A surface treatment method for improving corrosion resistance and wear resistance of silicon carbide bricks

Abstract

This invention discloses a surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks, comprising the following steps: (1) protective solvent impregnation; (2) heating and drying; (3) sealing suspension impregnation; (4) repeated drying and sealing suspension impregnation; (5) drying; and (6) firing. This invention utilizes the adsorption effect of the silicon carbide brick on the sealing suspension, and a secondary firing process, to use vacuum to block the pores on the surface of the silicon carbide brick's working surface with particles in the sealing suspension, reducing the channels for external gas to enter the brick body and improving the material's corrosion resistance. Furthermore, this surface treatment method does not affect the internal porosity of the brick and has no impact on the material's thermal shock resistance. Compared to existing methods of enhancing brick corrosion resistance through coatings, this invention solves the drawbacks of insufficient coating strength, easy peeling, and complex construction processes in existing technologies.

Description

Technical Field

[0001] This invention relates to surface treatment, and more particularly to a surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks. Background Technology

[0002] Refractory bricks have wide applications in high-temperature industries such as steel, ceramics, and glass. Damage to refractory materials in the inclined quenching zone of dry-quenching coke ovens mainly manifests as cracking of brick joints, brick breakage, and severe wear. Analysis of the damage mechanism of refractory materials in the inclined quenching zone of dry-quenching coke ovens, based on existing product usage experience, reveals that the circulating gas in dry-quenching coke ovens contains O2, CO, H2, and a small amount of alkali metal vapors. Under the corrosive influence of these gases, the internal phases and structure of the refractory materials in the inclined quenching zone change, leading to a decrease in strength. When the circulating gas flows through the cooling section of the dry-quenching furnace, it enters the annular air duct from the inclined quenching zone, carrying away some coke. The refractory materials in the inclined quenching zone are not only subjected to the impact force of the downward flow of coke but also to the scouring effect of coke powder carried upward by the circulating gas. Moreover, the temperature of the coke, circulating gas, and refractory materials changes continuously along the height of the inclined quenching zone, especially in the lower part of the inclined zone where the temperature varies between 300-700℃, generating significant thermal stress, thus causing tensile cracking and spalling of the refractory materials. Therefore, surface modification of refractory bricks to improve their resistance to erosion and wear has become an important research direction. Summary of the Invention

[0003] Purpose of the invention: The present invention aims to provide a surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks that is simple to operate, efficient in processing, and has excellent modification effect.

[0004] Technical solution: The surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks according to the present invention includes the following steps:

[0005] (1) Protective solvent impregnation: Place the silicon carbide bricks after surface cleaning on the shelf in the container, evacuate and maintain pressure, then inject solvent into the container until the silicon carbide bricks are completely submerged, and continue to maintain pressure until the solvent fully impregnates the silicon carbide bricks.

[0006] (2) Heating and drying: Take the silicon carbide brick out of the solvent, first wipe the solvent off the surface of the silicon carbide brick with a cloth strip soaked in solvent, and then use a hot air gun to circulate and dry the working surface of the silicon carbide brick. The drying depth of the working surface of the silicon carbide brick is controlled by controlling the drying regime.

[0007] (3) Sealing suspension impregnation: Place the dried silicon carbide bricks upside down on the shelf in the container with the working surface facing down, evacuate and maintain pressure, then inject sealing suspension into the container until the working surface is submerged, and continue to maintain pressure until the sealing suspension fully impregnates the working surface of the silicon carbide bricks.

[0008] (4) Repeat drying and sealing suspension impregnation: Remove the silicon carbide bricks from the sealing suspension and continue to repeat steps (2) and (3);

[0009] (5) Drying: Remove the silicon carbide bricks from the sealing suspension and place them with the working surface facing upwards for drying.

[0010] (6) Firing: The dried silicon carbide bricks are fired a second time, and then cooled and removed.

[0011] Further, in step (1), the surface cleaning includes cleaning the surface of the silicon carbide brick with tools such as sandpaper and grinding wheel to remove impurities and dust from the surface; the vacuum degree after vacuuming is ≤20 Torr, and the pressure holding time is 10-20 min; the protective solvent is water.

