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

Abstract

This invention discloses a low-smoke, odorless, environmentally friendly recycled coated sand process for cast iron. By combining powdered silica gel and modified erucamide to form a composite anti-adhesion agent, the anti-adhesion and refractory properties of the coated sand are significantly enhanced. The cured resin on the surface of the coated sand is removed by freezing and desquamation. By modifying aluminum nitride and preparing a desquamation aid, the desquamation rate of the coated sand waste is greatly improved. At the same time, a friction aid is prepared to enhance the particle shaping of the recycled coated sand, thereby enhancing the fluidity of the coated sand prepared from the recycled 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 cast iron environment-friendly regenerated coated sand process. BACKGROUND

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

[0003] The molten iron during cast iron casting has a lower temperature and a higher carbon content, and its viscosity is also larger than that of molten steel, so the anti-sticking property of most coated sand for cast iron is poor, which easily leads to quality problems caused by the adhesion of coated sand to castings, and then secondary processing of the castings is required, which reduces the quality of the castings and also reduces the efficiency, the coated sand prepared by the prior art has large smoke and heavy odor during use, and the used coated sand waste sand is difficult to regenerate, so the process has problems of large energy consumption, high cost and low yield, so the cost of regenerated coated sand is higher than that of new sand, which leads to the accumulation of coated sand waste sand and pollution to the environment.

[0004] Therefore, there is an urgent need for a cast iron coated sand process with good anti-sticking property, environmental protection and regeneration. SUMMARY

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

[0006] The second object of the application is to provide a cast iron environment-friendly coated sand waste sand regeneration process.

[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 cast iron environment-friendly coated sand preparation process, the specific steps are as follows:

[0009] (1) 120-130 parts of sand with a particle size of 0.15-0.3 mm are added into a stirrer, and then the temperature is raised to 110-140 DEG C for preheating and stirring for 25-35 min;

[0010] (2) After preheating, 5-7 parts of phenolic resin are added into the stirrer and stirred for 80-90 s;

[0011] (3) 40-50 parts of modified aluminum nitride and 15-25 parts of powder silica gel are continuously added into the stirrer and stirred for 60-80 s;

[0012] (4) 8-12 parts of urotropin and water are mixed according to a mass ratio of 1:1.4-1.8, and then added into a blender, and stirred for 40-50 s;

[0013] (5) finally, 2-4 parts of calcium stearate and 5-7 parts of modified erucylamide are added into the blender, and stirred for 45-55 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environment-friendly coated sand.

[0014] Further, the preparation method of the modified aluminum nitride in step (3) is as follows: aluminum nitride with a particle size of 0.07-0.1 mm is immersed in an ethanol solution with a volume fraction of 70%, and then cleaned by ultrasonic wave for 6-8 min; after cleaning, the aluminum nitride is immersed in oleyl oleate and heated to 35-37°C, and then stirred for 4-6 min to obtain the modified aluminum nitride.

[0015] Further, the preparation method of the modified erucylamide in step (5) is as follows: 3-5 parts of erucylamide is added into 6-8 parts of hot anhydrous ethanol with a temperature of 55-65°C, and stirred for 10 min; then 0.5-0.7 parts of melamine polyphosphate is added, and stirred for 3-5 min to obtain the modified erucylamide.

[0016] A cast iron environment-friendly coated sand waste sand regeneration process, and the specific steps are as follows:

[0017] (1) the cast iron 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;

[0018] (2) the mixture a is immersed in a sulfuric acid solution with a mass fraction of 46%-48%, and stirred for 25-35 min; after reaction, the mixture b is obtained by washing with deionized water until neutral;

[0019] (3) the mixture b is immersed in a shelling aid, and stirred for 4-6 min; then the mixture b is transferred into an environment with a temperature of-25--20°C, and frozen for 1.5-2.5 h; then the mixture c is obtained by stirring at a speed of 900-1100 r / min while cold.

[0020] (4) the mixture c and a friction aid with a mass of 1.5%-2.5% of the mass of the mixture c are transferred into a high-speed turbine type four-turn, and the mixture c is preheated by a turbine type preheater; then the high-speed turbine type four-turn is started, so that the mixture c collides and rubs with each other, and the duration is 40-50 s; then the coated sand regenerated sand is obtained by baking in a baking furnace for 20-30 s after cooling.

[0021] Further, the preparation method of the shelling aid in step (3) is as follows:

[0022] Mix 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate with a volume ratio of 1:0.25~0.35 to obtain the mixture.

[0023] Further, the preparation method of the friction aid in step (4) is:

[0024] Mix activated carbon and boron carbide with a mass ratio of 1:1.2~1.6, then put them into a muffle furnace, heat to 180~220℃ at a speed of 10℃ / min, keep for 50~70min, then continue to heat to 950~1050℃ at a speed of 10℃ / min, keep for 2~3h, then naturally cool to room temperature to obtain mixture a, then mix mixture a, phosphosilicate aluminum, fatty alcohol ether phosphate potassium salt and water with a mass ratio of 1.2~1.4:0.5~0.7:0.1~0.12:0.6~0.8, first mix the fatty alcohol ether phosphate potassium salt and water uniformly, then add mixture a and continue to stir for 4~5min, finally add phosphosilicate aluminum, heat the system to 30~32℃, keep for 10~12min, then add into a granulator to obtain the friction aid.

