US3341321A

US3341321A - Process for treating primarily metallic materials

Info

Publication number: US3341321A
Application number: US315086A
Authority: US
Inventors: Thomas W Morrison; Walp Harry Owen
Original assignee: SKF Industries Inc
Current assignee: SKF Industries Inc
Priority date: 1963-10-09
Filing date: 1963-10-09
Publication date: 1967-09-12
Anticipated expiration: 1984-09-12

Description

p 12, 1967 T. w. MbRmsoN ETAL 3,341,321

FROCEFSS FOR TREATING PRIMARILY METALLIC MATERIALS Filed Oct. 9, 1963 POWER 7 //2 SOURCE as; AND

CONTROL /0 PANEL VACUUM SYSTEM WATER OUT Z6 WATER IN V mvem'ons THOMAS WMORR SON HARRY O. WALP United States Patent ()fifice 3,341,321 Patented Sept. 12, 1967 Vania Filed Oct. 9, 1963, Ser. No. 315,086 5 Claims. (CL 75--12) This invention relates to processes for treating primarily metallic materials, including metal alloys, to control and improve the characteristics thereof, and particularly to processes for providing improved rolling-bearing materials and elements. In a more specific aspect it is especially concerned with producing ferrous alloys, and rolling-bean ing elements such as race rings and balls made therefrom, which are characterized by longer fatigue life.

In the production of metals it is common to produce an original body comprising metal desirable elements which it is intended to provide in the final metal product, which body however is often of inadequate quality and improper shape and form for a given application. For example, the original body may be an air-cast ingot poured from molten metal in a conventional arc furnace, or it may be formed of sponge or from sintered or compressed materials having undesirable e.g., gas. The latter process has been applied to a number of different metals, such as ferrous alloys, niobium, molybdenum, titanium, zirconium, high-melting nickel and cobalt base alloys, and numerous other mate rials, and has proved satisfactory for many purposes.

However, it has been found that ingots produced by consumable-electrode arc melting in an inert environment, as previously practiced, generally contain a substantial number of so-called non-metallic inclusions, which comprise small localized regions in the ingot having a composition differing drastically from the desired average composition of the ingot. For example, in an ingot of a ferrous alloy these inclusions may comprise aluminates, silicates, nitrides and sulfides. Furthermore, these nonmetallic inclusions tend to be non-uniformly dispersed through the ingot, especially Where the original metal body was formed by ordinary air casting. The presence of such non-metallic inclusions in substantial sizes and numbers per cubic centimeter, as well as their non-uniform dispersion through the ingot, are known to comprise a source of degradation in the quality and reproducibility of the characteristics of the ingot, to a degree which is particularly important where the metal is to be used in special, critical applications.

One special application in which the quality and reproducibility of the metal is of great importance is in the field of ferrous alloy metals for use as the load-bearing elements of rolling-bearing assemblies, for example in the inner and outer races and in the balls of a ball-bearing assembly. In this application it is extremely important that the metal used have the greatest possible resistance to fatigue during normal use.

Resistance to fatigue in a device such as a roller and ball bearing assembly is commonly measured by a quantity known as fatigue life, which is the amount of useful service, usually measured in bearing revolutions, which can be obtained from the bearing under conditions in which the limiting phenomenon is metal fatigue in the bearing material. More particularly, if a bearing is effectively protected from moisture, dirt, etc., is well lubricated and is otherwise properly handled, all causes of damage are eliminated except one, namely the fatigue of the material from which the bearing is formed, due to repeated stresses thereon during rotation. The effect of such fatigue is generally to produce a spalled area on one or more of the load-carrying surfaces of the bearing assembly, and the number of revolutions of the bearing required to produce such a spalled area is a measure of the fatigue life. Obviously, it is desirable that the fatigue life be as long as possible.

While the fatigue life of an individual bearing is easily measured by the abovedescribed criterion, a statistical definition of fatigue life becomes necessary when the lives it is necessary to formulate a of the term fatigue life for this purpose.

