Coating process method of high-temperature-resistant high-strength sealant

Abstract

The invention belongs to the field of aeronautical manufacturing technology assembly, and relates to a high-temperature-resistant high-strength sealant coating process method which comprises the following steps: step 1, preparing a sealant; 2, the surface of the structure needing to be coated with the sealant is pretreated; thirdly, the surface of the pretreated structure is coated with a bonding base coat and then aired; 4, the surface of the structure coated with the base coat is coated with a sealant and vulcanized; and 5, detecting whether sealant coating is qualified or not.

Description

Technical Field

[0001] The invention belongs to the field of aviation manufacturing technology assembly and relates to a high-temperature resistant and high-strength sealant coating process method. Background Art

[0002] The engine nacelle area of ​​the aircraft is a non-sealed area. In the tropical ocean environment of high temperature, high humidity, high salt fog and high solar radiation, a large number of parts and components inside the engine nacelle area of ​​the aircraft are corroded. In order to improve this situation, the process department decided to change the engine nacelle area to a sealed area. However, the engine nacelle area itself belongs to a high-frequency, multi-shock, and high-temperature environment. Traditional sealants such as XM22 and XM28 are not applicable. After coating, there are problems such as aging, peeling, pores, and degumming. Therefore, it is necessary to develop a new type of high-temperature resistant and high-strength sealant and focus on solving the process method of how to configure and coat it, which is a key problem in achieving sealed assembly in the engine nacelle area. Summary of the invention

[0003] The purpose of the present invention is to propose a new process method for configuring and coating a high-temperature resistant and high-strength sealant, so as to solve the key problem of sealing and assembling the engine nacelle area.

[0004] Technical Solution

[0005] A high temperature resistant and high strength sealant coating process method comprises the following steps:

[0006] Step 1: preparing sealant;

[0007] Step 2: Pre-treat the surface of the structure to be coated with sealant;

[0008] Step 3: Apply the bonding primer on the pre-treated surface of the structure and let it dry;

[0009] Step 4: Apply sealant on the surface of the structure after primer coating and vulcanize;

[0010] Step 5: Check whether the sealant coating is qualified.

[0011] Furthermore, in step 1, the sealant is HM321 I type sealant, and the mass ratio of base paste, vulcanizing agent, and catalyst is 100:0.9-1.0:0.6-1.5. Only when the sealant is prepared according to this ratio can the durability, vulcanization hardness, generation rate and other properties of the sealant be optimized.

[0012] Furthermore, the single preparation amount of sealant should not exceed 2kg, and the amount below 500g should be mixed by hand or machine, and 500g to 2kg should be mixed by machine. If the single preparation exceeds 2kg, a three-roll grinder with a larger capacity should be selected, otherwise the sealant is easy to overflow and be contaminated by the outside world.

[0013] Furthermore, in step 2, the pretreatment is to clean the surface of the structural part, and the process is as follows: wipe the grease and dust on the surface to be sealed with clean and dry absorbent cotton dipped in aviation washing gasoline or acetone, and then immediately wipe it dry with clean and dry absorbent cotton; repeat the above steps until there is no stain on the clean and dry absorbent cotton; dry it for 10 minutes to 20 minutes. Only when the cleaning is up to standard can the adhesion of the primer be maximized.

[0014] Furthermore, in the step 3, the coating primer is: NJD-6, and the NJD-6 coating primer is the primer with the best bonding performance with HM321 I type sealant at present;

[0015] The process of applying primer to the sealing surface is as follows: Dip the NJD-6 primer with a clean fine brush or cotton wool, and do not let the primer drip from the brush or cotton wool. Apply the NJD-6 primer to the clean surface to be sealed and let it air dry. If the air-drying time is exceeded or an opaque layer or contamination appears after air-drying, clean it again and apply the primer.

[0016] The process of fastener primer coating is as follows: immerse the fasteners in the primer coating to completely soak them, remove them and place them on a clean absorbent cotton cloth to air dry; if the air drying time exceeds or an opaque layer or contamination appears after air drying, clean them again and apply primer.

