US3311972A

US3311972A - Production of ingots for wrought metal products

Info

Publication number: US3311972A
Application number: US390103A
Authority: US
Inventors: Harvey D Burke
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1964-08-17
Filing date: 1964-08-17
Publication date: 1967-04-04
Anticipated expiration: 1984-04-04
Also published as: GB1072217A

Description

pril 4, 167 H. D. BURKE 393119972 PRODUCTION OF INC-0T5 FOR WROUGHT METAL PRODUCTS Filed Aug. 17, 1964 5 Sheets-Sheet 1 FIGURE 2 INVENTOR HARVEY DAVID BURKE ATTORNEY Bfifi, PRODUCTION OF INGOTS FOR WROUGHT METAL PRODUCTS Filed Aug. 17, 1964 H M H U E D H 5 Sheets-Shaet z F1 la I NV E NTO R HARVEY DAVID BURKE ATTORNEY April 4, 1967 H. D. BURKE 9 3 PRODUCTION OF INGOTS FOR WROUGHT METAL PRODUCTS Filed Aug. 17, 1964 5 Sheets-Sheet 5 FIGURE 5 INVENTOR HARVEY DAVID BURKE ATTORNEY United States Patent Ofiice 3,311,972 Patented Apr. 4, 1967 3,311,972 PRODUCTION OF INGUTS FGR WRGUGHT METAL PRQDUCTS Harvey D. Burke, Huntington, W. Va., assignor to The International Nickel Company, Inc, New York, N.Y.,

a corporation of Delaware Filed Aug. 17, 1964, Ser. No. 390,103 9 Claims. (Cl. 29-528) The present invention relates to production of wrought metal products and more particularly to processes for making malleable metal ingots which are wrought into metal products such as sheet, plate, rod, bar and the like.

It is well known that in order to produce wrought metal products of consistently high quality, it is generally necessary that the ingots from which the metal products are made be of good quality and thus be characterized by internal soundness and homogeneity of structure and be free from detrimental segregation including center-line segregation, inclusions, cracks, porosity and other defects. It is also known in the metallurgical art that various difierent metals and alloys pose special and different problems in the production of satisfactory ingots for making wrought products and even though a process is known to be highly satisfactory for making ingots, of one alloy or even of a broad category of alloys, the same process is frequently not satisfactory for making ingots of a different alloy. For instance, some prior art processes which have been highly satisfactory for production of steel ingots are not satisfactory for producing ingots of nickelbase alloys and even where a process has been found to be satisfactory for making ingots of some nickel-base 'alloys, the same process has been found unsatisfactory for making ingots of other nickel-base alloys. A nickel-base alloy or an iron-base alloy, as referred to herein, contains nickel or iron, respectively, in an amount greater than the amount of any one other element in the alloy and, similarly, a nickel-iron base alloy contains a total amount of nickel and iron which is greater than the amount of any one other element in the alloy. A major problem in producing ingots is avoiding various detrimental types of segregation. It has been found that many malleable, high melting point alloys having a base of nickel and/ or iron and containing chromium and titanium, e.g., about 4.5% to 23.5% chromium and 0.05% to 3.5% titanium, tend to develop in ingots a heterogeneous detrimental condition known as freckling, an extreme manifestation of microsegregation, and processes in the prior art are particularly deficient and unsatisfactory for consistently producing such alloys as ingots without freckling. Freckling, i.e., the presence of freckle defects, in an ingot is evidenced by the appearance in the etched ingot macrostructure of small islands having a shade contrasting to the metal of the surrounding matrix. These islands may appear in random fashion but frequently are arranged in a pat tern outlining the freezing front which prevailed during the solidification of the ingot. Freckling has been observed to be more severe in nickeland/or iron-base alloys containing substantial amounts of one or more elements from the group consisting of molybdenum, columbium and titanium, e.g., about 1% to 10% molydenum, 1% to 6% columbium and/or 0.5% to 3.5% titanium. Copper, when present in amounts such as 1% to 5%, is believed to accelerate development of freckling in alloys having a base of nickel and/ or iron. All compositional percentages set forth herein are by weight. Among other disadvantages which have been encountered in producing wrought products from ingots made by heretofore known methods are the formation of banded structurm, microsegregation and other undesirable metallurigcal segregates in the wrought products. Although there are many ways of evaluating the quality of ingots, one of the most important (and often the most important) criteria of ingot quality is that an ingot be capable, that is, have potentiality, of being worked into wrought products which are characterized by uniform and consistent satisfactory mechanical properties, such as tensile properties, including ultimate tensile strength, yield strength and elongation, at different locations and along different orientations, in the product. Deficiencies and disadvantages of processes for producing malleable metal ingots are especially evidenced by results of tests of wrought products made from the ingots produced by the processes. For instance, it has been found that detrimental inhomogeneities in ingots result in serious inconsistencies in tensile properties of rolled sheet when transverse tensile properties, especially elongation of the rolled sheet, are compared with longitudinal tensil properties thereof. (With respect to tensile properties of rolled products, the terms longitudinal and transverse refer to orientations with respect to the direction of rolling and the transverse orientation is in the plane of the workpiece during rolling.) Banded structures and laminar segregates are particularly detrimental to transverse tensile properties. Freckling and/or microsegregation also have unfavorable effects on corrosion resistance and local corrosion 'arising therefrom can lead to short service life and service failures. Although many attempts were made to develop improved processes for making malleable metal ingots, none, insofar as I am aware, was entirely successful in overcoming the foregoing difiiculties and disadvantages and achieving a wholly satisfactory process for production of high quality ingots when carried into practice on a commercial scale.

Further, it is pointed out that heretofore and at present, ingots of those malleable, high melting point alloys which are widely used on a commercial scale as wrought products for structural purposes, such as nickel-base, ironbase and nickel-iron base alloys, are, at least insofar as I am aware, universally made as vertically cast ingots, that is, the orientation of the ingot when cast is such that a plane containing both the longest axis and next-to-longest axis of the ingot lies in the vertical direction. Disadvantages, including development of detrimental center-line segregation, are inherent in vertical casting of ingots and a number of obvious advantages would appear to arise inherently if ingots for making wrought products were horizontally cast, i.e., cast with the shortest dimension in the vertical. However, it is clearly evident from the universal employment of vertical casting to produce ingots for wrought products of malleable, high melting point metals that, heretofore, when the disadvantages of any known horizontal casting process were weighed against any advantages which might be obtained thereby, the weight was in favor of casting vertically instead of horizontally. Insofar as I am aware, in the prior art there is no wholly satisfactory process which has been successfully carried out for producing malleable, high melting point alloys as horizontally cast ingots which are thereafter worked into wrought metal products.

