Casting coating composition and preparation and use method thereof

Abstract

The invention relates to a casting coating composition which is suitable for high-alloy steel castings and comprises a coating I, a coating II and a coating III, the refractory aggregate in the coating I comprises the refractory aggregate I and the refractory aggregate II, the refractory aggregate I comprises the following chemical components in percentage by mass: 5-30% of Cr2O3 and 70-95% of Al2O3, the refractory aggregate II comprises the following chemical components in percentage by mass: 10-50% of MgO and 50-90% of Al2O3, and the weight ratio of the refractory aggregate I to the refractory aggregate II is (1: 3)-(3: 1); the refractory aggregate III in the coating II comprises the following chemical components in percentage by mass: 20%-40% of ZrO2 and 60%-80% of Al2O3; the refractory aggregate IV in the coating III comprises the following chemical components in percentage by mass: 50%-70% of ZrO2 and 30%-50% of SiO2; the coating further comprises a carrier solvent accounting for 20%-50% of the weight of the refractory aggregate and a binder accounting for 0.5%-8% of the weight of the refractory aggregate. And the sand burning problem and the orange peel defect of the high-alloy steel casting are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of casting coatings, and more particularly to a casting coating composition suitable for the production of high-alloy steel castings and a preparation and use method thereof. Background Art

[0002] Alloy steel used in the casting state is also called cast alloy steel. According to its use, alloy cast steel is divided into cast alloy structural steel and special purpose alloy cast steel. The former is low and medium alloy cast steel, which is mainly used to make general mechanical structural parts. The latter is mostly high alloy cast steel, such as wear-resistant cast steel, stainless acid-resistant cast steel, heat-resistant cast steel, cast alloy tool steel, etc. High alloy cast steel is a cast steel with a total alloy element content generally greater than 10%, thus having special performance such as high wear resistance, heat resistance, corrosion resistance and electromagnetic properties. The alloy elements in high alloy castings, chromium and nickel account for a high proportion, and they belong to alkaline steel grades. They have strong corrosiveness at high temperatures. In the actual production of high alloy castings, especially thick-walled high alloy castings, if conventional coatings are used, the surface of the castings is prone to form more serious sand adhesion defects. The castings produced by the chromium ore sand molding process will reduce sand adhesion, but they are prone to form orange peel defects, which seriously affect the appearance quality of the cast steel. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention proposes a casting coating composition suitable for high alloy steel castings and a preparation and use method thereof, which effectively solves the sand-bonding defects and orange peel defects existing in the current high alloy steel casting process. To achieve its purpose, the present invention provides the following technical solutions:

[0004] In one aspect, the present invention provides a casting coating composition, which comprises coating one, coating two and coating three;

[0005] The refractory aggregate in the coating one includes refractory aggregate one and refractory aggregate two, the chemical composition of the refractory aggregate one includes 5% to 30% of Cr2O3 and 70% to 95% of Al2O3 by mass fraction, the chemical composition of the refractory aggregate two includes 10% to 50% of MgO and 50% to 90% of Al2O3 by mass fraction, the weight ratio of the refractory aggregate one to the refractory aggregate two is 1:3 to 3:1, and the coating one also includes a carrier solvent accounting for 20% to 50% of the weight ratio of the refractory aggregate and a binder accounting for 0.5% to 8% of the weight ratio of the refractory aggregate;

[0006] The chemical composition of the refractory aggregate three in the coating two includes 20% to 40% ZrO2 and 60% to 80% Al2O3 by mass fraction, and the coating two also includes a carrier solvent accounting for 20% to 50% by weight of the refractory aggregate three and a binder accounting for 0.5% to 8% by weight of the refractory aggregate three;

[0007] The chemical composition of the refractory aggregate No. 4 in the coating No. 3 includes 50% to 70% ZrO2 and 30% to 50% SiO2 by mass fraction. The coating No. 3 also includes a carrier solvent accounting for 20% to 50% by weight of the refractory aggregate No. 4 and a binder accounting for 0.5% to 8% by weight of the refractory aggregate No. 4.

[0008] Furthermore, refractory aggregate one is Cr2O3-Al2O3 solid solution, refractory aggregate two is MgO-Al2O3 solid solution; refractory aggregate three is ZrO2-Al2O3 solid solution; refractory aggregate four is ZrO2-SiO2 solid solution.

[0009] Furthermore, the mesh size of the refractory aggregate 1 and the refractory aggregate 2 is 325-400 mesh; the mesh size of the refractory aggregate 3 and the refractory aggregate 4 is 200-325 mesh.

[0010] Furthermore, the carrier solvent is a water-soluble solvent or an alcohol solvent; the binder is one or more of rosin, phenolic resin, rosin-modified phenolic resin, polyvinyl alcohol, and yellow dextrin.

[0011] Furthermore, the coating 1, the coating 2 and the coating 3 respectively include a suspending agent and a wetting agent, wherein the suspending agent is one or more of bentonite, attapulgite, sepiolite, and cellulose ether; and the wetting agent is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polyethylene glycol.

