US3123877A - Apparatus for and method of casting metal members - Google Patents

Description

2 Sheets-Sheet 1 E. Q- SYLVESTER March 10, 1964 APPARATUS FOR AND METHOD OF CASTING METAL MEMBERS Filed July 24, 1961 3,123,877 APPARATUS FOR AND METHOD OF CASTING METAL MEMBERS Filed July 24, 1961 March 10, 1964 Q. SYLVESTER 2 Sheets-Sheet 2 United States Patent M 3,123,877 APPARATUS FOR AND METHQD OF CASTING METAL MEMBERS Edmund Quincy Sylvester, Shaker Heights, Ohio Grifiin Wheel Co., 445 N. Sacramento Blvd,

Chicago, Ill.)

Filed July 24, 196i, Ser. No. 128,337 Claims. (Cl. 22l41) This invention relates to a method of casting metal slabs, blooms and billets, and has for its principal object the provision of a new and improved method of this kind.

This application is a continuation-in-part of my copending application Serial No. 804,317, filed April 6, 1959, now abandoned, for Method of Casting Metal Members.

It is a main object of the invention to provide a method of casting a metal member, such as a slab, a bloom or a billet, which can be rolled to produce a desired product without the necessity of first scarfing, machining, or otherwise treating the member other than heating it to a proper temperature for rolling.

Another object of the invention is to provide a method of casting rollable metal members, which method results in the production of a minimum of scrap and hence results in a high percentage of recovery from a supply of molten metal.

Another object of the invention is to provide a method of casting metal members that are capable of being rolled into various products, which method involves causing the member to cool rapidly initially so as to freeze inwardly from its sides and ends and thereby produce in the surface areas of the metal a crystalline structure capable of being rolled upon being heated to a proper temperature and without other further treatment.

Another object of the invention is to provide a method of casting metal members which are capable of being rolled into various shapes, which method includes hermetic sealing of the center or core of the member while the metal therein is still molten, thereby to prevent oxidation of the surfaces defining fissures or voids formed by shrinkage of the core metal upon cooling.

Another object of the invention is to provide a method of eliminating sprues and risers such as have been employed heretofore in the casting of metals.

Further objects of the invention not specifically mentioned here will be apparent from the detailed description and claims which follow, reference being had to the accompanying drawings in which a preferred embodiment of the invention is shown by way of example and in which:

FIG. 1 is a diagrammatic elevational View of a pouring ladle, spout and pressure bell;

FIG. 2. is a plan View of FIG. 1, with a part of the pressure bell broken away;

FIG. 3 is a fragmentary elevation-a1 view partly in cross section, showing the pouring spout with molds registered therewith in pouring position; and

FIG. 4 is a cross sectional view through a filled mold.

Presently, in the steel industry when a steel making furnace is tapped, the molten metal runs into a ladle from which it is poured into ingot molds which are open at the top. The molten metal falling into these molds produces splashing that forms surface imperfections such as scabs, wrinkles or buckles in the surfaces of the ingot, which must be removed to prepare the ingot for rolling.

After these imperfections have been removed from the surface of the ingot and the ingot brought up to proper rolling temperature, the ingots are then rolled into slabs which are of rectangular cross section, having a Width many times their thickness. Surface imperfections in the slabs produced by rolling must be removed as by scarfing 3,l23,877, Patented Mar. 10, 1396 or grinding, and the slabs re heated to prepare them for rolling into plate stock.

Blooms, which are rectangular or substantially rectangulai' members, are rolled from ingots after the surface imperfections thereon have been removed and the ingot heated to proper rolling temperature. Surface imperfections in the blooms produced by rolling must also be removed and the bloom rte-heated preparatory to rolling it into the desired shapes.

Billets, which are of smaller cross sectional area than blooms, have heretofore been produced by rolling blooms to the desired dimensions of the billet after the bloom has been prepared for rolling as above.

