US3375107A - Copper base alloy and method for its manufacture - Google Patents

Description

P. J. KRANZ March l26, 19,68

COPPER BASE ALLOY AND METHOD FOR ITS MANUFACTURE Filed oct. 11, 1965 \\\\\\\\&\\\\\' O/ H/// f QTTO, I2 N EY P. J. KRANZ March 26, 1968 COPPER BASE ALLOY AND METHOD FOR ITS MANUFACTURE Filed Oct. 11, 1965 E Sheets-Sheet 2 mvaNw-o PQUL'JOHN KRQNZ BVM? vHTTOIQNEY ited States Patent Ol'ce 3,375,107 IPatented Mar. 26, 1968 3,375,107 COPPER BASE ALLOY AND METHOD FOR ITS MANUFACTURE Paul J. Kranz, South Plainfield, NJ., assignor to American Smelting and Refining Company, New York, N.Y., a

corporation of New Jersey Filed Oct. 11, 1965, Ser. No. 494,533 Claims. (Cl. 75-156.5)

ABSTRACT OF THE DISCLOSURE A brass, .which when continuously cast, has mechanical properties equal to or superior to those of a high quality leaded tin bronze. The 'brass contains, by weight, 0.25 to 2.5% P, 1.5 to 4% Sn, 0.25 to 4% Ni, more than 3 to less than 20% Pb, about 4 to less than 20% Zn, and balance copper and contains more zinc than tin.

This invention relates to a copper-base alloy and method for its manufacture. More particularly the invention relates to a brass type copper-base alloy which is especially useful as a bearing material.

A copper-base bearing alloy desirably possesses a cornbination of mechanical properties providing a high yield strength and an elongation above a minimum together with a moderate hardness and also may posses high tensile strength; yield strength being the most important of these mechanical properties. Usually a good quality general purpose copper-base bearing alloy possesses a yield strength of at least 20,000 pounds per square inch, an elongation in excess of 5%, and a Brinell hardness of at least 50. Heretofore high quality general purpose copper-base bearing alloys have been comprised of relatively expensive metal which generally was a leaded tin bronze containing tin in amounts greater than about six percent by weight and zinc, if any, in amounts not in excess of the tin and generally less than, and usually substantially less than, the tin. A typical example of such high quality alloy is to be found in a leaded tin bronze which is widely available commercially and which contains, by weight, 83% copper, 7% tin, 7% lead, and 3% zinc.

I have invented a novel copper-base alloy which is a brass type alloy in that it contains tin in quantities not in excess of 4% and zinc in excess (generally in substantial excess) of the tin. I have found that my alloy in the as cast state, when cast by continuous casting procedures as opposed to permanent mold casting or sand casting procedures, possesses a combination of mechanical properties which is equal to and superiorto that of high quality leaded tin bronze and that my alloy can be readily substituted for such high quality bronzes, as a bearing material. My alloy is based on the discovery that tin, in the relatively high amounts that would otherwise be required, can be replaced in part by phosphorus and nickel; and that such replacement not only does not adversely affect the properties of the alloy but actually atords a 4brass type alloy of superior properties as compared to high quality leaded tin bronze.

The principal object and advantage of the invention is the provision of a high quality bearing material from a brass type alloy which can be made from scrap metal of the type which is relatively cheap and plentiful. Thus, for example, the instant alloys canbe made by adding phosphorus values to an appropriate mixture of automobile radiator scrap, yellow brass scrap, and relatively small amounts of nickel silver scrap, cupro nickel scrap or Monel metal scrap. Another advantage of the invention is that it provides a brass type alloy possessing an excellent combination ofmechanical properties. Thus, the instant alloys display excellent tensile strength, yield strength, elongation and hardness as well as excellent fatigue strength. For example, the instant alloys possess a tensile strength of at least 35,000 pounds per square inch, a yield strength of at least 20,000 pounds per square inch, a Brinell hardness of at least 50, and an elongation in excess of 5%. The preferred alloys typically possess a tensile strength of at least 42,000, and as high as V52,000 or more, pounds per square inch, a yield strength of at least 28,000, and as high as 31,000 or more, pounds per square inch, a Brinell hardness above 60, and as high as 90 or more, and an elongation of at least 5%, and as high as 20% or more. These and other objects and advantages will become apparent from the following description of the invention.

