Патент USA US2406910код для вставки
Patented Sept. 3, 1946 2,406,910 UNITED STATES PATENTOFFICE Robert A. Schoenlaub, Ti?in, Ohio, assignor to Basic Refractories, Inc., Cleveland, Ohio, a cor poration of Ohio No Drawing. Application January 6, 1943, Serial No. 471,455 6 Claims. 1 (01. 117-122) Refractories such as chrome ore, and periclase, casement without prior burning of the grains, while desirable in many respects, have certain . and such as to allow full latitude in application proclivities toward deterioration under furnace of the refractory material in desired kinds of condition. In exposure to high temperature usages, and the procedure is relatively‘simple and slags and oxide-bearing vapors, chrome ore for 01 of low cost. instance tends to. absorb ferrous or ferric oxide, To the accomplishment of the foregoing and as well as some other oxides, by solid solution, related ends, the invention, then, comprises the the absorbed substances diffusing into ‘the features hereinafter fully described, and partic chrome-spinel grains and becoming an integral ularly pointed out in the claims, the following part thereof. This changes their physical prop description setting forth in detail certain illus erties, and particularly‘ important and‘destruc trative embodiments of the invention, these being tive is the increase in volume, and this results indicative however, of but a few of the various in what is variously termed “bloating,” “cauli ways in which the principle of the invention may ?owering,” “swelling,” or “peeling,” all of which be employed. considerably reduce the ultimate service life of The refractory material to be treated, as for refractories made from chrome ore. Periclase instance chrome ore, magnesian refractory ma refractories are similarly affected, but to alesser terial, etc., and designated for convenience “basic extent. These refractories also have another dis refractory material,” is crushed and sized to‘de advantage in that chromite and periclase crys sired mesh, and the grains are subjected to coat tallize in the isometric system, usually in small 120 ing by a silicate material which permits ultimate equi-dimensional crystals. They therefore do moistening and molding or bringing into desired not intrinsically possess the keying action which shape or placement vfor use. Such silicate is in is imparted in some refractory substances by contrast to clays, bentonites, etc., as it is of a prismatic crystals, such as mullite, or by tabular chemical character not introducing deleterious crystals such as corundum. As a consequence alumina. Plastic hydrous magnesium silicates they are more sensitive to spalling and structural which with water swell to a voluminous gel, and failure than some of the more acid types of re are thereby distinguished from such silicates as fractories. Commonly, in an effort to mitigate serpentine are excellent materials for this pur the destructive effects of absorption and the pose, and although they may be provided syn structural de?ciencies of basic refractories, it has 30 thetically, they may be had‘from natural de been customary for refractory manufacturers to posits to advantage. For instance, one such de use as coarse a sizing as possible. Brick made posit occurs near Hector in San Bernardino from coarsely sized material are usually more re- - County, California. . It is, characterized by a ra sistant to spalling than brick made from similar material ?nely sized. Also, by the use of coarse DD tio of silica to magnesia usually slightly greater than 2:1 by weight, and it usually contains al kalies, of which lithia is notable. It differs from the aluminous bentonite in its X-ray diffraction sizing, the volume-surface relationship is favor ably affected, so that a smaller amount of sur face is exposed to destructive absorption. How ever, as the sizing increases, therworkability of pattern and indices of refraction. Analysis, as freed from associated ?ne calcite, shows ignition a refractory mixture and its permeability are ad 40 loss 5.7, MgO 25,1, SiOz 57.8,‘Naz0 2.9 per cent, versely affected. These factors constitute prac and traces of R203. Analysis including initially tical limits to advantages which may be gained associated calcite, and in the‘form in which‘it by sizing. A common expedient is to use coarse may also be used shows ‘ignition loss 25.55, MgO chrome ore and to use ?ner periclase clinker, 11.09, S102 26.14, NazO 1.30, CaO 29.28 per cent, 45 and traces of R203. Physically, the material is which is less sensitive to absorption. Efforts have been made to improve chrome unctuous and’ swells copiously to a voluminous, ore or periclase refractories by providing the stable gel when immersed in water. These gels grains with encasements of refractory silicates‘by are ‘variously tacky and plastic, depending upon means of calcium and magnesium silicates fused the . amount of water used and other factors. on the clinker grains by high temperature firing 50 Such‘ physical characteristics of plastic hydrous in a rotary kiln. The cost- of this is prohibitive magnesium silicate materials allow emplacement for what advantages result. In accordance with of a thin, persistent layer on the refractory grains the present invention however, basic refractory materials, chrome , ore, magnesia refractories, treated; This may be applied alone as the coat ing material, or it may carry other material, as _etc.,~'m_ayebe coated with a bene?cial silicate en .55 a thick gelatinous suspension. The‘ refractory 2,406,910 3 4 jected to elevated temperature, in burning or in grains in such addition or additions may be mixed in suitable mixing apparatus, as for in stance a pan mixer, the suspension being added furnace use. As an example: A massive chrome ore analyz ing CI'zOs 34.5 per cent, CaO 1.0, MgO 16.1, $102 4.0, F6203 15.4, and A1203 29.7 is crushed and sized, and with 45 parts of -—~8 +20 mesh par ticles and 20 parts of ~20 +50 mesh particles to the refractory grains, allowing suf?cient time for good distribution of the water and silicate material. The coated grains may then be pressed into brick or shapes which can be ?red, or alter and 22 parts of -150 mesh chrome ore there natively, with suitable bonding materials well are incorporated 3 parts of —150 mesh hydra known in the art, may as chemically bonded brick be sold and applied as un-?red brick. Al 10 tion-resistant high magnesia clinker, and 3.8 parts of —200 mesh hectorite (MgO 25 per cent, S102 5'7 per cent), and 2.8 parts of extremely ternatively also, the