It has now been discovered that horizontally cast ingots characterized by a sound homogeneous structure, without freckling, can be successfully produced 'by a new process that provides sound homogeneous ingots that can be worked to form wrought products having uniform and consistent satisfactory tensile properties.

It is an object of the present invention to provide a new and improved process for making ingots.

It is a further object of the invention to provide a process for making wrought metal products, especially wrought flat-products such as rolled plate, sheet and strip by casting and working ingots.

The invention also contemplates providing a new improvement in the process for producing ingots of nickelbase, iron-base or nickel-iron base alloys by introducing molten metal into molds, whereby there is produced an ingot characterized by improved soundness, homogeneity and freedom from segregation-type defects as compared with ingots of the same alloys when produced by methods of the prior art.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing, in which:

FIGS. 1 and 2 are reproductions of photomacrographs, taken at a magnification of eight diameters (8X which are illustrative, respectively, of the macrostructure of a wrought product made from an ingot produced in accordance with the invention and of the macrostructure of a wrought product made from an ingot which was produced by a process not in accordance with the invention.

FIGS. 3, 4 and are reproductions of photomicrographs, taken at a magnification of 100x, which are illustrative of the microstructure of a wrought product made from an ingot produced in accordance with the invention (illustrated by FIG. 3) and of two wrought products made from ingots produced by processes not in accordance with the invention (illustrated by FIGS. 4 and 5).

Generally speaking, the present invention contemplates a new process comprising introducing molten metal and molten flux characterized by a density less than the density of the molten metal into an ingot mold to form a molten metal body having proportions such that the ratio of the minimum transverse (horizontal) dimension of the body to the height of the body is 1.2 (1.2:1) or greater, e.g., 3, 6 or 15, and also to form a layer of molten fiux over the molten metal, chilling the metal from beneath and cooling and solidifying the metal into an ingot while maintaining an insulating layer of flux of a depth at least about three-quarter inch and not less than about 10% of the height of said metal until the metal is solidified. During solidification of the body the thermal-flux density at the bottom is maintained greater than the thermal-flux density at the sides and the thermal-flux density at the top is maintained less than the thermal-flux density at the sides. The process of the invention produces an ingot of proportions such that the ratio of the minimum transverse dimension of the ingot to the height of the ingot (the transverse/height ratio) is a least 1.2. The transverse/height ratio will usually not exceed about 20. As referred to herein in regard to an ingot, transverse and vertical refer to dimensions which are in horizontal and vertical directions, respectively, when the ingot is cast. Ingots made in accordance with the invention are referred to herein as broadtop ingots inasmuch as the ingots are generally (but not necessarily or invariably) of a rectilinear configuration with a rectangular transverse cross section, which is a configuration that is advantageous for ingots which are to be rolled, and the area of the top surface of such a rectilinear-shaped ingot is greater than the area of any one of the four sides of the ingot. As produced in accordance with the invention, ingots are characterized by a substantially level, smoothly contoured top surface without pipe and also by a high level of quality with respect to internal soundness, homogeneity, cleanliness and freedom from detrimental segregation, including detrimental carbide segregation. Further, while it is not implied that ingots made in accordance with the invention are always completely free of inclusions, a condition which is practically impossible to consistently obtain with any large scale production process, it has been found that any existing inclusions in wrought products from ingots made 'by the process of the invention are so disposed as not to form banded structures or gross metallurgical segregates that markedly diminish tensile properties.

In producing ingots in accordance with the process of the invention, molten metal and molten flux can be introduced into the mold by first pouring a layer of molten fiux into the mold and then casting the metal through the flux or the molten metal can be introduced by bottomcasting, i.e., flowing the metal up through the bottom of the mold, under the flux or can even be introduced by flowing the metal in from the side near the bottom of the mold. Other methods of introducing the metal and flux include simultaneously pouring the flux and casting the metal into the mold, this method having the advantage of avoiding prechilling of the flux. If desired, the flux can be placed in the ladle or furnace from which the metal is cast and then both fiux and metal can be poured at once into the mold.

In chilling the metal in the process of the invention, the metal must be cooled more rapidly from the bottom than from the sides until the metal has completely (or at least almost completely) solidified; that is, heat is withdrawn through the base (bottom) surface of the metal at a greater rate per unit area than the rate of heat transmission per unit area from the metal at the sides and thus the thermal-flux density through the base of the metal is greater than the thermal-flux density through the side surfaces of the metal. Chilling in accordance with the in vention is accomplished by providing a heat-withdrawing body at the bottom of the mold, e.g., a chill-base for the mold. A suitable chill-base can be a solid slab of high thermal conductivity material such as copper, nickel or graphite or can be fluid-cooled chill, or even cast iron, if desired. The heat-withdrawing body is designed in relation to the ingot mold sides and to the ingot which is to be cast so that the chilling power of the body is sufiicient to extract heat from the bottom surface of the ingot metal at a greater rate than the rate at which heat passes out through the side surfaces of the metal and in light of the teachings herein can be worked out by application of known principles of heat transmission. For example, when the height of an ingot that is to be pro duced by the process of the invention is from about three inches to about ten inches and the sides of the mold are of cast iron about two or three inches thick, the bottom surface of the ingot can be satisfactorily cooled by providing as the chill-base of the mold a solid copper slab having a mass of at least about 1 /2, advantageously about two to about three, times the mass of the ingot metal. If desired, the chill-base can be covered with a protective layer of graphite which serves to protect the base against erosion, e.g., by a stream of metal cast from a ladle, as well as to facilitate and improve fiowability of the molten metal over the chill-base. The entire chill-base may be constructed of graphite, or it may be made of cast iron. Cast iron may be used where only moderate chilling power is required, for example, ingot slabs less than about six inches thick.

Design and materials of the sides of molds in which ingots are cast by the process of the invention are not critical. It is sufiicient that the mold sides be high enough and strong enough to contain the molten metal and flux. Cast iron, about two inches or three inches thick, is satis' factory for the side walls in many instances. An insulat= ing lining of refractory material (sufliciently refractory so that it is not substantially melted by heat from the molten metal flux) can be provided inside the side walls of the mold. The molten flux, when floated up by the molten metal, usually provides a shell lining having some insulating benefit. Of course, the sides of the mold must not have such extreme chilling power as to negate practical possibility of providing a greater chill at the base than at the sides and must not be so highly insulating as to prevent maintaining a molten metal pool at the top of the ingot until the side surfaces of the ingot have solidified. Dimensions of the internal transverse cross section of the mold are slightly greater than the corresponding dimensions of the ingot which is to be cast in order to allow for metal shrinkage and for the thickness of any flux shell, if expected to be formed, although the mold dimensions may be expressed nominally as the same as the corresponding ingot dimensions. I

Advantageously, to produce sound homogeneous ingots in accordance with the invention, the ratio of thermalflux density at the bottom surface of the metal to the thermal-flux density at the top surface of the metal is at least about 100, the ratio of the thermal-flux density at the bottom surface of the metal to the thermal-flux density at any side surface of the metal is at least about 10 where the transverse/height ratio is less than about 2, e.g., 1.9, and the ratio of the thermal-flux density at the bottom surface of the metal to the thermal flux density at any side surface of the metal is greater than about 1, e.g., 1.1, where the transverse/height ratio is at least about 2.

