Abstract:
A pressurized tundish for controlling a continous flow of molten metal characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate.

Description:
The Government of the United States of America has rights in this invention pursuant to Contract No. DE-FC07-84IDI2545 awarded by the U.S. Department of Energy. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to the flow control of molten metal and more particularly to continuous flow of molten steel. 
     A variety of flow controls for molten metals have heretofore been proposed, illustrative of which are those described in U.S. Pat. No. 3,675,911, granted to Walter Kapun on July 11, 1972; U.S. Pat. No. 3,844,453, granted to Henry Eickelberg on Oct. 29, 1974; and U.S. Pat. No. 4,010,876 granted to Robert Steinemann on Mar. 8, 1977. These patents, while teaching the use of multi-compartmented apparatus for controlling metal flow by use of pressurization within one of the compartments, have nevertheless been limited to providing successive batches or sequences of molten metals rather than providing for continuous controlled measured flow. Other proposals have been made for controlling metallic flow from tundishes, illustrative of which is that described in U.S. Pat. No. 4,770,395 granted to Khuong Vo Thanh et al on Sept. 13, 1988. According to one such proposal, &#34;flow from the tundishes into the mold was controlled by a stopper rod suspended above the nozzle entry and linked to a manual lever.&#34; Accordingly, there has continued to be a need for apparatus that is long lived, economical and more readily controllable to provide for continuous flow control and flow of molten metal for such applications as continuous casting. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a two-compartment tundish is provided having within the first compartment a splash plate and holding area for receiving molten metal at a non-uniform input rate, e.g., by discrete batches of molten steel introduced thereto from suitable conveying means such as a ladle. The steel is introduced at a location offset from the center thereof and disposed toward the rear of the tundish so as to permit the interposition of suitable baffles to smooth out the turbulence and other adverse effects resulting from pouring of the molten metal into the first compartment. A longitudinal passageway within the tundish located near the lower extremity of the interior provides a passage for communication between the receiving compartment and the pressure compartment. Within the pressure compartment there exists a vertically oriented space that permits a substantial rise or fall of the level of steel therewithin; and at or near the front extremity of the tundish and located a relatively small predetermined distance above the bottom of the pressure chamber interior, there is located a nozzle through which molten steel is controllably exited. Inert gas preferably is employed as the pressurizing agent within the pressure chamber, and by controlling the pressure of such gas on the surface of the molten metal, the rate at which the metal is discharged through the nozzle can be readily controlled. Pressure integrity is provided by a particularly efficacious sealing mechanism comprising a walled box-like member and cooperating O-ring type seals. Thus, there is provided a multi-sectioned tundish which provides for entry of molten steel in discrete increments, yet provides for the smooth and continuous controlled discharge of the molten metal. 
     OBJECTS AND FEATURES OF THE INVENTION 
     One general object of the invention is to improve tundishes. 
     It is another object of the invention to provide a mechanism for receiving molten metal in discrete batches and for converting same into uniform continuous controlled flow. 
     It is still another object of the invention to provide pressure integrity within a pressurized chamber of the tundish. 
     It is yet another object of the invention to improve flow control in a horizontal continuous caster. 
     Accordingly, in accordance with one feature of the invention, a baffled receiving compartment is provided for the receipt of molten metal in discrete batches, provision being made to receive the metal toward the rear of the tundish thereby providing geometries conducive to positioning of intermediate baffles in the metal stream so as to smooth out the effects of pouring turbulence and impact. 
     In accordance with still another feature of the invention, a passageway connects the first compartment, i.e., the metal receiving compartment, from the second compartment which is adapted for maintaining a controlled gaseous pressure over the surface of any fluid material therein such as molten steel, thus enhancing elimination of turbulence or other non-steady state conditions within the molten stream while providing a necessary communication between the two chambers. 
     In accordance with yet another feature of the invention, the tundish exit nozzle is located a predetermined distance vertically above the lowest interior level within the tundish so as to further mitigate irregularities in metal flow while at the same time being positioned sufficiently low so as to permit a wide excursion of molten metal levels within the pressure chamber without exposing the nozzle entry aperture to pressurized gas. 
     In accordance with yet one further feature of the invention, a light gauge stainless steel box is positioned within the refractory walls of the pressure chamber, is protected by appropriate insulating refractories while providing, in combination with O-ring seals, an effective mechanism for sealing the pressure chamber and preventing undesired pressure leaks. 
    
    
     These and other objects and features of the invention will be apparent from the following detailed description, by way of example of a preferred embodiment, in which FIG. 1 depicts in section the tundish according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now turning to the drawing, it will be observed that it depicts in vertical section a two-chambered tundish 10 especially adapted for the handling of molten metal such as steel. Projecting from the front 11 is metal exit nozzle 12, and near the top rear 13 of the tundish there is provided aperture 14 through which molten metal may be poured into the tundish from any suitable source (not shown). Essentially centered beneath aperture 14 and at the bottom of receiving chamber 15 is conventional splashplate 16, which may be made of any suitable refractory material well-known in the art. 
