A coating for automotive cylinder block sand cores for wet sand casting and methods of making and using the same

Abstract

The application discloses a kind of coating for automobile cylinder body wet type casting sand core and its preparation, using method, and coating formula is by weight percentage composition: refractory aggregate 30-50%, suspending agent 5-10%, binder 3-7%, dispersing agent 0.9-2.5%, defoaming agent 0.1-0.3%, and suitable carrier liquid.Appropriate amount of water is first added in preparation process, start dispersing machine 450-600rpm, slowly add 2 / 3 suspending agent, then add dispersing agent, stir 5-10min;Afterwards, graphite powder, spodumene, talc and mullite are sequentially added, the speed is adjusted to 1100-1400rpm, and stirred for 30-40min;Afterwards, the speed is reduced to 500-800rpm, and the remaining suspending agent, binder, defoaming agent and appropriate amount of water are sequentially added, and stirred for 15-25min;The ratio of the dispersion disc of the dispersing machine equipment to the stirring barrel is 1:(3-4), and the dispersion disc is a rectangular-toothed circular disc type impeller.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of engine body process materials, and particularly relates to a coating for a wet-type casting sand core of an automobile cylinder body as well as a preparation method and a use method thereof. BACKGROUND

[0002] With the continuous improvement of national energy-saving and emission-reducing regulations and the development of automobile light weight, the wall thickness of an automobile engine cylinder body is required to be smaller and smaller, the shape design is required to be more and more complex, and the internal cavity cleanliness is required to be higher and higher. In the casting production, a series of physical and chemical actions occur between the interface of the molten metal and the surface of the core, which often causes defects such as sand sticking, veining and sand hole in the internal cavity of the cylinder body, thereby affecting the overall quality of the cylinder body and the performance of the engine. The casting coating, as the first line of defense for the sand core against the action of the molten metal in the production of the cylinder body, is of great significance to the guarantee of the internal cavity cleanliness of the cylinder body, which is closely related to the high-temperature resistance and coating hanging characteristics of the coating. The main components of the casting coating include aggregates, carrier liquid, suspending agent, binder and additives, etc. In the production, the main aggregate type and quality are selected according to the application characteristics, and different types of aggregates are matched to meet the high-temperature performance requirements, and then the suspending agent, binder and additives are selected to ensure that the coating has good coating performance.

[0003] At present, the selection of the coating used in the casting production of the automobile engine cylinder body is mainly based on the refractoriness of the coating and the strength of the coating at room temperature, and the coating is insufficiently analyzed under actual application conditions. Due to the selection problems of the material type, characteristics and ratio, the coating often falls off under the action of the high-temperature molten metal, resulting in sand hole and sintering in the internal cavity of the cylinder body, poor air permeability of the coating leading to pores in the casting, poor peeling property of the coating on the surface of the casting leading to sand sticking in the internal cavity of the cylinder body, and unreasonable selection of additives leading to serious flow marks on the surface of the sand core.

[0004] The disclosed casting coating technical solutions are as follows:

[0005] 1. Patent No. 201410737835.5, "Calcined quartz powder casting coating and its manufacturing method", which comprises 80-100 parts of quartz powder, 0-50 parts of corundum powder, 0-100 parts of mullite powder, 0-30 parts of bauxite powder, 0-100 parts of zirconium powder, 0-10 parts of flaky graphite, 0-20 parts of earthy graphite powder, 0-5 parts of red iron oxide, 6-8 parts of suspending agent, 5-8 parts of resin, and an appropriate amount of solvent. The suspending agent, resin and an appropriate amount of solvent are added to a stirrer and stirred for 10-30 minutes. Then, the quartz powder, corundum powder, mullite powder, bauxite powder, zirconium powder, flaky graphite, earthy graphite powder and red iron oxide are added and stirred for 30-60 minutes. An appropriate amount of solvent is added to adjust the specific gravity to obtain the casting coating. The coating uses quartz powder as the main aggregate, which will expand greatly under the action of high-temperature metal above 1440℃, resulting in cracking of the coating layer.

