US2356013A - Continuous casting of metals - Google Patents

Description

15, 1944- H. w. SPOONER 2,356,013

CONTINUOUS CASTING OF METALS Filed Aug. 3, 194:5

7 2 .v NT R ATTORNEY Patented Aug. 15,1944

UNITED STATES. PATENT OFFICE 2,358,013 oon'rnwou's cas'rmc'. or METALS w. Spooner, snmnun, n.1, assignor to Irving Ronl, West Orange, N. J.

Application August a, 1943, SeriallN'o. 491,155

G'Claims.

This invention relates to the continuous casting of metals, and pertains more particularly to apparatus for feeding molten metal continuously to the casting mold.

The invention is particularly applicable to, and constitutes improvements in, the process and apparatus disclosed in Junghans Patents Nos. 2,135,183 and 2,135,184 dated November 1, 1938, but it will be understood that the invention may also be used to advantage in connection with other processes or apparatus for the continuous casting of metals whereit is, desirable to feed molten metal continuously to a casting mold.

In such continuous casting processes,'it is advantageous to provide a holding furnace, as disclosed in the above-mentioned patents to serve as a reservoir in which a reasonable quantity of molten metal may be maintained at uniform temperature, and from which molten metal may be fed directly to the casting mold.

It is an object of the present invention to provide for the maintenance of a continuous flow of molten metal at a substantially constant rate from such reservoir to the casting mold, and also to provide for replenishing the supply of molten metal in said reservoir from timeto time without interrupting such flow to the casting mold.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for{ urposes of illustration is shown in the accomp' nying drawing, in which the figure is a semi-diagrammatic view, the holding furnace and casting moldbeing' shown in cross section.

Referring to the drawing, a holding furnace l is provided, serving as-,areservoir for a supply of molten metal. Preferably such furnace is heated electrically with suitable provision for establishing and maintaining uniform temperature conditions therein. A U-shaped,tube 2 is provided having one end extending into'the' molten metal, preferably to a point near the bbttonrof said furnace, and having its other end extending to the casting mold 3, such tube constituting a conduit through which molten metal may be fed con- ,tinuously from the furnace to the casting mold.

A filling tube I also extends from a point near the bottom of said furnace to a point above the level of the bend in the U-shaped tube, said'filling tube terminating at its upper end in an enlarged portion constituting a filling spout 5, the-'said tube constituting a conduit through which additional molten metal may be introduced into'the furnace from time ,to time as required. Such addisuitable manner as by pouring from a ladle into the filling spout.

The feeding of molten metal from the furnace to the casting mold through the U-shaped tube 2 is accomplished by applying pneumatic pressure to the interior of the furnace, the furnace be ng sealed, of course, to hold such pressure. The pressure applied must be sufficient to provide a hydrostatic head of a height equal to the vertical distance from the surface of the molten metal in the furnace to the bend in the tube 2, plus such additional distance above the bend as may be required to provide the desired rate of flow into the casting mold. If the level of the molten metal in the furnace remained fixed, it would only be necessary to maintain uniform pneumatic pressure in the furnace at all times in order to maintain a constant rate of flow to the casting mold. Actually, however, the level of the molten metal in the furnace shifts constantly during the casting operation, being lowered as molten metal is fed to the casting mold, and rising again whenever additional molten metal is poured into the filling spout. Consequently, in order to maintain the required hydrostatic head the pneumatic pressure applied to the furnace must be varied constantly.

According to the. present invention means are provided for automatically varying and controlling the pneumatic pressure applied to the furnace in order to maintain the hydrostatic head as required to maintain a constant rate of flow of molten metal to the casting mold.

For most purposes it is preferable to use an inert or non-oxidizing gas such as nitrogen, for example, in applying pneumatic pressure to the interior of the furnace. Such gas may be held under pressure in a container 1 connected by a tube 8 to the interior of the furnace, said tube having a valve 9 therein. If said valve is opened, gas flows through the tube 8 to increase the pressure in the furnace, and assuming that a charge of molten metal has previously-been placed in the furnace, the application of pressure will cause molten metal to rise in the U-shaped tube 2 until it reaches the bend in the tube, whereupon application of additional pressure will cause molten metal to flow through said tube to be discharged into the casting mold. The rate of flow will be determined, of course, by the pressure applied in excess of that required to raise the and if this excess or feeding pressure is maintional molten metal may be introduced in any tained at a constant level, the rate of flow of molten metal to the casting mold will remain constant.'

The application of pressure to the furnace will also cause molten metal to rise in the'fllling tube 4 and the filling spout 9, and the distance which the molten metal therein rises above the level of the bend in the tube 2 represents the excess or feeding pressure applied at any given time. Consequently if the molten metal in the filling tube and spout is maintained at a constant level, the feeding pressure will remain constant to provide a uniform rate of fiow of molten metal to the casting mold.

For this purpose a float I is mounted to ride on the molten metal in the filling spout, said float being connected to a lever ll pivoted at l2 and having an adjustable counterweight I! mounted on the other end of the lever to balance the weight of the float. A link I connects the lever H to switches l6 and H.

In the drawing, switches l9 and I! are shown diagrammatically, and in practice I prefer to use a pair of Mercoid switches mounted in a suitable housin and connected to the lever ll so as to be tilted thereby.

The switch I 6 is included in a circuit which also includes a solenoid It for operating the valve 9, so that whenever the level of the molten metal 'in the filling spout tends to drop slightly the switch it closes to energize the solenoid l8, and the valve 9 is opened to apply additional pressure to the furnace, thereby causing the level of the molten metal to rise until the switch It is opened to allow the valve 9 to close. Thus as, feeding of molten metal continues additional pressure is applied to the furnace from time to time as required.

