US3836358A

US3836358A - Addition agent

Info

Publication number: US3836358A
Application number: US00379565A
Authority: US
Inventors: R Jones
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1973-07-16
Filing date: 1973-07-16
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17
Also published as: DE2433511A1; CA1017170A; NO742499L; ZA744295B; JPS5070215A; FR2237972A1; AU7109474A

Abstract

Composition and process for improving the castability of nickelchronium alloys with addition agent comprising nickel, chromium, iron, silicon and boron.

Description

1111mm Mnms Enmm 1191 J nes Sept. 17, 1974 1 ADDTTTON AGENT [75] Inventor: Robin Maclray Forbes Jones, [56] References Cited Suffern, NY. UNITED STATES PATENTS 1,514,064 11/1924 Mandel! 75/170 [73] Assgnee' 1 g g figgfl y Company 2,875,043 2/1959 Tour 75/171 3,336,118 8/1967 Newitt 75/134 X [22] Filed: July 16, 11973 Primary Examiner-L. Dewayne Rutledge [21] Appl' 379565 Assistant Examiner-Arthur J. Steiner [52] US. Cl. 75/122, 75/128 C, 75/128 F, 57 ABSTRACT [51] 5 3 75/134 75/1305 75/ Composition and process for improving the castability [58] d 2 S of nickel-chronium alloys with addition agent compris- T g 5 171 2 IZSA ing nickel, chromium, iron, silicon and boron.

P, 128 w, 5 10 Claims, No Drawings ADDHTHUN AGENT The present invention relates to metallurgy and more particularly to metallurgic compositions, including alloys, compacts and mixtures, containing controlled proportions of silicon, boron and other elements.

There are many and various needs for corrosionresistant structurally serviceable alloy articles and it is often desirable to fulfill such needs by producing nickel-chromium alloy castings, particularly including austenitic stainless steel castings. Actually, nickelchromium alloy castings have been made for many years, with the majority being austenitic nickelchromium stainless steels. However, unsatisfactory results in the form of coldshuts, fold lines and misruns, or rough surfaces and burn-on from casting at very high pouring temperatures in sand molds, frequently occur due to poor castability characteristics of many conventional austenitic stainless steels, such as AISI Types 302 and 304 or AC! types CF40 and CF-0, and other nickel-chromium alloys. And of course, continual losses due to a proportion of defective castings add to the total cost for obtaining a proportion of satisfactory castings. Recently, improved castability characteristics have been achieved with certain special austenitic stainless steel compositions containing specially beneficial proportions of silicon and boron along with particularly controlled proportions of other elements required in austenitic nickel-chromium stainless steels.

For instance, special stainless steel alloy castings of compositions containing 2 to 5 percent silicon, 0.2 to 1.4 percent boron, 6 to 30 percent nickel and M to 26 percent chromium which are characterized by unusu ally good castability are referred to in my U.S. Patent application Ser. No. 337,278, filed Mar. 7. 1973. Yet, prior years of production of conventional stainless steels, both in cast forms and in wrought forms, have generated accumulations of scrap metals, e.g., gates and risers, croppings, and obsolete or defective castings or forgings, having austenitic nickel-chromium alloy compositions containing little or no silicon and boron, e.g., AISI Types 302 and 304!- and ACl Types CF-20 and CI -0. However, castability characteristics of many such conventional stainless steels are generally poor and disadvantageous for casting in thin-sectioned or complex mold cavities, especially after the steels are remelted in the recycling of scrap. Commercial benefit can be derived from improving the castability of known stainless steel scrap by converting such scrap into special silicon-boron stainless steel. But adding silicon and boron in elemental form, or as commercially available prealloys, e. g., ferrosilicon and ferroboron, has production disadvantages, such as uncertain recoveries and dilution of other elements that are required in the finished alloy. Adding compensating amounts of other required elements, e.g., nickel and chromium, further complicates the problem of recovering correct alloying proportions in the finished steel and involves extra costs and time for calculating, measuring and introducing a variety of individual additions. Moreover, as the number of alloying additions is increased, the possibilities of errors are increased and reliability decreases. It would be desirable to have a reliable, commercially economical means for improving the castability of scrap stainless steels or other alloys and concomittantly maintaining the required proportions of alloy ingredients in the steel.

