US2042625A - Method of producing lead alloys - Google Patents

Description

Patented June 2, 1936 UNITED STATES PATENT OFFICE 2,042,625 METHOD OF PRODUCING LEAD ALLOYS No Drawing. Application October 28, 1933,

Serial No. 695,665

11 Claims.

This invention relates to alloys and has for an object the provision of an improved method of making lead base alloys. More particularly, the invention contemplates the provision of an improved method of producing alloys comprising lead and copper.

Lead base alloys containing copper possess desirable properties and characteristics not possessed by similar substantially copper-free products. Thus, for example, an alloy consisting essentially of lead and an amount of copper up to about .06% of the weight of the lead possesses higher tensile and compression strength, has a finer crystal size and is more resistant to certain types of corrosion than ordinary copper-free refined lead, while at the same time, it retains the softness, workability, and other properties characteristic of refined lead. The following table shows the relative tensile strength of such an alloy:

Ult. tensile Type of lead strength Lbs. per sq. in.

Very pure lead 1600 to 1650 Desilvered refined lead 1750 to 1835 Copper bearing lead 2300 to 2370 This type of alloy is particularly desirable for use in lead cable sheathing and for chemical plant construction.

Copper is almost always 'present in unrefined lead bullion, but it is frequently removed in the refining process. In the refining of lead bullion by the Parkes process, silver-is removed therefrom by the addition of metallic zinc. Copper, if present in the lead bullion, is also removed by the zinc in this operation. Therefore, all lead bullion which carries values in silver and which is refined by the Parkes process produces a refined lead which is practically free from copper. On the other hand, lead produced from silverfree bullion which is not desilverized usually retains from .04 to .06% copper.

The amount of copper which is required to impart the above-mentioned beneficial properties to lead is very small and corresponds to the eutectic or solubility of copper in refined lead at its freezing point which, for all practical purposes, is .06% Cu. Concentrations of copper in excess of this amount usually add nothing to the advantages obtained at the eutectic composition. Also, there is no advantage derived from the addition of copper to lead unless the copper is uniformly distributed throughout the mass of lead.

It is difiicult to obtain high-grade alloys comprising copper and lead by mixing together and heating metallic copper and metallic lead because 5 of the high melting point of copper and the low solubility of copper in lead. The alloys formed by this method are invariably spotty, of uncertain compositions, and the properties of such alloys are, therefore, necessarily doubtful.

The present invention provides a method by means of which alloys comprising copper and lead in which the copper is uniformly distributed may be produced at reasonably low temperatures. The method of the invention involves the treat- 15 nient of a molten bath containing metallic lead and a copper compound under such conditions as to effect reduction of the copper compound and dispersion of the resulting metallic copper throughout the molten bath.

According to a. preferred method of the invention, copper is caused to chemically precipitate in a molten bath containing metallic lead by contacting the material of the bath with a reagent composed of chemical equivalent amounts 25 of copper and chlorine. In its simplest form, the reagent consists of cuprous or cupric chloride, but, in its commercial application, the reagent may comprise a mixture of one or more other salts of copper with one or more other metal chlorides such, for example, as alkali and alkaline earth metal chlorides in which the copper salts and chlorides are present in such proportions as to provide chemically equivalent amounts of copper and chlorine. A suitable reagent mixture may comprise, for example, equivalent amounts of copper sulphate, CUSO4'5H2O and sodium chloride, NaCl, in. which case the two react to form the active ingredient CuC12-2H2O and the inactive ingredient NazSO4. If molten metallic lead is allowed to come in contact with any of such reagents at about 900 F. the lead reacts ultimately with copper chloride to form lead chloride and metallic copper according to the following equation:

The following examples of methods of the invention are given for purposes of illustration and in order to provide a more complete disclosure of the invention, and it is to be understood that the invention is not to be limited by the specific procedures herein set forth.

Following is a description of a simple procedure for producing an alloy containing copper and lead in accordance with the method of the invention:

Lead is melted down in an iron kettle and the temperature adjusted to about 700 F. To the bath of lead, a calculated quantity of cuprous chloride, CuzCl-z, equivalent to 1.2 pounds copper per ton of lead is added. The temperature is gradually raised, the cuprous chloride melting to a fluid liquid at about 800 F.; and at 850 F., a reaction sets up between the lead and the CuzClz according to the following equation:

The bath is mixed with a mechanical mixer of suitable design to aid in the reaction, the whole operation requiring only a few minutes to, complete. With proper mixing at the correct temperature the reaction is quantitative, the chloride slag analyzing not more than a few hundredths of one percent of copper. The lead chloride produced by this reaction floats to the top of the bath and as the kettle is allowed to cool to 750 this slag freezes to a crust and is removed with the usual type of skimmer leaving a. clean bath of copper bearing lead. The lead may be molded out into suitable pigs and marketed,

