Preparation method of high-temperature-resistant low-expansion precoated sand

Abstract

The invention relates to a preparation method of high-temperature-resistant low-expansion precoated sand in the field of precoated sand, and the preparation method specifically comprises the following steps: adding quantitative crude sand heated to 130-135 DEG C into a main mixing part of a sand mixer, then adding quantitative phenolic resin, mixing and grinding for 40-50 seconds, then carrying out segmented cooling on the mixed and ground crude sand through a cooling part, primarily cooling by using cooling air flow, and then cooling by using cooling air flow to obtain the high-temperature-resistant low-expansion precoated sand. Further cooling to a set temperature T1 by using a cooling liquid, preheating the cooling liquid by using cooling airflow, recovering and storing the cooling liquid, cooling the crude sand to 90-110 DEG C, adding urotropine, mixing and grinding for 10 seconds, adding calcium stearate, mixing and grinding for 30-50 seconds to obtain a mixture A, then carrying out two-stage cooling on the mixture A by using the recovered cooling liquid, and carrying out crushing treatment after cooling, and finally, multi-stage screening is conducted through screening equipment, the adding amount of chromite sand is reduced, the heat energy utilization rate in the preparation process is increased, and therefore the production cost is reduced.

Description

Technical Field

[0001] The invention relates to a method for preparing coated sand, and in particular to a method for preparing high-temperature resistant and low-expansion coated sand applied in the field of coated sand. Background Art

[0002] Coated sand is a modeling material used in the foundry industry. It improves its performance by coating a thin film on the surface of sand particles. Traditional coated sand mainly uses a thermal process, that is, heating to melt the resin on the surface of the sand particles and form a thin film. Although this method can effectively improve the strength and fluidity of the sand particles, it has problems such as high energy consumption and low production efficiency. In recent years, with the improvement of environmental protection requirements and the advancement of production technology, the cold process has gradually received attention. The cold process solidifies the resin at room temperature by adding a specific curing agent or catalyst, thereby forming a thin film on the surface of the sand particles. This method has the advantages of low energy consumption, high production efficiency and low environmental pollution. At present, the preparation method of coated sand also includes a variety of composite technologies, such as the use of microcapsule technology to control the release of resin, and the use of nanomaterials to improve the performance of coated sand. The development of these technologies has not only improved the performance of coated sand, but also promoted the technological progress of the foundry industry.

[0003] Low-grade silica sand has low silicon dioxide content and poor high-temperature resistance, resulting in sand sticking to castings; high-grade silica sand has high silicon dioxide content and severe linear expansion, and defects such as "cracks, cold shuts, and shrinkage" are prone to occur on the surface of castings.

[0004] The Chinese invention patent CN110434278B specification discloses a high temperature resistant, low gassing, low expansion, and easy to disintegrate coated sand, which is made of the following raw materials by weight: silica sand, high-alumina ceramsite sand, clay, fast-polymerizing phenolic resin, high-strength phenolic resin, silane, acrylic acid ester, magnesium oxide, ferroferric oxide, curing agent and lubricant. The coated sand of the invention uses silica sand and high-alumina ceramsite sand as aggregates, and adds a variety of auxiliary agents at different production stages, so that the materials cooperate with each other, and improve the effect of preventing defects from multiple angles for casting defects. The formula of the coated sand of the invention can be applied to three types of metals at the same time, and can have excellent low-temperature disintegration and high-temperature heat resistance at the same time.

[0005] The Chinese invention patent CN202411151371.X specification discloses a high-strength coated sand preparation process, including the following steps: dissolving alkaline phenolic resin in ethanol to form an alkaline phenolic resin solution; preparing urotropine into an aqueous solution; preheating and stirring the raw sand, then adding the alkaline phenolic resin solution to mix the sand, then adding the urotropine aqueous solution to mix the sand, then adding the silane coupling agent, mixing the sand for 50 seconds, and finally adding calcium stearate to mix the sand for about 50 seconds to obtain the coated sand. The coated sand of the invention has high strength and a simple preparation process, and is most suitable for the production of shell casting processes.

