Tundish magnesium-calcium dry material for environment-friendly thin-strip cast-rolling short-process steelmaking and preparation method of tundish magnesium-calcium dry material

Abstract

The invention discloses an environment-friendly tundish magnesium-calcium dry material for thin-strip cast-rolling short-process steelmaking, and belongs to the technical field of refractory materials. The invention discloses an environment-friendly tundish magnesium-calcium dry material for thin-strip cast-rolling short-process steelmaking. The tundish magnesium-calcium dry material is prepared from the following raw materials in percentage by mass: 44-62.5% of magnesia aggregate, 22.5-24% of dolomite aggregate, 11-28% of magnesia fine powder and 3-5% of a binding agent, the binding agent is silica sol modified by a phosphate esterification aluminic acid ester coupling agent. The preparation method comprises the following specific steps: putting magnesia fine powder, a binding agent, magnesia aggregate and dolomite aggregate into a V-shaped mixing mill, uniformly stirring for 5 minutes, putting the stirred mixture into a mold, ramming, vibrating and molding to obtain a molded green body, curing at room temperature for 24 hours, demolding, drying at 200 DEG C for 24 hours, and carrying out heat treatment in an air atmosphere to obtain a dry material sample. According to the invention, the binding agent with good compatibility with a matrix is prepared by improving the binding agent, so that the binding agent can play a reinforcing role.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refractory materials, and particularly relates to an environment-friendly magnesium-calcium dry material for a tundish for thin strip casting and rolling short-process steelmaking and a preparation method thereof. BACKGROUND

[0002] The steel industry is an important pillar industry of the national economy in China, and the steel industry in China has rapidly risen. With the continuous progress of steelmaking process technology in China, the requirements for refractory materials for steelmaking are becoming more and more demanding. Thin strip casting and rolling is a near-net shape manufacturing technology that directly casts and rolls molten steel into thin strip, directly casts thin strip billets with a thickness of less than 15 mm, and directly cold-rolls the thin strip billets into strip without hot rolling. The core of thin strip casting and rolling is to integrate the continuous casting and rolling processes. In the thin strip continuous casting production process, the tundish, as one of the key equipment in the continuous casting process of molten steel, plays a crucial role, and its performance directly affects the molten steel temperature stability and the quality of the cast billet.

[0003] The tundish dry material mainly has magnesium and magnesium-calcium, and the raw materials used mainly include various types of magnesia and magnesia-calcia. The binder mainly includes phenolic resin, boric acid, and boric anhydride, etc. The additives include alumina micro powder, spinel powder, and polyphosphate, etc. The tundish dry material forms a dense working layer in the form of "sintered bonding", and has excellent resistance to the erosion, corrosion, and penetration of molten steel and slag, so the service life of the working layer of the dry material is relatively long.

[0004] The dry material binder mainly makes the material have a certain density and strength through solidification and carbonization of the binder during low-temperature and medium-temperature baking; and when used at high temperature, the binder undergoes chemical reactions to make the material have a strength meeting the use requirements. The binder includes low-temperature binder and medium-temperature binder, and the former mainly plays a shaping role. The low-temperature binder widely used at present is mainly phenolic resin. When used, the tundish is baked at low temperature, the phenolic resin gradually solidifies, the dry material obtains the ideal strength, and the tundish is easily demolded. When the temperature continues to rise, the solidified resin will decompose, release gas, and leave fixed carbon, and the residual carbon will cause the carbon pickup of molten steel, especially low-carbon steel. In addition, the irritating gas released by the phenolic resin during heating will also cause harm to the construction personnel and the environment. At the same time, the hydrogen pickup of molten steel caused by this type of binder is also an important problem. Moreover, the phenolic resin has a relatively high price, which will increase the production cost.

[0005] Patent CN102659430B provides a silicon sol combined magnesium tundish preform and a manufacturing method thereof. The patent uses silicon sol as a binder to obtain a tundish preform with excellent thermal shock resistance, which can meet the demand of higher continuous casting of the tundish, but the compatibility between the silicon sol and other components still has deficiencies, which weakens the strength of the silicon sol. SUMMARY

[0006] The present application aims to provide an environmentally friendly magnesium-calcium dry material for a tundish of a thin strip casting and rolling short process steelmaking and a preparation method thereof, so as to solve the problem of the poor compatibility between the silica sol and other components in the background art and weaken the effect of the silica sol.