[0025] The present application has the following advantages:

[0026] (1) The powder silica gel can form a composite anti-adhesion agent with erucic amide, the micron-sized powder silica gel can be uniformly mixed with erucic amide, and the two have a synergistic effect on the anti-adhesion of the coated sand, the powder silica gel also has the effect of anti-caking agent and helps calcium stearate, and the powder silica gel also has the effect of adsorbent, which can adsorb odor substances generated during casting, erucic amide has the effects of anti-adhesion, anti-caking, preventing sand settlement and improving the release property of the coated sand, and has high thermal stability and low friction coefficient, and has a synergistic effect after being compounded with the powder silica gel, and melamine pyrophosphate has the advantages of being more environmentally friendly and lower smoke emission than other flame retardants, which enhances the thermal stability of erucic amide and the fire resistance of the coated sand.

[0027] (2) Aluminum nitride can enhance the strength and fire resistance of the coated sand, it can generate an oxide film at high temperature to further enhance the fire resistance of the coated sand, and it has strong thermal conductivity, which can ensure the uniform heating of the casting and effectively dissipate heat to improve the quality of the casting, but the phenolic resin contains part of water, and aluminum nitride will hydrolyze when it comes into contact with water, and the dispersibility of aluminum nitride in the phenolic resin is poor, so a layer of oleyl linoleate is coated on the surface of aluminum nitride, which is water-insoluble and can well protect aluminum nitride, and has excellent dispersibility and lubricity, so that aluminum nitride can be uniformly distributed in the phenolic resin;

[0028] (3) The dodecyl alcohol amide phosphate has stronger surfactant performance than sodium dodecyl sulfonate, has stronger adhesion to the resin, can be dissolved in cold water, has no cloud point, can increase the viscosity of the propylene glycol solution, further increases the amount of the propylene glycol solution adhered to the coated sand waste sand, has greater tension to break the shell when freezing, and the powder silica gel can absorb water when washing the waste sand due to the microporosity and hygroscopicity, and then helps to break the shell when freezing without affecting the quality of the casting;

[0029] (4) The activated carbon as the friction aid component can adsorb the organic pollutants generated by the coated sand waste sand residual resin, and the activated carbon can be regenerated and reused after use, but the hardness of the activated carbon is not high, so the boron carbide is added to enhance the mechanical properties of the activated carbon, 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] (5) The fatty alcohol ether phosphate potassium salt has excellent lubricating, dispersing, 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, 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] 4 parts of erucic acid amide are added into 7 parts of hot anhydrous ethanol at 60℃, stirred for 10 min, then 0.6 parts of melamine polyphosphate is continuously added, and then the modified erucic acid amide is obtained after continuously stirring for 4 min.

[0033] (1) 125 parts of sand with a particle size of 0.15-0.3 mm are added into a stirrer, then the temperature is raised to 125℃, and preheating is performed for 30 min;

[0034] (2) After preheating, 6 parts of phenolic resin are added into the stirrer, and stirring is performed for 85 s;

[0035] (3) 45 parts of aluminum nitride and 20 parts of powder silica gel are continuously added into the stirrer, and stirring is performed for 70 s;

[0036] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6, and then added into the stirrer, and stirring is performed for 45 s;

[0037] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide were added into the blender, and after stirring for 50 s, the environmentally friendly coated sand for cast iron with little smoke and no odor was obtained by natural cooling to room temperature. Example 2

[0038] 3 parts of erucamide were added into 6 parts of hot anhydrous ethanol at 65℃, and after stirring for 10 min, 0.7 parts of melamine polyphosphate was continuously added, and then after stirring for 3 min, the modified erucamide was obtained.

[0039] (1) 120 parts of sand with a particle size of 0.15-0.3 mm were added into the blender, and then the temperature was raised to 110℃ for preheating and stirring for 35 min;

[0040] (2) After preheating, 7 parts of phenolic resin were added into the blender and stirred for 80 s;

[0041] (3) 40 parts of aluminum nitride and 25 parts of powder silica gel were continuously added into the blender and stirred for 80 s;

[0042] (4) 8 parts of urotropin and water were mixed according to a mass ratio of 1:1.8 and then added into the blender and stirred for 40 s;

[0043] (5) Finally, 4 parts of calcium stearate and 5 parts of modified erucamide were added into the blender, and after stirring for 45 s, the environmentally friendly coated sand for cast iron with little smoke and no odor was obtained by natural cooling to room temperature. Example 3

[0044] 5 parts of erucamide were added into 8 parts of hot anhydrous ethanol at 55℃, and after stirring for 10 min, 0.5 parts of melamine polyphosphate was continuously added, and then after stirring for 5 min, the modified erucamide was obtained.

[0045] (1) 130 parts of sand with a particle size of 0.15-0.3 mm were added into the blender, and then the temperature was raised to 140℃ for preheating and stirring for 25 min;

[0046] (2) After preheating, 5 parts of phenolic resin were added into the blender and stirred for 90 s;

[0047] (3) 50 parts of aluminum nitride and 15 parts of powder silica gel were continuously added into the blender and stirred for 60 s;

[0048] (4) 12 parts of urotropin and water were mixed according to a mass ratio of 1:1.4 and then added into the blender and stirred for 50 s;

[0049] (5) Finally, 2 parts of calcium stearate and 7 parts of modified erucamide were added into the blender, and after stirring for 55 s, the environmentally friendly coated sand for cast iron with little smoke and no odor was obtained by natural cooling to room temperature. Example 4

[0050] The 4 parts of erucamide are added into 7 parts of hot anhydrous ethanol at 60℃, stirred for 10 minutes, then 0.6 parts of triphenyl phosphate is added, and after stirring for 4 minutes, the modified erucamide is obtained.