[0006] The coated sand in the prior art has poor heat resistance, and high-temperature casting is prone to defects such as sand sticking and deformation of castings, with a low casting yield. In addition, the heat utilization rate is low during the production process of the coated sand, and the production cost is high. Summary of the invention

[0007] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is that the coated sand in the prior art has poor heat resistance, and high-temperature casting is prone to defects such as sand sticking and deformation of castings, the casting yield is low, and the heat utilization rate is low during the production process of the coated sand, resulting in high production costs.

[0008] In order to solve the above problems, the present invention provides a method for preparing high temperature resistant low expansion coated sand, comprising a blade type sand mixer for preparing coated sand, the blade type sand mixer comprising a main mixing part with a heating device, and a cooling part is installed at the outer end of the main mixing part. The specific preparation method comprises: A1, initial mixing, first heat a set amount of raw sand to 130-135°C through an external heating device, put the heated raw sand into the main mixing part of the blade-type sand mixer, and then add a set amount of phenolic resin into the raw sand and mix for 40-50 seconds; A2, one-stage cooling, using the cooling section to cool the raw sand after mixing and grinding in sections. During the section cooling, a cooling airflow with a set temperature is first introduced into the cooling section to exchange heat with the main mixing section, so that the raw sand in the main mixing section is initially cooled down; when the raw sand temperature drops to the set temperature T1, a coolant with a set temperature is introduced into the cooling section to cool down the raw sand by heat exchange between the coolant and the raw sand; The cooling airflow discharged from the cooling section is recovered and used for preheating the coolant, and the coolant discharged from the cooling section is recovered and stored; the raw sand temperature is cooled down to 90-110℃ before proceeding to the next step; A3, mix again, add 12%-15% hexamethylenetetramine, mix and grind for 10 seconds, then add 5% calcium stearate and continue to coagulate for 30-50 seconds; after the coagulation is completed, the mixture A is obtained; A4, conduct second-stage cooling to further reduce the temperature of mixture A; in the second-stage cooling process, first use the coolant recovered in step A2 to assist cooling, and after the recovered coolant is used up, identify whether the temperature of the raw sand drops below 80°C, if so, proceed to the next step; if not, input the coolant of the specified temperature into the cooling part for supplementary cooling, and the mixture A is discharged from the main mixing part after the temperature drops below 80°C; A5, crushing the mixture A to break up the large agglomerates in the mixture A; A6, the crushed mixture A is subjected to multi-stage screening by a screening device to obtain a product.

[0009] In the above-mentioned method for preparing high-temperature resistant low-expansion coated sand, the amount of chromite sand added is reduced, and the thermal energy utilization rate in the preparation process is improved, thereby reducing production costs.

[0010] As a further improvement of the present application, the raw sand is composed of a mixture of 60% silica sand, 35% chromite sand and 5% additive A; the particle size of the raw sand is 150-70 mesh, and the additive A includes 50% bisphenol A and 50% magnesium hydroxide.

[0011] As a further improvement of the present application, the main mixing part comprises a shell, a stirring shaft is rotatably connected in the shell, and a mixing blade and a grinding wheel are installed on the stirring shaft; The cooling part comprises a heat-insulating shell covering the shell, a feed pipe is installed on the heat-insulating shell, an air guide cavity is opened in the heat-insulating shell, and a liquid cooling pipe row is laid in the air guide cavity; A waste heat utilization pipe group is connected between the output end of the air guide cavity and the input end of the liquid cooling pipe row, the two ends of the air guide cavity are respectively connected to an upper nozzle and a lower guide pipe, and an air flow nozzle connected to the upper nozzle is installed at the top of the main mixing part; Solenoid valves are connected between the air guide cavity and the upper spray pipe and the lower guide pipe, and a guide ring is connected between the lower guide pipe and the stirring shaft; A plurality of air-conducting heat-exchange pipes connected to the guide ring are installed in the stirring shaft, a centralized output pipe connected to the plurality of air-conducting heat-exchange pipes is installed at the top of the stirring shaft, an upper exhaust pipe rotatably connected to the stirring shaft is installed at the top of the main mixing section, and the upper exhaust pipe is inserted into the stirring shaft and connected to the output end of the centralized output pipe.