[0007] The object of the present application can be achieved by the following technical solutions.

[0008] In a first aspect, the present application provides an environmentally friendly magnesium-calcium dry material for a tundish of a thin strip casting and rolling short process steelmaking, which is composed of the following raw materials in mass percentage:

[0009] 44-62.5% of magnesia aggregate, 22.5-24% of dolomite aggregate, 11-28% of magnesia fine powder, and 3-5% of a binding agent.

[0010] The binding agent is a silica sol modified by a phosphate esterized aluminate coupling agent.

[0011] Further, the magnesia aggregate is fused magnesia with a MgO content of ≥97%, and the particle size distribution of the magnesia aggregate is as follows: 5-3mm accounts for 11.5-35% of the magnesia aggregate, 3-1mm accounts for 25-41% of the magnesia aggregate, and 1-0.088mm accounts for 24-63% of the magnesia aggregate.

[0012] Further, the dolomite aggregate is light-burned dolomite with a CaO content of ≥32%, a MgO content of ≥56%, and a loss on ignition of 7-10%, and the particle size distribution of the dolomite aggregate is as follows: 3-1mm accounts for 0-29% of the dolomite aggregate, and 1-0.088mm accounts for 71-100% of the dolomite aggregate.

[0013] Further, the magnesia fine powder is fused magnesia fine powder with a MgO content of ≥97% and a particle size of ≤0.064mm.

[0014] Further, the preparation method of the binding agent is as follows:

[0015] The silica sol is added to deionized water and stirred uniformly, heated to 70-80℃, and then the phosphate esterized aluminate coupling agent is added, and the stirring and heat preservation reaction is continued for 30-50min, and then the filter is extracted, and dried to obtain the binding agent.

[0016] The amount ratio of the silica sol, deionized water, and phosphate esterized aluminate coupling agent is 2g:10-12mL:0.01-0.03g.

[0017] The hydroxyl groups on the surface of the silica sol react with the phosphate esterized aluminate coupling agent, so that the phosphate esterized aluminate coupling agent is coated on the surface of the silica sol, and the binding agent is obtained.

[0018] Further, the silica sol is an alkaline silica sol with a pH value of 8-11, a density of 1.15-1.38 g / cm 3 , a SiO2 content of 10-40%, and a SiO2 particle size of 5-40 nm.

[0019] Further, the preparation method of the phosphate esterified aluminic acid ester coupling agent is as follows:

[0020] 1) mixing polyethylene glycol and aluminum isopropoxide at a temperature of 80-90 DEG C to obtain a first mixture; dissolving stearic acid at a temperature of 70 DEG C and then adding the stearic acid into the first mixture at a dropping speed of 3 g / min, controlling the temperature at 100 DEG C, and stirring at a constant temperature until the reaction is completed to obtain a first reaction product;

[0021] wherein the mass ratio of the polyethylene glycol, the aluminum isopropoxide and the stearic acid is (22-26):(9-11):35.

[0022] 2) adding polyethylene wax into the first reaction product obtained in step 1) at a temperature of 80 DEG C to obtain a second mixture; adding ethanolamine phosphate into the second mixture to react, controlling the temperature at 120 DEG C, and continuing to stir for 10-20 min until cooling to obtain the phosphate esterified aluminic acid ester coupling agent.

[0023] wherein the mass ratio of the polyethylene wax and the ethanolamine phosphate is 25:(3-5).

[0024] In step 1), the polyethylene glycol as a chain structure can form a preliminary organic-inorganic composite structure with the aluminum isopropoxide to provide a basis for the subsequent reaction of the stearic acid, and then the carboxyl group of the stearic acid reacts with the aluminum atom of the aluminum isopropoxide to form a stable aluminic acid ester structure.

