CA1100762A - Chloride salt-silicon alloy slag composites for cast iron melts - Google Patents
Chloride salt-silicon alloy slag composites for cast iron meltsInfo
- Publication number
- CA1100762A CA1100762A CA293,083A CA293083A CA1100762A CA 1100762 A CA1100762 A CA 1100762A CA 293083 A CA293083 A CA 293083A CA 1100762 A CA1100762 A CA 1100762A
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- Prior art keywords
- silicon
- chloride salt
- magnesium
- chloride
- slag
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/08—Manufacture of cast-iron
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- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A slag composite formed of chloride salts and silicon or a silicon alloy applied to the surface of magnesium-inoculated cast iron melts retards magnesium fade from the melt.
A slag composite formed of chloride salts and silicon or a silicon alloy applied to the surface of magnesium-inoculated cast iron melts retards magnesium fade from the melt.
Description
110(J'7~i2 C~ILORIDE SALT-SILICON CONTAINING
SLAG COMPOSITES FOR CAST IRON MELTS
The present invention relates to slag compositions which prevent or retard the loss of magnesium from cast iron melts. The slags are essentially composites of chloride salts and silicon or ferrosilicon alloys, and are applied in powder or aggregate form to the surface of magnesium-inoculated cast iron melts.
"Ductile iron" is cast iron in which the carbon is present as graphite nodules dispersed throughout a soft iron matrix, and is frequently referred to as "nodular" or ~ -"spheroidal graphite iron". The tensile strength of such type of iron is considera~ly higher than that of "grey cast iron" in which the graphite is present in the form of flakes which disrupt the continuity of the iron matrix.
The nodularization or spherodi~ation of the graphite may be attained by incorporating magnesium into a cast iron melt. The mechanism by which magnesium spherodizes the graphite is not clearly understood; however, a small but definite amount of magnesium is essential for the formation of graphite nodules. Several alkali metals, alkaline earths, and rare earths (e.g. rubidium, barium, strontium, cerium, etc), will also spherodize the graphite to varying degrees and one or more of these ~ay be added in place of or in conjunction with magnesium. Magnesium is, however, the most widely used nodularizer in the cast iron industry due principally to its generally lower cost and greater effectiveness.
The degree of sphericity of the graphite nodule (nodularity) as well as the nodule count (particle density per unit volume) is dependent on the amount of magnesium present.
Small amounts of aluminum, calcium , strontium and other rare ~lOU762 earth elements, when present in conjunction with magnesium, are believed to increase the nucleation rate of graphite nodules and are fre~uently added for this purpose. If the graphite nodule count is too low the remaining carbon will precipitate as iron carbide, and if iron carbide is present in appreciable amounts the cast iron becomes hard and brittle, and is referred to as "white cast iron" due to its fracture characteristics.
The precipitation of carbon a~ a carbide rather than in graphite form increases with the cooling or solidification rate of the casting.
The inoculation of cast iron melts with magnesium and other inoculating elements such as cerium, aluminum, and calcium is ùsually accomplished by the addition to the cast iron melt of ferrosilicon alloys containing the above elements.
The role of the ferrosilicon is essentially that of a carrier for the above highly reactive metals, and ferrosilicons used for this purpose are known as nodularizing or inoculant alloys.
Most commercially available inoculant alloys are ferrosilicons containing from 2 to 10~ by weight magnesium, with some containing-as high as 25% by weight magnesium.
Incorporating and retaining magnesium in cast iron melts is a very difficult and troublesome problem in the foundry industry. This is due to magnesium's relatively low boiling point and high vapor pressure at foundry operating temperatures (1350-1500C), resulting in rapid volatilization of magnesium from the melt along with a corresponding decrease in noaularity and nodule count for the cast iron. This phenomenon is known in the foundry industry as "magnesium fade" and "inoculant fa~e".
Good to excellent nodularity resu~ts when a (residual) magnesium level of about 0.03 to 0.05~ by weight is obtained in the cast iron. When the magnesium drops to about 0.01% and lower the degree of nodularity diminishes to unacceptable levels with the )7~z graphite ultimately reverting to a flake form. On the other han~, if the residual magnesium level exceeds about 0.15 to 0.20% the graphite nodules become spiky and there is a corresponding drop in tensile strength of the cast iron from its maximum possible value.