There has now been discovered a composition of matter that is beneficial for improving the castability characteristics of many stainless steels.

It is an object of the present invention to provide a new composition of matter.

()ther objects and advantages of the invention will become apparent from the following description.

The present invention contemplates a metallurgical composition comprising, by weight percent, about 7 to 50 percent nickel, T2 to 40 percent silicon, 2 to 10 percent boron, to 30 percent chromium, up to 0.2 percent carbon, up to 6 percent manganese, up to 6 percent phosphorus, up to 10 percent molybdenum, up to 10 percent copper, and balance essentially iron in an amount of at least l0 percent. Sulfur and other impurities that may be detrimental to nickel-chromium alloys are limited to low levels, e.g., not more than 0.02 percent. If the composition is for use in making alloys wherein phosphorus is undesired, phosphorus should be restricted to not exceed 0.02 percent; similarly cop per and molybdenum can be restricted to not exceed 0.5 percent each. The composition is particularly useful for improving the castability characteristics of many presently known austenitic nickelchromium alloys. For instance, addition of the composition to a melt of AISI Type 302 wrought stainless steel scrap in weight proportions of parts of the composition to 100 parts of scrap improves the castability characteristics of the resulting alloy. Improvements provided by the composition of the invention are especially beneficial for ob taining good filling of thinsectioned complex cavities in foundry molds wherein the cast metal must flow and merge, or knit, cleanly with itself without formation of fold lines or cold shuts. The composition is also beneficial for improving the castability characteristics of other nickel-chromium alloys based on nickel and/or iron, particularly including alloys containing at least 7 percent nickel, at least 116 percent chromium, a total of at least 50 percent nickel-plus-iron and characterized by liquidus temperatures of about 2,300F. or higher.

Advantageously, an alloy comprising 7 to 50 percent nickel, 12 to 40 percent silicon, 2 to 10 percent boron, T6 to 30 percent chromium and 10 percent or more iron in accordance with the composition of the invention is provided by melting together the required elements, which can be in elemental or prealloyed forms, e.g., elemental nickel or ferrochromium. The proportioning of the ingredients provides good melting and solidification characteristics that provide a clean homogeneous alloy and avoid detrimentally excessive segregation or oxidation.

The alloy has good crushability characteristics which enable the alloy to be readily fractured into pieces suitable for weighing, conveying, or packaging to facilitate use as additions to furnace charges or metal baths. Incorporating the alloy of the invention in a furnace charge composed of metal scrap, or partially of scrap and partially raw materials, or even entirely of raw materials, is considered advantageous for aiding rapid meltdown and obtaining a clean melt.

Silicon and boron in the hereinbefore stated proportions of T2 to 40 percent silicon and 2 to 10 percent boron in the composition of the invention are important for achieving the improved castability of stainless steels and other more highly alloyed metals referred to herein and for obtaining reliable recoveries and safeguarding ductility characteristics. Additions of the composition amounting to about 5 to percent, e.g., 110 percent, of the scrap or other furnace charge ingredients are recommended for practical production operations in order to enhance melting and castability characteristics without excessive dilution of the basic charge.

The nickel in the addition composition (at least about 7 percent) is needed for maintaining an austenitic structure in casting alloys prepared with the addition composition Furthermore, the nickel in the addition composition aids in offsetting possible embrittling tendencies of silicon in castings. Chromium is included in the addition alloy to maintain the chromium level of the casting alloy. Excessive amounts of nickel and chromium are avoided in order to avoid undesirably shifting the alloy balance of the casting alloys.

Molybdenum and copper can be incorporated in the addition composition when it is to be used for steels containing these elements, which are sometimes in cluded for desired purposes such as corrosion resistance. Phosphorus, e.g., 4 percent or 6 percent phosphorus, can be included for improving fluidity and resistance to hot tearing, especially when producing steels for casting into metal molds.

The composition of the invention is proportioned to contain 10 to 63 percent iron, thereby enabling the composition to be prepared with commercially available low-cost raw materials such as ferrochromium, ferrosilicon and ferroboron.

