Casting refractory material composition and method of manufacture

Abstract

The invention discloses a method for manufacturing accessories in a steel tundish by using a basic refractory material. The method comprises the steps of preparing, mixing, die filling and forming. In the mixing step, the dead burnt magnesia, the olivine sand and the binder prepared in the preparation step are mixed according to a specific proportion to obtain the castable refractory material composition. In the step of die filling, the castable refractory material composition and water are mixed according to a specific proportion and filled into a die for forming. And finally, the molding steps are demolding and drying to obtain the refractory material unit.

Description

Technical Field

[0001] The present invention relates to a castable refractory composition, a molded refractory unit, a sintered refractory unit and related manufacturing methods and uses, and in particular to a method for manufacturing accessories in a steel tundish using basic refractory materials. Background Art

[0002] As we all know, the steel tundish is an indispensable and important container in the continuous casting process of molten steel. The steel tundish is mainly used to stabilize the flow of molten steel, realize the diversion and ensure the uninterrupted continuous casting of molten steel. Usually, a refractory unit, such as a slag retaining wall, is provided in the steel tundish. The function of the refractory unit is to even out the temperature of the molten steel, change the flow direction of the molten steel, and facilitate the floating, collision and aggregation of inclusions, thereby reducing the inclusions mixed into the billet, bloom or slab, thereby improving the cleanliness of the molten steel. Since the refractory unit needs to be immersed in high-temperature molten steel for a long time, it must have good load-bearing capacity and corrosion resistance.

[0003] At present, the common refractory units are mainly made of aluminosilicate. However, after actual use, it was found that the aluminosilicate units are easily corroded by the slag in the steel tundish, so that the aluminosilicate units are easily formed into inclusions and mixed into the cast steel (for example, billets, blooms or slabs) during operation. This causes the aluminosilicate units to contaminate the molten steel, resulting in the defect of poor cleanliness of the molten steel. When the aluminosilicate units are directly eroded by high-temperature molten steel and strong thermal stress, they are more likely to deform, perforate, crack or collapse, which really needs to be improved. Summary of the invention

[0004] One object of the present invention is to improve the load-bearing capacity and corrosion resistance of a refractory unit. Another object of the present invention is to provide a refractory unit that can effectively absorb impurities such as alumina particles, thereby improving the cleanliness of molten steel.

[0005] Another object is to provide a method for manufacturing steel tundish accessories using basic refractory materials. The method greatly improves the load-bearing capacity and corrosion resistance of the magnesia refractory unit, and the magnesia refractory unit can effectively absorb aluminum, thereby improving the cleanliness of molten steel.

[0006] According to a first aspect, a castable refractory composition comprises 30 to 50 wt% dead-burned magnesia sand, 40 to 60 wt% olivine sand and 2.5 to 10 wt% binder. It should be understood that the total weight of the castable refractory composition does not exceed 100 wt%.

[0007] The castable refractory composition may include 35% to 45% by weight, or 37% to 43% by weight, or 40% to 50% by weight, or 40% to 45% by weight, or 45% to 50% by weight of dead-burned magnesia. Dead-burned magnesia may also be referred to as dead-burned magnesia or dead-burned magnesite (i.e., dead-burned MgO). Dead-burned magnesia may have a purity of not less than about 90% by weight MgO. The particle size of dead-burned magnesia may be not more than 400 meshes, or not more than 200 meshes. The particle size of dead-burned magnesia may be not less than 10 meshes, or not less than 14 meshes.

[0008] The castable refractory composition may include 40% to 50% by weight olivine sand, such as 42% to 48% by weight olivine sand. The particle size of the olivine sand may be no greater than about 10 mm, such as no greater than about 5 mm. The particle size of the olivine sand may be no less than about 500 μm, such as no less than about 1 mm.

[0009] The castable refractory composition may include 2.5% to 7.5% by weight of a binder, or 5% to 10% by weight of a binder. The binder may be a hydraulic binder, a chemical binder, an organic binder, an adhesive binder, or a ceramic binder. The binder may be a cement-based binder or a cement-free binder. The binder may be a magnesium-based binder (e.g., magnesium sulfate or magnesium phosphate), a calcium-based binder (e.g., calcium aluminate), a sodium-based binder (e.g., sodium silicate), a potassium-based binder (e.g., potassium silicate), or an aluminum-based binder (e.g., aluminum phosphate or aluminum sulfate). The binder may be or include a phosphate (e.g., magnesium phosphate or aluminum phosphate), a sulfate (e.g., magnesium sulfate), or a silicate (e.g., potassium silicate or sodium silicate). In some examples, the binder is magnesium sulfate. In some examples, the binder is silica powder. In some examples, the binder includes aluminum sulfate, boric acid, and citric acid.

