Classifications

• • 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
  • C21C1/02—Dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics

Definitions

• ABSTRACT A composition of matter useful for treating a ferrous melt to reduce sulphur content thereof comprising a compressed porous refractory body of an alkaline earth metal oxide containing a ceramic binder, said body impregnated with magnesium, the particle size of the alkaline earth metal oxide beng less than 4 mesh, said refractory body containing at least about 2 parts by weight of alkaline earth metal oxide for each part of binder and said body being impregnated with at least 35 percent by weight of magnesium, based on the total weight of the impregnated composition
• This composition of matter is produced by admixing -4 mesh particles of alkaline earth metal carbonate with a binder, forming pellets of this mixture and firing the pellets to volatilize the carbon dioxide formed. The fired pellets are then immersed into molten magnesium to impregnate the pellets with magnesium metal.
• porous coke carbon, graphite, sponge iron and ceramic bodies such as quicklime, lump limestone or dolomite and the like.
• porous compositions of the instant invention possess advantages which are not present in the prior art porous bodies.
• a new composition of matter comprising a porous refractory body of an alkaline earth metal oxide containing a ceramic binder, said body impregnated with magnesium, the particle size of the alkaline earth metal oxide being less than 4 mesh, said refractory body containing at least about 2 parts by weight of alkaline earth oxide for each part of binder, and said body impregnated with at least 35 percent by weight of magnesium based on the total weight of the impregnated body.
• Such a product is useful for desulfurizing ferrous melts.
• Products produced by the instant invention generally contain from about 30 percent to about 50 percent alkaline earth metal oxide, from about 1 percent to percent binder and from about 35 percent to about 70 percent magnesium impregnated into the pores of the product, these percentages are based on the total weight of the impregnated body.
• the porous refractory body contemplated in the instant invention is produced by admixing a particulate alkaline earth metal carbonate and a ceramic binder, pelletizing the mixture, firing the pellets to convert the metal carbonate to metal oxide and to volatilize the carbon dioxide formed and then immersing the fired pellet in molten magnesium to impregnate the pores of the refractory body with magnesium.
• the amount of alkaline earth metal carbonate employed is from about 75 percent to about 99 percent while the amount of binder employed is from about 1 percent to about percent, all of the percentages are based on the weight of the mixture.
• the porous compositions of the instant invention which are infiltrated with magnesium are superior to the porous bodies of the prior art.
• the instant porous body not only may take up and retain magnesium in amounts greater than about 35 percent of its total weight, but in addition, contains alkaline earth metal oxides which are useful because of their fluxing properties.
• the porous bodies may be made with inexpensive raw material in an economical manner.
• alkaline earth metal carbonates such as limestone, dolomite and similar raw materials may be used.
• One very inexpensive raw material which may be used successfully is oolitic sands which are found in nature in large quantities. Oolitic sands in general contain from percent to percent calcium carbonate with the remainder usually being alumina and silica. It is necessary to use a particulate alkaline earth metal carbonate, not a massive body. If the source of thealkaline earth metal carbonate is in a massive form, it must be crushed into a particulate form before using.
• the alkaline earth metal carbonate raw material is particulate material (or as a massive body which is pulverized) which has an average size range below 4 mesh.
• Such particulate material is thoroughly mixed with a ceramic binder in amount from about 1 percent to about 25 percent by weight.
• a ceramic binder in amount from about 1 percent to about 25 percent by weight.
• Most any well-known ceramic binder may be used including clays, e.g., bentonite, water glass, Portland cement and the like. These binders may be used singly or in combination with one another.
• the sands themselves may contain sufficient amounts of clay which will act as the binder. In such cases it may not be necessary to add the binder as a separate ingredient. In any event however, the presence of the binder is necessary to form a cohesive compressed product.
• the alkaline earth metal carbonate and the binder are then mixed with sufficient water (about 2 percent to 6 percent) to form a moldable clay-like texture.
• This moist mixture is then pressed into pellets or briquettes at pressures from about 1,500 psi to about 30,000 psi.
• the pressed bodies are then dried preferably at to 250 C. Periods of 2 to 24 hours have been found to be sufficient to remove the moisture.