Accordingly, the term fatigue life as used hereinafter denotes that number of bearing revolutions, which is successfully reached or exceeded by a given percentage of the group of bearings tested. This fatigue life is designated by the letter L followed by a number sufiix; thus L indicates that only 10% of a given lot of bearings have failed due to fatigue phenomena after a stated number of bearing revolutions, and L indicates that only 50% have failed.

In the interest of increased service life and reliability, there has long been a need to increase the resistance of a ings having higher values of fatigue life L L etc. Copending application Ser. No. 250,507, of H. 0. Walp, filed Jan. 10, 1963, and entitled Ferrous Alloy, now US. Patent No. 3,249,427, discloses and claims a composition of ferrous alloy particularly suitable for providing rolling bearings of increased fatigue life. However, it remains desirable to increase further the fatigue life of rolling-bearing elements made from this composition of metal, or from other compositions.

Accordingly, it is an object of the invention to provide a new and improved process for the refinement of metalcontaining materials which enhances the quality and reproducibility of metal bodies derived therefrom.

Another object is to provide a new and improved process for reducing the non-metallic inclusion content of a body of metal.

A further object is to provide such a process which not only reduces the non-metallic inclusion content but also provides a more homogeneous distribution of any such inclusions which remain in the metal body.

A further object is to provide a process for reducing the non-metallic inclusion content and rendering it more homogeneously distributed, in a metal body produced by a consumable-electrode arc melting process.

It is also an object to provide the latter improvements where the consumable-electrode of the consumable-electrode arc melting process is derived from an air-cast ingot of metal.

It is a further object to provide the above-mentioned improvements in non-metallic inclusion content and homogeneity in a ferrous alloy having a composition particularly suited to produce long fatigue life in parts for bearing assemblies.

Another object is to provide a process for producing a body of ferrous alloy characterized by a fatigue life which is greater than that of alloys of substantially the same composition made by other processes.

It is also an object to provide a new and improved process for fabricating rolling-bearing elements of long fatigue life.

In accordance with the invention the above objects are achieved by subjecting an original primarily metallic body to repeated consumable-electrode arc meltings in an inert environment, the consumable-electrode for each melting after the first being derived from the lower portion of the ingot produced by the immediately preceding consumableelectrode melting, thereby to provide a quality-enhancing metal treatment of a highly advantageous nature. In particular, when such melting is applied repeatedly, for example at least three times and preferably five times, the non-metallic inclusion content of the final metal ingot is greatly reduced, and the homogeneity of the material with respect to non-metallic inclusions is also generally improved, as compared with the original material and with material resulting from a conventional single consumableelectrode arc melting step. The reduction in the nonmetallic inclusion content is apparently due to flotation of the lighter material of the inclusions to the top of the melt, where they are then frozen into the top portion of the ingot which is later discarded. Transformation of some of the material of the inclusions to gaseous 'form and re moval of the so-evolved gas during the melting steps also contributes to the improvement in the metal.

We have further found that rolling-bearing elements of improved fatigue life are obtained when they are made 4 from a ferrous alloy body which has been subjected to repeated consumable-electrode inert-environment arc melting of the lower portions of the successively produced ingots. Particularly long fatigue lives are obtained when this repeated consumable-electrode inert-environment arc melting treatment is applied to a starting body which is a ferrous alloy having substantially the composition described and claimed in said copending application and set forth in detail hereinafter. Preferably the repetitive consumable-electrode arc melting is applied five times in a vacuum environment, producing fatigue lives typically about three times as long as those obtained without consumable-electrode arc meltings and about twice as long as those obtained by a single consumable-electrode arc melting.

Other objects and features of the invention will be more readily appreciated from a consideration of the following detailed description taken in connection with the accompanying drawing, in which the single figure is a diagrammatic elevational view, partly in section, showing one form of conventional apparatus as it may be utilized in performing certain steps in accordance with the invention.