[0012] As a further improvement of the present application, the waste heat utilization tube group includes a front heat exchange section and a rear heat exchange section, a water pipe connected to the liquid cooling tube row is provided between the front heat exchange section and the rear heat exchange section, the front heat exchange section is connected to the output end of the air guide cavity, and the rear heat exchange section is connected to the upper exhaust pipe.

[0013] As another improvement of the present application, an electric motor for driving the mixing blades to rotate is installed in the stirring shaft, an extension arm matching the mixing blades is installed on the stirring shaft, the mixing blades are installed on a rotating bracket, and the rotating bracket and the extension arm are rotatably connected via a rotating shaft, a transmission belt is connected between the rotating shaft and the power output end of the motor, and a temperature sensor is installed at the mixing blades.

[0014] As another improvement of the present application, a discharge pipe with an electric gate is installed at the output end of the main mixing section, a gas insulation tank connected to the gas guide cavity is installed at the top end of the discharge pipe, a temperature detection sensor is installed in the gas insulation tank, and an injection pipe connected to the gas insulation tank is installed at the output end of the discharge pipe, and the output end of the discharge pipe is connected to the input end of the crushing screen.

[0015] As another improvement of the present application, the blade-type sand mixer further includes an auxiliary processing system, the auxiliary processing system includes a processor, and the processor is connected to a data processing module, a control module, a monitoring module and a data storage module; The control module is provided with a mixing and grinding control unit and a cooling control unit. The mixing and grinding control unit is used to control the main mixing part to perform mixing and grinding. The cooling control unit is used to control the cooling part and the waste heat utilization pipe group to cool the main mixing part. The cooling control unit is provided with a segmented cooling mode and a unified cooling mode. The monitoring module is used to collect monitoring data, including the fluid temperature in the cooling section, the waste heat utilization pipe group and the gas insulation tank, and the material temperature in the main mixing section; The data processing module is used to process the monitoring data and adjust the operation of the control module according to the monitoring data; The data storage module is used to store monitoring data and work logs.

[0016] As another improved supplement of the present application, when the segmented cooling mode is working, the cooling airflow and the cooling liquid are sequentially called to cool the main mixing part, and the segmented cooling mode is used to realize the segmented cooling work in A2; When the unified cooling mode is working, only one of the cooling air flow or the cooling liquid is called to cool the main mixing section. The unified cooling mode is used to implement the two-stage cooling work in A4.

[0017] In summary, this scheme reduces the amount of chromite added and reduces production costs through a reasonable formula, accelerates the cooling rate in the preparation process by arranging air-conducting heat exchange pipes and air-conducting cavities inside and outside the sand mixer, and recovers the waste heat of the airflow through the waste heat utilization tube group for preheating the coolant. On the one hand, the cooling airflow and coolant are used to realize segmented cooling of the materials in the preparation process, so that the materials are not easily affected by product quality due to excessive cooling, and on the other hand, the utilization rate of thermal energy in the preparation process is improved to further reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the preparation method of the first embodiment of the present application; Figure 2 A three-dimensional diagram of a blade-type sand mixer according to the first and second embodiments of the present application; Figure 3 This is a cross-sectional view of a blade-type sand mixer according to the first and second embodiments of the present application; Figure 4 for Figure 3 The structural diagram at A in the middle; Figure 5 for Figure 3 Schematic diagram of the structure at B in the middle; Figure 6It is a top view cross-sectional view of a blade-type sand mixer according to the first and second embodiments of the present application; Figure 7 A schematic diagram of the path of heat exchange between the exhaust gas and the coolant of the blade-type sand mixer in the first and second embodiments of the present application; Figure 8 This is a block diagram of the auxiliary processing system of the second embodiment of the present application.

