A processing method based on carbon fiber reinforced thin-walled metal cylinder

Abstract

The present application belongs to the technical field of mechanical processing and manufacturing, and particularly relates to a processing method of a carbon fiber reinforced thin-walled metal cylinder. The present application adopts a process method of first processing the outer circle of the cylinder, then winding carbon fiber on the outer circle of the cylinder, and then processing the inner hole of the cylinder. The inner hole is processed last, which reduces the stress deformation in the process of processing the outer circle of the cylinder and the welding deformation in the process of welding the connecting fence, and further reduces the influence of the tension in the process of winding carbon fiber on the deformation of the cylinder. By installing an inner support ring plate on all the to-be-welded parts of the inner hole of the cylinder, the outer diameter of the support ring plate is matched with the inner diameter of the cylinder in tolerance, so that the influence of the welding shrinkage stress on the wall thickness thinning in the subsequent processing process of the inner hole of the cylinder is effectively avoided in the process of welding the connecting fence.

Description

Technical Field

[0001] This invention belongs to the field of mechanical processing and manufacturing technology, and in particular relates to a processing method for a carbon fiber reinforced thin-walled metal cylinder. Background Technology

[0002] Today, aerospace, shipbuilding, and automotive industries have an urgent need for lightweight and long-life structures, with lightweighting being one of the core pathways. Winding carbon fiber onto the surface of a metal cylinder is a composite material technology that leverages the advantages of both rigidity and flexibility. Carbon fiber composites have a density of only 1.5–2.0 g / cm³, less than one-quarter that of steel and three-fifths that of aluminum alloys, significantly reducing structural weight. Simultaneously, it is resistant to chemical corrosion such as acids, alkalis, and salt spray, making it particularly suitable for harsh environments such as chemical plants and marine environments, greatly reducing maintenance costs.

[0003] During the processing of metal cylinders, the thin walls and poor structural rigidity of the metal parts make it difficult to withstand the enormous tension during the processing and subsequent winding processes. At the same time, when the cylinder needs to be welded to external connecting fences or other connecting parts, the welding area will undergo further deformation. The thin-walled metal parts cannot provide a stable and reliable "skeleton" for the composite material winding process.

[0004] Therefore, developing a processing method for carbon fiber reinforced thin-walled metal cylinders, and solving a series of problems such as large deformation during processing by innovating manufacturing processes and strengthening process control, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method for processing carbon fiber reinforced thin-walled metal cylinders, aiming to solve the problem that the large deformation during the processing of thin-walled metal cylinders cannot meet the dimensional accuracy requirements.

[0006] The technical solution adopted in this invention is as follows: A method for processing a carbon fiber reinforced thin-walled metal cylinder, the method comprising the following steps in sequence: Step S1: Cut, roll, and weld the material according to the cylinder size; Step S2: Weld the cylinder body to the upper and lower flanges; Step S3: Perform ultrasonic testing on the weld seams of the cylinder. Step S4: Anneal the cylinder to relieve stress; Step S5: Bor the inner hole of the cylinder, and simultaneously machine the reference to the outer circle of the upper and lower flanges; Step S6: Install inner support ring plates on all parts of the inner bore of the cylinder to be welded. The outer diameter of the inner support ring plate is tolerantly matched with the inner diameter of the cylinder; the assembly clearance between the outer diameter of the inner support ring plate and the inner diameter of the cylinder is 0-0.3mm. The inner support ring plates are used to constrain the radial shrinkage deformation of the cylinder wall during the welding process.

