US2826497A - Addition agent and method for making ferrous products - Google Patents

Description

United tates ADDITION AGENT AND METHQD 1 R MAKENG FERRGUS PRODUCTS 'Allbert Paul Gagnebin, Fair Haven, and li'ohn Trimhle -Eash,Westfield,- N. 5., assignors to The lnternatinuai :NickelrCompany, Inc., New York, N. a corporation of Delaware No Drawing. Original application March 28, 1952, Se-

rial No. 279,247. Divided and this application August 7,1953, Serial No. 373,048

13 Claims. (Cl. 75-=-=130) 'The present invention relates to a new magnesium- ,containingaddition agent for the treatment of iron-base .m'eltsandto'animproved. process utilizing said addition agent fortreatingiron-base melts to produce magnesiumcontainingferrousproducts, especially cast iron prod- .mcts.

For the: reasons explained in patents and the technical literature, including U. S. Patents No. 2,485,760, No. 2,485,761, No, 2,516,524, No. 2,529,346, No. 2,542,655, Non-2,563,859 and No. 2,578,794, the production of ironbase alloys, particularly cast iron, containing magnesium ishighly advantageous. For example, it is known that theretention of magnesium in iron-base melts, particularly cast iron melts, will induce the occurrence of graphite in a compacted form, especially a spheroidal form, in castings made from such melts. It is well known that the-addition of-elemental magnesium to molten iron leadswto 2a very violent reaction and all, or very nearly all, the: magnesium is lost unless special precautions are taken. If the tmagnesiumis added as an alloy with, for :examplanickel or copper or silicon or combinations thereof, there is still a reaction; and for a given type of sall0y,-the violence of this reaction increases with the magnesium content of the alloy. While prior art magnesium-containing agents employed for the purpose of introducing magnesium into molten iron have achieved somevdegree ofsuccess, the use of these agents was attendedi by practical disadvantages. Thus, these agents were. dilute with respect to magnesium. For example, in practice, the magnesium is at present commonly added tassanalloy containing up to. about 20% magnesium, say 14%- to: 16% magnesium. Even when such dilute alloys :haveibeen' employed, a reaction of considerable violence :has been-encountered. Even though the violence of the reaction when the prior alloys were used was not suffircient to: prohibit their use, it Was still enough to Warrant .specialoprecautions being taken and to lead to loss of a siibstantial proportion of'themagnesium in the addition alloy. Moreover, the fact that the magnesium content of the addition alloy is low means that the total amount of'ialloy w hichmust be added is high so that the molten iron is chilled to some extent and an undesirable amount of the metal or metals with which the magnesium is alloyed maybe. introduced into the cast iron treated.

Although attempts were made to overcome the fore- ,going and other disadvantages, none, as far as we are ra-ware, waslentirely successful when carried intopractti'ce commercially on an industrial scale.

It has now been discovered that the violence of addition reactions resulting when a magnesium-containing agent is added to molten cast iron is greatly reduced by incorporating in the magnesium-containing agent a spebialr'normally 'gaseous element and further that this effect is-obtained even though the magnesium content of the agent is substantially greater than that in prior magffiebiummontaining agents which *have been used for the hltposeoof'introducing magnesiuminto" cast: iron.

It is an object of the present invention to provide a new magnesium-containing agent containing substantial proportions of magnesium which enables quiet introduction of magnesium into molten iron-base compositions.

Another object of the invention is to provide an addition agent specially adapted to introduce useful amounts of magnesium into cast iron without attendant excessively violent addition reactions.

The invention also contemplates providing a magnesium-containing agent especially adapted for introducing magnesium into molten cast iron but: which may be devoid of strategic metals.

it is a further object of the invention to provide a process for producing magnesium-containing cast iron by means of a special magnesium-containing agent which enables substantial reduction in the violence of the magnesium addition reactions.

As another object, the invention contemplates an improved process for producing magnesium-containing cast iron wherein a special agent cooperates With the cast iron bath to incorporate magnesium in the bath and to yield magnesium-containing cast iron castings.