[0051] The rest is the same as example 1. Example 5

[0052] (1) 125 parts of sand with particle size of 0.15-0.3 mm are added into a stirring machine, then heated to 125℃ and preheated for 30 minutes;

[0053] (2) After preheating, 6 parts of phenolic resin are added into the stirring machine and stirred for 85 seconds;

[0054] (3) 45 parts of aluminum nitride and 20 parts of talcum powder are continuously added into the stirring machine and stirred for 70 seconds;

[0055] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6 and then added into the stirring machine and stirred for 45 seconds;

[0056] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirring machine, stirred for 50 seconds, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron.

[0057] The rest is the same as example 1. Example 6

[0058] The 4 parts of erucamide are added into 7 parts of hot anhydrous ethanol at 45℃, stirred for 10 minutes, then 0.6 parts of melamine polyphosphate is added, and after stirring for 4 minutes, the modified erucamide is obtained.

[0059] The rest is the same as example 1. Example 7

[0060] (1) 125 parts of sand with particle size of 0.15-0.3 mm are added into a stirring machine, then heated to 95℃ and preheated for 30 minutes;

[0061] (2) After preheating, 6 parts of phenolic resin are added into the stirring machine and stirred for 85 seconds;

[0062] (3) 45 parts of aluminum nitride and 20 parts of powder silica gel are continuously added into the stirring machine and stirred for 70 seconds;

[0063] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6 and then added into the stirring machine and stirred for 45 seconds;

[0064] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirring machine, stirred for 50 seconds, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron.

[0065] The rest is the same as example 1. Example 8

[0066] (1) 125 parts of sand with particle size of 0.15-0.3 mm were added into a mixer, and then heated to 125°C for preheating for 30 min;

[0067] (2) After preheating, 6 parts of phenolic resin were added into the mixer and stirred for 85 s;

[0068] (3) 45 parts of aluminum nitride and 20 parts of powder silica gel were continuously added into the mixer and stirred for 70 s;

[0069] (4) 10 parts of urotropin and water were mixed according to a mass ratio of 1:3.5 and then added into the mixer, and stirred for 45 s;

[0070] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide were added into the mixer, and stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron.

[0071] The rest is the same as example 1. Example 9

[0072] (1) 125 parts of sand with particle size of 0.15-0.3 mm were added into a mixer, and then heated to 125°C for preheating for 30 min;

[0073] (2) After preheating, 6 parts of phenolic resin, 45 parts of aluminum nitride, 20 parts of powder silica gel, 10 parts of urotropin, 16 parts of water, 3 parts of calcium stearate and 6 parts of modified erucamide were added into the mixer, and stirred for 250 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron.

[0074] The rest is the same as example 1.

[0075] The coated sand prepared in examples 1-9 was used for casting, the mass of the coated sand before casting m1, the mass of the coated sand adhered to the castings after casting m2, and the mass of the coated sand after casting m3 were determined, the coated sand adhesion rate was calculated by the formula a=(m1-m2) / m1, and the coated sand mass loss rate was calculated by the formula b=(m1-m2) / m1, and the specific data are shown in Table 1.

[0076] Table 1: Coated sand adhesion rate and mass loss rate data table of each example

[0077] Example Adhesion rate a (%) Mass loss rate b (%) Example 1 0.21 2.25 Example 2 0.24 2.34 Example 3 0.25 2.31 Example 4 1.06 4.19 Example 5 1.09 3.87 Example 6 0.52 2.75 Example 7 0.64 3.08 Example 8 0.72 3.74 Example 9 1.33 4.88

[0078] From Table 1, it can be seen that the adhesion rate and mass loss rate of Examples 1-3 are the lowest; the adhesion rate and mass loss rate of Example 4 and Example 5, which respectively replace melamine polyphosphate and powder silica gel, are obviously improved compared with Example 1; the reason for the increase of the adhesion rate and mass loss rate of Example 6 may be that the temperature of the hot anhydrous ethanol is changed, so that the erucic acid amide cannot be completely dissolved, affecting the dispersion of erucic acid amide and melamine polyphosphate in the reaction system; the reason for the increase of the adhesion rate and mass loss rate of Example 7 compared with Example 1 may be that the preheating temperature of the sand is not high, affecting the curing degree of the subsequent resin, and then affecting the anti-sticking property and fire resistance of the coated sand; Example 8 may be because the proportion of water in the urotropine solution is increased, and too much water affects the curing of the phenolic resin, and then affects the anti-sticking property and fire resistance of the coated sand; Example 9 changes the preparation process of the coated sand, and the components of the coated sand are added in one step instead of in steps, and the anti-sticking property and fire resistance of the prepared coated sand are obviously reduced. Example 10

[0079] The particle size of the aluminum nitride in the range of 0.07-0.1 mm is immersed in a 70% volume fraction of ethanol solution, and then ultrasonic cleaning is used for 7 min. After cleaning, the aluminum nitride is immersed in oleyl oleate and heated to 36℃. After sufficient stirring for 5 min, the modified aluminum nitride is obtained.

[0080] Mix 9% volume fraction of propylene glycol solution and dodecyl alcohol amide phosphate at a volume ratio of 1:0.3 to obtain a shelling aid.

[0081] Mix active carbon and boron carbide at a mass ratio of 1:1.4, then put them into a muffle furnace, heat to 200℃ at a speed of 10℃ / min, keep for 60 min, then continue to heat to 1000℃ at a speed of 10℃ / min, keep for 2.5 h, then naturally cool to room temperature to obtain mixture a. Then, mixture a, phosphosilicate aluminum, potassium salt of fatty alcohol ether phosphate, and water are mixed at a mass ratio of 1.3:0.6:0.11:0.7. First, mix the potassium salt of fatty alcohol ether phosphate and water uniformly, then add mixture a and continue to stir for 4.5 min, and finally add phosphosilicate aluminum. Heat the system to 31℃ and keep stirring for 11 min, then add it into a granulator to obtain a friction aid.

