Micro-smoke odorless cast steel environment-friendly regenerated coated sand process

Abstract

The application discloses a micro-smoke and odor-free cast steel environment-friendly regenerated coated sand process, which replaces a lubricant with hydroxyethyl ethylene bis-stearamide and corresponding auxiliary triisopropyl phosphate, significantly enhances the hot tensile strength and environmental protection of the coated sand, removes the solidified resin on the surface of the coated sand through a frozen shell breaking mode, greatly improves the shell breaking rate of the coated sand waste sand through modified aluminum nitride and preparation of a shell breaking auxiliary, and prepares a friction auxiliary to enhance the particle shaping of the coated sand regenerated sand, and further enhances the flowability of the coated sand prepared from the regenerated sand.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coated sand preparation, and particularly relates to a micro-smoke and odor-free environment-friendly regenerated coated sand process for casting steel. BACKGROUND

[0002] Coated sand casting has a long history in the field of casting, and there are two coating processes for coated sand, namely a cold method and a hot method: in the cold method, ethanol is used to dissolve resin, and urotropine is added in the sand mixing process, so that the two are coated on the surface of the sand particles, the ethanol is volatilized, and the coated sand is obtained; in the hot method, the sand is preheated to a certain temperature, resin is added to make it melt, and the resin is coated on the surface of the sand particles by stirring, and then urotropine aqueous solution and lubricant are added, and the coated sand is obtained after cooling, crushing and screening.

[0003] Since the pouring temperature of molten steel is higher than that of molten iron during casting steel, the coated sand for casting steel needs to have stronger fire resistance and thermal tensile strength than the coated sand for casting iron. If the fire resistance and thermal tensile strength are not good, the structural stability of the coated sand will be affected, and problems such as deformation and damage of the structure of the coated sand will occur during use. The coated sand prepared by the prior art has large smoke and heavy odor during use, and the waste coated sand after use is difficult to regenerate, which has the problems of high energy consumption, high cost and low yield, so that the cost of regenerated coated sand is higher than that of new sand, leading to the accumulation of waste coated sand and pollution to the environment.

[0004] Therefore, there is an urgent need for a coated sand process with high strength, environmental protection and regeneration. SUMMARY

[0005] The first object of the application is to provide a micro-smoke and odor-free environment-friendly coated sand preparation process for casting steel.

[0006] The second object of the application is to provide an environment-friendly coated sand waste sand regeneration process for casting steel.

[0007] In order to solve the above technical problems, the technical solution adopted by the application comprises the following steps:

[0008] A micro-smoke and odor-free environment-friendly coated sand preparation process for casting steel, comprising the following specific steps:

[0009] (1) 100-110 parts of sand with a particle size of 0.15-0.3 mm are added to a stirrer, and then the temperature is raised to 100-130 DEG C for preheating and stirring for 30-40 min;

[0010] (2) After preheating, 3-6 parts of phenolic resin are added to the stirrer and stirred for 75-85 s;

[0011] (3) 50-60 parts of modified aluminum nitride are continuously added to the stirrer and stirred for 50-70 s;

[0012] (4) 10-14 parts of urotropin and water are mixed in a mass ratio of 1:1.6-2, and then added into a blender, and stirred for 35-45 seconds;

[0013] (5) Finally, 4-6 parts of hydroxyethyl ethylene bis-stearamide and 2-3 parts of triisopropyl phosphate are added into the blender, and stirred for 50-60 seconds, and then naturally cooled to room temperature to obtain the micro-smoke and odor-free cast steel environment-friendly coated sand.

[0014] Further, the preparation method of the modified aluminum nitride in step (3) is as follows: the aluminum nitride with a particle size of 0.07-0.1 mm is immersed in an ethanol solution with a volume fraction of 75%, and then cleaned by ultrasonic waves for 5-7 minutes; after cleaning, the aluminum nitride is immersed in oleyl oleate and heated to 36-40°C, and then stirred for 3-5 minutes to obtain the modified aluminum nitride.

[0015] A cast steel environment-friendly coated sand regeneration process, and the specific steps are as follows:

[0016] (1) The cast steel environment-friendly coated sand waste sand is crushed and screened by a vibrating machine, and then the broken iron in the waste sand is removed by a magnet to obtain a mixture a;

[0017] (2) The mixture a is immersed in a sulfuric acid solution with a mass fraction of 40%-45%, and stirred for 30-40 minutes for reaction; after the reaction is completed, the mixture b is obtained by washing with deionized water until neutral;

[0018] (3) The mixture b is immersed in a shelling aid, and stirred for 3-5 minutes; then the mixture b is transferred into an environment of -20 to -15°C and frozen for 2-3 hours, and then stirred at a speed of 800-1000 r / min to obtain a mixture c;

[0019] (4) The mixture c and a friction aid with a mass fraction of 1%-2% of the mixture c are transferred into a high-speed turbine four-wheel, and the mixture c is preheated by a turbine preheater; then the high-speed turbine four-wheel is started, so that the mixture c collides and rubs with each other, and the duration is 50-60 seconds; then the mixture c is transferred into a calcination furnace and calcined for 15-25 seconds, and then cooled to obtain the coated sand regenerated sand.

[0020] Further, the preparation method of the shelling aid in step (3) is as follows:

[0021] A 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate are mixed in a volume ratio of 1:0.2-0.3 to obtain the shelling aid.

[0022] Further, the preparation method of the friction aid in step (4) is as follows:

[0023] Mix the activated carbon and boron carbide in a mass ratio of 1:1~1.4, then put them into a muffle furnace, heat to 150~200℃ at a speed of 10℃ / min, keep the temperature for 60~80min, then continue to heat to 900~1000℃ at a speed of 10℃ / min, keep the temperature for 1.5~2.5h, then naturally cool to room temperature to obtain mixture d, then mix mixture d, phosphosilicate aluminum, potassium fatty alcohol ether phosphate and water in a mass ratio of 1.2~1.4:0.6~0.8:0.08~0.12:0.5~0.7, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add mixture d and continue to stir for 2~3min, finally add phosphosilicate aluminum, heat the system to 32~34℃, keep stirring for 8~10min, then add it into a granulator to obtain the friction aid.

