US2962779A

US2962779A - Teeming nozzle valve for vacuum casting apparatus

Info

Publication number: US2962779A
Application number: US758152A
Authority: US
Inventors: John N Hornak; Michael A Orehoski
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1958-08-29
Filing date: 1958-08-29
Publication date: 1960-12-06
Anticipated expiration: 1977-12-06
Also published as: BE581993A; FR1243019A; GB892945A; LU37601A1

Description

TEEMING NOZZLE VALVE FOR VACUUM CASTING APPARATUS John N. Hornak, Munhall, and Michael A. Orehoski,

Duquesne, Pan, assignors to United States Steel Corporation, a corporation of New Jersey Filed Aug. 29, 1958, Ser. No. 758,152

Claims. (Cl. 22-85) This invention relates to apparatus for casting metal in vacuum and, more particularly, to valve mechanism for controlling the connection of a ladle teeming nozzle with an evacuated chamber in which the casting operation is performed. In a manner to be described, the valve mechanism of this invention has a normally closed position in which it is effective as a vacuum seal between the nozzle orifice and casting chamber, and is operated to open position to provide an evacuating connection therebetween in advance of the teeming flow of metal through the nozzle orifice.

The invention, more specifically, relates to vacuum casting apparatus of the type, for example, in which molten metal is cast in a mold by teeming from a ladle arranged above and usually supported on structure that provides an evacuated tank or enclosure for the mold. An apparatus of this character is shown in the copending application of George E. Pellissier Jr., Serial No. 641,- 588, filed February 21, 1957, to which reference is made for a detailed explanation of the problems encountered in evacuating the casting chamber and preventing air inleakage in amounts that may result in explosive gas mixtures during the metal teeming operation. For the purpose of this invention, it will be sufficient to indicate that the transfer ladle in such apparatus forms a closure for the vacuum casting tank on which it is supported, and that the ladle teeming nozzle and stopper rod, being constructed of refractory ceramic material, are a source of air leakage that interferes with evacuating the casting tank to a pressure and hydrogen concentration of the character desired. In order to eliminate air inleakage of this character by diffusion through the ceramic material of the ladle nozzle and stopper rod, a fusible metal diaphragm having a sealed connection with the bottom of the ladle about the teeming nozzle therein has been proposed and used. While such diaphragms have proved effective as vacuum seals, their use results in a space including the nozzle orifice below the bottom of the ladle stopper rod which is not evacuated and in which air is trapped. In normal vacuum-casting operations, vacuum pumps are initially overloaded when the metal first enters the vacuum chamber. Therefore, any means for evacuating all such regions wherein air is trapped before the metal enters the vacuum chamber would tend to decrease this tendency to overload the vacuum pumps. Air entrapment in the space including the nozzle orifice is further believed to interfere with the teeming of metal into the evacuated casting chamber and the mold supported therem.

This invention has as one of its principal objects the elimination in vacuum casting apparatus of the character referred to above of an air trap in and below the ladle teeming nozzle.

A further object of the invention is to provide a vacuum seal for the teeming nozzle of a transfer ladle which can be operated to provide an evacuating connection for the nozzle orifice with the casting chamber in advance of teeming flow of metal through the nozzle.

Another object of the invention is to provide a valve mechanism that normally occupies a closed position in which it is effective as a vacuum seal between a ladle teeming nozzle and an evacuated casting chamber, and has provision for operation to open position to provide an evacuating connection between the nozzle orifice and casting chamber in advance of teeming flow of metal through the ladle nozzle. A related object is to provide a valve mechanism of this character with a connection to the ladle stopper rod for actuating it to open position in response to actuation of the stopper rod to admit metal into the teeming nozzle.

Other objects and advantages of the invention Will become apparent from the following description.

In the drawings, there is shown a preferred embodiment of the invention. In this showing:

Figure 1 is a vertical sectional view of a vacuum casting apparatus that is provided with a teeming nozzle vacuum seal constructed in accordance with the principles of this invention;

Figure 2 is an enlarged and detailed sectional view of a. preferred embodiment of the teeming nozzle. valve mechanism shown in Figure l; and

Figure 3 is a plan view of the cupshaped metal diaphragm that forms the stationary valve part of the valve assembly shown in Figure 2.

Figure l of the drawings shows somewhat diagrammatically a vacuum casting apparatus of the type to which this invention relates. It comprises an ingot mold 1 supported on a stool 2 in a vacuum casting chamber 3 and a transfer ladle 4 for teeming metal into the mold 1. The chamber 3 is adapted to be evacuated through an exhaust duct 5 leading to a suitable evacuating pump (not shown), and is defined by a base member 6 and top member 7. The top member 7 is in the form of a cylindrical shell which has its lower end connected with and supported on the base member 6 by a suitable vacuum seal 8, and an annular plate 9 at its upper end that forms part of a top closure for the chamber 3. An opening 10 in the center of the plate 9 provides for teeming metal from the ladle 4 into the mold 1, and a refractory collar 11 about the opening 10 operates to guide the teeming movement of the molten metal into the mold 1.

