Scouring-resistant semi-dry-process magnesian gunning mix as well as preparation method and application thereof

Abstract

The invention discloses a fast-sintering scouring-resistant semi-dry-process magnesian gunning mix, a preparation method thereof and application of the gunning mix in repair of a furnace lining or an RH insert tube, and relates to the technical field of refractory materials for metallurgy. The magnesium gunning mix comprises the following raw materials in percentage by mass: 88%-96% of magnesia, 0.5%-2% of quick lime, 1.5%-5% of slaked lime, 0.1%-3% of sodium metaaluminate, 1.5%-4% of sodium polyphosphate and 0.1%-0.3% of organic fibers. The fast-sintering scouring-resistant semi-dry process magnesian gunning mix solves the problem that the service life of the gunning mix is short due to the fact that the gunning mix is low in adhesive rate, poor in high-temperature scouring resistance and long in binding time of a binding agent, and the magnesian gunning mix has the advantages of being high in adhesive force, long in adhesive duration, good in high-temperature resistance, slag corrosion resistance and high-temperature scouring resistance and long in service life.

Description

Technical Field

[0001] The invention relates to the technical field of refractory materials for metallurgy, and in particular to an erosion-resistant semi-dry magnesia gunning material and a preparation method and application thereof. Background Art

[0002] Magnesium gunning material is used for the maintenance of converter linings and RH inserts in metallurgical furnaces. This maintenance method uses a semi-dry method, which uses compressed air to force the gunning material into a spray gun. Water is added to the gun discharge port to moisten the material, creating a certain degree of adhesion before it is directly sprayed onto the area to be repaired. With the development of the metallurgical industry, the smelting pace continues to accelerate, and the gunning and sintering time continues to shorten, requiring further improvement in the performance of the gunning material.

[0003] Currently, magnesium gunning materials have the following problems: 1) After the gunning material is wetted with water, it is immediately gunned to the area to be repaired. The temperature in the area to be repaired is usually above 800°C, and the free water evaporates immediately. The plasticizer in the gunning material has too short a contact time with water, and the plasticizing and bonding effect is limited, resulting in a low gunning material adhesion rate and serious waste. 2) Some gunning materials contain plasticizers based on silica, such as clay or silica powder. These plasticizers react with magnesium oxide in magnesia at high temperatures to produce olivine-phase low-melting products, significantly reducing high-temperature erosion resistance. 3) Some magnesium gunning materials use polysodium phosphate as a binder. After the polysodium phosphate reacts with water, it reacts with magnesium oxide to form polyphosphates, which produce bonding strength. The bonding strength is low in the short term, and the reaction time needs to be shortened to quickly improve the bonding strength. These problems can lead to a short service life and frequent gunning repairs when magnesium gunning materials are used to repair furnace linings. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned technology, the purpose of the present invention is to provide a scour-resistant semi-dry magnesium gunning material and its preparation method and application, so as to solve the problems of low adhesion rate of gunning material, poor high-temperature scour resistance, and long binding time of binder resulting in short service life of gunning material.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: The invention discloses an erosion-resistant semi-dry magnesium gunning material, which is special in that the raw materials of the magnesium gunning material include magnesia, quicklime, slaked lime and sodium metaaluminate.

[0006] As a preferred embodiment, the magnesium gunning material further includes sodium polyphosphate and organic fiber; the mass percentages of each raw material in the magnesium gunning material are as follows: 88% to 96% magnesia, 0.5% to 2% quicklime, 1.5% to 5% slaked lime, 0.1% to 3% sodium metaaluminate, 1.5% to 4% sodium polyphosphate, and 0.1% to 0.3% organic fiber.

[0007] As a preferred solution, the magnesia includes one or both of fused magnesia and sintered magnesia.

[0008] As a preferred embodiment, the polysodium phosphate includes one or both of sodium tripolyphosphate and sodium hexametaphosphate.

[0009] As a preferred solution, the organic fiber is polypropylene fiber.

