US3922166A

US3922166A - Alloying steel with highly reactive materials

Info

Publication number: US3922166A
Application number: US522391A
Authority: US
Inventors: Peter J Koros; Jerry Silver
Original assignee: Jones and Laughlin Steel Corp
Current assignee: Ltv Steel Co Inc; Jones and Laughlin Steel Inc
Priority date: 1974-11-11
Filing date: 1974-11-11
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: CA1065118A; GB1475247A; JPS5170129A; DE2550620A1; FR2290498A1

Abstract

Reactive materials having a high affinity for oxygen are incorporated into molten steel while using an alkaline earth material to sacrificially tie-up oxygen and thereby prevent the formation of reactive material oxides. The steel must be in the killed condition prior to addition of the reactive material. The method is especially suited for the incorporation of rare earths into molten steel.

Description

United States Patent 11 1 1 1 3,922,166

Koros et al. [4 Nov. 25, 1975 15 ALLOYING STEEL WITH HIGHLY 2.980.529 4/1961 Knapp et al. .r 75/129 x REACTIVE NIATERIALS 3.623.862 11/1971 Spengler. .Ir. ct al 1 1 .v 164/57 3.816.103 6/1974 1 Inventors: Peter .I- K s gh. a; 3.829.312 8/1974 Avaki ct 111. 75/53 Jerry Silver, Cleveland Heights, Ohio Primary Examiner-L. Dewayne Rutledge [73] Assignee: Jones & Laughlin Steel Corporation, Assib'm'll Andrews Pittsburgh, Pa. Attorney. Agent, 01' Firm-Gerald K. White; T. A.

zl 122 Filed: Nov. 11, 1974 [21] Appl. No.: 522,391 [57] ABSTRACT Reactive materials having a high affinity for oxygen [52] 75/58; 75/123 E; 75/129; are incorporated into molten steel while using an alka- 164/57; 164/67 line earth material to sacrificially tie-up oxygen and [5 Cl. th by p t th f ti f ti t i l OX [58] held of Search 75/123 53*58; ides. The steel must be in the killed condition prior to l64/55 58* 66-68 addition of the reactive material. The method is especially suited for the incorporation of rare earths into [56] References Cited molten SteeL UNlTED STATES PATENTS 1683.663 7/1954 Tisdalc ct 111 75/123 E 30 Clams N0 Dramngs ALLOYING STEEL WITH HIGHLY REACTIVE MATERIALS Our invention relates to a technique for the uniform incorporation of elements having a high affinity for oxygen into steel baths without the formation of appreciable amounts of oxides of such elements. The ability to minimize oxide formation and, hence, to promote the incorporation of reactive elements in other more beneficial forms is a highly desirable but oftentimes difficult objective. in order to accomplish such result, one must exercise careful control of the steel manufacturing process from post-refining through ingot solidification. The invention, therefore, involves incorporating highly reactive material into molten steel in such manner that the formation of reactive material oxides is minimized and then further processing the reactive material treated steel into a solidified casting in a manner which prevents the subsequent occurrence of reactive material oxides.

The introduction of alloying elements having high affinity for oxygen is inefficient when such elements are added with the tapping stream providing the energy for mixing because oxidation due to air entrained by the liquid steel as well as oxygen contained in the unkilled steel exiting from the steelmaking furnace causes a loss of alloying elements. Additions made to the ladle while under the influence of a protective atmosphere such as inert gases or vacuum involve costly precautions and extensive treatment times. The use of injection devices such as described in U.S. Pat. No. 3,615,085 is also somewhat cumbersome and expensive. In the event that one chooses to add reactive material alloying elements to the ingot mold during teeming, problems similar to those encountered while making additions to the tapping stream are encountered. Moreover, oxidation of reactive material additions made to the teeming stream leads to the further disadvantage that the oxidation products frequently are trapped within the ingot and thereby adversely affect product quality. As will become more apparent at a later portion of the description, the process of the invention is believed to effectively overcome the problems discussed above.