Broadly stated, the agent provided by the invention essentially contains a large proportion of nitrogen, e. g., about 4% to about nitrogen by weight, and about to 75% magnesium. The nitrogen content of the agent is proportioned to the magnesium content of the agent such that said nitrogen content constitutes about 7% to about by Weight of the magnesium content. Nitrogen is present in the agents provided according to the invention in a releasable form, i. e., a form such that the agents Will react with Water in liquid or vapor form to yield a gaseous nitrogen-containing product, e. g., ammonia. The agents may optionally contain other elements, for example, up to about nickel, Lp to about 50% copper, up to about 30% iron, up to about 10% manganese, up to about 25% silicon, up to about 10% or 15% calcium, etc. When any of the foregoing elements are present in the agent, nickel preferably is present in amounts of about 10% to about 40%, copper preferably is present in amounts of about 20% to about 40%, iron preferably is present in amounts of about 10% to about 20%, silicon preferably is present in amounts of about 5% to about 20%, calcium preferably is present in amounts of about 5% to 10%, etc. Preferably the alloys are substantially devoid of manganese, although a small amount up to about 1% manganese may be present.

In its preferred embodiments, the agent contains about 40% up to about magnesium and about 10% to about 21% nitrogen, and the nitrogen content is about 15 to about 30% of the magnesium content. Other elements in the amounts indicated liereinbeiore may also be optionally present.

Particularly promising results have been obtained in accordance with the invention when nickel-containing nitrided magnesium alloys have been employed in the treatment of molten cast iron. These preferred alloys contain about 10% to about 35% nickel, about 10% to about 21% nitrogen and the balance essentially magnesium. Copper may bepresent in amounts up to about 35%, e. g., about 15% to about 30%; iron may be present in amounts up to about 15%, e. g., about 5% to about 10% manganese may be present in amounts up to about 1%, e. g., about 0.2% to about 0.6%; silicon may be present in amounts up to about 25%, e. g., about 10% to about 20%; and calcium may be present in amounts up to about 15%, e. g., about 5% to about 10%. The

7 preferred nickel-containing alloys yields a quiet reaction when added to molten castirou, particularly when the alloys are added to the top of the molten iron bath held assume 3 in a ladle or other container or are placed in the bottom of a ladle or other container and the molten iron is then poured over the alloy. In addition, these preferred alloys yield high efliciency in treating molten cast iron in that a high proportion of magnesium contained in the alloys is recovered in the molten cast iron.

The present invention also contemplates the treatment of molten iron-base baths, e. g., molten cast iron baths, with the agent provided in accordance with the invention, for the purpose of introducing magnesium into said molten baths. it has been found that these agents may be employed to introduce magnesium into molten cast iron with attendant quiet introduction and high magnesium recovery therefrom even though the magnesium content of the agent employed is substantial, e. g., at least about and preferably or more, magnesium. These factors enable the use of smaller total amounts of additions to introduce a given amount of magnesium into a particular molten cast iron composition than was the case heretofore. Thus, according to this invention, magnesium is added to molten cast iron in the form of mag-- nesium, or an alloy of magnesium, containing an appreciable amount of nitrogen. It is found that the reaction is then reduced in violence. When effective amounts of magnesium, e. g., about 0.02% or 0.03% to about 0.4%, or more preferably about 0.04% or about 0.05% to about 0.2%, are introduced into molten cast iron by means of the special nitrided agents and the magnesium-containing iron is thereafter inoculated with a graphitizing inoculant, e. g., silicon, ferrosilicon, calcium silicide, etc., and is cast in an inoculated condition to retain the aforesaid amounts of magnesium in the final castings, graphite in the castings is induced to occur in a compacted form, including a spheroidal form. A graphitizing inoculation is required with the great majority of cast iron baths which are treated with the special nitrided agent to contain the aforesaid amounts of magnesium when final graphitic castings are required, since magnesium contained in molten cast iron has been found by itself to have a very strong whitening effect. This effect usually leads to the production of white iron castings when magnesium within the aforementioned ranges is retained in cast iron unless this whitening effect is counteracted as by inoculation with an effective graphitizer. lnoculants are usually added in amounts of about 0.3% to about 2.5% of the melt treated.

