A scraping coating process for heat-resistant coating on the outside of an engine housing

Abstract

The present invention relates to a scraping coating process method for an outer heat-resistant coating of an engine casing, comprising step 1: using sandpaper to grind the outer surface of the engine casing; step 2: using a solvent or a special cleaning agent to degrease the outer surface of the engine casing; step 3: determining the single-pass scraping thickness and the scraping starting area before preparing the paint; step 4: determining the temperature and humidity range, and preparing a paint with a suitable viscosity; step 5: using a scraping tool to scrape the paint multiple times and repair the surface; step 6: measuring the thickness and air-drying the paint after the scraping is completed. The scraping coating process method for the outer heat-resistant coating of the engine casing proposed by the present invention can realize the scraping and molding of a large thickness coating, and can also adapt well to the arc surface of the engine casing. The heat-resistant coating obtained by the scraping process not only has good apparent quality, but also has a high bonding strength, and the reliability of the bonding between the casing and the outer protective coating is high.

Description

Technical Field

[0001] The invention relates to a scraping coating process method for an outer heat-resistant coating of an engine casing, and belongs to the technical field of forming an outer heat-resistant coating of an engine casing. Background Art

[0002] During the operation of a solid rocket engine, the outer surface of the engine will rub against the atmosphere violently, generating a temperature of thousands of degrees. In order to prevent the solid rocket engine casing from ablation and loss of strength due to overheating, it is necessary to coat the casing surface with a coating such as a thermal insulation material. At present, the outer thermal protection coating of the engine casing is usually applied by automatic spraying, but when the thermal insulation coating is thick, multiple intermittent spraying is required to ensure the spraying quality. The coating forming cycle is long, and it is difficult to avoid the hazards of paint mist. Moreover, for the coating forming of the special-shaped surface of the solid rocket engine casing, the spraying method is difficult to meet the thickness difference and smooth transition of the special-shaped surface. At present, scraping technology is the molding technology that most meets the current large-thickness coating production needs, but it is mostly used in building decoration, road paving and road marking spraying, and there is almost no scraping technology for solid rocket engine casings. Compared with the automatic spraying method of large-thickness external thermal protection coating, the scraping coating method has the advantages of high single-pass thickness rate, small solvent usage, and no paint mist influence. It can effectively shorten the molding cycle of large-thickness thermal insulation coating and adapt to the future group and batch production rhythm. Therefore, it is urgent to carry out research on scraping coating technology suitable for solid rocket engine external thermal protection coating. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and to propose a scraping coating process method for the heat-resistant coating on the outside of the engine housing, so as to achieve rapid molding of a thick coating and good bonding strength with the housing.

[0004] The technical solution of the present invention is:

[0005] A scraping coating process for an outer heat-resistant coating of an engine housing, comprising:

[0006] Step 1: Use sandpaper to polish the outer surface of the engine casing;

[0007] Step 2: Use solvent to degrease the outer surface of the engine housing;

[0008] Step 3: Determine the scraping method and area before preparing the paint;

[0009] Step 4: Determine the temperature and humidity range and prepare paint with appropriate viscosity;

[0010] Step 5: Use a scraping tool to apply multiple coats of paint and repair the surface;

[0011] Step 6: After the coating is completed, measure the thickness and solidify the surface.

[0012] Furthermore, the sandpaper is 80-120 mesh sandpaper.

[0013] Furthermore, the solvent is ethyl acetate.

[0014] Further, the scraping method and area are determined, specifically: the single-pass scraping thickness and the scraping starting area are determined;

[0015] According to different thickness requirements and curing shrinkage rates, the thickness of each scraping process, i.e., the thickness of a single scraping pass, is designed; the coating forming area is larger than the actual forming area, and the starting position of scraping starts from the lower side of the engine housing.

[0016] Furthermore, the forming structure of the thickness of a single scraping is:

[0017] "Base material + 0.5mm + 1~1.5mm + 0.5mm + 0.2mm". If the thickness is too large, it can be scraped multiple times on the middle layer with a thickness of 1~1.5mm.

[0018] Furthermore, the temperature and humidity range is determined, specifically: the temperature range is between 15°C and 35°C, and the humidity range is ≤70%.

[0019] Furthermore, the prepared paint is a heat-proof coating, which is divided into two components, A and B, and its diluent is 120# gasoline; component A is specifically a mixture of silica gel, glass beads, carbon fiber and diluent, and component B is a curing agent, specifically a mixture of plasticizer and catalyst.

