US3905804A

US3905804A - Method of decarburization of slag in the electroslag remelting process

Info

Publication number: US3905804A
Application number: US367941A
Authority: US
Inventors: Jr William W Scott
Original assignee: Lukens Steel Co
Current assignee: Lukens Inc
Priority date: 1973-06-07
Filing date: 1973-06-07
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16

Abstract

The introduction of an oxidizing agent, Fe3O4, FeO, Fe2O3, NiO, MoO2, CoO, Cu2O, Cr2O3, MnO, Mn2O3 or Mn3O4, or a combination thereof into slag in the bottom of the mold during the beginning of an electroslag remelting (ESR) process, but after the slag is fully molten and with an a.c. current at about 70 - 90 volts applied through the slag from the ESR consumable electrode in order to reduce the slag''s carbon content to less than about 0.02%, the slag having a composition of about 40% CaF2, 30% CaO, and 30% Al2O2, and having obtained a carbon content of roughly 0.04 - 0.05% upon being melted in a slag furnace having a graphite or carbon brick lining prior to being introduced into the ESR mold, the oxidizing agent being introduced into the slag during the ESR process being about 0.2% of the slag by weight.

Description

United States Patent [1 1 Scott, Jr.

[4 1 Sept. 16, 1975 METHOD OF DECARBURIZATION OF SLAG IN THE ELECTROSLAG REIVIELTING PROCESS [75] Inventor: William W. Scott, Jr., Parkesburg,

211 Appl. No.: 367,941

OTHER PUBLICATIONS Metals, 2 (10), March 1967, pp. 44, 45, 46, 47, 46A and 48. Duckworth et al Electra-slag Refining, TN 685.5,E4D8, Chapman & Hall Ltd., London, Feb. 2, 1971, (p. 67 relied on).

Mitchell, Trans of Metallurgical Society of AIME, TNLM57, December, 1968, Vol. 242, (pp. 2507-251 1 relied on).

British steelmaker, Sept. 1966, (pp. 48, 49 and 58 relied on).

Primary Examiner-L. Dewayne Rutledge Assistant Examiner-M. J. Andrews Attorney, Agent, or FirmMason, Mason & Albright [5 7 ABSTRACT The introduction of an oxidizing agent, Pe o. FeO, Fe O NiO, M00 CoO, Cu O, Cr O MnO, M11 0 or Mn,,o,, or a combination thereof into slag in the bottom of the mold during the beginning of an electroslag remelting (ESR) process, but after the slag is fully molten and with an ac current at about 70 90 volts applied through the slag from the ESR consumable electrode in order to reduce the slags carbon content to less than about 0.02%, the slag having a composition of about 40% CaF 30% CaO, and 30% A1 0 and having obtained a carbon content of roughly 0.04 0.05% upon being melted in a slag furnace having a graphite or carbon brick lining prior to being introduced into the ESR mold, the oxidizing agent being introduced into the slag during the ESR process being about 0.2% of the slag by weight.

28 Claims, 1 Drawing Figure METHOD OF DECARBURIZATION OF SLAG IN THE ELECTROSLAG REMELTING PROCESS I BACKGROUND OF THE INVENTION This invention relates to a method of decarburizing molten slag used in the electroslag remelting process. More specifically it relates to an effective method for removing carbon introduced into the molten slag by reason of being heated to a molten state in a furnace lined with graphite or carbon bricks.

The electroslag remelting process essentially comprises the fusing from a consumable electrode of metal which is to be refined under a blanket of molten slag or flux. The consumable electrode is generally suspended within a water cooled copper or steel mold and molten slag is introduced into the mold and acts as an electrical v conductor for electrical current passing between the consumable electrode and baseplate or stool of the rriold. The current heats the electrode and droplets of metal fusing off its lower end fall through the slag to the bottom of the mold where a pool of molten metal forms and solidifies upwards from the bottom pool. A refining action takes place in the molten metal as it passes through the molten slag and, as the electrode is progressively consumed, the refined metal builds up from the bottom of the mold to form an ingot. The molten slag floats on the pool of refined metal and remains in contact with the lower end of the consumable electrode. The refining process continues until the electrode is consumed or substantially consumed.