Appropriate agents may be made by subjecting magnesium or magnesium alloys to a nitriding process of the kind used in the nitriding of steel, e. g., a process in which the alloy is heated in an atmosphere of nitrogen, for example, as provided by the decomposition of ammonia, to say about 590 C. (1100 F.) for about 48 hours. To facilitate the nitriding process, the magnesium alloy thus treated is preferably in the form of small pieces, e. g., such as will pass through a sieve having ten meshes to the linear inch. Whether, in fact, some of the magnesium in the magnesium alloy thus treated is converted into magnesium nitride or whether perhaps the nitrogen is taken up by the alloy in some other form is uncertain but it is convenient to refer to the final magnesiumcontaining agent as nitrided. The nitrogen-containing materials used according to the invention are preferably in small pieces ranging from, say, the size of a pinhead or a matchhead to that of a pea, i. e., about inch to about A inch in diameter. In preparing the nitrided materials, the smaller the pieces the more easily is the nitriding completed but if very small particles in the nature of powder are added to the molten iron, the re covery of magnesium in the molten iron is lower. The gain in weight during the nitriding operation may be taken as a convenient measure of the nitrogen content of the nitrided alloys, although the nitrogen content may be determined by other analytical procedures.

The final nitrided agents may vary in composition as indicated hereinbefore. As an example, an alloy con- 4 taining 56% magnesium and 44% nickel may be nitrided to provide an excellent addition agent. Such a nitrided alloy, when introduced into molten iron, produces a reaction no more violent than that of an unnitrided alloy containing 14% magnesium and 86% nickel. Moreover, the use of the nitrided agent to introduce magnesium into molten iron containing elements detrimental to the production of spheroidal graphite appears to offset the detrimental effects of these elements to some extent so that final gra hitic magnesium-containing castings more of the graphite will be spheroidal than if an unnitrided agent is used.

Qther alloys, besides nickel-magnesium alloys, which may be nitrided and then used according to the invention are nichel-iron-magnesium, nickel-copper-magnesium, copper-magnesium, copper-iron-magnesium, nickel-siliconmagnesium alloys, etc. Such alloys before nitriding usually will contain at least about 50% magnesium, e. g., about 55% to about magnesium.

While the nitrided agents provided by the invention may be used in the form of small pieces, the agents may also be used in the form of a briquette with other materials, for example, iron or nickel particles, etc., or particles of graphitizing agents such as silicon-containing agents, etc., and may be bonded together with a binder. This may be convenient if the nitrided material is of low density since the density of the hriquette can be higher and it will therefore be easier to introduce it into molten iron.

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

Example I An alloy containing about 66% magnesium and 34% nickel was nitrided for about 15 hours at 590 C. in contact with nascent nitrogen obtained from the dissociation of ammonia. Sufiicient nitrogent reacted with the alloy to produce a weight gain of about 8.3%. When a sample of the nitrided product was moistened, strong ammonia fumes were generated. A cast iron melt containing about 0.05% sulfur was prepared in an induction furnace, and an addition of about 1.3% of the unnitrided 66% magnesium-34% nickle alloy was made to the surface of a part of this melt held in a ladle. A similar addition of the nitrided produce was made to another part of the same melt. The unnitrided agent reacted violently when added to the melt while the nitrided agent reacted much more quietly. Each part of the melt was then inoculated and cast to produce a graphitic cast iron. The iron casting produced with the unnitrided agent contained 0.028% magnesium and had graphite present principally in a flake form while the iron casting produced with the nitrided agent contained 0.052% magnesium and had graphite present predominantly in a spheroidal form. The following results were obtained upon subjecting the resulting castings to physical tests:

Example 11 An alloy containing about 66% magnesium and 34% nickel was nitrided for about 86 hours at 590 C. in contact with nascent nitrogen obtained from the dissociation of ammonia to produce a nitrided alloy in accordance with the present invention. A molten cast iron bath containing about 3.5% carbon and about 0.05% sulfur was established in an indirect arc furnace. Singlel).85%-portions of the aforementioned nitrided-zalloy and'of an unnitrided magnesium-nickel alloy containingabout 66% magnesium and 34% nickel were added to thesur-face of separate parts of this molten cast iron bath held in a 5 ladle, using the same procedure in. each case. The nitrided. alloy reacted considerably more slowly and less violentlythan the unnitrided alloy. Each it part of the thus-treated bath Was then inoculated and cast. It was found that the casting made using the nitrided alloy contained about 0.19% retained magnesium while the casting made using the unnitrided alloy contained about 0.056% retained magnesium.

Example III Ironcontaining about 0.02% sulfur was melted in an indirect arc furnace. While part of the melt wasbeing removed from the furnace, anitrided magnesium agent containing about 72% magnesium and about 226% nitrogen was added to the stream of molten metal in; an amount equal to about 0.6% by weight of the metal. Themetal was then inoculated and cast. The agent; reacted quietly with the metal and the metal poured clean. The resultant magnesium-containing casting was graphitic with substantially all the graphite in a spheroidalform. The magnesium content was 0.029%, which, is less than that usually required to convert all the graphite, into. the spheroidal form.

Example IV A cast iron bath containing about 3.6% carbon and about 0.02% sulfur was prepared and the temperature thereof adjusted to a proper casting heat. About 1% of a nitrided 67% magnesium-33% copper-agent which had been nitridedfor about 24 hours at 590 C. in nascent nitrogen resulting from the decomposition-of ammonia to produce a weight gain of about 5% was added to a portion of the melt by placing the agent in the bottom of the ladle and pouring the molten iron thereover, after which this portion was inoculated with 0.6% of ferrosilicon and cast. The casting contained 0.044%"magnesium and had a tensile strength of 103,000 pounds per square inch with an elongation of 8% and a hardness of 255 Brinell.

Examples of other agents within the scope of the invention are as follows:

The reason why magnesium can be more easily introduced into molten iron in the form of the agents provided by the invention is uncertain; but it appears likely that in the agents added to the iron, magnesium is present in the form of a compound which is thermally stable up to a high temperature and dissociates slowly to form gases or vapors without melting. In consequence there is, it seems, no violent evolution of magnesium vapor from liquid magnesium, but instead the magnesium vapor is absorbed by the melt as the magnesium compound dissociates in contact with the molten iron.

It may be pointed out that the agents provided by the invention which contain nickel are nevertheless dilute with respect to nickel and the use of these agents enables substantial nickel economy when they are used to produce spheroidal graphite cast iron. For example, the nickel-containing agents provided by the invention enable production of spheroidal graphite cast iron containing nickel as low as about 0.15% or even lower.

The special agents provided in accordance with the present invention are specifically contemplated to be used inthe production ofnotonly gray cast irons containing magnesium and containing graphite in a compacted ,or even ina spheroidal form but also white cast irons containing magnesium. Such white cast irons can then be heat treated to produce magnesium-containing malleable iron, In addition, the agents provided in accordance with the invention may be used as desulfurizers, deoxidizers and purifiers of ferrous melts and melts of metals. such as nickel, copper, etc. As those skilled inthe art know, the aforesaid cast ironproducts may vary con siderably in com-position and may containvarious alloy-. ing elements. This is. explained, for example, in U. S; Patents Nos. 2,485,760, 2,516,524, 2,529,346 and. 2,578,- 794. Thus, the cast iron products treated in accordance with the invention will usually contain. about-1.7% or 2% or 2.5% up to about 4% or 5% carbon about 0.4% or 1%.or 1.5% up to about 4% or 6% silicon, with the balance essentially iron, said balance usually being about 85% or 87% or more of the alloys. The molten com.-.

positions treated in accordance with the invention may also contain the usual alloying elements found in gray cast irons, white cast irons and, malleable irons, e. g., up to about 36% nickel, up to about 0.6% molybdenum, up to about 2.5% chromium, up to about 2.5% manganese, up to about 3% copper, etc. phosphorus and sulfur may be present in amounts up to about 0.25% and up to about 0.3%, respectively, but it is preferred that the contents of these impurities be below about 0.15%, respectively.

