, but be capable, under the influence of the heat of the molten metal, of transformation into a friable skeleton of low strength, loosely bound, finelydivided particles.

Broadly, any conventional core-sand-binder composition known to the foundry industry in the making of cores and molds where a high degree of collapsibility after firing is required, can be utilized as the heat-degradable refractory material from which the hot top casings are fabricated. The cured composition must have a crushing or compressive strength of at least 200 lbs. per square inch and preferably be in the range of about 2504200 lbs. per square inch or more. This refractory material must degrade when subjected to temperatures of molten steel, e.g., about 2600-3000 F., to a fragile and friable skeleton of powder, having a compressive strength of 100 lbs. per inch or less, preferably in the range of about 10-50 lbs. -per square inch. Where desired, a conventional exothermic layer or cake can advantageously be employed with the heat degradable casings.

It has now been discovered that sand-binder mixes which cure to a heat-degradable refractory mixture can be formulated so that they undergo an exothermic reaction when activated by heating. Such sand mixes comprise in the range of 95-98 parts by weight of core sand admixed with in the range of about 1.5 to 5.0 parts of a furan resinous binder and a phosphoric acid catalyst, preferably in the range of about 0.03 to 1.75 parts, that is, about 2.0 to 35% by weight of the resinous binder utilized. They are prepared by mixing the sand with the acid and then blending the resinous binder into the sandacid mix in a conventional muller. The uniform mixture is then poured with tapping, ramming or the like, or can be blown at 50-100 lbs. into a mold designed to form a suitable hot top casing. The composition is thereafter cured at a temperature of about 75 to 500 F. for about /2 to 120 minutes at higher temperatures and about 30 minutes to 5 hours at lower temperatures depending upon the curing temperature utilized and the concentrations of the resinous binder and acid in the sand mix. The casing is then removed from the mold, banded and is ready for use.

To more fully illustrate the invention, the following examples are presented. It is to be understood that these are given for illustrative purposes only, and are not to be 'construed as limiting in any way the scope of the present invention.

Example I parts by weight of sand of the Ottawa Bond type was mixed with from 0.5 to 1.0 part of 85 percent phosphoric acid for about one minute in a standard blender. Thereafter, three parts of furan resinous binder was added having the following formula:

Urea lbs 216 Urea-formaldehyde mix lbs 1228 25% urea. 60% formaldehyde. 15% water. Water lbs 311 Furfural alcohol lbs 4000 Triethanolamine gms 3420 Lactic acid gms 3420 This binder was prepared using conventional resin formulation techniques with heating at about 220230 F. for 1 hour.

The mixture was then mulled for an additional three minutes prior to molding. Molding was accomplished by ramming the sandbinder mix into molds after the reinforcing wires and chill bar had been placed in the empty molds. The molds were heated to approximately to F. to cure the mix and stripped about ten minutes thereafter depending upon concentration of the furan resin used. Molded plugs in the shape of 2 x 2" cylindrical specimens, made using a five pound rammer, were aged for 40 hours under various temperature and humidity conditions and examined for compressive strength. High 1y satisfactory compressive strengths were obtained in each test in the range of 250 lbs. per square inch to 1300 lbs. per square inch.

In a series of tests, hot tops of the above refractory composition material were filled with molten metal, approximately 2800 F. and the decomposition observed. Gas, generated by the heat under a reducing atmosphere, burst into a lazy blue flame which covered the entire outside portion of the disposable hot top forming a blanket of hot gas. As the exothermic reaction continued the sinkhead was maintained at a high temperature so that the metal therein remained relatively plastic as the ingot cooled. It is believed that the resinous liquid utilized as the binder is catalysed by the strong mineral acid and polymerized when the hot top is molded. A relatively rigid matrix of sand and high molecular weight resin is thereby formed. Thereafter, when this matrix is subjected to high temperature when the steel is poured, further polymerization occurs with eventual decomposition releasing heat in an exothermic reaction to the sinkhead. The fragile and friable skeleton which remained had a retained compressive strength in each case in the range of about 10-100 p.s.i.

