Preparation method of alumina-based crucible for high-temperature alloy smelting

Abstract

According to the preparation method of the alumina-based crucible for high-temperature alloy smelting, through reasonable design of the grain composition of the alumina powder raw material, formation of uniformly-distributed air holes in the crucible is promoted, the thermal shock resistance of the crucible is improved, crack expansion of the crucible in a rapid cooling and rapid heating environment is prevented, and the crucible is free of cracks after being used; by adding the coarse particles, better structural support can be provided, and thermal stress concentration is reduced, so that the thermal shock resistance of the crucible is enhanced; the aluminum oxide powder is high in lattice energy and stable in crystal structure, particle diffusion needs high activity, and the strength of the crucible is improved by adding the sintering aid.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic crucible preparation, and in particular relates to a method for preparing an alumina-based crucible for high-temperature alloy smelting. Background Art

[0002] Crucible is a key component for vacuum induction melting of high-temperature alloys. High-temperature alloy melting places extremely high demands on crucibles. The crucible needs to withstand high temperatures when melting alloys, and cool rapidly after melting. It must withstand repeated heating and cooling processes during use, so the crucible is required to have excellent thermal shock stability. Before melting the alloy, the crucible needs to be clamped with a tool and placed in a vacuum melting furnace. After melting, it needs to be taken out of the furnace. During the melting process, it needs to bear a certain weight of high-temperature alloy, so the crucible is required to have excellent mechanical properties.

[0003] Pores can inhibit thermal shock cracks. A certain amount of evenly distributed pores can reduce the thermal expansion coefficient, prevent crack propagation, and improve thermal shock resistance. Thermal shock cracks in non-dense crucibles are often inhibited by pores. Pores play a role in passivating crack tips, reducing stress concentration, and reducing thermal conductivity to act as a heat insulator; on the contrary, dense high-strength crucibles are prone to bursting under thermal shock. The thermal shock resistance of the crucible can be improved by appropriately increasing the porosity. The pores can prevent crack propagation and change the crack propagation path, so that the crack can only propagate statically within a relatively short distance. Summary of the invention

[0004] The present invention provides a method for preparing an alumina-based crucible for high-temperature alloy smelting, and preparing an alumina-based crucible having excellent thermal shock resistance and strength, which is specifically as follows:

[0005] A method for preparing an alumina-based crucible for high-temperature alloy smelting, comprising:

[0006] Step 1: First, pour deionized water into the material tank, add monomers and cross-linking agents, and disperse until completely dissolved to prepare a premixed solution;

[0007] Then, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, and sintering aid are sequentially added to the premixed liquid, and dispersed evenly at high speed to obtain ceramic slurry;

[0008] Among them, aluminum oxide A, aluminum oxide B, aluminum oxide C, and aluminum oxide D are four groups of aluminum oxide powders with different D50 particle size ranges, and the D50 particle size ranges of aluminum oxide A, aluminum oxide B, aluminum oxide C, and aluminum oxide D are 0.1-1 μm, 1-10 μm, 10-100 μm, and 100-150 μm, respectively;

[0009] The mass proportions of deionized water, monomer, cross-linking agent, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, sintering aid, initiator and catalyst are 8-15wt%, 1-4wt%, 0.05-0.35wt%, 0.3-0.8wt%, 0.01-0.05wt%, 12-18wt%, 30-36wt%, 5-10wt%, 20-35wt%, 0.2-0.8wt%, 0.1-0.4wt% and 0.01-0.1wt% respectively.

[0010] Step 2: vacuum stirring the ceramic slurry to achieve a defoaming effect, thereby obtaining a defoamed ceramic slurry;

[0011] Step 3: Add initiator and catalyst to the defoamed ceramic slurry in sequence, then pour into a preheated mold, solidify and shape to obtain a crucible blank, dry at room temperature, dry and sinter to obtain an alumina-based crucible.

[0012] Furthermore, in step 1, the dispersion speed when preparing the premix is ​​400 to 1000 rpm.