Slags used in electroslag remelting processes have a high dielectric constant in the solid form, but are conductive to some extent in the liquid phase. Also, in the molten state, the slag has a low viscosity and slags utilizingcalcium fluoride as one component havea corrosive effect on ordinary refractory. For this reason, a furnace for melting slag prior to its introduction into the mold may be lined with carbon or graphite in brick or monolithic wall form or both. However, it has been found that the graphite or carbon lining, together with the graphite electrodes for melting same, are responsible for introduction of carbon into the molten slag which has presented a problem of removing same. Otherwise, the carbon is transferred to the bottom of the ingot which thus has a higher carbon content than specifications for the steel may call for and, in any event, different from the carbon content at the top of the ingot.

The known method for reducing the carbon level in the molten slag is to blow oxygen into it; while in the slag furnace. This method is operable but somewhat unwieldy and it is difficult to estimate when the carbon content has been lowered by the desired amount. Furthermore the carbon or graphite lining is needlessly oxidized by the excess oxygen, causing early failure of the lining.

As an experiment, iron oxide was added to themolten slag in the slag furnace. A highly undesirable foaming action resulted and a crust was formed on the molten slag. It was found, however, by adding the iron oxide very slowly, the carbon content of the slag could be successfully reduced in spite of its foaming action and formation of a crust on the top of the molten slag. The advantages of this method over the introduction of oxygen were that thequantity of carbon removed was more easily gaged and the furnace lining was not detrimentally affected. But both methods leave much to be desired in their operational aspects.

SUMMARY OF THE INVENTION I have discovered that if the required amount of iron oxide (mill scale, F6304) is added directly into the mold as soon as practicable after molten slag has been introduced therein and the melting process has commenced, (the slag being in the molten state) the iron oxide can be added at a relatively rapid rate (within 30 seconds to up to five minutes) without causing discernible or harmful foaming or crusting of the molten slag around the consumable electrode. The addition of about 0.2% iron oxide removes about 0.034% carbon from the molten slag. The slag then has a carbon level of about 0.006 0.016% which is insufficient to affect adversely the quality of the ingot produced by the process.

Other advantages of the invention will be appreciated from the description and with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic view, partly in section which illustrates the preferred mode of carrying out the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, a consumable electrode 10 is suspended by a suspension structure 23 in a water cooled copper or steel mold 11. The mold is supported by a base plate or stool 12 and includes a passageway 18 between the outer shell 14 and the inner mold wall 15. The passageway 18 functions to receive the heat exchange medium 20 for retaining the inner mold wall 15 in an appropriately cooled condition. An inlet 16 and outlet 17 are provided for the cooling medium 20, preferably water. A cap 21 of molten slag or flux receives the lower end of the electrode 10 and, due to heat generated by electric current passing through electrode 10 and cap 21, the lower end of electrode 10 is progressively melted and molten metal drops 22 fall through the cap 12 to form a molten metal pool 24, which, due to the cooling effects of medium 20, solidifies in the form of an ingot 25. The slag blanket or cap 21 is preferably such that it will not, liberate deletiorious gas either as to quantity or kind during the metal depositing operation and it should not add substantial quantities of undesirable ingredients to or remove substantial quantities of desirable ingredients from the molten metal. Rather it should flux out impurities. The molten slag should, furthermore, be such that it will readily free itself from the molten metal and it has been found that a wide variety of slags or fluxes may be used satisfactorily. A calcium fluoride flux has been found advantagous.

The molten slag which comprises the cap 21 may be passed into mold 11 from a convenient source of supply such as slag furnace 40 by any suitable means as it would occur to one skilled in the art such as the conduit 27 which is preferably water cooled and composed of steel. As shown in the drawing, the conduit 27 enters into the interior of the mold 1 1 through a snugly fitting opening in stool 12 (which also has cooling passageways designated 19 for receiving cooling medium 20) and also through an opening in a starter plate 28 which is disposed between the stool l2 and the lower ends of the mold 11. The function of starter plate 28 is to provide a dependable electric conductor under mold 1 l to high alumina refractory bricks 47, an expansion joint 50 comprising powdered alumna, a graphite shell 51 which may be integral and have the shape of a cup or be formed of graphite bricks as shown and finally on resistance heating between graphite" electrodes 60. Ad-

ditional dry slag isadded'until the' d es ired amount has been introduced into the slag furnace 40 and the temperature of the slag is brought up to 2800 '2900F.