Thus it will be seen that in order to prepare billets capable of being rolled or extruded into rods, bars or wires, it has been necessary heretofore to employ a plurality of preliminary preparatory operations intervening between the tapping oi the steel producing furnace and the formation of the billet.

The present invention seeks to eliminate this plurality of preliminary' steps.

In accordance with the teachings of the present invention, molten metal :from the steel producing furnace is placed in a ladle that is equipped with a pouring spout that communicates with the bottom of the ladle and extends upwardly exteriorly thereof, terminating above the maximum height to which metal is placed in the ladle. The ladle and spout are preferably pre-heated, prior to receiving the metal, to minimize the cooling of the metal therein. A pressure bell fits over the ladle and is secured thereto in. such manner as to form a hermetic seal between the bell and the ladle.

The external pouring spout terminates in nozzles with which the gates of the molds are registered to connect the cavity therein to the spout. The cavity in the mold may be positioned vertically; however, when long members such as billets are being cast, the cavity should be inclined slightly from horizontal so as to reduce the static head of the metal in the cavity.

Pressure is then built up in the pressure bell acting on the surface of the molten metal therein to force that metal upwardly through the pouring spout and nozzle into the mold cavity. The rate of flow of the metal is maintained sufilciently rapid to prevent undue cooling of the metal, but at a rate insufficient to cause turbulence in the cavity.

In accordance with the teachings of the present invention, the mold cavities are open at both ends and the lower end of the cavity registered with the nozzle of the pouring spout. As the metal flows into the cavity it torms a ram or piston which forces air out of the cavity through the open upper end thereof. Since there is no turbulence of the metal, air is not entrapped in it and the formation of blow holes is prevented. As soon as the cavity' is completely filled, this open upper end is closed to arrest the flow of metal in the cavity and thereafter a gate valve, incorporated in the gate structure of the mold, is close-d to confine the metal in the mold. Pressure built up in the pressure bell is then partially relieved and the molten metal in the spout and nozzle falls away from the closed gate valve, permitting the filled mold to be disengaged from the nozzle and an empty mold registered therewith in readiness for filling.

The molds of the present invention are composed of a material such as graphite that has high thermal con ductivity and high thermal shock resistance, and is unaffected by exposure to high temperature, and the mold structure includes a sufficient quantity of graphite to result in rapid dissipation of heat from the sides of the cavity, causing the metal therein to freeze rapidly. The plug by which the upper end of the cavity was closed, and the gate valve, are likewise preferably composed of material having high heat conductivity, such as brass,

copper or steel, which withdraw heat rapidly from the ends of the member, causing tie metal to freeze rapidly at the ends as well as the sides of the member.

After the cast member has been cooled sufficiently to have at least a shell of solid metal sufficient in thickness to permit handling of the member, and even before the molten metal in the center region thereof has solidified, the mold may be opened and the member removed therefrom and cooled more slowly than the initial cooling.

As a result of this procedure, the surfaces of the member upon cooling contain a relatively fine crystalline structure suitable for rolling and the surfaces are free from imperfections. Bringing the molten metal into contact with the graphite or other material of high thermal conductivity, thereby causing a rapid rate of initial cooling, has the desirable result of creating an outer cast surface comprised of as-cast "rains or dendrites of minimal size. Additionally, such grains or dendrites have undergone only a slight degree of chemical segregation which is a definite advantage in subsequent rolling or extruding operations. Voids, internal fissures, and the like, formed in the center region of the member as the molten metal thereat freezes, are effectively sealed off from external air, and as a consequence are not oxidized and thus capable of being welded together in the subsequent rolling operation which takes place at an elevated temperature which is above the welding temperature.

It has been found that billets formed in accordance with the teachings of the present invention, upon being cropped to remove small sections from the ends thereof and then heated to proper rolling temperature, can be rolled or extruded into bars, rods, or wires, without additional preparation.

Since the number of preliminary operations eliminated in the formation of billets, in accordance with the teachings of the present invention, is greater than the number of such operations eliminated in the formation of slabs and blooms, the present invention, therefore, has maximum utility in connection with billet formation.