[0012] Furthermore, the refractory aggregate in the coating is prepared by a high temperature solid phase sintering method, which specifically includes the following steps:

[0013] Preparation of refractory aggregate 1: Cr2O3 powder and Al2O3 powder are fully mixed, and then pressed into shape. The formed green body is heated to 1800-1850°C for high temperature sintering, kept at this temperature for 1-2 hours, and then cooled, crushed and ball-milled to 325-400 meshes;

[0014] Preparation of refractory aggregate II: MgO powder and Al2O3 powder are fully ball-milled and mixed, and then pressed into shape. The formed body is heated to 1800-1900°C for high-temperature sintering, kept warm for 1-2 hours, and then cooled, crushed and ball-milled to 325-400 mesh.

[0015] Furthermore, the refractory aggregate three is prepared by an electric melting method, which specifically includes the following steps: ZrO2 powder and Al2O3 powder are fully mixed, placed in an electric arc furnace, heated to 2000-2200°C for melt molding, and crushed and ball-milled to 200-325 mesh after cooling.

[0016] Furthermore, refractory aggregate 4 is prepared by a high-temperature solid-phase sintering method, which specifically includes the following steps: ZrO2 powder and SiO2 powder are fully ball-milled and mixed, and then pressed into shape after mixing, and the formed body is heated to 1600-1800°C for high-temperature sintering, kept warm for 1-2 hours, and then cooled, crushed and ball-milled to 200-325 mesh.

[0017] On the other hand, the present invention also aims to provide a method for preparing a casting coating composition, which is as follows:

[0018] The preparation method of coating one comprises the following steps:

[0019] Add a carrier solvent into the coating dispersion kettle, start high-speed dispersion, then add a binder, a suspending agent, and a wetting agent, and disperse at a high speed of 800 to 1500 rpm for 20 to 30 minutes; add the refractory aggregate 1 and the refractory aggregate 2 into the dispersion kettle, and disperse at a high speed of 800 to 1500 rpm for 20 to 30 minutes to obtain coating 1;

[0020] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes, adding the refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes, and thus obtaining coating 2; the preparation method of coating 3 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes, adding the refractory aggregate 4 into the dispersion kettle, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes, and thus obtaining coating 3.

[0021] The present invention also provides a method for using the casting coating composition, which is applied in three layers when applied to the casting sand mold / core, and has a Baume degree of 80 to 110 Be;

[0022] First layer: Apply the coating and dry the coating at the same time, the coating thickness is ≥500μm;

[0023] Second layer: Apply coating 2 and dry the coating, the coating thickness is ≥300μm;

[0024] The third layer: Apply the third coating and dry the coating, the coating thickness is ≥ 200μm;

[0025] The total coating thickness is controlled at 1000-1500 μm;

[0026] When applying the second and third layers, the surface of the previous layer must be dried to at least the point where it does not stick to your fingers before applying the next layer. Air spray or high-pressure airless spray is recommended as the application method.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a coating composition for casting and a preparation and use method thereof. The inventive point of the present invention is that three coatings are used for combined application, and the coatings are specially prepared for refractory aggregates. The refractory aggregates of the three coatings in the present invention are all solid solutions synthesized from high-purity metal oxide refractory materials at high temperature, have low impurity content, higher refractoriness, and better sintering performance. The refractoriness and sintering performance are both better than those of conventional refractory aggregates.

[0029] The coating composition of the present invention is applied in combination using three different types of coatings. The generation of orange peel defects is caused by the corrosion reaction and solid phase diffusion sintering of the basic alloy components in the high alloy casting with the acidic chemical components in the sand mold at high temperature. The refractory aggregate of coating one is a mixture of Cr2O3-Al2O3 solid solution and MgO-Al2O3 solid solution, and its pH is alkaline, which belongs to the same pH category as the high alloy casting of alkaline steel. It does not corrode the molten metal of the high alkaline steel, and effectively isolates the silicon dioxide in the molding silica sand so that it does not react with the highly alkaline molten metal, thereby improving the orange peel defect problem of the high alloy casting. The coating material 2 is a ZrO2-Al2O3 solid solution, which has a neutral pH value and has the characteristics of high refractoriness and being difficult to sinter. The neutrality ensures the corrosion resistance under high temperature conditions, and the characteristic of being difficult to sinter ensures that there will be no large shrinkage tendency during the casting process, ensuring the effective thickness and integrity of the coating, preventing the coating from shrinking and cracking, which leads to coating failure, especially at the R corner position, reducing the risk of coating failure at the R corner and the tendency of metal liquid to penetrate and stick to sand; the refractory aggregate of the coating material 3 is a ZrO2-SiO2 solid solution, which has the characteristic of being easy to sinter, so that it is easy to form a sintering peeling layer at the casting temperature, ensuring the high peeling characteristics of the coating material. The combined coating material of the present invention has good resistance to erosion by molten steel, forms an erosion-resistant layer, and the surface coating material forms a sintering peeling layer, thereby improving the corrosion resistance and anti-sticking sand performance of the coating material, solving the problem of sticking sand of high-alloy steel castings and the orange peel defect of high-alloy steel castings, and improving the peeling property of the coating material. DETAILED DESCRIPTION

[0030] To facilitate understanding of the present invention, the present invention will be described more fully below.