The foregoing describes the preferred method of the invention in its simplest form. For practical purposes, however, it has been found to be desirable to modify the above-described operation with respect to the nature of the reagent employed, as, for example, by substituting the more common and less expensive salt, cupric chloride, C11C12.2H2O. Otherwise, the procedure followed is substantially the same as that described, and the resultant products are identical. To the bath of molten lead at 700 F., a calculated quantity of this reagent equivalent to 1.2 pounds of copper per ton of lead is added. In this case the reaction proceeds as follows:

A further modification of the procedure, and one which is preferred for economic reasons, involves the use of a reagent comprising a mixture of chemical equivalent proportions of hydrated cupric sulphate, CllSO4.5H2O and sodium chloride, NaCl. A suitable reagent may be prepared by mechanically mixing together the finely pulverized salts in the proper proportions. This reagent is added to the bath of metal in amount equivalent to 1.2 pounds of copper per ton of metal to be treated. The reaction takes place according to the following equations:

The procedure followed in carrying out this modified method may be substantially the same as when a copper chloride is employed. Owing to the presence of the inactive constituent, NazSOr, the melting point of the mixture is somewhat increased and it has been found necessary to heat the bath to about 975 F. to insure the complete liquefaction of the reagent and terminate the reaction. The reagent employed in this method is preferred because of its relative cheapness. The copper sulphate represents a cheaper form which can be used, for example, as a reagent for dezincing desilverized lead.

In the specific examples given above, the

amount of copper has been specified as 1.2 pounds per ton of lead to be treated which is equivalent to the eutectic of copper in lead of .06% Cu. However, it is to be understood that the quantity of copper introduced in this manner is not him ited to any specific amount, it may be greater or less than this quantity depending on the results desired.

The method of the invention may be employed for incorporating copper in any suitable leadbearing product. Thus, the method of the invention may be employed for incorporating copper in lead refined by the Parkes processor any other process, lead base alloys, lead recovered from scrap materials, such, for example, as scrap cable sheathing, scrap battery plate metal, scrap Babbitt or type metals, or any other form of lead regardless of its source. Furthermore, it is to be understood that the method of the invention as described herein and illustrated in the foregoing specific examples is not limited to the incorporation of copper in refined lead only. The reagent may be added to the lead at any point in the refining operation subsequent to desilverization, if desilverization is necessary, the difference being that where metals are present which are above lead in the electromotive series such as zinc or tin, chlorides of these metals will form in preference to lead. For example, if the copper chloride is added to desilverized unrefined lead which contains residual zinc, the product formed will be zinc chloride rather than lead chloride which forms when relatively pure refined lead is used. The copper is uniformly precipitated and is retained by the lead throughout any subsequent operation. The chloride slag produced by this treatment is recovered, zinc and lead chlorides finding many uses in the trades.

I claim:

1. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of a copper salt other than a chloride and a metal chloride capable of reacting with the copper salt to form a copper chloride.

2. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of a copper salt other than a chloride and a chloride of an alkali metal.

3. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of a copper salt other than a chloride and a chloride of an alkaline earth metal.

4. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of copper sulphate and a metal chloride capable of reacting with copper sulphate to form a copper chloride.

5. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of copper sulphate and an alkali metal chloride.

6. The method of forming an alloy comprising 7 copper and lead which comprises subjecting a molten bath containing metallic lead to the action of copper sulphate and an alkaline earth metal chloride.

7. The method of forming an alloy comprising copper and lead which comprises subjecting a molten bath containing metallic lead to the action of copper sulphate and sodium chloride.

8. The method of forming an alloy comprising copper and lead which comprises adding copper chloride to a molten bath of metallic lead at a temperature of about 700 F., agitating the bath to mix the lead and copper chloride, and heating the mixture to a temperature of about 850 F.

9. The method of forming an alloy comprising copper and lead which comprises adding a reagent comprising a mixture of copper sulphate and sodium chloride to a molten bath of metallic lead at a temperature of about 700 F. agitating the bath to mix the lead and the reagent, and

heating the mixture to a temperature of about.

10. The method of forming an alloy comprisingcopper and lead which comprises forming a mixture comprising metallic lead, copper sulphate and sodium chloride, heating the mixture to a tempreature of about 975 F., thereby to efiect the production of lead chloride and a molten metal bath having elemental copper dispersed therein, cooling the bath to eflect the solidification of lead chloride-bearing slag on the surface of the molten metal, and pouring the molten metal into suitable molds.

11. The method of forming an alloy comprising copper and lead which comprises forming a mixture comprising metallic lead, copper sulphate and sodium chloride, heating the mixture to a temperature of about 975 F., thereby to effect the production of lead chloride and a molten metal bath having elemental copper dispersed therein, cooling the bath to eflect the solidification of lead chloride-bearing slag on the surface of the molten metal, and pouring the molten metal, into suitable molds, the amount of copper sulphate employed being equivalent to about 1.2 pounds of copper per ton of metallic lead in the mixture, and the amount of sodium chloride employed being at least chemically equivalent to the copper sulphate employed.

FERNANDO B. PE'I'ERMAN.