It is contemplated that the ladle used in connection with the practice of the present invention will have capacity sufiicient to receive the entire quantity of steel produced in a heat of the steel making furnace and will be preferably preheated before receiving the molten metal. It is further intended that the casting of members such as billets be carried out with sufficient rapidity to permit so casting the entire quantity of the metal in the heat before the temperature thereof falls too low for eflicient casting. Since the mold cavities are closed off immediately adjacent their ends, and since no risers or sprues are employed, the percentage of conversion of the steel in the heat into cast members such as billets is higher than has been possible heretofore.

The invention will be best understood by reference to the accompanying drawings, particularly FIGS. 1 and 2, wherein there is diagrammatically illustrated a ladle 1, from the bottom of which a pouring spout 2 is extended. This ladle, which may be of the type shown in my copending application Serial No. 708,558, filed January 13, 1958, preferably consists of a metal shell 3 containing a refractory lining 4 capable of withstanding the heat of the molten metal. The spout 2 like-wise consists of a metal casing and refractory lining. The present invention may also be practiced in conjunction with a ladle equipped with an immersed pouring spout, such a ladle being shown in my prior Patent 2,847,739, issued August 19, 1958.

Fitted over and secured to the ladle is a pressure bell 5 which is hermetically sealed onto the ladle, as indicated by the gaskets 6. Fluid pressure is admitted to the pressure bell through a suitable fitting 7 from a source not shown.

As will be seen best in FIG. 3, the pouring spout 2 terminates in generally frusto-conical nozzles 8 into which the refractory lining of the spout is extended. The nozzles 8 are located above the maximum height to which molten metal may be placed in the ladle 1. Registered with the nozzles 8 are molds, indicated generally at 10, each of which consists of a gate portion 11 having a socket which registers in seal forming engagement with a nozzle 8. The molds are supported upon suitable supports 12 which are shown inclined at an angle of approximately 10 with respect to the horizontal, which is preferable when the cavities are of considerable length, as shown.

The mold proper consists of the usual cope and drag formed of a material of high thermal conductivity such as graphite, as indicated at 13. Within the mold is a cavity 14 to be filled with a molten metal. The parting line 15 between the cope and drag sections of the mold is positioned so that the axis of the nozzle 8 coincides with the plane of the parting line 15.

The cavity 14 will be of shape and size depending upon the member to be cast, If the product to be cast is a billet, the mold may contain more than one cavity 14 within the teachings of the invention.

The gate structure 11 contains a gate valve 16 having a refractory lined opening 17 registered with the cavity 14 and the opening in the nozzle 8 when the mold is in pouring position. Preferably the gate valve 16 is composed of a metal having high thermal conductivity, brass or copper having been found to be satisfactory for this purpose. The upper end of the cavity 14 is open during the pouring operation and the mold is equipped with a plug valve 13 by which this end of the cavity is closed, as will presently appear.

As shown in FIG. 3, two molds are registered with the two nozzles of the pouring spout, so as to be filled simultaneously. The number of molds will, of course, be determined by the volume of the member to be cast, and the dual arrangement shown is by way of example only.

With the molds registered with the pouring spout nozzles as shown in FIG. 3, and secured in place, pressure is then admitted to the pressure bell 5 through the fitting 7, which pressure acting upon the surface of the metal in the ladle forces that metal upwardly through the pouring spout and through the nozzles into the mold cavities. Pressure in the pressure bell is built up sufficiently rapidly to cause movement of the metal through the spout to be sulficiently rapid to prevent undue cooling of the metal. The rate of flow of the metal is, however, maintained at a speed below that which would cause turbulence in the mold. As a result, the column of metal indicated at 20, moves upwardly in the mold cavity and forms therein a ram or piston which forces air in the cavity outwardly through the upper open end thereof.

As soon as the column of metal 20 reaches the upper end of the mold, plug 18 is forced into registration with the seat formed in the end of the mold, thereby to arrest further movement of the metal in the cavity. The cavity thus being completely filled with metal, gate valve 16 is closed by suitable power means, indicated generally at 21, to confine the metal in the mold.