To facilitate carrying the invention into practice for production of special casting compositions, the invention provides the following special restricted compositional ranges, referred to herein as compositions (or alloys) A, B and C, for alloys or other composition forms, e.g., briquettes:

Composition A 30 to 45 percent nickel, 14 to 22 percent silicon, 2.5 to 5 percent boron, 116 to 30 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 5 percent molybdenum, up to 5 percent copper, and balance iron in an amount of at least 10 percent;

Composition B 40 to 50 percent nickel, 25 to 35 percent silicon, 3.5 to 5.5 percent boron, 16 to 22 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 6 percent molybdenum, up to 9 percent copper, and balance iron in an amount of 10 to 20 percent; and

Composition C 7 to 20 percent nickel, 30 to 40 percent silicon, 5 to 9 percent boron, 116 to 22 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 2 percent phosphorus, up to 10 percent molybdenum, up to 5 percent copper, and balance iron.

Compositions A and B are beneficial for improving the castability of stainless steels and nickel-chromiumiron heatresisting alloys. For instance, the castability of a furnace charge of type 304 stainless steel scrap is improved by adding about W to 115 pounds of Composition A or 5 to 10 pounds of Composition B per hundred pounds of furnace melt of type 304 scrap. Although Composition B may be more expensive to manufacture with raw materials having relatively low iron contents, Composition B is particularly well suited for improving the castability of high nickel stainless steels or heat resisting steels such as type HU (40% Ni) or HW(60% Ni). Composition A can be made largely from ferroalloys and elemental nickel. Composition C is particularly useful for improving castability with small additions to nickel-base alloys. For instance, addition of about 5 to 9 pounds of Composition C per one hundred pounds of melt of a nickel-base alloy containing about 45 percent or more nickel, 22 percent chromium, 18 percent iron, 9 percent molybdenum, up to 1.5 percent silicon, up to 1.5 percent manganese and up to 0.15 percent carbon provides improved castability for satisfactorily filling 3/l6-inch thick cavities in sand molds and avoids defects such as folds, cold shuts or unfilled corners.

For using the composition of the invention it is recommended that the composition, advantageously an alloy, be added in a proportion sufficient to raise the silicon and boron contents of the furnace charge, after melting and addition, to at least 2 percent silicon and at least 0.2 percent or preferably 0.25 percent boron,

advantageously 2.5 percent or more silicon and 0.3 percent or more boron, in order to obtain advantageously good castability characteristics. Generally, for most purposes, the addition proportions will be about 5 to 25 parts per 100 of the furnace charge weight before the addition.

A specially advantageous composition (Composition D) for improving castability in commercial production of austenitic nickel-chromium stainless steels contains 30 to 40 percent nickel, M to 18 percent silicon, 2 to 3.5 percent boron, 20 to 25 percent chromium, up to 0.2 percent carbon, advantageously not more than 0.15 percent carbon, up to 2 percent manganese, up to 0.02 percent phosphorus or, if phosphorus is desired, 4 to 6 percent phosphorus, balance iron. Additions of an alloy of Composition D to stainless steel melts or furnace charges containing about 6 to 12 percent nickel, 15 to 20 percent chromium, up to 1.5 percent silicon, up to 0.02 percent boron, up to 0.15 percent carbon, and balance essentially iron is particularly recommended in proportions of about 10 to 20 parts of addition alloy D per 100 parts of the stainless steel melt in order to improve the castability of the melt, especially when the melt is made from scrap. When desired for use in stainless steels containing molybdenum and/or copper, possibly about i to 10 percent molybdenum and/or 1 to 10 percent copper, the same proportions of molybdenum and/or copper can be included in the addition alloy.

Combinations of special embodiments of the alloy of the invention, e.g., a combination of alloy A and alloy B, are desirable for incorporating specially required proportions of the addition alloy elements into the furnace charge.

For the purpose of giving those skilled in the art a better understanding of the invention and the advantageous thereof, the following illustrative examples are given.

EXAMPLE I A composition comprising nominally 20 percent silicon, 3.5 percent boron, 30 percent nickel, 19 percent chromium and balance iron was prepared as an addition alloy (Alloy I) using, as raw materials, electrolytic nickel, low carbon ferrochromium percent chromium), ferrosilicon percent silicon) and ferroboron (20 percent boron). Melting procedure was to charge the nickel, ferrochromium and ferroboron, melt down, then add the ferrosilicon and pour the melt at 2,050F. The melting done in a magnesia-lined induction furnace; both melting and pouring were in an air atmosphere. Proportions of the raw materials were about 30 percent nickel, 27 percent ferrochromium, 21 percent ferroboron and 22 percent ferrosilicon. The molten alloy was cast in graphite molds for circular cross-sectioned tapered ingots. After solidifying the alloy was fractured into pieces for use as melt additions. Chemical analysis of the resulting alloy 1 was 19.7 percent silicon, 30.5 percent nickel, 16.9 percent chromium, 3.041 percent boron and balance iron (about 35 percent iron by difference).