[0012] Furthermore, in step (2), the drying depth is 10mm-15mm.

[0013] Further, in step (3), the sealing suspension comprises the following components by mass: 8-13 parts fused silica powder, 3-8 parts metallic silicon powder, 15-25 parts silicon carbide powder, 1-6 parts zirconium dioxide, 3-7 parts alumina, 1.5-3 parts titanium carbide powder, 25-35 parts silica sol, 15-25 parts aluminum chloride solution, 12-17 parts aluminum sol, and 0.5-1 parts sodium carboxymethyl cellulose.

[0014] Further, the silica sol has a mass fraction of 25-30 wt%, preferably 30 wt%; the aluminum chloride solution has a mass fraction of 20-30 wt%, preferably 30 wt%; and the aluminum sol has a mass fraction of 15-20 wt%, preferably 20 wt%.

[0015] Furthermore, the method for preparing the sealing suspension is as follows: fused silica powder, metallic silicon powder, silicon carbide powder, zirconium dioxide, alumina, titanium carbide powder, silica sol, aluminum chloride solution, aluminum sol, and sodium carboxymethyl cellulose are mixed according to mass parts. The resulting mixed solution is then ball-milled until the particle size d in the mixed solution is reduced. 85 ≤2μm, thus obtaining the sealing suspension.

[0016] Furthermore, in step (3), the sealing suspension is submerged to 15-20 mm above the working surface.

[0017] Furthermore, in step (4), steps (2) and (3) are repeated 3-4 times.

[0018] Furthermore, in step (5), the drying conditions are: drying at 105-120℃ for 5-6 hours.

[0019] Furthermore, in step (6), the conditions for the secondary firing are: a heating rate of 5-7℃ / min, and holding at 1420±10℃ for 3-4 hours.

[0020] Invention Principle: This invention first uses a protective solvent impregnation method to fully saturate the interior of the brick. Then, localized drying with a hot air gun ensures that the sealing suspension only seals the surface layer to a specified depth during the subsequent sealing process, without affecting the internal porosity of the brick. This maintains the overall thermal shock resistance of the silicon carbide brick. During the sealing process, continuous drying and adsorption ensure the effectiveness of pore sealing. The sealing suspension incorporates fused silica powder, metallic silicon powder, silicon carbide powder, zirconium dioxide, alumina, and titanium carbide powder. These components ensure a series of physicochemical changes during the secondary firing process, resulting in volume effects and sintering effects. This allows the sealing material to firmly bond to the surface layer of the silicon carbide brick, reducing the channels for external gases to enter the brick and improving the material's corrosion and wear resistance. The particle size of the sealing suspension is controlled through ball milling, ensuring the particle size d... 85 With a particle size ≤2μm, over 70% of the pore-sealing particles within the silicon carbide brick can penetrate, ensuring a reliable sealing effect. The addition of silica sol and aluminum sol to the sealing suspension enhances the sintering performance of the sealing material. The addition of aluminum chloride solution further seals even smaller pores on the working surface of the brick, significantly improving the sealing effect.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) The present invention uses silicon carbide and titanium carbide particles for surface modification treatment. These particles have excellent anti-erosion and anti-wear properties, which can significantly improve the performance of refractory bricks.

[0023] (2) The present invention uses a secondary firing process and the adsorption effect of the brick body on the sealing suspension to block the pores on the working surface of the brick body by vacuuming, thereby reducing the channels for external gas to enter the brick body and improving the corrosion resistance of the material.

[0024] (3) The surface modification treatment method of the present invention will not affect the porosity inside the brick, will not affect the thermal shock resistance of the material, and is simple to operate, has a short processing time, low cost, high product cost performance, and is suitable for large-scale production and application.

