US3687700A - Method of applying a thermal insulating coating to an ingot wall - Google Patents

Method of applying a thermal insulating coating to an ingot wall Download PDF

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Publication number
US3687700A
US3687700A US886138A US3687700DA US3687700A US 3687700 A US3687700 A US 3687700A US 886138 A US886138 A US 886138A US 3687700D A US3687700D A US 3687700DA US 3687700 A US3687700 A US 3687700A
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Prior art keywords
suspension
weight
coating
screen
binder
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Expired - Lifetime
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US886138A
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English (en)
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Pierre Blancquart
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DOITTAU PRODUITS METAL
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DOITTAU PRODUITS METAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/36—Linings or coatings, e.g. removable, absorbent linings, permanent anti-stick coatings; Linings becoming a non-permanent layer of the moulded article
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/035—Discharge apparatus, e.g. electrostatic spray guns characterised by gasless spraying, e.g. electrostatically assisted airless spraying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
    • B05B7/0807—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point to form intersecting jets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/24—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device
    • B05B7/2489—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device an atomising fluid, e.g. a gas, being supplied to the discharge device

Definitions

  • ll75.l 6 Claims ABSTRACT OF THE DISCLOSURE A method and composition for applying thermally insulating coatings to ingot molds, by spray coating a substantially nonaqueous suspension of refractory material such as silica, alumina, zirconia or magnesia, passing through a screen having a mesh opening of 0.149 mm., a low density heat-insulating material such as pearlite, diatomaceous earth or wood flour, passing through .a screen having a mesh opening of 0.297 mm., a binder for green strength which is a flocculable clay such as bentonite, and a binder for dry strength which is a synthetic resin or sodium silicate or gum arabic, in suspension in an alcohol having 1-3 carbon atoms, white spirit or toluene.
  • the sprayed particles and the sprayed surface are given opposite electrical charges to attract the particles to the surface.
  • a method is known on the other hand, of projecting paints by utilising a spray gun, bringing into operation merely the pressure of the liquid or of the thick suspension, which is projected without employing a gaseous vehicle.
  • This spray-gun projecting known as airless
  • This spray-gun projecting has the advantage that the speed of projection of the liquid is less, and decreases more rapidly, than in the case of a compressed-air spray gun. From this there results a greater precision in the application, and an absence of splashes and mist in the immediate neighbourhood, these being disadvantages which are encountered with the conventional air spray guns.
  • the present invention relates to a method of applying thermally insulating coatings in ingot moulds and similar moulds, characterised by the feature that there is projected, by means of a nozzle, against the wall surface to be coated, a non-aqueous or very slightly aqueous liquid suspension of finely granulated refractory products, organic materials or materials of but slight density and fine granulation, products of agglomeration in a green state and products of agglomeration in a dry state, under a pressure of at least 20 kilogrammes per squgire centimetre, so as to obtain a coating, which is then dri
  • the liquid of the suspension is an electrically insulating liquid, and the particles, or the wall to be coated, or both, are electrically charged in such a way as to ensure an electrical attraction between the particles and the wall.
  • the liquids utilised for transporting the solid materials should contain very little water, or none at all, the coating produced in the ingot mould or other mould not being stoved, strictly speaking, and it must not contain more than 1.50% of water at the time of casting.
  • These liquids are preferably alcohols, such as ethyl, methyl or propyl alcohol, white spirit or toluene. It is preferable to use an isopropyl alcohol on account of its price, and the freedom from noxious vapours.
  • the finely granulated refractory materials are highly refractory materials such as silica, alumina, zirconia, and magnesium oxide.
  • the granulometry of these materials should be such that they pass almost completely through a screen having a mesh opening of 0.149 mm. They may be put into operation in their natural form after crushing and screening.
  • silica it is preferable to use light natural silicas, known as fossil silicas, the versed density of which glue.
  • This slip is purified, to eliminate from its impurities which make it less refractory, and in particularly oxides of iron are eliminated by supplementary washing with acid, and decantation.
  • the slip is presented in the form of a foam, which is either projected into a high-temperature flame, or poured into moulds, to be then cooked at a high temperature, and crushed.
  • the percentage of refractory materials brought into operation is from to 96% of the total weight of the various components, not including the agglomerants and the carrier liquid.
  • the aim of the organic or low-density materials is to increase the porosity of the coatings, and to improve its thermal insulation at high temperatures.
  • They may consist of perlite, diatomaceous earths, or wood flour. Their granulometry should be such that they pass almost completely through a screen having a mesh aperture of 0.297 mm., and preferably through a screen with a mesh aperture of 0.210 mm.
  • the very porous materials are subjected to an impermeabilising treatment by projecting them into a bath consisting of a saturated dilution of a wax, particularly paraflin wax, in a solvent, particularly kerosene.
  • the percentage of these organic or low-density materials is from 4 to 15% of the total weight of the various components, not including the agglomerants and the carrier liquid.
  • the products of green agglomeration are designed to ensure the adhesion of the coating to the support, and the adhesion of the particles to one another before drying. It is mainly days that can be flocculated, such as bentonite. a v
  • the products of dry agglomeration are synthetic resins
  • the percentage of agglomerants brought into play is variable, according to the products and the operating conditions. It is most frequently between 3 and 18% of the total weight of the dry materials.
  • the drying is adapted to the agglomerants used.
  • the coating may be flame-treated.
  • the drying is elfected by mere natural evaporation when the coating is effected in a hot ingot mould.
  • the coating contains rather a high percentage of water, the drying is eflected by an exothermic reaction occasioned in the coating before the pouring of the steel.
  • a heating reaction based upon aluminium and caustic soda at the rate of from 5 to 12% of atomised aluminium and from 0.20 to 0.50% of dilute caustic soda in relation to the total weight of the elements involved, the aluminium being introduced into the suspension and the caustic soda being projected by means of a spray gun with separate arr.
  • the coating may be rendered exothermic by adding to it from to 40% by weight of an exothermic composition based on a readily oxidisable body such as aluminium, silicocalcium, silica-aluminium, and a silico-aluminium-iron alloy, and an oxidising agent, particularly manganese dioxide, oxide of iron, or potassium nitrate.
