Method for removing attachments on inner wall of silicon carbide mold sleeve

Abstract

The invention provides a method for removing attachments on the inner wall of a sleeve of a silicon carbide mold. The method is thorough in removal and does not damage the inner wall surface of the sleeve. The method comprises the following steps: rinsing the sleeve by adopting a rinsing solution containing a surfactant under an ultrasonic condition; soaking the sleeve in a pickling agent; the sleeve is cleaned with pure water under the ultrasonic condition; the inner wall of the sleeve is polished through aluminum oxide polishing paste; rinsing the sleeve by adopting a rinsing solution containing a surfactant under an ultrasonic condition; pure water is used for cleaning the sleeve in ultrasonic waves; and the cleaned sleeve is dried. The chemical reagent is adopted to dissolve attachments on the surface of the inner wall of the silicon carbide sleeve, removal is more thorough, uniformity is better, meanwhile, the inner wall face of the sleeve is not damaged, and it is guaranteed that the size precision of the sleeve is maintained at the micron level.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-precision molding, and particularly relates to a method for removing attachments on the inner wall of a silicon carbide mold sleeve. Background Art

[0002] In the process of molding aspherical lenses, the preform is molded in a viscoelastic state. At this time, the sleeve is subjected to the combined action of high temperature and mold friction. In order to meet the characteristics of thermal conductivity, high hardness, and high wear resistance, and at the same time to ensure the misalignment and inclination between the two surfaces of the lens, silicon carbide molds are usually selected as hot pressing molds. Silicon carbide is suitable as a hard sleeve material under high temperature and high pressure. Its expansion coefficient is slightly smaller than that of tungsten carbide, which can ensure that the assembly gap of the mold is large enough at room temperature for normal loading and unloading, and the assembly gap can be controlled at the micron level at the molding temperature to ensure the eccentricity of the aspherical lens.

[0003] Both the upper mold 1 and the lower mold 2 of the silicon carbide mold are made of tungsten carbide, and a silicon carbide sleeve 3 is used to laterally limit the upper mold 1 and the lower mold 2, as Figure 1 shown. Although there is a clearance fit between the silicon carbide sleeve 3 and the upper mold 1 and the lower mold 2, there is friction between the cylindrical surfaces of the upper mold 1 and the lower mold 2 and the inner wall of the silicon carbide sleeve 3 during the molding process. Although the molding is carried out in an oxygen-free environment, glass 4 will release oxygen at high temperature and contact the material of the silicon carbide sleeve 3. An oxide layer will form on the inner wall surface of the silicon carbide sleeve 3 and an attachment formed after the glass volatilizes. As the use time increases, the attachments on the inner wall of the silicon carbide sleeve 3 gradually accumulate. These attachments will cause a series of problems such as changes in the assembly tolerance, thermal expansion amount, and roughness between the upper mold 1 and the lower mold 2 and the silicon carbide sleeve 3, resulting in a negative assembly tolerance in some areas between the upper mold 1 and the lower mold 2 and the silicon carbide sleeve 3 at the molding temperature, causing jams during the molding process of the upper mold 1 and the lower mold 2, resulting in abnormal molding and inability to form products. In severe cases, it will also cause the sleeve to break and the mold to be damaged. At present, physical methods are used to remove the attachments on the inner wall of the silicon carbide sleeve 3, but the physical methods are time-consuming and laborious, and it is difficult to completely remove the attachments on the inner wall of the sleeve, and it will also affect the size and shape of the silicon carbide sleeve 3. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for removing attachments on the inner wall of a silicon carbide mold sleeve that can be removed thoroughly and does not damage the inner wall surface of the sleeve.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for removing attachments on the inner wall of a silicon carbide mold sleeve, the method comprising the following steps:

[0006] 1) Rinsing the sleeve with a rinsing solution containing a surfactant at a temperature of 40 - 60 °C under ultrasonic conditions with a frequency of 30 - 40 KHZ;

[0007] 2) Immerse the sleeve in the pickling agent.

[0008] The components of the pickling agent are: 10 - 15 parts of hydrofluoric acid (by mass, and the following components are all by mass), 15 - 20 parts of citric acid, 1 - 2 parts of sodium chloride, and 100 parts of pure water.

[0009] 3) Clean the sleeve with pure water under ultrasonic conditions with a frequency of 30 - 40 KHZ.

[0010] 4) Polish the inner wall of the sleeve with alumina polishing paste.

[0011] 5) Rinse the sleeve with a rinsing solution containing a surfactant at a temperature of 40 - 60 °C under ultrasonic conditions with a frequency of 30 - 40 KHZ.

