CN110653331B - Preparation method of molding sand binder for casting - Google Patents
Preparation method of molding sand binder for casting Download PDFInfo
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- CN110653331B CN110653331B CN201910931287.2A CN201910931287A CN110653331B CN 110653331 B CN110653331 B CN 110653331B CN 201910931287 A CN201910931287 A CN 201910931287A CN 110653331 B CN110653331 B CN 110653331B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/167—Mixtures of inorganic and organic binding agents
Abstract
The invention discloses a preparation method of a molding sand binder for casting, which is prepared from the following raw materials in parts by weight: 70-90 parts of water glass, 3-5 parts of modified starch, 2-8 parts of aluminum tripolyphosphate, 0.5-2 parts of sodium tetraborate, 1-2 parts of bentonite, 2-4 parts of vinyl phenolic resin, 2-4 parts of methyl silicone oil and 0.3-0.6 part of coupling agent. The invention determines the optimal formula through scientific material selection and repeated tests, and adds modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass for modification, thereby realizing synergistic interaction, greatly improving the bonding strength and the aging resistance, and remarkably improving the collapsibility and the moisture absorption resistance of the molding sand.
Description
Technical Field
The invention relates to the technical field of casting, in particular to a preparation method of a molding sand binder for casting.
Background
Casting is one of the basic processes of the modern mechanical manufacturing industry, the casting technology is a high-efficiency and low-cost forming means for a large number of high-performance complex metal workpieces in the equipment manufacturing industry, and workpieces with complex inner cavities cannot be replaced by other forming methods. In high-end equipment manufacturing, national defense construction and national major engineering of strategic emerging industries such as aviation, satellite, rail transit, new energy automobiles and the like, a plurality of key core components need to be formed by adopting a casting technology, the development level of the casting technology restricts and promotes the development of the equipment manufacturing industry, the level of the casting industry is not improved, and the development of the equipment manufacturing industry and the improvement of the overall level are not mentioned.
The sand binder is a molding material that can bind loose foundry sand together into molding sand. The surface of the sand grains is coated with the mixed binder and sand grains to form a binder film, so that the sand grains are adhered to each other, and the sand mould is endowed with enough strength, so that the sand mould is not deformed and broken in the processes of carrying, assembling and pouring. The molding sand binder has direct influence on the quality of cast parts and the yield, the air holes, scabs, hot cracks and surface quality of castings are all in important relation with molding sand and the molding sand binder, and the research and the improvement of the molding sand binder have great significance for improving the quality of the castings.
The molding sand binder used in the casting production at present mainly includes organic and inorganic ones. Most of organic binders are resin polymers, the bonding strength is high, in the production process, from sand mulling modeling, pouring cleaning to old sand regeneration, pollution and damage are caused to operators and the environment in each link, the resin polymers belong to petrochemical products, resources are not renewable, the cost is high, and the use of the organic binders is greatly limited. The inorganic binder can gradually replace resin organic binders due to the advantages of environmental protection performance, wide resources, low cost and the like. Among all types of inorganic binders, water glass binders are widely used. The water glass is an inorganic binder synthesized by quartz sand and soda ash, is one of the most abundant substances on the earth, and is also a casting binder which has the smallest environmental pollution at present. However, the sand mold prepared by using water glass as a binder has the problems of low binding strength, easy aging, poor moisture resistance, poor collapsibility, difficult regeneration and reuse and the like in the using process, influences the production efficiency and the casting quality, and restricts the application of the sand mold in the field of cast iron.