[0006] 2. The patent with the application number 202210358647.6, "A coating for automobile engine gray iron cylinder body sand core and its preparation method", comprises the following raw materials by weight fraction: graphite 5-12 parts, kaolin 2-9 parts, quartz powder 1-8 parts, mica powder 3-9 parts, high-purity bauxite 5-15 parts, base 4-10 parts, and water in appropriate amount. The coating has poor suspensibility, thixotropy, and resistance to metal liquid scouring, which is not suitable for large cylinder body complex structure sand core dipping coating, but only for small cylinder body casting production; and has high gas emission, which is not conducive to casting quality control.

[0007] 3. The patent with the application number 201910904985.3, "Coating for nodular iron wheel hub of wind turbine, preparation method and application", comprises sand core coating and sand mold coating in two independent units: the coating is composed of carrier liquid 20-50 parts by weight, binder 2-5 parts by weight, suspending agent 4-7 parts by weight, and refractory aggregate 50-70 parts by weight; wherein the refractory aggregate of the sand core coating is composed of quartz powder, pyrophyllite, mica powder, mullite, and iron oxide red in a weight ratio of 10-13:9-12:1-4:3-8:0.5-2; the refractory aggregate of the sand mold coating is composed of earthy graphite, flaky graphite, bauxite, and zirconium powder in a weight ratio of 3-7:0.5-3:3-7:1-2. The carrier liquid used in the coating is an organic solvent, which pollutes the environment and has safety risks, and the coating layer on the surface of the corresponding casting after pouring has poor peelability. SUMMARY

[0008] To solve the above problems existing in the prior art, the present application provides a coating for automobile cylinder body wet-type casting sand core and its preparation and use method. The coating has good structure forming ability at room temperature, and the corresponding coating layer is uniform and smooth after being used for complex structure sand core dipping coating, without problems such as flow marks and dripping.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] As a first aspect of the present application, a coating for automobile cylinder body wet-type casting sand core is provided, which has a formulation consisting of refractory aggregate 30-50%, suspending agent 5-10%, binder 3-7%, dispersant 0.9-2.5%, defoaming agent 0.1-0.3%, and carrier liquid in appropriate amount by weight percentage.

[0011] Further, the refractory aggregate is composed of pyrophyllite, mullite, high-purity graphite powder, and spodumene in a weight percentage of (15-20):(10-15):(5-10):(2-6).

[0012] Further, the refractory aggregate is composed of pyrophyllite:mullite:high-purity graphite powder:spodumene in a weight percentage of 17:12:8:3.

[0013] Preferably, the refractory aggregate is composed of the following materials in percentage by mass: 65%≤SiO2%≤70%, 25%≤Al2O3%≤35%, loss on ignition ≤5.5%, particle size of 150-350 mesh; mullite is alumina-based electrically fused, mullite phase ≥75%, glass phase <10%, porosity ≤6%, 66%≤SiO2%≤79%, 20%≤Al2O3%≤28%, particle size of 150-350 mesh; high-purity graphite powder is flaky graphite, fixed carbon 85-90%, moisture ≤0.5%, particle size of 250-350 mesh.

[0014] Further, the suspending agent is composed of one or two of attapulgite, sodium-based bentonite and sepiolite.

[0015] Preferably, the suspending agent is composed of attapulgite and sodium-based bentonite at a ratio of 1:1.

[0016] Further, the binder is one or a mixture of water-based phenolic resin and PVA.

[0017] Further, the dispersing agent is polycarboxylate; the defoaming agent is water-based silicone; and the carrier liquid is water.

[0018] As a second aspect of the present application, a preparation method of a coating for a wet-type casting sand core of an automobile cylinder body is provided, comprising:

[0019] First, a proper amount of water is added, a dispersing machine is started at 450-600 rpm, 2 / 3 of the suspending agent is slowly added, then the dispersing agent is added, and stirring is performed for 5-10 min; then, in sequence, graphite powder, spodumene, pyrophyllite and mullite are added, the stirring speed is adjusted to 1100-1400 rpm, and stirring is performed for 30-40 min; then, the stirring speed is reduced to 500-800 rpm, the binder, the defoaming agent and the remaining suspending agent are added in sequence, a proper amount of water is added, and stirring is performed for 15-25 min; the ratio of the dispersing disc to the stirring barrel of the dispersing machine equipment is 1:(3-4), and the dispersing disc is a rectangular-toothed disc type impeller.

