Cement-free Al2O3-SiC-C refractory castable and use method thereof

Abstract

The invention discloses a cement-free Al2O3-SiC-C refractory castable and a use method of the cement-free Al2O3-SiC-C refractory castable. The invention relates to the technical field of refractory castable. The refractory castable is composed of aggregate, a matrix material and a water reducing agent. The aggregate is corundum particles and silicon carbide particles. The matrix material comprises corundum fine powder, alpha-Al2O3 micro powder, silicon micro powder, silicon carbide fine powder, ball pitch and various metal microcapsules. The use method of the refractory castable comprises the following steps: uniformly mixing the water reducing agent and the matrix material to obtain a premixed matrix material; uniformly stirring the aggregate and the premixed matrix material, adding water, and stirring to obtain slurry; pouring the slurry into a mold, and performing vibration molding and maintenance. The refractory castable disclosed by the invention is high in normal-temperature strength, excellent in medium-temperature and high-temperature mechanical properties, good in erosion resistance and thermal shock resistance, long in service life, energy-saving and environment-friendly; and in the using process, water adding amount is small, fluidity is good, production is stable, and the agent is suitable for molten iron grooves, ladle working layers and other parts.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory castables, in particular to a cement-free Al 2 O 3 -SiC-C refractory castable and method of using the same. Background Art

[0002] Al 2 O 3 -SiC-C refractory castables need to add calcium aluminate cement, ρ-Al 2 O 3 , water glass or silica sol as a binder to obtain a sufficiently high room temperature strength. Among them, calcium aluminate cement is the most widely used binder. The binding mechanism is that CA and CA in cement 2 , C 12 A 7 After mixing with water, Ca 2+ With Al(OH) 4 - The plasma quickly dissolves into water to form Ca 2+ With Al(OH) 4 - The aqueous solution quickly reaches saturation, and then crystallizes from the solution to form hydrates. These hydrates are interconnected to form an interlaced network structure, which solidifies and hardens. However, since the composition contains a certain amount of CaO, the introduced CaO reacts at high temperature to form calcium feldspar (CaO·Al 2 O 3 ·2SiO 2 ), gehlerite (2CaO·Al 2 O 3 ·SiO 2 ) or calcium aluminate low melting phase, which reduces the high temperature performance of the castable, and affects the corrosion resistance and service life.

[0003] In order to improve the high temperature performance of refractory castables, domestic and foreign technicians have studied and proposed cement-free castables, such as silica sol or hydrated alumina (ρ-Al 2 O 3 ) to replace cement and provide early strength for castables. As a cement-free binder, silica sol mainly forms silicon-oxygen bonds (Si-O-Si) to connect into a three-dimensional network structure to give castables early strength and good high-temperature strength. However, the use of silica sol on site has problems such as construction difficulties, high temperature impact on site, and large amount of water addition. The construction performance cannot meet the site requirements and the use effect is not good. ρ-Al 2 O 3It is also a binder that does not introduce CaO impurities. It can spontaneously hydrate and form gel at room temperature to solidify the castable and produce early strength. However, when hydrated alumina completely replaces cement in castables, not only the bonding strength is low, but also the stability is poor. In particular, the hydration rate is extremely sensitive to temperature. At the same time, the process of losing crystal water at medium temperature often produces micro cracks, which affects the structural density of the material. For example:

[0004] (1) Patented technology of "A cement-free iron ditch castable for blast furnace tapping and its preparation method" (CN106587958A), using ρ-Al 2 O 3 Ultrafine powder is used as a binder, where the amount of binder added is 3-7%, and the bonding strength of the material is low. 2 O 3 It is also unstable in itself and is greatly affected by the ambient temperature in the castable, and the reaction activity varies greatly. (2) The patented technology of "cement-free castable" (CN110776312A) does not use cement as a functional component, but uses the form of premixing boric anhydride in corundum aggregate. The construction adopts the sintering method. The construction surface is heated from room temperature to 450-550℃, and the boric anhydride generates a viscous liquid phase, which then reacts with α-Al 2 O 3 After a solid-liquid reaction occurs, a compound with a higher melting point is generated, which then consolidates the corundum aggregate together. However, the on-site construction conditions are complex and the use effect is not good. (3) The patented technology of "A dense high-strength SiAlON bonded iron ditch castable and its preparation method" (CN103804000B) uses silica sol as a binder, wherein the amount of binder added is 2-6%. However, the iron ditch castable using silica sol as a binder is difficult to construct, is greatly affected by high temperatures on site, and requires a large amount of water to be added. (4) The patented technology of "A method for preparing a cement-free castable" (CN102491772B) uses hydrated alumina (ρ-Al 2 O 3 ) and MgO-SiO 2 -H 2 O is the bonding system, and the prepared cement-free Al 2 O 3 -SiC refractory castables after high temperature treatment generate a large amount of cordierite phase and a small amount of spinel and mullite phase in the matrix, which improves the Al 2 O 3 -SiC castables have medium temperature sintering properties, which improves the mechanical properties, oxidation resistance, wear resistance, alkali resistance and thermal shock stability of the castables. 2 This will cause the material to produce too much liquid phase at high temperatures, seriously affecting its performance at high temperatures. (5) "A whisker-reinforced Al 2 O 3-SiC-C iron ditch castable and its preparation method" (CN110240486B) patented technology uses calcium aluminate cement as a binder, wherein the amount of binder added is 4-6%. Due to the large amount of cement added, more low melting point phases are produced at high temperature, resulting in poor high temperature performance of the material. Summary of the invention

[0005] The present invention aims to overcome the shortcomings of the prior art and to provide a cement-free Al 2 O 3 -SiC-C refractory castable and its use method solve the problem of low initial strength of cement-free castable, improve the medium-temperature and high-temperature mechanical properties of castable, and extend the service life.

[0006] To achieve the above object, the present invention provides a cement-free Al 2 O 3 -The technical solution adopted by the SiC-C refractory castable is: the refractory castable is composed of aggregate, matrix material and water reducing agent.

[0007] The aggregates are:

[0008] 10-15 parts of corundum particles with a particle size less than 15 mm and greater than or equal to 8 mm;

[0009] 20-25 parts of corundum particles with a particle size less than 8 mm and greater than or equal to 5 mm;

[0010] 15-20 parts of corundum particles with a particle size less than 5 mm and greater than or equal to 3 mm;

[0011] 5-10 parts of corundum particles with a particle size less than 3 mm and greater than or equal to 1 mm;

[0012] 3 to 8 parts of silicon carbide particles with a particle size less than 1 mm and greater than 0 mm.

[0013] The base material is:

[0014] 10-15 parts of corundum fine powder;

[0015] α-Al 2 O 3 15-25 parts of micro powder;

[0016] 1 to 4 parts of silicon powder;

[0017] 2-7 parts of silicon carbide fine powder;

[0018] 1 to 5 parts of ball asphalt;

[0019] 2 to 8 parts of various metal microcapsules.

[0020] The preparation method of the metal microcapsule is:

[0021] S1. placing metal powder in deionized water, adding ammonia water to adjust the pH value of the solution to 9-11, heating and stirring to obtain metal powder with surface corrosion;

[0022] S2, placing the metal powder with surface corrosion in aluminum sol and stirring to obtain a mixed slurry;

[0023] S3, filtering the mixed slurry, and completely drying the filtration residue to obtain metal microcapsules.

[0024] In the preparation method of the metal microcapsules, the metal powder is one of aluminum powder, aluminum silicon alloy powder and aluminum silicon iron alloy powder, and aluminum microcapsules, aluminum silicon alloy microcapsules and aluminum silicon iron alloy microcapsules are prepared respectively; the Al content in the various metal microcapsules is ≥80%.

[0025] Furthermore, among the plurality of metal microcapsules, the mass ratio of the aluminum microcapsules, the aluminum silicon alloy microcapsules and the aluminum silicon iron alloy microcapsules is 2-4:4-6:1-3.

[0026] Furthermore, in the preparation method of metal microcapsules, the particle size of the aluminum-silicon alloy microcapsules is 5μm to 400μm; the particle grading of the aluminum-silicon alloy microcapsules is such that the mass ratio of aluminum-silicon alloy microcapsules with a particle size less than 50μm and greater than or equal to 5μm: aluminum-silicon alloy microcapsules with a particle size less than 400μm and greater than or equal to 50μm is 5-7:3-5.

