Environment-friendly water-based quick-drying casting coating with low organic matter content

Abstract

The invention relates to the technical field of casting coatings, and discloses an environment-friendly low-organic-matter-content water-based quick-drying casting coating which comprises the following components in parts by mass: 50-75 parts of a refractory filler, 8-15 parts of a binder, 2-6 parts of a coalescing agent, 1-5 parts of a quick-drying regulating agent, 0.5-3 parts of a wetting agent, 0.2-2 parts of a dispersing agent, 0.1-2 parts of a reinforcing agent and 10-30 parts of water. The refractory filler is selected from at least one of aluminum oxide, zircon sand, ceramic microbeads and nano silicon dioxide, and the binder comprises silica sol and an inorganic binder. By optimizing a bonding system and introducing an efficient quick-drying auxiliary agent and a low-organic-matter environment-friendly formula, the problems that an existing water-based casting coating is low in drying speed, low in production efficiency, high in organic matter content and poor in environment-friendly performance are solved, and quick drying, excellent sand burning resistance, high high-temperature stability and long service life are achieved. And the efficient and green production requirements of the modern casting industry are met.

Description

Technical Field

[0001] The present invention relates to the technical field of foundry coatings, and particularly to an environment-friendly water-based quick-drying foundry coating with low organic matter content. Background Art

[0002] Existing ordinary water-based foundry coatings generally have problems such as slow drying speed, long drying time, high energy consumption, and low production efficiency during the production process, and it is difficult to meet the requirements of modern foundry industry for energy conservation, consumption reduction, and high-efficiency production. With the increasingly strict environmental protection regulations, the industry's demand for environment-friendly water-based quick-drying foundry coatings is growing. However, the current water-based quick-drying foundry coatings on the market still have many deficiencies. For example, Chinese Patent Invention CN201410465956.9 discloses a coating for small cast iron parts suitable for lost foam casting. This coating relies on a large amount of organic matter as a binder and auxiliary components. After aluminum chromium phosphate decomposes at high temperature, hexavalent chromium compounds are formed, which pollute water sources and soil for a long time and have serious environmental and health hazards. In addition, this coating still needs 1 hour to dry in a hot air environment at 80°C, and the drying speed is slow, and the production efficiency is difficult to meet the requirements of large-scale casting production.

[0003] Some existing water-based foundry coatings for large castings also have limitations. For example, Chinese Patent Inventions CN201210530768.0 and CN201010103175.7 mainly describe a coating using an organic binder and zircon powder as the main solid materials. Such coatings not only have certain radioactive hazards, but also do not optimize the quick-drying performance, still belonging to the category of traditional water-based coatings and lacking technological advancement. In addition, although Chinese Patent Invention CN201910071909.9 proposes a water-based quick-drying foundry coating suitable for large cast steel parts and reduces the content of organic components, the key index of the drying speed of the coating is not disclosed, making it difficult to evaluate its quick-drying performance, and at the same time, it fails to show significant advantages in environmental protection performance and technological uniqueness. Therefore, the existing technology still lacks an environment-friendly water-based quick-drying foundry coating that simultaneously has fast drying, low organic matter content, and excellent anti-adhesion performance to meet the comprehensive requirements of modern foundry production for safety, environmental protection, and high-efficiency production. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides an environment-friendly water-based quick-drying foundry coating with low organic matter content, and solves the problems of slow drying speed, low production efficiency, high organic matter content, and insufficient environmental protection performance of the existing water-based foundry coatings.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: An environment-friendly water-based quick-drying foundry coating, comprising the following components in parts by mass:

[0006] 50 - 75 parts of refractory filler,

[0007] 8 - 15 parts of binder,

[0008] 2 - 6 parts of film - forming aid,

[0009] 1 - 5 parts of quick - drying regulator,

[0010] 0.5 - 3 parts of wetting agent,

[0011] 0.2 - 2 parts of dispersant,

[0012] 0.1 - 2 parts of reinforcing agent,

[0013] 10 - 30 parts of water.

[0014] Preferably, the refractory filler is selected from at least one of alumina, zircon sand, ceramic microspheres, and nano - silica, the binder includes silica sol and inorganic binders, and the inorganic binder is selected from at least one of phosphates, borates, and silicates.

[0015] Preferably, the film - forming aid includes organosilicon, low - molecular - weight organic salts, and composite oxides.

[0016] Preferably, the quick - drying regulator includes intelligent phase - change microcapsules and inorganic acid - base regulators.

[0017] Preferably, the wetting agent includes high - efficiency non - ionic surfactants and interfacial modifiers.

[0018] Preferably, the dispersant includes nano - silica and low - molecular - weight polycarboxylates, the reinforcing agent includes carbon nanotubes, nano - graphite, and magnesium oxide, the viscosity of the coating is 500 - 2000 cP, the pH value is 6.5 - 9.5, and the solid content is 50 - 75 wt%.

