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US3660081A - Method making ferrosilicon alloy - Google Patents

Method making ferrosilicon alloy Download PDF

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Publication number
US3660081A
US3660081A US5766A US576670A US3660081A US 3660081 A US3660081 A US 3660081A US 5766 A US5766 A US 5766A US 576670 A US576670 A US 576670A US 3660081 A US3660081 A US 3660081A
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copper
ferrosilicon
alloy
percent
content
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US5766A
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John W Farrell
William D Forgeng
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Elkem Metals Co LP
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Union Carbide Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C35/00—Master alloys for iron or steel
    • C22C35/005—Master alloys for iron or steel based on iron, e.g. ferro-alloys

Definitions

  • This invention relates to ferrosilicon alloys. More particularly, this invention is related to a method for producing ferrosilicon material which is strong, dense, non-friable, and nondisintegrating.
  • Ferrosilicon is a material widely used as an addition agent in the steel industry, and is usually produced by smelting a mixture of silica, carbon, and iron-bearing materials to obtain a molten alloy which is cast into shapes which are particulated to obtain the size desired by the customer.
  • ferrosilicon Since ferrosilicon is often transported considerable distances from the point of manufacture to the site of ultimate use, and is commonly stored for long periods and exposed to the elements during storage, it is important that the alloy be tough, non-friable, and non-disintegrating.
  • an object of the present invention to provide a method for preparing ferrosilicon material which is both non-friable and non-self disintegrating, in addition to being strong and dense.
  • a method in accordance with the present invention comprises preparing a molten ferrosilicon alloy containing about 38 to 90 percent silicon; admixing a copper-bearing material with the molten ferrosilicon to provide between about 0.10 percent and 0.50 percent, and preferably from 0.15 to 0.30 percent copper in the molten ferrosilicon; casting and solidifying the thus treated alloy; and cooling the solidified alloy at a rate such that the amount of zeta phase (Fe Si in the final alloy is not more than about percent.
  • the zeta phase, Fe Si which is normally present in substantial amounts in the ferrosilicon alloys hereinabove noted, has been regarded as a cause of disintegration in ferrosilicon alloys.
  • Zeta phase, Fe Si can be observed and the amount present calculated from polished and etched microscopic sections of the alloy in which Fe si appears as a separate and distinct phase.
  • Very slow cooling of the ferrosilicon alloy castings has been found to cause some transformation of the zeta phase, Fe Si to FeSi Si, and a reduction in disintegration to some extent. However, there is still need for further improvement in disintegration characteristics.
  • molten ferrosilicon is prepared, e.g., percent silicon, balance essentially iron, and from about 0.10 to about 0.50 percent, preferably 0.15 to 0.30 percent, copper is incorporated in the melt by the addition of elemental copper, e.g., copper clippings, or copper alloys containing 10 percent or more copper so as to avoid introducing objectionable amounts of undesired elements into the ferrosilicon.
  • elemental copper e.g., copper clippings, or copper alloys containing 10 percent or more copper so as to avoid introducing objectionable amounts of undesired elements into the ferrosilicon.
  • the molten ferrosilicon is cast and solidified, and the casting is caused to cool at a rate such that the final material contains not more than 10% Fe Si illl It is important that the FegSi5 content of the alloy be not more than about 10 percent; otherwise, no significant benefit is obtained from the copper addition.
