US2768102A

US2768102A - Wrought nickel bronze

Info

Publication number: US2768102A
Application number: US269331A
Authority: US
Inventors: Carl M Zvanut
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1952-01-31
Filing date: 1952-01-31
Publication date: 1956-10-23
Anticipated expiration: 1973-10-23

Description

United States PatentO 2,768,102 ,WROUGHT NICKEL BRONZE Carl M. Zvanut, Midland, Mich., assignor to Olin Mathieson Chemical Corporation, a corporation of Yirginia NoDrawing. Application January 31,1952,

Serial N0..269,331 1 10 Claims. (Cl. 1482) J This invention relates to a method of l processing of copper alloys and pertains more specifically to the making of a novel tough, wear and corrosion resistant alloy of the nickel bronze type in the wrought form in contradistinction to the cast form. Generally, the term nickel bronze includes age-hardenable alloys containing from about 3 /2% to 50% nickel, from about 3% to 20% tin, not more than about 10% zinc, if any, and the balance copper. A commercially well-known composition of this type consists of about 88% copper, 5% nickel, 5% tin, and 2% zinc and is referred to by the industry as 88552 nickel bronze.

Heretofore, the most commercially desirable copper base alloys containing tin,- nickel and frequently some zinc in addition to copper, have been generally employed in theform of castings largely because these alloys are not readily worked while cold and also lack the hot ductility necessary for hot rolling. It has been customary to cast these alloys by meltingthem in a suitable furnace having a clay-graphite crucible, for example, undera cover of carbon, generally charcoal, .or no applied cover at all, and after a suitable oxidizing treatment with cuprous oxide and a final deoxidizing treatment with phosphorus, the molten metal. is poured into a mold having a carbonaceous dressing, including either graphite or lampblack. Although it has been known that such bronzes, after casting in the form of an ingot, could be fabricated 2,768,102 Patented Oct. 23, 1956 It is, therefore, an object of this invention to provide a commercially feasible method. of producing wrought nickel bronze of the type described. Another object is the simplification of the manufacture of nickel bronze sheet metal and particularly elimination of the long and costly annealing treatment for the cast metal heretofore considered necessary prior to reduction by rolling. Another object is the provision of a novel alloy of the nickel bronze type amenable to rolling. Still another object is to provide a new and improved method of making wrought articles of such bronzes. Other objects will be apparent from the accompanyingdescription.

This invention is predicated on the discovery that an age-hardenable nickel bronze may be directly worked as cast to form a wrought article, such as rolled strip,of excellent quality provided the cast metal is produced substantially free from carbon phosphorus, and slag inclusions and provided the metal is treated with manganese. To avoid carbon, no charcoal, graphite, lampblack or the like is employed in the walls of the molten metal bath holding crucible, or in the molten metal bath cover as a deoxidizing agent, or in the dressing for the mold into which the metal is cast to, form the desired ingot. The molten metal is cast into a mold coated with a non-volatile carbon free dressing, preferably bone-ash, to avoid intro-' duction of any carbon into the metal during pouring from the crucible into the mold. Phosphorus, heretofore re garded by the art as a suitable deoxidizer for many copper base alloys including nickel bronze, is not suitable for the purposes of this invention because phosphorus, when present, even in small amounts, was found to-accentuate the age-hardening properties of the bronze in such a way as to render the metal unfit for cold rolling by the usual methods. Manganese, which also accentuates the agehardenability of these bronzes, which in itself is not undesirable, was found toresult in no impairment of the workas a wrought product, such as sheet, working of the cast ing. While the quenchedmetalcan be worked well initially, upon subsequent cold rolling after the usual anneal at around 750 C. the surface of the strip in rolling develops severe fire cracks renderingv the metal utterly useless for further fabrication to desiredgauge and temper. On the other hand, the specially treated metal which is slowly cooled, unlike the quenched metal, is rather brittle and on breakdown rolling develops edge cracks necessitating removal of a considerable portion of metal including these cracks before further finishing operations can be conducted on the metal. Furthermore, this type of bronze exhibits while molten a tendency to take up inclusions of anon-metallic character, believed to be slag, which may be so widely distributed within the solid metal of the casting as to render it unfit for further processing preparatory to ultimate use of the metal in manufacture of articles requiring asurface free of blemishes. Because of i ability of bronze deoxidized with the manganese. .In deoxidizing the molten metal, therefore, manganese is employed and preferably is included as a residue in theresulting nickel bronze to the extent of not more than. about 0.2%. To protect the metal during the melting operation from excessive contact with the atmosphere and to control any slag formed, a' cover is employed on the molten metal bath such that slag will be entrained in the cover and such as is sufiiciently viscous or coherent that the cover itself is not a source of undesirable inclusions in the cast metal. A cover which produces favorable results consists largely of particles of a refractory material, i. e., of sand, the fluidity of which is modified by the inclusion of more easily fused materials such as common salt, borax, a glass or the like. A preferred composition consists of about or more sand and the balance salt. In accordance with this invention, wrought nickel bronze is made by a process involving melting the metal under a cover which prevents carry-over of slag into the casting during pouring, deoxidizing the metal with manganese, pouring the molten metal thus prepared into a mold coated with a non-volatile carbon free dressing and thereafter directly working the solidified ingot by cold rolling.