[0031] Implementation case 1:

[0032] This embodiment provides a composite coating for casting, including coating 1, coating 2 and coating 3, and the raw materials and proportions thereof are as follows:

[0033] Coating 1: Coating 1 includes, by mass fraction, 100 parts of refractory aggregate, 40 parts of carrier solvent deionized water, 5 parts of binder polyvinyl alcohol, 5 parts of suspending agent attapulgite, and 0.5 parts of wetting agent fatty alcohol polyoxyethylene ether. Among them, the mesh size of the refractory aggregate is 400 mesh, including refractory aggregate 1 and refractory aggregate 2. The chemical composition of refractory aggregate 1 is 10% Cr2O3 and 90% Al2O3, and the chemical composition of refractory aggregate 2 is 50% MgO and 50% Al2O3. The weight ratio of refractory aggregate 1 to refractory aggregate 2 is 1:3.

[0034] Coating 2: Coating 2 includes 100 parts of refractory aggregate 3, 40 parts of carrier solvent deionized water, 5 parts of binder polyvinyl alcohol, 5 parts of suspending agent attapulgite, and 0.5 parts of wetting agent fatty alcohol polyoxyethylene ether according to the mass fraction ratio. Among them, the chemical composition of refractory aggregate 3 is 20% ZrO2 and 80% Al2O3, and the mesh size is 240 mesh.

[0035] Coating 3: Coating 3 includes 100 parts of refractory aggregate 4, 35 parts of carrier solvent deionized water, 5 parts of binder polyvinyl alcohol, 5 parts of suspending agent attapulgite, and 0.5 parts of wetting agent fatty alcohol polyoxyethylene ether according to the mass fraction ratio. Among them, the chemical composition of refractory aggregate 4 is 70% ZrO2 and 30% SiO2, and the mesh size is 200 mesh.

[0036] The refractory aggregate in coating 1 is prepared by high-temperature solid-phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: The above-mentioned Cr2O3 powder and Al2O3 powder are fully mixed, and the mixture is pressed into shape, and the formed body is heated to 1850°C for high-temperature sintering, kept warm for 1.5 hours, cooled, crushed and ball-milled to 400 mesh. Preparation of refractory aggregate 2: The above-mentioned MgO powder and Al2O3 powder are fully ball-milled and mixed, and the mixture is pressed into shape, and the formed body is heated to 1900°C for high-temperature sintering, kept warm for 2 hours, cooled, crushed and ball-milled to 400 mesh.

[0037] The refractory aggregate three in the coating two is prepared by an electric melting method, specifically comprising: fully mixing the above-mentioned ZrO2 powder and Al2O3 powder, placing them in an electric arc furnace, heating them to 2100°C for melting and forming, and crushing and ball-milling them to 240 mesh after cooling.

[0038] The refractory aggregate 4 in the coating 3 is prepared by a high-temperature solid-phase sintering method, which specifically includes: fully ball-milling and mixing the above-mentioned ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1700°C for high-temperature sintering, keeping it warm for 2 hours, then cooling it, crushing it and ball-milling it to 200 mesh.

[0039] The present embodiment provides a method for preparing a casting coating composition. The method for preparing coating 1 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 30 minutes; adding the above-prepared refractory aggregate 1 and refractory aggregate 2 into a dispersion kettle, and dispersing at a high speed of 1000 rpm for 30 minutes to obtain coating 1;

[0040] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, dispersing at a high speed of 1000 rpm for 30 minutes, adding the above-prepared refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 1000 rpm for 30 minutes to obtain coating 2;

[0041] The preparation method of coating three includes the following steps: adding a carrier solvent into the coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 30 minutes, adding the above-prepared refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 1000 rpm for 30 minutes to obtain coating three.

[0042] The coatings 1, 2 and 3 prepared in the embodiment of the present invention are successively applied to the casting sand mold. In the production of high alloy steel castings, the spraying object is applied in three layers.

[0043] First layer: dilute the coating to 90Be, then apply the first layer of coating by air spraying. After the coating is completed, dry the coating. The first layer of coating is 600μm thick.

[0044] Second layer: dilute the coating 2 to 90Be, then apply the second layer of coating by air spraying. After the coating is completed, dry the coating. The thickness of the second layer of coating is 400μm.

[0045] Second layer: dilute the paint three, the Baume degree is diluted to 90Be, and then use air spray to apply the third layer of paint. After application, the coating is dried. The third layer of coating is applied with a thickness of 300μm.

[0046] Implementation case 2:

[0047] This embodiment provides a composite coating for casting, including coating 1, coating 2 and coating 3, and the raw materials and proportions thereof are as follows:

[0048] Coating 1: Coating 1 includes, by mass fraction, 100 parts of refractory aggregate, 35 parts of carrier solvent ethanol, 3 parts of binder alcohol-soluble phenolic resin, 3 parts of suspending agent sepiolite, and 0.5 parts of wetting agent polyethylene glycol. Among them, the mesh size of the refractory aggregate is 325 meshes, including refractory aggregate 1 and refractory aggregate 2. The chemical composition of refractory aggregate 1 is 20% Cr2O3 and 80% Al2O3, and the chemical composition of refractory aggregate 2 is 40% MgO and 60% Al2O3. The weight ratio of refractory aggregate 1 to refractory aggregate 2 is 1:2.

