US1789131A - Refractory article and furnace lining made therefrom - Google Patents

Description

Patented 3m. 13, 1931 UNITED STATES PATENT OFFICE,

RAYMOND c. IBENNEB AND GEORGE J. EASTER, or NIAGARA frALLs, rinw Your.

ASSIGNORS no man CARBORUNDUM comrm, or NIAGARA FALLS, NEW YORK, A

CORPORATION OF PENNSYLVANIA REFRACTORY ARTICLE AND FURNACE LINING MADE THE REFROH No Drawing.

dize or decompose under the influence of furnace gases, and a method for making same. We refer particularly to refractories containing graphite, carbon, silicon carbide, etc.

The object of our invention is to provide refractory articles, which, while made from the same substances as in the past, offer greater resistance to the penetration of furnace gases, particularly at high temperatures and hence do not deteriorate so rapidly.

It is evident that within the limits of the speed of the reaction between the furnace gas or slag and the active constituent of the refractory, the life of the refractory is dependent upon the number and size of the permeable pores, as they permit the penetration of slags and gases, which accelerate the 'destruction of the article. I

It'is recognized in the art that the permeability of a refractory brick may be decreased in two ways. The first consists in closing the pores of the bricks by various means, such as those described in U. S. Patent #1,472,386,

to E. B. Forse. This relief is, however, only..-

temporary and is lost as soon as the original facing glaze of the bricks is destroyed to even the entire article.

a slight extent. The second way comprises the use of mulled grain, i. e., grain from which.

the sharp corners have been removed, so that better packing of particles is achieved with consequentreduction in porosity throughout This method is described in copending application of F. J. Tone, Serial No. 455,716, filed May 26" 1930, for an improvement in low permeable refractory and method of making the same.

We have discovered that in spite of these precautions there is a markedpermeability in bricks as ordinarily made, particularly in the direction perpendicular to that in which ressure is applied informingthe piece. or instance, we have observed the Application filed April 6,

1927; Serial No. 181,602.

followin 'in representative cominercially made re actories (measurements being as described below) r For measuring the permeabilities above, we

the brick and allow it to escape only at the opposite face (the others being sealed by immersion in mercury). The air flow through the specimen is then measured by -a meter in the air line ahead of the brick. In order to compare the value of air flow in one direction with that in the other, it is 'of course necessary to reduce the values to a common basis. sult is secured by multiplying theobserved flow by the thickness and dividing the product by the area and pressure. In this way the permeability is expressed in terms of air flow through a unit cube under unit pressure.

The difiernce in permeability in difier- We have found that the desired reent directions is due to a sort of lamination of the brick. In cut and polished microscopic specimens this lamination is often discernible, particularly in used brick which bination of permanent and temporary bonds,

the plasticity being supplied by the bonds and water. The grains. are of irregular apply air at a known pressure to one face of 5 a pressure is applied, i. e., the brick becomes.

degree, having layers shapes and include many comparatively broad thin pieces. As pressure is applied to these irregular pieces they must either resist it rigidly or twist until they assume a position presenting a broad surface to resist the pressure (the situation being analogous to their arrangement if each were placed on a plate and allowed to come to rest under the influence of gravity). Of course most of them twist, displacing the more plastic bond material from their path and forcing it to flow into positions where there is the minimum pressure on it. In this way a relatively large proportion of broad flat faces become completely or partly perpendicular to the pressure and the corresponding narrow edges are parallel to the pressed face.

This results in the crystals approaching one another more-closely at their sides than in the direction parallel to that in which stratified to a certai in which crystals predominate'separated by layers in which bond predominates. Upon burning, the temporary bond is removed and the permanent bond usually shrinks slightly, thus leaving open pores. between grains. Since the bond occurs in strata it is only natural that the pores should thus be stratified also and greater permeability perpendicular to the direction of pressure results. A

, Heretofore this factor has not been known and brick are commonly pressed on the broad face. This makes the laminations parallel to the broad face and leaves the spaces between them open to entrance from theside or end of the brick which for reasons of structural stability is practically al ways the face exposed in the furnace. Thus the brick is placed so as to offer the greatest opportunity for its destruction by entrance of. slag or oxidizing gases.

Having thus described the underlying I phenomena of our invention and the method of measuring the factors involved, our invention consists in pressing the block in such manner that the minimum permeability is in a direction perpendicular to that face of the block which is exposed in the furnace wall. This may be attained by pressing the piece from the face in question during the in the case of thic er ware, by pressing from both that face and the opposite one.

The blocks are then laid in the furnace lining so that the exposed face-isa face which has been subjected to direct pressure in the forming of the blocks. A furnace lining formed in this'way has a permeability'in: a direction parallel to the opposite faces of greatest area and perpendicular to. the longitudinal axis of theblocks of which it is composed, which'is less than.'75% of ular to the exposed pfocess of manufacture, or

of the other faces.

the permeability in directions at right an gles thereto. y r

In this way advantage is taken of the structural nature of the blocks to give minimum permeability to the exposed surface of the furnace lining. This is of particular importance in a lining which is of an oxidizable nature, such as one formed at least wholly or in part of silicon carbide and a bonding agent.

We claim: a l I A 1. A furnace lining comprised of refractory blocks which have been pressed in"a direction perpendicular to the plane of the exposed faces of the blocks.

2. vA, method of making furnace linings which consists in moulding and pressing refractory mass into a block with the pressure applied in a direction at right angles to the surface of the block adapted to'be exposed, then laying the blocks so that the'exposed faces of the blocks are perpendicular tosurfaces of the blocks which have been subjected to direct pressure' 3. A furnace lining comprised of refractory blocks which have the lowest permeability in a direction perpendicular to the exposed faces of the blocks.

4; A furnace lining comprised of refractory blocks havingaermeability erpendic- V faces of the locks less than ;0% of the permeability parallel to said faces.

I 5. A furnace lining comprising refractory blocks having a permeability perpendicular use to the exposed. face thereof lower than the I permeabilityin a direction parallel to the exposed face and made at least in part of silicon carbide. c

6. A furnace lining comprised of refractory blocks having a permeability perpendicular to their exposed surfaces less than 7 5.0%?

of their permeability in a direction arallel to their exposed faces and made at east in part of sicilon carbide.

7 A furnace lining madeat least in part from blocks of an oxidizable material and having a permeability perpendicular to the exposed faces thereof lower than that in the direction parallel to said exposed faces.

8. A refractory wall made at least in part from blocks of an oxidizable material, said blocks having a permeability perpendicular to the exposed faces thereof less than 75.0% of-the permeability parallel to the said-exposed faces.

- -9. A refractory article composed of bonded grains and having the shape of a brick occursin which the minimum permeability in a direction parallel to the opposite faces of greatest area and perpendicular to .one

10. A refractory article composed of bonded grains of an oxidizable material and hav- 7 ing the Shape of a r k in which t hemini mum permeability occurs in a direction parallel to the opposite faces of greatest area and perpendicular to one of the other faces.

11. A refractory article composed of bonded grains of an oxidizable material and having the shape of a brick in which the permeability in a direction parallel to the opposite faces of greatest area and perpendicular to one of the other faces is less than 75% of the permeability in either of the mutually perpendicular directions.

12. A refractory article composed of bonded silicon carbide grains and having the shape of a brick in which the permeability in a direction parallel to the opposite faces of greatest area and perpendicular to one of the other faces is less than 75% of the permeability in either of the mutually perpendicular directions.

In testimony whereof we have hereunto set our hands.

' RAYMOND C. BENNER. GEORGE J. EASTER.