coating material can be in corporated dry with the refractory grains, and may ?nally be tempered with water in amount ?nely divided magnesium hydrate, and 2 parts of 7 “goulao” or waste sulphite liquor bond. After for desired molding condition. mixing in a pan mixer and tempering to desired As indicated, the plastic hydrous magnesium silicate may be applied alone to the refractory grains, or it may be used with other materials. For the latter, there may be employed for in pressing consistency the material is formed into shapes under high pressure, dried and ?red. Al ternatively, the dried bricks may be set in a fur stance magnesium hydrate. The plastic hydrous nace in un-?red condition. In the latter case, it may be desired to also incorporate in the ma terial a chemical bond. magnesium silicate or hectorite, and the magnesia can conveniently for instance be added dry to the refractory grains. On mixing, and temper ing with water, the coating substance will be distributed over the particles. With small amounts, the material may be applied as a thick slurry in water. By coating refractory grains Other modes of applying the principle of the invention may beemployed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed. I therefore particularly point out and distinctly thus with plastic hydrous magnesium silicate and claim as my invention: magnesium hydrate, and exposing to a high tem *1. A process of treating refractory material, perature, as in the furnace heat if the material is applied un~burned, or in the ?ring process if 30 which comprises coating the surface of basic refractory material particles with an alkaline molded bricks or shapes are burned before being earth compound of the group consisting of mag used, there is a reaction, hectorite '(free from nesium and calcium hydroxides and oxides, and lime) and the magnesium hydrate forming to react therewitha substantially non-aluminous 2MgO.SlO2. Amounts of for instance 2 to 10 per cent of the magnesium silicate and particu 35 gel-forming hydrous magnesium silicate of the composition of hectorite from 'San Bernardino larly a range around 5 per cent give very desir County, California, and contacting the reaction able results, and for example for one part of mixture with water for swelling the gel-forming hectorite 1/2 part or more of magnesium oxide material, and compacting the coated particles or its equivalent in magnesium hydrate may make 40 ‘together. up the reaction materials. 2. A process of treating refractory material, If desired, instead of allowing reaction with which comprises applying to the surface of basic plastic hydrous magnesium silicate to the forma refractory material particles a coating of mag tion of 2MgO.SiO2 as ultimately ?red, the coating nesium hydroxide, and to react therewith a sub material may be chosen to eventuate in stantially non-aluminous gel-forming hydrous 2CaO.SiO2. For this, lime-bearing hectorite may magnesium ‘silicate of the composition of hec be used, and correcting lime, such as ?nely torite from San Bernardino County; California, ground, chemical grade hydrate may be added to and contacting the reaction mixture with water bring up the molecular ratio of vlime to silica as 2:1. Borax to give for instance 0.05 per cent of 5.1 for swelling the gel-forming material, and com pacting the coated particles together. B203 or slightly more in the ?nished refractory 3. A process of ‘treating refractory material, may be added, as with the tempering water. Sili which comprises applying to the surface of basic cate for coating purposes should not be added in refractory material particles a coating of lime, amount larger than required for effective coat and to react therewith a substantially non ing. It is generally more susceptible than other constituents to fluxing. Consequently, a desir or CA aluminous gel-forming hydrous magnesium sili cate of the composition of ‘hectorite from San able balance may be made between the absorp Bernardino County, California, and contacting tion mitiation and fluxing tendency. Usually, 3 the reaction mixture with water for swelling the to 1-5 per cent of coating silicate material is gel-forming material, and compacting the coated satisfactory. Other silicates, present as impur 2 particles together. ities or otherwise, are omitted from present con 4. A process of treating refractory material, sideration. which comprisesapplying to the surface of un Refractory particles so coated with plastic ?red basic refractory material particles a coating hydrous magnesium silicate, with optional inclu of an alkaline earth compound of the group con ' sisting of magnesium and calcium hydroxides sion of a reactive alkaline earth compound, such as hydrate or oxide or carbonate, with a suit and oxides, and to react therewitha substantially able amount of moistening and tempering water, non-aluminous gel-forming ihydrous magnesium may be compacted to form furnace linings, or molded shapes, etc. And, it is a particular con Bernardino County, California, and contacting silicate of the composition of hectorite from San venience that such refractory materials, involv 10 the reaction mixture with water for swelling the ing particles of chromite or of magnesia char gel-forming material, compacting the coated par ticles together, and ?nally heating to react the acter, may thus be employed in either un-?red coating. or in ?red condition, the ?nal reaction of the -5. A process of ‘treating refractory material, plastic hydrous magnesian silicate to a refrac tory silicate occurring when the material is sub 75 which comprises applying to the surface of basic I 2,406,910 refractory material particles a coating 01' mag nesium hydroxide, and to react therewith a sub which comprises applying to the surface of basic refractory material particles a coating of lime, stantially non-aluminous gel-forming hydrous and to react therewith a substantially non-alumi nous gel-forming hydrous magnesium silicate of the composition of hectorite from San Bernardino County, California, and contacting the reaction mixture with water for swelling the gel-forming magnesium silicate of the composition of hec torite from San Bemardino County, California, and contacting the reaction mixture with water for swelling the gel-forming material, compact ing the coated particles together,‘ and ?nally heating to react the coating. 6. A process of treating refractory material, 10. ‘material, compacting the coated particles to gether, and finally heating to react the coating. ' ROBERT A. SCHOENLAUB.