[0049] Coating 2: Coating 2 includes 100 parts of refractory aggregate 3, 35 parts of carrier solvent ethanol, 3 parts of binder alcohol-soluble phenolic resin, 3 parts of suspending agent sepiolite, and 0.5 parts of wetting agent polyethylene glycol according to the mass fraction ratio. Among them, the chemical composition of refractory aggregate 3 is 30% ZrO2 and 70% Al2O3, and the mesh size is 325 mesh.

[0050] Coating 3: Coating 3 includes 100 parts of refractory aggregate 4, 35 parts of carrier solvent ethanol, 3 parts of binder alcohol-soluble phenolic resin, 3 parts of suspending agent sepiolite, and 0.5 parts of wetting agent polyethylene glycol according to the mass fraction ratio. Among them, the chemical composition of refractory aggregate 4 is 60% ZrO2 and 40% SiO2, and the mesh size is 270 mesh.

[0051] The refractory aggregate in coating 1 is prepared by high-temperature solid-phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: The above-mentioned Cr2O3 powder and Al2O3 powder are fully mixed, and then pressed into shape after mixing. The formed green body is heated to 1850°C for high-temperature sintering, kept warm for 1.5 hours, cooled, crushed and ball-milled to 325 mesh. Preparation of refractory aggregate 2: The above-mentioned MgO powder and Al2O3 powder are fully ball-milled and mixed, and then pressed into shape after mixing. The formed green body is heated to 1850°C for high-temperature sintering, kept warm for 1.5 hours, cooled, crushed and ball-milled to 325 mesh.

[0052] The refractory aggregate three in the coating two is prepared by an electric melting method, specifically comprising: fully mixing the above-mentioned ZrO2 powder and Al2O3 powder, placing them in an electric arc furnace, heating them to 2000°C for melting and forming, and crushing and ball-milling them to 325 mesh after cooling.

[0053] The refractory aggregate 4 in the coating 3 is prepared by a high-temperature solid-phase sintering method, specifically comprising: fully ball-milling and mixing the above-mentioned ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1700°C for high-temperature sintering, keeping it warm for 1.5 hours and then cooling it, crushing and ball-milling it to 270 mesh.

[0054] The present embodiment provides a method for preparing a casting coating composition. The method for preparing coating 1 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1200 rpm for 25 minutes; adding the above-prepared refractory aggregate 1 and refractory aggregate 2 into a dispersion kettle, and dispersing at a high speed of 1200 rpm for 25 minutes to obtain coating 1;

[0055] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, dispersing at a high speed of 1200 rpm for 25 minutes, adding the above-prepared refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 1200 rpm for 25 minutes to obtain coating 2;

[0056] The preparation method of coating three includes the following steps: adding a carrier solvent into the coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1200 rpm for 25 minutes, adding the above-prepared refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 1200 rpm for 25 minutes to obtain coating three.

[0057] The coatings 1, 2 and 3 prepared in the embodiment of the present invention are successively applied to the casting sand mold / core. In the production of high alloy steel castings, the spraying object is applied in three layers.

[0058] First layer: dilute the Baume degree of coating 1 to 95Be, then use air spray to apply the first layer of coating, and dry the coating after application. The first layer of coating is applied with a thickness of 600μm;

[0059] Second layer: dilute the Baume degree of coating 2 to 95Be, then apply the second layer of coating by air spraying, dry the coating after application, and the thickness of the second layer of coating is 300μm;

[0060] Second layer: dilute the Baume degree of coating three to 95Be, and then use air spray to apply the third layer of coating. After application, the coating is dried. The third layer of coating is applied with a thickness of 300μm.

[0061] Implementation case three:

[0062] This embodiment provides a composite coating for casting, including coating 1, coating 2 and coating 3, and the raw materials and proportions thereof are as follows:

[0063] Coating 1: Coating 1 includes, by mass fraction, 100 parts of refractory aggregate, 38 parts of carrier solvent isopropyl alcohol, 3 parts of binder rosin-modified phenolic resin, 3 parts of suspending agent cellulose ether, and 0.3 parts of wetting agent alkylphenol polyoxyethylene ether. Among them, the mesh size of the refractory aggregate is 350 mesh, including refractory aggregate 1 and refractory aggregate 2. The chemical composition of refractory aggregate 1 is 30% Cr2O3 and 70% Al2O3, and the chemical composition of refractory aggregate 2 is 40% MgO and 60% Al2O3. The weight ratio of refractory aggregate 1 and refractory aggregate 2 is 1:1.

[0064] Coating 2: Coating 2 includes 100 parts of refractory aggregate 3, 38 parts of carrier solvent isopropyl alcohol, 3 parts of binder rosin modified phenolic resin, 3 parts of suspending agent cellulose ether, and 0.3 parts of wetting agent alkylphenol polyoxyethylene ether according to the mass fraction ratio. Among them, the chemical composition of refractory aggregate 3 is 40% ZrO2 and 60% Al2O3, and the mesh size is 325 mesh.

