US1752474A - Method of treating metals - Google Patents

Description

Patented Apr. 1, 1930 STATES CARTER HENRY ANDERSON, 01? OAK PARK, ILLINOIS, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK . METHOD OF TREATING METALS No Drawing.

This invention relates to methods of treat ing metals and has for its object the provision of a method of treating metals which when employed results in the production of 5 ingots or castings which possess commercially enhanced properties, such as toughness, desirable crystalline structure, freedom from blow-holes, etc.

In carrying out the object of the invention,

1 in one embodiment thereof,metal, such as an alloy of palladium and copper, is melted under controlled conditions and allowed to solidify. The solidified material produced by the above operations is then remelted under controlled conditions of another character and the molten material cast into either an ingot or a casting. The cast material resulting from the above treatment will have a desirable crystalline structure and will be free from other conditions, such as the presence of large blow-holes, which would render it commercially unsound, which characteristics would not be present if the material were not remelted under altered conditions.

The invention will be clearly understood from the following detailed description of a specific application of the method to the production of a contact alloy composed of approximately. 60% palladium and 40% copper, which is especially useful for the production of contact members to be used in electri' cal apparatus.

In this embodiment of the invention either an alloy of the desired composition or the constituentmetals in the proper proportions are placed in a graphite crucible and melted in a suitable furnace in a reducing atmosphere to prevent the formation of oxides and their association with the molten metals. Among the numerous reducing materials which may be used to supply a reducing atmosphere around'the alloy being treated in the melting step, which has just been described, the; preferred one is a mixture of carbon monoxide and carbon dioxide, in which the carbon inonoxide acts as a reducing agent and the carbon dioxide is'inert. Other reducing materials which may be used are hydrogen and pro-,

ducer gas. The molten material is then pouredinto an ingot mold without any at- Application filed March 31, 1927. Serial No. 180,066.

tempt being made to prevent occlusion of the reducing gases by the material and the material-is allowed to solidify in the mold. An examination of material which has been treated in the manner just described will show that the material is full of large blow-holes which result from the absorption of gases by the material and which render castings containing them commercially unsound.

The ingot produced by the above operations is placed in a non-reducing crucible com posed of a material other than pure graphite, such as magnesia, lime or zirconia, and the material is heated in a non-reducing atmosphere, such as air, until the material is molten and until the resultant vigorous evolution of entrapped or dissolved gas ceases. When the material becomes molten and the evolution of gas ceases, the material is immediately poured into an ingot mold and allowed to solidify, after which it may be worked in any desired manner to produce contact members therefrom.

An examination of the material resulting from the final treatment outlined above will show that it has a very *desirable crystal structure and that 'it is free from numerous large blow-holes. An ingot having these characteristics is considered commercially sound and may be readily worked into articles having desirable physical properties.

Where it is desired to produce an article by casting directly from the molten state, it is advantageous to treat the material to be cast in such a manner that the material will when solidified have what is termed a modified type of crystalline structure. By the term modified crystalline structure is meant a crystalline structure obtained in a material cast directly from the molten state without subsequent working or heat treating and which is very fine as compared to an uninterrupted grain growth from the outside toward the center of a cast section.

It has been found that by properly controlling the conditions under which the last melt is made in the above described process, the metal when solidified will have a modified type of crystalline structure and that material produced by the above described operunder the usual conditions under which they ill) ations may be cast directly into the desired form to produce castings which will not fail are intended to be used.

Insteadof melting the material in a graphite crucible and casting it into an ingot before the final melt and casting, the material may be melted in a non-reactive crucible under reducing conditions, allowed to solidify in the crucible and remelted in the same crucible under non-reducing conditions until the evolution of gas ceases and then cast into an ingot as described above. Such material will also possess desirable physical characteristics and will be free from objectionable voids resulting from absorbed gases.

It is, of course, to be understood that the invention is-not limited to the use of the above described method With a palladium-copper alloy of the exact composition stated above,

' but is equally applicableto palladium-copper .1 found that commercial lead may be improved by remelting it under conditions different from those from which it was solidified in the last stage of the smelting operations. This,

example illustrates the important feature that the invention applies to the removal of deleterious conditions in metals other than the presence of blow-holes or voids, for it is believed that the lead is freed by the above mentioned process from oxides or other com- 1 pounds which are present insmelted lead and whiah are objectionable when pure lead is desire It is also to be understood that the invention is not limited to a method wherein the material is melted in a reducing atmosphere and remelt'ed under, non-reducing conditions, but the invention embraces .any method in which metallic material is melted under one set'of controlled conditions, is allowed to so- 1i ify and is remeltednnder controlled condi ions different from those under whichthe first melt is made.

-The terms metallic material or metal as used. hereinbefore and in the appended claims are intended to embrace commercially pure metals and alloys of two or more metals.

at is claimed is: Y

I 1. A method of treating metals, which con in melting a metal in the presence of T u-a' reducing material, allowing the metal to solidify, and remelting the metal in the presence of a non-reducing material.

2. A method of treating metallic materials, which consists in melting a metallic material in a reducing atmosphere, casting the material into an ingot, remelting the material: in a non-reducing atmosphere, and re-X casting the material.

3. -A method of treating metallic materials having the property of absorbing gases while in the molten state, which consists in melting a metallic material of said type in a reducing atmosphere, allowing the material to solidify, remelting the material in a nonreducing atmosphere to cause an evolution of gas from the material, heating the material until the evolution of gas substantially ceases, and casting the material.

4. A method of treating metallic materials,

which consists in melting a palladium con-- taining material under reduclng conditions, allowing the material to solidify, and remelting the material under non-reducing conditions.

5. A method of treating metallic materials,

which consists in melting a palladium-copper. alloy in a reducing atmosphere, allowing the alloy to solidify, remelting the alloy in a non-reducing atmosphere, and casting thealloy into an ingot.

6. A method of treating metals, which consists in melting an alloy comprising substantially 60% palladium and 40% copper under reducing conditions, casting the alloy into an ingot, remelting the alloy under non-reducing conditions to cause an evolution of entrapped gases, maintaining the alloy in a molten state until the evolution'of gases substantially ceases, and recasting the material.

7. A method of treating metals, which consists in melting a metal under reducing conditions, allowing the metal to solidify, and

remelting 'ditions.

8. A method of treating metals, which consists in melting a metal in a reducing atmosthe metal under non-reducing conphere, allowing the metal to solidify, and remelting the metal in air.

9. A method of treating metals, which consists in melting a metal in the presence of carbon monoxide, allowing the metal to solidify, and remelting the metal in air. j 10. A method of treating metals, which consists in meltin a metal in a reducing atmosphere in a re ucing crucible, casting the metal, remeltingthe metal in air in a nonreducing crucible, and recasting the metal. 11. A method of treating metals, which consists in melting a palladium-copper alloy in the presence of carbon monoxide, casting the alloy into an ingot, remelting the alloy in air to cause the evolution of entrapped gases, and recastin the material.

12. A method ot treating metals, which.

consists in melting a palladium-copper alloy comprising substantially 60% palladium and 40% co per in a graphite crucible in the presence carbon monoxide, casting the alloy into an ingot, remelting the alloy in a nonreducing crucible in the presence of air to cause an evolution of entrapped gases, maintaining the alloy in a molten state until the evolutlon of gases substantially ceases, and recasting the material.

In witnesswhereof, I hereunto subscribe my name this 18th day of March, A. D., 1927. CARTER HENRY ANDERSON.