[0082] Add 4 parts of erucic acid amide to 7 parts of 60℃ hot anhydrous ethanol, stir for 10 min, then continue to add 0.6 parts of melamine polyphosphate, and then continue to stir for 4 min to obtain modified erucic acid amide.

[0083] (1) Add 125 parts of sand with a particle size of 0.15-0.3 mm into a stirrer, then heat to 125℃ and preheat for 30 min;

[0084] (2) After preheating is completed, 6 parts of phenolic resin is added into the blender, and stirring is performed for 85s;

[0085] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel are continuously added into the blender, and stirring is performed for 70s;

[0086] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6, and then added into the blender, and stirring is performed for 45s;

[0087] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the blender, and stirring is performed for 50s, and then the mixture is naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environment-friendly coated sand;

[0088] (6) The micro-smoke and odorless cast iron environment-friendly coated sand obtained in step (5) is used for casting iron to obtain cast iron environment-friendly coated sand waste sand, and then the cast iron environment-friendly coated sand waste sand is crushed and screened by a vibrating machine, and then the broken iron in the waste sand is separated by a magnet to obtain a mixture a;

[0089] (7) The mixture a is immersed in a 47% mass fraction sulfuric acid solution, and fully stirred for 30 min, and then washed with deionized water to neutral to obtain a mixture b;

[0090] (8) The mixture b is immersed in a shelling aid, and stirred for 5 min, and then the mixture b is transferred into a-22.5℃ environment and frozen for 2h, and then stirred at a speed of 1000r / min to obtain a mixture c;

[0091] (9) The mixture c and a friction aid accounting for 2% of the 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, so that the mixture c collides and rubs with each other, and the duration is 45s, and then the mixture c is transferred into a calcination furnace and calcined for 25s, and then cooled to obtain coated sand regenerated sand. Example 11

[0092] The particle size of the aluminum nitride in the range of 0.07-0.1mm is immersed in a 70% volume fraction ethanol solution, and then ultrasonic cleaning is performed for 6 min, and then the aluminum nitride is immersed in oleyl oleate and heated to 37℃, and then fully stirred for 4 min to obtain modified aluminum nitride.

[0093] A shelling aid is obtained by mixing 9% volume fraction propylene glycol solution and dodecyl alcohol amide phosphate according to a volume ratio of 1:0.25.

[0094] The activated carbon and boron carbide are mixed by stirring at a mass ratio of 1:1.2, then heated to 220℃ at a rate of 10℃ / min in a muffle furnace, and kept for 50 min, then heated to 950℃ at a rate of 10℃ / min, and kept for 3 h, then naturally cooled to room temperature to obtain mixture a, then mixture a, phosphosilicate aluminum, potassium fatty alcohol ether phosphate, and water are mixed at a mass ratio of 1.2:0.7:0.12:0.6, the potassium fatty alcohol ether phosphate and water are first mixed uniformly, then the mixture a is added and stirred for 4 min, and finally the phosphosilicate aluminum is added, the system is heated to 32℃ and stirred for 10 min, then added into a granulator to obtain the friction aid.

[0095] 4 parts of erucic acid amide are added into 7 parts of hot anhydrous ethanol at 60℃, stirred for 10 min, then 0.6 parts of melamine polyphosphate is added, and then stirred for 4 min to obtain the modified erucic acid amide.

[0096] (1) 125 parts of sand with a particle size of 0.15-0.3 mm are added into a stirring machine, then heated to 125℃ and preheated for 30 min;

[0097] (2) After preheating, 6 parts of phenolic resin are added into the stirring machine and stirred for 85 s;

[0098] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel are continuously added into the stirring machine and stirred for 70 s;

[0099] (4) 10 parts of urotropin and water are mixed at a mass ratio of 1:1.6 and then added into the stirring machine and stirred for 45 s;

[0100] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucic acid amide are added into the stirring machine and stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environmentally friendly coated sand;

[0101] (6) The micro-smoke and odorless cast iron environmentally friendly coated sand obtained in step (5) is used for casting iron to obtain cast iron environmentally friendly coated sand waste sand, then the cast iron environmentally friendly coated sand waste sand 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;

[0102] (7) The mixture a is immersed in a 46% mass fraction of sulfuric acid solution, and stirred for 25 min, then washed with deionized water to neutral to obtain mixture b;

[0103] (8) The mixture b is immersed in a shelling aid, stirred for 6 min, then transferred into a-25℃ environment and frozen for 1.5 h, then stirred at a speed of 900 r / min to obtain mixture c;

[0104] (9) Put the mixture c and 1.5% of the mass of the friction aid into a high-speed turbo four-roller, preheat the mixture c through a turbo preheater, then start the high-speed turbo four-roller, so that the mixture c collides and rubs against each other, for 40s, then put it into a baking furnace and bake for 30s, and the coated sand regenerated sand is obtained after cooling. Example 12

[0105] Submerge the aluminum nitride with a particle size of 0.07-0.1mm in a 70% volume fraction ethanol solution, then use ultrasonic cleaning for 8min, after cleaning, submerge the aluminum nitride in oleyl oleate and heat to 35℃, fully stir for 6min, and the modified aluminum nitride is obtained.

[0106] Mix 9% volume fraction propylene glycol solution and dodecyl alcohol amide phosphate at a volume ratio of 1:0.35 to obtain the shelling aid.