[0019] Description of the numbers in the figure: 1. Main mixing section; 11. Shell; 12. Stirring shaft; 121. Air guide heat exchange pipe; 122. Centralized output pipe; 13. Mixing blades; 14. Grinding wheel; 15. Upper exhaust pipe; 2. Cooling section; 21. Insulation shell; 22. Air guide cavity; 221. Upper nozzle; 222. Lower guide pipe; 23. Liquid cooling pipe row; 3. Guide ring; 4. Solenoid valve; 5. Waste heat utilization pipe group; 51. Front heat exchange section; 52. Rear heat exchange section; 53. Water pipe; 6. Discharge pipe. DETAILED DESCRIPTION

[0020] The following describes two implementation modes of the present application in detail with reference to the accompanying drawings.

[0021] The first implementation method: Figure 1-3 It is shown that a method for preparing high-temperature resistant low-expansion coated sand includes a blade-type sand mixer for preparing coated sand, the blade-type sand mixer includes a main mixing part 1 with a heating device, and a cooling part 2 is installed at the outer end of the main mixing part 1. A suitable heating device is used by a person skilled in the art to install it, so as to ensure that the raw sand in the main mixing part 1 can be heated to the required temperature and heat-insulated, such as a steam heating device; the heating device adopts the existing technology, and the specific heating implementation method of the heating device for the main mixing part 1 is not within the protection scope of this scheme, and will not be described in detail in this scheme; The specific preparation method of this scheme includes: A1, initial mixing, first heat a set amount of raw sand to 130-135°C by an external heating device (a person skilled in the art may heat the raw sand by using a suitable external heating device, such as a drum heating furnace), put the heated raw sand into the main mixing part 1 of the blade-type sand mixer, and then put a set amount of phenolic resin into the raw sand and mix and grind for 40-50 seconds; A2, one-stage cooling, using the cooling part 2 to cool the raw sand after mixing and grinding in sections. During the section cooling, a cooling airflow with a set temperature is first introduced into the cooling part 2 to exchange heat with the main mixing part 1, so that the raw sand in the main mixing part 1 is initially cooled down; when the raw sand temperature drops to the set temperature T1, a coolant with a set temperature is introduced into the cooling part 2, and the cooling treatment is performed by heat exchange between the coolant and the raw sand; The cooling airflow discharged from the cooling part 2 is recovered and used for preheating the coolant, and the coolant discharged from the cooling part 2 is recovered and stored; the temperature of the raw sand is cooled down to 90-110°C before proceeding to the next step; A3, mix again, add 12%-15% hexamethylenetetramine, mix and grind for 10 seconds, then add 5% calcium stearate and continue to coagulate for 30-50 seconds; after coagulation is completed, mixture A is obtained; A4, conduct second-stage cooling, further reduce the temperature of mixture A by liquid cooling; in the second-stage cooling process, first use the coolant recovered in step A2 for auxiliary cooling, after the recovered coolant is used up, identify whether the temperature of the raw sand drops below 80°C, if so, proceed to the next step; if not, input the coolant of the specified temperature into the cooling part 2 for supplementary cooling, and the mixture A is discharged from the main mixing part 1 after the temperature drops below 80°C; A5, using an existing breaking device to break up the mixture A to break up the large agglomerates in the mixture A; A6, the crushed mixture A is subjected to multi-stage screening by screening equipment to obtain high temperature resistant low expansion coated sand, and the mixture A is crushed by a crushing device in the prior art.

[0022] The raw sand is composed of 60% silica sand, 35% chromite sand and 5% additive A; the particle size of the raw sand is 150-70 mesh, and the additive A includes 50% bisphenol A and 50% magnesium hydroxide; bisphenol A: has the functions of increasing strength, flame retardancy and heat resistance; magnesium hydroxide loses water at a temperature of 350°C to generate magnesium oxide, and the water turns into steam to take away heat. Magnesium oxide has high temperature resistance, and its melting point is 2852°C. The heat resistance of the final product is improved by magnesium oxide; The high temperature resistant and low expansion coated sand obtained by the above preparation method has a reasonable raw material ratio. Compared with the existing technology, it can ensure product quality while reducing the amount of chromite sand added, thereby reducing production costs.