My alloys contain more zinc than tin and comprise, in weight percent, G25-2.50% phosphorus (P), 1.54% tin (Sn), .2S-4% nickel (Ni), more than 3 to less than 2.0% (preferably 5-15%) lead (Pb), about 4 to less than 20% (preferably 5-l7%) zinc (Zn) and copper (Cu) less than More preferably my alloys comprise, by weight, .Z5-1.5% P, l.5-3.5% Sn, .2S-2.5% Ni, 5-15% Pb, 6-15% Zn, 70-80% Cu. The most preferred alloy comprises, by weight, approximately .8% P, 3% Sn, 2% Ni, 10% Pb, 8% Zn, and up to 77% Cu. My alloys may contain other constituents in beneticial amounts or in amounts which are not unduly detrimental. Preferably, the total amount .of such other constituents, including normal commercial impurities, should not exceed about 5%. Thus, for example, iron (Fe) may be benecially present in amounts up to 1% and preferably, when present, in the range .U5-.75%, while sulfur should not exceed .1%, and 'preferably should not exceed .05%, to avoid an undesirable effect.

Phosphorus, tin, nickel, and lead are essential constituents in my brass type copper-base alloys and, in the amounts specified, hereinafter are critically important to the invention. Phosphorus in the range .2S-2.50% is critically important in that below .25% P, the mechanical properties of the alloy are unsatisfactory. On the other band, above 2.5% P, .segregation occurs in the metal and an unsatisfactory casting is obtained. It will be understood that phosphorus as referred to in this specication is phosphorus present in the alloy as alloyed phosphrous as opposed to phosphorus which may be added to the molten vmetal to deoxidize the latter. I have found that the mechanical properties are unsatisfactory also when the alloys contain less than 1.5% tin and less than .25% nickel. On the other hand, with more than 4% tin and more than 4% nickel, the cost of the alloy `increases rela- :tively sharply without commensurate increase in the mechanical properties of the alloy. In addition, more than 3% lead `is needed in the alloys to provide satisfactory machinability; and for best results the alloy should contain at least 5% Pb to provide an alloy which in itself tends to preserve the bearing function in the temporary absence of a conventional lubricant in the bearing surface. On 'the other hand, segregation occurs with alloys containing 20% and more lead. Accordingly the present alloys contain from more than 3% to less than 20% lead; the preferred amount being in the range 5-15% lead. The instant alloys likewise display segregation with zinc in amounts in excess of 20%. On" the other hand with decreased amounts of Zinc below about 4%, the cost of the alloy increases relatively sharply without commensurate increase in the desired properties. Accordingly the instant alloys contain from about 4% to less than 20% zinc and preferably 6-15% zinc.

As already indicated, sound castings of my alloy possessing the above mentioned mechanical properties are obtained only when they have been cast by continuous casting procedures. In such continuous casting procedures,

an open ended mold of any desired or conventional construction may be usedfThe mold may be provided with a cooled section (a so-called chill section) only or it may possess an uncooled section as well as a chill section. During the casting the mold may be disposed in any desired position and the molten metal to be cast may be introduced into the mold in any suitable manner. Thus, for example, the mold may be disposed horizontally, vertically or at any angle to the vertical and may be fed at either of its open ends. Where the mold is provided with a chill section only, the mold is preferably vertically disposed and the level of the metal in the mold is maintained below the top of the mold. Preferably the mold is provided with an uncooled section as well as a chill section and the molten metal is fed into the unchilled sect'ion of the mold preferably in amounts to fill the chill section and at least a portion of the uncooled section of the mold. In addition, the latter mold is preferably attached to a holder for molten metal such as, for example, a furnace or a tundish; the uncooled section of the mold being preferably disposed in the side wall or, more preferably, in the bottom of the molten metal holder with both sections of the mold being filled with metal during the casting. Preferably the mold cavity presents a graphite surface to the metal being cast; more preferably the mold is a graphite mold having a water jacket mounted thereon to provide the chill section for the mold.

