A rapid heat-conducting sand mold material and a method for preparing the same

Abstract

The present application relates to a kind of quick heat-conducting sand mould material and its preparation method, and the sand mould material is mainly composed of heat-conducting aggregate and high-temperature working matrix, and the raw material is alpha-alumina powder, additional high-thermal-conductivity aggregate, magnesium oxide aggregate, binder RTV silicone rubber, wherein the main raw material of heat-conducting aggregate is sintered magnesium oxide particle aggregate, graphite particle, water glass solution and silica ash.By using the present application as a casting mold, the stress cracking phenomenon on the surface of zirconium-chromium corundum blank is significantly reduced, and the product qualification rate of the material is significantly increased.The present application can effectively solve the stress cracking problem during the annealing process of melting and casting zirconium-chromium corundum.

Description

Technical Field

[0001] This invention patent relates to shaped refractory products, and in particular to a rapid heat-conducting sand mold material used in the annealing process of cast materials and its preparation method. Background Technology

[0002] Sand molds are a core consumable in the process of casting refractory materials, and their importance is self-evident. They must not only withstand the impact of high-temperature molten metal and cool it to room temperature, but also ensure the shape and dimensional accuracy of the castings. Currently, raw materials such as magnesia, quartz sand, graphite, and periclase-spinel are widely used to prepare sand molds, such as the resin sand mold disclosed in patent CN102341550B, the magnesia sand mold and graphite sand mold described in patent CN100381400C, and novel negative pressure sand molds, such as the novel negative pressure sand molds described in patents CN102674867B and CN102672794B. However, while these traditional sand molds show good adaptability when used for casting AZS or alumina refractory materials at casting temperatures of 1700-1900℃, when used for casting zirconium-chromium corundum, the castings often exhibit edge and corner cracking after demolding. In-depth research revealed that the aluminum-chromium solid solution has a wide crystallization temperature range, resulting in a higher overall temperature of the casting after casting. The rate of liquid-to-solid phase transformation on the casting surface is slow, leading to a thinner hard shell formed during the high-temperature stage. In this situation, the hard shell on the casting surface is highly susceptible to fracture under external force, causing stress-induced fractures. This problem significantly reduces the product yield. Currently, a common method to address this issue is to replace the low thermal conductivity medium surrounding the sand mold with a high thermal conductivity medium. This aims to rapidly dissipate the internal temperature of the casting, quickly reducing the external surface temperature to the solidification temperature range, thereby forming a solid shell of a certain thickness on the outer surface to prevent stress-induced fractures. However, this method may lead to excessively rapid temperature drop in the casting, creating a large internal and external temperature difference and gradient, causing localized thermal stress concentration. When the thermal stress exceeds the fracture toughness of the casting material, the material will crack, affecting the product yield. Therefore, this method cannot effectively solve the stress fracture problem during the annealing process of fused zirconium-chromium corundum. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a rapid thermally conductive sand mold material and its preparation method. The technical solution of this invention is as follows: A rapid thermally conductive sand-like material, with the following formula based on weight percentage: (1) α-alumina powder 20wt%-40wt%, particle size <0.088mm; (2) High thermal conductivity aggregate 10wt%-40wt%, particle size 5mm-3mm; (3) Magnesium oxide aggregate, 20wt%-90wt%, particle size 1mm-0.5mm; (4) Binder RTV silicone rubber 5wt%-25wt%.

[0004] The high thermal conductivity aggregate, calculated by weight percentage, consists of the following: (1) Sintered magnesium oxide granular aggregate 40wt%-80wt%, particle size 3mm-1mm (2) Graphite particles 5wt%-10wt%, particle size 5mm-3mm; (3) Water glass solution 10wt%-30wt%; (4) Silica fume 10wt%-20wt%.

[0005] The preparation method of the high thermal conductivity aggregate includes the following steps: (1) Weigh the high-temperature thermally conductive aggregate raw materials according to a certain weight ratio; (2) Place the raw materials into a planetary mixer and mix rapidly for 5 min-10 min at a speed of 80-200 rad / min; (3) Place the mixed material into a sagger and introduce CO2 gas into the sagger for 5-10 minutes. (4) After the gas delivery process is completed, the sagger is placed on the vibrator platform for vibration for 2 min-5 min. After vibration, it is placed in the drying room and dried at 60℃-110℃ for 20 min-90 min to obtain high thermal conductivity aggregate.