[0023] The main mixing part 1 of the present invention comprises a housing 11, a stirring shaft 12 is rotatably connected in the housing 11, a mixing blade 13 and a grinding wheel 14 are mounted on the stirring shaft 12, and a motor for driving the mixing blade 13 to rotate is mounted in the stirring shaft 12; The cooling part 2 includes a heat-insulating shell 21 covering the shell 11, a feed pipe is installed on the heat-insulating shell 21, an air guide cavity 22 is opened in the heat-insulating shell 21, an air inlet pipe and an air outlet pipe communicating with the air guide cavity 22 are installed at the lower end of the heat-insulating shell 21, and the cooling airflow in step A2 is passed into the air guide cavity 22 through the air inlet pipe; A liquid cooling pipe row 23 is laid in the air guide cavity 22, and the liquid cooling pipe row 23 includes a hot water exchange pipe covering the shell 11; the coolant in steps A2 and A3 is passed into the liquid cooling pipe row 23; Optionally, the high-temperature steam output by the steam heating device can be input into the air guide cavity 22, so that the raw sand in the shell 11 is heated by heat exchange with the steam; those skilled in the art can also use existing technology to heat the raw sand using appropriate heating equipment and heating methods; The two ends of the air guide cavity 22 are respectively connected with an upper nozzle 221 and a lower guide pipe 222. An air flow nozzle communicating with the upper nozzle 221 is installed at the top of the main mixing section 1. The air flow nozzle is used to output a dry air flow into the shell 11 so that the air flow directly contacts the material in the shell 11 for heat exchange. An exhaust valve for exhaust is installed on the shell 11. The electromagnetic valve 4 is connected between the air guide cavity 22 and the upper nozzle 221 and the lower guide pipe 222, and the guide ring 3 is connected between the lower guide pipe 222 and the stirring shaft 12; the guide ring 3 and the stirring shaft 12 are rotatably sealed, and the airflow at the output end of the lower guide pipe 222 enters the guide ring 3; A plurality of air-conducting heat-exchange pipes 121 connected to the guide ring 3 are installed in the stirring shaft 12. One side surface of the air-conducting heat-exchange pipe 121 is exposed outside the stirring shaft 12 and is used for heat exchange with the raw sand. The input end of the air-conducting heat-exchange pipe 121 is located in the guide ring 3, and the output end of the air-conducting heat-exchange pipe 121 is located at the top of the stirring shaft 12. A centralized output pipe 122 connected to the plurality of air-conducting heat-exchange pipes 121 is installed at the top of the stirring shaft 12. An upper exhaust pipe 15 rotatably connected to the stirring shaft 12 is installed at the top of the main mixing section 1, and the upper exhaust pipe 15 is inserted into the stirring shaft 12 and is connected to the output end of the centralized output pipe 122.

[0024] The air-conducting heat exchange pipe 121 is used to cool the raw sand from the middle of the main mixing section 1. In this solution, the inside and outside of the main mixing section 1 are cooled synchronously by the air-conducting heat exchange pipe 121 and the air-conducting cavity 22, which is easy to accelerate the cooling rate of the raw sand in the main mixing section 1. A waste heat utilization pipe group 5 is connected between the output end of the air guide cavity 22 and the input end of the liquid cooling tube row 23. The waste heat utilization pipe group 5 includes a front heat exchange section 51 and a rear heat exchange section 52. A water pipe 53 communicating with the input end of the liquid cooling tube row 23 is passed between the front heat exchange section 51 and the rear heat exchange section 52. The front heat exchange section 51 is communicated with the output end of the air guide cavity 22, and the rear heat exchange section 52 is communicated with the upper exhaust pipe 15.

