CA1273963A

CA1273963A - Refractory concrete

Info

Publication number: CA1273963A
Application number: CA000555468A
Authority: CA
Inventors: Harald Boess; Hartmut Heilmann; Klaus Kreuels
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1986-12-30
Filing date: 1987-12-29
Publication date: 1990-09-11
Anticipated expiration: 2007-09-11
Also published as: DE3644666A1; FR2609020A1; BE1003222A4; NL8703163A; FR2609020B1

Abstract

ABSTRACT OF THE DISCLOSURE
This invention is concerned with a refractory concrete based on zircon and aluminous cement. In known refractory con-crete based on zircon and aluminous cement, which is used in particular for manufacturing linings or molded bodies resistant to molten metal, particularly aluminum melts, the high thermal con-ductivity due to the high bulk density is often detrimental. The new refractory concrete should have a lower thermal conductivity with good resistance to molten metal and in particular to aluminum melts. The new refractory concrete contains as a further consti-tuent 10 to 50% by weight, based on the solid constituents, of light refractory materials, particularly expanded vermiculite, expanded perlite, light fireclay and/or mineral fibers.

Description

~27~3 23~43-190 The inven-tion relates to refractory concrete for manufacturing linings or molded bodies resistant to molten metal, in particular aluminum melts, comprising zircon, i.e. zirconium silicate, as the refractory aggregate and aluminous cement as the hydraulic binder.
Refractory concrete based on zircon and aluminous cement is known. If such refractory concrete is used for manufacturing linings or molded bodies resistant to aluminum mel-ts, this refractory concrete should not contain any other silicates or free sio2 if possible, apart from the SiO2 bound in the zircon, since the resistance particularly as against aluminum melts is sharply reduced by such other constituents containing SiO2. Linings or molded bodies manufactured from the known refractory concrete based on zircon and aluminous cement have a high thermal conductivity as a result of their high bulk density caused by the zirconium silicate.
It is the object of ths present invention to provide a refractory concrete for manufacturing linings or molded bodies which are resistant to molten metal, and in particular aluminum melts, and which have a lower thermal conductivity, i.e. better insulating properties.
It was surprisingly found that it is possible to reduce the bulk density of such refractory concrete despite the use of materials of a silicate nature.
The invention therefore relates to refractory concrete of the aforenamed kind, characterized in that it ad~itionally contains 10 - 50% by weight, based on the solid constituents, of ~, ~ 3 light refractory materials.
According to a preferred embodiment, the refractory concrete according to the invention contains as light material vermiculite, perlite, light fireclay and/or mineral fibers. The vermiculite and perlite are used for this invention in their expanded form. The li~ht fireclay is a fireclay which has a low bulk density. Such a light fireclay can be obtained, for example, by mixing fireclay powder and a burn-out material, for example sawdust or cork powder, manufacturing molded bodies, calcining the molded bodies, burning out the burn-out materials and comminuting the obtained light fireclay molded bodies to the desired granulation.
Mineral fibers can also be used as the light materials in refractory concrete according to the invention, i.e. fibers which do not melt the linings or molded bodies manufactured from the refractory concrete according to the invention. Examples of such mineral fibers include rock wool fibers, and also the so-called ceramic fibers, i.e. fibers having an A12O3 content less than or equal to 45% by weight. Ceramic fibers with an A1203 content have, for example, application temperature limits of less than or equal to 1260C.
In accordance with a preferred embodiment the refractory concrete according to the invention contains 30 to 50% by weight, based on the solid constituents, of light refractory materials.
Through this it is possible to keep the bulk density of the linings or molded bodies manufactured from the refractory concrete especially low.
In accordance with a further preferred embodiment the ~ 3 23843-lgo aluminous cement content in the refractory concrete according to the invention amounts to 15 to 25% by weight. ~hese quantities of aluminous cement have proven particularly advantageous in order to satisfactorily introduce the light tnaterials into the refractory concrete, i.e. to avoid separation during processing.
In accordance with a further preferred embodiment the refractory concrete according to the invention contains 40 - 60%
by weight, based on the solid constituents, of zircon, i.e.
zirconium silicate.
In accordance with a further preferred embodiment the zircon contained in the refractory concrete has a grain size such that 40 - 60% by weight is present as so-called "zirconium sand", i.e. with a grain size of 0.09 to 0.5mm, whereas the remaining 60 - 40% by weight of the zircon is present as so-called "zirconium powder", i.e. with a grain size less than or equal to O.O9mm.
This embodiment has the advantage that during processing of the refractory concrete, i.e. with the addition of water, the light materials of a silicate nature contained in the refractory concrete according to the invention are preferably coated not only with the fine constituents of the aluminous cement but also with this very fine zirconium powder so that a particularly good resistance as against molten metal, in particular aluminum melts, is achieved~
The invention is explained in greater detail herebelow on the basis of the following examples and the comparison test.
Example 1 A mixture of 22.5 parts by weight aluminous cement, 17.5 . .

