Flame-retardant coating for improving sand casting surface quality and preparation method thereof
By preparing and processing flame retardant coatings, the problem of insufficient surface quality of magnesium alloy castings at high temperatures is solved, good fire resistance and surface finish are achieved, and the quality of castings is improved.
Patent Information
- Application Number
- CN202411668976.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-21
- Publication Date
- 2025-03-11
AI Technical Summary
Existing flame retardant coatings cannot meet the surface quality requirements of magnesium alloy castings at high temperatures, and are prone to defects such as insufficient pouring and cold separation, and are prone to react with the air medium to cause oxidation and combustion.
By preparing a flame retardant including boric acid and NH4BF4, and subjecting to ball milling, combined with refractory powder, suspension agent, binder and anhydrous ethanol, it is thoroughly mixed and stirred, and finally low-temperature pretreatment is carried out to produce a flame retardant coating with a Baumide value in the range of 20-40.
The flame-retardant coating has good fire resistance and a small thermal expansion coefficient, which can effectively prevent oxidation and combustion of magnesium alloys, improve the surface quality of the sand, and thus improve the quality of the castings.
Smart Images
Figure CN119588885A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of material casting, and in particular to a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof. Background Art
[0002] As an important component in rare earth magnesium alloy sand casting, flame retardant coating has the functions of flame retardancy, high air permeability and improving surface quality. Its material is required to have the properties of high temperature resistance, good use effect and low use cost.
[0003] The pouring temperature of magnesium alloy castings is lower than that of cast iron and cast steel by more than 700℃. The thermal effect of magnesium alloy liquid on the coating is much smaller than that of cast iron and cast steel. However, the magnesium alloy liquid has a fast cold-short speed during the filling process and has a large flow resistance, which is prone to defects such as insufficient pouring and cold shut. In addition, magnesium alloy liquid is easy to react with the medium in the air, especially with oxygen to produce oxidation combustion reaction.
[0004] However, the flame retardant coatings in the prior art cannot meet the requirements. Summary of the invention
[0005] The embodiments of the present application provide a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof, which can improve the surface quality of the sand mold and thus improve the quality of the casting.
[0006] The present application embodiment provides a method for preparing a flame retardant coating for improving the surface quality of sand casting, comprising:
[0007] Preparing a flame retardant and ball-milling the flame retardant to obtain a first mixture;
[0008] Fully mixing refractory powder, suspending agent, binder and the first mixture to prepare a second mixture;
[0009] adding anhydrous ethanol to the second mixture and stirring to obtain a third mixture;
[0010] The third mixture is subjected to low temperature pretreatment to obtain a Baume value within the range of 20-40.
[0011] In a feasible implementation, the flame retardant includes 2 wt.%-5 wt.% of boric acid and 1 wt.%-3 wt.% of NH4BF4.
[0012] In a feasible implementation, the ball milling the flame retardant includes using a ball mill to ball mill the flame retardant, and the ball milling uses stainless steel balls with a diameter of 3 mm.
[0013] In a feasible implementation, the ball milling time of the ball milling treatment ranges from 2 min to 15 min.
[0014] In a feasible implementation, the refractory powder includes 20wt.%-30wt.% of zircon powder, 15wt.%-30wt.% of red iron oxide, 12wt.%-24wt.% of high-alumina bauxite and 5wt.%-10wt.% of quartz powder.
[0015] In a feasible implementation, the suspending agent includes 2 wt.%-8 wt.% of attapulgite clay.
[0016] In a feasible implementation, the binder includes 2wt.%-5wt.% of silica gel and 1wt.%-5wt.% of phenolic resin.
[0017] In a feasible implementation, the second mixture and the anhydrous ethanol are stirred by wet ball milling, wherein the wet ball milling uses graphite balls with a diameter of 5 mm;
[0018] and / or, the ball milling time ranges from 30 min to 60 min;
[0019] And / or, the ball milling speed ranges from 300r / min to 500r / min.
[0020] In a feasible implementation, the temperature range of the low-temperature pretreatment is 80°C-100°C.
