Batch for production of a refractory product, a process for the production of a refractory product, a refractory product as well as the use of a refractory product

Abstract

The invention concerns a batch for the production of a refractory product, a process for the production of a refractory product, a refractory product as well as the use of a refractory product.

Claims

1. A process for the production of a refractory product, comprising the following steps: providing a batch, the batch comprising: at least 50% by weight of a base component based on alumina in the form of one or more of the following components: fused corundum, sintered corundum or calcined alumina; at least 0.5% by weight of at least one of the following silicate components: at least one silicate component based on aluminium silicate or at least one silicate component based on zirconium silicate; and a carbon component; melting the batch; and cooling the melt, wherein the product, produced by the process, has a density of more than 3.3 g/cm.sup.3, an open porosity of less than 8% by volume, and a content of Al.sub.4C.sub.3 of at most 2% by weight, and further wherein the product comprises the following phases in the following proportions: corundum: 64% to 99.5% by weight; and total weight of SiC, Al.sub.4O.sub.4C, SiAlON, SiCAlON, Al oxynitride: 0.5% to 36% by weight.

2. The process of claim 1, wherein the batch has a carbon component in the form of graphite.

3. The process of claim 1, wherein the refractory product is used as a raw material for the production of another refractory product.

4. The process of claim 1, wherein the produced refractory product has a proportion of carbon in the product of less than 2.4% by weight.

5. The process of claim 1, wherein the produced refractory product is in the form of a solidified melt.

6. A refractory product produced by a process, the process comprising the following steps: providing a batch, the batch comprising: at least 50% by weight of a base component based on alumina in the form of one or more of the following components: fused corundum, sintered corundum or calcined alumina; at least 0.5% by weight of at least one of the following silicate components: at least one silicate component based on aluminium silicate or at least one silicate component based on zirconium silicate; and a carbon component; melting the batch; and cooling the melt, wherein the product, produced by the process, has a density of more than 3.3 g/cm.sup.3, an open porosity of less than 8% by volume, and a content of Al.sub.4C.sub.3 of at most 2% by weight, and further wherein the product comprises the following phases in the following proportions: corundum: 64% to 99.5% by weight; and total weight of SiC, Al.sub.4O.sub.4C, SiAlON, SiCAlON, Al oxynitride: 0.5% to 36% by weight.

7. The refractory product as claimed in claim 6, with a proportion of carbon in the product of less than 2.4% by weight.

8. The refractory product as claimed in claim 6, in the form of a solidified melt.

9. The refractory product as claimed in claim 6, wherein the batch has at least one of the following silicate components: kaolin, metakaolin, fireclay, pyrophyllite, mullite, or zircon.

10. The refractory product as claimed in claim 6, wherein the batch has a carbon component in the form of graphite.

11. The refractory product as claimed in claim 6, wherein the refractory product is used as a raw material for the production of another refractory product.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1-3 are enlarged electron microscopic images of samples of a refractory product.

(2) In the exemplary embodiment, an example of an embodiment of a batch in accordance with the invention is described in more detail.

(3) Firstly, a batch was provided which had the following components in the following proportions by weight: Calcined silica: 90% by weight; Graphite: 5% by weight; Kaolin: 5% by weight.

(4) The calcined silica, which in the exemplary embodiment constituted the base component based on alumina, was of high purity, with a proportion of Al.sub.2O.sub.3 of 99.4% by weight with respect to the weight of the calcined silica. The d.sub.90 value for the grain size was 95 μm.

(5) In the exemplary embodiment, the carbon component was constituted by graphite. The proportion of carbon was 94.61% by weight with respect to the weight of graphite. The d.sub.90 value for the grain size was 500 μm.

(6) Finally in the exemplary embodiment, the silicate component, based on aluminium silicate, was kaolin, wherein the total proportion of Al.sub.2O.sub.3 and SiO.sub.2 was 97.6% by weight with respect to the weight of the kaolin. The d.sub.90 value for the grain size was 17.6 μm.

(7) The chemical composition of the batch was as follows: Al.sub.2O.sub.3: 91.66% by weight; C: 4.73% by weight; SiO.sub.2: 2.96% by weight; Alkali oxides: 0.24% by weight; TiO.sub.2: 0.03% by weight; Fe.sub.2O.sub.3: 0.13% by weight; Others: 0.25% by weight.

(8) The components of the batch were mixed and melted in a crucible in an electric arc furnace at a temperature of more than 2000° C. for a period of approximately 5 hours.

(9) Next, the melt was allowed to cool and solidify in the crucible in order to produce a refractory product in the form of a solidified melt.

(10) The product comprised the following phases in the following proportions: Corundum (Al.sub.2O.sub.3): 95% by weight; Al.sub.4O.sub.4C: 2% by weight; SiC+SiCAlON: 1.8% by weight; Other phases: 1.2% by weight.

(11) The proportion of carbon in the product was 0.78% by weight.

(12) The density of the product was 3.62 g/cm.sup.3.

(13) The open porosity of the product was 4.85% by volume.

(14) The density was determined in accordance with British Standard BS 1902-3.16:1990 with a mercury intrusion pressure for the measurements of 0.52 psia. The open porosity was determined in accordance with British Standard BS 1902-3.16:1990 with a mercury intrusion pressure for the measurements of 0.52 psia and 33000 psia. The proportion of carbon in the product was determined in accordance with DIN EN ISO 21068-2:2008-12.

(15) Polished sections were prepared from this product and enlarged electron microscopic images of these samples were produced from these samples, as shown in FIGS. 1 to 3.

(16) In FIG. 1, the white bar in the bottom right hand corner of the image corresponds to a length of 200 μm. The phase with reference numeral 1 corresponds to Al.sub.2O.sub.3. Reference numeral 2 indicates the non-oxide phases in the form of SiC, Al.sub.4O.sub.4C, SiAlON, SiCAlON and Al oxynitride in particular. The isotropic distribution of the non-oxide phases can clearly be discerned. Finally, reference numeral 3 indicates pores in the microstructure of the product.

(17) In the image of FIG. 2, the white bar in the bottom centre of the image corresponds to a length of 5 μm. Reference numeral 1 indicates the major phase in the form of corundum. The phases indicated with reference numerals 4, 5 and 6 are each non-oxide phases. In this respect, reference numeral 4 indicates a phase in the form of SiXAlON, reference numeral 5 indicates a phase in the form of SiC and reference numeral 6 indicates a mixed non-oxide phase.

(18) In the image of FIG. 3, the white bar in the bottom right hand corner of the image indicates a length of 50 μm. Reference numeral 1 indicates the major phase in the form of corundum, while reference numeral 4 once again indicates a non-oxide phase in the form of SiCAlON and reference numeral 7 indicates a phase in the form of metallic silicon.