US2433430A - Dry press insulating firebrick - Google Patents

Description

Patented Dec. 30, 194'? UNITED STATES creme vastness Glen W. Charles, Mexico, Mm, assigns: to Green Fire Brick Company, Mexico, -Mo.=, a

corporation of Missouri in issing. o l-[sisal amiss an his,

' Serial No. 468,109., Divided and this applieseon October 19, I946, seiiaiiwo. unset 1 Claim. (01. 106-41) tant defects inherent in the manufacture of such T insulating fire brick. by the stifi mud and slop mud methods-heretofore commonly used in the manufacture thereof, such as the necessity for making the brick oversize to alloy for the high degree of shrinkage in drying and burning and to correct the deformation resulting from drying, as well as to minimize the loss resulting from grinding oversized brick "or dobies to correct size and shape. V Such insulating fire; brick'alie of a. light weight porous structure due to the presence in the miii of small particles of sawdust, coke or other combustibles which are burned out in the process of burning the "brick. Because of thelow percentage of clayin such fire brick, it has heretofore been thought necessary totemper the mix to a soft consistency the addit-ion of a large amount of water; and animportant object of the present invention is to reduce the amount of water reduired inthe manufacture of such insulating fire brick. Other objeetsand advantages of the invention will appear hereinafter. I

.The intention consists principally in the use a: plast r er pans; sawdust and fire clay grog in a mix'that has "a dry flbies's consistency and is molde imp 'ieen masks, hymns customary dry press process and'apparatus, although the amount of water in theinix'is larger than is added in the usual drypress process; Thelnv'ention also consistsfin the process, in the proportions "of ing-rediehts iii the mix and in the "sequence of operations hereinafter described and claimed.

Typical examples of insulatingfire brick "for whose manufacture my process is particularly well ad'apt'edare the lighter weight types designated by the American Society for Testing Ma'- terials arelBOOf F. and 2000 F. types 'that is, suit able fbr use'attnbse temperatures; The approxi mate mix by weight ma ing these two types of brick" by my process is as follows 2' PlasteiotPaxis-(No.'2 molding -Plaste' 11. s 12. 8 Sawdust (dry basis). v a, l7. 4 18. 1

including substantialampunt of nes. Plastic Fire Clay .;.s omefines; Y Y I W 25. 6; 28.1 FireOla'yGrog size 28 mesh, but Including some v "fi ne's. "1. '7;O 7.6 Water 38. 4 '33. 4

The sawdust is shown on the dry basis, but in practice. it is, desirable to mix the water with thesawdust in they portion of about 110 to 120% of water to the sawdust,,before the sawdust is added to the mix. Sawdust from any type :of wood may be used, but hard woods such as oak, walnut orcherryare preferred sources.

The sawdust may be obtained in wet form, as being wetted and weathered in outside storage piles, or water may be added to dry sawdust.

As indicated in the table of ingredients, the sawdust should have a maximum size of approxim'ately 6 mesh and it is desirable to include sub"- s t'a'ntial amounts. of smaller sizes or fines In the tempering operation, the sawdust, the

lil'as tic fi re clay and calcined fire clay (grog) added and water, (either in the sawdust or add [separately to the mix) -aremi xed until a 'iiniforfn mixture is obtained. .The plaster of Paris is then added, and the mixing; continued until a unirdnfrmii; is obtained. if Sumner water was not added to the sawdust originally. it may be necessary to add more water during the mixing 1 permits, A's'abbve'indi'cated, it would bpo'ssibl" to add 'bfth' water in the course """peratioh butiithas to add all or iiiiist of the mixm yoperat n innate one simula ng the action bf, the haiidjin rolling and stirring the mix a can. A munmg or sdueiiiig m ii ls net permissible, 'aii it] would 7 cinnpress the in'iii too m ch andeause the resumes, brick to be too heavy. A properly. t mpered mix, ready for pressing. is frel'at "ely free from ballsor lumps, the present: or which'indicates too'ih uch mining or sque zing ur ng the mixing and temper ng operation-a re-q ires adi'slin'te'gratir'i difiratibii e th" balls and umps.

so ms sass water 'cbht'nt at as as 2,433,430 'i w r what higher than that of usual heavy fire clay mixes for making dry pressed brick, but the consistency of the mix is substantiallythe same as that of the ordinary dry press mix, so that it is possible to form the brick in the conventional 5 manner on a standard type dry pressing machine. The similarity in consistency of the two mixes, notwithstanding the highe water content of my mix, is believed to be accounted for by the high water carrying capacity of the sawdust in the mix; just as in the case of the ordinary use of sawdust in a soft mud hand mold mix, the water content is from 80 to 90 per cent, as compared with the 18 to 23 per cent water content of a soft mud fire clay grog mix without sawdust. The term dry press consistency herein refers not to the actual water content of the mix but to the physical consistency and characteristics of the mix.