While the above mentioned mechanical properties are obtained when the metal is cast by continuous casting procedures in which the casting is withdrawn from the mold at constant speed or variable speed or intermittently, I have found that, where any one or more of such factors as a relatively high volume production or a relatively prolonged casting operation or a relatively high net casting speed are desired or required for commercial considerations, the casting must be withdrawn intermittently with respect to the mold. I have also found that, in general in casting my alloys, highest volume, longest operation and highest net casting speeds are obtained by practicing an intermittent withdrawal procedure in which a withdrawal cycle is employed in which the down period (i.e. that part of the cycle in which the metal is stationary with respect to the mold) is at least as long as the go period (i.e. the period during the cycle in which the casting is moving relative to the mold). In practicing the invention, the speed during withdrawal of the casting may be any desired speed and preferably is as high as practicable within the cooling capacity of the casting facilities. The intermittent 4withdrawal may be obtained in any suitable manner, for example, by reciprocating the mold on the moving casting in an appropriate cycle; preferably however, the intermittent withdrawal is accomplished by holding the mold stationary and moving the casting intermittently in an appropriate cycle. In practicing an intermittent withdrawal procedure, cycles of regular or irregular down and go periods may be employed as well as cycles which recur regularly or irregularly. For best results regular cycles which recur regularly are employed. In addition, I have found that the Zinc content of the metal affects the operating period and that longest operating periods are obtained in cast ing the instant alloys when the alloys contain less than about Zinc and, accordingly in the preferred mode of practicing the invention, the alloys contain less than about 15 zinc.

In practicing the invention, the molten phosphoruscontaining metal to be cast is preferably maintained under a non-oxidizing atmosphere, more preferably in a closed vessel, at least until the molten metal is to be fed into the mold. In the preferred procedure for preparing such molten metal, the phosphorus is added separately to an appropriate molten basis metal; the phosphorus preferably being in the form of a suitable phosphorus master alloy such as, for example, a phosphorus-copper master alloy. In practicing the preferred procedure to produce A the instant alloys from scrap so as to obtain the benefit of one of the principal advantages of the invention, appropriate amounts of a sui-table scrap material and a suitable phosphorus-containing master alloy are selected to provide an alloy having the composition of the instant alloys. The scrap material may be, and preferably is, selected from one or more readily available and relatively cheap scrap metal, such as automobile radiator scrap, yellow brass scrap, nickel silver scrap, cupro-nickel scrap or Monel metal. In this preferred procedure, the scrap material may be, and preferably is melted to form a molten basis metal and then the solid phosphorus master alloy is added thereto. If desired or convenient the scrap for the basis metal may be collected, melted and cast in any conventional manner into ingots in one location and the ingots shipped to another location where they may be remelted, the phosphorus master alloy added thereto to provide a molten metal of the composition of the presen-t alloys, and the thus prepared molten metal may then be cast by a continuous cas-ting procedure as herein described.

Alloys of the present composition when cast by the continuous casting procedures described herein are characterized by the presence on at least a part of their surface of lead rich exudatio-ns, i.e. exudations having a lead content which is greater than that of the body of the casting. On the other hand, the distribution of the constituents in the body of lthe casting is, typically, uniform. In general such exudations have the appearance of small pimples on the casting as it emerges from the mold. In general also, such pimples will occur throughout the surface of the casting with a frequency which is characteristic of the continuous cas-ting procedure employed. Thus, for example, when the casting is continuously withdrawn from the mold at a constant speed, the exudations will be distributed relatively uniformly over the entire surface of the casting. On the other hand, when the casting is withdrawn intermittently from the mold, the exudations occur with relatively high frequency in bands about the periphery of the casting emerging from the mold and, since the exudations are darker in color lthan the underlying metal, thereby give the surface of the cast product a banded appearance. I have found that one peripheral band is formed on the casting each time the casting is stopped during the intermittent casting procedure so that the number of bands on a casting will coincide with the number of down periods that took place while the casting was made. In addition, I have found that the distance between the forward edge of two adjacent bands corresponds to the distance moved by the casting in the mold during the go period of the cycle employed in the intermittent withdrawal procedure. In practicing the invention, an intermittent withdrawal procedure which provides any desired distance between such edges may be used. In general it is desirable that such distance between bands be less than about twelve inches, preferably less than five inches and most preferably less than two inches.

