Machining process of stainless steel ventilating duct

Abstract

The invention discloses a machining process of a stainless steel ventilation pipeline. The machining process comprises the following steps that S1, blanking and pretreatment are conducted; s2, preparing a functional material composite layer; s3, synchronous hot press molding and curing; s4, pipeline forming and welding; s5, carrying out local strengthening treatment on the welding area; s6, carrying out online passivation and cleaning; s7, quality detection and packaging.A continuous and integrated manufacturing process is formed through the systematic process steps of blanking pretreatment, functional material composite layer preparation, synchronous hot press forming, pipeline forming and welding, welding area strengthening, online passivation and quality detection, and the process fundamentally changes the production mode of a traditional ventilation pipeline; sealing layer preparation and anti-corrosion treatment are integrated in the forming process, the problems that sealing performance depends on field gasket installation, the anti-corrosion procedure is independent and low in efficiency, and potential leakage points exist at the connecting position are effectively solved, and source control and overall improvement of the pipeline performance are achieved.

Description

Technical Field

[0001] This invention relates to the field of metal ventilation duct manufacturing technology, and in particular to a processing technology for stainless steel ventilation ducts. Background Technology

[0002] Stainless steel ventilation ducts are widely used in chemical, laboratory, food and pharmaceutical cleanrooms due to their excellent corrosion resistance and strength. However, current mainstream processing techniques (such as plate flanges or angle steel flanges) have the following inherent defects: The sealing performance depends entirely on the on-site installation: the sealing performance of the pipeline depends on the quality of the rubber, PTFE and other gaskets installed between the flanges during on-site installation and the level of construction. Gasket aging and improper installation will lead to air leakage. The corrosion prevention process is fragmented and inefficient: For pipes that require welding (such as angle steel flanges and thick plate pipes), after welding, the entire weld and even the entire pipe must be pickled and passivated to restore its corrosion resistance. This process is independent, time-consuming, generates chemical waste, and is difficult to operate on large-diameter pipes. Potential leakage points: The seams or flange joints themselves are potential corrosion initiation points and weak points for leakage. Therefore, this invention proposes a processing technology for stainless steel ventilation ducts to solve the above problems. Summary of the Invention

[0003] Given the limitations of the prior art, where sealing performance is entirely dependent on on-site installation—the sealing performance of pipelines depends on the quality and installation level of rubber, PTFE, and other gaskets installed between flanges during on-site installation, gasket aging and improper installation can lead to air leakage; the corrosion protection process is fragmented and inefficient—for pipelines requiring welding (such as angle steel flanges and thick plate pipelines), the entire weld and even the entire pipeline must undergo pickling and passivation treatment after welding to restore its corrosion resistance. This process is independent, time-consuming, generates chemical waste, and is difficult to operate on large-diameter pipelines; and there are potential leakage points—the seams or flange connection gaps themselves are potential corrosion initiation points and weak points for leakage. Therefore, this invention proposes a processing technology for stainless steel ventilation ducts.

[0004] The present invention proposes a processing technology for stainless steel ventilation ducts, comprising the following steps: S1: Material cutting and pretreatment; S2: Preparation of functional material composite layer; S3: Synchronous hot pressing molding and curing; S4: Pipe forming and welding; S5: Local reinforcement treatment of the welding area; S6: Online passivation and cleaning; S7: Quality Inspection and Packaging.

[0005] Preferably, in step S1, the stainless steel sheet is cut to the designed dimensions, and the area of ​​the sheet to be welded is laser-cleaned to remove oil and oxide layers, exposing the metal. The laser cleaning uses a pulsed fiber laser with a power of 50-100W and a scanning speed of 100-500mm / s.

[0006] Furthermore, the material preparation step employs laser cleaning technology to pre-treat the welding area, which can thoroughly remove oil and oxide layers from the surface of the sheet metal, exposing a clean metal substrate. This creates an ideal interface for subsequent welding and composite layer bonding. This method replaces traditional chemical or mechanical cleaning, avoids surface damage and secondary pollution, significantly improves the quality of welded joints and the bonding strength between functional materials and the substrate, and lays a reliable foundation for the overall performance of the pipeline.