Reactive metals such as rare earths, aluminum, zirconium and titanium are extremely difficult to incorporate into liquid steel due to their very high affinity for oxygen dissolved in the steel bath. Inasmuch as such elements may be beneficially utilized to influence certain product properties provided that they do not combine with oxygen, it has been a long standing problem in the art to efficiently incorporate reactive metals into molten steel without incurring the formation of significant amounts of rare earth oxides. Oxide formation is undesirable from the standpoint of increased costs due to the necessity of adding excessive amounts of reactive materials to compensate for the proportion of the materials that form useless oxides and also from the standpoint that certain reactive material oxides are detrimental to product properties and thereby cause portions of the product to be scrapped. This latter standpoint also results in increased cost due to lower finished product yield.

The addition of rare earths to steel baths is illustrative of typical problems associated with reactive material additions. Rare earth oxides have one of the most negative standard free energies of formation of any metallic element, and, hence, rare earths readily form very stable oxides when introduced into steel baths. One is thereby faced with developing a technique which minimizes the opportunity for rare earths and oxygen to combine; both when the addition is made and at subsequent times in the process while the steel is still liquid. This invention is directed toward a technique which minimizes rare earth-oxygen contact.

Rare earth additions to molten steel serve the function of promoting the uniform formation of globular sulfides and/or oxy-sulfides. Such inclusions are retained in wrought products with resultant beneficial influence upon sheared edge bend properties and mechanical property uniformity in flat rolled products. This effect is more extensively explained in U.S. Pat. No. 3,666,570. Generally, rare earths are added in amounts of about 0.01 to 0.10% to achieve sulfide shape control. Thus, it may be seen that a technique capable of incorporating rare earths or other sulfide shape control agents into the useful sulfide or oxysulfide form rather than the harmful oxide form is of considerable practical importance to the producer of sulfide shape controlled steel products.

To maximize the beneficial effect of sulfide shape control agents such as rare earths, zirconium, and/or titanium it is not sufficient merely to uniformly incorporate the shape control agent into the molten steel in the sulfide or oxy-sulfide form. One must also take precautions to ensure that the reactive material sulfide does not later contact oxygen and thereby preferentially form an oxide. The potential for oxygen to scavenge reactive materials from sulfur exists from the point at which the sulfide has been formed upon incorporation of the reactive material. Thus precautions during ingot teeming and solidification must be observed so as to minimize exposure to oxidation. These necessary steps also form a portion of the inventive process.

It is thus an object of the invention to provide a technique for the efficient incorporation of reactive materials into molten steel in which the formation of reactive metal oxides is minimized.

It is a further objective to minimize the occurrence of reactive material oxides after the reactive material has been incorporated into molten steel thereby preserving the beneficial effect of the incorporated reactive material.

It is an additional objective to provide a reactive material incorporation procedure that will result in maximizing reactive material recovery and product yield.

It is yet a further objective to obtain a reactive material treated steel product in which the reactive material is uniformly distributed throughout the product.

These and additional objects and advantages will become more apparent to those skilled in the art from the following description of the invention.

According to the invention, reactive metals are incorporated into molten steel through utilization of four essential interrelated process steps. As will become more apparent later, all four steps are not necessarily performed in the sequence shown below.

First of all, liquid steel is tapped from a steelmaking furnace into a suitable container such as a ladle and deoxidized with a suitable deoxidizing agent to kill the steel. Silicon and/or aluminum are suitable commercially available deoxidizers. The purpose of this step is to reduce or minimize the amount of oxygen that is available for subsequent combination with reactive material additions.

Secondly, an alkaline earth is utilized to sacrificially tie-up whatever oxygen remains in the molten steel prior to or concurrently with the reactive material addition. This procedure prevents or substantially minimizes the formation of reactive material oxides. This step is accomplished either in the ladle or in the mold in a manner to be described in more detail.

Thirdly, the killed steel is teemed from the ladle into ingot molds while being surrounded with a gaseous reducing atmosphere. This technique prevents the harmful oxidation of the liquid steel and, if the reactive material already has been added to the killed steel, serves to protect the incorporated reactive material from oxidation.

The fourth step comprises providing a reactive gas generating material at the mold prior to teeming. Upon contact with the teeming stream, the material is vaporized into a reactive gas which purges air from the mold and creates a reducing atmosphere in the mold. This procedure further minimizes oxidation of the killed steel.