[0020] Furthermore, during scraping, the relationship between the mass ratio of paint to thinner, the single scraping thickness and the purpose is specifically as follows:

[0021] When A:B:diluent=100:1.0:30, the thickness is 0.5-1.0mm, and the substrate is bonded;

[0022] When A:B:diluent=100:1.0:35, the thickness is 1.0-1.5mm, and the coating is thickened;

[0023] When A:B:diluent=100:1.0:40, the thickness is 0.5-1.2mm, and it is applied by hand scraping;

[0024] When A:B:diluent=100:1.0:50, the thickness is 0.2-0.3mm and the surface is wetted.

[0025] Furthermore, the scraping tool is a rubber scraper. First, the rubber scraper is pressed against the surface of the engine housing, and then the gap between the scraper and the housing is adjusted to control the required scraping thickness; then the housing is started to rotate automatically, and the paint is evenly released onto the scraper by the discharge mechanism, and the amount of paint is controlled to completely fill the rubber scraper but not flow out; when the paint accumulates to meet the scraping requirements, a coating with uniform thickness and smooth surface can be formed between the scraper and the housing; when scraping manually, the housing is fixed, and the hand-held scraper is moved at a uniform speed above the housing for scraping, and the inclination angle between the scraper and the surface of the housing to be scraped is 50° to 60°;

[0026] Multiple passes of scraping can be completed by adjusting the scraping force, angle, time interval, and single scraping thickness. Scrape in one direction and do not scrape back and forth multiple times.

[0027] Furthermore, the thickness of the coating after scraping is measured, and after meeting the thickness requirements, it is cured at room temperature to obtain the heat-resistant coating on the outer surface of the shell by manual scraping.

[0028] The beneficial effects of the present invention compared with the prior art are:

[0029] (1) The scraping coating process for the outer heat-resistant coating of the engine housing proposed in the present invention can realize the scraping molding of a large-thickness coating, and can also well adapt to the arc surface of the engine housing. The heat-resistant coating obtained by the scraping coating process not only has good surface quality, but also has high bonding strength, and the bonding reliability between the housing and the outer protective coating is high.

[0030] (2) The scraping coating process for the heat-resistant coating on the outside of the engine housing proposed in the present invention can improve the molding efficiency of the coating. Compared with the single-time thickness of 0.1-0.3 mm of spray molding, the single-time molding thickness of scraping molding reaches 1.5 mm. In addition, due to the small proportion of diluent, the interval time of operations can be shortened.

[0031] (3) The scraping coating process method for the heat-resistant coating on the outside of the engine casing proposed in the present invention can improve the utilization rate of the coating. The main loss in the spraying process is due to pipeline loss and paint mist loss, and the paint loss in the scraping coating process is mainly caused by equipment hanging on the wall. The smaller the loss rate is during large-scale operations, the higher the coating utilization rate is.

[0032] (4) The scraping process for applying the heat-resistant coating on the outside of the engine housing proposed by the present invention can improve the safety during the operation. 120# gasoline is used as the diluent. The smaller the diluent, the smaller the hazard source. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a flow chart of the scraping process. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0035] After a large number of experimental studies, the present invention conducted orthogonal analysis on the mechanical and heat-resistant properties of coatings after molding with paints of different proportions, and obtained the available diluent ratio. At the same time, a multi-parameter control variable analysis was performed on the scraping process, and the control method of the diluent ratio under different working conditions was studied to obtain paint preparation parameters that meet different processes.

[0036] refer to Figure 1 As shown, the present invention discloses a scraping coating process method for a heat-resistant coating on the outside of an engine housing, and the scraping coating process method comprises the following steps:

[0037] Step 1: Use sandpaper to polish the outer surface of the engine casing;

[0038] Step 2: Use solvent to degrease the outer surface of the engine housing;

[0039] Step 3: Determine the scraping method and area before preparing the paint;

[0040] Step 4: Determine the temperature and humidity range and prepare paint with appropriate viscosity;

[0041] Step 5: Use a scraping tool to apply multiple coats of paint and repair the surface;

[0042] Step 6: After the coating is completed, measure the thickness and solidify the surface.

[0043] Furthermore, the sandpaper is 80-120 mesh sandpaper.

[0044] Furthermore, the solvent is ethyl acetate.

[0045] Further, the scraping method and area are determined, specifically: the single-pass scraping thickness and the scraping starting area are determined;

[0046] According to different thickness requirements and curing shrinkage rates, the thickness of each scraping process, i.e., the thickness of a single scraping pass, is designed; the coating forming area is larger than the actual forming area, and the starting position of scraping starts from the lower side of the engine housing.

[0047] Furthermore, the forming structure of the thickness of a single scraping is:

[0048] "Base material + 0.5mm + 1~1.5mm + 0.5mm + 0.2mm". If the thickness is too large, it can be scraped multiple times on the middle layer with a thickness of 1~1.5mm.

[0049] Furthermore, the temperature and humidity range is determined, specifically: the temperature range is between 15°C and 35°C, and the humidity range is ≤70%.