[0012] 6) Clean the sleeve with pure water in ultrasonic waves with a frequency of 30 - 40 KHZ.

[0013] 7) Dry the cleaned sleeve.

[0014] Further, for the rinsing solution in steps 1) and 5), 1 - 2 parts of surfactant are added to 180 - 220 parts of pure water, heated to 40 - 60 °C and mixed evenly to obtain the rinsing solution.

[0015] Further, the surfactant in steps 1) and 5) is one or more of linear alkylbenzene sulfonate, sodium dodecyl sulfate, and α - olefin sulfonate.

[0016] Further, step 2) is: Immerse the sleeve in the pickling agent for 300 ± 30 S at room temperature.

[0017] Further, the cleaning time in step 3) is 60 - 90 S, and the pure water used has a resistivity higher than 15 MΩ.

[0018] Further, step 4) is: Use a wool ball brush to polish the inner wall of the sleeve with alumina polishing paste for 60 - 120 S.

[0019] Further, the alumina polishing paste in step 4) is obtained by mixing 1 - 2 parts of pure water with 1 - 3 parts of alumina powder evenly.

[0020] Further, step 6) is: Clean the sleeve with pure water at a temperature of 25 - 35 °C in ultrasonic waves with a frequency of 30 - 40 KHZ for 300 - 330 S, and the pure water used has a resistivity higher than 15 MΩ.

[0021] Furthermore, the step 7) is: using a dryer to dry the cleaned sleeve at a drying temperature of 60-80°C.

[0022] The beneficial effects of the present invention are: chemical reagents are used to dissolve the attachments on the inner wall surface of the silicon carbide sleeve, replacing the traditional physical removal method, thereby improving production efficiency, removing more thoroughly and with better uniformity, and being able to thoroughly process the dead corners of the inner wall of the sleeve without damaging the inner wall surface of the sleeve, thereby ensuring that the dimensional accuracy of the sleeve is maintained at the micron level. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of a silicon carbide mold. DETAILED DESCRIPTION

[0024] The method for removing the attachments on the inner wall of the silicon carbide mold sleeve of the present invention comprises the following steps:

[0025] 1) Rinsing: Rinse the sleeve with a rinsing solution at a temperature of 40-60°C under ultrasonic conditions at a frequency of 30-40KHZ;

[0026] The rinsing solution is prepared by adding 1-2 parts of a surfactant to 180-220 parts of pure water, heating to 40-60° C. and mixing evenly to obtain a rinsing solution. The surfactant may be one or more of linear alkylbenzene sodium sulfonate, sodium dodecyl sulfate and α-olefin sulfonate.

[0027] During the production process, the sleeve may be contaminated by sweat, dust, impurities, and glass fragments. During the molding process, high temperature and high pressure will cause these impurities to adhere to the surface of the sleeve. These impurities will hinder the removal of the attachments on the inner wall of the sleeve. The rinsing step is to remove impurities on the surface of the sleeve.

[0028] 2) Pickling: Soak the sleeve in the pickling agent for 300±30S at room temperature;

[0029] The components of the pickling agent are: 10-15 parts of hydrofluoric acid, 15-20 parts of citric acid, 1-2 parts of sodium chloride and 100 parts of pure water, and the room temperature can be 25°C;

[0030] 3) Water washing: Use pure water to clean the pickled sleeve for 60-90 seconds under ultrasonic conditions with a frequency of 30-40KHZ;

[0031] The above-mentioned pure water is preferably pure water with a resistivity higher than 15MΩ;

[0032] 4) Polishing: Use a wool ball brush to polish the inner wall of the sleeve with alumina polishing paste. The polishing time is 60-120S;

[0033] The aluminum oxide polishing paste is prepared by adding 1-2 parts of pure water to 1-3 parts of aluminum oxide powder and mixing them evenly to obtain the aluminum oxide polishing paste;

[0034] 5) Rinsing: Rinse the sleeve with a rinsing solution at a temperature of 40-60° C. under ultrasonic conditions at a frequency of 30-40 KHZ;

[0035] The rinsing solution is the same as the rinsing solution used in step 1);

[0036] 6) Water washing: clean the rinsed sleeve with pure water at a temperature of 25-35°C for 300-330 seconds under ultrasonic conditions at a frequency of 30-40KHZ;

[0037] The above-mentioned pure water is preferably pure water with a resistivity higher than 15MΩ;

[0038] 7) Drying: Use a dryer to dry the washed sleeve at a temperature of 60-80°C.

[0039] The method for removing attachments on the inner wall of the silicon carbide mold sleeve of the present invention is a chemical removal method. Compared with the physical removal method, the present invention does not damage the surface quality of the inner wall of the sleeve after removing the attachments, ensures that the surface accuracy of the inner wall of the sleeve is maintained at the micron level, and can extend the service life of the sleeve.

