US2142835A - Lead alloys - Google Patents

Description

Patented Jan. 3, 1939 UNITED STATES PATENT OFFICE LEAD ALLOYS Jesse 0. Better-ton, Metuchen, Albert J. Phillips, Plainfield, and Albert A. Smith, Jr., Metuchen, N. L, assignors to American smelting and Refining Company,-New York, N. Y., a corporation of New Jersey No Drawing. Application March 19, 1937,

Serial No. 131,860

Claims. I (01. 75-167) Broadly speaking, the invention may be saidto provide ternary alloys of lead, calcium and magnesium possessing certain highly beneficial physical properties, and alloys comprising the base-alloy of lead, calcium and magnesium with at least one additional alloying constituent-imparting further desired properties to the alloy while at the same time retainingpr enhancing the beneficial physical properties possessed by the base alloy itself.

More specifically, the invention provides alloys of lead, calcium and magnesium in which the combined calcium and magnesium content does .0 ,not substantially exceed 0.4% of the alloy with the magnesium content being within the approximate limits of one'quarter to three times the calcium content. While 0.03% to 0.05% each of calcium and magnesium is preferred, compositions 12:5 containing magnesium and calcium within the limits of 0.01% to 0.3% and 0.01% to 0.1%, respectively, may be employed. 2

Among metals which may be added to the leadmagnesium-calcium composition are cadmium,

copper, mercury and tin, all of which modify the behavior of the alloy under corrosive influences Without adversely affecting the fundamental physical nature of the ternary alloy. In addition, copper stiifens the alloy moderately and accelerates its aging; mercury improves its lustre and to a moderate extent its casting properties; tin slightly improves its fluidity and casting properties. The amount of modifying or improvement.

metal which may be incorporated should fall within the approximate limits of 0.03%; to 3% with a minimum of about three oriour times the magnesium content.

The superior properties exhibited by the alloys of the invention are best shown by the following data comparing same with several of the conventional alloy compositions available and often recommended for various specific purposes:

Brinell hardness I Lead alloyed With- Material tested 8% Sb .05% Ca Pgg fg' Castings as" thick 12.1 7. 0 5. 2 Above aged 21 days at 30 C, l2. 9 8, 0 13.4 Same heated 2 hours at 100 C 13.4 9. i 15.4 Grid castings 063 thick 11.8 5.0 Above aged 21 days at 30 C 13.8 11.4 14. 8 Same heated 2 hours at C 14.0 12. 5 l5. 4

The above data clearly shows that. the new. magnesium-calcium alloy is readily hardened without elaborate heat treatment to a value equal to or better than that of antimonial lead grid metal, the latter in turn being superior to the cal- 2 cium-lead alloy. Conventional lead cable alloys, containing, e. g., 1% antimony or 2% tin, are too soft to merit comparison.

Tensile strength (Lbs/Sara.)

The superior strength of the rolled lead-magnesium-calcium sheet metal is quite evident from the above data and the high strength values demarkable.

Composition stability In almost any process in which metal is past there is always a certain amount, of material' in veloped' by simply'ag-ing arolled strip, either at 4 room or an elevated temperature, are quite rethe nature of risers, gates, spillage and spoilage which must be returned to the process without special treatment or material loss if reasonably low costs are to be obtained. In the manufacture of storage battery grids the weight of-material that must be remelted commonly approximates the weight of satisfactory grids produced but fortunately ordinary antimonial grid metal can be repeatedly remelted without a very great change in composition. This is illustrated by the following test in which grid metal analyzing 7.83% Sb and 0.222% Sn was tested in a special machine equipped with a revolving paddle which swept the surface of the molten metal (temperature 355 C.) at exactly 100 R. P. M. for 10 minutes. At the end of the test the composition analyzed 7.77% Sb and 0.215% Sn. Applying the same test to a calcium-lead alloy containing initially 047% calcium, the calcium content dropped to .023% which represented a loss of 50% of the vital alloying constituent. However, when the test was applied to a calcium-magnesium-lead alloy of the present invention'which contained 047% Ca and 020% Mg, the calcium and magnesium contents were only very slightly affected-the final metal analyzing 045% Ca and .018% Mg. Similarly, a calcium-magnesium.- lead alloy modified withtin (.05% Ca, .02% Mg, 26% Sn) was remelted and cast twice with no detectable change in composition, while a calcium-lead alloy suflered a decrease in its calcium content from .05% down to .005% with the same treatment. 4

