US1916496A - Method of making lead alloys - Google Patents

Description

Patented July 4, 1933 UNITED STATES PATENT OFFICE ROBERT 3". SEOEMAKER, OF CHICAGO, ILLINOIS, ASSIGNOR TO B. & T. METALOOMPANY,

OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS METHOD OI MAKING LEAD ALLOYS Io Drawing.

This invention relates to the production of lead alloys and its object is to provide certain novel procedures in the compounding of such alloys, having in view convenience of .operation, low cost of manufacture, uniformity and homogeneity of the product and particularly the provision of a method whereby small quantities of metals, such as calclum, aluminum, magnesium and the like, whlch are susceptible of oxidation may be introduced into and dissolved in a molten batch of'calcium, tin, mercury, magnesium and aluminum. The mercury is optional, where maximum hardness is not required; and for some purposes, potassium and/or lithium may be used for (part or all of the magneslum with the disa vantage, however, of making the alloy somewhat unstable and subject.

to drossing or corrosion.

The composition of this particular type of alloy, according to the preferred formula is as follows:

Calcium 0.3% to 1.0%Preferred amount 0 5% Tin 0.5% to 2.0%P1eferred amount 1.0% Mercury 0.1g; to 0.5%Preferred amount 0.25% Magnesium 0.0 to 0.1 %Preferred amount 0.07 Aluminum 0.02% to 0.1%Preferred amount 0.05%

Lead to make up 100%.

In the batch, the quantities of the readily oxidizable ingredients, calcium, magnesiumand aluminum, may be somewhat greater than indicated, depending upon the care taken to prevent or limit oxidation in compounding and remelting.

The mercury is optional, but preferred. It is essential if a high degree of "hardness is required, and it acts cumulatively with the calcium, tin and magnesium, in increasing the hardness of the lead. Calcium, mercury, tin and magnesium all act as hardeners of the lead and can be used in an aggregate amount considerablv greater than the amount of any single one of them which it is practical to use.

The allo also comprises .aluminum, the function 0 which is to prevent the calcium and magnesium from drossing out while the alloy is being compounded and also in relting, for example, in melting up the inots for casting. The amount used may vary between the limits as above indicated Application filed October 24, 1930. Serial No. 491,081.

but apparently only about 0.03% remains in the alloy. The rest is carried off by the flux or covering which is employed in compounding the metals as will be described. It is preferable to use, however, more aluminum than actually goes into the compound in order to be certain that a sufficient amount is actually dissolved in the lead.

Alloys containing magnesium and/or lithium and/ or potassium may be represented by the following table:

Calcium 0.3% to 1.0% Preferable amount 0.5% Tin 0.5% to 2.0% Preferable amount 1.0% Mercury 0.1% to 0.5% Preferable amount 0.25% Aluminum 0.02% to 0.05%-Preferab1e amount 0.03%

. Magnesium" 0.05% to 0.1% -Preterab1e amount 0.075% Lithium 0.02% to 0.06%-Preferable amount 0.04% Potassium 0.02% to 0.06%'Preferable amount 0.04%

Lead to make up 100%.

The addition of the lithium and potassium increases the hardness of the alloy where hardness is a desideratum, but at the cost of increased corrosibility.

The hardness of the alloy may vary from 18 to 26 Brinell. It may be raised to 28 Brinell by increase of the calcium, but in this .case the danger of corrosion and drossing is somewhat increased.

The alloy, as above described, or other hardened or toughened lead compound containing easily oxidizable metals, may be made by one of the two following methods:

7 First method.The lead is melted and covered with calcium chloride and the temperature raised to approximately 1600 Fahronheit, to insure the melting of the calcium chloride, which may form a layer of an inch in thickness on the lead. The metals to be compounded with the lead and which are of a readily oxidizable character are introduced into the molten lead through the calcium chloride flux or covering stratum. The tinand aluminum may be so introduced either as separate metals or, (which is preferable as a matter of convenience), the aluminum and the tin, in whole or part, may be introduced as tin-aluminum .alloy. The batch is stirred until the aluminum is completely dissolved in the lead, or so much dissolved as can be held in solution in the lead. The magnesium is next introduced into the batch in the same manner and thereafter the calcium, as metallic calcium. The calcium is introduced into the lead' after the other ingredients above named, in order to prevent foaming of the calcium chloride covering, which is like- 1y to occur if the calcium is put in first or if all of the before mentioned ingredients are introduced into the lead at the same time. The lead is now allowed to cool down to a temperature of about 600 to 700 F. the calcium chloride covering stripped off, at

' about 1000 F., and themercury added, preferably as a mercury tin alloy. Alternatively the crucible may be removed from the furnace and allowed to cool to dull red heat, approximately 1200 to 1300 F. and the mercury tin alloy introduced through the flux. This causes a slight loss of mercury but tends to give a better pouring metal. If lithium and/or potassium are used, they are introduced into the melt with the mercury, that is while the batch is at a relatively low temperature, and rosin is added, which by burning creates fumes which keep the air from coming in contact with the metal.

