Document OJRQ147JyJqy1kDvbj0Drqeow

FILE NAME: ALCOA (ALC) DATE: 1968 Feb 23 DOC#: ALC103 DOCUMENT DESCRIPTION: US Patent Describing Alternatives to Hazardous Asbestos in Hot Tops & Mould Linings [Filed 1968, Approved 1971] U nited States Patent Office Patented M3ar,5. 62,7,1696771 1 2 3,567,667 MOULD LININGS COMPOSITION COMPRISING BALL MILL DUST AND CALCIUM SILICATE, ALUMINUM SILICATE OR CALCIUM ALUMINO SILICATE FIBROUS REFRACTORY MATERIAL Bernard Carl Rumbold, Nechells, England, assignor to Foseco International Limited, Birmingham, England N o Drawing. Filed Feb. 23, 1968, Ser. No. 707,471 Claims priority, application, Great Britain, Mar. 22, 1967, conductivity and brittleness, and their formation by slurry dewatering techniques is easier than with asbestos-con taining materials. Many types of calcium silicate, aluminium silicate and calcium aluminosilicate fibres may be used. The preferred material, for reasons of economy, is slag wool. The ma terial known as Eldorite may be used with satisfactory results. Analysis of Eldorite and of a slag wool are given below. 13,587/67 Int. Cl. B22c 1/ 22; C08g 51/18 U.S. CL 260-- 17.2 10 ELDORITE 7 Claims Chemical analysis (byweight): Percent Si02 -------------------------------------------------- 33.84 Fe20 3 -------------------------------------------- 0.85 ABSTRACT OF THE DISCLOSURE 15 Hot topping and mould lining materials which contain a major proportion of ball mill dust and proportions of refractory fibrous materials selected from calcium silicate, aluminium silicate and calcium aluminosilicate having ad vantageous properties compared with prior art similar 20 materials containing asbestos. A1 ---------------------------------------------------- 16.35 CaO ---------------------------------------------------- 42.06 M gO -------------------------------------------------- 6.53 S03 ---------------------------------------------------- 0.10 S ------------------------------------------------------- 0.24 Eldorite sinters at 750C.-8000 C. and melts at 1,300 C. SLAG WOOL Chemical analysis (byweight) Percent The present invention relates to slabs, sleeves and the Fe20 3 --------------------------------------------- 1.2 like used for lining foundry moulds or the heads of ingot 25 M g O ---------------------------------------------------- 7.8 moulds or head boxes for such moulds, and is an improve Si02 ---------------------------------------------------- 33.8 ment of the invention described and claimed in Patent M n O __________________________________ 1.0 No. 3,326,273. A120 3 ----------------------------------------'______ 12.5 In Patent No. 3,326,273 there is described a composi CaO ___________________________________ 34.7 tion suitable for lining the inner surface of a casting 30 T i02 ---------------------------------------------------- 0.8 mould for casing metal or of a hot top for such a mould which comprises at least 50% by weight ball mill dust The melting point of this material is 1,260 C. its con and is free from oxidising agents. The composition may tinuous operating temperature being 800-900 C. Fibre also contain 2 to 30% by weight of organic fibrous ma length is generally 6-20 mm. terial, 1 to 10% by weight of a binding medium and 1 to 35 The ball mill dust used may vary widely in properties. 10% by weight of a fibrous refractory material. Thus a In making former materials of this type difficulties have suitable composition comprises 78-94% by weight of ball been found in controlling the permeability of the final mill dust, 3 to 9% by weight of organic fibrous material product, since this depends greatly on the particular type and 1-8% of a binding agent. of ball mill dust employed. Using the compositions of the This composition may contain a proportion of asbestos. 40 present invention, products of more controllable perme In use, hot tops made of such a composition tend to dis ability may be prepared, if necessary using lower grade integrate under the action of the heat of the cast molten Ball Mill dust, i.e. ball mill dust with a high proportion metal. The spent composition will generally fall away as of powdery material therein. In addition, the permeability, a loose powder from the solidified casting or ingot during as noted^ above, generally tends to be higher using the the stripping operation. Workmen involved in these opera 45 compositions of the present invention, thus decreasing the tions may therefore be exposed to the risk of asbestosis tendency toward boiling of the molten metal during cast by inhalation of the dust-laden atmosphere. I have now ing. Both