US2517931A - Apparatus for the continuous casting of metal - Google Patents

Description

ROSS! APPARATUS FOR THE CONTINUGUS CASTING 0F' METAL Filed May 15. 1947 Aug. 8, 1950 2 Sheets-Sheet 1 lill/:(1111,

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ATTORNEY l. ROSS! APPARATUS FOR THE CONTINUOUS CASTING OF METAL Filed May l5, 194.7

Aug., s, 195o 2 Sheets-Sheet 2 i N ENTOR.

Mm* ATTORNEY Patented Aug. 8, 1950 APPARATUS FOR THE CONTINUOUS CASTING F METAL Irving Rosal, Morristown, N. J. Application May l5, 1947, Serial No. 748.181

(Cl. 22-5'L2) 3 Claims.

'I'his invention relates to the continuous casting of metal, andllertalns particularly to means for conveying the molten metal from a reservoir or holding furnace to the casting mold where the metal is solidified.

In certain prior art processes for the continuous casting of metal, as exemplified by Patents Nos. 1,868,099, 2,145,438 and 2,195,809 the casting mold is secured directly to the reservoir or holding furnace, and the molten metal flows directly from the reservoir into the mold. In other prior art processes, as exemplified by Patents Nos.

2,079,644, 2,284,703 and 2,301,027 the molten.

metal is poured from a ladle into the open upper end of the casting mold. In still other prior art processes, however, as exemplified by Junghans Patents Nos. 2,135,183 and 2,135,184 the molten metal is conveyed from the reservoir to the casting mold by means of a pipe or tube which extends from the reservoir to a point below the surface of the molten metal pool in the upper end of the casting mold. The latter procedure has many advantages, but diillculty has been experienced in finding a suitable material for the conveying pipe or tube. Due to the high temperature of the molten metal and the chemical action on the conveying pipe or tube, such pipes or tubes have been found to deteriorate fairly rapidly, causing frequent shut downs for replacement. y

The rate of deterioration varies with the metal being cast and the material used for the conveying pipe or tube. 'I'hus while pipes or tubes of chrome-steel alloy have been found to give reasonably good service when casting brass, they are wholly unsatisfactory for casting aluminum.

-In casting aluminum, no really satisfactory solution has been found. for cast iron, which has given the best results so far, is erratic and unpredictable in performance. For example, a cast iron pipe may last three or four hours or three or four days.

Refractories have .been tried without success, and are objectionable due to the fact that it has been observed that pieces tend to chip off. and when such pieces get into the casting, they cause serious trouble when the metal is subsequently worked, as in extruding it. for example.

Furthermore, the lack of a satisfactory material for such conveying pipes or tubes has been an important factor in delaying the application of such continuous casting processes to the casting of steel, for the problems encountered in casting brass and aluminum are multiplied in the case of steel due to the higher temperatures required.

It is an object of the present invention to overcome these dimculties and to provide a conveying pipe or tube which will be serviceable for extended periodsrof time.

It is a further object of the invention to take advantage of the additional external cooling area which may be provided to improve the casting operation.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which:

Figure 1 is a plan view.

Figure 2 is a section on the line 2-2 of Figure 1.

. Figure 3 is a plan view of a modified form. Figure 4 is a section on the line 4-4 of Figure 3.

In all previous eiorts to solve this problem, it has been sought to find a material which would resist deterioration at the temperature of the molten metal being conveyed. According to the present invention. on the contrary, I prevent the material of the conveying pipe or tube from rising to a temperature suiilcient to cause deterioration. I do this by usingl a tube having a relatively thin wall made of metal preferably of relatively high heat conductivity, and cooling the outside of the tube. so that the metal of the tube always remains at relatively low temperature, as for example 300 F. .or less, at which temperatures there is little or no tendency for the metal to deteriorate. Furthermore, in order to prevent solidiilcation of the molten metal in the tube. I use a tube having an interior cross sectional area which is ,relatively small as compared with the cross sectional area of the mold, so that the molten metal flows through the tube at relatively high velocity. Under these conditions. even though there is a large differential in temperature between the molten metal and the tube wall, the quantity of heat absorbed through the tube is small and the drop in temperature of the molten metal from the point where it enters the tube to the point where it is discharged into the mold is small. As a result, even though the tube wall .is relatively cool. there is no tendency for molten tube i is a water jacket 4 having diametrically analisi lopposed inlet passages 5 and 5a and diametrlcally opposed .outlet passages 6 and Ca. Mounted within the jacket l and connected thereto at a point just above the inlet passages is a tubular baule 1 which f rees the cooling water to follow the path indicated by the arrows. At the bottom. the ends of the tube l and jacket 4 are connected and the space therebetween is closed by an annular ring I.

The baule wall is spaced rather closely to the wall of the conveying tube to insure rapid circulation of water, and it will be noted that the direction of now of the water is upward along the.

tube wall so that the coolest water is in contact with the bottom f the tube.

