US2568014A

US2568014A - Graphitic nickel tin alloy and method of making same

Info

Publication number: US2568014A
Application number: US17438A
Authority: US
Inventors: Eash John Trimble; Lee Gerald Linfield
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1948-03-27
Filing date: 1948-03-27
Publication date: 1951-09-18
Anticipated expiration: 1968-09-18

Description

p 18, 1951 J T. EASH ET AL v, 2,563,014

GRAPHITIC NICKEL TIN ALLOY AND METHOD OF MAKING SAME Filed March 27. 1948 INVENTORS ATTORNEY mama s. 1a, 1951 GBAPHITIC NICKEL TIN ALLOY AND METHOD OF MAKING SAME John Trlmble Bash, Weatflcld. and Gerald Linileid Lee, Plainiield, N. 1., assignors to The International Nickel Company,

Inc., New York,

a corporation of Delaware Application March 27,1948, Serial No. 17,438

' scum. (c1. rs-1m The present invention relates to nickel alloys and, more particularly, to nickel alloys having improved castability, machinability, a high combination of physical and mechanical properties together with high resistance to galling or seizing under frictional loads; and to articles manufactured therefrom.

Many attempts have been made in the art to provide nickel alloy castings which would have high mechanical and physical properties in combination with good castability, good machinability and a high order of resistance to gelling and wear. In practice, it has been found that prior art attempts to solve these problems and to provide nickel alloy castings having such COM- tions of properties have not been completely successful. Prior art alloys having the desired mechanical and physical properties have had poor resistance to galling and wear, while prior art alloys having good resistance to galling and wear have not had the desired high combination of strength, ductility and impact resistance, together with good castability, good machinability, etc.

I It has now been discovered that the aforementioned problems may be solved in a particularly effective manner and that the art may be provided with articles made of nickel alloys having a greatly improved combination of properties, including improved mechanical and physical properties. castability, machinability, to gelling and wear, etc.

It is an object of the present invention to provide cast nickel articles such as bushings and bearings which will be corrosion-resistant and which will exhibit greatly improved non-galling characteristics under heavy loads.

It is another object of the present invention to provide a nickel alloy having a high combination of mechanical and physical properties together with high resistance to galling.

It is still another object of the present inven- Table I Element Percentage Carbon. 1-1.5

Magnesium (excess) 0. 06-0. 12 Tin 2-4 1. 5-2

tion to provide a unique nickel alloy having an improved combination of mechanical and physical properties together with good castability and good machinability.

It is a further object of the present invention to provide improved pressure-tight cast nickel articles having an excellent surface when machined or ground.

It is a still further object of the present invention to provide cast nickel articles having greatly improved bearing properties in combination with high strength and ductility.

It is another object of the present invention to provide cast nickel articles having high strength and ductility in combination with greatly improved resistance to galling and wear.

Other objects and advantages of the invention at 500 diameters showing the lightly etched structure of the alloy of the invention; and

Fig. 2 is a reproduction of a photomicrograph at 500 diameters showing the structure of the same alloy when more heavily etched.

It has now been found that nickel alloys containing critically controlled proportions of carbon, magnesium, tin, manganese and silicon possess especially useful properties a; castings in applications where soundness of casting, good castability, good strength. ductility and machinability together with high resistance to galling and wear and good bearing properties are required. These properties are obtained in nickel alloys having a composition which is preferably maintained within the approximate ranges given in Table I.

The balance of the compositions set forth in Table I is essentially or substantially all nickel, except for small amounts of minor constituents and/or impurities usually found in-nickel alloy castings containing over 90% nickel. A feature of the compositions set forth in Table I is that they are essentially not age hardenable.

A particularly distinctive microstructural fea ture of the preferred product of the invention is that substantially all the carbon in the alloy occurs as uncombined carbon, i. e., graphite, and is present in the form of randomly distributed nodules. iii-addition, an excess white phase, or beta phase' ha ifig a eutectic structure within itself is presentm. the microstructure. This excess white phase tends to occur in'a dendritic istic nodular form and the excess white phase. The "graphite particles will vary in size, some be larger and some smaller than those shown in Figs. 1 and 2. The particles may have a well-defined radial rosette pattern or may as rounded chunks. Heavier etching, as in Fig. 2, tends to reveal coring near the white phase and away from the graphite.