[0013] Furthermore, in step 1, the monomer is acrylamide, the cross-linking agent is N,N-methylenebisacrylamide, and the dispersion speed for high-speed dispersion to uniformly obtain the ceramic slurry is 400-1000 rpm.

[0014] Furthermore, in step 1, the dispersant is a 20% concentration of isobam06 alkaline solution.

[0015] Furthermore, in step 1, the type of sintering aid is Sm2O3, La2O3, kaolin or Y2O3.

[0016] Furthermore, in step 2, the vacuum degree is -0.05 to -0.09 MPa, and the stirring speed is 30 to 60 rpm.

[0017] Furthermore, in step three, the initiator is ammonium persulfate and the catalyst is tetramethylethylenediamine.

[0018] Furthermore, in step three, the mold preheating temperature is 40° C. and the curing time is 20 to 60 minutes.

[0019] Further, in step three, drying is performed at room temperature for 20 to 40 hours, and the drying procedure is as follows: heating at a rate of 5°C to 40°C, keeping warm for 4 to 8 hours, heating at a rate of 5°C to 80°C, keeping warm for 4 to 8 hours, heating at a rate of 5°C to 150°C, keeping warm for 4 to 8 hours.

[0020] Furthermore, in step three, the sintering system is to start from room temperature, increase the temperature to 300°C at a rate of 0.5-2°C, keep it warm for 1-8 hours, increase the temperature to 600°C at a rate of 1-3°C, keep it warm for 1-8 hours, increase the temperature to 1250-1500°C at a rate of 1-3°C, keep it warm for 1-8 hours, and then cool to room temperature with the furnace.

[0021] The present invention promotes the formation of evenly distributed pores inside the crucible by reasonably designing the raw material particle grading, thereby increasing the thermal shock resistance of the crucible and preventing the expansion of cracks in the crucible under a rapid cooling and heating environment. The crucible is crack-free after use; adding coarse particles can provide better structural support and reduce thermal stress concentration, thereby enhancing the thermal shock resistance of the crucible; the alumina powder has a high lattice energy and a stable crystal structure, and particle diffusion requires a high activity, and the strength of the crucible is improved by adding a sintering aid. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0023] Example 1

[0024] Step 1: First, pour deionized water into the material tank, add monomers and cross-linking agents, and disperse until completely dissolved to prepare a premixed solution;

[0025] Then, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, and sintering aid are sequentially added to the premixed liquid, and dispersed evenly at high speed to obtain ceramic slurry;

[0026] Step 2: vacuum stirring the ceramic slurry to achieve a defoaming effect, thereby obtaining a defoamed ceramic slurry;

[0027] Step 3: Add initiator and catalyst to the defoamed ceramic slurry in sequence, then pour into a preheated mold, solidify and shape to obtain a crucible blank, dry at room temperature, dry and sinter to obtain an alumina-based crucible.

[0028] In this embodiment, the monomer is acrylamide, the cross-linking agent is N,N-methylenebisacrylamide, and the dispersion speed of the prepared premix and the prepared ceramic slurry is 1000 rpm;

[0029] The dispersant is a 20% concentration of isobam06 alkaline solution;

[0030] The D50 particle size ranges of aluminum oxide A, aluminum oxide B, aluminum oxide C, and aluminum oxide D are 0.1-1 μm, 1-10 μm, 10-100 μm, and 100-150 μm, respectively;

[0031] The mass proportions of deionized water, monomer, cross-linking agent, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, sintering aid, initiator, and catalyst are 14wt%, 1.8wt%, 0.2wt%, 0.5wt%, 0.03wt%, 18wt%, 33.8wt%, 6wt%, 24.87wt%, 0.4wt%, 0.3wt%, and 0.1wt%, respectively;

[0032] The type of sintering aid is La2O3;

[0033] In step 2, the vacuum degree was -0.08 MPa and the stirring speed was 40 rpm;