Example II A series of hot tops was manufactured in the manner of the hot top illustrated in FIGURE 3 using the above sand-binder mix. Each was 24 inches square at the base, 20 /2 inches square at the top with an overall height of 27 inches. They were used with 24 /2 x 24 /2 x 107 inch steel molds having a volume of 40,531 cu. inches (ingot weight 14,200 lbs.). Four hanger tabs 4" x 1%" x were used to hold the hot top on the ingot mold with the lower 4 inches inserted into the opening of the mold. Each hot top was poured 2 inches short of the top so that the ingot body contained 14,200 lbs. of steel. The hot tops each contained 2,170 lbs. of steel or 13.3% of the total Weight.

Each of the ingots were poured using a 2" nozzle in approximately 2 minutes. In some instances the body was poured first allowing a 10 sec. pause before the hot top was filled. In other cases, the ingot was poured straight up Without pause to simulate a full running stopper. No leaking, run out or floating was observed in any test with four. hot tops. Ingots were stripped after about 2 hours and rolled into a 9% x 9% inch bloom on a 44 mill. Each ingot was cut into two equal cuts and four feet of prime steel on the hot top. All pieces were weighed. The hot top and four feet of prime was subjected to the usual laboratory tests. In each case the yield of prime steel was approximately 88%. Microetch slices taken where no indication of pipe was detected showed carbon segregation in the range of from 2.22.3% in each case.

Example 111 Four large hot tops 34 x 34" x 35 having cylindrical shrinkhead configurations similar to the hot top of FIG- URE 1 were made on Unreco sand blend and 3% of the furan resinous binder of Example I. 22.2% of an 85% H PO was used as a catalyst. 1200 pound sand mixes were used to mold the hot tops in the manner described above. Four 1 /2 inch steel banding straps were used for external reinforcing.

Each hot top was poured 2" from the top on large 133" molds with the hot tops inserted 4" into the molds. Each ingot mold had a volume of 104,420 cu. inches. The hot tops each held 14,800 cu. inches of steel or 12.1% of the total volume. They were poured at approximately 250 lbs. of molten steel per second using a 1% inch nozzle. In each case results proved that the corner chill irons made from /2" x 11 /2" bar stock and /2" reinforcing rod provided rapid freezing-in of the hot top and no float-oh was observed.

Various hot tops have been tested with and Without internal reinforcing wires and with and without chill irons using only chill channels of the type heretofore described to provide freeze-in. Each experiment together with those described above clearly shows the advantages of the novel discovery in which exposed chill means of various types on the lower end of the shrinkhead casing provide rapid chilling of the molten metal coming in contact with such means to freeze-in and lock the entire hot top and thereby prevent floating-off.

In the example given above, each of the hot tops was easily stripped from the siukhead of the ingot by reason of the friable nature of the heat degradable refractory composition material of which the casing was made, thereby illustrating another embodiment of the present invention. The fragile skeleton simply collapses upon the application of slight force and can be brushed or knocked off when it is time to strip the ingot.

From the above examples, one can see that the ranges of concentration of each component of the sand mixture, the method of molding, the cure time and the like may be varied over relatively wide limits. Much depends upon the size of the hot top to be molded, the physical strength desired, the temperature of the metal to be poured therethrough, the way the top. is to be banded and reinforced, the degree of handling expected, and the like. Now as to the specific components utilizable, the resinous binder.

component can be a thermosetting resin, such as ureaformaldehyde, phenol-formaldehyde, melamine-formaldehyde, furfural alcohol-formaldehyde, furan, or combinations thereof, and the like or other binder system such as is known in the foundry industry.

The acid utilizable with the resin may be an inorganic mineral acid such as hydrochloric, sulfuric, phosphoric, or an organic acid, such as maleic, benzoic, fumaric, phthalic, oxalic and the like. Generally, enough acid is used to work at a pH of between 2.0 to 6.0 in the sand mix.

Now as to the sand, any suitable foundry sand may be used, such as Ludington Lake sand, Ottawa silica sand and the like. Grain size distribution can range from 45- V 10 on an A.F.S. scale depending upon the size and type of hot top used.

Typical binder compositions are as follows:

COMPOSITION I Urea lbs Flake formaldehyde lbs 835 Water lbs 334 Furfuryl alcohol lbs 4000 Acetic acid cc 3800 25% NaOH cc 3800 Triethanolamine cc 3000 COMPOSITION II Lbs.

Urea 22 Flake formaldehyde 22 Furfuryl alcohol 396 Boric acid COMPOSITION III Lbs.