[0025] In the second aspect, the application provides a preparation method of an environment-friendly magnesium-calcium dry material for a tundish of a thin strip casting and rolling short process steelmaking, which comprises the following steps:

[0026] mixing the magnesium sand fine powder, the binder, the magnesium sand aggregate and the dolomite aggregate in a V-shaped mixing mill to stir uniformly for 5 min, placing the stirred mixture in a mold to be vibrated and formed to obtain a formed body, demolding after room temperature curing for 24 h, drying at 200 DEG C for 24 h, and obtaining a dry material sample after heat treatment in an air atmosphere.

[0027] Further, the temperature of the heat treatment is 1500-1700 DEG C, and the time is 2-4 h.

[0028] The application has the following beneficial effects:

[0029] 1. After the silica sol is modified with the phosphated aluminate coupling agent obtained in the present invention, the dispersibility of the silica sol is improved and the degree of agglomeration of the silica sol in the system is reduced. This helps the silica sol to play its role as a binder and improves the compressive strength and other properties of the dry material.

[0030] 2. The phosphated aluminate coupling agent of the present invention is hydrolyzed to generate Al-OH, which condenses with the Si-OH of the silica sol to effectively form a Si-O-Al hybrid network. This structure is not easily decomposed at high temperatures (the operating temperature of the tundish), can resist bond breakage caused by thermal shock, significantly improves the high-temperature stability of the binder, avoids the problem of high-temperature carbonization failure of traditional organic binders, and thus improves the overall performance of the material at high temperatures.

[0031] 3. The phosphated aluminate coupling agent of the present invention contains phosphate groups, which can combine with metal cations in magnesia aggregate, dolomite aggregate or magnesia fine powder, thereby improving the dispersibility of the binder in the matrix, making the binder more evenly spread on the aggregate surface, forming a continuous interface transition layer; avoiding the "interface voids" or "weak bonding areas" caused by uneven dispersion of traditional binders, and significantly improving the room temperature compressive strength and high temperature compressive strength of the dry material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 This is the surface morphology of the dry material samples of Examples 1-4 of the present invention after sintering at 1600° C. for 3 h in air atmosphere;

[0034] Figure 2 This is a photo of the working layer after use in the steel plant of Example 5 of the present invention. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0036] The average molecular weight of the polyethylene glycol in the present invention is 400.

[0037] Preparation Example 1

[0038] The preparation method of the binder is:

[0039] Add 2 g of silica sol to 12 mL of deionized water, stir evenly, heat to 75°C, add 0.01 g of phosphate aluminate coupling agent, continue stirring and keep warm for 40 minutes, then filter and dry to obtain a binder.

[0040] Silica sol is alkaline silica sol with the following specifications: pH 9, density 1.24g / cm 3SiO2 content 25%, SiO2 particle size 30 nm.

[0041] The preparation method of the phosphate esterified aluminic acid ester coupling agent is:

[0042] 1) 22 g of polyethylene glycol and 9 g of aluminum isopropoxide are mixed under stirring at a temperature of 85°C to obtain a first mixture; 35 g of stearic acid is dissolved at a temperature of 70°C and then added to the first mixture at a dropping speed of 3 g / min, the temperature is controlled at 100°C, and constant temperature stirring is carried out until the reaction is completed to obtain a first reaction product;

[0043] 2) polyethylene wax is added to the first reaction product obtained in step 1) under the condition of 80°C, and stirring is carried out to obtain a second mixture; ethanolamine phosphate is added to the second mixture and stirring reaction is carried out, the temperature is controlled at 120°C, and stirring is carried out until cooling, and a phosphate esterified aluminic acid ester coupling agent is obtained.

[0044] 2) 25 g of polyethylene wax is added to the first reaction product obtained in step 1) under the condition of 80°C, and stirring is carried out to obtain a second mixture; 3 g of ethanolamine phosphate is added to the second mixture and stirring reaction is carried out, the temperature is controlled at 120°C, and stirring is carried out for 15 min and then continues until cooling, and a phosphate esterified aluminic acid ester coupling agent is obtained.

[0045] Preparation Example 2

[0046] The preparation method of the binder is:

[0047] 2 g of silica sol is added to 12 mL of deionized water, stirring is uniformly carried out, the temperature is raised to 75°C, 0.03 g of phosphate esterified aluminic acid ester coupling agent is added, stirring and reaction are continuously carried out and the temperature is kept for 40 min, and then suction filtration and drying are carried out to obtain a binder.

