US3054155A - Pouring spout and method of using - Google Patents

Description

Sept. 18, 1962 E. J. ZICKEFOOSE I POURING SPOUT AND METHOD OF USING Filed April 7, 1958 United States Patent 3,054,155 POURING SPOUT AND METHOD OF USING Ellis .1. Zielrefoose, Chicago Heights, 111., assignor to Amsted Industries Incorporated, Chicago, 111., a corporation of New Jersey Filed Apr. 7, 1958, Ser. No. 726,802 1 Claim. (Cl. 22-409) This invention relates to the pressure casting of molten metals and more particularly to a method of treating pouring tubes of the type employed in pressure casting operations.

The invention is concerned with the provision of a method for treating a ceramic pouring tube prior to its use in a pressure casting operation in order to render it less susceptible to damage resulting from thermal shock.

As disclosed in applicants co-pending application, Serial No. 507,055, filed May 9, 1955, now U.S. Patent No. 2,874,424 issued February 2, 1959, in the name of Ellis J. Zickefoose, this invention relates to a pressure casting operation of the type wherein molten metal disposed within a container is forced by the application of fluid pressure thereagainst from the container through a pouring tube into a mold disposed without the container.

Inasmuch as the pouring tubes commonly employed in pressure casting operations of this type are generally formed from a refractory such as an alumino-silicate, they are extremely fragile or frangible and easily broken or cracked when improperly handled, mounted, or otherwise used. This is due, of course, to the nature of these compositions, and particularly to their physical characteristics with regard to thermal expansion, which are largely reponsible for the damage frequently resulting from thermal shock when they are subjected to sudden or excessive temperature changes.

It is, therefore, a primary object of this invention to provide a method of using a frangible pouring tube, formed of a refractory composition, in a manner calculated to materially increase the service life of the tube.

Another object of the invention is to provide a method of treating a ceramic pouring'tube to reduce the possibility of its being damaged as a result of thermal'shock.

A more specific object of the invention is to provide a particular method of pre-heating a ceramic pouring tube in a manner appropriate to the particular thermal expansion characteristics of the material of which the tube is comprised in order to materially reduce the possibility of damage to the tube resulting from thermal shock due to sudden excessive temperature changes.

These and other objects of the invention will be apparent from an examination of the following description and drawing, wherein:

FIGURE 1 is a top plan view illustrating a pouring tube structure of the type with which my invention is concerned, only one-half of the structure being shown, as opposite halves are identical; and

FIGURE 2 is a vertical sectional view taken along line 22 of FIGURE 1.

Referring now to the drawing for a better understanding of the invention, it will be seen that the pressure casting apparatus with which my invention is concerned comprises a pouring tube structure indicated generally at 5,

which is shown'as mounted upon a horizontally disposed cover 6 of a sealed container (not shown) adapted to house a ladle (not shown) containing a bath of molten metal (not shown). The molten metal is adapted to be directed upwardly through the pouring tube structure into thecasting cavity of a mold 7, disposed above the container and preferably tilted to prevent the entrapment of air within the casting cavity.

The pouring tube structure 5 is shown as comprising a wedge shaped ring 8, welded as at 9', to the upper surface of container cover 6 and presenting an upper surface 11 inclined at an angle of, for example, 3% degrees from the plane of the cover. The ring 8 is adapted to receive and support for rotational movement a tube assembly comprising a tubular housing 12 and a ceramic tube 21. The housing 12 is formed with a downwardly facing annular shoulder 13 for abutting engagement against the upper surface 11. To provide an air-tight seal between the ring surface .11 and the housing shoulder 13, a ring gasket 14 is interposed therebetween.

The housing 12 is formed with a frusto-conical outer surface 16 extending upwardly from the shoulder 13 for telescopic engagement by a retainer ring 17 secured to the wedge shape ring 8 by means of cap screws 18. As illustrated in FIGURE 2 in the drawing, the longitudinal axis A of the housing 12 is perpendicular to the ring surface 11, the housing being formed with a bore 19 having its axis B disposed at an angle of, for example, 3 /2 degrees from the axis A and perpendicular to the plane of the cover 6.