[0010] As a preferred embodiment, the magnesium oxide content of the magnesia is ≥90%, and the particle size is ≤5mm; the CaO content of the quicklime is ≥90%, the activity is ≥280ml, and the particle size is 0.1~0.5mm; the Ca(OH)2 content of the slaked lime is ≥90%, and the particle size is -100 mesh; the NaAlO2 content of the sodium aluminate is ≥80%, and the particle size is -100 mesh.

[0011] Furthermore, the magnesia gunning material includes the following raw materials in percentage by mass: 45% sintered magnesia, 45% fused magnesia, 1% quicklime, 4% slaked lime, 2% sodium metaaluminate, 2.8% sodium tripolyphosphate, and 0.2% organic fiber.

[0012] As a preferred solution, the compressive strength of the magnesium gunning material under the test conditions of 1550°C×3h is ≥28MPa.

[0013] The special feature of the above-mentioned method for preparing the erosion-resistant semi-dry magnesium gunning material is that it comprises the following steps: mixing the raw materials of the magnesium gunning material according to a set ratio.

[0014] The application of the above-mentioned erosion-resistant semi-dry magnesia gunning material in the repair of furnace lining or RH insert pipe is special in that the raw materials of the magnesia gunning material are mixed and then the furnace lining or RH insert pipe is repaired by the semi-dry method.

[0015] In the present invention, magnesia is used as the main refractory matrix material, providing high fire resistance, high temperature resistance and resistance to slag erosion. Magnesia forms a stable structure at high temperatures, ensuring the material's resistance to erosion and thermal shock.

[0016] The quicklime particle size of the present invention is 0.1-0.5 mm, and the added amount is no more than 2%, which can effectively prevent the gunning material from collapsing due to excessive volume expansion in a short time caused by excessive lime reaction.

[0017] In the present invention, slaked lime serves as a slow-release calcium source, which can adjust the alkalinity and reaction rate of the system, avoid shrinkage and cracking caused by the intense heat release of quicklime, and synergistically optimize the bonding performance with quicklime to improve the structural stability after construction.

[0018] This invention utilizes a combination of quicklime and slaked lime, effectively utilizing the quick reaction of quicklime with water to quickly generate Ca(OH)2 crystals, which quickly adhere to the repaired area and compensate for defects and cracks. Slaked lime itself possesses a certain degree of gelling activity and good volume stability, providing excellent and sustained adhesion. When added to the magnesium gunning mix, it achieves rapid sintering and continuously enhanced adhesion. Furthermore, the Ca(OH)2 produced by the quicklime and slaked lime combination reacts with magnesia (MgO) at high temperatures with slag to form high-melting-point calcium-magnesium olivine (CaMgSiO4) and magnesium rhodonite (Ca3Mg(SiO4)2), enhancing high-temperature resistance and resistance to slag erosion.

[0019] The sodium metaaluminate in this invention rapidly hydrates upon contact with water to form a viscous solution, significantly improving the gunning material's adhesion and reducing rebound. At operating temperatures above 1000°C, sodium metaaluminate rapidly reacts with magnesium oxide to form high-temperature spinel phases, such as magnesium aluminate. This enhances the sintering strength between gunning material particles and improves the material's high-temperature erosion resistance. At high temperatures, sodium metaaluminate reacts with calcium oxide to form a dense reaction layer, which prevents slag penetration and further improves the gunning material's slag resistance.

[0020] The polysodium phosphate in the present invention can form a phosphate glass phase at high temperature, thereby enhancing the resistance to slag penetration and improving the density of the material.

[0021] The organic fibers in this invention can provide temporary support during the initial drying and sintering phases, reducing shrinkage cracks and improving the plasticity of the gunning mix, ensuring adhesion and structural integrity during spraying. Furthermore, they can form micropores after high-temperature decomposition, alleviating thermal stress.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a fast-sintering, erosion-resistant semi-dry magnesia gunning material, a preparation method thereof, and an application thereof. The magnesia gunning material has strong adhesion, long adhesion duration, high temperature resistance, slag erosion resistance, and high temperature erosion resistance, thereby increasing its service life.