[0048] The silica sol is an alkaline silica sol, and the specifications are: pH value 9, density 1.24 g / cm 3 SiO2 content 25%, SiO2 particle size 30 nm.

[0049] The preparation method of the phosphate esterified aluminic acid ester coupling agent is:

[0050] 1) 22 g of polyethylene glycol and 9 g of aluminum isopropoxide are mixed under stirring at a temperature of 85°C to obtain a first mixture; 35 g of stearic acid is dissolved at a temperature of 70°C and then added to the first mixture at a dropping speed of 3 g / min, the temperature is controlled at 100°C, and constant temperature stirring is carried out until the reaction is completed to obtain a first reaction product;

[0051] 2) polyethylene wax is added to the first reaction product obtained in step 1) under the condition of 80°C, and stirring is carried out to obtain a second mixture; ethanolamine phosphate is added to the second mixture and stirring reaction is carried out, the temperature is controlled at 120°C, and stirring is carried out until cooling, and a phosphate esterified aluminic acid ester coupling agent is obtained.

[0052] 2) 25 g polyethylene wax was added into the first reactant prepared in step 1) under the environment of 80℃, and stirred to obtain a second mixture; 5 g ethanolamine phosphate was added into the second mixture and stirred to react, the temperature was controlled at 120℃, and after stirring for 15 min, the stirring was continued until cooling, to obtain the phosphate aluminate coupling agent.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Preparation Example 1 is that the phosphate aluminated coupling agent is replaced by a commercially available aluminated coupling agent.

[0055] Comparative Example 2

[0056] The binder of this comparative example is silica sol, and the silica sol is an alkaline silica sol with the following specifications: pH value 9, density 1.24 g / cm 3 , SiO2content 25%, and SiO2particle size 30 nm.

[0057] Example 1

[0058] An environment-friendly magnesium-calcium dry mix for a tundish for short-process steelmaking by thin strip casting, which is composed of the following raw materials in percentage by mass: 52% of magnesia aggregate, 23.5% of dolomite aggregate, 21.5% of magnesia fine powder, and 3% of the binder prepared in Preparation Example 1.

[0059] The magnesia aggregate is fused magnesia with MgO content ≥ 97%, and the particle size distribution of the magnesia aggregate is as follows: 5-3 mm accounts for 35% of the magnesia aggregate, 3-1 mm accounts for 41% of the magnesia aggregate, and 1-0.088 mm accounts for 24% of the magnesia aggregate.

[0060] The dolomite aggregate is light-burned dolomite with CaO content ≥ 32%, MgO content ≥ 56%, and loss on ignition 8%, and the particle size distribution of the dolomite aggregate is as follows: 3-1 mm accounts for 29% of the dolomite aggregate, and 1-0.088 mm accounts for 71% of the dolomite aggregate.

[0061] The magnesia fine powder is fused magnesia fine powder with MgO content ≥ 97% and particle size ≤ 0.064 mm.

[0062] The preparation steps are as follows:

[0063] The magnesia fine powder, the binder, the magnesia aggregate, and the dolomite aggregate were placed in a V-type mixing mill and stirred uniformly for 5 min, and then the stirred mixture was placed in a mold and vibrated to form a green body, which was demolded after room temperature curing for 24 h, dried at 200℃ for 24 h, and then heat-treated at 1600℃ for 3 h in air atmosphere to obtain a dry mix sample.

[0064] Example 2

[0065] An environment-friendly magnesium-calcium dry material for tundish of thin strip casting and rolling short process steel making is prepared from the following raw materials in percentage by mass: 51.5% of magnesia aggregate, 23.5% of dolomite aggregate, 21.5% of magnesia fine powder, and 3.5% of the binder prepared in Preparation Example 1.

[0066] The magnesia aggregate is fused magnesia with MgO content ≥ 97%, and the particle size distribution of the magnesia aggregate is: 5-3mm accounting for 35% of the magnesia aggregate, 3-1mm accounting for 41% of the magnesia aggregate, and 1-0.088mm accounting for 24% of the magnesia aggregate.