[0019] Preparation method of an environmentally friendly water - based quick - drying casting coating with low organic matter content, comprising the following steps:

[0020] S1. Liquid - phase pretreatment: Add water, dispersant, and wetting agent according to the mass ratio into a stirring container, and stir at a low speed for 5 - 10 minutes to form a uniform liquid - phase basic system;

[0021] S2. Powder mixing: Add solid fillers including alumina, high - temperature ceramic powder, silica fume, magnesium oxide powder, magnesium silicate, or zirconium oxide powder in sequence according to the mass percentage, and stir for 30 - 40 minutes to ensure uniform dispersion of the powder;

[0022] S3. Addition of the bonding system: Add composite inorganic binders including water glass, modified silica sol, or aluminum phosphate - based binders, and stir for 15 - 20 minutes to enhance the adhesion of the coating;

[0023] S4. Addition of functional additives: Add quick-drying additives, defoamers, and anti-cracking and strengthening agents, and stir for 10 - 15 minutes to improve the coating performance;

[0024] S5. Coating and drying: Uniformly coat the prepared coating on the surface of the casting by spraying, brushing, or flow coating process, and dry it at 100 - 150 °C for 5 - 20 minutes to form a uniform coating with excellent rapid drying and anti-adhesion to sand properties.

[0025] Preferably, the mass percentage of alumina in the powder mixture is 30% - 45%, the high-temperature ceramic powder is 10% - 20%, the silica fume is 5% - 10%, and the magnesia powder is 5% - 15%. The mass ratio of sodium silicate to modified silica sol in the binder system is 2:1 to 3:1, and the total binder content accounts for 8% - 15% of the total mass of the coating.

[0026] Preferably, the quick-drying additive is an inorganic additive, and the addition ratio is 1% - 3% of the total mass of the coating. The anti-cracking and strengthening agent is nano-silica or nano-calcium carbonate, and the addition ratio is 0.5% - 2% of the total mass of the coating. In the drying process, the initial drying temperature is 100 - 120 °C for 5 - 10 minutes; the subsequent curing temperature is 130 - 150 °C for 10 - 20 minutes.

[0027] Preferably, the stirring speed in the preparation process is 200 - 300 rpm in the liquid-phase pretreatment stage and 500 - 700 rpm in the powder mixing and binder system addition stage. The coating process preferably adopts the spraying method, and the coating thickness is controlled between 0.3 - 0.5 mm.

[0028] The present invention provides an environmentally friendly water-based quick-drying casting coating with a low organic matter content. It has the following beneficial effects:

[0029] 1. The present invention adopts a low-organic-matter environmental protection formula, optimizes the solid powder system, reduces or even avoids the use of zircon powder, ensures non-toxic, harmless, and non-radioactive, achieving the technical effect of reducing organic matter emissions and improving the working environment. Compared with the high-pollution and high-cost traditional zircon powder-based coating solution, it successfully reduces VOC emissions and improves the environmental protection standard of the foundry, solving the problems of serious environmental pollution and damaged workers' health during the casting production process.

[0030] 2. The present invention adopts a composite refractory filler and a high-temperature stable binder system, optimizes the coating structure, improves the ability to resist the erosion of molten metal, makes the coating non-bubbling, non-cracking, and non-peeling, achieving the technical effect of a smooth casting surface and strong anti-adhesion to sand ability. Compared with the traditional water-based coating solution that is prone to cracking and burning out, it completely solves the problems of unstable casting surface quality and easy coating peeling. It is applicable to large-scale alloy steel and stainless steel castings, ensuring no sand adhesion defects on the casting surface.

[0031] 3. The present invention adopts an intelligent quick-drying control technology, combines with a high-efficiency wetting agent and a dispersion system, precisely controls the water evaporation rate, enables the coating to be quickly dried in a low-temperature environment of 80 - 150 °C, achieves the technical effect of matching the production rhythm of the automated production line and improving production efficiency. Compared with the traditional water-based coating with a long drying time and unable to meet the requirements of high-speed production lines, it realizes that the green sand molding line can be completely dried in 4 - 9 minutes and the resin sand production line can complete drying in 13 - 25 minutes, thoroughly solving the problem that water-based coatings cannot be adapted to high-speed molding production.

[0032] 4. The present invention adopts a water penetration depth control technology to ensure that the water penetration layer does not exceed 2 mm. Even if it is naturally dried for a long time, it will not affect the strength of the sand mold, achieving the technical effect of being applicable to resin sand and sodium silicate sand molds and expanding the application field of water-based coatings. Compared with the traditional water-based coatings that are easy to penetrate and cause the decline of sand mold strength, it successfully solves the industry problem that large and extra-large castings cannot use water-based coatings. At the same time, the water-based quick-drying formula of the present invention is applicable to special functional coatings such as crucible coatings, riser pipe coatings, chill coatings, and magnesium alloy flame retardant coatings, further expanding the application range of water-based coatings.

[0033] 5. The present invention adopts a fully inorganic binder plus inorganic reinforcing agent system, reduces the dependence on organic binders, completely eliminates the flammable and explosive risks of alcohol-based coatings, achieves the technical effect of improving foundry safety and reducing fire hazards. Compared with the traditional alcohol-based coatings with fire risks caused by alcohol volatilization, the water-based coatings of the present invention are safer during production and storage, providing a more stable safe production environment for the foundry workshop and solving the problem of flammability and explosiveness of alcohol coatings in high-temperature environments.

[0034] 6. In high-temperature climate regions, the present invention can complete the drying of the coating by natural drying, without additional energy consumption, reducing production costs, achieving the technical effect of energy conservation and consumption reduction and optimizing the foundry process. Compared with the traditional coatings that rely on long-term high-temperature baking, it greatly reduces energy consumption and improves the economic efficiency of foundry production. It is especially suitable for foundries in the south. By natural drying, the operating costs can be further reduced, providing an economically feasible solution for green casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a method step diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Please refer to the attached Figure 1 , the embodiments of the present invention provide an environmentally friendly water-based quick-drying casting coating with low organic matter content, which is applicable to various castings such as cast steel, cast iron, aluminum alloy, and magnesium alloy, and can achieve rapid drying while ensuring excellent anti-adhesion and sand-bonding performance, and reduce organic matter emissions to improve environmental performance.

