US3428111A - Continuous casting method using a rotating wheel - Google Patents

Description

Feb 1969 GYONGYOS ETAL 3,4 8,

CONTINUOUS CASTING METHOD USING A ROTATING WHEEL Filed April 15. 1965 I23 3 i g mv m WAN eyoueyos HELMUT KonHAus THE/IE arrazlvex' United States Patent M 5,07 7/ 64 US. Cl. 164-87 Claims Int. Cl. B22d 11/06 ABSTRACT OF THE DISCLOSURE A method of continuously casting metal into a casting groove of a cooled rotating wheel that has a cover band defining a mold, feeding molten metal into the mold at a point close to the top of the wheel, and correlating the feeding of the molten metal with the rotation of the wheel so as to maintain molten metal above the highest point of the base of the mold.

A continuous casting machine that comprises a cooled wheel rotatable about its axis and has an annular groove and a cover defining with the groove a continuous casting mold, and a tundish supplying molten metal to the mold that includes a spout fitting for sealing the mold.

The invention relates to continuous casting, and relates more particularly to continuous casting of aluminum alloys; still more particularly, it relates to continuous casting of the type wherein the casting mold is formed by a portion of the grooved peripheral annular rim, open towards the exterior, of a rotating cooled casting wheel and a cover band that covers that portion and moves synchronously therewith.

Casting wheels of this type are known. The cover band is usually endless; the liquid metal to be cast is poured into the mold which is formed between the rim and the cover band, and the solidified metal leaves the wheel together with the cover band, and is subsequently removed as continuous strip or bar.

Continuous casting in accordance with rotating watercooled casting wheel molds of the prior art has generally been satisfactory; these molds have, however, been found to be deficient in that the metal was delivered to the mold from a tundish to a point on the wheel that moved downwards so that the metal flowed down through the mold to meet a mass of liquid and solidifying metal located lower down. The surface at the level of this mass of liquid metal was small in comparison with the depth of the mass. This depth, however, is easily affected by very small variations in the feed, and this may result in irregularity of structure in the casting. Moreover, turbulence occurred when the metal flowed down from the tundish into the mold and this favored the occlusion of oxide. This was particularly likely to happen if the metal entered the mold under throttle valve control as a thin jet at a point well below the top of the wheel. The metal then tended to trickle onto the base of the mold without coming into contact with the cover band until it reached the mass of molten metal. The distance between the throttling valve and this mass was so great that the formation and entrainment of films of oxide was almost inevitable.

It is accordingly among the principal objects of the invention to provide methods of and means for avoiding the aforesaid drawbacks of the prior art.

It is another object of the invention to provide that the sump, namely the liquid metal in the mold upstream of 3,428,111 Patented Feb. 18, 1969 the solidified part, extends at all times upwardly above the highest point of the base of the mold.

It is a further object of the invention to arrange for the aforesaid upward extension of the sump by adjustment of the rate of rotation of the casting wheel and rate of feeding of the molten metal.

It is still another object of the invention to feed the molten metal in such a manner that it enters the mold at or near the top of the casting wheel.

It is yet a further object of the invention to feed the liquid metal into the mold and tundish in such a manner that the liquid metal in the mold and the tundish are kept at the same level, with the tundish extending substantially horizontally and being in liquid-tight contact with the mold.

It is still a further object of the invention to provide such a tundish with side walls extending above the rim of the wheel and to provide a seal between the frontal parts of the side walls of the tundish and the cover band, whereby the level of the metal in the tundish may be kept above the highest point of the side Walls of the mold, so that the liquid metal will come into contact with the cover band before it actually touches any part of the wheel.

It is yet a further object of the invention to provide for a constant level of molten metal in the tundish, without need for any level regulating device in the sump itself.

It is another object of the invention to provide for level constancy by means of a constant-level device in the tundish, which device may include a float. Alternatively, such a device may make use of variations in capacity between an electrode formed by the surface of the metal and another electrode formed by a metal plate arranged above it, signals from the device being used to control the tilting of a ladle or furnace from which the liquid metal is supplied to the tundish. This has the advantage that the liquid metal will be fed from the supply ladle or furnace into the tundish and from there into the mold with but a minimum of turbulence.

In accordance with a preferred embodiment of the invention, the sump, namely the liquid metal in the mold upstream of the solidified part, extends on both sides of the highest point of the base of the mold. The molten metal is fed through the tundish at a point slightly below said highest point of the base of the mold, thus in advance of that highest point counted in the direction of rotation of the wheel. On the other side of said highest point, the sump is terminated by the solidification front. The position of the solidification front is determined by the cooling adjustment of the casting wheel.