washed and unwashed ball mill dust may be found that by the incorporation of fibrous refractory ma used. terials other than asbestos, such as spun mineral fibre e.g. The compositions of the present invention may also calcium silicate and alumino silicate fibres, and slag wool, 50 contain up to 10% by weight particulate refractory fillers, complete disintegration during use may be avoided and for example silica flour, sand, crushed olivine, chamotte the properties of products made from the compositions or grog, and fibrous organic materials, preferably cellu- may be improved. losic, such as paper pulp, wood pulp or wood flour. According to the present invention therefore there is The binders used may be any known per se for the provided a composition suitable for lining the inner surface 55 purpose, e.g. phenolformaldehyde or ureaformaldehyde of a casting mould for casting metal or of a hot top for resin, furane resins, or any of the binders disclosed in such a mould which comprises ball mill dust, fibrous Patent No. 3,326,273. organic material, fibrous refractory material selected from The quantities used will generally be in the following calcium silicate, aluminium silicate and calcium alumino ranges by weight: silicate fibre, and a binder therefore, the proportion of ball 60 Percent mill dust being at least 50% by weight of the composition. Ball mill d u st__________________________ 50-85 Such compositions may contain some asbestos as well as Fibrous refractory material (other than asbes the other fibrous refractory material, principally for rea tos) ----------------------------------------------- i to 20 sons of economy, but the proportion of asbestos must be Fibrous organic m aterial________________ Up to 10 less than half the total fibrous refractory material present. 65 Binder ----------------------------------------------- 1 to 5 Preferably the proportion of asbestos is not greater than In general, the higher the proportion of fibrous refrac 10% of the total composition. tory material other than asbestos used, the lower will Products made from compositions according to the pres be the proportion of fibrous organic material used, and in ent invention generally display increased permeability, some compositions the proportion of organic fibrous ma green strength and resistance to mechanical shock as com 70 terial may be extremely low. However, compositions for pared with earlier ball mill dust containing products. In use in high temperature casting, for example in casting addition, they are generally of decreased density, thermal steel at 1600 C., will generally contain lower propor- 3, 567,667 3 tions of fibrous refractory materials since otherwise they 4 These ingredients were made up into a 15-20% solids tend not to be sufficiently refractory. This difficulty may aqueous slurry, and slabs formed by dewatering quan be partially avoided by using a high proportion of alu tities of said slurry at a pressure of 20-22 p.s.i. for about minosilicate fibres, but their cost generally makes such 20 seconds. The resulting green products, which were of upsreefeurnreedcofnoormreiacs.onCsaolcfieucmonosmiliyc.ate fibres are generally 5 gstroevaetedrtostdrerinvgethoffththaen retmhoasieninogf wEaxtearm. pTleests1,onwtehree ptrhoedn The fibre length chosen is preferably a few mm., though uct slabs showed densities of about 0.7 gm./cc., and per longer or shorter fibred materials may be used. meabilities from 17 to 19 AFS units, depending on the It is possible to produce heat insulating materials con type and grade of ball mill dust used. The product slabs taining other refractory fibrous materials than those 10 were easy to handle and did not show as high a tendency noted above, but the cost of such materials is prohibitive. to breakage when dropped from a height of one metre as If the proportion of organic fibrous material is too those of Example 1. high, the products tend to have an undesirably low per The slabs were used to line the heads of ingot moulds meability. into which fully killed steel was poured at 1600 C. The It is generally desirable to include in the composition 15 products burnt out smoothly and no gassing was observed, 1-7% by weight of a fluoride, generally fluorspar, to act as sintered. The steel surface had a smooth surface finish. as an initiator for the burning of the products. I claim as my invention: The products of the present invention have the prop 1. A composition suitable for lining the inner surface erty of sintering during the casting operation. This has of a casting mould for casting