Through a combination of all of the above mentioned four steps, reactive materials are incorporated into steel melts without incurring a harmful degree of oxidation and then are retained in such state without further oxidation during subsequent casting and solidification. In this fashion reactive materials may be beneficially incorporated into steel products in a relatively simple, but effective, manner.

The method of the invention is applicable to any steel in which it is desired to incorporate a reactive material. Thus carbon may be included in low, medium and high amounts and the steel may or may not include significant amounts of commonly added alloying elements. Such steels may be manufactured by conventional techniques including the open hearth, basic oxygen, and electric furnace processes. The important consideration is that, upon completion of the steelmaking process, the stee must be deoxidized to the killed state. The term, Killed steel is used in accordance with the description contained in The Making, Shaping, and Treating of Steel, United States Steel, '1964, 8th edition, pages 548-549. Killed steel typically contains a maximum total oxygen content of on the order of 60ppm. Deoxidation is commonly performed during or after tapping the refined steel from the steelmaking furnace into a container such as a ladle.

The objectives of the invention may be accomplished through use of at least three process embodiments which incorporate the principles disclosed herein.

The first process embodiment comprises the following four essential steps:

The first step comprises deoxidizing refined steel to the extent that the steel is placed in the killed condition. This step is conveniently accomplished by making silicon and/or aluminum additions in the required amount to the refined steel after or during its transfer from the refining vessel to the ladle.

Following deoxidation in the ladle, a mixture of an alkaline earth and a reactive material is added to the killed steel bath at a sub-surface location. This step serves to alloy the reactive material throughout the bath in a substantially uniform manner. The alkaline earth portion of the mixture performs two functions. First of all, the alkaline earth vaporizes upon contact with the molten steel and causes a stirring action in the bath. Secondly, the alkaline earth will sacrificially tieup remaining oxygen in the bath and thus protect the reactive material portion of the additive mixture from oxidation. To perform the stirring function, the mixture must contain an effective amount of alkaline earth material to cause stirring of the bath to the extent that a substantially uniform alloyed distribution of the reactive material is obtained throughout the bath. Excessive alkaline earth levels in the mixture tend to create undue bath turbulance and splashing and should be avoided for this reason.

Magnesium, calcium, and barium are respresentative of alkaline earths that may be utilized in the practice of the invention. From 2 to 8% magnesium, from 10 to 20% calcium, and from 10 to 20% barium should be contained in the mixture to achieve the desired results of the invention. The respective lower limits are necessary to achieve the desired degree of stirring which results in uniform incorporation of the reactive material in the bath. The above specified minimum amounts are also needed to ensure that sufficient alkaline earth is present to protect the reactive material from oxidation through sacrificial combination with oxygen. The respective upper limits of the ranges are selected with an aim toward preventing the occurrence of an undue degree of turbulence in the bath.

Calcium, calcium alloys, or calcium compounds, are a preferred alkaline earth component for several reasons. Calcium oxide has a more negative standard free energy at 3000F than any of the reactive material oxides such as those of rare earths, titanium, zirconium or aluminum. On the other hand, magnesium oxide (MgO) has a somewhat higher, or, stated another way, a less negative, standard free energy of formation at 3000F than the four above named reactive material oxides. Barium oxide (BaO) has a less negative standard free energy of formation than rare earth oxides but has a more negative value than aluminum, zirconium and titanium oxides. This means that calcium would, in theory, be relatively more sacrificial or protective than barium or magnesium. Of course, when one considers that typical production conditions do not follow equilibrium conditions due to mass effects, etc. and that alkaline earths are strong oxide formers, all three alkaline earth metals will function in a protective manner in spite of relative differences in oxide formation propensity. Suitable calcium containing materials include CaSi, CaAl, CaBaAl, CaBaSi, CaAlSi, and CaRESiAl.

The reactive material portion of the additive mixture may include aluminum, rare earths, zirconium or titanium or admixtures thereof. Such materials may be in elemental or alloyed form. Compounds containing reactive material components are also suitable for use in conjunction with the practice of the invention. For example, rare earths may be added as an elemental form, as mischmetal, or as a rare earth silicide. The amount of reactive material contained in the mixture, of course, is a function of the amount of material desired to be incorporated into the steel.