Although care is taken to introduceonly the amount of slag desired into the slag furnace 40, there is some variability which appears to be inherent inthe system and, with the knowledge of such variability, electrode is. initially positionedv a shortbut sufficient distance (about 2 inches) from the highest level 'of slag expected tobe introduced within mold; 11 from furnace 40 in view of prior experience as to the volumetric parame-, ters of the molten slag charges, The slag furnace 40 is caused by appropriatemeans (not shown) to tilt about the interior a layerof graphite or carbon bricks 52. The

roof 54 is composed of a high alumina ram refractory which is tamped in place to form a monothlic roof structure. The roof includes three main openings, an exhaust conduit 55, a feed pipe 56 and a central opening 57 which receives three graphite electrodes 60 which are connected to an appropriate electrical power source not shown. Before slag furnace 40 is pivoted about trunnion 42, the electrodes 60 and roof 56 are raised to the position shown in dot-dash lines.

Dry slag placed within the slag furnace 40 isheated by graphite electrodes 60 and due to its resistance is melted whereby the electrodes become immersed in the slag which is heated to a temperature of 2800 29 00F. for tapping.

It has been'found that slag furnace 40 gives very few problems and may be used for over 100 heats with bricks 52 replaced every 25 beats more or less. The graphite working lining comprising carbon or graphite bricks 52 together-with graphite electrodes 60 introduce, however, more than a desirable amount of carbon into the slag. This carbon, after the slag is introduced into the mold l 1, is transferred to the steel'forming the ingot 25 so that the carbon content of the ingot is greater in its lower portion than upper portion.

As previously indicated, it is possible to reduce the carbon level in the slag by blowing oxygen into the molten slag bath in slag furnace 40 or by the slow introduction of an oxide such as an iron oxide to the bath which reacts with the carbon to form carbon monoxide and carbon dioxide that is expelled from the molten slag as a gas. Both of these methods have definite drawbacks "in that they cause an undue amount of foaming within the slag furnace 40 and also cause a crust to form on top of the slag.

heat causes the gases generated by addition of theoxide to be carried off in such a way that harmful foaming action does not occur.

Iron oxide is added at the top of the mold l 1 between the inner mold wall and the sides of the electrode 10 by means of a metering device 61 which meters the desired amount of the oxide into the mold via a pipe 62..

In operation, dry slag material having a composition of about 40% Cal- 30% CaO and 30% A1 0 is added into slag furnace 40 via feed pipe 56 and is melted by trunnion 42 and thus empty them olten slag into the spout portion 29 of conduit 27 whereupon it enters through said conduit into the bottomof the mold 11 The slag furnace 40 is tilted to over for this purpose in order to ensure that it is emptied insofar as possible of molten slag. When. the ,slag pouring is complete, electrode l0.is prornpt ly lowered atiaspeed of say 1 inch per 15 30 seconds until it contacts the surface of cap 21 where-upon ahcurrent flow is immediately registered and .cap 21 becomeshighly liquid within a relatively short period. However, immediately following contact of electrode 10 with cap 21, there may rejmain a slight crust at the top of the cap 21 and the additionof any oxide at'this, time would remain on the crust possibly causing operating'pr oble'rns by' 'arcing for ex-' ample, although this has not been experienced. After waiting a period of say 5' minutes when it is known that the crust 'has disappeared and slag is completely liquid. The oxide can be added and the desired 'decai burization reactions proceeds. Accordingly, metering device 61 is then activated whereupon the oxide enters the cap 2l via pipe 62 andthe space between the inner mold Wall 15 and" electrode 10.6 g .The amount of iron oxide added "depends upon the approximate carbon composition of the slag prior t6 pouring which, in turn, depends on a number of variables suchas the'ope'rati'ng te'chiiiciu'e, the temperature of the slag, the slag chemistry, etc. However,-it has been found that two pounds-of iron oxide (Fe O per 1,000 pounds of molten slago'r, in other words, 0.2% is sufficient to remove about 0.034% carbon from the slag. Inasmuch as the average carbon'content of the slag is usually about 0.04 0.05%, the carbon level is lowered to a safe or tolerable level; that is, less than 0.02% with an aim of about 0.01%, but it is not removed altogether: In the event t'oo. much of the oxide is added, the characteristics' of the slag may then believed that the limits of theloxide addition rate should be kept within a range from 0.1% to 1% in order to remove between about 0.017 to 0.17% carbon in the case of iron oxide (Fe O r t It has been determined that the method as disclosed in thisinvention successfully reduces the carbon in the slag whereby unduecarbon content in the lower portion of the ingot 25 is avoided. Whatever'mino'r "carbon "pick -up affects the bottom r the anger iseventually eliminated through providing practices;

