GB2070582A - Refractory Materials - Google Patents

Abstract

A refractory material for steel melts in a casting process comprises 20 to 32% Al2O3; 60 to 70% SiO2, and up to 10% of accompanying oxides. The accompanying oxides at least include CaO and MgO in an amount of at least 1.5%, but may also comprise other oxides such as TiO2, Fe2O3, and Na2O.

Description

SPECIFICATION A Refractory Material for Steel Melts The invention relates to a refractory material for the casting of steel, such as for example runner and trumpet bricks. It relates particularly to a refractory material for steel melts being cast in a bottom casting process.

Hitherto, high-grade abrasion-resistant fireclay bricks have been used for the above purpose, to keep the content of non-metallic endogenous inclusions in the steel as small as possible. The relatively coarse inclusions emanating from the refractory material are often the cause of defects in the steel which result in iarge portions of a melt being rejected or having to be downgraded in quality. More particularly in the casting of aluminium-kilied steel qualities, inclusions of alumina particles as residual products of the deoxidation treatment occur as further causes of defects. These inclusions are particularly unpleasant since they are usually contained in the steel in relatively large clusters.This is due to the fact that the fine Al203 particles first of all separate out from the steel in the runner system, coagulate there, and then are carried along by the throughflowing steel at a point of time during casting, and no longer have any opportunity of separating from the ingot.

The invention seeks to obviate these disadvantages, and enable the production of a cast product with an increased degree of purity.

To this end, the invention provides a refractory material for steel melts in a casting process, having 20 to 32% Al203; 60 to 70% SiO2 and up to 10% of accompanying oxides which comprise CaO and MgO, the total CaO and MgO content being in the range 1.5 to 10%. The accompanying oxides will normally include at least one of TiO2, Fe203, and Na20.

At least a part of the CaO and MgO content may be formed by fine-grained basic blast furnace slag. Alternatively, or additionally, at least a part of the CaO and MgO content may be formed by the admixture of minerals, such as olivine, magnesite, diopside, hornblends and wollastonite.

In any event, the grain size of the CaO and MgO content preferably does not amount to more than 100,us.

The composition of the refractory material according to the invention deliberately aims at achieving a situation wherein under the temperature influence of the steel melt and the impurities carried along in the steel and intensified dissolution of the refractory material occurs. It has been found, surprisingly, that the dissolved constituents of the refractory material together with the deoxidation products contained in the steel over the entire casting process form such a liquid slag phase at the refractory material/steel interface as is suitable for dissolving the deoxidation products and converting them into a consistency and form capable of being separated easily out of the steel, and thus for improving the purity of the steel.

The composition of two refractory materials embodying the invention are set forth hereinafter, by way of example.

Example 1 SiO2 67.0% Al203 22.0% CaO 0.4% MgO 3.0% Remainder: accompanying oxides Softening point 14200C Melting point 14800C Softening under load T05 11 850C T5 12750C Example 2 SiO2 61.0% Awl203 26.0% CaO 6.3% MgO 0.1% Remainder: accompanying oxides Softening point 13800C Melting point 14700C Softening under load T05 11300C T5 122500.

Claims

1. A refractory material for steel melts in a casting process, having 20 to 32% Awl203; 60 to 70% SiO2; and up to 10% of accompanying oxides which comprise CaO and MgO, the total CaO and MgO content being in the range 1.5 to 10%.

2. A material according to Claim 1 wherein the accompanying oxides include at least one of TiO2, Fe203, and Na20.

3. A material according to Claim 1 or Claim 2 wherein at least a part of the CaO and MgO content is formed by fine-grained basic biast furnace slag.

4. A material according to any preceding Claim wherein at least a part of the CaO and MgO content is formed by the admixing of minerals.

5. A material according to Claim 4 wherein the admixed minerals comprise a selection from olivine, magnesite, diopside, hornblends, and wollastonite.

6. A material according to any preceding Claim wherein the grain size of the CaO and MgO content amounts to no more than 100 ,um.

7. A refractory material substantially as described in the Examples herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A Refractory Material for Steel Melts The invention relates to a refractory material for the casting of steel, such as for example runner and trumpet bricks. It relates particularly to a refractory material for steel melts being cast in a bottom casting process. Hitherto, high-grade abrasion-resistant fireclay bricks have been used for the above purpose, to keep the content of non-metallic endogenous inclusions in the steel as small as possible. The relatively coarse inclusions emanating from the refractory material are often the cause of defects in the steel which result in iarge portions of a melt being rejected or having to be downgraded in quality. More particularly in the casting of aluminium-kilied steel qualities, inclusions of alumina particles as residual products of the deoxidation treatment occur as further causes of defects. These inclusions are particularly unpleasant since they are usually contained in the steel in relatively large clusters.This is due to the fact that the fine Al203 particles first of all separate out from the steel in the runner system, coagulate there, and then are carried along by the throughflowing steel at a point of time during casting, and no longer have any opportunity of separating from the ingot. The invention seeks to obviate these disadvantages, and enable the production of a cast product with an increased degree of purity. To this end, the invention provides a refractory material for steel melts in a casting process, having 20 to 32% Al203; 60 to 70% SiO2 and up to 10% of accompanying oxides which comprise CaO and MgO, the total CaO and MgO content being in the range 1.5 to 10%. The accompanying oxides will normally include at least one of TiO2, Fe203, and Na20. At least a part of the CaO and MgO content may be formed by fine-grained basic blast furnace slag. Alternatively, or additionally, at least a part of the CaO and MgO content may be formed by the admixture of minerals, such as olivine, magnesite, diopside, hornblends and wollastonite. In any event, the grain size of the CaO and MgO content preferably does not amount to more than 100,us. The composition of the refractory material according to the invention deliberately aims at achieving a situation wherein under the temperature influence of the steel melt and the impurities carried along in the steel and intensified dissolution of the refractory material occurs. It has been found, surprisingly, that the dissolved constituents of the refractory material together with the deoxidation products contained in the steel over the entire casting process form such a liquid slag phase at the refractory material/steel interface as is suitable for dissolving the deoxidation products and converting them into a consistency and form capable of being separated easily out of the steel, and thus for improving the purity of the steel. The composition of two refractory materials embodying the invention are set forth hereinafter, by way of example. Example 1 SiO2 67.0% Al203 22.0% CaO 0.4% MgO 3.0% Remainder: accompanying oxides Softening point 14200C Melting point 14800C Softening under load T05 11 850C T5 12750C Example 2 SiO2 61.0% Awl203 26.0% CaO 6.3% MgO 0.1% Remainder: accompanying oxides Softening point 13800C Melting point 14700C Softening under load T05 11300C T5 122500. Claims

1. A refractory material for steel melts in a casting process, having 20 to 32% Awl203; 60 to 70% SiO2; and up to 10% of accompanying oxides which comprise CaO and MgO, the total CaO and MgO content being in the range 1.5 to 10%.

2. A material according to Claim 1 wherein the accompanying oxides include at least one of TiO2, Fe203, and Na20.

3. A material according to Claim 1 or Claim 2 wherein at least a part of the CaO and MgO content is formed by fine-grained basic biast furnace slag.

4. A material according to any preceding Claim wherein at least a part of the CaO and MgO content is formed by the admixing of minerals.

5. A material according to Claim 4 wherein the admixed minerals comprise a selection from olivine, magnesite, diopside, hornblends, and wollastonite.

6. A material according to any preceding Claim wherein the grain size of the CaO and MgO content amounts to no more than 100 ,um.

7. A refractory material substantially as described in the Examples herein.