A readily worked nickel bronze alloy produced in accordance with this invention comprises copper, nickel, tin, usually zinc, and a residual amount of manganese, and is further characterized by freedom from carbon and phosphorus and by a high density in the as cast condition. A residual manganese content of the order of about 0.2% or less and preferably not in excess of about 0.05% is contemplated. The as cast density of an 88- 5-5-2 type of nickel bronze made as described herein is better than 8.72 gram per cubic centimeter and is high relative to' the density of the rolled metal which is 8.93 grams per centimeter. For the 88-552 type alloy,

which is about the only commercially important nickel bronze, an as cast density of about 8.75 grams per centimeter or better is consistently one of the characteristics of metal which may be directly cold rolled to strip with intermediate annealing at a temperature of about 650 C.

In carrying out a preferred embodiment of this invention, constituent metals of suitable purity, beginning with copper and nickel, are charged into any suitable melting apparatus, such as the low frequency electric induction furnace of the type shown in U. S. Patent No. 1,201,671, having a molten metal bath holding crucible, the walls of which consist of a refractory ceramic material of the sillimanite type or the like, but in no instance of claygraphite, or any other carbonaceous mixture. In order to prevent oxidation of the molten metal and inhibit the formation of slag in the crucible, a cover is provided over the melt and consists of about 80% or more sand and the balance common salt or the like in amounts suflicient to adjust the fluidity of the cover as desired. This protective cover is capable of entraining any slag formed and has a viscosity and coherency such that on casting of the metal no part of the cover will carry over so as to form slag inclusions in the casting. Since the melting and pouring of nickel bronze is done at a temperature of around 1250 C. or 1300 C., relatively high for copper base alloys, many cover materials such as common salt and borax, like the naturally occurring slag, prove entirely too fluid at this elevated temperature, and, if used, allow formation of inclusions folded into the surface and even into the body of the casting which must then be either subject to intensive milling to remove surface defects before it can be rolled or must be entirely scrapped as where the inclusions are distributed throughout the body of the casting. At all times during the melting operation the surface of the molten metal is maintained under the cover since it has been found that skimming the surface, as is customary with many alloys, is detrimental and reflected by the inclusion of slag in the casting. About 30 minutes before the melt has reached the emperature for pouring, electrolytic manganese is added in amounts sufficient to deoxidize the molten metal, leaving a residue of about 0.05 manganese. For strip rolling the molten metal is poured at a temperature around 1250 C. and preferably around 1300 C. into a suitable mold such as a vertical water-cooled metal mold having a casting cavity measuring 15 /2 X 2 /2" x 96", for example, coated with a dressing of bone-ash.

On solidification 88-5-52 type of nickel bronze cas ingots made as described are found to contain substantially only manganese in residual amounts in addition to the chief constituent metals of nickel bronze; and the ingots are further characterized by high density. Typical analyses and densities of ingots produced are shown in the table which follows. The low density figure for each ingot is obtained on a test sample selected at a central portion of the casting; and the high density figure for each ingot is obtained on a test sample selected at and including one or more lateral original surface areas of the casting including the most dense portion of metal. The center sample is bounded by cut surfaces and includes none of the original lateral surfaces of the casting.

The nickel bronze ingots produced have an average density at least as high as about 8.75 grams per cubic 30 minutes to one hour.

centimeter and are characterized by physical properties such as a ductility suflicient to render the metal amenable to fabrication to wrought metal and particularly to rolled strip of any desired gauge by a cold rolling and intervening annealing technique to which the non-ferrous rolling mill is adapted. The difiicultly workable 88-5-5-2 nickel bronze made by the heretofore common prior art method is as a rule characterized by average densities low in comparison'to that of the ingots produced.