  • the calcium and aluminum contents of a ferrosilicon alloy significantly affect the cooling rate required for providing a material containing not more than about 10% Fegsl5. Further, the relative proportions of calcium and aluminum in the alloy are significant. That is to say, the presence of a given amount of calcium in a ferrosilicon alloy requires a slower cooling rate as compared to the presence of an equal content of aluminum. The calcium actually has an effect of fivefold as compared to aluminum.
  • the maximum cooling rate which is permissable to obtain a ferrosilicon alloy containing not more than about 10% Fe Si is determined through the use of the graph of the drawing by locating the curve on the graph corresponding to the effective calciumaluminum content of the alloy, the effective calcium-aluminum content being %Ca %Al/S. This is referred to herein as the Calcium Equivalent" content.
  • the maximum cooling rate for such alloy is then determined by the intersection of the copper content of the alloy with the previously determined curve for the Calcium Equivalent content of the alloy.
  • the 5 Equivalent content 2 0.1% and the maximum cooling rate is 7 C/min. between 850 and 700l0% illustrated in the drawing at A. It can be stated more generally that for any given copper content, the cooling rate should be to the left of the curve of the drawing corresponding to the Calcium Equivalent content of the alloy.
  • the graph shown sets forth the maximum desirable cooling rates for copper-containing ferrosilicon alloys containing 38 to percent silicon and the indicated Calcium Equivalent contents.
  • the cooling rates are for the temperature range of about 850 to 700C. since it has been found that this is the range in which controlled cooling is the most critical to achieve transformation of Fe,Si in copper-containing ferrosilicon.
  • the cooling rate at temperalnnAiA M- tures above about 850C. and below about 700C. can be as fast (or as slow) as desired.
  • EXAMPLE I A 65 -pound heat of 50 percent ferrosilicon was prepared from an alloy analyzing 48.3 percent silicon, 0.05 percent calcium, 0.70 percent aluminum, 0.0l5'percent phosphorous, and 0.06 percent copper. The metal was cast at 1,300C., in -pound increments, into separate clay-graphite crucibles which had been preheated to 1,000C. No additions were made to the first crucible and copper additions, as elemental copper, were made to provide copper contents of 0.16 percent, 0.35 percent, 1.04 percent in the metal in the remaining crucibles. Immediately after pouring, all crucibles were buried in sand to produce a very slow cooling rate.
  • Example II The procedure of Example 1 was followed to provide ferrosilicon alloys containing 0.06 percent, 0.15 percent, 0.35 percent, 0.55 percent, 0.80 percent and 1.0 percent copper. After 7 days exposure to the outdoor atmosphere, the alloy containing 0.06 percent copper had noticeably disintegrated. The other alloys showed no sign of disintegration.
  • Example Ill The procedure of Example I was followed in preparing ferrosilicon alloys containing (A): 0.008% Ca, 0.22% Al and 0.16% Cu and (B): 0.008% Ca, 0.22% A1 and 0.22% Cu.
  • Alloy (A) contained approximately 25% Fe,Si,-, while alloy (B) was essentially free of Fe Si It has also been found that with ferrosilicon alloys which contain copper, but in which the Fe si phase has not transformed, e.g., rapidly quenched alloys containing 0.16 percent copper, no significant disintegration tendency is observed although the material is easily abraded.
  • the copper addition is made to the ferrosilicon alloy by mixing a reducible copper compound such as copper oxide, with a silica-carbon charge.
  • a reducible copper compound such as copper oxide
  • the copper compound is reduced concurrently with the silica, and copper is thereby directly'incorporated in the ferrosilicon alloy product.
  • a method for producing an essentially non disintegrating ferrosilicon alloy which comprises preparing a molten ferrosilicon alloy containing from about 38 to percent silicon and minor amounts of calcium and aluminum; admixing a copperrich material with the molten ferrosilicon to provide in the ferrosilicon alloy a copper content of from about 0.10 to 0.50 percent; casting and solidifying the thus treated alloy; and cooling the solidified alloy at a rate such that the amount of zeta phase, Fe Si in the alloy is less than about 10 percent.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