[0038] The key technologies of the present invention include refractory filler optimization, inorganic binder compounding, quick-drying additive regulation, dispersion and stabilization system, etc., so that the coating can form a film quickly and also have high-temperature stability and erosion resistance, thereby improving the surface quality of the casting and reducing the defect rate.

[0039] I. Composition and ratio

[0040] The coating of the present invention mainly consists of four parts: a liquid phase system, solid fillers, a binder system, and functional additives.

[0041] 1. Liquid phase system

[0042] The liquid phase system is mainly deionized water, and is combined with appropriate amounts of wetting agents, dispersants, and defoamers to improve the rheology and spraying adaptability of the coating.

[0043] Deionized water: 25 - 40%

[0044] Wetting agent: 0.2 - 0.5%

[0045] Dispersant: 0.4 - 1%

[0046] Defoamer: 0.1 - 0.3%

[0047] 2. Solid fillers

[0048] The solid fillers determine the high-temperature resistance and anti-adhesion and sand-bonding effects of the coating. The present invention uses a variety of refractory powders, including alumina, zirconia, silicon carbide, silica fume, magnesia, etc., and reasonably controls the particle size distribution to improve the packing density.

[0049] Alumina: 30 - 45%

[0050] Zirconia / silicon carbide: 5 - 15%

[0051] Silica fume: 3 - 8%

[0052] Magnesia: 3 - 10%

[0053] 3. Binder system

[0054] The present invention adopts an inorganic binder system such as modified silica sol + water glass + phosphate to improve the bonding strength and avoid the problem of gas generation caused by the combustion and decomposition of organic binders.

[0055] Modified silica sol: 5 - 12%

[0056] Water glass (modulus 3.0 - 3.5): 3 - 10%

[0057] Phosphate (aluminum phosphate / sodium phosphate): 2 - 8%

[0058] 4. Functional additives

[0059] In order to further optimize the quick-drying property and coating stability, the present invention introduces inorganic quick-drying additives, nano-enhancers, anti-cracking additives, etc.

[0060] Inorganic quick-drying additive: 1 - 3%

[0061] Nano-silica / calcium carbonate enhancer: 0.5 - 2%

[0062] II. Preparation process

[0063] The present invention adopts processes such as step-by-step dispersion, multi-stage mixing, and high-speed shear stirring to ensure the uniformity and stability of the coating system, which specifically includes the following steps:

[0064] 1. Liquid-phase pretreatment

[0065] Add deionized water into a stirring container, and successively add a dispersant, a wetting agent, and an antifoaming agent, and stir at a low speed for 5 - 10 minutes to make the liquid phase uniform.

[0066] 2. Mixing of powder fillers

[0067] On the basis of the liquid phase, successively add powders such as alumina, zirconia (or silicon carbide), silica fume, and magnesia, and stir at a high speed with shear for 20 - 30 minutes to uniformly disperse the powders and avoid agglomeration. This step can be combined with ultrasonic dispersion to improve the uniformity of the fillers.

[0068] 3. Addition of binder

[0069] Slowly add modified silica sol, water glass or phosphate, and at the same time keep stirring at a speed of 400 - 600 rpm for 10 - 15 minutes to uniformly coat the filler particles with the binder and improve the adhesion of the coating.

[0070] 4. Regulation of functional additives

[0071] Add inorganic quick-drying additives, nano-enhancers, etc., and continue to stir for 5 - 10 minutes to make the additives fully distributed and improve the quick-drying performance.

[0072] 5. Coating Process

[0073] Spraying method: The coating thickness is controlled at 0.3 - 0.5 mm, suitable for large-scale casting production.

[0074] Flow coating method: Suitable for castings with complex shapes to ensure uniform coverage.

[0075] Brushing method: Suitable for local repair or small castings, with convenient operation.

[0076] 6. Drying and Curing

[0077] Quick drying: Pre-bake at 120°C for 5 - 8 minutes, final bake at 150°C for 8 - 10 minutes, and the total drying time is 12 - 18 minutes.

[0078] Low-temperature drying (suitable for magnesium alloys): Pre-bake at 100°C for 8 minutes, final bake at 120°C for 7 minutes, and the total drying time is 15 minutes.

[0079] Example 1: Environmentally Friendly Water-based Quick-drying Casting Coating with Low Organic Content

[0080] This example is applicable to steel castings, and the coating has the properties of quick drying, high-temperature stability, and excellent anti-adhesion to sand.

[0081] 1. Raw Material Ratio (by Mass Percentage)

[0082] Liquid Phase Components:

[0083] Deionized water: 32%

[0084] Dispersant: 0.5%

[0085] Wetting agent: 0.3%

[0086] Defoamer: 0.2%

[0087] Solid Filler:

[0088] Aluminum oxide powder: 38%

[0089] High-temperature ceramic powder (zirconia): 14%

[0090] Silica fume: 6%

[0091] Magnesium oxide powder: 7%

[0092] Binder System:

[0093] Modified silica sol: 8%

[0094] Water glass (modulus 3.2): 5%

[0095] Functional Additives:

[0096] Quick-drying additive (inorganic type): 2%

[0097] Anti-cracking and strengthening agent (nano-silica): 1%

[0098] 2. Preparation process

[0099] Liquid-phase pretreatment:

[0100] Add deionized water, dispersant, wetting agent and defoaming agent into a stirring container, stir at a low speed (250 rpm) for 10 minutes to make the liquid-phase system uniform.