[0020] As a third aspect of the present application, a use method of a coating for a wet-type casting sand core of an automobile cylinder body is provided: the coating is suitable for a cold core prepared by phenolic urea alkane resin, before use, the coating is diluted to 37-40°Bé by water, and the hot exposure level is detected to be grade I; the sand core is immersed in the coating for 2-5 seconds to obtain a uniform and smooth wet coating layer with a thickness of 200-400 um; and the sand core after coating is subjected to surface drying at 170°C for 70 min, and is placed for 4-72 hours before being used for pouring.

[0021] The present application has the following beneficial effects:

[0022] The application provides a coating for a wet-type casting sand core of an automobile cylinder body and a preparation and use method thereof.

[0023] 1. The coating has strong resistance to high-temperature molten metal, and can be ceramized under high temperature to form a dense and solid structure layer to prevent the molten metal from penetrating;

[0024] 2. The coating has suitable thermal conductivity to accelerate the solidification of the molten metal near the surface of the coating;

[0025] 3. The coating has a wide sintering temperature range and forms a thin shell, and the coating can appropriately shrink and expand with temperature change during the heating process, and has very good stripping property;

[0026] 4. The coating has low volatile organic content and low high-temperature gas emission;

[0027] 5. The coating can meet the high-temperature action of 1440-1450 DEG C molten iron for 30 seconds, and the inner cavity of the cylinder body is clean, without sand sticking, vein lines and dust sticking and other impurities, the product has low porosity waste rate, and the impurities in the inner cavity of the product are easy to clean, and the production efficiency is improved. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiments of the application will be described in more detail below. The described embodiments are part of the embodiments of the application, rather than all the embodiments. The embodiments described below are exemplary and are intended to explain the application, and cannot be understood as a limitation on the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0029] In the description of the application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the embodiments, and is only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the application.

[0030] A coating for a wet-type casting sand core of an automobile cylinder body, the formula of the coating comprises, by weight percentage: refractory aggregate 30-50%, suspending agent 5-10%, binder 3-7%, dispersing agent 0.9-2.5%, defoaming agent 0.1-0.3%, and suitable carrier liquid.

[0031] Further, the refractory aggregate is composed of 15-20% by weight of pyrophyllite, 10-15% by weight of mullite, 5-10% by weight of high-purity graphite powder, and 2-6% by weight of spodumene.

[0032] Further, the refractory aggregate is composed of 15-20% by weight of pyrophyllite, 10-15% by weight of mullite, 5-10% by weight of high-purity graphite powder, and 2-6% by weight of spodumene.

[0033] Preferably, the refractory aggregate is composed of the following materials in percentage by mass: 65%≤SiO2%≤70%, 25%≤Al2O3%≤35%, ignition loss≤5.5%, and particle size of 150-350 mesh for pyrophyllite; 66%≤SiO2%≤79%, 20%≤Al2O3%≤28%, particle size of 150-350 mesh for mullite which is prepared by alumina-based electric melting, and mullite phase≥75%, glass phase<10%, and porosity≤6%; and 85-90% of fixed carbon, water content≤0.5%, and particle size of 250-350 mesh for high-purity graphite powder which is flaky graphite.

[0034] Further, the suspending agent is composed of one or two of attapulgite, sodium-based bentonite, and sepiolite.

[0035] Preferably, the suspending agent is composed of attapulgite and sodium-based bentonite at a ratio of 1:1.

[0036] Further, the binder is one or a mixture of water-based phenolic resin and PVA.

[0037] Further, the dispersant is polycarboxylate, the defoaming agent is water-based organic silicon, and the carrier liquid is water.