Method for producing tough non-friable, non-disintegrating ferrosilicon by the addition of copper to the ferrosilicon in the molten state and controlling the cooling rate of the resultant casting in accordance with the copper content and the calcium and aluminum contents of the casting.

Description

D United States Patent [151 3,660,081
Farrell et al. 1 May 2, 1972 54] METHOD MAKING FERROSILICON [56] References Cited ALLOY UNITED STATES PATENTS [72] Inventors: John W. Farrell, North Tonawanda; Wil- I 2,906,653 9/1959 Peras ..75/125 X l D. F N F 1] b th f "gens agara a 8 3,323,899 6/1967 Forgeng.. ..75/0.5 3,350,197 10/1967 Beeton ..75/125 X [73] Assignee: Union Carbide Corporation, New York,
N.Y. Primary Examiner-L. Dewayne Rutledge Assistant Examiner-J. E. Legru [22] Filed 1970 Att0rneyPaul A. Rose, Frederick J. McCarthy, Jr. and [21] Appl. No.: 5,766 RobertC. Cummings Related US. Application Data 57 1 S C Continuation-impart of 6521884, y 12, Method for producing tough non-friable, non-disintegrating 1967, abandQnedferrosilicon by the addition of copper to the ferrosilicon in the molten state and controlling the cooling rate of the resultant [52] U.S. Cl ..75/ 129, 75/123 L, 75/125 casting in accordance with the copper content and the calci. 39/44 C229 39/54 um and aluminum contents of the casting. [58] Fieldof Search ..75/125,129
4 Claims, 1 Drawing Figure Jttllil :1.:...!1 .bsZcALc/uM h 4 .e w
EQUIVALENT I v o ..1 t V i .0 CALCIUMEQl IIl ALENT g 1 1 i l 1 r l 2 I l i 0.30 (I) o o: a: LU ll- 5 1 o r r e\ I MAXIMUM COOLING RATE-'6 PER MINUTE IN RANGE OF 850'C TO 700'C METHOD MAKING FERROSILICON ALLOY This application is a continuation-in-part of Ser. No. 652,884, filed July 12, 1967 now abandoned.
This invention relates to ferrosilicon alloys. More particularly, this invention is related to a method for producing ferrosilicon material which is strong, dense, non-friable, and nondisintegrating.
Ferrosilicon is a material widely used as an addition agent in the steel industry, and is usually produced by smelting a mixture of silica, carbon, and iron-bearing materials to obtain a molten alloy which is cast into shapes which are particulated to obtain the size desired by the customer.
Since ferrosilicon is often transported considerable distances from the point of manufacture to the site of ultimate use, and is commonly stored for long periods and exposed to the elements during storage, it is important that the alloy be tough, non-friable, and non-disintegrating.
These requirements present a substantial challenge since ferrosilicon does not inherently possess the above characteristics.
Various techniques, such as slow cooling of the as produced ferrosilicon castings, have been used to improve the toughness of the material and thus reduce friability. However, the problem of self-disintegration during extended storage still remains.
Very rapid cooling of as-produced ferrosilicon castings has been found to significantly suppress self-disintegration; however, such materials are rendered more friable by this type of treatment.
It is, therefore, an object of the present invention to provide a method for preparing ferrosilicon material which is both non-friable and non-self disintegrating, in addition to being strong and dense.
Other objects will be apparent from the following description and claims taken in conjunction with the drawings which shows a graph illustrating cooling rates in accordance with the present invention.
A method in accordance with the present invention comprises preparing a molten ferrosilicon alloy containing about 38 to 90 percent silicon; admixing a copper-bearing material with the molten ferrosilicon to provide between about 0.10 percent and 0.50 percent, and preferably from 0.15 to 0.30 percent copper in the molten ferrosilicon; casting and solidifying the thus treated alloy; and cooling the solidified alloy at a rate such that the amount of zeta phase (Fe Si in the final alloy is not more than about percent.
The zeta phase, Fe Si which is normally present in substantial amounts in the ferrosilicon alloys hereinabove noted, has been regarded as a cause of disintegration in ferrosilicon alloys. Zeta phase, Fe Si can be observed and the amount present calculated from polished and etched microscopic sections of the alloy in which Fe si appears as a separate and distinct phase. Very slow cooling of the ferrosilicon alloy castings, as previously mentioned, has been found to cause some transformation of the zeta phase, Fe Si to FeSi Si, and a reduction in disintegration to some extent. However, there is still need for further improvement in disintegration characteristics.
It has now been discovered, as part of the present invention, that by adding copper to the ferrosilicon alloy in the manner hereinafter described, that a ferrosilicon alloy which is both non-friable, and essentially non-disintegrating, can be produced even with the use of rather rapid cooling rates.
In the practice of a particular embodiment of the present invention, molten ferrosilicon is prepared, e.g., percent silicon, balance essentially iron, and from about 0.10 to about 0.50 percent, preferably 0.15 to 0.30 percent, copper is incorporated in the melt by the addition of elemental copper, e.g., copper clippings, or copper alloys containing 10 percent or more copper so as to avoid introducing objectionable amounts of undesired elements into the ferrosilicon.
After adding the copper, the molten ferrosilicon is cast and solidified, and the casting is caused to cool at a rate such that the final material contains not more than 10% Fe Si illl It is important that the FegSi5 content of the alloy be not more than about 10 percent; otherwise, no significant benefit is obtained from the copper addition.
It has further been discovered that, in addition to the copper content, the calcium and aluminum contents of a ferrosilicon alloy significantly affect the cooling rate required for providing a material containing not more than about 10% Fegsl5. Further, the relative proportions of calcium and aluminum in the alloy are significant. That is to say, the presence of a given amount of calcium in a ferrosilicon alloy requires a slower cooling rate as compared to the presence of an equal content of aluminum. The calcium actually has an effect of fivefold as compared to aluminum.