[0067] The dolomite aggregate is light-burned dolomite with CaO content ≥ 32%, MgO content ≥ 56%, and loss on ignition of 8%, and the particle size distribution of the dolomite aggregate is: 3-1mm accounting for 29% of the dolomite aggregate, and 1-0.088mm accounting for 71% of the dolomite aggregate.

[0068] The magnesia fine powder is fused magnesia fine powder with MgO content ≥ 97% and particle size ≤ 0.064mm.

[0069] The preparation steps are as follows:

[0070] The magnesia fine powder, the binder, the magnesia aggregate, and the dolomite aggregate are uniformly stirred in a V-type mixing mill for 5min, and then the stirred mixture is placed in a mold for ramming and vibration forming to obtain a formed green body, which is demolded after room temperature curing for 24h, dried at 200℃ for 24h, and then heat treated at 1600℃ for 3h in air atmosphere to obtain a dry material sample.

[0071] Example 3

[0072] An environment-friendly magnesium-calcium dry material for tundish of thin strip casting and rolling short process steel making is prepared from the following raw materials in percentage by mass: 51% of magnesia aggregate, 23.5% of dolomite aggregate, 21.5% of magnesia fine powder, and 4% of the binder prepared in Preparation Example 2.

[0073] The magnesia aggregate is fused magnesia with MgO content ≥ 97%, and the particle size distribution of the magnesia aggregate is: 5-3mm accounting for 35% of the magnesia aggregate, 3-1mm accounting for 41% of the magnesia aggregate, and 1-0.088mm accounting for 24% of the magnesia aggregate.

[0074] The dolomite aggregate is light-burned dolomite with CaO content ≥ 32%, MgO content ≥ 56%, and loss on ignition of 8%, and the particle size distribution of the dolomite aggregate is: 3-1mm accounting for 29% of the dolomite aggregate, and 1-0.088mm accounting for 71% of the dolomite aggregate.

[0075] The magnesia fine powder is fused magnesia fine powder with MgO content ≥ 97% and particle size ≤ 0.064mm.

[0076] The preparation steps are as follows:

[0077] The magnesia fine powder, the binder, the magnesia aggregate and the dolomite aggregate are placed in a V-type mixing mill and stirred uniformly for 5 min, the stirred mixture is placed in a mold and vibrated to form a green body, the green body is demolded after room temperature curing for 24 h, dried at 200 DEG C for 24 h, and then heat treated at 1600 DEG C for 3 h in an air atmosphere to obtain a dry mix sample.

[0078] Example 4

[0079] An environment-friendly magnesium-calcium dry mix for a tundish used in thin strip casting and rolling and short process steelmaking is composed of the following raw materials in percentage by mass: 50.5% of magnesia aggregate, 23.5% of dolomite aggregate, 21.5% of magnesia fine powder and 4.5% of the binder prepared in Preparation Example 2.

[0080] The magnesia aggregate is fused magnesia with MgO content ≥97%, and the particle size distribution of the magnesia aggregate is as follows: 5-3 mm accounts for 35% of the magnesia aggregate, 3-1 mm accounts for 41% of the magnesia aggregate, and 1-0.088 mm accounts for 24% of the magnesia aggregate.

[0081] The dolomite aggregate is light-burned dolomite with CaO content ≥32%, MgO content ≥56% and loss on ignition of 8%, and the particle size distribution of the dolomite aggregate is as follows: 3-1 mm accounts for 29% of the dolomite aggregate, and 1-0.088 mm accounts for 71% of the dolomite aggregate.

[0082] The magnesia fine powder is fused magnesia fine powder with MgO content ≥97% and particle size ≤0.064 mm.

[0083] The preparation steps are as follows:

[0084] The magnesia fine powder, the binder, the magnesia aggregate and the dolomite aggregate are placed in a V-type mixing mill and stirred uniformly for 5 min, the stirred mixture is placed in a mold and vibrated to form a green body, the green body is demolded after room temperature curing for 24 h, dried at 200 DEG C for 24 h, and then heat treated at 1600 DEG C for 3 h in an air atmosphere to obtain a dry mix sample.