[0038] A preparation method of a coating for a wet-type sand core of an automobile cylinder, comprising:

[0039] First, a proper amount of water is added, a dispersing machine is started at 450-600 rpm, 2 / 3 of the suspending agent is slowly added, then the dispersant is added, and stirring is performed for 5-10 min; then, the graphite powder, spodumene, pyrophyllite, and mullite are sequentially added, the stirring speed is adjusted to 1100-1400 rpm, and stirring is performed for 30-40 min; then, the stirring speed is reduced to 500-800 rpm, the binder, the defoaming agent, and the remaining suspending agent are sequentially added, a proper amount of water is added, and stirring is performed for 15-25 min; the ratio of the dispersing disc to the stirring barrel of the dispersing machine equipment is 1:(3-4), and the dispersing disc is a rectangular-toothed circular disc type impeller.

[0040] Preferably, the ratio of the dispersing disc to the stirring barrel of the dispersing machine equipment is 1:3.2.

[0041] A method for using a coating for a wet sand core of an automobile cylinder block: the coating is suitable for a cold core prepared from a phenolic urea alkane resin, before use, the coating is diluted to 37-40 °Bé with water, and the hot shock level is grade I; the sand core is immersed in the coating for 2-5 seconds to obtain a uniform and smooth wet coating layer with a thickness of 200-400 um; the coated sand core is dried at 170 °C for 70 min, and is left to stand for 4-72 hours before being used for pouring.

[0042] Example 1

[0043] A coating for a wet sand core of an automobile cylinder block, by weight percentage, refractory aggregate 30-50%, suspending agent 5%, binder 3%, dispersing agent 0.9%, defoaming agent 0.1%, and carrier liquid.

[0044] The refractory aggregate is composed of pyrophyllite, mullite, high-purity graphite powder, and spodumene in a weight percentage of 15:10:5:2; the suspending agent is composed of attapulgite and sodium-based bentonite in a ratio of 1:1; the binder is water-based phenolic resin; the dispersing agent is polycarboxylate; the defoaming agent is water-based organic silicon; and the carrier liquid is water.

[0045] The characteristics and compositions of the raw materials are as follows: pyrophyllite: 65% SiO2, 25% Al2O3, 5.5% loss on ignition, and particle size of 150-350 mesh; mullite is prepared by electric melting based on bauxite, with mullite phase of 75%, glass phase of 10%, porosity of 6%, 66% SiO2, 20% Al2O3, and particle size of 150-25 mesh; and high-purity graphite powder is flaky graphite with fixed carbon of 85%, water content of ≤0.5%, and particle size of 250-350 mesh.

[0046] Example 2

[0047] A coating for a wet sand core of an automobile cylinder block, by weight percentage, refractory aggregate 30-50%, suspending agent 5%, binder 3%, dispersing agent 0.9%, defoaming agent 0.1%, and carrier liquid.

[0048] The refractory aggregate is composed of pyrophyllite: mullite: high-purity graphite powder: spodumene in a weight percentage of 17:12:8:3; the suspending agent is composed of attapulgite and sodium-based bentonite in a ratio of 1:1; the binder is water-based phenolic resin; the dispersing agent is polycarboxylate; the defoaming agent is water-based organic silicon; and the carrier liquid is water.

[0049] The characteristics and compositions of the raw materials are as follows: pyrophyllite: 65% SiO2, 25% Al2O3, 5.5% loss on ignition, and particle size of 150-350 mesh; mullite is prepared by electric melting based on bauxite, with mullite phase of 75%, glass phase of 10%, porosity of 6%, 66% SiO2, 20% Al2O3, and particle size of 150-25 mesh; and high-purity graphite powder is flaky graphite with fixed carbon of 85%, water content of ≤0.5%, and particle size of 250-350 mesh.

[0050] Example 3

[0051] A coating for a wet sand core of a cylinder body of an automobile, by weight percentage, refractory aggregate 50%, suspending agent 10%, binder 7%, dispersing agent 2.5%, defoaming agent 0.3%, and carrier liquid as appropriate.