[0101] Powder mixing:

[0102] Add alumina powder, high-temperature ceramic powder, silica fume and magnesia powder in sequence, stir at a high speed (600 rpm) for 30 minutes to ensure uniform dispersion of the powder materials.

[0103] Addition of bonding system:

[0104] Gradually add modified silica sol and water glass, continue to stir (500 rpm) for 15 minutes to make the binder uniformly coat the filler and improve the coating adhesion.

[0105] Addition of functional additives:

[0106] Add quick-drying additive and anti-cracking and strengthening agent, stir (400 rpm) for 10 minutes to ensure uniform distribution of the additives.

[0107] Coating and drying:

[0108] Use the spraying process to uniformly coat the surface of the casting, and the coating thickness is 0.3 - 0.5 mm.

[0109] After pre-baking at 120°C for 5 minutes, raise the temperature to 150°C for final baking for 10 minutes, and the total drying time is 15 minutes to form a dense and high-temperature-resistant anti-adhesive sand coating.

[0110] Results

[0111] Drying time: Pre-baking at 120°C for 5 minutes, final baking at 150°C for 10 minutes, total drying time is 15 minutes.

[0112] Adhesive sand rate: 0.5%, significantly lower than that of traditional water-based coatings (4 - 6%).

[0113] Adhesion: Strong, the coating is complete without cracking or peeling.

[0114] Example 2: Low-temperature quick-drying water-based casting coating

[0115] This example optimizes the formula for magnesium alloy castings to achieve rapid drying at a lower temperature.

[0116] 1. Raw material ratio (mass percentage)

[0117] Liquid components:

[0118] Deionized water: 35%

[0119] Dispersant: 0.4%

[0120] Wetting agent: 0.3%

[0121] Defoamer: 0.3%

[0122] Solid fillers:

[0123] Aluminum oxide powder: 35%

[0124] High-temperature ceramic powder (aluminum silicate): 10%

[0125] Silica fume: 6%

[0126] Magnesium oxide powder: 5%

[0127] Binder system:

[0128] Aluminum phosphate-based binder: 9%

[0129] Modified silica sol: 6%

[0130] Functional additives:

[0131] Quick-drying additive: 1.5%

[0132] Crack prevention and strengthening agent (nano calcium carbonate): 1%

[0133] 2. Preparation process

[0134] Liquid phase pretreatment:

[0135] First, mix deionized water, dispersant, wetting agent, and defoamer, and stir (200 rpm) for 8 minutes.

[0136] Powder mixing:

[0137] Add aluminum oxide, high-temperature ceramic powder, silica fume, and magnesium oxide powder in sequence, and stir at high speed (650 rpm) for 25 minutes to ensure uniform dispersion of the powder materials.

[0138] Binder system addition:

[0139] Add aluminum phosphate-based binder and modified silica sol in sequence, and stir (500 rpm) for 15 minutes.

[0140] Functional additive addition:

[0141] Add quick-drying additive and crack prevention and strengthening agent, and continue to stir (450 rpm) for 10 minutes to stabilize the coating system.

[0142] Coating and drying:

[0143] It is coated on the surface of the casting by the flow coating process, and the coating thickness is 0.4 - 0.6 mm.

[0144] Pre-dry at 100 °C for 8 minutes, final dry at 120 °C for 7 minutes, and the total drying time is 15 minutes.

[0145] Results

[0146] Drying time: Pre-dry at 100 °C for 8 minutes, final dry at 120 °C for 7 minutes, total 15 minutes. Thermal shock resistance: Crack density < 10 μm / cm 2 , better than traditional water-based coatings (> 50 μm / cm 2 ).

[0147] Environmental protection: Low organic content, meeting the requirements of green casting.

[0148] Example 3: High-temperature wear-resistant enhanced water-based casting coating

[0149] This example is designed specifically for high-temperature casting environments and is especially suitable for steel castings with high wear resistance requirements.

[0150] 1. Raw material ratio (mass percentage)

[0151] Liquid phase components:

[0152] Deionized water: 28%

[0153] Dispersant: 0.6%

[0154] Wetting agent: 0.5%

[0155] Defoaming agent: 0.2%

[0156] Solid fillers:

[0157] Aluminum oxide powder: 40%

[0158] High-temperature ceramic powder (zirconia): 15%

[0159] Silica fume: 7%

[0160] Magnesium oxide powder: 8%

[0161] Binder system:

[0162] Modified silica sol: 9%

[0163] Water glass (modulus 3.2): 5%

[0164] Functional additives:

[0165] Quick-drying additive (inorganic type): 2%

[0166] Anti-cracking enhancer (nano-silicon oxide): 1%

[0167] 2. Preparation Process

[0168] Liquid-phase Pretreatment:

[0169] Add deionized water, dispersant, wetting agent and defoamer into a stirring container, and stir at a low speed (250 rpm) for 10 minutes to make the liquid-phase system uniform.

[0170] Powder Mixing:

[0171] Add alumina powder, high-temperature ceramic powder, silica fume and magnesia powder in sequence, and stir at a high speed (600 rpm) for 30 minutes to ensure uniform dispersion of the powder materials.

