US3867977A

US3867977A - Method of casting copper anodes using a preheated mold coating

Info

Publication number: US3867977A
Application number: US430740A
Authority: US
Inventors: Ramon C Cruz; Clyde L Light; Donald J Nelson
Original assignee: Kennecott Copper Corp
Current assignee: Kennecott Utah Copper LLC; Kennecott Corp
Priority date: 1974-01-04
Filing date: 1974-01-04
Publication date: 1975-02-25
Anticipated expiration: 1992-02-25
Also published as: CA1049743A

Abstract

In the coating of interior surfaces of copper molds with a slurry of a release material prior to the casting thereinto of molten impure copper for the production of anodes for use in the electrolytic refining of such impure copper, the improvement wherein the slurry is heated to a temperature of from about 150* to about 200*F. prior to its being applied, resulting in greatly increasing the operating life of the molds.

Description

United States Patent [191 Cruz et a1.

[451 Feb. 25, 1975 METHOD OF CASTING COPPER ANODES USING A PREHEATED MOLD COATING [75] Inventors: Ramon C. Cruz, Hayden; Clyde L.

Light, Winkleman; Donald .1. Nelson, Kearny, all of Ariz.

[73] Assignee: Kennecott Copper Corporation,

New York, N.(.

[22] 7 Filed: Jan. 4, 1974 [21] Appl. No.; 430,740

[52] us. Cl. 164/72, 117/523 51 Int. Cl. 1322c 3/00 [58] Field of Search 164/72, 130; 117/53 [56] References Cited UNITED STATES PATENTS 1,662,354 3/1928 'williams 164/72 3/1964 Pichler 164/72 X 6/1970 Zimmerman; 164/72 X Primary Examiner-Francis S. Husar Assistant Examiner-John E. Roethel Attorney, Agent, or Firm-Mallinckrodt & Mallinckrodt [57] ABSTRACT 4 Claims, N0 Drawings METHOD OF CASTING COPPER ANODES USING A PREHEATED MOLD COATING BACKGROUND OF THE INVENTION 1. Field The invention relates to the production of copper anodes for use in the electrolytic refining of impure copare cast in solid copper molds weighing up to 6,000 or more pounds. It is common practice to treat the interior surfaces of such a mold before each pour with a slurry made up ofa finely divided inorganic release material, such as silica, suspended in a liquid medium, such as water. The liquid medium is vaporized by the heat of the mold, resulting in the deposition of a coating of the release material on the interior surfaces of the mold. The temperature of the mold during the treatment with the slurry is normally between about 200 and 1,000F. Molten copper, at a temperature of 2,000F. or more is introduced into the treated mold and the mold is then cooled until the molten metal has solidified. The cast copper anode is removed, and the mold is again treated with the slurry for the subsequent pour. Cracking of the molds is a serious problem that has long plagued the casting operation. Small cracks develop in a mold after about a week of use, and the small cracks rapidly enlarge to an extent that makes it necessary to take the mold out of service and replace it with a new mold. The cracking problem has long been considered to be a difficulty that simply had to be tolerated, and molds have customarily been replaced after only short intervals of use.

SUMMARY OF THE INVENTION In accordance with the present invention, the slurry that is normally applied at room temperature or below to the interior surfaces of a copper anode mold is heated, before application, to a temperature of from about 150 to about 200F. and is applied to the mold within that temperature range.

The release agent may be selected from the group consisting of silica, bone ash, alumina, clay, ganister, lime, and graphite, and is slurried with a liquid medium capable of being volatilized at the temperature of the mold, i.e., from about 200 to 1,000F. In accordance with conventional practice, the release agent is finely divided silica and the liquid medium is water. The heated slurry is applied to the interior surfaces of the mold by conventional means, usually by spraying, but other methods of applying it may be used, e.g., painting, splashing, or otherwise allowing the slurry to flow over the surfaces of the mold to form a coating thereon.

, The residual heat remaining in the mold from pour to DETAILED DESCRIPTION OF THE BEST MODE CONTEM PLATED Conventional casting procedures are preferably followed in carrying out the invention. Thus, the usual casting which is normally employed, with the molten copper being poured sequentially from the usual ladle into a series of solid copper molds carried circumferen tially of the wheel. The only difference over conventional practice is the heating of the usual slurry prior to its application to the interior surfaces of the molds.

Heating of the slurry may be accomplished in any suitable manner, but is conveniently carried out by injecting steam into the reservoir of slurry maintained at the usual mold-coating station.

The sequence of steps involved in conventional casting operations comprises pouring molten copper into the mold, cooling the mold, removing the solidified copper casting from the mold, and applying a coating of the slurry to the interior surfaces of the empty molds. The empty molds are then returned to the pour step and the sequence is repeated. The slurry comprises a finely divided release material suspended in a liquid medium. The residual heat remaining in the mold from pour to pour vaporizes the liquid medium from the slurry coating, leaving a coating of the release material on the interior surfaces of the mold. The molds can be cycled through the sequence of steps as a group, or, preferably, they are cycled therethrough sequentially in a continuous series.

