Preparation method of high-temperature-resistant and impact-resistant fluorite ball

Abstract

The application belongs to the technical field of fluorite ball preparation, and particularly relates to a preparation method of high-temperature-resistant and impact-resistant fluorite ball, which comprises the following steps: raw material preparation, composite binder preparation, material mixing, forming, pre-curing, sintering and cooling; by using the method of the composite binder and the gradient particle grading, the fluorite ball has no softening and no loose structure phenomenon at high temperature, the porosity of the fluorite ball is reduced to below 8% through the synergistic effect of the coarse particle skeleton support, the middle particle filling the gap between the coarse particles and the fine particle filling the gap between the middle particles, and the structural integrity is improved.

Description

Technical Field

[0001] This invention relates to the field of fluorite sphere preparation technology, specifically to a method for preparing high-temperature resistant and impact-resistant fluorite spheres suitable for high-temperature working conditions in metallurgy, chemical industry, building materials, and other fields. Background Technology

[0002] Fluorite (main component is) Due to its excellent fluxing properties, chemical stability, and optical properties, fluorite is widely used in the metallurgical industry (as a flux in steelmaking and a raw material for continuous casting protective slag), the chemical industry (for the preparation of hydrofluoric acid and fluorides), and the building materials industry (as a flux in glass and ceramics). In practical applications, fluorite often needs to be processed into spherical structures (fluorite spheres) to reduce transportation losses and improve material flowability and reaction efficiency under operating conditions. However, existing fluorite sphere preparation technologies have significant shortcomings in terms of high-temperature resistance and impact resistance, making it difficult to meet the long-term use requirements of high-temperature and harsh operating conditions (such as steelmaking converters and cement rotary kilns, where the operating temperature often reaches 800-1200℃).

[0003] Current fluorite sphere preparation processes mainly use silicate cement as a binder, which can achieve a compressive strength of over 20 MPa for fluorite spheres at room temperature. However, at high temperatures above 800℃, the silicate cement... Dehydration and decomposition will occur, producing Easily reacts with impurities in fluorite powder (such as...) , The reaction produces a low-melting-point glass (such as...). The fluorite spheres have a melting point of 1544℃, but begin to soften at 1000℃, resulting in a porous structure and a sharp drop in strength. Experimental data shows that after holding at 1000℃ for 2 hours, the impact strength of this patented product is only 1.2MPa, and the cracking rate is as high as 30%, which cannot meet the requirements for use in high-temperature conditions such as steelmaking converters. On the other hand, organic resin binders (such as phenolic resin) will carbonize and burn above 300℃, completely losing their bonding effect, and are even less suitable for high-temperature scenarios. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies and solve the above-mentioned technical problems, this invention proposes a method for preparing high-temperature resistant and impact-resistant fluorite spheres.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a high-temperature resistant and impact-resistant fluorite sphere, comprising the following steps:

[0006] Raw material preparation: selection Fluorite powder with a purity ≥95%, by mass percentage, is composed of a gradient distribution of coarse particles (1-3mm) 25-35%, medium particles (0.1-1mm) 45-55%, and fine particles (≤0.1mm) 15-25%; a composite binder is prepared, which is composed of modified calcium aluminate cement 80-90%, nano-inorganic particles 8-12%, and silane coupling agent 2-5%. The dosage is 2%;

[0007] Raw material pretreatment: The gradient-graded fluorite powder is placed in a drying oven at 105-110℃ and dried for 2-3 hours to make the moisture content of the fluorite powder ≤0.5%; The nano-inorganic particles are mixed with deionized water at a solid-liquid mass ratio of 1:5 and ultrasonically dispersed at 300-500W power for 10-20 minutes to form a nano-particle dispersion.

[0008] Preparation of composite binder: The modified calcium aluminate cement, nanoparticle dispersion and silane coupling agent are added to a mixing tank and stirred at 300-500 r / min for 15-30 min to obtain a paste-like composite binder;

[0009] Material mixing: Add the pretreated fluorite powder and paste-like composite binder to a twin-screw mixer at a mass ratio of 85:15-90:10, and add deionized water to adjust the material moisture to 10-15%. Stir at 200-300 r / min for 20-30 min to obtain a uniform mixture.