[0010] The castable refractory composition may include a peptizing agent. The peptizing agent may also be referred to as a dispersant or a deflocculant. When the castable refractory composition is mixed with water during the molding process, the peptizing agent may help break and / or disperse the particles. Therefore, the use of a peptizing agent may effectively break up the micropowder during the mixing process, and the tiny particles may be filled into the pores through the mixing process, thereby reducing the surface pores of the resulting refractory unit. This may not only greatly improve the load-bearing capacity and corrosion resistance of the refractory unit, but may also enable the magnesium refractory unit to effectively absorb aluminum during operation, thereby improving the cleanliness of the molten steel. The peptizing agent may be a sulfate, such as magnesium sulfate, or a phosphate, such as sodium hexametaphosphate. The castable refractory composition may include less than 1% by weight, such as less than 0.5% by weight of a peptizing agent. In some examples, the castable refractory composition includes not less than about 0.01% by weight, such as 0.01% by weight to 1% by weight, or 0.01% by weight to 0.5% by weight of a peptizing agent. In other examples, the castable refractory composition is substantially free of a peptizing agent. For example, the castable refractory composition may include no more than about 0.01 wt %, such as no more than about 0.005 wt %, of a peptizer.

[0011] In some examples, binding agent can serve as peptizing agent. For example, magnesium sulfate can serve as binding agent and peptizing agent. In such examples, only a part of binding agent may serve as peptizing agent. For example, enough part of binding agent can serve as peptizing agent, so it can be considered that the whole composition contains peptizing agent less than 1 weight %.

[0012] The castable refractory composition may include an anti-hydrating agent. The anti-hydrating agent may act to coat the castable refractory composition particles to reduce (e.g., prevent) the absorption of water. In particular, the anti-hydrating agent may reduce the water absorption of MgO. The anti-hydrating agent may be a carboxylic acid (e.g., oleic acid, stearic acid, citric acid, or lactic acid) or a salt thereof. For example, the anti-hydrating agent may be a lactate, such as aluminum lactate. The castable refractory composition may include an anti-hydrating agent of less than 1 wt%, such as less than 0.5 wt%. In some examples, the castable refractory composition includes no less than about 0.01 wt%, such as 0.01 wt% to 1 wt%, or 0.01 wt% to 0.5 wt%. In other examples, the castable refractory composition is substantially free of an anti-hydrating agent. For example, the castable refractory composition includes no more than about 0.01 wt%, such as no more than about 0.005 wt% of an anti-hydrating agent.

[0013] In addition to dead-burned magnesia sand and olivine sand, the castable refractory composition may also include one or more refractory aggregate materials. One or more refractory aggregate materials may include one or more of aluminum oxide, bauxite, spinel, granite, basalt, corundum, clinker, moroite, sillimanite, gibbsite, vermiculite, diatomaceous earth, perlite, etc. For example, one or more refractory aggregate materials may include aluminum oxide, bauxite and / or spinel. Alumina may be reactive aluminum oxide or semi-reactive aluminum oxide. The castable refractory composition may include no more than about 20% by weight or no more than about 10% by weight of the one or more refractory aggregate materials. The castable refractory composition may include no less than about 1% by weight or no less than about 5% by weight of the one or more refractory aggregate materials. The castable refractory composition may include 1% by weight to 20% by weight, such as 1% by weight to 10% by weight or 5% by weight to 10% by weight of the one or more refractory aggregate materials.

[0014] In addition to the above-mentioned peptizing agent and / or anti-hydrating agent, the castable refractory composition can also include one or more additives. For example, the castable refractory composition can include one or more drying aids, such as fibers, such as organic fibers and / or metal fibers, which can be melted, decomposed and / or reacted at a temperature lower than about 150°C or lower than about 100°C. It should be understood that the fiber can contribute to the crack-free heating of the refractory. After the fiber melts and / or decomposes, the pore network can be retained to promote water transmission and evaporation from the refractory (for example, from MgO).