The ladle 4 has an essentially conventional construction that includes a refractory lining 12 in a steel jacket 13,, a refractory nozzle 14 in its bottom that opens through the lining 12 and jacket 13, a refractory stopper rod 15 for controlling the teeming of metal through the nozzle 14, and a linkage 16 for actuating the stopper rod 15 vertically to and from a closed position in which its lower end has seating engagement against the upper end of the nozzle 14. It is supported on the plate 9 at the upper end of the chamber 3 by a suitable vacuum seal 17 that extends around the periphery of the opening 10. In addition, a valve assembly 18 constructed in accordance with the principles of this invention provides a vacuum seal against leakage of air through the teeming nozzle opening in the ladle steel jacket 13 and refractory lining 12. In this manner, the valve assembly 18 and seal 17, in conjunction with the annular portion of the ladle jacket 13 therebetween, operate as a vacuumsealed closure against leakage of air through the opening 10 into the casting chamber 3.

Figure 2 shows the stopper rod 15 in its closed position with its lower end seated against the upper end of the nozzle 14 and closing its orifice 19 to the flow of metal from the ladle 4, and the stationary and movable parts of the valve assembly 18 in their closed position sealing the space 20 about the opening 21 in the ladle jacket 13 through which the nozzle 14 extends against leakage of air through the opening 10 into the vacuum chamber 3.

' The stationary parts of the valve assembly 18 include a. pair of

clamping rings

22 and 23, and a cup-shaped metal diaphragm that has a flat bottom 24 with a centrally located aperture or valve port 25 therein as shown in Figure 3. The port .25 is defined by an integral depending lip.26 as shown in Figure 2. The bottom 24 is joined to the lower edge of the diaphragm side wall 27 which has a mounting flange 28 extending outwardly from its upper edge. As shown in Figure 2, the flange 28 is secured in position by clamping between the

rings

22 and 23, vacuum sealing gaskets 29 being provided .on the upper and lower surfaces of the flange 28 to prevent leakage of air over the facing surfaces of the

rings

22 and 23 in a direction radially inwardly with respect to the space 20. A vacuum tight peripheral weld 30 secures the clamping ring 22 to the ladle jacket 13 and operates to seal the opening 21 against air leakage in a direction radially inwardly over the upper surface of the ring 22. Clamping pressure is applied to the ring 23 by fastening bolts 31 engaged in tapped openings in the ring 22 which have a depth less than its thickness and thus do not admit air leakage through the ring 22.

The movable parts of the valve assembly 18 include a rubber stopper 32 which has seated engagement in the valve port 25 when moved to its closed position as shown in Figure 2. The stopper 32 may be either natural or synthetic rubber and is mounted on a threaded shaft 33 extending axially thereof by a pair of clamping nuts 34 which have clamping engagement with opposite ends thereof. The shaft 33 and rubber stopper 32 supported thereon are connected with the lower end of ladle stopper rod 15 for operation thereby in a manner to be described by a pair of upper and lower links 35 and 36 in the form of tubes which extend axially with respect to the nozzle orifice 19. The upper link 35 has threaded engagement in an internally threaded graphite plug 37 secured in the lower end of the stopper rod 15, and the lower end of the tube 36 has a threaded connection with the shaft 33 to which the rubber stopper 32 is secured. Adjacent ends of the tubes 35 and 36 are joined by an articulated connection comprising a connecting member 38 and connecting pins 39 at right angles to each other which provide for adjusting movement of the lower tube 36 and the rubber stopper 32 secured thereto to assure seating engagement of the rubber stopper 32 in the valve port 25 upon movement of the stopper rod 15 to its closed position.

In operation, the ladle 4 is assembled on the casting chamber 3 with its stopper rod 15 and the rubber stopper 32 in their closed positions as shown in Figure 2. When the rubber stopper 32 is in its closed position seated in the valve port 25 as shown in Figure 2, the valve assembly 18 provides a vacuum seal against leakage of air from the space 20, which includes the nozzle orifice 19 and the ladle jacket opening 21, into the casting chamber 3 by way of the opening 10. As indicated above, the seal 17 and the portion of the ladle jacket 13 between it and the valve assembly 18 cooperate to seal the opening 10 against air leakage from all points on the outer surface of the ladle 4. With the ladle 4 supported in this manner, the chamber 3 is evacuated through the exhaust duct in the usual manner and molten metal is then transferred to the ladle 4. After filling the ladle 4 with the required amount of metal needed for casting an ingot in the mold 1, the linkage 16 is operated to move the stopper rod 15 upwardly and admit metal to the teeming orifice 19. Simultaneously with upward movement of the stopper rod 15 in this manner, the rubber stopper 32 is moved upwardly to its open position out of seating engagement with the lip 26 defining the port 25 to provide an evacuating connection between the space 20 and the evacuating chamber 3. This evacuating connection is eflected in advance of the flow of metal through the orifice 19 and thus operates to eliminate an air trap in the Qfififl? 1.

and space 20 which would tend to initially overload the vacuum pumps and would otherwise interfere with the initial downward flow of metal through the orifice 19. The movable parts 32-39 of the valve assembly 13, as well as the bottom 25 of the cup-shaped diaphragm 24, are melted by the metal teeming through the nozzle 14 and must be replaced after each casting operation.