[0027] Furthermore, in step S1 of the method for preparing metal microcapsules, heating and stirring are performed at 50 to 80° C. for 15 to 30 minutes.

[0028] Furthermore, in step S2 of the method for preparing metal microcapsules, the pH value of the aluminum sol is 4-7, and the aluminum oxide content in the aluminum sol is 10%-20%; stirring is performed at 30-40° C. for 10-50 minutes.

[0029] Furthermore, in step S3 of the method for preparing metal microcapsules, the drying temperature is 100-120°C.

[0030] Furthermore, the α-Al 2 O 3 Al in micro powder 2 O 3 Content ≥97wt%, α-Al 2 O 3 The particle size of the micro powder is ≤8μm; the SiO 2 Content ≥92wt%, silicon micropowder particle size ≤0.6μm.

[0031] Furthermore, the water reducing agent content is 0.1-0.4% of the sum of the aggregate and the matrix material, and the water reducing agent is one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and sodium silicate.

[0032] Furthermore, the cement-free Al 2 O 3 -The method for using the SiC-C refractory castable is as follows: 0.1-0.4% of the water reducing agent of the sum of the aggregate and the matrix material is mixed with the matrix material to obtain a premixed matrix material; the aggregate and the premixed matrix material are stirred evenly, and 3-4% of water of the sum of the aggregate and the matrix material is added, and stirred for 1-3 minutes to obtain a slurry; the slurry is poured into a mold, vibrated and formed, and cured for 1-3 days.

[0033] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. After being heated in a water bath, a large amount of loose boehmite is generated on the surface of the metal powder, which is then placed in aluminum sol and stirred. The aluminum oxide colloid particles in the aluminum sol are nanometer-sized and fill the surface of the metal powder to obtain a metal microcapsule coated with a dense inorganic shell layer on the surface. When bonded with refractory aggregates and micropowders, the hydrated alumina micelles on the surface of the metal microcapsule will form a -O-Al-O- three-dimensional network structure, which gives the refractory material a certain initial strength. The melting points of aluminum silicon alloy microcapsules, aluminum microcapsules and aluminum silicon iron alloy microcapsules are different. At different temperature stages, some microcapsules break. When the temperature is greater than 600°C, some aluminum silicon alloy microcapsules break, and the aluminum silicon alloy is exposed, which combines with oxygen to form Al in situ. 2 O 3 Whiskers, micro expansion, filling pores and improving material density; at temperatures above 700°C, some aluminum microcapsules rupture, further filling pores to produce whiskers, fibers and other reinforcement phases; at temperatures above 900°C, some aluminum silicon ferrosilicon microcapsules rupture, and a small amount of iron in aluminum silicon ferrosilicon can also act as a catalyst to promote Al 2 O 3 Whisker formation. At different temperature stages, some microcapsules break, resulting in micro-expansion to fill the pores, and produce whiskers, fibers and other reinforcement phases, which can significantly improve the medium-temperature strength of the material, and no liquid phase is produced at high temperatures, which can also improve the performance of the material at high temperatures.

[0035] 2. The aluminum-silicon alloy microcapsules are made of particles of different sizes. The large and small aluminum-silicon alloy microcapsules have different reaction activities. The small-sized aluminum-silicon alloy microcapsules have a large specific surface area and a high reaction activity. During high-temperature service, they first react to form multiphase reinforcement phases such as flaky aluminum oxide, silicon carbide whiskers, and mullite whiskers, thereby improving the high-temperature performance of the material. However, the small-sized aluminum-silicon alloy microcapsules react and expand greatly in a concentrated period of time, and the material will rupture. The amount added at one time cannot be too much; the large and small particles are mixed and added to effectively control the reaction. The large-sized aluminum-silicon alloy microcapsules have a small specific surface area and a low reaction activity. At the beginning, only a small amount of reaction occurs, resulting in a slight expansion. When the small-sized aluminum-silicon alloy microcapsules are completely reacted, the large-sized aluminum-silicon alloy microcapsules will further react to form reinforcement phases such as whiskers and fibers at the microcracks, thereby preventing the cracks from expanding and having a self-repairing effect.