[0017] Furthermore, in step 4, if the surface of the structure is a bonding surface, the sealant coating process is as follows:

[0018] Apply the prepared sealant evenly on the surface to be sealed;

[0019] Check whether there is uniform sealant on 100% of the bonding surface area of ​​the sealing area, and the thickness of the sealant coating is controlled at 0.2mm~1.0mm;

[0020] Do not close the mold for the parts coated with sealant yet, and close the mold when they are close to the active period.

[0021] Furthermore, in step 4, if the structural surface is a gap sealing surface, the sealant coating process is as follows:

[0022] A protective tape is attached to the seam edge of the gap sealing surface, and the protective tape is removed after the sealant is vulcanized;

[0023] Use an injection gun to evenly apply sealant along the sealing surface of the gap.

[0024] Furthermore, in step 4, if the structural surface is a fillet, the sealant coating process is as follows:

[0025] Use an injection gun to apply sealant along the edges of both ends of the fillet, and use a shaping tool to trim the sealant fillet;

[0026] The shaping is performed using shaping tools during the active period of the sealant. If soapy water is used for appearance shaping, the shaping is performed once on the surface in one direction using soapy water. Repeated shaping is not allowed.

[0027] Small-diameter plastic nozzles should be used for fillet seals not exceeding 90°, and large-diameter plastic nozzles should be used for fillet seals exceeding 90°.

[0028] Furthermore, in step 4, if the structural surface is a fastener surface, the sealant coating process is as follows:

[0029] The sealant is applied on the surface of the installed fastener and within a range of 2mm to 5mm around the connection area between the fastener and the connected part.

[0030] Further, in step 5, the detection method is as follows:

[0031] Rub the edge of the fully vulcanized sealant with a rubber, and there should be no peeling;

[0032] There shall be no missing coating, lack of glue, process pores with a diameter exceeding 1mm and debonding on the sealant surface.

[0033] Beneficial effects: The present invention can solve the problem of sealing and assembling in the nacelle area of ​​an aircraft engine. The new high-temperature resistant and high-strength sealant configuration method adopted is scientific and reasonable. The sealant has good fluidity and construction properties. The coating process method is safe and effective, and the sealing and anti-corrosion effect is remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention includes 8 drawings, and the drawings and the descriptions of the drawings are as follows:

[0035] Figure 1 It is a schematic diagram of the structure of the aircraft engine nacelle area;

[0036] Figure 2 It is a diagram of the areas and typical sealing forms of the aircraft engine nacelle area seal;

[0037] Figure 2-1 Schematic diagram of skin butt joint and joint sealing;

[0038] Figure 2-2 Schematic diagram of sealing at frame edge and long stringer;

[0039] Figure 2-3 Schematic diagram of sealing at the leading edge and fairing foreskin;

[0040] Figure 2-4 Schematic diagram of typical sealing of the flap;

[0041] Figure 3 This is a typical sealing diagram of the structural parts of the aircraft engine nacelle;

[0042] Figure 3-1Schematic diagram of typical sealing of the mating surfaces;

[0043] Figure 3-2 Schematic diagram of a typical fillet seal (upper - low angle side, lower - high angle side);

[0044] Figure 3-3 Schematic diagram of typical gap sealing;

[0045] Figure 3-4 Schematic diagram of typical fastener sealing (left) and packaging (right);

[0046] Figure 4 This is a schematic diagram of adding soft aluminum gaskets during positioning and pressing;

[0047] Figure 5 It is a schematic diagram of sealing coating of the fitting surface;

[0048] Figure 5-1 Schematic diagram of sealing coating of the fitting surface;

[0049] Figure 5-2 Schematic diagram of sealing coating and trimming of the fitting surface;

[0050] Figure 6 It is a schematic diagram of the tool used for fillet sealing;

[0051] Figure 6-1 Schematic diagram of sealing coating of the fitting surface;

[0052] Figure 6-2 Adhesive layer shaping tools;

[0053] Figure 7 This is a schematic diagram of the appearance inspection after the high temperature resistant and high strength sealant is applied;

[0054] Figure 7-1 Schematic diagram of sealing thickness control of the fitting surface;

[0055] Figure 7-2 Schematic diagram of fillet seal shape and dimensions;

[0056] Figure 7-3 Schematic diagram of the appearance and dimensions of the gap seal;

[0057] Figure 7-4 Schematic diagram of fastener sealing shape and size control;

