Cement-bonding-free iron runner castable reinforced and toughened by multi-scale whiskers and preparation method of cement-bonding-free iron runner castable

Abstract

The invention belongs to the technical field of iron runner castable, and discloses a multi-scale whisker reinforced and toughened cement-free combined iron runner castable and a preparation method of the multi-scale whisker reinforced and toughened cement-free combined iron runner castable. The raw materials of the non-cement-bonded castable for the iron hook comprise high-aluminum aggregate, silicon carbide aggregate, silicon carbide micro powder, aluminum oxide micro powder, a first binding agent, a second binding agent, a carbon source and an antioxidant, and explosion-proof fibers and water are additionally added, the first binding agent is prepared by heating silicon dioxide micro powder, graphite fine powder, polyvinyl alcohol, a silane coupling agent and water to react and then drying, and the second binding agent is prepared by mixing silicon dioxide micro powder, pseudo-boehmite micro powder, boric acid micro powder, acrylamide and aluminum fluoride micro powder. The silicon carbide whisker, the aluminum borate whisker and the mullite whisker are generated in different areas and at different temperatures in the iron runner castable through two binders with different components, so that multi-scale strengthening and toughening as well as improvement of oxidation resistance and erosion resistance are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of trough castables, and particularly relates to a cement-free bonded trough castable reinforced and toughened by multi-scale whiskers and a preparation method thereof. Background Art

[0002] The trough castable for blast furnace tapping is one of the most important materials for blast furnace tapping, and its performance directly affects the tapping volume and service life. With the increase in the volume of large blast furnaces, higher and more stable performance of the trough castable is required. During service, the trough castable is mainly subjected to the scouring and wear of hot molten iron, the erosion and penetration of molten iron slag, and the thermal shock caused by periodic contact with molten iron. Therefore, to prepare a trough castable with stable and excellent performance, it is necessary to improve its bonding strength, erosion resistance, and thermal shock resistance. The binder of traditional trough castables is mainly calcium aluminate cement. The introduction of CaO promotes the formation of low-melting phases, seriously reducing the high-temperature strength, thermal shock resistance, and slag erosion resistance of the castable, resulting in the attenuation of the performance of the trough castable and the reduction of its service life. Therefore, it is necessary to develop a cement-free bonded trough castable. However, the existing cement-free bonding technical solutions have poor anti-burst performance, toughness, oxidation resistance, and erosion resistance, resulting in the lack of large-scale application of cement-free castables.

[0003] CN110937883A discloses a cement-free trough castable. Without adding cement as a binder, on the one hand, the calcium hydroxide generated by the hydration of calcium carbide powder promotes the hardening and strength of the castable, and on the other hand, the anti-slag performance and anti-permeability performance of the trough material are improved by the formation of mullite by SioxX-Zero powder at high temperature. However, the CaO introduced by calcium carbide powder in this invention still has the defect of generating low-melting phases, and the pores generated after hydration reduce the oxidation resistance of the material. The improvement of the anti-slag performance and anti-permeability performance of the trough material by mullite is limited. At the same time, SioxX-Zero powder is relatively expensive and cannot be widely used in trough castables. CN110372342A discloses a cement-free trough castable for a skimmer precast part, adopting a trough castable system combined with pure micro-powders of high-purity silica powder and alumina powder, and using German-produced N990R-type nano-carbon black as a coagulant for the micro-powder-bonded trough castable. Then, the comprehensive performance of the trough castable is synergistically improved by various micro-powders such as silicon nitride powder, boron carbide powder, metal silicon powder, metal aluminum powder, and silicon carbide powder. However, the high-purity silica powder and N990R-type nano-carbon black used in this invention significantly increase the production cost. The use of nearly ten kinds of micro-powders also increases the mixing difficulty, affects the production efficiency, and reduces the practicability of this invention. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide, in view of the deficiencies in the prior art, a cement-free bonded iron runner castable with multi-scale whisker reinforcement and toughening, and a preparation method thereof. By using two binders with different components, silicon carbide whiskers, aluminum borate whiskers, and mullite whiskers are generated in different regions and at different temperatures inside the iron runner castable, thereby achieving multi-scale reinforcement and toughening as well as improving oxidation resistance and erosion resistance.

