CN110625061A - Multifunctional coating for casting and preparation method thereof - Google Patents
Multifunctional coating for casting and preparation method thereof Download PDFInfo
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- CN110625061A CN110625061A CN201910965116.1A CN201910965116A CN110625061A CN 110625061 A CN110625061 A CN 110625061A CN 201910965116 A CN201910965116 A CN 201910965116A CN 110625061 A CN110625061 A CN 110625061A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/03—Sand moulds or like moulds for shaped castings formed by vacuum-sealed moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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Abstract
The invention provides a multifunctional coating for casting and a preparation method thereof, and particularly relates to the technical field of casting coatings. The invention firstly adopts polystyrene molten liquid and a sintered compound to sequentially and repeatedly coat quartz sand powder and bentonite to prepare a coating compound, and then the coating compound is added with calcined gypsum powder, sweet wormwood wax, trehalose and zinc oxide whiskers to prepare the multifunctional coating for casting. The coating disclosed by the invention can be simultaneously used for two processes of lost foam casting and V-method casting, has no cracking, foaming and wrinkling after being coated, has the advantages of wear resistance, high drying speed, strong adhesive force and high air permeability, and can effectively prevent the defects of sand sticking, shrinkage porosity and air holes of a casting. The invention also aims to provide a preparation method of the multifunctional coating for casting, which is simple to operate, controllable in parameters, stable in process and suitable for large-scale production.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of casting coatings, in particular to a multifunctional coating for casting and a preparation method thereof.
[ background of the invention ]
The casting coating is one of the most important casting raw and auxiliary materials and plays a key role in ensuring the surface quality of a casting. With the continuous innovation and development of the casting industry, a novel process different from the traditional sand casting, namely lost foam casting and V-method casting, appears. The two novel processes are different from sand casting in the property of the selected coating, and the sand casting is to attach the coating to a sand casting mold and a sand core, so that the air permeability of the coating is not required to be too large, and the gas generated by the core is prevented from entering molten iron to influence the product quality; the novel process is to attach the coating to a plastic model or a plastic film, so that the expansion gas in the cavity can be smoothly discharged only by requiring high air permeability of the coating, and higher requirements are provided for the fire resistance, the adhesive force and the mechanical property of the coating. Therefore, the coating for sand casting cannot meet the use requirement of the novel process, and the coating adaptive to the novel process must be developed to cast qualified products.
In V-method casting, the coating is attached to the foam plastic made of EPS, STMMA and EPMMA, and in lost foam casting, the coating is attached to an EVA plastic film, and in the process of researching the coating, people often start to screen the coating formula and research and develop a preparation method from the material selected by an attached object and the structure of the attached object, so that the research on the two process coatings is basically carried out independently. In fact, the requirements of the two processes on the characteristics of the coating are basically consistent, namely, the coating has high wear resistance, quick drying property, high air permeability and high adhesive force, which are the most important points to be neglected in the coating research process, so that the coating which can be simultaneously used for the two processes is rarely researched so far, and the coating becomes the current difficulty and the future hot spot. Chinese patent No. CN102836950B, entitled lost foam coating and its preparation method, discloses a method for preparing lost foam coating by using bauxite chamotte, quartz powder, flake graphite, sodium bentonite, etc. as raw materials, which solves the problems of coating permeability and adhesion to a certain extent, but it can only be used in lost foam process, and is inevitably single in use. The alcohol-based coating prepared by the patent document with the Chinese patent grant publication No. CN102527928B and named as the alcohol-based coating for V-process casting and the preparation method thereof has the advantages of high drying speed, strong adhesive force and good wear resistance, but still can only be used for V-process casting. Although patent documents with Chinese patent publication No. CN105499481A and named as novel vitrified paint for casting process mention that the prepared magnetized paint can be used for the two novel processes, the raw material composition and the proportion of the paint still have great difference aiming at the two processes of lost foam casting and V-method casting, the paint is not really applied to the two processes, the deep exploration on the drying property, the adhesive force, the wear resistance and the air permeability of the paint is not carried out, and the effect is not ideal in practical application.
Therefore, in order to promote the steady development of the casting industry, it is necessary to develop a multifunctional coating which can be applied to both the lost foam casting process and the V-process casting process.