[0107] Mix the activated carbon and boron carbide at a mass ratio of 1:1.6, then put them into a muffle furnace, heat to 180℃ at a speed of 10℃ / min, keep the temperature for 70min, then continue to heat to 1050℃ at a speed of 10℃ / min, keep the temperature for 2h, then naturally cool to room temperature to obtain the mixture a, then mix the mixture a, phosphosilicate aluminum, fatty alcohol ether phosphate potassium salt and water at a mass ratio of 1.4:0.5:0.1:0.8, first mix the fatty alcohol ether phosphate potassium salt and water uniformly, then add the mixture a and continue to stir for 5min, finally add the phosphosilicate aluminum, heat the system to 30℃, keep the temperature and stir for 12min, then put it into a granulator to obtain the friction aid.

[0108] Add 4 parts of erucic acid amide to 7 parts of hot anhydrous ethanol at 60℃, stir for 10min, then continue to add 0.6 parts of melamine polyphosphate, then continue to stir for 4min to obtain the modified erucic acid amide.

[0109] (1) Put 125 parts of sand with a particle size of 0.15-0.3mm into a stirrer, then heat to 125℃ and stir for preheating for 30min;

[0110] (2) After preheating, add 6 parts of phenolic resin into the stirrer and stir for 85s;

[0111] (3) Continue to add 45 parts of modified aluminum nitride and 20 parts of powder silica gel into the stirrer and stir for 70s;

[0112] (4) Mix 10 parts of urotropin and water at a mass ratio of 1:1.6, then add them into the stirrer and stir for 45s;

[0113] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide were added into the blender, and after stirring for 50 s, the micro-smoke odorless environmentally friendly coated sand for cast iron was obtained by naturally cooling to room temperature;

[0114] (6) The micro-smoke odorless environmentally friendly coated sand for cast iron obtained in step (5) was used for casting iron, and then the cast iron environmentally friendly coated sand waste sand was obtained. Subsequently, the cast iron environmentally friendly coated sand waste sand was crushed and screened by a vibrating machine, and then the mixture a of the broken iron in the waste sand was separated by a magnet;

[0115] (7) The mixture a was immersed in a 48% 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;

[0116] (8) The mixture b was immersed in a shelling aid, and after stirring for 4 min, the mixture b was transferred into a-20℃ environment and frozen for 2.5 h. Subsequently, the mixture b was stirred at a speed of 1100 r / min while cold to obtain the mixture c;

[0117] (9) The mixture c and the friction aid accounting for 2.5% 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. Subsequently, the high-speed turbine type four-roller was started, so that the mixture c was impacted and rubbed with each other, and the duration was 50 s. Subsequently, the mixture c was transferred into a calcination furnace and calcined for 20 s. After cooling, the coated sand regenerated sand was obtained. Example 13

[0118] The particle size of the aluminum nitride was 0.07-0.1 mm. The aluminum nitride was immersed in a 70% volume fraction of ethanol solution, and then ultrasonic cleaning was performed for 7 min. After the cleaning was completed, the aluminum nitride was immersed in ethylene glycol monobutyl ether and heated to 36℃. After fully stirring for 5 min, the modified aluminum nitride was obtained.

[0119] The rest was the same as in Example 10. Example 14

[0120] The shelling aid was obtained by mixing a 9% volume fraction of propylene glycol solution and sodium dodecyl sulfonate at a volume ratio of 1:0.3.

[0121] The rest was the same as in Example 10. Example 15

[0122] The particle size of the aluminum nitride was 0.07-0.1 mm. The aluminum nitride was immersed in a 70% volume fraction of ethanol solution, and then ultrasonic cleaning was performed for 7 min. After the cleaning was completed, the aluminum nitride was immersed in ethylene glycol monobutyl ether and heated to 36℃. After fully stirring for 5 min, the modified aluminum nitride was obtained.

[0123] The rest was the same as in Example 10. Example 16

[0124] (1) 125 parts of sand with particle size of 0.15-0.3 mm were added into a stirring machine, and then heated to 125°C for preheating and stirring for 30 min;

[0125] (2) After preheating, 6 parts of phenolic resin were added into the stirring machine, and stirred for 85 s;

[0126] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel were continuously added into the stirring machine, and stirred for 70 s;

[0127] (4) 10 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 45 s;

[0128] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide were added into the stirring machine, and stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environment-friendly coated sand;

[0129] (6) The micro-smoke and odorless cast iron environment-friendly coated sand obtained in step (5) was used for casting iron to obtain cast iron environment-friendly coated sand waste sand, and then the cast iron environment-friendly coated sand waste sand was crushed and screened by a vibrating machine, and the mixture a of scrap iron in the waste sand was separated by a magnet;

[0130] (7) The mixture a was immersed in a 30% mass fraction of sulfuric acid solution, and fully stirred for 30 min, and then washed with deionized water to neutral to obtain mixture b;

[0131] (8) The mixture b was immersed in a shelling aid, stirred for 5 min, and then transferred into a-22.5°C environment for freezing for 2 h, and then stirred at a speed of 1000 r / min while cold to obtain mixture c;

[0132] (9) The mixture c and 2% of friction aid by 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 45 s, and then transferred into a calcination furnace for calcination for 25 s, and then cooled to obtain coated sand regenerated sand.