To overcome the fade problem the usual foundry practice is to inoculate the cast iron melt with an excess of magnesium and to cast the melt as soon as possible after inoculation. The maximum holding time permitted will vary depending on the particular foundry practice (i.e. iron chemistry, furnace temperature and size, inoculant alloy composition, casting method, etc.), but it is generally from 2 to 3 minutes and r2rely exceeds 10 minutes. For example, one published report shows that half of the magnesium is lost within 5 to 6 minutes after inoculation, and that after 15 minutes the residual magnesium level drops to 0.015~ and lower (c.f. M. Robinson, AFS Trans., 1976, vol. 84, page 585). To obtain optimum nodularization some foundries inoculate directly in the mold or the metal stream as it enters the mold (referred to as inmold and instantaneous ladle inoculation) in attempts to virtually eliminate the holding time with correspondingly reduced magnesium fade. The inmold and instantaneous ladle inoculationmethods however introduce other problems, in particular, the tendency for incomplete dissolution of the inoculant alloy due to insufficient reaction time and the lack of uniformity in the distribution of magnesium throughout the casting.
The benefits to the cast iron foundry industry would be substantial if magnesium fade could be prevented or significantly retarded. One immediately obvious benefit would be the increase in the allowable holding time after inoculation. Thus more or longer interruptions in the casting phase could be accommodated ilO07~Z
without risking the necessity of scrapping the metal due to insufficient nodularity resulting from the loss of magnesium during the holding time.
The primary object of the present invention is to provide a simple and economical means by which magnesium 105s from magnesium-inoc~lated cast iron melts is prevented or significantly retarded. Another object of this invention is to provide novel slag compositions which, when applied to the surface of magnesium-inoculated cast iron melts, prevent or markedly reduce the~ rate of magnesium fade in the cast iron.
I have now developed slags for cast iron melts which significantly retard the rate of loss of magnesium. The application of my slags to inoculated cast iron mel~s enables good nodularity to be maintained for holding times of at least 30 minutes or longer at operating temperatures exceeding 1500C.
The slags of my invention are composites consisting essen-tially of chloride salt and silicon, silicon carbide or ferro-silicon alloy mixtures. The preferred salt constituent of my slags is barium chloride (BaC12), but calcium chloride (CaC12) and mixtures of ~arium chloride and calcium chloride are also effectiv~. Barium chloride is less volatile than calcium chloride and is thus more suitable for higher foundry operating temperatures. I have found that sodium chloride (NaCl), although miscible with either barium chloride or calcium chloride, vaporizes too readily at the operating temperatures involved, resulting in copious fuming of the slag to the detriment of the environment and the slagls protective effectiveness. The preferred silicon alloy constituents of my slags are essentially pure silicon or a ferrosilicon containing at least 50% by weight silicon. Commercial puri~y silicon and the high silicon-content ferrosilicons impart greater fluidity and magnesium fade protection to the slags than the high iron-content iLll~JV762 ferrosilicons; however, slags containing as little as 5% by weight silicon, incorporated into the composite either as pure silicon or as a ferrosilicon alloy, will provide acceptable protection against magnesium fade for the cast iron melts.
While not being confined to any theory, the slags of my invention appear to provide a magnesium absorbing and `!
retaining medium that exert a magnesium "back pressure" to counter the magnesium vapor pressure of the melt, thereby preventing or significantly retarding the rate of magnesium volatilization from the melt. The silicon alloy constituent of my slag may contain magnesium for this purpose although I have found that composites containing no magnesium in the silicon alloy constituent produce slags that provide equally good protection against magnesium fade as those slags that contain some magnesium in the silicon alloy constituent of the slag composite. It appears to be evident that the silicon or ferrosilicon alloy constituent in the slag would rapidly absorb magnesium from the melt, thereby developing a magnesium potential or "back pressure". As there is very little slag relative to the total amount of cast iron melt the amount of magnesium transfer from the melt to the slag is small.
The silicon or ferrosilicon alloy constituent of the slag composite may contain other elements besides magnesium that are known to promote nodularization of the graphite, e.g.
aluminum, strontium, cerium and other rare earths, since small amounts of these elements are frequently contained in commercial ferrosilicon base alloys. I have found that the presence of these other elements in the ferrosilicon or silicon alloy constituent of the slag does not significantly improve the effectiveness of the slag in preventing or retarding the rate of magnesium fade.
If the salt constituent of the slag is essentially .
llr~ iz barium chloride, calcium in the silicon or ferrosilicon constituent (usually present as calcium silicide) of the slag should be absent or kept at least to low levels, as calcium reduces the barium chloride at the melt temperatures involved and thereby tends to destroy the continuity of the slag. I
have found that silicon alloys containing as low as 14% by weight calcium effectively prevented the formation of a lasting, continuous and uniformly dense s]ag layer on the metal surface.