[0052] The refractory aggregate is composed of 20% by weight of pyrophyllite, 15% by weight of mullite, 10% by weight of high-purity graphite powder, and 6% by weight of spodumene; the suspending agent is composed of 1:1 of attapulgite and sepiolite; the binder is composed of a mixture of water-based phenolic resin and PVA; the dispersing agent is a polycarboxylate; the defoaming agent is a water-based organic silicone; and the carrier liquid is water.

[0053] The characteristics and compositions of the raw materials are as follows: pyrophyllite, 70% SiO2, 35% Al2O3, loss on ignition 5.5%, and particle size 150-350 mesh; mullite, prepared by electric melting of bauxite, mullite phase 75%, glass phase 9%, porosity 5%, 79%≤SiO2, 28% Al2O3, and particle size 150-350 mesh; and high-purity graphite powder, flaky graphite, fixed carbon 90%, moisture content ≤0.5%, and particle size 250-350 mesh.

[0054] Example 4

[0055] A preparation method of a coating for a wet sand core of a cylinder body of an automobile:

[0056] In the preparation process, an appropriate amount of water is first added, a dispersing machine is started at 450 rpm, 2 / 3 of the suspending agent is slowly added, the dispersing agent is then added, and stirring is performed for 5 min; then the graphite powder, spodumene, pyrophyllite, and mullite are sequentially added, the stirring speed is adjusted to 1100 rpm, and stirring is performed for 30 min; then the stirring speed is reduced to 500 rpm, the binder, defoaming agent, and remaining suspending agent are sequentially added, an appropriate amount of water is added, and stirring is performed for another 15 min; the ratio of the dispersion disc to the stirring barrel of the dispersing machine used is 1:3, and the dispersion disc is a rectangular-toothed disc-type impeller.

[0057] Example 5

[0058] A preparation method of a coating for a wet sand core of a cylinder body of an automobile:

[0059] In the preparation process, an appropriate amount of water is first added, a dispersing machine is started at 500 rpm, 2 / 3 of the suspending agent is slowly added, the dispersing agent is then added, and stirring is performed for 8 min; then the graphite powder, spodumene, pyrophyllite, and mullite are sequentially added, the stirring speed is adjusted to 1200 rpm, and stirring is performed for 35 min; then the stirring speed is reduced to 600 rpm, the binder, defoaming agent, and remaining suspending agent are sequentially added, an appropriate amount of water is added, and stirring is performed for another 20 min; the ratio of the dispersion disc to the stirring barrel of the dispersing machine used is 1:3.2, and the dispersion disc is a rectangular-toothed disc-type impeller.

[0060] Example 6

[0061] A method for preparing a coating for a wet-type casting sand core of an automobile cylinder block:

[0062] In the preparation process, a proper amount of water is first added, the dispersing machine is started at 600 rpm, 2 / 3 of the suspending agent is slowly added, the dispersing agent is then added, and stirring is performed for 10 min; then, the graphite powder, spodumene, talc, and mullite are sequentially added, the stirring speed is adjusted to 1400 rpm, and stirring is performed for 40 min; then, the stirring speed is reduced to 800 rpm, the binder, defoaming agent, and the remaining suspending agent, and a proper amount of water are sequentially added, and stirring is performed for another 25 min; the ratio of the dispersion disc to the stirring barrel of the dispersing machine equipment is 1:4, and the dispersion disc is a rectangular-toothed disc type impeller.

[0063] Example 7

[0064] Application of the coating for a wet-type casting sand core of an automobile cylinder block:

[0065] The coating is suitable for cold cores prepared from phenolic urethane resin, and before use, the coating is diluted to 37-40°Bé with water, the density of the diluted coating is 1.2-1.3 g / cm 3 , the 24 h suspensibility is ≥97%, the viscosity is 12-16 s, the gas evolution amount is ≤28 ml / g, and the hot flash level is grade I; the sand core is immersed in the coating for 2-5 seconds to obtain a uniform and smooth wet coating layer with a thickness of 200-400 um; and the sand core after coating is subjected to surface drying at 170℃ for 70 min, and is used for pouring after being placed for 4-72 hours.