The flux which is introduced into the mold in the process of the invention can in general be of any material meeting the requirements for conventional flux casting of vertical ingots. For use in the process of the invention, the flux should be a noninflammable, nonexplosive material characterized by a melting temperature that is from about 100 F. to about 400 F. below the melting temperature of the ingot metal, chemical inertness to detrimental reaction with the ingot metal and very low volatility at temperatures up to the casting temperatures of the metal. A satisfactory flux for producing, by the process of the invention, ingots of high melting point nickel-base alloys, such as nickel-base alloys containing up to about 35% chromium, up to about 48% copper, up to about 48% iron, up to about 35% cobalt, up to about aluminum, up to about 5% titanium, up to about 25% molybdenum, up to about 5% tungsten, up to about 6% columbium with the usual small amounts of tantalum and balance substantially nickel, is a flux (Type A) which contains about 30% to 40% aluminum oxide, about 32% to 40% calcium oxide (CaO), about 6% to 8% titanium oxide (TiO about 8% to 12% silica, about 3% to 6% magnesium oxide (MgO), about 4% to 8% calcium fluoride and about 2% to 7% sodium oxide (Na O) in suitable proportions to characterize the flux with a melting temperature from about 2300 F. to about 2500 F. Another satisfactory flux for use with nickel-base alloys is a low-silica flux containing about 40% to 45% aluminum oxide, about 40% to 45% calcium oxide, about 5% to titanium oxide, about 5% to 10% cryolite and up to about 10% sodium oxide. Other fluxes characterized by greater fluidity and/or lower melting points may be use, e.g., fluxes of the above composition further modified by additions of cryolite, and/or by additions of alkali or alkaline earth fluorides, chlorides or oxides, either singly or in combination.

In the process of the invention the flux layer insulates the top surface of the metal and also protects the metal from oxidation and, accordingly, flux compositions having high thermal conductivity or oxidizing effects are avoided. An important function of the flux is to facilitate smooth flow of metal over all areas, especially corner areas, of the mold base when ingot metal is cast in the process of the invention and a flux having good fluidity at the casting temperature of the metal is needed. Preheating of the mold and base is a good standard practice and for preheating and protecting the mold base and also for facilitating flow of metal it is advantageous, but not always necessary, to provide a preliminary layer of flux about one-half inch to about one inch thick on the mold bottom and have the preliminary layer of flux solidify before introducing the molten metal and additional flux. When ingots are cast by the process of the invention, a layer of molten flux floats on top of the metal and inhibits emission of heat from the metal. The molten flux must, of course, be characterized by a density substantially less than the density of the molten metal so that it readily floats above the metal. The molten flux layer above the metal is of a depth at least about threequarter inch and not less than about 10% of the height of the metal. A highly important major function of the flux in the process of the invention is to insulate the upper surface of the metal, i.e., retard emission or other loss of heat from the metal, and a thin layer of flux, e.g., a layer about one-half inch or less deep, such as is frequently present after flushing on the top of a vertical ingot made by conventional flux casting, is insuflicient. In the process of the invention the layer of flux above the metal is sufficiently deep so that when factors such as the height of the ingot metal and the thermal conductivity of the flux, as well as other solidification inhibiting measures such as are referred to hereinafter, are taken into consideration, the thermal-flux density through the top surface of the metal is less than the thermal-flux density through the sides of the metal while the ingot metal is solidifying. To aid the flux layer in inhibiting and delaying solidification at the top surface of the metal, exothermic material, e.g., mixtures containing iron-oxide and aluminum, can be spread on the flux and/ or a layer of granular or powdered insulating material, e.g., vermiculite, can be provided above the flux. The flux may also provide some incidental beneficial surface effects at the sides of the mold, such as cleansing effects, but these benefits are only incidental inasmuch as the side surfaces of ingots made by the process of the invention are only minor surfaces and are largely or completely removed during subsequent processing, e.g., by side and end trimming of the ingots or wrought products.

While an ingot is solidifying in accordance with the invention, a relatively broad (in relation to depth) molten metal pool is maintained, protected and insulated 011 the top surface by the molten flux and feeds crystallites growing in the ingot. From metallurgical examination of ingots made by the process of the invention, it is evident that solidification of the ingots progressed significantly both upwardly from the bottom and inwardly from the sides and was not unidirectional from bottom to top. In view of presently available metallurgical evidence, it appears in theory that during solidification of an ingot in the process of the invention favorable convection currents in the molten metal pool maintain great chemical uniformity at the liquid-solid interface and discourage formation of locally depleted or stagnant micropools, thereby suppressing reactions involving formation of massive particles of intermetallic phases. Whatever the explanation, it has been found as a result of extensive metallurgical examination and testing that the process of the invention produces highly homogeneous ingots which are capable of being Worked into wrought products characterized by consistent and uniform tensile characteristics.

A highly distinctive result of the process of the invention is that ingots produced thereby have no pipe and, accordingly, wrought products made therefrom have no pipe or weak center in the conventional sense. The invention further provides for making wrought products by vertical-axis working of ingots, whereby ingots made by the process of the invention are worked with substantial working pressure exerted parallel to the vertical axis of the ingot and the ultimate metal flow is wholly, and thus only transverse with no elongation along the vertical axis of the ingot. For instance, a broadtop ingot is rolled in accordance with the invention by passing the ingot between vertically opposed rolls, located one above the other, with the major plane of the ingot horizontal and with roll pressure exerted parallel to the vertical axis of the ingot. Vertical-axis working of ingots made by the process of the invention results in deformation which is of a different kind than that resulting from conventional horizontal-axis working of vertically cast ingots and has, among other important advantages, an advantage that any centrally located defects which might be present in the ingot remain confined to the surface, are visible and can be readily removed by grinding, machining, etc. This advantage is exemplified in Example IV hereinafter and is in opposite contrast with a corresponding disadvantage of horizontal-axis working of vertically cast ingots whereby defects such as excessive pipe and center-line segregation are spread throughout the interior of most of the wrought products that are being made by working the ingot.