[0172] Addition of Binder System:

[0173] Gradually add modified silica sol and water glass, and continue stirring (500 rpm) for 15 minutes.

[0174] Addition of Functional Auxiliaries:

[0175] Add quick-drying auxiliary and crack-proof strengthening agent, and continue stirring (400 rpm) for 10 minutes.

[0176] Coating and Drying:

[0177] Evenly coat on the surface of the casting by spraying process, and the coating thickness is 0.3 - 0.5 mm.

[0178] Pre-bake at 120°C for 5 minutes, then raise the temperature to 150°C for final baking for 10 minutes, and the total drying time is 15 minutes.

[0179] Results

[0180] Drying Time: Pre-bake for 5 minutes, final bake for 10 minutes.

[0181] Wear Resistance: The loss of the coating in the friction test is less than 1%, which is better than traditional coatings.

[0182] High-temperature Resistance: The high-temperature resistance reaches 1600°C, and there is no cracking in the coating.

[0183] Example 4: Ultra-low Viscosity Spraying-type Water-based Foundry Coating

[0184] This example is applicable to automated spraying equipment, especially suitable for mass production, and the coating has excellent fluidity.

[0185] 1. Raw Material Ratio (mass percentage)

[0186] Liquid-phase Components:

[0187] Deionized Water: 38%

[0188] Dispersant: 0.5%

[0189] Wetting agent: 0.4%

[0190] Defoaming agent: 0.2%

[0191] Solid filler:

[0192] Aluminum oxide powder: 30%

[0193] High-temperature ceramic powder (zirconia): 10%

[0194] Silica fume: 5%

[0195] Magnesium oxide powder: 4%

[0196] Binder system:

[0197] Modified silica sol: 10%

[0198] Water glass (modulus 3.2): 5%

[0199] Functional additives:

[0200] Quick-drying additive (inorganic type): 1.5%

[0201] Crack prevention and strengthening agent (nano-silicon dioxide): 0.8%

[0202] 2. Preparation process

[0203] The preparation process is similar to that of Example 1, but the proportion of water is increased in the formulation to reduce the viscosity.

[0204] Drying process: Pre-bake at 120°C for 4 minutes, final bake at 150°C for 8 minutes, total drying time 12 minutes.

[0205] Results

[0206] Viscosity: 500 cP, suitable for automatic spraying.

[0207] Coating uniformity: The coating thickness is uniform, and the spraying effect is excellent.

[0208] Example 5: High-adhesion casting coating

[0209] This example is specifically designed for castings with complex shapes to improve the adhesion between the coating and the substrate.

[0210] 1. Raw material ratio (mass percentage)

[0211] Liquid-phase components:

[0212] Deionized water: 30%

[0213] Dispersant: 0.4%

[0214] Wetting agent: 0.3%

[0215] Defoamer: 0.2%

[0216] Solid filler:

[0217] Aluminum oxide powder: 40%

[0218] High-temperature ceramic powder (zirconia): 12%

[0219] Silica fume: 5%

[0220] Magnesium oxide powder: 8%

[0221] Binder system:

[0222] Modified silica sol: 10%

[0223] Water glass (modulus 3.2): 5%

[0224] Functional additives:

[0225] Quick-drying additive: 1.5%

[0226] Anti-cracking and strengthening agent (nano calcium carbonate): 1%

[0227] 2. Preparation process

[0228] The spraying process is adopted, and the coating thickness is 0.4 - 0.5 mm.

[0229] Drying process: Pre-bake at 120°C for 5 minutes, final bake at 150°C for 10 minutes, and the total drying time is 15 minutes.

[0230] Results

[0231] Adhesion improvement: 30%, suitable for complex castings.

[0232] Sand sticking rate: 0.6%, 1.2% lower than that of conventional coatings.

[0233] Example 6: Alkali-resistant and corrosion-resistant water-based foundry coating

[0234] This example optimizes the formula for high-alkaline or strong-corrosion environments to improve the coating stability and is suitable for special alloy castings.

[0235] 1. Raw material ratio (mass percentage)

[0236] Liquid-phase components:

[0237] Deionized water: 29%

[0238] Dispersant: 0.5%

[0239] Wetting agent: 0.3%

[0240] Defoamer: 0.2%

[0241] Solid filler:

[0242] Aluminum oxide powder: 45%

[0243] High-temperature ceramic powder (zirconia + silicon carbide): 10%

[0244] Silica fume: 5%

[0245] Magnesium oxide powder: 5%

[0246] Binder system:

[0247] Phosphate binder: 10%

[0248] Modified silica sol: 5%

[0249] Functional additives:

[0250] Alkali-resistant stabilizer (nano-titanium oxide): 2%

[0251] Crack-proof enhancer (nano-silicon oxide): 1%

[0252] 2. Preparation process

[0253] Liquid-phase pretreatment:

[0254] Stir at low speed (250 rpm) for 8 minutes to fully dissolve the dispersant, wetting agent and defoamer.

[0255] Powder mixing:

[0256] Add aluminum oxide, high-temperature ceramic powder, silica fume and magnesium oxide powder in sequence, and stir at high speed (600 rpm) for 25 minutes to ensure uniform dispersion of the powder.

[0257] Binder addition:

[0258] Add phosphate binder and modified silica sol in sequence, and continue to stir (500 rpm) for 15 minutes to ensure uniform coating of the filler particles.