[0065] Coating 3: Coating 3 includes, by mass fraction, 100 parts of refractory aggregate 4, 38 parts of carrier solvent isopropyl alcohol, 3 parts of binder rosin modified phenolic resin, 3 parts of suspending agent cellulose ether, and 0.3 parts of wetting agent alkylphenol polyoxyethylene ether. Among them, the chemical composition of refractory aggregate 4 is 50% ZrO2 and 50% SiO2, and the mesh size is 325 mesh.

[0066] The refractory aggregate in coating 1 is prepared by high-temperature solid-phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: The above-mentioned Cr2O3 powder and Al2O3 powder are fully mixed, and then pressed into shape after mixing. The formed green body is heated to 1830°C for high-temperature sintering, kept warm for 1.5 hours, cooled, crushed and ball-milled to 350 mesh. Preparation of refractory aggregate 2: The above-mentioned MgO powder and Al2O3 powder are fully ball-milled and mixed, and then pressed into shape after mixing. The formed green body is heated to 1880°C for high-temperature sintering, kept warm for 1.5 hours, cooled, crushed and ball-milled to 350 mesh.

[0067] The refractory aggregate three in the coating two is prepared by an electric melting method, specifically comprising: fully mixing the above-mentioned ZrO2 powder and Al2O3 powder, placing them in an electric arc furnace, heating them to 2150°C for melting and forming, and crushing and ball-milling them to 325 mesh after cooling.

[0068] The refractory aggregate 4 in the coating 3 is prepared by a high-temperature solid-phase sintering method, specifically including: fully ball-milling and mixing the above-mentioned ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1650°C for high-temperature sintering, keeping it warm for 2 hours and then cooling it, crushing and ball-milling it to 325 mesh.

[0069] The present embodiment provides a method for preparing a casting coating composition. The method for preparing coating 1 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 28 minutes; adding the above-prepared refractory aggregate 1 and refractory aggregate 2 into a dispersion kettle, and dispersing at a high speed of 1000 rpm for 28 minutes to obtain coating 1;

[0070] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, dispersing at a high speed of 1000 rpm for 28 minutes, adding the above-prepared refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 1000 rpm for 28 minutes to obtain coating 2;

[0071] The preparation method of coating three includes the following steps: adding a carrier solvent into the coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 28 minutes, adding the above-prepared refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 1000 rpm for 28 minutes to obtain coating three.

[0072] The coatings 1, 2 and 3 prepared in the embodiment of the present invention are successively applied to the casting sand mold / core. In the production of high alloy steel castings, the spraying object is applied in three layers.

[0073] First layer: dilute the Baume degree of coating 1 to 90Be, then use high-pressure airless spray to apply the first layer of coating, and dry the coating after application. The first layer of coating is applied with a thickness of 500μm;

[0074] Second layer: dilute the Baume degree of coating 2 to 90Be, and then use high-pressure airless spray to apply the second layer of coating. After the application, the coating is dried. The thickness of the second layer of coating is 300μm;

[0075] Second layer: dilute the Baume degree of coating three to 90Be, and then use high-pressure airless spray to apply the third layer of coating. After application, the coating is dried. The third layer of coating is applied with a thickness of 300μm.

[0076] Implementation Case 4:

[0077] This embodiment provides a composite coating for casting, including coating 1, coating 2 and coating 3, and the raw materials and proportions thereof are as follows:

[0078] Coating 1: Coating 1 includes, by mass fraction, 100 parts of refractory aggregate, 30 parts of carrier solvent methanol, 3 parts of binder rosin modified phenolic resin, 8 parts of suspending agent bentonite, and 0.7 parts of wetting agent fatty alcohol polyoxyethylene ether. Among them, the mesh size of the refractory aggregate is 380 mesh, including refractory aggregate 1 and refractory aggregate 2. The chemical composition of refractory aggregate 1 is 25% Cr2O3 and 75% Al2O3, and the chemical composition of refractory aggregate 2 is 20% MgO and 80% Al2O3. The weight ratio of refractory aggregate 1 to refractory aggregate 2 is 2:1.

[0079] Coating 2: Coating 2 includes, by mass fraction, 100 parts of refractory aggregate 3, 30 parts of carrier solvent methanol, 3 parts of binder rosin modified phenolic resin, 8 parts of suspending agent bentonite, and 0.7 parts of wetting agent fatty alcohol polyoxyethylene ether. Among them, the chemical composition of refractory aggregate 3 is 40% ZrO2 and 60% Al2O3, and the mesh size is 270 mesh.

[0080] Coating 3: Coating 3 includes, by mass fraction, 100 parts of refractory aggregate 4, 30 parts of carrier solvent methanol, 3 parts of binder rosin modified phenolic resin, 8 parts of suspending agent bentonite, and 0.7 parts of wetting agent fatty alcohol polyoxyethylene ether. Among them, the chemical composition of refractory aggregate 4 is 66% ZrO2 and 34% SiO2, and the mesh size is 270 mesh.