Plug 18 is but one of a number of devices that may be used to close the upper end of the mold when the cavity is filled. The plug may be operated manually or by manually controlled power. Preferably, however, closing of this end of the cavity is automatic and controlled by the molten metal in the cavity. To this end, in FIG. 3, the plug 18 is shown supported upon a rod that is journaled for axial movement in a bracket 26 carried by the mold structure. A coil spring 27 encircles the rod and urges the plug 18 into closed position. A wire 28 is interposed between the plug 18 and its seat, to hold the plug away from the seat against the force of the spring. The wire 28 is composed of a low melt-point metal such as aluminum, and the molten metal on coming into engagement with the wire melts it, thereby permitting the spring to seat the plug. This arrangement is shown by way of example.

When both molds have been completely filled and their respective gate valves closed, pressure in the pressure bell 5 is relieved sufficiently to cause the metal in the spout to recede out of engagement with the gate valves and out of the nozzles 8. The molds are then disconnected from the nozzles and empty molds registered therewith, and the foregoing cycle of operation repeated to fill those molds. The cycle is, of course, repeated until all, or virtually all, of the molten metal in the ladles is forced into mold cavities.

In FIG. 4 there is shown a filled mold cavity after removal from the pouring spout. The volumes of graphite 13 in the cope and drag sections of the mold are large in comparison with the volume of the metal 20 filling the mold cavity. Graphite having high thermal conductivity rapidly withdraws heat from the surfaces of the metal, causing that metal to freeze around the edges of the member 20. Plug valve 18 and gate valve 16 both being composed of material of high thermal conductivity, rapidly withdraw heat from the ends of the metal member 24 causing freezing of the metal at the ends as well as the sides of the member. This rapid cooling of the metal from the outside in, soon forms a solid metal shell of suflicient strength to permit the mold to be opened and the metal member removed therefrom while the metal in the center or core section of the member is still in the molten state. After removal from the mold, the metal may be cooled at a rate slower than the rate of initial cooling and under controlled conditions, if desired.

As a result of this procedure the molten metal at the center of the member, upon shrinking as it cools, forms in the center of the member voids or internal fissures. Since the core section is hermetically sealed by the solid metal shell, while that core section is still in molten state the surfaces of the metal defining the voids and fissures will not be oxidized, and hence When the metal is subsequently heated to welding temperature preparatory to rolling, these voids and fissures will be closed and welded together during the rolling process. Although rolling temperatures may vary to some extent being dependent on, for example, the size of the casting to be rolled and the speed at which rolling operations are carried out, it has been found that castings produced in accordance with the teachings of this invention can be Welded at normal rolling temperatures which at the start of rolling would be in the range of 1800 F. to 2300 F. Of course, if welding of the internal voids is to be accomplished by extrusion, the casting would be heated to the same temperature range.

Air having been extruded from the mold during the filling thereof, and the molten metal having been brought into intimate contact with the graphite surfaces defining the mold cavity, which surfaces do not react chemically with the metal, that metal, upon cooling, is free from scabs or other imperfections and consequently, at the most, it is only necessary to crop off the ends of the member and to heat the member to proper temperature to prepare it for rolling.

I am aware that in common practice of pouring molten metal into a mold cavity through a sprue which rises above the highest point of the cavity, molds have been equipped with a riser into which the molten metal flows, so as to seal off the cavity while the metal is still molten. The theory behind such practice is to keep the metal in the mold cavity under static pressure until it cools sufficiently to freeze. While sprues and risers may produce this effect in thin wall castings, they will not in the castings of larger and thicker members such as slabs, blooms and billets, since the volume of metal in the riser and sprue is much less than the volume in the member being cast.