[0005] To solve the technical problems proposed by the present invention, the present invention provides a cement-free bonded iron runner castable with multi-scale whisker reinforcement and toughening, which comprises raw materials with the following mass percentage contents: 45-53% of high-aluminum aggregate, 15-20% of silicon carbide aggregate, 4-12% of silicon carbide micropowder, 14-18% of alumina micropowder, 2-4% of the first binder, 2-4% of the second binder, 1-4% of carbon source, and 1-3% of antioxidant; and additionally adding 0.1-0.3% of explosion-proof fiber based on the total mass of the above raw materials and 3-5% of water.

[0006] In the above solution, the high-aluminum aggregate is one or more of brown fused alumina, bauxite, and fused white alumina.

[0007] In the above solution, the Al 2 O 3 content of the high-aluminum aggregate is ≥98.0 wt%, and the Fe 2 O 3 content is ≤0.3 wt%.

[0008] In the above solution, the particle size of the high-aluminum aggregate is 1-8 mm.

[0009] Preferably, in the high-aluminum aggregate, the mass ratio of coarse particles with a particle size of 5-8 mm, medium particles with a particle size of 3-5 mm, and fine particles with a particle size of 1-3 mm is (2-3):(1-2):1.

[0010] In the above solution, the SiC content of the silicon carbide aggregate is ≥98.5%, and the particle size is 0.1-1 mm.

[0011] In the above solution, the SiC content of the silicon carbide micropowder is ≥98.5%, and the particle size is ≤0.043 mm.

[0012] In the above solution, the Al 2 O 3 content of the alumina micropowder is ≥98.0%, and the particle size is ≤0.043 mm.

[0013] In the above solution, the carbon source is at least one of artificial graphite, spherical pitch, and graphite electrode powder.

[0014] In the above solution, the particle size of the carbon source is ≤1 mm.

[0015] In the above solution, the antioxidant is at least one of metallic silicon powder and metallic aluminum powder.

[0016] In the above solution, the particle size of the antioxidant ≤ 0.043 mm.

[0017] In the above solution, the explosion-proof fiber is polypropylene fiber, with a diameter of 40 - 80 μm, a length of 5 - 8 mm, and a melting point of 150 ± 5 °C.

[0018] In the above solution, the first binder is prepared by heating and reacting silica fine powder, graphite fine powder, polyvinyl alcohol, silane coupling agent, and water, and then drying.

[0019] Further, the SiO of the silica fine powder in the first binder 2 content ≥ 99.0%, and the particle size ≤ 0.020 mm.

[0020] Further, the C content of the graphite fine powder ≥ 99.5%, and the particle size ≤ 0.020 mm.

[0021] Further, the polyvinyl alcohol is solid, with a viscosity of 3.0 - 4.5 mPa·s.

[0022] Further, the silane coupling agent is one of 3-glycidoxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxyethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0023] Further, the mass ratio of silica fine powder, graphite fine powder, polyvinyl alcohol, silane coupling agent, and water in the first binder is 100:(1 - 8):(3 - 5):(0.1 - 0.5):(100 - 160).

[0024] Preferably, the mass ratio of silica fine powder, graphite fine powder, polyvinyl alcohol, silane coupling agent, and water in the first binder is 100:(2 - 4):(3 - 4):(0.2 - 0.4):(120 - 140).

[0025] Further, the heating temperature of the heating reaction is 40 - 80 °C, and the reaction time is 12 - 24 h.

[0026] Further, the heating reaction is carried out under stirring, and the stirring rate is 1000 - 1200 rpm.

[0027] In the above solution, the second binder is prepared by mixing silica fine powder, pseudo-boehmite fine powder, boric acid fine powder, acrylamide, and aluminum fluoride fine powder.

