US2089939A - Alloy - Google Patents

Description

Patented Aug. 17, 1937 Y "UNITED STATES PATENT OFFICE ALLOY Jesse 0. Bctterton, Metuchen,

and Albert J.

Phillips, ,Plainfield, N. J.-, assiznors to American smelting and Refining Company, New

York, N. Y., a corporation of New Jersey No Drawinz. Application my 2, 1930,

v Serial No. 77,614

.2 Claims. (01.- 75-166) rather necessary evil in many forms of com-v merciaL leads, in view of the presence of such element in the raw materials from which the lead is derived. gLead ores from many localities con- '1 tai'n substantial amounts of bismuth which is carried on through the reduction of the ores and is present in varying amounts in the commercial forms of lead which areproduced from-such sources. s, e

When present in commercial lead in 'the amounts usually associated with the lead, it is generally recognized that the presence-oi this bismuthadversely influences certain or the properties of the lead with particular reierence 0 to" its rate of corrosion toward sulphuric acid, and the reduction in creep strength of the lead. I Because of these properties, lead containing substantial amounts of. bismuth, even as low as in, the neighborhood of 10.1% has been accepted as being unsuitable for purposes where high resistance to sulphuric acid corrosion, as, for example, in the manufacture of the lead chambers customarily used in the production of. sulphuric acid, and o in the production of 'cablesheaths' where a hi h creep resistance is desirable.

In view of these facts, it has become the practice to treat such leads witliuitable debismuthizing agents for-the purpose of eliminating the bismuth content, thereby removing the source of 5 the objectionable'properties above referred to, it

for many years that a bisin which the having been accepted ninth-free leadecontaining copper copper content ranges-from 0.04 to 0.08% is the standard acid corrosion-resisting lead alloy.

It has been discovered that the corrosion re-' sistance of this alloyis due to the fact that the lead becomes coa ed with a protective layer of basic lead sulphate when exposed to sulphuric acid, which coating prevents iurthercontact be- 45 tween the lead and the sulphuric acid. I

.This coating will form, of course, regardless of the presence or absence of bismuth in the lead being exposed; but it is believed that where the bismuth is present insubstantial amounts, for

.50 instance around 0.1% and over, the reduction in the creep resistance of the lead will cause a ing, producing breaks in the same, so that the acid may continuously gain access to fresh metal 65 sothat the corrosion will proceed notwithstanding the presence copper alloyed with present invention,

' continuous deformation of this protective coator the besic lead sulphate referred to above. In the case of the bismuth free lead-copper alloys mentioned above, therev is high creep resistance, with consequent elimination of any appreciable deformation of this protective coating.

In accordance with the present invention, there is produced an improved corrosion resisting lead alloy, which exhibits substantially improved corrosion-resisting properties over the usual lead alloy' compositions employed for sulphuric acid work. p

The present improved composition is based upon the discovery that the low creep resistance manl-' tested by bismuth-containing leads is due not to bismuth alone, but to the presence in the lead of other constituents also present as the impurities-therein, which act in a cumulative manner to decrease the, resistance. to creep and to corrosion.

It has been the presence of silver, which is a very common contaminant of lead, very substantially reduces the creep resistance of the lead, and also increases the corrosion rate of the lead in sul- 'phuric acid.

Other common constituents irequently-associated with lead which 'act in a similar manner are zinc, antimony, tin and arsenic. v

In connection with the present invention, it has been discovered that when these common contaminantsare eliminated from the lead, and the lead in the proportions indicated; bismuth vin controlled amounts is actually helpful in the matter oi corrosion resistance, whereas it does not adversely affect the creep properties of the alloy, v

It has ,been' mum, 'in connection with the that the presence 01 amounts of bismuth, but'not exceeding 0.0225% demonstrated, for example, that actually increases the corrosion resistance of the alloy because in the presence of such-amounts oi bismuth there is formed a protective-coating oi basic lead sulphate on the lead, which coating is very hard and dense, having ceramic character- It is observed that such a coating is formed between bismuth limits oi 0.005% to 0,0225%, and with a copper content of from' 0.04% to 0.08%. Above the above-specified maximum, bismuth is found to be definitely hurtful to istics.

I corrosion, as evidenced, among other facts, by

the lowering of the flash point of the alloy.