[0024] The present application has the following advantages:

[0025] (1) Hydroxyethyl ethylene bis-stearamide has stronger lubricity, demolding effect and heat resistance than calcium stearate, can make the components in the reaction system more uniformly mixed together, thereby promoting the complete curing of the resin, consuming the free formaldehyde and free phenol contained therein, enhancing the performance of the coated sand while improving the environmental protection, and its dispersibility in phenolic resin is also better, which can make hydroxyethyl ethylene bis-stearamide better play its lubricating effect, and the migration of hydroxyethyl ethylene bis-stearamide is weaker, overcoming the defect that calcium stearate is easy to precipitate;

[0026] (2) Triisopropyl phosphate has the effects of penetration and dispersion, and has a synergistic effect with hydroxyethyl ethylene bis-stearamide, and also has the effects of flame retardation and plasticization, can inhibit the combustion of coated sand, reduce the emission of smoke and harmful gas, and enhance the ductility of coated sand, and the viscosity of triisopropyl phosphate is also low, which can adjust the viscosity of the whole system so that it will not be too thick;

[0027] (3) Aluminum nitride can enhance the strength and fire resistance of coated sand, and can produce an oxide film at high temperature to further enhance the fire resistance of coated sand, and has strong thermal conductivity, which can ensure the evenness of the casting and effective heat dissipation to improve the quality of the casting, but the phenolic resin contains part of moisture, and aluminum nitride will hydrolyze when it comes into contact with water, and the dispersibility of aluminum nitride in phenolic resin is poor, so a layer of oleyl oleate is coated on the surface of aluminum nitride, which is insoluble in water and can well protect aluminum nitride, and has excellent dispersing and lubricating properties, so that aluminum nitride can be uniformly distributed in the phenolic resin and has a synergistic effect on hydroxyethyl ethylene bis-stearamide;

[0028] (4) The dodecyl alcohol amide phosphate has stronger surfactant performance than sodium dodecyl sulfonate, has stronger adhesion to resin, can be dissolved in cold water, has no cloud point, can increase the viscosity of propylene glycol solution, further increases the amount of propylene glycol solution adhered to the coated sand waste sand, so that greater tension is generated when freezing to remove the shell, and the hydroxyethyl ethylene bis-stearamide and triisopropyl phosphate can form hydrogen bonds with water, adsorb more water molecules to further enhance the shell breaking tension;

[0029] (5) The activated carbon used as the friction aid component can adsorb organic pollutants generated by the residual resin of the coated sand waste sand, and the activated carbon can be regenerated and reused after use, but the hardness of the activated carbon is not high, so boron carbide is added to enhance the mechanical properties of the activated carbon, and the phosphosilicate aluminum has stronger high temperature resistance, water resistance and oxidation resistance than the sodium silicate binder, and has greater bonding strength and better toughness at high temperature, and is not easy to produce cracks;

[0030] (6) The fatty alcohol ether phosphate potassium salt has excellent lubricity, dispersion, antistatic, chemical resistance and high temperature resistance, can uniformly mix the activated carbon, boron carbide and phosphosilicate aluminum, the antistatic effect can prevent the detached resin from being re-adsorbed on the coated sand, increase the workload of subsequent processing, the chemical resistance and high temperature resistance can prolong the service life of the friction aid, the fatty alcohol ether phosphate potassium salt has good biodegradability and does not pollute the environment. DETAILED DESCRIPTION

[0031] The application will be further described in detail below in combination with examples. Example 1

[0032] (1) 105 parts of sand with a particle size of 0.15-0.3 mm were added to a stirrer, and then the temperature was raised to 115°C and stirred for preheating for 35 min;

[0033] (2) After preheating, 4.5 parts of phenolic resin were added to the stirrer and stirred for 80 s;

[0034] (3) 55 parts of aluminum nitride were further added to the stirrer and stirred for 60 s;

[0035] (4) 12 parts of urotropin and water were mixed according to a mass ratio of 1:1.8 and then added to the stirrer and stirred for 40 s;

[0036] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate were added to the stirrer, stirred for 55 s, and then naturally cooled to room temperature to obtain micro-smoke and odor-free environmentally friendly coated sand for casting steel. Example 2

[0037] (1) 100 parts of sand with particle size of 0.15-0.3 mm was added into a stirring machine, and then heated to 100°C for preheating and stirring for 40 min;

[0038] (2) After preheating, 3 parts of phenolic resin was added into the stirring machine, and stirred for 75 s;

[0039] (3) 60 parts of aluminum nitride was continuously added into the stirring machine, and stirred for 50 s;

[0040] (4) 14 parts of urotropin and water were mixed according to a mass ratio of 1:1.6, and then added into the stirring machine, and stirred for 35 s;

[0041] (5) Finally, 4 parts of hydroxyethyl ethylene bis-stearamide and 3 parts of triisopropyl phosphate were added into the stirring machine, and stirred for 60 s, and then naturally cooled to room temperature to obtain the micro-smoke and odorless environmentally-friendly coated sand for cast steel. Example 3

[0042] (1) 110 parts of sand with particle size of 0.15-0.3 mm was added into a stirring machine, and then heated to 130°C for preheating and stirring for 30 min;

[0043] (2) After preheating, 6 parts of phenolic resin was added into the stirring machine, and stirred for 85 s;

[0044] (3) 50 parts of aluminum nitride was continuously added into the stirring machine, and stirred for 70 s;

[0045] (4) 10 parts of urotropin and water were mixed according to a mass ratio of 1:2, and then added into the stirring machine, and stirred for 45 s;

[0046] (5) Finally, 6 parts of hydroxyethyl ethylene bis-stearamide and 2 parts of triisopropyl phosphate were added into the stirring machine, and stirred for 50 s, and then naturally cooled to room temperature to obtain the micro-smoke and odorless environmentally-friendly coated sand for cast steel. Example 4

[0047] (1) 105 parts of sand with particle size of 0.15-0.3 mm was added into a stirring machine, and then heated to 115°C for preheating and stirring for 35 min;

[0048] (2) After preheating, 4.5 parts of phenolic resin was added into the stirring machine, and stirred for 80 s;

[0049] (3) 55 parts of aluminum nitride was continuously added into the stirring machine, and stirred for 60 s;

[0050] (4) 12 parts of urotropin and water were mixed according to a mass ratio of 1:1.8, and then added into the stirring machine, and stirred for 40 s;

[0051] (5) Finally, 5 parts of calcium stearate and 2.5 parts of triisopropyl phosphate are added into the blender, and after stirring for 55 s, the micro-smoke and odorless environmentally-friendly coated sand for cast steel is obtained by naturally cooling to room temperature. Example 5

[0052] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added into the blender, and then heated to 115°C for preheating and stirring for 35 min;

[0053] (2) After preheating, 4.5 parts of phenolic resin are added into the blender, and stirred for 80 s;

[0054] (3) 55 parts of aluminum nitride are continuously added into the blender, and stirred for 60 s;

