US1792146A - Copper alloy and process of treating same - Google Patents

Description

Patented Feb. 10,1931

" "UNITED ISTATVESQ'PATENTQ 01:15a

MICHAEL G; CORSON, or .mcxsoir HEIGHTS,\NEW YORK, ASSIGNOR or animu- 'rwEN rIETHs 'ro GEORGE E. COREY, or 'IBAYSIDE, 'Nnw Yum:

corrEnALLoY AND riioozessor TREATING sum 2N0 Drawing.

This invention relates to a process of treating alloys to impart desirable properties thereto and the product-produced thereby. In particular, the invention relates to a class 5 of alloys consistingprincipally of copper,

tin and zinc, and characte'rized,when treated according to the process hereinafter disclosed, by properties giving them special utility when used in forming lubricated Wearing surfaces, such, for example, as in bearings,

bushings, pump cylinders, gears, etc.-

' The most important feature ofthe coppertin alloys (tin bronzes) that causes them to be especially suitable for use in bearings and in similar situations where resistance to wear is desirable, is their peculiar structure inthe cast state, which is characterized by the presence of a soft ground mass serving as amatrix for, and containing inclusions of, a sec- 0nd constituent,-the delta phase,of considerable hardness, so forming a very desir able complex possessing goodlbearing qualities.

Other alloys used for bearings,'or more specifically for bushings,

zinc brasses composed of a high proportion of copper in alpha phase and a low proportion in beta or delta phase. These alloys, while they are cheaper than the high tin bronzes and can be hot worked ,with ease, since at high temperatures they transform into a uniform beta phase, are less satis actory for bearing purposes than the tin bronzes, either because of insufficient hardness (too great a 5 proportion of the softer alpha phase as com-- pared with the harder beta phase) or because of the distribution of the harder phase in the softer ground mass in such a way as to present an excessive amount thereof at the wearing surface with consequent lack of ability to retain an adequate oil film thereon.

While alpha copper' alloys are workable cold and to a slight extent when hot and the beta alloys are all workable hot,'such alloys as are beta phases, at any temperature below the freezing point, are noteasily workable by pressure or tension either in the hot or cold state. High tin bronzes are not exempt from the are certain high built up of mixtures of the alpha and Application filed February 1e, 1929. Serial no} 340,651.

The bronzes containing between 6 and 18% tin cannot be worked :wli'ile hot. Such alloys containing above 18%, and up t r27%, tin are easily workable while hot, but are relatively expensive, and,

action of this rule.

what is more important, are at room temperatures too brittle. and hard throughout their structure to be useful as structural materials or for bearings and bushings' v I havefound that ternary bronzes can be 'inade to behave much like complex brasses (alpha plus beta) in their ability to be hot to retain a high, strength with-considerable ductility iii the cold state. Also, they possess the property of high tin bronzes of being able toform a well distributed delta tin constituent of high hardness, which makes them good for wear resistance, not only because of V the inherent hardness of such constituent, but also because theuniform distribution of the delta constituent in suitably sized particles throughout the ground mass or matrix im-' parts to a wearing surface prepared therefrom the abilityuto become covered with a substantial film of lubricant, in the regions .occupied by the softer alpha constituent of the matrix. y

,I have also found that such ternary bronzes can be markedly improved by structural changes resultingfrom a process of heat treatment.

. Alloys coming within the present invention can be prepared within the following range The amounts of zinc and tin depend each upon the other. The more zinc the alloy conworked when brought into the beta state and tains, the less tin it may contain. Small" Q amounts of nickel up-to 10%, and preferably around to 3%, may be substituted for an equal amount oficopper, and either a part-of the tin or the zinc may be, replaced by about half its weight of aluminum, aluminum preferably, however, not being added in amounts greatly exceeding 1% of the total. Iron and cobalt in amounts of from-0.3 to2.0% may also form useful but not absolutely necessary additions. These alloys may. also contain small amounts of magnesiumfphosphorus, silicon or manganese-used as deoxidizers. When aluminum is present-amounts of manganese up to-4% may be added with very benelieial results. l