[0007] Step S7: Complete the outer circle of the cylinder to the finished size. The outer circle of the cylinder must be concentric with the inner hole. Step S8: Rough mill the two end faces of the upper and lower flanges; Step S9: Mill the opening areas such as the connecting fence of the cylinder; Step S10: Welding and connecting the fence, etc.; Step S11: Perform magnetic particle testing on the welded areas such as the connecting fence; Step S12: The cylinder undergoes secondary annealing to relieve stress; Step S13: Sandblast the outer wall of the cylinder. Step S14: Apply an elastic layer to the outer wall of the cylinder and heat-cure it; this is used to isolate the metal cylinder from the carbon fiber layer to prevent electrochemical corrosion. Step S15: Apply another layer of carbon fiber winding to the outer wall of the cylinder and cure it; Step S16: Perform ultrasonic non-destructive testing on the composite material winding area on the outer wall of the cylinder; Step S17: Machin the composite material winding area on the outer wall of the cylinder to the required dimensions; Step S18: Remove the inner bore support ring plate of the cylinder and check the roundness of the inner bore; Step S19: Use an ultrasonic thickness gauge to measure the wall thickness of the cylinder, measuring the distance between quadrants I to IV; Step S20: Rough boring of the inner bore of the cylinder; Step S21: After standing for 5 days, the ultrasonic thickness gauge is used to check the wall thickness of the cylinder again. Step S22: Semi-finish boring of the inner bore of the cylinder; Step S23: After standing for 5 days, the ultrasonic thickness gauge is used to check the wall thickness of the cylinder again. Step S24: Perform dye penetrant testing on the welding locations such as the inner hole connecting fence; Step S25: Precision boring of the inner bore of the cylinder; Step S26: Boring and milling the two end faces of the upper and lower flanges to the required dimensions; Boring and milling the bolt holes of the upper and lower flanges; Step S27: Boring and milling the sealing grooves on both ends of the upper and lower flanges; Step S28: Spray anti-rust oil onto the machined surface for protection; Step S29: Conduct an internal water pressure test of 2MPa on the cylinder; Step S30: Perform an internal airtightness test on the cylinder at 0.5 MPa.

[0008] Beneficial effects Compared with existing technologies, the method of this invention designs a more reasonable process flow route to control deformation during the processing of thin-walled cylinders. It adopts a process of first processing the outer circumference of the cylinder, then winding carbon fiber around the outer circumference, and finally processing the inner hole. This post-processing of the inner hole reduces stress deformation during the outer circumference processing and welding deformation during the welding connection process, further reducing the impact of tension on cylinder deformation during carbon fiber winding.

[0009] By installing inner support ring plates on all parts to be welded in the inner hole of the cylinder, and ensuring that the outer diameter of the support ring plate is tolerant to the inner diameter of the cylinder, the effect of welding shrinkage stress on the wall thickness reduction during the subsequent machining of the inner hole of the cylinder can be effectively avoided during the welding connection of fences and other processes. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the processing flow of the present invention; Figure 2 A schematic diagram of a carbon fiber reinforced thin-walled metal launch tube structure; Figure 3 A magnified view of a thin-walled metal launch tube reinforced with carbon fiber.

[0011] In the figure, 1 is the upper flange, 2 is the cylinder body, 3 is the first external connecting fence, 4 is the second external connecting fence, 5 is the third external connecting fence, 6 is the fourth external connecting fence, 7 is the lower flange, 8 is the fifth external connecting fence, and 9 is the carbon fiber layer. Detailed Implementation

[0012] To demonstrate that the processing method proposed in this invention can objectively and accurately process carbon fiber reinforced thin-walled metal cylinders, the following example is provided.

[0013] Example 1 Background: A carbon fiber reinforced thin-walled metal launch tube is currently available, made of both metal and non-metal materials. The thickness of both the metal and non-metal layers is only 5mm, with an inner diameter of φ780mm and a length of 2000mm. The metal portion mainly uses Q355B low-alloy structural steel, while the non-metal portion mainly uses carbon fiber material, which is wound around the circumference of the outer wall of the metal tube.

[0014] According to step S1, the cylinder is cut with a plate thickness of δ25mm. After calculating the unfolded length based on the middle diameter, it is cut, milled, rolled, and welded.

[0015] Following step S2, the cylinder body is rolled into a circle and then welded to the upper and lower flanges respectively. The inner hole is rolled into a circle and its size is adjusted to φ753.

[0016] Following step S3, ultrasonic testing is performed on the longitudinal weld seam of the cylinder and the circumferential weld seam between the cylinder and the upper and lower flanges. Following step S4, after flaw detection, the cylinder is annealed to relieve stress at a temperature of 550±10℃ for 4 hours.