[ summary of the invention ]
The invention aims to: aiming at the problem that the coating which has the effects of drying property, adhesive force, wear resistance and air permeability and can be simultaneously used for lost foam casting and V-method casting is lacked, the multifunctional coating and the preparation method thereof are provided. The coating disclosed by the invention can be simultaneously used for two processes of lost foam casting and V-method casting, has no cracking, foaming and wrinkling after being coated, has the advantages of wear resistance, high drying speed, strong adhesive force and high air permeability, and can effectively prevent the defects of sand sticking, shrinkage porosity and air holes of a casting. The invention also aims to provide a preparation method of the multifunctional coating for casting, which is simple to operate, controllable in parameters, stable in process and suitable for large-scale production.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the multifunctional coating for casting at least comprises the following raw materials in parts by weight: 51-72 parts of quartz sand powder, 5.5-14.5 parts of crystalline flake graphite powder, 4-14 parts of bentonite, 3-15 parts of zircon powder, 1-11 parts of polystyrene and 1-9 parts of bauxite.
The optimized fertilizer also comprises the following raw materials in parts by weight: 4-15 parts of calcium fluoride, 11-25 parts of calcined gypsum powder, 2-7 parts of sweet wormwood wax, 3-7 parts of trehalose and 6-20 parts of zinc oxide whisker.
Further optimized, the particle size of the quartz sand powder is 150-250 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:3.5-5.5, heating at the temperature of 110-; the polystyrene molten liquid is continuously kept at the temperature of 110-130 ℃ to keep a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 1/4-1/3 weight of calcium fluoride, firing at 800 ℃ of 700-;
c. packaging for several times: heating quartz sand powder and bentonite to 150-170 ℃, then spraying 1/5-1/3 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 11-21 minutes, then adding 1/7-1/5 weight of firing compound, keeping the temperature and mixing uniformly for 8-16 minutes, then spraying 1/5-1/3 weight of polystyrene melt liquid and adding the rest of compound firing compound in sequence, carrying out the operation of keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 15-25 minutes, and obtaining a wrapping compound;
d. adding water for suspension: cooling the coated compound to room temperature, adding water, stirring to obtain suspension, and adding water to adjust Baume degree to 50-70 to obtain coated suspension;
e. homogenizing suspension: adding plaster powder, sweet wormwood wax and trehalose into the coating suspension, and then homogenizing to obtain a homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the baume degree to 53-67, thereby obtaining the multifunctional coating for casting.
Preferably, the water temperature of the water sprayed in the step b is 5-15 ℃.
Preferably, the water spraying method in step b comprises the following steps: spraying in the form of water mist while stirring.
Preferably, in the step b, the fired and taken-out materials are flatly paved into a thickness of 5-10cm, and the water mist is 20-40ml/m per minute2The spraying amount of the water spray is sprayed on the materials。
Still further preferably, the spraying is intermittent spraying; the intermittent spraying is stopped for 8-16 seconds every 25-45 seconds, and continuous stirring is still carried out when the spraying is stopped.
And (e) further optimizing, wherein the homogenizing pressure in the step (e) is 35-55MPa, and the homogenizing times are 2-6.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the invention firstly adopts polystyrene molten liquid and a sintered compound to sequentially and repeatedly coat quartz sand powder and bentonite to prepare a coating compound, and then the coating compound is added with calcined gypsum powder, sweet wormwood wax, trehalose and zinc oxide whiskers to prepare the multifunctional coating for casting. The coating disclosed by the invention can be simultaneously used for two processes of lost foam casting and V-method casting, has no cracking, foaming and wrinkling after being coated, has the advantages of wear resistance, high drying speed, strong adhesive force and high air permeability, and can effectively prevent the defects of sand sticking, shrinkage porosity and air holes of a casting. The invention also aims to provide a preparation method of the multifunctional coating for casting, which is simple to operate, controllable in parameters, stable in process and suitable for large-scale production.
2. The polystyrene in the invention is of an olefin structure, is similar to or the same as the structure of an attached target object in lost foam casting and V-method casting, and is easy to attach to the target object according to the similar compatibility principle, and simultaneously, the polystyrene is combined with the gypsum powder, so that the coating has the performance of quick drying, and the formed coating can be prevented from cracking to influence the adhesive force and the wear resistance. When the coating is coated on a target object, after partial moisture is volatilized in the heating and drying process, and the temperature is reduced to be below 40 ℃, the polystyrene and the plaster can be quickly solidified, but the polystyrene is quickly solidified and is easy to shrink and crack, and the plaster can slightly expand after being hardened to play a role in preventing cracking.
