US1944709A - Refractory body and process of manufacturing the same - Google Patents

Description

Patented Jan. 23, 1934 UNITED STATES PATENT OFFICE REFRACTORY BODY AND PROCESS OF MANUFACTURING THE SAME No Drawing. Application December 30, 1930, Serial No. 505,581, and in Germany January 4,

22 Claims. (Cl. 25-156) My invention relates to improvements in refractory bodies and the process of manufacturing the same, and more particularly in refractory blocks or bricks. The object of the improvements is to manufacture bodies which have high resistance against thermic and chemical influences of any type. As is known to those skilled in the art the durability of bodies made from non-plastic compositions such as chamotte, coi-undum, chromite, magnesite, quartzite, and the like largely depends on the character of the grain of the said compositions. Thus for certain purposes substances for diminishing plasticity are used which have a coarse grain, while for other purposes substances are used which have a fine grain. Generally speaking stones having a coarse grain are used wherever the article is subject to considerable differences of temperature, and substances of fine grain are used where the article is subject to chemical attack or to the attack by slag. Substances of fine grain are used for the reason that the density of the article is sup-= posed to be increased, and for further increasing the density it has been proposed to add powdered substances to the composition.

It has heretofore been proposed to make compositions to be burnt into blocks from materials of different grain for reducing the plasticity, and the best composition of matter has been determined according to the Fuller curve.

I have found that by the known methods bodies can be manufactured only in which the porosity is not below a certain minimum, unless the particles are fused together by sintering the granular substances or the binding medium thereof, in which case however the bodies are subject to shrinkage, andtheir refractory property is reduced. By adding more powdered ma-- terial to the composition the porosity has not been reduced, but in some cases it has even been increased. Only when adding a high excess of clay to the material comparatively dense bricks have been produced by means of powdered matter which, however, is objectionable particularly where large size bricks are manufactured. I

have found that it is impossible to manufacture very dense bricks from matter of fine grain, even if the material is composed according to the Fuller curve, and I have discovered that very dense articles are produced when using matter of coarse grain as a base, adding thereto so much matter of finer grain that the said finer grain is able to fill out the interstices between the coarser grains without separating the same from one another, and finally filling out the remaining smallest interstices with very fine matter. Thus the base of the composition consists of coarse grains having practicallyeven size, and having finer grains added thereto, the size and amount of the said finer grains being such that only the interstices between the coarse grains are filled out without separating the same from one another, and in some cases the remaining small interstices are filled out by very fine matter.

Experiments have shown that the thick grains used as a base in the composition and having practically the same size may be disposed so tightly that they take up to or more per cent of the space of the composition. The percentage varies according to the shape of the grains, grains which are more or less round filling out a comparatively large proportion of the space. For further filling out the space I add grains which are so small that they fill the interstices between the irregular coarse grains without however pressing the same apart. Mixtures of grains thus produced are so tight that the non-filled space left between the same and providing pores is comparatively small. If the said small spaces are filled with exceedingly fine filling matter a minimum of a binding medium is needed for producing an exceedingly dense article and binding the grains together. Of course, the components of the composition must be uniformly and homogeneously intermingled, for which purpose very effective mixers or other methods may be used by means of which very homogeneous mixtures are produced.

To the base of the composition-lumps or fragments of larger size may be added. Preferably I use only so much of coarser grains, fragments or lumps in the composition prepared as stated above that, after. uniformly preparing and distributing all the components, in the moulded article the big pieces added to the base material are only embedded in the composition.

All or a part of the coarse grains or the fine grains, or both kinds of grains may consist of materials which when burnt change their volume.

A preferred method of adding the finest particles of the grain or the binding medium or of the grain and the binding medium consists in adding the said particules after blowing the same by means of a current of gas. Thereby a minimum of liquid is needed, because for distributing the fine matter or the binding medium the gas is'used, and the object of the liquid is merely to cause adhesion of the particles. When adding only a minimum of liquid the porosity of the article is reduced to a minimum, because by drying or burning only a slight amount of water escapes from the moulded article.

In addition to the finest powdered particles of the base material and the .binding medium or in addition to the base materialor the binding.

medium fluxing media, mineralizers or the like may be added in a state of finest distribution.

The finest particles or the binding medium may be added in a dry state, or in suspension in water, or in the form of a colloidal solution.