~3~63 23843-190 parts by weight zirconium powder with a grain size less than or equal to O.O9mm, 25 parts by weight zirconium sand with a granulation of 0.09 to 0.5mm and 35 parts by weight light fireclay with a grain size of 0 to Smm is prepared. 100 parts by weig'nt of this dry mixture is mixed with 12 1 of water to refractory concrete and test blocks are manufactured from this prepared refractory concrete. The form work time totalled approximately five hours. It is also to be noted that the processing time of the refractory concrete according to the invention is approximately one hour.
Comparison Test As a comparison, refractory concrete using only aluminous cement and zircon is prepared. The proportion of aluminous cement in the dry mixture totals approximately 18~ by weight, the remainder consists of zirconium sand and zirconium powder in the ratio of the weight 2 : 1. Refractory concrete is likewise prepared from this dry mixture, using 8 1 of water per 100 kg of dry mixture, and shaped into test blocks.
The physical properties of the test blocks obtained are ~0 compiled in the following table:

~2~ 3 O Lr u~ o co O
,~ ~ ~ o o o ~ ,~ o h ~) ~) ~ ~ O ~ t`l ~ r~
O ,_ U

00 ~ ~ ~ ~ ~ O
O ~ CO
~L ~ ~'3 ~ ~ ~) t~ ~ O o O
~e a U U U U U U U U U
O O O O O O O O O
-100 .-100 000 O ~ ~O ~~ ~D CO

U~
O O O O
E~ a~
~ 0 ~ ~
h rl U U --1 U U
U U ~ U tJ

- ~ u Ei ~ U
rl O
~ ~ ~ o o r~ CO
a) ~ ~ ~

U ~> h O
O ~ ~ o~
-- ,, u a U~ ~ O JJ ~
a) u rl h ~3 0 a) ~1 ~
0 ~ U ~ u) a) o z ~1 u u ~
h h X ~ rl U Q~
o a ~ ~
:q O X E~ ~

~LZ73~3~,3 23843-lgO

Example 2 The procedure of Example 1 is repeated, however, expanded vermiculite is used instead of light fireclay.
Test blocks are likewise manufactured frorn this refractory concrete, said blocks having properties comparable to the tes-t blocks of the composition given in Example 1.
Example 3 The procedure of Example 1 is repeated, however, expanded perlite is used instead of the light fireclay of Example 1.
Test blocks are likewise manufactured from this refractory concrete, said blocks having properties comparable to the test blocks of the composition given in Example 1.
Example 4 The procedure of Example 1 is repeated, whereby a mixture containing 15 parts by weight aluminous cement, 35 parts by weight zirconium powder, 30 parts by weight ~irconium sand and 20 parts by weight ceramic fibers with an application temperature limit of 1260C is used.
Test blocks manufactured from this refractory concrete mixture likewise have a low thermal conductivity and yet exhibit good resistance to an aluminum melt.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Refractory concrete for manufacturing linings or molded bodies resistant to molten metal, in particular aluminum melts, comprising zircon as the refractory aggregate and aluminous cement as the hydraulic binder, characterized in that it continues to comprise 10 - 50% by weight, based on the solid constituents, of light refractory materials.

2. Refractory concrete according to claim 1, characterized in that the light refractory material includes vermiculite, perlite, light fireclay and/or mineral fibers.

3. Refractory concrete according to claim 1 or 2, characterized in that it comprises 30 to 50% by weight, based on the solid constituents, of light refractory materials.

4. Refractory concrete according to claim 1, characterized in that it comprises 15 - 25% by weight, based on the solid constituents, of aluminous cement.

5. Refractory concrete according to claim 1, characterized in that it comprises 40 - 60% by weight, based on the solid constituents, of zircon.

6. Refractory concrete according to claim 5, characterized in that the proportion of zircon with a grain size less than or equal to 0.09mm totals 60 - 40% by weight, based on the total amount of zircon present.