[0006] The preparation method of the rapid thermally conductive sand mold material includes the following steps: (1) According to the above raw material ingredients, put them into a planetary mixer for mixing, and mix for 5 min - 15 min; (2) Pour the mixture into a wooden mold and pound it, then let it stand for 10-30 minutes; (3) After the cured template is removed from the wooden mold, it is placed in a drying kiln for drying for 10 min-50 min at a drying temperature of 60℃-100℃. After drying, it is assembled into a mold as required and ready for use.

[0007] The significant technical effects of this invention are as follows: The introduction of high thermal conductivity aggregates improves the thermal conductivity of the mold, facilitating the rapid formation of a solidified layer on the surface of the zirconium-chromium corundum casting. The addition of these high thermal conductivity aggregates endows the sand mold with new functional characteristics, enhancing the speed at which high-temperature heat is transferred from the interior to the exterior of the casting, resulting in an overall heat transfer rate higher than that of ordinary sand molds. Testing showed that at 1200℃, sand molds with 15% high thermal conductivity aggregates achieved a thermal conductivity of 90 W / (m·K)-200 W / (m·K), while traditional magnesia sand molds only achieved a thermal conductivity of 20 W / (m·K)-30 W / (m·K).

[0008] This invention aims to avoid increasing thermal stress in localized areas, which can lead to thermal stress cracking in castings. Traditional magnesia molds, due to processing limitations, use molds of uniform thickness, resulting in consistent thermal conductivity. However, during annealing, different areas of the casting experience uneven heat dissipation, leading to significant temperature gradients and a predisposition to thermal stress cracking. This invention allows for adjusting the amount of high thermal conductivity aggregate added to different areas of the casting, thereby controlling the overall heat dissipation rate. Increased thermal conductivity ensures more even heat distribution throughout the casting volume, reducing temperature differences between the interior and exterior, and thus minimizing the temperature gradient.

[0009] The recycling of high thermal conductivity aggregates can reduce the production cost of sand molds. Statistics show that the average recovery rate of high thermal conductivity aggregates can be controlled within the range of 68%-72%. Because the preparation of high thermal conductivity aggregates is carried out separately, these aggregates possess a certain mechanical strength. The recycled aggregates can be obtained by screening after use. These recycled high thermal conductivity aggregates still possess good thermal conductivity. This is because during the use of high thermal conductivity aggregates, silica fume forms a large amount of glassy phase, which coats the flake graphite on the surface of the magnesia particles, forming a uniform structure. After use, the flake graphite on the surface of the high thermal conductivity aggregates does not show significant detachment. In summary, by using this invention as a casting mold, the stress cracking phenomenon on the surface of the zirconium chromium corundum billet is significantly reduced, and the product qualification rate of the material is significantly increased. This invention can effectively solve the stress fracture problem in the annealing process of fused zirconium chromium corundum. Detailed Implementation Example 1

[0010] A rapid thermally conductive sand-like material comprises, by weight percentage: 20wt% α-alumina powder, 10wt% 5mm-3mm high thermal conductivity aggregate, 55wt% 1mm-0.5mm magnesium oxide aggregate, and 15wt% RTV silicone rubber binder. The thermally conductive aggregate includes: 62wt% sintered magnesium oxide granular aggregate with a particle size of 3mm-1mm; 10wt% graphite particles with a particle size of 5mm-3mm; 18wt% water glass solution; and 10wt% silica fume.

[0011] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 60℃ for 90 minutes for later use.

[0012] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use. Example 2

[0013] A rapid thermally conductive sand-like material has the following formulation by weight percentage: 20wt% α-alumina powder, 20wt% added 5mm-3mm high thermal conductivity aggregate, 45wt% 1mm-0.5mm magnesium oxide aggregate, and 15wt% RTV silicone rubber binder. The thermally conductive aggregate formulation by weight percentage includes: 62wt% sintered magnesium oxide granular aggregate (3mm-1mm particle size); 10wt% graphite granules (5mm-3mm particle size); 18wt% water glass solution; and 10wt% silica fume.