For moulding the composition any known or preferred method may be used. Preferably the composition'is moulded by pressure or by similar methods, for example by heating or ramming, which methods are particularly effective substances which when burnt change their volume.

Eatample.60 parts of chamotte having a grain of from 5 to 7 millimeters are intimately mixed with 10 parts of chamotte having a grain of from 1 to 2 millimeters, to the mixture 30 parts of chamotte of a grain of from 0,1 to.0,2 millimeters are added while continuing the mixing operation. While the matter is being intermingled in the mixer binding media or exceedingly fine matter of the character of chamotte are added in a state of finest distribution, while simultaneously or separately water is sprinkled on the matter.

After being thus prepared the composition is moulded by pressure and burned.

If it is desired to prepare for the burning process, a ceramic. composition having a very high percentage of stable matter and accordingly a particularly low plasticity I prefer to use the method described hereafter.

The prepartion for the burning process of compositions which contain a large proportion of stable matter is difiicult, and special expedients are needed for moulding the same and imparting thereto the density necessary in a high class article. This difiiculty is observed in any ceramic compositions containing a high proportion of stable matter, but particularly in compositions used in the manufacture of refractory bodies.

' I have found that ceramic-compositions of this character may be prepared as follows: The basic components which mainly are in granular form are mixed with the finely atomized binding medium and if desired with other matter, so that a mixture is produced which by itself is not plastic. To the said mixture organic matter is added, and it is moulded under mechanical pressure while heating the same. In a modification of the .method I add organic matter to the mixture and thereafter I mould the same at ordinary temperature. In another modification I do not add organic matter, and I mould the composition at elevated temperature. Finally moulding under pressure may be carried out after heating the composition.

Thus at first the basic matter and the binding Further, the density of the bricks may be varied by using such medium or other finely divided matter are intermingled.

The basic matter such for example as chamotte, corundum, quartzite, magnesite, chromite, and the like used for manufacturing refractory articles is mixed with the binding medium which before has been brought to the finest possible state of distribution. At first the binding medium is ground to an exceedingly fine powder and atomized by means of gas as a distributing medium. The current of dust is carried onto the basic matter such as chamotte, etc. within a mixer. It is immaterial whether a foreign matter as a binding medium or finest matter of even character and origin as the basic matter is used. The matter may be comminuted in a dry state or by means of or in the presence of a liquid, water being preferred as a liquid. In this operation the object of the water is merelyto cause adhesion of the binding medium to the grain of the basic matter. Therefore only an exceedingly small proportion of liquid is needed. In a similar way other substances may be admixed, such as fluxing media, mineralizers, and the like orthe "organic matter to be added to the composition.

I If comminution is effected by means of a liquid, binding media and other substances may be atomized in a state of suspension in water or in the form of a colloidal solution.

By thus intermingling the basic matter, which may be in a ground state or in the form of coarse grain, a thorough mixture of the components is obtained, and it is possible to attain a similar or even a higher effect by means of a-slight amount of binding medium or other matter added to the components, than by means of mixing methods now in use.

In the manufacture of refractory bodies the basic matter will ordinarily be used in the form of coarse grains, and the said grains are provided with an exceedingly thin coat by means of my improved mixing method.

The basic body, binding medium, liquid, and if desired other matter added to the said main components are used in such proportions that a non-plastic moist or half-dry composition is produced. The composition is moulded by mechanical pressure. For more readily and effectively moulding the composition I prefer to add organic matter to the composition before moulding the same. For example I add slight amounts of dextrin, albumen. oil, soap, tar, glutinous matter or the like. Ordinarily high molecular organic matter is added, which preferably is added to the components in the form of an emulsion or solution and preferably together with the binding medium, so that it intermingles with the basic body in a comminuted state. Only slight amounts of such organic matter are needed,

ordinarily from a fraction of 1 per cent to about 2 per cent.

Instead of adding organic matter moulding may be facilitated or made more effective by heating the composition. In this case moulding is effected by mechanical pressure after heating or while heating the composition. Of course, both expedients may be simultaneously carried out.- If heat is used for moulding together with organic substances very small amounts of organic matter are sufficient.

While moulding the composition may be heated to moderate temperature, so that as far as possible none of the components escapes by distillation.