The following tables show the specifications and physical properties of the improved lead of the present invention with'other grades of com- 50 Properties which as Grade I corroding refers'to" thegrade of lead which is usually employed forthe production of lead pigments, such as white lead Grade 5 II chemical refers to the grade of lead com-1 Grade III common .is the usual commercial lead employed throughout the arts for the production of pipes, usages for lead.

solder, and the more common- 2,089,989 menial leads. In the tables, the lead indicated It is believed that the substantially complete elimination of all impurities from the lead which detract from the creep resistance properties of lead, particularly the silver being removed from the lead to asubstantiallycomplete elimination, '5

produced in conjunction with'the copper content vof the alloy, t e high resistancefto creep, which eflect is in no way oifset by the controlled quantities of bismuth that are present in the alloy, so that this from the standpoint of lowered creep or lowered flash point; but additional bismuth over the Improved acid A. B. T. M. speeiiications 10 resisting i ead I Grade I oor- Grade II Gradem "PP roding I chemical common Silver 0.002%max. 6.001% max. q gg 0.002%:m.

Ooppea. I .0i-.08% .0015% max. :3 .0025%max. Copper silver 0026 a max. it? y tin $2 113 mon Arsenic, antimony and tin. o max. .015 max. Zinc .00157 max. .001 max. m. I 0 max. .0015 a max. 0 ml!- .05% max. ,005? max. 16% max.

f Physical pr perties Tensile strength lbs/sq. in--- 1700 2300 1700 po tlbs.pers 9 m. 000 1050 coo Elongation hrs in BB 50 50 40 50 35 o t. @21 0 3535561 ,5. at 0%.; 0.2 see to B i a 4 sile load in inches per inch per year. ma

'In the above. tests, the tensile determinations maximum i fl h r n dv y ffects both 40 wereconducted at a temperature of 25 C. and the p re th and the flash po n as has 40 .with a speed of .05 inch per inch per minute;

The Brinell hardness values were determined by using a 10 mm. ball, with 100 kgm. loads at 30 seconds test periodat 23 ('3. plus-orminus five degrees, and are based onv data obtained over a' specimens were in three year test period. The the "as rolled" condition.

The present improved alloy possesses the fol lowing improved one-fifth that of chemical lead, and by slightly more than one- The tenth that of grade I corroding lead. improved alloy is characterized by the following. noteworthy properties: (1) .Very high creep 60 strength; (2) Exceptionally high resistance to acid corrosion: (3) -Ciean and free. flowing, adaptable to the-sound, castings in slab mold and cylinder necessary'to the proper productionof rolled-sheet and extruded pipe, free from foreign inclusions, lending itself to such melting operations where it is required that drossingbe minimized; (4) Constant uniformity, lending itself to be worked with" minimum variation of pressure on a die-block or roll-neck intojaccu-r rate pipe and sheet; (5) Adaptable in sheet or v pipe to the requirements of lead burners; (6) Be ing an idealalloying basetowhichfabricators may add antimony, or other elements which conditions of use indicate it to bewise to incorporate I 75 for given conditions and purposes.

'- corrosion exhibited by the i of high density of the improved.

been indicated abov V The extremely high resistance to sulphuric acid present alloy may be ,attributedto the fact that there is produced on the alloy when in contact'with sulphuric acid the hard, dense, extremely adherent protective coat-' ing which has been'referred-to above; and it is found that this. coating, in the case of the present improved alloy, may be separatedgfrom the. alloy only with" a substantial amount of'difllculty, and that this coating is substantially non-porous and impervious, so that a stable protective sheath and of a higher degree of adheren c'e is produced on the alloy; and this coating is-not subject to deformation in view of the fact that the alloy is so highly resistant to creep. Comparative testsrega'rding the formation of this protective coating show by way ofillustra-L tive example that the present alloy with the upper limits of bismuth tolerance will have produced upon it 0132 gram of this protective coating per square inch of surface, whereas the chem ical lead referred to above, with a bismuth 'content of 0.004%, and contain copper between 0.04% and 0.08%, will produce, under'the sameconditionaonl 0.005 gram per square inch of surface of the Dr tective coating. It is' not know defln t ly towhat this is attributable, but the fact so remains as indicated, it. being thought that the presence of the bismuth inthe. indicated 6 porous character thereof.

' If the lead used should bismuth free. or contain bismuth below the herein-specified mini- 7 bismuth content as specified herein 10 can be tolerated without any disadvantageeither mum limit of 0.005%, the present improved properties may be secured by incorporating bismuth as well as copper into the lead. base, until the herein-specified composition is reached. Except for the bismuth and copper as herein'specified,

moved to within harmless limits and containing 15 from 0.04% to 0.08% copper and from 0.005% to 0.0225% of bismuth.

2. A lead base alloy containing 0.04 to 0.08% copper, 0.005 to 0.0225% bismuth, the balance being fully refined lead in which the silver content does not exceed 0.002% maximum. and having the commonly occurring corrosion producing impurities removed to within harmless limits.

v 3. A lead base alloy containing0.04 to 0.08%

copper. 0.005 to 0.0225% bismuth, the balance being fully refined lead in which the aggregate of contaminating impurities does not exceed substantially 0.008% as the maximum.

JESSE o. BE'I'IERTON. mam J. PHILLIPS.