The inorganic release material contained in the slurry includes such materials as silica, bone ash, alumina, clay, ganister, lime and graphite, preferably silica. The liquid medium is preferably water. The slurry itself may vary in the concentration of solids present depending upon the method of applying the slurry to the surfaces of the molds. For spraying operations, the solids concentration may be as low as 2 percent to 5 percent by weight, but generally will be between about 10 percent and 25 percent by weight. In splashing and other methods of applying theslurry to the mold surfaces, the solids concentration may be as high as percent by weight. The particle size of the solids in the slurry can also vary over a wide range depending upon the method of applying the slurry to the surfaces of the molds. For spraying operations, the particle size is preferably such that the dry solids are capable of passing through a 200 mesh screen. For other methods of applying the slurry to the mold surfaces, the particle size of the solids is not critical, the only requirements being that a homogeneous slurry be maintained, and that the coating of solids applied to the mold surfaces is uniform. Generally, the solids will have a particle size capable of passing through a 200 mesh screen.

The temperature of the mold during the application of the slurry thereto is generally between about- 200and 1,000F. The residualheat remaining in the molds from pour to pour, as mentioned hereinbefore, vaporizes the liquid medium from the slurry coating, leaving a residual coating of the release material on the interiorsurfaces of the mold.

Cooling of the mold following a pour can be accomplished by circulating water through internal passage- EXAMPLE A comparison test was run using the apparatus of a conventional, operating facility for producing cast copper anodes. The apparatus comprised a casting wheel which supported a series of copper molds, each were weighing approximately 6,000 pounds. Each mold was capable of casting a 700 pound copper anode. As the casting wheel rotated, each of the molds supported thereon progressively advanced from a filling station wherein molten copper was charged to the molds, to an anode discharge station where the anodes, which had cooled and solidified during their travel between the filling station and the discharge station, where removed from the molds. The empty molds then moved past a mold wash station wherein a slurry of silica in water was applied as a coating to the interior surfaces of the mold. The temperature of the molds during the application of the silica slurry generally was between about 300F. and 1,000F., and the heat content of the molds rapidly vaporized the water content of the slurry coating, leaving only a coating of silica on the surfaces of the mold. The molds were then returned to the filling station.

This casting cycle had been operated commercially for several years using a slurry comprising approximately 500 pounds of silica to 500 gallons of water. The silica used had a particle size capable of passing through a 200 mesh screen. The temperature of the silica solution as it was applied to the molds was approximately that of the ambient atmosphere, i.e., between about 50and about 100F. Experience with this process indicated that small cracks developed in the molds after about one week of use, and the small cracks would rapidly increase in size to where the mold had to be discarded.

In the comparison test, all of the molds on the casting wheel, with the exception of one, were replaced with new molds. One old mold, which had developed one small crack, was left in place on the casting wheel. The procedure used in casting anodes with the new molds was exactly as given hereinabove with the single exception that the silica slurry was heated to a temperature about 150and 200F. prior to its being applied to the surface of the empty molds. Following a two months period in which these molds were continuously used in casting copper anodes, not a single crack developed in any of the new molds which had been installed on the casting wheel. The one old mold, which has a small crack therein at the start of the two months test, still had only one crack therein, and that one crack was of the same size that it had been at the beginning of the two months test.

Whereas, there is here described a certain preferred procedure which is presently regarded as the best mode of carrying out the invention, it should be understood that various changes may be made and other procedures adopted without departing from the disclosed inventive concepts particularly pointed out and claimed hereinafter.

What we claim is:

1. In the casting of copper anodes wherein copper molds are successfully filled with molten copper and the solidified anodes are successively removed therefrom on a cyclic basis, and coatings of a release material are applied as a slurry thereof in a liquid medium to the internal surfaces of the respective molds prior to the introduction of the molten copper thereinto, the improvement wherein the slurry is heated and applied to the interior surfaces of said molds at a temperature of from about 150 to about 200F.

2. A method in accordance with claim 1, wherein the liquid medium is water.

3. A method in accordance with claim 2, wherein the release agent is silica, and the temperature of the mold during the application of the release agent thereto is within the range of about 200 to about 1,000F.

Claims

1. IN THE CASTING OF COPPER ANODES WHEREIN COPPER MOLDS ARE SUCCESSFULLY FILLED WITH MOLTEN COPPER AND THE SOLIDIFIED ANODES ARE SUCCESSIVELY REMOVED THEREFROM ON A CYCLIC BASIS, AND COATINGS OF A RELEASE MATERIAL ARE APPLIED AS A SLURRY THEREOF IN A LIQUID MEDIUM TO THE INTERNAL SURFACES OF THE RESPECTIVE MOLDS PRIOR TO THE INTRODUCTION OF THE MOLTEN COPPER THEREINTO, THE IMPROVEMENT WHEREIN THE SLURRY IS HEATED AND APPLIED TO THE INTERIOR SURFACES OF SAID MOLDS AT A TEMPERATURE OF FROM ABOUT 150* TO ABOUT 200*F.

2. A method in accordance with claim 1, wherein the liquid medium is water.

3. A method in accordance with claim 2, wherein the release agent is silica, and the temperature of the mold during the application of the release agent thereto is within the range of about 200* to about 1,000*F.

4. A method in accordance with claim 1, wherein the release agent is a member selected from the group consisting of silica, bone ash, alumina, clay, ganister, lime, and graphite.