The foregoing bands appear to form on that part of the casting in the mold, that shrinks away from contact with the mold wall during the down period of the intermittent withdrawal cycle. The width of the bands in the casting as it emerges from the mold may vary depending upon the casting conditions. It appears, in general, Ithat the width of the bands on the casting as the same emerges from the mold is controlled largely by the duration of the down period and the temperature of the metal during the down period in that portion of the casting which shrinks away from the mold wall during the down period. I have also found that the pimple-like exudations are relatively soft and are relatively easily attened or smeared under pressure. Thus, for example, if the casting is passed through a conventional straightening device, such as, for example, a conventional roll straightener, Ithe pimple exudations in the bands may be so attened or smeared as to increase the width of the bands and form the exudations into a substantially continuo-us peripheral coating in each of the bands. In addition I have found that, in general, the thickness of such coating and of the pimple-like exudations on the surface o-f the body of the casting is less than about .005 inch.

The invention is further illustrated in the accompanying drawings and examples. It should be understood, however, that the drawings and examples are given for purposes of illustration and that the invention in its broader aspects is not limited thereto.

In the drawings:

FIG. 1 is a view partly in vertical section illustrating the preferred mode and apparatus for practicing the invention.

FIG. 2 is a horizontal cross-section of the mold of FIG. 1.

FIGS. 3 and 4 are similar to FIG. 2 and show molds of different cross-sectional shapes.

FIG. 5 illustrates the appearance of the casting of FIG. l as the same emerges from the mold.

FIG. `6 illustrates the appearance of the casting of FIG. 5 after the casting has been straightened.

Referring now to the drawings, FIG. l shows an assembly of a molten metal holding furnace 1, mold 2 and intermittent withdrawal means indicated generally by the numeral 3 for withdrawing casting 4 from the mold. The mold 2 extends through the bottom of the furnace 1 and in contact with the molten metal 5 therein. The mold is xedly attached to the bottom of the furnace by means of threads y6 which engage mating threads 7 in the furnace bottom. The lower section of the mold is surrounded by water jacket S which preferably is xedly attached thereto. Water or other coolant is circulated through jacket 8 in any desired manner; the water jacket dividing the mold into an uncooled section 9 and a cooled section 10.

The casting 4 is withdrawn intermittently from the mold by withdrawal means 3 which includesrolls 11, at least one of which, as shown, may be driven by electric motor 12 by means of belt 13. Operatively connected to motor '12 is starting and stopping switch 14 operating the motor intermittently and thereby cause the casting to be withdrawn intermittently from the mold. Means 3 may also be provided with a suitable braking means such as is illustrated by the shoe 15 which engages the brake drum 16 on roll 11. The shoe may be operatively connected by levers 17 and 18 to switch 14 so as to brake and stop the wheels when the motor 12 is turned off. The switch 14 may be manually operated or any suitable interval timer rnay be used which automatically makes and brakes the electrical supply to motor 12.

In operating the apparatus of FIG. 1, the level of molten metal in furnace 1 is maintained above the upper edge 19 of mold 2 so that, as casting 4 is withdrawn, the molten metal flows into the mold and the mold is thereby maintained lled with a column of metal during the casting. After the casting passes below rolls 11 it may be severed into any desired length by movable saw 2t) driven by motor 21.

Molten metal as needed may be supplied to holding furnace 1 from a suitable conventional tilting melting furnace the molten metal being poured into pour box 26 from which it ows into the pool of molten metal 5 in furnace 1. In producing the instant alloys, appropriate amounts of ingots of suitable basis metal, or scrap metal or a mixture of scrap metal to provide the basis metal, are melted in furnace 25; the basis metal being a metal of such composition that when appropriate amounts of a suitable phosphorus master alloy are added thereto, the resulting alloy will have a composition within the limits of the instant alloys. A suitable phosphorus master alloy, preferably a -copper-base phosphorus master alloy, in amounts appropriate for the charge of basis alloy melted in furnace 25 is incorporated into the basis metal by placing the phosphorus master alloy into pour box 26 6 and dissolving the master alloy in the basis metal by pouring the charge of basis metal in furnace 1 onto themaster alloy when furnace 1 is to be yreplenished with molten metal for casting. Such procedure for separating introducing the phosphorus into the instant alloys is advantageous in that the phosphorus is incorporated into the alloys just before the metal is cast, thereby reducing the possibility of loss of phosphorus from the molten metal. To further reduce the possibility of phosphorus loss from the metal, furnace 1 may be, and preferably is, provided with re- -movable cover plates 27 and 28'; the latter being removed while pouring metal from furnace 25 into furnace 1. Cover plate 27 may be provided with pipe 29 for introducing a non-oxidizing gas into furnace 1. To reduce loss of zinc from the molten metal, furnace 25 may be, and preferably is, provided with removable covers 30 and 31.