• the dried pressed bodies are then calcined at a temperatur from about 875 C to about l,450 C for l to 10 hours.
• the use of temperatures which lie somewhat below or above this specified temperature range is also contemplated in the instant invention.
• the temperature range specified above merely is the preferred temperature which may be employed.
• Two different types of products are obtained when low orhigh temperature ranges are employed. Using a lower temperature .range of about 875 C to about l,lO C produces a product which decomposes relatively rapidly during the desulfurization treatment. The magnesium is released rapidly, thus increasing the rate of desulfurization.
• the low temperature product When the low temperature product is prepared, it is necessary to plunge the product into molten magnesium while still hot, i.e., about 750 to 850 C. Periods of from about 2 to about 15 minutes have been found to be adequate to complete the infiltration.
• the low temperature product should not be cooled below 700 C before introduced into the molten metal.
• the magnesium infiltrated refractory body when removed from the molten magnesium must be protected from an oxidizing atmosphere during cooling.
• One particularly satisfactory method is to plunge the hot refractory body in oil during cooling.
• the cooled refractory body also should be protected from the atmosphere and moisture during storage and shipping.
• the ceramic porous bodies prepared in the instant invention may be impregnated with either substantially pure magnesium or magnesium alloys. Alloys particularly desirable to use are magnesium alloys containing calcium, sodium, lithium and mixtures of these metals.
• the term magnesium hereinafter referred to is meant to include magnesium metal and alloys of magnesium metal.
• the mixture may be subjected to extrusion and then cut into pellets.
• the alkaline earth metal carbonate of 4 mesh in size is mixed preferably with I from about percent to about 25 percent clay and to this mixture is added from about 2 percent to about 6 percent water. The mixture is then extruded through a die.
• the extruded material is then cut into pellets and fired in the manner described previously.
• composition which combines the features of having alkaline earth metal oxide present for fluxing properties combined with the presence of magnesium which is useful for desulfurizing molten iron metal;
• the impregnated pellets produced may be structurally strong and capable of withstanding high temperalures. These pellets are those fired at high temperatures;
• the impregnated pellets produced may be very active when introduced into molten iron, thus capable of desulfurizing rapidly the molten iron. These pellets are those fired at the lower temperatures;
• the magnesium infiltrated pellets made by the instant invention are uniform in composition and when they are used to desulfurize molten iron reproducible results are obtained.
• EXAMPLE 1 In this example, a calcium carbonate sand briquette was prepared. The briquette contained 5.0 percent by weight of bentonite clay.
• the briquette was removed from the kiln and while still hot was immersed in a bath of molten magnesium at 800 C for about 1 minute. The briquette was quickly drawn below the surface of the molten magnesium and the level of magnesium dropped sharply indicating infiltration of the briquette. After the briquette was removed from the molten magnesium, it was immediately quenched in a bath of oil to prevent oxidation. The cooled impregnated briquette was then placed in a sealed container for storage. Upon analysis of a sample of the briquette, it was found that 45.0 gms. of magnesium had been infiltrated. This amount is equal to 47 percent magnesium by weight of the infiltrated briquette.
• a treating ladle was preheated to 1,480 C and the hot metal was tapped into the ladle.
• a plunging bell assembly was preheated and 495 gms. of the magnesium infiltrated pellets described above were placed in the bell.
• a steel plate was placed under the pellets and was secured to the walls of the bell with steel wires.
• the plunging temperature of the molten iron was allowed to drop to 1,400 C and the bell was plunged at high speed into the iron. After 2% minutes, the plunging reaction was over and the bell was raised.
• Spectrographic buttons were cast and analyzed for sulfur. The sulfur content was found to be .10 percent. The retained magnesium in the iron was 0.020 percent.
• the desulfurization efficicncy was 81 percent while the efficicncy of magnesium utilization was 22 percent.
• the time of immersion of the porous refractory body in the molten iron preferably should be from 1 to minutes to desulfurize the molten iron.
• EXAMPLE 2 In this example another calcium carbonate sand briquette was prepared. The briquette contained 2.35 percent by weight of bentonite clay.