[0025] (4) Compared with enhancing the erosion resistance of bricks through coating, this invention solves the drawbacks of insufficient coating strength, easy peeling off in pieces, and complex construction process. Detailed Implementation

[0026] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0027] Example 1: The surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks provided in this example includes the following steps:

[0028] Silicon carbide bricks were cut into 40mm×40mm×50mm samples (sample 1). The samples were cleaned to remove impurities and dust. Sample 1 was placed in a container and placed in a vacuum desiccator with a vacuum level ≤20 Torr, held for 10 minutes. Water was then slowly injected into the container over 5 minutes, submerging sample 1. The pressure was then maintained at ≤20 Torr for another 10 minutes. Sample 1, along with the container, was removed and allowed to stand for 15 minutes. Sample 1 was then removed from the container and its surface moisture was wiped off with a water-soaked cloth. It was then placed on a worktable. A 40mm×40mm end face (the sealing surface, i.e., the working surface) of sample 1 was circulated and dried using a hot air gun, controlling the drying process to ensure the 40mm×40mm end face (the sealing surface, i.e., the working surface) of the sample was dried. The sealing surface is dried to a depth of approximately 10 mm. The sample 1 is quickly placed upside down on a rack in the container with its 40 mm × 40 mm end face (sealing surface) facing downwards. It is then placed in a vacuum dryer and vacuumed to ≤20 Torr, maintaining the pressure for 10 minutes. Within 3 minutes, the sealing suspension (formulation shown in Table 1) is slowly injected into the container, submerging the 40 mm × 40 mm end face (sealing surface) of the sample by 15 mm. The pressure is then maintained at ≤20 Torr for 10 minutes. The sample 1, along with the container, is removed and allowed to stand for 5 minutes. The 40 mm × 40 mm end face (sealing surface) of the sample is then dried using a hot air gun in a circulating manner, controlling the drying process to ensure a drying depth of approximately 10 mm for the sample 1 (sealing surface). The above sealing steps are repeated three times. Afterward, the sample 1 is removed and placed in an oven, where the temperature is slowly increased to 120°C for 5 hours. The dried sample 1 was placed in a kiln and heated to 1420℃±10℃ at a rate of 5℃ / min and held for 3 hours, and then cooled with the kiln.

[0029] Table 1. Formulation of the blocking suspension used in Example 1

[0030] Components Number of parts by weight Fused Quartz Powder 10 Metallic silicon powder 3 silicon carbide powder 16 Zirconium dioxide 3 Alumina 5 Titanium carbide powder 2 30wt% silica sol 33.5 30wt% aluminum chloride solution 15 20wt% aluminum sol 12 Sodium carboxymethyl cellulose 0.5

[0031] Comparative Example 1: Silicon carbide bricks were cut into 40mm×40mm×50mm samples 2. The samples were cleaned to remove impurities and dust. Sample 2 was placed upside down on a rack in a container with the 40mm×40mm end face (sealing surface) facing down. The container was then placed in a vacuum desiccator with a vacuum level ≤20 Torr, held at that pressure for 10 minutes. Then, within 3 minutes, a sealing suspension (formulation shown in Table 2) was slowly injected into the container, submerging the 40mm×40mm end face (sealing surface) of the sample by 15mm. The pressure was then maintained at ≤20 Torr for another 10 minutes. Sample 2, along with the container, was removed and allowed to stand for 5 minutes. The 40mm×40mm end face (sealing surface) of the sample was then dried using a hot air gun in a circulating manner, controlling the drying process to ensure a drying depth of approximately 10mm for the sample 2 (sealing surface). The sealing process was repeated three times. Sample 2 was then removed and placed in an oven, where it was slowly heated to 120℃ and dried for 5 hours. The dried sample 2 was placed in a kiln and heated to 1420℃±10℃ at a rate of 5℃ / min and held for 3 hours, and then cooled with the kiln.

[0032] The silicon carbide brick was cut into sample 3, which is 40mm×40mm×50mm in size. Sample 3 was not treated.

[0033] The performance of cooled samples 1, 2, and 3 is shown in Table 3 below.

[0034] Table 3 shows that the porosity of sample 1, which was impregnated with a protective solvent, was higher than that of sample 2, which was not impregnated with a protective solvent. This indicates that the protective solvent impregnation effect of sample 1 was very ideal, ensuring the porosity inside the brick and achieving the ideal sealing depth on the working surface. The porosity of sample 3, which was not treated in any way, was higher than that of sample 1, indicating that the sealing suspension achieved the ideal sealing effect and significantly reduced the porosity of the working surface. During operation, the circulating gases O2, CO, H2, and a small amount of alkali metal vapors from the dry quenching coke oven were difficult to penetrate into the brick, greatly improving the erosion resistance of the silicon carbide bricks.