[0023] 1) The present invention utilizes the gelling properties of slaked lime, the adhesion generated by the rapid reaction of quicklime and water, and the viscous liquid formed by the hydration of sodium metaaluminate to significantly improve the adhesion of the product. It does not require the addition of clay, silica powder, or other silica-based plasticizers, thereby reducing the formation of liquid phase at high temperatures in the gunning material and improving the scour resistance of the gunning material.

[0024] 2) The present invention utilizes the adhesion generated by the rapid reaction of quicklime and water and the continuous adhesion of slaked lime. After compounding, it can be quickly adhered and sintered, and the adhesion is continuously enhanced, quickly improving the high-temperature strength and preventing it from being washed away by molten steel.

[0025] 3) The CaO in the quicklime and slaked lime of the present invention, the magnesia (MgO) and the slag in the gunning material can react at high temperature to form calcium forsterite (CaMgSiO4) and magnesium rhodonite (Ca3Mg(SiO4)2), thereby improving the high temperature resistance and resistance to slag erosion.

[0026] 4) In the present invention, the reaction between sodium metaaluminate and magnesium oxide can generate spinel high-temperature phases such as magnesium aluminate, thereby improving the sintering strength between the gunning material particles (compressive strength ≥28 MPa under the test conditions of 1550°C×3h), further improving the high-temperature erosion resistance of the gunning material. DETAILED DESCRIPTION

[0027] In order to better explain the present invention, the main contents of the present invention are further illustrated below in conjunction with specific examples, but the contents of the present invention are not limited to the following examples.

[0028] The raw materials and their contents in the magnesia gunning materials of Examples 1-6 and Comparative Examples 1-6 are shown in Table 1. The method for preparing the fast-sintering, erosion-resistant, semi-dry magnesia gunning material of the present invention comprises mixing the raw materials of the magnesia gunning material in a predetermined ratio. The magnesia gunning materials of the Examples and Comparative Examples were used to repair furnace linings using the semi-dry method. The gunning material performance parameters are shown in Table 2.

[0029] Table 1: Raw materials and proportions of magnesium gunning mix, % The raw materials used in the embodiments and comparative examples are as follows: the magnesium oxide content of magnesia is ≥90%, and the particle size is ≤5 mm; the CaO content of quicklime is ≥90%, the activity is ≥280 ml, and the particle size is 0.1-0.5 mm; the Ca(OH)2 content of slaked lime is ≥90%, and the particle size is -100 mesh; the NaAlO2 content of sodium metaaluminate is ≥80%, and the particle size is -100 mesh; and the organic fiber is polypropylene fiber.

[0030] Table 2: Comparison of performance parameters of magnesium gunning materials It can be seen from Tables 1 and 2 that in Comparative Example 1, no slaked lime and sodium aluminate were added, and clay, silicon powder and other plasticizers based on silicon dioxide were added; in Comparative Example 2, sodium aluminate was not added; in Comparative Example 3, no quicklime, slaked lime and sodium aluminate were added, and magnesium sand, sodium polyphosphate, organic fiber combined with clay and silicon powder and other silicon dioxide-based plasticizers were used to prepare magnesium gunning material; in Comparative Example 4, no quicklime and sodium aluminate were added, and silicon powder was used as a plasticizer; in Comparative Example 5, no quicklime was added, and clay and silicon powder were used as plasticizers; in Comparative Example 6, no slaked lime was added, and clay and silicon powder were used as plasticizers.

[0031] In Comparative Examples 1, 3, 4, 5, and 6, since quicklime and slaked lime were not used at the same time, the effect of compounding quicklime and slaked lime could not be achieved, resulting in low high temperature resistance and slag erosion resistance; Comparative Examples 1 to 4 lack sodium metaaluminate, resulting in low sintering strength of the gunning materials in the comparative examples.

[0032] In summary, the compressive strength and service life of the magnesium gunning materials in Comparative Examples 1 to 6 are relatively low. The maximum compressive strength under the test conditions of 110℃×24h is only 14MPa, and the maximum compressive strength under the test conditions of 1550℃×3h is only 19MPa. The service life is relatively low, only 1 or 2 furnaces.

