US1808793A - Bearing metal - Google Patents

Description

Patented June 9, 1931 I UNITED STATES PATENT OFFICE ROBERT-JAY snormam, or cnroneo, rumors; assrenon re s. a r. METAL com:- rm, or CHICAGO, rLLrNors, A. oonrom'rron or ILLINOIS BEARING mural.

80 Drawing.

The invention relates to metallic compositions suitable for bearings, bushings, or other machine elements or parts or articles requiring anti-friction properties or for which a hardened or toughened lead is a proper material.

The rincipal object of the invention is to provide a lead alloy of this type of suitable hardness, toughness and rigidity for the purposes indicated, which will also have a low coeflicient of friction, from which the hardening agents will not drosswhen the alloy is melted, for example in casting, and which will effectively resist corrosion when exposed to moisture.

A further object is to provide a metallic composition of this type which can be produced conveniently and at low cost. The metallic composition is composed principally of lead to which is added small amounts of other substances, the function of which is to give the lead hardness, toughness, and rigidity; The substances, which may. be termed, because of the relatively large quantities used, primary hardeners are tin and calcium. The addition of thesesubstances increases the hardness and toughness of the lead up to a certain point. After a certain amount of calcium and tin have been added to the lead further additions do not result in proportionate increase of hardness. In the case of calcium, particularly, the increase above a certain amount, also gives an the use of tin in excessive amount above this percentage is postively a detriment and involves needless expense, tin being more cost ly than lead. H wever the detrimental ef- Application filed August 2, 1928. Serial No. 297,119.

feet of some excess may be slight, so that it 1s not possible to definitely fix an upper limit for the tin ingredient, to exclude permissible, through undesirable excesses. The calclum goes into solid solution, apparently, with, the lead to the extent of about 0.3% and gives a hardening efi'ect. Above this amount the calcium reacts with the lead to form lead-calcium crystals, when the melt freezes, and these crystals, which are evenly distributed through the mass because they are of substantially the same specific gravity as the lead, give the alloy wearing qualit and apparently add some-what to the bar ness. If the calcium is used in excess of 1.0% the metal compound, in its melted state, is viscous and when in the solid state is subject to excessivecorrosion in the presence of moisture. I have discovered, further, that if very small amounts of what may be termed secondary hardeners, namely, magnesium, potassium or lithium are incorporated in the lead with the primary hard-- ening agents tin and calcium the hardness and toughness ofthe compound is increased to quite a surprising extent, without, however, makin the alloy either undesirably brittle'or su ject to drossing or corrosion. These secondary hardeners are to be used in amounts not substantially in excess of their capacities to go into solid solution with the lead. Any excess will react with the lead forming crystals which give rise to inter-crystalline brittleness in the alloy and corrosion along the crystal'faces. The practical upper limit for these substances are as given below. Mercury may also be used as a hardening agent, particularly when the secondary hardener is magnesium or potassium, and in'any of these compositions the mercury is a desirable element because it decreases the coefficient of friction and gives the surface of the metal, when machined, as

in the case-of a bearing, a highly polished finish which will remain smooth and shiny for a long time. The alloy also comprises aluminum. The function of the aluminum is to prevent the calcium, magnesium, potassium and lithium from drossing out while the alloy is being compounded also in remelting the ingots for casting for example.

The metallic composition consists of the substances above named in proportions, by weight, substantially as follows:

Tin Calci m Mercury (optional) singly as indicated or two of them may be em-. ployed or all three. Where two or three of the secondary hardeners are employed they may Preferable amount 1.0% Preferable amount 0.5%

Preferable amount 0.25%

Aluminum 0.0 to 0.1% Preferable amount 0.05%; Magnesium 0.05% to 0.1% Preferable amount 0.075% and/or Potassium 0.02% to 0.06% Preferable amount 0.04%; and/ or Lithium 0.02% to 0.06% Preferable amount 0.04%;

Lead to make up 100%.

hereinafter described. They all apparently -form a solid solution with the lead, to the extent noted, except possibly the aluminum.

The amount of aluminum might be increased over that indicated but this would serve no useful purpose and, in fact, amounts larger than those indicated are detrimental in that they make the metal porous. Y

The substances termed secondary hardeners, that is the magnesium, potassium or lithium, appear to heequivalents in some re spects. However magnesium is referred as it appears to give a more sta le alloy which can be melted for example in open babbit kettles without excessive drossing or appreciable loss of hardness.

The mercury also has the same effect, as a hardener, whether magnesium or potassium or lithium be used but the increase in hardness which it produces when the .last named substances are used is not the same in the case of each of such substances.