According to the invention, the sweet wormwood wax is added, and the higher fatty acid and the polystyrene have similar compatibility, so that the adhesive force of the coating can be enhanced together, and the wear resistance is also enhanced to a certain extent.
3. The invention carries out firing treatment on the scaly graphite powder, the zircon powder, the bauxite and the calcium fluoride with the weight of 1/4-1/3, and cools in a water spraying and quenching way, so that the internal structure of the material particles can generate instant deformation and cracks under the quenching condition, the exhaust space is enlarged, and the air hole defect of the casting is prevented.
The invention sprays in the form of water mist, controls the spraying amount and the water temperature, simultaneously optimizes the spraying mode, adopts the intermittent operation of stirring and spraying, can enable the materials to be cooled more uniformly, achieves the redistribution of heat through stirring in the gap of stopping spraying, and enables the temperature of the materials to be kept integrally consistent, thereby enabling the cracks generated in the material particles to be uniform, and realizing the high uniformity of air permeability.
4. The invention adopts a fractional coating method to coat the polystyrene melt and the firing compound on the outer layers of the quartz sand powder and the bentonite at intervals, thereby enhancing the wear resistance and the adhesive force of the whole coating, ensuring that the coating is not easy to fall off, and playing a role in avoiding the defects of sand sticking and shrinkage cavity of the casting. According to the invention, polystyrene for enhancing the adhesive force and a firing compound for enhancing the fire resistance and wear resistance are alternately added, and the quartz sand powder and the bentonite are coated layer by layer, so that the coating particle coated compound with good wear resistance and adhesive force on each layer is obtained, and the coating is effectively prevented from falling off.
The zinc oxide whiskers are added into the paint, and due to the special three-dimensional four-needle structure of the zinc oxide whiskers, the zinc oxide whiskers and the crystalline flake graphite powder and the zircon powder form different external and internal adding modes to play a role together, so that the wear resistance of the paint is enhanced, and the paint is prevented from falling off due to the fact that the paint surface is impacted in the filling process of filling sand.
5. According to the invention, the trehalose is added, so that excessive moisture is not dissipated in the heating and drying process of the coating, the coating is kept wet to a certain extent, the coating wrinkles caused by excessive moisture dissipation are effectively avoided, the dryness, the adhesiveness and the wear resistance are prevented from being influenced, and the sand-sticking defect of the casting is prevented.
6. The calcium fluoride is added in the invention, so that the shrinkage porosity and the pore defect of the casting can be prevented. In the pouring process, when the molten iron joint edge contacts filling sand with lower temperature in a sand box and the temperature drops suddenly under the action of heat conduction, the molten iron joint edge is easy to partially solidify to cause shrinkage porosity and air holes, and after calcium fluoride is added into the coating, the coating can enter the molten iron during pouring and can form eutectic with various metal oxides in the molten iron, so that the melting point of the molten iron is reduced, and the occurrence of the partial solidification phenomenon is avoided.
7. The invention adjusts the concentration of the coating to a reasonable Baume degree range, so that the coating has good fluidity and is easy to disperse on a target object to form a coating with uniform thickness.
[ detailed description ] embodiments
The present invention will be further described with reference to the following examples.
Example 1
The multifunctional coating for casting at least comprises the following raw materials in parts by weight: 51 parts of quartz sand powder, 5.5 parts of crystalline flake graphite powder, 4 parts of bentonite, 3 parts of zircon powder, 1 part of polystyrene, 1 part of bauxite, 4 parts of calcium fluoride, 11 parts of calcined gypsum powder, 2 parts of sweet wormwood wax, 3 parts of trehalose and 6 parts of zinc oxide whisker.