Accordingly, in the 30 of the present invention, the maximum cooling rate which is permissable to obtain a ferrosilicon alloy containing not more than about 10% Fe Si is determined through the use of the graph of the drawing by locating the curve on the graph corresponding to the effective calciumaluminum content of the alloy, the effective calcium-aluminum content being %Ca %Al/S. This is referred to herein as the Calcium Equivalent" content. The maximum cooling rate for such alloy is then determined by the intersection of the copper content of the alloy with the previously determined curve for the Calcium Equivalent content of the alloy.
For example, with an alloy containing 0.05% Ca, 0.25% A1 and 0.26% Cu, the 5 Equivalent content 2 0.1% and the maximum cooling rate is 7 C/min. between 850 and 700l0% illustrated in the drawing at A. It can be stated more generally that for any given copper content, the cooling rate should be to the left of the curve of the drawing corresponding to the Calcium Equivalent content of the alloy.
The casting cooling rates determined in the foregoing manner have been found to ensure substantially complete TABLE 1 Maximum Coating Copper Content Calcium Equivalent Rate in Range of Content% 850C to 700C 0.1 0.05 l.5per minute 0.1 0.2 .75C per minute 0.1 0.3 0.4C per minute 0.2 0.05 5C per minute 0.2 0.2 1.5C per minute 0.2 0.3 0.7C per minute 0.3 0.05 14C per minute 0.3 0.2 5C per minute 0.3 0.3 13C per minute 0.35 0.05 24C per minute 0.35 0.2 8.5C per minute 0.35 0.3 225C per minute 50 .05 53C per minute 50 0.2 22C per minute .50 0.3 C per minute Copper-containing ferrosilicon prepared in the manner aforedescribed is remarkable in that it is both tough, i.e., nonfriable, and non-disintegrating.
With further reference to the drawing, the graph shown sets forth the maximum desirable cooling rates for copper-containing ferrosilicon alloys containing 38 to percent silicon and the indicated Calcium Equivalent contents. The cooling rates are for the temperature range of about 850 to 700C. since it has been found that this is the range in which controlled cooling is the most critical to achieve transformation of Fe,Si in copper-containing ferrosilicon. The cooling rate at temperalnnAiA M- tures above about 850C. and below about 700C. can be as fast (or as slow) as desired.
The following example will further illustrate the present invention.
EXAMPLE I A 65 -pound heat of 50 percent ferrosilicon was prepared from an alloy analyzing 48.3 percent silicon, 0.05 percent calcium, 0.70 percent aluminum, 0.0l5'percent phosphorous, and 0.06 percent copper. The metal was cast at 1,300C., in -pound increments, into separate clay-graphite crucibles which had been preheated to 1,000C. No additions were made to the first crucible and copper additions, as elemental copper, were made to provide copper contents of 0.16 percent, 0.35 percent, 1.04 percent in the metal in the remaining crucibles. Immediately after pouring, all crucibles were buried in sand to produce a very slow cooling rate. After cooling to room temperature, the solidified alloy from each crucible was broken with a hammer and pieces of each sample were exposed to the outdoor atmosphere for 10 days. At this time the base alloy sample containing 0.06 percent copper had begun to crumble and was easily abraded by rubbing pieces of the alloy together. The samples containing 0.16 percent, 0.35 percent, and 1.04 percent copper showed no sign of disintegration and were solid, tough, and abrasion resistant.
EXAMPLE II The procedure of Example 1 was followed to provide ferrosilicon alloys containing 0.06 percent, 0.15 percent, 0.35 percent, 0.55 percent, 0.80 percent and 1.0 percent copper. After 7 days exposure to the outdoor atmosphere, the alloy containing 0.06 percent copper had noticeably disintegrated. The other alloys showed no sign of disintegration.
EXAMPLE Ill The procedure of Example I was followed in preparing ferrosilicon alloys containing (A): 0.008% Ca, 0.22% Al and 0.16% Cu and (B): 0.008% Ca, 0.22% A1 and 0.22% Cu.
Castings prepared from both alloys were cooled in the temperature range of 850C to 700C at a rate of 4 to 5C per minute. Alloy (A) contained approximately 25% Fe,Si,-, while alloy (B) was essentially free of Fe Si It has also been found that with ferrosilicon alloys which contain copper, but in which the Fe si phase has not transformed, e.g., rapidly quenched alloys containing 0.16 percent copper, no significant disintegration tendency is observed although the material is easily abraded.
In a further embodiment of the present invention, the copper addition is made to the ferrosilicon alloy by mixing a reducible copper compound such as copper oxide, with a silica-carbon charge. The copper compound is reduced concurrently with the silica, and copper is thereby directly'incorporated in the ferrosilicon alloy product.
The percentages given herein and in the claims are all by weight, unless specified to the contrary.
What is claimed is:
1. A method for producing an essentially non disintegrating ferrosilicon alloy which comprises preparing a molten ferrosilicon alloy containing from about 38 to percent silicon and minor amounts of calcium and aluminum; admixing a copperrich material with the molten ferrosilicon to provide in the ferrosilicon alloy a copper content of from about 0.10 to 0.50 percent; casting and solidifying the thus treated alloy; and cooling the solidified alloy at a rate such that the amount of zeta phase, Fe Si in the alloy is less than about 10 percent.
2. A methodin accordance with claim 1 wherein between about 0.15 and 0.30 percent copper is provided in the ferrosilicon alloy.
3. A method in accordance with claim 1 wherein, for a given copper content, the solidified copper-containing ferrosilicon is cooled in the range of 850to 750C. at a rate which is in the area to the left of the curve shown in the graph of the drawing corresponding to the Calcium Equivalent content of the alloy