The reduction of barium chloride by calcium metal or calcium silicide is the basis of the process disclosed in Canadian Patent 537,980, wherein calcium silicide, barium chloride and molten metal are brought together for the purpose of reducing the barium chloride so that the released barium is incorporated into the metal and acts as the nodularizing agent.
My slags have no significant nodularizing potential, and the slag's effectiveness in preventing or retarding the rate of magnesium fade from prior-inoculated cast iron melts depends on providing and maintaining a continuous, protective slag lay~r over the metal surface. It is essential, therefore, that elements that tend to reduce barium chloride be absent in the silicon or ferrosilicon alloy constituent of the slag composite, or kept at low ineffectual levels. When calcium chloride is used as the salt constituent in the slag composite, there is no tendency for r~duction of the calcium chloride salt by calcium or calcium silicide, thus calcium silicide or calcium may be incorporated in the silicon or ferrosilicon alloy constituent of the slag composite.
The chloride salt constituent of the slag composite serves two principal functions: it rapidly liquifies on contact with the high temperature melt, uniformly spreading and retaining the silicon or ferrosilicon alloy particles ~which also melt but at a slower rate as the silicon or ferrosilicon alloy particles 1()7~Z
have higher melting temperatuxes than the chloride salt) over the surface of the melt, and it also provides oxidation pro-tection for the silicon and ferrosilicon alloy components which are highly reactive. The higher the chloride salt to silicon alloy ratio for the composite the more fluid the slag but the less its magnesium retaining ability. I have found that slags comprising only 10% weight of chloride salt will provide protection for the cast iron melt; however, for adequate slag fluidity a chloride salt to silicon alloy weight ratio of about 1:1 and up to 2:1 is preferred. I have further found that there is no significant difference in the ability of the slag to prevent or retard magnesium fade from the cast iron melt whether it is prepared as a powder composite by mixing powders of the chloride salts and silicon alloys, or fusing mixtures of chloride salt and silicon alloy constituents to form an aggregate and then grinding the aggregate to a powder state of desired particle size.
The effectiveness of the slag in preventing or retarding the loss of magnesium from the cast iron melt depends on the thickness and continuity of the slag layer. I have found that slag in amounts of about 2~ to 4% by weight of the cast iron melt provide adequate magnesium fade protection.
Thus according to one aspect of my invention there is now ,provided a chloride salt-silicon containing composite comprising:
(a) 5-99% by weight of a salt composition containing at least one of the salts selected from barium chloride and calcium chloride, and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, or a ferrosilicon alloy containing at least 5~
by weight silicon and the remainder essentially iron. --For the purposes of illustration and not limitation a number of examples that are representative of my invention are pre-sented in Table 1. The approximate composition of the cast iron used :llV(~7~Z
for the in~ots given in Table 1 is as follows: 3.4% carbon, 3.1% silicon, 0.60~ manganese, 0~01% sulfur, and 0.02~ phos-phorous with the remainder iron. In preparing the melts, approximately 4 grams of ferrosilicon containing magnesium and other inoculating agents were added to 100 grams of cast iron to give a resultant initial magnesium level of about 0.08%
to 0.12% by weight. Following the inoculation operation the cast iron melts were covered with approximately 4 grams of the chloride salt-silicon alloy powder composite, held at various temperatures for various times and then cast into pyrex tube molds and solidified at approximately 20C per second. The cooling rate is in the chill rate range and would generally result in carbide formation in the absence of effective inoculation or loss of magnesium from the melt.
Following casting the ingots were analyzed spectrographically for residual magnesium content and metallorgraphically examined for nodularity of the graphite. The compositions for the inoculant alloys and slags referred to in Table 1 are provided in Table 2. A total of approximately 200 ingots were cast under various conditions and slags.