To start the casting system illustrated in FIG. 1, a conventional starting bar (not shown) of appropriate length and having a cross-section of a size and shape conforming to that of the mold cavity of mold 2 is employed. The starting bar may also have a conventional threaded tip of reduced size in the top thereof. The top of the starting bar is inserted into the bottom of the mold a suitable distance with the lower end of the rod extending below rolls 1.1 so that, as the initial molten metal freezes in the mold, it freezes around the threaded tip and thereby the subsequently formed casting is pulled downwardly and out of the mold by rolls 11. 'In starting the system the starting rod is inserted into the mold while the mold and furnace 1 are empty of metal after which molten rnetal is poured into furnace 1, the rolls 11 are started and then circulation of coolant through jacket 8 is begun.

The invention may be practiced to produce castings of any desired cross-sectional shape. Thus, to produce a rod having a round cross-section such as the cssting of FIG. 1, a mold having a circular mold cavity as illustrated in FIG. 2 is employed. To produce a casting of rectangular cross-section, a mold having a rectangular mold cavity i i as illustrated in FIG. 3 is employed. FIG. 4 illustrates a mold 32 provided with a mandrel 33 for casting a hollow shape such as a tube.

The cast product of the invention as shown in FIG. 5 characteristically possesses pimple-like exudations 34 on its surface as its emerges from the mold. When an intermittent withdrawal procedure is practiced, the pimplelike exudations occur more frequently in the banded areas 35 thereby giving the casting the banded appearance illustrated in FIG. 5; the forward edge of the bands being illustrated by the numeral 37, the casting emerging from the mold in the direction of the arrow. When the casting is straightened in a conventional roller straightener the pressure of the straightening rolls smears the exudations in the bands into the coating illustrated by the coating 36 in FIG. 6; the forward edge of the bands being illustrated by the numeral 38.

In the examples set forth in the table below, Examples 1 through 12 were cast in apparatus of the type shown in FIG. 1, employing an intermittent withdrawal procedure. In each of Examples 1 through l2 a pool `of metal 5 of the composition set forth in the table was established in furnace 1 from a mixture of a copper-base master alloy and automobile radiator scrap, yellow brass scrap, nickel silver scrap, cupro-nickel scrap or Monel metal. A nitrogen atmosphere was maintained over the metal pool by introducing nitrogen gas through pipe 29 of cover 27. In Examples 1 through ll, a rod having a diameter of threequarters of an inch was cast in a mold having a crosssection of the shape shown in FIG. 2. In Example 12, a tube having an outside diameter of four inches and an inside diameter of two and one half inches was cast in a moldfhaving a cross-section of that shown in FIG. 4. In each of Examples l through l2, the casting was withdrawn from the mold in a cycle having a down period of three seconds and a go period of two seconds. In Examples 1 through 11 the actual speed during the go period was 15 inches per minute and the net speed of withdrawal was 6 inches per minute while in Example 12 an actual speed of 12.5 inches per minute was employed during the go period and the net casting speed was inches per minute. In each of Examples 1 through 12, the casting emerging from the mold had the banded appearance of the casting shown in FIG. 5 and, when the casting is passed through a conventional roll straightener, has the banded appearance shown in FIG. 6. Example 13 was sand cast in a conventional sand mold and Example 14 was ch1ll cast 1n a conventlonal permanent metal mold.

COMPOSITION Ex'zmple P Sn Ni Pb Zn Cu Others 1.6 .92 10.1 7. 7 79.6 3.3 1. 9 8. 6 6.1 78. 6 .27 Sb, .41 Fe,

s. 7 3. 8 9. 2 6. 2 76. 5 2. 5 2.3 10.4 7.9 73. 5 1. 5 .94 10.0 6. 3 79. s 4. 3 1. 9 9. 2 7. 6 75.2 4. 0 .06 9. 7 7. 5 77. 7 4.4 3. 4 9. 2 7. 0 74. 4 2.1 1. 6 20.8 7. 7 59. 0 2.6 2. 0 10. 4 3. 7 79. 7 .35 A1, V.16 si. 2.7 2.3 14.2 1.9 74.6 3.3 A1. 3. 4 2. 3 10.5 8.5 74.8 .04 S. 2. 6 1.8 9. 6 7. 5 78. 6 3. 3 1. 9 8. 6 6.1 78.6

.27 Sb, .4l Fe,

MECHANICAL PROPERTIES Unsound casting In thousands of pounds per square inch.