Metals which are cast in the process of the invention are malleable, high melting point metals or alloys characterized by a hi gh, but not extremely high, melting point from about 2200 F. to about 2700" F. and include nickel, iron and high melting point alloys having a base of metal selected from the group consisting of nickel and iron, i.e., high melting point nickel-base alloys, high melting point iron-base alloys and high melting point nickeliron base alloys. The process of the invention is especially applicable to producing ingots of complex, high melting point alloys having a base of nickel and/or iron which tend to develop detrimental freckles and other detrimental segregates in ingots produced by conventional vertical casting methods. Highly satisfactory results have been obtained when the metal for the process of the invention was air-melted and it is contemplated that additional improvement in results, e.g., improvement in tensile properties at room temperature and/ or at elevated temperatures, can be obtained by vacuum melting the ingot metal and by carrying out the process of the invention in vacuum.

A special merit of the process of the invention is that it has overcome problems involving freckling and formation of banded structures and other detrimental metallur gical segregates in highly alloyed metals and thus enables obtaining clean homogeneous wrought products of complex highly alloyed metals. Heretofore, freckling has occurred, more or less frequently depending upon the specific composition of the alloy, in complex, highly alloyed metals such as malleable, high melting point nickel-iron base alloys (including nickel-base alloys and iron-base alloys) containing about 4.5% to about 35% metal from the group consisting of chromium and molybdenum, about 0.05% to about 3.5% titanium, about 0.01% to about 0.5% carbon, up to about 35% cobalt, up to about 6% columbium, up to about 1% vanadium, up to about 6% tungsten, up to about 6% copper, up to about 4% aluminum, up to about 2.5% manganese, up to about 2% silicon with balance substantially metal selected from the group consisting of nickel and iron in an amount not less than about 40%. Where the balance of an alloy is referred to herein as substantially or essentially nickel and/or iron, it is to be understood that small amounts of residuals, malleabilizers, deoxidizers, etc., such as boron, magnesium, Zirconium, sulfur and phosphorus, can also be present in a total amount not greater than about 1%. Moreover, where amounts of columbium are referred to, it is to be understood that tantalum in amounts up to about 10% of the columbium may also be present. More particularly, and of greater importance in regard to the present invention, freckling has been a specially difficult problem to overcome in producing satisfactory wrought metal products of malleable, high nickel alloys containing about 11% to about 23.5% chromium, about 0.01% to about 0.15% carbon, about 0.05% to about 3.35% titanium, about 0.05 to about 3.75% aluminum, about 0.1% to about 40% iron, up to about 31% cobalt, up to about 10% molybdenum, up to about 6% columbium, up to about 3% copper, up to 2.5% manganese, up to 1.5% silicon and the balance substantially nickel in an amount of at least about 40%. Freckling, where it has occurred to a detrimental exent, has caused inconsistency in tensile properties of wrought products and rejection of metal as unsaleable.

Further advantages of the process of the invention include capability for production of broadtop ingots of generous width and length in relation to thickness while avoiding the bad metallurgical effects of having the long ingot axis in the vertical position during casting. The process of the invention also has advantages of flexibility in production by enabling the use of the same mold for making ingots of relatively large differences in weight, inasmuch as with a broad'top configuration the height of the ingot is changed only a small amount when fairly large changes are made in weight. A broadtop ingot lends itself especially well to the production of high quality wrought flat-products such as hot rolled plate and both hot rolled and/ or cold rolled sheet or strip in a variety of widths. For this purpose ingots are cast having appropriate and preferred ratios of the minimum transverse ingot dimension to the ingot height. Table I hereinafter shows examples of rectilinear broadtop ingot configurations which are advantageous for producing wrought flatproducts of widths shown in the table. Ingots are generally made wider than the desired final width of the product in order to allow for edge trimming:

Also, the process of the invention provides for casting ingots of circular transverse cross section with the diameter at least 1.2 times the height of the ingot and for verticalaxis hot working of such circular ingots directly into wrought disks.

In carrying the invention into practice, it is advantageous in order to consistently produce sound, homogeneous ingots of malleable, high melting point metal,

and especially when making ingots malleable of high nickel alloys containing about 11% to about 23.5% chromium, about 0.01% to about 0.15% carbon, about 0.05% to about 3.35% titanium, about 0.05% to about 3.75% aluminum, about 0.1% to about 40% iron, up to about 31% cobalt, up to about 10% molybdenum, up to about 6% columbium, up to about 3% copper, up to 2.5% manganese, up to 1.5% silicon with the balance substantially nickel in an amount of at least 40% of the alloy, that the height of the ingot metal be about three inches to about ten inches, the ratio of the minimum transverse dimension of the ingot to the ingot height be about 1.2 to about 20, the depth of the layer of molten flux be at least 10% of the ingot height but not less than about three-quarter inch and that during solidification the ratio of the thermal-flux density at the top surface of the ingot metal to the thermal-flux density at the bottom surface of the metal be less than 0.01, the ratio of the thermalflux density at any side of the metal to the thermal-flux density at the bottom of the metal be less than 0.10 where the transverse/height ratio is less than about 2, and the ratio of the thermal-flux density at any side of the metal to the thermal-flux density at the bottom surface of the metal be less than 1.0 Where the transverse/height ratio is equal to or greater than about 2. Of course, during solidification in any specific process in accordance with the invention, the thermal-flux density at the top surface of the metal is less than the thermal-flux density at any side surface of the metal. In converting an ingot made by 'the process of the invention into a wrought product where the ingot is of a metal which is prone to develop cracks during the early stages of hot working, it is advantageous to hot forge or hot press the ingot With pressure directed parallel to the vertical axis of the ingot before rolling the ingot. Particular care should be taken in initially hot Working the center of the top surface of the ingot.

For the purpose of giving those skilled in the art a better understanding of the invention and a better appreciation of the advantages of the invention, the following illustrative examples are given:

Example I A cast iron ingot mold with an internal horizontal cross section about 18 inches wide and 30 inches long and having a copper chill-base of rectilinear configuration about eight inches vertically and 24 inches by 48 inches horizontally was provided for casting an ingot in accordance with the process of the invention. The mold did not have an insulating lining. A one-inch deep layer of molten Type A flux, at a temperature of about 2960 F., was provided on the bottom of the mold and while the flux was still molten, a molten nickel-ohromium-ironcolumbium alloy, referred to herein as Alloy No. 1 and of the chemical composition set forth in Table II, was cast at a temperature of about 2860" F. into the mold through the flux. The molten metal filled a depth of approximately 7 /2 inches of the mold and the molten flux floated on top of the metal. No exothermic material was placed over the metal. A layer of vermiculite about two inches deep was provided on top of the molten flux. The ingot solidified and cooled and thereafter was stripped from the mold. Removal of the flux, which had solidified on top of the ingot, was accomplished without dimculty and revealed that the top surface of the ingot was smooth, slightly concave and free of shrinkage cavity. The ingot, which weighed about 1000 pounds, had a height of about 7% inches and a rectangular horizontal cross section of about 17% inches by 28 /2 inches and, thus, the ratio of the minimum transverse (horizontal) dimension of the ingot to the ingot height was about 2.38. The ingot was successfully wrought to plate by the following procedure:

(a) Ingot ground on all sides and planed parallel on top and bottom with bevelled edges.

