US1549137A - Alloy of lead and alkaline earth metal - Google Patents

Description

Patented Aug. 11, 1925.

a if" i WALT HER MATHESI'US, OF CHAR-LOTTENBURG, GERMANY.

ALLOY O'F LEAD AND ALKALINE EARTH METAL.

No Drawing. Application filed May 16,

To all whom it may concern:

Be it known that I, WALTHER MATHESIUS, a citizen of the German Republic, residing at Charlottenburg, Germany, have invented certain new and useful Improvements in an Alloy of Lead and Alkaline Earth Metal, for which I have filed application for-pat-' ent in Germany on January 7,192.), of which the following is a specification.

This invention relates to an alloy of lead with metals of the alkaline earths, calcium,

strontium, barium. An alloy of lead with about 3% of calcium, and containing also about l3% of cadmium or bismuth or both, has been described in the German Patent No. 297210. A

Metallographic examination of the alloy in question shows that substantially harder crystals are embedded in uniformdistribution in a homogeneous main mass. On closer examination of the texture, it can be easily shown that these harder crystals are constituted by an alloy of lead and calcium,

. harden the main lead portion ofthe alloy to a certain extent and. to reduce its melting point, moreover, as owing to the addition even of a few per cent of calcium to lead, the melting point of the latter is considerably raised.

A metal of the composition referred to is eminently'suitable, as shownby experience, for use-as metal for liningv bearings inthe same manner in which the so-called tinwhite metals have been exclusively employed. As shown by metallographic examination, even *in good tin-white metals, the structural conditions are exactly the same, only here the harder crystals are uniformly distributed in the softer main mass, are composed of a copper-tin alloy.

In both cases the harder crystals embedded in the softer main mass, form, during the use of the alloys as bearing metals, those ingredients of the alloy which, after a' cer- 1921. Serial N0. 469,959.

tain running-in of the shaft has taken place, form the bearing surface proper.

Exhaustive experiments have now proved that it is possible to obtain alloys which are eminently suitable for use as bearing metals, exclusively from lead with an addition of calcium, strontium, and barium, and without cadmium or bismuth. The metals, strontium and barium, form with lead definite chemical compounds exactly in the same Way as calcium. Met-allographic examination of the texture of such an alloy on a ground surface shows that strontium-lead alloy is exactly similar to calcium-lead alloy in a peritectic structure, whilst'barium-lead compound solidifies with the excess of lead at the same tim to form a eutectic.

The barium-lead compound produces therefore in the alloy chiefly a hardening of the main mass, whilst strontium-lead like calcium-lead, chiefly assists in the formation of harder crystals.

Examination of melting or softening temperatures of such alloys shows, however, that when the alloy solidifies, the three compounds do not completely crystallize out of the same, on the contrary some traces of the said compounds are still left in the alloy in the state of solid solution, for a considerable lowering of the melting or softening temperature takes place when, in addition to calcium which is most easily obtained in large quantities, are also added to the alloy certain quantities of strontium or barium, or preferably, both.

While, the addition of the calcium to the lead increases the melting temperature, the addition of two, '(or still better, all three) of the alkalin earth metal ingredients, produces a lowering of the meltin temperature and increases thefluidity" of t e alloy withe in moderate limits.

On these observations is based the manufacture of a new bearing metal alloy from lead with about 3% calcium or about 1% each of strontium and barium.

It is possible to produce an alloy of such composition having a degree of hardness of 3540 Brinell units, the said alloy having a melting point of 450500 C. and therefore being excellently adapted for use as bearing metal. 7 g

Metallographic tests have shown that, in an alloy of this kind, an extremely uniform distribution of the harder crystals exists,.

which has heretofore only been true of the ,best tin-white metals. In itself, the propoadded to the lead, or if three such metalshave been used, it has been considered necessary to further add other metals to affect the physical roperties of the alloy. It has never before en realized that, by the addition of calcium to the lead, there can be obtained the formation of the hard lead-calcium crystals and that, by the addition of barium and strontium, there results a hardening of the basic mass, and, at the same time, a lowering of the melting point, which is increased considerably by the addition of the calcium. This commercial result which as stated, is reproduced in the metalloaphlc image, can only be obtained when,

t e proportions stated for the additions of the three alkaline-earth metals, (viz., about 3% calcium and about 1% each of strontium and barium), are maintained. The applicant has proven by tests that onlywith these proportions can an alloy be produced having the desired hardness of the basic mass and the uniform distribution of the crystals, together with a satisfactory liquidity.

I claim:

1. A lead alloy containing about 3% of calcium and about 1 to 2% of another alkaline earth metal, such alloy being substantially free from metals other than those stated.

2. An alloy of lead containing about 3% of calcium and about 1% each of strontium and barium, such alloy being substantially free from metals other'than those stated.

3. An alloy of lead containing about 3% of calcium, together with smaller percentages of strontium and barium, such alloy being-substantially free from metals other than those stated.

In testimony whereofI aflix my signature in presence of two witnesses.

VVALTHER MATHESIUS. Witnesses:

O'r'ro SCHNEIDER, GERTRUD DOMKONSKI.