Fatigue properties The following table illustrates the fatigue properties of several typical lead alloys as compared with the magnesium-calcium-lead alloy of the invention modified with tin:

Fatigue strength;

All tests were for 20,000,000reversals on a rotating beam machine at 2,000 R. P. M.

Creep tests The following creep data were obtained from tests conducted at room temperature for periods of from 1 to 4 years and illustrate the marked superiority of the magnesium-calcium base alloys to all others:

Lead alloyed with- Time to creep 1% gg Dag/a 2% Sn 350 190 1% Sb 175 233 10% Sb- 220 232 0.00% C 240 437 0 13% 0a-. 1,200 578 0.03%'Oa p 290 700 0.045% Ga, 0.03% Mg More than 1,200 732 Corrosion resistance Corrosion resistance of'any series of alloys is very diflicult to evaluate because an alloy that is superior in one particular set of circumstances may be inferior in another. For instance, in

- battery strength sulphuric acid a lead alloy containing .04'% Mg and 05% Ca was found to have excellent corrosion resistance as measured by loss in weight but suffered'from a peculiar penetration of the alloy in about 3 months time when the temperature was raised to 70 C. However, this difliculty was completely avoided by adding 0.25% tin to the alloy with no loss in physical properties. A lead alloy containing 03% Mg, 04% Ca and Sn was found to be equal toregular 8% antimony grid metal in general corrosion resistance and superior to it for battery purposes due to the formers freedom from the evils of sulphation and galvanic action which accompany the use of antimonial lead grid metal. For cable purposes the use of the calcium-magnesium-lead base metal modified with either copper or tin is recommended since certain brands of lead now on the market contain a desirable amount of the fourth metal, e. g., leadcopper alloy containing 0.06% of the latter element. Such leads are generally used for acid exposures. For other specific purposes other additions may be made within the scope of the invention.

From the data herein adduced, it will be readily apparent that the alloys of the'invention possess and exhibit properties which ideally fit them for numerous uses. Accordingly, while their value has been specifically mentioned with reference to grid metal and cable sheathing, it will be understood that they may be successfully utilized in many other fields.

The alloy compositions of the invention may be readily compounded by conventional processes employed by those skilled in the art for producing other lead alloys, as, for example, by simply incorporating the requisite amounts of the alloying constituents in a proper quantity of molten lead without any particular regard to the sequence of their addition. Once compounded, the new alloy compositions can be manufactured into cable sheathing, battery grids and other products by methods well known in the respective arts.

What is claimed is:

1. An alloy consisting of 0.01% to 0.3% magnesium, 0.01% to 0.1% calcium, 0.03% to 3% of a corrosion resistant constituent selected from the group consisting of cadmium, copper, mercury and tin, and the balancelead.

2. An alloy consisting of 0.01% to 0.1% calcium, 0.01% to 0.3% magnesium, cadmium not exceeding 3%, and the balance lead.

3. An alloy consisting of 0.01% to 0.1% calcium, 0.01% to 0.3% magnesium, copper not exceeding 3% and the balance lead.

4. An alloy consisting of 0.01%. to 0.1% calcium, 0.01% to 0.3% magnesium, tin not exceeding 3%, and the balance lead.

' 5. A cable sheath containing about 0.01% to about 0.1% calcium and about 0.01% to about 0.3% magnesium, the balance being substantially all lead, characterized by marked resistance to both fatigue and creep.

JESSE O. BETTERTON. ALBERT J. PHILLIPS. ALBERT A. SMITH, JR.