[0055] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8, and then added into the blender, and stirred for 40 s;

[0056] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of polyethylene glycol are added into the blender, and after stirring for 55 s, the micro-smoke and odorless environmentally-friendly coated sand for cast steel is obtained by naturally cooling to room temperature. Example 6

[0057] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added into the blender, and then heated to 90°C for preheating and stirring for 35 min;

[0058] (2) After preheating, 4.5 parts of phenolic resin are added into the blender, and stirred for 80 s;

[0059] (3) 55 parts of aluminum nitride are continuously added into the blender, and stirred for 60 s;

[0060] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8, and then added into the blender, and stirred for 40 s;

[0061] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate are added into the blender, and after stirring for 55 s, the micro-smoke and odorless environmentally-friendly coated sand for cast steel is obtained by naturally cooling to room temperature. Example 7

[0062] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added into the blender, and then heated to 115°C for preheating and stirring for 50 min;

[0063] (2) After preheating, 4.5 parts of phenolic resin are added into the blender, and stirred for 80 s;

[0064] (3) 55 parts of aluminum nitride are continuously added into the blender, and stirred for 60 s;

[0065] (4) 12 parts of urotropin and water were mixed in a mass ratio of 1:1.8 and then added into the blender, stirred for 40 s;

[0066] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate were added into the blender, stirred for 55 s, and then naturally cooled to room temperature to obtain the micro-smoke and odorless environmentally friendly coated sand for casting steel. Example 8

[0067] (1) 105 parts of sand with a particle size of 0.15-0.3 mm were added into the blender, and then heated to 115°C and stirred for preheating for 35 min;

[0068] (2) After preheating, 4.5 parts of phenolic resin were added into the blender and stirred for 80 s;

[0069] (3) 55 parts of aluminum nitride were continuously added into the blender and stirred for 60 s;

[0070] (4) 12 parts of urotropin and water were mixed in a mass ratio of 1:3 and then added into the blender, stirred for 40 s;

[0071] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate were added into the blender, stirred for 55 s, and then naturally cooled to room temperature to obtain the micro-smoke and odorless environmentally friendly coated sand for casting steel. Example 9

[0072] (1) 105 parts of sand with a particle size of 0.15-0.3 mm were added into the blender, and then heated to 115°C and stirred for preheating for 35 min;

[0073] (2) After preheating, 4.5 parts of phenolic resin, 55 parts of aluminum nitride, 12 parts of urotropin, 21.6 parts of water, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate were added into the blender, stirred for 235 s, and then naturally cooled to room temperature to obtain the coated sand for casting steel.

[0074] The hot tensile strength of the environmentally friendly coated sand for casting steel prepared in Examples 1-9 was determined according to JB / T8583-2008, and the content of formaldehyde generated was measured by combustion. The specific data are shown in Table 1.

[0075] Table 1: Data table of hot tensile strength and formaldehyde content of coated sand of each example

[0076] Embodiment Hot tensile strength (MPa) Formaldehyde content (ppm) Example 1 2.2 4 Example 2 2.1 5 Example 3 2.1 5 Example 4 1.5 6 Example 5 1.6 6 Example 6 1.8 10 Example 7 2.0 5 Example 8 1.7 9 Example 9 1.2 14

[0077] As can be seen from Table 1, the hot tensile strength of the coated sand prepared in Examples 1-3 is the highest and the content of formaldehyde generated by combustion is the lowest; the hot tensile strength of the coated sand prepared in Example 4 and Example 5 is obviously decreased compared with that of Example 1, and the content of formaldehyde is also increased compared with that of Example 1, which may be because the lubrication effect is poorer after changing the two components, resulting in poor fluidity of the coated sand, uneven mixing of the system, affecting the curing of the phenolic resin, and then affecting the hot tensile strength of the coated sand and the content of formaldehyde generated; the hot tensile strength of the coated sand prepared in Example 6 is also obviously decreased compared with that of Example 1, and the content of formaldehyde is obviously increased, which may be because the preheating temperature and the subsequent reaction temperature in the preparation process of the coated sand are too low, resulting in lower curing degree of the phenolic resin, and then affecting the performance of the coated sand; the hot tensile strength and the content of formaldehyde of the coated sand prepared in Example 7 are not much different from those of Example 1, indicating that the preheating time of Example 1 is the best; the reason why the hot tensile strength of the coated sand prepared in Example 8 is decreased and the content of formaldehyde is increased compared with those of Example 1 may be that more urotropin water causes the free formaldehyde in the phenolic resin to be more easily desorbed in water, thereby affecting the curing of the phenolic resin, and after the water evaporates, the formaldehyde in the water will be re-adsorbed in the resin, increasing the content of free formaldehyde in the resin, and more formaldehyde will be generated during combustion; the preparation process of the coated sand is changed in Example 9, and the coated sand components added in steps are changed to one-step addition, and the hot tensile strength of the coated sand prepared is significantly decreased and the content of formaldehyde generated is significantly increased. Example 10

[0078] The particle size of aluminum nitride in the range of 0.07-0.1 mm was immersed in a 75% volume fraction of ethanol solution, and then ultrasonic cleaning was performed for 6 min. After cleaning, the aluminum nitride was immersed in oleyl oleate and heated to 38℃, and then fully stirred for 4 min to obtain modified aluminum nitride.

[0079] A 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate were mixed in a volume ratio of 1:0.25 to obtain a de-shelling aid.

[0080] Active carbon and boron carbide were fully stirred and mixed in a mass ratio of 1:1.2, and then placed in a muffle furnace and heated to 175℃ at a rate of 10℃ / min, and then kept for 70 min. Then, the temperature was continuously increased to 950℃ at a rate of 10℃ / min, and then kept for 2 h. Then, the mixture was naturally cooled to room temperature to obtain mixture d. Then, mixture d, phosphosilicate aluminum, fatty alcohol ether phosphate potassium salt and water were mixed in a mass ratio of 1.3:0.7:0.1:0.6. The fatty alcohol ether phosphate potassium salt and water were first mixed uniformly, then mixture d was added and stirred for 2.5 min, and finally phosphosilicate aluminum was added. The system was heated to 33℃ and kept for 9 min, and then added to a granulator to obtain a friction aid.