. It is to be pointed out that when the magnesium content of the alloy is discussed herein, the amounts of magnesium referred to are those retained in excess of the sulfur content of the alloy. For general purposes and for the purposes of the invention, it may be said that one part by weight of magnesium should be introduced into the alloy for each part by weight of sulfur-present in the with the amounts of manganese alloy, and that the excess retained magnesium content required by the invention is that in excess of this amount.

Alloys made in accordance with the present invention will usually exhibit mechanical properties within the approximate ranges given in Table II.

Table II Tensile strength, p. s.'i 00. 000-8 Yield strength, p. s. i... 34, 000-45. 000 Elongation. Per Cent in 12-16 Charpy impact, 20-1 Brinell hardness number 135-155 1 Ydield strength determined at 0.5% elongation under It is to be pointed out that the unusual combination of properties possessed by the nickel alloy of the invention, including the properties shown in Table II, is obtained as a result of the cooperative effect of the carbon, magnesium, tin, silicon and manganese contents of the alloy.

when the carbon content of the alloy is raised above the range set forth in Table I, the ductility of the resulting alloys is decreased rather markedly from the values possessed by alloys having compositions within the ranges set forth in Table I. However, where high strength is still the primary consideration and ductility is of lesser importance, carbon contents up to about 2.5% can be employed. Although it is preferred that the carbon be present largely in the form of graphite, it has been found that asmall amount .of 'carbon in the combined form contributes importantly to the desired properties of the alloy. A combined carbon content of about 0.10% to about 0.15% is preferred, and the amount of combined carbon should not exceed about 0.25%, with the remainder of the carbon being in the uncombined or graphitic form. Tin, in combination with the other elements contemplated in the alloy, hardens the matrix. As the tin is increased up to about 4%. the strength is increased. When tin is present in amounts less than about 2% but at least about 1%, the physical properties, with the exception of impact resistance, are reduced. One important effect of the excess magnesium content of the alloy is that of causing the graphite to occur in a nodular form. An excess magnesium content lower than about 0.06% and down to about 0.03% is not always sufficient to cause all the graphite to occur in'this nodular form, and the resulting alloy may have a microstructure containing both creases, together with a corresponding increase in the microstructure. This effect is accompanied 'by increased hardness and often by decreased ductility, particularly when the excess magnesium is substantially above 0.12%, e. g., 0.20%. Silicon within the range of 0.5% to 4% improves the strength of the alloy, particularly in combination disclosed herein. Silicon also acts in combination with these amounts of manganese to improve the fluidity and casting properties of the alloy and tends to increase the recovery of magnesium and manganese in the melting operation. Manganese, in amounts of about 0.5% to about 4%, has a marked effect on the castability and fluidity of the alloys when used in combination with silicon and the other elements of the composition, and proper control of composition within the ranges set forth herein leads to the production of sound castings which fill the mold sharply and are free of internal defects such as laps, folds, etc. The

compositions defined by Table I may be iron-free Table III Element con Manganese. Nickel.

Nickel preferably constitutes at least about of the alloy. Alloys having compositions within the ranges defined in Table 111 may be devoid of iron or may containup' to 10% iron, e. g., 0.1% or 0.2% up to 10% iron. When tin is employed in amounts above the preferred amounts specifled in Table I, the magnesium employed preferably should be increased correspondingly in order to insure that all or substantially all graphite will be in a nodular form. Thus, if the tin content slightly exceeds 4 e. g., 4.5%, the excess magnesium content preferably should be about 0.12% or more, while with a tin content of 5% the excess magnesium content preferably should be about 0.13 or more, and with a tin content of 6% the excess magnesium content preferably should be about 0.15% or more.

