A laser cutting process and apparatus for thick pipes combined with electrochemical jet slag removal

Abstract

This invention relates to the field of laser processing technology and discloses a laser cutting process and apparatus for thick-walled tubes combined with electrochemical jet slag removal. The process includes: an automatic buffer material feeding and recovery mechanism pushes a high-temperature resistant ceramic-based inner liner tube into the inner cavity of a thick-walled tube as a buffer material for laser cutting; after cutting, the buffer material is removed, a physical sliding isolation sealing door is closed in conjunction with a flexible clearance pad, and a positive pressure air curtain blowing device is activated to seal the processing area; the thick-walled tube is connected to the anode of a power source, and the inner and outer jet nozzles are connected to the cathode, spraying high-pressure sodium nitrate passivation electrolyte into the residual slag area. The slag removal mechanism, which combines physical shielding at the slag source with electrochemical anodic dissolution and high-pressure liquid flow flushing, eliminates the contact stress caused by mechanical hard cutting and avoids the problem of micro-cracks at the tube wall wear ports; a spatial isolation protection mechanism prevents salt spray from eroding the optical lenses of the fiber laser cutting head and the machine tool transmission guide, completing a non-destructive slag removal operation.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, specifically to a laser cutting process and apparatus for thick pipes combined with electrochemical jet slag removal. Background Technology

[0002] Thick-walled pipes are widely used in industrial manufacturing. When using lasers to cut through thick-walled pipes, the molten metal droplets generated after the high-temperature laser beam penetrates one side of the pipe wall usually splash and drip directly onto the inner surface of the pipe on the opposite side. After the high-temperature metal cools and solidifies, it forms a hard solid slag. Traditional mechanical slag removal methods are difficult to penetrate and clean the solid slag accumulated deep inside the thick-walled pipe. Using special scraping tools to forcibly extend into the pipe cavity for mechanical scraping often causes hard scratches and abrasions to the inner wall of the pipe itself, resulting in a decrease in the smoothness of the inner surface of the pipe.

[0003] Currently, conventional methods for removing residual slag adhering to the pipe end are mostly based on contact cutting with grinding tools. This purely physical, hard-contact slag removal method introduces mechanical stress into the pipe end. As the cutting force continues to be applied, microcracks will form at the cut edge of the pipe, compromising the overall mechanical strength of the finished pipe.

[0004] The industry is attempting to integrate laser cutting with subsequent liquid cleaning and descaling operations onto a single composite machining platform. However, hot laser cutting requires a relatively dry environment, while liquid descaling often involves liquid spraying. Existing composite machining equipment generally lacks a robust spatial isolation and protection mechanism during the transition between these two processes. Water vapor splashes generated during the descaling stage, along with salt spray containing corrosive substances, are prone to spillage. Once these corrosive splashes adhere to and corrode laser optical lenses and machine tool transmission guides, which are sensitive to environmental conditions, it shortens the lifespan of precision machining equipment and increases subsequent maintenance costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a laser cutting process and apparatus for thick-walled pipes combined with electrochemical jet slag removal. This process solves the problems of molten metal condensing into slag on the inner wall of the pipe cavity during laser penetration cutting of thick-walled pipes, which is difficult to clean and easily wears down the pipe wall; conventional physical cutting slag removal methods introduce mechanical stress at the fracture point, leading to microcracks; and water vapor and salt spray overflowing and corroding optical lenses and machine tool guideways when hot cutting and liquid slag removal are alternately performed on the same processing platform.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a laser cutting process for thick pipes combined with electrochemical jet slag removal, employing the following technical solution: A laser cutting process for thick-walled pipes combined with electrochemical jet slag removal involves clamping the thick-walled pipe in a three-chuck centering mechanism, and using an automatic buffer material feeding and recovery mechanism to push a high-temperature resistant ceramic-based inner liner as a buffer material into the inner cavity of the thick-walled pipe. The outer wall of the buffer material is controlled to fit closely to the inner wall of the thick-walled pipe with a radial gap of 0.03 to 0.10 mm, completely covering the predetermined laser cutting area. A fiber laser cutting head is used to perform penetrating cuts on thick-walled pipes. The thick-walled pipes and buffer materials rotate synchronously and at a uniform speed. The high-temperature molten slag produced drips onto the surface of the buffer material, forming a cut surface and a residual molten slag area. After the laser cutting action is completed, the buffer material is completely extracted from the processing area along the axial direction by the automatic feeding and recycling mechanism. The electrochemical jet slag removal device moves to the original cutting position, closes the physical sliding isolation sealing door, and, together with the flexible clearance pad on the outer wall of the pipe, completely isolates and seals the processing area and opens the positive pressure air curtain blowing device. A 10-20% NaNO3 aqueous solution was used as the passivation electrolyte. The thick-walled pipe was connected to the anode. The inner and outer jet nozzles on the C-type synchronous linkage cantilever of the electrochemical jet slag removal device were connected to the cathode. The electrolyte injection pressure was controlled at 3.0-6.0 MPa, and the DC regulated power supply voltage was controlled at 150-250 V. The inner and outer jet nozzles simultaneously sprayed high-pressure electrolyte onto the cut surface and residual slag area.