  • the exothermic composition may for instance be constituted by 56 to 80% by weight of silico-calcium, or silico-aluminiumiron alloy (containing from 45 to 75% silicon) and 20 to 44% oxide of manganese or of iron, or by 36 to 54% of atomised aluminium, 6 to 30% of potassium nitrate. 24 to 36% of iron oxide, 1.5 to 4.5% of fluorspar, and 6 to of cryolite.
  • the suspension In setting the process going, the suspension is placed in a storage reservoir resistant to abrasion, and is kept under constant agitation, .by mechanical stirring for example. It is subjected to pressure by a pump so as to be projected by means of a spray gun, the active elements of which are made of very hard materials, such as tungsten carbide, under a pressure of about to 30 kilogrammes per square centimetre or at least 20 kilogrammes per square centimetre.
  • a spray gun the active elements of which are made of very hard materials, such as tungsten carbide
  • the present invention likewise covers a liquid suspension for the production of thermally insulating coatings, comprising a charge consisting of from 85 to 96% by weight of refractory products such as silica, alumina, zirconia and magnesium oxide, passing through a screen having a mesh opening of 0.149 mm., from 4 to 15% by weight of an organic material or a material of low density such as perlite, diatomaceous earth or wood flour passing through a screen having a mesh aperture of 0.297 mm., green agglomerants such as flocculable clays, and dry agglomerants such as synthetic resins, sodium silicate or gum arabic, in suspension in an alcohol, white spirit or toluene.
  • refractory products such as silica, alumina, zirconia and magnesium oxide
  • the process may likewise be utilised in casting systems for forming an insulating deposit for the casting or pouring cups, and for analogous applications.
  • EXAMPLE 1 There were put in suspension in a suflicient quantity of isopropyl alcohol 92 parts by weight of alumina foamed in a colophany glue as described above, -and sprayed so as to pass through a screen having an aperture of 0.149 mm., 6 parts by weight of wood flour, impermeablised with paratfin wax as described above, and 2part'sby weight of diatomaceous earth. To the suspension were added 4 parts by weight o-bentonite, mixed withi'soprop'yl alcohol to form a sludge, and 3.5 parts by weight of a pulverulent phenol resin, which is marketed under the mark Novolak.
  • the mixture was maintained in suspension by: mechanical stirring, and fed, under a pressure of 22 kgJcmF, to a spray gun of the Airless type, comprising control valves and needles for adjustingthe flow of ;tu ngsten carbide, so as to be applied in the form of a coating 8 mm. thick and 220 mm. high in the lift of an ingot mould for an ingot of 1200 kgs. a a
  • the coating was dried by flamet'reatment with isopropyl alcohol.
  • the coating obtained had an apparent density of 0.72, a porosity of 83%, and :a thermal conductivity, in Kcal./m./h./ C., ranging from 0.80 to 0.65 between 220 and 1000 C.
  • EXAMPLE 3 The same composition was utilised as in Example 1, except that the alumina was replaced by silica which had undergone the same foaming treatment, and the isopropyl alcohol was replaced by toluene. This composition was set to work in the same manner as in Example 1.
  • the coating obtained had an apparent density of 0.54, a porosity of 8l%, and a thermal conductivity, in
  • cal./m./h./ C. ranging from 0.12 to 0.20 between 2 ,0 and 680 c.
  • EXAMPLE 4 In a special case, in which a highly refractory product was being sought for, the same composition was used as in Example I, but the silica was replaced by zirconia.
  • EXAMPLE 5 To the mixture described in Example 1 were added 25 parts by weight of an exothermic mixture consisting, to by weight, ofsilico-calcium, and 35% by weight of manganese dioxide. This'composition was set to work in thesame manner as in Example 1. The coating obtained had the same exothermic character as the usual exothermic coatings.
  • EXAMPLE 6 To the mixture described in Example I, but in. which the isopropyl alcohol contained 30% of water, were added 30 parts by weight of an exothermic mixture consisting of 50% by weight of atomised aluminium, 10% by weight of potassium nitrate, 25% by weight of iron oxide, 3% by weight of fiuorspar, and 12% by weight'of cryolite.
  • an exothermic mixture consisting of 50% by weight of atomised aluminium, 10% by weight of potassium nitrate, 25% by weight of iron oxide, 3% by weight of fiuorspar, and 12% by weight'of cryolite.
  • the accompanying drawing diagrammatically illustrates apparatus for putting this example into practice.
  • the mixture provided in a tank 1 is maintained in suspension by mechanical stirring by means of an agitator 2,
  • This spray gun comprises an adjusting valve 6 and a needle 7 for adjusting the flow, the active elements of which consist of tungsten carbide, so as to project the mixture in the form of a jet 8.
  • this jet is placed one electrode 9 of an electrostatic generator 10, the other pole of which is connected by a clip 11 to the body 12 of the metallic rise or of the ingot mould to be coated.
  • Airless spray gun 5 is combined a small separate-air spray gun 13, which is supplied, by a dosing pump 14, with a measured quantiy, at the rate of about 0.50% by weight of the mixture projected by the spray gun 5, of dilute caustic soda obtained from a reservoir 15, and by a compressor 16, with atomising air.
  • the two jets which mix were projected on to the internal surface of the rise 12 to form a layer 17.
  • the caustic soda reacts with a part of the atomised aluminium to give a heating reaction, which drove out the isopropyl alcohol and the water.
  • the coating obtained showed an exothermic character, like that of Example 5.
  • a method of applying thermally insulating coatings to a metallurgical mold wall comprising airlessly spraying under a pressure of at least 20 lcg./cm. against the mold wall to be coated a suspension in an organic liquid selected from the group consisting of ethyl, methyl and propyl alcohols, white spirit and toluene, a mixture of finely granulated materials consisting essentially of 85 to 96% by weight of refractory materials and 4 to 15% by weight of perlite, diatomaceous earth, or wood flour, in combination with a binder that imparts green strength to the coating and a binder that imparts dry strength to the coating, and then drying the coating.
  • an organic liquid selected from the group consisting of ethyl, methyl and propyl alcohols, white spirit and toluene, a mixture of finely granulated materials consisting essentially of 85 to 96% by weight of refractory materials and 4 to 15% by weight of perlite, diatomaceous earth, or wood flour
  • a method as claimed in claim 1, and electrostatically charging said suspension by placing one electrode of an electrostatic generator in a stream of material projected by said spray gun and connecting the other electrode of said generator to said mold wall.
  • a method as claimed in claim 1, and rendering said coating exothermic by including in said suspension 10 to 40% by weight of an exothermic composition consisting essentially of a readily oxidizable substance and an oxidizing agent for said oxidizable substance.
  • said oxidizable substance being selected from the group consisting of aluminum, silico calcium and silico aluminum, said oxidizing agent being selected from the group consisting of manganese dioxide and iron oxide.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Mold Materials And Core Materials (AREA)
  • Paints Or Removers (AREA)
  • Ceramic Products (AREA)
US886138A 1968-12-31 1969-12-18 Method of applying a thermal insulating coating to an ingot wall Expired - Lifetime US3687700A (en)