Each of the elements present in the alloy of the invention should be maintained within the ranges shown in Table III, as otherwise the effect produced by these combinations of elements is impaired. Thus, when the carbon content is decreased below 0.8% the strength, machinability and gall resistance are markedly decreased, and when the carbon content is increased above 2.5% strength and ductility are impaired. The combined carbon content of alloys having compositions within the ranges defined in Table III should be between about 0.08% and 0.25%. Alloys containing less than 1% tin have poorer gall resistance, while those having more than about v w ascaou.

6% tin have poor ductility, impact resistance and machinability. when the excess magnesium is decreased below 0.03%, the graphite is substantially entirely present in the flake form and the alloy has poor strength and gall resistance, while when the excess magnesium is increased above about 0.25% the ductility of the alloys is markedly reduced. When either silicon or manganese are present in amounts of less than 0.5%, difliculties are encountered in' the alloys and the resultant castings are porous and/or are otherwise defective. Wh these elements are present in amounts of over 1%, no beneficial effect is found and, in the case of silicon, diiliculties are encountered due to silicon segregation.

Other elements which may be present as minor constituents and/or impurities include cobalt, copper, chromium, zinc, etc. "The alloy may be devoid of any of these minor constituents and/or impurities or it may include amounts of cobalt from about 0.1% to 5%, of copper from about 0.1% to 10%, of chromium from about 0.1% to 5%, and/or of zinc from about 0.1% to 3%. Generally, the nickel'content will be at least 70% of the alloy, and preferably is at least 80% of the alloy. It has been found that amounts of lead up to about 1% reduce the ductility but otherwise have no particularly deleterious eifect. It is to be understood that when nickel is said to constitute the balance or when it is said that the balance is substantially or essentially all nickel, it is not intended to exclude minor constituents and impurities which may be present in amounts which occur in comparable nickel products, or in amounts not adversely affecting the desired properties of the alloy.

The alloy of the invention is characterized by excellent machinability, and is comparable in this regard to gray cast irons. As an empirical illustration of machinability, it may be pointed out that this material was out without lubrication by a power hack saw at about the same rate as cast iron and with little loss of blade life. In addition, it has been found that threading operations can be performed without lubrication at feeds and speeds regularly used in threading cast iron and that an excellent finish is obtained on the threads. Castings made of the alloy of the present invention were found to have an excellent finish after being subjected to machining operations without lubrication. An excellent ground finish was also obtained on the alloy when grinding operations were performed thereon.

In order that those skilled in the art may have a better understanding of the present invention, examples illustrating the analyses of preferred alloy compositions and resulting physical properties, together with comparative examples illustrating the effect of variations in composition, are given in Tables IV and V. The balance of the compositions in Table IV is essentially nickel.

Table V Tensile Elonga- Oharpy Y. 8 Alloy N o Strength, tion, pac BHN p. s 1 Per Cent mm? 1. M, 400 05, 000 14 21 146 2- 36. 700 70, 3!!! Y 17 3- 44, 800 m. 250 16 150 4. 36, 500 53. 300 7 13) 5- 31, 000 40, 5M 9 36 118 6- 33. 21) 55, 300 10 1% 7. 24, W0 60, 750 '27 110 '8. m, 000 35, 000 10 92 Y. 8.:Yield strength. determined at 0.5% elongation under load.

In the foregoing Tables IV and V, alloy No. 1 and alloy No. 2 are within the preferred ranges of composition. In alloy No. 3, the tin content was increased to 4%. This alloy had high strength and hardness combined with quite good ductility. Alloy No. 4 illustrates the effect on the properties caused by increasing the carbon content to 2%.

It will be seen that the elongation is sharply reduced and that the tensile strength is lowered by this increase in carbon content. Alloy No. 5, which had a tin content of 1.2% and a carbon content of 0.76% had low elongation together with low yield strength, low tensile strength and low hardness. In alloy No. 6, which had a tin content of 1.5% and a carbon content of 1%, the yield strength, tensile strength and hardness were higher than the values found for alloy No. 5. Alloy No. '1 was made of substantially the same base metal as alloy No. 1, with the exception that no tin was incorporated in alloy No. 7. It is to be noted that this alloy exhibited low hardness and yield strength but 'had high elongation. This alloy is representative of 'a class of tin-free alloys containing about 0.65% to 3% of carbon, about 0.035% to 0.45% magnesium, about 1% to 4% of silicon, about 0.5% to 4% of manganese, and the balance essentially nickel. Alloys having compositions within these ranges have a good com-- bination of properties but are less strong and have poorer anti-galling properties than the alloys of the present invention. In alloy No. '7, the graphite was controlled to the form of well-distributed nodules, and it is believed the high elonexcess magnesium in combination with tin.