In order to solve the problems of poor collapsibility and difficult recycling of sand molds by using a water glass binder in the prior art, for example, CN108672648A discloses a binder for casting sand molds, a preparation method and application thereof. The binder for casting the sand mold comprises the following raw material components in percentage by weight: 1-90% of sodium water glass, 1-90% of potassium water glass, 1% of lithium water glass, 0.5% of dextrin, 0.5% of sodium carboxymethylcellulose, 0.5% of sodium alginate, 0.5% of carbon dioxide hardened phenolic resin and 3% of water. The adhesive of the invention compounds the inorganic adhesive and the organic adhesive, can be hardened by carbon dioxide when in use, is convenient and rapid to harden, and has the normal temperature strength of more than 1MPa within 24 hours. The wet strength of the molding sand is improved (up to 0.2MPa), and the strength of the molding sand after high-temperature casting is lower than 0.6MPa, so that the collapsibility of the molding sand is obviously improved. According to the invention, the binder for the molding sand, which is environment-friendly and has good collapsibility, is obtained by selecting and proportioning the water glass and the resin according to specific components. CN105344920A discloses a water glass binder for improving collapsibility, which is characterized by comprising the following raw materials in parts by weight: 110-130 parts of water glass solution, 20-30 parts of modified synthetic resin, 10-15 parts of phosphate and 5-8 parts of vegetable oil. CN101941046A discloses a composite water glass binder for sand molds and a preparation method thereof, wherein the composite water glass binder is prepared by mixing the following components in parts by weight: 100 parts of water glass, 5-10 parts of straw powder and 0.5-2 parts of water. The manufacturing method comprises the following steps: firstly, drying and crushing the straws, and sieving the straws by a sieve with no less than 325 meshes to obtain straw powder; secondly, adding 0.5 to 2 weight parts of water into 5 to 10 weight parts of the straw powder obtained in the step one, and uniformly stirring to obtain wet straw powder; and thirdly, adding 100 parts by weight of water glass into the wetted straw powder. The invention solves the problems of poor collapsibility and difficult recycling of the sand mold by adopting water glass as a binder; and cheap straws are used as raw materials, so that compared with other methods for improving collapsibility of the sodium silicate sand, the cost of the sand mold (core) is obviously reduced.
However, in the process of implementing the embodiments of the present application, the inventors of the present application found that the above-mentioned technology has at least the following technical problems: the modified water glass binder in the prior art overcomes the defects of poor collapsibility and difficulty in sand cleaning of single water glass to a certain extent, but the binding strength, the aging resistance and the moisture resistance of the existing water glass binder still need to be further improved.
Disclosure of Invention
In order to make up for the defects of the prior art, the invention provides the preparation method of the molding sand binder for casting, and the binder has the advantages of high binding strength, excellent aging resistance, moisture resistance, collapsibility and other properties, improvement on casting quality, reduction in production cost, easiness in old sand regeneration, stable system, environmental friendliness, no toxicity and great benefit to operators and environment.
The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a preparation method of a molding sand binder for casting, which is prepared from the following raw materials in parts by weight: 70-90 parts of water glass, 3-5 parts of modified starch, 2-8 parts of aluminum tripolyphosphate, 0.5-2 parts of sodium tetraborate, 1-2 parts of bentonite, 2-4 parts of vinyl phenolic resin, 2-4 parts of methyl silicone oil and 0.3-0.6 part of coupling agent.
Further, the feed additive is prepared from the following raw materials in parts by weight: 75-85 parts of water glass, 3-4 parts of modified starch, 3-6 parts of aluminum tripolyphosphate, 1-1.5 parts of sodium tetraborate, 1-1.5 parts of bentonite, 2-3 parts of vinyl phenolic resin, 2-3 parts of methyl silicone oil and 0.4-0.5 part of coupling agent.
Further, the water glass comprises one or two of sodium water glass and potassium water glass.
Further, the coupling agent is a silane coupling agent.
Further, the silane coupling agent is selected from one or a mixture of two of gamma-aminopropyltriethoxysilane, gamma- (2,3) epoxy (propoxy) propyl-trimethoxysilane, gamma-methacryloxypropyl-trimethoxysilane and N- (beta aminoethyl) -gamma-aminopropylmethyldimethoxysilane.
Further, the preparation method of the modified starch comprises the following steps: (1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1; (2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch.
Further, in the step (1), the alkaline condition means that the pH of the mixed solution is 8-11, and the pH regulator for regulating the mixed solution is a sodium hydroxide solution, a potassium hydroxide solution and a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3.
Further, in the step (2), the mass ratio of the propylene oxide and the dichlorodiethyl ether to the wheat starch is 45:0.02: 100.
Further, the method comprises the following specific steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
The invention has the following beneficial effects:
the invention determines the optimal formula through scientific material selection and repeated tests, and adds modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass for modification, thereby realizing synergistic interaction, greatly improving the bonding strength and the aging resistance, and remarkably improving the collapsibility and the moisture absorption resistance of the molding sand.
The binder for preparing the sand sample has no any unpleasant odor from sand mixing, molding, core making and pouring in the whole casting process and production process, is nontoxic and tasteless, green and environment-friendly, has low cost, and basically has no special requirements on the existing casting equipment.
The invention has simple production process, wide application prospect of the product, and good economic and social benefits.
Detailed Description
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
Unless otherwise defined, terms used in the present specification have the same meaning as those generally understood by those skilled in the art, but in case of conflict, the definitions in the present specification shall control.
The use of "including," "comprising," "containing," "having," or other variations thereof herein, is meant to encompass the non-exclusive inclusion, as such terms are not to be construed. The term "comprising" means that other steps and ingredients can be added that do not affect the end result. The term "comprising" also includes the terms "consisting of …" and "consisting essentially of …". The compositions and methods/processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any of the additional or optional ingredients, components, steps, or limitations described herein.
All numbers or expressions referring to quantities of ingredients, process conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term "about". All ranges directed to the same component or property are inclusive of the endpoints, and independently combinable. Because these ranges are continuous, they include every value between the minimum and maximum values. It should also be understood that any numerical range recited herein is intended to include all sub-ranges within that range.
The preparation method of the molding sand binder for casting is prepared from the following raw materials in parts by weight: 70-90 parts of water glass, 3-5 parts of modified starch, 2-8 parts of aluminum tripolyphosphate, 0.5-2 parts of sodium tetraborate, 1-2 parts of bentonite, 2-4 parts of vinyl phenolic resin, 2-4 parts of methyl silicone oil and 0.3-0.6 part of coupling agent.
In the present invention, the amount of the water glass is 70 to 90 parts, and may be, for example, 70 parts, 75 parts, 80 parts, 85 parts or 90 parts, or a range defined by these values.
In the present invention, the amount of the modified starch is 3 to 5 parts, and may be, for example, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.5 parts or 5 parts, or a range defined by these values.
In the present invention, the amount of aluminum tripolyphosphate is 2 to 8 parts, and may be, for example, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, or 8 parts, or a range formed by these values.
In the present invention, the amount of sodium tetraborate is 0.5 to 2 parts, and may be, for example, 0.5 parts, 0.8 parts, 1 part, 1.5 parts, or 2 parts, or a range defined by these values.
In the present invention, the amount of bentonite is 1 to 2 parts, and may be, for example, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, or 2 parts, or a range defined by these values.
In the present invention, the amount of the vinyl phenol resin is 2 to 4 parts, and may be, for example, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, or a range of values therebetween.
In the present invention, the amount of the methyl silicone oil is 2 to 4 parts, and may be, for example, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, or a range defined by these values.
In the present invention, the amount of the coupling agent is 0.3 to 0.6 parts, and may be, for example, 0.3 parts, 0.4 parts, 0.5 parts, or 0.6 parts, or a range defined by these values.
According to the invention, the molding sand binder for casting is prepared by taking water glass as a base material, and adding modified starch, aluminum tripolyphosphate, sodium tetraborate and bentonite, so that the binding strength and the aging resistance can be greatly improved, and the collapsibility of molding sand is remarkably improved; however, the modified starch, the aluminum tripolyphosphate, the sodium tetraborate and the bentonite are added to influence the moisture absorption resistance, and the inventor finds that the addition of the vinyl phenolic resin and the methyl silicone oil can obviously improve the moisture absorption resistance of the molding sand of the system aiming at the technical problems.
In the invention, the modified starch prepared by a specific method is added into the water glass, so that the compact adhesive film layer formed on the surface of sand grains by the water glass is crackedLines, thereby achieving the purpose of improving collapsibility. In the invention, aluminum tripolyphosphate is adopted, and the glassy state substance formed by the aluminum tripolyphosphate after high-temperature pouring is greatly different from the glassy state substance formed by water glass in the cooling process, so that a bonding bridge is cracked due to the great difference of internal stress, and the collapsibility of the molding sand is improved. According to the invention, sodium tetraborate can enter a Si-O-Si network, and during the cooling process after high-temperature casting, the sodium tetraborate and the sodium silicate have different thermal expansion coefficients, so that a bonding film on the surface of sand grains generates larger stress during the cooling process of the molding sand, the bonding film is cracked, and the purpose of improving collapsibility is achieved. The aluminum tripolyphosphate can react with the bentonite to form a substance with high viscosity and good thermal state strength to form a composite vitreous body network, and the bonding strength of the water glass can be improved. In the invention, sodium tetraborate and aluminum tripolyphosphate are added into water glass to react under the condition of heating and boiling to form a gel network structure, so that SiO is reduced3]2-Effective collision among ions enables the water glass binder to have good aging resistance, and meanwhile, silicon, boron and phosphorus form a stable space three-dimensional structure net under the action of chemical crosslinking, so that the binding efficiency of the water glass binder is greatly increased, and the surface stability of molding sand can be improved. In the invention, modified starch, aluminum tripolyphosphate, sodium tetraborate and bentonite are creatively added into the water glass for modification, and the components have synergistic interaction, so that the bonding strength and the aging resistance can be greatly improved, the collapsibility of the molding sand is obviously improved, and an unexpected technical effect is obtained.
In order to avoid the influence of the addition of the modified starch, the aluminum tripolyphosphate, the sodium tetraborate and the bentonite on the moisture absorption resistance of the water glass, the vinyl phenolic resin and the methyl silicone oil are added in the molding sand, and the vinyl phenolic resin and the methyl silicone oil have synergistic effect, so that the moisture absorption resistance of the molding sand can be obviously improved. In the invention, a small amount of vinyl phenolic resin is adopted, and because the nodes of the space grid part have hydrophobic ethylene groups, the water absorption probability is obviously reduced, so that the sand mold has good moisture absorption resistance, and the moisture resistance of the molding sand is greatly improved. The combustion process of the ethylene group after casting and pouring does not generate any toxic gas emission due to incomplete combustion similar to benzene ring, so the ethylene group is an environment-friendly casting binder.
The silane coupling agent is added to form a high-strength net structure, so that the interface effect of the water glass and the casting can be improved, and the bonding strength is improved.
The water glass of the present invention is not particularly limited, and may be water glass known to those skilled in the art, prepared by a known method, or commercially available. Preferably, the water glass comprises one or both of sodium water glass and potassium water glass.
The silane coupling agent is not particularly limited in the present invention, and may be a silane coupling agent known to those skilled in the art, and may be prepared by a known method or may be commercially available. Preferably, the silane coupling agent is one or a mixture of two selected from gamma-aminopropyltriethoxysilane, gamma- (2,3) epoxy (propoxy) propyl trimethoxysilane, gamma-methacryloxypropyl trimethoxysilane and N- (beta aminoethyl) -gamma-aminopropylmethyldimethoxysilane.
The preparation method comprises the following steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
The present invention will be described in detail with reference to examples, which are only preferred embodiments of the present invention and are not intended to limit the present invention.
Example 1
The preparation method of the molding sand binder for casting is prepared from the following raw materials in parts by weight: 80 parts of water glass, 4 parts of modified starch, 6 parts of aluminum tripolyphosphate, 1 part of sodium tetraborate, 1.5 parts of bentonite, 3 parts of vinyl phenolic resin, 3 parts of methyl silicone oil and 0.4 part of coupling agent.
The water glass comprises one or two of sodium water glass and potassium water glass; the coupling agent is gamma-aminopropyl triethoxysilane.
The preparation method of the modified starch comprises the following steps: (1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1; (2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch. In the step (1), the alkaline condition means that the pH of the mixed solution is 8-11, and the pH regulator for regulating the mixed solution is a sodium hydroxide solution, a potassium hydroxide solution and a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3; in the step (2), the mass ratio of the propylene oxide to the dichlorodiethyl ether to the wheat starch is 45:0.02: 100.
The preparation method comprises the following steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
Example 2
The preparation method of the molding sand binder for casting is prepared from the following raw materials in parts by weight: 70 parts of water glass, 3 parts of modified starch, 2 parts of aluminum tripolyphosphate, 0.5 part of sodium tetraborate, 1 part of bentonite, 2 parts of vinyl phenolic resin, 2 parts of methyl silicone oil and 0.3 part of coupling agent.
The water glass comprises one or two of sodium water glass and potassium water glass; the coupling agent is gamma- (2,3) epoxy (propoxy) propyl trimethoxy silane.
The preparation method of the modified starch comprises the following steps: (1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1; (2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch. In the step (1), the alkaline condition means that the pH of the mixed solution is 8-11, and the pH regulator for regulating the mixed solution is a sodium hydroxide solution, a potassium hydroxide solution and a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3; in the step (2), the mass ratio of the propylene oxide to the dichlorodiethyl ether to the wheat starch is 45:0.02: 100.
The preparation method comprises the following steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
Example 3
The preparation method of the molding sand binder for casting is prepared from the following raw materials in parts by weight: 90 parts of water glass, 5 parts of modified starch, 8 parts of aluminum tripolyphosphate, 2 parts of sodium tetraborate, 2 parts of bentonite, 4 parts of vinyl phenolic resin, 4 parts of methyl silicone oil and 0.6 part of coupling agent.
The water glass comprises one or two of sodium water glass and potassium water glass; the coupling agent is gamma-methacryloxypropyl trimethoxy silane.
The preparation method of the modified starch comprises the following steps: (1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1; (2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch. In the step (1), the alkaline condition means that the pH of the mixed solution is 8-11, and the pH regulator for regulating the mixed solution is a sodium hydroxide solution, a potassium hydroxide solution and a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3; in the step (2), the mass ratio of the propylene oxide to the dichlorodiethyl ether to the wheat starch is 45:0.02: 100.
The preparation method comprises the following steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
Example 4
The preparation method of the molding sand binder for casting is prepared from the following raw materials in parts by weight: 90 parts of water glass, 3 parts of modified starch, 6 parts of aluminum tripolyphosphate, 1 part of sodium tetraborate, 1 part of bentonite, 3 parts of vinyl phenolic resin, 4 parts of methyl silicone oil and 0.3 part of coupling agent.
The water glass comprises one or two of sodium water glass and potassium water glass; the coupling agent is N- (beta aminoethyl) -gamma-aminopropyl methyldimethoxysilane.
The preparation method of the modified starch comprises the following steps: (1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1; (2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch. In the step (1), the alkaline condition means that the pH of the mixed solution is 8-11, and the pH regulator for regulating the mixed solution is a sodium hydroxide solution, a potassium hydroxide solution and a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3; in the step (2), the mass ratio of the propylene oxide to the dichlorodiethyl ether to the wheat starch is 45:0.02: 100.
The preparation method comprises the following steps: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
Comparative example 1
Based on example 1, the difference is only that: this comparative example 1 contained no modified starch.
Comparative example 2
Based on example 1, the difference is only that: this comparative example 2 does not contain aluminum tripolyphosphate.
Comparative example 3
Based on example 1, the difference is only that: this comparative example 3 does not contain sodium tetraborate.
Comparative example 4
Based on example 1, the difference is only that: this comparative example 4 does not contain bentonite.
Comparative example 5
Based on example 1, the difference is only that: comparative example 5 contained no vinyl phenol resin.
Comparative example 6
Based on example 1, the difference is only that: this comparative example 6 contained no methyl silicone oil.
Test examples
The binder obtained in examples 1-4 and comparative examples 1-6 was used as molding sand, 70 mesh quartz sand was used as the molding sand, and the molding sand formulation was formed by matching the binder in a proportion of 1-5% of the molding sand, the binder was slowly added to the molding sand in a sand mixer while stirring until it was uniform, and the mixture was beaten into a standard compression-resistant sample of phi 50 × 50mm, and the strength test, collapsibility test and moisture absorption test were performed.
And (3) detecting the intensity: the method refers to GB2684-81 original sand and mixture test method for casting, and detects the compressive strength of the raw sand and mixture for 1h, 4h and 24h after being cured at room temperature. The test result shows that: the compressive strength of 1h of curing at room temperature is ranked from high to low: example 1> example 3= example 2> example 4> comparative example 6> comparative example 5> comparative example 2> comparative example 1> comparative example 3> comparative example 4; wherein the compressive strength in example 4 reached 1.28MPa and the compressive strength in comparative example 6 was 0.87 MPa. The compressive strength of 4h curing at room temperature ranged from high to low: example 1> example 3> example 4> example 2> comparative example 6> comparative example 5> comparative example 1> comparative example 2> comparative example 3> comparative example 4; wherein the compressive strength in example 2 reached 4.75MPa and the compressive strength in comparative example 6 was 3.25 MPa. The compressive strength of 24h curing at room temperature ranged from high to low: example 1> example 2> example 3> example 4> comparative example 6> comparative example 5> comparative example 2> comparative example 1> comparative example 3> comparative example 4; wherein the compressive strength in example 4 reached 5.6MPa and the compressive strength in comparative example 6 was 4.02 MPa.
Residual strength (collapsibility) test of molding sand: the residual strength of the molding sand is an index for evaluating the easiness of sand production of the molding sand. It reflects the ease of cleaning sand from the casting, the lower the residual strength, the better. And heating the sample solidified for 24 hours to a certain temperature, taking out the sample, cooling the sample to room temperature, and detecting the residual compressive strength of the sample by using a hydraulic universal testing machine. The test results show that the residual compressive strength is arranged from high to low when heated to 600 ℃: comparative example 4> comparative example 3> comparative example 2> comparative example 1> comparative example 6> comparative example 5> example 1> example 3> example 2> example 4 >; in which the residual compressive strength in example 1 reached 0.24MPa and in comparative example 5 0.58 MPa. The residual compressive strength was ranked from high to low when heated to 800 ℃: comparative example 4> comparative example 2> comparative example 3> comparative example 1> comparative example 6> comparative example 5> example 1> example 2> example 3> example 4 >; in which the residual compressive strength in example 1 reached 0.35MPa and in comparative example 5 0.68 MPa.
Moisture absorption resistance test: it means the strength retention at a relative humidity of 65%. The test result shows that: anti-moisture absorption is arranged from high to low: example 1> example 4> example 2> example 3> comparative example 4> comparative example 3> comparative example 2> comparative example 1> comparative example 6> comparative example 5. Wherein the moisture absorption resistance of example 3 was 84% and that of comparative example 4 was 68%.
The above-mentioned embodiments only express the embodiments of the present invention, and the description is more specific and detailed, but not understood as the limitation of the patent scope of the present invention, but all the technical solutions obtained by using the equivalent substitution or the equivalent transformation should fall within the protection scope of the present invention.
Claims (8)
1. The preparation method of the molding sand binder for casting is characterized by comprising the following raw materials in parts by weight: 70-90 parts of water glass, 3-5 parts of modified starch, 2-8 parts of aluminum tripolyphosphate, 0.5-2 parts of sodium tetraborate, 1-2 parts of bentonite, 2-4 parts of vinyl phenolic resin, 2-4 parts of methyl silicone oil and 0.3-0.6 part of coupling agent;
the preparation method of the modified starch comprises the following steps:
(1) mixing wheat starch with water to form a slurry, raising the temperature of a mixed solution to 40-50 ℃ under an alkaline condition, adding hypochlorous acid into the mixed solution, and reacting for 1-3 hours under a heat preservation condition to obtain a reaction solution 1;
(2) adding 2-3wt% of soda ash solution prepared by soda ash to adjust the pH value of the reaction solution 1 to 10.8-11.2, and then adding propylene oxide and dichlorodiethyl ether; reacting at 31-33 ℃ for 15-18h, adjusting the pH value to 6-7.5, and performing post-treatment to obtain the modified starch.
2. The method for preparing the molding sand binder for casting according to claim 1, wherein the molding sand binder is prepared from the following raw materials in parts by weight: 75-85 parts of water glass, 3-4 parts of modified starch, 3-6 parts of aluminum tripolyphosphate, 1-1.5 parts of sodium tetraborate, 1-1.5 parts of bentonite, 2-3 parts of vinyl phenolic resin, 2-3 parts of methyl silicone oil and 0.4-0.5 part of coupling agent.
3. The method of preparing a foundry sand binder of claim 1 wherein the water glass comprises one or both of sodium water glass and potassium water glass.
4. The method of preparing a foundry molding sand binder of claim 1, wherein the coupling agent is a silane coupling agent.
5. The method of claim 4, wherein the silane coupling agent is selected from the group consisting of gamma-aminopropyltriethoxysilane, gamma- (2,3) epoxy (propoxy) propyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, and N- (beta aminoethyl) -gamma-aminopropylmethyldimethoxysilane, or a mixture thereof.
6. The method of preparing the molding sand binder for casting according to claim 1, wherein the alkaline condition in the step (1) means that the pH of the mixed solution is 8 to 11, and the pH adjusting agent for adjusting the pH of the mixed solution is a sodium hydroxide solution, a potassium carbonate solution; the mass ratio of the wheat starch to the hypochlorous acid is 100: 3.
7. The method of preparing a molding sand binder for casting according to claim 1, wherein in the step (2), the mass ratio of propylene oxide, dichlorodiethyl ether and the wheat starch is 45:0.02: 100.
8. The preparation method of the molding sand binder for casting according to claim 1, comprising the specific steps of: adding modified starch, aluminum tripolyphosphate, sodium tetraborate, bentonite, vinyl phenolic resin and methyl silicone oil into water glass at the temperature of 50-65 ℃, stirring for 20 minutes, finally adding a coupling agent, stirring uniformly, and cooling.
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| CN111687374A (en) * | 2020-07-07 | 2020-09-22 | 曲阜市铸造材料厂 | Water glass reclaimed sand and preparation method thereof |
| CN114535500B (en) * | 2021-12-31 | 2023-11-14 | 北京航空航天大学宁波创新研究院 | Modified silica fume suspension for casting, modified water glass and use method |
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| CN1721103A (en) * | 2004-07-17 | 2006-01-18 | 王继启 | Molding sand adhesive for casting |
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