Wherein the particle size of the quartz sand powder is 150 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:3.5, heating at 110 ℃ to melt the polystyrene, and then uniformly stirring to obtain polystyrene molten liquid; keeping the polystyrene molten liquid at 110 ℃ for keeping a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 1/4 weight of calcium fluoride, firing at 700 ℃ for 30 minutes, taking out, spraying water, cooling to 100 ℃, and naturally cooling to obtain a fired compound; the water temperature of the water spray is 5 ℃;
wherein, the method of water spray is: spraying in the form of water mist while stirring.
c. Packaging for several times: heating quartz sand powder and bentonite to 150 ℃, spraying 1/5 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 11 minutes, adding 1/7 weight of fired compound, keeping the temperature and mixing uniformly for 8 minutes, then spraying 1/5 weight of polystyrene melt liquid and adding the rest of composite fired material in sequence, keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 15 minutes to obtain a wrapped compound;
d. adding water for suspension: cooling the coating compound to room temperature, adding water, stirring to obtain a suspension, and then continuously adding water to adjust the Baume degree to 50 to obtain a coating suspension;
e. homogenizing suspension: adding Gypsum Fibrosum Preparatum powder, herba Artemisiae Annuae wax, and trehalose into the coating suspension, and homogenizing under 35MPa for 2 times to obtain homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the Baume degree to 53, thereby obtaining the multifunctional coating for casting.
Example 2
The multifunctional coating for casting at least comprises the following raw materials in parts by weight: 72 parts of quartz sand powder, 14.5 parts of crystalline flake graphite powder, 14 parts of bentonite, 15 parts of zircon powder, 11 parts of polystyrene, 9 parts of bauxite, 15 parts of calcium fluoride, 25 parts of calcined gypsum powder, 7 parts of sweet wormwood wax, 7 parts of trehalose and 20 parts of zinc oxide whisker.
Wherein the particle size of the quartz sand powder is 250 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:5.5, heating at 130 ℃ to melt the polystyrene, and then uniformly stirring to obtain polystyrene molten liquid; keeping the polystyrene molten liquid at 130 ℃ for keeping a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 1/3 weight of calcium fluoride, firing at 800 ℃ for 60 minutes, taking out, spraying water, cooling to 120 ℃, and naturally cooling to obtain a fired compound; the water temperature of the water spray is 15 ℃;
wherein, the method of water spray is: spreading the fired material to a thickness of 5cm, intermittently spraying water in the form of water mist of 20 ml/m/min2The spraying amount of the water is sprayed on the materials, and the materials are stirred while being sprayed; the intermittent spraying is stopped for 8 seconds every 25 seconds, and continuous stirring is still carried out when the spraying is stopped.
c. Packaging for several times: heating quartz sand powder and bentonite to 170 ℃, spraying 1/3 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 21 minutes, adding 1/5 weight of fired compound, keeping the temperature and mixing uniformly for 16 minutes, then spraying 1/3 weight of polystyrene melt liquid and adding the rest of composite fired material in sequence, keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 25 minutes to obtain a wrapped compound;
d. adding water for suspension: cooling the coating compound to room temperature, adding water, stirring to obtain a suspension, and then continuously adding water to adjust the Baume degree to 70 to obtain a coating suspension;
e. homogenizing suspension: adding Gypsum Fibrosum Preparatum powder, herba Artemisiae Annuae wax, and trehalose into the coating suspension, and homogenizing under 55MPa for 6 times to obtain homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the Baume degree to 67, thereby obtaining the multifunctional coating for casting.
Example 3
The multifunctional coating for casting at least comprises the following raw materials in parts by weight: 60 parts of quartz sand powder, 8 parts of crystalline flake graphite powder, 8 parts of bentonite, 3-15 parts of zircon powder, 1-11 parts of polystyrene, 3 parts of bauxite, 5 parts of calcium fluoride, 14.5 parts of calcined gypsum powder, 3 parts of sweet wormwood wax, 4 parts of trehalose and 9.5 parts of zinc oxide whisker.
Wherein the particle size of the quartz sand powder is 170 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:4, heating at 115 ℃ to melt the polystyrene, and then uniformly stirring to obtain polystyrene molten liquid; keeping the polystyrene molten liquid at 115 ℃ for keeping a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 7/24 weight of calcium fluoride, firing at 725 ℃ for 37 minutes, taking out, spraying water, cooling to 105 ℃, and naturally cooling to obtain a fired compound; the water temperature of the water spray is 7 ℃;
wherein, the method of water spray is: spreading the fired material to a thickness of 10cm, intermittently spraying water in the form of water mist of 40 ml/m/min2The spraying amount of the water is sprayed on the materials, and the materials are stirred while being sprayed; the intermittent spraying is stopped for 16 seconds every 45 seconds, and continuous stirring is still performed when the spraying is stopped.