[0085] Example 5

[0086] An environment-friendly magnesium-calcium dry mix for a tundish used in thin strip casting and rolling and short process steelmaking is composed of the following raw materials in percentage by mass: 50% of magnesia aggregate, 23.5% of dolomite aggregate, 21.5% of magnesia fine powder and 5% of the binder prepared in Preparation Example 2.

[0087] The magnesia aggregate is fused magnesia with MgO content ≥97%, and the particle size distribution of the magnesia aggregate is: 5-3mm, accounting for 35% of the magnesia aggregate, 3-1mm, accounting for 41% of the magnesia aggregate, and 1-0.088mm, accounting for 24% of the magnesia aggregate;

[0088] The dolomite aggregate is light-burned dolomite with CaO content ≥32%, MgO content ≥56%, and loss on ignition of 8%, and the particle size distribution of the dolomite aggregate is: 3-1mm, accounting for 29% of the dolomite aggregate, and 1-0.088mm, accounting for 71% of the dolomite aggregate;

[0089] The magnesia fine powder is fused magnesia fine powder with MgO content ≥97% and particle size ≤0.064mm.

[0090] The preparation steps are:

[0091] The magnesia fine powder, the binder, the magnesia aggregate, and the dolomite aggregate are placed in a V-type mixing mill and stirred uniformly for 5min, the stirred mixture is placed in a mold and vibrated to form a green body, the green body is demolded after room temperature curing for 24h, dried at 200℃ for 24h, and then heat treated at 1600℃ for 3h in an air atmosphere to obtain a dry sample.

[0092] Comparative Example 1

[0093] The only difference between this comparative example and Example 1 is that the binder prepared in Preparation Example 1 is replaced by the binder in Comparative Example 1.

[0094] Comparative Example 2

[0095] The only difference between this comparative example and Example 1 is that the binder prepared in Preparation Example 1 is replaced by the binder in Comparative Example 2.

[0096] Performance tests are performed on Examples 1-5 and Comparative Examples 1 and 2:

[0097] The cold crushing strength after 24h of heat preservation at 200℃ and after 3h of heat treatment at 1600℃ are tested according to GB / T5072-2018;

[0098] The permanent linear change rate after 3h of heat treatment at 1550℃ is tested according to GB / T5988-2022;

[0099] The slag corrosion depth is tested according to GB / T8931-2007 using a static crucible method at 1550℃ for 3h; the test results are shown in Table 1:

[0100] Table 1

[0101] As can be seen from Table 1, the comprehensive performance of the intermediate ladle magnesium-calcium dry material prepared in Examples 1-5 is better than that of Comparative Examples 1 and 2.

[0102] The comprehensive performance of Comparative Example 1 is decreased because it does not contain phosphate groups, which can combine with metal cations in the magnesia aggregate, dolomite aggregate or magnesia fines, thereby improving the dispersibility of the binder in the matrix, making the binder more evenly spread on the aggregate surface to form a continuous interfacial transition layer; avoiding the "interfacial gap" or "weakly bonded area" caused by uneven dispersion of the traditional binder, and significantly improving the cold compressive strength and high-temperature compressive strength of the dry material.

[0103] The comprehensive performance of Comparative Example 2 is decreased because it does not contain phosphate-modified aluminate coupling agent, which can hydrolyze to form Al-OH that condenses with Si-OH of the silica sol to effectively form a Si-O-Al hybrid network. This structure is not easily decomposed at high temperatures (intermediate ladle working temperature) and can resist bond breakage caused by thermal shock, significantly improving the high-temperature stability of the binder, avoiding the problem of carbonization failure of traditional organic binders at high temperatures, and thereby improving the comprehensive performance of the material at high temperatures. After the phosphate-modified aluminate coupling agent modifies the silica sol, it can form steric hindrance to improve the dispersibility of the silica sol and reduce the degree of agglomeration of the silica sol in the system. This is conducive to the silica sol playing its role as a binder and improving the compressive strength of the dry material.

[0104] Figure 1 The apparent morphology of the dry material samples of Examples 1-4 after being fired at 1600℃ for 3h in an air atmosphere was observed. Figure 1 It can be seen that the dry material samples do not undergo large deformation after heat treatment, have a small linear change rate, are easy to turn over, and meet the conditions for use in a steel plant.