[0007] By adopting the above technical solution, this invention combines physical isolation for slag reduction at the source with electrochemical-hydraulic composite slag removal, effectively achieving non-destructive removal of molten slag from the cut surface and inner wall. During the specific operation, when the laser penetrates the pipe wall, the high-temperature resistant ceramic-based inner liner inserted within prevents liquid splashes and droplets from directly contacting the inner wall of the pipe. Typically, the molten high-temperature metal drips and adheres to the surface of the inner liner for condensation, thus reducing slag deposition inside the pipe at the source. Furthermore, the set radial gap of 0.03–0.10 mm allows for thermal expansion, reducing the risk of jamming and enabling the buffer material to be smoothly removed after cutting.

[0008] After the inner liner is removed, the processing area forms a relatively enclosed space with the closure of the physical sliding isolation sealing door and the flexible clearance pad, as well as the opening of the positive pressure air curtain. This isolation mechanism is mainly to confine the charged liquid splashes and strong oxidizing gases generated by the subsequent electrochemical reaction to a local area, thereby reducing the probability of electrolyte corrosion of optical components or machine tool guideways.

[0009] During the slag removal stage, when the NaNO3 passivating electrolyte is sprayed onto the pipe surface, thanks to the oxidizing properties of nitrate ions, an oxidation reaction occurs in the non-processed areas and on the smooth surface of the pipe body, generating a dense oxide passivation film. This passivation film acts to block local current conduction, thereby inhibiting the corrosion of the substrate to a certain extent. Simultaneously, for the cut edges and areas with residual slag, the high-pressure jet of 3.0–6.0 MPa generates strong fluid shear force. This shearing action continuously destroys the local passivation film on the surface of the protruding slag, allowing the irregularly shaped slag portions to remain exposed as highly active anode areas.

[0010] After the DC power is switched on, the slag area not effectively covered by the passivation film forms a high current density region. At this time, the iron-based slag adhering to the pipe acts as the anode, undergoing electrochemical oxidation and dissolution. Its metal atoms lose electrons and transform into metal cations, escaping the crystal lattice and entering the electrolyte. Meanwhile, on the cathode nozzle surface, a reduction reaction occurs in the aqueous solution, releasing gas. As the electrochemical dissolution progresses, the root of the slag gradually becomes loose. Combined with the fluid kinetic energy of the high-voltage electrolyte jet, this slag with increased porosity and weakened structure is forcibly hydrostatically stripped and flushed out with the liquid flow, continuously exposing new reaction interfaces. This method of material removal through the superposition of electrochemical anodic dissolution and hydrostatic flushing avoids the contact stress caused by traditional direct physical cutting, thereby reducing the occurrence of microcracks at the pipe opening.