[0021] In the second aspect, an embodiment of the present application provides a flame retardant coating for improving the surface quality of sand casting, which is prepared using the preparation method of the flame retardant coating for improving the surface quality of sand casting as described in the first aspect. According to the weight percentage of the ingredients, the flame retardant coating for improving the surface quality of sand casting includes 2wt.%-5wt.% of boric acid, 1wt.%-3wt.% of NH4BF4, 20wt.%-30wt.% of zircon powder, 15wt.%-30wt.% of red iron oxide, 12wt.%-24wt.% of high alumina, 5wt.%-10wt.% of quartz powder, 2wt.%-8wt.% of attapulgite clay, 2wt.%-5wt.% of silica melt, 1wt.%-5wt.% of phenolic resin and anhydrous ethanol.
[0022] The embodiment of the present application provides a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof. When preparing the flame retardant coating, first, a flame retardant is prepared, and the flame retardant is ball-milled to obtain a first mixture. Then, refractory powder, a suspending agent, a binder and the first mixture are fully mixed to obtain a second mixture. Next, anhydrous ethanol is added to the second mixture and stirred to obtain a third mixture. Finally, the third mixture is subjected to low-temperature pretreatment so that its Baume value is within the range of 20-40 to obtain a flame retardant coating. The flame retardant coating has the characteristics of good refractoriness and a small thermal expansion coefficient, and can improve the surface quality of the sand mold, thereby improving the quality of the casting. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present application and do not constitute improper limitations on the present invention.
[0024] In the attached picture:
[0025] Figure 1 This is a flow chart of a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof provided in one embodiment of the present application. DETAILED DESCRIPTION
[0026] In order to enable those skilled in the art to better understand the technical solutions in this application, the following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.
[0027] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.
[0028] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
[0029] As an important component in rare earth magnesium alloy sand casting, flame retardant coating has the functions of flame retardancy, high air permeability and improving surface quality. Its material is required to have the properties of high temperature resistance, good use effect and low use cost.
[0030] The pouring temperature of magnesium alloy castings is lower than that of cast iron and cast steel by more than 700℃. The thermal effect of magnesium alloy liquid on the coating is much smaller than that of cast iron and cast steel. However, the magnesium alloy liquid has a fast cold-short speed during the filling process and has a large flow resistance, which is prone to defects such as insufficient pouring and cold shut. In addition, magnesium alloy liquid is easy to react with the medium in the air, especially with oxygen to produce oxidation combustion reaction.
[0031] However, the flame retardant coatings in the prior art cannot meet the requirements.
[0032] In order to solve the above problems, the embodiment of the present application provides a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof, so as to improve the surface quality of the sand mold and thus improve the quality of the casting. The scheme provided by the embodiment of the present application will be described below in conjunction with the drawings of the specification.
[0033] Figure 1 This is a flow chart of a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof provided in one embodiment of the present application.
[0034] Reference Figure 1 As shown, the embodiment of the present application provides a flame retardant coating for improving the surface quality of sand casting and a preparation method thereof, comprising:
[0035] S100: preparing a flame retardant, and ball-milling the flame retardant to obtain a first mixture.
[0036] The flame retardant includes 2wt.%-5wt.% of boric acid and 1wt.%-3wt.% of NH4BF4. The flame retardant is ball-milled using a ball mill, wherein a stainless steel ball with a diameter of 3 mm is used for the ball milling. The ball milling time ranges from 2min to 15min. The ball milling speed ranges from 100r / min to 200r / min.
[0037] Boric acid is easy to lose water after heating and turns into metaboric acid HBO2. After further heating, it can turn into perboric acid H2B4O7. When the temperature rises, it will eventually turn into boric anhydride. Adding boric acid to the coating can form a thin layer of boric anhydride on the surface of the sand mold during the pouring process, which can dissolve metal oxides such as MgO to form a series of fusible compounds, effectively preventing the oxidation of magnesium alloys. Boric anhydride reacts with magnesium to form a dense Mg3B2 film, which plays a role in preventing reaction and combustion.
[0038] S200: fully mixing the refractory powder, the suspending agent, the binder and the first mixture to obtain a second mixture.