it can be centered between walls 115 with gaps ofabout 1V2 to 2 inches in width on each 'side. rurnacq to has a capacity of about 1 /2 tons,of slag or at least about bring 1,000 pounds of slag to the desired temperature. For 2,800 pounds, the requiredtime is about 4 hours. When-electrode contacts the toplof the slag cap 21 a current flow is immediately registered andan initial voltageof about 90 volts reduces within abo ut a few minutes to about 70 voltswith the current being on the order of about 10,000 amps. The current is a single phase-60 cycle a.c. current; v I .t

Although Fe O lis-preferable because it is readily availableas millscalefother oxides are thermodynamically capable of causing the desired reaction. These include Fe O FeO, NiO, M 0 CoO, Cu O,.Cr O MnO, Mn O and Mn 'O particular oxide may-{be chosen wherein the metal element involved may be advantageously added for alloying in the-lower portion :of the ingot, for example,where the lower portion of the electrode contains less than the desired amount of such element. In this connection, it should beunderstood that the metering device 61 is also utilized in the process involved fort he selective addition to the molten slag of materials such as lead, molybdenium, aluminum, copper, chromium, and manganese as and when needed to compensate for deficiencies in the electrode. Moreover, the problem of continually adjusting relative movement between theelectrodel0 an'dino ld 11 may be alleviated or, indeed, eliminated by thefladdition" of sufficient steel pellets of desired chemistry of thelike from device 62 during the process so that the ingot grows atsubstantially the same rate that the' electrode 10 shortens.

.In practice, electrode may be'energized prior to or as the slag is charged-into the mold 11, or immediately before lowering same, However, preferably., it is energizedasslag is chargedin to the moldl Also, prefer ably, the slag charging time via funnel portion should not normally exceed four minutes.

For the purpose of the claims, flux is considered to be included in the term slag. Also, unless otherwise stated, percentages are by weight.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. An electroslag remelting process which comprises:

melting of slag in a furnace by means of at least one graphite electrode whereby the carbon content of the molten slag is increased;

transferring said molten slag into the bottom of an electroslag remelting mold wherein an ingot of improved homogeneity is formed by the continued melting of a metal consumable electrode the end portion of said electrode being immersed in said molten slag whereby melted metal from said end portion falls through said molten slag and solidifies to form said ingot in said mold while an electrical current passes through said slag between said electrode and 'said ingot being formedfor maintaining said slag in a molten condition; and 'introducing an' oxidizingagent into said molten slag v "in said mold while said current is passing therethrough, the amount and rate of said introduction of said oxidizing agent being such as to perform the K function of removing carbon from said moltenslag we without causing excessive foaming of said slag. 2. In a method of decarburizing flux havingan under e sired high carbon content, the flux being used in an 2,800 pounds. It takes about 1 /2 to '2 hoursto melt and electroslag remelting process wherein 'it'is in-a molten state in an electroslag' refining mold, the lower portion a consumable metal electrode immersed in the upper portion of the molten flux, 'the 'flux being heated by an electrical current flow provided therethrough, melted metal from the electrode passing through said molten flux to the bottom of the mold into a molten metal pool where it solidifies as a more homogeneous metal, the improvement comprising the step of adding iron oxide ,to said molten flux in said mold while continuing said current flow whereby decarburiiation of said flux takes place without excessiveforming of said flux. 7 s 3. Amethod of accordance with elairn 2 wherein the .-iron oxide added to said flux is about 0.2% of the amount of flux by weight. e A I I 4.-A method in accordance with .claim 3 wherein said iron oxide is mill scale. i i i 5. A method in accordance with claim; 3 wherein said iron oxide is introduced into said flux within atime range of 30 seconds to 5;minutes, e