The alkaline earth-reactive material mixture may be added to the molten steel bath through submersion of a suitable container such as that described in US. Pat. No. 2,585,404 or the mixture may be simply dunked into the ladle with use of an overhead crane or the like. Depending upon the addition technique employed, the alkaline earth component of the additive may be simply loosely mixed with the reactive material or formed into a physical dispersion of one component within the other. Alternatively, the components may be combined by briquetting or the mixture may be melted and cast into a shape suitable for use in the process.

After completion of the ladle addition step, the reactive material containing steel is teemed into a mold so ultimately as to solidify in the form of a casting. During teeming it is necessary to protect further the molten steel stream from oxidation because of the tendency of the reactive material to form oxides and thus destroy the results of the carefully controlled incorporation step. To provide adequate stream protection a reducing gaseous atmosphere may be established around the stream through use of either a tube-like container filled with a moving reducing gas or by causing a reducing gas to flow along and substantially envelope the sides of the pouring stream with use of a ring having downwardly and/or upwardly directed orifices for directing the flow of the reducing gas. Stream shrouding with a reducing gas is effective because of the sacrificial role of the gas when it combines with atmospheric oxygen to form spent combustion gases which do not cause stream oxidation. Suitable reducing gases include propane, butane, natural gas, coke oven gases, various other hydrocarbons and admixtures thereof. The reducing gas should be released around the teeming stream at a rate sufficient to prevent entry of air and/or to consume whatever atmospheric oxygen leaks through the shrouding gas envelope. Typical rates that are adequate to protect 2% to 3% inch diameter teeming streams are from about 25,000 SCfh to 50,000 scfh of natural gas.

Prior to the introduction of the teeming stream into the mold, a mold powder containing a reducing gasgenerating material is placed at the mold bottom. Upon contact with the molten steel stream, the reducing gasgenerating material is vaporized so as to purge air from the mold and to create a gaseous reducing atmosphere within and above the mold. Depending upon the amount of reducing vapor generated within the mold, the rising vapor may be employed to supplement or to even replace the reducing gas atmosphere establishment technique described in the preceding paragraph. The reducing gas-generating material may be a hydrocarbon or a calcium vapor-generating material such as calcium or calcium silicide. The mold powder may also contain slag forming ingredients such as calcium fluoride and/or sodium carbonate which serve to protect further the molten steel contained in the mold from harmful oxidation. The slag forming ingredients float to the top of the steel while it rises in the mold and thereby form a protective slag on the surface of the steel. Mold powders which contain both a hydrocarbon and a slag former or fluxing agent and are suitable for use in the invention may contain from about 5 to 50% hydrocarbon and 50 to 95% slag forming agent. Commercially available mold powders falling within the above criteria include the following: (1) equal parts stearic acid, calcium carbonate, and sodium fluoride, (2) equal parts tartaric acid, calcium carbonate, and sodium fluoride, and (3) stearic acid and equal parts of calcium carbonate and sodium fluoride.

It is also pointed out that it is within the scope of this embodiment to provide for the addition of reactive materials directly to the molten steel contained in the mold. Such additions may be made in the elemental alloyed, or compound form as described previously during the ladle addition step. Mold additions may be made for the purpose of correcting inaccuracies in the amount of original ladle additions or for preparation of 6 ingots of differing reactive metal analyses based on the same ladle chemistry.

A second process embodiment that may be utilized in accordance with the principles of the invention involves adding the alkaline earth-reactive reactive material mixture in the ingot mold rather than in the ladle. In accordance with this embodiment, liquid steel is tapped from the refining furnace, deoxidized in the ladle or transfer vessel and teemed from the ladle, while surrounded with a gaseous reducing atmosphere, into a mold having at least a reducing gas generating material at its bottom. These steps are accomplished in the same manner as described for the first process embodiment.