[0081] The refractory aggregate in coating 1 is prepared by high-temperature solid-phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: The above-mentioned Cr2O3 powder and Al2O3 powder are fully mixed, and then pressed into shape after mixing. The formed green body is heated to 1820°C for high-temperature sintering, kept warm for 1.9 hours, cooled, crushed and ball-milled to 380 mesh. Preparation of refractory aggregate 2: The above-mentioned MgO powder and Al2O3 powder are fully ball-milled and mixed, and then pressed into shape after mixing. The formed green body is heated to 1825°C for high-temperature sintering, kept warm for 2 hours, cooled, crushed and ball-milled to 380 mesh.

[0082] The refractory aggregate three in the coating two is prepared by an electric melting method, specifically comprising: fully mixing the above-mentioned ZrO2 powder and Al2O3 powder, placing them in an electric arc furnace, heating them to 2150°C for melting and forming, and crushing and ball-milling them to 270 mesh after cooling.

[0083] The refractory aggregate 4 in the coating 3 is prepared by a high-temperature solid-phase sintering method, which specifically includes: fully ball-milling and mixing the above-mentioned ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1650°C for high-temperature sintering, keeping it warm for 1.3 hours and then cooling it, crushing and ball-milling it to 270 mesh.

[0084] The present embodiment provides a method for preparing a coating composition for casting, and the preparation method of coating 1 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, and then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 25 minutes; adding the above-prepared refractory aggregate 1 and refractory aggregate 2 into a dispersion kettle, and dispersing at a high speed of 1000 rpm for 25 minutes to obtain coating 1;

[0085] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, dispersing at a high speed of 1000 rpm for 25 minutes, adding the above-prepared refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 1000 rpm for 20 to 30 minutes, thereby obtaining coating 2;

[0086] The preparation method of coating three includes the following steps: adding a carrier solvent into the coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1000 rpm for 25 minutes, adding the above-prepared refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 1300 rpm for 30 minutes to obtain coating three.

[0087] The coatings 1, 2 and 3 prepared in the embodiment of the present invention are successively applied to the casting sand mold / core. In the production of high alloy steel castings, the spraying object is applied in three layers.

[0088] First layer: dilute the Baume degree of coating 1 to 90Be, then use high-pressure airless spray to apply the first layer of coating, and dry the coating after application. The first layer of coating is applied with a thickness of 500μm;

[0089] Second layer: dilute the Baume degree of coating 2 to 90Be, and then use high-pressure airless spray to apply the second layer of coating. After the application, the coating is dried. The thickness of the second layer of coating is 300μm;

[0090] Second layer: dilute the Baume degree of coating three to 100Be, and then use high-pressure airless spray to apply the third layer of coating. After application, the coating is dried. The third layer of coating is applied with a thickness of 250μm.

[0091] Implementation Case 5:

[0092] This embodiment provides a composite coating for casting, including coating 1, coating 2 and coating 3, and the raw materials and proportions thereof are as follows:

[0093] Coating 1: Coating 1 includes, by mass fraction, 100 parts of refractory aggregate, 30 parts of carrier solvent water, 3 parts of binder yellow dextrin, 5 parts of suspending agent attapulgite, 0.7 parts of wetting agent polyethylene glycol, and other additives are 0.25 parts of dispersant and 0.15 parts of preservative. Among them, the mesh number of refractory aggregate is 400 mesh, including refractory aggregate 1 and refractory aggregate 2. The chemical composition of refractory aggregate 1 is 30% Cr2O3 and 70% Al2O3, and the chemical composition of refractory aggregate 2 is 10% MgO and 90% Al2O3. The weight ratio of refractory aggregate 1 and refractory aggregate 2 is 3:1.

[0094] Coating 2: Coating 2 includes, by mass fraction, 100 parts of refractory aggregate 3, 30 parts of carrier solvent water, 3 parts of binder yellow dextrin, 5 parts of suspending agent attapulgite, 0.7 parts of wetting agent polyethylene glycol, and other additives are 0.25 parts of dispersant and 0.15 parts of preservative. Among them, the chemical composition of refractory aggregate 3 is 40% ZrO2 and 60% Al2O3, and the mesh size is 240 mesh.

[0095] Coating 3: Coating 3 includes, by mass fraction, 100 parts of refractory aggregate 4, 30 parts of carrier solvent water, 3 parts of binder yellow dextrin, 5 parts of suspending agent attapulgite, 0.7 parts of wetting agent polyethylene glycol, and other additives are 0.25 parts of dispersant and 0.15 parts of preservative. Among them, the chemical composition of refractory aggregate 4 is 66% ZrO2 and 34% SiO2, and the mesh size is 280 mesh.

[0096] The refractory aggregate in coating 1 is prepared by high-temperature solid phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: the above-mentioned Cr2O3 powder and Al2O3 powder are fully mixed, pressed into shape after mixing, the formed body is heated to 1800°C for high-temperature sintering, kept warm for 2 hours, cooled, crushed and ball-milled to 400 mesh. Preparation of refractory aggregate 2: the above-mentioned MgO powder and Al2O3 powder are fully ball-milled and mixed, pressed into shape after mixing, the formed body is heated to 1900°C for high-temperature sintering, kept warm for 1 hour, cooled, crushed and ball-milled to 400 mesh.