[0105] Figure 2 The working layer after use of Example 5 is shown in the photo, with a residual thickness of 85mm. From the condition of the permanent layer after use and the residual condition of the casting surface, it can be seen that the use is normal and easy to turn over.

[0106] The above disclosure is only a few specific embodiments of the present application, but the embodiments of the present application are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the scope of the present application.

Claims

1. An environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting, characterized in that: It is composed of the following raw materials in the following mass percentages: 44-62.5% magnesia aggregate, 22.5-24% dolomite aggregate, 11-28% magnesia fines, 3-5% binder; The binder is silica sol modified by a phosphated aluminate coupling agent.

2. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 1, characterized in that: The magnesia aggregate is fused magnesia with MgO content of ≥97%. The particle gradation of the magnesia aggregate is as follows: 5-3 mm accounts for 11.5-35% of the magnesia aggregate, 3-1 mm accounts for 25-41% of the magnesia aggregate, and 1-0.088 mm accounts for 24-63% of the magnesia aggregate.

3. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 1, characterized in that: The dolomite aggregate is lightly burned dolomite with a CaO content of ≥32%, a MgO content of ≥56%, and a loss on ignition of 7-10%. The particle size distribution of the dolomite aggregate is as follows: particles of 3-1 mm account for 0-29% of the dolomite aggregate, and particles of 1-0.088 mm account for 71-100% of the dolomite aggregate.

4. The environmentally friendly magnesium-calcium dry material for tundish for short-process steelmaking of thin strip casting according to claim 1, characterized in that: The magnesia fine powder is fused magnesia fine powder with a MgO content of ≥97% and a particle size of ≤0.064 mm.

5. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 1, characterized in that: The preparation method of the binder is: Add silica sol into deionized water, stir evenly, heat to 70-80°C, add phosphated aluminate coupling agent, continue stirring and keep warm for 30-50 minutes, then filter and dry to obtain a binder.

6. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 5, characterized in that: The dosage ratio of silica sol, deionized water, and phosphated aluminate coupling agent is 2g:10-12mL:0.01-0.03g; The silica sol is alkaline silica sol with the following specifications: pH value 8-11, density 1.15-1.38 g / cm 3 , SiO2 content is 10-40%, and SiO2 particle size is 5-40nm.

7. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 5, characterized in that: The preparation method of the phosphated aluminate coupling agent is: 1) polyethylene glycol and aluminum isopropoxide are stirred and mixed at a temperature of 80-90° C. to obtain a first mixture; stearic acid is dissolved at a temperature of 70° C. and added dropwise to the first mixture at a rate of 3 g / min, the temperature is controlled at 100° C., and the mixture is stirred at a constant temperature until the reaction is complete to obtain a first reactant; 2) adding polyethylene wax to the first reactant prepared in step 1) at 80° C. and stirring to obtain a second mixture; adding ethanolamine phosphate to the second mixture and stirring to react at 120° C. for 10-20 minutes and then continuing to stir until cooled to obtain a phosphated aluminate coupling agent.

8. The environmentally friendly magnesium-calcium dry material for tundish used in short-process steelmaking of thin strip casting according to claim 7, characterized in that: In step 1), the mass ratio of polyethylene glycol, aluminum isopropoxide, and stearic acid is (22-26): (9-11): 35; In step 2), the mass ratio of polyethylene wax to ethanolamine phosphate is 25:(3-5).

9. A method for preparing an environmentally friendly tundish magnesium-calcium dry material for short-process steelmaking using thin strip casting, used for preparing the tundish magnesium-calcium dry material according to any one of claims 1 to 8, characterized in that: The following steps are involved: Magnesia fine powder, binder, magnesia aggregate and dolomite aggregate are placed in a V-type mixer and stirred evenly for 5 minutes. The stirred mixture is placed in a mold and rammed and vibrated to obtain a molded body. The molded body is cured at room temperature for 24 hours, dried at 200°C for 24 hours, and heat treated in an air atmosphere to obtain a dry material sample.

10. The method for preparing an environmentally friendly magnesium-calcium dry material for tundish for short-process steelmaking of thin strip casting according to claim 9, characterized in that: The heat treatment temperature is 1500-1700° C. and the time is 2-4 hours.

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