[0025] Since the air-conducting heat exchange tube 121 has a smaller space than the air-conducting cavity 22 and the air-flow heat exchange path is short, the air-flow outputted from the air-conducting heat exchange tube 121 has a higher temperature than the air-flow outputted from the air-conducting cavity 22, that is, the air-flow outputted from the air-conducting heat exchange tube 121 is used for post-processing of preheating the water delivery pipe 53, and the air-flow outputted from the air-conducting cavity 22 is used for pre-processing of preheating the water delivery pipe 53; When cooling by introducing coolant, first use the waste heat of airflow to preheat the coolant. After preheating, the coolant exchanges heat with the material first, so that the material is not easy to cool down too quickly. During the coolant input process, it gradually exchanges heat with the airflow, so that the input coolant temperature gradually cools down, which makes it easy to prevent the material from cooling down too quickly and avoid the resin in the original sand from solidifying due to rapid cooling. A motor for driving the mixing blade 13 to rotate is installed in the stirring shaft 12, an extension arm matching the mixing blade 13 is installed on the stirring shaft 12, the mixing blade 13 is installed on the rotating bracket, and the rotating bracket and the extension arm are rotatably connected through a rotating shaft, a transmission belt is connected between the rotating shaft and the power output end of the motor, a temperature sensor is installed at the mixing blade 13, and the mixing blade 13 is installed using a blade suitable for a sand mixer in the prior art; When the motor is working, it drives the transmission belt to move, thereby causing the mixing blades 13 to rotate for stirring; A discharge pipe 6 with an electric gate is installed at the output end of the main mixing section 1, and a discharge hole matching the electric gate is opened on the shell 11 and the insulation shell 21. A sealing plate for closing the discharge hole is provided on the electric gate. The electric gate is installed by a person skilled in the art using a suitable electric control gate in the prior art. A gas insulation tank communicating with the air guide cavity 22 is installed at the top of the discharge pipe 6, and a temperature detection sensor is installed in the gas insulation tank. An injection pipe communicating with the gas insulation tank is installed at the output end of the discharge pipe 6, and the output end of the discharge pipe 6 is connected to the input end of the crushing device; Optionally, the cooling airflow output from the air guide cavity 22 can also be input into the gas insulation tank for storage. After the gas temperature in the gas insulation tank is stabilized and cooled to the set temperature, the gas in the gas insulation tank can be output through the jet pipe, so that the jet pipe can air-cool the material output from the discharge pipe 6. In the preparation method of the present scheme, a sand mixer with segmented cooling is used to assist the work, and in the segmented cooling process, after the cooling airflow used for one stage of cooling completes the cooling work, it can be used to preheat the coolant for subsequent liquid cooling work. On the one hand, it is easy to ensure that the material temperature is not easily cooled down too quickly, and on the other hand, it provides thermal energy utilization.

[0026] Second implementation method: Figure 8 As shown, the blade-type sand mixer also includes an auxiliary processing system, which includes a processor connected to the blade-type sand mixer signal, and the processor is connected to a data processing module, a control module, a monitoring module and a data storage module; The control module is provided with a mixing and grinding control unit and a cooling control unit. The mixing and grinding control unit is used to control the main mixing part 1 to perform mixing and grinding. The cooling control unit is used to control the cooling part 2 and the waste heat utilization pipe group 5 to cool the main mixing part 1. The cooling control unit is connected to a liquid pump and an air pump, which are used to transport cooling liquid and cooling air flow respectively. The cooling control unit is provided with a segmented cooling mode and a unified cooling mode; in the segmented cooling mode, the cooling airflow and the cooling liquid are sequentially called to cool the main mixing part 1, and the segmented cooling mode is used to implement the segmented cooling work in step A2; in the unified cooling mode, only one of the cooling airflow or the cooling liquid is called to cool the main mixing part 1, and the unified cooling mode is used to implement the two-stage cooling work in step A4; The monitoring module is used to collect monitoring data, including the fluid temperature in the cooling section 2, the waste heat utilization pipe group 5 and the gas insulation tank, and the material temperature in the main mixing section 1; the gas guide cavity 22, the liquid cooling pipe row 23 and the waste heat utilization pipe group 5 are all equipped with fluid temperature sensors connected to the monitoring module signal; The data processing module is used to process the monitoring data and adjust the operation of the control module according to the monitoring data; The data storage module is used to store monitoring data and work logs.