[0259] Functional additive addition:

[0260] Add alkali-resistant stabilizer and crack-proof enhancer, and stir (400 rpm) for 10 minutes to ensure uniform distribution.

[0261] Coating and drying:

[0262] Adopt brushing or spraying process, and the coating thickness is 0.3 - 0.5 mm.

[0263] Pre-bake at 130°C for 6 minutes and final-bake at 150°C for 8 minutes, with a total drying time of 14 minutes.

[0264] 3. Results

[0265] Alkaline resistance: The coating is stable in a strong alkaline solution with pH 13 for 48 hours without obvious degradation.

[0266] Corrosion resistance: Resistant to sulfuric acid and chloride corrosion, with a coating strength retention rate of 90%.

[0267] Enhanced adhesion: Increased by 35%, suitable for special casting environments.

[0268] Comparative example 1: Using a traditional organic binder (comparative example 1)

[0269] This comparative example uses traditional phenolic resin as the binder, and other formulations are the same as those in Example 1 to compare the differences between the organic binder and the inorganic binder of the present invention.

[0270] 1. Formulation adjustment

[0271] Binder:

[0272] Modified silica sol (present invention) → 0%

[0273] Sodium silicate (present invention) → 0%

[0274] Changed to phenolic resin: 10%

[0275] Other components are the same as those in Example 1.

[0276] 2. Preparation process

[0277] Liquid-phase pretreatment: Mix deionized water, dispersant, wetting agent, and defoamer, and stir at low speed for 5 minutes.

[0278] Powder filler mixing: Add alumina powder, high-temperature ceramic powder, silica fume, and magnesia powder, and stir at high speed for 30 minutes.

[0279] Binder addition: Add phenolic resin and continue stirring for 15 minutes.

[0280] Functional additive addition: Quick-drying additive, anti-cracking and strengthening agent, and stir for 10 minutes.

[0281] Coating and drying:

[0282] Pre-bake at 100 °C for 20 minutes (longer than the present invention).

[0283] Final bake at 160 °C for 30 minutes (longer than the present invention).

[0284] Result: Increase in drying time: The pre-bake time is extended to 20 minutes, and the final bake time is extended to 30 minutes, which is 50% longer than the present invention.

[0285] Increase in VOC emissions: Combustion of organic binders produces volatile organic compounds (VOCs), and the emission is about 80 - 120 mg / m 3, while the present invention is lower than 10 mg / m 3 .

[0286] Adhesion reduction: The coating is prone to peeling, and the adhesion is reduced by about 40%.

[0287] Coating crack resistance reduction: The coating is prone to cracking at high temperatures, and the overall integrity is poor.

[0288] Comparative example 2: Reducing the proportion of refractory fillers (comparing with Example 2)

[0289] In this comparative example, the proportions of alumina and zirconia are reduced, and low-temperature fillers (talc powder) are added to compare the effects of optimized fillers on high-temperature tolerance and anti-adhesion sand effects.

[0290] 1. Formula adjustment

[0291] Alumina (40% in the present invention) → 25%

[0292] Zirconia (15% in the present invention) → 5%

[0293] Newly added talc powder: 20%

[0294] Other components are the same as those in Example 2.

[0295] 2. Preparation process

[0296] The same as that in Example 2, only the filler ratio is different.

[0297] Result: Anti-adhesion sand performance reduction: The sand adhesion rate increases to 2.5% - 4% (0.3% - 0.5% in the present invention).

[0298] Coating strength reduction: After the reduction of alumina, the high-temperature resistance performance decreases, and the coating performs poorly at a high temperature of 1400 °C.

[0299] The surface quality of the casting decreases: The surface roughness Ra increases by 25%, and more defects appear.

[0300] Comparative example 3: Removing the nano-enhancer (comparing with Example 5)

[0301] In this comparative example, the nano-enhancer is removed to compare the effects of the enhancer on the hardness, adhesion and impact resistance of the coating.

[0302] 1. Formula adjustment

[0303] Nano-enhancer (in the present invention) → 0%

[0304] Other components are the same as those in Example 5.

[0305] 2. Preparation process

[0306] The same as that in Example 5, only the nano-enhancer is removed.

[0307] Result: The adhesion of the coating decreases: the result of the peel test decreases by 30%.

[0308] The crack resistance decreases: cracks are likely to occur during the high-temperature cooling process of the coating, and the number of cracks is 2 times more than that of the present invention.

[0309] The coating strength decreases: the wear resistance decreases by 25%.

[0310] Comparative Example 4: Using low-temperature fillers to reduce the fire resistance (compared with Example 3)

[0311] This comparative example uses low-temperature fillers (calcium carbonate) to compare the high-temperature tolerance ability.

[0312] 1. Formula adjustment

[0313] Aluminum oxide (40% in the present invention) → 20%

[0314] Zirconia (15% in the present invention) → 5%

[0315] Newly added calcium carbonate: 20%

[0316] Other components are the same as those in Example 3.

[0317] 2. Preparation process

[0318] The same as that in Example 3, only the fillers are different.

[0319] Result: The anti-adhesion performance decreases severely: the sand adhesion rate is as high as 5% - 7%, which is 10 times higher than that of the present invention.

[0320] The high-temperature stability decreases: the coating starts to decompose above 1200 °C and cannot meet the requirements of high-temperature casting.

[0321] The surface quality of the casting decreases: a large amount of metal penetrates, the surface of the casting is rough, and the post-treatment difficulty increases.