The invention will first be described in a form in which it can be used to provide ferrous alloy ingots suitable for use in rolling-bearing elements of increased fatigue life. For this purpose the starting material is preferably an airmelt pre-cast ingot with any peripheral slag removed, shaped to suitable form for use as the cylindrical con- A Cu Mo Ni 25 0.015 0.0e 0.04.0 0.0s0 0.

sumable-electrode 10 in the figure, and preferably having substantially the following composition:

Element: Percent by weight C (about) arbon 0.95 to 1.10 Chromnun 1.30 to 1 60 Manganese 0.25 to 0:45 Silicon 0.20 to 0.35 Phosphorus Up to 0.025

Sulfur Do Aluminum Up to 0.015 Copper Up to 0.060 Molybdenum Up to 0.020 Nickel Up to 0.080 Vanadium Up to 0.003 Iron Remainder.

the respective amounts of the elements aluminum, copalloy being such as to provide a value of not re t r than about 3.5 in the formula: g a e application and falling Within the composition formula set forth above; for example for best results the original material consists substantially of about 0.010% aluminum up to about 0.050% copper, up to about 0.015% mo lybdenum, up to about 0.055% nickel and up to about 0.002% vanadium, and the value of is preferably not greater than about 3 .0.

This consumable-electrode is first subjected to a consumable-electrode inert-environment are melting process. As indicated in the drawing, in a typical form of this 5 process the consumable electrode 10 having the above composition is disposed in an electric furnace 12 with its aXls vertical and its lower end adjacent, but spaced above a thermally and electrically conductive ingot mold 14 which may be of copper, the mold 14 being in thermal heat exchange relation with a cooling jacket 16 through which cool water is circulated. An inert environment is provided in the furnace 12 by sealing it appropriately and connecting a vacuum system 18 thereto, although in some cases a sweep of an inert gas such as argon, neon, helium,

or nitrogen may be provided through the furnace, instead.

A power source and control panel 20 applies electric potential between electrode holder 22 and conductive mold 14, which are insulated from each other, and conventional means (not shown) are provided to move electrode holder 22 and hence consumable-electrode 10 along the vertical axis in such a manner that an electric are discharge 24 is produced and maintained, for as long a period as desired, between the lower end of the consumableelectrode 1-0 and the conductive mold 14 or the upper surface of any metal which may be deposited therein in the course of the process. The current in the arc is suflicient to cause a progressive melting of the lower end of the consumable-electrode 10 and a depositing of the resultant molten metal in mold 14 to form an ingot therein.

The forced cooling provided for mold 14 is such as to produce a continuously upward-growing resolidified body 26 of deposited metal nearer the bottom of the mold, while the upper surface of the deposited metal is continuously supplied by electrode 10 with new molten metal material forming a molten pool 30. When the desired amount of consumable electrode 1 has thus been melted and resolidified as a new ingot in the mold, the electric current is terminated to permit resolidification to proceed to the uppermost portion of the ingot.

During the above-described consumable-electrode melting process, the amperage of the arc current is maintained sufiiciently high to assure a complete melting of each increment of the consumable-electrode which is deposited in the mold, and to assure that the so-deposited molten steel metal is at a sufficiently high temperature to assure rapid intermingling of all of the constituents of the ferrous alloy and to permit undesired non-metallic inclusions to float to the surface of the molten pool. The cooling of mold 14 is sufficient to provide for resolidification of the metal deposited therein from the bottom upwards as the process continues, while causing the molten metal pool 30 to remain at sufiicient volume and high enough temperature that newly-deposited metal remains molten long enough to insure its complete intermingling and homogenization with the molten metal of pool 30. However the cooling is sufiiciently great so that each added increment of molten material does not remain in the liquid state long enough for undesirable separation or segregation of the constituents of the ferrous alloy to take place during resolidification.