The mass of liquid metal of the sump is such that the area of the free surface of the metal is large in comparison with the depth of the sump. The sump is therefore given a greater cushioning or buffer action and is capable of absorbing the small variations in the supply of the molten metal which are unavoidable in spite of any automatic regulation of the level of the surface of the metal.

The instant invention therefore offers the advantage that the stream of molten metal passes from the tundish to join the liquid mass in the mold at a regular rate without falling through air. The metal is accordingly distributed uniformly over the width of the mold and flows without turbulence until it solidifies. At the same time, the formation and entrainment of oxide films are effectively and simply prevented.

With the above and other objects of the invention in view, the invention consists in the novel methods, construction, arrangement and combination of various devices, elements and parts, as set forth in the claims hereof, one embodiment of the same being illustrated in the accompanying drawings and described in the specification.

In the accompanying drawing:

FIG. 1 is a schematic view of a continuous casting machine of the rotating wheel type, in accordance with the invention;

FIG. 2 is a large scale fragmentary vertical central sectional view thereof;

FIG. 3 is a fragmentary sectional view on a still larger scale, taken on the line 3-3 of FIG. 2, and

FIG. 4 is a fragmentary sectional view similar to FIG. 3, but taken on the line 4-4 of FIG. 2.

In carrying the invention into effect in one of the embodiments which has been selected for illustration in the accompanying drawings and for description in this specification, and referring now particularly to FIGS. 1 and 2, there is provided a continuous casting machine of the rotating wheel type. It comprises a casting wheel 1 which rotates about an axis x in the direction of an arrow A, and has a rim 2. The rim 2 is recessed and defines an annular groove 4 which is open towards the outside. The groove 4 extends throughout the entire circumference of the wheel 1, and for a sector portion thereof forms a part of the arcuate casting mold. An endless cover band 3 is provided that runs around guide rolls 7, 8, 9 and 10 and, throughout the mold portion of the groove 4, makes contact with the guiding wheel 1 covering the groove 4 thereby completing therewith the arcuate mold.

Metal to be cast is supplied from a supply vessel (not shown) to a tundish 5, and flows from the tundish into the mold. The wheel 1 is internally cooled by a stream of water, and the cover band 3 is cooled by water sprays 11, with the result that the metal solidifies in the mold to form a continuous casting 6, which leaves the wheel with the cover band 3 as shown in FIG. 1 and thereafter is continuously drawn away from the machine.

Although the groove 4 may have any desired form in cross-section, it is preferably substantially U-shaped, and has a peripheral base and sides that are inclined outwardly (FIG. 3) so that the removal of the casting is facilitated. The cover band 3, which is advantageously made of steel, is preferably driven by the casting wheel 1 and hence moves in synchronism with the rim 2 of the wheel.

The guide wheel 7 is placed immediately above the top of the wheel 1 and presses the band 3 against the wheel 1, so that at its inlet the mold groove 4 is substantially horizontal.

The discharge end of the tundish 5 exactly matches the cross section of the mold 4 and bears against the rim 2 to make an effective seal at a point where the rim 2 is moving upwards. The tundish 5 is substantially horizontal, and is pivotally mounted about a rod 14 which is parallel to the axis x of the wheel 1, so that the'delivery end or spout of the tundish 5 is pressed against the rim walls of the groove 4 by gravity. Additional pressure may be exerted by means of a piston 16 that may be subjected to hydraulic or pneumatic pressure, or again the tundish 5 may be loaded by a spring or a weight so that its spout 15 is firmly pressed into contact with the groove 4. It is important that a good seal should be made at the spout 15 and the spout 15, as described below, may be covered with suitable sealing material for the purpose.

The pivotal mounting of the tundish about the rod 14 presents the advantage that a seal is still maintained if the casting wheel is not truly circular or loses its circular shape as a result of thermal distortion. It is desirable that the rod 14 should be at the end of the tundish remote from the spout 15 so that the amplitude of any rocking movement is small.

Because the spout 15 engages the groove 4 of the wheel at a point where this is moving upwards there is a fairly smooth transition between the base of the tundish 5 and the base of the groove 4, and the metal flows from the tundish 5 to the mold horizontally as a steady smooth stream without turbulence, in contrast to the thin free cascading of the liquid metal onto the bottom of the mold in previous practice (see FIGS. 3 and 4).

It is, however, also possible to feed the molten metal instead to a point downstream of the highest point 18 of the base of the groove 4, by leading the spout 15 of the tundish 5 to a point to the left (of FIG. 2, though not shown) of said highest point 18, provided, however, that the level of the sump will at all times be above any point of the base of the groove 4.