[0050] Furthermore, the prepared paint is a heat-proof coating, which is divided into two components, A and B, and its diluent is 120# gasoline; component A is specifically a mixture of silica gel, glass beads, carbon fiber and diluent, and component B is a curing agent, specifically a mixture of plasticizer and catalyst.

[0051] Furthermore, during scraping, the relationship between the mass ratio of paint to thinner, the single scraping thickness and the purpose is specifically as follows:

[0052] When A:B:diluent=100:1.0:30, the thickness is 0.5-1.0mm, and the substrate is bonded;

[0053] When A:B:diluent=100:1.0:35, the thickness is 1.0-1.5mm, and the coating is thickened;

[0054] When A:B:diluent=100:1.0:40, the thickness is 0.5-1.2mm, and it is applied by hand scraping;

[0055] When A:B:diluent=100:1.0:50, the thickness is 0.2-0.3mm and the surface is wetted.

[0056] The above four categories correspond to "substrate + 0.5mm + 1~1.5mm + 0.5mm + 0.2mm".

[0057] Furthermore, the scraping tool is a rubber scraper. First, the rubber scraper is pressed against the surface of the engine housing, and then the gap between the scraper and the housing is adjusted to control the required scraping thickness; then the housing is started to rotate automatically, and the paint is evenly released onto the scraper by the discharge mechanism, and the amount of paint is controlled to completely fill the rubber scraper but not flow out; when the paint accumulates to meet the scraping requirements, a coating with uniform thickness and smooth surface can be formed between the scraper and the housing; when scraping manually, the housing is fixed, and the hand-held scraper is moved at a uniform speed above the housing for scraping, and the inclination angle between the scraper and the surface of the housing to be scraped is 50° to 60°;

[0058] Multiple passes of scraping can be completed by adjusting the scraping force, angle, time interval, and single scraping thickness. Scrape in one direction and do not scrape back and forth multiple times.

[0059] Furthermore, the thickness of the coating after scraping is measured, and after meeting the thickness requirements, it is cured at room temperature to obtain the heat-resistant coating on the outer surface of the shell by manual scraping.

[0060] The present invention is further described below with reference to specific embodiments.

[0061] At present, the solid rocket engine shells using thick outer heat protection coatings mainly include carbon fiber / epoxy resin, aramid fiber / epoxy resin, carbon fiber / polytriazole and other composite material shells. The specific scraping process methods for this type of engine shells include:

[0062] Step 1: Use 80-120 grit sandpaper to polish the shell surface. Polishing increases the surface roughness of the shell and can increase the adhesion between the coating and the engine shell to a certain extent.

[0063] Step 2: Use a solvent to degrease the outer surface of the shell. In this embodiment, the degreasing solvent selected for the composite material shell is ethyl acetate.

[0064] Oil, release agent or dust on the surface of composite shell will affect the adhesion of the outer protective coating. Ethyl acetate solvent can be used to wipe the surface to achieve the purpose of surface cleaning and degreasing. After wiping, wait for the solvent to completely evaporate and there is no trace of solvent wiping on the shell surface before proceeding to the next step.

[0065] Step 3: Determine the scraping area and coating thickness before scraping the engine housing. According to different thickness requirements and curing shrinkage, design the thickness of each scraping process. The thickness of a single scraping generally adopts the molding structure of "substrate + 0.5mm + 1~1.5mm + 0.5mm + 0.2mm (ultra-low viscosity)". If the thickness is too large, it can be scraped multiple times in the middle layer with a thickness of 1~1.5mm; the coating molding area is generally required to be larger than the actual molding range, and the scraping start position starts from the lower side of the engine housing.

[0066] Step 4: Prepare paint as heat-resistant coating, use 120# gasoline as diluent, and the ratio of paint components A and B to diluent is: component A: component B: diluent = 100:1.0:35.

[0067] At 15℃~35℃, humidity ≤70%, weigh 1000g of component A paint, 350g

[0068] Mix the diluent and stir evenly. When no lumps or agglomerates are observed in the paint, add 10g of component B and continue stirring evenly to obtain a scraper paint with suitable viscosity.

[0069] Step 5: First, place the rubber scraper close to the surface of the engine housing, and then adjust the gap between the scraper and the housing to control the required scraping thickness; then start the automatic rotation of the housing, and the discharge mechanism will release the paint evenly onto the scraper, and control the amount of paint to completely fill the rubber scraper but not flow out; when the paint accumulates to meet the scraping requirements, a coating with uniform thickness and smooth surface can be formed between the scraper and the housing; when scraping manually, fix the housing, and move the handheld scraper at a constant speed above the housing for scraping, with the inclination angle between the scraper and the surface of the housing being scraped being 50° to 60°. Multiple scrapings can be completed by adjusting the scraping force, angle, time interval, and single scraping thickness. Scrape in one direction during scraping, and do not scrape back and forth multiple times.