     Receiving chamber 15 is fitted with vertical baffles 17 and 18, which, again, may be formed of any suitable conventional refractory material well-known in the art. Baffle 17 provides a partial barrier to prevent or mitigate propogation of the fluid anomolies such as turbulence and waves resulting from the pouring of molten metal into the tundish. Baffle 18 acts in a similar fashion, and the geometrical positioning of baffle 17 and 18 provides for a passageway from the left side of compartment 15, that is, subcompartment 15a to subcompartment 15b and thence through the passageway 19 which provides ready fluid communication between receiving chamber 15 and pressure chamber 20. The interior walls that are to come in contact with molten metal are lined in the conventional way with any one of a variety of known refractory materials. This is illustrated for chamber 15 by rear refractory lining 21 (tundish boards or insulating spray material), bottom refractory lining 22 (similar to lining 21) and inner wall refractory lining 23 (also similar to lining 21). The tundish boards or insulating spray material overlie other conventional refractories, e.g., refractory brick 22g, 22h, 22i. 
     The tundish generally is enclosed within an exterior casing 9, preferably of steel, shown as sections 9a-9j on the figure. Within that exterior steel casing, there are included conventional insulating and refractory layers such as layers 22a-22h. These layers of insulation and refractory materials (e.g., refractory bricks) provide protection to the exterior steel casing from the extreme heat of the molten metal. 
     Now returning to input chamber 15, it will be observed that it further includes within a location essentially central to the top of subchamber 15b, a closable opening 24 which, when opened, provides access to the interior of subchamber 15b, thus permitting access for inspection. 
     In order to provide a means for completely emptying the tundish, there is provided in the bottom thereof a drain port 26 which is normally closed to prevent unwanted exit of molten metal, but which may be opened when it is desired to drain the remaining molten metal from the tundish. Such drain is conventional and is actuated in a conventional manner as is known to those skilled in the art 
     As mentioned above, pressure chamber 20 communicates with reception chamber 15 by way of passage 19, which permits the flow of metal therebetween. However, as will be observed from reference to the drawing, there are vertically disposed members that provide separation for the upper portion 27 of chamber 20 from the upper portion of subchamber 15b. These include two spaced apart portions of exterior casing 9i and 9j into the bottom space of which there is piped a source of cooling air 28. Lining these extensions 9i and 9j are sections of insulating material 29 together with other insulating and protective materials 30. 
     Because of the necessity of maintaining pressure integrity within the upper portion 27 of pressure section 20, provision is made for gas tight construction by the advantageous inclusion of a light gauge stainless steel box 31 which lines the refractory walls of the pressure chamber and is protected from the extreme heat of the molten metal by 11/2-inch thick magnesite tundish boards 25. Also provided is 1-inch thick layer 36 of similar tundish boards. 
     Box 31 is made of four steel walls, the opposing walls being parallel. Steel box 31 is additionally supplemented in its maintenance of gas-tight integrity by the efficacious employment of a pair of O-rings 32 and 32a which seal the flange 33 of the burner cover (9d and 9e). The innermost O-ring 32a contacts the flange of the stainless steel box. 
     Between steel casing section 9f and wall 37 of steel box 31 there are positioned a refractory castable 38 and layer 39 of insulating brick. 
     Horizontal feeding system 12 is in fluid communication with compartment 20 through port 34. Molten metal therefore can be controllably flowed from the lower portion of pressure chamber 20 through port 34 and thence into the fluid-conducting passageway 35 to an internal passageway (not shown) and thence to the nozzle exit opening 37. 
     Although the base region of horizontal feeding system 12 is affixed to the tundish exterior, provision may be made within an intermediate part of horizontal feeding system 12 for the end section to be swiveled, thereby to provide for adjustment. 
     For a description of horizontal feeding system 12, reference is made to U.S. Patent Application Ser. No. 218,689 filed on even date herewith. 
     Returning now to the pressure chamber, it will be observed that at the top thereof there is an opening 45 which is a burner outlet. The burner (not shown) is employed to preheat the tundish and horizontal feeding system. 
     It is contemplated that an inert gas such as argon be employed as the gaseous medium overlying the molten metal within the pressure chamber 20. However, other types of inert gases may also be employed. Pressure to the pressure chamber is controlled by conventional pressure controlling mechanism (not shown), and the entry of the gas into the pressure chamber is preferably made to the pressure chamber at the upper region thereof e.g., through burner port 45. This also is accomplished by conventional means. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but, on the contrary, it is intended to cover such alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.