[0028] Further, the SiO of the silica fine powder in the second binder 2The content is ≥97.5%, and the particle size is ≤0.043 mm.

[0029] Furthermore, the purity of the pseudo-boehmite micropowder is ≥99.9%, and the particle size is ≤90 μm.

[0030] Furthermore, the boric acid micropowder is of analytical purity or higher, and the particle size is ≤0.043 mm.

[0031] Furthermore, the acrylamide is of analytical purity or higher.

[0032] Furthermore, the aluminum fluoride micropowder is of analytical purity or higher, and the particle size is ≤0.043 mm.

[0033] Furthermore, the mass percentage content of each raw material in the second binder is as follows: silica micropowder 35 - 70%, pseudo-boehmite micropowder 25 - 60%, boric acid micropowder 1 - 3%, acrylamide 1 - 3%, aluminum fluoride micropowder 1 - 6%.

[0034] Preferably, the mass percentage content of each raw material in the second binder is as follows: silica micropowder 48 - 60%, pseudo-boehmite micropowder 32 - 45%, boric acid micropowder 1 - 2%, acrylamide 2 - 3%, aluminum fluoride micropowder 2 - 4%.

[0035] The present invention also provides a preparation method of a multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable, comprising the following steps:

[0036] 1) Mix the high-alumina aggregate and the silicon carbide aggregate evenly to obtain an aggregate mixture.

[0037] 2) Add the second binder to the silicon carbide micropowder and the alumina micropowder, and mix evenly to obtain a fine powder mixture.

[0038] 3) Add the first binder to the carbon source and the antioxidant, and mix evenly to obtain a non-oxide mixture.

[0039] 4) After mixing the aggregate mixture, the fine powder mixture, the non-oxide mixture and the explosion-proof fiber evenly, add water and mix evenly again to obtain a multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable.

[0040] In the above scheme, the flow value of the cement-free bonded high-alumina castable is 180 - 200 mm, and the pourable time is 120 - 150 min.

[0041] In the above solution, the room temperature flexural strength of the cement-free bonded high-alumina castable at 110°C × 24 h is 10 - 12 MPa, the room temperature flexural strength at 1100°C × 3 h is 11.5 - 12.5 MPa, the room temperature flexural strength at 1450°C × 3 h is 15.5 - 17 MPa, the high temperature flexural strength at 1450°C × 3 h is 5.5 - 6.5 MPa, and the anti-explosion temperature is 750 - 800°C.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The present invention aims to develop a cement-free bonded trough castable. However, the cement-free bonded trough castable often has deficiencies in strength, toughness, oxidation resistance, and erosion resistance. Therefore, the present invention specifically develops two binders with different components:

[0044] 1) During the preparation process of heating and stirring the first binder, the silane coupling agent improves the bonding force between the silica powder and graphite, and polyvinyl alcohol produces a bridging effect between the combination of the silica powder and graphite, improving the fluidity of the castable. After the first binder is mixed with the carbon source and antioxidant, the intermolecular adsorption and stirring effects can increase the bonding force among the three. At high temperatures, the first binder reacts internally and with the carbon source and antioxidant. Due to the tight combination, it is easier to generate silicon carbide whiskers to fill the pores generated during the oxidation process of the raw materials, improving the density of such non-oxides, thereby preventing further oxidation and enhancing the oxidation resistance and erosion resistance of the castable;

[0045] 2) In the second binder, boric acid improves the pH, promotes acrylamide to play a role in dispersing the silica powder, and at the same time promotes the formation of a bridge between the silica powder and the pseudo-boehmite powder, promoting the mullitization reaction in the castable during heating to be more uniform and rapid, reducing the baking time of the castable, enabling rapid construction, and at the same time improving the medium and high temperature strength, erosion resistance, and anti-explosion performance of the castable; boric acid can also react with the pseudo-boehmite powder at a lower temperature to generate borate whiskers, filling the pores and enhancing toughening at the same time, improving the medium temperature strength of the castable, and boric acid can partially volatilize during the low-temperature baking process to generate fine pores, which is beneficial to the discharge of water, reducing the baking time of the castable and improving the anti-explosion performance of the castable; after the second binder is mixed with the oxide fine powder, aluminum fluoride can react with the silica powder and the second binder to generate mullite whiskers for strengthening and toughening;