6. Anlelectroslag remelting process'which-comprises the steps of: I

- heating a chargeof slag ina slag furnace to a molten 'state'wherein the slag is exposed to .carbon'and'the carbon content of the slag is increased toan undesired level; introducing said slag into an electroslagrefining'mold in 'its'molten' state;

"4"O in rriersi'ngbf the lower end of a' consumable metal electrode into said molten slag in said mold andfestablishing an electric current-therethrough which 'is s'ufficient 't'o maintain'said slag in said mold in a molten state and to melt said electrode immersed I therein whereby molten metalis received through immediately'with said slag in a molten state after int roducing same into saidmold adding' an oxidizing agent to said molten sl'ag'while continuing saidcurrent through said slag and the melting of said electrode whereby the decarburization of said slag takes place without excessive foaming thereof and said slag retains its characteristic as a reducing slag. 7. A process according to claim 6 wherein said oxidizing agent is a substance selected from the group consisting of Feo, Fe O Fe O NiO, M00 CoO, Cu O MnO, Mn O and Mn O 8. A process according to claim 6 wherein said oxidizing agent comprises iron oxide.

9. A process according to claim 8 wherein said iron oxide is mill scale. 10. A process in accordance with claim 6 wherein the amount of oxide added to said slag is about 0.2% of said slag and is introduced in a period of 30 seconds to 5 minutes.

11. An electroslag remelting process which comprises: 1

melting of slag in a furnace which is lined at least in part by carbonaceous material whereby the carbon content of molten slag is increased; transferring said molten slag into the bottom of an electroslag remelting mold wherein an ingot of improved homogeneity is formed by the continued melting of a metal consumable electrodes end portion immersed in said moltenslag whereby melted metal from said end portion falls through said molten slag and solidifies to form said ingot in said mold while an electric current passes through said slag between said electrode and said ingot being formed maintaining said slag in a molten condition;

, and

introducing an oxidizing agent into said molten slag in said mold while said current is passing'therethrough, the amount and rate of said introduction a of said oxidizing agent being such as to perform the function of removing carbon from said molten slag without causing excessive foaming of said slag.

12. An electroslag remelting process in accordance with claim 11 wherein after said molten slag has been introduced into said mold, said electrode is lowered into contact with said slag and a current flow through said slag is established, the introducing of an oxidizing agent into said slag being thereafter delayed until the s'lag'between said mold and said electrode is in a fully fluid condition.

13. An electroslag remelting process in accordance with claim 12 wherein the period of said delay is about 40 minutes.

14. An electroslag remelting process in accordance with claim 11 wherein said oxidizing agent is introduced into said slag within a period of less than 5 minutes.

" 15. .An electroslag .remelting process in accordance with claim 11 wherein said oxidizing agent is a sub- .stanceselected from the group consisting of FeO, -Fe O Fe O NiO, M00 C00, Cu O, Cr O MnO, =.Mn O and M11304.

.16. An electroslag remelting process in accordance with claim 11 wherein said oxidizing agent consists essentially of iron oxide.

17. An electroslag remelting process in accordance with claim 16 wherein said oxidizing agent consists essentially of mill scale.

18. An electroslag remelting process in accordance with claim 1 1 wherein said electrical current is an alternating current with a voltage of between about 70 and 90 volts.

. 19. An-electroslag remelting process in accordance with claim 11 wherein about 800 watts of power per" pound of slag is being applied to said molten slag when lower the carbon content of the molten slag in said I mold from the range of about 0.04 to 0.05% carbon to a range of about 0.006 0.0l6%.

22. An electroslag remelting process in accordance with claim 19 wherein the oxidizing agent is mill scale and not more thanabout 2 pounds of same is introduced to said molten slag for each 1,000 pounds of said slag.

23. An electroslag remelting process in accordance with claim 22 wherein said mill scale is introduced to said molten slag during a period of about one-half minute.