While the drawings and above description disclose a preferred embodiment of the invention in which the rubber stopper valve 32 is opened in response to operation of the ladle stopper rod 15 to provide an evacuating connectionin advance of the flow of metal through the orifice 19, it will be understood that other mechanisms for operating the valve 32 independently of and prior to operation of the ladle stopper rod 15 may be used and are contemplated. In this respect, it will be appreciated that a separate manually operated mechanism may be used which will permit opening of the valve 32 a few seconds in advance of opening movement of the stopper rod 15 to assure more complete evacuation of the orifice 19 and space 20 before molten metal is permitted to teem through the orifice 19. Other adaptations and modifications of the invention may be made within the scope of the following claims.

We claim:

1. In vacuum casting apparatus, the combination with a tank to be evacuated, a casting mold in said tank, a ladle for molten casting metal, a teeming nozzle in the bottom of said ladle providing a downwardly opening orifice for the flow of metal from said ladle into said mold, and a stopper rod at the upper end of said nozzle controlling the flow of metal through said orifice, of valve means comprising a stationary valve part in the form of a metal plate having a vacuum sealing connection with said ladle about the lower end of said nozzle and a valve port in said plate, a second valve part mounted for movement to and from a closed position in which it has vacuum seating engagement in said valve port and renders said plate effective as a vacuum seal between said orifice and tank, and means for actuating said second valve part to its open position in response to upward opening movement of said stopper rod to provide an evacuating connection between said orifice and tank.

2. In vacuum casting apparatus, the combination with a tank to be evacuated, a casting mold in said tank, a ladle for molten casting metal, a teeming nozzle in the bottom of said ladle providing a downwardly opening orifice for the flow of metal from said ladle into said mold, and a stopper rod at the upper end of said nozzle controlling the flow of metal through said orifice, of valve means at the lower end of said nozzle comprising a stationary valve part, a second valve part mounted for movement between open and closed positions relative to said stationary valve part and normally occupying said closed position in which said valve means provides a vacuum seal between said orifice and tank, and means for actuating said second valve part to its open position to provide an evacuating connection between said orifice and tank, said movable valve part having an operating connection with said stopper rod for movement to its open position in response to operation of said stopper rod to admit molten metal into said orifice.

3. In vacuum casting apparatus, the combination with a tank to be evacuated, a casting mold in said tank, and a refractory lined steel ladle having a refractory nozzle in the bottom thereof providing a downwardly opening orifice for teeming metal into said mold, of a stopper rod mounted for vertical movement to and from a position in seating engagement with the upper end of said nozzle to control the flow of metal through said orifice, a metal plate having a peripheral vacuum sealing connection with said ladle about the lower end of said nozzle and a central opening axially aligned with said orifice, a closure valve disposed for vertical movement to and from a closed position in vacuum seating engagement in said opening in which it renders said plate efiective as a vacuum seal between said orifice and the interior of said tank, and connecting means secured at its upper end to the lower end of said stopper rod and at its lower end to said valve for operating said valve to open position in response to upward opening movement of said stopper rod to thereby provide an evacuating connection between said orifice and tank.

4. Vacuum casting apparatus as defined in claim 3 characterized by said connecting means comprising a pair of links arranged in end-to-end relation and extending axially of said opening, and an articulated connection joining adjacent ends of said links and providing for aligning the position of the lower one of said links in said orifice for seating engagement of said closure valve in said opening.

5. In vacuumrcasting apparatus, the combination comprising a refractory lined steel ladle having a refractory nozzle opening through its bottom and providing a 20 downwardly extending teeming orifice, a stopper rod mounted for vertical movement to and from a position in seating engagement with the upper end of said nozzle to control the flow of metal through said orifice, a metal plate having a peripheral vacuum sealing connection with said ladle about the lower end of said nozzle and an opening therethrough in axial alignment with said orifice, a closure valve disposed for vertical movement to and from a closed position in vacuum seating engagement in said opening in which it renders said plate effective as a vacuum seal between said orifice and the interior of said tank, and connecting means extending axially of said orifice and secured at its upper end to the lower end of said stopper rod and at its lower end to said valve for operating said valve to open position in response to upward opening movement of said stopper rod.

References Cited in the file of this patent UNITED STATES PATENTS 1,363,402 Fort Dec. 28, 1920 1,519,290 Baurichter Dec. 16, 1924 FOREIGN PATENTS 524,812 Belgium Dec. 31, 1953