The use of risers and sprues results in the formation of a considerable amount of scrap, since the risers and sprues must be removed from the completed article. I

am also aware that in prior art pressure molding, risers have been provided in communication with the highest point of the mold cavity to seal off the cavity when the metal therein rises in the riser. The present method, through the elimination of sprues and risers and the closing off of the mold cavity at the extremities thereof, results in the production of a substantially smaller quantity of scrap and hence high recovery of the metal in the ladle is achieved.

From the foregoing, it will be apparent that application of the teachings of the present invention to the pressure casting of billets results in a substantial saving in the cost of producing such billets since the billets so produced require no further processing other than heating to proper temperature to condition them for either extrusion or rolling as the case may be. Furthermore, the process of the present invention eliminates a substantial number of preliminary steps heretofore found necessary in the production of such billets.

The foregoing description of the invention used in connection with the molding of steel members such as slabs, blooms and billets, is given by way of example only. While the invention is of great utility in connection with steel, its teachings are not limited to steel. All metals, both'ferrous and non-ferrous, may, of course, be cast advantageously in the manner taught by this invention.

While I have chosen to illustrate my invention by showing and describing a preferred embodiment of it, I have done so by way of example only, as there are many modifications and adaptations which can be made by one skilled in the art within the teachings of the invention.

Having thus complied with the statutes and shown and described a preferred embodiment of the invention, what I consider new and desire to have protected by Letters Patent is pointed out in the appended claims.

I claim:

1. An apparatus for casting steel into directly rollable slabs, blooms, billets and the like, comprising a pressure container for holding molten metal, a pouring tube having one end extending upwardly from said container and the other end in communication with said molten metal, a graphite mold having a cavity formed therein secured to said upper end of said pouring tube in a manner causing said cavity to be slightly inclined from the horizontal, a first passageway formed in said mold for at times communicating between the upper end of said pouring tube and the lower portion of said cavity, a second passageway formed in said mold for at times communicating between the upper end of said cavity and the ambient atmosphere, a chill member for closing said first passageway when said cavity is filled, and means for at times completely closing said second passageway, said means comprising a support member secured to said mold, a second chill member axially aligned with said second passageway and slideably received by said support member, resilient means urging said second chill member toward said second passageway, and temperature responsive abut ment means interposed between said second passageway and said second chill member preventing reception of said second chill member by said second passageway until the molten metal within said cavity causes said abutment means to melt.

2. A method of pouring meal castings and eliminating surface imperfections therein comprising the steps of first positioning a mold having an internal casting cavity and a bottom pouring opening so that all surfaces defining the cavity extend upwardly from that opening to a top opening communicating with atmosphere, then forcing molten metal from a container through said bottom opening until said cavity is completely filled, then closing said top opening with a chill member which with adjoining surfaces of the cavity forms a regular and unbroken surface portion of the casting, then closing said bottom end of the casting with a chill member traversing said bottom opening without changing the volume of the cavity and which with the adjoining surfaces of the cavity forms a regular and unbroken surface portion of the casting, the entire outer surface of the molten metal thereby being sealed within the cavity from atmosphere, and then allowing the molten metal to solidify within said cavity to the degree permitting removal from the mold.

3. A method of producing rolled metal products from molten metal in a container, comprising the steps of first positioning a mold having an internal casting cavity and a bottom pouring opening so that all surfaces defining the cavity extend upwardly from that opening to a top opening communicating with atmosphere, then forcing under superatmospheric pressure the molten metal at a non-turbulent rate of flow from the container through said bottom opening until said cavity is completely filled, then closing said top opening with a chill member which with adjoining surfaces of the cavity forms a regular and unbroken surface portion of the casting, then closing said bottom end of the casting with a chill member traversing said bottom opening without changing the volume of the cavity and which with the adjoining surfaces of the cavity forms a regular and unbroken surface portion of the casting, the entire outer surface of the molten metal thereby being sealed within the cavity from atmosphere, immediately chilling the entire outer surface of the molten metal in the mold in order to solidify that outer surface and maintain it against the surface of the cavity, allowing the remainder of the molten metal to solidify to the degree permitting removal from said chill mold, removing the so solidified metal member from the mold and placing it in an atmosphere conducive to causing said metal member to cool at a rate slower than the initial rate of cooling in said chill mold, reheating said solidified metal member until its tempearture throughout is above the welding temperature of the metal, and immediately to rolling the reheated metal member in order to weld the internal shrinkage voids therein.

