Classifications

• • 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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
• • 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
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
• • 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
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
  • C04B35/521—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained by impregnation of carbon products with a carbonisable material
• • 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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/52—Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
• • 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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
  • C04B41/81—Coating or impregnation
  • C04B41/89—Coating or impregnation for obtaining at least two superposed coatings having different compositions
• • 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
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/42—Constructional features of converters
  • C21C5/44—Refractory linings
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/30—Self-sustaining carbon mass or layer with impregnant or other layer

Definitions

• This invention relates to a method of manufacturing carbonaceous refractory product having improved corrosion proof property and sporing proof property.
• Cabonaceous refractories are used as bricks for fabricating discharge ports of converters or for metal melting crucibles, because they have higher resistance to wear at elevated temperatures and because they are more difiicult to be wetted by molten metals or molten slags when compared with refractories of the oxide type such as clayish refractories, refractories containing alumina at high percentage or magnesia refractories.
• the porosity of carbonaceous refractories ordinarily amounts to to they are rapidly damaged by slag or molten metals, so that their useful life is relatively short. It has been proposed to decrease the percentage of graphite for the purpose of decreasing porosity, but as this approach decreases the sporing proof characteristic of the products, the products tend to crack during their use, thus shortening their life.
• this object can be attained by providing a method of manufacturing carbonaceous refractories comprising a first step of preparing carbonaceous refractories by a conventional method including mixing, moulding, reducing by firing, a second step of immersing said refractories in molten tar pitch to impregnate the tar pitch into the pores of the refractories, heating said impregnated refractories to carbonize the impregnated tar pitch, and a third step of applying a glaze onto the outer surface of the refractories and then heating the same to fire said glaze.
• the first to third steps are performed in the following manner.
• the first step may be any one of well known methods.
• the starting material essentially comprises a carbonaceous substance such as graphite and silicon carbide, but if desired, suitable quan- 3,682,686 Patented Aug. 8, 1972 tities of oxide refractories such as chamotte, pagodite, silimanite or synthetic mulite; a binder such as clay or pitch, etc.; and a sintering agent such as borax, boric acid, frit, ferrosilicon and the like may be incorporated.
• These raw materials are pulverized to have a suitable particle size and are then mixed together. After incorporating a suitable quantity of water and tar, the mixture is kneaded, shaped, and reduced by firing. Where water is incorporated after kneading the shaped body is dried and then reduced by firing.
• the tired body obtained by the first step is immersed in a bath of hot molten tar pitch to impregnate the tar pitch into the pores of the fired product to fill most of the pores.
• Preheating of the fired product and evacuation of the impregnation chamber enhance the impregnation.
• the impregnated body is taken out of the chamber and is then heated to evaporate off about half of the impregnated tar pitch and to carbonize the remaining half, thus depositing it in the pores as amorphous carbon.
• This decreases the porosity and increases the mechanical strength of the product and hence increases the corrosion proof property as well as the wear resistant property.
• the precipitated carbon remains in the pores, in spite of the decrease in the porosity, sporing proof property would not be affected.
• the carbon deposited in this manner is amorphous and especially inflammable so that this method is effective only when the heat receiving surface of brick is heated in the absence of oxygen as in the case when the refractory prepared in this manner is used in contact with high temperature molten metal. Accordingly, when the refractory is heated from outside by flame or electric heat while the refractory is maintained in contact with oxygen as in a metal melting crucible, the deposited carbon will be lost by oxidation, thus losing the effect of tar impregnation.
• a glaze is applied onto the surface of the refractory "prepared by the second step and the glazed refractory is fired.
• This third step provides an air impermeable layer on the surface of the product so that the carbon deposited by heating the impregnated tar pitch is not oxidized by air during operation at elevated temperatures thus preserving the low porosity and low air permeable properties of the product over a long period of use.