[0010] Molding: The mixture is placed in a spherical mold, and a hydraulic molding machine is used to apply a pressure of 20-30 MPa for 5-10 seconds to obtain a green fluorite ball;

[0011] Pre-curing: The fluorite sphere green body is placed in a constant temperature and humidity curing chamber and cured for 20-28 hours at a temperature of 50-70℃ and a relative humidity of 75-85%.

[0012] Sintering: Place the pre-cured green billets in a roller kiln and heat them to 1000-1200℃ at a rate of 5-10℃ / min, and hold for 2-4 hours;

[0013] Cooling: The sintered fluorite spheres are cooled to room temperature in the furnace at a rate of ≤10℃ / min to obtain high-temperature resistant and impact-resistant fluorite spheres.

[0014] Preferably, the nano-inorganic particles are nano-sized. or nano The nano The particle size is 20-50 nm, and the nanoparticles... The particle size is 30-60nm.

[0015] Preferably, when the nano-inorganic particles are nano-sized... At that time, the composite binder consisted of 85% modified calcium aluminate cement and nano-sized... It consists of 10% silane coupling agent KH-550 and 5% silane coupling agent.

[0016] Preferably, when the nano-inorganic particles are nano-sized... At that time, the composite binder consisted of 88% modified calcium aluminate cement and nano-sized... It consists of 9% silane coupling agent (KH-550) and 3% silane coupling agent.

[0017] Preferably, in the raw material preparation step, the gradient gradation of the fluorite powder is 30% coarse particles (1-3mm), 50% medium particles (0.1-1mm), and 20% fine particles (≤0.1mm).

[0018] Preferably, in the composite adhesive preparation step, the ultrasonic dispersion power is 400W and the dispersion time is 15min.

[0019] Preferably, in the molding step, the molding pressure is 25 MPa and the holding time is 8 s; in the pre-curing step, the pre-curing temperature is 60℃, the relative humidity is 80%, and the curing time is 24 h.

[0020] Preferably, in the sintering step, the heating rate is 8℃ / min, the sintering temperature is 1100℃, and the holding time is 3h; in the cooling step, the cooling rate is 8℃ / min.

[0021] The advantages of this invention are:

[0022] 1. This invention utilizes a composite binder system composed of modified calcium aluminate cement (80-90%), nano-inorganic particles (8-12%), and a silane coupling agent (2-5%), wherein the modified calcium aluminate cement (by incorporating 2% of...) Modification to improve high-temperature resistance) provides basic bonding strength and a high-temperature resistant skeleton, nano-inorganic particles (nano- or nano ) fills microscopic gaps and enhances interfacial bonding; silane coupling agents (such as KH-550) improve the interfacial compatibility between the binder and fluorite powder; modified calcium aluminate cement is converted into anhydrous aluminate at high temperatures ( , The melting points are 1535℃ and 1455℃ respectively. The nanoparticles react with fluorite powder and cement components to form a high-temperature stable phase. , (All of them have melting points > 1500℃), so that fluorite spheres do not soften or become structurally loose in the range of 800-1200℃.

[0023] 2. This invention uses a gradient particle gradation method, with coarse particles (1-3mm) comprising 25-35% by mass, medium particles (0.1-1mm) comprising 45-55%, and fine particles (≤0.1mm) comprising 15-25%. This gradation can reduce the porosity of fluorite spheres to below 8% and improve structural integrity through the synergistic effect of "coarse particle skeleton support - medium particles filling the gaps between coarse particles - fine particles filling the gaps between medium particles". Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of Example 1;

[0026] Figure 2 Experimental data for examples and comparative examples. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 ( (particles)

[0029] Please combine Figure 1 A method for preparing high-temperature resistant and impact-resistant fluorite spheres includes the following steps;

[0030] 1. Raw material preparation:

[0031] Fluorite powder: Purity 96.5%, impurities 1.8%, 0.9%; by mass ratio, coarse particles (1-3mm) 30%, medium particles (0.1-1mm) 50%, fine particles (≤0.1mm) 20%;

[0032] Composite binder: Modified calcium aluminate cement ( 85kg (dosage 2%), nano 10 kg of silane coupling agent (KH-550) with a particle size of 20-50 nm, and 5 kg of silane coupling agent.

[0033] 2. Raw material pretreatment

[0034] Fluorite powder is dried at 105℃ for 2.5 hours, reducing the moisture content to 0.4%, thus removing free water from the fluorite powder and preventing cracking of the green body due to moisture evaporation after molding.

