Improvements in the Casting and Tempering of Pure Copper.
Year: 1892

page_text: Date of Application, 5th Feb., 1892
Complete Specification Left, 7th Apr., 1892-Accepted, 28th May, 1892
PROVISIONAL SPECIFICATION.
Improvements in the Casting and Tempering of Pure Copper.
I TURNER D. BOTTOME, Electrician, Hoosick, New York U.S.A do hereby
declare the nature of this invention to be as follows:-
This invention relates to an improved method of casting and tempering pure
copper.
It is a well known fact that by the addition of tin, zinc or aluminium to copper in
sufficient quantity will enable good castings to be made therefrom, yet the alloys so
prepared which produce the various well known brasses and bronzes do not retain
the characteristic toughness and fibrous texture of the copper to which property it
owes its value, but instead a brittle and crystalline alloy is usually formed.
Mechanically the various alloys of copper find wide application on account of the
ease with which they can be worked, but for electrical purposes their conductance
is so small that they are wholly unsuitable therefor pure copper must be used in
such cases and recourse is had to drop forgings when such are practicable, it is
obvious that forgings are expensive compared to castings.
The objects of this invention are to produce refined copper castings having all of
the valuable properties of tough fibrous copper of high specific gravity and free
from blow holes or other defects inherent in the ordinary cast copper and forgings
as heretofore produced for industrial purposes. An additional object of this inven-
tion is to "temper" copper castings imparting to them a certain degree of hardness
whereby they may be more readily worked than heretofore possible with ordinary
pure soft copper.
These objects are obtained in the following manner, it being first stated that I
have discovered the lost art of casting tempered copper and this discovery lies in
the fact that very small quantities of metallic sodium introduced into molten
copper has the extraordinary property of eliminating all of the dissolved gases in
the copper and also of imparting to the copper a certain degree of hardness. I
have found that the quantity necessary to exhibit a marked improvement in a
specimen of copper need not exceed one tenth of one per cent. of its weight and
in practice this quantity is usually sufficient; a greater quantity produces consider-
able shrinkage in the copper when it cools with a corresponding degree of hardness
due evidently to impaction of the molecules of the copper.
I have specially named sodium as the metal for producing these properties but
the metals potassium and lithium as well as others of the alkaline groups have this
property to a certain extent, but sodium is the most practical on account of its
cheapness and the ease with which it can be handled. In the actual use of the
metal prefer to make a preliminary alloy containing from one to 10 parts
of copper and one part of sodium, in this way if the special alloy contained 10%
sodium it would only be necessary to add 1% of the alloy to a given quantity of
molten copper to effect the desired result. In melting the copper I prefer to use a
covering or flux composed essentially of about one part sodium carbonate, two parts
of powdered anthracite coal or charcoal and a small quantity of common salt, this
flux melts and floats on the surface of the copper, the requisite amount of sodium
alloy is now put under the surface of the copper and the whole is stirred with a
carbon rod until thorough mixture is had. The copper is then ready to be poured
in the moulds. The proportions of ingredients given in the above mixture are only
approximate, as it is sometimes necessary to alter the proportions according to the
quality of the copper to be operated upon. Very impure copper has to be refined
before the tempering process takes place, and to this end the copper is melted under
a covering of common salt and when perfectly fluid a mixture composed of nitre

