US2869196A - Refractory composition containing slag, sand, magnesium oxide, and aqueous phenolic resin, method of making and product obtained - Google Patents

Description

Jan. 20,

1959 R H COOPER ETAL 2,369,196

REFRACTORY COMPOSITION CONTAINING SLAG. SAND, MAGNESIUM OXIDE, AND AQUEOUS PHENOLIC RESIN, METHOD OF MAKING AND PRODUCT OBTAINED Filed Sept. 26, 1956 Ho lop device br/ca/ec/ rif'om coa/eo/a reya e cqmposl' for) com rllsi d o par/icu/a/eo .b/as/ urnace s/ag arm con aim/n9 ca)- INVENTORS. Rona/db. Cooper Gera/aM Camber? HTTORNEYS from such drawbacks.

REFRACTORY COMPOSITION CONTAINING SLAG, SAND, MAGNESIUM OXIDE, AND AQUEOUS PHENOLIC RESIN, METHGD OF MAKING AND PRODUCT OBTAINED Ronald H. Cooper, Clare, and Gerald M. Corbett, Midland, Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Application September 26, 1956, Serial 'No. 612,288

13 Claims. (Cl. 22-193) This invention relates to improved compositions for the fabrication of porous refractory structures that are capabio of withstanding heat at extreme temperature elevations such as is encountered from contact with molten metals, including iron and steel alloys. In particular, the invention relates to improved compositions that are especially suitable for the fabrication of the structures of such devices as hot tops which are frequently utilized when pouring ingots of iron and steel into certain mold forms. It also has reference to a method for the fabri cation of such structures with the compositions and to the structures thereby provided.

Hot tops, as is well known in the art, are devices that i are often employed with ingot molds during the poui'ing of iron and steel ingots to'keep the molten metal that is in the upper p ortion of the ingot in a molten condition for as long a period of time as may be possible. They are usually employed when certain types of killed steels (which contract substantially upon solidification from a molten state) are being poured into ingot molds. The hot top acts as a feeder supply for the molten metal during its solidification and accompanying contraction in the ingot mold. It thus causes the shrinkage cavity (or pipe) which forms in the ingot to occur in the upper portion of the mold or in the hot top device itself in order to provide more nearly perfect ingots that have less associated waste than ingots in which the pipe ocours in the main portion of the mold form.

Many of the conventionally employed hot top devices refractory hot toprnaterial to adhere tenaciously to the ingot after it has been poured and to thereafter fuse and .run down over the ingot when it has been transferred .to a soaking pit. Such behavior may well provide subsequent difliculties of considerable magnitude with' the ingot in'the blooming mill. Another disadvantage with many of the commonly employed hot tops, especially those that have been fabricated fromceramic refractory materials, is the considerable incidence of breakage which often occurs in the course of their normal shipment and handlingprior to use.

It would be advantageous to provide compositions that could be fabricated into hot tops and the like porous refractory structures that would be substantially free It would also be advantageous if the structures prepared from such compositions hadexceptiopal insulating characteristics. This would be Pal '1 Zfibdldb Patented Jan. 2%, 19 59 ice ticularly beneficial for hot top devices, wherein it is, as has been mentioned, desirable to maintain the molten metal contained therein in a liquid condition as long as possible to minimize the severity of the piping in the ingot. It would be additionally advantageous if the structures from such compositions were strong and tough. This would also be beneficial for hot top devices to enable them to withstand the considerable ferrostatic head that is developed by the liquid metal in the ingot being poured. Other characteristics that would be advantageous for structures fabricated from such compositions include adequate and uniform porosity to allow eflicient negotations therethrough of fluids (such as hot gases from molten metals) and the capability of being readily and quickly fabricated in the course of their manufacture. Another desideration of not inconsequential proportion for such structures and the compositions adapted to provide them is in their being of a significantly economical nature in order that their attractiveness in other aspects is maintained within the realm of practicality.

In accordance with the present invention, these and many other advantages and benefits may be achieved by a composition that comprises a preponderant proportion of a filler material that consists of a quantity of particulated blast furnace slag in the amount of at least about 10 percent by weight, based on the weightv of the composition, and, optionally, relatively coarse sand; and a binding minor proportion of an aqueous phenolic liquid thermosetting resin. Advantageously, the composition may be comprised of a filler material that consists of a quantity of finely divided blast furnace slag particles in an amount between about 20 and 60 percent by weight with the balance a relatively coarse sand; and between about 4 and 10 percent by weight based on the weight of the composition, of an aqueous phenolic liquid thermosetting resin binder. Optionally, particularly when relatively small proportions of low magnesia slag are employed in the filler, the resin binder may be catalyzed with a small quantity, say from 10 to 25 percent by Weight, based on the weight of the resin in the composition, of an active powdered magnesium oxide catalyst. Relatively greater proportions of sand in the filler provide structures that, generally, are more readily disintegratable after having been subject to heat at such eX- treme temperatures as may decompose the organic resin binder. This may often be a desirable feature for such structures-as hot top devices in order that they may be easily disintegrated and dispensed with after their utilization. However, in the event that it is desired for the structure, after having had its resin binder burned out, to retain a sturdier structure that is less prone to disinte' grate, the proportion of finely divided blast furnace slag 'can be increased until it is greater than 60 percent by weight or until the entire filler material consists of slag without any sand being present in the composition.

The compositions, freshly after being prepared, are wet, plastic and fiowable coated sand mixtures that can be shaped in the cold to a desired structure of the agglomerated, integrated mixture. This can easily be accomplished by cold pressing the freshly prepared composition, as by ramming it into a mold under pressures that advantageously may be between about and 1200 pounds per square inch. Or, if desired, they may be literally sprayed or forced into shape with the assistance of a pneumatic blast under pressures of, say, 80 to 100 pounds per square inch much in the manner of the commonly employed core blowing techniques for fabricating sand mixtures in the foundry. During or after the wet formation of the desired structure, such as a hot top device, the agglomerated composition will self-set or auto-harden to an integrated, bonded magma structure, due primarily to the catalytic action of the magnesia and lime in the blast furnace slag and also with the assistance of any optionally added magnesium oxide on the applied resin that coats the filler in the composition. The selfsetting or auto-hardening of the wet-formed composition ordinarily occurs within an hour at room temperature, after which the structure may be cured conveniently at temperatures between about 250 and 600 F. until it has been completely thermoset to a strong rigid form suitable for the intended employment. Higher curing temperatures may also be employed if suitable adjustment of the exposure time is made, although in relatively thick structures, care should be taken to avoid decomposition of the thermosetting binder during the curing by means of too hot an atmosphere for excessive periods of time. Generally, the auto-hardened structures may be satisfactorily cured by exposure to a thermosetting temperature of about 475-500" F. for a period of time of at least about 45 to 60 minutes.

The cured structure, when it is a hot top device, may then be employed in conjunction with an ingot mold during the pouring of hot top ingots. The extreme heat from the molten metal that is being poured will decompose and burn out the cured phenolic resin binder to leave a strong and uniformly porous refractory structure that provides an easy escape for the gases that are being evolved from the molten metal while being capable of readily withstanding the ferrostatic head that is developed by the charge of molten metal. In this connection, care should also be taken when curing the refractory structure prepared according to the invention to utilize a suf ficiently high thermosetting temperature. The employment of too low a temperature for this purpose may not only cause a relatively weak structure to be encountered but may cause difi'iculties in the decomposition of the resin binder upon contact with heat from the molten metal or other sources. Improperly cured hot top devices may evolve considerable quantities of first and smoke upon contact with the molten metal and may severely carbonize the ingot being poured. In contrast,

properly cured structures display greatly minimized tendencies for such behavior. Hot top devices that are prepared from the compositions of the invention containing relatively high proportions of sand as a filler, say about half or more, can be broken away readily after the ingot has beenpoured and it is desired to strip the hot top from the mold. In addition, difficulties due to adherence of the burned out structure to the solidified metal are extremely rare when utilizing hot top devices from certain of the compositions of the invention, especially those containing a fair proportion of sand in the filler. A unitary hot top device that has been prepared from a composition in accordance with the present invention is schematically illustrated in the accompanying drawing.

The particulated blast furnace slag that may advantageously be employed as a filler material in the compositions of the invention may be a typical slag, in finely divided form, that has been obtained from a blast furnace making basic iron. Such a slag is often found to contain about 48 percent by weight of a mixture of silica (SiO and alumina (A1 0 in which the proportion of alumina may vary from .10 to 15 percent by weight of the entire slag and about 48 percent by weight of a mixture of lime (CaO) and magnesia (MgO) in which the proportion of magnesia seldom, if ever, exceeds 10 percent by weight of the entire slag, with the balance usually being comprised of minor proportions of calcium sulfide and ferrous and manganese oxides. Representative analyses of suitable blast furnace slags for employment in the practice of the invention are as follows:

In many cases the finely divided blast furnace slag may be suitably employed in the physical condition of subdivision in which it may be received from the crusher. Such a material may have characteristics of physical particle size that are closely in accordance with those represented by the following sieve analysis for a crushed and powdered slag that was analyzed upon receipt from the source:

Percent By Weight of Slag Powder Retained On Screen Mesh Size In U. S. Sieve Series Of Screen It may sometimes be desired to utilize a particulated blast furnace slag that has a more nearly uniform average particle size. In such event, it is usually beneficial to employ a finely divided slag that is comprised of preponderant or total proportion of particles having an average size that is finer than about 5 and coarser than about 28 mesh in the U. S. Sieve Series. Generally, the employment of a slag having a relatively coarser average particle size facilitates the achievement of structures having correspondingly greater porosity.

Any ordinary, relatively coarse sand may optionally and frequently with great benefit be employed in combination with the blast furnace slag powder as a filler in the practice of the present invention. Advantageously, the sand that is employed has a fineness in accordance with the Values proposed by the American Foundrymans Society (AFS) that is in the numerical range between about 25 and 125. Such sands, for example, as the varieties that are commonly employed as core sands including the types which are known as Berkeley Float Sand, Juniata Sand, Lake Sand, Vassar Sand, Wedron Sand, Portage Sand 40-60, Gratiot Bank Sand and the like may be beneficially employed. It is desirable that the sand be clean and substantially free from foreign metal oxides, clay, moisture and organic matter. In many cases it may be more advantageous to employ a sand having an AFS fineness number from about 30 to 75. If desired, it may sometimes be beneficial to add small quantities of other materials, such as fusible silica glass powder, to the mixtures to assist in more strongly binding the formed and cured structure when it is being exposed to heat at extreme temperatures, such as a hot top in contact with molten metal, after the resinous binder has been decomposed. Soda ash may also be added to the compositions of the invention in small quantities, as between about and 25 percent by weight of the resin binder, to achieve a similar effect. In such instances it may sometimes be possible to achieve suitable structures for high temperature exposure that may be fabricated from compositions prepared with relatively smaller proportions of the resin binder. In addition, small quantities.oflamp-black, carbon flour, graphite, pitch or tar and the like may also be incorporated in the compositions to further reduce any tendency they may have to adhere to the solidified ingot.

As has been indicated, theyresin binder that is employed in the compositions of the present invention is an aqueous phenolic liquid thermosetting phenol-formaldehyde liquid resin, that is caused to be self-setting at room temperatures by the magnesia in the blast furnace slag or any supplementary magnesium oxide that may have been added'to the composition. Theactive magnesia, as in dry slag, is capable of dehydrating and auto-hardening the liquid resin at room temperatures to a dry thermoplastic-thermosetting mass. A resin binder for filler materials catalyzed by means of active powdered magnesium oxide is describedin the copendiug application of Ronald H. Cooper covering Improved Phenolic Resin Compositionshaving Serial No. 612,283 that was filed on September 26, 1956. Thus, the phenolic liquid resin that is employe'd'may be phenol-formaldehyde condensation product, of "the type that is oftentimes characterized as being a stage A resin, that has been prepared by reactlng aqueous mixtures of phenol and formaldehyde, in a known manner, under the influence of basic catalysis. Such liquid resins usually have a greater than 1:1 mole ratio of formaldehyde to phenol, respectively, in their compositions. It is oftentimes desirable fora phenol-formaldehyde liquid resin to be employed that has a mole ratio .of formaldehyde to phenol in the neighborhood of 1.45:1. The-solids content of :the liquid resin should be at least 50 to 160 percent by-weight and it may have a viscosity from about 1.00 to 1,000 centipoises at 77 F., and a pH .from about 5 to 9.. v 1.

,When small quantitiesof an active powdered magnesirum oxide is supplementaril-y added to the composition as an auxiliary catalyst for the phenolic liquid resin to helpachieve its auto-hardening properties, it advantageously may be a finely divided powder that has initial setting characteristics, measured as afunction of time according to the procedure set forth in A. S. T. M. Specification No. (1254-50 1, that is between about 0.1 and 6 hours. Generally, it-is beneficial to utilize a magnesium oxide powder for such purposes that has an average particle size-not coarser than about 40 mesh in the U. S. Sieve Series and an initial setting time between about 0.5 and 3 hours.

As has been detailedin the referred to copending application, the time that is required for a magnesium oxide catalyzed phenolic liquid resin to-self-set or auto-harden due to the involved catalystic. ettectdependsto a great extent upon the activity of'the magnesium oxide. Thus, in general analogy thereto, the auto-hardening times of the compositions of the present invention depend to a great extent upon the activity of the magnesia in the slag and also upon the activity or initial setting time characteristics of any magnesium oxide powder that may have been supplcmentally added to the composition, and also on the proportion in which the magnesia from any source is; included. in the composition with phenolic liquid resin in the binder. This, of course, limits the time in which composition prepared with such a liquid resin binder is plastic and flowable so that it maybe cold formed to a desired porous refractory structure (such as a hot top I device) as a wet, coated fillerconiposition after its initial preparation; Generally, slags containing moreactive forms of magnesia and supplemental addition of more active magnesium' oxide powders (materials having a shorter initial setting time) and greater proportions of included magnesia in the composition from either or both of the sources result in wet mixtures that auto-harden in shorter periods of time after their initial preparation. Compositions that are in accordance with those of the present invention may ordinarily be found to be autohardenable within about an hour or so of their initial preparation.

The compositions of the present invention should not be formulated with too much of a content of the resin binder if they are intended to be subjected to heat at highly elevated temperatures in their use due to the problems that may be introduced by the decomposition of too great an included quantity of the cured resin binder. Hot top devices, for example, that contain too much binder, say in the neighborhood of 14 or more percent by weight of the composition, may fire and smoke excessively, cause intolerable degrees of metal splattering and result in carbonization of the ingot when contacted by the molten metal. They may, as a matter of fact, not even be capable of the primary requisite to hold the hot metal during the pouring of a heat.

In the formulation of the compositions of the invention, it is essential to achieve a uniform and thorough dispersion and interblending of' all the ingredients. If additional magnesium oxide powder is to be included, it is particularlyadvantageous to prepare the compositions by intimately premixing the powdered magnesium oxide catalyst with the finely divided filler before homogeneously incorporating the liquid resin therein with sufiicient mixing to thoroughly coat the particles of filler. The

I formulation can be achieved readily using many available varieties of etficient mixing and mulling apparatus.

By way of further illustration, several mixtures in accordance with the compositions of the present invention were prepared by intimately premixing the filler materials, and gradually adding to the dry mixture, with efficient continuous mulling, theliquid resin to coat the filler. The wet mixtures were then cold formed by being packed in molds under a ram pressure of about 100 pounds per square inch into hot top structures. After being molded, the formed hot top devices were permitted to autoharden at room temperature to an agglomerated, composite, integral mass. :This was accomplished in about an hour after which the hot tops were cured for about minutes in a gas fired oven at a temperature of about 482 F. Each of the hot top devices, without gagers or internal reinforcement, were then tested for their performance in pour tests with molten iron and steel. All of them performed in a highly satisfactory manner. They retained the liquid metal at temperatures between 2900 and 3000 F., provided adequate escape for the hot gases, did not display excessive tendencies to cause piping, did not adhere to the solidified metal in an objectionable manner and could be stripped from the molding with relative case, being readily disintegrable within phenol mole ratio of about 1.45:1, a solids content between 50 and 60 percent by weight, a pH of about 8 and a viscosity at 77 F. of about 300 centipoises. About 40 mesh magnesium oxide powder with a /2 hour initial setting time was employed in the composition (mixture F) in which supplemental quantities were utilized.

hisumixturexwas formulated by intimately dispersing the magnesium oxide powder in the filler before introducing the liquid resin. Some of the compositions (mixtures through E), as indicated, also contained small quantities of soda ash.

81 6. The composition of claim 1, wherein the finely -'divided.blast .furnace slag has an average particle size Percent by Wt. oi Slag Percent by Wt. Average of Sand Tensile Percent Strength Mixture by Wt. of Cured Remarks of Resin As 6-28 100 Gratiot Portage Hot Tops,

Received Mesh Mesh Bank 40-60 p. s. 1.

AFS 67 AFS 33 e 0" 55.80 275 0.30 percent NaiCO; In

mixture. D 54.50 390 0.50 percent N11100: in

' mixture. r E 81. 40 452 0.60 percent NniCOa'in mixture. 1 "F 81.40 490 0.60 percent MgO in mixture. G 35.00 200 "H 75.00 406-460 "J" 35.00 360402 K 75.00 566-638 In a similar manner other refractory structures were formulated from compositions that contained the blast furnace slag powder as the only filler with from 6 to percent by weight of the liquid resin as a binder. Some of the all slag filler compositions also contained about V2 percent by weight of soda ash in their formulations. These structures, after being formed and cured in the same manner as the hot top devices, were easily capable of withstanding heat at temperatures in the 3,000 F. range. After having the resin binder burned out, however, the all-slag filler structures were more difiicult to disintegrate than were the structures from the sand-containing compositions.

Certain changes and modifications in the practice of the present invention can be entered into readily without departing substantially from its intended spirit and scope. Therefore, it is to be fully understood that the invention is not to be limited or in any way restricted to or by the foregoing didactic description and specification. Rather, it is to be interpreted and construed in the light of what is set forth and defined in the hereto appended claims.

What is claimed is:

1. Composition for the fabrication of porous refractory structures which comprises a preponderant proportion of between about 96 and 90 percent by weight, based on. the weight of the composition, of a filler material that consists of a quantity of a particulated, finely divided blast furnace slag in the amount of at least about 10 percent by weight, based on the weight of the composition, any balance of said filler material being relatively coarse sand;

and a binding minor proportion of from 4 to 10 percent by weight, based on the weight of the composition, of an aqueous phenolic liquid thermosetting. resin, said resin being a phenol-formaldehyde condensation product that has a greater than 1:1 mole ratio of formaldehyde to phenol, respectively, a solids content of at least about 50 percent by weight, a pH between about 5 and 9 and a viscosity at 77 F. between about 100 and 1000 centipoises.

2. The composition of claim 1 and including a small quantity of an active powdered magnesium oxide catalyst having an initial setting time from about 0.5 to 3.0 hours.

3. The composition of claim 1 in the form of a wet, plastic and fiowable mixture.

4. The composition of claim 1, wherein the quantity of finely divided blast furnace slag that is contained as filler in the composition is an amount between about and 60 percent by weight, based on the weight of the composition, the balance of said filler being relatively coarse sand.

5. The composition of claim 1, wherein substantially all of the filler that is contained therein is the finely divided blast furnace slag.

finer than about 5 mesh and coarser than about 28 mesh 7 in the U. S. Sieve Series.

7. The composition of claim 1, wherein any sand that is contained in the filler has an AFS fineness number between about 30 and 75.

8. The composition of claim 1, wherein the aqueous phenolic liquidthermosetting resin is a phenol-formaldehyde condensation product that has about a 1.45:1 mole ratio of formaldehyde to phenol, respectively, a solids content of at least about 50 percent by weight, a pH between 5 and 9 and a viscosity at 77 F. between about 100 and 1,000 centipoises.

9. A cured, rigid formed, porous, refractory structure prepared from a composition that is in accordance with the composition set forth in claim 1.

:10. A hot top device prepared from a composition that is in accordance with the composition set forth in claim 1.

11. Method for fabricating porous refractory structures which comprises preparing a wet, auto-hardenable mixture of a preponderant proportion of between about 96 and 90 percent by weight, based on the weight of the composition of a filler and a binding minor proportion of from about 4 to about 10 percent by weight, based on the weight of the mixture, of an aqueous phenolic liquid thermosetting resin, said resin being a phenol-formaldehyde condensation product that has a greater than 1:1

mole ratio of formaldehyde to phenol, respectively, a solids content of at least about 50 percent by weight, a pH between about 5 and 9 and a viscosity at 77 F. between about and 1000 centipoises, said filler consisting of a quantity of a finely divided blast furnace slag in the amount of at least about 10 percent by weight, based on the weight of the'mixture, any balance of said filler being relatively coarse sand; forming said wet mixture into a desired structure before it has auto-harden- References Cited in the file of this patent UNITED STATES PATENTS 2,133,245 Brice et a1 Oct. 11, 1938 FOREIGN PATENTS 305,237 Great Britain May 2, 1930 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,869,196 January 20, 1959 Ronald H. Cooper et .al.

ppears in the printed specification It is hereby certified that error a orrection and that the said Letters of the above numbered patent requiring 0 Patent should read as corrected below.

Column 3, line 45, for "first" read fire column 8, line 39, aft the syllable "tween" insert about Signed and sealed this. 22nd c1221; of September 1959'.

Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

Claims (1)

1. COMPOSITION FOR THE FABRICATION OF POROUS REFRACTORY STRUCTURES WHICH COMPRISES A PREPONDERANT PROPORTION OF BETWEEN ABOUT 96 AND 90 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF THE COMPOSITION, OF A FILLER MATERIAL THAT CONSISTS OF A QUANTITY OF A PARTICULATED, FINELY DIVIDED BLAST FURNACE SLAG IN THE AMOUNT OF AT LEAST ABOUT 10 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF THE COMPOSITION, ANY BALANCE OF SAID FILLER MATERIAL BEING RELATIVELY COARSE SAND; AND A BINDING MINOR PROPORTION OF FROM 4 TO 10 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF THE COMPOSITION, OF AN AQUEOUS PHENOLIC LIQUID THERMOSETTING RESIN, SAID RESIN BEING A PHENOL-FORMALDEHYDE CONDENSATION PRODUCT THAT HAS A GREATER THAN 1:1 MOLE RATIO OF FORMALDEHYDE TO PHENOL, RESPECTIVELY, A SOLIDS CONTENT OF AT LEAST ABOUT 50 PERCENT BY WEIGHT, A PH BETWEEN ABOUT 5 AND 9 AND A VISCOSITY AT 77* F. BETWEEN ABOUT 100 AND 1000 CENTIPOISES.

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