In both cases, the narrow spaces between the spout 15 and the groove 4 are subject to a metallostatic pressure and need good sealing. The spout 15 therefore needs to be made of a proper material for proper sealing. The spout 15, may, as shown in FIG. 2, be made of a separate piece, and may be composed of a material, namely a sealing material, that may be different from the material of the remainder of the tundish 5. If the tundish 5 is made of a material that does provide enough sealing, then the spout 15 may be made of one piece with the tundish 5. If, on the other hand, the tundish 5 is made of a material that does not provide the needed sealing, then those surfaces of the tundish 5 that make contact with respective surfaces of the groove 4 may be provided with a sealing layer or coating.

The molten metal is supplied from the tundish 5 through a trough 12 and a nozzle 19 thereof, and the supply is controlled by a valve member that cooperates with the nozzle 19, and which includes a circular float 13. The float control ensures that the surface of the liquid metal in the tundish 5 is kept at a substantially constant level.

It is desirable to restrain oxide on the surface of the molten metal from entering the mold, and for this purpose a stripping bar 17 may be provided just above the spout 15. There is thus substantially no opportunity for reoxidation of the metal that actually enters the mold.

In operation, the rate of feed of the metal to the mold and the speed of rotation of the wheel 1 are correlated so that at all times there is molten metal on both sides of the highest point 18 of the base of the mold. The actual solidification front, that is to say the point where the metal starts to solidify, is preferably maintained fairly close to the top of the wheel.

As best shown in FIG. 2, the solidification front is to the left of the highest point 18 of the base of the groove 4 of the wheel 1. The front in FIG. 2 is shown merely by way of exemplification; the front may, in practice, extend instead further in the direction of the arrow A of FIG. 2, throughout an angle of 40 or even 50.

If the metal level in the tundish 5 is higher than the plane where the cover band 3 makes contact with the rim 2 near the point 18, the forward portions 21 of the side walls 20 of the tundish 5 will make sealing contact with the lateral extensions of the cover band 3. The side walls 20 extend above the rim 2 of the wheel 1. These portions 21 will be concavely shaped (see FIG. 2), in order to match the convex bend of the cover band 3. In accordance with a preferred embodiment, the concave frontal portions 21 may be provided with sealing material of elastic refractory properties, for instance material available under the trade names Marinite or Fiberfrax. The tundish 5 will thus be sealed against the cover band 3, and the liquid metal will come into contact with the cover band 3 before it actually touches any part of the wheel 1.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to aperson skilled in the art.

Having thus described the invention, what we claim as new and desire to be secured by Letters Patent, is as follows:

1. A method of continuously casting strips of aluminum metal and aluminum alloys metal from a substantially horizontally disposed tundish into a mold formed by a portion of a groove with substantially smooth surface recessed in the rim of a cooled on a horizontal axis rotating wheel and a cover band moving substantially synchronously with the rim of the wheel throughout said portion, the inlet of the mold being substantially on the top of the wheel, the steps comprising feeding molten metal into the unobstructed mold at a point close to the top of the wheel, simultaneously sealing the mold against running of the metal out of the mold, and correlating the feeding of the molten metal with the rotation of the wheel so that at all times there is a controlled amount of molten metal above the highest point of the base of the mold.

2. A method of continuously casting strips of aluminum metal and aluminum alloys metal from a substantially horizontally disposed tundish into a mold formed by a portion of a groove with substantially smooth surface recessed in the rim of a cooled on a horizontal axis rotating wheel and a cover band moving substantially synchronously with the rim of the wheel throughout said portion, the inlet of the mold being substantially on the top of the wheel, the steps comprising feeding molten metal into the mold at a point close to the top of the wheel, and correlating the feeding of the molten metal with the rotation of the wheel so that at all times there is molten metal above the highest point of the base of the mold, the liquid metal in the mold and in the tundish being kept at the same level, the tundish extending substantially horizontally and being in liquid-tight contact with the mold.

3. A method according to claim 1 in which the metal is fed to the mold at a point where the base of the mold is moving upwards in its rotation.

4. A method according to claim 1, and maintaining the liquid metal in the mold on both sides of said highest point of the base of the mold.

5. A method according to claim 1, and controlling the supply of liquid metal to the tundish in response to the level of the metal in the tundish.

References Cited UNITED STATES PATENTS 2,393,213 1/1946 Willard 164-276 X 3,193,888 7/1965 Rochester 164-278 510,808 12/1893 Lloyd 164276 X 745,786 12/1903 Cole 164-276 1,600,668 9/1926 Hazelett 164-276 X 3,080,627 3/1963 Hoteka 164155 FOREIGN PATENTS 242,063 12/ 1962 Australia.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

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