The upper end of a ceramic tube 21, the composition of which is hereinafter described, is disposed'within the bore 19 and secured to the housing 12 by means of a suitable wet type air setting refractory 22 comprising, for example, a mix of 5% combined water.

The mix 22 is poured into an annular chamber 20 defined between the tube 21 and housing bore 19, and then dried by heating the housing by means of a flame. During pouring, the mix 22 is retained within the chamber 20 by means of a sealer ring (not shown) positioned and supported against the bottom of the housing 12, thus preventing leakage of the mix downwardly from the chamber. After the mix has solidified, the sealer ring is removed. The bore 19 and tube 21 are coaxial and perpendicular to the horizontally disposed cover 6. The mix 22, mixed to a putty consistency, is used to fill all voids and to form a small fillet 34 at the bottom of the mix junction between the housing 12 and the ceramic tube 21, thus providing a better seal.

In order to afford a bearing surface between the mold and the top of the housing 12, a ring or washer 23 preferably formed of graphite or cast iron, may be mounted within the bore 19 and secured in fixed position by means of cap screws 24. Inasmuch as the outside diameters of the tubes vary slightly, it is desirable to provide the washer 23 with an inside diameter slightly larger than the average outside diameter of standard tubes.

The space hetween the washer and tube may then be filled in with the mix 22.

After the tube 21 has been cemented to the housing 12, the outer surface of the tube and the entire outer surface of the fillet 34, and the junctions of the fillet and the housing, and the fillet and the tube are coated with glaze 25 from the bottom of the housing to within 18 or 20 inches from the lower end of the tube to prevent leakage of air through the wall of the tube into the interior thereof and thence into the molten metal. The glaze 25 may comprise, for example, the following mix:

Percent z 57 A1 12 PhD 6 N320 7 K 0 7 B 0 11 To mount the tube 21 and housing 12 in the cover 6, the retainer ring 17 is first removed from the structure and the housing is manually rotated about its axis until the longitudinal axis of the tube is normal to the surface of the metal. This can be done by means of a suitable tool or rod inserted into one of the circumferentially spaced sockets 26 provided in the housing. The housing 12 is then secured in its adjusted position by means of the retainer ring 17 and screws 18.

The retainer ring 17 is formed with an outer frustoconical surface 27 for snug engagement against a complementary frusto-conical opening 28 formed in the bottom 29 of the drag 31 of the mold 7, the mold being provided with a gate 32 in registry and axial alignment with the passageway 33 of the tube 21. When a mold is seated upon the retainer ring 17, the mold and casting cavity therein are inclined for the purpose of preventing the entrapment of air within the cavity as the latter is being filled with molten metal, as disclosed in said patent application.

In order to insure a satisfactory pouring operation with the above described pressure casting apparatus, it is essential that the pouring tube 21 be formed of a refractory composition.

Although pouring tubes of this type have been formed of various refractory materials, it has been found that the most satisfactory results are obtained by the use of a ceramic tube formed of a refractory such as an aluminasilicate. This invention is not limited in its application to use in connection with a pouring tube of one particular composition, but is concerned with or related to the use of ceramic tubes in general, all of which have a common physical characteristic, namely, that of being extremely frangible and subject to thermal shock; however, in order to better illustrate the invention and its applicability, it is believed that the invention can best be ex plained by reference to a tube of a known composition.

It has been found that excellent results in a pressure casting operation in the above described nature can be obtained by the use of a pouring tube formed of a refractory such as alumino-silicate comprised of the fol lowing ingredients:

Percent SiO 51-53 A1 0 42-44 Balance-usual ingredients commonly found in fire clay refractories in various percentages, for example:

no, MgO F6203 N320 CaO K 0 Additionally, it has been discovered that the glassy form of silica, known commonly as vitreous silica, serves as an excellent constituent for the above described composition.

It will be understood that a common physical characteristic peculiar to almost all of the above known ceramic compositions is a combination of low thermal diffusivity and a relatively high rate of thermal expansion which renders them extremely sensitive to thermal shocks caused by sudden or excessive temperature changes.