[0007] Preferably, in step S2, the functional composite slurry comprises a high-temperature resistant elastic polymer matrix, a fluorocarbon polymer, nano-stainless steel powder, a coupling agent, and a curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future using an automatic coating device, with a coating thickness of 0.5-2mm.

[0008] Furthermore, the functional material composite layer preparation step involves coating a special functional slurry in a pre-defined area of ​​the board. This slurry contains components such as high-temperature resistant elastic polymers, fluorocarbon polymers, and nano-metal powders, which can form a pre-installed sealing and anti-corrosion layer that is firmly bonded to the stainless steel substrate in subsequent processes. This design replaces the external independent gaskets that are relied upon during traditional installation, embedding the sealing function into the pipe structure, eliminating the risk of leakage caused by gasket aging or improper installation, and improving sealing reliability and durability.

[0009] Preferably, in step S3, the plate coated with composite slurry is fed into a CNC flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is subjected to staged hot pressing and curing through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 120-150℃, and the second stage is completely cured at a high temperature of 180-220℃ under forming pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection.

[0010] Furthermore, the simultaneous hot pressing and curing steps combine the mechanical forming of the flange with the hot pressing and curing of the composite slurry in the same process. The heating unit integrated in the mold provides precise temperature control, allowing the composite material to undergo two stages under forming pressure: preliminary shaping at medium temperature and complete curing at high temperature. This achieves a high-strength integrated bond with the stainless steel matrix. This process solves the problem of needing to add additional seals and interrupt the anti-corrosion treatment process after the traditional flange forming, greatly improving production efficiency and structural integrity.

[0011] Preferably, in step S4, the sheet metal is rolled or bent into the shape of a duct, the longitudinal seam is closed, and the parts that need to be welded are welded.

[0012] Furthermore, the pipe forming and welding steps process the pre-treated plates into the final duct shape and weld the joints. Since the welding area has been laser-cleaned and the flange area has been prefabricated with a functional layer in the early stage, the welding quality of this step is higher and the forming accuracy is better. This provides a workpiece base with accurate geometry and excellent surface condition for subsequent local strengthening treatment, ensuring the strength of the main structure of the pipe.

[0013] Preferably, in step S5, after welding is completed, a layer of alloy powder with a composition matching the base material but containing more passivating elements is clad on the surface of the weld and heat-affected zone using a laser micro-cladding device or a precision plasma spraying device to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of the laser micro-cladding is 500-1500W, the scanning speed is 5-20mm / s, and the cladding layer thickness is 0.1-0.3mm.

[0014] Furthermore, the local strengthening treatment step in the welding area is specifically designed for the weld and heat-affected zone, which are traditionally weak links. A layer of alloy with optimized composition is fused onto its surface using high-energy beam cladding technology to form a dense metallurgical bond strengthening layer. This strengthening layer can effectively fill micro-defects, improve the corrosion resistance and mechanical properties of the area, thereby blocking the risk of the weld as a corrosion initiation point and potential leakage point, and achieving the equal life design of the pipeline.

[0015] Preferably, in step S6, the entire pipeline is subjected to online spray passivation treatment using an environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air.

[0016] Furthermore, the online passivation and cleaning step uses a spray method to quickly passivate the outer surface of the pipeline. Since the flange sealing surface has built-in protection and the weld area has been specially reinforced, this step only needs to treat the remaining exposed surfaces. Therefore, the processing time is short, the amount of environmentally friendly passivation liquid used is small, and the amount of waste liquid generated is extremely low. This effectively solves the problems of difficult operation, time-consuming and material-intensive operation, and large environmental pollution of the traditional whole-pipe pickling and passivation process.

[0017] Preferably, in step S7, the thickness and hardness of the cured sealing layer are tested, and the dimensions of the pipe are verified by laser three-dimensional scanning. After passing the verification, the pipe is packaged.

[0018] Furthermore, the quality inspection and packaging process uses instruments to precisely verify the thickness and hardness of the cured sealing layer and the three-dimensional dimensions of the pipe, ensuring that every product leaving the factory meets the design standards. This systematic final inspection process puts performance control into practice, avoiding quality fluctuations caused by reliance on on-site construction in traditional processes, and providing users with finished pipes that are consistent in performance, reliable in quality, and ready for direct installation.

