A method for preparing a foundry coating for reducing sand inclusion defects

Abstract

The application relates to the technical field of casting, and discloses a preparation method of casting coating capable of reducing sand inclusion defects, which comprises the following steps: adding modified composite refractory powder, phenolic resin, a surfactant and bentonite into a solvent in sequence, mixing to obtain a base material; adding hydroxymethyl cellulose and an additive into the base material in sequence, adding mullite powder, and mixing again to obtain the casting coating; the process is capable of greatly improving the comprehensive performance of the casting coating by optimizing the components of the existing casting coating, introducing multiple components for cooperation, and significantly reducing the waste product rate of the casting; through a large number of tests, the waste product rate of the casting can be reduced from 1.88% to 1.05% on average, so that the quality of the casting can be greatly improved, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of casting technology, in particular to a casting coating preparation method for reducing sand inclusion defects. BACKGROUND

[0002] Casting sand inclusion defects are a common problem in production, which belong to surface defects of castings. They are mostly generated on the surface of large castings. According to the statistics of a large number of sand inclusion defects, the average scrap rate of castings caused by sand inclusion defects in a batch of castings is 1.88%. Due to the high scrap rate, the average quality of castings is seriously reduced, and the economic cost is increased.

[0003] The prior art with the application number 201410855011.8 discloses an alcohol-based ceramic casting coating consisting of the following components by weight: high-aluminum powder 250-350 parts, silicon powder 50-150 parts, pyrophyllite powder 150-200 parts, cosolvent 30-50 parts, suspending agent 20-30 parts, binder 8-15 parts, surfactant 1-3 parts, and solvent 250-350 parts. The present application overcomes the shortcomings of the prior art and provides an alcohol-based ceramic casting coating with high refractoriness, good sintering and peeling effect, low price, and excellent comprehensive performance. The casting coating prepared by the prior art is prone to cause sand inclusion defects, thereby increasing the scrap rate.

[0004] Therefore, we propose a casting coating preparation method for reducing sand inclusion defects, hoping to solve the shortcomings of the prior art. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the shortcomings of the prior art, the present application provides a casting coating preparation method for reducing sand inclusion defects.

[0007] (II) Technical solutions

[0008] To achieve the above purpose, the present application provides the following technical solutions:

[0009] A casting coating preparation method for reducing sand inclusion defects comprises:

[0010] The modified composite refractory powder, phenolic resin, surfactant, and bentonite are sequentially added to the solvent, and after mixing, a base material is obtained.

[0011] Hydroxymethyl cellulose, an additive, and mullite powder are sequentially added to the base material, and the mixture is uniformly mixed again to obtain a casting coating.

[0012] As a further technical solution, the modified composite refractory powder preparation method comprises:

[0013] After the graphite, tetraethyl orthosilicate, zirconium powder are mixed uniformly, then add chlorinated salt, continue to stir uniformly, put into the crucible, under the protection of inert atmosphere, heating treatment for 2-2.5 hours, then cooling, get the reaction mixture;

[0014] Washing the reaction mixture, drying, get it.

[0015] As a further technical solution, the graphite is modified:

[0016] Dissolve N-hydroxy succinimide isostearate in acetone, then add graphite, stir uniformly, then add amino acid, triethylamine aqueous solution, stir for 1-2 hours, then filter, wash with water, dry, get it.

[0017] As a further technical solution: the mixing mass ratio of N-hydroxy succinimide isostearate, acetone, graphite, amino acid, triethylamine aqueous solution is 3-5:30-40:10-12:1-3:5-8.

[0018] As a further technical solution, the mass fraction of triethylamine aqueous solution is 5.8%.

[0019] As a further technical solution, the mixing mass ratio of graphite, tetraethyl orthosilicate, zirconium powder, chlorinated salt is 15-18:3-5:1-1.8:2-3.

[0020] As a further technical solution: the chlorinated salt is a mixture of sodium chloride and potassium chloride;

[0021] The mixing mass ratio of sodium chloride and potassium chloride is 3:1.

[0022] As a further technical solution: the inert atmosphere is nitrogen atmosphere;

[0023] The heating temperature is not less than 800℃.

[0024] As a further technical solution: the surfactant is sodium dodecyl benzene sulfonate;

[0025] The auxiliary agent is glycerol;

[0026] The solvent is methanol.

[0027] As a further technical solution: the mixing weight ratio of phenolic resin, surfactant, solvent, hydroxymethyl cellulose, auxiliary agent, mullite powder is 13-15:1-2:80-85:5-7:2-3;

[0028] The mass fraction of the composite refractory powder in the casting coating is 10-12%;

[0029] The bentonite accounts for 7-8% of the mass fraction of the casting coating.

[0030] (Three) beneficial effects

[0031] Compared with the prior art, the casting coating preparation method for reducing sand inclusion defects has the following beneficial effects:

[0032] The process greatly improves the comprehensive performance of the casting coating by optimizing the components of the existing casting coating, introducing various components for cooperation, and significantly reducing the scrap rate of the casting. Through a large number of tests, the scrap rate of the casting can be reduced from an average of 1.88% to 1.05%, thereby greatly improving the quality of the casting and reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The suspension of the casting coating. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0035] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the scope of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0036] A casting coating preparation method for reducing sand inclusion defects, comprising:

[0037] The modified composite refractory powder, phenolic resin, surfactant and bentonite are sequentially added to the solvent, and after mixing in the stirring device, the base material is obtained.

[0038] The bentonite parameters are: montmorillonite: 60%-88%, swelling capacity: 25-50ml / g, gum price: ≥99ml / 15g, 2h water absorption: 250-350%, moisture: ≤12%, wet compressive strength: ≥0.23 (Mpa), blue absorption: ≥80mmol / 100g, Na2O: ≥1.28;

[0039] The phenolic resin is a yellow and transparent substance, which is soluble in alcohol and insoluble in water; the phenolic resin is obtained by catalytic reaction of 30% (mass fraction) formaldehyde aqueous solution in a mass ratio of m (phenol) :m (formaldehyde) =1:1.12.

[0040] The hydroxymethyl cellulose, the auxiliary agent and the mullite powder are sequentially added into the base material, and then mixed uniformly to obtain the casting coating; the mullite powder is a fine powder with a particle size of 800 meshes; the mullite powder helps the casting coating to form a smooth and dense coating film.

[0041] The modified composite refractory powder is prepared by the following method:

[0042] The graphite, the tetraethyl orthosilicate and the zirconium powder are mixed uniformly, and then the chlorinated salt is added; after uniform stirring, the mixture is placed in a crucible and heated for 2-2.5 hours under an inert atmosphere, and then cooled to obtain a reaction mixture.

[0043] The reaction mixture is washed and dried to obtain the product.

[0044] The graphite is modified by the following method:

[0045] The N-hydroxysuccinimide isostearate is dissolved in acetone, and then the graphite is added; after uniform stirring, the amino acid and the triethylamine aqueous solution are added and stirred for 1-2 hours; then the mixture is filtered, washed with water and dried.

[0046] The mixing mass ratio of the N-hydroxysuccinimide isostearate, the acetone, the graphite, the amino acid and the triethylamine aqueous solution is 3-5:30-40:10-12:1-3:5-8.

[0047] The mass fraction of the triethylamine aqueous solution is 5.8%.

[0048] The mixing mass ratio of the graphite, the tetraethyl orthosilicate, the zirconium powder and the chlorinated salt is 15-18:3-5:1-1.8:2-3.

[0049] The chlorinated salt is a mixture of sodium chloride and potassium chloride; the mixing mass ratio of the sodium chloride and the potassium chloride is 3:1.

[0050] The inert atmosphere is a nitrogen atmosphere, and neon, helium or the like can also be selected.

[0051] The heating temperature is not less than 800℃, preferably 1000℃, and more preferably 1100℃.

[0052] Graphite is a kind of transitional crystal between atomic crystal, metal crystal and molecular crystal. In the crystal, the same layer of carbon atoms form covalent bonds by sp2 hybridization, each carbon atom is associated with another three carbon atoms, and six carbon atoms form a regular hexagonal ring in the same plane, which extends to form a sheet structure. Because the distance between layers is large, the binding force (van der Waals force) is small, and each layer can slide, so the density of graphite is smaller than that of diamond, it is soft and has a smooth feeling. Through the modification treatment of graphite, the modified composite refractory powder prepared has better coating and lubricity, which can be introduced into the casting coating, can withstand temperature changes at high temperature without being damaged, has little volume change at high temperature, and is not easy to produce cracks, so as to better avoid the coating from falling off during casting process and cause the generation of sand inclusion defects. At the same time, its lubricity can facilitate the falling off of the casting, improve the flatness of the casting surface, greatly improve the surface quality of the casting, and reduce the scrap rate of the casting.

[0053] The surfactant is sodium dodecyl benzene sulfonate;

[0054] The auxiliary agent is glycerol; melting point 18.17℃, boiling point 290℃ (decomposition); flash point (open cup) 177℃; density 1.261g / cm 3 ; refractive index nD (20℃) 1.474; viscosity (20℃) 1499mPa·s;

[0055] The solvent is methanol.

[0056] The weight ratio of the phenolic resin, surfactant, solvent, hydroxymethyl cellulose, auxiliary agent and mullite powder is: 13-15: 1-2: 80-85: 5-7: 2-3;

[0057] The mass fraction of the composite refractory powder in the casting coating is 10-12%;

[0058] The mass fraction of the bentonite in the casting coating is 7-8%.

[0059] The following is a specific embodiment:

[0060] Example 1

[0061] A casting coating preparation method for reducing sand inclusion defects, comprising:

[0062] The modified composite refractory powder, phenolic resin, surfactant, bentonite are sequentially added into the solvent, and after mixing in the stirring device, the base material is obtained; the surfactant is sodium dodecyl benzene sulfonate; the solvent is methanol. The bentonite parameters are: montmorillonite: 80%, swelling capacity: 30ml / g, gum price: ≥99ml / 15g, 2h water absorption: 320%, moisture: ≤10%, wet compressive strength: ≥0.23 (Mpa), blue absorption: ≥80mmol / 100g, Na2O: ≥1.28;

[0063] The hydroxymethyl cellulose, auxiliary agent, mullite powder are sequentially added into the base material, and after mixing uniformly, the casting coating is obtained; the auxiliary agent is glycerol.

[0064] The modified composite refractory powder preparation method:

[0065] The graphite, tetraethyl orthosilicate, zirconium powder are uniformly mixed, and then the chlorinated salt is added, the chlorinated salt is a mixture of sodium chloride and potassium chloride, the mass ratio of sodium chloride to potassium chloride is 3:1; after uniform stirring, it is placed in a crucible, under the protection of an inert atmosphere, the inert atmosphere is a nitrogen atmosphere; heating treatment is carried out for 2 hours, the heating temperature is 1100℃; then cooling is carried out, and the reaction mixture is obtained; the reaction mixture is washed and dried, and the modified composite refractory powder is obtained. The graphite is modified by dissolving N-hydroxysuccinimide isostearate in acetone and adding graphite, stirring uniformly, then adding amino acid and triethylamine aqueous solution for stirring reaction for 1 hour, and then filtering, washing with water and drying. The mass ratio of N-hydroxysuccinimide isostearate, acetone, graphite, amino acid and triethylamine aqueous solution is 3:30:10:1:5. The mass fraction of triethylamine aqueous solution is 5.8%. The mass ratio of graphite, tetraethyl orthosilicate, zirconium powder and chlorinated salt is 15:3:1:2. The mass ratio of phenolic resin, surfactant, solvent, hydroxymethyl cellulose, auxiliary agent and mullite powder is 13:1:80:5:2. The mass fraction of the composite refractory powder in the casting coating is 10%, and the mass fraction of the bentonite in the casting coating is 7%.

[0066] Cracking resistance:

[0067] The casting coating of Example 1 is uniformly coated on the surface of a standard sand sample (φ50mm×50mm), dried at 100℃ for 1 hour, and then naturally cooled, and the surface condition of the formed coating is observed; the mass fraction of the composite refractory powder in the casting coating in Example 1 is compared:

[0068] Table 1

[0069] Composite refractory powder mass fraction of the casting coating 0 4 8 12 16 20 Crack presence Yes Yes No No Yes Yes

[0070] As can be seen from Table 1, too low composite refractory powder introduction or too high composite refractory powder introduction will cause the coating to crack.

[0071] Abrasion resistance detection:

[0072] The abrasion resistance of the coating formed by the casting coating of Example 1 with different mass fractions of composite refractory powder is detected, and the abrasion resistance of the coating is measured by using a SUM coating surface strength tester. The coating is uniformly coated on the surface of a standard sand sample (φ50mm*50mm), and after drying, the test extra load is 200g, and the test time is 60s.

[0073] Table 2

[0074] Composite refractory powder mass fraction of the casting coating Wear resistance / g 0 0.038 2 0.033 4 0.030 6 0.026 8 0.023 10 0.021 12 0.023 14 0.026 16 0.030 18 0.031

[0075] As can be seen from Table 2, with the increase of the addition amount of the composite refractory powder in the application, the adhesion of the coating formed by the casting coating first increases and then decreases.

[0076] Example 2

[0077] A casting coating preparation method for reducing sand inclusion defects, comprising:

[0078] The modified composite refractory powder, phenolic resin, surfactant and bentonite are sequentially added to the solvent, and after mixing in the stirring device, a base material is obtained. The surfactant is sodium dodecyl benzene sulfonate, and the solvent is methanol. The parameters of the bentonite are as follows: montmorillonite: 80%, swelling capacity: 30ml / g, gum price: ≥99ml / 15g, 2h water absorption rate: 320%, moisture content: ≤10%, wet compressive strength: ≥0.23 (Mpa), blue absorption: ≥80mmol / 100g, Na2O: ≥1.28.

[0079] Hydroxymethyl cellulose, an auxiliary agent and mullite powder are sequentially added to the base material, and mixed again to obtain a casting coating. The auxiliary agent is glycerol.

[0080] The preparation method of the modified composite refractory powder is as follows:

[0081] The graphite, tetraethyl orthosilicate, zirconium powder are mixed uniformly, then the chlorinated salt is added, the chlorinated salt is a mixture of sodium chloride and potassium chloride, the mass ratio of sodium chloride to potassium chloride is 3:1, after uniform stirring, it is put into a crucible, under the protection of inert atmosphere, the inert atmosphere is nitrogen atmosphere, heating treatment is carried out for 2.2 hours, the heating temperature is 1100℃, then cooling is carried out, the reaction mixture is obtained, the reaction mixture is washed and dried, and the modified graphite is obtained. The N-hydroxysuccinimide isostearate is dissolved in acetone, then the graphite is added, after uniform stirring, the amino acid and triethylamine aqueous solution are added, stirring reaction is carried out for 1.5 hours, then filtration, water washing and drying are carried out, and the modified graphite is obtained. The mass ratio of N-hydroxysuccinimide isostearate, acetone, graphite, amino acid and triethylamine aqueous solution is 4:33:11:2:6. The mass fraction of the triethylamine aqueous solution is 5.8%. The mass ratio of the graphite, tetraethyl orthosilicate, zirconium powder, chlorinated salt is 16:4:1.2:2.5. The weight ratio of the phenolic resin, surfactant, solvent, hydroxymethyl cellulose, additive and mullite powder is 14:1.5:82:6:2.5. The mass fraction of the composite refractory powder in the casting coating is 11%. The mass fraction of the bentonite in the casting coating is 7.3%.

[0082] Example 3

[0083] A casting coating preparation method for reducing sand inclusion defects comprises the following steps.

[0084] The modified composite refractory powder, phenolic resin, surfactant and bentonite are sequentially added to the solvent in a stirring device, and after mixing, the base material is obtained. The surfactant is sodium dodecyl benzene sulfonate, and the solvent is methanol. The bentonite parameters are as follows: montmorillonite: 80%, swelling capacity: 30ml / g, colloid value: ≥99ml / 15g, 2h water absorption: 320%, moisture content: ≤10%, wet compressive strength: ≥0.23 (Mpa), blue absorption: ≥80mmol / 100g, Na2O: ≥1.28.

[0085] The hydroxymethyl cellulose, additive and mullite powder are sequentially added to the base material, and mixing is carried out again to obtain the casting coating. The additive is glycerol.

[0086] The modified composite refractory powder preparation method comprises the following steps.

[0087] The graphite, tetraethyl orthosilicate, zirconium powder are mixed uniformly, then the chlorinated salt is added, the chlorinated salt is a mixture of sodium chloride and potassium chloride, the mass ratio of sodium chloride to potassium chloride is 3:1, after uniform stirring, it is put into a crucible, under the protection of inert atmosphere, the inert atmosphere is nitrogen atmosphere, heating treatment is carried out for 2.3 hours, the heating temperature is 1100℃, then cooling is carried out, the reaction mixture is obtained, the reaction mixture is washed and dried, and the modified graphite is obtained. The N-hydroxysuccinimide isostearate is dissolved in acetone, then the graphite is added, after uniform stirring, the amino acid and triethylamine aqueous solution are added, stirring reaction is carried out for 1.5 hours, then filtration, water washing and drying are carried out, and the modified graphite is obtained. The mass ratio of N-hydroxysuccinimide isostearate, acetone, graphite, amino acid and triethylamine aqueous solution is 4:35:11:2.5:7. The mass fraction of the triethylamine aqueous solution is 5.8%. The mass ratio of the graphite, tetraethyl orthosilicate, zirconium powder and chlorinated salt is 17:4:1.6:2.5. The weight ratio of the phenolic resin, surfactant, solvent, hydroxymethyl cellulose, additive and mullite powder is 14:1-2:80-85:6:2.8. The mass fraction of the composite refractory powder in the casting coating is 11.5%. The mass fraction of the bentonite in the casting coating is 7.6%.

[0088] Example 4

[0089] A casting coating preparation method for reducing sand inclusion defects comprises the following steps.

[0090] The modified composite refractory powder, phenolic resin, surfactant and bentonite are sequentially added to the solvent in a stirring device, and after mixing, the base material is obtained. The surfactant is sodium dodecyl benzene sulfonate, and the solvent is methanol. The bentonite parameters are as follows: montmorillonite: 80%, swelling capacity: 30ml / g, gum price: ≥99ml / 15g, 2h water absorption: 320%, moisture: ≤10%, wet compressive strength: ≥0.23 (Mpa), blue absorption: ≥80mmol / 100g, Na2O: ≥1.28.

[0091] The hydroxymethyl cellulose, additive and mullite powder are sequentially added to the base material, and mixing is carried out again to obtain the casting coating. The additive is glycerol.

[0092] The modified composite refractory powder preparation method comprises the following steps.

[0093] Graphite, tetraethyl orthosilicate, and zirconium powder are mixed evenly, and then a chloride salt, a mixture of sodium chloride and potassium chloride, is added; the mass ratio of sodium chloride to potassium chloride is 3:1. After stirring evenly, the mixture is placed in a crucible and heated for 2.5 hours at 1100℃ under an inert atmosphere (nitrogen). The mixture is then cooled to obtain a reaction mixture. The reaction mixture is washed and dried to obtain the final product. The graphite is modified by dissolving N-hydroxysuccinimide isostearate in acetone, adding graphite, stirring evenly, and then adding amino acids and triethylamine aqueous solution. The mixture is stirred and reacted for 2 hours, then filtered, washed with water, and dried. The mass ratio of N-hydroxysuccinimide isostearate, acetone, graphite, amino acids, and triethylamine aqueous solution is 5:40:12:3:8. The mass fraction of the triethylamine aqueous solution is 5.8%. The graphite, tetraethyl orthosilicate, zirconium powder, and chloride salt are mixed in a mass ratio of 18:5:1.8:3. The phenolic resin, surfactant, solvent, hydroxymethyl cellulose, additives, and mullite powder are mixed in a weight ratio of 15:2:85:7:3. The composite refractory powder accounts for 12% of the casting coating by mass, and the bentonite accounts for 8% of the casting coating by mass.

[0094] test:

[0095] The density of the coatings in the examples was tested: the density was measured using a graduated cylinder weighing method, with 10 measurements taken for each group and the average value recorded.

[0096] Table 3

[0097] Density g / cm3 Example 1 1.575 Example 2 1.588 Example 3 1.582 Example 4 1.594

[0098] As can be seen from Table 3, the casting coating prepared by the present invention has a more suitable density. This is because if the density of the casting coating is too high, it will easily cause the fluidity of the casting coating to deteriorate, the coating thickness to be too thick, and more brush marks to be formed on the coating surface, which will easily cause sand inclusions to form on the surface of the casting. If the density of the casting coating is too low, the anti-flow properties of the casting coating will be poor, the coating thickness will be uneven, thinner at the top and thicker at the bottom, which will also reduce the smoothness of the casting surface.

[0099] The suspension properties of the casting coating in the example were measured using the graduated cylinder method, such as... Figure 1 ,Depend on Figure 1 It can be seen that the casting coating of the present invention has excellent suspension properties.

[0100] By enhancing the suspension properties of the casting coating of this invention, the cured coating forms a three-dimensional network structure with increased viscosity. If the suspension properties of the casting coating decrease, the network structure is easily damaged by shear force, thereby reducing the smoothness of the coating and affecting the quality of the casting.

[0101] While embodiments of the present application have been shown and described, it is to be understood that the embodiments described are merely divergences of the principles and spirit of the present application, and that various changes in form and substitutions can be made by those skilled in the art without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a foundry coating for reducing sand inclusion defects, characterized by, The application relates to a casting coating and a preparation method thereof. The modified composite refractory powder, phenolic resin, surfactant and bentonite are sequentially added into a solvent, and the base material is obtained after mixing; The hydroxymethyl cellulose, auxiliary agent and mullite powder are sequentially added into the base material, and the casting coating is obtained after mixing; The preparation method of the modified composite refractory powder comprises the following steps: The graphite, ethyl silicate and zirconium powder are uniformly mixed, then the chlorinated salt is added, and the mixture is continuously stirred and uniformly mixed, and then the mixture is placed into a crucible, heated for 2-2.5 hours under the protection of an inert atmosphere, and then cooled to obtain a reaction mixture; The reaction mixture is cleaned and dried to obtain the modified composite refractory powder; The graphite is modified by the following steps: The N-hydroxysuccinimide isostearate is dissolved in acetone, and then the graphite is added, and the mixture is stirred and uniformly mixed, then the amino acid and the triethylamine aqueous solution are added, and the mixture is stirred and reacted for 1-2 hours, and then the mixture is filtered, washed with water and dried to obtain the modified graphite; The mixing mass ratio of the N-hydroxysuccinimide isostearate, acetone, graphite, amino acid and triethylamine aqueous solution is 3-5:30-40:10-12:1-3:5-8; The mixing mass ratio of the graphite, ethyl silicate, zirconium powder and chlorinated salt is 15-18:3-5:1-1.8:2-3; The mass fraction of the composite refractory powder in the casting coating is 10-12%; The mass fraction of the bentonite in the casting coating is 7-8%.

2. The method of claim 1, wherein the method is characterized by: The mass fraction of the triethylamine aqueous solution is 5.8%.

3. The method of claim 1, wherein the method is characterized by: The chlorinated salt is a mixture of sodium chloride and potassium chloride; The mixing mass ratio of the sodium chloride and potassium chloride is 3:

1.

4. The method of claim 1, wherein the method is characterized by: The inert atmosphere is nitrogen atmosphere; The heating temperature is not lower than 800 DEG C.

5. The method of claim 1, wherein the method is characterized by: The surfactant is sodium dodecyl benzene sulfonate; The auxiliary agent is glycerol; The solvent is methanol.

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