Refractory batch, a method for producing an unshaped refractory ceramic product from the batch and an unshaped refractory ceramic product obtained by the method

Abstract

The invention relates to a refractory batch, to a method for producing an unshaped refractory ceramic product from the batch, and to an unshaped refractory ceramic product obtained by said method.

Claims

1. A refractory batch comprising the following components: 1.1 a basic component comprising one or more raw materials based on magnesia; 1.2 a carbon component comprising one or more carbon carriers; 1.3 an aluminum component comprising one or more metallic aluminum carriers; 1.4 an aqueous binder; and 1.5 aluminum sulfate.

2. The refractory batch according to claim 1, wherein the basic component consists of at least 90% by mass of magnesia.

3. The refractory batch according to claim 1, wherein the basic component consists of one or more of the following raw materials based on magnesia: sintered magnesia and fused magnesia.

4. The refractory batch according to claim 1, wherein the basic component is present in a proportion of at least 75% by mass relative to a total mass of the refractory batch.

5. The refractory batch according to claim 1, wherein the aluminum component consists of one or more of the following carriers of metallic aluminum: metallic aluminum and at least one metal alloy comprising aluminum.

6. The refractory batch according to claim 1, wherein the aluminum sulfate is present in a proportion in range from 0.05 to 1.0 % by mass relative to a total mass of the refractory batch.

7. The refractory batch according to claim 1, wherein the aqueous binder is present in a proportion in range from 4.0 to 15.0% by mass relative to total mass of the refractory batch.

8. A method for producing an unshaped refractory ceramic product, comprising the following steps: 9.1 providing a refractory batch, the refractory batch comprises: a basic component comprising one or more raw materials based on magnesia; a carbon component comprising one or more carbon carriers; an aluminum component comprising one or more metallic aluminum carriers; an aqueous binder; and aluminum sulfate; 9.2 providing a vessel for holding a molten steel in a steel treatment plant; 9.3 casting the refractory batch onto a portion of the vessel which comes into contact with the molten steel when the vessel is used in the plant; and 9.4 heating the vessel so that the refractory batch cast on the portion forms an unshaped refractory ceramic product.

9. A product obtained by a method, the method comprising: providing a refractory batch, the refractory batch comprises: a basic component comprising one or more raw materials based on magnesia; a carbon component comprising one or more carbon carriers; an aluminum component comprising one or more metallic aluminum carriers; an aqueous binder; and aluminum sulfate; providing a vessel for holding a molten steel in a steel treatment plant; casting the refractory batch onto a portion of the vessel which comes into contact with the molten steel when the vessel is used in the plant; and heating the vessel so that the batch cast on the portion forms an unshaped refractory ceramic product, wherein the product comprises the following phases: periclase; magnesia spinel; and aluminum oxycarbide.

10. The product according to claim 9, having at least one of the following physical properties: bulk density: 2.55 to 2.70 g/cm.sup.3; open porosity: 16 to 22% by volume; cold bending strength: 0.5 to 5 MPa; cold compressive strength: 15 to 40 MPa; hot bending strength at 1,400 C. in a reducing atmosphere: 5 to 8 MPa; or hot bending strength at 1,500 C. in a reducing atmosphere: 4 to 7 MPa.

Description

EXAMPLE 1

(1) According to an exemplary embodiment of the invention, a batch was provided, which consisted of the following components in the following mass proportions, each related to the total mass of the batch:

(2) A basic component of sintered magnesia: 82% by mass;

(3) a carbon component in the form of microcrystalline graphite: 5.5% by mass;

(4) an aluminum component in the form of an AlSi alloy: 3.8% by mass;

(5) an aqueous binder: 7% by mass;

(6) water-soluble sulfate: 0.5% by mass;

(7) microsilica: 1% by mass; and

(8) dispersant: 0.2% by mass.