This application is a division of copending U. S.,appl,i-

cation Serial No. 279,247, filed March 28, 1952,.now.

abandoned.

Although the present invention has been described in,

conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as tnose skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the inventionand;

appended claims.

We claim:

1. As a new article of manufacture, an addition agent; specially adapted for the introduction of magnesium into molten cast iron comprising about 10% to about 21% nitrogen content being about 15% to about 30% of the magnesium content.

2. As a new article of manufacture, an addition agent specially adapted for the introduction of magnesium into molten cast iron comprising essentially about 10% to about 35% nickel, about 15% to about 30% copper, about 40% to about magnesium and about 10% to about 21% nitrogen, with the nitrogen content being about 15% to about 30% of the magnesium content.

3. As a new article of manufacture, an addition agent specially adapted for the introduction of magnesium into molten cast iron comprising about 40% to about 70% magnesium, about 10% to about 21% nitrogen, about 10% to about 35% nickel, up to about 35% copper, up to about 15% iron, up to about 1% manganese, about 10% to about 20% silicon, and up to about 15% calcium, with the magnesium and nitrogen contents being so proportioned that the nitrogen content is about 15 to about 30% of the magnesium content.

4. As a new article of manufacture, an addition agent specially adapted for the introduction of magnesium into molten cast iron comprised of an alloy containing about 4% to 25% nitrogen, about 30% to about magnesium, about 10% to about 40% nickel, up to about 50% copper, up to about 30% iron, up to about 10% manganese, up to about 25% silicon, and up to about 15 calcium, with the magnesium and nitrogen content The impurities.-

being so proportioned that the nitrogen content is about 7% to about 35 of the magnesium content.

5. As a new article of manufacture, an addition agent specially adapted for the introduction of magnesium into molten cast iron and containing nickel, magnesium and nitrogen, with the magnesium content being about 40% to about 70%, the nitrogen being about 7% to about 35% of the magnesium content, and the balance being essentially nickel.

6. As a new article of manufacture, an addition agent specially adapted for the introduction of magnesium into molten cast iron and essentially containing magnesium and nitrogen, with the magnesium content being about 30% to about 75% and the nitrogen being about 7% to about 35% of the magnesium content.

7. In the process for introducing magnesium into molten cast iron to produce magnesium-containing castings, the steps comprising adding said magnesium to said molten cast iron in the form of an agent comprised of an alloy essentially containing magnesium and nitrogen wherein the nitrogen content is about 7% to about 35 of the magnesium content, and casting the magnesiumcontaining molten cast iron.

8. In the process for introducing magnesium into molten cast iron in the production of cast iron castings containing graphite in a spheroidal form, the steps comprising adding said magnesium to said molten cast iron in the form of an agent comprised of an alloy containing about 40% to about 70% magnesium and containing nitrogen in proportions from about 15% to about 30% of the magnesium content, and thereafter inoculating the molten magnesium-containing cast iron and casting said molten iron in an inoculated condition.

9. In the process for introducing magnesium into molten cast iron in the production of cast iron castings containing graphite in a spheroidal form, the steps comprising adding said magnesium to said molten cast iron in the form of an agent comprised of an alloy containing about to about 21% nitrogen, up to about 50% nickel, up to about 50% copper, up to about 30% iron, up to about 10% manganese, up to about 25% silicon, up to about calcium, the balance essentially magnesium, with the magnesium and nitrogen contents being so proportioned that the nitrogen content is about 15% to about 30% of the magnesium content, and thereafter inoculating the molten magnesium-containing cast iron and casting said molten iron in an inoculated condition.