lt()()762 Representative Slag Test Data Ingot Inoculant Slag Temp Time Residual Mg Nodularity Alloy (C) (min) (Wt %) (~) A10 I none 1500 0 0.086 90-100 A13 I none 1500 15 0.001 0 YY3 I A 1500 20 0.040 90-100 YY71 II B 1550 20 0.100 80-90 YY72 II B 1500 30 0.053 80-90 YY74 none B 1500 20 0.001 0 YY96 II C 1500 20 0.058 60-70 YY97 II D 1500 20 0.015 50-60 YY98 II E 1500 20 0.055 90-100 YY104 II F 1550 20 0.082 80-90 YY107 II K 1500 20 0.017 50-60 YY108 II G 1500 20 0.038 90-100 YYlll II H 1500 20 0.013 50-60 YY117 I J 15Q0 20 0.018 50-60 YY127 I K lS00 20 0.017 50-60 .~ TABLE 2 Approximate Compositions of Inoculant Alloys and Slags (wt ~) Alloy I: 47% Si, 47% Fe, 6% Mg, 0.3% Ce (or equivalent rare earths) Alloy II: 51% Si, 42% Fe, 5% Mg. 1% Al, 1% Ca, 0.1% Ce (or equivalent rare earths) Alloy III: 78% Si, 19% Fe, 1.5% Al, 1.5% Ca Alloy IV: 10% Si, 90% Fe Alloy V: 67~ Si, 30~ Ca, 3% Fe Slag A: 50% CaC12, 50% Alloy I
Slag B: 50% BaC12, 50% Alloy II
Slag C: 20% BaC12, 80% Alloy I
Slag D:25% BaC12, 25% CaC12, 25% Alloy I, 25% Alloy II
Slag E: 90% BaC12, 10% Alloy II
Slag F: 50% BaC12, 50% Alloy III `
Slag G: 50% BaC12, 50% Si Slag H: 95% BaC12, 5% Si Slag K: 50% BaC12, 50% Alloy IV
Slag J: 50% CaC12, 50% Alloy V
; Slag R: 50% BaC12, 50% SiC
.
_g_ .
()7f~;2 The results of Table 1 show that the chloride salt-silicon alloy slags, whose compositions are given in Table 2, prevent or significantly retard the loss of magnesium from cast iron melts for holding periods of at least 30 minutes and temperatures up to 1550C or higher, and the corresponding ingots show good to excellent nodularity. A nodularity of 50% or higher would be accepta~le for most ductile iron applications.
In a closer examination of the results, it should be noted the ingot A13 which had no slag cover lost virtually all of its magnesium within 15 minutes of inoculation. Ingot YY74 received no prior inoculation with magnesium but was covered with slag, and the absence of nodularity shows that the slag in itself has no effective nodularizing ability.
Attention may be had to the drawings wherein:
Fig. la, lb, and lc are photomicrographs of 100 magnification of three ingots showing ~arying degrees of nodularity. To assist in understanding these photomicrographs the black regions are the graphite nodules or flakes.
Fig. la shows the microstructure of ingot YY3 of TABLE 1 employing the slag composite A of TABLE 2 clearly showing the nodular form of the graphite.
Fig. lb shows the microstructure of ingot YY96 of TABLE 1 employing the slag composite C of TABLE 2 showing clearly nodularization had been effected.
Fig. lc shows the microstructure of ingot A13 of TABLE 1 wherein no slag was employed and showing no nodular form of graphite.
There was little or no carbide phase evident in the microstructures.
~hile this invention has been specifically illustrated and described with respect to certain preferred embodiments thereof; it should ~e understood that other embodiments can 71~;2 be construed from the teachings thereof without departing from the inventive concept defined by the claims.
SLAG COMPOSITES FOR CAST IRON MELTS
The present invention relates to slag compositions which prevent or retard the loss of magnesium from cast iron melts. The slags are essentially composites of chloride salts and silicon or ferrosilicon alloys, and are applied in powder or aggregate form to the surface of magnesium-inoculated cast iron melts.
"Ductile iron" is cast iron in which the carbon is present as graphite nodules dispersed throughout a soft iron matrix, and is frequently referred to as "nodular" or ~ -"spheroidal graphite iron". The tensile strength of such type of iron is considera~ly higher than that of "grey cast iron" in which the graphite is present in the form of flakes which disrupt the continuity of the iron matrix.
The nodularization or spherodi~ation of the graphite may be attained by incorporating magnesium into a cast iron melt. The mechanism by which magnesium spherodizes the graphite is not clearly understood; however, a small but definite amount of magnesium is essential for the formation of graphite nodules. Several alkali metals, alkaline earths, and rare earths (e.g. rubidium, barium, strontium, cerium, etc), will also spherodize the graphite to varying degrees and one or more of these ~ay be added in place of or in conjunction with magnesium. Magnesium is, however, the most widely used nodularizer in the cast iron industry due principally to its generally lower cost and greater effectiveness.
The degree of sphericity of the graphite nodule (nodularity) as well as the nodule count (particle density per unit volume) is dependent on the amount of magnesium present.
