US3468361A - Continuous metal casting method - Google Patents

Description

p 3, 1969 H. A. FROMSON CONTINUOUS METAL CASTING METHOD Filed Nov. 22, 1966 l I l |ll\i i Wm. i|| 11 La Q Q! n l H H wl i uflf \w m l I i I I I N- I 1 mm WWMMMWHMMWMM W mu A w I:

INV N OR 1901mm wmw/v WIM ORNEYS United States Patent ABSTRACTHOF THE DISCLOSURE I Patented Sept. 23, 1969 ICC In the mold bore 17 the molten metal contacts the interior walls, freezes, and forms a solid shell 18 surrounding a molten core 19. As the ingot 25 leaves the mold bore 17 it proceeds horizontally through a bath of molten salt 20, which may be barium chloride. The salt is contained in a chamber comprised of refractory walls 21 and The disclosure relates to a method of continuously casting metal in which a molten metal is cast continuously by introducing molten metal under pressure through a mold to form a partially solidified casting with a solid shell. The casting so formed is advanced horizontally didepth at which the pressure acting on the periphery of the solid casting shell sufficiently counteracts the pressure of the molten core in this casting to prevent rupture. The casting is maintained substantially at this depth until the casting is sufficiently solidified in the coolant to prevent outbreak of the molten core, and the casting so sufiiciently solidified is discharged continuously from the coolant bath.

This invention relates to the art of continuous casting of molten metal.

In the continuous casting of a molten metal, such as steel, such metal is led into one end of a water-cooled mold, which may be made of copper or a copper alloy. The mold is open at both ends and may be of any convenient cross-sectional shape, but is usually round or rectangular in cross-section. The metal in contact with the mold walls solidifies, forming a solid shell which remains filled with a molten metal core. This shell is continually pulled from the exit end of the mold and, as further cooling progresses, the molten core gradually solidifies.

In order that economic advantage may be derived from the use of continuous casting the rate of flow of metal through the mold must be increased as far as possible. This requirement means that a withdrawal rate which allows the formation of a thick shell within the mold is too slow. These portions of the shell which are either still within the mold or adjacent the exit thereof are apt to be weak. This weakness is the result of the high temperature of the solidified metal and the relative thinness of the shell. As a result of this weakness the shell may rupture and the liquid metal in the core break forth. It is an object of the invention to lessen the strain on the thin shell of solidified metal and thus avoid such breakthroughs.

It is a further object of the invention to increase the casting rate by lessening the strain upon the thin shell.

It is a still further object of the invention to establish the emerging ingot in a horizontal position, thereby reducing the height of the space required to contain the casting equipment.

In the drawing a ladle 10 is shown. The ladle supplies molten metal to a refractory tundish 11 through ladle pipe 12. An exit pipe 13 provides a path by which the molten metal 14 in the tundish may reach a mold 15. Water passages 16 allow cooling of mold 15, which may be made of copper. The mold has interior surfaces defining a mold bore 17. The walls of the mold bore 17 may be parallel or, as shown in the drawing, they may have a straightsided portion and an exit portion where the walls flare outward so that the cross-sectional area of the bore increases from the entrance to the exit.

a refractory floor 22. Cooling passages 23 are embedded in the chamber walls to facilitate the removal of heat from the salt and a rotatable stirrer 24 may be provided to direct a current of salt against the ingot 25 as it emerges from the mold.

The static pressure of the head of molten salt above the ingot tends to counteract the static head of molten metal within the ingot core. This external pressure thus balances the internal pressure and lessens the tendency I of the latter to rupture the solid shell 18. Since the ingot rectly into contact with a bath of liquid coolant and at a is horizontal the desired pressure balance can be maintained along its whole length even though the metal being cast may be considerably denser than the salt.

As the ingot progresses through the bath of molten salt it is supported by rollers 26 which may be rotatably held in loose metal journals, The salt will tend to lubricate such bearings. In addition, the apparent weight of the ingot on the rollers is reduced by the flotation effect of the salt bath.

An opening for the ingot to leave the salt bath is provided by a copper exit ring 27 having internal passages 28 through which a cooling solution may be passed. A central opening defined by surface 29 is provided through the exit ring, said opening being alined with the opening in mold bore 17. The central opening is shaped to conform to the surface of the ingot as it passes therethrough, but preferably a small space is left between the surface 29 and the surface of the ingot in order to prevent wear of the exit ring. Molten salt enters this space and freezes due to contact with the exit ring 27. This salt acts as packing to prevent undue loss of salt from the mass within the chamber. The film of salt left upon the emerging ingot may be cracked therefrom by rolls or other devices, or washed off by cooling water. A tray 30 is provided to receive such salt fragments, which may be periodically returned to the salt chamber.

Further cooling of the ingot may be accomplished by water spray nozzle 31, after which the ingot may be cut into pieces of a desired length by any suitable means.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.

What is claimed is:

1. A method of continuously casting a molten metal comprising the steps of continuously introducing said molten metal into a mold having a bore extending in a substantially horizontal direction, cooling a portion of said molten metal below its freezing point in said mold bore by contact with said mold and thereby forming a solid shell, moving said solid shell from the mold bore into a bath of molten coolant of a temperature lower than the melting point of the molten metal and thereby removing heat from the solid shell and passing the solid shell in a substantially horizontal direction from the bath of molten coolant through an orifice defined by surfaces which are cooler than the melting point of the molten coolant and which conform to the surface of the shell to form thereby a thin layer of solidified coolant on the surface of the shell, as it passes through said orifice.

2. A method of continuously casting a molten metal comprising continuously introducing molten metal under pressure into a mold having a bore with cooling walls to produce a partially solidified casting comprising a solid shell surrounding a molten core, continuously advancing said casting as it is formed and while in partially solidified condition substantially horizontally from said mold directly into contact with a bath of liquid coolant at a rate to cause a substantial length of said casting to be immersed in said coolant While in said partially solidified condition and at a depth in which the pressure of the coolant acting on the periphery of said partially solidified casting is sufliciently high to counteract the core pressure in said casting and thereby to prevent rupturing of said solid shell due to said core pressure, maintaining said casting While it is advancing in said coolant substantially at said depth to maintain said counteracting pressure action substantially constant until the casting is sufliciently solidified in said coolant to prevent outbreak of the molten core in the absence of coolant pressure, and continuously discharging the casting from said coolant bath.

4 3. A method as described in claim 2, wherein the liquid coolant is a molten salt.

4. A method as described in claim 2, wherein the liquid coolant is barium chloride.

References Cited UNITED STATES PATENTS 2,754,559 7/1956 Fromson 16482 X 2,789,327 4/1957 Corley l642 83 X 3,128,513 1/1964 Charlton et a1. 164-89 3,151,366 /1964 Fromson l64283 X FOREIGN PATENTS 878,023 9/ 1942 France. 669,725 12/ 1940 Germany.

I. SPENCER OVERHOLSER, Primary Examiner R. SPENCER ANNEAR, Assistant Examiner US. Cl. XtR. l64-81, 283

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