(b) lngot heated 12 hours at 2100 F. and hot forged to a billet 4%" x 17" x 30 /2".

(c) Billet ground on all sides.

(d) Heated 12 hours at 2100 F. and forged to a billet 2%" x 15" x 51". i

(e) Billet ground on all sides and ends cut square.

(f) Billet heated for 12 hours at 2100 F. and air cooled.

(g) Billet heated to 2100 F. and rolled to sheet-bar 1 /2" x 28" x 46".

(h) Sheet-bar ground on all sides, pickled and spot ground.

(i) Sheet-bar heated to 2100" F. and hot rolled to plate 0.450" x 46 /2" x 80".

Macroscopic and microscopic examination of etched slices which were cut from center and end locations of the plate confirmed that the plate was characterized by a sound, homogeneous structure, as illustrated in FIGS. 1 and 3 of the drawing. Tensile test specimens oriented transverse to the direction of rolling were cut from center and end locations of the plate and tested. Tensile test results set forth in Table III show that the plate of this Example I was characterized by satisfactory and highly consistent tensile properties at both end and center locations and that the tensile properties, in three different conditions of heat treatment, did not vary significantly between the end and center locations.

Example II An ingot mold having side walls of cast iron, an interior, insulating lining of refractory tile at the sides and a copper slab for the bottom was provided for casting an ingot in accordance with the process of the invention. The insulating lining was about two inches thick and the interior of the mold, inside the lining, was square in horizontal cross section, the sides being about 18 inches wide at the bottom of the mold and about 16 inches wide at the top. Depth of the mold was about 12 inches. The copper slab which was the chill-base or chill-bottom of the mold was about 24 inches square and six inches thick. .Molten Type A flux, at a temperature of about 2950 F., was poured onto the bottom of the mold to form a layer about one inch thick. While the flux was still molten, a molten nickel-chromium-iron alloy, referred to herein as Alloy No. 2 and of the chemical composition set forth in Table II, was cast, at a temperature of about 2900 E, into the mold. The molten metal passed through the molten flux and the flux floated on top of the metal. When all the metal was cast, the top surface of the flux was about seven inches from the bottom of the mold and the metal was about six inches deep. A thin layer (about one inch deep) of exothermic compound was spread on top of the flux immediately after pouring of the metal was completed and then a two-inch deep layer of vermiculite was provided on top of the exothermic compound. The ingot was allowed to solidify and cool for about two hours with the flux and other added materials on top thereof and then was stripped from the mold. The flux layer came off easily from the ingot, revealing on the ingot a smooth top surface having a gentle concavity without a deep shrinkage cavity. The other surfaces of the ingot also had a good condition of appearance. The ingot was about 5% inches in height and averaged about 17 inches transversely (horizontally) along each side with a minimum transverse dimension of about 16 inches and, thus, the ratio of minimum transverse dimension to height was about 2.9. To confirm the success of the process in producing a sound ingot of high quality in accordance with objects of the invention, a slice measuringabout one inch thick, 5% inches deep and 17 inches long was cut from the center of the ingot and macroetched. The etched slice exhibited a sound, homogeneous, high quality interior structure characterized by freedom from detrimental segregation including center-line segregation, shrinkage voids, macroinclusions, cracks and freckling.

The ingot of Example II was processed into wrought metal products according to the following procedures. It is to be understood, of course, that the ingot was divided approximately into halves when the center slice was removed for examination. The cast surfaces of the two halves were ground and then the halves were hot forged in two steps, with intermediate surface grinding and heating, to make two billets of three inches by three inches cross section and another billet of three inches by 7% inches cross section. Transverse slices were cut from opposite ends of one three-inch square billet and the slices were macroetched and found to be sound. The other threeinch square billet was hot rolled to 1 ,4 inches diameter bar and put through a straightening machine. Metallurgical inspection, including sonic testing, macroetching and microexamination, showed the bar to be of high quality characterized by a sound, clean, homogeneous interior structure. Tensile test results from specimens cut from the 1 inches diameter bar of Alloy No. 2 are set forth in Table III hereinafter and show the bar was characterized by highly satisfactory tensile properties in the transverse direction that were, for practical purposes, as good as the tensile properties in the longitudinal direction. The three inches by 7% inches cross section billet was sawed to square ends and hot rolled to produce a A" x 29" x 70" sheet. The sheet was annealed, pickled and leveled and tensile test specimens were cut from the sheet in the direction transverse to rolling of the sheet. Results set forth in Table III show that the hot-rolled sheet was characterized by transverse tensile properties that were as good as or better than the longitudinal tensile properties of the hot-rolled 1 inches diameter bar.

Example III An ingot mold having an insulating lining with an internal horizontal cross section about 1.8 inches square at the base was provided as set forth in Example 11. A one-inch deep layer of molten Type A flux at a temperature of about 2970" F. was poured on the copper bottom of the mold and a sufficient amount of a molten nickelchromium-iron-columbium alloy, referred to herein as Alloy No. 3 and of the chemical composition set forth in Table II, at about 2900 F., was poured through the molten flux to provide a depth of metal of about six inches. A thin layer of exothermic material was spread on the 'molten flux which floated on the molten alloy and a layer of vermiculite about two inches deep was spread over the exothermic material. The ingot then solidified and cooled with the flux and other materials maintained on top thereof and thereafter a six-inch deep, one-inch wide slice was cut from the center of the ingot and macroetched. Examination of the etched slice confirmed that the ingot was of high quality characterized by a sound, homogeneous structure that did not contain detrimental freckling, center-line segregation, porosity or cracks. The two remaining pieces of the ingot were heat treated for ten hours at 2080 F. and, after cooling, were cleaned up by grinding. The pieces were then hot forged in two steps, with intermediate surface grinding and reheating, to produce two billets. One billet was cut up for metallurgical inspection and found to be of high quality characterized by a homogeneous structure without banding. The other billet was successfully hot rolled to produce a A" x 35" x 73" sheet. The sheet was annealed and pickled and tensile specimens oriented in the direction transverse to rolling were cut from center and end locations in the sheet. Test results set forth in Table III show that the sheet made from the ingot of Example III was characterized, in two different conditions of heat treatment, by highly satisfactory tensile properties which were consistent and substantially equal at both the end and the center of the sheet.