c. Packaging for several times: heating quartz sand powder and bentonite to 155 ℃, spraying 1/4 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 13 minutes, adding 1/6 weight of fired compound, keeping the temperature and mixing uniformly for 10 minutes, then spraying 1/4 weight of polystyrene melt liquid and adding the rest of composite fired material in sequence, keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 18 minutes to obtain a wrapped compound;
d. adding water for suspension: cooling the coating compound to room temperature, adding water, stirring to obtain a suspension, and then continuously adding water to adjust the Baume degree to 55 to obtain a coating suspension;
e. homogenizing suspension: adding Gypsum Fibrosum Preparatum powder, herba Artemisiae Annuae wax, and trehalose into the coating suspension, and homogenizing under 40MPa for 3 times to obtain homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the Baume degree to 56, thereby obtaining the multifunctional coating for casting.
Example 4
The multifunctional coating for casting at least comprises the following raw materials in parts by weight: 67 parts of quartz sand powder, 13 parts of crystalline flake graphite powder, 11.5 parts of bentonite, 10 parts of zircon powder, 8.5 parts of polystyrene, 6 parts of bauxite, 12 parts of calcium fluoride, 21.5 parts of calcined gypsum powder, 5.5 parts of sweet wormwood wax, 6 parts of trehalose and 16.5 parts of zinc oxide whisker.
Wherein the particle size of the quartz sand powder is 230 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:5, heating at 125 ℃ to melt the polystyrene, and then uniformly stirring to obtain polystyrene molten liquid; keeping the polystyrene molten liquid at 125 ℃ for keeping a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 7/24 weight of calcium fluoride, firing at 775 ℃ for 53 minutes, taking out, spraying water, cooling to 115 ℃, and naturally cooling to obtain a fired compound; the water temperature of the water spray is 12 ℃;
wherein, the method of water spray is: spreading the fired material to a thickness of 7cm, intermittently spraying water in the form of water mist at a rate of 25 ml/m/min2The spraying amount of the water is sprayed on the materials, and the materials are stirred while being sprayed; the intermittent spraying is stopped for 10 seconds every 30 seconds, and continuous stirring is still carried out when the spraying is stopped.
c. Packaging for several times: heating quartz sand powder and bentonite to 165 ℃, spraying 1/4 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 19 minutes, adding 1/6 weight of fired compound, keeping the temperature and mixing uniformly for 14 minutes, then spraying 1/4 weight of polystyrene melt liquid and adding the rest of composite fired material in sequence, keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 22 minutes to obtain a wrapped compound;
d. adding water for suspension: cooling the coating compound to room temperature, adding water, stirring to obtain a suspension, and then continuously adding water to adjust the Baume degree to 65 to obtain a coating suspension;
e. homogenizing suspension: adding Gypsum Fibrosum Preparatum powder, herba Artemisiae Annuae wax, and trehalose into the coating suspension, and homogenizing under 50MPa for 5 times to obtain homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the baume degree to 63, thereby obtaining the multifunctional coating for casting.
Example 5
The multifunctional coating for casting at least comprises the following raw materials in parts by weight: 62 parts of quartz sand powder, 10 parts of crystalline flake graphite powder, 9 parts of bentonite, 9 parts of zircon powder, 6 parts of polystyrene, 5 parts of bauxite, 9.5 parts of calcium fluoride, 18 parts of calcined gypsum powder, 4.5 parts of sweet wormwood wax, 5 parts of trehalose and 13 parts of zinc oxide whisker.
Wherein the particle size of the quartz sand powder is 200 meshes.
The preparation method of the multifunctional coating for casting comprises the following steps:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:4.5, heating at 120 ℃ to melt the polystyrene, and then uniformly stirring to obtain polystyrene molten liquid; keeping the polystyrene molten liquid at 120 ℃ for keeping a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 7/24 weight of calcium fluoride, firing at 750 ℃ for 45 minutes, taking out, spraying water, cooling to 110 ℃, and naturally cooling to obtain a fired compound; the water temperature of the water spray is 10 ℃;
wherein, the method of water spray is: spreading the fired material to a thickness of 9cm, intermittently spraying water in the form of water mist of 35 ml/m/min2The spraying amount of the water is sprayed on the materials, and the materials are stirred while being sprayed; the intermittent spraying is stopped for 14 seconds every 40 seconds, and continuous stirring is still performed when the spraying is stopped.