[0019] The beneficial effects of this invention are: 1. The flange sealing layer is prefabricated in the factory and integrally formed with the structure. Its bonding strength, uniformity and durability are far superior to the gaskets installed on site, which fundamentally eliminates leakage caused by gasket problems and realizes "gasket-free" installation. 2. The most critical anti-corrosion treatment (functional layer composite, weld reinforcement) is moved to be carried out before welding or immediately after welding, avoiding the drawbacks of traditional overall pickling. The weld reinforcement layer has better performance than the base material, which greatly improves the corrosion resistance of weak areas. 3. It simplifies the on-site installation process (no need for selection, cutting, or installation of gaskets), reduces the amount of chemical agents used in the overall pickling and passivation process and the cost of wastewater treatment, which is in line with the trend of green manufacturing; 4. The entire process (coating, hot-press curing, laser treatment) is easily integrated into automated production lines, ensuring high consistency and traceability of product quality; This invention forms a continuous and integrated manufacturing process through systematic steps including material pretreatment, preparation of functional material composite layers, simultaneous hot pressing, pipe forming and welding, weld zone strengthening, online passivation, and quality inspection. This process fundamentally changes the traditional production method of ventilation ducts, integrating sealing layer preparation and anti-corrosion treatment into the forming process. It effectively solves the problems of reliance on on-site gasket installation for sealing performance, inefficient independent anti-corrosion processes, and potential leakage points at joints, achieving source control and overall improvement of pipe performance. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the workflow proposed in this invention. Detailed Implementation

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] Reference Figure 1 Example 1 This embodiment proposes a processing technology for stainless steel ventilation ducts, including the following steps: S1: Blanking and pretreatment. The stainless steel sheet is cut to the design size, and the area to be welded is laser cleaned to remove oil and oxide layer and expose the metal. The laser cleaning uses pulsed fiber laser with a power of 85W and a scanning speed of 450mm / s. S2: Preparation of functional material composite layer. The functional composite slurry contains a high-temperature resistant elastic polymer matrix, fluorocarbon polymer, nano stainless steel powder, coupling agent and curing agent. It is precisely coated on the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future through an automatic coating device. The coating thickness is 1mm. S3: Synchronous hot pressing molding and curing. The plate coated with composite slurry is fed into a CNC plate flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is hot-pressed and cured in stages through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 130℃. The second stage is fully cured at a high temperature of 200℃ under molding pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection. S4: Pipe forming and welding, rolling or bending sheet metal into duct shape, closing longitudinal seams, and welding the parts that need to be welded; S5: Local strengthening treatment of the weld area. After welding, a layer of alloy powder with the same composition as the base material but containing more passivating elements is fused onto the surface of the weld and heat-affected zone using laser micro-cladding equipment or precision plasma spraying equipment to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of laser micro-cladding is 800W, the scanning speed is 15mm / s, and the cladding layer thickness is 0.25mm. S6: Online passivation and cleaning, the entire pipeline is sprayed with passivation solution, using environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air; S7: Quality inspection and packaging. The thickness and hardness of the cured sealing layer are inspected, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the inspection, the pipeline is packaged.

[0023] Reference Figure 1 Example 2 This embodiment proposes a processing technology for stainless steel ventilation ducts, including the following steps: S1: Blanking and pretreatment. The stainless steel sheet is cut to the design size, and the area to be welded is laser cleaned to remove oil and oxide layer and expose the metal. The laser cleaning uses pulsed fiber laser with a power of 50W and a scanning speed of 100mm / s. S2: Preparation of functional material composite layer. The functional composite slurry contains a high-temperature resistant elastic polymer matrix, fluorocarbon polymer, nano stainless steel powder, coupling agent and curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future through an automatic coating device. The coating thickness is 0.5mm. S3: Synchronous hot pressing molding and curing. The plate coated with composite slurry is fed into a CNC common plate flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is hot-pressed and cured in stages through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 120℃. The second stage is fully cured at a high temperature of 180℃ under molding pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection. S4: Pipe forming and welding, rolling or bending sheet metal into duct shape, closing longitudinal seams, and welding the parts that need to be welded; S5: Local strengthening treatment of the weld area. After welding, a layer of alloy powder with the same composition as the base material but containing more passivating elements is fused onto the surface of the weld and heat-affected zone using laser micro-cladding equipment or precision plasma spraying equipment to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of laser micro-cladding is 500W, the scanning speed is 5mm / s, and the cladding layer thickness is 0.1mm. S6: Online passivation and cleaning, the entire pipeline is sprayed with passivation solution, using environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air; S7: Quality inspection and packaging. The thickness and hardness of the cured sealing layer are inspected, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the inspection, the pipeline is packaged.