[0081] (1) 105 parts of sand with particle size of 0.15-0.3 mm was added into a stirring machine, and then heated to 115°C for preheating and stirring for 35 min;

[0082] (2) After preheating, 4.5 parts of phenolic resin was added into the stirring machine and stirred for 80 s;

[0083] (3) 55 parts of modified aluminum nitride was continuously added into the stirring machine and stirred for 60 s;

[0084] (4) 12 parts of urotropin and water was mixed according to the mass ratio of 1:1.8 and then added into the stirring machine and stirred for 40 s;

[0085] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate was added into the stirring machine, and after stirring for 55 s, the micro-smoke and odorless environmental protection coated sand for casting steel was obtained by natural cooling to room temperature;

[0086] (6) The micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) was used for casting steel to obtain the waste coated sand for casting steel, and then the waste coated sand for casting steel was crushed and screened by a vibrating machine, and the mixture a was obtained by separating the iron scraps from the waste coated sand for casting steel by a magnet;

[0087] (7) The mixture a was immersed in a 42.5% mass fraction of sulfuric acid solution, and fully stirred for 35 min. After the reaction was completed, the mixture b was obtained by washing with deionized water until neutral;

[0088] (8) The mixture b was immersed in a shelling aid, and after stirring and impregnating for 4 min, the mixture b was transferred into a-17°C environment and frozen for 2.5 h, and then shelled by stirring at a speed of 900 r / min to obtain the mixture c;

[0089] (9) The mixture c and the friction aid accounting for 1.5% of the mass of the mixture c were transferred into a high-speed turbine type four-roller, and the mixture c was preheated by a turbine type preheater, and then the high-speed turbine type four-roller was started to make the mixture c collide and rub with each other, and the duration was 55 s, and then the mixture c was transferred into a roasting furnace and roasted for 20 s, and after cooling, the coated sand regenerated sand was obtained. Example 11

[0090] The particle size of the aluminum nitride was 0.07-0.1 mm, which was immersed in an ethanol solution with a volume fraction of 75%, and then cleaned by ultrasonic wave for 7 min. After cleaning, the aluminum nitride was immersed in oleyl oleate and heated to 36°C, and fully stirred for 5 min to obtain the modified aluminum nitride.

[0091] A solution of 9% volume fraction of propylene glycol and dodecyl alcohol amide phosphate was mixed according to the volume ratio of 1:0.2 to obtain.

[0092] The activated carbon and boron carbide are mixed by fully stirring at a mass ratio of 1:1, then put into a muffle furnace, heated to 200°C at a rate of 10°C / min, kept for 60 min, then continue to heat to 900°C at a rate of 10°C / min, keep for 2.5h, then naturally cool to room temperature to obtain mixture d, then mixture d, phosphosilicate aluminum, potassium salt of fatty alcohol ether phosphate and water are proportioned at a mass ratio of 1.2:0.8:0.12:0.7, first mix the potassium salt of fatty alcohol ether phosphate and water uniformly, then add mixture d and continue to stir for 2 min, finally add phosphosilicate aluminum, heat the system to 34°C, keep stirring for 8 min, then add it into a granulator to obtain a friction aid.

[0093] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added to a stirring machine, then heated to 115°C and preheated for 35 min;

[0094] (2) After preheating, 4.5 parts of phenolic resin are added to the stirring machine and stirred for 80 s;

[0095] (3) Continue to add 55 parts of modified aluminum nitride to the stirring machine and stir for 60 s;

[0096] (4) Mix 12 parts of urotropin and water at a mass ratio of 1:1.8, then add them to the stirring machine and stir for 40 s;

[0097] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate are added to the stirring machine, stirred for 55 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmental protection coated sand for casting steel;

[0098] (6) The micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) is used for casting steel to obtain environmental protection coated sand waste sand for casting steel, then the environmental protection coated sand waste sand for casting steel is crushed and screened by a vibrating machine, and the broken iron in the waste sand is separated by a magnet to obtain mixture a;

[0099] (7) Submerge mixture a in a 40% mass fraction of sulfuric acid solution, fully stir for 40 min, and then wash to neutral with deionized water to obtain mixture b;

[0100] (8) Submerge mixture b in a shelling aid, stir for 3 min, then transfer mixture b to a-20°C environment and freeze for 2h, then stir at a speed of 1000 r / min while cold to obtain mixture c;

[0101] (9) Put the mixture c and 1% mass of friction aids of the mixture c into a high-speed turbine four-roller, and preheat the mixture c through a turbine preheater, then start the high-speed turbine four-roller, so that the mixture c collides and rubs with each other, for 50 s, then put into a baking furnace and bake for 25 s, and the coated sand regenerated sand is obtained after cooling. Example 12

[0102] Put the aluminum nitride with a particle size of 0.07-0.1 mm into a 75% volume fraction of ethanol solution, then clean for 5 min using ultrasonic waves, and then immerse the aluminum nitride in oleyl oleate and heat to 40℃, and after fully stirring for 5 min, the modified aluminum nitride is obtained.

[0103] Mix 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate at a volume ratio of 1:0.3 to obtain the mixture.

[0104] Mix the activated carbon and boron carbide at a mass ratio of 1:1.4, then put into a muffle furnace, heat to 150℃ at a speed of 10℃ / min, and keep for 80 min, then continue to heat to 1000℃ at a speed of 10℃ / min, keep for 1.5 h, then naturally cool to room temperature to obtain the mixture d, then mix the mixture d, phosphosilicate aluminum, potassium fatty alcohol ether phosphate, and water at a mass ratio of 1.4:0.6:0.08:0.5, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add the mixture d and continue to stir for 3 min, and finally add the phosphosilicate aluminum, heat the system to 32℃, keep for 10 min, then put into a granulator to obtain the friction aid.

[0105] (1) Put 105 parts of sand with a particle size of 0.15-0.3 mm into a stirring machine, then heat to 115℃ and stir for preheating for 35 min;

[0106] (2) After preheating, add 4.5 parts of phenolic resin into the stirring machine and stir for 80 s;

[0107] (3) Continue to add 55 parts of modified aluminum nitride into the stirring machine and stir for 60 s;

[0108] (4) Mix 12 parts of urotropin and water at a mass ratio of 1:1.8, then add into the stirring machine and stir for 40 s;

[0109] (5) Finally, add 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate into the stirring machine, stir for 55 s, and then naturally cool to room temperature to obtain the micro-smoke and odor-free environmental protection coated sand for casting steel;

[0110] (6) The micro-smoke and odor-free coated sand for steel casting obtained in step (5) is used for steel casting to obtain coated sand for steel casting waste sand, and then the coated sand for steel casting waste sand is crushed and screened by a vibrating machine, and the mixture a of the crushed iron in the waste sand is separated by a magnet;