Pieces of addition alloy I were added to a molten bath of type 304 stainless steel scrap. Prior to the addition, the scrap melt composition was 0.096 percent carbon, 0.85 percent silicon, 1.6 percent manganese, 9. 1 percent nickel, 18.4 percent chromium, 0.025 percent phosphorus, 0.017 percent sulfur and balance iron. The proportion of the addition alloy was about 13 percent of the total charge after addition; or in other words, about 15 parts of alloy I were added per 100 parts of melted scrap. The addition alloy melted and blended cleanly into the molten bath of stainless steel scrap and then the blended metal (Steel IA) was cast into shell molds for escutcheon plates (about 3 inches diameter by A to %inch thick) and into a green-sand CP (Chinese Puzzle) pattern mold. Pouring of molds began at about 2,700F. with the escutcheon plate molds and finished at around 2,650F. with the CP mold. The CP pattern, which heretofore was designed by others to test castability characteristics of metals, such as the ability of molten metal to run through the passages of a complex mold with abrupt changes in flow direction that are conductive to turbulence, comprises eight partially adjoining plate-shaped cavities, each about 3/16- inch thick and 1 /2 inch square. Accordingly, production of good castings with the CP pattern requires more than simple capability of metal to remain fluid over the coarse of a long run, such as in a fluidity spiral, inasmuch as the CP mold requires the flowing metal to change flow direction abruptly in re-entrant flow patterns with the flow meeting and then merging with itself, thus presenting multiple possibilities of entrapping surface films and forming fold line defects, e.g., cold shuts; moreover, this pattern requires filling of many sharp corners. Difficult casting flow situations presented in the CP mold are often encountered similarly in commerical production of thin-sectioned complex sand castings. Visual examination of the escutcheon plates and CP pattern casting (CPI) of steel IA showed that the metal ran cleanly in the mold and filled fine detailed sections. The examination also showed the castings were of good quality, with no evidence of other defects, such as hot tears, and confirmed that good castability was obtained with the addition of alloy 1 to produce steel IA. Dropping of an escutcheon plate casting onto concrete from a height of about eight feet and a subsequent visual examination finding that no visible cracking had occurred confirmed that sand castings of steel IA had good impact resistance to rough handling.

EXAMPLE II Another example of an addition alloy (Alloy ll) of the invention was prepared for a nominal alloy composition containing 35 percent nickel, 15 percent silicon, 3 percent boron, percent chromium and balance iron by air-induction melting in a magnesia lined furnace. The melt was poured at about 2,700F. and then solidified in tapered graphite molds for ingots. Chemical analysis of the solidified alloy II was 34.6 percent nickel, 15.1 percent silicon, 2.0 percent boron, 19.8 percent chromium, 0.092 percent carbon and balance iron. A freezing point determination showed that dur-.

ing cooling alloy ll commenced solidifying at about 2,150]F. Alloy II had good crushability characteristics and was easily fractured by dropping and hammering.

An air-induction melt of an austenitic stainless steel (Steel II) having a chemical analysis of 8.3 percent nickel, 0.42 percent silicon, 17.7 percent chromium,.