[0027] When the auxiliary processing system of this embodiment is working, the processor adjusts the operation of the mixing and grinding control unit and the cooling control unit in real time according to the data provided by the monitoring module and the processing step status; The mixing and grinding control unit dynamically adjusts the speed and mixing time of the main mixing section 1 according to the mixing degree and temperature of the materials to ensure that the materials are mixed evenly and reach the expected temperature; The cooling control unit selects the appropriate cooling mode to implement according to the temperature change of the material and the processing steps being performed; In the staged cooling mode, the processor will first call the cooling airflow to pre-cool the main mixing section 1, and then call the coolant for deep cooling; In the unified cooling mode, the processor will choose to use cooling air flow or coolant for continuous cooling according to the temperature of the material and the temperature of the coolant.

[0028] In summary, this solution accelerates the cooling rate in the preparation process by arranging the air guide heat exchange pipes 121 and the air guide cavity 22 inside and outside the sand mixer, and recovers the waste heat of the air flow through the waste heat utilization pipe group 5 for preheating the coolant. On the one hand, the material in the preparation process is cooled in sections by cooling the air flow and the coolant, so that the material is not easily affected by the product quality due to excessive cooling. On the other hand, the thermal energy utilization rate in the preparation process is improved to reduce the production cost.

[0029] In view of current practical needs, the above-mentioned implementation mode adopted in this application is not limited to the scope of protection. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the scope of protection of the present invention.

Claims

1. A method for preparing high temperature resistant low expansion coated sand, comprising a blade type sand mixer for preparing coated sand, the blade type sand mixer comprising a main mixing part (1) with a heating device, a cooling part (2) being installed at the outer end of the main mixing part (1), characterized in that: The specific preparation method includes: A1, initial mixing, firstly heat a set amount of raw sand to 130-135°C by an external heating device, put the heated raw sand into the main mixing part (1) of the blade-type sand mixer, then put a set amount of phenolic resin into the raw sand and mix and grind for 40-50 seconds; A2, one-stage cooling, using the cooling section (2) to cool the raw sand after mixing and grinding in stages. During the staged cooling, a cooling airflow at a set temperature is first introduced into the cooling section (2) to exchange heat with the main mixing section (1), so that the raw sand in the main mixing section (1) is initially cooled. When the temperature of the raw sand is reduced to a set temperature T1, a cooling liquid at a set temperature is introduced into the cooling section (2), and a cooling treatment is performed by heat exchange between the cooling liquid and the raw sand; The cooling airflow discharged from the cooling part (2) is recovered and used for preheating the coolant, and the coolant discharged from the cooling part (2) is recovered and stored; the temperature of the raw sand is cooled down to 90-110° C. before proceeding to the next step; A3, mix again, add 12%-15% hexamethylenetetramine, mix and grind for 10 seconds, then add 5% calcium stearate and continue to coagulate for 30-50 seconds; after coagulation is completed, mixture A is obtained; A4, performing a second stage cooling to further reduce the temperature of the mixture A; during the second stage cooling process, the coolant recovered in step A2 is first used for auxiliary cooling, and after the recovered coolant is used up, it is determined whether the temperature of the raw sand has dropped below 80°C, and if so, proceed to the next step; if not, a coolant of a specified temperature is input into the cooling section (2) for supplementary cooling, and the mixture A is discharged from the main mixing section (1) after the temperature of the mixture drops below 80°C; A5, crushing the mixture A to break up the large agglomerates in the mixture A; A6, the crushed mixture A is subjected to multi-stage screening by a screening device to obtain a product.

2. The method for preparing high temperature resistant low expansion coated sand according to claim 1, characterized in that: The raw sand is composed of a mixture of 60% silica sand, 35% chromite sand and 5% additive A; the particle size of the raw sand is 150-70 meshes, and the additive A includes 50% bisphenol A and 50% magnesium hydroxide.