[0046] Therefore, the two binders are prepared separately, and at the same time, in combination with the design of other raw materials in the trough castable, the mixing order is controlled to achieve the generation of silicon carbide whiskers, borate whiskers, and mullite whiskers in different regions and at different temperatures, realizing multi-scale strengthening and toughening, and improving the oxidation resistance and erosion resistance. Specific Embodiments

[0047] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments only.

[0048] In the following embodiments, the brown fused alumina used has an Al 2 O 3 ≥ 98.0 wt%, Fe 2 O 3 ≤ 0.3 wt%; the SiC content of the silicon carbide aggregate is ≥ 98.5%, and the particle size is 0.1 - 1 mm; the SiC content of the silicon carbide fine powder is ≥ 98.5%, and the particle size is ≤ 0.043 mm; the Al 2 O 3 content of the alumina fine powder is ≥ 98.0%, and the particle size is ≤ 0.043 mm; the explosion-proof fiber is polypropylene fiber, with a diameter of 40 - 80 μm, a length of 5 - 8 mm, and a melting point of 150 ± 5 °C; the SiO 2 content of the silica fine powder in the first binder is ≥ 99.0%, and the particle size is ≤ 0.020 mm; the C content of the graphite fine powder is ≥ 99.5%, and the particle size is ≤ 0.020 mm; the polyvinyl alcohol is solid, with a viscosity of 3.0 - 4.5 mPa·s; the SiO 2 content of the silica fine powder in the second binder is ≥ 97.5%, and the particle size is ≤ 0.043 mm; the purity of the pseudo-boehmite fine powder is ≥ 99.9%, and the particle size is ≤ 90 μm; the boric acid fine powder is of analytical purity, and the particle size is ≤ 0.043 mm; acrylamide is of analytical purity; the aluminum fluoride fine powder is of analytical purity, and the particle size is ≤ 0.043 mm.

[0049] Example 1

[0050] The multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable of this example includes raw materials with the following mass percentage contents: 50% high-alumina aggregate, 20% silicon carbide aggregate, 6% silicon carbide fine powder, 14% alumina fine powder, 4% first binder, 4% second binder, 1% carbon source (artificial graphite with a particle size ≤ 1 mm), 1% antioxidant (metallic silicon powder with a particle size ≤ 0.043 mm); and additionally 0.2% explosion-proof fiber and 3.5% water based on the total mass of the above raw materials. Among them:

[0051] The high-alumina aggregate is brown fused alumina, with a particle size of 1 - 8 mm, and the mass ratio of the coarse particles with a particle size of 5 - 8 mm, the medium particles with a particle size of 3 - 5 mm, and the fine particles with a particle size of 1 - 3 mm is 2:2:1;

[0052] The first binder consists of silica fine powder, graphite fine powder, polyvinyl alcohol with a viscosity of 3.0, 3-glycidoxypropyltrimethoxysilane CH 2 -CHOCH 2 OC 3 H 6 Si(OMe) 3It is prepared by drying after reacting for 24 h under the conditions of a temperature of 80 °C and a stirring rate of 1200 rpm after mixing with water in a mass ratio of 100:2:4:0.3:130.

[0053] The second binder is prepared by mixing silica fine powder, pseudo-boehmite fine powder, boric acid fine powder, acrylamide and aluminum fluoride fine powder. The mass percentage contents of each raw material are: 55% of silica fine powder, 36% of pseudo-boehmite fine powder, 2% of boric acid fine powder, 3% of acrylamide, and 4% of aluminum fluoride fine powder.