1.17 percent manganese, 0.12 percent carbon and balance iron was air-induction melted and a portion of the melt was poured at 2,750F. into a green sand CP mold (CPU-1 After pouring CPlI-ll, fractured pieces of addition alloy II were added to the remainder of the molten bath of steel ll ina proportion of 15 parts alloy ll per parts of steel Il. Blending of alloy ll into molten steel II in the furnace resulted in steel IIA. Then, a portion of the bath of steel IIA was poured at 2,750F. into another CP pattern mold to produce casting CPU-2. Next, the temperature of the bath of steel IIA was lowered to 2,650F. and casting CPII-3 was poured. Then, the remaining bath was held for 10 minutes at 2,650F. and thereafter another portion of steel IIA was cast at 2,650F. into a CP mold to produce casting CPU-4. Examination of the foregoing four (CP pattern castings showed that: CPU-1 had more than 20 visible fold line defects with at least one in each of five cavities, al though the metal had run into six of the cavities (3/16 inch by 1 inch square) and about half-way into the seventh cavity; CPIl-2 had only one minor fold, in the fith cavity, although the metal had run only partly into the sixth cavity; CPIl-3 had all eight cavities filled without any folds, but had one other kind of defect in one cavity; and CP-fil had six cavities filled without any folds. Surfaces of CPlI-ll and CPll-2 had some burn-on" roughness near the mold entrance, which was indicative of the higher pouring temperature, whereas CPll-3 and CPIll did not have any burn-on and had better, smoother surfaces. From an overall inspection and comparison of the four CPII casting it was evident that, while differences in the number of cavities that were filled were probably due to small variations in pouring temperatures and pouring techniques, the three castings poured from steel IlA after addition of alloy II were greatly superior in quality of freedom from foldline defects, thus confirming that addition of alloy II had benefited castability for production of austenitic nickel-chromium alloy sand castings. Moreover, the good results obtained when pouring CPlI-4l after the holding period of 10 minutes between CPII-3 and CPlI-4l showed that the addition of alloy ll provided an enduring benefit that resisted fading, which has importance for foundry practice where a large number of molds are poured from one melt.

The present invention is applicable for production of metal articles composed of nickel-chromium alloys containing silicon and boron, e.g., escutcheon plates, door handles, pipe fittings and other decorative or functional hardware made of austenitic nickelchromium stainless steels containing about 3 percent silicon and 0.5 percent boron. Alloying addition agents, in forms of alloys, briquettes or loose particles mixtures, having chemical compositions in accordance with the invention are particularly useful for improving the castability of previously made alloys, e.g., scrap metal and master melt ingots, by adding the agent to a furnace charge of a previously made alloy, or the agent may be used to flux a furnace charge of raw materials for an alloy. And, as mentioned hereinbefore, the agent is particularly useful as an addition to molten alloy melts. It is further contemplated that the composition be provided in forms of alloy metal shot, sintered compacts, or canned or otherwise packaged particles or fragments. Furthermore, the carbon content may, in special instances, be restricted to not exceed 0.15 percent, advantageously not more than 0.08 percent or 0.03 percent, for instance, carbon in a range of 0.005 percent to 0.03 percent, especially for use in production of corrosion resistant alloys, e.g., ACI-CF3.

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

I claim:

1. A composition of matter consisting essentially of 7 to 50 percent nickel, 12 to 40 percent silicon, 2 to percent boron, 16 to 30 percent chromium, up to 0.2 percent carbon, up to 6 percent manganese, up to 6 percent phosphorus, up to 10 percent molybdenum, up to 10 percent copper and balance essentially iron in an amount of at least 10 percent.

2. An alloy having the chemical composition set forth in claim 1.

3. A composition as set forth in claim 1 containing 30 to 45 percent nickel, 14 to 22 percent silicon, 2.5 to 5 percent boron, upvto 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 5 percent molybdenum and up to 5 percent copper.

4. A composition as set forth in claim 1 containing 40 to 50 percent nickel, 25 to 35 percent silicon, 3.5 to 5.5 percent boron, 16 to 22 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 6 percent molybdenum, up

to 9 percent copper, and balance essentially iron in an amount of 10 percent to 20 percent.

5. A composition as set forth in claim 1 containing up to 20 percent nickel, 30 to 40 percent silicon, 5 to 9 percent boron, 16 to 20 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 2 percent phosphorus, up to 10 percent molybdenum, and up to 5 percent copper;

6. A composition as set forth in claim 1 containing 30 to 40 percent nickel, 14 to 18 percent silicon, 2 to 3.5 percent boron, 20 to 25 percent chromium, up to 2 percent manganese, andup to 0.02 percent phosphorus.

7. An alloy in accordance with claim 2 consisting essentially of 30 to 40 percent nickel, 14 to 18 percent silicon, 2 to 3.5 percent boron, 20 to 25 percent chromium, up to 2 percent manganese, up to 0.5 percent copper, up to 0.5 percent molybdenum, up to 0.02 percent phosphorus and balance essentially iron.