'15 prepared from the test alloys. The gelling or The foregoing Tables IV and V illustrate the unusual combination of mechanical and physical properties imparted to the alloy of the invention by a critical combination of magnesium, tin, carbon, silicon and manganese. However, another unusual and distinctive property possessed by the alloy of the invention is that of high resistance to galling and seizing under a frictional load. As those skilled in the art know, it is difficult to measure and evaluate the anti-gelling and anti-seizing properties of metallic materials, but a suitable method which has been employed to determine galling and seizing resistance of the alloy of the invention and which has been found to give results comparable with those obtained in practice is as follows:

Test specimens one-half inch wide, about onequarter inch thick, and several inches long were 7 seizing tests were performed. upon specimens which had been ground so that the grinding marks were parallel with the direction of movement of the movable specimen when the test the load" values were nearly the same throughout the test. On the other hand, the poor antigalling properties of both alloys No. '1 and No. 8

. are confirmed by their appearance after testing specimens were assembled in the fixture. Grindand by the values under the "load column for ing was done with .a silicate bonded aluminum these alloys which show that the load had to be oxide abrasive grinding wheel having a grit size arkedly increased during the test to move the of 46 mesh, using a 0.0005" cut at 60 feet per specimen. Similar tests conducted on a magminute and 0.032 transverse feed per stroke. S um-free alloy containing about 1% c The grinding wheel was rotated at 2300 revoluabout 2.5% tin, about 1.5% manganese, about tions per minute, equivalent to about 6000 sur- 2% silicon, and the balance nickel, and on a face feet per minute. Two specimens of the alloy carbon-free alloy containing about 2.5% tin, were fixed in face-to-iace relationship in each about 0.1% magnesium, about 1.5% manganese, of two slotted plates of a testing fixture. A third, about 2% silicon and the balance nickel, conmovable, test specimen 0: the same alloy was fi e t these alloys. w ich are outside the then placed between the two fixed specimens 1 the P sent t o li ewi e had 9 and perpendicular thereto such that between the gall resistance. movable specimen and each of the fixed speci- Alloys within the scope of the invention had mens two contacting surfaces /g" by square excellent wear-resistance when tested in the and on directly opposite sides of the ov ble o Amsler wear test described in Transactions of test specimen were provided. A spring load was the American Institute of Mining and Metallurthen applied to the fixture in such manner that 8 0 En rs, V P e et 0- (1946) the contact'surfaces were stressed in compresemploying for lubrication a high-grade turbine sion at the constant value of 3000 pounds per oil having a viscosity of 300 Saybolt. Thus, oilsquare inch during the course of the test. The lubricated specimens of a preferred alloy conassembled fixture was then placed in a comprestaining about 2.5% tin and the other elements sion test machine and a load was applied to the in the same amounts as in alloy No. 6 showed a movable specimen to cause it to move perpendicweight loss of only 4.9 milligrams after 2,000,000 ularly to the fixed specimens and to keep the revolutions when tested against itself, and a contact surface area constant at by A" weight loss of only 2.8 milligrams after 2,000,000 square on each opposite side of said movable test revolutions when tested against a heat treated specimen. The movable specimen was forced S. A. E. 3140 steel having a Brin'ell hardness of through about one-half inch of travel at a speed 300.

of one-half inch per minute without lubrication. The alloy of the invention can be produced in During the test, the load required to move the 5 any of the furnaces normally used in melting specimen was measured at regular intervals over nickel alloys, e. g., the direct arc furnace, inducthe distance traveled by the movable specimen. tion furnace, crucible furnace, etc. A convenient These data are shown in Table VI. method to employ in melting the alloy is to first Table VI Alloy No l 3 5 0 7 8 Movement, in. 1000,1115. Load,lbs. Load, lbs. Load, lbs. fg