[0133] The rest was the same as in Example 10. Example 17

[0134] (1) 125 parts of sand with particle size of 0.15-0.3 mm were added into a stirring machine, and then heated to 125°C for preheating and stirring for 30 min;

[0135] (2) After preheating, 6 parts of phenolic resin were added into the stirring machine, and stirred for 85 s;

[0136] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel were continuously added into the stirring machine, and stirred for 70 s;

[0137] (4) 10 parts of urotropin and water are mixed in a mass ratio of 1:1.6 and then added into the stirring machine, and stirred for 45 s;

[0138] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirring machine, stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron;

[0139] (6) The micro-smoke and odorless environmentally friendly coated sand for cast iron obtained in step (5) is used for cast iron to obtain environmentally friendly coated sand waste sand for cast iron, and then the environmentally friendly coated sand waste sand for cast iron is crushed and screened by a vibrating machine, and the mixture a of the scrap iron in the waste sand is separated by a magnet;

[0140] (7) The mixture a is immersed in a 47% mass fraction of sulfuric acid solution, fully stirred and reacted for 50 min, and then washed with deionized water to neutral to obtain mixture b;

[0141] (8) The mixture b is immersed in a shelling aid, stirred and soaked for 5 min, then transferred into a-22.5℃ environment and frozen for 2 h, and then stirred at a speed of 1000 r / min to obtain mixture c;

[0142] (9) The mixture c and 2% of the mass 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 collides and rubs with each other, and the duration is 45 s, and then transferred into a calcination furnace and calcined for 25 s, and then cooled to obtain coated sand regenerated sand.

[0143] The rest is the same as in Example 10. Example 18

[0144] (1) 125 parts of sand with a particle size of 0.15-0.3 mm are added into the stirring machine, and then heated to 125℃ and stirred for preheating for 30 min;

[0145] (2) After preheating, 6 parts of phenolic resin are added into the stirring machine, and stirred for 85 s;

[0146] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel are continuously added into the stirring machine, and stirred for 70 s;

[0147] (4) 10 parts of urotropin and water are mixed in a mass ratio of 1:1.6 and then added into the stirring machine, and stirred for 45 s;

[0148] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirring machine, stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless environmentally friendly coated sand for cast iron;

[0149] (6) the micro-smoke and odorless cast iron environmentally-friendly coated sand obtained in step (5) is used in cast iron to obtain cast iron environmentally-friendly coated sand waste sand, and then the cast iron environmentally-friendly coated sand waste sand 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;

[0150] (7) the mixture a is immersed in a 47% mass fraction sulfuric acid solution, fully stirred and reacted for 30 min, and then the mixture b is obtained by washing with deionized water until neutralization;

[0151] (8) the mixture b is immersed in a shelling aid, stirred and soaked for 5 min, then transferred into a-30℃ environment and frozen for 2 h, and then stirred at a speed of 1000 r / min to obtain the mixture c;

[0152] (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, then the high-speed turbine four-roller is started, so that the mixture c collides and rubs with each other, the duration is 45 s, and then transferred into a calcination furnace for calcination for 25 s, and the coated sand regenerated sand is obtained after cooling.

[0153] The rest is the same as in example 10. Example 19

[0154] (1) 125 parts of sand with a particle size of 0.15-0.3 mm are added into a stirring machine, and then heated to 125℃ and stirred for preheating for 30 min;

[0155] (2) after preheating, 6 parts of phenolic resin are added into the stirring machine, and stirred for 85 s;

[0156] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel are continuously added into the stirring machine, and stirred for 70 s;

[0157] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6, and then added into the stirring machine, and stirred for 45 s;

[0158] (5) finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirring machine, and stirred for 50 s, and then naturally cooled to room temperature to obtain the micro-smoke and odorless cast iron environmentally-friendly coated sand;

[0159] (6) the micro-smoke and odorless cast iron environmentally-friendly coated sand obtained in step (5) is used in cast iron to obtain cast iron environmentally-friendly coated sand waste sand, and then the cast iron environmentally-friendly coated sand waste sand 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;

[0160] (7) the mixture a is immersed in a 47% mass fraction sulfuric acid solution, fully stirred and reacted for 30 min, and then the mixture b is obtained by washing with deionized water until neutralization;

[0161] (8) Submerge mixture b in a de-shelling aid, after stirring for 5 minutes, transfer mixture b into an environment of -22.5°C and freeze for 4 hours, then stir at a speed of 1000 r / min while cold to obtain mixture c;

[0162] (9) Transfer mixture c and 2% of friction aid by mass into a high-speed turbine four-roller, preheat mixture c through a turbine preheater, then start the high-speed turbine four-roller, so that mixture c collides and rubs against each other, for a duration of 45 seconds, then transfer into a baking furnace and bake for 25 seconds, after cooling, obtain coated sand regeneration sand.

[0163] The rest is the same as example 10. Example 20

[0164] (1) Add 125 parts of sand with a particle size of 0.15-0.3 mm into a stirrer, then heat to 125°C and stir for 30 minutes for preheating;

[0165] (2) After preheating, add 6 parts of phenolic resin into the stirrer and stir for 85 seconds;

[0166] (3) Continue to add 45 parts of modified aluminum nitride and 20 parts of powder silica gel into the stirrer and stir for 70 seconds;

[0167] (4) Mix 10 parts of urotropin and water according to a mass ratio of 1:1.6, then add into the stirrer and stir for 45 seconds;

[0168] (5) Finally, add 3 parts of calcium stearate and 6 parts of modified erucamide into the stirrer, stir for 50 seconds, and then naturally cool to room temperature to obtain micro-smoke and odorless cast iron environment-friendly coated sand;

[0169] (6) After the micro-smoke and odorless cast iron environment-friendly coated sand obtained in step (5) is used for casting iron, cast iron environment-friendly coated sand waste sand is obtained, then the cast iron environment-friendly coated sand waste sand is crushed and screened through a vibrating machine, and then the broken iron in the waste sand is separated by a magnet to obtain mixture a;

[0170] (7) Submerge mixture a in a 47% mass fraction of sulfuric acid solution, fully stir for 30 minutes, then wash to neutral with deionized water to obtain mixture b;

[0171] (8) Submerge mixture b in a de-shelling aid, after stirring for 5 minutes, transfer mixture b into an environment of -22.5°C and freeze for 2 hours, then stir at a speed of 1200 r / min while cold to obtain mixture c;

[0172] (9) Put the mixture c and 2% of the mass of the friction aids 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 45s, then put into a baking furnace for baking for 25s, and the coated sand regenerated sand is obtained after cooling.