Urea-formaldehyde (25-60) concentrate 135.5

Urea 66 Furfuryl alcohol 198.5

Boric acid 5 Triethanolamine.

It should thus be seen that the objects set forth above and those made apparent from the preceding description, are efliciently attained.

It is to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements to the scope of the invention, which as a matter of language might be said to fall therebetween.

What is claimed is:

"1. The combination of a disposable hot top and an ingot mold, said mold comprising a metallic body having an opening in its upper end, said hot top comprising a siukhead casing having a lower end of such shape and dimensions as to be adapted for insertion into the opening in the body of said ingot mold in close proximity to the inner surfaces of the walls of said opening, said casing comprising a formed structure of heat degradable refractory material having sufiicient strength to withstand necessary handling and to contain molten metal when the ingot is poured, at least one half-round chill channel dam integral with and extending outwardly from the outer wall of said casing and encircling the lower portion thereof, independent support means holding the casing in position in the Opening of the body of the mold with said chill channel dam spaced slightly from the inner surfaces of the walls of said opening and exposed to the molten metal which rises in the space between the hot top and the walls of said opening, whereby the molten metal which is chilled by the Wall of the ingot mold will set rapidly, anchoring the hot top to the chilled metal on the inner surface of the ingot mold preventing upward displacement of the hot top by the buoyant force of the molten metal in the mold.

2. The combination of a disposable hot top and an ingot mold, said mold comprising a metallic body having an opening in its upper end, said hot top comprisiing a siukhead casing having a lower end of such shape and dimensions as to be adapted for insertion into the opening of an ingot mold in close proximity to the inner surfaces of the opening in the body of the ingot mold, said casing comprising a formed structure of heat degradable retractory material having sufiicient strength to withstand necessary handling and to contain molten metal when the ingot is poured, a plurality of spaced parallel halfround chill channel dams integral with and extending outwardly from the outer wall of said casing with each dam encircling the lower portion of said casing and support means holding said casing in the opening in said mold body with said chill channel dams being spaced slightly from the inner surfaces of the mold walls and exposed to the molten metal which rises in the space between the hot top and the inner surface of said opening, whereby molten metal rising in the space between the dam and the inner surface of the wall is restricted and sets rapidly, anchoring the hot top to the chilled metal on the inner surface of the ingot mold to prevent upward displacement of the hot top by the buoyant force of the molten metal in the mold.

3. The combination of a disposable hot top and an ingot mold, said mold comprising a metallic body having an opening in its upper end,

said hot top comprising a sinkhead casing having a lower end of such shape and dimensions as to be adapted for insertion into the opening in the body of said ingot mold in close proximity to the inner surfaces of the walls of said opening,

said casing comprising a formed structure of heat degradable refractory material having suflicient strength to withstand necessary handling and to contain molten metal when the ingot is poured,

at least one chill channel dam integral with and extending outwardly from the outer wall of said casing and encircling the lower portion thereof,

said lower portion of said casing being tapered downwardly and inwardly with said chill channel dam being located on said tapered section,

independent support means holding the casing .in position in the opening of the body of the mold with said chill channel dam spaced slightly from the inner surfaces of the walls of said opening and exposed to the molten metal which rises in the space between the hot top and the walls of said opening, whereby the molten metal which is chilled by the wall of the ingot mold will set rapidly, anchoring the hot top to the chilled metal on the inner surfaces of the ingot mold preventing upward displacement of the hot top by the buoyant force of the molten metal in the mold.

4. The combination of a disposable hot top and an ingot mold,

said mold comprising a metallic body having an opening in its upper end,

said hot top comprising a sinkhead casing having a lower end of such shape and dimensions as to be adapted for insertion into the opening of an ingot mold in close proximity to the inner surfaces of the opening in the body of the ingot mold,

said casing comprising a formed structure of heat degradable refractory material having sufiicie'nt strength to withstand necessary handling vand to contain molten metal when the ingot is poured,

a plurality of spaced parallel chill channel dams integral with and extending outwardly from the outer walls of said casing with each dam encircling the lower portion of said casing, said lower portion of said casing being tapered downwardly and inwardly with one of said chill channel dams being located on the vertical side wall of said casing,

and support means holding said casing in the opening in said mold body with said chill channel dams being spaced slightly from the inner surfaces of the mold walls and exposed to the molten metal which rises in the space between the hot top and the inner surface of said opening, whereby molten metal rising in the space between the dams and the inner surface of the wall is restricted and sets rapidly, anchoring the hot top to the chilled metal on the inner surface of the ingot mold to prevent upward displacement of the hot top by the buoyant force of the molten metal in the mold.