The mold addition step comprises adding an alkaline earthreactive material mixture to the liquid steel contained within the mold. The mixture contains an effective amount of alkaline earth which, upon contact with the molten steel functions to stir the steel to an extent or degree that a substantially uniform alloyed distribution of reactive material is ultimately obtained in the ingot. Stirring action is sufficiently vigorous to result in a uniform dispersion regardless of the depth to which the additive mixture is added within the mold. The aklaline earth portion of the mixture also functions to sacrificially tie up whatever amount of oxygen is contained in the molten steel, thus protecting the reactive material from oxidation. The alkaline earthreactive material mixture should be added from about 2 to 4 minutes after the mold has been filled. Such time delay is required so as to allow a solidified steel shell to be formed at the ingot sides and to permit inclusions to float up to and be trapped by the mold slag. Shell formation is important from the standpoint of being able toobtain a resultant product characterized by good surface properties. Following the formation of the shell, the alkaline earth-reactive material is added to the molten steel contained within the mold by one of several later described techniques.

Approximately within 2 to 4. minutes after the completion of teeming, a mixture of an alkaline earth and a reactive material is added to the molten steel contained in the mold at a sub-surface location. This step serves to alloy the reactive material throughout the steel in a substantially uniform manner. The alkaline earth portion of the mixture performs three functions. First of all, the alkaline earth vaporizes upon contact with the molten steel and thus causes a stirring action in the mold. Secondly, alkaline earth vapor passing from the top of the molten steel also serves to protect further the teeming stream. Finally, the alkaline earth will sacrificially tie-up remaining oxygen in the bath and thus protect the reactive material portion of the additive mixture from oxidation. To perform the stirring function, the mixture must contain an effective amount of alkaline earth material to cause stirring of the bath to the extent that a substantially uniform alloyed distribution of the reactive material is obtained throughout the mold. Excessive alkaline earth levels in the mixture tend to create undue mold turbulence and splashing and should be avoided for this reason.

Magnesium, calcium, and barium are representative of alkaline earths that may be utilized in the mixture. From 0.5 to 2% magnesium, from 5 to 10% calcium, and from 5 to 10% barium should be contained in the mixture to achieve the desired results of the invention. The respective lower limits are necessary to achieve the desired degree of stirring which results in uniform incorporation of the reactive material in the steel contained within the mold. The above specified minimum amounts are also needed to ensure that sufficient alkaline earth is available to protect the reactive material from oxidation through sacrificial combination with oxygen. The respective upper limits of the ranges are selected with an aim toward preventing the occurrence of an undue degree of turbulence and splashing in the mold. Hence, by selection of the amount of alkaline earth material in the additive mixture, a controlled stirring reaction may be obtained.

The amount of reactive material in the mixture, of course, is a function of the amount of reactive material desired to be incorporated into the steel.

The alkaline earth-reactive material mixture may be added to the molten steel contained within the mold by either plunging or dunking a cannister containing the mixture into the fully teemed ingot. This step may be accomplished by attaching a rod to the cannister and utilizing an overhead crane to control movement of the cannister. The components of the mixture may be loosely placed within the canister or may be combined in solid form by briquetting or by melting and casting. Alternatively, the cannister may be placed within or attached to the ingot mold prior to teeming the killed steel into the mold. If such technique is followed, the cannister must consist of a material of appropriate composition and thickness that will withstand destruction for the desired time interval of about 2 to 4 minutes. Otherwise, the benefits of the 2 to 4 minute time interval would not be obtained.

A third process embodiment also involves the addition of alkaline earth and reactive materials to the ingot mold. As in the case of the two previously described embodiments, a killed steel stream is teemed through a gaseous reducing atmosphere into a mold having at least a reducing gas generating material at its bottom. However, the alkaline earth materials and reactive materials are added to the mold while it is being filled with molten steel. The materials may be added in any convenient manner. The two materials may be added consecutively or simultaneously. If added consecutively, the alkaline earth material should be added first because its sacrificial function is to provide a wash of highly reducing gas which ties-up any oxygen in the steel so as to minimize the opportunity for the reactive material to form harmful oxides. Of course, the number of consecutive addition steps may vary from one to several. In addition, the alkaline earth material serves to form a protective slag in conjunction with any flux additives contained at the mold bottom. For example, when making rare additions to the mold, CaSi serves as a suitable alkaline earth material due to its sacrificial nature and slag making properties. However, any of the materials discussed previously will also function for this embodiment.