[0015] The aluminum oxide (Al2O3) contained in the castable refractory composition may be less than 10% by weight. The castable refractory composition may include 45 to 75% magnesium oxide (MgO), 25 to 35% silicon dioxide (SiO2), <8% aluminum oxide (Al2O3), <5% iron oxide (Fe2O3) and <1.5% calcium oxide (CaO).

[0016] The castable refractory composition may be a basic (ie alkaline) refractory composition.

[0017] According to a second aspect, a method for manufacturing a refractory material unit includes, in sequence, the steps of preparing, mixing, molding and forming; wherein, in the preparing step, dead-burned magnesia, olivine sand and a binder are provided; in the mixing step, 30 to 50 weight percent of dead-burned magnesia, 40 to 60 weight percent of olivine sand and 2.5 to 10 weight percent of the binder are mixed to obtain a castable refractory material composition; in the molding step, the castable refractory material composition and 5 to 10 weight percent of water are poured into a mold; in the forming step, demolding and drying are performed to obtain a refractory material unit.

[0018] The castable refractory composition may have any of the features described above in relation to the first aspect (eg its components and their relative amounts).

[0019] The mixing step may include uniformly mixing the components together to obtain a castable resistant Fire material composition.

[0020] The drying of the refractory unit can be carried out at a temperature higher than 300° C. After drying, the refractory unit can be sintered. The sintering of the refractory unit can be carried out at a temperature higher than 1300° C.

[0021] The refractory unit may be a refractory unit used in a steelmaking tundish. For example, the refractory unit may be a retaining wall (such as a dam or weir), a flow nozzle or a square brick. The refractory unit may be referred to as a magnesia refractory unit.

[0022] According to the third aspect, the method of manufacturing accessories in a steel tundish using basic refractory materials of the present invention comprises the steps of preparation, mixing, molding and forming in sequence; wherein, in the preparation step, dead-burned magnesia sand, olivine sand, a binder, a peptizing agent and a hydration inhibitor are provided; in the mixing step, 30 wt % to 50 wt % of dead-burned magnesia sand, 40 wt % to 60 wt % of olivine sand, 5 wt % to 10 wt % of a binder, less than 1 wt % of a peptizing agent, and less than 1 wt % of a hydration inhibitor are uniformly mixed to obtain a magnesia castable refractory material, wherein the alumina (Al2O3) contained in the magnesia castable refractory material is less than 10 wt %; in the molding step, a mold is provided, and the above-mentioned magnesia castable refractory material and 5 wt % to 10 wt % of water are poured into the mold for molding; in the molding step, demolding and drying are performed to obtain a magnesia refractory unit.

[0023] In this way, the particles are coated with the anti-hydrating agent, the micropowder is effectively broken up by the peptizing agent during the mixing process, and the tiny particles are filled into the pores through the mixing process, thereby reducing the surface pores of the magnesia refractory unit. This not only greatly improves the bearing capacity and corrosion resistance of the magnesia refractory unit, but also enables the magnesia refractory to effectively absorb aluminum during the operation process, thereby improving the cleanliness of the molten steel.

[0024] According to a fourth aspect, a molded refractory unit obtained or obtainable by the method according to the second aspect or the third aspect is provided. The molded refractory unit may have been dried (i.e. it may be a dried refractory unit), but it is generally not sintered. The molded refractory unit may be used immediately, for example in a tundish for steelmaking.

[0025] According to a fifth aspect, there is provided a sintered refractory unit obtained or obtainable by sintering the moulded refractory unit according to the fourth aspect.The sintered refractory unit may be used immediately, for example in a tundish for steelmaking.

[0026] According to a sixth aspect, there is provided the use of a molded refractory unit according to the fourth aspect or a sintered refractory unit according to the fifth aspect as a refractory fitting, such as a slag retaining wall, in a tundish during steelmaking to improve the cleanliness of molten steel. The use of the molded refractory unit or the sintered refractory unit can improve the cleanliness of molten steel relative to molten steel processed in a tundish using a corresponding refractory unit made of a different refractory composition not according to the present invention. The molded refractory unit or the sintered refractory unit can be used to absorb impurities, such as aluminum oxide, from the steel.