[0039] Exemplarily, the refractory powder includes 20wt.%-30wt.% zircon powder, 15wt.%-30wt.% red iron oxide, 12wt.%-24wt.% high alumina and 5wt.%-10wt.% quartz powder. The suspending agent includes 2wt.%-8wt.% attapulgite clay. The binder includes 2wt.%-5wt.% silica gel and 1wt.%-5wt.% phenolic resin.
[0040] Zircon powder, red iron oxide, high-alumina bauxite and quartz powder all have good refractoriness and low thermal expansion coefficient. At the same time, red iron oxide, high-alumina bauxite and quartz powder are cheap, which is conducive to reducing the cost of coatings. The four refractory materials are matched with each other, which helps to increase the gap between the refractory materials and improve the air permeability of the coating. The binder uses silica gel and phenolic resin to give the coating strength and coating properties; the suspending agent uses attapulgite clay to improve the suspension performance of the coating.
[0041] S300: adding anhydrous ethanol to the second mixture and stirring to obtain a third mixture.
[0042] Exemplarily, the second mixture and anhydrous ethanol are stirred by wet ball milling, using graphite balls with a diameter of 5 mm; the ball milling time ranges from 30 min to 60 min; and the ball milling speed ranges from 300 r / min to 500 r / min.
[0043] It is understood that anhydrous ethanol is used as the carrier liquid.
[0044] S400: performing low-temperature pretreatment on the third mixture to make its Baume value within the range of 20-40.
[0045] The temperature range of low temperature pretreatment can be 80° C.-100° C. During pretreatment, a Baume meter is used to detect the Baume degree of the coating. If the Baume degree does not reach 20-40, anhydrous ethanol is repeatedly added and stirred at high speed until the Baume degree of the coating reaches the set range to obtain the flame retardant material.
[0046] When in use, the flame retardant material can be sprayed on the sand mold surface by air pressure spraying, and each position of the sand core can be brushed 3-4 times. After the brushing is completed, ignite and burn off the alcohol on the surface of the sand core. Use a brush to clean the enriched coating layer on the surface of the sand core, and then blow it clean before assembling and using it.
[0047] This flame retardant material has good effect, can effectively prevent the casting from bulging and burning, the casting surface is smooth and has no surface burnt spots, and the surface roughness of the sand casting can reach 6.3μm. Therefore, the coating has the advantages of low cost, good flame retardancy, and high surface finish of the casting after use, which is conducive to the promotion and application of rare earth magnesium alloy sand casting and meets the manufacturing needs of parts in related fields such as aerospace.
[0048] Example
[0049] Step 1: Flame Retardant Ball Milling
[0050] The ball mill mills a flame retardant of a certain proportion to obtain a first mixture.
[0051] Among them, the proportion of flame retardants is: boric acid added in an amount of 4wt.%, and NH4BF4 added in an amount of 1wt.%.
[0052] The ball milling process uses stainless steel balls with a diameter of 3 mm, a ball milling time of 10 min, and a ball milling speed of 200 r / min.
[0053] Step 2: Binder Mixing
[0054] A certain proportion of refractory powder, a certain proportion of suspending agent and a ball-milled flame retardant are mixed for 5 minutes, and then a certain proportion of binder is added and mixed to obtain a second mixture.
[0055] The refractory powder ratio is 20wt.% of zircon powder, 30wt.% of red iron oxide, 20wt.% of high-alumina bauxite and 10wt.% of quartz powder.
[0056] The suspending agent is 5 wt.% of attapulgite clay.
[0057] The binder ratio is 4wt.% of silica gel and 1wt.% of phenolic resin.
[0058] Step 3: Blend at high speed
[0059] Anhydrous ethanol was added to the second mixture, and the mixture was stirred by wet ball milling to obtain a third mixture.
[0060] The ball milling balls used for stirring in wet ball milling are graphite balls with a diameter of 5 mm, the ball milling time is 40 min, and the ball milling speed is 500 r / min.
[0061] Step 4: Low temperature pretreatment
[0062] The third mixture is subjected to low-temperature pretreatment at 100° C., and the Baume degree of the coating is detected by a Baume meter. If the Baume degree does not reach 20-40, the steps of adding anhydrous ethanol and high-speed stirring are repeated until the Baume degree of the coating reaches the set range, thereby completing the preparation of the flame retardant coating.