3. The method for preparing high temperature resistant low expansion coated sand according to claim 1, characterized in that: The main mixing section (1) comprises a shell (11), a stirring shaft (12) is rotatably connected inside the shell (11), and a mixing blade (13) and a grinding wheel (14) are mounted on the stirring shaft (12); The cooling part (2) comprises a heat-insulating shell (21) covering the shell (11), a feed pipe being installed on the heat-insulating shell (21), an air guide cavity (22) being provided in the heat-insulating shell (21), and a liquid cooling pipe row (23) being laid in the air guide cavity (22); A waste heat utilization pipe group (5) is connected between the output end of the air guide cavity (22) and the input end of the liquid cooling pipe row (23); the two ends of the air guide cavity (22) are respectively connected to an upper nozzle (221) and a lower guide pipe (222); and an air flow nozzle in communication with the upper nozzle (221) is installed at the top of the interior of the main mixing section (1); A solenoid valve (4) is connected between the air guide cavity (22) and the upper nozzle (221) and the lower guide pipe (222); and a guide ring (3) is connected between the lower guide pipe (222) and the stirring shaft (12); A plurality of air-conducting heat-exchange pipes (121) in communication with the guide ring (3) are installed in the stirring shaft (12); a centralized output pipe (122) in communication with the plurality of air-conducting heat-exchange pipes (121) is installed at the top end of the stirring shaft (12); an upper exhaust pipe (15) rotatably connected to the stirring shaft (12) is installed at the top end of the main mixing section (1); the upper exhaust pipe (15) is inserted into the stirring shaft (12) and is in communication with the output end of the centralized output pipe (122).

4. The method for preparing high temperature resistant low expansion coated sand according to claim 3, characterized in that: The waste heat utilization tube group (5) comprises a front heat exchange section (51) and a rear heat exchange section (52); a water delivery pipe (53) communicating with the liquid cooling tube row (23) is provided between the front heat exchange section (51) and the rear heat exchange section (52); the front heat exchange section (51) is communicated with an output end of the air guide cavity (22); and the rear heat exchange section (52) is communicated with an upper exhaust pipe (15).

5. The method for preparing high temperature resistant low expansion coated sand according to claim 4, characterized in that: An electric motor for driving the mixing blade (13) to rotate is installed in the stirring shaft (12); an extension arm matching the mixing blade (13) is installed on the stirring shaft (12); the mixing blade (13) is installed on a rotating bracket, and the rotating bracket and the extension arm are rotatably connected via a rotating shaft; a transmission belt is connected between the rotating shaft and the power output end of the electric motor; and a temperature sensor is installed at the mixing blade (13).

6. The method for preparing high temperature resistant low expansion coated sand according to claim 5, characterized in that: The output end of the main mixing section (1) is equipped with a discharge pipe (6) with an electric gate, the top end of the discharge pipe (6) is equipped with a gas insulation tank connected to the gas guide cavity (22), a temperature detection sensor is installed in the gas insulation tank, the output end of the discharge pipe (6) is equipped with an injection pipe connected to the gas insulation tank, and the output end of the discharge pipe (6) is connected to the input end of the crushing screen.

7. The method for preparing high temperature resistant low expansion coated sand according to claim 6, characterized in that: The blade-type sand mixer also includes an auxiliary processing system, which includes a processor, and the processor is connected to a data processing module, a control module, a monitoring module and a data storage module; The control module is provided with a mixing and grinding control unit and a cooling control unit, the mixing and grinding control unit is used to control the main mixing section (1) to perform mixing and grinding, the cooling control unit is used to control the cooling section (2) and the waste heat utilization pipe group (5) to perform cooling treatment on the main mixing section (1), and the cooling control unit is provided with a segmented cooling mode and a unified cooling mode; The monitoring module is used to collect monitoring data, the monitoring data including the temperature of the fluid in the cooling section (2), the waste heat utilization pipe group (5) and the gas insulation tank, and the temperature of the material in the main mixing section (1); The data processing module is used to process monitoring data and adjust the operation of the control module according to the monitoring data; The data storage module is used to store monitoring data and work logs.

8. The method for preparing high temperature resistant low expansion coated sand according to claim 7, characterized in that: When the segmented cooling mode is in operation, the cooling airflow and the cooling liquid are sequentially used to cool the main mixing section (1). The segmented cooling mode is used to implement the segmented cooling operation in A2. When the unified cooling mode is in operation, only one of the cooling airflow or the cooling liquid is used to cool the main mixing section (1). The unified cooling mode is used to implement the two-stage cooling operation in A4.

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