[0058] Figure 8 It is the sealing riveting of high temperature resistant and high strength sealants for engine nacelle structural parts;

[0059] Among them: 1- hub fairing, 2- front section, 3- middle section upper cover, 4- load-bearing section, 5- tail cover, 6- middle section side cover, 7- middle section lower cover, 8- propeller root fairing foreskin. DETAILED DESCRIPTION

[0060] The present invention provides a process for preparing and coating a high-temperature resistant and high-strength sealant, which mainly includes the following steps:

[0061] Step 1: Based on the aircraft's engine nacelle area structure (see Figure 1 ) and connection characteristics to determine the area that needs to be sealed (see Figure 2 ) and typical sealing forms.

[0062] Step 2: Adjust the ambient temperature and humidity for the preparation and coating of the high temperature resistant and high strength sealant, and complete the preparation of the high temperature resistant and high strength sealant preparation materials and coating tools.

[0063] Step 3: Complete the pre-assembly, hole making, countersinking, deburring and other tasks of typical structural parts.

[0064] Step 4: Complete the configuration of high temperature resistant and high strength sealant.

[0065] Step 5: First clean the surface of the structural parts to be coated with sealant, then apply the high-temperature resistant and high-strength sealant bonding primer, and after the bonding primer is dried, finally complete the high-temperature resistant and high-strength sealant sealing coating.

[0066] Step 6: Carry out coating and appearance inspection of high temperature resistant and high strength sealant.

[0067] Step 7: Complete the sealing assembly of the aircraft engine nacelle structural parts.

[0068] The invention is described in detail with reference to the accompanying drawings to describe the high temperature resistant and high strength sealant coating process method for the aircraft engine nacelle area:

[0069] Step 1: Identify the sealing area and typical sealing form of the aircraft's engine nacelle area: Determine the sealing area based on the structure and connection characteristics of the aircraft's engine nacelle (see Figure 2 ) and typical sealing forms (see Figure 3 ), the sealing areas and sealing forms are summarized in Table 1 below.

[0070] Table 1 High temperature sealant sealing application location and sealing form

[0071]

[0072] Step 2: Adjust the ambient temperature and humidity for the configuration and coating of the high-temperature resistant and high-strength sealant, and complete the preparation of the materials required for the configuration of the high-temperature resistant and high-strength sealant and the various tools for coating:

[0073] 1) Adjust the working environment of high temperature resistant sealant coating to the following requirements: temperature 10℃~15℃, relative humidity 30%~80% or temperature 15℃~32℃, relative humidity 20%~80%.

[0074] 2) The tools required for sealing and coating with high-temperature resistant and high-strength sealants are shown in Table 2 below.

[0075] Table 2 High temperature resistant and high strength sealant coating tools

[0076] Serial number Tool Name Material grade Material Standards Remark 1 scraper —— —— Mainly used for fitting surfaces and gap sealing 2 roller —— —— Mainly used for sealing of fitting surfaces 3 Glue gun —— —— Mainly used for filling corners, sealing and packaging 4 Filling nozzle —— —— Mainly used for filling corners, sealing and packaging 5 Fine bristle brush —— —— Assistive tools 6 Hair dryer —— —— Drying of bonding primer 7 Observation mirror —— —— Assistive tools

[0077] 3) The materials required for coating with high temperature resistant and high strength sealant are shown in Table 3;

[0078] Table 3 High temperature resistant and high strength sealant coating materials

[0079]

[0080] Step 3: Use the assembly fixture to complete the pre-assembly (positioning, clamping), hole making, deburring and other processes of the aircraft's engine nacelle structural parts. The specific contents are as follows:

[0081] 1) Pre-assembly: Position, clamp, repair and pre-assemble parts or assemblies according to the requirements of the engineering drawings. The sealing surface should be flat and without step difference. The mating surfaces of the matching parts and assemblies should have no gap after positioning and pressing, but a local gap of no more than 0.2mm is allowed within 80mm of the connection without fasteners.