[0111] (7) The mixture a is immersed in a 45% mass fraction of sulfuric acid solution, and is fully stirred for 30 min, and after the reaction is completed, the mixture b is obtained by washing with deionized water to neutral;

[0112] (8) The mixture b is immersed in a shelling aid, and after stirring and impregnating for 3-5 min, the mixture b is transferred into a-15℃ environment and frozen for 3 h, and then the shelling is carried out by stirring at a speed of 800 r / min to obtain the mixture c;

[0113] (9) The mixture c and 2% of the friction aid by mass are transferred into a high-speed turbine four-roller, and the mixture c is preheated by a turbine preheater, and then the high-speed turbine four-roller is started, so that the mixture c collides and rubs with each other, and the duration is 60 s, and then it is transferred into a roasting furnace and roasted for 15 s, and after cooling, the coated sand regenerated sand is obtained. Example 13

[0114] The particle size of the aluminum nitride is 0.07-0.1 mm, which is immersed in a 75% volume fraction of ethanol solution, and then ultrasonic cleaning is used for 6 min, and after cleaning is completed, the aluminum nitride is immersed in ethylene glycol monobutyl ether and heated to 38℃, and after fully stirring for 4 min, the modified aluminum nitride is obtained.

[0115] The rest is the same as example 10. Example 14

[0116] The shelling aid is obtained by mixing 9% volume fraction of propylene glycol solution and sodium dodecyl sulfonate at a volume ratio of 1:0.25.

[0117] The rest is the same as example 10. Example 15

[0118] The particle size of the aluminum nitride is 0.07-0.1 mm, which is immersed in a 75% volume fraction of ethanol solution, and then ultrasonic cleaning is used for 6 min, and after cleaning is completed, the aluminum nitride is immersed in ethylene glycol monobutyl ether and heated to 38℃, and after fully stirring for 4 min, the modified aluminum nitride is obtained.

[0119] The rest is the same as example 10. Example 16

[0120] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added to a stirring machine, and then heated to 115℃ and stirred for preheating for 35 min;

[0121] (2) After preheating is completed, 4.5 parts of phenolic resin are added into the stirring machine, and stirring is performed for 80s;

[0122] (3) 55 parts of modified aluminum nitride are continuously added into the stirring machine, and stirring is performed for 60s;

[0123] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8, and then added into the stirring machine, and stirring is performed for 40s;

[0124] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate are added into the stirring machine, and after stirring for 55s, the mixture is naturally cooled to room temperature to obtain micro-smoke and odorless environmentally-friendly coated sand for casting steel;

[0125] (6) The micro-smoke and odorless environmentally-friendly coated sand for casting steel obtained in step (5) is used for casting steel to obtain environmentally-friendly coated sand waste sand for casting steel, and then the environmentally-friendly coated sand waste sand for casting steel is crushed and screened by a vibrating machine, and then the mixture a of the crushed iron in the waste sand is separated by a magnet;

[0126] (7) The mixture a is immersed in a 30% mass fraction of sulfuric acid solution, and fully stirred for 35 min, and after the reaction is completed, the mixture b is obtained by washing with deionized water until neutral;

[0127] (8) The mixture b is immersed in a shelling aid, and after stirring and impregnating for 4 min, the mixture b is transferred into a-17℃ environment and frozen for 2.5h, and then shelling is performed by stirring at a speed of 900r / min to obtain the mixture c;

[0128] (9) The mixture c and 1.5% of friction aid by mass are transferred into a high-speed turbine type four-roller, and the mixture c is preheated by a turbine type preheater, and then the high-speed turbine type four-roller is started, so that the mixture c collides and rubs with each other, and the duration is 55s, and then the mixture c is transferred into a roasting furnace and roasted for 20s, and after cooling, the coated sand regenerated sand is obtained.

[0129] The rest is the same as in Example 10. Example 17

[0130] (1) 105 parts of sand with a particle size of 0.15-0.3mm are added into a stirring machine, and then the temperature is raised to 115℃ and stirring is performed for 35 min;

[0131] (2) After preheating is completed, 4.5 parts of phenolic resin are added into the stirring machine, and stirring is performed for 80s;

[0132] (3) 55 parts of modified aluminum nitride are continuously added into the stirring machine, and stirring is performed for 60s;

[0133] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8, and then added into the stirring machine, and stirring is performed for 40s;

[0134] (5) Finally, 5 parts of hydroxyethyl ethylene bis stearate amide and 2.5 parts of triisopropyl phosphate are added into the blender, and after stirring for 55s, it is naturally cooled to room temperature to obtain micro-smoke and odorless cast steel environmentally friendly coated sand;

[0135] (6) The micro-smoke and odorless cast steel environmentally friendly coated sand obtained in step (5) is used for casting steel to obtain cast steel environmentally friendly coated sand waste sand, and then the cast steel environmentally friendly coated sand waste sand is crushed and screened by a vibrating machine, and the mixture a of the broken iron in the waste sand is separated by a magnet;

[0136] (7) The mixture a is immersed in a 42.5% mass fraction of sulfuric acid solution, and fully stirred for 50min. After the reaction is completed, the mixture b is washed to neutral with deionized water;

[0137] (8) The mixture b is immersed in a shelling aid, and after stirring for 4min, the mixture b is transferred to a-17℃ environment and frozen for 2.5h, and then stirred at a speed of 900r / min to obtain the mixture c;

[0138] (9) The mixture c and 1.5% of the friction aid are transferred into a high-speed turbine four-roller, and the mixture c is preheated by a turbine preheater, and then the high-speed turbine four-roller is started, so that the mixture c is impacted and rubbed with each other, and the duration is 55s, and then it is transferred into a roasting furnace and roasted for 20s, and after cooling, the coated sand regenerated sand is obtained.