4. The method set out in claim 2 wherein the entire outer surface of the molten metal in the mold is caused to rapidly solidify against the surface of the cavity so as to arrest undesirable grain growth therein, and allowing the internal portion of said molten metal to cool at a rate slower than the initial rate of cooling thereby allowing all contraction of the metal during solidification thereof to progress inwardly from the solidified outer surface so as to prevent oxidation of the internal voids occurring within the internal portion of the cast metal article.

5. The method set out in claim 2 wherein because of the sealing of the entire casting from atmosphere, all of the shrinkage thereof results in internal fissures that can be Welded together by the rolling of the casting at a welding temperature of 1800 F.

References Cited in the file of this patent UNITED STATES PATENTS 131,332 Durfee Sept. 17, 1872 1,634,482 Youtsey July 5, 1927 1,912,981 Hoy June 6, 1933 2,310,703 McGlincy Feb. 9, 1943 2,401,491 Lyons June 4, 1946 2,632,216 McQuaid Mar. 24, 1953 2,838,816 Strom June 17, 1958 2,943,369 Szwed July 5, 1960 OTHER REFERENCES Gates and Risers For Casting by P. Dwyer (3rd ed.), pub. by The Penton Publishing Co., Cleveland 13, Ohio, 1949, page relied on. (Copy in Div. 3, US. Patent Office.)

Claims (1)

1. AN APPARATUS FOR CASTING STEEL INTO DIRECTLY ROLLABLE SLABS, BLOOMS, BILLETS AND THE LIKE, COMPRISING A PRESSURE CONTAINER FOR HOLDING MOLTEN METAL, A POURING TUBE HAVING ONE END EXTENDING UPWARDLY FROM SAID CONTAINER AND THE OTHER END IN COMMUNICATION WITH SAID MOLTEN METAL, A GRAPHITE MOLD HAVING A CAVITY FORMED THEREIN SECURED TO SAID UPPER END OF SAID POURING TUBE IN A MANNER CAUSING SAID CAVITY TO BE SLIGHTLY INCLINED FROM THE HORIZONTAL, A FIRST PASSAGEWAY FORMED IN SAID MOLD FOR AT TIMES COMMUNICATING BETWEEN THE UPPER END OF SAID POURING TUBE AND THE LOWER PORTION OF SAID CAVITY, A SECOND PASSAGEWAY FORMED IN SAID MOLD FOR AT TIMES COMMUNICATING BETWEEN THE UPPER END OF SAID CAVITY AND THE AMBIENT ATMOSPHERE, A CHILL MEMBER FOR CLOSING SAID FIRST PASSAGEWAY WHEN SAID CAVITY IS FILLED, AND MEANS FOR AT TIMES COMPLETELY CLOSING SAID SECOND PASSAGEWAY, SAID MEANS COMPRISING A SUPPORT MEMBER SECURED TO SAID MOLD, A SECOND CHILL MEMBER AXIALLY ALIGNED WITH SAID SECOND PASSAGEWAY AND SLIDABLY RECEIVED BY SAID SUPPORT MEMBER, RESILIENT MEANS URGING SAID SECOND CHILL MEMBER TOWARD SAID SECOND PASSAGEWAY, AND TEMPERATURE RESPONSIVE ABUTMENT MEANS INTERPOSED BETWEEN SAID SECOND PASSAGEWAY AND SAID SECOND CHILL MEMBER PREVENTING RECEPTION OF SAID SECOND CHILL MEMBER BY SAID SECOND PASSAGE UNTIL THE MOLTEN METAL WITHIN SAID CAVITY CAUSES SAID ABUTMENT MEANS TO MELT.

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