Small amounts of aluminum, calcium , strontium and other rare ~lOU762 earth elements, when present in conjunction with magnesium, are believed to increase the nucleation rate of graphite nodules and are fre~uently added for this purpose. If the graphite nodule count is too low the remaining carbon will precipitate as iron carbide, and if iron carbide is present in appreciable amounts the cast iron becomes hard and brittle, and is referred to as "white cast iron" due to its fracture characteristics.
The precipitation of carbon a~ a carbide rather than in graphite form increases with the cooling or solidification rate of the casting.
The inoculation of cast iron melts with magnesium and other inoculating elements such as cerium, aluminum, and calcium is ùsually accomplished by the addition to the cast iron melt of ferrosilicon alloys containing the above elements.
The role of the ferrosilicon is essentially that of a carrier for the above highly reactive metals, and ferrosilicons used for this purpose are known as nodularizing or inoculant alloys.
Most commercially available inoculant alloys are ferrosilicons containing from 2 to 10~ by weight magnesium, with some containing-as high as 25% by weight magnesium.
Incorporating and retaining magnesium in cast iron melts is a very difficult and troublesome problem in the foundry industry. This is due to magnesium's relatively low boiling point and high vapor pressure at foundry operating temperatures (1350-1500C), resulting in rapid volatilization of magnesium from the melt along with a corresponding decrease in noaularity and nodule count for the cast iron. This phenomenon is known in the foundry industry as "magnesium fade" and "inoculant fa~e".
Good to excellent nodularity resu~ts when a (residual) magnesium level of about 0.03 to 0.05~ by weight is obtained in the cast iron. When the magnesium drops to about 0.01% and lower the degree of nodularity diminishes to unacceptable levels with the )7~z graphite ultimately reverting to a flake form. On the other han~, if the residual magnesium level exceeds about 0.15 to 0.20% the graphite nodules become spiky and there is a corresponding drop in tensile strength of the cast iron from its maximum possible value.
To overcome the fade problem the usual foundry practice is to inoculate the cast iron melt with an excess of magnesium and to cast the melt as soon as possible after inoculation. The maximum holding time permitted will vary depending on the particular foundry practice (i.e. iron chemistry, furnace temperature and size, inoculant alloy composition, casting method, etc.), but it is generally from 2 to 3 minutes and r2rely exceeds 10 minutes. For example, one published report shows that half of the magnesium is lost within 5 to 6 minutes after inoculation, and that after 15 minutes the residual magnesium level drops to 0.015~ and lower (c.f. M. Robinson, AFS Trans., 1976, vol. 84, page 585). To obtain optimum nodularization some foundries inoculate directly in the mold or the metal stream as it enters the mold (referred to as inmold and instantaneous ladle inoculation) in attempts to virtually eliminate the holding time with correspondingly reduced magnesium fade. The inmold and instantaneous ladle inoculationmethods however introduce other problems, in particular, the tendency for incomplete dissolution of the inoculant alloy due to insufficient reaction time and the lack of uniformity in the distribution of magnesium throughout the casting.
The benefits to the cast iron foundry industry would be substantial if magnesium fade could be prevented or significantly retarded. One immediately obvious benefit would be the increase in the allowable holding time after inoculation. Thus more or longer interruptions in the casting phase could be accommodated ilO07~Z
without risking the necessity of scrapping the metal due to insufficient nodularity resulting from the loss of magnesium during the holding time.
The primary object of the present invention is to provide a simple and economical means by which magnesium 105s from magnesium-inoc~lated cast iron melts is prevented or significantly retarded. Another object of this invention is to provide novel slag compositions which, when applied to the surface of magnesium-inoculated cast iron melts, prevent or markedly reduce the~ rate of magnesium fade in the cast iron.
I have now developed slags for cast iron melts which significantly retard the rate of loss of magnesium. The application of my slags to inoculated cast iron mel~s enables good nodularity to be maintained for holding times of at least 30 minutes or longer at operating temperatures exceeding 1500C.