[0040] Embodiment 1:

[0041] The method for removing the attachments on the inner wall of the silicon carbide mold sleeve comprises the following steps:

[0042] 1) Soak the sleeve in a rinsing solution at a temperature of 60°C, an ultrasonic frequency of 40KHZ, and a rinsing time of 10 minutes;

[0043] The rinse solution components are one part of linear alkylbenzene sodium sulfonate, one part of sodium dodecyl sulfate and 200 parts of pure water;

[0044] 2) pickling the rinsed sleeve with a pickling agent, the pickling temperature is 25° C., the pickling time is 320 seconds, and the components of the pickling agent are: 10 parts of hydrofluoric acid, 15 parts of citric acid, 1 part of sodium chloride and 100 parts of pure water;

[0045] 3) Use pure water with a resistivity higher than 15MΩ to clean the pickled sleeve, the cleaning time is 80S, the ultrasonic frequency is 40KHZ, and the cleaning temperature is 60℃;

[0046] 4) using a wool ball brush to polish the inner wall of the sleeve with an alumina polishing paste for 90 seconds, wherein the alumina polishing paste comprises: 2 parts of alumina powder and 1 part of pure water;

[0047] 5) Soaking the polished sleeve in a rinsing solution at a temperature of 40° C., an ultrasonic frequency of 40 KHZ, and a rinsing time of 10 min, wherein the rinsing solution comprises one part of linear alkylbenzene sulfonate, one part of sodium dodecyl sulfate, and 200 parts of pure water;

[0048] 6) Use pure water with a resistivity higher than 15MΩ to wash the rinsed sleeve, the washing time is 300S, the ultrasonic frequency is 40KHZ, and the washing temperature is 35°C;

[0049] 7) Use a dryer to dry the cleaned sleeve at a drying temperature of 80°C.

[0050] The surface of the silicon carbide mold sleeve after the attachments were removed was observed and the performance was tested. Intuitively, there was no black oxide layer visible to the naked eye, and the entire mold was the light gray color of the original silicon carbide.

[0051] The roundness test was performed on the inside of the silicon carbide mold sleeve aperture: the three-point apertures before removal of the attachments were 17.0043mm (test height 2mm), 17.0039mm (test height 4mm), and 17.0012mm (test height 8mm). There was a PV of more than 2μm inside the aperture, which affected the stress conditions during mold assembly and molding; after removal of the attachments, the three-point apertures were 17.0044mm (test height 2mm), 17.0040mm (test height 4mm), and 17.0047mm (test height 8mm). The PVs were all within 1μm, which met the design accuracy requirements of the silicon carbide sleeve (the design value is 17.0045±0.0005mm), and there was no abnormality in the lens after molding.

[0052] Scanning electron microscope analysis of the removal of Example 1 shows that the oxides and impurity elements are completely removed, leaving only carbon, tungsten and adhesive chromium, so the inner wall surface of the sleeve is completely removed. From the above test results, it can be seen that Example 1 uses a combination of acid washing and alkali washing to remove the oxide layer of the sleeve, which does not affect the inner diameter of the sleeve. Chemical reagents are used for maintenance, the process is simple, and the oxides and impurities are completely removed.

[0053] Embodiment 2:

[0054] The method for removing the attachments on the inner wall of the silicon carbide mold sleeve comprises the following steps:

[0055] 1) Soak the sleeve in a rinsing solution at a temperature of 40°C, an ultrasonic frequency of 40KHZ, and a rinsing time of 10 minutes;

[0056] The rinse solution comprises one part of linear alkylbenzene sodium sulfonate, one part of sodium dodecyl sulfate and 200 parts of pure water;

[0057] 2) The pickled sleeve after rinsing is pickled with a pickling agent. The pickling temperature is 25°C and the rinsing time is 300S. The components of the pickling agent are: 15 parts of hydrofluoric acid, 20 parts of citric acid, 2 parts of sodium chloride, and 100 parts of pure water;

[0058] 3) The pickled sleeve is cleaned with pure water having a resistivity higher than 15 MΩ. The cleaning time is 80S, the ultrasonic frequency is 40KHZ, and the cleaning temperature is 60°C;

[0059] 4) The inner wall of the sleeve is polished with a wool ball brush through alumina polishing paste. The polishing time is 120S. The components of the alumina polishing paste are: 3 parts of alumina powder and 2 parts of pure water;

[0060] 5) The polished sleeve is immersed in a rinsing solution at a temperature of 40°C. The ultrasonic frequency is 40KHZ and the rinsing time is 10 min. The components of the rinsing solution are: 1 part of linear alkylbenzene sulfonate, 1 part of sodium dodecyl sulfate, and 200 parts of pure water;

[0061] 6) The rinsed sleeve is washed with pure water having a resistivity higher than 15 MΩ. The washing time is 5 min, the ultrasonic frequency is 40KHZ, and the washing temperature is 40°C;

[0062] 7) The cleaned sleeve is dried with a dryer. The drying temperature is 60°C.