Example IV An ingot mold having side walls of cast iron, an interior insulating lining of silicate-bonded sand at the sides and a copper slab for hte bottom was provided for casting an ingot in accordance with the process of the invention. The insulating lining was about three inches thick and the interior of the mold, inside the lining, was rectangular in horizontal cross section with sides about 14 inches wide and about 40 inches long. Depth of the mold was about 12 inches. The copper slab which was the chill-base of the mold was about 12 inches deep, about 22 inches wide and about 52 inches long. Molten Type A flux, at a temperature of about 2850 F., was poured into the bottom of the mold to form a layer about one inch thick. While the flux was still molten, a molten nickel-chromium-iron-columbium alloy, referred to herein as Alloy No. 4 and of the chemical composition set forth in Table II, was cast at a temperature of about 2850 F. into the mold. The molten metal passed through the molten flux and the flux floated on top of the metal. The molten metal formed a layer about 3 /2 inches deep over the bottom of the mold. A two-inch deep layer of vermiculite was spread directly on top of the metal and no exothermic compound was added. The ingot was allowed to solidify and cool with the flux and other added materials on top thereof and then was stripped from the mold. The flux and other materials were removed without difficulty from the ingot and it was found that the top surface of the ingot was smooth, slightly concave and free of any shrinkage cavity. The ingot had a height of about 3 /2 inches and a rectangular horizontal cross section of about 13 inches by 39 inches and thus the ratio of the minimum transverse dimension of the ingot to the ingot height was about 3.72. The ingot was ground on all sides and then a two-inch crop was cut from each end of the ingot to provide specimens for macroscopic examination and to square the ends'of the ingot. The m'acrostructure of the ingot was sound and free from segregation and freckling. Thereafter the ingot was salt bath annealed for one hour at 900 F. and water quenched. Next, the ingot was heated for ten hours at 2100 F., hot rolled to a thickness of about 2% inches, reheated and then rolled to a size of about 1% x 25" x 35". The top and bottom surfaces of the rolled metal were ground and then the piece was pickled and spot ground. After reheating for three hours at 2100 F., the piece was hot rolled with several reheats to a sheet about A" x 36" x 106". The sheet which was produced by the foregoing steps of this example was of satisfactory good quality over substantially the entire area of the sheet and the single crescent-shaped rupture that developed was confined in a one inch by three inches area in the middle of the sheet, which area amounted to less than 0.1% of the area of the sheet. Tensile test specimens oriented transverse to the direction of hot rolling were cut from end and middle locations in the sheet. Results of tensile tests of specimens from both end and middle locations are set forth in Table III and showed that the sheet was characterized by satisfactory tensile properties which were consistently good at both end and middle locations.

It is to be noted that in the foregoing examples, ingots were rolled into sheet by vertical-axis working inasmuch as the roll pressure was exerted substantially in a direction parallel to the vertical-axis of the ingot.

To further illustrate the improved results produced by the process of the invention, the following description of processes and results not in accordance with the invention is provided for comparative purposes. A vertically cast ingot of a nickel-chromium-iron-columbium alloy, referred to herein as Alloy X and of the chemical composition set forth in Table II, was cast at a temperature of about 2900 F. in a vertical mold, of rectangular cross section, with cast iron sides and a copper base. Molten Type A flux was present in the bottom of the mold when the metal was cast and floated on the metal during casting. After pouring was complete, a thin layer of flux remained on top of the ingot and a one-inch thick layer of exothermic compound was provided on top of the flux. The flux layer on the ingot was maintained at a temperature higher than the solidification temperature of the ingot metal by the heating action and insulating properties of the exothermic compound until the ingot was substantially solidified and the circumstances influencing solidification of the ingot were such that the ingot solidified progressively upward from the bottom to the top without developing horizontal columnar grains of length exceeding 90% of the distance from the mold wall to the central vertical axis of the ingot and the top of the ingot remained molten until the ingot had s-olidified up to a high proportion (at least of its height. The ratio of minimum transverse dimension of the ingot to ingot height was about 0.29, which ratio is not in accordance with the present invention. The ingot was ground, heated, forged and rolled, in accordance with established good practices for working the alloy thereof, to produce hot-rolled plate. Macro scopic and microscopic examination of specimens cut from hot-rolled plate of Alloy X showed that the plate contained detrimental lamellar segregates, as illustrated in FIG. 5. Results of tensile tests of transversely oriented tensile specimens cut from center and end locations from the plate of Alloy X are set forth in Table IV and show that the plate was characterized by inconsistent tensile properties, especially elongation, which varied substantially between end and center locations.

Another vertical ingot made by a process not in accordance with the invention was cast of a nickel chromiurn-iron-columbium alloy referred to herein as Alloy Y and of the composition set forth in Table II. Alloy Y was induction melted and cast in vacuum, Whereas the alloys of the foregoing Examples I through IV and Alloy X were induction melted and cast in an air atmosphere. In casting the ingot of Alloy Y, the metal was poured at a temperature of about 2900 F. into a vertical mold with cast iron sides and bottom. No flux or exothermic compound was provided in the mold or on the metal. The height of the ingot was about 25 inches and the transverse cross section was rectangular, measuring about 5 /2 inches by 12% inches at the top and about four inches by 11% inches at the bottom. Thus, the ratio of minimum trans- 13 verse dimension of the ingot to ingot height of Alloy Y was about 0.16. The ingot of Alloy Y was heated for 24 hours at 2100" F., hot forged to sheet-bar of three inches by 12 inches cross section and head cropped. The sheetbar was ground on all sides, spot ground, heat treated at 2100" F. and air cooled. Then the sheet-bar was reheated to 2100 F. and hot rolled to produce a plate 0.45 inch by 40 inches by 80 inches. A five inches by 40 inches panel was cut from the center of the plate. The ends of the panel were of metal from locations near the head and 10 toe ends of the ingot and are accordingly referred to as head end and toe end inasmuch as the sheet-bar had been 1 1 panel and oriented transverse to the direction of rolling are set forth in Table V and show that the plate of Alloy Y was not characterized by uniform and. consistent tensile properties.

Chemical compositions. of Alloys Nos. 1 through 4, which were cast as ingots by the process of the invention, and of Alloys X and Y, which were cast as ingots by the af oredescribed processes that were not in accordance with the invention, are set forth in Table II hereinafter. Alloys Nos. 1 through 4 and X and Y are examples of malleable, high melting point alloys.

1 Up to 10 of columbium content may be tantalum. 2 Balance, which also includes small amounts of residual impurities, deoxidizers, etc., e.g.,

up to about 0.01% sulfur, 0.05% magnesium, 0.1% copper and 0.4% cobalt.

cross rolled, that is, rolled in a direction transverse to the axis thereof that corresponded to the vertical axis of the ingot, and the orientation of the long dimension of the panel was transverse to the direction of rolling the plate. 30

By microscopic examination, it was found that the plate of Alloy Y contained a detrimental banded structure, such as illustrated in FIG. 4. Results of tensile tests of specimens cut from end locations in the five inches by 40 inches Results of tensile tests of specimens cut from wrought products which were made from ingots that were produced in accordance with the invention are set forth in Table III. Further, results of tensile tests of specimens cut from plate made from ingots of Alloys X and Y, which ingots were not produced in accordance with the invention, are set forth in Tables IV and V, respectively.