Claims (3)

  1. 2. A method in accordance with claim 1 wherein between about 0.15 and 0.30 percent copper is provided in the ferrosilicon alloy.
  2. 3. A method in accordance with claim 1 wherein, for a given copper content, the solidified copper-containing ferrosilicon is cooled in the range of 850* to 750* C. at a rate which is in the area to the left of the curve shown in the graph of the drawing corresponding to the Calcium Equivalent content of the alloy where the Calcium Equivalent % Ca + % Al/5.
  3. 4. A method in accordance with claim 1 wherein the copper-rich material is a copper alloy containing at least about 10 percent copper.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4045536A (en) * 1975-07-08 1977-08-30 Ppg Industries, Inc. Method of casting bismuth, silicon and silicon alloys
US20100116600A1 (en) * 2008-11-07 2010-05-13 Knor-Bremse Systeme Fuer Nutzfahrzeuge Gmbh Fixedly connected pad retaining spring for a brake pad
WO2018104961A1 (en) * 2016-12-06 2018-06-14 Pankaj Jain Postproduction treatment to prevent disintegration of ferro silicon

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2906653A (en) * 1955-02-01 1959-09-29 Renault Die-casting of iron in chill-moulds
US3323899A (en) * 1964-03-10 1967-06-06 Union Carbide Corp Casting process for ferroalloys
US3350197A (en) * 1963-06-25 1967-10-31 South African Iron & Steel Ferrosilicon alloys

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2906653A (en) * 1955-02-01 1959-09-29 Renault Die-casting of iron in chill-moulds
US3350197A (en) * 1963-06-25 1967-10-31 South African Iron & Steel Ferrosilicon alloys
US3323899A (en) * 1964-03-10 1967-06-06 Union Carbide Corp Casting process for ferroalloys

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4045536A (en) * 1975-07-08 1977-08-30 Ppg Industries, Inc. Method of casting bismuth, silicon and silicon alloys
US20100116600A1 (en) * 2008-11-07 2010-05-13 Knor-Bremse Systeme Fuer Nutzfahrzeuge Gmbh Fixedly connected pad retaining spring for a brake pad
WO2018104961A1 (en) * 2016-12-06 2018-06-14 Pankaj Jain Postproduction treatment to prevent disintegration of ferro silicon

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