c. Packaging for several times: heating quartz sand powder and bentonite to 160 ℃, spraying 1/4 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 16 minutes, adding 1/6 weight of fired compound, keeping the temperature and mixing uniformly for 12 minutes, then spraying 1/4 weight of polystyrene melt liquid and adding the rest of composite fired material in sequence, keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 20 minutes to obtain a wrapped compound;
d. adding water for suspension: cooling the coating compound to room temperature, adding water, stirring to obtain a suspension, and then continuously adding water to adjust the Baume degree to 60 to obtain a coating suspension;
e. homogenizing suspension: adding Gypsum Fibrosum Preparatum powder, herba Artemisiae Annuae wax, and trehalose into the coating suspension, and homogenizing under 45MPa for 4 times to obtain homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the baume degree to 60, thereby obtaining the multifunctional coating for casting.
Example 6
The difference from example 5 is that the temperature is not lowered by spraying water after firing in step b. The rest of the procedure was the same as in example 5.
Example 7
The difference from example 5 is that instead of intermittent spraying, continuous spraying is used in step b. The rest of the procedure was the same as in example 5.
Example 8
The difference from example 5 is that the wrapping method in step c is: heating quartz sand powder and bentonite to 160 ℃, then spraying polystyrene melt on the surface, keeping the temperature and mixing uniformly for 16 minutes, then adding a fired compound, keeping the temperature and mixing uniformly for 12 minutes, then adding the rest calcium fluoride, keeping the temperature and mixing uniformly for 20 minutes to obtain a wrapped compound. The rest of the procedure was the same as in example 5.
Example 9
The difference from example 5 is that no plaster powder was added in step e. The rest of the procedure was the same as in example 5.
Example 10
The difference from example 5 is that no artemisia apiacea wax is added in step e. The rest of the procedure was the same as in example 5.
Example 11
The difference from example 5 is that no trehalose is added in step e. The rest of the procedure was the same as in example 5.
Example 12
The difference from example 5 is that no calcium fluoride is added. The rest of the procedure was the same as in example 5.
Example 13
The difference from example 5 is that no zinc oxide whiskers were added in step f. The rest of the procedure was the same as in example 5.
Example 14
The coating was prepared according to the method of example 3 in the patent document entitled lost foam coating and its preparation method, which is granted under chinese patent No. CN 102836950B.
Example 15 comparison of effects
1. Preparation of Experimental samples
The multifunctional dope for casting was prepared in accordance with the methods of examples 1, 5 to 14 to obtain experimental samples 1, 5 to 14.
2. Evaluation method
The appearance, air permeability, drying property, adhesion and abrasion resistance of the test samples 1, 5 to 11, 13 and 14 were measured. The castings were produced by the lost foam casting and the V-method casting using the test samples 5 and 6, 7 and 12, respectively, and the appearance of the castings was observed for evaluation.
2.1 appearance measurement
Respectively coating the coating on EPS foam plastics and EVA films which are cut into small blocks, wherein the thickness of the coating on the EPS foam plastics is 2mm, the thickness of the coating on the EVA film is 0.8mm, placing the EPS foam plastics and the EVA film in an oven, baking the EPS foam plastics and the EVA film for 1 hour at 50 ℃, and observing whether cracking, foaming and wrinkling exist.
2.2 method of measuring air permeability
The thickness of the coating formed on the apparatus was 1mm when measured by a direct-reading air permeability measuring apparatus.
2.3 method for measuring drying Property
Respectively coating the coating on EPS foam plastics and EVA films which are cut into small pieces, wherein the coating thickness of the EPS foam plastics is 2mm, and the coating thickness of the EVA films is 0.8mm, then placing the films in an oven, drying the films for 4 minutes at 45 ℃, and taking one out of the oven every 1 minute to carry out a hand crank method test: (1) the powder is dropped by touching or rubbing the coating with fingers, which indicates that the coating is not dried thoroughly; (2) the powder is removed only by scratching the coating with the fingernail, which shows that the drying degree meets the requirement; the time (to the nearest minute) spent in states (1) to (2) was recorded as the dryness of the coating.