[0011] Preferably, in the penetration cutting, the operating parameters are set as follows: laser output power is 2000W, cutting axial feed speed is 2m / min, pure oxygen is used as the auxiliary cutting gas and the gas ejection pressure is maintained at 0.3MPa, and the laser focus position is set on the tube wall surface. In the high-pressure electrolyte spraying, the solution conductivity is controlled to be 7–14 S / m, the operating temperature is kept constant at 25℃, the jet distance from the inner and outer jet nozzles to the workpiece surface is adjusted to 1.0–4.0 mm, and the continuous slag removal processing time is 10–60 s. After spraying the high-pressure electrolyte, the processing power is automatically cut off and the electrolyte spraying stops. The inner and outer walls of the tube are then rinsed with clean water, high-pressure compressed air is turned on to dry the tube surface and inner cavity, the physical sliding isolation sealing door is opened, the electrochemical slag removal device returns to its initial position, the jaws of the three-chuck centering mechanism are released, and the finished tube with non-destructive slag removal is directly discharged.

[0012] By adopting the above technical solutions and setting specific process parameters, a relatively stable processing environment can be constructed. For example, using pure oxygen as an auxiliary gas and focusing the laser on the pipe wall surface can improve the penetration effect on thick-walled pipes and maintain the stability of the kerf width to a certain extent. In the electrochemical machining process, maintaining the solution conductivity at 7–14 S / m and controlling the operating temperature at around 25°C is to ensure that the ion migration rate within the electrochemical reaction system remains relatively uniform. This effectively reduces sudden changes in conductivity caused by local heating of the electrolyte, thereby reducing the probability of short-circuit burns. Simultaneously, controlling the jet distance within the range of 1.0–4.0 mm maintains the stability of the liquid column as a conductive channel and also helps maintain the accumulation of fluid kinetic energy. After electrochemical machining, rinsing with clean water and supplementing with high-pressure air purging removes the strong electrolyte nitrates remaining on the pipe surface and inner cavity, preventing secondary chemical corrosion that may occur after shutdown, and facilitating the direct output of the workpiece as a finished product.

[0013] Preferably, the high-temperature resistant ceramic-based inner liner is made from raw materials comprising the following parts by weight: 5-10 parts of hexagonal boron nitride micro powder; 30-40 parts of aluminum phosphate inorganic binder solution based on solid content; and 50-60 parts of continuous alumina ceramic fiber bundle.

[0014] The preparation method of high-temperature resistant ceramic-based inner liner tube includes: adding hexagonal boron nitride micro powder to an aluminum phosphate inorganic binder solution based on solid content, and dispersing it at high speed using a mechanical stirring device at room temperature to obtain a uniformly mixed ceramic slurry suspension; continuously drawing continuous alumina ceramic fiber bundles through the ceramic slurry suspension for thorough impregnation, and using a CNC winding machine to tightly wind the fiber bundles impregnated with inorganic slurry at cross angles onto the outer surface of a standard molding mandrel, controlling the cumulative thickness of single-layer and multi-layer winding so that the final tube wall thickness is 0.2-1 mm, thus obtaining a preform; transferring the wound molding mandrel as a whole into an oven for constant temperature maintenance to remove physical moisture from the system, demolding the dried preform from the mandrel, and transferring it into a high-temperature sintering furnace for gradient high-temperature sintering, so that the inorganic matrix and alumina fibers are completely sintered and solidified into a ceramic matrix.

[0015] By employing the above technical solution, the above process aims to prepare a buffer substrate with high thermal shock resistance and low surface adhesion rate. Specifically, the continuous alumina (Al2O3) ceramic fiber bundles, combined with a cross-winding molding process, construct a mechanical framework for the inner liner tube under high-temperature conditions, helping to resist the risk of thermal shock cracking caused by molten metal droplets; while the aluminum phosphate inorganic binder, after curing, forms a high-temperature resistant matrix network that tightly encapsulates and bonds the aforementioned fiber structure.