[0139] The rest is the same as example 10. Example 18

[0140] (1) 105 parts of sand with a particle size of 0.15-0.3mm are added into the blender, and then heated to 115℃ and stirred for 35min;

[0141] (2) After preheating, 4.5 parts of phenolic resin are added into the blender and stirred for 80s;

[0142] (3) 55 parts of modified aluminum nitride are continuously added into the blender and stirred for 60s;

[0143] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8 and then added into the blender and stirred for 40s;

[0144] (5) Finally, 5 parts of hydroxyethyl ethylene bis stearate amide and 2.5 parts of triisopropyl phosphate are added into the blender, and after stirring for 55s, it is naturally cooled to room temperature to obtain micro-smoke and odorless cast steel environmentally friendly coated sand;

[0145] (6) the micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) is used for casting steel to obtain the waste coated sand for casting steel, and then the waste coated sand for casting steel is crushed and screened by a vibrating machine, and the mixture a is obtained by separating the iron scraps in the waste sand by a magnet;

[0146] (7) the mixture a is immersed in a 42.5% mass fraction sulfuric acid solution, and is fully stirred for 35 min, and then the mixture b is obtained by washing with deionized water until neutral;

[0147] (8) the mixture b is immersed in a shelling aid, and is stirred for 4 min, and then the mixture b is transferred into an environment at -30℃ and is frozen for 2.5 h, and then is stirred at a speed of 900 r / min to obtain the mixture c;

[0148] (9) the mixture c and 1.5% of friction aid by mass of the mixture c are transferred into a high-speed turbine type four-roller, and the mixture c is preheated by a turbine type preheater, and then the high-speed turbine type four-roller is started to make the mixture c collide and rub with each other, and the duration is 55 s, and then is transferred into a baking furnace and is baked for 20 s, and the coated sand regenerated sand is obtained after cooling.

[0149] The rest is the same as in example 10. Example 19

[0150] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added into a stirring machine, and then the temperature is raised to 115℃ and is stirred for 35 min;

[0151] (2) after the preheating is completed, 4.5 parts of phenolic resin are added into the stirring machine, and are stirred for 80 s;

[0152] (3) 55 parts of modified aluminum nitride are continuously added into the stirring machine, and are stirred for 60 s;

[0153] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8, and are added into the stirring machine, and are stirred for 40 s;

[0154] (5) finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate are added into the stirring machine, and are stirred for 55 s, and then are naturally cooled to room temperature to obtain the micro-smoke and odorless environmental protection coated sand for casting steel;

[0155] (6) the micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) is used for casting steel to obtain the waste coated sand for casting steel, and then the waste coated sand for casting steel is crushed and screened by a vibrating machine, and the mixture a is obtained by separating the iron scraps in the waste sand by a magnet;

[0156] (7) immerging the mixture a in a 42.5% mass fraction sulfuric acid solution, fully stirring for 35 min, after the reaction is completed, washing with deionized water until neutral to obtain mixture b;

[0157] (8) immerging the mixture b in a shelling aid, stirring for 4 min, then transferring the mixture b into a -17 ℃ environment and freezing for 4 h, then stirring at a speed of 900 r / min while cold to obtain mixture c;

[0158] (9) transferring the mixture c and 1.5% of the mass of the friction aid into a high-speed turbine four-roll mill, preheating the mixture c through a turbine preheater, then starting the high-speed turbine four-roll mill, so that the mixture c collides and rubs against each other, for a duration of 55 s, then transferring into a baking furnace and baking for 20 s, after cooling, obtaining the coated sand regeneration sand.

[0159] The rest is the same as in Example 10. Example 20

[0160] (1) adding 105 parts of sand with a particle size of 0.15-0.3 mm into a stirring machine, then heating to 115 ℃ and stirring for 35 min;

[0161] (2) after the preheating is completed, adding 4.5 parts of phenolic resin into the stirring machine, and stirring for 80 s;

[0162] (3) continuously adding 55 parts of modified aluminum nitride into the stirring machine, and stirring for 60 s;

[0163] (4) mixing 12 parts of urotropin and water according to a mass ratio of 1:1.8, then adding into the stirring machine, and stirring for 40 s;

[0164] (5) finally adding 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate into the stirring machine, stirring for 55 s, and then naturally cooling to room temperature to obtain the micro-smoke and odorless environmental protection coated sand for casting steel;

[0165] (6) after the micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) is used for casting steel, obtaining the environmental protection coated sand waste sand for casting steel, then crushing and screening the environmental protection coated sand waste sand for casting steel through a vibrating machine, and separating the scrap iron in the waste sand through a magnet to obtain mixture a;

[0166] (7) immerging the mixture a in a 42.5% mass fraction sulfuric acid solution, fully stirring for 35 min, after the reaction is completed, washing with deionized water until neutral to obtain mixture b;

[0167] (8) immerging the mixture b in a shelling aid, stirring for 4 min, then transferring the mixture b into a -17 ℃ environment and freezing for 2.5 h, then stirring at a speed of 1200 r / min while cold to obtain mixture c;

[0168] (9) Put the mixture c and 1.5% of the mass of the friction aid into a high-speed turbine four-roll mill, preheat the mixture c through a turbine preheater, then start the high-speed turbine four-roll mill, so that the mixture c collides and rubs against each other, for 55 seconds, then put into a baking furnace and bake for 20 seconds, and after cooling, the coated sand is obtained.

[0169] The rest is the same as in Example 10. Example 21

[0170] Mix the activated carbon and boron carbide in a mass ratio of 1:1, then put into a muffle furnace, heat to 200℃ at a rate of 10℃ / min, keep for 60 min, then continue to heat to 900℃ at a rate of 10℃ / min, keep for 2.5h, then naturally cool to room temperature to obtain mixture d, then mix the mixture d, carboxymethyl cellulose, potassium fatty alcohol ether phosphate and water in a mass ratio of 1.2:0.8:0.12:0.7, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add the mixture d and continue to stir for 2 min, finally add the carboxymethyl cellulose, heat the system to 34℃, keep stirring for 8 min, then add into a granulator to obtain the friction aid.

[0171] The rest is the same as in Example 11. Example 22

[0172] Mix the activated carbon and boron carbide in a mass ratio of 1:1, then put into a muffle furnace, heat to 200℃ at a rate of 10℃ / min, keep for 60 min, then continue to heat to 900℃ at a rate of 10℃ / min, keep for 2.5h, then naturally cool to room temperature to obtain mixture d, then mix the mixture d, phosphosilicate aluminum, sodium dodecyl sulfate and water in a mass ratio of 1.2:0.8:0.12:0.7, first mix the sodium dodecyl sulfate and water uniformly, then add the mixture d and continue to stir for 2 min, finally add the phosphosilicate aluminum, heat the system to 34℃, keep stirring for 8 min, then add into a granulator to obtain the friction aid.

[0173] The rest is the same as in Example 11. Example 23

[0174] Mix the activated carbon and boron carbide in a mass ratio of 1:1 to obtain mixture d, then mix the mixture d, phosphosilicate aluminum, potassium fatty alcohol ether phosphate and water in a mass ratio of 1.2:0.8:0.12:0.7, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add the mixture d and continue to stir for 2 min, finally add the phosphosilicate aluminum, heat the system to 34℃, keep stirring for 8 min, then add into a granulator to obtain the friction aid.