[0054] Example 2

[0055] The multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable of this example includes raw materials with the following mass percentage contents: 51% of high-aluminum aggregate, 22% of silicon carbide aggregate, 6% of silicon carbide fine powder, 12% of alumina fine powder, 2% of the first binder, 2% of the second binder, 2% of carbon source (spherical pitch with a particle size ≤ 1 mm), 3% of antioxidant (aluminum powder with a particle size ≤ 0.043 mm), and additionally 0.2% of explosion-proof fiber and 4.0% of water based on the total mass of the above raw materials. Among them:

[0056] The high-aluminum aggregate is brown fused alumina, with a particle size of 1 - 8 mm, and the mass ratio of coarse particles with a particle size of 5 - 8 mm, medium particles with a particle size of 3 - 5 mm, and fine particles with a particle size of 1 - 3 mm is 2:1.5:1;

[0057] The first binder is prepared by mixing silica fine powder, graphite fine powder, polyvinyl alcohol with a viscosity of 3.5, vinyltriethoxysilane ViSi(OEt) 3 and water in a mass ratio of 100:4:4:0.4:140, and drying after reacting for 18 h under the conditions of a temperature of 60 °C and a stirring rate of 1100 rpm.

[0058] The second binder is prepared by mixing silica fine powder, pseudo-boehmite fine powder, boric acid fine powder, acrylamide and aluminum fluoride fine powder. The mass percentage contents of each raw material are: 50% of silica fine powder, 45% of pseudo-boehmite fine powder, 1% of boric acid fine powder, 2% of acrylamide, and 2% of aluminum fluoride fine powder.

[0059] Example 3

[0060] The multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable of this example includes raw materials with the following mass percentage contents: 45% of high-aluminum aggregate, 15% of silicon carbide aggregate, 12% of silicon carbide fine powder, 18% of alumina fine powder, 3% of the first binder, 3% of the second binder, 2% of carbon source (graphite electrode powder with a particle size ≤ 1 mm), 2% of antioxidant (aluminum powder with a particle size ≤ 0.043 mm), and additionally 0.3% of explosion-proof fiber and 4.5% of water based on the total mass of the above raw materials. Among them:

[0061] The high-aluminum aggregate is brown fused alumina with a particle size of 1 - 8 mm. The mass ratio of coarse particles with a particle size of 5 - 8 mm, medium particles with a particle size of 3 - 5 mm, and fine particles with a particle size of 1 - 3 mm is 3:2:1;

[0062] The first binder is prepared by mixing silica fume, graphite fine powder, polyvinyl alcohol with a viscosity of 4.5, 3-mercaptopropyltrimethoxysilane HSC 3 H 6 Si(OMe) 3 and water in a mass ratio of 100:2:3:0.2:130, reacting for 12 h at a temperature of 40 °C and a stirring rate of 1150 rpm, and then drying.

[0063] The second binder is prepared by mixing silica fume, pseudo-boehmite fine powder, boric acid fine powder, acrylamide, and aluminum fluoride fine powder. The mass percentage content of each raw material is: silica fume 60%, pseudo-boehmite fine powder 32%, boric acid fine powder 2%, acrylamide 2%, and aluminum fluoride fine powder 4%.

[0064] The multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable in Examples 1 - 3 is prepared according to the following method:

[0065] 1) Mix the high-aluminum aggregate and silicon carbide aggregate evenly to obtain an aggregate mixture;

[0066] 2) Add the second binder to silicon carbide fine powder and alumina fine powder, and mix evenly to obtain a fine powder mixture;

[0067] 3) Add the first binder to the carbon source and antioxidant, and mix evenly to obtain a non-oxide mixture;

[0068] 4) Mix the aggregate mixture, fine powder mixture, non-oxide mixture, and explosion-proof fiber evenly, and then add water and mix evenly again to obtain the multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable.

[0069] Comparative Example 1

[0070] The difference between Comparative Example 1 and Example 1 is only that: the second binder is not added, and the first binder is increased to 8%.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 2 is only that: the first binder is not added, and the second binder is increased to 4%.