[0034] In step 3, the initiator is ammonium persulfate and the catalyst is tetramethylethylenediamine;

[0035] The mold preheating temperature is 40°C and the crucible curing time is 40 minutes;

[0036] Dry at room temperature for 36 hours. The drying procedure is as follows: increase the temperature to 40°C at a rate of 5°C, keep warm for 6 hours, increase the temperature to 80°C at a rate of 5°C, keep warm for 6 hours, increase the temperature to 150°C at a rate of 5°C, keep warm for 6 hours;

[0037] The sintering system is as follows: starting from room temperature, heating up to 300°C at a rate of 2°C, keeping warm for 4 hours, heating up to 600°C at a rate of 1°C, keeping warm for 4 hours, heating up to 1300°C at a rate of 2°C, keeping warm for 4 hours, and then cooling to room temperature with the furnace.

[0038] The alumina-based crucible prepared in this embodiment has a thermal shock resistance of 10 times at 1200° C. and a flexural strength of 16.3 MPa.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is:

[0041] In step 1, the dispersion speed when preparing the premix is ​​800 rpm;

[0042] The monomer is acrylamide, the cross-linking agent is N,N-methylenebisacrylamide, and the dispersion speed when preparing the ceramic slurry is 1000 rpm;

[0043] The dispersant is a 20% concentration of isobam06 alkaline solution;

[0044] The mass proportions of deionized water, monomer, cross-linking agent, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, sintering aid, initiator, and catalyst are 12wt%, 2.5wt%, 0.3wt%, 0.8wt%, 0.03wt%, 14.72wt%, 32.25wt%, 8.8wt%, 27.8wt%, 0.4wt%, 0.3wt%, and 0.1wt%, respectively;

[0045] The type of sintering aid is Sm2O3.

[0046] In step 2, the vacuum degree was -0.07 MPa and the stirring speed was 30 rpm;

[0047] In step 3, the crucible solidification time is 30 minutes;

[0048] Dry at room temperature for 40 hours. The drying procedure is as follows: heat up to 40°C at a rate of 5°C, keep warm for 8 hours, heat up to 80°C at a rate of 5°C, keep warm for 8 hours, heat up to 150°C at a rate of 5°C, keep warm for 8 hours.

[0049] The sintering system is as follows: starting from room temperature, heating up to 300°C at a rate of 1°C, keeping warm for 3 hours, heating up to 600°C at a rate of 1°C, keeping warm for 6 hours, heating up to 1350°C at a rate of 1°C, keeping warm for 4 hours, and then cooling to room temperature with the furnace.

[0050] The alumina-based crucible prepared in this embodiment has a thermal shock resistance of 13 times at 1200° C. and a flexural strength of 13.8 MPa.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is:

[0053] In step one,

[0054] The dispersion speed when preparing the premix was 900 rpm;

[0055] The mass proportions of deionized water, monomer, cross-linking agent, dispersant, ammonia water, alumina A, alumina B, alumina C, alumina D, sintering aid, initiator and catalyst are 11wt%, 1.6wt%, 0.1wt%, 0.6wt%, 0.03wt%, 19.5wt%, 35.4wt%, 7.97wt%, 23wt%, 0.4wt%, 0.3wt% and 0.1wt% respectively.

[0056] The type of sintering aid is Y2O3.

[0057] In step 2, the stirring speed is 45 rpm;

[0058] In step three,

[0059] Crucible curing time 50min.

[0060] Dry at room temperature for 28 hours. The drying procedure is as follows: increase the temperature to 40°C at a rate of 5°C, keep warm for 5 hours, increase the temperature to 80°C at a rate of 5°C, keep warm for 5 hours, increase the temperature to 150°C at a rate of 5°C, and keep warm for 5 hours.

[0061] The sintering system is as follows: starting from room temperature, heating up to 300°C at a rate of 1°C, keeping warm for 6 hours, heating up to 600°C at a rate of 2°C, keeping warm for 5 hours, heating up to 1280°C at a rate of 2°C, keeping warm for 6 hours, and then cooling to room temperature with the furnace.