TABLE III Alloy Product Heat Orientation Location U.T. S. Y.S Elong, No. Treatment (K 5.1.) (K 5.1.) percent Plate.. A Transverse 196.0 179.0 16 1 Transverse" 204. 0 178. 0 15 B Transverse 186.0 160.0 26 Transverse.. 187. 0 158. 0 26 C Transverse 194. 0 160.0 23 Transverse 196. 0 164.0 23 2 Rod D Longitudinal 90. 5 44. 5 44 Longitudinal 90. 5 41. 0 46 Transverse 89. 7 41. 2 42 Transverse. 89. 6 41. 7 42 Transverse. 95. 0 42. 0 44 95.0 44. 5 44 203. 5 190. 0 11 201. 5 188.0 11 207. 5 194. 0 11 206. 5 193.0 14 192. 5 163. 0 19 192. 0 163. 0 19 4 Sheet. AA. 202. 5 191. 0 12 203. 5 189.0 13 206.0 194. 5 14 202. 5 192.0 14 C 193.0 164.0 19 Transverse Center 185.0 152. 21

U.T.S. (K s.i.) =Ultimate Tensile Strength, in units of 1,000 pounds per square inch. Y.S. (K s.i.)=Yiel(1 Strength at 0.2% ofiset, in units of 1,000 pounds per square inch. Elong.= Elongation.

TABLE IV Ingot Heat Plate Orientation U.T.S Y.S Elong., Location Treatment Location (K s.i.) (K s.1 Percent Toward Toe Transverse. 178.0 147. 5 23 Longitutlin 176. 5 145. 0 15 Transverse 169. 5 144. 0 9 ongitudin 173. 0 145.0 12 Head Transverse. 173. 0 143. 0 24 Longitudin 175. 5 145. 0 20 Transverse. 162.0 135. O 13 Longitudinal" 176. 5 145. 0 15 Middle Transverse.-. 177. 5 156. 0 20 LongitudinaL. 180.0 153. 0 21 Transverse 177.0 151.0 18 LongitudinaL. 180.0 152. 0 17 Middle Transverse. 179. 0 153. 0 20 Longitudinah. 181. 0 152.0 20 Transverse.-- 167. 0 148.0 4 Longitudinal. 175. 0 146.0 14

In the foregoing Tables III and IV, orientation refers to the orientation of the longitudinal axis of the tensile specimen with respect to the direction of rolling. In Table III, End and Center under Location refer to locations of the tensile specimens in the product. End and Center also correspond generally to side or end locations and center locations, respectively, in the ingots from which the products were produced. The heat treatments referred to in Tables III, IV and V are as follows:

A1 hour at 1750 F. to 1800 F., air cool, 8 hours at'l3i25 F., furnace cool at 20 F. .per hour to 1150 F. and air cool.

AAAs for A above without the initial treatment at 1750 F. to 1800 F.

B1 hour at 1950 F., air cool, 8 hours at 1350" F, furnace cool at 100 F. per hour to 1200 F. and air cool.

C1 hour at 1950 F., air cool, 10 hours .at 1400 F., furnace cool at 100 F. per hour to 1200 F, hold at 1200 F. for 8 hours and air cool.

DAs-rolled temper, no heat treatment.

EAnnealed 10 minutes at 1900 F. and furnace cooled.

F1 hour at 1800 F., air cool, 16 hours at 1325 F.

The results set forth in Table III illustrate the consistent uniform tensile properties which are characteristic of wrought products made from ingots produced in accordance with the invention and show that the process of the invention results in ingots characterized by a highly homogeneous structure that further characterizes the ingots with a capability of being worked into wrought products having consistently uniform tensile properties. In contrast to the uniform properties illustrated in Table III, which flow from producing ingots in accordance with the invention, Tables IV and V show inconsistent and nonuniform tensile characteristics which are obtained when ingots are vertically cast by methods not in accordance with the invention.

In the accompanying drawing, FIG. 1 illustrates the homogeneous macrostructure which was present in the middle of the plate made from the ingot of Example I and which is characteristic of wrought products made from ingots produced in accordance with the invention. FIG. 2 :shows a detrimental, banded macrostructure which was present in plate made from the ingot produced by the hereinbef-ore described process of producing the ingot of Alloy Y. FIG. 3 illustrates the homogeneous microstructure which was present in plate made from the ingot of Example I and which is characteristic of wrought products made from ingots produced in accordance with the invention. FIG. 4 shows a detrimental, banded microstruoture which was present in plate made from the ingot produced by the hereinbefore described process of producing the ingot of vacuum induction melted Alloy Y. FIG. 5 shows a detrimental lamellar segregate, appearing as the small light particles in segregated bands, which was present in plate made from the ingot of Alloy X referred to hereinbefore. Comparison of FIGS. 1 and 3 with FIGS. 2, 4 and 5 shows that the process of the invention achieves homogeneous metal and avoids detrimental banding and segregation. The specimens shown in FIGS. 1 through 5 were electrolytically etched using an aqueous solution of 5% CIO3.

It is to be noted that the present invention is not to be confused with processes for achieving unidirectional upward solidification in vertically cast ingots. Upon metallurgical examination, highly satisfactory ingots which were made by the process of the invention exhibited an outer zone of columnar crystallites extending inward from the sides and upward from the base and also a central zone of randomly oriented crystallites extending to the top surface. The presence of such zones in ingots is'st-rong and probably conclusive evidence that solidification was not unidirectional; nevertheless, satisfactory wrought products which possessed uniform mechanical properties and a homogeneous structure were successfully made from ingots which were produced in accordance with the invention and contained such zones of nonuniformly oriented crystallites.

The present invention is particularly applicable to production of malleable metal ingots of high melting point alloys containing at least 40% nickel and/ or iron which are made into wrought products by forging and/ or rolling. Moreover, the invention is especially advantageous for overcoming problems in producing high quality, homogeneous ingots of those high melting point alloys which tend to develop detrimental segregation, including freckling, in ingots produced by processes in the prior art, Wrought products made from ingots produced in accordance with the invention include sheet, strip, plate,

bar, rod, forgings and clad products and are useful in the product form as structural materials, e.g., structural sheeting, support rods, etc. Furthermore, the invention is applicable to the production of malleable metal products which are fabricated into corrosion resistant containers, pressure vessels, impellers, turbine wheels, including blades, vanes and disks, springs, heating elements, combustion chambers, valve components, etc.