We claim:

1. A method of incorporating a highly reactive material into molten steel, comprising:

a. deoxidizing a steel bath in a container to kill said steel;

b. adding an alkaline earth-reactive material mixture to said killed steel bath at a sub-surface bath location, said alkaline earth-reactive material mixture containing an effective amount of alkaline earth to stir the steel bath so as to obtain a substantially uniform alloyed distribution of the reactive material throughout said killed steel bath; and

c. teeming a stream of reactive material containing steel from said container, while surrounding the stream with a gaseous reducing atmosphere, into an air containing mold have a reducing gas generating material on its bottom so that, upon contact with the reactive material containing steel, said reducing gas generating material is vaporized so as to purge air from the mold and to create a gaseous reducing mold atmosphere.

2. A method of incorporating a highly reactive material into molten steel according to claim I, wherein:

said alkaline earth-reactive material mixture contains an alkaline earth element selected from the group consisting of 2 to 8% magnesium, 10 to 20% calcium, and 10 to 20% barium. 3. A method of incorporating a highly reactive material into molten steel according to claim 2, wherein:

said alkaline earth-reactive material mixture contains from 10 to 20% calcium.

4. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein:

said alkaline earth-reactive material mixture contains a rare earth. 5. A method of incorporating a highly reactive material into molten steel according to claim 2, wherein:

said alkaline earth-reactive material mixture contains a rare earth. 6. A method of incorporating a highly reactive material into molten steel according to claim 3, wherein:

said alkaline earth-reactive material mixture contains a rare earth. 7. A method of incorporating a highly reactive material into molten steel according to claim 4, wherein:

said alkaline earth-reactive material mixture contains a member selected from the group consisting of mischmetal and a rare earth silicide. 8. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein:

said steel stream surrounding gaseous reducing atmosphere comprises a member selected from the group consisting of propane, butane, natural gas, coke oven gas, and admixtures thereof 9. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein:

said reducing gas generating material comprises a hydrocarbon.

10. A method of incorporating highly reactive material into molten steel according to claim 1, wherein:

said reducing gas generating material further includes a flux so as to form a protective surface covering for the steel contained in said mold therefy further protecting the steel from oxidation.

11. A method of incorporating highly reactive material into molten steel according to claim 10, wherein:

said reactive gas generating material contains from about 5 to 50% hydrocarbon material and from about 50 to flux material.

12. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein:

said gaseous reducing atmosphere comprises calcium.

13. A method of incorporating a highly reactive ma terial into molten steel comprising:

a. deoxidizing a steel bath in a container to kill said steel; b. teeming a stream of said killed steel from said container, while surrounding the stream with a gaseous reducing atmosphere, into an air containing mold 9 having a reducing gas generating material on its bottom so that, upon contact with the teemed steel, said reducing gas generating material is vaporized so as to purge air from the mold and to create a gaseous reducing mold atmosphere;

c. filling the mold with the teemed steel and permitting the steel to stand in the mold for about 2 to 4 minutes; and

d. then adding an alkaline earth-reactive material mixture to the steel contained in the mold at a subsurface location, said alkaline earth-reactive material containing an effective amount of alkaline earth to stir the steel within the mold so as to obtain a substantially uniform alloyed distribution of reactive material throughout the steel.

14. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said alkaline earth-reactive material mixture contains an alkaline earth element selected from the group of 0.5 to 2% magnesium, 5 to calcium, and 5 to 10% barium.

15. A method of incorporating a highly reactive material into molten steel according to claim 14, wherein: said alkaline earth-reactive material mixture contains from about 5 to l0% calcium.

16. A method of incorporating a highly reactive material intomolten steel according to claim 13, wherein: said alkaline earth-reactive material mixture contains a rare earth. 17. A method of incorporating a highly reactive material into molten steel according to claim 15, wherein: said alkaline earth-reactive material mixture contains a rare earth. 18. A method of incorporating a highly reactive material into molten steel according to claim 16, wherein: said alkaline earth-reactive material mixture contains a member selected from the group consisting of mischmetal and a rare earth silicide.

19. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein:

the killed steel teeming stream is surrounded by a gaseous reducing atmosphere comprising a member selected from the group consisting of propane, butane, natural gas, coke oven gas and admixtures thereof.

20. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein:

said reducing gas generating material comrises a hydrocarbon.

21. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said reducing gas generating material includes a flux so as to form a protective surface covering on the steel contained in the mold thereby further protecting the steel from oxidation. 22. A method of incorporating a highly reactive material into molten steel according to claim 21, wherein: said reducing gas generating material contains from about 5 to 50% hydrocarbon material and from about 50 to 95% flux material. 23. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein:

said gaseous reducing atmosphere comprises calcium. 24. A method of incorporating a highly reactive material into molten steel, comprising:

a. deoxidizing a steel bath in a container to kill said steel;

b. teeming a stream of said killed steel from said container, while surrounding the stream with a gaseous reducing atmosphere, into an air containing mold having a reducing gas generating material on its bottom so that, upon contact with the teemed steel, said reducing gas generating material is vaporized so as to purge air from the mold and to create a gaseous reducing mold atmosphere; and

c. adding an alkaline earth material and a reactive material to the mold while the mold is being filled with the teemed steel; said alkaline earth material being added in an amount sufficient to sacrificially tie-up oxygen in the teemed steel so as to minimize the occurrence of reactive material oxides.

25. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said alkaline earth and reactive materials are added to the mold in a consecutive manner; said alkaline earth material being added prior to said reactive material. 26. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said alkaline earth and reactive materials are added to the mold simultaneously. 27. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein:

said alkaline earth material comprises CaSi. 28. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein:

said reactive material comprises a rare earth. 29. A method of incorporating a highly reactive material into molten steel according to claim 27, wherein:

said reactive material comprises a rare earth. 30. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein:

said reducing gas generating material comprises calcium.

Claims

1. A METHOD OF INCORPORATING A HIGHLY REACTIVE MATERIAL INTO MOLTEN STEEL, COMPRISING: A. DEOXIDIZING A STEEL BATH IN A CONTAINER TO KILL SAID STEEL; B. ADDING AN ALKALINE EARTH-REACTIVE MATERIAL MIXTURE TO SAID KILLED STEEL BATH AT A SUB-SURFACE BATH LOCATION, SAID ALKALINE EARTH-REACTIVE MATERIAL MIXTURE CONTAINING AN EFFECTIVE AMOUNT OF ALKALINE EARTH TO STIR THE STEEL BATH SO AS TO OBTAIN A SUBSTANTIALLY UNIFORM ALLOYED DISTRIUTION OF THE REACTIVE MATERIAL THROUGHOUT SAID KILLED STEEL BATH; AND C. TEEMING A STREAM OF REACTIVE MATERIAL CONTAINING STEEL FROM SAID CONTAINER, WHILE SURROUNDING THE STREAM WITH A GASEOUS REDUCING ATMOSPHERE, INTO AN AIR CONTAINING MOLD HAVE A REDUCING GAS GENERATING MATERIAL ON ITS BOTTOM SO THAT, UPON CONTACT WITH THE REACTIVE MATERIAL CONTAINING STEEL, SAID REDUCING GAS GENERATING MATERIAL IS VAPORIZED SO AS TO PURGE AIR FROM THE MOLD AND TO CREATE A GASEOUS REDUCING MOLD ATMOSPHERE.

2. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein: said alkaline earth-reactive material mixture contains an alkaline earth element selected from the group consisting of 2 to 8% magnesium, 10 to 20% calcium, and 10 to 20% barium.

3. A method of incorporating a highly reactive material into molten steel according to claim 2, wherein: said alkaline earth-reactive material mixture contains from 10 to 20% calcium.

4. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein: said alkaline earth-reactive material mixture contains a rare earth.

5. A method of incorporating a highly reactive material into molten steel according to claim 2, wherein: said alkaline earth-reactive material mixture contains a rare earth.

6. A method of incorporating a highly reactive material into molten steel according to claim 3, wherein: said alkaline earth-reactive material mixture contains a rare earth.

7. A method of incorporating a highly reactive material into molten steel according to claim 4, wherein: said alkaline earth-reactive material mixture contains a member selected from the group consisting of mischmetal and a rare earth silicide.

8. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein: said steel stream surrounding gaseous reducing atmosphere comprises a member selected from thE group consisting of propane, butane, natural gas, coke oven gas, and admixtures thereof

9. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein: said reducing gas generating material comprises a hydrocarbon.

10. A method of incorporating highly reactive material into molten steel according to claim 1, wherein: said reducing gas generating material further includes a flux so as to form a protective surface covering for the steel contained in said mold therefy further protecting the steel from oxidation.

11. A method of incorporating highly reactive material into molten steel according to claim 10, wherein: said reactive gas generating material contains from about 5 to 50% hydrocarbon material and from about 50 to 95% flux material.

12. A method of incorporating a highly reactive material into molten steel according to claim 1, wherein: said gaseous reducing atmosphere comprises calcium.

13. A method of incorporating a highly reactive material into molten steel comprising: a. deoxidizing a steel bath in a container to kill said steel; b. teeming a stream of said killed steel from said container, while surrounding the stream with a gaseous reducing atmosphere, into an air containing mold having a reducing gas generating material on its bottom so that, upon contact with the teemed steel, said reducing gas generating material is vaporized so as to purge air from the mold and to create a gaseous reducing mold atmosphere; c. filling the mold with the teemed steel and permitting the steel to stand in the mold for about 2 to 4 minutes; and d. then adding an alkaline earth-reactive material mixture to the steel contained in the mold at a sub-surface location, said alkaline earth-reactive material containing an effective amount of alkaline earth to stir the steel within the mold so as to obtain a substantially uniform alloyed distribution of reactive material throughout the steel.

14. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said alkaline earth-reactive material mixture contains an alkaline earth element selected from the group of 0.5 to 2% magnesium, 5 to 10% calcium, and 5 to 10% barium.

15. A method of incorporating a highly reactive material into molten steel according to claim 14, wherein: said alkaline earth-reactive material mixture contains from about 5 to 10% calcium.

16. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said alkaline earth-reactive material mixture contains a rare earth.

17. A method of incorporating a highly reactive material into molten steel according to claim 15, wherein: said alkaline earth-reactive material mixture contains a rare earth.

18. A method of incorporating a highly reactive material into molten steel according to claim 16, wherein: said alkaline earth-reactive material mixture contains a member selected from the group consisting of mischmetal and a rare earth silicide.

19. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: the killed steel teeming stream is surrounded by a gaseous reducing atmosphere comprising a member selected from the group consisting of propane, butane, natural gas, coke oven gas and admixtures thereof.

20. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said reducing gas generating material comrises a hydrocarbon.

21. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said reducing gas generating material includes a flux so as to form a protective surface covering on the steel contained in the mold thereby further protecting the steel from oxidation.

22. A method of incorporating a highly reactive matErial into molten steel according to claim 21, wherein: said reducing gas generating material contains from about 5 to 50% hydrocarbon material and from about 50 to 95% flux material.

23. A method of incorporating a highly reactive material into molten steel according to claim 13, wherein: said gaseous reducing atmosphere comprises calcium.

24. A method of incorporating a highly reactive material into molten steel, comprising: a. deoxidizing a steel bath in a container to kill said steel; b. teeming a stream of said killed steel from said container, while surrounding the stream with a gaseous reducing atmosphere, into an air containing mold having a reducing gas generating material on its bottom so that, upon contact with the teemed steel, said reducing gas generating material is vaporized so as to purge air from the mold and to create a gaseous reducing mold atmosphere; and c. adding an alkaline earth material and a reactive material to the mold while the mold is being filled with the teemed steel; said alkaline earth material being added in an amount sufficient to sacrificially tie-up oxygen in the teemed steel so as to minimize the occurrence of reactive material oxides.

25. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said alkaline earth and reactive materials are added to the mold in a consecutive manner; said alkaline earth material being added prior to said reactive material.

26. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said alkaline earth and reactive materials are added to the mold simultaneously.

27. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said alkaline earth material comprises CaSi.

28. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said reactive material comprises a rare earth.

29. A method of incorporating a highly reactive material into molten steel according to claim 27, wherein: said reactive material comprises a rare earth.

30. A method of incorporating a highly reactive material into molten steel according to claim 24, wherein: said reducing gas generating material comprises calcium.