[0322] Comparative Example 5: Using a single binder system (compared with Example 6)

[0323] This comparative example uses a single sodium silicate binder to compare the advantages of the composite binder system.

[0324] 1. Formula adjustment

[0325] Modified silica sol (in the present invention) → 0%

[0326] Phosphate (in the present invention) → 0%

[0327] Sodium silicate used alone: 12%

[0328] Other components are the same as those in Example 6.

[0329] 2. Preparation Process

[0330] Same as Example 6, only the binder is different.

[0331] Result: The adhesion of the coating decreases: The adhesion of the single sodium silicate binder system decreases by 35%, and it is easy to peel off.

[0332] The toughness of the coating decreases: Due to the lack of the synergistic effect of the composite binder, the impact resistance decreases by 30%.

[0333] The high-temperature stability decreases: The single sodium silicate is prone to phase change above 1000 °C, resulting in the pulverization of the coating.

[0334] Comparative Example 6: Remove the dispersant and wetting agent (compare with Example 4)

[0335] In this comparative example, the dispersant and wetting agent are removed to compare the effect of rheology control on the coating uniformity.

[0336] 1. Formula adjustment

[0337] Dispersant (in the present invention) → 0%

[0338] Wetting agent (in the present invention) → 0%

[0339] Other components are the same as in Example 4.

[0340] 2. Preparation Process

[0341] Same as Example 4, only the dispersant and wetting agent are removed.

[0342] Result: The coating is unevenly dispersed: The powder particles agglomerate, resulting in a 40% increase in the surface roughness Ra of the coating.

[0343] The spraying adaptability becomes worse: The spraying is uneven and clogging occurs.

[0344] The strength of the coating decreases: Due to the uneven particle distribution, the hardness of the local coating decreases by 20%.

[0345] Experimental Example 1: Anti-adhesion sand test for cast iron engine cylinder block

[0346] Experimental purpose

[0347] Verify the anti-adhesion sand effect of the present invention in complex structure castings (such as engine cylinder block) and compare the performance with traditional water-based casting coatings.

[0348] Experimental materials

[0349] Casting material: HT250 gray cast iron

[0350] Casting method: Green sand molding, negative pressure casting

[0351] Coating formula: The formula of Example 1 of the present invention is adopted (inorganic bonding system + quick-drying additive + optimized refractory filler)

[0352] Control group: Use Comparative Example 1 (organic phenolic resin binder)

[0353] Pouring temperature: 1420 °C

[0354] Molding sand: 80% quartz sand + 5% bentonite + 3% water glass

[0355] Experimental steps

[0356] Coating preparation: The coatings of Example 1 and Comparative Example 1 are evenly sprayed onto the inner surface of the mold, with a thickness of 0.4 mm, and left to dry for later use.

[0357] Casting process: The same molding, pouring, and cooling methods are used to ensure consistent test conditions.

[0358] After cooling, the mold is disassembled, and the surface of the casting is cleaned using ultrasonic waves to measure the amount of residual adhering sand.

[0359] Experimental data:

[0360]

[0361] Experimental Example 2: Wear resistance test of coatings for precision aluminum alloy castings

[0362] Experimental purpose

[0363] Evaluate the wear resistance, adhesion, and uniformity of the coatings of the present invention in precision aluminum alloy castings, which are applicable to parts with high surface requirements (such as aerospace components).

[0364] Experimental materials

[0365] Casting material: Al Si 10Mg

[0366] Casting method: Investment casting (ceramic mold shell)

[0367] Coating formula: The formula of Example 5 of the present invention is adopted (nano-enhancer + high-adhesion formula)

[0368] Control group: Use Comparative Example 4 (without nano-enhancer)

[0369] Testing equipment: Grinding wheel wear resistance testing machine, pull-off adhesion tester

[0370] Experimental steps

[0371] Coating preparation: The coating is evenly applied to the surface of the wax mold by pouring three times, with a thickness of 0.3 mm for each layer. It is dried at room temperature for 10 minutes and finally dried at 120 °C for 20 minutes.

[0372] Coating abrasion resistance test: Apply a 10N load, wear the grinding wheel 1000 times, and measure the mass loss.

[0373] Adhesion test: Use the pull-off test to measure the bond strength.

[0374] Experimental data:

[0375]

[0376] Experimental Example 3: High-temperature alloy coating stability test

[0377] Experimental purpose

[0378] Verify the stability of the coating of the present invention in a high-temperature environment and ensure its applicability to the casting of high-temperature-resistant materials such as nickel-based alloys. Experimental materials

[0379] Casting material: Incone l 718 nickel-based alloy

[0380] Casting method: Investment casting

[0381] Coating formulation: Use Example 3 of the present invention (high-temperature refractory filler + optimized binder system)

[0382] Control group: Use Comparative Example 3 (low-temperature filler)

[0383] Testing equipment: High-temperature resistance furnace (1600 °C)

[0384] Experimental procedure

[0385] Coating preparation: Spray the coating on the surface of the ceramic shell and cure it after drying.

[0386] High-temperature stability test: Heat to 1400 °C and 1600 °C respectively, hold for 30 minutes, and observe the integrity of the coating.

[0387] Experimental data:

[0388]

[0389] Experimental Example 4: Environmental friendliness test (VOC emission comparison)

[0390] Experimental purpose

[0391] Verify the environmental protection advantages of the coating of the present invention, compare the VOC emission situation, and meet the requirements of green casting.