[0063] The surface of the silicon carbide mold sleeve after peroxide removal is observed and performance tested. Intuitively, there is no visible black oxide layer to the naked eye, and the entire mold presents the light gray color of the original silicon carbide; the roundness of the inner diameter of the silicon carbide sleeve is tested with a roundness instrument: before oxide removal, the three-point inner diameters are 17.0041 mm (test height 2 mm), 17.0041 mm (test height 4 mm), 17.0017 mm (test height 8 mm), and there is PV above 2 μm inside the inner diameter, which affects the force condition during mold assembly and molding. After removal, the three-point inner diameters are 17.0044 mm (test height 2 mm), 17.0046 mm (test height 4 mm), 17.0041 mm (test height 8 mm), and the PV is within 1 μm, meeting the design accuracy requirements of the silicon carbide sleeve, and there is no abnormality in the lens after molding.

[0064] It can be seen from the above test results that the PV of the silicon carbide mold sleeve in Example 2 has no significant difference compared with that in Example 1, and the PV is still controlled within 1 μm. The size of the processed sleeve meets the design value and does not affect the molding production.

[0065] The present invention removes by chemical means, and through repeated stamping and friction at high temperature, the removal is more thorough, more uniform and faster. At the same time, by measuring the inner diameter size of the sleeve before and after treatment multiple times, it is found that the method of the present invention does not cause the size of the sleeve to change. The method of the present invention not only improves production efficiency, but also avoids the wear and scratching of the inner wall of the sleeve caused by physical removal methods, and improves the service life of the sleeve. The present invention is of great significance for the manufacture and production of optical aspheric lenses.

Claims

1. A method for removing attachments from the inner wall of a silicon carbide mold sleeve, characterized in that: The method comprises the following steps: 1) Rinse the sleeve with a rinsing solution containing a surfactant at a temperature of 40-60° C. under ultrasonic conditions at a frequency of 30-40 KHZ; 2) Soak the sleeve in the pickling agent; The components of the pickling agent are: 10-15 parts by mass of hydrofluoric acid, 15-20 parts by mass of citric acid, 1-2 parts by mass of sodium chloride and 100 parts by mass of pure water; 3) Clean the sleeve with pure water in an ultrasonic wave with a frequency of 30-40KHZ; 4) Polishing the inner wall of the sleeve with alumina polishing paste; 5) rinsing the sleeve with a rinsing solution containing a surfactant at a temperature of 40-60° C. under ultrasonic conditions at a frequency of 30-40 KHZ; 6) Clean the sleeve with pure water in an ultrasonic wave with a frequency of 30-40KHZ; 7) Dry the cleaned sleeve.

2. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: In step 1) and step 5), the rinsing solution is prepared by adding 1-2 parts of a surfactant into 180-220 parts of pure water, heating to 40-60° C. and mixing evenly to obtain a rinsing solution.

3. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1 or 2, characterized in that: The surfactant in step 1) and step 5) is one or more of linear alkylbenzene sulfonate, sodium dodecyl sulfate and α-olefin sulfonate.

4. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: The step 2) is: soaking the sleeve in a pickling agent for 300±30S at room temperature.

5. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: The cleaning time in step 3) is 60-90 seconds.

6. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: The step 4) is: using a wool ball brush to polish the inner wall of the sleeve with aluminum oxide polishing paste for 60-120 seconds.

7. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1 or 6, characterized in that: Step 4) The aluminum oxide polishing paste is prepared by adding 1-2 parts of pure water to 1-3 parts of aluminum oxide powder and mixing them evenly to obtain an aluminum oxide polishing paste.

8. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: The step 6) is: using pure water at a temperature of 25-35° C. to clean the sleeve for 300-330 seconds in an ultrasonic wave at a frequency of 30-40 KHZ.

9. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 5 or 8, characterized in that: The pure water in step 1) and step 5) has a resistivity higher than 15 MΩ.

10. The method for removing the attachments on the inner wall of the silicon carbide mold sleeve according to claim 1, characterized in that: The step 7) is: using a dryer to dry the cleaned sleeve at a drying temperature of 60-80°C.

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