[0016] The hexagonal boron nitride micropowder introduced into the formulation acts like a non-metallic solid lubricant. When uniformly dispersed in the pipe wall matrix, it reduces the surface energy of the inner liner. This low-energy surface treatment prevents significant interfacial wetting or deep chemical reactions from occurring when molten metal droplets generated during laser cutting come into contact with the pipe wall. This significantly hinders the penetration and bonding of slag into the pores of the buffer material, making slag removal easier during subsequent maintenance and cleaning. Furthermore, in the gradient high-temperature sintering process, segmented control of dehydration and sintering temperatures allows the crystalline water in the binder to vaporize and escape relatively smoothly. This helps avoid blistering and delamination defects in the ceramic substrate's microstructure caused by rapid expansion of water vapor, thus maintaining the required density of the matrix.

[0017] Secondly, this invention provides a thick-tube laser cutting combined with electrochemical jet slag removal device, which adopts the following technical solution: A laser cutting and electrochemical jet slag removal device for thick pipes includes: The three-chuck centering mechanism is used to clamp and drive the thick-walled pipe to rotate synchronously and uniformly in one operation. An automatic buffer material feeding and retrieval mechanism is used to push and pull the buffer material into and out of the inner cavity of the pipe to be cut. Fiber laser cutting head, used for penetrating cuts of thick-walled pipes; The electrochemical jet deslagging unit includes internal and external jet nozzles and a DC regulated power supply installed on a C-type synchronous linkage cantilever. Physical sliding isolation sealing doors, flexible clearance pads, and positive pressure air curtain blowing devices are used to completely isolate and seal off the processing area.

[0018] By adopting the above technical solution, the present invention integrates physical protection components with electrochemical processing units, enabling hot laser thermal cutting and cold electrochemical slag removal to be continuously connected on a single equipment platform.

[0019] In the initial stage of equipment operation, the three-chuck centering mechanism is responsible for locking the spatial position of the thick-walled tube and providing continuous rotational driving force to maintain the coaxiality of the processing area; at the same time, the automatic feeding and recovery mechanism of the buffer material plays a role, pushing the buffer liner tube, which acts as a shield, into the inner cavity of the tube to receive the high-temperature melt dripping during fiber laser penetration cutting.

[0020] Once the cutting operation is complete, the automatic feeding and recovery mechanism pulls the inner liner tube, still containing molten slag, outwards. To accommodate transitions between different process environments, a physical sliding isolation sealing door, combined with a flexible clearance pad, closes at this point, physically defining the laser cutting area and the slag removal area. This, along with a positive pressure air curtain blowing device that sprays gas outwards, often forms a pneumatic barrier to maintain unidirectional fluid flow within the slag removal space. This combined physical and pneumatic isolation design primarily aims to suppress the outward leakage of water vapor or salt spray generated in subsequent processes, thereby protecting the machine tool's transmission guides and laser optical lenses from corrosion.

[0021] As the electrochemical jet deslag removal unit moves to its operating position, the internal and external jet nozzles mounted on the C-type synchronous linkage cantilever spray electrolyte onto the areas with residual slag, forming a conductive liquid column channel. After the DC regulated power supply is connected, a local electric field environment is established between the pipe fracture surface and the nozzle. Under this electrolytic system, the iron-based slag adhering to the pipe surface mainly undergoes anodizing, where metal atoms lose electrons and transform into free metal cations that enter the electrolyte. Conversely, water molecules in the electrolyte sprayed from the nozzle gain electrons at the cathode interface, reducing and releasing hydrogen gas and hydroxide ions.

[0022] During the electrochemical dissolution process that causes the material at the root of the slag to peel off and thin, the high-pressure liquid jet ejected from the nozzle simultaneously applies a hydrodynamic impact. The resulting fluid shear force peels off the metal oxides and loose layer formed on the surface of the slag, causing the unreacted fresh metal matrix at the bottom to be re-exposed to the electrolyte for further dissolution. Finally, the products of electrolytic dissolution, along with the debris removed by hydraulic exfoliation, are discharged from the processing area with the fluid backflow, thus achieving automated slag removal.

[0023] Preferably, the inner and outer jet nozzles are made of titanium alloy, and the inner diameter of the inner and outer jet nozzles is 1.50 to 2.50 mm; the DC regulated power supply is connected to the anode to the stainless steel pipe and to the cathode to the inner and outer jet nozzles.