[0073] Comparative Example 3

[0074] The difference between Comparative Example 3 and Example 1 is only that: in the preparation process of the first binder, no heating reaction is carried out, and the silica micropowder, graphite fine powder, polyvinyl alcohol, silane coupling agent and water are mixed and then dried to obtain the product.

[0075] Comparative Example 4

[0076] The difference between Comparative Example 4 and Example 3 is only in the preparation method, which is prepared by the following steps:

[0077] 1) Mix the high-aluminum aggregate and silicon carbide aggregate evenly to obtain an aggregate mixture;

[0078] 2) Add the second binder and the first binder to the silicon carbide micropowder, alumina micropowder, carbon source and antioxidant, and mix evenly to obtain a fine powder mixture;

[0079] 3) After mixing the aggregate mixture, the fine powder mixture and the explosion-proof fiber evenly, add water and mix evenly again to obtain a multi-scale whisker-reinforced and toughened cement-free bonded iron runner castable.

[0080] Perform performance tests on the cement-free bonded iron hook castables prepared in the above examples and comparative examples. Among them, the flow value and the pourable time are measured by the slump method, the room temperature flexural strength is measured with reference to GB / T 3001-2017 "Test Method for Room Temperature Flexural Strength of Refractories", the high temperature flexural strength is measured with reference to GB / T 3002-2017 "Test Method for High Temperature Flexural Strength of Refractories", and the anti-explosion temperature is measured with reference to YB / T 4117-2003 "Test Method for Anti-explosion Property of Dense Refractory Castables".

[0081] Table 1 Performance test results

[0082]

[0083]

[0084] Comparative Example 1, compared with the Example, did not add the second binder, with poor fluidity and low anti-burst temperature, and could not generate aluminum borate whiskers at 1100°C, resulting in poor strength after firing at 1100°C; could not generate mullite whiskers at 1450°C, resulting in poor strength after firing at 1450°C, and at the same time, poor toughness and low high-temperature flexural strength. Comparative Example 2, compared with the Example, did not add the first binder, with poor fluidity and low anti-burst temperature, and could not generate silicon carbide whiskers at 1450°C, resulting in poor strength after firing at 1450°C, and at the same time, poor toughness and low high-temperature flexural strength. Comparative Example 3, compared with the Example, the preparation process of the first binder was to mix silica fine powder, graphite fine powder, polyvinyl alcohol, silane coupling agent and water and then dry to obtain, without heating reaction, resulting in poor interaction between them, thus poor fluidity and low strength; Comparative Example 4, compared with the Example, did not mix the binders separately, resulting in the formation of some mullite / aluminum borate two-oxide whiskers around the silicon carbide / carbon source, unable to prevent the oxidation of the silicon carbide / carbon source, resulting in reduced strength.

[0085] The above examples are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or modifications thus extended are still within the protection scope of the present invention.

Claims

1. A cement-free iron ditch castable reinforced and toughened by multi-scale whiskers, characterized in that: The invention comprises the following raw materials in percentage by weight: 45-53% high-alumina aggregate, 15-20% silicon carbide aggregate, 4-12% silicon carbide powder, 14-18% alumina powder, 2-4% first binder, 2-4% second binder, 1-4% carbon source and 1-3% antioxidant; and 0.1-0.3% explosion-proof fiber and 3-5% water are added as the total weight of the above raw materials; the first binder is prepared by heating and reacting silicon dioxide powder, graphite powder, polyvinyl alcohol, silane coupling agent and water and then drying; the second binder is prepared by mixing silicon dioxide powder, pseudo-boehmite powder, boric acid powder, acrylamide and aluminum fluoride powder.

2. The multi-scale whisker reinforced and toughened cement-free iron ditch castable according to claim 1, characterized in that: The mass ratio of silica powder, graphite powder, polyvinyl alcohol, silane coupling agent and water in the first binder is 100:(1-8):(3-5):(0.1-0.5):(100-160); the heating temperature of the heating reaction is 40-80°C, and the reaction time is 12-24h.