[0392] Experimental materials

[0393] Coating formulation: Use Example 6 of the present invention (inorganic binder + low-VOC design)

[0394] Control group: Use Comparative Example 1 (organic phenolic resin)

[0395] Testing equipment: Gas chromatograph (GC)

[0396] Experimental procedures

[0397] VOC release test: Take 10 g of the coating sample respectively and place it in an incubator at 150 °C to measure the VOC emission within 30 minutes.

[0398] Experimental data:

[0399]

[0400] The test results show that the coating of the present invention exhibits excellent technical performance under different casting scenarios. In terms of anti-adhesion to sand, the sand adhesion rate in the gray iron engine block test of Example 1 decreased by 90.6%, and the surface quality was significantly improved; in terms of wear resistance, after using the nano-enhancer in Example 5, the wear resistance of the coating increased by 63.6% and the adhesion increased by 85.7%; in terms of high-temperature stability, Example 3 remained intact at 1600 °C, while severe spalling occurred in Comparative Example 3; in terms of environmental protection, the VOC emission of Example 6 was only 8.2 mg / m 3 , far lower than the traditional phenolic resin solution (95.4 mg / m 3 ).

[0401] These experiments not only verify the feasibility of the technical solution of the present invention, but also further highlight its creative improvement over the prior art. Key technologies such as the optimized bonding system, filler gradation, quick-drying additives, and nano-enhancers enable the coating to achieve quick drying, low sand adhesion, and low VOC while ensuring high-temperature stability, providing a more efficient and environmentally friendly solution for modern casting.

[0402] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly, low-organic-content, water-based, quick-drying casting coating, characterized in that: The composition includes the following components in parts by weight: Refractory filler 50-75 parts, 8-15 parts of binder, 2-6 parts of film-forming aid, 1-5 parts of quick-drying regulator, Wetting agent 0.5-3 parts, Dispersant 0.2-2 parts, Enhancer 0.1-2 parts, 10-30 parts of water.

2. The environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 1, characterized in that: The refractory filler is selected from at least one of alumina, zircon sand, ceramic microbeads, and nano-silicon dioxide. The binder includes silica sol and an inorganic binder, wherein the inorganic binder is selected from at least one of phosphate, borate, and silicate.

3. The environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 1, characterized in that: The film-forming aids include organic silicon, low-molecular organic salts and composite oxides.

4. The environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 1, characterized in that: The quick-drying regulator comprises intelligent phase-change microcapsules and inorganic acid-base regulators.

5. The environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 1, characterized in that: The wetting agent comprises a high-efficiency nonionic surfactant and an interface modifier.

6. The environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 1, characterized in that: The dispersant includes nano silicon dioxide and low molecular weight polycarboxylate, the reinforcing agent includes carbon nanotubes, nano graphite and magnesium oxide, the coating has a viscosity of 500-2000 cP, a pH value of 6.5-9.5, and a solid content of 50-75 wt%.

7. A method for preparing an environmentally friendly water-based quick-drying casting coating with low organic content, which is used to prepare an environmentally friendly water-based quick-drying casting coating with low organic content according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Liquid phase pretreatment: add water, dispersant and wetting agent into a stirring container according to the mass ratio, stir at a low speed for 5-10 minutes to form a uniform liquid phase base system; S2. Powder mixing: add solid fillers in order of mass percentage, including alumina, high temperature ceramic powder, silica fume, magnesium oxide powder, magnesium silicate or zirconium oxide powder, and stir for 30-40 minutes to ensure that the powder is evenly dispersed; S3, adding the bonding system: adding a composite inorganic bonding agent, including water glass, modified silica sol or aluminum phosphate-based bonding agent, and stirring for 15-20 minutes to enhance the adhesion of the coating; S4. Addition of functional additives: Add quick-drying additives, defoaming agents, and anti-cracking enhancers, and stir for 10-15 minutes to improve coating performance; S5. Coating and drying: The prepared coating is evenly coated on the surface of the casting by spraying, brushing or flow coating, and dried at 100-150°C. The drying time is controlled within 5-20 minutes to form a uniform coating with fast drying and excellent anti-sand adhesion performance.

8. The method for preparing the environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 7, characterized in that: The mass percentage of aluminum oxide in the powder mixture is 30%-45%, the high-temperature ceramic powder is 10%-20%, the silica ash is 5%-10%, and the magnesium oxide powder is 5%-15%. The mass ratio of water glass to modified silica sol in the bonding system is 2:1 to 3:1, and the total binder content accounts for 8%-15% of the total mass of the coating.

9. The method for preparing the environmentally friendly, low-organic-content, water-based quick-drying casting coating according to claim 7, characterized in that: The quick-drying additive is an inorganic additive, and the addition ratio is 1%-3% of the total mass of the coating. The anti-cracking reinforcing agent is nano-silicon oxide or nano-calcium carbonate, and the addition ratio is 0.5%-2% of the total mass of the coating. In the drying process, the initial drying temperature is 100-120°C, and the time is 5-10 minutes; the subsequent curing temperature is 130-150°C, and the time is 10-20 minutes.

10. The method for preparing the environmentally friendly water-based quick-drying casting coating with low organic matter content according to claim 7, characterized in that: The stirring speed in the preparation process is 200-300 rpm in the liquid phase pretreatment stage, and 500-700 rpm in the powder mixing and bonding system addition stage. The coating process preferably adopts a spraying method, and the coating thickness is controlled between 0.3-0.5 mm.

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