The lower end of the tube projects into the open upper end of the casting mold 9 a distance such that the lower end is submerged in the pool of metal in the mold as illustrated in the draw- Preferably the tube I and the jacket I are made of copper as this metal is a good heat conductor and is resistant to heat shock. However, the invention is not limited to the use of copper for other metals such as chrome-steel alloys may be used successfully. Ordinarily the tube is cylindrical in shape, i. e. having a uniform inside diameter, although, if desired it may be tapered in a manner such that the inside diameter at the bottom of the tube is somewhat greater than at the top. While there is no tendency for metal to freeze in the tube after full flow-has been established, it has been observed that when starting an operation the first metal poured into the tube may trickle down one side of the tube wall and freeze thereon before full flow is established. With the tapered form of tube, however, such frozen metal will quickly free itself frcm the tube wall as soon as full flow is established.

In the embodiment shown in Figures i and 2, it will be noted that the exterior walls of the water jacket, including the bottom wall 8 are cooled by the cooling water flowing through the jacket, and being immersed in the molten metal in the mold for a substantial distance, exert an important cooling effect on the molten metal in the mod, and particularly on that portion of the maten metal which is near the center of the mold and thus furtherest removed from the chilled mold wall. Fo-r example, if we assume that the water Jacket has an outsidel diameter of 2", that the conveying tube has an inside diameter of and that the water jacket extends 2" below the surface of the molten metal, it wi.l be seen that the exterior surfaces of the water` jacket provide a cooling area of over l sq. in. which is suillcient to withdraw a substantial quantity of heat.

This effect may be greatly increased by increasing the diameter of the water jacket in the manner illustrated in Figures 3 and 4. In this case the diameter c-f the water jacket l' is greatly increased, being more than two thirds of the inside diameter of the mold, and in order to insure rapid circulation of the cooling water, the baille 1 is replaced by a, hollow baille chamber 'l' occupying a large portion of the intericr of the jacket, leaving relatively narrow outer and inner channels for water circulation. Again, as in the embodiment shown in Figures 1 and 2 the direction of water iiow is upward along the tube wa'l, and it will also be noted that since thc cosling water enters the outer channel and moves downwardly and transversely to the inner channel, the maximum cooling effect is exerted through the exterior walls of the jacket on the molten metal in the mold. In the embodiment illustrated the water is introduced tangentially through the inlet passage l' and is discharged through outlet passages C and Ia. l If e now assume an outside diameter of the water jacket of 8", with a conveying tube having a cooling area of over sq. in. If we now make the further assumption that a jacket of these dimensions is used with a mold having a diameter of 11", the mold wall to a distance 2" below the surface of the molten metal will provide a cooling surface of approximately 69 sq. in. Thus, the area of the cooling surface provided by the submerged portion of the water jacket is greater than the area of the cooling surface provided by the opposed portion of the mold wall.

In the use of water Jacketed conveying tubes of the'type described, I have found it highly advantageous to design the apparatus in such manner that the above described relationship is maintained during casting operations. That is, for best results,v the outside diameter of the water jacket and the extent of submergence of the lower end of the jacket in molten metal is so adjusted with relation to the diameter of the mold that the cooling area of the submerged side and bottom walls of the jacket is at least equal to and preferably exceeds the cooling area of the opposed portion of the mold wall.

When these conditions are maintained, so that a very substantial portion of the heat is withdrawn lfrom the interior of the pool of molten metal in the mold, it will be observed that this tends to equalize the temperatures across the mold with the result that the depth of the central crater is reduced very substantially, with the metal freezing almost in a horizontal plane. 'I'his has substantial advantages, not only in the fact that it makes possible a more rapid rate of casting, but also in producing an lngot or billet of superior crystal structure with little or no poromty in the center.

It will be understood that the invention may be variously modified andembodied within the scope of the subjoined claims.

I claim as my invention:

l. In an apparatus for the continuous casting of metal, in combination, a chilled mold, a metal tube for conveying molten metal from a source of supply to said mold, a water cooled Jacket surrounding said tube throughout its length and maintaining the cooling water in contact with said tube throughout its length, the lower end of said tube and jacket extending into said mold and being submerged in the molten metal therein.

2. In an apparatus for the continuous casting of metal. in combination, a chilled mold. a metal tube for conveying molten metal from a source of supply to said mold, a water cooled jacket surrounding said tube throughout its length and maintaining the cooling water in contact with said tube throughout its length, the lower end 0f said tube and jacket extending into said mold and being submerged in the molten metal therein, the exterior surfaces of the submerged portions of said water jacket being cooled and exerting a cooling effect on the molten metal in the mold.

3. In an apparatus for the continuous casting of metal, in combination, a chilled mold, a metal tube for conveying molten metal from a source of supply to said mold. a water cooled jacket sur.

rounding said tube throughout its length and REFERENCES CITED maintaining the cooling water in contact with said tubo throughout its length, the lower ond or sold myx; lllilggxfferences are of record m the tube and jacket extending into said mold and being submerged in the molten metal therein, the 5 UMTED STATES PATENTS exterior surfaces of the submerged portions oi' Number Name Date said water jacket being cooled and exerting a 1,996,335 Jones et ai Apr. 2, 1935 cooling effect on the molten metal in the mold, 2,154,234 Eppensteiner Apr. 11, 1939 the cooling area. of said submerged exterior sur- 2,224,303 Junghans Dec. 10, 1940 faces being at least equal to the cooling area of I0 2,290,083 Webster July 14, 19,42 the opposed portion o! the mold woll. 2,357,780 Mueller Sept. 5, 1944 IRVING ROSSI. 2,380,109 Hopkins July 10, 1945

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