DE2639522C2 - Ceramic veneer - Google Patents

Description

35

The invention relates to a ceramic veneer, which is made of a thin liquid slip by drying and Burning of the slip is established.

The manufacture of such veneers takes place among other things. so that the slip on an endless revolving belt in Applied as evenly as possible, dried on this tape and then in a kiln is burned. A shortcoming of this process is that a large percentage of the veneers produced in this way is unusable because the veneers are uneven and / or bulged at the edges. The object of the invention is the formation of a veneer made from a slip that occurs during firing and during the subsequent Cooling down remains.

A veneer according to the invention is characterized in that it consists of at least two different ones Layers produced with slip are made up of either different degrees of shrinkage during firing and / or ho have different coefficients of thermal expansion in the fired state, and that shrinkage and The expansion coefficients of the individual layers are determined so that the veneer is flat.

In and of itself, there is ^{no reason for a veneer made from an h} 5 uniform slip to shrink unevenly on firing or to expand unevenly on cooling. As has been found, however, the composition of the wet slip layer does not remain uniform when it dries. Slurry consists of fine clay particles and coarser hard particles, such as. B. finely ground chamotte etc. When drying, the coarser particles settle at the bottom, the fine particles stay on top. The shrinkage and expansion coefficients along the height of the layer become uneven, and the veneer deforms during firing and cooling.

The uneven distribution of the slip particles which occurs when a slip layer dries not even with the two layers of the veneer according to the invention, but you can Select additives to the two different slurries so that the mean values of the shrinkage and the Thermal expansion coefficients assume values that deform the veneer in the oven and during Prevent subsequent cooling. Differences in the shrinkage can e.g. B. with otherwise the same Achieve the composition of two slips by using finely ground fireclay for one slip and finely ground fired chamotte is added to the other. More examples are given later named in the description.

The invention is described below with the aid of examples.

example 1

30th

Lower class Upper layer 40% 30% 20% 30% 40% 40%

Hard-fired chamotte
Feldspar

Both layers have different shrinkage rates. Different shrinkage rates of both layers can be can also be achieved by partially replacing the usual hemp fired chamotte with annealed chamotte replaced, e.g. B. with the following composition:

Example 2

Lower class Upper layer volume 30% 30% Hard fire chamotte 15% 30% Fireclay 15% Feldspar 40% 40%

With the specified composition, the lower and upper layers have different shrinkage rates. If you want different coefficients of thermal expansion at the same time, this can be done, for. B. with the following composition can be achieved:

Example 3

Lower class

Upper
layer

Fireclay with high
Coefficient of thermal expansion

30%

15%

30%

26th continuation 39 522 Upper layer Lower class Chamotte with low heat expansion 30% coefficients Fireclay with - high warmth expansion coefficients 40% Feldspar 15% 40%

When composing the layers, the influence of the glaze can also be taken into account it contributes to the deformation of the flat slurry layers.

Claims (5)

Patent claims: 1. Ceramic, from a thin liquid slip by drying and firing the slip manufactured veneer, characterized in that that it consists of at least two different layers made from slip, the either different degrees of shrinkage during firing and / or different coefficients of thermal expansion in the fired state, and that the shrinkage and expansion coefficients of the individual layers are determined so that the veneer is flat. 2. Veneer according to claim 1, characterized in that it consists of a lower layer of 40% clay, 20% hard-fired chamotte and 40% feldspar and an upper layer of 30% clay, 30% hard-fired chamotte and 40% feldspar is made. 3. Veneer according to claim 1, characterized in that it consists of a lower layer of 30% clay, 15% hard-fired chamotte. 15% fired chamotte and 40% feldspar and a top layer of 30% Clay, 30% hard-fired chamotte and 40% feldspar is made. 4. Veneer according to claim 1, characterized in that it consists of a lower layer of 30% clay, 15% chamotte with a high coefficient of thermal expansion, 15% annealed chamotte with a high coefficient of thermal expansion and 40% feldspar and a top layer of 30% clay, 30% chamotte with a low coefficient of thermal expansion and 40% feldspar is made. 5. Veneer according to claim 1, characterized in that either on the topmost slip layer and / or between two slip layers
Glass fleece is placed. one 15th