[0035] Table 2 shows the formulation of the plugging suspension used in Comparative Example 1.

[0036] Components Number of parts by weight Fused Quartz Powder 10 Metallic silicon powder 3 silicon carbide powder 16 Zirconium dioxide 3 Alumina 5 Titanium carbide powder 2 30wt% silica sol 33.5 30wt% aluminum chloride solution 15 20wt% aluminum sol 12 Sodium carboxymethyl cellulose 0.5

[0037] Table 3 Performance of Sample 1, Sample 2 and Untreated Sample 3

[0038] Sample 1 Sample 2 Sample 3 Apparent porosity (%) 11.15 6.13 14.83 <![CDATA[Volume density (g / cm 3 )]]> 2.60 2.66 2.56 Water absorption rate (%) 4.29 2.30 5.79

[0039] Example 2: The surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks provided in this example includes the following steps:

[0040] Silicon carbide bricks were cut into 230mm×114mm×65mm samples (sample 4). The samples were cleaned to remove impurities and dust. Sample 4 was placed in a container and placed in a vacuum desiccator with a vacuum level ≤20 Torr, held for 10 minutes. Water was then slowly injected into the container over 5 minutes, submerging sample 4. The pressure was then maintained at ≤20 Torr for another 10 minutes. Sample 4, along with the container, was removed and allowed to stand for 15 minutes. Sample 4 was then removed from the container and its surface moisture was wiped off with a damp cloth. It was then placed on a worktable. A hot air gun was used to circulate heat and dry one 114mm×65mm end face (the sealing surface, i.e., the working surface) of sample 4, controlling the drying process to ensure the 114mm×65mm end face of the sample was properly dried. The drying depth of the (sealing surface) is 15 mm. Quickly place sample 4 upside down (114 mm × 65 mm end face, sealing surface) on the shelf in the container, and place it in a vacuum dryer with a vacuum level ≤20 Torr. Hold the pressure for 10 minutes, then slowly inject the sealing suspension (formula shown in Table 3) into the container within 3 minutes, submerging the 114 mm × 65 mm end face (sealing surface) of the sample by 20 mm. Maintain a pressure of ≤20 Torr for another 10 minutes. Remove sample 4 along with the container and let it stand for 5 minutes. Use a hot air gun to circulate and dry the 114 mm × 65 mm end face (sealing surface) of the sample, controlling the drying process to ensure a drying depth of 15 mm for sample 4 (sealing surface). Repeat the above sealing steps three times. After sealing, remove sample 4 and place it in an oven to slowly heat to 120℃ and dry for 5 hours. The dried sample 4 was placed in a kiln and heated to 1420℃±10℃ at a rate of 5℃ / min and held for 3 hours, and then cooled with the kiln.

[0041] Table 4. Formulation of the plugging suspension used in Example 2.

[0042] Components Number of parts by weight Fused Quartz Powder 8 Metallic silicon powder 3 silicon carbide powder 18 Zirconium dioxide 2 Alumina 7 Titanium carbide powder 1.5 30wt% silica sol 25 30wt% aluminum chloride solution 23 20wt% aluminum sol 12 Sodium carboxymethyl cellulose 0.5

[0043] Comparative Example 2: Silicon carbide bricks were cut into sample 5, which was 230mm×114mm×65mm. After cleaning the surface to remove impurities and dust, the sample 5 was placed on a shelf in a container and placed in a vacuum desiccator. The vacuum was ≤20 Torr and held for 10 minutes. Then, the sealing suspension (composition shown in Table 5 below) was slowly injected into the container over 3 minutes to submerge sample 5. The pressure was then maintained at ≤20 Torr for 10 minutes.

[0044] Take out sample 5 along with the container and let it stand for 5 minutes. Then use a hot air gun to heat and dry sample 5 in a cycle. Put the dried sample back into the container and repeat the sealing operation. After sealing 3 times, take out sample 5 and put sample 5 into the oven and slowly heat it to 120℃ to dry for 5 hours.