[0033] In Examples 1 to 6, the quicklime, slaked lime, and sodium metaaluminate of the present invention are combined. The addition of sodium metaaluminate to react with magnesium oxide can generate high-temperature spinel phases such as magnesium aluminate, thereby improving the high-temperature strength between the gunning material particles. No clay or silica powder is added, ensuring the high-temperature strength of the gunning material. Under the test conditions of 110°C × 24h, the compressive strength is a minimum of 16MPa and a maximum of 28MPa. Under the test conditions of 1550°C × 3h, the compressive strength is a minimum of 28MPa and a maximum of 42MPa. The service life is long, ranging from 4 to 6 furnaces. Among them, Example 3 has both high compressive strength and service life, making it the best example.

[0034] In summary, the strength and service life of the magnesium gunning material designed by the present invention are significantly better than those of ordinary magnesium gunning materials.

[0035] The above embodiments are merely preferred examples and are not intended to limit the embodiments of the present invention. In addition to the above embodiments, the present invention has other embodiments. Any technical solution formed by equivalent substitution or equivalent transformation falls within the scope of protection claimed by the present invention.

Claims

1. A scour-resistant semi-dry magnesium gunning material, characterized by: The raw materials of the magnesia gunning material include magnesia, quicklime, slaked lime and sodium metaaluminate.

2. The erosion-resistant semi-dry magnesium gunning material according to claim 1, characterized in that: The magnesium gunning material also includes sodium polyphosphate and organic fiber; the mass percentages of each raw material in the magnesium gunning material are as follows: 88% to 96% magnesia, 0.5% to 2% quicklime, 1.5% to 5% slaked lime, 0.1% to 3% sodium metaaluminate, 1.5% to 4% sodium polyphosphate, and 0.1% to 0.3% organic fiber.

3. The erosion-resistant semi-dry magnesium gunning material according to claim 1, characterized in that: The magnesia includes one or both of fused magnesia and sintered magnesia.

4. The erosion-resistant semi-dry magnesium gunning material according to claim 2, characterized in that: The polysodium phosphate includes one or both of sodium tripolyphosphate and sodium hexametaphosphate.

5. The erosion-resistant semi-dry magnesium gunning material according to claim 2, characterized in that: The organic fiber is polypropylene fiber.

6. The erosion-resistant semi-dry magnesium gunning material according to any one of claims 1 to 5, characterized in that: The magnesium oxide content of the magnesia is ≥90%, and the particle size is ≤5mm; the CaO content of the quicklime is ≥90%, the activity is ≥280ml, and the particle size is 0.1~0.5mm; the Ca(OH)2 content of the slaked lime is ≥90%, and the particle size is -100 mesh; the NaAlO2 content of the sodium aluminate is ≥80%, and the particle size is -100 mesh.

7. The erosion-resistant semi-dry magnesium gunning material according to claim 6, characterized in that: The magnesia gunning material includes the following raw materials in percentage by mass: 45% sintered magnesia, 45% fused magnesia, 1% quicklime, 4% slaked lime, 2% sodium metaaluminate, 2.8% sodium tripolyphosphate, and 0.2% organic fiber.

8. The erosion-resistant semi-dry magnesium gunning material according to claim 6, characterized in that: The compressive strength of the magnesium gunning material under the test conditions of 1550°C×3h is ≥28MPa.

9. The method for preparing the erosion-resistant semi-dry magnesium gunning material according to any one of claims 1 to 8, characterized in that: The following steps are involved: The raw materials of the magnesium gunning material are mixed according to a set ratio.

10. Use of the erosion-resistant semi-dry magnesia gunning material according to any one of claims 1 to 8 in repairing furnace linings or RH insertion pipes, characterized in that: After the raw materials of the magnesia gunning material are mixed according to a set ratio, the furnace lining or the RH insertion pipe is repaired by a semi-dry method.

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