[0014] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 110℃ for 90 minutes for later use.

[0015] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use. Example 3

[0016] A rapid thermally conductive sand-like material has the following formulation by weight percentage: 20wt% α-alumina powder, 25wt% added 5mm-3mm high thermal conductivity aggregate, 45wt% 1mm-0.5mm magnesium oxide aggregate, and 15wt% RTV silicone rubber binder. The thermally conductive aggregate formulation by weight percentage includes: 62wt% sintered magnesium oxide granular aggregate (3mm-1mm particle size); 10wt% graphite granules (5mm-3mm particle size); 18wt% water glass solution; and 10wt% silica fume.

[0017] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry it at 60℃-110℃ for 90 minutes for later use.

[0018] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use. Example 4

[0019] A rapid thermally conductive sand-like material has the following formulation by weight percentage: 20wt% α-alumina powder, 35wt% added 5mm-3mm high thermal conductivity aggregate, 35wt% 1mm-0.5mm magnesium oxide aggregate, and 10wt% RTV silicone rubber binder. The thermally conductive aggregate formulation by weight percentage includes: 62wt% sintered magnesium oxide granular aggregate (3mm-1mm particle size); 10wt% graphite granules (5mm-3mm particle size); 18wt% water glass solution; and 10wt% silica fume.

[0020] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 110℃ for 90 minutes for later use.

[0021] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use. Example 5

[0022] A rapid thermally conductive sand-like material has the following formulation by weight percentage: 20wt% α-alumina powder, 35wt% added 5mm-3mm high thermal conductivity aggregate, 35wt% 1mm-0.5mm magnesium oxide aggregate, and 10wt% RTV silicone rubber binder. The thermally conductive aggregate formulation by weight percentage includes: 65wt% sintered magnesium oxide granular aggregate (3mm-1mm particle size); 7wt% graphite granules (5mm-3mm particle size); 18wt% water glass solution; and 10wt% silica fume.

[0023] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry it at 60℃-110℃ for 90 minutes for later use.

[0024] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use. Example 6

[0025] A rapid thermally conductive sand-like material has the following formulation by weight percentage: 20wt% α-alumina powder, 35wt% added 5mm-3mm high thermal conductivity aggregate, 35wt% 1mm-0.5mm magnesium oxide aggregate, and 10wt% RTV silicone rubber binder. The thermally conductive aggregate formulation by weight percentage includes: 61wt% sintered magnesium oxide granular aggregate (3mm-1mm particle size); 9wt% graphite granules (5mm-3mm particle size); 18wt% water glass solution; and 12wt% silica fume.

[0026] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 60℃-110℃ for 20-90 minutes for later use.

[0027] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use.

[0028] Comparative Example 1 A rapid thermally conductive sand-like material and its preparation method are formulated by weight percentage as follows: 20wt% α-alumina powder, 10wt% 5mm-3mm high thermal conductivity aggregate, 55wt% 1mm-0.5mm magnesium oxide aggregate, and 15wt% RTV silicone rubber binder. The thermally conductive aggregate is formulated by weight percentage as follows: 70wt% sintered magnesium oxide particle aggregate (3mm-1mm particle size); 1wt% graphite particles (5mm-3mm particle size); 19wt% water glass solution; and 10wt% silica fume.

[0029] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 60℃-110℃ for 20-90 minutes for later use.

[0030] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has solidified, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. After drying, it is ready for use.

[0031] Comparative Example 2 The formulation of a rapid thermally conductive sand-like material and its preparation method, calculated by weight percentage, is as follows: 20wt% α-alumina powder, 10wt% added 5mm-3mm high thermal conductivity aggregate, 55wt% 1mm-0.5mm magnesium oxide aggregate, and 15wt% RTV silicone rubber binder. The thermally conductive aggregate formulation, calculated by weight percentage, is as follows: 60wt% sintered magnesium oxide particle aggregate (3mm-1mm particle size); 16wt% graphite particles (5mm-3mm particle size); 18wt% water glass solution; and 10wt% silica fume.