[0070] The first scraping can be applied with a thickness of 0.5mm to improve the bonding performance of the foundation; if the thickness of the first scraping does not meet the set requirements, it can be scraped again. When bubbles, depressions, wrinkles, scratches, etc. appear on the scraping coating surface, they should be repaired immediately. Only after the repairs are complete can the next scraping construction be carried out. Generally, 3 to 7 scrapings are required, and the total scraping thickness is 4mm to 8mm; after the required thickness is achieved, ultra-low viscosity paint can be used for 0.2mm scraping, which can improve the surface quality.

[0071] Step 6: Measure the wet film thickness of the coating after scraping. If it meets the thickness requirements, cure it at room temperature. After the coating is completely cured, you can get the heat-resistant coating on the engine housing outside by manual scraping. The scraper pressure combined with the surface grinding of the housing during scraping increases the bonding force between the coating and the surface of the engine housing, making the coating after scraping have good adhesion.

[0072] It can be seen from the above embodiments that compared with the automatic spraying process method, the solid rocket engine scraping process method of the present invention can achieve a single-pass thickness of about 1 mm, has a high thickness rate, uses less solvent, and obtains a coating with good bonding performance and no pollution.

[0073] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

Claims

1. A scraping coating process for the heat-resistant coating on the outside of an engine housing, characterized in that include: Step 1: Use sandpaper to polish the outer surface of the engine casing; Step 2: Use solvent to degrease the outer surface of the engine housing; Step 3: Determine the scraping method and area before preparing the paint; specifically: determine the single-pass scraping thickness and the scraping starting area; design the thickness of each scraping process according to different thickness requirements and curing shrinkage rates, that is, the single-pass scraping thickness; the coating forming area is larger than the actual forming area, and the scraping starting position starts from the lower side of the engine housing; The forming structure of the thickness of a single scraping is: "Base material + 0.5mm + 1~1.5mm + 0.5mm + 0.2mm", if the thickness is too large, apply scraping multiple times on the middle layer with a thickness of 1~1.5mm; Step 4: Determine the temperature and humidity range and prepare paint with appropriate viscosity; The prepared paint is a heat-resistant paint, which is divided into two components, A and B, and the diluent is 120# gasoline; the A component is specifically a mixture of silica gel, glass beads, carbon fiber and diluent, and the B component is a curing agent, specifically a mixture of plasticizer and catalyst; When scraping, the relationship between the mass ratio of paint and thinner, the thickness of a single scraping and the purpose is as follows: When A:B:diluent=100:1.0:30, the thickness is 0.5~1.0mm, and the substrate is bonded; When A:B:diluent=100:1.0:35, the thickness is 1.0~1.5mm, and the coating is thickened; When A:B:thinner=100:1.0:40, the thickness is 0.5~1.2mm, and it is applied by hand scraping; When A:B:diluent=100:1.0:50, the thickness is 0.2~0.3mm and the surface is wetted; Step 5: Use a scraping tool to apply multiple coats of paint and repair the surface; The scraping tool is a rubber scraper. First, the rubber scraper is pressed against the surface of the engine housing, and then the gap between the scraper and the housing is adjusted to control the required scraping thickness; then the housing is started to rotate automatically, and the paint is evenly released onto the scraper by the discharge mechanism, and the amount of paint is controlled to completely fill the rubber scraper but not flow out; when the paint accumulates to meet the scraping requirements, a coating with uniform thickness and smooth surface can be formed between the scraper and the housing; when scraping manually, the housing is fixed, and the hand-held scraper is moved at a uniform speed above the housing for scraping, and the inclination angle between the scraper and the surface of the housing to be scraped is 50°~60°; Multiple scrapings can be completed by adjusting the scraping force, angle, time interval, and single scraping thickness. When scraping, scrape in one direction and do not scrape back and forth multiple times; Step 6: After the coating is completed, measure the thickness and solidify the surface.

2. The scraping coating process of the heat-resistant coating on the outer surface of the engine housing according to claim 1 is characterized in that: The sandpaper is 80-120 mesh sandpaper.

3. The scraping coating process of the heat-resistant coating on the outer surface of the engine housing according to claim 1 is characterized in that: The solvent is ethyl acetate.

4. The scraping coating process of the heat-resistant coating on the outer surface of the engine housing according to claim 1 is characterized in that: Determine the temperature and humidity range, specifically: the temperature range is between 15℃~35℃, and the humidity range is ≤70%.

5. The scraping coating process of the heat-resistant coating on the outer surface of the engine housing according to claim 1 is characterized in that: The thickness of the coating after scraping is measured, and after meeting the thickness requirements, it is cured at room temperature to obtain the heat-resistant coating on the outer shell under manual scraping.

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