Typically the temperature at the lower end of electrode during the process is between about 2600 and 8500 F., depending on the nature of the material, and the approximate melting rate of the ferrous alloy for a 2.5 ton furnace is from about 0.5 to 1 ton of ferrous alloy per hour. While outstanding results have been obtained by using a direct current supply for the arc, it is also possible to use alternating current or the combination of alternating current superimposed upon a direct current component for this purpose. Apparatus and techniques for providing the above-described consumable-electrode process are well known in the art and hence need not be described in further detail herein.

It has been found that, during the course of the abovedescribed consumable-electrode inert-environment arc melting step, non-metallic inclusions originally present in the consumable-electrode and deposited in mold 14 in molten form tend to rise to the top of molten pool 30 thus producing a heavy concentration of non-metallics at the upper end of the ingot as represented by the heavy line 34 in the figure. The solidified ingot which is the product of this procedure therefore contains a substantial proportion of the non-metallic inclusions concentrated at its upper axial end. A minor amount of non-metallics is generally also present in the form of a thin scale on the other surfaces of solidified ingot. After the ingot is removed from mold 14 the peripheral non-metallic regions are removed from the outer diameter of the ingot, as by machining or grinding. Except for the very top, the ingot then has a substantially lower concentration of the undesired non-metallic inclusions. This top is discarded.

In addition, the mobility of the non-metallic inclusion material in the molten metal pool 30 during the arc melting process tends to produce a more homogeneous distribution of the remaining non-metallic inclusions, particularly in the direction transverse to the growth access of the ingot. The resultant improvement in homogeneity in the ingot as compared with that in the consumableelectrode is particularly pronounced where the consumable-electrode was formed by ordinary air-melt techniques.

In addition, the use of an inert environment during the consumable-electrode process not only prevents the formation of further undesired materials in the ingot, but also tends to remove dissolved gases or other volatile substance originally present in the consumable-electrode which otherwise would contribute toward porosity or impurity of the solidified ingot. These gaseous substances become relatively highly volatile at the elevated temperatures produced during the process, and are sucked away by the vacuum or are swept away by the inert gas sweep. Where a vacuum is used, pressures from about 5 to about 50 microns are preferred, although during the initial portion of the consumable-electrode melting step the volatilization of gas may occur at such a high rate that it is impractical to maintain the pressure below about to 200 microns of mercury. This temporary rise in pressure is not harmful so long as it is brought down to the above-described lower level during the re mainder of the melting step. Where a gas sweep is employed, super-atmospheric pressures are preferably employed, for example from about 1 to 20 atmospheres.

Further in accordance with the invention, the lower portion of the ingot remaining after grinding away of its outer surface is remelted in another consumable-electrode inert-environment arc melting process substantially the same as that described above, and the finished ingot resulting from this melting step is again machined or ground to remove peripheral slag portions and the remainder used again as a consumable-electrode in a similar melting step. In each case the upper portion of the ingot near or in the holder is not remelted but instead is discarded. In this way the consumable-electrode melting step is performed at least three times and preferably five times, with progressive reduction in the concentration of non-metallic inclusions and improvement in the homogeneity of their distribution, as well as further reduction in the content of volatile impurities. Upon each successive consumable-electrode melting these characteristics of the metal are improved, although after three such meltings most of the possible improvement has been realized and after the fifth melting any further improvement is generally insufficient to warrant the additional steps.

The ingot resulting from the last melting step, after appropriate cogging, cropping and conditioning may be formed into load-carrying bearing elements, such as the inner races of ball bearing assemblies. The bearing elements so made typically exhibit a fatigue life L which is at least three times that of bearings made from the original air-melted ingot and at least twice that of bearings made from material of the ingot produced by the first consumable-electrode melting step above described.

Furthermore, by sectioning the final ingot and subjecting it to microscopic examination, it can be determined that the non-metallic inclusion content, including the number and individual size of inclusions, is decreased by each succeeding melt, although after the fifth melt the number of inclusions is no longer greatly reduced by further repetition of the process.