0.05. 505 410 420 405 055 450 0.1. 000 375 410 495 720 415 0.15. 505 400 400 495 755 500 I 0.2.. 595 410 385 500 780 525 0.25. 505 425 500 510 000 500 0.3.. 515 400 380 520 835 500 0.55. 565 375 ,zso 530 835 505 0.4. 550 400 375 535 m 000 0.45 545 425 575 530 Appearance of test not galled not gelled not galled not gelled gelled gelled The shape of the curve obtained upon plotting the data obtained in the aforedescribed test indicates the anti-galling or anti-seizing properties of the alloy in actual service. Thus, if when load is plotted as ordinate against the distance traveled by the movable specimen as abscissa, a curve having a sharply ascending slope (i. e., one which would show that a. continually increasing load was required in order to move the specimen) is indicative of poor antigalling properties, while a curve which is nearly horizontal with the abscissa or actually slopes downwardly is indicative of good anti-galling properties. I

Referring to Table VI, it may be seen that the very good anti-galling properties of alloys within the scope of the invention, i. e., alloys No. 1, No. 3, No. 5 and No. 6, are confirmed by the appearance of the alloys after testing and by the values prepare a nickel melting stock containing 2% or more of carbon. This melting stock can then be remelted and, if necessary, diluted with nickel (e. g., electronickel) to produce the desired final carbon content in the solidified alloy. In this manner. good control of carbon content can be effected. The other additions can then be made to obtain the desired final alloy.

In order to illustrate a satisfactory method for producing the alloy of the present invention, the following illustrative example is given:

Using either an induction furnace having a clay graphite crucible or an electric arc furnace having a basic lined bottom, either carbon-nickel stock with or without electronickel to adjust the carbon concentration or electronickel with an amount of carbon equivalent to about 125% of the desired final carbon content is melted down. The carbon may be in the form of crushed elecunder the "load column for these alloys since trode butts, graphite, low sulfur coke, etc. When the bath is molten, about half the desired silicon is added; e. g., as ferro-silicon containing about 97% silicon, together with the required manganese, e. g., as ferro-manganese containing 97% .mangane'se. The bathis stirred to insure solution of the manganese; then the required amount of tin is added. About 3 ounces of 67% mag-, nesium-33% nickel alloy per 100 pounds of charge are added by thrusting the alloy beneath the surface of the melt; then the remainder of the required silicon is added. A pouring temperature of about2650" F. is satisfactory, although temperatures within the range of about 2450 to about 2750 F. may be used depending on the section being cast. The split addition of silicon in the foregoing manner appears to have an important iluxing effect which increases recovery of manganese and magnesium. It is preferred that the final silicon addition be at least 0.25% of the alloy, e. g., 0.25% to 2.5%, preferably 0.5% to- 1%. When high carbon nickel melts (e. g., melts containing over about 2% carbon) are being made, there may be a rejection of kish" graphite from the melt when the silicon addition is made.

If an indirect arc furnace is used, the molten metal is usually tapped into a hot ladle, and the tin, magnesium and final silicon can be ladle additions. As with all high nickel alloys, risers and gates should be generous and a shrinkage allowance of about /4 inch per foot should be made. Of course, the moisture content of the molding sand should be carefully controlled and, if all bonded cores are used, they should be completely baked and dried; otherwise, some difliculties may be encountered which may produce porosity, etc., as a result of a reaction between the molten metal and the sand mold and/or sand core.

As pointed out hereinhefore, distinctive features of the microstructure of the alloys of the invention are the presence of a randomly distributed graphite excess phase having a nodular structure and the presence of another excess white or beta phase having a eutectic structure. This other excess white phase tends to appear in a dendritic pattern. The relative amounts of these excess phases appearing in the microstructure of the cast alloy are largely a function of the chemical composition of the alloy. Since the occurrence of graphite in a nodular form is a property conferred by a cooperative effect of the magnesium and carbon contents of the alloy, the amount of nodular graphite appearing in the structure is directly proportional to the uncombined carbon content of the alloy when magnesium is present in amounts'within the preferred range. The excess white .phase increases in amount with increases in the magnesium content and/or of the tin content of the alloy. It has been found that increases in the magnesium content tend to increase the combined carbon content of the alloy, 1. e., to increase the ratio of combined carbon to uncombined carbon in the alloy. Some of the combined carbon appears to occur as a component of the beta phase which apparently contains magnesium, tin, carbon and nickel. It is believed that this microstructure contributes importantly to the unique combination of properties possessed by the alloy.