[0062] The alumina-based crucible prepared in this embodiment has a thermal shock resistance of 12 times at 1200° C. and a flexural strength of 15.4 MPa.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that no sintering aid is added in step 1. The thermal shock resistance of the prepared crucible at 1200°C is 15 times, and the flexural strength is 9.6 MPa, which does not meet the quality requirements of alumina-based crucibles.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that in step 1, no alumina A, alumina C, or alumina D is added. The prepared crucible has a thermal shock resistance of 5 times at 1200° C. and a flexural strength of 19.2 MPa, which does not meet the quality requirements of alumina-based crucibles.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an alumina-based crucible for high-temperature alloy smelting, characterized in that: A method for preparing an alumina-based crucible for high-temperature alloy smelting, comprising: Step 1: First, pour deionized water into the material tank, add monomers and cross-linking agents, and disperse until completely dissolved to prepare a premixed solution; Then, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, and sintering aid are sequentially added to the premixed liquid, and dispersed evenly at high speed to obtain ceramic slurry; Among them, aluminum oxide A, aluminum oxide B, aluminum oxide C, and aluminum oxide D are four groups of aluminum oxide powders with different D50 particle size ranges, and the D50 particle size ranges of aluminum oxide A, aluminum oxide B, aluminum oxide C, and aluminum oxide D are 0.1-1 μm, 1-10 μm, 10-100 μm, and 100-150 μm, respectively; The mass proportions of deionized water, monomer, cross-linking agent, dispersant, ammonia water, aluminum oxide A, aluminum oxide B, aluminum oxide C, aluminum oxide D, sintering aid, initiator and catalyst are 8-15wt%, 1-4wt%, 0.05-0.35wt%, 0.3-0.8wt%, 0.01-0.05wt%, 12-18wt%, 30-36wt%, 5-10wt%, 20-35wt%, 0.2-0.8wt%, 0.1-0.4wt% and 0.01-0.1wt% respectively. Step 2: vacuum stirring the ceramic slurry to achieve a defoaming effect, thereby obtaining a defoamed ceramic slurry; Step 3: Add initiator and catalyst to the defoamed ceramic slurry in sequence, then pour into a preheated mold, solidify and shape to obtain a crucible blank, dry at room temperature, dry and sinter to obtain an alumina-based crucible.

2. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 1, the dispersion speed when preparing the premix is ​​400 to 1000 rpm.

3. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 1, the monomer is acrylamide, the cross-linking agent is N,N-methylenebisacrylamide, and the dispersion speed for high-speed dispersion to uniformly obtain the ceramic slurry is 400-1000 rpm.

4. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 1, the dispersant is a 20% concentration of isobam06 alkaline solution.

5. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 1, the sintering aid is Sm2O3, La2O3, kaolin or Y2O3.

6. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 2, the vacuum degree is -0.05 to -0.09 MPa, and the stirring speed is 30 to 60 rpm.

7. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 3, the initiator is ammonium persulfate and the catalyst is tetramethylethylenediamine.

8. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step 3, the mold preheating temperature is 40° C. and the curing time is 20 to 60 minutes.

9. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step three, dry at room temperature for 20 to 40 hours, and the drying procedure is as follows: heat up to 40°C at a rate of 5°C, keep warm for 4 to 8 hours, heat up to 80°C at a rate of 5°C, keep warm for 4 to 8 hours, heat up to 150°C at a rate of 5°C, keep warm for 4 to 8 hours.

10. The method for preparing an alumina-based crucible for high-temperature alloy smelting according to claim 1, characterized in that: In step three, the sintering system is to start from room temperature, heat up to 300°C at a rate of 0.5-2°C, keep warm for 1-8 hours, heat up to 600°C at a rate of 1-3°C, keep warm for 1-8 hours, heat up to 1250-1500°C at a rate of 1-3°C, keep warm for 1-8 hours, and then cool to room temperature with the furnace.