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FR182512 1968-12-31

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US3687700A true US3687700A (en) 1972-08-29

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US (1) US3687700A (enrdf_load_stackoverflow)
DE (1) DE1963989A1 (enrdf_load_stackoverflow)
FR (1) FR1601639A (enrdf_load_stackoverflow)
GB (1) GB1288292A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189457A (en) * 1977-11-03 1980-02-19 H. L. Clement Company Method of sealing coke ovens
US4400335A (en) * 1981-12-15 1983-08-23 Hoganas Ab Process for repairing refractory linings

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CL2014000872A1 (es) 2014-04-08 2014-08-22 Asesorias Y Servicios Innovaxxion Spa Proceso para la conformacion de anodos de cobre en una rueda de moldeo desde que el cobre esta en estado liquido fundido en una canaleta basculante y es traspasado a una cuchara, porque comprende los pasos de verter cobre liquido fundido desde una canaleta distribuidora basculante hacia una cuchara, conectar los componentes metalicos de la cuchara, arrojar hacia el labio de la cuchara un chorro de aire, conectar los componentes metalicos.

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189457A (en) * 1977-11-03 1980-02-19 H. L. Clement Company Method of sealing coke ovens
US4400335A (en) * 1981-12-15 1983-08-23 Hoganas Ab Process for repairing refractory linings

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DE1963989A1 (de) 1970-07-16
FR1601639A (enrdf_load_stackoverflow) 1970-09-07
GB1288292A (enrdf_load_stackoverflow) 1972-09-06

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