[0175] The rest is the same as in Example 11. Example 24

[0176] The activated carbon and boron carbide were mixed by stirring at a mass ratio of 1:1, then placed in a muffle furnace, heated to 200°C at a rate of 10°C / min, kept for 60 min, then continued to heat to 900°C at a rate of 10°C / min, kept for 2.5 h, then naturally cooled to room temperature to obtain mixture d, then mixture d, phosphosilicate aluminum, potassium fatty alcohol ether phosphate, and water were mixed at a mass ratio of 1.2:0.8:0.12:0.7, the potassium fatty alcohol ether phosphate and water were first mixed uniformly, then mixture d was added and stirred for 2 min, and finally the phosphosilicate aluminum was added, the system was heated to 40°C, kept for 8 min, then added to a granulator to obtain the friction aid.

[0177] The rest is the same as in Example 11. Example 25

[0178] (1) 105 parts of sand with a particle size of 0.15-0.3 mm were added to a stirring machine, then heated to 115°C and preheated by stirring for 35 min;

[0179] (2) After preheating, 4.5 parts of phenolic resin were added to the stirring machine and stirred for 80 s;

[0180] (3) 55 parts of modified aluminum nitride were continuously added to the stirring machine and stirred for 60 s;

[0181] (4) 12 parts of urotropine and water were mixed at a mass ratio of 1:1.8 and then added to the stirring machine and stirred for 40 s;

[0182] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate were added to the stirring machine, stirred for 55 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for casting steel;

[0183] (6) The micro-smoke and odorless environmentally friendly coated sand for casting steel obtained in step (5) was used for casting steel to obtain environmentally friendly coated sand waste sand for casting steel, then the environmentally friendly coated sand waste sand for casting steel was crushed and sieved by a vibrating machine, and the broken iron in the waste sand was separated by a magnet to obtain mixture a;

[0184] (7) Mixture a was immersed in a 40% mass fraction of sulfuric acid solution and stirred for 40 min, then washed with deionized water to neutral to obtain mixture b;

[0185] (8) Mixture b was immersed in a shelling aid, stirred for 3 min, then transferred to a-20°C environment and frozen for 2 h, then shelled by stirring at a speed of 1000 r / min to obtain mixture c;

[0186] (9) The mixture c and 1% of the mass of the friction aid are transferred into a high-speed turbo four-roll mill, and the mixture c is preheated through a turbo preheater, then the high-speed turbo four-roll mill is started, so that the mixture c collides and rubs with each other, for 70 s, then transferred into a baking furnace and baked for 25 s, and the coated sand regenerated sand is obtained after cooling.

[0187] The rest is the same as in Example 11. Example 26

[0188] (1) 105 parts of sand with a particle size of 0.15-0.3 mm are added into a stirring machine, then heated to 115°C and stirred for preheating for 35 min;

[0189] (2) After preheating, 4.5 parts of phenolic resin are added into the stirring machine and stirred for 80 s;

[0190] (3) 55 parts of modified aluminum nitride are continuously added into the stirring machine and stirred for 60 s;

[0191] (4) 12 parts of urotropin and water are mixed according to a mass ratio of 1:1.8 and then added into the stirring machine and stirred for 40 s;

[0192] (5) Finally, 5 parts of hydroxyethyl ethylene bis-stearamide and 2.5 parts of triisopropyl phosphate are added into the stirring machine, stirred for 55 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmental protection coated sand for casting steel;

[0193] (6) The micro-smoke and odorless environmental protection coated sand for casting steel obtained in step (5) is used for casting steel to obtain coated sand waste sand for casting steel, then the coated sand waste sand for casting steel is crushed and screened through a vibrating machine, and the broken iron in the waste sand is separated through a magnet to obtain a mixture a;

[0194] (7) The mixture a is immersed in a 40% mass fraction of sulfuric acid solution, and fully stirred and reacted for 40 min, then washed with deionized water to neutral to obtain a mixture b;

[0195] (8) The mixture b is immersed in a shelling aid, stirred and soaked for 3 min, then transferred into a-20°C environment and frozen for 2 h, then stirred at a speed of 1000 r / min while cold to obtain a mixture c;

[0196] (9) The mixture c is transferred into a high-speed turbo four-roll mill, and the mixture c is preheated through a turbo preheater, then the high-speed turbo four-roll mill is started, so that the mixture c collides and rubs with each other, for 50 s, then transferred into a baking furnace and baked for 25 s, and the coated sand regenerated sand is obtained after cooling.

[0197] The rest is the same as in Example 11.

[0198] The mass m1 of the dried mixture b, the mass m2 of the dried mixture c and the mass m3 of the coated sand reclaimed sand in Examples 10-20 were weighed, and the hulling rate of the coated sand waste sand was calculated by the formula a=(m1-m2) / (m1-m3), and the specific data are shown in Table 2. Meanwhile, the angular factor of the coated sand reclaimed sand in Examples 10-12 and 21-26 was determined according to GB / T9442-2010, and the flowability of the coated sand prepared by using the coated sand reclaimed sand was determined according to JB / T8583-2008, and the specific data are shown in Table 3. The coated sand reclaimed sand and the raw sand were mixed in the proportions of 85:15, 90:10 and 95:5 respectively, and then the coated sand was prepared, and then the hot tensile strength and the room temperature tensile strength were determined, and the specific data are shown in Table 4.

[0199] Table 2 Hulling rate of coated sand waste sand in Examples 10-20

[0200] Embodiment Coated sand waste sand hulling rate (%) Example 10 95.1 Example 11 94.8 Example 12 94.9 Example 13 80.8 Example 14 79.5 Example 15 88.2 Example 16 86.6 Example 17 94.5 Example 18 94.2 Example 19 94.1 Example 20 94.6

[0201] It can be seen from Table 2 that the hulling rate of Examples 10-12 is at the highest level, and the hulling rate of Examples 18-20 changes the freezing temperature, freezing time and stirring speed, which has little difference with Example 10, indicating that the three process parameters of Example 10 are the best process parameters; Examples 13 and 14 replace oleyl linoleate and dodecyl alcohol amide phosphate respectively, and the hulling rate is obviously lower than that of Example 10, which may be due to the fact that ethylene glycol monobutyl ether dissolves in water and cannot isolate water from contacting with aluminum nitride, so that aluminum nitride reacts with water, thereby reducing the amount of aluminum nitride attached to the coated sand, and the performance of sodium dodecyl sulfonate is worse than that of dodecyl alcohol amide phosphate in various aspects, such as adhesion, which affects the hulling effect during freezing, and then affects the hulling rate; the reason for the decrease of the hulling rate of Example 15 compared with Example 10 may be that the reaction temperature is too high, so that part of the oleyl linoleate reacts, affecting its performance; Example 16 reduces the mass fraction of sulfuric acid, affecting the reaction between aluminum nitride and sulfuric acid, and part of the aluminum nitride may not have reacted completely, thereby affecting the hulling rate; Example 17 prolongs the reaction time of aluminum nitride and sulfuric acid, but the hulling rate has little difference with Example 10, indicating that the reaction time of Example 10 is the best reaction time.