[0097] The refractory aggregate three in the coating two is prepared by an electric melting method, specifically comprising: fully mixing the above-mentioned ZrO2 powder and Al2O3 powder, placing them in an electric arc furnace, heating them to 2100°C for melting and forming, and crushing and ball-milling them to 240 mesh after cooling.

[0098] The refractory aggregate 4 in the coating 3 is prepared by a high-temperature solid-phase sintering method, specifically comprising: fully ball-milling and mixing the above-mentioned ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1800°C for high-temperature sintering, keeping warm for 1 hour and then cooling, crushing and ball-milling to 280 mesh.

[0099] The present embodiment provides a method for preparing a casting coating composition. The method for preparing coating 1 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1500 rpm for 20 minutes; adding the above-prepared refractory aggregate 1 and refractory aggregate 2 into a dispersion kettle, and dispersing at a high speed of 1500 rpm for 20 minutes to obtain coating 1;

[0100] The preparation method of coating 2 comprises the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, dispersing at a high speed of 1500 rpm for 20 minutes, adding the above-prepared refractory aggregate 3 into the dispersion kettle, and dispersing at a high speed of 1500 rpm for 20 minutes to obtain coating 2;

[0101] The preparation method of coating three includes the following steps: adding a carrier solvent into the coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 1500rpm for 20 minutes, adding the above-prepared refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 1500rpm for 20 minutes to obtain coating three.

[0102] The coatings 1, 2 and 3 prepared in the embodiment of the present invention are successively applied to the casting sand mold / core. In the production of high alloy steel castings, the spraying object is applied in three layers.

[0103] First layer: dilute the Baume degree of coating 1 to 100Be, then use high-pressure airless spray to apply the third layer of coating, and dry the coating after application. The first layer of coating is applied with a thickness of 700μm;

[0104] Second layer: dilute the Baume degree of the second coating to 110Be, and then use high-pressure airless spraying to apply the third layer of coating. After the application, the coating is dried. The second layer of coating is applied with a thickness of 400μm;

[0105] Second layer: dilute the Baume degree of coating three to 120Be, and then use high-pressure airless spray to apply the third layer of coating. After application, the coating is dried. The third layer of coating is applied with a thickness of 300μm.

[0106] The properties of the coating composition prepared in the examples were tested. The coating compositions prepared in the comparative examples (currently available coatings on the market) and the above examples were used to verify the coating's anti-sand adhesion performance, peeling performance, and appearance quality of the casting test block.

[0107] The results show that the test pieces of the coatings in Comparative Examples 1 and 2 have signs of sand sticking at the R corners, and there is a slight oxide layer on the surface of the test pieces, with obvious orange peel defects.

[0108] The test piece of the coating prepared in the embodiment of the present invention has no sand adhesion, and the peeling area reaches more than 95%, which can be basically considered to be completely peeled off, and there is no oxide layer on the surface of the test piece and no orange peel defects.

[0109] The coating composition prepared in the embodiment of the present invention is applied in combination. Coating 1 as a base coating has excellent resistance to erosion by molten steel and forms a corrosion-resistant layer, and coating 3 as a surface coating forms a sintered peeling layer, thereby improving the corrosion resistance and anti-sand sticking performance of the coating, solving the problem of sand sticking to high-alloy steel castings; and solving the orange peel defect of high-alloy steel castings.

[0110] Table 1 Performance data comparison table of the embodiments of the present invention and the comparative examples

[0111] Example Anti-sand Peeling layer Surface quality - presence or absence of orange peel defects Comparative Example 1 R corner has sand sticking Stripping area 75% There is a slight oxidation layer, and the orange peel defect is obvious Comparative Example 2 R corner has sand sticking Stripping area 70% There is a slight oxidation layer, and the orange peel defect is obvious Example 1 R corner without sand Stripping area ≥95% No orange peel defects Example 2 R corner without sand Stripping area ≥95% No orange peel defects Example 3 R corner without sand Stripping area ≥95% No orange peel defects Example 4 R corner without sand Stripping area ≥95% No orange peel defects

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A casting coating composition, characterized in that: It comprises coating 1, coating 2 and coating 3; the coating 1 comprises refractory aggregate, the refractory aggregate comprises refractory aggregate 1 and refractory aggregate 2, the chemical composition of the refractory aggregate 1 comprises 5% to 30% of Cr2O3 and 70% to 95% of Al2O3 by mass fraction, the chemical composition of the refractory aggregate 2 comprises 10% to 50% of MgO and 50% to 90% of Al2O3 by mass fraction, the weight ratio of the refractory aggregate 1 to the refractory aggregate 2 is 1:3 to 3:1, and the coating 1 further comprises a carrier solvent accounting for 20% to 50% of the weight ratio of the refractory aggregate and a binder accounting for 0.5% to 8% of the weight ratio of the refractory aggregate; The coating 2 includes refractory aggregate 3, the chemical composition of the refractory aggregate 3 includes 20% to 40% ZrO2 and 60% to 80% Al2O3 by mass fraction, and the coating 2 also includes a carrier solvent accounting for 20% to 50% by weight of the refractory aggregate 3 and a binder accounting for 0.5% to 8% by weight of the refractory aggregate 3; The coating three includes refractory aggregate four, and the chemical composition of the refractory aggregate four includes 50% to 70% ZrO2 and 30% to 50% SiO2 by mass fraction. The coating three also includes a carrier solvent accounting for 20% to 50% of the weight proportion of the refractory aggregate four and a binder accounting for 0.5% to 8% of the weight proportion of the refractory aggregate four.