(9) The sintered magnesia of the basic component was available in high-purity form with a MgO content of 98.0% by mass, relative to the total mass of the sintered magnesia. In addition, the sintered magnesia had an SiO.sub.2 content of 0.2% by mass and a CaO content of less than 0.9% by mass. The sintered magnesia had a maximum average grain size of 6 mm and over 90% by mass, relative to the total mass of the sintered magnesia, had a grain size of less than 5 mm.

(10) The aluminum component was present in the form of an AlSi alloy, i.e. a metal alloy of aluminum and silicon, consisting of 88% by mass of metallic aluminum and 12% by mass of metallic silicon, each relative to the total mass of the aluminum component.

(11) The aqueous binder consisted of water and polyacrylic acid with a proportion of water of 88% by mass and a proportion of polyacrylic acid of 12% by mass, in each case relative to the total mass of the binder, the polyacrylic acid in turn being present in a concentration of 50% by mass polyacrylic acid to 50% by mass water.

(12) The water-soluble sulfate was present in the form of aluminum sulfate dissolved in the water of the binder.

(13) The dispersant was present in the form of a free-flowing powder based on modified polycarboxylate.

(14) The particle size distribution of these components, determined according to ISO 13320:2009-10, was as shown in Table 1 below:

(15) TABLE-US-00001 TABLE 1 Proportion of d10 d50 d90 component <63 m Component [m] [m] [m] [% by mass] Graphite 2.5 20.5 79.1 82 AlSi alloy 20.8 68.6 130.1 44.4 Aluminum sulfate 24.4 183.1 399.4 20.3 Microsilica 1.3 9.8 141.1 77.0 Dispersant 10.6 44.9 122.0 65.2

(16) The components of the batch were intimately mixed together so that a homogeneous batch was subsequently present. The batch was then used in the form of a castable. For this purpose, the batch was cast onto the portion of a ladle for casting molten steel, which would be in the area of the slag zone of the molten steel when using the ladle. When using the ladle, it was then heated to a temperature of about 1,600 C. During the heating method, the AlSi alloy initially formed aluminum oxycarbides with the carbon component and atmospheric oxygen, which already gave the basic component a certain degree of strength until sintering began. From a temperature of about 1,300 C. onwards, the aluminum also formed magnesia spinel with the magnesia of the basic component. Finally, from a temperature of about 1,450 C., a sinter bond formed between the grains of the basic component. After sintering, an unshaped refractory ceramic product was obtained from the batch, which consisted of the following phases: periclase, magnesia spinel and aluminum oxycarbide for more than 95% by mass, relative to the total mass of the product.

(17) The oxide analysis of the product (XRF) was as follows:

(18) MgO: 89.8% by mass

(19) Al.sub.2O.sub.3: 6.6% by mass

(20) SiO.sub.2: 2.3% by mass

(21) CaO: 0.8% by mass

(22) Fe.sub.2O.sub.3: 0.5% by mass

(23) The loss on ignition was 5.8% by mass (after XRF at 1,050 C. annealing). The carbon content was 5.0% by mass, based on the product without the carbon (according to LECO-C analysis before annealing).

(24) The product was characterized by the following physical properties, determined according to DIN EN ISO 1927-6:2012:

(25) Test values after 110 C. under reducing conditions:

(26) Bulk density: 2.64 g/cm3

(27) Open porosity: 14% by volume

(28) Cold bending strength: 8 MPa

(29) Cold compressive strength: 34 MPa.

(30) The product was also characterised by the following physical properties, determined according to DIN EN ISO 1927-8:2012:

(31) Test values after 1.000 C. under reducing conditions:

(32) Bulk density: 2.60 g/cm.sup.3

(33) Open porosity: 20% by volume

(34) Cold bending strength: 2 MPa.

(35) Cold compressive strength: 20 MPa.