8. A process for improving the castability characteristics of a nickel-chromium alloy comprising providing a furnace charge for a nickel-chromium alloy containing at least 7 percent nickel, at least 16 percent chromium and wherein the total of nickel and any iron present'is at least 50 percent and characterized by a liquidus temperature of at least 2300F. and addingto the furnace charge an addition agent having the chemical composition set forth in claim 1.

9. A process as set forth in claim 8 wherein the weight proportion of the amount of the added composition to the furnace charge is 5 to 25 parts of the added composition per parts of the furnace charge.

110. A process for improving the castability characteristics of an austenitic nickel-chromium alloy comprising establishing a molten bath of an austenitic nickelchromium alloy containing at least 7 percent nickel, at least 16 percent chromium and wherein the total of nickel and any iron present is at least 50 percent and characterized by a liquidus temperature of at least 2,300F. and adding to said molten bath an alloy having the chemical composition set forth in claim 1.

122g UMTED srmrs PATENT 0mm @ERTIFICATE OF CQRRWTTWN 3,836,358 September 17, 1974 Patent No.

hwentoflg) ROBIN MACKAY FORBES JONES re in the above-identified patent It is certified that error appea by corrected as shown below:

and that said Letters-Patent are here Column 1, line 2, for "Jones" read --Forbes Jones-.

Column 2, line 10, for "chronium", read --chromium--; line 24, for "nickelchromium" read -nickel-ohromium--.

Column 5, line 33, for "conductive", read -conducive.

Column 6, line 33, for "1'' read --ll/2--; line 34, for "fith" read --fifth; line 38, for GP-4" read --CPII-4-- and line 44, for. "casting" read -castings-.

Signed and sealed this 11th day of March 1975.

(SEAL) Attest:

C. MARSHALL 'DANN RUTH C: MASON Commissioner of Patents Attesting Officer and Trademarks

Claims

2. An alloy having the chemical composition set forth in claim
3. A composition as set forth in claim 1 containing 30 to 45 percent nickel, 14 to 22 percent silicon, 2.5 to 5 percent boron, up to 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 5 percent molybdenum and up to 5 percent copper.
4. A composition as set forth in claim 1 containing 40 to 50 percent nickel, 25 to 35 percent silicon, 3.5 to 5.5 percent boron, 16 to 22 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 5 percent phosphorus, up to 6 percent molybdenum, up to 9 percent copper, and balaNce essentially iron in an amount of 10 percent to 20 percent.
5. A composition as set forth in claim 1 containing up to 20 percent nickel, 30 to 40 percent silicon, 5 to 9 percent boron, 16 to 20 percent chromium, up to 0.15 percent carbon, up to 2 percent manganese, up to 2 percent phosphorus, up to 10 percent molybdenum, and up to 5 percent copper.
6. A composition as set forth in claim 1 containing 30 to 40 percent nickel, 14 to 18 percent silicon, 2 to 3.5 percent boron, 20 to 25 percent chromium, up to 2 percent manganese, and up to 0.02 percent phosphorus.
7. An alloy in accordance with claim 2 consisting essentially of 30 to 40 percent nickel, 14 to 18 percent silicon, 2 to 3.5 percent boron, 20 to 25 percent chromium, up to 2 percent manganese, up to 0.5 percent copper, up to 0.5 percent molybdenum, up to 0.02 percent phosphorus and balance essentially iron.
8. A process for improving the castability characteristics of a nickel-chromium alloy comprising providing a furnace charge for a nickel-chromium alloy containing at least 7 percent nickel, at least 16 percent chromium and wherein the total of nickel and any iron present is at least 50 percent and characterized by a liquidus temperature of at least 2300*F. and adding to the furnace charge an addition agent having the chemical composition set forth in claim 1.
9. A process as set forth in claim 8 wherein the weight proportion of the amount of the added composition to the furnace charge is 5 to 25 parts of the added composition per 100 parts of the furnace charge.
10. A process for improving the castability characteristics of an austenitic nickel-chromium alloy comprising establishing a molten bath of an austenitic nickel-chromium alloy containing at least 7 percent nickel, at least 16 percent chromium and wherein the total of nickel and any iron present is at least 50 percent and characterized by a liquidus temperature of at least 2,300*F. and adding to said molten bath an alloy having the chemical composition set forth in claim 1.