US2128089A - Article of manufacture - Google Patents

Description

- Patented Au 23, 1938 v UNITED STATES PATENT OFFICE 2.128.089 7 ARTICLE or MANUFACTURE .Franz R. Hcnsel and Earl I. Larsen, Indianapolis, Ind., assignors to Westinghouse Electric & Manufacturing Company, East PittsburgL'Pa" a corporation-of Pennsylvania No Drawing. Application March 12, 1938, Serial No.-68,452 I 2 Claims.

Q This application is a continuation in part of copending application Serial -No. 714,614, filed March 8, 1934, and directed to copper alloys.

In preparing copper base alloys containing chromium, it is found to be quite difilcult to introduce the chromium into the molten copper. The

chromium has a high melting point and dissolves but slowly in copper. Further, since the chromium is lighter than copper, it is difficult to keep the chromium submerged for the time necessary ll to: dissolve it. The chromium tends to rise to the surface of the melt where it is oxidized. The

oxides formed contaminate the resulting alloy,"

and the loss of chromium increases the expense of manufacture. I Where free chromium is added'to the melt it may tend to segregate either during melting or during freezing, since the free chromium difiers in density from the copper. Such segregation causes clack of homogeneity in the resulting 28 solid product. This is particularly true if the amount of chromium exceeds the solid solubility limit of chromium and copper.

An object of this invention is to prepare chromium in a form for use in the making of alloys 80 to facilitate a good alloying dispersion throughout a melt of molten copper.

In making the copper base alloys, chromium is introduced into the copper melt in a finely divided form prepared in accordance with the teachings.

a of this invention.

In preparing the metallic product to be introduced into the copper melt, chromium is pow-' dered in any suitable manner as in a ball mill, well known to the trade, to a size of between 10 do and 500 mesh and preferably between 100 and 200 mesh, and then thoroughly intermixed with copper powder of approximately the same size.

The copper and chromium powders of predetermined fineness are then thoroughly inter- 45 mixed and placed in a suitable die. and subjected to a pressure ranging from a. few hundred pounds per square inch, to a pressure as great as 200,000 pounds per square inch, inorder to compact them. The pressure under which the unit is compacted 5o depends on the conditions to be met.

In preparing the copper base alloys containing chromium, the copper is first melted and the chromium is then added to the molten copper. In practice, the copper melt is sometimes provided with a protective film of slag; such as borax,

I to protect the melt from the atmosphere. Where such a protective film is employed to cover the melt, it is found that the powdered metallic product compacted under the lower pressures to give form and coherence to the powdered mixture is 5 suitable for. obtaining a good dispersion of chromium when it is introduced into the melt.

If the compacted mixture of the powders is to be added to a copper melt which is not protected from the atmosphere, the intermixed powders of predetermined fineness maybe subjected -to a pressure sufficient to impart a density to V the compacted mixture greater than that of molten copper. Unless a'density greater than that of the molten copper is imparted to the compacted mixture of copper and chromium powders,the resulting metallic product has a tendency to float on the surface of the molten copper which-may result in high loss of chromium caused by oxidation, particularly in" the absence of a protective fiux or atmosphere over the copper.

Where such a high density is impartedto the .mixture of copper and chromium powders, the

compacted mixture sinks in and is dispersed throughout the molten copper. In practice, it

has been found that with a pressure of about 60,000 pounds per square inch, a density of about 8.5 may be imparted to a mixture of copper and chromium powders in which the chromium content is about 10% by weight.

In a modification of this invention the copper and chromium powders of predetermined fineness may be subjected to a low pressure sumcient to give form and coherence to the powdered mix-' ture, after which the compacted mixture is heat.- ed in a reducing atmosphere to sinter the powders. In sintering the compacted mixture, it is heated to a temperature of between 900 C. and

' the eutectic temperature of copper-chromium (approximately 1060 C.) in a reducing atmos- 40 v phere and held at that temperature for a period of time ranging from a few minutes to several hours depending on the fineness of the powders and the pressure employed to compact the powders. V

In practice, the chromium content of the compacted mixture of the chromium and copper powders depends upon the amount of chromium which it is desired to add to the .copper melt.

As a general rule, the compacted mixture contrains approximately the same amount of chromium which it-is desired that the final alloy contain but since the finished product is small and compact the chromium is usually present in aconcentration of about ten times that desired in the final alloy. It is, therefore, desirable that the chromium content in the compacted mixture fall within the range of from 1% to 25% by weight of the finished product where it is desired that the final alloy contain from .1% to 2.5% by weight of chromium.

Where this invention is-to be employed in making the copper chromium alloys containing an additional hardener such as silver, as covered in Patent No. 2,033,709, issued March 10, 1936, or zirconium or thorium, as covered in'Patent No. 2,025,662, issued December 24, 1935, or cadmium, as covered in Patent No. 2,033,710, issued March 10, 1936, the third alloying element, silver, zirconium, thorium or cadmium, may be addedto the copper melt as an integral portion of the metallic product. This is accomplished by powdering the third alloying element to approximately the same size as that of the copper and chromium powders, and thoroughly intermixing the three powders in the proportions desired before subjecting them to the pressure necessary to give form and coherence to the finished product. Where these alloying elements are added to the mixture of copper and chromium powders, they are added, in general, in approximately the same concentration as the chromium content in the mixture with respect to the amount of the diilerent alloying elements desired in the final alloy. The 'silver,'-'zirconium, thorium and cadmium additions to the compacted mixture of copper-and chromium powders may be from .1% .to 25% by weight of the finished product depending upon the amount of the elements desire'din the alloy.

In many cases, itis found to be desirable to add slag forming ingredients to the mixed metallic powders in order to dissolve metallic oxides in the molten bath. Where this is desirable, slag forming ingredients, such as boric oxide, b orax' or fluor spar may be added and intermixed with the alloying powders before compressing them. Deoxidizing materials, such as calcium, barium, boron, beryllium," calcium boride, magnesium, phosphorus or silicon, may also' be added in ,5 amounts 'up to 10% by weight to the alloying powders before compressing them. These deoxldizing materials speed up the alloying action with the result that an excellent dispersion of the alloying elements is secured. Where such deoxidizers are employed it is found that the products compacted under the lower pressure are satisfac tory for addition to the melt.

.Where the metallic product of the compacted alloying elements, as herelnbefore described, is

formed, it is easily introduced into the *copper melt and the alloying elements are dispersed throughout the resulting alloy. By introducing them inthis manner, oxidation of the alloying elements is prevented, the tendency to segregate is,lowered and a homogeneous solid product results.

It is to be understood that various modifications may be made in the metallic product as above described, without in any way departing from the spirit of the invention, as set forth in the appended claims.

We claim as our invention:

1. An article of manufacture for use as an addition agent to molten metal, comprising, a mixture of from 1% to 25% by weight of chr0- mium powder, not more than 10% by weight of a deoxidizing material with the balance substantially copper p'owder the mixture being subjected to a sufilciently high pressure .to compact the mixed elements into the desired form.

2. An article of r'nanufacturefor use as an addition agent to molten metal, comprising a mixture of =from 1% 'to 25% by weight of chromium powder, from .1% to 25% by weight of ametal powder selected from the hardeners consisting of silver, zirconium, thorium, and cadmium powders, from small but efiectivezamounts 'up to 10% by weight 'of a'deoxidizing material with the balance substantiallycopper powder,

the mixture being subjected to a sufilciently high pressure to compact th mixture into the desired