[0024] Reference Figure 1 Example 3 This embodiment proposes a processing technology for stainless steel ventilation ducts, including the following steps: S1: Blanking and pretreatment. The stainless steel sheet is cut according to the design size, and the area of ​​the sheet to be welded is laser cleaned to remove oil and oxide layer and expose the metal. The laser cleaning uses pulsed fiber laser with a power of 80W and a scanning speed of 450mm / s. S2: Preparation of functional material composite layer. The functional composite slurry contains a high-temperature resistant elastic polymer matrix, fluorocarbon polymer, nano stainless steel powder, coupling agent and curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future through an automatic coating device. The coating thickness is 1.25mm. S3: Synchronous hot pressing molding and curing. The plate coated with composite slurry is fed into a CNC common plate flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is hot-pressed and cured in stages through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 135℃. The second stage is fully cured at a high temperature of 195℃ under molding pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection. S4: Pipe forming and welding, rolling or bending sheet metal into duct shape, closing longitudinal seams, and welding the parts that need to be welded; S5: Local strengthening treatment of the weld area. After welding, a layer of alloy powder with the same composition as the base material but containing more passivating elements is fused onto the surface of the weld and heat-affected zone using laser micro-cladding equipment or precision plasma spraying equipment to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of laser micro-cladding is 1300W, the scanning speed is 15mm / s, and the cladding layer thickness is 0.125mm. S6: Online passivation and cleaning, the entire pipeline is sprayed with passivation solution, using environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air; S7: Quality inspection and packaging. The thickness and hardness of the cured sealing layer are inspected, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the inspection, the pipeline is packaged.

[0025] Reference Figure 1 Example 4 This embodiment proposes a processing technology for stainless steel ventilation ducts, including the following steps: S1: Blanking and pretreatment. The stainless steel sheet is cut to the design size, and the area to be welded is laser cleaned to remove oil and oxide layer and expose the metal. The laser cleaning uses pulsed fiber laser with a power of 75W and a scanning speed of 350mm / s. S2: Preparation of functional material composite layer. The functional composite slurry contains a high-temperature resistant elastic polymer matrix, fluorocarbon polymer, nano stainless steel powder, coupling agent and curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future through an automatic coating device. The coating thickness is 1.35mm. S3: Synchronous hot pressing molding and curing. The plate coated with composite slurry is fed into a CNC common plate flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is hot-pressed and cured in stages through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 140℃. The second stage is fully cured at a high temperature of 190℃ under molding pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection. S4: Pipe forming and welding, rolling or bending sheet metal into duct shape, closing longitudinal seams, and welding the parts that need to be welded; S5: Local strengthening treatment of the weld area. After welding, a layer of alloy powder with the same composition as the base material but containing more passivating elements is fused onto the surface of the weld and heat-affected zone using laser micro-cladding equipment or precision plasma spraying equipment to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of laser micro-cladding is 1350W, the scanning speed is 12mm / s, and the cladding layer thickness is 0.23mm. S6: Online passivation and cleaning, the entire pipeline is sprayed with passivation solution, using environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air; S7: Quality inspection and packaging. The thickness and hardness of the cured sealing layer are inspected, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the inspection, the pipeline is packaged.