[0045] The dried sample 5 was placed in a kiln and heated to 1420℃±10℃ at a rate of 5℃ / min and held for 3 hours, and then cooled with the kiln.

[0046] The silicon carbide brick was cut into sample 6, which measures 230mm × 114mm × 65mm, and was not treated in any way.

[0047] After cooling, sample 4 and control samples 5 and 6 were subjected to a water-cooled thermal shock test at 1100℃. The heated surface of samples 4 and 5 was the sealing surface. The results are shown in Table 6 below.

[0048] Table 6 shows that the number of water-cooled thermal shock cycles for samples 6 and 4 is very similar. This indicates that by using protective solvent impregnation and controlling the sealing depth, the thermal shock resistance of the samples did not decrease significantly. However, the thermal shock resistance of sample 5, which was completely sealed, decreased significantly. Numerous studies have shown a strong correlation between the porosity of bricks and their thermal shock resistance. During rapid cooling or heating, cracks extend from the inside of the brick outwards, causing structural damage and catastrophic failure. The pores inside the brick can alter the direction of crack growth and blunt cracks, thereby improving the thermal shock resistance of the brick.

[0049] Table 5 shows the formulation of the plugging suspension used in Comparative Example 2.

[0050] Components Number of parts by weight Fused Quartz Powder 8 Metallic silicon powder 3 silicon carbide powder 18 Zirconium dioxide 2 Alumina 7 Titanium carbide powder 1.5 30wt% silica sol 25 30wt% aluminum chloride solution 23 20wt% aluminum sol 12 Sodium carboxymethyl cellulose 0.5

[0051] Table 6. Test results of samples 4, 5, and 6 under 1100℃ water-cooled thermal shock test.

[0052]

[0053] Example 3: The surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks provided in this example includes the following steps:

[0054] Silicon carbide bricks were cut into 110mm×110mm×65mm samples (sample 7). The samples were cleaned to remove impurities and dust. Sample 7 was placed in a container and placed in a vacuum desiccator with a vacuum level ≤20 Torr, held for 10 minutes, and then water was slowly injected into the container over 5 minutes to submerge sample 7. The pressure was then maintained at ≤20 Torr for another 10 minutes. Sample 7 was removed from the container and allowed to stand for 15 minutes. Sample 7 was then removed from the container and its surface moisture was wiped off with a water-soaked cloth and placed on a worktable. A hot air gun was used to circulate and dry one 110mm×110mm surface (the sealing surface, i.e., the working surface) of sample 7, controlling the drying process to ensure the drying of the 110mm×110mm surface (the sealing surface, i.e., the working surface). The sealing surface is dried to a depth of approximately 10 mm. The sample 7 is quickly placed upside down (110 mm × 110 mm, sealing surface) on a rack in the container and placed in a vacuum dryer. A vacuum of ≤20 Torr is applied and maintained for 10 minutes. Then, within 3 minutes, the sealing suspension (formulation shown in Table 7) is slowly injected into the container, submerging the 110 mm × 110 mm surface (sealing surface) of the sample by 15 mm. The pressure is then maintained at ≤20 Torr for 10 minutes. The sample 7, along with the container, is removed and allowed to stand for 5 minutes. The 110 mm × 110 mm surface (sealing surface) of the sample is then dried using a hot air gun in a circulating manner, controlling the drying process to ensure a drying depth of approximately 10 mm. The sealing steps are repeated three times. After this, the sample 7 is removed and placed in an oven, where the temperature is slowly increased to 120°C for 5 hours. The dried sample 7 was placed in a kiln and heated to 1420℃±10℃ at a rate of 5℃ / min and held for 3 hours, and then cooled with the kiln.

[0055] Table 7. Formulation of the plugging suspension used in Example 3.

[0056] Components Number of parts by weight Fused Quartz Powder 10 Metallic silicon powder 3 silicon carbide powder 16 Zirconium dioxide 3 Alumina 5 Titanium carbide powder 2 30wt% silica sol 33.5 30wt% aluminum chloride solution 15 20wt% aluminum sol 12 Sodium carboxymethyl cellulose 0.5

[0057] The silicon carbide brick was cut into 110mm×110mm×65mm sample 8 and left untreated.