While in the preferred embodiment of the invention the first consumable-electrode is in the form of a precast ingot produced according to standard air melting practice, in other applications of the invention it may be produced in other ways or forms. For example it may be provided in sponge form or as a sintered particulate body, and may be produced by processes involving vacuum melting or induction heating. Where the invention is to be used for making bearings, the composition of the starting material may depart substantially from that described above, at least some of the advantages of the invention being obtained with any of a large variety of compositions suitable for use in bearings. In. general, the process of the invention may be applied to any material suitable for use in consumable-electrode inert-environment arc melting.

The following specific example further illustrates the advantages of this invention and is not intended to limit the scope of this invention.

A ferrous alloy having a of 3.54 was melted initially according to a commercial basic electric arc furnace Carbon 0.99 Manganese 0.30 Silicon 0.38 Phosphorus 0.009 Sulfur 0.005 Chromium 1.47 Aluminum 0.006 Copper 0.060 Molybdenum 0.011 Nickel .070 Vanadium 0.002 Iron Remainder The alloy was in the form of an 18-inch diameter ingot weighing approximately 3700 pounds. The ingot was cogged down to a diameter of 12 inches, then annealed and ground. A piece was cut from this ingot and rolled to 2 /2 inches round. This piece of the air-melt ingot was later used in bearing tests described below. The remainder of the 12-inch diameter ingot was used as the first electrode in the first melting step of the repetitive consumable-electrode vacuum-melting process described above, to produce a first vacuum melt ingot 1 6- inches in diameter. The vacuum melt ingot was then cogged to 12 inches round, annealed, ground, and a portion of the ingot removed and finished to 2 /2 inches round and used in bearing tests to be described below. The remainder of said first vacuum melt ingot was used as a second consumable electrode in the above-described process to produce a second vacuum melt ingot. The second vacuum melt ingot was cogged to 12 inches round, then annealed and ground. A portion of the ingot was removed and finished to 2 /2 inches round and used in bearing tests to be described below. A third vacuum melt ingot was produced in a similar manner, although no material was removed for bearing tests. Fourth and fifth vacuum melt ingots were produced similarly, except that the fourth and fifth consumable electrodes used were 9 inches round and the resulting ingots 12" round. A 2 /2 inch diameter bar was produced from the fifth vacuum melt ingot and used in bearing tests described below.

Thirty inner rings for deep-groove ball bearing assemblies were machined from each of the four 2 /2 inch bars from the air-melt ingot and the first, second and fifth vacuum melt ingots. The deep-groove ball bearing assemblies containing these inner rings differed only in the steps by which the inner ring alloy was produced, as described above. Since the inner ring of deep-groove bearing assemblies is generally the first element of the assembly to evidence fatigue failure, the use of bearings in which only the inner ring is made of the material to be tested for fatigue resistance is an accepted procedure. The bearing assemblies were tested for fatigue life expressed as L under substantial load and with oil lubrication. These inner rings were identified by stamping and then intermixed for heat treatment and final grinding. A normal quench cycle was used, and the inner rings were tempered for stabilization at 455 F. for 4 hours. Hardness of all the inner rings was held between 60.5 and 61 R The inner rings were assembled with stock outer rings and balls and subjected to endurance testing under a radial load of 4240 lbs. per bearing.

As can be seen by reference to Table A below, listing the source of the bearing material, the test speed and the L life, the L fatigue life of the fifth consumable melt in this example of the invention was more than 3 times that of the air-melt alloy and over 2 times that of the first consumable melt. Furthermore the L life of bearings made from the fifth vacuum melt is superior to any obtained by previously-known processes.