[0173] The rest is the same as in Example 10. Example 21

[0174] Mix the activated carbon and boron carbide in a mass ratio of 1:1.2, then put into a muffle furnace, heat to 220℃ at a rate of 10℃ / min, keep for 50min, then continue to heat to 950℃ at a rate of 10℃ / min, keep for 3h, then naturally cool to room temperature to obtain mixture a, then mix the mixture a, carboxymethyl cellulose, potassium fatty alcohol ether phosphate and water in a mass ratio of 1.2:0.7:0.12:0.6, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add to the mixture a and continue to stir for 4min, finally add the carboxymethyl cellulose, heat the system to 32℃, keep stirring for 10min, then put into a granulator to obtain the friction aids.

[0175] The rest is the same as in Example 11. Example 22

[0176] Mix the activated carbon and boron carbide in a mass ratio of 1:1.2 to obtain mixture a, then mix the mixture a, phosphosilicate aluminum, sodium dodecyl sulfate and water in a mass ratio of 1.2:0.7:0.12:0.6, first mix the sodium dodecyl sulfate and water uniformly, then add to the mixture a and continue to stir for 4min, finally add the phosphosilicate aluminum, heat the system to 32℃, keep stirring for 10min, then put into a granulator to obtain the friction aids.

[0177] The rest is the same as in Example 11. Example 23

[0178] Mix the activated carbon and boron carbide in a mass ratio of 1:1.2 to obtain mixture a, then mix the mixture a, phosphosilicate aluminum, potassium fatty alcohol ether phosphate and water in a mass ratio of 1.2:0.7:0.12:0.6, first mix the potassium fatty alcohol ether phosphate and water uniformly, then add to the mixture a and continue to stir for 4min, finally add the phosphosilicate aluminum, heat the system to 32℃, keep stirring for 10min, then put into a granulator to obtain the friction aids.

[0179] The rest is the same as Example 11. Example 24

[0180] The activated carbon and boron carbide were mixed by stirring at a mass ratio of 1:1.2, then heated to 220°C at a rate of 10°C / min in a muffle furnace, and kept for 50 min, then continued to heat to 950°C at a rate of 10°C / min, and kept for 3 h, then naturally cooled to room temperature to obtain mixture a, then mixture a, phosphosilicate aluminum, potassium fatty alcohol ether phosphate, and water were mixed at a mass ratio of 1.2:0.7:0.12:0.6, the potassium fatty alcohol ether phosphate and water were first mixed uniformly, then mixture a was added and stirred for 4 min, and finally the phosphosilicate aluminum was added, the system was heated to 40°C, and kept for 10 min, then added to a granulator to obtain the friction aid.

[0181] The rest is the same as Example 11. Example 25

[0182] (1) 125 parts of sand with a particle size of 0.15-0.3 mm were added to a stirring machine, then heated to 125°C and preheated by stirring for 30 min;

[0183] (2) After preheating, 6 parts of phenolic resin were added to the stirring machine and stirred for 85 s;

[0184] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel were continuously added to the stirring machine and stirred for 70 s;

[0185] (4) 10 parts of urotropin and water were mixed at a mass ratio of 1:1.6 and then added to the stirring machine and stirred for 45 s;

[0186] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide were added to the stirring machine, stirred for 50 s, and then naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environmentally friendly coated sand;

[0187] (6) The micro-smoke and odorless cast iron environmentally friendly coated sand obtained in step (5) was used in cast iron to obtain cast iron environmentally friendly coated sand waste sand, then the cast iron environmentally friendly coated sand waste sand 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;

[0188] (7) Mixture a was immersed in a 46% mass fraction of sulfuric acid solution, and stirred for 25 min, then washed with deionized water to neutral to obtain mixture b;

[0189] (8) Mixture b was immersed in a shelling aid, stirred for 6 min, then transferred to a-25°C environment and frozen for 1.5 h, then stirred at a speed of 900 r / min while cold to obtain mixture c;

[0190] (9) The mixture c and 1.5% 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 70s, then transferred into a baking furnace for baking for 30s, and the coated sand regenerated sand is obtained after cooling.

[0191] The rest is the same as example 11. Example 26

[0192] (1) 125 parts of sand with a particle size of 0.15-0.3mm are added into a stirrer, then heated to 125℃ and stirred for preheating for 30min;

[0193] (2) After preheating, 6 parts of phenolic resin are added into the stirrer and stirred for 85s;

[0194] (3) 45 parts of modified aluminum nitride and 20 parts of powder silica gel are continuously added into the stirrer and stirred for 70s;

[0195] (4) 10 parts of urotropin and water are mixed according to a mass ratio of 1:1.6, then added into the stirrer and stirred for 45s;

[0196] (5) Finally, 3 parts of calcium stearate and 6 parts of modified erucamide are added into the stirrer, stirred for 50s, and then naturally cooled to room temperature to obtain micro-smoke and odorless cast iron environment-friendly coated sand;

[0197] (6) The micro-smoke and odorless cast iron environment-friendly coated sand obtained in step (5) is used for casting iron to obtain cast iron environment-friendly coated sand waste sand, then the cast iron environment-friendly coated sand waste sand is crushed and screened by a vibrating machine, and the scrap iron in the waste sand is separated by a magnet to obtain a mixture a;

[0198] (7) The mixture a is immersed in a 46% mass fraction of sulfuric acid solution, and fully stirred for 25min, then washed with deionized water to neutral to obtain a mixture b;

[0199] (8) The mixture b is immersed in a shelling aid, stirred and soaked for 6min, then transferred into a-25℃ environment and frozen for 1.5h, then stirred at a speed of 900r / min while cold to obtain a mixture c;

[0200] (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 40s, then transferred into a baking furnace for baking for 30s, and the coated sand regenerated sand is obtained after cooling.