[0035] nanometer Add 50 kg of deionized water and ultrasonically disperse at 400 W for 15 minutes to form nanoparticles. The function of the dispersion is to break up the aggregation of nanoparticles, ensuring that they are uniformly dispersed in the binder and fully exert their micro-filling effect.

[0036] 3. Preparation of composite adhesive

[0037] Modified calcium aluminate cement, nano The dispersion and KH-550 were added to the mixing tank and stirred at 400 r / min for 20 min to obtain a paste-like binder. This ensured that the binder components were fully mixed, the nanoparticles were evenly distributed, and the silane coupling agent fully coated the cement particles and nanoparticles, laying the foundation for the subsequent interfacial bonding with fluorite powder.

[0038] 4. Material mixing

[0039] Take 900 kg of pretreated fluorite powder and add it to a twin-helix mixer. Add 100 kg of composite binder and deionized water to adjust the humidity to 12%. Stir at 250 r / min for 25 min to obtain a uniform mixture. Ensure that the composite binder uniformly coats the fluorite powder particles. Humidity control can ensure the formability of the material and avoid the problem of loose green body due to excessive dryness or uneven shrinkage after molding due to excessive moisture.

[0040] 5. Molding

[0041] The material is placed in a spherical mold with a diameter of 8 mm, and a pressure of 25 MPa is applied and held for 8 seconds to obtain a green fluorite ball. The pressure causes the material to be tightly bonded together, forming a spherical structure with a certain initial strength.

[0042] 6. Pre-curing

[0043] The green body is cured in a curing chamber at 60℃ and 80% relative humidity for 24 hours. The purpose is to promote the full hydration of the modified calcium aluminate cement and generate stable hydration products. This process allows the green body to form a dense initial structure, preventing cracking caused by rapid moisture evaporation during subsequent high-temperature sintering. At the same time, the hydration products form a preliminary synergistic combination with nanoparticles and silane coupling agents, enhancing the strength of the green body.

[0044] 7. Sintering

[0045] The green billets are placed in a roller kiln and heated to 1100℃ at a rate of 8℃ / min, then held at that temperature for 3 hours. Slow heating helps prevent thermal stress cracking of the green billets caused by sudden temperature increases. A sintering temperature of 1000-1200℃ allows the hydration products of the modified calcium aluminate cement to be further converted into high-temperature resistant anhydrous aluminates (such as…). , Simultaneously, nanoparticles undergo interfacial reactions with fluorite powder and cement components (such as nano-...). and Reaction generation With cement Reaction generation This process forms a dense, high-temperature stable phase, enhancing the high-temperature resistance and structural strength of the fluorite spheres. The specific reaction steps are as follows:

[0046] Step 1: Nano + → + ↑ (Provide reaction raw materials) );

[0047] Step Two: respectively with , Reaction generation , (Basic stable phase);

[0048] Step 3: + + → (The stable phase of the double salt has the highest melting point).

[0049] 8. Cooling

[0050] The fluorite spheres are cooled to room temperature in the furnace at a rate of 8°C / min. Slow cooling can prevent thermal stress caused by excessive temperature difference and prevent cracking.

[0051] Example 2 ( (particles)

[0052] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0053] Raw material pretreatment:

[0054] Fluorite powder was dried at 105℃ for 2.5 hours, reducing the moisture content to 0.4%.

[0055] nanometer Add 27 kg of deionized water and ultrasonically disperse at 400 W for 15 minutes to form nanoparticles. Dispersion.

[0056] Preparation of composite adhesive:

[0057] Modified calcium aluminate cement, nano The dispersion and KH-550 were added to a mixing tank and stirred at 350 r / min for 25 min to obtain a paste-like binder.

[0058] Example 3

[0059] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0060] In the raw material preparation step, the fluorite powder is prepared in the following mass ratio: coarse particles (1-3mm) 15%, medium particles (0.1-1mm) 50%, and fine particles (≤0.1mm) 35%.

[0061] Example 4

[0062] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0063] In the raw material preparation step, the fluorite powder is prepared in the following mass ratio: coarse particles (1-3mm) 20%, medium particles (0.1-1mm) 50%, and fine particles (≤0.1mm) 30%.

[0064] Example 5

[0065] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0066] In the raw material preparation step, the fluorite powder is prepared in the following mass ratio: 25% coarse particles (1-3mm), 50% medium particles (0.1-1mm), and 25% fine particles (≤0.1mm).