TABLE A Test Speed L10 Life Melt (r.p.m.) (millions of revolutions) 9, 300 21. 7 9, 700 38.0 2nd Vacuum Melt. 9, 700 60. 0 5th Vacuum Melt. 9. 300 77. 0

After the fatigue life of the inner rings had been determined, the rings were analyzed for non-metallic inclusions, with the inclusion counts determined at 1000 magnification acording to the Johnson and Sewell method (R. F. Johnson, J. F. Sewell, The Bearing Properties of 1% C-Cr Steel as Influenced by Steelmaking Practice, Journal of The Iron & Steel Institute, vol. 196, December 1960, 414-444). The average total inclusions observed in .0033 square inch for the inner rings from the various melts were as follows: air melt 102, first vacuum melt 37, second vacuum melt 23 and fifth vacuum melt 15. It is apparent that the average inclusion count for the lair-melt alloys was over 6 times greater than for the fifth melt, and the count for the first melt alloy was about 2 /2 times that for the fifth melt. The distribution of the remaining inclusions was also substantially more uniform in bearings from the fifth melt than in bearings from the original air melt or the first vacum melt.

While this invention has ben described with particular reference to certain embodiments thereof, it will be understood that modifications and variations thereof can be made within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A process for the treatment of original material of the class capable of use as the consumable electrode in consumable-electrode arc melting in an inert environment, comprising the steps of forming a first consumable electrode of said material and subjecting material of said lastnamed electrode to repeated consumable-electrode arc melting in an inert environment to form successive ingots, each of said ingots after the first being formed by melting of a limited portion of the immediately-precedingly formed ingot located below the top thereof, said original material consisting substantially of the following:

Element: Percent by weight (about) Carbon 0.95 to 1.10 Chromium 1.30 to 1.60 Manganese 0.25 to 0.45 Silicon 0.20 to 0.35 Phosphorus Up to 0.025 Sulfur Do. Aluminum Up to 0.015 Copper Up to 0.060 Molybdenum Up to 0.020 Nickel Up to 0.080 Vanadium Up to 0.003 Iron Remainder.

the respective amounts of the elements almuinum, copper, molybdenum, nickel and vanadium present in said alloy being such as to provide a value of not greater than about 3.5 in the formula:

Al Cu Mo Ni V 0.015 0.060 0.020 0.080 0.003

Where the element symbols Al, Cu, Mo, Ni and V represent the percent by weight of each such element present in said alloy.

2. The process of claim 1, in which said original material consists substantialy of about 0.010% aluminum, up to about 0.050% copper, up to about 0.015% molybdenum, up to about 0.055% nickel and up to about 0.002% vanadium, and wherein said value of 4 is not greater than about 3.0.

3. A process for the treatment of a body of metal including metal alloys, to reduce the number of non-metallic inclusions therein and to improve the homegeneity there of, comprising: forming from said body of metal a first consumable electrode; melting said electrode in an inert environment by a consumable-electrode process to form a first ingot having peripheral non-metallic regions and having other portions of low non-metallic inclusion content; using a portion of said first ingot of low non-metallic inclusion content as a consumable electrode in an inertenvironment consumable-electrode remelting process to form from said portion a second ingot having peripheral non-metallic regions and having other portions of low non-metallic inclusion content; and, starting with said second ingot, sequentially performing a plurality of consumable-electrode inert-environment remeltings in which the consumable-electrode melted in each of said plurality of remeltings constitutes the first-solidified portion of the immediately-precedingly formed ingot; said first consumable electrode consisting essentially of the following elements in the following percentages by weight:

Element: Percent by weight Carbon About 0.95 to about 1.10. Chromium About 1.30 to about 1.60. Manganese About 0.25 to about 0.45. Silicon About 0.20 to about 0.35. Phosphorus Up to about 0.025. Sulfur Do. Aluminum Up to about 0.015. Copper Up to about 0.060. Molybdenum Up to about 0.020. Nickel Up to about 0.080. Vanadium a- Up to about 0.003. Iron Remainder.

the respective amounts of the elements, aluminum, copper, molybdenum, nickel and vanadium present in said alloy being such as to provide a value of not greater than about 3.5 in the formula:

A Cu Mo Ni v 0.015 0.060 0.020 0.0s 0.00s

4. The method of fabricating a metal alloy having increased resistance to fatigue when used as a rolling bearing element, comprising: forming a first consumable electrode of a metal alloy having essentially the following the respective amounts of the elements aluminum, copper, molybdenum, nickel and vanadium present in said alloy being such as to provide a value of 5 not greater than about 3.5 in the formula:

Al Cu Mo Ni 0.015 0.060 0.020 0.080 0.003 where the element symbols Al, Cu, Mo, Ni and V represent the percent by weight of each such element present in said alloy; melting said electrode in an inert environment by a consumable electrode process to form a first ingot; subjecting the lower portion of said first ingot to consumable-electrode remelting in an inert-environment to form a second ingot; and, starting with said second ingot, sequentially performing a plurality of consumable-electrode inert-environment remeltings in which the portion of the consumable electrode melted in each of said plurality of remeltings is derived from the lower portion of the immediately precedingly-formed ingot, thereby to produce an ingot having substantially said composition but significantly increased resistance to fatigue.

5. A process for fabricating a rolling bearing element of improved fatigue resistance, comprising: forming of I an original body of metal, a first consumable electrode; melting said electrode in an inert environment by a consumable electrode process to form a first ingot having peripheral non-metallic regions on the sides thereof; separating said non-metallic regions from the remainder of said first ingot; using the lower part of said. first ingot after said separation of non-metallic regions as a consumable electrode in an inert-environment consumable-electrode remelting process to form a second ingot having peripheral non-metallic regions on the sides thereof; separating said last-named non-metallic regions of said second ingot from the remainder thereof; starting with said remainder of said second ingot, sequentially performing a plurality of alternate consumable-electrode inert-environment remeltings and peripheral non-metallic region separations, in which the consumable electrode for each of said plurality of remeltings is derived from the lower portion of the immediately precedingly-formed ingot after separation of peripheral non-metallics therefrom; and forming at least a part of the lower portion of the ingot produced by the last remelting into a rolling-bearing element; said original body and said last-named part both consisting essentially of the following:

Element: Percent by weight (about) Carbon 0.95 to 1.10 Chromium 1.30 to 1.60 Manganese 0.25 to 0.45 Silicon 0.20 to 0.35 Phosphorus Up to 0.025 Sulfur Do. Aluminum Up to 0.015 Copper Up to 0.060 Molybdenum Up to 0.020 Nickel Upto 0.080 Vanadium Up to 0.003 Iron Remainder.

the respective amounts of the elements aluminum, copper, molybdenum, nickel and vanadium present in said alloy being such as to provide a value of 5 not greater than about 3.5 in the formula:

Al Cu M0 Ni V 0.0l5 0.060 0.020 0.080 0.003

References Cited UNITED STATES PATENTS 3,067,473 12/1962 Hopkins 3,235,373

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,541,321 September 12 1967 Thomas W. Morrison et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 25, in the equation, for

M0 read MO 0 040 D 020 column 5, line 9, strike out "steel".

Signed and sealed this 24th day of September 1968.

testing Officer Commissioner of Patents

Claims

1. A PROCESS FOR THE TREATMENT OF ORIGINAL MATERIAL OF THE CLASS CAPABLE OF USE AS THE CONSUMABLE ELECTRODE IN CONSUMABLE-ELECTRODE AARC MELTING IN AN INERT ENVIRONMENT, COMPRISING THE STEPS OF FORMING A FIRST CONSUMABLE ELECTRODE OF SAID MATERIAL AND SUBJECTING MATERIAL OF SAID LASTNAMED ELECTRODE TO REPEATED CONSUMABLE-ELECTRODE ARC MELTING IN AN INERT ENVIRONMENT TO FORM SUCCESSIVE INGOTS, EACH OF SAID INGOTS AFTER THE FIRST BEING FORMED MELTING OF A LIMITED PORTION OF THE IMMEDIATELY-PRECEDINGLY FORMED INGOT LOCATED BELOW THE TOP THEREOF, SAID ORIGINAL MATERIAL CONSISTING OF SUBSTANTIALLY OF THE FOLLOWING: