US1956894A - Method of making refractories - Google Patents

Description

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METHOD OF MKING REFRCTORES Filed Feb. 27, lQZ

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Patented May l, 1934 UNITED STATES PATENT OFFICE METHGD F MAKING REFIEACTORIES a corporation of Ohio Application February 27,1932, Serial No. 595,579

8 Claims.

This invention relates to refractories for hot tops, and has reference particularly to the chemical constituents of such refractories and the method of producing the same. The refractories which are the subject of the invention may be employed for the production directly of hot tops either as unitary or built-up assemblies, or they may be employed as lining elements for metal casings or frames. 4

One of the objects of the invention is the provision of a refractory of this character which shall be economical to produce, and one which can be formed with a relatively high degree of accuracy in comparatively large units, the large units facilitating the assembly of' the hottop or its reconditioning after use.

Another object is the provision of a hard rigid refractory which shall be resistant to deterioration during storage and capable of withstanding rough handling in shipment.

In the drawing:

Figure 1 is a perspective View looking downwardly upon a one-piece lower lining ring for a hot top, this ring being formed of the composition of matter and by the method of the present invention.

Fig. 2 is a transverse sectional view of the same taken substantially on the line 2-2 of Fig. 1, thereby showing the ring in an inverted position.

The ring illustrated in the drawing is merely one example of a hot top refractory which may be formed of the composition and by the method of the present invention. Complete hot tops consisting of refractory material alone may be built up of a plurality of molded elements, or in some cases may be molded as a unitary structure employing the present compositionn and method, and Where a metal casing orframe is employed it may be protected by means of a refractory' lining in one or a plurality of pieces formed or" the composition and by the method of this invention. The ring herein illustrated constitutes one element of a lining for a hot top casing, being intended to be used as a substitute for a lower lining course formerly constructed of a plurality of refractory blocks, such for instance as those illustrated in Patent 1,804,206 to Charman et al, dated May 5, 1931.

In the drawing the ring 10 is a homogeneous, one-piece structure having a perimeter formed with a contour corresponding with the inner contour of the ingot mold with which the hot top is to be used. Along its inner edge the ring is formed with an upstanding rim 1l which is adapted to protect the inner edge of the casing ledge,

by means of which the other lining elements of the hot top are supported. It also aords a means for centering the ring on the hot top. Any suitable means may be employed for attaching the ring 10 to the casing, holes 12 being provided in the present instance for the reception of Wire ties.

The ingredients whichwe employ in making up these refractories include a suitable aggregate that is free from any impurity that will react chemically in a harmful manner with the binder, and one in which the particles are of suitable size, The size of particles should be such that the resulting article is dense enough to have considerable strength, and yet not too dense to prevent any vapors or gases, set free at the time the metal is poured, from Venting ofi". The aggregate which We prefer to employ is silica sand of a relatively ne grade, washed to remove any impurities.

While it is possible to employ various binders with diierent degrees of success, we have discovered after extensive experiments that by far the best results are obtained, particularly with silica sand as the aggregate, from the use of sodium silicate. This is employed preferably in solution. and although the moisture content may be varied more or less, we prefer to employ one containing 36.47% solids and 63.53% water. To produce the maximum adhesive strength of sodium silicate the ratio of sodium oxide to silicon oxide should be approximately one to three. Any material deviation from this ratio will cause a marked decrease in adhesiveness. For reasons of manufacture, and to obtain the proper physical condition, we prefer to use sodium silicate having a ratio of one to 3.25. As the alkalinity of sodium silicate increases the water resistance decreases quite rapidly. The quantity of silicate solution which should be used may be varied within workable limits, the maxium of which would be twenty percent by weight.

The amount of moisture in the batch isof a high degree of importance. For example, when the aggregiate and binder used are as above stated, the added water content may be varied only within the small limits of three-tenths percent to one percent by weight of the whole mass, the proportion depending somewhat upon the screen analysis of the sand and to a slight extent also upon the exact character of the silicate. When the batch is too dry it is extremelyl difficult to ram it properly or otherwise compact it within the mold, Whereas if too much moisture is employed the compound sticks to the mold box bad- .one percent by Weight of the whole mass.

ly and it becomes impossible to turn out a perfectly formed article.

