Modifying agent for foundry inorganic sand, composite modifying powder additive, and preparation method and application thereof
By using composite modified powder additives with particle size distribution design, the problems of poor moisture resistance and collapsibility of inorganic sand cores were solved, achieving high strength and stability of castings and improving industrial production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIHANG UNIV
- Filing Date
- 2022-09-16
- Publication Date
- 2026-06-16
AI Technical Summary
Existing inorganic sand cores for casting suffer from poor moisture resistance and reduced collapsibility when using modifiers, leading to difficulties in cleaning castings and affecting industrial production efficiency and yield.
The composite modified powder additive with particle size distribution design is prepared by a graded mixing process to homogenize and disperse the components, including sodium aluminate, inorganic phosphate, nano calcium carbonate and whiskers, to form a fiber composite material, which improves the water resistance and strength of the sand core.
It improves the moisture resistance and collapsibility of inorganic sand cores, enhances the overall performance and industrial production efficiency of sand cores, and strengthens the strength and stability of castings.
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Figure CN117753922B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of metal casting technology, and in particular to a modifier for inorganic casting sand, a composite modified powder additive, its preparation method and application. Background Technology
[0002] With the increasing emphasis placed on environmental protection by the state and the strict control of pollution emissions from the foundry industry, two-component inorganic binders are receiving more and more attention from foundry professionals at home and abroad. Their production, molding, and casting processes do not generate harmful gases, and old sand can be dry-regenerated, making them the most environmentally friendly binders for foundry applications.
[0003] Two-component inorganic binders consist of a liquid and a powder. The liquid is typically modified water glass, while the powder is usually a mixture of one or more powders. These powders can be categorized as curing agents, fillers, and modifiers based on their dosage and function. Curing agents and fillers, as the main components of the powder additive, primarily ensure the basic strength, flowability, and stability of the molding sand. Modifiers are added in smaller quantities and come in a variety of types and functions, usually used to adjust the overall properties of the inorganic sand. However, during use, due to the small dosage and varying particle size distribution of the modifier, it is often not well dispersed and cannot fully exert its function, resulting in material waste. The addition of large amounts of composite powder often leads to a decrease in the moisture resistance of the inorganic sand core, resulting in poor collapsibility of the obtained inorganic sand core and difficulty in cleaning the castings, thus affecting the efficiency and yield of industrial production.
[0004] Therefore, research was conducted on modifiers in powder additives to prepare a high-performance modified powder additive to solve the problems of poor moisture resistance and reduced collapsibility of inorganic sand cores. This is crucial for improving the overall performance of sand cores and ensuring industrial production efficiency. Summary of the Invention
[0005] The first technical problem to be solved by this application is to provide a modifier for inorganic sand in order to address the current state of the prior art. This modifier is used to modify the matrix material of inorganic sand powder additives, so that the modified powder additives can solve the problems of poor moisture resistance and poor collapsibility of inorganic sand cores.
[0006] The second technical problem to be solved by this application is to provide a composite modified powder additive for casting inorganic sand modified by the above-mentioned modifier.
[0007] The third technical problem to be solved by this application is to provide a method for preparing the above-mentioned composite modified powder additive, which adopts a graded mixing preparation procedure based on particle size distribution to uniformly disperse the components of the powder additive, so that the characteristics of each component can be fully utilized.
[0008] The fourth technical problem to be solved by this application is to provide an application of the above-mentioned composite modified powder additive for casting inorganic sand in the preparation of a two-component inorganic binder for casting.
[0009] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows:
[0010] In a first aspect, this application provides a modifier for a powder additive for casting inorganic sand, comprising the following components in the following mass percentages: sodium aluminate 5wt.%-15wt.%, inorganic phosphate 5wt.%-15wt.%, nano calcium carbonate 5wt.%-15wt.%, and whiskers 5wt.%-10wt.%.
[0011] This application emphasizes the use of inorganic phosphates and nano-calcium carbonate in the raw material composition of the modifier. Inorganic phosphates have a high coefficient of thermal expansion, while nano-calcium carbonate decomposes at high temperatures, reducing the high-temperature residual strength of the sand core and improving the collapsibility of the inorganic sand. Furthermore, this application emphasizes the use of whiskers with diameters between 10,000 and 300,000 mesh and sodium aluminate in the raw material composition of the modifier. Sodium aluminate has a reinforcing effect. The whiskers themselves have a fine structure and excellent mechanical properties such as high strength and high modulus. In the composite modified binder, they can be uniformly dispersed, acting as a skeleton to form fiber composite materials. The presence of whiskers can develop a directional structure without producing anisotropy, reducing defect formation, effectively transferring stress, and preventing crack propagation. This can increase the cohesive strength of the cured product, reduce weak points, and significantly improve mechanical strength. At the same time, the fiber shape can form a crisscrossing network structure similar to a woven bag in the curing system, which can lock in solid particles such as curing agents and fillers, improving the water resistance of the sand core.
[0012] Furthermore, the sodium aluminate has a particle size between 300 mesh and 2000 mesh, the inorganic phosphate has a particle size between 3000 mesh and 5000 mesh, the nano-calcium carbonate has a particle size between 7000 mesh and 10000 mesh, and the whiskers have a whisker diameter between 10000 mesh and 300000 mesh and an aspect ratio between 50 and 1000.
[0013] According to the technical solution of this application, the material formulation of the modifier adopts a particle size distribution design, which uses particle size distribution to uniformly disperse each component, improves the packing efficiency of the powder, makes the modifier more uniformly dispersed during mixing, and allows each component to fully exert its own characteristics during use.
[0014] Preferably, the sodium aluminate can be selected from one or more particles with a particle size between 300-450 mesh, 600-900 mesh, or 1000-2000 mesh.
[0015] Preferably, the inorganic phosphate can be selected from one or more substances selected from orthophosphate, condensed phosphate, pyrophosphate, metaphosphate, and phosphite.
[0016] Preferably, the nano-calcium carbonate can be selected from one or more particles with a particle size between 7000 mesh-8500 mesh or 9000 mesh-10000 mesh.
[0017] Preferably, the whiskers can be one or more of the following substances: silicon carbide whiskers, silicon nitride whiskers, calcium carbonate whiskers, and potassium titanate whiskers.
[0018] Secondly, this application provides a composite modified powder additive for casting inorganic sand, the powder additive comprising a matrix material and the modifier described in the first aspect, wherein the matrix material is modified by the modifier to form the composite modified powder additive.
[0019] Preferably, the matrix material comprises the following components by mass percentage as follows: 20wt.%-60wt.% microsilica powder, which constitutes the main component of the powder additive and is used as a curing agent. More preferably, the microsilica powder can be non-crystalline silica, which is more conducive to improving the strength of the casting sand core and ensuring its performance. Even more preferably, the microsilica powder is selected as high-purity microsilica powder with a silica content of over 95%, which is more conducive to improving the strength and moisture resistance of the sand core.
[0020] Furthermore, the matrix material also includes the following components by mass percentage as described in the composite modified powder additive: 5wt.%-15wt.% of lamellar island material; the lamellar island material is a powdered inorganic material belonging to the monoclinic or hexagonal crystal system, and its microscopic morphology is an irregular island-shaped block. When viewed in longitudinal section, its structure presents a lamellar structure. This type of material has excellent slipperiness when touched by fingers, and the particles are very fine. It is a type of lamellar inorganic mineral powder that can withstand high temperatures above 800℃. Its special shape and physical properties help reduce the agglomeration problem of microsilica powder, allowing microsilica powder to better exert its curing effect.
[0021] Furthermore, the average particle size of the microsilica powder is less than 1 μm, and the particle size of the lamellar island material is between 50 mesh and 1250 mesh. The lamellar island material forms a particle size distribution with the microsilica powder, and the larger particle size of the lamellar island material allows it to fill the spaces between the microsilica powder particles. More preferably, the microsilica powder is amorphous silica with an average particle size between 0.2 and 0.4 μm.
[0022] Preferably, the layered island material can be selected from one or more of the following: muscovite powder, biotite powder, sericite powder, graphite, sodium bentonite, calcined kaolin, hydrotalcite, and montmorillonite.
[0023] Furthermore, the matrix material also includes components comprising the following percentages by mass of the composite modified powder additive: 5 wt.%-10 wt.% spherical silicates; the particle size of the spherical silicates is between 200 mesh and 1500 mesh. The matrix material composition emphasizes the role of spherical silicates. The ultrafine, spherical silicate powder acts as a flow aid, ensuring its uniform distribution on the rough, uneven surface of the sand particles. This isolates the sand particles from direct contact, and the movement of the sand particles is achieved through the rolling of the ultrafine spheres. This significantly reduces the frictional resistance between the sand particles and changes the original interlocking state between the sand particles to interlocking between the sand particles and the spherical flow aid, as well as interlocking between the spherical flow aids. This greatly reduces the interlocking frictional resistance of the molding sand system and improves the flowability of the molding sand.
[0024] Preferably, the spherical silicate can be selected from one or more of the following substances: hollow glass microspheres, solid glass microspheres, and spherical silica powder.
[0025] Furthermore, the matrix material also includes components comprising, by mass percentage of the composite modified powder additive, the following: 5 wt.%-10 wt.% active metal oxide; the particle size of the active metal oxide is between 5000 mesh and 10000 mesh. The use of active metal oxide is emphasized in the matrix material composition. Active metal oxide itself possesses characteristics such as fine particle size, large specific surface area, and the ability to absorb moisture. In addition, it can chemically react with liquid binders and participate in the curing process of the binder, thereby improving the strength of the inorganic sand core.
[0026] Preferably, the active metal oxide can be selected from one or more substances selected from active alumina, active magnesium oxide, active iron oxide, and active copper oxide.
[0027] According to the technical solution of this application, the various components of the composite modified powder additive utilize particle size distribution design, which can effectively improve the packing efficiency of the powder and improve the agglomeration problem.
[0028] Thirdly, this application provides a method for preparing the above-mentioned composite modified powder additive for casting, comprising the following steps:
[0029] A. Prepare a powder additive for inorganic sand casting. Measure each component of the matrix material and add each component to a mixer in descending order of particle size for mixing and dispersion. During the feeding and mixing process, start the mixer for mixing and stirring each time a new material is added to obtain a powder additive for inorganic sand casting based on particle size distribution.
[0030] B. Modify the powder additive for inorganic sand in casting obtained in step A. Measure each component of the modifier and add them to the material obtained in step A in descending order of particle size. During the feeding and stirring process, start the mixing machine for each added raw material. After all the above steps are completed, continue stirring for a period of time to obtain a composite modified powder additive for inorganic sand in casting based on particle size distribution.
[0031] According to the technical solution of this application, the powder additive is prepared by using a graded mixing process based on particle size distribution to achieve dispersion and mixing of each component. This can make the components in the powder additive uniformly dispersed, and allow small-diameter particles to fill the gaps between large-diameter particles, effectively improving the packing efficiency of the powder.
[0032] Preferably, the preparation of the powder additive for inorganic foundry sand in step A may include the following steps: Measuring the following raw materials: 1. Microsilica powder, 2. Layered lamellar / island material, 3. Spherical silicates, 4. Active metal oxides; First, 30%-100% by mass of microsilica powder is added to a mixer for stirring and dispersion; Second, the layered lamellar / island inorganic material is added to the mixer from the first step and dispersed and mixed evenly; Third, the remaining percentage by mass of microsilica powder is added to the mixer from the second step and dispersed and mixed evenly; Then, the remaining raw materials are added sequentially according to their labels to the material obtained in the third step. During the addition and stirring process, the mixer is turned on and stirred after each addition of a raw material; After all the above steps are completed, the mixer is turned on for a period of time to obtain a powder additive for inorganic foundry sand based on particle size distribution. The main reason for adding microsilica powder in two steps is that the amount of microsilica powder added is relatively large and it tends to agglomerate significantly during use. In order to better and more evenly disperse the microsilica powder, it is dispersed in two steps using layered lamellar / island material, which can further achieve a very good dispersion effect.
[0033] Preferably, in order to achieve thorough mixing, in steps A and B, the machine is turned on and mixed for 1-5 minutes after each addition of a raw material, and after the last raw material is added, the machine is turned on and mixed for 3-5 minutes.
[0034] Fourthly, this application provides an application of the composite modified powder additive described in the second aspect above in the manufacture of a two-component inorganic binder for casting.
[0035] Based on the above applications, the technical solution of this application provides a two-component inorganic binder for casting, which includes a water glass-based binder and the composite modified powder additive mentioned in the second aspect above, wherein the amount of the composite modified powder additive used accounts for 1 / 3 to 2 / 3 of the amount of the binder.
[0036] Furthermore, the technical solution of this application also provides an inorganic sand mixture for casting, comprising: raw sand and the aforementioned two-component inorganic binder, wherein the amount of binder used in the two-component inorganic binder is 2-3% of the raw sand, and the amount of composite modified powder additive used is 1 / 3 to 2 / 3 of the amount of binder used. This inorganic sand mixture has good fluidity and mold filling performance, and inorganic sand cores prepared using it have high strength and stability.
[0037] Furthermore, the technical solution of this application also provides a method for using the above-mentioned composite modified powder additive. The method utilizes the prepared composite modified powder additive to prepare inorganic sand cores, and evaluates the performance of the powder additive for casting inorganic sand by assessing the fluidity, strength, stability, and other properties of the prepared inorganic sand core samples. This method includes the following steps:
[0038] (1) Sand mixing:
[0039] After obtaining the composite modified powder additive for casting inorganic sand, commercially available industrial liquid water glass binder and commercially available industrial raw sand are packaged separately. The raw sand, liquid water glass binder, and composite modified powder additive are mixed evenly to obtain an inorganic sand composition.
[0040] (2) Preparation of inorganic sand cores:
[0041] Inorganic sand composition is used to make inorganic sand cores.
[0042] For uniform mixing, step (1) preferably includes the following steps: at room temperature, the composite modified powder additive and the original sand are first mixed in a sand mixer for 0.5 to 3 minutes. After uniform mixing, the resulting mixture is then uniformly mixed with liquid water glass binder for another 0.5 to 3 minutes. After uniform mixing, the sand can be discharged to obtain inorganic mortar. If a large amount of material is added, the mixing time can be increased by 1 to 2 minutes, but the time should not exceed 5 minutes. This is because if the time is too long, the friction between the sand and the sand mixer will generate heat, causing the sand to start to solidify prematurely, affecting its strength.
[0043] To ensure the moisture resistance and collapse resistance of the sand core, step (2) preferably includes the following steps: adding inorganic mortar to the sand hopper of the core shooter, preheating the sample mold to 180-200℃, and using compressed air to inject the inorganic sand composition into the mold cavity under a pressure of 0.1-0.6 MPa. Then, blowing hot air at 180-200℃ into the mold cavity at a pressure of 0.1-0.6 MPa for 10-120 seconds. After the sand core hardens, the box is opened and the sand core is ejected. The sand core can be used on the same day or stored for more than 3 days before use.
[0044] Compared with the prior art, the advantages of the present invention are as follows: the material formulation of the composite modified powder additive, especially the graded mixing preparation process based on particle size distribution, is used to uniformly disperse the components of the composite modified powder additive by utilizing particle size distribution, thereby improving the packing efficiency of the powder. During use, each component can give full play to its own characteristics, thereby solving the problems of poor moisture resistance and poor collapsibility of inorganic sand cores, improving the overall performance of sand cores and ensuring industrial production efficiency. Attached Figure Description
[0045] Figure 1 The residual strength comparison diagrams of the sand cores in Comparative Example 1 and Examples 1-3 provided in this application are used to evaluate the collapsibility of inorganic sand.
[0046] Figure 2 This is a schematic diagram of the sample preparation mold used to prepare long strip-shaped sand core samples in the sand core bending strength test in each embodiment and comparative example;
[0047] Figure 3 This is a schematic diagram of the sample preparation mold used to prepare cylindrical sand core samples in the sand core collapse test in each embodiment and comparative example. Detailed Implementation
[0048] The technical features and advantages of this application will be described in more detail below with reference to embodiments and comparative examples, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of this invention.
[0049] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0050] In each embodiment and comparative example, several elongated sand core samples were prepared to assess the strength properties of the inorganic sand. The sample preparation mold for the elongated samples is described in [reference needed]. Figure 2 As shown; several cylindrical sand core samples were prepared to assess the collapsibility of inorganic sand. The sample preparation mold for the cylindrical samples is shown in [reference needed]. Figure 3 As shown.
[0051] Comparative Example 1:
[0052] Step (1), Preparation of powder additives for casting inorganic sand
[0053] Weigh out 10g of microsilica powder, 5g of 325-mesh muscovite powder, 2.5g of 200-1500-mesh hollow glass microspheres, and 2.5g of 5000-mesh activated alumina according to the formula. Add 5g of microsilica powder to a conical double-helix mixer and stir for 1 minute. Then, add 5g of muscovite powder, 5g of microsilica powder, 2.5g of hollow glass microspheres, and 2.5g of activated alumina to the conical double-helix mixer in sequence and stir for 2 minutes after each addition. After all the above steps are completed, continue stirring for 5 minutes to obtain a powder additive for foundry inorganic sand.
[0054] Step (2), weighing
[0055] Weigh 50g of industrial liquid sodium silicate water glass with a modulus of 2.3 and a solid content of 43%, 15g of powder additive for casting inorganic sand prepared in step (1), and 2.5kg of Dalin scrubbing silica sand with a particle size of 50 / 100 mesh, and pour them into containers for later use.
[0056] Step (3), Sand mixing
[0057] According to the formula, first mix 15g of powdered additive for foundry inorganic sand with 2.5kg of 50 / 100 mesh Dalin scrubbed silica sand in a sand mixer for 0.5 to 3 minutes. After mixing evenly, mix the resulting mixture with 50g of liquid sodium silicate and continue mixing for 0.5 to 3 minutes. After mixing evenly, the sand can be discharged.
[0058] Step (3), prepare inorganic sand cores
[0059] The mixed core-making composition is added to the core shooter hopper. The experimental molds for elongated and cylindrical specimens are preheated to 200°C. Under a pressure of 0.3 MPa, the core-making composition is injected into the mold cavity using an inorganic core shooter with compressed air. Then, 180°C hot air is blown into the core cavity at a pressure of 0.3 MPa for 60 seconds. After the core hardens, it is ejected from the box. The core can be used on the same day or stored for more than 3 days before use.
[0060] Example 1:
[0061] Step (1): Preparation of composite modified powder additives for casting inorganic sand
[0062] Weigh out 10g of microsilica powder, 5g of 325-mesh muscovite powder, 2.5g of 200-1500-mesh hollow glass microspheres, and 2.5g of 5000-mesh activated alumina according to the formula. Add 5g of microsilica powder to a conical double-helix mixer and stir for 1 minute. Then, add 5g of muscovite powder, 5g of microsilica powder, 2.5g of hollow glass microspheres, and 2.5g of activated alumina to the conical double-helix mixer in sequence and stir for 2 minutes after each addition. After all the above steps are completed, continue stirring for 5 minutes to obtain a powder additive for foundry inorganic sand.
[0063] The above-prepared powder additive for inorganic foundry sand was subjected to composite modification. The following raw materials were measured: 12.5g of 300-450 mesh sodium aluminate, 22.5g of 3000 mesh metaphosphate, 32.5g of 10000 mesh nano calcium carbonate, and 41g of 15000 mesh potassium titanate whiskers as the modifying raw materials for the powder additive for inorganic foundry sand. These raw materials were added to the powder additive for inorganic foundry sand in the order of their labels. During the addition and stirring process, the mixing machine was turned on and stirred after each addition of a raw material. After all the above steps were completed, the mixing machine was turned on for a period of time to obtain a composite modified powder additive for inorganic foundry sand based on particle size distribution.
[0064] Step (2), weighing
[0065] Weigh 50g of industrial liquid sodium silicate water glass with a modulus of 2.3 and a solid content of 43%, 15g of composite modified powder additive for casting inorganic sand prepared in step (1), and 2.5kg of Dalin scrubbing silica sand with a particle size of 50 / 100 mesh, and pour them into containers for later use.
[0066] Step (3), Sand mixing
[0067] According to the formula, first mix 15g of composite modified powder additive for foundry inorganic sand with 2.5kg of 50 / 100 mesh Dalin scrubbed silica sand in a sand mixer for 0.5-3 minutes. After mixing evenly, mix the resulting mixture with 50g of liquid sodium silicate and continue mixing for 0.5-3 minutes. After mixing evenly, the sand can be discharged.
[0068] Step (3), prepare inorganic sand cores
[0069] The mixed core-making composition is added to the core shooter hopper. The experimental molds for elongated and cylindrical specimens are preheated to 200°C. Under a pressure of 0.3 MPa, the core-making composition is injected into the mold cavity using an inorganic core shooter with compressed air. Then, 180°C hot air is blown into the core cavity at a pressure of 0.3 MPa for 60 seconds. After the core hardens, it is ejected from the box. The core can be used on the same day or stored for more than 3 days before use.
[0070] Example 2:
[0071] Step (1): Preparation of composite modified powder additives for casting inorganic sand
[0072] Weigh out 10g of microsilica powder, 5g of 325-mesh muscovite powder, 2.5g of 200-1500-mesh hollow glass microspheres, and 2.5g of 5000-mesh activated alumina according to the formula. Add 5g of microsilica powder to a conical double-helix mixer and stir for 1 minute. Then, add 5g of muscovite powder, 5g of microsilica powder, 2.5g of hollow glass microspheres, and 2.5g of activated alumina to the conical double-helix mixer in sequence and stir for 2 minutes after each addition. After all the above steps are completed, continue stirring for 5 minutes to obtain a powder additive for foundry inorganic sand.
[0073] The above-prepared powder additive for inorganic foundry sand was subjected to composite modification. The following raw materials were measured: 12.5g of 600-900 mesh sodium aluminate, 22.5g of 5000 mesh metaphosphate, 32.5g of 7000 mesh nano calcium carbonate, and 41g of 200000 mesh potassium titanate whiskers as the modifying raw materials for the powder additive for inorganic foundry sand. These raw materials were added to the powder additive for inorganic foundry sand in the order of their labels. During the addition and stirring process, the mixing machine was turned on and stirred after each addition of raw materials. After all the above steps were completed, the mixing machine was turned on for a period of time to obtain a composite modified powder additive for inorganic foundry sand based on particle size distribution.
[0074] Step (2), weighing
[0075] Weigh 50g of industrial liquid sodium silicate water glass with a modulus of 2.3 and a solid content of 43%, 15g of composite modified powder additive for casting inorganic sand prepared in step (1), and 2.5kg of Dalin scrubbing silica sand with a particle size of 50 / 100 mesh, and pour them into containers for later use.
[0076] Step (3), Sand mixing
[0077] According to the formula, first mix 15g of composite modified powder additive for foundry inorganic sand with 2.5kg of 50 / 100 mesh Dalin scrubbed silica sand in a sand mixer for 0.5-3 minutes. After mixing evenly, mix the resulting mixture with 50g of liquid sodium silicate and continue mixing for 0.5-3 minutes. After mixing evenly, the sand can be discharged.
[0078] Step (3), prepare inorganic sand cores
[0079] The mixed core-making composition is added to the core shooter hopper. The experimental molds for both elongated and cylindrical specimens are preheated to 200°C. Under a pressure of 0.3 MPa, the core-making composition is injected into the mold cavity using compressed air via an inorganic core shooter. Then, 180°C hot air is blown into the core cavity at a pressure of 0.3 MPa for 60 seconds. After the core hardens, it is ejected from the mold. The core can be used on the same day or stored for more than 3 days before use.
[0080] Example 3:
[0081] Step (1): Preparation of composite modified powder additives for casting inorganic sand
[0082] Weigh out 10g of microsilica powder, 5g of 325-mesh muscovite powder, 2.5g of 200-1500-mesh hollow glass microspheres, and 2.5g of 5000-mesh activated alumina according to the formula. Add 5g of microsilica powder to a conical double-helix mixer and stir for 1 minute. Then, add 5g of muscovite powder, 5g of microsilica powder, 2.5g of hollow glass microspheres, and 2.5g of activated alumina to the conical double-helix mixer in sequence and stir for 2 minutes after each addition. After all the above steps are completed, continue stirring for 5 minutes to obtain a powder additive for foundry inorganic sand.
[0083] The above-prepared powder additive for inorganic foundry sand was subjected to composite modification. The following raw materials were measured: 12.5g of 1000-2000 mesh sodium aluminate, 22.5g of 4000 mesh metaphosphate, 32.5g of 8000 mesh nano calcium carbonate, and 41g of 250000 mesh potassium titanate whiskers as the modifying raw materials for the powder additive for inorganic foundry sand. These raw materials were added to the powder additive for inorganic foundry sand in the order of their labels. During the addition and stirring process, the mixing machine was turned on and stirred after each addition of raw materials. After all the above steps were completed, the mixing machine was turned on and stirred for a period of time to obtain a composite modified powder additive for inorganic foundry sand based on particle size distribution.
[0084] Step (2), weighing
[0085] Weigh 50g of industrial liquid sodium silicate water glass with a modulus of 2.3 and a solid content of 43%, 15g of composite modified powder additive for casting inorganic sand prepared in step (1), and 2.5kg of Dalin scrubbing silica sand with a particle size of 50 / 100 mesh, and pour them into containers for later use.
[0086] Step (3), Sand mixing
[0087] According to the formula, first mix 15g of composite modified powder additive for foundry inorganic sand with 2.5kg of 50 / 100 mesh Dalin scrubbed silica sand in a sand mixer for 0.5-3 minutes. After mixing evenly, mix the resulting mixture with 50g of liquid sodium silicate and continue mixing for 0.5-3 minutes. After mixing evenly, the sand can be discharged.
[0088] Step (3), prepare inorganic sand cores
[0089] The mixed core-making composition is added to the core shooter hopper. The elongated and cylindrical specimen molds are preheated to 200°C. Under a pressure of 0.3 MPa, the core-making composition is injected into the elongated specimen mold cavity using compressed air via an inorganic core shooter. Then, 180°C hot air is blown into the core cavity at a pressure of 0.3 MPa for 60 seconds. After the core hardens, it is ejected from the box. The core can be used on the same day or stored for more than 3 days before use.
[0090] The prepared elongated sand samples were tested using a strength tester at the same temperature and humidity. The thermal strength (<1 min) and cold strength (1 h, 24 h, 72 h) of the samples were measured. Five samples were measured each time, and the truncated average value was taken as the final strength to evaluate its strength performance. The elongated samples were placed at 25℃ and 80%RH for 8 hours, and then tested again using a strength tester. Five samples were measured each time, and the truncated average value was taken as the final strength. This was compared with the highest cold strength, and the percentage decrease in strength was used as the standard for measuring water resistance. Specific performance data are detailed in Table 1. In Examples 1 to 3, inorganic binder sand was prepared using modified powders with different proportions. Comparative Example 1 was a blank group, using inorganic binder sand prepared with unmodified powder additives.
[0091] Table 1. Test results of strength and water resistance of inorganic binder sand
[0092]
[0093] As shown in Table 1, compared with Comparative Example 1, Examples 1-3 showed improved cold strength and hot strength, and water resistance was improved by more than 20% to 30%. The composite modified powder additive improved the strength and water resistance of inorganic sand, indicating that the modifier had good dispersibility during the sand mixing process. The addition of the modifier played a positive role in improving the strength and water resistance of the sand core.
[0094] The residual strength of the prepared cylindrical specimens after calcination at 710℃ for 5 minutes and subsequent exposure to room temperature was tested to evaluate their collapsibility. Specific performance parameters are detailed in [link to relevant documentation]. Figure 1 .Depend on Figure 1It can be seen that the collapsibility of the modified inorganic sand is better, which also indicates that the modifier has good dispersibility during the sand mixing process. The addition of the modifier plays a good role in improving the collapsibility of the sand core.
[0095] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made based on the content of this specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.
Claims
1. A modifier for inorganic casting sand, used to modify the matrix material of powder additives for inorganic casting sand, characterized in that, The modifier comprises the following components in the following mass percentages of the powder additive: sodium aluminate 5wt.%-15wt.%, inorganic phosphate 5wt.%-15wt.%, nano calcium carbonate 5wt.%-15wt.%, and whiskers 5wt.%-10wt.%. The sodium aluminate has a particle size between 300 mesh and 2000 mesh, the inorganic phosphate has a particle size between 3000 mesh and 5000 mesh, the nano-calcium carbonate has a particle size between 7000 mesh and 10000 mesh, and the whiskers have a whisker diameter between 10000 mesh and 300000 mesh and an aspect ratio between 50 and 1000.
2. The modifier according to claim 1, characterized in that, The inorganic phosphate is selected from one or more substances selected from orthophosphate, condensed phosphate, pyrophosphate, metaphosphate, and phosphite.
3. The modifier according to claim 1, characterized in that, The whiskers are selected from one or more of the following substances: silicon carbide whiskers, silicon nitride whiskers, calcium carbonate whiskers, and potassium titanate whiskers.
4. A composite modified powder additive for casting inorganic sand, characterized in that, The additive comprises a matrix material and the modifier as described in claim 1, wherein the matrix material is modified using the modifier to form the composite modified powder additive.
5. The composite modified powder additive according to claim 4, characterized in that, The matrix material comprises the following components in the following mass percentages of the composite modified powder additive: 20wt.%-60wt.% microsilica powder, 5wt.%-15wt.% lamellar island material; wherein the lamellar island material is a powdered inorganic material belonging to the monoclinic or hexagonal crystal system, and its microscopic morphology is an obvious irregular island block, and its structure is a lamellar structure when viewed from the longitudinal section. The average particle size of the microsilica powder is less than 1 μm; the particle size of the lamellar island material is between 50 mesh and 1250 mesh.
6. The composite modified powder additive according to claim 5, characterized in that, The layered island-like material is selected from one or more of the following: muscovite powder, biotite powder, sericite powder, graphite, sodium bentonite, calcined kaolin, hydrotalcite, and montmorillonite.
7. The composite modified powder additive according to claim 5, characterized in that, The matrix material further comprises the following components in the mass percentage of the composite modified powder additive: 5wt.%-10wt.% spherical silicates; the particle size of the spherical silicates is between 200 mesh and 1500 mesh.
8. The composite modified powder additive according to claim 7, characterized in that, The matrix material further includes the following components by mass percentage as described in the composite modified powder additive: 5 wt.%-10 wt.% active metal oxide; the particle size of the active metal oxide is between 5000 mesh and 10000 mesh.
9. The method for preparing the composite modified powder additive according to any one of claims 4 to 8, characterized in that, Includes the following steps: A. Prepare a powder additive for inorganic sand casting. Measure each component of the matrix material and add each component to a mixer in descending order of particle size for mixing and dispersion. During the feeding and mixing process, start the mixer for mixing and stirring each time a new material is added to obtain a powder additive for inorganic sand casting based on particle size distribution. B. Modify the powder additive for inorganic sand in casting obtained in step A. Measure each component of the modifier and add them to the material obtained in step A in descending order of particle size. During the feeding and stirring process, start the mixing machine for each added raw material. After all the above steps are completed, continue stirring for a period of time to obtain a composite modified powder additive for inorganic sand in casting based on particle size distribution.
10. The application of the composite modified powder additive for casting inorganic sand according to any one of claims 4 to 8 in the preparation of a two-component inorganic binder for casting.
11. The application of the composite modified powder additive for casting inorganic sand according to claim 10 in the preparation of a two-component inorganic binder for casting, characterized in that, The two-component inorganic binder includes a water glass-based binder and a composite modified powder additive as described in any one of claims 4-8, wherein the amount of the composite modified powder additive used accounts for 1 / 3 to 2 / 3 of the amount of the binder.