Test samples of the cast metal are capable of withstanding a 180 bend on a. /2" radius without fracture indicating that the casting produced is sufficiently ductile to be amenable to cold working by rolling and the like. The dense slag-free cast metal of this invention can be cold rolled without a special preliminary homogenizing heat treatment and between cold rolling reductions the metal may be annealed in conventional apparatus at a temperature of about 650 C., for a period from about Reduction by rolling proceeds without development of edge or surface cracks; and the metal surface may be finished to a high lustre free of blemishes such as would be formed by slag inclusions.

The rolled and otherwise wrought nickel bronze may be age-hardened after fabrication to obtain optimum properties such as high strength attainable with these bronzes. In addition to the constituents specified the metal may contain other elements in such amounts as do not impair the desired properties and nature of the alloy produced.

It is to be understood that deviations may be made from the embodiment of the invention described herein without departing from the spirit and scope thereof as defined in the appended claims.

The invention claimed is:

1. In the art of making nickel bronze consisting essentially of 88% copper, 5% nickel, 5% tin and 2% zinc amenable to cold rolling directly from the as cast condition the process which comprises forming a melt substantially free from phosphorus and carbon, maintaining over said melt a protective cover of at least about sand and the balance salt, deoxidizing said melt by the addition of electrolytic manganese to leave a residue of about 0.05% manganese in said bronze, and pouring the molten metal of said melt into a vertical water-cooled mold coated with a bone-ash dressing, thereby forming an ingot having an as cast average density of at least about 8.75 grams per cubic centimeter and substantially completely free from phosphorus, carbon and slag inclusions.

2. The process of making wrought nickel bronze consisting of about 88% copper, about 5% nickel, about 5% tin and about 2% zinc, comprising forming in a crucible a melt of the constituent metals, maintaining a protective cover of at least about 80% sand and the balance salt over the molten metal of said crucible, deoxidizing the melt by addition of manganese to leave a residue not in excess of about 0.2%, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a bone-ash dressing to form a dense ingot substantially completely free from carbon, phosphorus and slag inclusions and subsequently subjecting said ingot to a series of cold working and intermediate annealing steps to reduce the ingot to a desired article shape.

3. The process of making rolled nickel bronze which comprises forming in a crucible a melt consisting essentially of about 88% copper, about 5% nickel, about 5% tin and about 2% zinc, maintaining a protective cover predominantly of sand free from carbonaceous material over the molten metal in said crucible, deoxidizing the melt by addition of manganese to leave a residue not in excess of 0.2%, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a bone-ash dressing, thereby forming an ingot having an as cast density of at least about 8.72 grams per cubic centimeter and substantially completely free from carbon, phosphorus and slag inclusions, and subsequently subjecting said ingot to a series of cold working and intermediate annealing steps to reduce the ingot to a desired gauge.

4. The process of making wrought nickel bronze which comprises forming in a crucible a melt consisting essentially of copper, nickel, tin and zinc, maintaining over the molten metal in said crucible, a protective cover predominantly of sand free from carbonaceous material modified with a fused salt, deoxidizing the melt by addition of manganese to leave not more than a residue of manganese, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a boneash dressing to form an ingot substantially completely free from phosphorus, carbon and slag inclusions, and working said ingot as cast to deform the ingot to a desired article shape.

5. The process of making wrought nickel bronze consisting of about 88% copper, about nickel, about 5% tin and about 2% zinc, forming a melt of said constituent elements, maintaining a protective cover of at least 80% sand and the balance salt over the molten metal, deoxidizing the melt by addition of manganese to leave a residue not in excess of 0.2% in said bronze, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a bone-ash dressing, thereby forming an ingot having an as cast density of at least 8.75 grams per cubic centimeter and substantially completely free from phosphorus, carbon and slag inclusions, and subsequently subjecting said ingot to a series of cold Working and intermediate annealing steps to reduce the ingot to a desired gauge and temper.

6. The process of producing Wrought nickel bronze consisting essentially of about 3 /z% to 50% nickel, about 3% to 20% tin, less than about 10% zinc, with the balance copper, which comprises forming a melt of said constituent elements, maintaining a protective cover predominantly of sand free from carbonaceous material over said melt, introducing electrolytic manganese in amounts sufficient to deoxidize said melt to leave a residue not in excess of about 0.2%, chill casting the molten metal into a water-cooled mold coated with a non-volatile carbon-free dressing to form a dense ingot, substantially completely free from carbon, phosphorus and inclusions of slag, and subsequently subjecting said ingot to a series of cold-working and intermediate annealing steps to reduce the ingot to a desired article shape.