(36) Test values after 1.500 C. under reducing conditions:

(37) Bulk density: 2.57 g/cm.sup.3

(38) Open porosity: 21% by volume

(39) Cold bending strength: 3 MPa

(40) Cold compressive strength: 20 MPa

(41) Hot bending strength (1,400 C., reducing atmosphere): 6.5 MPa

(42) Hot bending strength (1,500 C., reducing atmosphere): 5.5 MPa.

EXAMPLE 2

(43) Within the scope of a second exemplary embodiment, a corrosion test according to the so-called Induction Crucible Furnace Test (ITO test) was carried out to check the corrosion resistance of a product in accordance with the invention.

(44) For this purpose, an exemplary embodiment of a batch V1 according to the invention and a batch V2 according to the state of the art were first produced.

(45) The batch V1 according to the invention consisted of the following components in the following mass proportions, each related to the total mass of the batch:

(46) A basic component of sintered magnesia: 81% by mass;

(47) a carbon component in the form of microcrystalline graphite and soot: 7% by mass;

(48) an aluminum component in the form of an AlSi alloy: 4% by mass; metallic silicon: 0.5% by mass;

(49) an aqueous binder: 7.2% by mass;

(50) water-soluble sulfate: 0.3% by mass.

(51) The batch V2 according to the state of the art consisted of the following components in the following mass proportions, each related to the total mass of the batch:

(52) A basic component of sintered magnesia: 82% by mass;

(53) a carbon component in the form of microcrystalline graphite and soot: 6.5% by mass;

(54) metallic silicon: 2% by mass;

(55) microsilica: 2.5% by mass;

(56) an aqueous binder: 7% by mass.

(57) The sintered magnesia, the aluminum component, the aqueous binder, the water-soluble sulfate and the microsilica were present as shown in example 1.

(58) The components of the batches V1 and V2 were each intimately mixed together, then cast into molds and finally heated to about 1,600 C. after drying.

(59) Products V1 were then obtained from the batch V1 and products V2 from the batch V2.

(60) To test the corrosion resistance of the products V1 and V2, they were used as part of a furnace lining, on which a corrosion test was carried out according to the so-called Induction Crucible Furnace Test (ITO test) as follows: First of all, a furnace was constructed with a refractory lining made of stone segments on the wall side. In the later slag area, the lining was made of stone segments of products V1 and V2. The refractory lining enclosed a circular-cylindrical furnace chamber, in which a suitable circular-cylindrical metal insert (60 kg steel) was placed. The metal insert was heated to 1,700 C. and melted by coils which were guided in a ring around the outside of the lining.

(61) A slag powder (3 kg with the chemical composition according to Table 2; ratio CaO/SiO.sub.2 of 0.7) was added to the molten steel, which melted and formed a slag area with a corrosive slag. The slag reacted in this slag area with the stone segments V1 and V2 and corrosively damaged them. The stone segments were corroded by the slag for a total of about 4 hours, whereby the slag was replenished by 5% by mass fluorspar in each case after 30, 60 and 90 minutes and by 10% fluorspar in each case after 120, 150, 180 and 210 minutes. The lining was then removed and the degree of corrosion was tested on the stone segments V1 and V2, namely the wear depth and the wear surface.

(62) TABLE-US-00002 TABLE 2 Proportion in the slag [% by mass in relation to Component of the slag total mass of slag] SiO.sub.2 42.0 CaO 31.0 Al.sub.2O.sub.3 11.0 Fe.sub.2O.sub.3 10.0 MnO 3.8 MgO 0.8 Others 1.4

(63) Table 3 shows the results of this corrosion test. The wear surface indicates the average value of the maximum cross-sectional area of the corroded areas of the stone segments V1 and V2, while wear depth indicates the average value of the maximum wear depth of the stone segments V1 and V2. As the values in Table 3 show, these values for the stone segments V1 according to the invention are significantly below the values for the stone segments V2 according to the state of the art.

(64) TABLE-US-00003 TABLE 3 Size V1 V2 Wear surface [cm.sup.2] 18.3 34.7 Wear depth [mm] 27.5 44.0