[0036] 3. The present invention does not contain cement Al 2 O 3 -The various metal microcapsules added to the SiC-C refractory castable can also improve the castable's oxidation resistance, extend the castable's service life, and prolong its service life.

[0037] 4. The present invention does not contain cement Al 2 O 3 -SiC-C refractory castable: high strength at room temperature, excellent mechanical properties at medium and high temperatures, good corrosion resistance and thermal shock stability, long service life, energy saving and environmental protection; less water addition during use, good fluidity, stable production, suitable for iron water ditch, iron ladle working layer and other parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The microstructure of the metal microcapsules prepared in the present invention.

[0039] Figure 2 The present invention is cement-free Al 2 O 3 -Microstructure of SiC-C refractory castable after calcination at 1500℃×3h. DETAILED DESCRIPTION

[0040] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0041] Example 1

[0042] Refractory castables are composed of aggregate, matrix material and water reducing agent.

[0043] The aggregates are:

[0044] 15 parts of corundum particles with a particle size less than 15 mm and greater than or equal to 8 mm;

[0045] 25 parts of corundum particles with a particle size less than 8 mm and greater than or equal to 5 mm;

[0046] 20 parts of corundum particles with a particle size less than 5 mm and greater than or equal to 3 mm;

[0047] 10 parts of corundum particles with a particle size less than 3 mm and greater than or equal to 1 mm;

[0048] 3 parts of silicon carbide particles with a particle size less than 1 mm and greater than 0 mm.

[0049] The base material is:

[0050] 10 parts of corundum fine powder;

[0051] α-Al 2 O 3 15 parts of micro powder;

[0052] 1 part of silicon powder;

[0053] 2 parts of silicon carbide fine powder;

[0054] 1 part of ball asphalt;

[0055] 2 parts of various metal microcapsules.

[0056] The preparation method of metal microcapsules is as follows: placing metal powder in deionized water, adding ammonia water to adjust the pH value of the solution to 9, heating and stirring at 50°C for 15 minutes to obtain surface-corroded metal powder; placing the surface-corroded metal powder in aluminum sol with a pH value of 4, stirring at 30-40°C for 10-50 minutes to obtain a mixed slurry; filtering the mixed slurry, and drying the filtration residue in an oven at 100°C for 24 hours until it is completely dried to obtain metal microcapsules.

[0057] The mass ratio of aluminum microcapsules, aluminum silicon alloy microcapsules and aluminum silicon iron alloy microcapsules is 3:5:2.

[0058] The particle size of the aluminum-silicon alloy microcapsules is 5μm to 400μm; the particle size distribution of the aluminum-silicon alloy microcapsules is that the mass ratio of aluminum-silicon alloy microcapsules with a particle size less than 50μm and greater than or equal to 5μm: aluminum-silicon alloy microcapsules with a particle size less than 400μm and greater than or equal to 50μm is 7:3.

[0059] Cement-free Al 2 O 3 -The method of using SiC-C refractory castable is as follows: 0.1% of the water reducing agent of the sum of the aggregate and the matrix material is mixed with the matrix material to obtain a premixed matrix material; the aggregate and the premixed matrix material are stirred evenly, and 4% of water of the sum of the aggregate and the matrix material is added, and stirred for 1 to 3 minutes to obtain a slurry; the slurry is poured into a mold, vibrated into a mold, and cured for 1 to 3 days.

[0060] The cement-free Al prepared in Example 1 of the present invention 2 O 3 -SiC-C refractory castable, after being tested in a drying oven at 110℃×24h, the results show that the room temperature flexural strength is 15MPa and the room temperature compressive strength is 70MPa.

[0061] After heat treatment at 1100℃×3h, the test results show that the room temperature flexural strength is 25MPa, the room temperature compressive strength is 230MPa, the apparent porosity is 16%, and the volume density is 3g / cm 3 .

[0062] After heat treatment at 1500℃×3h, the test results show that the room temperature flexural strength is 30MPa, the room temperature compressive strength is 145MPa, the apparent porosity is 13.3%, and the volume density is 3.17g / cm 3 .