[0082] 2) Positioning and clamping: When using process bolts, bow clamps and other tools to fix and clamp parts and assemblies, paper pads should be placed on the contact points of the structural parts to avoid damaging the surface of the structural parts. For parts with arcs or parts with a thickness of less than or equal to 10mm, the positioning spacing is 80-100mm; for parts with a thickness of more than 10mm, the positioning spacing is 200-250mm; when positioning parts with more than two fitting surfaces, a 0.3mm thick soft aluminum gasket ( Figure 4 ) to prevent the misalignment of the connecting holes during secondary positioning due to the thickness of the glue layer; the gap between the pressed parts and assemblies should not exceed 0.2mm.

[0083] 3) Hole making and countersinking: Before applying the sealing material, all holes must be drilled to the final size and all countersunk sockets must be made. A vertical drill sleeve should be used when making the sockets to ensure the verticality and accuracy of the countersunk sockets. The size of the countersunk sockets can be checked with matching product rivets.

[0084] 4) Deburring: Disassemble all pre-assembled parts and assemblies in reverse order of assembly and place them neatly. Mark parts with similar shapes, large numbers of parts and difficult to identify to avoid misassembly during reassembly. Use a brush or vacuum cleaner to remove metal chips and debris in the interlayer of parts. Remove burrs from all holes and end faces of parts.

[0085] Step 4: The configuration of high temperature resistant and high strength sealant is as follows:

[0086] 1) The mass ratio of each component of the sealant is shown in Table 4;

[0087] Table 4 Proportions of HM321 Type I sealant

[0088] Serial number Ingredients Quality ratio 1 Base cream 100 2 Vulcanizing agent 0.9～1.0 3 catalyst 0.6～1.5

[0089] Note: For seam external sealing, it is recommended to prepare it in a mass ratio of 100:0.9:1, with an active period (coating period) of about 4 hours and a non-stick period of about 24 hours. For seam internal sealing, it is recommended to prepare it in a mass ratio of 100:0.9:0.6, with an active period of about 5 hours, and riveting should be completed within 12 hours.

[0090] 2) Due to the short activity period of the sealant, the amount of sealant prepared each time should not exceed 2kg. 0.5kg to 2kg should be mixed by machine, and hand mixing is allowed if it does not exceed 500g.

[0091] 3) Operation steps of machine mixing: First, use a three-roll grinder dedicated to silicone sealants for mixing (Note: The three-roll grinder dedicated to silicone must not mix non-silicone sealants, and must not be mixed with XM22 and XM28 sealant mixing equipment). The three-roll grinder should be cleaned with aviation washing gasoline or acetone before use. Then weigh the base paste, vulcanizer and catalyst according to the ratio in Table 4, add the vulcanizer to the base paste first, mix it on a tray or flat plate with a scraper for 2min to 3min, then add the catalyst and continue to mix it with a scraper for 3min to 10min. If the base paste is greater than 1kg, the vulcanizer should be added and mixed in multiple times, and mixed on a tray or flat plate with a scraper for 3min. Then grind it twice on the grinder. Mix it with a scraper for 3min between the two times. After the last grinding, spread it flat on the enamel plate for use.

[0092] 4) Manual mixing: When the mixing amount of the sealant does not exceed 500g and there is no three-roll mill for mixing, manual mixing can be used. First, accurately weigh each component according to the proportion in Table 4, mix the base paste and the vulcanizer for 3min to 5min, then add the catalyst and mix with a scraper for 5min to 15min.

[0093] Step 5: First clean the surface of the structural parts to be coated with sealant, then apply the high temperature resistant and high strength sealant bonding primer, wait for the bonding primer to dry, and finally complete the sealing coating of the high temperature resistant and high strength sealant. The specific operation steps are as follows:

[0094] 1) Cleaning of structural parts surface: Anodized aluminum alloy, epoxy primer and polyurethane topcoat surfaces to be sealed do not need to be polished, but there should be no adhesive residue on the surface. Use clean and dry cotton wool dipped in aviation washing gasoline or acetone to wipe off grease, dust and other dirt on the surface to be sealed, and then immediately wipe it dry with clean and dry cotton wool. Repeat the above steps until there is no stain on the clean and dry cotton wool, and dry it for 10 to 20 minutes.