[0066] Example 8

[0067] Application of the coating for a wet-type casting sand core of an automobile cylinder block:

[0068] The coating is suitable for cold cores prepared from phenolic urethane resin, and before use, the coating is diluted to 37-40°Bé with water, the density of the diluted coating is 1.2-1.3 g / cm 3 ; the sand core is immersed in the coating for 3 seconds to obtain a uniform and smooth wet coating layer with a thickness of 200-400 um; the 24 h suspensibility of the coating layer is ≥97%, the viscosity is 12-16 s, the gas evolution amount

[0069] is ≤28 ml / g, and the hot flash level is grade I; the sand core after coating is subjected to surface drying at 170℃ for 70 min, and is used for pouring after being placed for 24 hours; the pouring temperature is 1445℃, and the pouring time is 30 seconds.

[0070] The sand core surface coating layer forms effective physical barrier during heat action, prevents heat and mass exchange, promotes the coating to form continuous and dense carbon layer structure, has strong chilling ability to metal liquid, is not wetted by metal liquid or metal oxide, does not react with metal liquid, produces weak reducing atmosphere during pouring, and is more beneficial to sand sticking resistance; after pouring for 8 hours, the castings are subjected to sand shaking and shot blasting, the cylinder inner cavity is clean, and there are no pulse lines, sand sticking and dust sticking and other impurities.

[0071] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application should be covered within the protection scope of the present application. Meanwhile, the contents not described in detail in the specification are all prior art known by those skilled in the art.

Claims

1. A coating for a wet sand core for an automobile cylinder block, characterized by comprising a binder, a lubricant, a binder solvent, and a water-repellent agent. The formula is composed of 30-50% refractory aggregate, 5-10% suspending agent, 3-7% binder, 0.9-2.5% dispersant, 0.1-0.3% defoaming agent, and suitable carrier liquid by weight percentage; the refractory aggregate is composed of 17% pyrophyllite, 12% mullite, 8% high-purity graphite powder, and 3% spodumene by weight percentage; the refractory aggregate is composed of the following materials by mass percentage: 65%≤SiO2%≤70%, 25%≤Al2O3%≤35%, loss on ignition ≤5.5%, and particle size of 150-350 mesh; the mullite is prepared by electric smelting of bauxite-based, with mullite phase ≥75%, glass phase <10%, porosity ≤6%, 66%≤SiO2%≤79%, 20%≤Al2O3%≤28%, and particle size of 150-350 mesh; the high-purity graphite powder is flaky graphite with fixed carbon 85-90%, moisture ≤0.5%, and particle size of 250-350 mesh; the suspending agent is composed of one or two of attapulgite, sodium-based bentonite, and sepiolite; the dispersant is polycarboxylate; the defoaming agent is water-based organic silicone; and the carrier liquid is water.

2. A coating for a sand core used in wet-type casting of an automobile cylinder block according to claim 1, characterized in that, The suspending agent is composed of attapulgite and sodium-based bentonite at a ratio of 1:

1.

3. The coating for a sand core of a wet-type casting of an automobile cylinder block according to Claim 1, wherein The binder is composed of one or both of water-based phenolic resin and PVA.

4. The method of preparing a coating for a sand core for wet-type casting of an automobile cylinder block according to claim 1, characterized by, It comprises: First, add an appropriate amount of water, start the disperser at 450-600 rpm, slowly add 2 / 3 of the suspending agent, then add the dispersant, and stir for 5-10 min; then add the graphite powder, spodumene, pyrophyllite, and mullite in sequence, adjust the speed to 1100-1400 rpm, and stir for 30-40 min; then reduce the speed to 500-800 rpm, add the binder, defoaming agent, and the remaining suspending agent in sequence, add an appropriate amount of water, and stir for another 15-25 min; the ratio of the dispersion disc to the stirring barrel of the disperser equipment used is 1:(3-4), and the dispersion disc is a rectangular-toothed disc-type impeller.