[0063] Step 5: Air pressure spraying
[0064] Use air pressure spraying to spray the prepared flame retardant coating on the surface of the sand mold. Brush each position of the sand core 3-4 times. After brushing, ignite and burn off the alcohol on the surface of the sand core. Use a brush to clean the coating layer on the surface of the sand core, then blow it clean and use it for molding. The surface roughness of the treated sand mold can reach 6.3μm, the surface is smooth, and the flame retardant effect is good, with high quality.
[0065] In the second aspect, an embodiment of the present application provides a flame retardant coating for improving the surface quality of sand casting, which is prepared using the preparation method of the flame retardant coating for improving the surface quality of sand casting as described in the first aspect. According to the weight percentage of the ingredients, the flame retardant coating for improving the surface quality of sand casting includes 2wt.%-5wt.% of boric acid, 1wt.%-3wt.% of NH4BF4, 20wt.%-30wt.% of zircon powder, 15wt.%-30wt.% of red iron oxide, 12wt.%-24wt.% of high alumina, 5wt.%-10wt.% of quartz powder, 2wt.%-8wt.% of attapulgite clay, 2wt.%-5wt.% of silica melt, 1wt.%-5wt.% of phenolic resin and anhydrous ethanol.
[0066] The flame retardant coating has the characteristics of good refractoriness and small thermal expansion coefficient, and can improve the surface quality of sand molds and thus improve the quality of castings.
[0067] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on the several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.
[0068] The above specific implementation methods further explain in detail the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.
Claims
1. A method for preparing a flame retardant coating for improving the surface quality of sand casting, characterized in that: include: Preparing a flame retardant, and ball-milling the flame retardant to obtain a first mixture; Fully mixing refractory powder, suspending agent, binder and the first mixture to prepare a second mixture; adding anhydrous ethanol to the second mixture and stirring to obtain a third mixture; The third mixture is subjected to low temperature pretreatment to obtain a Baume value within the range of 20-40.
2. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The flame retardant includes 2wt.%-5wt.% of boric acid and 1wt.%-3wt.% of NH4BF4.
3. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The ball milling treatment of the flame retardant includes using a ball mill to ball mill the flame retardant, and the ball milling treatment uses stainless steel balls with a diameter of 3 mm.
4. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 3, characterized in that: The ball milling time of the ball milling treatment ranges from 2 min to 15 min.
5. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The refractory powder includes 20wt.%-30wt.% of zircon powder, 15wt.%-30wt.% of red iron oxide, 12wt.%-24wt.% of high-alumina bauxite and 5wt.%-10wt.% of quartz powder.
6. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The suspending agent comprises 2wt.%-8wt.% of attapulgite clay.
7. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The binder includes 2wt.%-5wt.% of silica gel and 1wt.%-5wt.% of phenolic resin.
8. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The second mixture and the anhydrous ethanol are stirred by wet ball milling, wherein the wet ball milling uses graphite balls with a diameter of 5 mm; and / or, the ball milling time ranges from 30 min to 60 min; And / or, the ball milling speed ranges from 300r / min to 500r / min.
9. The method for preparing a flame retardant coating for improving the surface quality of sand casting according to claim 1, characterized in that: The temperature range of the low temperature pretreatment is 80°C-100°C.
10. A flame retardant coating for improving the surface quality of sand casting, characterized in that: The flame retardant coating for improving the surface quality of sand casting is prepared using the preparation method of the flame retardant coating for improving the surface quality of sand casting as described in any one of claims 1 to 9. According to the weight percentage of the components, the flame retardant coating for improving the surface quality of sand casting includes 2wt.%-5wt.% of boric acid, 1wt.%-3wt.% of NH4BF4, 20wt.%-30wt.% of zircon powder, 15wt.%-30wt.% of red iron oxide, 12wt.%-24wt.% of high alumina, 5wt.%-10wt.% of quartz powder, 2wt.%-8wt.% of attapulgite clay, 2wt.%-5wt.% of silica melt, 1wt.%-5wt.% of phenolic resin and anhydrous ethanol.