[0095] 2) Application of NJD-6 bonding primer: HM321 high temperature resistant silicone sealant must be used with NJD-6 bonding primer. Application of NJD-6 bonding primer: Dip NJD-6 primer with a clean fine brush or cotton wool, so that the primer does not drip from the brush or cotton wool. Apply NJD-6 primer to the clean surface to be sealed, and let it air dry in the air for 1 hour before applying the sealant. If it is not dry, it can be blown dry with a hair dryer on the cold wind setting, but the longest air-drying time shall not exceed 5 hours. If it exceeds 5 hours, it should be re-cleaned and the primer should be re-applied according to Article 1. After the applied NJD-6 bonding primer dries, there should be no opaque layer, otherwise it will affect the bonding performance. It should be re-cleaned and the primer should be re-applied. After the NJD-6 bonding primer is applied and the air-drying time is met, the next process should be carried out in time to prevent surface contamination. If the surface is contaminated during the primer drying process, it should be cleaned and re-coated with primer. The fastener surface is coated with NJD-6 adhesive primer. The fastener is completely soaked with NJD-6 adhesive primer, and then removed and placed on clean absorbent cotton cloth, cotton yarn or paper to dry. After drying for 1 hour, it can enter the next process. The other requirements are the same as above.

[0096] 3) High temperature resistant and high strength sealant sealing coating:

[0097] 3.1 Sealing coating of the mating surface

[0098] a) Use rollers, scrapers, brushes and other tools to evenly apply the prepared sealant to the surface to be sealed (if conditions permit, a pneumatic injection gun with a dedicated roller nozzle can be used for even spraying);

[0099] b) Check whether there is uniform sealant on 100% of the bonding surface area of ​​the sealing area. If necessary, a sealant strip can be applied near the edges of the two bonding surfaces to ensure that the sealant is squeezed out. The thickness of the sealant coating is generally controlled at 0.2mm~1.0mm to ensure that the sealant can be squeezed out continuously and evenly after the secondary assembly. Figure 5 As shown;

[0100] c) The fitting surface seal belongs to the inner seam seal, so the parts coated with sealant should not be molded for the time being (depending on the on-site assembly conditions), and the mold should be closed when it is close to the active period to avoid premature mold closing, which may cause bubbles in the inner layer of the sealant;

[0101] d) Fasteners for face seal assembly must be completed within the sealant application period.

[0102] 3.2 Surface sealing (gap sealing) coating

[0103] a) Before construction, ensure that the skin seams are positioned and clamped, and the seam seals are tightly fitted;

[0104] b) Before applying the gap sealant coating on the joint of the outer skin, a protective tape should be attached to the edge of the joint to prevent the sealant from leaking out. The protective tape should be removed after the sealant is vulcanized;

[0105] c) Use an injection gun or similar tool to apply evenly along the joint.

[0106] 3.3 Coating of fillet seal

[0107] a) Apply additional sealant along the edge of the joint with an injection gun or similar tool to fillet the corners and use a special shaping tool (see Figure 6 ) Trim the fillet of the sealant. The shaping should be done with shaping tools during the active period of the sealant. If soapy water must be used for appearance shaping, it can only be shaped once along one direction on the surface. Repeated shaping is not allowed to prevent soapy water from mixing into the sealant.

[0108] b) Small-diameter plastic nozzles should be used to seal the corners of low-angle edges, and moderately large-diameter plastic nozzles should be used to seal the corners of high-angle edges.

[0109] 3.4 Coating of fasteners

[0110] a) According to the requirements of the engineering drawings, use cleaned process bolts or positioning pins to position and fix the parts and components to be sealed and assembled. The spacing of the parts and process fasteners shall be in accordance with the corresponding technical regulations;

[0111] b) During the installation of rivets, the sealant on the rivet ends should be cleaned off in time to prevent the rivets from forming a horseshoe shape when they are thickened;

[0112] c) The installation of fasteners must be completed during the construction period of the sealant;

[0113] d) After the fastener is installed, a circle of continuous rubber stem should be formed around the fastener head. If there are no other requirements, this rubber stem should be retained.

[0114] Step 6: Carry out coating and appearance inspection of high temperature resistant and high strength sealant.

[0115] Use visual inspection, and the edge of the fully vulcanized sealant should not peel off when rubbed with rubber. The sealing part is not allowed to have defects such as missing coating, lack of glue, process pores with a diameter exceeding 1mm, and debonding. The coating of high-temperature resistant and high-strength sealant and the external dimensions of the sealant after vulcanization shall be in accordance with the attached Figure 7 Conduct testing.