[0201] The rest is the same as example 11.

[0202] 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 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 Examples 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 a ratio 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.

[0203] Table 2 Hulling rate of coated sand waste sand in Examples 10-20

[0204] Example Coated sand waste sand hulling rate (%) Example 10 95.3 Example 11 94.9 Example 12 94.8 Example 13 80.2 Example 14 79.7 Example 15 87.7 Example 16 86.2 Example 17 94.7 Example 18 94.4 Example 19 94.3 Example 20 94.5

[0205] 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 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.

[0206] Table 3 Performance table of coated sand reclaimed sand in Examples 10-12 and 21-26

[0207] Example Angular factor Flowability (s) Example 10 1.05 16 Example 11 1.07 17 Example 12 1.06 16 Example 21 1.20 24 Example 22 1.21 25 Example 23 1.14 21 Example 24 1.14 21 Example 25 1.09 18 Example 26 1.27 29

[0208] 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.

[0209] Table 4: Performance of coated sand prepared by using each proportion of regenerated sand and original sand

[0210] Reclaimed sand: virgin sand Hot tensile strength (MPa) Room temperature tensile strength (MPa) 95：5 1.9 3.9 90：10 2.0 4.0 85：15 2.1 4.2 0：100 2.1 4.2

[0211] 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 process for preparing low-smoke, odorless, environmentally friendly coated sand for cast iron, characterized in that: The specific steps are as follows: (1) Add 120-130 parts of sand with a particle size of 0.15-0.3 mm to the mixer, and then heat it to 110-140℃ and stir for 25-35 minutes. (2) After preheating, add 5-7 parts of phenolic resin to the mixer and stir for 80-90 seconds; (3) Continue to add 40-50 parts of modified aluminum nitride and 15-25 parts of powdered silica gel to the mixer and stir for 60-80 seconds; (4) Mix 8-12 parts of hexamethylenetetramine and water in a mass ratio of 1:1.4-1.8 and add them to a mixer, then stir for 40-50 seconds; (5) Finally, add 2-4 parts of calcium stearate and 5-7 parts of modified erucamide to the mixer, stir for 45-55 seconds and then cool naturally to room temperature to obtain cast iron environmentally friendly coated sand with little smoke and no odor. The method for preparing the modified aluminum nitride is as follows: Aluminum nitride particles with a diameter of 0.07~0.1 mm were immersed in a 70% volume fraction ethanol solution and then ultrasonically cleaned for 6~8 min. After cleaning, the aluminum nitride was immersed in oleyl alcohol linoleate and heated to 35~37℃. After stirring thoroughly for 4~6 min, modified aluminum nitride was obtained. The modified erucamide is prepared by: Add 3-5 parts of erucamide to 6-8 parts of hot anhydrous ethanol at 55-65℃, stir for 10 minutes, then add 0.5-0.7 parts of melamine polyphosphate, and continue stirring for 3-5 minutes to obtain modified erucamide.

2. A waste sand recycling process for use in the environmentally friendly coated cast iron sand prepared by the preparation process described in claim 1, characterized in that: The specific steps are as follows: (1) After the cast iron environmentally friendly coated sand waste with little smoke and no odor is crushed and screened by a vibrating machine, the scrap iron in the waste sand is removed by magnetic separation to obtain mixture a; (2) Immerse mixture a in a 46%~48% sulfuric acid solution and stir thoroughly for 25~35 min. After the reaction is complete, wash with deionized water until neutral to obtain mixture b. (3) Immerse mixture b in the desiccant and stir for 4 to 6 minutes. Then transfer mixture b to a -25 to -20°C environment and freeze for 1.5 to 2.5 hours. Then stir and desiccate while cold at a speed of 900 to 1100 r / min to obtain mixture c. (4) The mixture c and friction additive accounting for 1.5% to 2.5% of its mass are transferred into a high-speed turbine four-wheel wheel. At the same time, the mixture c is preheated by a turbine preheater. Then the high-speed turbine four-wheel wheel is started, so that the mixture c impacts and rubs against each other for 40 to 50 seconds. Then it is transferred to a roasting furnace for roasting for 20 to 30 seconds. After cooling, the coated sand regenerated sand is obtained.

3. The waste sand recycling process as described in claim 2, characterized in that: The method for preparing the desquamation aid is as follows: The solution is obtained by mixing a 9% volume fraction of propylene glycol solution and dodecyl alcohol phosphate at a volume ratio of 1:0.25~0.

35.

4. The waste sand recycling process as described in claim 2, characterized in that: The method for preparing the friction aid is as follows: Activated carbon and boron carbide are thoroughly mixed at a mass ratio of 1:1.2~1.6, then placed in a muffle furnace and heated to 180~220℃ at a rate of 10℃ / min, held for 50~70min, then heated to 950~1050℃ at a rate of 10℃ / min, held for 2~3h, and then naturally cooled to room temperature to obtain mixture 1. Then, mixture 1, aluminum phosphosilicate, potassium salt of fatty alcohol ether phosphate, and water are mixed at a mass ratio of 1.2~1.4:0.5~0.7:0.1~0.12:0.6~0.

8. First, the potassium salt of fatty alcohol ether phosphate and water are mixed evenly, then mixture 1 is added and stirred for 4~5min, and finally aluminum phosphosilicate is added. The system is heated to 30~32℃ and stirred for 10~12min, then granulated in a granulator to obtain the friction aid.