The supernatant calcium chloride stratum on the lead batch serves to keep the air from contact with the molten metal and thereby prevents or materially lessens oxidation of the lead and other metals. Any metal susceptible to oxidation is likely to be covered with a film of oxide. In passing the pieces of tinaluminum alloy, magnesium and calcium through the calcium chloride stratum, the oxide films on these metals are dissolved by the calcium chloride- The lead will also be, ordinarily, superficially oxidized and in the melting of the lead the oxide will rise to the top of the batch and be dissolved andretained by the calcium chloride stratum. It is only possible to dissolve metals of the t e ind1- cated in the lead if such metals are ree from oxide and the lead itself is. free from oxide. The batch must be stirred and if the calcium chloride were not present to absorb floating oxides of the metals, these oxides would be stirred into the body of the lead. The stratum of molten calcium chloride serves the triple function of cleansing the metals introduced into the lead, absorbing oxide from the lead itself and protecting the melt from oxidation by contact with the air.

Secmid method-The lead is melted and covered with a calcium chloride covering, as described in connection with the first method. The tin and aluminum, preferably as aluminum-tin alloy and metallic magnesium are introduced into the lead through the flux, as in the first method. The calcium is next introduced, not as metallic calcium, but as calcium-lead alloy. The amount of calcium in this case may be slightly less than when metallic calcium is used. The crucible is taken from the furnace and the melt allowed to cool to 600 to 700 F., the flux being stripped off. The mercury is then added as mercury-tin alloy; or one may introduce this ingredient to the flux as in the first method.

One advantage of using calcium-lead alloy instead of metallic calcium is that the alloy is .cheaper. It also contains less impurities into the molten than metallic calcium. Moreover, for a hear ing metal compound, the alloy will be slightly harder, stronger and in machining will cut more smoothly than when metallic calcium is used. There are fewer defects, such as laps, porous spots and shrinkages.

Except for the matter of expense, it is possible to use another halogen salt of calcium,

calcium bromide or calcium iodide in place of calcium chloride for the flux stratum.

This application is a continuation in part of my copending application Serial No. 297,- 119, filed Aug. 2, 1928, for Bearing metal.

I claim:

1. Method of compounding a lead alloy which consists in melting the lead under a. molten covering; introducing the tin, aluminum and magnesium into the lead through said covering and thereafter the calcium; and introducing the mercury, lithium, or potassium into the metallic body while it is at a temperature not substantially in excess of 700 degrees Fahrenheit.

2. Method of compounding a lead alloy which comprises: melting the lead and holding the same at a temperature of approxi mately ,1600 degrees Fahrenheit under 2. molten covering of calcium chloride; introduc ing the tin, aluminum and magnesium into the lead under said covering and thereafter the calcium; allowing the melt to come down to a temperature of approximately 600 degrees to 700 degrees Fahrenheit and introducing the mercury, lithium and potassium body at approximately this temperature.

3. Method of compounding a lead allo which comprises: melting the lead and hol ing the same at a temperature of approximately 1600 de rees Fahrenheit under a moltencovering 0 calcium chloride; introducing the tin, aluminum, and magnesium into the lead under said covering and thereafter the calcium; introducing rosin into the lead when the latter is at a temperature of about 600 to 700 degrees Fahrenheit, and while the rosin is burning introducing lithium or potassium into the molten body.

4. Method of making a lead alloy containing aluminum, magnesium and calcium in which the lead in the molten state is covered by a stratum vof calcium chloride and the aluminum and magnesium first introduced into the lead and thereafter the calcium, all through said calcium chloride stratum.

5. Method of compounding a hardened lead alloy which comprises melting the lead under a covering of calcium chloride, introducing tin, aluminum, magnesium and calcium into the lead through the calcium chloride covering, reducin the temperature of the melt and introduclng mercury into the