[0024] By adopting the above technical solution, titanium alloy was selected as the material for both the inner and outer jet nozzles primarily because of its excellent oxidation resistance and resistance to nitrate solution corrosion. This helps the nozzle maintain relative stability of its inner diameter under long-term electric field environment and high-pressure liquid flow scouring. The limitation of the inner diameter to 1.50–2.50 mm aims to control the cross-sectional area of ​​the jet stream, ensuring that the ejected electrolyte maintains a concentrated laminar flow state. This constrains the effective range of the processing current without excessive dispersion of jet kinetic energy. Furthermore, the electrical circuit design, with the stainless steel pipe connected to the DC power supply anode and the nozzle connected to the cathode, designates the workpiece side as the dissolution and consumption end where electrons are lost, allowing the electrochemical material removal reaction to proceed smoothly in the expected anodic dissolution direction.

[0025] This invention provides a process and apparatus for laser cutting of thick pipes combined with electrochemical jet slag removal. It offers the following advantages: 1. This invention uses an automatic feeding and recovery mechanism to feed a high-temperature resistant ceramic-based inner liner into the inner cavity of a thick-walled tube as a physical shielding buffer. This allows the high-temperature liquid metal generated when the laser penetrates the tube to drip down and adhere to the surface of the inner liner, where it condenses. This physical isolation mechanism severs the connection between the molten metal and the inside of the tube, reduces the amount of solid slag remaining inside the tube, eliminates the metal wear problem caused by subsequent scraping with mechanical tools, and maintains the smoothness of the inner surface of the workpiece.

[0026] 2. This invention employs a combined electrochemical anodic dissolution and high-pressure jet slag removal mechanism. The sodium nitrate passivating electrolyte, sprayed at high pressure from internal and external jet nozzles, generates fluid shear force at the residual slag, continuously peeling away the passivation film generated on the protruding parts, exposing the slag and causing anodic oxidation dissolution. Electrochemical material removal loosens the slag root structure, allowing it to be directly discharged with the high-pressure liquid flow. This eliminates the hard-contact physical slag removal method, removes residual mechanical stress from tool cutting, and reduces the risk of micro-cracks at the pipe ends.

[0027] 3. This invention isolates and seals the processing space by arranging a physical sliding isolation sealing door in the processing unit in conjunction with a flexible clearance pad and a positive pressure air curtain blowing device. This isolates and seals the processing space when transitioning from hot cutting to cold deslag removal. The pneumatic barrier, the physical sealing door, and the flexible pad together create a unidirectional flow protective environment, preventing corrosive salt spray from spilling out and falling into non-deslag removal areas. This also avoids moisture erosion of the optical lenses of the fiber laser cutting head and the machine tool transmission guide rails, thus extending the overall service life of the composite processing equipment. Attached Figure Description

[0028] Figure 1 Potential dynamic polarization curves for analyzing the passivation and dissolution mechanism of the electrolyte system of this invention; Figure 2This is the dynamic contact angle evolution curve of the interface between the buffer material and molten stainless steel of the present invention; Figure 3 This is a two-dimensional cross-sectional diagram showing the height distribution of the micro-profile of the pipe section of the present invention. Figure 4 This is the electrodynamic polarization curve of the pipe processing surface according to the present invention; Figure 5 This is a schematic diagram of the overall structure of the thick pipe laser cutting and electrochemical jet slag removal device of the present invention; Figure 6 This is a flow chart of the composite anti-adhesion and electrochemical slag removal process of the present invention.

[0029] Among them, 1. Automatic feeding and recycling mechanism for buffer material; 2. Three-chuck centering mechanism; 3. Physical sliding isolation sealing door; 4. Positive pressure air curtain blowing device; 5. Flexible clearance pad; 6. C-type synchronous linkage cantilever; 7. Fiber laser cutting head; 8. High temperature resistant ceramic base inner lining tube. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a high-temperature resistant ceramic-based inner liner tube, including the following steps: Mixing: Accurately weigh 5 parts by weight of hexagonal boron nitride micro powder and add it to 30 parts by solid content of aluminum phosphate inorganic binder solution. Disperse at high speed for 60 minutes at room temperature using a mechanical stirring device to obtain a uniformly mixed ceramic slurry suspension.