When the composition is prepared in the manner described above, moulding under pressure or by heating results in a very tight assemblage of the individual grains of the composition. Thus for example by applying a pressure of 200 atmospheres and more a very dense and hard moulded body is produced. But the manufacture of'big blocks is still difficult if a minimum of binding medium is used.

By means of my improved mixing method and heating the composition while moulding the same or adding organic matter thereto, the necessary amount of the binding medium is further reduced as compared to methods now in use. For example, in the manufacture of chamotte inlieu of 7 per cent of the binding medium; which heretofore has-been used only about 5 per cent are sufficient, to which binding medium if desired per cent of oil such as a vegetable oil is added. This reduction of the amount of the binding medium is objectionable in the manufacture of big blocks,'because when moulding the same by heating or ramming each blow is transmitted substantially at the same strength through the whole body of the composition. Therefore I prefer to use moulds which practically are not plastic, because otherwise by vibration of the mould and the composition con-.

tained therein the said composition is made loose rather than solidified. Moulds which do not vibrate are obtained by reinforcing the plates of the mould for example by means of T-irons or channel irons. By means of screw or other connections the plates of the mould may be connected with one another and with the base plate. When comparatively light moulds are used the base plate may be fixed to a table of iron, concrete or similar rigid material the weight of which largely exceeds that of the mould, so that vibration is prevented.

I have found that when moulding the compositions made by the methods described above and other compositions which mainly or in part consist of coarse grains ramming is preferably carried out as follows:

I fill only so much of the composition into the mould by means of a ladle or other filling means that the matter to be rammed is not brought under the ram in the form of layers but separately and in the form of individual bodies. The layer to be rammed should not be thicker than the diameter of the coarsest grain of the composition. Thereby each grain is pressed into the layer located below the same, and each individual grain, which is thicker than the layer being rammed, is directly engaged by the ramming tool, whereby the particles are assembled into a tight body in which there are no cavities, hollow spaces and bridges.

Where ceramic compositions containing much stable matter are worked the surface of the moulded article is not sufficiently dense and smooth, which is also the case in articles made by my improved process, so much the more as I use a comparatively small amount of the binding medium. Ordinarily in the manufacture of refractory bodies I use from 2 to 10 per cent binding medium, according to the character of the main components of the composition.

In order to produce a moulded body from coarse components, which has a tight, smooth and plane surface, I coat the surfaces of the moulded body with a solution of an electrolyte or with a liquid adapted to distribute or colloidize the binding medium. The said solution or other liquid .may be applied by spreading the same on the surface by means of a brush, or by sprinkling the liquid on the surface of the body a or immersing the same into the liquid. For example, the solution of an electrolyte, for example alkali carbonate or another alkali salt may be used, or ammonia, humic acid or other known media adapted to render the argile liquid may be used in suitable concentration. By the increase of the volume and the liquation of the binding clay, which may be used as a binding medium, the surfaces are made smooth and plane. The planing medium will be different according to the binding medium used in the manufacture of the bodies. Therefore, in lieu of the electrolyte or in addition thereto protective colloids may be used, such for example as high-molecular organic compounds, such as dextrin, albumen, glutinous matter etc.

When thus rendering the outer coat of the moulded body smooth it is preferred to add minutely powdered matter of a similar or the same composition as the basic body to the finishing liquid. Such finishing liquids in which powdered matter is dissolved in colloidal form or in suspension are adapted to remove any 100 rough or non-plane parts of the surface of the moulded body.

I claim:

1. The herein described method of manufacturing refractory bodies, which consists in first 105 making a composition of a base material in the vform of coarse grains of similar size, grains of smaller size, the size and amount of the said grains of smaller size being such that they are adapted to fill out the interstices between the coarser grains withoutforcing the same apart, matter smaller in size than the said grains of smaller size and having a size such that it is adapted to fill out the interstices between thegrains of larger and smaller size, adding pieces of stable matter larger in size than the said coarse grains, and manufacturing bodies from said composition.

2. The herein described method of manufacturing refractory bodies, which consists in first making a composition of a. base material in the form of coarse grains of similar size, grains of smaller size, the size and amount of the said grains of smaller size being such that they are adapted to fill out the interstices between the coarser grains without forcing the same apart, matter smaller in size than the said grains of smaller size and having a size such that it is adapted to fill out the interstices between the grains of larger-and smaller size, and grains larger in size than the said coarse grains uniformly distributed in the composition, the amount of the said grains larger in size being such that they are only imbedded in the composition, and manufacturing bodies from said composition.

3. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, heating the said composition, and moulding the same under pressure.

4. The herein described method of manufacturing ceramic bodies containing a large propor tion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, and molding the said composition under pressure and at elevated temperature, the said organic matter and binding material being added simultaneously to the composition.

5. The herein described method of manufacturing ceramic bodies containing-a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, and molding the said composition under pressure and at elevated temperature. the pressure applied for molding the composition being exerted by beating or ramming in non-vibratory molds.

6. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, and molding the said composition under pressure and at elevated temperature, said molding under pressure being effected by successively placing layers in the mold which are not thicker than the largest body of the composition and ramming or beating the said successive layers.

7. The herein described method of manufacturing ceramic bodies containing a large proportion of .non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, molding the said composition under pressure and at elevated temperature, and treating the molded body with the solution of an electrolyte.

8. The herein described method of manufacturing ceramic bodies containing 'a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, molding the said composition under pressure and at elevated temperature, and coating the molded body with an electrolyte containing powdered matter similar in character to the basic bodies.

9. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, molding the said composition under pressure and at elevated temperature, and treating the molded body with an electrolyte containing powdered matter differentin character from the said basic body.

10. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, molding the said composition under pressure and at elevated temperature, and treating the molded body by means of a liquid which distributes the binding medium.

11. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition organic matter, molding the said composition under pressure and at elevated temperature, and treating the molded body by means of a liquid adapted to colloidize the binding medium.

12. The herein described method of manufacturing refractory bodies, which consists in first making a composition of a base material in the 1 form of coarse grains of practically the same size and in an essentially greater proportion than pro portions of the other components, of a material comprised of grains of smaller size which fill the interstices between the said coarse grains without forcing said coarse grains apart, and of exceedingly fine matter which fills the still remaining interstices, and manufacturing bodies from said composition.

13. The herein described method of manufacturing exceedingly dense refractory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition and that the interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse and the still remaining interstices with a minimum of a binding medium, and manufacturing bodies fromsaid composition. v

15. The herein described method of manufacturing exceedingly dense refraciory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition and that the interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart and still remaining interstices with exceedingly fine matter and a minimum of a binding medium, and manufacturing bodies from said composition.

16. The herein described method of manufacturing exceedingly dense refraclory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition and that the infersticesbetween the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart and the still remaining interstices with exceedingly fine matter and a minimum of a binding medium, the said coarse grains consisting of a material which changes is volume at burning temperature, and manufacturing bodies from said composition.

17. The herein described method of manufacturing exceedingly dense refractory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition and thatthe interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart and the still remaining. interstices with exceedingly fine matter'and a minimum of a binding medium, the said coarse grains and the said grains of smaller size consisting of a material which changes its volume at burning temperature,

. and manufacturing bodies from said composition.

18. The herein described method of manufacturing exceedingly dense refractory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition, andthat the interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart, and adding to the composition a small quantity of a very fine dry matter similar in character to the said material, filling out the interstices between the said grains of larger and smaller size, and manufacturing bodies from the final composition thus produced.

19. The herein described method of manufacturing exceedingly dense refractory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly.

that they take up more than one half of the space of the composition, and that the interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart, and adding to the composition thus prepared an exceedingly small proportion of a liquid, of a very fine matter similar in character to the said material, and of a powdered material of a character different from the said coarse grains, grains of smaller size and matter, and manufacturing bodies from the final composition thus produced.

20. The herein described method of manufacturing exceedingly dense refractory bodies, which consists in first making a composition of a base material in the form of coarse grains of practically the same size being disposed so tightly that they take up more than one half of the space of the composition, and that the interstices between the said coarse grains are filled with grains of smaller size without forcing the said coarse grains apart, and very fine matter, adding to the composition thus prepared, dry powdered material of character different from the said coarse grains, grains of smaller size and matter, and manufacturing articles from said composition. 4

21. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in mixing basic bodies and a powdered binding medium into a non-plastic composition, adding to the said composition high-molecular organic matter, preferably in a liquid state, heating the said composition, and molding the same under pressure.

22. The herein described method of manufacturing ceramic bodies containing a large proportion of non-plastic matter, which consists in