The slags of my invention are composites consisting essen-tially of chloride salt and silicon, silicon carbide or ferro-silicon alloy mixtures. The preferred salt constituent of my slags is barium chloride (BaC12), but calcium chloride (CaC12) and mixtures of ~arium chloride and calcium chloride are also effectiv~. Barium chloride is less volatile than calcium chloride and is thus more suitable for higher foundry operating temperatures. I have found that sodium chloride (NaCl), although miscible with either barium chloride or calcium chloride, vaporizes too readily at the operating temperatures involved, resulting in copious fuming of the slag to the detriment of the environment and the slagls protective effectiveness. The preferred silicon alloy constituents of my slags are essentially pure silicon or a ferrosilicon containing at least 50% by weight silicon. Commercial puri~y silicon and the high silicon-content ferrosilicons impart greater fluidity and magnesium fade protection to the slags than the high iron-content iLll~JV762 ferrosilicons; however, slags containing as little as 5% by weight silicon, incorporated into the composite either as pure silicon or as a ferrosilicon alloy, will provide acceptable protection against magnesium fade for the cast iron melts.
While not being confined to any theory, the slags of my invention appear to provide a magnesium absorbing and `!
retaining medium that exert a magnesium "back pressure" to counter the magnesium vapor pressure of the melt, thereby preventing or significantly retarding the rate of magnesium volatilization from the melt. The silicon alloy constituent of my slag may contain magnesium for this purpose although I have found that composites containing no magnesium in the silicon alloy constituent produce slags that provide equally good protection against magnesium fade as those slags that contain some magnesium in the silicon alloy constituent of the slag composite. It appears to be evident that the silicon or ferrosilicon alloy constituent in the slag would rapidly absorb magnesium from the melt, thereby developing a magnesium potential or "back pressure". As there is very little slag relative to the total amount of cast iron melt the amount of magnesium transfer from the melt to the slag is small.
The silicon or ferrosilicon alloy constituent of the slag composite may contain other elements besides magnesium that are known to promote nodularization of the graphite, e.g.
aluminum, strontium, cerium and other rare earths, since small amounts of these elements are frequently contained in commercial ferrosilicon base alloys. I have found that the presence of these other elements in the ferrosilicon or silicon alloy constituent of the slag does not significantly improve the effectiveness of the slag in preventing or retarding the rate of magnesium fade.
If the salt constituent of the slag is essentially .
llr~ iz barium chloride, calcium in the silicon or ferrosilicon constituent (usually present as calcium silicide) of the slag should be absent or kept at least to low levels, as calcium reduces the barium chloride at the melt temperatures involved and thereby tends to destroy the continuity of the slag. I
have found that silicon alloys containing as low as 14% by weight calcium effectively prevented the formation of a lasting, continuous and uniformly dense s]ag layer on the metal surface.
The reduction of barium chloride by calcium metal or calcium silicide is the basis of the process disclosed in Canadian Patent 537,980, wherein calcium silicide, barium chloride and molten metal are brought together for the purpose of reducing the barium chloride so that the released barium is incorporated into the metal and acts as the nodularizing agent.
My slags have no significant nodularizing potential, and the slag's effectiveness in preventing or retarding the rate of magnesium fade from prior-inoculated cast iron melts depends on providing and maintaining a continuous, protective slag lay~r over the metal surface. It is essential, therefore, that elements that tend to reduce barium chloride be absent in the silicon or ferrosilicon alloy constituent of the slag composite, or kept at low ineffectual levels. When calcium chloride is used as the salt constituent in the slag composite, there is no tendency for r~duction of the calcium chloride salt by calcium or calcium silicide, thus calcium silicide or calcium may be incorporated in the silicon or ferrosilicon alloy constituent of the slag composite.
The chloride salt constituent of the slag composite serves two principal functions: it rapidly liquifies on contact with the high temperature melt, uniformly spreading and retaining the silicon or ferrosilicon alloy particles ~which also melt but at a slower rate as the silicon or ferrosilicon alloy particles 1()7~Z
have higher melting temperatuxes than the chloride salt) over the surface of the melt, and it also provides oxidation pro-tection for the silicon and ferrosilicon alloy components which are highly reactive. The higher the chloride salt to silicon alloy ratio for the composite the more fluid the slag but the less its magnesium retaining ability. I have found that slags comprising only 10% weight of chloride salt will provide protection for the cast iron melt; however, for adequate slag fluidity a chloride salt to silicon alloy weight ratio of about 1:1 and up to 2:1 is preferred. I have further found that there is no significant difference in the ability of the slag to prevent or retard magnesium fade from the cast iron melt whether it is prepared as a powder composite by mixing powders of the chloride salts and silicon alloys, or fusing mixtures of chloride salt and silicon alloy constituents to form an aggregate and then grinding the aggregate to a powder state of desired particle size.