[0027] According to a third aspect, the subject matter listed in the following numbered paragraphs is provided: 1. A method for manufacturing a steel tundish fitting using a basic refractory material, comprising: Preparation steps, providing dead-burned magnesia sand, olivine sand, a binder, a peptizing agent, and an anti-hydration agent; a mixing step, wherein 30 to 50 weight percent of dead-burned magnesia sand, 40 to 60 weight percent of olivine sand, 5 to 10 weight percent of a binder, less than 1 weight percent of a peptizing agent, and less than 1 weight percent of a hydration inhibitor are uniformly mixed to obtain a magnesia castable refractory material, wherein the magnesia castable refractory material contains less than 10 weight percent of alumina (Al2O3), so that the particles are coated with the hydration inhibitor, the fine powder is broken by the peptizing agent during the mixing process, and the tiny particles are filled into the pores through the mixing process, thereby reducing the surface pores; A mold filling step, providing a mold, pouring the magnesium castable refractory material and 5 wt % to 10 wt % of water into the mold for molding; and In the forming step, the mold is demoulded to obtain a magnesium castable refractory material, which is then installed into a steel tundish for use after being allowed to dry. 2. A method for manufacturing accessories for a steel tundish using basic refractory materials according to item 1, wherein the main chemical composition of the magnesia castable refractory material is magnesium oxide (MgO) 45 to 75%, silicon dioxide (SiO2) 25 to 35%, aluminum oxide (Al2O3) <8%, iron oxide (Fe2O3) <5% and calcium oxide (CaO) ≦1.5%. 3. According to the method for manufacturing accessories in a steel tundish using basic refractory materials as described in Item 1, the magnesia refractory material unit can be a retaining wall, a flow nozzle or a square brick.

[0028] The skilled person will appreciate that, unless mutually exclusive, the features described in connection with any one of the above aspects may be applied to any other aspect after necessary modifications. In addition, unless mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic block diagram of a preferred embodiment of the present invention.

[0030] Figure 2 An image showing a magnesia refractory unit according to an exemplary embodiment of the present invention is shown. Detailed description

[0031] The above and other technical contents, features and effects of the present invention will become apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

[0032] like Figure 1 As shown, an exemplary embodiment of the method for manufacturing accessories in a steel tundish 3 with basic refractory materials according to the present invention comprises a preparation step 31, a mixing step 32, a mold loading step 33 and a forming step 34; wherein, in the preparation step 31, dead-burned magnesia sand, olivine sand, a binder, a peptizing agent and an anti-hydrating agent are provided; in the step 32, 49 wt% of dead-burned magnesia sand, 45 wt% of olivine sand, 5 wt% of a binder, less than 1 wt% of a peptizing agent and less than 1 wt% of an anti-hydrating agent are uniformly mixed to obtain 100 wt% of a magnesia castable refractory material, wherein the magnesia castable refractory material contains less than 10 wt% of alumina (Al2O3), so that the chemical composition of the magnesia castable refractory material is 45 to 75% of magnesium oxide (MgO), 25 to 35% of silicon dioxide (SiO2), <8% of aluminum oxide (Al2O3), <5% of ferric oxide (Fe2O3) and ≦1.5% of calcium oxide (CaO).

[0033] Next, in the mold filling step 33, a mold is provided, wherein the shape of the mold can be adjusted according to the shape of the unit to be molded, and then the magnesia castable refractory material obtained in the mixing step 32 is mixed with 6.2 wt% of water and poured into the mold to mix the magnesia castable refractory material with water to form. Finally, in the molding step 34, the mold is demolded, and the magnesia refractory unit is obtained after the mold is taken out.

[0034] The magnesia refractory material unit can be an accessory that needs to be installed in the steel tundish and contacts with molten steel, such as a retaining wall, a nozzle or square bricks, etc. The magnesia refractory material unit can be installed in the steel tundish for use after being dried.

[0035] In an exemplary embodiment of the refractory composition comprising a peptizing agent and an anti-hydration agent, the micropowder (having a d 50) is effectively broken up by the peptizing agent during the mixing process, the particles are completely coated with the anti-hydrating agent, and the tiny particles (particle size of about 0.1 mm) are filled into the pores through the mixing process, thereby reducing the surface pores of the magnesia refractory after molding, so the corrosion resistance of the magnesia refractory unit is greatly improved. In addition, the magnesia refractory unit will not crack after drying, demoulding is smooth, and it has good workability and strength. Moreover, through test evaluation and pre-casting, filling and molding, the mass production of magnesia refractory units can be achieved, thereby further enhancing market competitiveness. In addition, the magnesia refractory unit can be hung and installed after completion and can be used in a very good state.