The alloy of the invention possesses a unique combination of properties which make it useful in a wide number of applications. Thus, the

alloy of the invention has excellent foundry characteristics, i. e., it has good fluidity in the molten 10 state, fills the mold sharply when cast. and has little tendency toward the production of internal voids and shrinkage cavities, provided proper mom design is employed. For example, castings -which have to be prmsure-tight may safely be Castings in the form of castings in many amilications,

including liners, such as are used in pumps pump housings; pistons and pistonrings; impellers; bushings; bearings; valve bodies; fittings; etc.

Although the present invention has been described in conjunction with preferred embodiments. it is to be understood that modifications and variations may beresorted to' without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Variations and modifications apparent to those skilled in the art are considered to be within the purview and scope of the invention and appended claims.

We claim: V

1. As a new article of manufacture, a casting made of a graphitic alloy having graphite present in a nodular form and comprising 0.8% to 2.5% carbon including0.08% to 0.25% combined carbon, 1% to 6% tin, 0.5% to 4% silicon, 0.5% to 4% manganese, sulfur inan amount not subversive to the occurrence of nodular graphite, magnesium in an'amount exceeding the amount of sulfur present by 0.03% to 0.25%, up to 10% iron and the balance essentially nickel, the nickel content constituting at least of the alloy, said alloy being characterized by a microstructure containing an interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

2. A nickel alloy casting containing 1% to 1.5% carbon, 2% to 4% tin, sulfur in an amount which occurs in graphiticnickel product, magnesium in an amount exceeding the amount of sulfur present by 0.06% to 0.12%, 1.5% to 2% silicon, 1% to 1.5% manganese, up to 5% iron and the balance essentially nickel, said alloy being characterized by a microstructure containing an intermediate phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gallresistance.

3. A nickel alloy casting containing 1% to 1.5% carbon, 1% to 4% tin, sulfur in an amount which occurs in graphitic nickel alloy castings, magnesium in an amount exceeding the amount of sulfur present by 0.06% to 0.12%, 1.5% to 2% silicon, 1% to 1.5% manganese. up to 5% iron and the balance essentially nickel, said alloy being characterized by a microstructure containing an' interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength in an amount exceeding' present by 0.06% to 0.12%,

. 11 ceeding' the amount ofsulfnr present by 0.03% to 0.25%, 1.5% to 2% silicon, 1% to 1.5% manganese, up to 5% iron and the balance essentially nickel, said alloy being characterized by a microstructure containing an interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

5. A nickel alloy casting containing 0.8% to 2.5% carbon including 0.08% to 0.25% combined carbon, 1% to 6% tin, sulfur in an amount which occurs in graphitic nickel products, magnesium the amount of sulfur 0.5% to 4% silicon, 0.5% to 4% manganese, up to-10% iron and the balance essentially nickel, said alloy being characterized by a microstructure containing an interdentritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

6. A nickel alloy casting containing 0.8% to 2.5% carbon including to 0.25% c m i e carbon, 1% to 6% tin, sulfur in an amount which occurs in graphitic nickel alloy castings, magnesium in an amount exceeding the amount of sulfur present by 0.03% to 0.25%, 0.5% to 4% silicon, 0.5% to 4% manganese, up to 10% iron and the balance essentially nickel, said alloy being characterized by a microstructure containing an interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