2. A casting coating composition according to claim 1, characterized in that: The refractory aggregate one is a Cr2O3-Al2O3 solid solution, the refractory aggregate two is a MgO-Al2O3 solid solution; the refractory aggregate three is a ZrO2-Al2O3 solid solution; the refractory aggregate four is a ZrO2-SiO2 solid solution.

3. A casting coating composition according to claim 1, characterized in that: The mesh sizes of the refractory aggregate 1 and the refractory aggregate 2 are 325 to 400 meshes; the mesh sizes of the refractory aggregate 3 and the refractory aggregate 4 are 200 to 325 meshes.

4. A casting coating composition according to claim 1, characterized in that The carrier solvent is a water-soluble solvent or an alcohol solvent; the binder is one or more of rosin, phenolic resin, rosin-modified phenolic resin, polyvinyl alcohol, and yellow dextrin.

5. A casting coating composition according to claim 1, characterized in that: The coating 1, the coating 2 and the coating 3 also include a suspending agent and a wetting agent respectively. The suspending agent is one or more of bentonite, attapulgite, sepiolite and cellulose ether; the wetting agent is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and polyethylene glycol.

6. A casting coating composition according to claim 1, characterized in that: The refractory aggregate 1 and the refractory aggregate 2 are prepared by a high temperature solid phase sintering method, which specifically includes the following steps: Preparation of refractory aggregate 1: Cr2O3 powder and Al2O3 powder are fully mixed, and then pressed into shape. The formed green body is heated to 1800-1850°C for high temperature sintering, kept at this temperature for 1-2 hours, and then cooled, crushed and ball-milled to 325-400 meshes; Preparation of refractory aggregate II: MgO powder and Al2O3 powder are fully ball-milled and mixed, and then pressed into shape. The formed body is heated to 1800-1900°C for high-temperature sintering, kept warm for 1-2 hours, and then cooled, crushed and ball-milled to 325-400 mesh.

7. A casting coating composition according to claim 1, characterized in that: The refractory aggregate three is prepared by an electric melting method, which specifically includes the following steps: ZrO2 powder and Al2O3 powder are fully mixed, placed in an electric arc furnace, heated to 2000-2200°C for melting and forming, and then crushed and ball-milled to 200-325 meshes after cooling.

8. A casting coating composition according to claim 1, characterized in that: The refractory aggregate 4 is prepared by a high-temperature solid-phase sintering method, which specifically includes the following steps: fully ball-milling and mixing ZrO2 powder and SiO2 powder, pressing and molding after mixing, heating the molded body to 1600-1800°C for high-temperature sintering, keeping warm for 1-2 hours and then cooling, crushing and ball-milling to 200-325 meshes.

9. The method for preparing a casting coating composition according to any one of claims 1 to 8, characterized in that: The preparation method of coating one comprises the following steps: A carrier solvent is added to the coating dispersion kettle, high-speed dispersion is started, and then a binder, a suspending agent and a wetting agent are added, and the mixture is dispersed at a high speed of 800 to 1500 rpm for 20 to 30 minutes; the refractory aggregate 1 and the refractory aggregate 2 are added to the dispersion kettle, and the mixture is dispersed at a high speed of 800 to 1500 rpm for 20 to 30 minutes to obtain coating 1; the preparation method of coating 2 comprises the following steps: a carrier solvent is added to the coating dispersion kettle, high-speed dispersion is started, and then a binder, a suspending agent and a wetting agent are added, and the mixture is dispersed at a high speed of 800 to 1500 rpm for 20 to 30 minutes; the refractory aggregate 3 is added to the dispersion kettle, and the mixture is dispersed at a high speed of 800 to 1500 rpm for 20 to 30 minutes to obtain coating 2; The preparation method of coating three includes the following steps: adding a carrier solvent into a coating dispersion kettle, starting high-speed dispersion, then adding a binder, a suspending agent, and a wetting agent, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes, adding the refractory aggregate four into the dispersion kettle, and dispersing at a high speed of 800 to 1500 rpm for 20 to 30 minutes to obtain coating three.

10. A method for using a casting coating composition according to any one of claims 1 to 8, characterized in that: When applying casting sand molds / cores, apply in three layers, with a Baume degree of 80 to 110 Be. First layer: Apply the coating and dry the coating at the same time, the coating thickness is ≥500μm; Second layer: Apply coating 2 and dry the coating, the coating thickness is ≥300μm; The third layer: Apply the third coating and dry the coating, the coating thickness is ≥ 200μm; The total coating thickness is controlled at 1000-1500 μm.