7. The process of making wrought nickel bronze which comprises forming in a crucible a melt consisting essential of copper, nickel, tin and zinc, maintaining a protective cover predominantly of sand substantially free from carbonaceous material over the molten metal in said crucible, deoxidizing the melt by addition of manganese to leave a residue of manganese not in excess of about 0.05% in said bronze, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a bone-ash dressing, thereby forming an ingot composed of about 88% copper, about 5% nickel, about 5% tin and about 2% zinc, having an as cast density of at least 8.72 grams per cubic centimeter and free from phosphorus, carbon and slag inclusions, and subsequently subjecting said ingot to a series of cold working and intermediate annealing steps to reduce the ingot to a desired article shape.

8. In the art of making nickel bronze amenable to cold working directly from the as-cast condition the process which comprises forming a melt consisting essentially of copper, nickel, and tin maintaining over the melt a protective cover of sand at least about and the balance a salt more readily fused than sand, said cover being substantially free from carbonaceous material, deoxidizing said melt with manganese to leave a residual amount of manganese, if any, not in excess of about 0.05%, and chill casting the molten metal in a mold coated with a non-volatile carbon-free dressing to produce a dense ingot substantially completely free from phosphorus, carbon and slag inclusions.

9. In the art of making nickel bronze amenable to cold working directly from the as-cast condition the process which comprises forming a melt consisting essentially of copper, nickel, and tin, maintaining over the melt a protective cover predominantly of sand substantially free from carbonaceous material and modified by the inclusion of a more readily fused material, deoxidizing said melt with manganese to leave a residue of manganese not substantially in excess of about 0.2% in the cast metal, and chill casting the molten metal into a mold coated with a non-volatile, carbon-free dressing to produce a dense ingot substantially completely free from phosphorus, carbon and slag inclusions.

10. The process of making wrought nickel bronze which comprises forming in a crucible a melt consisting essentially of copper, nickel, tin and zinc, maintaining over the molten metal in said crucible, a protective cover predominantly of sand free from carbonaceous material modified with a fused salt, deoxidizing the melt by addition of manganese to leave a residue of manganese not substantially in excess of about 0.2%, pouring the molten metal from said crucible into a vertical water-cooled mold coated with a bone-ash dressing to form a dense ingot substantially free from phosphorus, carbon and slag inclusions, and cold working said ingot as cast to deform the ingot to a desired article shape.

References Cited in the file of this patent UNITED STATES PATENTS 598,632 Johnston Feb. 8, 1898 1,586,871 White June 1, 1926 1,851,218 Stone Mar. 29, 1932 1,906,567 Fritschle May 2, 1933 1,928,747 Wise Oct. 3, 1933 2,116,207 Lindner et .al. May 3, 1938 2,266,734 Behrendt Dec. 23, 1941 2,372,202 Hensel et al. Mar. 27, 1945 2,401,818 Eckel June 11, 1946 2,445,868 Berwick July 27, 1948 2,577,426 McCullough Dec. 4, 1951 OTHER REFERENCES Melting and Casting of German Silver Alloys, by Edmund R. Thews, Fiat Final Report No. 878, Oifice of Military Government for Germany (U. 8.), Field Information Agency Technical, July 23, 1946, pages 9 and 10.

Claims

1. IN THE ART OF MAKING NICKEL BRONZE CONSISTING ESSENTIALLY OF 88% COPER, 5% NICKEL, 5% TIN AND 2% ZINC AMENABLE TO COLD ROLLING DIRECTLY FROM THE AS CAST CONDITION THE PROCESS WHICH COMPRISES FORMING A MELT SUBSTANTIALLY FREE FROM PHOSPHORUS AND CARBON, MAINTAINING OVER SAID MELT A PROTECTIVE COVER OF AT LEAST ABOUT 80% SAND AND THE BALANCE SALT, DEOXIDIZING SAID MELT BY THE ADDITION OF ELECTROLYTIC MANGANESE TO LEAVE A RESIDUE OF ABOUT 0.05% MAGANESE IN SAID BRONZE, AND POURING THE MOLTEN METAL OF SAID MELT INTO A VERTICAL WATER-COOLED MOLD COATED WITH A BONE-ASH DRESSING, THEREBY FORMING AN INGOT HAVING AN AS CAST AVERAGE DENSITY OF AT LEAST ABOUT 8.75 GRAMS PER CUBIC CENTIMETER AND SUBSTANTIALLY COMLETELY FREE FROM PHOSPHORUS, CARBON AND SLAG INCLUSIONS.