24. In an electroslag remelting process of the type wherein slag is melted in a separate container and sufficient carbon is received by the rriolten slag in said container so that the carbon content of the molten slag becomes undesirably high, said slag subsequently being introduced into an electroslag refining mold in a molten state, an end portion of a metal consumable electrode being immersed in said molten slag in said mold and an electrical current going through said slag generating heat to fuse metal from the end of said electrode through the molten slag into a molten pool of metal at the bottom thereof where it solidifies to form a metal ingot of improved homogeneity the improvement comprising the step of adding an oxidizing agent into the molten slag in said mold while said current and said molten metal are passing through said molten slag thereby decarburizing said slag without the occurrence of excessive foaming of the molten. slag in said mold.

25. In a process according to claim 24 wherein said oxidizing agent comprises iron oxide. I

26. In a process according to claim 25 wherein said iron oxide is mill scale.

27. In a process according to claim 24 wherein said electric current is an alternating'current of about cy-

Claims

1. AN ELECTROSLAG REMELTING PROCESS WHICH COMPRISES: MELTING OF SLAG IN A FURNACE BY MEANS OF AT LEAST ONE GRAPHITE ELECTRODE WHEREBY THE CARBON CONTENT OF THE MOLTEN SLAG IS INCREASED: TRANSFERRING SAID MOLTEN SLAG INTO THE BOTTOM OF AN ELECTROSLAG REMELTING MOLD WHEREIN AN INGOT OF IMPROVED HOMOGENEITY IS FORMED BY THE CONTINUED MELTING OF A METAL COMSUMABLE ELECTRODE THE END PORTION OF SAID ELECTRODE BEING IMMERSED IN SAID MOLTEN SLAG WHEREBY MELTED METAL FROM SAID END PORTION FALLS THROUGH SAID MOLTEN SLAG AND SOLIDIFES TO FORM SAD INGOT IN SAID MOLD WHILE AN ELECTRICAL CURRENT PASSES THROUGH SAID SLAG BETWEEN SAID ELECTRODE AND SAID INGOT BEING FORMED FOR MAINTAINING SAID SLAG IN A MOLTEN CONDITION: AND INTRODUCING AN OXIDIZING AGENT INTO SAID MOLTEN SLAG IN SAID MOLD WHILE SAID CURRENT IS PASSING THERETHROUGH, THE MOLD WHILE SAID CURRENT IS PASSING THERETHROUGH, THE MOLD WHILE SAID CURRENT IS PASSING THERETHROUGH, THE AMOUNT AND RATE OF SAID INTRODUCTION OF SAID OXIDIZING AGENT BEING SUCH AS TO PERFORM THE FUNCTION OF REMOVING CARBON FROM SAID MOLTEN SLAG WITHOUT CAUSING EXCESSIVE FOAMING OF SAID SLAG.

2. In a method of decarburizing flux having an undesired high carbon content, the flux being used in an electroslag remelting process wherein it is in a molten state iN an electroslag refining mold, the lower portion of a consumable metal electrode immersed in the upper portion of the molten flux, the flux being heated by an electrical current flow provided therethrough, melted metal from the electrode passing through said molten flux to the bottom of the mold into a molten metal pool where it solidifies as a more homogeneous metal, the improvement comprising the step of adding iron oxide to said molten flux in said mold while continuing said current flow whereby decarburization of said flux takes place without excessive forming of said flux.

3. A method of accordance with claim 2 wherein the iron oxide added to said flux is about 0.2% of the amount of flux by weight.

4. A method in accordance with claim 3 wherein said iron oxide is mill scale.

5. A method in accordance with claim 3 wherein said iron oxide is introduced into said flux within a time range of 30 seconds to 5 minutes.

6. An electroslag remelting process which comprises the steps of: heating a charge of slag in a slag furnace to a molten state wherein the slag is exposed to carbon and the carbon content of the slag is increased to an undesired level; introducing said slag into an electroslag refining mold in its molten state; immersing of the lower end of a consumable metal electrode into said molten slag in said mold and establishing an electric current therethrough which is sufficient to maintain said slag in said mold in a molten state and to melt said electrode immersed therein whereby molten metal is received through said molten slag in a molten metal pool in the bottom of said mold where it solidifies to form a more homogeneous ingot; immediately with said slag in a molten state after introducing same into said mold, adding an oxidizing agent to said molten slag while continuing said current through said slag and the melting of said electrode whereby the decarburization of said slag takes place without excessive foaming thereof and said slag retains its characteristic as a reducing slag.