These alloys can be used as cast or be hot 7 worked by forging, rollingfor especially, by m extrusion; but-to improve their structural features and ensuing properties it is nec-' essary to subject them to heat treatment, as follows:

Y. The cast or hot workedpiece is-heated up 15 to orabove a point where the alloy forms a homogeneous beta phase or a mixture of the .two betas possible,,650-800 Cl, according to the composition,-and then quenched or air cooled. This brings it into a hard mar 'gn tensitoidal or acicul'ar form. It is next heat ed to a point above the eutectoidal point, or from 550625 C., and kept at this temperal ture for from one to six hours,*or until the acicular structure is destroyed and the beta 2.. phase divorces from the.'alpha; the first ,coa=

lescing in the form of ,well-rounded dense grainlets 'sufliciently well spaced within the .matrix of alpha to permit the formation of a lubricating film on the surface when in use.

perature preferably to 450525 C., and not below 250 C., and holding such temperature (fior such time as to' allow thejbeta phase to i'ssociate into alpha-plus delta, the latter 55 forming very fineparticles within each original-grainlet of beta, When this condition is reached the structure will have become stabilized. g

WhatI claim is 1. Process of treating alloys containing 4.-18% tin and 35% zinc, with the balance principally, copper, to improve their properties for use as lubricated wearingrsurfaces, comprising heating the alloyto The next step consists in lowering the tem om 650? to 800 (1., and qulckly cooling toproduce a "hard acicular structure, then reheating to alloy to produce a structure characterizedby the presence of beta crystals uniformly distributed throughout 'a matrix. of alpha crystals, followed by slow cooling to produce bilized.

zinc, withthe balance'principally copper, and kchar'acterized' by a. physical structure and d into alpha 1'75 then reso. plusdelta and ,the structure has become stav M article of. manufacture consisting. of an alloy containing 4.918% tin and 10-35% properties such as areproduced when an alloy of like composition is heated to from 050. to 800 quickly cooled, then reheated yto from 550 to 625 C; and held at such temperature for sufficient-time to destroy the acicul'ar structure"? and produce .a stru ture characterized by the presence of a beta ase constituent uniformly distributed through out; a matrix of an alpha phaseconstituent,

and finally gradually cooled at such a rate as to'promote dissociation of the beta form into alpha plus delta. l In testimony whereof, I have signed my. name to' this specification this 11th Feb. ,1929.

MIQHAEL G. coasoN;

day or 1 10 lee.

from 550 to 625 0., maintaining the alloy at such temperature for suflicient time; to destroy the acicularstructure-and produce 50 a structure characterized by the presenceof 4 beta'crystals uniformly distributed throu' h out a matrix of alpha crystals, and finally.

, gradually pooling the alloy at-s'uch a rate as to promote dissociation of the alpha plus delta.

2. Process of ties as lubricated wearing surfaces, compr1sbeta form into treating alloys containing 4-18% tin and 10-35% zinc, yviththe balance principally copper, to improve their proper-.

ing heating the alloy for such time and at such temperature as to bring about a uniform beta stateof the alloy constituents, then quickly cooling to produce a hard aeicular;

structure, then reheating to .a point above the eutectoidal transformation point forthe t CERTIFICATE or connncrrou;

LP a tent No;"1,7 92, l46.' i GrantedfFehru arj lm i931,to I

t. MICHAEL q. CORSDN.

* It is hereby certified that error appears inthe printed specificationf of the above numbered patent requiring correction as follows: .Page -l, strike out the table between lines 85to 89, and in sertinstead ,Tin 41s%- Zinc '10 35% v Copper balance;

and that the said Letters Patent should be read with this correction therein that 7 Q the same may conform to the record of the case in the Patent'office.

. Signed and sealed this 17th day of March, '1931.

v '(Senl) I Acting Commissioner of Pntentg.