• the glaze applied by the third step greatly improves the wear resistant and corrosion resistant properties of the product on the following ground. More particularly, the carbon deposited in the pores, especially in those near the heat receiving surface of the product, is converted into hard and non-inflammable state by the high temperature heating utilized to fire the glaze and by the heating in the absence of oxygen encountered during the use of the product. Further, it is considered that a portion of the deposited carbon is diffused into the glassy composition of the product to render it more non-inflammable and resistant against corrosion.
• the glaze can be applied in the same manner as the conventional ceramics. It is advantageous to use a glaze of the borosilicate type which does not lose its viscosity at elevated temperatures, for example, a fine powder of 4 with tar pitch, heated to carbonize, applied with glaze and then fired to produce a novel brick product. Following table shows various characteristics of the brick before and after impregnation.
• the firing temperature normally ranges from about 1000 to 1100 C.
• EXAMPLE 1 35% of natural graphite, 40% of silicon carbide, of ferrosilicon and 10% of borosilicate frit (all in weight ratio) were mixed together and 40%, based on the weight of the mixture, of a mixture of coal tar and pitch was incorporated to the first mixture, and the resulted mixture was heated, kneaded, shaped and fired to reduce at a temperature of 1320 C. to obtain a graphite crucible, 52 cm. high, 35.5 cm. in diameter at the top opening, 22 cm. in bottom diameter and 25 cm. in wall thickness.
• the crucible was then put in a vessel, the vessel was evacuated and then molten tar pitch was poured into the evacuated vessel to impregnate the soft pitch into the pores of the crucible.
• the impregnated crucible was taken out of the vessel, and heated at a temperature of 800 C. in a reducing atmosphere to remove the volatile component and to carbonize the impregnated pitch.
• a mixture of a powder of borosilicate frit and water was sprayed onto the surface of the crucible so as to coat and impregnate the crucible with the mixture. Then the crucible was heated at a temperature of 1050 C. to fire the frit to obtain the finished crucible.
• the crucible Before impregnation the crucible had a weight of 34 kg., a volume of 18,400 cm. the total volume of the pores of 4,500 cm.. The quantity of tar pitch impregnated was 5.4 kg., and the quantity of carbon remained after the heat treatment was 2.8 kg. Following table shows various characteristics of the ceramic before and after im- The coefiicient of hot linear expansion was obtained by heating the crucible from normal temperature to 800 C.
• the invention provides novel carbonaceous refractory products having lower porosity, higher bulk specific gravity, bending strength and compression strength than the prior carbonaceous refractory products by the deposition of carbon in the pores of the products. Further, as the deposited carbon is protected against high temperature oxidation by the non-permeable layer of the glaze applied on the surface of the products, it is possible to efiiciently prevent the impregnation of the fiux, slag and molten metal during operation. Moreover, as the mechanical strength is improved and as the layer of graphite, one of the principal compositions, is prevented frome peeling off, the useful life of the products is greatly prolonged.
• a method of manufacturing a pore-filled glazed carbonaceous refractory product which comprises the steps of kneading, shaping and firing a composition essentially consisting of carbonaceous material, and pulverized silicon-containing sintering agents, thus obtaining a fired, shaped, porous carbonaceous refractory body, immersing said fired, shaped, porous carbonaceous refractory body in molten tar pitch so as to substantially impregnate the pores of said body with the molten tar pitch heating the thus impregnated shaped, carbonaceous refractory body to a temperature suificicntly high to carbonize said tar pitch, thereby obtaining said carbonaceous refractory body with amorphous carbon deposited in the pores thereof, applying a layer of pregnation. glaze on the surface of the thus obtained carbonaceous Compres- Poros- Percentage Apparent Bulk Bending sion it of water specific specific strength, strength, percent absorption, gravity gravity kgJcm.
• the crucible not impregnated showed a useful life of 130 hours where as after impregnation, the novel crucible showed a useful life of 244 hours.
• EXAMPLE 2 refractory body having amorphous carbon deposited in the pores thereof, and firing said layer of glaze, thereby forming an air impermeable layer which retains said deposited carbon in the pores thereof.
• composition consists of 30 to 35%, by weight, of natural graphite, 40 to 50%, by weight, of silicon carbide, 10 to 15%, by weight, of ferrosilicon, 5 to 10%, by weight of borosilicate and 40%, based on the total weight of the above described ingredients, of a mixture of coal tar and pitch.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Structural Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Metallurgy (AREA)
• Ceramic Products (AREA)
• Compositions Of Oxide Ceramics (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=13385417

Family Applications (1)

Country Status (4)

Cited By (12)

Families Citing this family (1)

• 1970
  • 1970-10-21 US US82857A patent/US3682686A/en not_active Expired - Lifetime
  • 1970-11-05 GB GB52634/70A patent/GB1284188A/en not_active Expired
  • 1970-11-16 FR FR7040961A patent/FR2101323A5/fr not_active Expired
  • 1970-11-17 DE DE2056567A patent/DE2056567C3/de not_active Expired

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