In forming the brick in a dry press machine, care must be exercised against the use of excessive pressure, which would cause the brick to pressure crack and to swell on leaving the mold box. In my process, the pressure is in the order of 300-600 pounds per square inch, as compared with the 25 usual pressure in the order of 2000-4000 pounds per square inch in the case of ordinary heavy fire clay mixes which can stand such higher pressure without the formation of pressure cracks or swelling. It is necessary, of course, in the case of my mix, as in the case of ordinary dry press mixes. to have suflicient pressure to satisfactorily fill out the brick to obtain uniform structure and satisfactory bond.

The green brick leaving the dry press have sufficien't strength to permit them to be easily handled. Because of the relatively low water content of the green brick of my process, as compared with green brick of the usual slop mud process, little or no preliminary drying is required before burning. Such partial or total preliminary drying is permissible, but not required, it being feasible to set the brick as they come from the dry press directly into the burning kiln and to do the drying in the preliminary stages of the burning operation.

Green brick of the mix hereinbefore illustrated for the lighter weight types of insulating fire brick are relatively weak during the burning process and considerable deformation and marking will result if the green brick are set more than one or two deep on edge. Because of the low permissible setting height, it is desirable to burn the brick as rapidly as possible, as a matter of economy. Except for the matter of economy, it is not necessary to burn the brick rapidly nor to dry and burn the brick in a single operation in order to obtain a satisfactory final product. The brick can be dried in a separate operation and burned slowly in the conventional manner and still produce a final product of the desired weight and strength, the only objection, as above stated, being the higher cost of manufacture, due to the low permissible setting height of the green brick. 65

A burning schedule requiring seven to ten hours, to reach the firing temperature of 2250 to 2350 Fahrenheit may be used for burning green brick made from the above mix and set one deep. Only eight to ten hours is required to cool the burned brick from burning temperature to approximately room temperature. Insulating fire brick made by the above process have a manufacturing shrinkage (total drying and burning shrinkage) of approximately one-half to three-fourths inch per 7 foot as compared to the manufacturing shrinkage of approximately one and one-half to one and three-fourth inches per foot for insulating fire brick made by the soft mud process. The low manufacturing shrinkage of. the brick made by my process and the setting of the green brick only one deep during the burning operation permit their being manufactured within comparatively small tolerance limits as to size and shape; so that it is necessary to do little, if any, grinding to obtain brick of uniform size. This elimination or reduction of grinding is an important economy feature of my process.

The properties of refractories made as hereinbefore set forth, when tested in accordance with A. S. T. M. Method C93-39T. are as follows:

Weight per Cubic Foot"; 34.7 lbs 40.8 lbs. Modulus of Ruplure Strength 0 77.0.

Pounds per Square Inch. Linear change when reheated 24 0.44% Expanhours at 1550 Fahrenheit. sion. Linear change when reheated 24 0.50% Expanhours at 1950 Fahrenheit. sion.

By making suitable modifications in the proportions of the mixes, the tempering operation and the drying and burning operations, insulating fire brick of heavier and stronger types such, for example, as those used for 2300" and 2600 Fahrenheit service maybe produced. Examples of such mixes follow:

In the case 'of these heavier and stronger brick intended for high temperature use, the sawdust, coal, grog, clay and water are first placed in the pan and mixed for approximately one minute. The plaster of paris is then added and the tempering continued for an additional period of one minute. It is desirable that the mixing and tempering operation be such as to produce a squeezing or mulling action and cause lumping and balling of the mix. It is then necessary to disintegrate the balls and lumps of the mix before pressing. The pressing operation isthe same as that in the case of the light weight brick.

These green brick intended for final high temperature use are much heavier and stronger and may be piled as many as seven courses deep without objectionable deformation or marking. If sawdust alone is used, the same rapid schedule may be followed for burning as in the case of the lower temperature brick, but if coal is used with the sawdust, the burning schedule must be lengthened by as much as six to eight hours because of the longer time required for oxidization of the coal than of sawdust particles and higher temperatures are permissible.

The properties of these higher temperature refractories, when tested in accordance with A. S. T. M. Method C93-39T are as follows:

The hereinbefore described process has the very important advantage of making insulating fire brick of uniform size and shape, thereby minimizing grinding and other sizing operations and minimizing loss due to warpage and shrinkage in burning. The resulting insulating fire brick are fully equal to those produced by the usual stiff mud or slop mud process, if not actually superior thereto.- I have given typical examples of mix, but it will be obvious that variations may be made as required by diiferences in types of clay and the like and I do not wish to be limited to the precise proportions of ingredients hereinbefore set forth.

What I claim is:

The process of making insulating refractories which comprises mixing and tempering to dry press consistency about 15.4 per cent by weight of sawdust, about 9.9 per cent of Missouri bituminous coal, about 29.6 per cent of Georgia Kaolin, about 5 per cent of Georgia Kyanite, about 14.8 per cent of fire clay grog, about 1.3

per cent of plaster of paris and about 24 per cent of water, dry pressing said mix into green brick and burning said green brick.

GLEN W. CHARLES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,743,803 Arensberg Jan. 14, 1930 1,967,311 Kern July 24, 1934 2,318,574 Harter May 4, 1943