10. The. method for producing cast iron containing spheroidal graphite which comprises establishing a bath of such composition that if cast would result in gray cast iron containing flake graphite, adding magnesium as an alloy containing about 40% to about magnesium and about 10% to about 21% nitrogen with the nitrogen being about 15% to about 30% of the magnesium content of the alloy, said alloy being added in an amount such that the treated melt would result in a substantially white iron, graphitizing the thus-treated melt such that the graphitized melt would result in gray iron and casting metal from the graphitized melt to produce gray iron castings containing spheroidal graphite.

11. The method for producing cast iron containing graphite in a spheroidal form which comprises establishing a molten cast iron bath having such a composition as to be gray cast iron if cast in an inoculated condition, introducing into said bath an agent containing about 30% to about magnesium, up to about 50% nickel, up to about 50% copper, up to about 30% iron, up to about 10% manganese, up to about 25 silicon, up to about 15 calcium and about 4% to about 25% nitrogen, with the nitrogen being about 7% to about 35 of the magnesium content, said agent being added in an amount sufficient to provide a retained magnesium content of about 0.03% to about 0.4% in castings made from said bath, and casting metal from the thus-treated bath in an inoculated condition to produce castings containing graphite in a spheroidal form.

12. The method for producing cast iron containing graphite in a compacted form which comprises establishing a molten cast iron bath having such a composition as to be gray cast iron if cast in an inoculated condition, introducing into said bath an agent containing about 30% to about 75% magnesium and about 4% to about 25 nitrogen, with the nitrogen being about 7% to about 35 of the magnesium content, said agent being added in an amount sufficient to provide a retained magnesium content of about 0.02% to about 04% in castings made from said bath, and casting metal from the thus-treated bath in an inoculated condition to produce castings containing graphite in a compacted form.

13. In a process for the introduction of magnesium into cast iron melts in order to obtain cast iron with wholly or partly spheroidal graphite, the step of adding the magnesium to the cast iron melt as magnesium nitride obtained by incomplete nitriding of magnesium.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NOo 2,826 49'7 March 11 1958 Albert Paul Gagnebin et al0 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction. and that the said Letters Patent shouldv read as corrected. belowo Column 2 line 70, for "yields" read m yield column 4, line 44, for niekle" read W nickel line 4.6, for "produce" read M product column 6, line 6, after "iron" change comma to a period; line 16, after "carbon" ineert a comma,

Signed and sealed this 29th day of July 1958:,

(SEAL) Attest:

KARL E0. TEN? ROBERT c. WATSON Attesting Officer Commissioner of Patents

Claims (1)

11. THE METHOD FOR PRODUCING CAST IRON CONTAINING GRAPHITE IN A SPHERODIAL FORM WHICH COMPRISES ESTABLISHING A MOLTEN CAST IRON BATH HAVING SUCH A COMPOSITION AS TO BE GRAY CAST IRON IF CAST IN AN INOCULTED CONDITION, INTRODUCING INTO SAID BATH AN AGENT CONTAINING ABOUT 30% TO ABOUT 75% MAGNESIU, UP TO ABOUT 50% NICKEL, UP TO ABOUT 50% COPPER, UP TO ABOUT 30% IRON, UP TO ABOUT 10% MANGANESE, UP TO ABOUT 25% SILICON, UP TO ABOUT 15% CALCIUM AND ABOUT 4% TO ABOUT 25% NITROGEN, WITH THE NITROGEN BEING ABOUT 7% TO ABOUT 35% OF THE MAGNESIUM CONTENT, SAID AGENT BEING ADDED IN AN AMOUNT SUFFICIENT TO PROVIDE A RETAINED MAGNESIUM CONTENT OF ABOUT 0.0O% TO ABOUT 0.4% IN CASTINGS MADE FROM SAID BATH, AND CASTING METAL FROM THE THUS-TREATED BATH IN AN INOCULATED CONDITION TO PRODUCE CASTINGS CONTAINING GRAPHITE IN A SPHEROIDAL FORM.