[0036] After the magnesium refractory material is completed, it is necessary to carry out a fracture test (MOR) and a compression test (CCS). The results show that the fracture test is >7.0N / mm 2 , compression test>30.0N / mm 2 , that is, the magnesia refractory unit has a higher initial strength.

[0037] The crucible test results of the magnesium refractory unit showed that its erosion rate was 2.1% and its permeability was 8.9%. The above results are better than the crucible test results of the conventional aluminosilicate refractory unit (erosion rate 18.9%, permeability 16.1%), indicating that the magnesium refractory unit has better erosion resistance and permeability resistance.

[0038] In the hydration test, the magnesium refractory unit was completely immersed in water, covered, and placed at a constant temperature of 80°C for 240 hours. The results showed that the weight increase rate of the magnesium refractory unit was 2.3%, the fracture test increased by 3.7%, and the compression test increased by 16.4%. After the hydration test, the magnesium refractory unit had no cracks, that is, the magnesium refractory unit had good hydration resistance and was very stable. In addition, after the magnesium refractory unit was dried at 110°C for 24 hours and stored at room temperature for 40 days, there was no significant change in strength. The test results are as follows:

[0039] The enlarged picture of the magnesia refractory unit is as follows: Figure 2 The residual mass composition and composition analysis of the magnesia refractory unit are as follows:

[0040] As can be seen from the above, before use, the magnesia refractory unit initially contains less than 8% by weight of alumina (Al2O3), but the alumina (Al2O3) content in the slag line area and the molten steel area is higher than 8% by weight, which further proves that the magnesia refractory unit can effectively absorb aluminum (Al) during operation and form magnesium aluminum spinel (MgAl2O4), as shown in the aforementioned enlarged figure. In addition, the amount of inclusions added to the billet is greatly reduced, thereby further improving the cleanliness of the molten steel, and the magnesia refractory unit has good corrosion resistance and load-bearing capacity. Moreover, the magnesia refractory unit can effectively reduce the defect rate of steel. Although the cost of magnesia refractory materials is slightly higher, the thickness of the magnesia refractory unit can be reduced, and while maintaining sufficient load-bearing capacity and corrosion resistance, the overall cost can be further reduced, thereby improving market competitiveness.

[0041] In summary, according to the method for manufacturing accessories in a steel tundish with basic refractory materials of the present invention, in the preparation step, dead-burned magnesia sand, olivine sand, a binder, an optional peptizing agent, and an optional anti-hydrating agent are provided; in the mixing step, 30 wt % to 50 wt % of dead-burned magnesia sand, 40 wt % to 60 wt % of olivine sand, 2.5 wt % to 10 wt % such as 5 wt % to 10 wt % of a binder, less than 1 wt % of an optional peptizing agent, and less than 1 wt % of an optional anti-hydrating agent are uniformly mixed to obtain a magnesia castable refractory material, wherein the alumina (Al2O3) contained in the magnesia castable refractory material is less than 10 wt %; in the molding step, a mold is provided, the above-mentioned magnesia castable refractory material and 5 wt % to 10 wt % of water are mixed, and poured into the mold for molding; finally, in the molding step, demolding and drying are performed to obtain a magnesia refractory unit. In this way, the corrosion resistance of the magnesia refractory unit is greatly improved, and the magnesia refractory unit has better load-bearing capacity. At the same time, the magnesia refractory unit can effectively absorb aluminum during operation, thereby further improving the cleanliness of molten steel.

[0042] However, the above description only provides a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All simple equivalent changes and modifications made according to the claims of the present invention and the description of the present invention should still fall within the scope covered by the claims of the present invention. Description of Reference Numerals

[0043] (The present invention) 3: Method for manufacturing accessories in steel tundish using basic refractory materials 31: Preparation steps 32: Mixing step 33: Moulding steps 34: Molding step.

Claims

1. A castable refractory composition comprising 30 to 50 wt % of dead-burned magnesia sand, 40 to 60 wt % of olivine sand and 2.5 to 10 wt % of a binder.

2. The castable refractory composition according to claim 1, wherein the castable refractory composition comprises 5 wt% to 10 wt% of a binder.

3. The castable refractory composition according to claim 1 or claim 2, wherein the castable refractory composition comprises a peptizing agent and / or an anti-hydrating agent, for example, wherein the castable refractory composition comprises less than 1 wt % of the peptizing agent and / or less than 1 wt % of the anti-hydrating agent.