5. The combination of a disposable hot top and an ingot mold,

said mold comprising a metallic body having an opening at its upper end,

said casing comprising a formed structure of heat degradable refractory material having sufiicient strength to withstand necessary handling and to contain molten metal when the ingot is poured,

at least one channel in the outer wall of said casing encircling the lower portion thereof,

said lower portion of said casing being tapered downwardly and inwardly with said chill channel being located on said tapered portion, and

independent support means holding said casing in the opening in said mold body with said channel spaced slightly from the inner surfaces of the mold walls and exposed to the molten metal which rises in the space between the hot top and the walls of said opening, whereby the molten metal which enters the space between the hot top and the walls of said opening and sets rapidly will also set in said channel, anchoring the hot top to the chilled metal on the inner surface of the body of ingot mold preventing upward displacement of the hot top by the buoyant force of the molten metal in the mold.

6. The combination of a disposable hot top and an ingot mold,

said mold comprising a metallic body having an opening at its upper end,

said casing comprising a formed structure of heat degradable refractory material having sufiicient structural strength to withstand necessary handling and to contain molten metal when the ingot is poured,

a plurality of spaced parallel channels in the outer wall of said casing encircling the lower portion thereof,

said lower portion of said casing being tapered downwardly and inwardly with said channels being located on said tapered portion, and

independent support means holding the lower portion of said casing in the opening in said mold with said channels being spaced slightly from the inner surfaces of the mold walls, and exposed for filling to the molten metal which rises in the space between the hot top casing and the walls of the opening in said hot top when the ingot is poured, said metal which enters said space chilling rapidly and anchoring the hot top to the chilled metal on the inner walls of the ingot mold and preventing any upward displacement of the hot top by the buoyant force of the molten metal in the mold.

References Cited by the Examiner UNITED STATES PATENTS 1,500,733 7 1924 Howard et al. 2,341,589 2/ 1944 Anthony. 2,361,386 10/1944 Eayrs. 2,821,000 1/ 1958 N ouveau. 2,914,825 12/ 1959 Marburg. 2,946,103 7/ 1960 Vallak. 3,015,139 1/ 1962 Marburg. 3,103,046 9/ 1963 La Bate. 3,109,211 11/ 1963 Wagner et al.

FOREIGN PATENTS 838,676 6/ 1960 Great Britain. 926,204 5/1963 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, MICHAEL V. BRINDISI,

WILLIAM J. STEPHENSON, Examiners.

R. DLBALDWIN, Assistant Examiner.

Claims

1. THE COMBINATION OF A DISPOSABLE HOT TOP AND AN INGOT MOLD, SAID MOLD COMPRISING A METALLIC BODY HAVING AN OPENING IN ITS UPPER END, SAID HOT TOP COMPRISING A SINKHEAD CASING HAVING A LOWER END OF SUCH SHAPE AND DIMENSIONS AS TO BE ADAPTED FOR INSERTION INTO THE OPENING IN THE BODY OF SAID INGOT MOLD IN CLOSE PROXIMITY TO THE INNER SURFACES OF THE WALLS OF SAID OPENING, SAID CASING COMPRISING A FORMED STRUCTURE OF HEAT DEGRADABLE REFRACTORY MATERIAL HAVING SUFFICIENT STRENGTH TO WITHSTAND NECESSARY HANDLING AND TO CONTAIN MOLTEN METAL WHEN THE INGOT IS POURED, AT LEAST ONE HALF-ROUND CHILL CHANNEL DAM INTEGRAL WITH AND EXTENDING OUTWARDLY FROM THE OUTER WALL OF SAID CASING AND ENCIRCLING THE LOWER PORTION THEREOF, INDEPENDENT SUPPORT MEANS HOLDING THE CASING IN POSITION IN THE OPENING OF THE BODY OF THE MOLD WITH SAID CHILL CHANNEL DAM SPACED SLIGHTLY FROM THE INNER SURFACES OF THE WALLS OF SAID OPENING AND EXPOSED TO THE MOLTEN METAL