[0017] According to step S5, the inner hole of the cylinder is machined to φ763+0.2 +0.1 using a CNC floor-type boring and milling machine. The machining datum is then simultaneously machined to the outer circle of the upper and lower flanges to provide a datum for the subsequent machining of the outer circle of the cylinder, ensuring that the inner and outer circles are concentric.

[0018] According to step S6, all openings in the inner bore of the cylinder to be welded are spot-welded with inner support ring plates. The outer diameter of the support ring plate is tolerant to the inner diameter of the cylinder. The inner diameter tolerance of the cylinder is: φ763+0.2 +0.1, and the outer diameter tolerance of the support ring plate is: φ763-0.1-0.2.

[0019] According to step S7, the outer circle of the overall cylinder and the outer circles of the upper and lower flanges are made to the finished size. During the cylinder clamping process, the outer circles of the upper and lower flanges should be used as a reference to ensure that the inner and outer circles are concentric after machining.

[0020] Following step S8, use a CNC floor-type boring and milling machine to rough mill the two ends of the upper and lower flanges, leaving a 5mm allowance on each side.

[0021] According to step S9, a CNC floor-type boring and milling machine is used to mill the opening areas such as the external connecting fence of the cylinder to facilitate the subsequent welding of the connecting fence; the connecting fence includes the first to the fifth connecting fence; Following step S10, weld the external connecting fence, grind the outer side with a C10 bevel, weld only the outer side, and weld the weld leg 5mm high.

[0022] According to step S11, magnetic particle testing is performed on the welded areas such as the outer connecting fence, and any defective parts are repaired in a timely manner.

[0023] According to step S12, the cylinder is subjected to secondary annealing to relieve stress. The annealing temperature is 550±10℃ and the holding time is 4 hours.

[0024] Following step S13, the outer wall of the cylinder is sandblasted to facilitate subsequent carbon fiber winding.

[0025] In step S14, to avoid electrochemical corrosion between the carbon fiber layer and the metal, an elastic layer is applied to the outer wall of the cylinder and then heated and cured.

[0026] Following step S15, another layer of carbon fiber winding is applied to the elastic layer on the outer wall of the cylinder and then cured.

[0027] In step S16, in order to identify defects such as pores and delamination inside the composite winding area, ultrasonic non-destructive testing is performed on the composite winding area on the outer wall of the cylinder, and the uniformity of the composite thickness is detected based on the time and speed of ultrasonic wave propagation in the material.

[0028] According to step S17, after the cylinder is cured, the carbon fiber winding area of ​​the cylinder is machined to size using a lathe, the area where the external connecting fence intersects with the cylinder is machined using a boring and milling machine, and the remaining areas that cannot be machined are ground to size.

[0029] According to step S18, the inner hole support ring plate of the cylinder is removed by grinding, and the roundness of the inner hole is detected by laser tracker.

[0030] Following step S19, the uniformity of the cylinder wall thickness is checked using an ultrasonic thickness gauge, with measurements taken at 100mm intervals along the entire length of quadrants I to IV.

[0031] According to step S20, rough boring of the inner hole of the cylinder is carried out using a CNC floor-type boring and milling machine.

[0032] Following step S21, after standing for 5 days, use an ultrasonic thickness gauge to check again whether the wall thickness of the cylinder is uniform. If the wall thickness difference exceeds 0.5mm, adjust the machining center accordingly.

[0033] According to step S22, the inner hole of the cylinder is semi-finished using a CNC floor-type boring and milling machine.

[0034] Following step S23, after standing for 5 days, use an ultrasonic thickness gauge to check again whether the wall thickness of the cylinder is uniform. If the wall thickness difference exceeds 0.5mm, adjust the machining center accordingly.

[0035] According to step S24, in order to inspect the welding quality, dye penetrant testing is performed on the welding areas such as the inner hole connecting fence.

[0036] According to step S25, the inner hole of the cylinder is precision bored to the required size using a CNC floor-type boring and milling machine.

[0037] According to step S26, bore and mill the two end faces of the upper and lower flanges to the required dimensions; bore and mill the bolt holes of the upper and lower flanges to the required dimensions.