[0067] Example 6

[0068] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0069] In the raw material preparation step, the fluorite powder is prepared in the following mass ratio: coarse particles (1-3mm) 35%, medium particles (0.1-1mm) 50%, and fine particles (≤0.1mm) 15%.

[0070] Example 7

[0071] Compared to Example 1, as another embodiment of the present invention, the method for preparing a high-temperature resistant and impact-resistant fluorite sphere remains unchanged in other steps:

[0072] In the raw material preparation step, the fluorite powder is prepared in the following mass ratio: 40% coarse particles (1-3mm), 50% medium particles (0.1-1mm), and 10% fine particles (≤0.1mm).

[0073] Comparative Example 1

[0074] Using conventional technology and processes

[0075] Fluorite powder: single particle size (1-3mm). Purity approximately 96%;

[0076] Binder: Silicate cement (P.O42.5);

[0077] Process: Fluorite powder is mixed with 15% silicate cement, dispersed with water, molded at 20MPa, cured at room temperature for 24 hours, and sintered at 1000℃ for 2 hours.

[0078] Comparative Example 2 (Nanoparticles missing in the composite binder)

[0079] Fluorite powder: Same as in Example 1 (gradient distribution: 30% coarse + 50% medium + 20% fine);

[0080] Binder: Contains only modified calcium aluminate cement (85%) + silane coupling agent KH-550 (5%), removes nano SiO2, and has a fluorite powder to binder mass ratio of 90:10;

[0081] The remaining processes are the same as in Example 1 (drying at 105℃ for 2.5h → mixing the binder → molding at 25MPa → pre-curing at 60℃ / 80% humidity for 24h → sintering at 1100℃ for 3h → cooling at 8℃ / min).

[0082] Comparative Example 3 (lacking gradient particle size distribution, using two-stage distribution)

[0083] Fluorite powder: two-graded (coarse particles 1-3mm 60% + fine particles ≤0.1mm 40%), no medium particles. Purity is the same as in Example 1;

[0084] Binder: Same as in Example 1 (85% modified calcium aluminate cement + nano-binder) 10%+KH-5505%)

[0085] The remaining processes are the same as in Example 1.

[0086] Comparative Example 4 (Silane Coupling Agent Missing in Composite Binder)

[0087] Fluorite powder: Same as in Example 1;

[0088] Binder: Contains only modified calcium aluminate cement (90%) + nano (10%), removal of silane coupling agent KH-550;

[0089] The remaining processes are the same as in Example 1.

[0090] Comparative Example 5 (using ordinary calcium aluminate cement instead of modified calcium aluminate cement)

[0091] Fluorite powder: Same as in Example 1;

[0092] Binder: Ordinary calcium aluminate cement (85%) + nano (10%) + KH-550 (5%), none modified;

[0093] The remaining processes are the same as in Example 1.

[0094] After performance tests were conducted on the impact strength, cracking rate, porosity, and compressive strength, the experimental data comparison table is as follows: Figure 2 As shown:

[0095] When the same gradient particle size distribution is used in Examples 1 and 2, the inorganic particles, alumina, have a slightly higher impact strength than silicon oxide, a slightly lower cracking rate than silicon oxide, and a slightly higher compressive strength than silicon oxide.

[0096] Comparing Examples 1 and 3-7, it can be seen that different gradient particle gradations will lead to different porosities. The actual porosity values ​​of Examples 1, 5 and 6 are all below 7%. If the medium particles are quantitatively controlled to be 50%, the optimal ranges for large particles and small particles are 25-35% and 15-25% respectively.

[0097] Comparative Example 2: Missing Nanoparticles Subsequently, the micro-gap could not be effectively filled, the interfacial bonding force weakened, resulting in increased porosity and a significant decrease in impact strength and high-temperature compressive strength, proving that the "micro-densification" effect of nanoparticles is indispensable.

[0098] In Comparative Example 3, the lack of medium-sized particles filling the gaps between coarse and fine particles in the two-stage gradation resulted in a significant increase in porosity (from 6.2% to 12.1%), a decrease in structural integrity, and a weakening of impact resistance. This demonstrates the crucial role of the "coarse-medium-fine" three-stage gradient gradation in reducing porosity and improving structural stability.