One of the requisites of a good commercial refractory for hot tops is that it shall satisfactorily withstand hard usage, particularly in shipment, and shall remain hardand rigid after being exposed to the atmosphere for a considerable time, as when stored in an unprotected or damp place. We have found that the refractories in question may be rendered practically permanent regardless of atmospheric conditions by including in the mixture from which they are molded a certain quantity of the oxide of some metal, preferably zinc or lead. Aluminum oxide is suitable for the purpose, but on account of its greater cost, we prefer to employ instead either zinc or lead oxide. Although the amount of this water-proofing agent may be increased to some little extent, the proportion which we have found sufficient is Less than five-tenths would be too little to be effective, and more than five percent would increase the cost of the article Without corresponding benents.

A metal reenforcement of any suitable form is desirable but not essential. A steel rod for this purpose is indicated at 13 in Fig. 2 of the drawmg.

Referring now to the method of making the refractories, the sand and the zinc or lead oxide are rst mixed in any suitable type of mixer until they are thoroughly blended. The sodium silicate and the Water are then added and the mixing is continued until the entire batch has become uniform. The mold is then coated with some suitable material, as for instance lycopodium, toform a good parting surface. The mixture is placed in the mold and compacted by ramming or otherwise., When the refractory is thus molded, it is placed in anroven and dried by baking it at a fairly high temperature, that is to say at a maximum of 500 F. A somewhat lower maximum is preferred however, say between 375 and 425 F. It should be further understood that somewhat lower temperatures could be used, and the drying time lengthened accordingly, without affecting the quality of the product. The drying should be done in an atmosphere substantially free from carbon monoxide and carbon dioxide, as for instance in an electric oven or in a munie type oven. If a substantial amount of carbon monoxide or carbon dioxide is present the silicate is converted to a carbonate and loses the attributes of a binder, with the result that the article crumbles and has no strength. been found that if the oven temperature exceeds 500 F., and such high temperature is maintained for any considerable period of time, an excessive loss of moisture will result, and the bonding qualities of the silicate will be impaired to a greater or lesser extent. Also, if the refractories are cooled too rapidly they will crack. On the other hand, if they are heated up too rapidly at the beginning of the drying operation, the silicate on the surface will dry and harden very quickly and will retard the escape of water vapor from the interior of the refractory. This may cause bulging and warping. 'We have therefore determined that in the drying operation the oven heat should be increased slowly until a given high It has temperature is reached, and that when the drying is substantially completed the temperature of the refractories should be lowered very gradually preferably until normal room temperature is reached. l

Having thus described our invention, we claim:

1. The method of making refractories which consists in thoroughly commingling sodium silicate solution and an aggregate chemically inert to sodium silicate, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide at a temperature no greater than 500 F.

2. The method of making refractories which consists in thoroughly commingling sodium silicate solution and silica sand, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide at a temperature no greater than 500 F.

3. The method of making refractories which consists in thoroughly commingling an aggregate chemically inert to sodium silicate with a sodium silicate solution having an alkalinity approximating one part of sodium oxide to three and one-fourth parts of silica, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide at a temperature no greater than 500 F.

4. The method of making refractories which consists in thoroughly commingling sodium silicate solution and silica sand, adding moisture to the extent of three-tenths per cent to one per cent of the whole by Weight, compacting the mixture, and drying it in an atmosphere substantially free from carbon monoxide and carbon dioxide.

5. The method of making refractories comprising as ingredients sodium silicate solution, a metal oxide, and an aggregate chemically inert to sodium silicate, the sodium silicate solution being present in a maximum proportion by weight of twenty percent and the metal oxide being present in proportion by weight of approximately fivetenths percent to ve percent, which consists in thoroughly commingling the aggregate with the metal oxide, adding the sodium silicate solution, remixing, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide.

6. The method of making refractories which consists in thoroughly commingling sodium silicate solution and an aggregate chemically inert to sodium silicate, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide.

7. The method of making refractories which consists in thoroughly commingling sodium silicate solution and silica sand, compacting the mixture, .and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide.

8. The method of making refractories which consists in thoroughly commingling an aggregate chemically inert to sodium silicate with a sodium silicate solution having an alkalinity approximating one part of sodium oxide to three and onefourth parts of silica, compacting the mixture, and baking it in an atmosphere substantially free from carbon monoxide and carbon dioxide.

WALTER M. CHARMAN. PHILIP R. WARD.

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