The effectiveness of the slag in preventing or retarding the loss of magnesium from the cast iron melt depends on the thickness and continuity of the slag layer. I have found that slag in amounts of about 2~ to 4% by weight of the cast iron melt provide adequate magnesium fade protection.
Thus according to one aspect of my invention there is now ,provided a chloride salt-silicon containing composite comprising:
(a) 5-99% by weight of a salt composition containing at least one of the salts selected from barium chloride and calcium chloride, and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, or a ferrosilicon alloy containing at least 5~
by weight silicon and the remainder essentially iron. --For the purposes of illustration and not limitation a number of examples that are representative of my invention are pre-sented in Table 1. The approximate composition of the cast iron used :llV(~7~Z
for the in~ots given in Table 1 is as follows: 3.4% carbon, 3.1% silicon, 0.60~ manganese, 0~01% sulfur, and 0.02~ phos-phorous with the remainder iron. In preparing the melts, approximately 4 grams of ferrosilicon containing magnesium and other inoculating agents were added to 100 grams of cast iron to give a resultant initial magnesium level of about 0.08%
to 0.12% by weight. Following the inoculation operation the cast iron melts were covered with approximately 4 grams of the chloride salt-silicon alloy powder composite, held at various temperatures for various times and then cast into pyrex tube molds and solidified at approximately 20C per second. The cooling rate is in the chill rate range and would generally result in carbide formation in the absence of effective inoculation or loss of magnesium from the melt.
Following casting the ingots were analyzed spectrographically for residual magnesium content and metallorgraphically examined for nodularity of the graphite. The compositions for the inoculant alloys and slags referred to in Table 1 are provided in Table 2. A total of approximately 200 ingots were cast under various conditions and slags.
lt()()762 Representative Slag Test Data Ingot Inoculant Slag Temp Time Residual Mg Nodularity Alloy (C) (min) (Wt %) (~) A10 I none 1500 0 0.086 90-100 A13 I none 1500 15 0.001 0 YY3 I A 1500 20 0.040 90-100 YY71 II B 1550 20 0.100 80-90 YY72 II B 1500 30 0.053 80-90 YY74 none B 1500 20 0.001 0 YY96 II C 1500 20 0.058 60-70 YY97 II D 1500 20 0.015 50-60 YY98 II E 1500 20 0.055 90-100 YY104 II F 1550 20 0.082 80-90 YY107 II K 1500 20 0.017 50-60 YY108 II G 1500 20 0.038 90-100 YYlll II H 1500 20 0.013 50-60 YY117 I J 15Q0 20 0.018 50-60 YY127 I K lS00 20 0.017 50-60 .~ TABLE 2 Approximate Compositions of Inoculant Alloys and Slags (wt ~) Alloy I: 47% Si, 47% Fe, 6% Mg, 0.3% Ce (or equivalent rare earths) Alloy II: 51% Si, 42% Fe, 5% Mg. 1% Al, 1% Ca, 0.1% Ce (or equivalent rare earths) Alloy III: 78% Si, 19% Fe, 1.5% Al, 1.5% Ca Alloy IV: 10% Si, 90% Fe Alloy V: 67~ Si, 30~ Ca, 3% Fe Slag A: 50% CaC12, 50% Alloy I
Slag B: 50% BaC12, 50% Alloy II
Slag C: 20% BaC12, 80% Alloy I
Slag D:25% BaC12, 25% CaC12, 25% Alloy I, 25% Alloy II
Slag E: 90% BaC12, 10% Alloy II
Slag F: 50% BaC12, 50% Alloy III `
Slag G: 50% BaC12, 50% Si Slag H: 95% BaC12, 5% Si Slag K: 50% BaC12, 50% Alloy IV
Slag J: 50% CaC12, 50% Alloy V
; Slag R: 50% BaC12, 50% SiC
.
_g_ .
()7f~;2 The results of Table 1 show that the chloride salt-silicon alloy slags, whose compositions are given in Table 2, prevent or significantly retard the loss of magnesium from cast iron melts for holding periods of at least 30 minutes and temperatures up to 1550C or higher, and the corresponding ingots show good to excellent nodularity. A nodularity of 50% or higher would be accepta~le for most ductile iron applications.
In a closer examination of the results, it should be noted the ingot A13 which had no slag cover lost virtually all of its magnesium within 15 minutes of inoculation. Ingot YY74 received no prior inoculation with magnesium but was covered with slag, and the absence of nodularity shows that the slag in itself has no effective nodularizing ability.