In the pressure casting of molten steel the temperatures at the initial stage of the pour usually reach as high as from 2900 F. to 2950 F. The instantaneous exposure of ceramic pouring tubes to such temperatures is a serious problem because of the high rate of tube breakage due to thermal shock. This breakage increases appreciably the cost of production of steel castings from the standpoint of both replacement and installation of tubes.

Although the basic concept of pre-heating a pouring tube or any other article subject to thermal shock is not new, applicant has discovered a particular method of pre-heating ceramic pouring tubes that aiford greater protection against tube breakage, due to thermal shock, than any other pre-heating process known to the applicant.

My invention consists in the provision of a method of pre-heating a ceramic pouring tube, which method includes the following steps: (1) Placing the tube, which has already been mounted in the previously described pouring tube supporting structure, in a pre heat furnace, the temperature of which is lower than any discontinuity in the thermal expansion curve of the particular composition of the tube. In the case of the composition previously described in detail, the lower critical temperature is 350 F. and the preferable temperature for the initial pre-heat stage is not over 250 F.; (2) Increasing the temperature of the furnace in which the tube is exposed (either by raising the temperature of the pre-heat furnace if only one pre-heat furnace is used, or by sequentially transferring the tube through several pre-heat furnaces in the event a plurality of pre-heat furnaces are used) at a rate of not greater than 200 F. per hour until such time as the tube is at a temperature in excess of any discontinuity in the expansion curve of the composition. In the case of the previously described composition the preferable temperature for the final pre-heating stage is 1800 F.; (3) Transferring the pouring tube supporting structure to the pressure casting apparatus for use in the pressure casting operation; and (4) Upon completion of the pour, returning the pouring tube supporting structure to a pre-heat furnace.

Inasmuch as it is impossible to cement the tube in the housing in the manner described above, after the tube has been heated, it is necessary that the tube first be mounted in the supporting structure before the pre-heating is begun. It is optional, however, whether the housing be mounted within the cover before the pre-heat treatment, as this question is logically determined by the arrangement and type of equipment available in the foundry plant.

One basic reason for pre-heating is to raise the temperature of the refractory body to a level at which at least 50% of the total thermal dilation has occurred and to a heat content closer to that which will be maintained in elevated temperature service.

Accordingly, the real essence of the invention lies in the provision of a method of pre-heating a ceramic pouring tube in sequential stages of uniformly increasing temperature at a rate of increase which will not damage the refractory by thermal shock and to an upper limit as close as practical to the expected service temperature.

It will be understood that the tube can be subjected to the various pro-heating stages in a single pre-heat furnace by changing the temperature of the furnace at regular intervals or by passing the tube through a series of separate pre-heat furnaces, or, of course, by a combination of these systems wherein the final pre-heat furnace is maintained at a constant temperature at all times.

My invention is not limited to the use of any particular one of the above described systems, as regard to the numher of furnaces employed, as all of these systems can be utilized to effect the temperature increases required by my invention. It is believed that the choice of systems is most logically determined by the physical arrangement and equipment available in the foundry plant whereat the invention is to be practiced.

I claim:

A method for treating a pouring tube to be used in the pouring of molten metal at a temperature in excess of 2700" F which tube is formed of a ceramic refractory material in which there are no discontinuities in the thermal expansion curve at temperatures in excess of 1800 F., comprising uniformly increasing the temperature of the tube in sequential stages until the tem- 6 perature throughout the entire tube is slightly in excess of 1800 F. and at such temperature initiating pouring of the metal.

References Cited in the file of this patent UNITED STATES PATENTS 969,539 Kitchen Sept. 6, 1910 1,944,733 Doerschuk et al. Ian. 23, 1934 2,044,817 Schroeder June 23, 1936 10 2,549,790 Finkeldey et al. Apr. 24, 1951 FOREIGN PATENTS 446,686 Great Britain May 5, 1936 643,800 Great Britain Sept. 27, 1950

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