A sample of the exudations in the banded areas of the casting of Example 3 was scraped from the surface of the casting and analyzed for lead content. It was found that the exudations contained 12.1% lead, by weight, whereas the body of the casting was found to contain 9.2% lead, by weight.

It will be noted from the foregoing examples that, when alloys of the composition of the instant alloys are cast by continuous casting procedures, sound castings are produced which possess mechanical properties which are equal or superior to those of a high quality leaded tin bronze.

What is claimed is:

1. A continuously cast brass casting consisting essentially of, by weight, .25 to 2.50% phosphorus, 1.5 to 4% tin, .25 to 4% nickel, more than 3 to less than 20% lead, about 4 to less than 20% zinc and the balance copper, said copper being present in an amount less than 80%, said casting containing more zinc than tin, said casting in the as cast state having a yield strength of at least 20,000 pounds per square inch, a tensile strength of at least 35,-

000 pounds per square inch, an elongation of at least 5% and a Brinell hardness above 50.

2. A continuously cast brass casting consisting essentially of by weight, .25% to 2.50% phosphorus, 1.5 to 4% tin, .25 to 4% nickel, more than 3 to less than 20% lead, about 4 to less than 20% zinc and balance copper, said casting containing more zinc than tin.

3. A brass casting according to claim 2 in which said casting possesses a plurality of peripheral bands of exudations on its surface; said exudations having a lead content which is greater than that of the body of the casting.

4. A brass casting according to claim 3 in which said bands occur regularly on the surface of the casting.

5. A continuously cast brass casting which consisting essentially of, by weight, .25 to 1.5% phosphorus, 1.5 to 3.5% tin, .25 to 2.5% nickel, 5-15% lead, 6 to 15% zinc, and the balance copper.

6. A copper-base alloy casting according to claim 5 in which said casting consisting essentially of, by weight, approximately .8% phosphorus, 3% tin, 2% nickel, 10% lead, 8% zinc and upto 77% copper.

7. A method of producing a brass casting which comprises establishing a pool of molten metal consisting essentially of, by weight, 0.25 to 2.5% phosphorus, 1.5 to 4% tin, .25 to 4% nickel, more than 3 to less than 20% lead, about 4 to less than 20% zinc and the balance copper, said molten metal containing more zinc than tin, said pool being established by melting a mixture of copperbase scrap metal and adding thereto a phosphorus master alloy, introducing molten metal from said pool into one end of an open ended mold provided with a cooling section, and withdrawing a continuous casting from the other end of the mold.

8. A method according to claim 7 in which said mold is vertically disposed with its uncooled section disposed in the bottom of said vessel, said casting is withdrawn intermittently from the mold, and said pool is maintained under a nonoxidizing atmosphere until the molten metal in the pool is cast.

9. A brass casting according to claim 2 in which said casting contains iron in an amount up to 1%.

10. A brass casting according to claim 2 in which said casting contains `sulphur in an amount up to 0.1%.

References Cited UNITED STATES PATENTS 1,868,099 7/1932 Eldred 164-89 2,195,809 4/1940 Betterton et al. 164-82 2,319,539 5/1943 Dodd 75-156.5 2,342,608 2/1944 Dodd 75-l56.5 X 2,460,991 2/1949 LeBrasse et al. 75-1565 X 2,740,177 4/1956 Smart 164-283 X 2,802,733 8/1957 Bungardt 75-163 OTHER REFERENCES Iron Age, Aug. 26, 1948, Continuous Casting-The Arsarco Process, Smart et al.

Foundry Trade Journal, vol. 102, No. 2119, May 23, 1957, relie-d on pp. 627-633.

Journal of The Institute of Metals, 1955-56, vol. 84, renee on pp. 319-326.

CHARLES N. LOVELL, Primary Examiner.

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