page_text: 3 parts and tartar or argols 2 parts is thrown on the surface and the copper
vigorously stirred during the reaction which takes place.
Dated this 25th day January 1892.
TURNER D. BOTTOME.
COMPLETE SPECIFICATION.
Improvements in the Casting and Tempering of Pure Copper.
I TURNER D. BOTTOME of the Town of Hoosick in the State of New York U.S.
Electrician, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
This invention relates to improvements in the casting and tempering of pure
copper and its objects are to produce castings that are free from the usual imper-
fections of ordinary copper castings and also to produce much harder copper than
heretofore obtained directly in ingots or castings.
These objects are obtained by treating pure or ordinary ingot copper while in a
state of fusion, with metallic sodium or a vapor of sodium in the nascent state, the
amount of sodium required is ordinarily about one tenth of one per cent. of the weight
of the copper.
To carry my objects of this invention out in a practical way I have a choice of
two typical methods both of which give good results. In the first method which is
an especially convenient one for treating small quantities of copper (ten pounds or
under) but unsafe when much larger masses are treated on account of violent and
often explosive reaction. The requisites for this method are firstly a graphite
crucible with cover of the same material, a few carbon rods like used for electric
are lamps but with one end drilled with a hole an inch or so deep this hole is filled
with the required amount of pure metallic sodium; the copper to be cast is placed
in the crucible (previously in a good fire and heated up) a quantity of common salt
is then thrown in the crucible on the copper, which, when melted forms a moderately
heavy covering. The heat of the fire is increased and as soon as the copper is
melted a carbon rod charged with sodium is quickly pushed to the bottom of the
crucible and with it the molten copper is thoroughly stirred, the copper is then
ready for casting and it is simply poured with a steady stream into the previously
prepared mould which is prepared in the same manner as for brass castings. A
dry mould gives better results than a green one. When the carbon rod is pushed
into the crucible with its charge it should be provided with a loose shield made
from sheet asbestos which is slipped over the rod and drops down to form a temporary
cover for the crucible thus preventing any globules of copper from spitting out of
the pot. Instead of pure sodium an alloy composed of sodium and copper may be
prepared by taking a quantity of precipitated powdered copper and mixing it with
a quantity of sodium in an iron mortar when the two metals are well ground together
they combine with evolution of heat and form an alloy. This alloy used in the
place of pure sodium in the proper proportions does not cause as violent a reaction
and is therefor safer to use.
The second method and perhaps the best when large quantities of copper are to
be treated is to prepare a mixture of say equal parts of common salt, bicarbonate
of soda and powdered anthracite coal, place some of this in the crucible, then put
in the copper and finally cover the copper with some of the same mixture lastly
cover the pot with its graphite cover, when the copper melts stir it carefully with
preferably a carbon rod for a minute or so then replace the cover a strong yellow
flame shows that metallic sodium is being produced in the nascent state and the
molten copper becomes acted upon. After the sodium vapor has acted for some
minutes and just before its disappearance the copper is ready for casting and it is
treated in very much the same manner as molten brass, care being taken at all

page_text: times to prevent the air from direct contact with it, and in all cases it is best to keep
the pot covered as much as possible.
.
The castings should be left to cool fully before taking them from the moulds and
if they are then not sufficiently hardened they should be reheated quickly to redness
and placed in dry and warm or even hot powdered graphite dust to cool off very slowly
and fully cooled before removed. The more thoroughly the copper is acted upon
with sodium or its vapor the harder and more perfect will be the castings produced.
Over-heating of the copper should be avoided and it should not be poured at a
higher temperature than necessary for filling the corners of the pattern otherwise
the shrink will be considerable ordinarily the shrink is about ths of an inch per
foot.
Castings produced by this process are actually tempered because the resulting
metal has greatly increased tensile strength and resistance to compression and for
anti-friction purposes such as bearings for locomotives or other heavy machinery or
commutators or brushes for dynamo electric machines it positively shows much
greater endurance than forged copper under like circumstances. Its great tensile
strength and high conductivity makes it especially desirable and valuable for the
transmission of power and other electrical purposes where overhead wires are used.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is ;
1. The art of making tempered copper castings, which consists in treating melted
copper with sodium, casting the same in suitable moulds and finally heating the
castings red hot then embedding them in powdered graphite to cool very slowly.
2. The art of producing tempered copper castings, which consists in melting
copper under a layer of salt, subjecting the copper to the action of sodium or a
vapor thereof then casting, reheating and slowly cooling as described.
3. The art of tempering copper which consists in quickly heating to redness and
slowly cooling copper which has previously been subjected to the action of sodium.
4. The art of tempering copper which consists in subjecting molten copper to the
action of sodium or vapor thereof, in a covered crucible and under a layer of melted
salt, or to the action of a mixture of salt, anthracite and carbonate of soda as
herein before described.
Dated this 24th day of March 1892.
TURNER D. BOTTOME.