To illustrate this, a lead alloy compounded in accordance with the preferred proportions,'as given in the above table, usin magnesium as a secondary hardener will ave a hardness of approximately 16 Brinnell if mercu is not used and a. hardness of 24 Brinnel when the mercury ingredient is included. An alloy of the same composition exce t usin potassum instead of magnesium will ave a ardness of 20 Brinnell without mercury and 26 Brinnell with mercury. Practically it is very difiicult to kee more than 0.25% of mercury in the melt ecause of the tendency of this metal to volatilize at the melting temperatures of the other metals. Its presence 'in excess of the upper limit indicated is, a detriment, for reasons other than expense, because it reduces the meltin point of the alloy. Apparently 0.25% o mercurywill remain in t e alloy regardless vof temperature and time of heating.

when the secondary hardener is magnesium or potassium than when it is lithium. The

lidified and t be used in amounts which in the aggregate are considerably larger than the upper'limit.

of any of'the secondary hardeners used singly. For example, one may add to the lead magnesium up to approximately 0.1 per cent and potassium and also lithium each up to 0.06per cent, and thereby obtain increased hardness, whereas if any single .one of the secondary hardeners be used, in an amount corresponding to the aggregate amount in which two or more of the substances are usable the alloy will be unstable and subject to corrosion and drossing. Some increase of the amount of the secondary hardener, magnesium for example, when used alone, over the preferred upper limit as given above is possible although the tendency of the metal to corrosion will be increased somewhat.

It has been-proposed to use lithium, but in relativel large quantities, as a hardener for lead. is substance, however, is very'expensive and somewhat difiicult to obtain. In the composition above described the lithium is used in such small quantities that the alcost. The same may be said of the magnesium and potassium pens1ve substances. v

The alloy is compounded preferablym renheit under a covering of molten calcium chloride. The inn andaluminum are intro- -l0y can be manufactured at a very reasonable whichare also relatively ex:

duced into 'the lead through the calcium 1 chloride covering, either .as metallic tin and aluminum or, which is preferable asa mat ter-of convenience, The ma esium is next introduced into the lead in tile same'manner, assuming that this substance is used as a secondary hardener,-

and thereafter the calcium. The introduction of the calcium into the lead after the other ingredientsis a matter of some importance in order to prevent foaming of the calcium chloride coverin which will occur if- .st or if all of the be-;

the calcium is'put in forementioned ingredients are introduced into the lead at one time. 1 The lead is new allowed to cool down to a temperature of about 6009 to 700 Fahrenheit; or, if desired, the lead with its contents of tin, aluminum,.caldam and maesium may be completely so an .remelted to a temperature as a tin-aluminum alloy.

which will be at the temperature of about 1000 Fahrenheit; If mercury is used, or if the secondary hardener be lithium or p0,- tassium these substances, or whichever of them are used, are introduced intothe lead while the latter is in a molten state but at the relatively low temperature of 600 to 700 Fahrenheit. At higher temperatures these substances will be volatilized. When lithium or potassium is added it is best to throw some pieces of rosin in the melt and cover the crucible. The rosin burns and drives the air out of the melt and the fumes, if retained in the crucible, prevent the air from coming in contact with the metal. The lithium or potassium should be introduced into the lead while this condition prevails.

One of the important advantages of this form of lead alloy is that it is uniform throughout. There is nosegregation as between the upper and lower portions of the in ot. It can be manufactured at low cost. It is very stable, that is it does not readily corrode when exposed to moist atmosphere, nor will the hardening agents dross out to any extent either during the compounding or later if the alloy is melted for casting.

The pro ortion as between the ingredients, as given a ove, do not necessarily represent with accuracy the proportions of the substances actually introduced into the molten lead. There Wlll be a certain loss due to oxidation and volatilization. This loss willbe greater or less according to the care taken in making the compound. Where the method above described is followed and reasonable precautions are taken the figures in the above table representing the quantities of alloy in substances in the finished composition will very closely represent the guantities introduced into the lead. These res, however,

can only be approximate, an in the present I case are arrived at by estimating the losses during compounding and subtracting such estimated losses from the amounts of the ingredients used.

I do not claim herein the method described, as such method is claimed in a copending a plication, filed October 24, 1930, Serial 0. 491,081 as a continuation in part of this 'application. i

I claim:

1. Metallic compound consisting ofthe following substances in proportions by weight approximately as follows: calcium 0.3% to 1.0%; tin 0.5% to 2.0%; mercury 0.1% to 0.5%; aluminum 0.02% to 0.1%; and metal from the group consisting of magnesium, potassium and lithium 0.02% to 0.22%; together with lead to make up 100%.

2.. Metallic compound consisting of the following substances in proportions by.

weight substantially as follows: calcium 0.5%; tin 1.0%; mercury 0.25%; aluminum 0.05%; and metal from the grou consistmg7 of magnesium, potassium an lithium, 0.05%, 0.04% and 0.04% respectively; to-

gether with lead to make up 100%.

3. Metallic compound containin the following substances in TLproportions y weight approximately as fol ows: calcium 0.3% to 1.0%; tin,0.5% to 2.0%; aluminum 0.02% to 0.1%; and metals from "the group consisting of magnesium, potassium, and lithium 0.02% and 0.22%; together with lead to makeu 100%.

4. Meta lie compound containin the following substances in proportions y weight substantially as follows: calcium 0.5%; tin 1.0%; aluminum 0.05%; and metal from the grou consisting of magnesium, potassium and ithium 0.0 5%, 0.04% and 0.04% respectively together with lead to make up 100%.

5. Metallic compound consisting of the following substances in proportions by weight approximately as follows: tin 0.5%

following substances in proportions by weight approximately as follows: tin 1.0%; calcium 0.5%; mercury 0.25%; magnesium 0.075%; aluminum 0.05%; and lead to make p ROBER T JAY SHOEMAKER.