7. The method of producing a graphitic nickel alloy casting which comprises establishing a molten nickel bath containing sulfur in an amount which occurs in graphitic nickel alloy castings and 0.8% to 2.5% carbon, adjusting the, bath temperature within the range of about 2450 to about 2750 F., introducing 0.5% to 4% manganese together with a portion of the silicon required to produce a silicon content of 0.5% to 4% in the solidified casting, introducing 1% to 6% tin, introducing megnesium in an amount exceeding the amount of sulfur present by 0.03% to 0.25%, introducing as a final addition 0.25% to 2.5% silicon to provide a silicon content of 0.5% to 4% in the solidified casting and casting the bath to obtain a nickel alloy casting containing sulfur in an amount which occurs in graphitic nickel alloy castings and 0.8% to 2.5% carbon, 1% to 6% tin, magnesium in an amount exceeding the amount of sulfur present by 0.03% to 0.25%, 0.5% to 4% silicon, 0.5% to 4% manganese and thebalance essentially nickel, and characterized by a microstructure containing an interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

'8. The method of producing a graphitic nickel alloy casting which comprises establishing a molten nickel bath containing sulfur in an amount which occurs inwgraphitic nickel alloy castings and 0.8% to 2.5% carbon. adjus i g t e 12 bath temperature within the range 01' about 2450' to about 2750 F., introducing 0.5% to 4% manganese together with about half of the silicon required to produce a silicon content of 0.5% to 4% in the solidified castmg, introducing 1% to 6% tin, introducing magnesium in an amount exceeding the amount of sulfur present by 0.03% to 0.25% magnesium. introducing as a final addition the remainder of the silicon required to produce a silicon content of 0.5% to 4% in the solidi,- fled castingand casting the bath toobtain a nickel alloy casting and characterized by a microstructure containing an interdendritic phase having a eutectic structure within itself and nodular graphite and by an improved combination of tensile strength and gall resistance.

9. As a new article of manufacture, a casting comprised of a graphitic nickel alloy having graphite present in a nodular form and containing 0.8% to 2.5% carbon including 0.08% to 0.25%; 1% to 6% tin; the tin content having subversive to the occurrence of nodular graphite in the alloy;-magnesium in an amount exceeding thee-mount of sulfur present by 0.06% to 0.25%; 1% to 6% tin; the tin content having such a relation to the magnesium content in excess of the amount of sulfur that with 4.5% tin said magnesium content is at least 0.12%, with 5% tin said magnesium content is at least 0.13% and with 6% tin said magnesium content is at least 0.15%; 0.5% to 4% silicon; 0.5% to 4% manganese; up to 10% iron and the balance essentially nickel; said alloy being characterized by a microstructure containing a white phase and substantially all the graphite in a nodular form and by improved tensile strength and gall resistance as compared to a similar graphitic nickel alloy containing flake graphite.

JOHN TRINEBLE EASH. GERALD LINFIELD LEE.

REFERENCES CITED The following references are of record in the file of this patent:

1947; pages 3574359, 366, 367 (complete article pages 321-371.

Willings Press Guide, 1947, published by Willings Press Service, Ltd., London, England; 9 88s 1, 125.

Claims

1. AS A NEW ARTICLE OF MANUFACTURE, A CASTING MADE OF A GRAPHITIC ALLOY HAVING GRAPHITE PRESENT IN ANODULAR FORM AND COMPRISING 0.8% TO 2.5% CARBON INCLUDING 0.08% TO 0.25% COMBINED CARBON 1% TO 6% TIN, 0.5% TO 4% SILICON, 0.5% TO 4% MANGANESE, SULFUR IN AN AMOUNT NOT SUBVERSIVE TO THE OCCURENCE OF NODULAR GRAPHITE, MAGNESIUM IN AN AMOUNT EXCEEDING THE AMOUNT OF SULFUR PRESENT BY 0.03% TO 0.25%, UP TO 10% IRON AND THE BALANCE ESSENTIALLY NICKEL, THE NICKEL CONTENT CONSTITUTING AT LEAST 80% OF ALLOY, SAID ALLOY BEING CHARACTERIZED BY A MICROSTRUCTURE CONTAINING AN INTERDENDRITIC PHASE HAVING A EUTECTIC STRUCTURE WITHIN ITSELF AND NODULAR GRAPHITE AND BY AN IMPROVED COMBINATION OF TENSILE STRENGTH AND GALL RESISTANCE.