Attention may be had to the drawings wherein:
Fig. la, lb, and lc are photomicrographs of 100 magnification of three ingots showing ~arying degrees of nodularity. To assist in understanding these photomicrographs the black regions are the graphite nodules or flakes.
Fig. la shows the microstructure of ingot YY3 of TABLE 1 employing the slag composite A of TABLE 2 clearly showing the nodular form of the graphite.
Fig. lb shows the microstructure of ingot YY96 of TABLE 1 employing the slag composite C of TABLE 2 showing clearly nodularization had been effected.
Fig. lc shows the microstructure of ingot A13 of TABLE 1 wherein no slag was employed and showing no nodular form of graphite.
There was little or no carbide phase evident in the microstructures.
~hile this invention has been specifically illustrated and described with respect to certain preferred embodiments thereof; it should ~e understood that other embodiments can 71~;2 be construed from the teachings thereof without departing from the inventive concept defined by the claims.
Claims (10)
1. A chloride salt-silicon containing composite comprised of:
(a) 5-99% by weight of a salt composition containing at least one of the salts selected from barium chloride and calcium chloride, and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, and a ferrosilicon alloy containing at least 5%
silicon and the remainder essentially iron.
(a) 5-99% by weight of a salt composition containing at least one of the salts selected from barium chloride and calcium chloride, and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, and a ferrosilicon alloy containing at least 5%
silicon and the remainder essentially iron.
2. The chloride salt-silicon containing composite of Claim 1 wherein the said chloride salt is essentially barium chloride.
3. The chloride salt-silicon containing composite of Claim 1 wherein the said chloride salt is essentially calcium chloride.
4. The chloride salt-silicon containing composite of Claim 1 wherein the said silicon containing material is essentially pure silicon.
5. The chloride salt-silicon containing composite of Claim 1 wherein the said silicon containing material is essentially pure silicon carbide.
6. The chloride salt-silicon containing composite of Claim 1 wherein the said silicon containing material is essentially a ferrosilicon alloy containing up to 25% by weight magnesium.
7. A chloride salt-silicon containing composite comprised of:
(a) 5-99% by weiqht of at least calcium chloride or barium chloride and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, and a silicon alloy containing at least 5%
silicon.
(a) 5-99% by weiqht of at least calcium chloride or barium chloride and (b) 1-95% by weight of at least one silicon containing material selected from the group consisting of silicon, silicon carbide, and a silicon alloy containing at least 5%
silicon.
8. The chloride salt-silicon containing composite of Claim 1 or 7 in powder form and prepared by mixing requisite amounts of said chloride salt powder and a powder of said silicon material.
9. The chloride salt-silicon containing composite of Claims 1 or 7 prepared by fusing a mixture of said chloride salt and said silicon material at temperatures above 750°C to form an aggregate and grinding said aggregate to a powder state of desired particle size.
10. The chloride salt-silicon containing composite of Claims 1 or 7 applied to the surface of magnesium inoculated cast iron melts for the purpose of forming protective slags to prevent or retard the loss of magnesium from the melt.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA293,083A CA1100762A (en) | 1977-12-14 | 1977-12-14 | Chloride salt-silicon alloy slag composites for cast iron melts |
| IN692/DEL/78A IN148879B (en) | 1977-12-14 | 1978-09-21 | |
| US06/021,875 US4224070A (en) | 1977-12-14 | 1979-03-19 | Chloride salt-silicon containing slag compositions for cast iron melts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA293,083A CA1100762A (en) | 1977-12-14 | 1977-12-14 | Chloride salt-silicon alloy slag composites for cast iron melts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1100762A true CA1100762A (en) | 1981-05-12 |
Family
ID=4110288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,083A Expired CA1100762A (en) | 1977-12-14 | 1977-12-14 | Chloride salt-silicon alloy slag composites for cast iron melts |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1100762A (en) |
| IN (1) | IN148879B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0805216A1 (en) * | 1996-05-03 | 1997-11-05 | Metal Trading International S.r.l. | Preconditioning of cast iron smelted in an electric furnace to produce safety part castings |
-
1977
- 1977-12-14 CA CA293,083A patent/CA1100762A/en not_active Expired
-
1978
- 1978-09-21 IN IN692/DEL/78A patent/IN148879B/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0805216A1 (en) * | 1996-05-03 | 1997-11-05 | Metal Trading International S.r.l. | Preconditioning of cast iron smelted in an electric furnace to produce safety part castings |
Also Published As
| Publication number | Publication date |
|---|---|
| IN148879B (en) | 1981-07-04 |
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