2.4 adhesion determination method
Respectively coating a coating on EPS foam plastic and an EVA film which are cut into small blocks, wherein the thickness of an upper coating of the EPS foam plastic is 2mm, the thickness of an upper coating of the EVA film is 0.8mm, placing the film in an oven for drying, marking the number of grids by using a ball pen point to form an angle of about 45 degrees with the surface of the coating, wherein the marking depth needs to penetrate through the coating, 50 grids with the side length of 5mm are marked, counting the area of stripping of the coating, and the larger the stripping area is, the poorer the coating adhesive force is. The evaluation was carried out according to the criteria of Table 1.
TABLE 1 evaluation criteria for coating adhesion points
| Counting number | Description of the peeling conditions |
| 10 | The two sides of each cutting line are fine and smooth, square grids are clearly formed at the intersection points of the cutting lines, and the coating is not stripped. |
| 8 | The intersection points of the cutting lines are slightly stripped, square grids are clear, and the total area of stripped parts of the coating accounts for less than 5% of the area of the whole square. |
| 6 | The coating at the two sides of the cutting line and the intersection point is stripped, but the total area of the stripped part accounts for 5 to 15 percent of the area of the whole square. |
| 4 | The cutting line has larger stripping amplitude and the total surface of the stripped part of the coatingThe area of the square accounts for 15 to 35 percent of the area of the whole square. |
| 2 | The stripping amplitude of the secant is larger, and the total area of the stripped part of the coating accounts for 35 to 65 percent of the area of the whole square |
| 0 | The total area of the coating peeled off was 65% or more of the total area of the squares. |
2.5 method for measuring abrasion resistance
Respectively coating a coating on EPS foam plastic and an EVA film which are cut into small pieces, wherein the thickness of the coating on the EPS foam plastic is 1mm, the thickness of the coating on the EVA film is 0.4mm, placing the EPS foam plastic in an oven to dry, fixing the EPS foam plastic on a plane plate inclined at 45 degrees, then erecting a funnel above the plane plate (the distance between the funnel and the plane plate is 500mm when the EPS foam plastic is measured, and the distance between the funnel and the plane plate is 100mm when the EVA film is measured), and extending a conduit at the bottom end of the funnel to a position 2mm above the plane plate; (b) adding standard sand into the funnel (the total loading amount of the shakeout sand is preferably 90-93% of the capacity of the funnel), and controlling a switch to enable the standard sand to flow out from the funnel along the guide pipe at a constant speed (the time spent after the standard sand flows out of the funnel for 2L is about 16-18 s), and fall on the EPS foam plastic or EVA film coated with the coating. The abrasion of the coating surface is increased along with the continuous sliding of the sand, an abrasion area is formed near a sand falling point, and finally, small holes with the diameter of 4mm are abraded in the abrasion area to expose an EPS foam plastic substrate or an EVA film substrate. Calculated according to the formula A ═ V/T, the A-abrasion resistance index (L/mum), the V-standard sand usage amount (L) and the T-coating thickness (mum) are higher, and the higher the abrasion resistance index is, the better the abrasion resistance is.
3. Evaluation results
3.1 coating Property evaluation results
TABLE 2 evaluation results of coating properties of lost foam casting-EPS foam
TABLE 3 evaluation results of coating Properties on cast EVA films by V method
3.2 practical evaluation results of coating
The experimental sample 5 was used for coating, and the castings produced by the two processes were smooth in surface and free from shrinkage porosity and porosity defects.
The castings produced by the two processes respectively coated by the experimental sample 6 have rough surfaces and obvious shrinkage porosity and air hole defects.
The experimental sample 7 was used for coating, and the castings produced by the two processes respectively had rough surfaces and had many fine pore defects.
The experimental sample 12 was used for coating, and the castings produced by the two processes, respectively, had rough surfaces and had significant shrinkage porosity and porosity defects.
4. Results of the experiment
As can be seen from tables 2 and 3 and the practical results of the coating, the quality of the experimental sample 5 was the best.
The experiment sample 6 does not spray water for cooling after the scale graphite powder, the zircon powder, the bauxite and the calcium fluoride are fired, so that the coating has poor air permeability, the surface of the casting is rough, and obvious shrinkage porosity and pore defects exist.
In the experimental sample 7, after the scale graphite powder, the zircon powder, the bauxite and the calcium fluoride are fired, continuous spraying water mist is adopted to replace intermittent spraying, so that the coating is slightly poor in air permeability, the surface of a casting is rough, and fine shrinkage porosity and air hole defects exist.
The experimental sample 8 does not use the interval wrapping method, so that the wear resistance and the adhesive force of the coating are poor, and the air permeability is slightly reduced due to the change of the composition structure of the coating.
In the experimental sample 9, no gypsum powder is added, so that the coating is easy to crack in the solidification process, and the wear resistance and the adhesive force of the coating are directly influenced.
In the experimental sample 10, no sweet wormwood wax is added, so that the adhesive force of the coating is reduced, and the wear resistance is directly influenced.
In the experimental sample 11, trehalose is not added, so that the water retention of the coating is reduced, the coating is wrinkled, and the dryness, the adhesion and the wear resistance are affected.
In the experimental sample 12, calcium fluoride is not added, so that local premature condensation of molten iron is easy to occur during pouring, and the casting has obvious shrinkage porosity and air hole defects.
The experiment sample 13 does not add zinc oxide whiskers, so that the wear resistance of the coating is reduced.
Experimental sample 14 was prepared using a prior art technique, resulting in a coating that was easily cracked, blistered, and peeled off, and also had low drying, adhesion, and abrasion resistance.
The above description is intended to describe in detail the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the claims of the present invention, and all equivalent changes and modifications made within the technical spirit of the present invention should fall within the scope of the claims of the present invention.
Claims (7)
1. The multifunctional coating for casting is characterized by at least comprising the following raw materials in parts by weight: 51-72 parts of quartz sand powder, 5.5-14.5 parts of crystalline flake graphite powder, 4-14 parts of bentonite, 3-15 parts of zircon powder, 1-11 parts of polystyrene and 1-9 parts of bauxite.
2. The multifunctional paint for casting as claimed in claim 1, further comprising the following raw materials in parts by weight: 4-15 parts of calcium fluoride, 11-25 parts of calcined gypsum powder, 2-7 parts of sweet wormwood wax, 3-7 parts of trehalose and 6-20 parts of zinc oxide whisker.
3. The multifunctional coating for casting as claimed in claim 1 or 2, wherein the particle size of the quartz sand powder is 150-250 mesh.
4. A method for preparing the multifunctional paint for casting according to claim 1 or 2, comprising the steps of:
a. preparation of a polystyrene melt: taking polystyrene according to the weight part ratio, adding water according to the material-liquid ratio of 1:3.5-5.5, heating at the temperature of 110-; the polystyrene molten liquid is continuously kept at the temperature of 110-130 ℃ to keep a molten state;
b. firing treatment: uniformly mixing the flake graphite powder, zircon powder, bauxite and 1/4-1/3 weight of calcium fluoride, firing at 800 ℃ of 700-;
c. packaging for several times: heating quartz sand powder and bentonite to 150-170 ℃, then spraying 1/5-1/3 weight of polystyrene melt liquid on the surface, keeping the temperature and mixing uniformly for 11-21 minutes, then adding 1/7-1/5 weight of firing compound, keeping the temperature and mixing uniformly for 8-16 minutes, then spraying 1/5-1/3 weight of polystyrene melt liquid and adding the rest of compound firing compound in sequence, carrying out the operation of keeping the temperature and mixing uniformly according to the steps, then adding the rest of polystyrene melt liquid and the rest of calcium fluoride, keeping the temperature and mixing uniformly for 15-25 minutes, and obtaining a wrapping compound;
d. adding water for suspension: cooling the coated compound to room temperature, adding water, stirring to obtain suspension, and adding water to adjust Baume degree to 50-70 to obtain coated suspension;
e. homogenizing suspension: adding plaster powder, sweet wormwood wax and trehalose into the coating suspension, and then homogenizing to obtain a homogeneous coating solution;
f. preparing a finished product: adding zinc oxide whiskers into the homogeneous coating liquid, stirring uniformly, and then adding water to adjust the baume degree to 53-67, thereby obtaining the multifunctional coating for casting.
5. The method for preparing multifunctional paint for casting as claimed in claim 4, wherein the water temperature of the water spray in step b is 5-15 ℃.
6. The preparation method of the multifunctional paint for casting according to claim 4, wherein the water spraying method in the step b is as follows: spraying in the form of water mist while stirring.
7. The method for preparing multifunctional foundry coating according to claim 4, wherein the homogenizing pressure in step e is 35-55MPa, and the number of homogenizing times is 2-6.
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