On the other hand,.let it be assumed that additional molten metal is introduced into the furnace through the filling spout. In this case, the level valve 9 should be relatively small so that when I the valve is fully opened by operation of the solenoid the fiow of gas will be only moderately greater than the flow required to maintain the desired pressure for the normal rate of feed of molten metal. Otherwise on opening the valve, a large inrush of cold gas might occur before the inertia of the molten metal in the filling tube and spout could be overcome to close the valve, and thereafter, as the cold gas rises to furnace temperature,

expansion of the gas and a tendency toward a considerable excess of pressure may result. It will be noted, however, that this excess will be promptly relieved by the raising of the float to close the switch l'l to open the valve 20, but this results in wastage of gas which can be avoided in the manner described. If desired, an ordinary adjustable globe valve may be inserted in the tube 9 adjacent the valve 9 so that the rate of flow of gas may be adjusted as desired; a

A relatively short travel of the float will suffice for satisfactory operation. For example, the switches'may be set to permit travel of one half .to three quarters of an inch in the neutral posiaesaoi-s sumcient uniformity to provide a substantially constant rate of flow of molten metal.

If it is desired to change the rate of flow of molten metal, it is only necessary to raise or lower the entire control assembly including the pivot.

l2 and the switch assembly so as to change its position with respect to the filling tube. If the assembly is raised, the hydrostatic head will be increased to increase the rate of fiow, and ii lowered the hydrostatic head will be lowered to decrease the rate of flow. Any suitable form of adiustable mounting of the assembly may be used ior this purpose.

It will be understood that the invention may be variously modified and embodied within the scope of the subioined claims.

I claim as my invention:

1. Apparatus for casting metals continuously, comprising,-in combination, a casting mold, a reservoir for molten metal, a U-shaped tube for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal in said reservoir and the other end'extending to said mold, a filling tube tion, 1. e. with both switches open. This setting 18 having one end extending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, means to apply pneumatic pressure to the molten metal in said reservoir to cause the same to fiow through said U-tube and to cause the same to rise in said filling tube, and means controlled by the level of the molten metal in said filling tube to vary the pneumatic pressure appliedto the molten metal in the reservoir tomaintain the flow of molten metal through said U-shaped tube at a substantially constan rate.

2. Apparatus for casting metals continuously, comprising, in combination, a casting mold, a reservoir for molten metal, a U-shaped tube for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal in said reservoir and the other end extending to said mold, a filling tube having one end extending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, means to apply pneumatic pressure to the molten metal in said reservoir to cause the same to fiow through said U-tube and to cause the same to rise in said filling tube, and means controlled by the level of the molten metal in said filling tube to increase the pneumatic pressure applied to the molten metal in the reser voir as the level of the molten metalin said reservoir is lowered by flow of molten metal through said U-shaped tube to maintain such fiow at a substantially constant rate.

3. Apparatus for casting metals continuously, comprising, in combination, a casting mold, a reservoir for molten metal, a U-shaped tube for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal insaid reservoir and the other end extending to said mold, a filling tube having one end extending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, means to apply pneumatic pressure to the molten metal in said reservoir to cause the same to flow through said U-tube and to oause the same to rise in said filling tube, and means controlled by the level of the molten assaors metal in said filling tube, to decrease the pneumatic pressure applied to the molten metal in the reservoir as the level of the molten metal in said reservoir is raised by introducing additional molten metal through said filling tube to maintain the flow of molten metal through sai d U-shaped tube at a substantially constant rate.

4. Apparatus for casting metals continuously, comprising, in combination, a casting mold, a reservoir for molten metal, a U-shaped tube for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal in said reservoir and the other end extending to said mold, a filling tube having one end extending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, means to apply pneumatic pressure to the molten metal in said reservoir to cause the same to flow through said U-tube and to caus the same to rise in said filling tube, and means to vary the pneumatic pressure applied to the molten metal in said reservoir to maintain a hydrostatic head 01' molten metal in said filling tube at a substantially fixed level in space.

5. Apparatus for casting metals continuously, comprising, in combination, a casting mold, a

reservoir for molten metal, a U-shaped tube-for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal in said reservoir and the other end extending to said mold, a filling tube having one end extending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, a tube leading into said reservoir and having branch passages to gas under pressure and to atmosphere, a valve controlling each oi said passages, a float in said filling tube supported by the molten metal therein, a pair of switches connected to said float for operationthereby, and a solenoid for operating each of said valves, said solenoids being controlled by said switches, the switch which controls the solenoid operating the valve in the passage to gas under pressur being opened when said float rises and closed when said float falls, and the switch which controls the solenoid operating the valve in the passage to atmosphere being closed when said float rises and opened when said float tails.

6. Apparatus for casting metals continuously, comprising, in combination, a casting mold, a

reservoir for molten metal, a U-shaped tube for conveying molten metal from said reservoir to said mold, said tube having one end extending into the molten metal in said reservoir and the other end extending to said mold, a filling tube having one endextending into the molten metal in said reservoir and the other end extending vertically to a point above the level of the bend in said U-shaped tube, a tube leading into said reservoir and having branch passages to gas under pressure and to atmosphere, a valve controlling each of said passages, a float in said filling tube supported by the molten metal therein, a pair of switches connected to said float for operation thereby, and a solenoid for operating each of said valves, said solenoids being controlled by said switches, the switch which controls the solenoid operating the valve in the passage to gas under pressure being opened when said float rises and closed when said float falls, and the switch which controls the solenoid operating the valve in the passage to atmosphere being closed when said float rises and opened when said float falls, the effective aperture in the passage to gas under pressure being such that the flow oi gas when said valve is opened is only moderately greater than the flow required to maintain the desired pressure for the normal rate 0! feed of molten metal.

. HENRY W. SPOONER.

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