[0202] Table 3 Performance table of coated sand reclaimed sand in Examples 10-12 and 21-26

[0203] Embodiment Angular factor Fluidity (s) Example 10 1.06 16 Example 11 1.07 17 Example 12 1.07 17 Example 21 1.18 24 Example 22 1.20 25 Example 23 1.15 22 Example 24 1.13 21 Example 25 1.08 18 Example 26 1.26 28

[0204] From Table 3, it can be seen that the corner factor and flowability of Examples 10-12 are all at the best level; among them, Example 25 increases the impact time of the mixture c, but the corner factor and flowability are very close to those of Example 11, indicating that the impact time of Example 11 is already the best time; Examples 21 and 22 replace the phosphosilicate aluminum and the fatty alcohol ether phosphate potassium salt, respectively, and the corner factor and flowability thereof are greatly different from those of Example 11; the reason why the corner factor and flowability of Example 23 are not as good as those of Example 11 is that the activated carbon and boron carbide are not subjected to high-temperature treatment, on the one hand, the impurities contained therein are not removed, which affects the adhesion and adsorption performance thereof, and on the other hand, high-temperature treatment can also enhance the mechanical properties and stability thereof; the reason why the corner factor and flowability of Example 24 are not as good as those of Example 11 is that the adhesion temperature is changed, and the reason is that the temperature is too high, so that the solidification time is advanced, and the components of the friction aid are not uniformly mixed, resulting in that the performance of part of the friction aid is not up to the standard; Example 26 does not add the friction aid, so the corner factor and flowability thereof are the worst.

[0205] Table 4: Performance of coated sand prepared by using each proportion of regenerated sand and original sand

[0206] Reclaimed sand: virgin sand Hot tensile strength (MPa) Tensile strength at room temperature (MPa) 95：5 2.0 4.0 90：10 2.0 4.1 85：15 2.1 4.1 0：100 2.1 4.2

[0207] From Table 4, it can be seen that after the proportion of the regenerated sand is expanded to 95%, the coated sand prepared thereby has only a slight gap in performance compared with the coated sand prepared by using 100% original sand, indicating that the regenerated sand obtained by the present application can be well replaced by the original sand, on the one hand, the environment is protected, and on the other hand, the cost is also reduced compared with the traditional hot method regeneration process.

Claims

1. A micro-smoke, odorless, environmentally friendly coated sand for steel casting process, characterized in that: The specific steps are: ​ (1) 100~110 parts of sand with a particle size of 0.15~0.3 mm is added into a stirring machine, and then heated to 100~130℃ and stirred for 30~40 min for preheating; (2) After preheating, 3~6 parts of phenolic resin is added into the stirring machine and stirred for 75~85 s; (3) 50~60 parts of modified aluminum nitride is continuously added into the stirring machine and stirred for 50~70 s; (4) 10~14 parts of urotropin and water are mixed according to a mass ratio of 1:1.6~2 and then added into the stirring machine and stirred for 35~45 s; (5) Finally, 4~6 parts of hydroxyethyl ethylene bis-stearamide and 2~3 parts of triisopropyl phosphate are added into the stirring machine, and after stirring for 50~60 s, the mixture is naturally cooled to room temperature to obtain micro-smoke and odorless environmentally-friendly coated sand for casting steel; The preparation method of the modified aluminum nitride is: The aluminum nitride with a particle size of 0.07~0.1 mm is immersed in an ethanol solution with a volume fraction of 75%, and then ultrasonic cleaning is performed for 5~7 min. After cleaning, the aluminum nitride is immersed in oleyl oleate and heated to 36~40℃, and then fully stirred for 3~5 min to obtain the modified aluminum nitride.

2. A waste sand regeneration process for the micro-smoke odorless environmentally friendly coated sand for steel casting prepared by the preparation process as claimed in claim 1, characterized in that: The specific steps are: (1) The micro-smoke and odorless environmentally-friendly coated sand for casting steel waste sand is crushed and screened by a vibrating machine, and then the broken iron in the waste sand is removed by a magnet to obtain a mixture a; (2) The mixture a is immersed in a sulfuric acid solution with a mass fraction of 40%~45%, and fully stirred for 30~40 min. After reaction, the mixture b is obtained by washing with deionized water until neutral; (3) The mixture b is immersed in a shelling aid, and after stirring and impregnating for 3~5 min, the mixture b is transferred into a-20~-15℃ environment and frozen for 2~3 h. Then, the mixture b is stirred at a speed of 800~1000 r / min to obtain a mixture c; (4) The mixture c and a friction aid with a mass of 1%~2% of the mixture c are transferred into a high-speed turbine four-wheel, and the mixture c is preheated by a turbine preheater. Then, the high-speed turbine four-wheel is started, so that the mixture c collides and rubs with each other, and the duration is 50~60 s. Then, the mixture c is transferred into a calcination furnace and calcined for 15~25 s. After cooling, the coated sand regenerated sand is obtained.

3. A spent sand reclamation process as claimed in claim 2, wherein: The preparation method of the shelling aid is: A 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate are mixed according to a volume ratio of 1:0.2~0.3 to obtain the shelling aid.

4. A spent sand reclamation process as defined in claim 2, wherein: The preparation method of the friction aid is: Mix activated carbon and boron carbide with a mass ratio of 1:1~1.4, then put into a muffle furnace, heat to 150~200℃ at a speed of 10℃ / min, keep for 60~80min, then continue to heat to 900~1000℃ at a speed of 10℃ / min, keep for 1.5~2.5h, then cool to room temperature naturally to obtain mixture d, then mix mixture d, phosphosilicate aluminum, potassium fatty alcohol ether phosphate and water with a mass ratio of 1.2~1.4:0.6~0.8:0.08~0.12:0.5~0.7, first mix potassium fatty alcohol ether phosphate and water uniformly, then add mixture d and continue to stir for 2~3min, finally add phosphosilicate aluminum, heat the system to 32~34℃, keep stirring for 8~10min, then add into a granulator to obtain a friction aid.