[0116] Step 7: Complete the sealing assembly of the aircraft engine nacelle structural parts.

[0117] According to the attached Figure 8 Based on the principle of sealing and riveting with high temperature resistant and high strength sealants of the engine nacelle structural parts are completed during the construction period.

Claims

1. A high temperature resistant and high strength sealant coating process, characterized in that: The method comprises the following steps: Step 1: preparing sealant; Step 2: Pre-treat the surface of the structure to be coated with sealant; Step 3: Apply the bonding primer on the pre-treated surface of the structure and let it dry; Step 4: Apply sealant on the surface of the structure after primer coating and vulcanize; Step 5: Check whether the sealant coating is qualified.

2. The method according to claim 1, characterized in that: In the step 1, the sealant is HM321I sealant, and the mass ratio of base paste, vulcanizing agent and catalyst is 100:0.9-1.0:0.6-1.

5.

3. The method according to claim 2, characterized in that: The single preparation amount of sealant shall not exceed 2kg. The amount below 500g shall be mixed by hand or machine, and 500g to 2kg shall be mixed by machine.

4. The method according to claim 3, characterized in that: In the step 2, the pretreatment is to clean the surface of the structural part, and the process is as follows: wipe the grease and dust on the surface to be sealed with clean and dry cotton wool dipped in aviation washing gasoline or acetone, and then immediately wipe it dry with clean and dry cotton wool; repeat the above steps until there is no stain on the clean and dry cotton wool; dry it for 10 minutes to 20 minutes.

5. The method according to claim 4, characterized in that: In the step 3, the primer is 2) NJD-6; The process of applying primer to the sealing surface is as follows: Dip the NJD-6 primer with a clean fine brush or cotton wool, and do not let the primer drip from the brush or cotton wool. Apply the NJD-6 primer to the clean surface to be sealed and let it air dry. If the air-drying time is exceeded or an opaque layer or contamination appears after air-drying, clean it again and apply the primer. The process of fastener primer coating is as follows: immerse the fasteners in the primer coating to completely soak them, remove them and place them on a clean absorbent cotton cloth to air dry; if the air drying time exceeds or an opaque layer or contamination appears after air drying, clean them again and apply primer.

6. The method according to claim 5, characterized in that: In step 4, if the structural surface is a bonding surface, the sealant coating process is as follows: Apply the prepared sealant evenly on the surface to be sealed; Check whether there is uniform sealant on 100% of the bonding surface area of ​​the sealing area, and the thickness of the sealant coating is controlled at 0.2mm~1.0mm; Do not close the mold for the parts coated with sealant yet, and close the mold when they are close to the active period.

7. The method according to claim 6, characterized in that: In step 4, if the structural surface is a gap sealing surface, the sealant coating process is as follows: A protective tape is attached to the seam edge of the gap sealing surface, and the protective tape is removed after the sealant is vulcanized; Use an injection gun to evenly apply sealant along the sealing surface of the gap.

8. The method according to claim 7, characterized in that: In step 4, if the structural surface is a fillet, the sealant coating process is as follows: Use an injection gun to apply sealant along the edges of both ends of the fillet, and use a shaping tool to trim the sealant fillet; The shaping is performed using shaping tools during the active period of the sealant. If soapy water is used for appearance shaping, the shaping is performed once on the surface in one direction using soapy water. Repeated shaping is not allowed. Small-diameter plastic nozzles should be used for fillet seals not exceeding 90°, and large-diameter plastic nozzles should be used for fillet seals exceeding 90°.

9. The method according to claim 8, characterized in that: In step 4, if the structural surface is a fastener surface, the sealant coating process is as follows: The sealant is applied on the surface of the installed fastener and within a range of 3mm to 5mm around the connection area between the fastener and the connected part.

10. The method according to claim 9, characterized in that: In step 5, the detection method is as follows: Rub the edge of the fully vulcanized sealant with a rubber, and there should be no peeling; There shall be no missing coating, lack of glue, process pores with a diameter exceeding 1mm and debonding on the sealant surface.

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