[0038] According to step S27, the sealing grooves on both ends of the upper and lower flanges are bored and milled to the required dimensions.

[0039] Following step S28, all machined surfaces are sprayed with anti-rust oil for protection.

[0040] Following step S29, blind flanges were sealed at both ends of the cylinder, and an internal 2 MPa water pressure test was conducted, with pressure maintained for 10 minutes. No leakage was observed.

[0041] Following step S30, after the water pressure test, an airtightness test of 0.5 MPa is performed inside the cylinder, and the pressure drop is no greater than 0.03 MPa after holding the pressure for 10 minutes.

[0042] This completes all the above processing. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for processing a carbon fiber reinforced thin-walled metal cylinder, characterized in that, Includes the following steps: (1) Weld the rolled and welded cylinder body to the upper flange and the lower flange, process the inner hole of the cylinder to the pre-processing reference size, and use the inner hole as the reference to process the outer circle of the upper flange and the lower flange to the concentric reference simultaneously; (2) An inner support ring plate is installed in the welding opening area of ​​the inner hole of the cylinder, and the outer diameter of the inner support ring plate and the inner diameter of the cylinder adopt a transition fit. (3) Using the outer circles of the upper and lower flanges as a reference, turn the outer circle of the cylinder to the finished size of the outer circle of the upper and lower flanges to ensure that the outer circle of the cylinder is concentric with the inner hole; (4) The outer wall of the cylinder is sandblasted, an elastic layer is laid and heated and cured, and a carbon fiber winding layer is laid and cured in sequence; (5) Remove the inner support ring plate and perform fine machining on the inner hole of the cylinder according to the following path: rough boring of the inner hole → first settling period → use an ultrasonic thickness gauge to measure the cylinder wall thickness in quadrants I to IV → semi-finish boring of the inner hole → second settling period → use an ultrasonic thickness gauge again to measure the cylinder wall thickness in quadrants I to IV → finish boring of the inner hole to the final size.

2. The processing method according to claim 1, characterized in that, In step (2), the inner support ring plate is temporarily fixed to the inner wall of the cylinder by spot welding, and is removed by grinding in step (5).

3. The processing method according to claim 1, characterized in that, In step (4), the elastic layer is an epoxy resin-based elastomer layer.

4. The processing method according to claim 1, characterized in that, In step (5), the first settling period and the second settling period are each 4 to 7 days independently; in the wall thickness detection, if the wall thickness deviation at any position in quadrants I to IV exceeds 0.5 mm, the machining center will be offset to compensate during subsequent boring.

5. The processing method according to claim 1, characterized in that, After step (1) and before step (2), the process also includes ultrasonic testing of the weld seam of the cylinder and first annealing stress relief treatment of the cylinder; after step (3) and before step (4), the process also includes milling the opening area, welding the external connecting fence, magnetic particle testing of the weld area, and second annealing stress relief treatment of the cylinder.

6. The processing method according to claim 1, characterized in that, In step (4), after the carbon fiber winding layer is cured, the step of performing ultrasonic non-destructive testing on the carbon fiber winding area is also included; in step (5), after the inner hole is precision bored to the final size, the step of performing dye penetrant testing on the inner hole welding area is also included.

7. The processing method according to claim 1, characterized in that, After step (5), the process also includes: boring and milling the two end faces of the upper and lower flanges, the connecting bolt holes and the sealing grooves to the required dimensions, and spraying all machined surfaces with anti-rust oil for protection.

8. The processing method according to claim 1, characterized in that, After step (5), the following steps are also included: conducting an internal water pressure test on the cylinder with a test pressure of 2 MPa and a pressure holding time of 10 min; conducting an internal air tightness test on the cylinder with a test pressure of 0.5 MPa and a pressure drop of no more than 0.03 MPa after holding the pressure for 10 min.

9. The processing method according to claim 1, characterized in that, The thin-walled metal cylinder has a wall thickness of 4-6 mm, an inner diameter of φ750-φ800 mm, and a length of 1800-2200 mm.

10. A carbon fiber reinforced thin-walled metal cylinder, characterized in that, It is manufactured using the processing method described in any one of claims 1 to 9.

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