metal, or a hot top for the advantage that when the burnt out product is removed 20 such a mould, consisting essentially of 50-85 weight per from the cast metal, it falls away in coherent pieces and cent ball mill dust, up to 10 weight percent of a fibrous not as dust, thus minimising the asbestosis risk, even with organic material selected from the group consisting of materials containing a substantial proportion of asbestos. paper pulp, wood pulp, and wood flour, 1-20 weight per The present invention includes not only the composi cent of a fibrous refractory material selected from the tions used for making slabs and sleeves and the like, but 25 group consisting of calcium silicate, aluminium silicate shaped articles such as slabs and sleeves so made. and calcium aluminosilicate, and 1-5 weight percent of The present invention will be further illustrated in the a binder. following specific examples. In these examples, Example 2. Slabs, sleeves and the like for lining foundry moulds 1 describes the production and use of a composition ac and the heads of ingot moulds and head boxes for such cording to Patent No. 3,326,273 and Example 2 describes 30 moulds consisting essentially of 50-85 weight percent the production and use of a composition according to the ball mill dust, up to 10 weight percent of a fibrous or present invention. ganic material selected from the group consisting of paper Example 1 pulp, wood pulp, and wood flour, 1-20 weight percent of Various compositions were made up using various types 35 asisftiibnrgouosfrecfaralccituomry smilaicteatreia, l asleulmecitneidumfromsilitchaeteg, roaunpd ccoanl of ball mill dust and the following proportions by weight cium aluminosilicate and 1-5 weight percent of a binder. of the ingredients listed. 3. A composition according to claim 1 which contains Percent up to 10% by weight of asbestos. Ball mill dust (unwashed) ____________________ 85 4. A composition according to claim 1 which contains Mixed phenolformaldehyde/ureaformaldehyde resin _ 4 40 up to 10% by weight of particulate refractory filler se Mixed phenolformaldehyde/ureaformaldehyde res lected from the group consisting of sand, silica flour, in _______________________________________ 4 Asbestos____________________________________ 1.5 crushed olivine, chamotte and grog. 5. A composition according to claim 1 wherein the Paper pulp __________________________________ 6.5 binder is selected from the class consisting of urea-formal Fluorspar (initiator) _________________________ 3 45 dehyde and phenolformaldehyde resins. These ingredients were made up into a 15-25% solids 6. A composititon according to claim 1 which com aqueous slurry, and test sleeves of height 6", internal prises 1-7% by weight of a fluoride. diameter 6" and external diameter 7" were formed by 7. A composition according to claim 6 wherein the dewatering quantities of said slurry at a pressure of 28-30 p.s.i. for about 15 seconds. The resulting green products 50 fluoride is fluorspar. were then stoved to drive off remaining water. Tests on the product sleeves showed densities of from 0.9 to 0.95 References Cited gm./cc., and permeabilities from 3.8 to 14.8 AFS units, Tdehpeenpdroindgucotnslteheevetsypreequanirdedgrfaadirelyocfabreaflul lmhiallnddluinstg.uTsehde. 55 3,300,322 UNITED STATES PATENTS 1/1967 D e G e e r_________ 106--38.35 sleeves were stood on a refractory base and filled with fully killed steel at 1650 C. The products burnt out with only a little gassing and did not sinter. The burnt-out OTHER REFERENCES Chem. Abst., vol. 67: 67196v, Jago et al., "Exothermic sleeves fell to dust when stripped from the solidified steel 00 Hot Top," June 1967 (December 1965). cylinders, and the cylinders had only a fair surface finish. Chem. Abst.: 2138f, Bunbury, "Bonding--Molds," Example 2 1959. Chem. Abst., vol. 66: 13344c, Rietz et al., "Synthetic Various compositions were prepared using various Slag for Casting Steel," August 1966. types of ball mill dust and the following proportions by 65 Chem. Abst., vol. 64: 17144q, Doittau, "Exothermic weight of the ingredients listed: Composition," April 1965. Percent Ball mill dust (unw ashed)____________________ 75 Mixed phenolformaldehyde/ureaformaldehyde res WILLIAM H. SHORT, Primary Examiner in _______________________________________ 4 70 E. WOODBERRY, Assistant Examiner Asbestos ____________________________________ 1.5 Paper pulp __________________________________ 6.5 U.S. Cl. X.R. Spun mineral fib re ___________________________ 10 164--43; 260--17.3 Fluorspar (initiator) _________________________ 3