• the briquette was impregnated with magnesium metal in the same manner as that described in Example 1.
• the impregnated briquette was weighed and it was found that 45 gms of magnesium had been impregnated. This amount is equal to 53 percent magnesium by weight of the infiltrated briquette.
• Example 3 The procedure of Example 2 was followed except that a pressure of 7,500 psi was used to compress the sand mixture instead of 1,500 psi.
• a finely divided cellulosic mate rial such as sawdust, corn cob grits, corn stalks, oat hulls and the like which have been ground to mesh.
• this cellulosic material produces a product which is more porous than the previous product and therefore the product is able to absorb more molten magnesium.
• the alkaline earth metal carbonate should be present in the mixture in amount from 55 percent to percent, the binder present in amount from 1 percent to 15 percent and the cellulosic material in amount from 10 percent to 30 percent.
• the following example illustrates the preparation of calcium oxide pellets which are prepared by admixing calcium carbonate, a binder and a cellulosic material and calcining the mixture to form the product.
• EXAMPLE 4 This example illustrates the preparation of a calcium carbonate sand briquette which contains 2.4 percent by weight of bentonite clay and ll percent by weight of sawdust.
• Example 2 788 gms of calcium carbonate sand as used in Example 2 was hand mixed with 38 gms of 325 mesh bentonite clay and 110 gms of 100 mesh sawdust. The procedure of Example 1 was followed to produce the briquette.
• EXAMPLE 5 This example illustrates an extrusion process for the production of magnesium infiltratable pellets comprising percent calcium carbonate sand, 10 percent Tennessee ball clay and 5 percent bentonite clay.
• EXAMPLE 6 This example illustrates the use of water glass (Na SiO 2H O) as a ceramic binder instead of bentonite clay as given in Example 1.
• Example 1 The procedure of Example 1 was followed using 1 percent water glass instead of 5 percent bentonite clay as a binder. gms of oolitic sand were mixed with 1 gm of water glass. The mixture was formed into a briquette and the briquette was calcined at l,l00 C. The fired briquette weighed 66.9 gms after calcination. The briquette was then immersed in molten magnesium metal and the briquette weighed 133.4 gms after infiltration. After infiltration, it was found that 49.9 percent magnesium had been infiltrated into the briquette.
• EXAMPLES 7 8 These examples illustrate the production of calcium carbonate sand briquettes containing 5 percent benton- 2. Composition according to claim 1 in which there are from about 2 to about 50 parts by weight of the alkaline earth metal oxide for each part of binder.
• composition according to claim 1 in which the alite clay infiltrated with alloys of magnesium. 5
• Example 1 The procedure of Example 1 was followed except kalme earth Petal i f 19 that two alloys of magnesium in the molten state were Composltlo according 9 F w whlch the P used to infiltrate two separate briquettes instead of submus refractory qy PQ impregnated stantiaily pure magnesium as in Example 1.
• the first an alloy of gnc alloy was a M g-Ca alloy containing 5 percent calcium to 5- A porous compressed refractory body composition and the remainer magnesium; the second was a comprising a porous structure of an alkaline earth M (j ,i allgys containing 5 percent l i 2 metal oxide and a ceramic binder, said binder selected cent lithium and the remainder magnesium.
• a process for producing a porous, compressed retrated briquettes are useful for 'desulfurizing molten fractory body comprising a porous structure of an alkametal in an efficient manner without forming a violent line earth metal oxide and a ceramic binder, said binder reaction.
• a porous compressed refractory body composi n cent to about 99 percent, said ceramic binder being comprising a porous structure of an alkaline earth present in amount from about 1 percent to about 25 metal oxide and a ceramic binder, said binder selected percent, all of the percentages expressed on a weight fmm the g p consisting 0f clay, Water g Cement basis, forming pellets of said mixture, drying and firing and mixtures thereof, Said tur ntaining magnesaid pellets at a temperature sufficient to convert the sium absorbed in interstices of said porous structure, metal carbonate to metal oxide and to volatilize the said refractory body composition having at least about carbon dioxide formed, thus forming a porous, com- 2 parts by weight of alkaline earth metal oxide present pressed structure of a ceramic body, and impregnating in said composition for each part of binder, said alkathe pores of said body with magnesium.