[0058] The cooled sample 7 and the control sample 8 were subjected to abrasion resistance tests. The test surface of sample 7 was a 110mm × 110mm surface (sealing surface), and the test surface of sample 8 was a single 110mm × 110mm surface. The experimental results are shown in Table 8 below.

[0059] Table 8. Test results for abrasion resistance of samples 7 and 8.

[0060] Sample 7 Sample 8 <![CDATA[Wear resistance at normal temperature (cm 3 )]]> 3.12 4.27

[0061] As shown in Table 8, the wear resistance of the sealed sample 7 is significantly better than that of the untreated sample 8. This indicates that the sealing suspension has a significant effect on improving the wear resistance of the brick, suggesting that after the sample is fired twice, the sealing material adsorbed on the working surface is well sintered, reducing the porosity of the working surface, increasing the strength of the working surface, and thus improving the wear resistance of the brick.

Claims

1. A surface treatment method for improving the corrosion resistance and wear resistance of silicon carbide bricks, characterized in that, The following steps are involved: (1) Protective solvent impregnation: After surface cleaning, place the silicon carbide bricks on the container rack, evacuate and maintain pressure, then inject protective solvent into the container until the silicon carbide bricks are completely submerged, and continue to maintain pressure until the solvent fully impregnates the silicon carbide bricks. (2) Heating and drying: Take the silicon carbide brick out of the solvent, first wipe the solvent off the surface of the silicon carbide brick with a cloth strip soaked in solvent, and then use a hot air gun to circulate and dry the working surface of the silicon carbide brick. The drying depth of the working surface of the silicon carbide brick is controlled by controlling the drying regime; the drying depth of the working surface is 10mm-15mm. (3) Impregnation with sealing suspension: After the silicon carbide bricks have been dried to the desired thickness, they are placed upside down on the shelf in the container with the working surface facing down. After vacuuming and maintaining pressure, sealing suspension is injected into the container until the working surface is submerged. Pressure is maintained until the sealing suspension fully impregnates the working surface of the silicon carbide bricks. The sealing suspension comprises the following components by mass: 8-13 parts fused silica powder, 3-8 parts metallic silicon powder, 15-25 parts silicon carbide powder, 1-6 parts zirconium dioxide, 3-7 parts alumina, 1.5-3 parts titanium carbide powder, 25-35 parts silica sol, 15-25 parts aluminum chloride solution, 12-17 parts alumina sol, and 0.5-1 parts sodium carboxymethyl cellulose. The sealing suspension covers the working surface to a depth of 15-20 mm. (4) Repeat drying the working surface and impregnation with the sealing suspension: Remove the silicon carbide bricks from the sealing suspension and continue to repeat steps (2) and (3). (5) Drying: Remove the silicon carbide bricks from the sealing suspension and place them with the working surface facing upwards for drying. (6) Firing: The dried silicon carbide bricks are fired a second time, and then cooled and removed. The conditions for the second firing are: heating rate of 5-7℃ / min, and holding at 1420±10℃ for 3-4h.

2. The surface treatment method according to claim 1, characterized in that, In step (1), the vacuum degree after evacuation is ≤20 Torr, and the pressure holding time is 10-20 min; the protective solvent is water.

3. The surface treatment method according to claim 1, characterized in that, The silica sol has a mass fraction of 25-30 wt%; the aluminum chloride solution has a mass fraction of 20-30 wt%; and the aluminum sol has a mass fraction of 15-20 wt%.

4. The surface treatment method according to claim 1, characterized in that, The method for preparing the sealing suspension is as follows: fused silica powder, metallic silicon powder, silicon carbide powder, zirconium dioxide, alumina, titanium carbide powder, silica sol, aluminum chloride solution, aluminum sol, and sodium carboxymethyl cellulose are mixed according to mass parts. The resulting mixed solution is then ball-milled until the particle size d in the mixed solution is reduced. 85 ≤2μm, thus obtaining the sealing suspension.

5. The surface treatment method according to claim 1, characterized in that, In step (4), steps (2) and (3) are repeated 3-4 times.

6. The surface treatment method according to claim 1, characterized in that, In step (5), the drying conditions are: drying at 105-120℃ for 5-6 hours.

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