4. The castable refractory composition according to any one of the preceding claims, wherein the castable refractory composition further comprises one or more refractory aggregate materials, such as alumina, bauxite and / or spinel, wherein the castable refractory composition further comprises no more than about 20 wt. % or no more than about 10 wt. % of the one or more refractory aggregate materials.

5. A castable refractory composition according to any one of the preceding claims, wherein the castable refractory composition further comprises one or more drying aids, such as fibres.

6. A method for manufacturing a refractory unit, comprising: a preparation step, wherein dead-burned magnesia sand, olivine sand and a binder are provided; a mixing step, wherein 30 wt % to 50 wt % of the dead-burned magnesia sand, 40 wt % to 60 wt % of the olivine sand and 2.5 wt % to 10 wt % of the binder are mixed to obtain a castable refractory composition; a mold filling step, wherein the castable refractory composition and 5 to 10 weight percent water are poured into the mold; and A molding step, in which the refractory material unit is demolded to remove the refractory material unit from the mold, and the refractory material unit is dried.

7. The method of claim 6, wherein the castable refractory composition comprises 5 to 10 weight percent of a binder.

8. The method according to claim 6 or claim 7, wherein the castable refractory composition comprises a peptizing agent and / or an anti-hydrating agent, for example, wherein the castable refractory composition comprises less than 1 wt % of the peptizing agent and / or less than 1 wt % of the anti-hydrating agent.

9. The method of any one of claims 6 to 8, wherein the castable refractory composition further comprises one or more refractory aggregate materials, such as alumina, bauxite and / or spinel, wherein the castable refractory composition further comprises no more than about 20 wt. % or no more than about 10 wt. % of the one or more refractory aggregate materials.

10. A method according to any one of claims 6 to 9, wherein the castable refractory composition further comprises one or more drying aids, such as fibres.

11. The method according to any one of claims 6 to 10, wherein the aluminum oxide (Al2O3) contained in the castable refractory composition is less than 10% by weight, optionally wherein the castable refractory composition comprises magnesium oxide (MgO) 45 to 75%, silicon dioxide (SiO2) 25 to 35%, aluminum oxide (Al2O3) <8%, iron oxide (Fe2O3) <5% and calcium oxide (CaO) ≦1.5%.

12. The method according to any one of claims 6 to 11, wherein the refractory material unit is a retaining wall, a spout or a square brick.

13. A moulded refractory unit obtained or obtainable according to the method of any one of claims 6 to 12.

14. A sintered refractory unit obtained or obtainable by sintering the moulded refractory unit according to claim 13.

15. Use of a molded refractory unit according to claim 13 or a sintered refractory unit according to claim 14 as a refractory fitting, such as a slag retaining wall, in a tundish during steelmaking to improve the cleanliness of molten steel.

16. A method for manufacturing a steel tundish fitting using a basic refractory material, comprising: A preparation step, wherein dead-burned magnesia sand, olivine sand, a binder, a peptizing agent and a hydration inhibitor are provided; a mixing step, wherein 30 to 50 weight percent of dead-burned magnesia sand, 40 to 60 weight percent of olivine sand, 5 to 10 weight percent of a binder, less than 1 weight percent of a peptizing agent, and less than 1 weight percent of a hydration inhibitor are uniformly mixed to obtain a magnesia castable refractory material, wherein the alumina (Al2O3) contained in the magnesia castable refractory material is less than 10 weight percent, so that the particles are coated with the hydration inhibitor, the fine powder is broken by the peptizing agent during the mixing process, and the tiny particles are filled into the pores through the mixing process, thereby reducing the surface pores; a mold filling step, wherein a mold is provided, and a magnesium castable refractory material and 5 to 10 weight percent of water are poured into the mold for molding; as well as The forming step includes demoulding the mold to obtain a magnesia castable refractory unit, and allowing the magnesia refractory unit to stand and dry for installation in a steel tundish for use.

17. The method for manufacturing fittings in a steel tundish with basic refractory materials according to claim 16, wherein the main chemical composition of the magnesia castable refractory material is magnesium oxide (MgO) 45 to 75%, silicon dioxide (SiO2) 25 to 35%, aluminum oxide (Al2O3) <8%, iron oxide (Fe2O3) <5% and calcium oxide (CaO) ≦1.5%.

18. The method for manufacturing steel tundish accessories using basic refractory materials according to claim 16, wherein: The magnesia refractory material unit may be a retaining wall, a spout or a square brick.

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