[0063] After heat treatment at 1400℃×0.5h, the high temperature flexural strength is 22MPa.

[0064] The process parameters of Examples 1-4 are shown in Table 1-2:

[0065] Table 1

[0066]

[0067] Table 2

[0068]

[0069] Table 3

[0070]

[0071] Table 4 is the cement-free Al 2 O 3 -Performance test results of SiC-C refractory castables

[0072] Table 4

[0073]

[0074] Figure 1 The microstructure of the metal microcapsule is prepared in the present invention. Figure 1 It can be seen that there are a large number of densely structured nano-inorganic shells on the surface of the sample.

[0075] Figure 2 The present invention is cement-free Al 2 O 3 -The microstructure of SiC-C refractory castable after calcination at 1500℃×3h. Figure 2It can be seen that some unreacted metal microcapsules still exist after calcination at 1500°C for 3 h, indicating that the metal microcapsules of the present invention are continuously reacted.

[0076] For matters not mentioned above, the prior art applies.

[0077] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A cement-free Al2O3-SiC-C refractory castable, characterized by: The refractory castable is composed of aggregate, matrix material and water reducing agent; The aggregate is: The base material is: The preparation method of the metal microcapsule is: S1. placing metal powder in deionized water, adding ammonia water to adjust the pH value of the solution to 9-11, heating and stirring to obtain metal powder with surface corrosion; S2, placing the metal powder with surface corrosion in aluminum sol and stirring to obtain a mixed slurry; S3, filtering the mixed slurry, and completely drying the filtered residue to obtain metal microcapsules; In the preparation method of the metal microcapsule, the metal powder is one of aluminum powder, aluminum silicon alloy powder and aluminum silicon iron alloy powder, and aluminum microcapsules, aluminum silicon alloy microcapsules and aluminum silicon iron alloy microcapsules are prepared respectively; the Al content in the metal microcapsules is ≥80%.

2. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: Among the various metal microcapsules, the mass ratio of the aluminum microcapsules, the aluminum silicon alloy microcapsules and the aluminum silicon iron alloy microcapsules is 2-4:4-6:1-3.

3. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: In the preparation method of metal microcapsules, the particle size of the aluminum-silicon alloy microcapsules is 5μm to 400μm; the particle grading of the aluminum-silicon alloy microcapsules is such that the mass ratio of aluminum-silicon alloy microcapsules with a particle size less than 50μm and greater than or equal to 5μm to aluminum-silicon alloy microcapsules with a particle size less than 400μm and greater than or equal to 50μm is 5-7:3-5.

4. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: In step S1 of the method for preparing metal microcapsules, heating and stirring are performed at 50 to 80° C. for 15 to 30 minutes.

5. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: In step S2 of the method for preparing metal microcapsules, the pH value of the aluminum sol is 4-7, the aluminum oxide content in the aluminum sol is 10%-20%, and the mixture is stirred at 30-40° C. for 10-50 minutes.

6. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: In step S3 of the method for preparing metal microcapsules, the drying temperature is 100-120°C.

7. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: The Al2O3 content in the α-Al2O3 micropowder is ≥97wt%, and the particle size of the α-Al2O3 micropowder is ≤8μm; the SiO2 content in the silicon micropowder is ≥92wt%, and the particle size of the silicon micropowder is ≤0.6μm.

8. The cement-free Al2O3-SiC-C refractory castable according to claim 1, characterized in that: The water reducing agent content is 0.1-0.4% of the sum of the aggregate and the matrix material, and the water reducing agent is one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and sodium silicate.

9. A method for using the cement-free Al2O3-SiC-C refractory castable according to any one of claims 1 to 8, characterized in that: The water reducing agent of 0.1-0.4% of the sum of the aggregate and the matrix material is mixed with the matrix material to obtain a premixed matrix material; the aggregate and the premixed matrix material are stirred evenly, and water of 3-4% of the sum of the aggregate and the matrix material is added, and stirred for 1-3 minutes to obtain a slurry; the slurry is poured into a mold, vibrated and formed, and cured for 1-3 days.

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