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. In the process for producing an ingot of a malleable, high melting point alloy by introducing molten metal into an ingot mold, the improvement which comprises, in combination, introducing molten metal and molten flux into the ingot mold, said metal being a malleable high melting point alloy and said flux being characterized by a density less than the density of the molten metal, to form a molten metal body having proportions such that the ratio of the minimum transverse dimension of the body to the height of the body is at least 1.2 and to also form a layer of molten flux over the metal, said layer having a depth of at least three-quarter inch and at least 10% of the height of the molten metal body, spreading exothermic material over said flux layer and chilling the molten metal body primarily at the bottom surface thereof to produce a thermallux density of heat extraction through the bottom surface of said body that is greater than the thermal-flux density of heat extraction through any side surface of said body, and cooling and solidifying said body while maintaining the aforesaid flux layer on top of said body to insulate the top surface of the body and to maintain the thermal-flux density through the top surface of the body less than the thermal-flux density of heat extraction through the side surface of the body.

2. A process as set forth in claim 1 wherein a layer of granular insulating material is provided over the exothermic material.

3. A process as set forth in claim 1 wherein the malleable, high melting point alloy is a nickel-iron base alloy.

4. A process as set forth in claim 1 wherein the malleable, high melting point alloy is a nickel-iron base alloy consisting essentially of about 4.5% to about 35% metal from the group consisting of chromium and molybdenum, about 0.05% to about 3.5% titanium, about 0.01% to about 0.5% carbon, up to about 35% cobalt, up to about 6% columbium, up to about 6% tungsten, up to about 6% copper, up to about 4% aluminum, up to about 2.5 manganese, up to about 2% silicon, up to about 1% vanadium, with the balance essentially metal selected from the group consisting of nickel and iron in an amount constituting at least 40% of the alloy.

5. A process as set forth in claim 1 wherein the malleable, high melting point alloy is a nickel-base alloy consisting essentially of about 11% to about 23.5% chromium, about 0.01% to about 0.15% carbon, about 0.05% to about 3.35% titanium, about 0.05% to about 3.75 aluminum, about 0.1% to about 40% iron, up to about 31% cobalt, up to about molybdenum, up to about 6% columbium, up to about 3% copper, up to 2.5% manganese, up to 1.5% silicon, with the balance essentially nickel in an amount constituting at least 40% of the alloy.

6. A process as set forth in claim 1 wherein the ratio of the minimum transverse dimension of the molten metal body to the height of said body is at least about 2 and wherein the ratio of the thermal-flux density of heat extraction at the bottom surface of the metal to the thermal-flux density at the top surface of the metal is at least about 100-.

7. In the process for producing an ingot of a malleable, high melting point alloy by casting molten metal into a mold, the improvement which comprises, in combination, pouring molten flux into the mold to form a layer of molten flux having a depth of at least three-quarter inch and at least 10% of the height of the ingot to be cast, said molten flux being characterized by a density less than the density of the molten metal to be cast, casting molten metal of a malleable high melting point alloy through said molten flux layer to form a molten metal body having proportions such that the ratio of the minimum transverse dimension of said body to the height of said body is at least 1.2, spreading exothermic material over said flux and chilling the molten metal body at the bottom surface thereof to produce a thermal-flux density of heat extraction through the bottom surface of said body that is greater than the thermal-flux density of heat extraction through the side surface of said body, and cooling and solidifying said body while maintaining the aforesaid flux layer on top of said body to insulate the top surface of the body and to maintain the thermal-flux density through the top surface of the body less than the thermal-flux density of heat extraction through the side surface of the body.

8. In the process for producing a wrought metal product of a malleable, high melting point alloy by introducing molten metal into a mold to make an ingot and thereafter working the ingot, the improvement which comprises, in combination, introducing molten metal and molten flux into the ingot mold, said metal being a malleable high melting point alloy and said flux being characterized by a density less than the density of the molten metal, to form a molten metal body having proportions such that the ratio of the minimum transverse dimension of the body to the height of the body is at least 1.2 and to also form a layer of molten flux over the metal, said layer having a depth of at least three-quarter inch and at least 10% of the height of the molten metal body, chilling the molten metal body at the bottom surface thereof to produce a thermal-flux density of heat extraction through the bottom surface of said body that is greater than the thermal-flux density of heat extraction through the side surface of said body, cooling and solidifying said body into an ingot having a vertical axis and a horizontal transverse axis while maintaining the afore said flux layer on top of said body to insulate the top surface of the body and to maintain the thermal-flux density through the top surface of the body less than the thermal-flux density of heat extraction through the side surface of the body, removing said ingot from the mold and removing the flux from said ingot and thereafter Working said ingot with pressure exerted substantially parallel to the vertical axis of the ingot to flow the metal of said ingot transversely without elongation of the ingot metal along the vertical axis of said ingot.

9. A process as set forth in claim 8 wherein the malleable, high melting point alloy is a nickel-base alloy consisting essentially of about 11% to about 23.5% chromium, about 0.01% to about 0.15% carbon, about 0.05% to about 3.35% titanium, about 0.05% to about 3.75% aluminum, about 0.1% to about iron, up to about 31% cobalt, up to about 10% molybdenum, up to about 6% columbium, up to about 3% copper, up to 2.5% manganese, up to 1.5% silicon, with the balance essentially nickel in an amount constituting at least 40% of the alloy.

References Cited by the Examiner UNITED STATES PATENTS 4/1926 Coates 29-526.6 6/1932 Antisell 29528

Claims

8. IN THE PROCESS FOR PRODUCING A WROUGHT METAL PRODUCT OF A MALLEABLE, HIGH MELTING POINT ALLOY BY INTRODUCING MOLTEN METAL INTO A MOLD TO MAKE AN INGOT AND THEREAFTER WORKING THE INGOT, THE IMPROVEMENT WHICH COMPRISES, IN COMBINATION, INTRODUCING MOLTEN METAL AND MOLTEN FLUX INTO THE INGOT MOLD, SAID METAL BEING A MALLEABLE HIGH MELTING POINT ALLOY AND SIAD FLUX BEING CHARACTERIZED BY A DENSITY LESS THAN THE DENSITY OF THE MOLTEN METAL, TO FORM A MOLTEN METAL BODY HAVING PROPORTIONS SUCH THAT THE RATIO OF THE MINIMM TRANSVERSE DIMENSION OF THE BODY TO THE HEIGHT OF THE BODY IS AT LEAST 1.2 AND MATERIAL HAVING AT LEAST SUBSTANTIALLY THE SAME CO-EFFICIENT OF THERMAL EXPANSION AS THAT OF THE DIFFUSION TUBE WITH WHICH IT IS TO BE ASSOCIATED AND BEING SO DIMENSIONED AS TO FORM A TIGHTFIT IN SAID DIFFUSION TUBE WHEN INSERTED