7. A process according to claim 6 wherein said oxidizing agent is a substance selected from the group consisting of Feo, Fe2O3, Fe3O4, NiO, MoO2, CoO, Cu2O3, MnO, Mn2O3 and Mn3O4.

8. A process according to claim 6 wherein said oxidizing agent comprises iron oxide.

9. A process according to claim 8 wherein said iron oxide is mill scale.

10. A process in accordance with claim 6 wherein the amount of oxide added to said slag is about 0.2% of said slag and is introduced in a period of 30 seconds to 5 minutes.

11. An electroslag remelting process which comprises: melting of slag in a furnace which is lined at least in part by carbonaceous material whereby the carbon content of molten slag is increased; transferring said molten slag into the bottom of an electroslag remelting mold wherein an ingot of improved homogeneity is formed by the continued melting of a metal consumable electrode''s end portion immersed in said molten slag whereby melted metal from said end portion falls through said molten slag and solidifies to form said ingot in said mold while an electric current passes through said slag between said electrode and said ingot being formed maintaining said slag in a molten condition; and introducing an oxidizing agent into said molten slag in said mold while said current is passing therethrough, the amount and rate of said introduction of said oxidizing agent being such as to perform the function of removing carbon from said molten slag without causing excessive foaming of said slag.

12. An electroslag remelting process in accordance with claim 11 wherein after said molten slag has been introduced into said mold, said electrode is lowered into contact with said slag and a current flow through said slag is established, the introducing of an oxidizing agent into said slag being thereafter delayeD until the slag between said mold and said electrode is in a fully fluid condition.

13. An electroslag remelting process in accordance with claim 12 wherein the period of said delay is about 5 - 40 minutes.

15. An electroslag remelting process in accordance with claim 11 wherein said oxidizing agent is a substance selected from the group consisting of FeO, Fe2O3, Fe3O4, NiO, MoO2, CoO, Cu2O, Cr2O3, MnO, Mn2O3, and Mn3O4.

16. An electroslag remelting process in accordance with claim 11 wherein said oxidizing agent consists essentially of iron oxide.

18. An electroslag remelting process in accordance with claim 11 wherein said electrical current is an alternating current with a voltage of between about 70 and 90 volts.

19. An electroslag remelting process in accordance with claim 11 wherein about 800 watts of power per pound of slag is being applied to said molten slag when said oxidizing agent is introduced therein.

20. An electroslag remelting process in accordance with claim 19 wherein said oxidizing agent is iron oxide and the amount of said iron oxide added to said molten slag is about 0.1% of the weight of said slag for each 0.02% carbon to be removed from said flux.

21. An electroslag remelting process in accordance with claim 20 wherein sufficient iron oxide is added to lower the carbon content of the molten slag in said mold from the range of about 0.04 to 0.05% carbon to a range of about 0.006 - 0.016%.

22. An electroslag remelting process in accordance with claim 19 wherein the oxidizing agent is mill scale and not more than about 2 pounds of same is introduced to said molten slag for each 1,000 pounds of said slag.

24. In an electroslag remelting process of the type wherein slag is melted in a separate container and sufficient carbon is received by the molten slag in said container so that the carbon content of the molten slag becomes undesirably high, said slag subsequently being introduced into an electroslag refining mold in a molten state, an end portion of a metal consumable electrode being immersed in said molten slag in said mold and an electrical current going through said slag generating heat to fuse metal from the end of said electrode through the molten slag into a molten pool of metal at the bottom thereof where it solidifies to form a metal ingot of improved homogeneity the improvement comprising the step of adding an oxidizing agent into the molten slag in said mold while said current and said molten metal are passing through said molten slag thereby decarburizing said slag without the occurrence of excessive foaming of the molten slag in said mold.

25. In a process according to claim 24 wherein said oxidizing agent comprises iron oxide.

26. In a process according to claim 25 wherein said iron oxide is mill scale.

27. In a process according to claim 24 wherein said electric current is an alternating current of about 60 cycles.

28. In a process according to claim 24 wherein said slag is composed of about 40% CaF2, 30% CaO, and 30% Al2O3.