3. The multi-scale whisker reinforced and toughened cement-free bonded iron ditch castable according to claim 1, characterized in that: The mass percentage content of each raw material in the second binder is: 35-70% of silicon dioxide powder, 25-60% of pseudo-boehmite powder, 1-3% of boric acid powder, 1-3% of acrylamide, and 1-6% of aluminum fluoride powder.

4. The multi-scale whisker reinforced and toughened cement-free bonded iron ditch castable according to claim 1, characterized in that: The high-alumina aggregate is one or more of brown corundum, high-alumina bauxite, and fused white corundum; the Al2O3 of the high-alumina aggregate is ≥98.0wt%, Fe2O3 is ≤0.3wt%, and the particle size is 1-8mm.

5. The multi-scale whisker reinforced and toughened cement-free iron ditch castable according to claim 1, characterized in that: In the high-alumina aggregate, the mass ratio of coarse particles with a particle size of 5 to 8 mm, medium particles with a particle size of 3 to 5 mm, and fine particles with a particle size of 1 to 3 mm is (2 to 3):(1 to 2):

1.

6. The multi-scale whisker reinforced and toughened cement-free bonded iron ditch castable according to claim 1, characterized in that: The SiC content of the silicon carbide aggregate is ≥98.5%, and the particle size is 0.1-1mm; the SiC content of the silicon carbide micropowder is ≥98.5%, and the particle size is ≤0.043mm; the Al2O3 content of the alumina micropowder is ≥98.0%, and the particle size is ≤0.043mm; the carbon source is at least one of artificial graphite, spherical asphalt, and graphite electrode powder, and the particle size is ≤1mm; the antioxidant is at least one of metallic silicon powder and metallic aluminum powder, and the particle size is ≤0.043mm; the explosion-proof fiber is polypropylene fiber, with a diameter of 40-80μm, a length of 5-8mm, and a melting point of 150±5℃.

7. The multi-scale whisker reinforced and toughened cement-free iron ditch castable according to claim 1, characterized in that: The SiO2 content of the silica fine powder in the first binder is ≥99.0%, and the particle size is ≤0.020mm; the C content of the graphite fine powder is ≥99.5%, and the particle size is ≤0.020mm; the viscosity of the polyvinyl alcohol is 3.0-4.5mPa·s; the silane coupling agent is one of 3-glycidoxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxyethoxysilane, and 3-mercaptopropyltrimethoxysilane.

8. The multi-scale whisker reinforced and toughened cement-free iron ditch castable according to claim 1, characterized in that: The SiO2 content of the silicon dioxide micropowder in the second binder is ≥97.5%, and the particle size is ≤0.043mm; the particle size of the pseudo-boehmite micropowder is ≤90μm; the particle size of the boric acid micropowder is ≤0.043mm; and the particle size of the aluminum fluoride micropowder is ≤0.043mm.

9. A method for preparing a cement-free high-alumina castable according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) Evenly mixing high-alumina aggregate and silicon carbide aggregate to obtain an aggregate mixture; 2) adding a second binder to the silicon carbide micropowder and the alumina micropowder, mixing them evenly to obtain a fine powder mixture; 3) adding the first binder to the carbon source and the antioxidant, mixing them evenly to obtain a non-oxide mixture; 4) After the aggregate mixture, the fine powder mixture, the non-oxide mixture and the explosion-proof fiber are uniformly mixed, water is added and mixed again to obtain a cement-free iron ditch castable reinforced and toughened with multi-scale whiskers.

10. The method for preparing the cement-free high-alumina castable according to claim 9, characterized in that: The flow value of the cement-free high-alumina castable is 180-200 mm, the pouring time is 120-150 min, the room temperature flexural strength at 110°C×24 h is 10-12 MPa, the room temperature flexural strength at 1100°C×3 h is 11.5-12.5 MPa, the room temperature flexural strength at 1450°C×3 h is 15.5-17 MPa, the high temperature flexural strength at 1450°C×3 h is 5.5-6.5 MPa, and the anti-burst temperature is 750-800°C.

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