• line earth metal oxide having
• fractory body comprising a porous structure of an alkaline earth metal oxide and a ceramic binder, said binder selected from the group consisting of clay, water glass, cement and mixtures thereof, said structure containing magnesium absorbed in the interstices of said porous structure, said process which comprises admixing a particulate alkaline earth metal carbonate and a ceramic binder, said alkaline earth metal carbonate being present in amount from about 75 percent to about 99 percent, said ceramic binder being present in amount from about 1 percent to about 25 percent, all of the percentages expressed on a weight basis, adding to said mixture sufficient water to form a moldable mixture, forming pellets from said mixture, drying and firing said pellets at a temperature from about 875 C to about 1,450 C to convert the metal carbonate to metal oxide and to volatilize the carbon dioxide formed, thus forming a porous, compressed and open structure of a ceramic body, immersing said body with magnesium and removing said impregnated body from said molten metal.
• said binder selected from the group
• a process for producing a porous, refractory body comprising a porous structure of an alkaline earth metal oxide and a ceramic binder, said binder selected from the group consisting of clay, water glass, cement and mixtures thereof, said structure containing magnesium absorbed in the interstices of said porous structure, said process which comprises admixing a particulate alkaline earth metal carbonate, a ceramic binder and a cellulosic material, the amount of said alkaline earth metal carbonate being present in amount from about 55 percent to about 70 percent, said cellulosic material being present in amount from 10 percent to 30 percent, all of the percentages expressed on a weight basis, adding to said mixture from about 2 percent to about 6 percent water to form a moldable mixture, forming pellets from said mixture, drying and firing said pellets at a temperature from about 875 C to about l,450 C to volatilize the carbon dioxide formed and to burn off the cellulosic material, thus forming pellets of a porous ceramic body having an open structure
• the cellulosic material is selected from the group consisting of sawdust, corn cob grits, corn stalks and oat hulls, and mixtures thereof.
• a process for treating molten iron which comprises immersing a porous structure comprising a refractory body composition impregnated with magnesium into said molten iron to reduce the sulfur content thereof, the porous refractory body composition comprising an alkaline earth metal oxide and a ceramic binder, said binder selected from the group consisting of clay, water glass, cement and mixtures thereof, said refractory binder having from about 2 to about 50 parts by weight of alkaline earth metal oxide for each part of binder, the alkaline earth metal oxide present in said composition having an average particle size below 4 mesh, and said composition being impregnated into the pores of said structure with at least about 35 percent by weight of magnesium.
• a process for treating molten iron which comprises immersing a porous structure comprising a refractory body impregnated with magnesium into said molten iron to reduce the sulfur content thereof, said porous refractory body comprising from about 30 percent to about 50 percent alkaline earth metal oxide, from about 1 percent to about 15 percent of a ceramic binder, said binder selected from the group consisting of clay, water glass, cement and mixtures thereof, and
• said body impregnated into the pores of said structure with from about 35 percent to about percent magnesium, all of the percentages expressed on a weight ba sis.
• a process for desulfurizing molten iron which comprises immersing a porous structure comprising a refractory body impregnated with magnesium into said molten iron for a period of about 1 to about 10 minutes and removing said body from said molten iron after said period, said refractory body comprising from about 30 percent to about 50 percent alkaline earth metal oxide, from about 1 percent to about 15 percent of a ceramic binder, said binder selected from the group consisting of clay, water glass, cement and mixtures thereof, and said body impregnated into the pores of said structure with from about 35 percent to about 70 percent magnesium, all of the percentages expressed on a weight basis.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Ceramic Engineering (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Compositions Of Oxide Ceramics (AREA)

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Cited By (10)

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• 1972
  • 1972-07-13 US US00271364A patent/US3801303A/en not_active Expired - Lifetime
• 1973
  • 1973-07-10 FR FR7325298A patent/FR2192988A1/fr not_active Withdrawn
  • 1973-07-11 JP JP48078851A patent/JPS4959111A/ja active Pending

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