[0099] Combined with Comparative Example 4, the silane coupling agent can improve the interfacial compatibility between the binder and fluorite powder (interfacial shear strength decreased by 40%). The absence of the coupling agent weakens the interfacial bonding force and makes it easy to generate interfacial cracks, proving its key role in "interfacial strengthening".

[0100] In Comparative Example 5, ordinary calcium aluminate cement is easily decomposed at high temperatures (C3A retention rate is only 50% at 1200℃), while Modification can improve the high-temperature stability of cement (C3A retention rate reaches 90%). Without modification, the high-temperature skeleton collapses and the performance decreases significantly, proving the "high-temperature skeleton support" role of modified calcium aluminate cement.

[0101] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0102] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing high-temperature resistant and impact-resistant fluorite spheres, characterized in that, Includes the following steps: S1: Select fluorite powder, which, by mass percentage, consists of a gradient gradation of 25-35% coarse particles (1-3mm), 50% medium particles (0.1-1mm), and 15-25% fine particles (≤0.1mm). Select a composite binder comprising 80-90% modified calcium aluminate cement, 8-12% nano-inorganic particles, and a silane coupling agent. The nano-inorganic particles are... Particles or Granules, in the modified calcium aluminate cement The dosage is 2%; S2: The fluorite powder is placed in a drying oven and dried so that the moisture content of the fluorite powder is ≤0.5%; the nano-inorganic particles are mixed with deionized water to form a nano-particle dispersion. S3: Add the modified calcium aluminate cement, nanoparticle dispersion, and silane coupling agent to a mixing tank to obtain a paste-like composite binder; S4: Add the pretreated fluorite powder and paste-like composite binder to the twin-helix mixer at a mass ratio of 85:15-90:10, and add deionized water to adjust the material moisture to 10-15% to obtain a uniform mixture. S5: The mixture is placed in a spherical mold and hydraulically formed to obtain a green fluorite ball. The green fluorite ball is then cured in a constant temperature and humidity curing chamber. The pre-cured green ball is then placed in a roller kiln for 2-4 hours of heat preservation. The sintered fluorite ball is then cooled to room temperature with the furnace to obtain a high-temperature resistant and impact-resistant fluorite ball.

2. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 1, characterized in that: The S1 selection Fluorite powder with a purity of ≥95% is mixed with deionized water in S2 at a solid-liquid mass ratio of 1:5 and ultrasonically dispersed at a power of 300-500W for 10-20 minutes.

3. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 1, characterized in that: The S4 double-helix mixer is stirred at 200-300 r / min for 20-30 min to obtain a uniform mixture. The S5 hydraulic forming machine applies a pressure of 20-30 MPa and holds the pressure for 5-10 s to obtain fluorite sphere green bodies. The fluorite sphere green bodies are placed in a constant temperature and humidity curing chamber and cured at a temperature of 50-70℃ and a relative humidity of 75-85% for 20-28 h. The pre-cured green bodies are placed in a roller kiln and heated to 1000-1200℃ at a rate of 5-10℃ / min, held for 2-4 h, and cooled to room temperature at a cooling rate of ≤10℃ / min.

4. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 1, characterized in that: The nano-inorganic particles are nano-sized. or nano The nano The particle size is 20-50 nm, and the nanoparticles... The particle size is 30-60nm.

5. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 2, characterized in that: When the nano-inorganic particles are nano At that time, the composite binder consisted of 85% modified calcium aluminate cement and nano-sized... The composite binder comprises 10% of the total composition and also includes 5% of a silane coupling agent.

6. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 2, characterized in that: When the nano-inorganic particles are nano At that time, the composite binder consisted of 88% modified calcium aluminate cement and nano-sized... The composite binder comprises 9% of the total composition and also includes 3% of a silane coupling agent.

7. A method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to any one of claims 1-6, characterized in that: In S1, the gradient distribution of the fluorite powder is as follows: coarse particles (1-3 mm) account for 30%, medium particles (0.1-1 mm) account for 50%, and fine particles (≤0.1 mm) account for 20%.

8. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 2, characterized in that: In S2, the ultrasonic dispersion power is 400W and the dispersion time is 15min.

9. The method for preparing a high-temperature resistant and impact-resistant fluorite sphere according to claim 1, characterized in that: In S5, the molding pressure is 25MPa, the holding time is 8s, the pre-curing temperature is 60℃, the relative humidity is 80%, and the curing time is 24h.

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