[0032] First, prepare high thermal conductivity aggregate. Weigh the raw materials according to the proportion and put them into a planetary mixer for rapid mixing. The mixing time is 5 minutes and the mixing speed is 80 rad / min. Put the mixed high thermal conductivity aggregate into a sagger and introduce CO2 gas into the sagger for 10 minutes. After the gas introduction process is completed, place the sagger on a vibrator platform for vibration for 2 minutes. After vibration and sieving, place it in a drying room and dry at 60℃-110℃ for 20-90 minutes for later use.

[0033] Weigh the raw materials according to the proportion of the rapid heat-conducting sand mold material, put them into a planetary mixer and mix for 5 minutes. Pour the mixture into a wooden mold frame, tamp it down and let it stand for 10 minutes. After the mold has cured, remove the wooden mold and place it in a drying kiln to dry for 30 minutes at a drying temperature of 80℃. Let it dry until ready for use.

[0034] The average thermal conductivity of each embodiment and comparative example was tested according to the YB / T 4130-2005 standard for determining thermal conductivity by the water flow plate method, as shown in Table 1.

[0035] Table 1

[0036] As shown in Table 1, the thermal conductivity of the examples gradually increases with the increase of the amount of high thermal conductivity aggregate added. When the amount of high thermal conductivity aggregate added is the same, the thermal conductivity gradually increases with the increase of the amount of graphite added to the high thermal conductivity aggregate. Compared with the traditional magnesia sand mold material, the thermal conductivity of the magnesia sand mold material is significantly lower than that of the sample in this example. Therefore, using this example is beneficial for increasing the solidification layer thickness of the zirconium-chromium corundum casting. The surface quality of the castings after 30 minutes of casting is shown in Table 2.

[0037] Table 2

[0038] Table 2 shows that using a high thermal conductivity template resulted in a thicker solidified layer after 1 hour of casting, effectively preventing stress cracking in the early stages of casting due to a thin solidified layer. In Comparative Examples 1 and 2, the amount of graphite particles added was either below or above the range specified in the instructions. In Comparative Example 1, the amount of graphite particles added was below the specified range. At 1100℃, the thermal conductivity of the sand mold was 28 W / (m·K), which is similar to that of traditional magnesia sand mold materials. This comparative example did not possess a significant rapid overall heat conduction function. When the amount of graphite particles added exceeded the specified range, the excessive amount of graphite particles significantly reduced the bonding strength of the sand mold plate, leading to sand mold plate breakage during casting.

Claims

1. A rapid thermally conductive sand mold material, characterized in that: The sand molding material, calculated by weight percentage, consists of the following components: (1) α-alumina powder 20wt%-40wt%, particle size <0.088mm; (2) High thermal conductivity aggregate 10wt%-40wt%, particle size 3mm-5mm; (3) Magnesium oxide aggregate 20wt%-55wt%, particle size 0.5mm-1mm; (4) Adhesive RTV silicone rubber 5wt%-25wt%; The high thermal conductivity aggregate is composed of the following components by weight percentage: (1) Sintered magnesium oxide granular aggregate 40wt%-65wt%, particle size 1mm-3mm; (2) Graphite particles 5wt%-10wt%, particle size 3mm-5mm; (3) Water glass solution 10wt%-30wt%; (4) Silica fume 10wt%-20wt%; The high thermal conductivity aggregate is prepared by the following method: (1) Weigh the high thermal conductivity aggregate raw materials according to the proportion; (2) Place the raw materials into a planetary mixer and mix rapidly for 5 min-10 min at a speed of 80-200 rad / min; (3) Place the mixed material into a sagger and introduce CO2 gas into the sagger for 5-10 minutes. (4) After the air supply process is completed, the sagger is placed on the vibrator platform for vibration for 2 min-5 min. After vibration, it is placed in the drying room and dried at 60℃-110℃ for 20 min-90 min to obtain high thermal conductivity aggregate.

2. The method for preparing the rapid thermally conductive sand mold material according to claim 1, characterized in that, Includes the following steps: (1) Prepare the ingredients according to the formula of claim 1, put them into a planetary mixer and mix for 5 min-15 min; (2) Pour the mixture into a wooden mold and pound it, then let it stand for 10-30 minutes; (3) After the cured template is removed from the wooden mold, it is placed in a drying kiln for drying for 10 min-50 min at a drying temperature of 60℃-100℃. After drying, it is assembled into a mold as required and ready for use.

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