[0026] Reference Figure 1 Example 5 This embodiment proposes a processing technology for stainless steel ventilation ducts, including the following steps: S1: Blanking and pretreatment. The stainless steel sheet is cut to the design size, and the area to be welded is laser cleaned to remove oil and oxide layer and expose the metal. The laser cleaning uses pulsed fiber laser with a power of 65W and a scanning speed of 420mm / s. S2: Preparation of functional material composite layer. The functional composite slurry contains a high-temperature resistant elastic polymer matrix, fluorocarbon polymer, nano stainless steel powder, coupling agent and curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future through an automatic coating device. The coating thickness is 1.5mm. S3: Synchronous hot pressing molding and curing. The plate coated with composite slurry is fed into a CNC plate flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is hot-pressed and cured in stages through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 120℃. The second stage is fully cured at a high temperature of 220℃ under molding pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection. S4: Pipe forming and welding, rolling or bending sheet metal into duct shape, closing longitudinal seams, and welding the parts that need to be welded; S5: Local strengthening treatment of the welding area. After welding, a layer of alloy powder with the same composition as the base material but containing more passivating elements is fused onto the surface of the weld and heat-affected zone using laser micro-cladding equipment or precision plasma spraying equipment to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of laser micro-cladding is 1400W, the scanning speed is 17.5mm / s, and the cladding layer thickness is 0.2mm. S6: Online passivation and cleaning, the entire pipeline is sprayed with passivation solution, using environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air; S7: Quality inspection and packaging. The thickness and hardness of the cured sealing layer are inspected, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the inspection, the pipeline is packaged.

[0027] The stainless steel ventilation ducts prepared in Examples 1 to 5 are compared with those prepared in Examples 1 to 5, as shown in the table below:

[0028] As can be seen from the table above, the processing technology of the stainless steel ventilation duct proposed in this invention has been significantly improved, and implementation one is the best embodiment.

[0029] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A processing technology for stainless steel ventilation ducts, characterized in that, Includes the following steps: S1: Material cutting and pretreatment; S2: Preparation of functional material composite layer; S3: Synchronous hot pressing molding and curing; S4: Pipe forming and welding; S5: Local reinforcement treatment of the welding area; S6: Online passivation and cleaning; S7: Quality Inspection and Packaging.

2. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S1, the stainless steel sheet is cut to the designed dimensions, and the area to be welded is laser-cleaned to remove oil and oxide layers, exposing the metal. The laser cleaning uses a pulsed fiber laser with a power of 50-100W and a scanning speed of 100-500mm / s.

3. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S2, the functional composite slurry contains a high-temperature resistant elastic polymer matrix, a fluorocarbon polymer, nano-stainless steel powder, a coupling agent, and a curing agent. It is precisely applied to the bonding surface of the folded edge area of ​​the plate that will form the flange sealing surface in the future using an automatic coating device, with a coating thickness of 0.5-2mm.

4. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S3, the plate coated with composite slurry is fed into a CNC flange forming machine with heating function. While mechanically pressing the flange shape, the composite slurry is subjected to staged hot pressing and curing through the heating unit in the mold. The first stage is initially shaped at a medium temperature of 120-150℃, and the second stage is completely cured at a high temperature of 180-220℃ under forming pressure, so that it is firmly bonded to the stainless steel substrate to form an integrated seal and corrosion protection.

5. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S4, the sheet metal is rolled or bent into the shape of a duct, the longitudinal seam is closed, and the parts that need to be welded are welded.

6. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S5, after welding is completed, a layer of alloy powder with a composition matching the base material but containing more passivating elements is clad onto the surface of the weld and heat-affected zone using a laser micro-cladding device or a precision plasma spraying device to form a dense metallurgical bonding layer. This process is completed under inert gas protection. The power of the laser micro-cladding is 500-1500W, the scanning speed is 5-20mm / s, and the cladding layer thickness is 0.1-0.3mm.

7. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S6, the entire pipeline undergoes online spray passivation treatment using an environmentally friendly organic acid passivation liquid, which is atomized and sprayed, and then quickly dried with hot air.

8. The processing technology of a stainless steel ventilation duct according to claim 1, characterized in that, In step S7, the thickness and hardness of the cured sealing layer are tested, and the dimensions of the pipeline are verified by laser three-dimensional scanning. After passing the verification, the pipeline is packaged.

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