[0032] Impregnation and winding: Weigh 50 parts by weight of continuous alumina (Al2O3) ceramic fiber bundle and continuously draw the fiber bundle through the ceramic slurry suspension prepared above for thorough impregnation. Then, use a CNC winding machine to tightly wind the fiber bundle impregnated with inorganic slurry onto the outer surface of a standard molding mandrel at a cross angle, controlling the cumulative thickness of single-layer and multi-layer winding so that the final tube wall thickness is 0.2 mm.

[0033] Gradient high-temperature sintering: The wound mandrel is transferred into an oven and kept at 80℃ for 2 hours to remove physical moisture from the system. The dried preform is then demolded from the mandrel and transferred to a high-temperature sintering furnace for gradient high-temperature sintering. The specific high-temperature sintering temperature and time are set as follows: the temperature is increased to 400℃ at a rate of 3℃ / min and held for 1 hour to dehydrate the inorganic binder; then the temperature is increased to 1100℃ at a rate of 5℃ / min and sintered for 2 hours to completely sinter and solidify the inorganic matrix and alumina fibers into a ceramic matrix, ensuring a high-temperature resistance limit ≥1500℃.

[0034] Product acquisition: After the high-temperature sintering furnace heating process is completed and the material is naturally cooled to room temperature, the fully sintered ceramic-based tubular workpiece is taken out, which yields a high-temperature resistant ceramic-based inner liner tube 8 with a wall thickness of 0.2 mm, which is used as an internal buffer material (i.e., high-temperature resistant ceramic-based inner liner tube 8).

[0035] Preparation Example 2: This preparation example provides a method for preparing a high-temperature resistant ceramic-based inner liner tube, including the following steps: Mixing: Accurately weigh 7.5 parts by weight of hexagonal boron nitride micro powder and add it to 35 parts by solid content of aluminum phosphate inorganic binder solution. Disperse at high speed for 60 minutes at room temperature using a mechanical stirring device to obtain a uniformly mixed ceramic slurry suspension.

[0036] Impregnation and winding: Weigh 55 parts by weight of continuous alumina (Al2O3) ceramic fiber bundles and continuously draw the fiber bundles through the ceramic slurry suspension prepared above for thorough impregnation. Then, use a CNC winding machine to tightly wind the fiber bundles impregnated with inorganic slurry onto the outer surface of a standard molding mandrel at a cross angle, controlling the cumulative thickness of single-layer and multi-layer windings so that the final tube wall thickness is 0.6 mm.

[0037] Gradient high-temperature sintering: The wound mandrel is transferred into an oven and kept at 80℃ for 2 hours to remove physical moisture from the system. The dried preform is then demolded from the mandrel and transferred to a high-temperature sintering furnace for gradient high-temperature sintering. The specific high-temperature sintering temperature and time are set as follows: the temperature is increased to 400℃ at a rate of 3℃ / min and held for 1 hour to dehydrate the inorganic binder; then the temperature is increased to 1100℃ at a rate of 5℃ / min and sintered for 2 hours to completely sinter and solidify the inorganic matrix and alumina fibers into a ceramic matrix, ensuring a high-temperature resistance limit ≥1500℃.

[0038] Product acquisition: After the high-temperature sintering furnace heating process is completed and the material is naturally cooled to room temperature, the fully sintered ceramic-based tubular workpiece is taken out, which yields a high-temperature resistant ceramic-based inner liner tube 8 with a wall thickness of 0.6 mm. This tube is the preferred choice for use as an internal buffer material (i.e., the high-temperature resistant ceramic-based inner liner tube 8).

[0039] Preparation Example 3: This preparation example provides a method for preparing a high-temperature resistant ceramic-based inner liner tube, including the following steps: Mixing: Accurately weigh 10 parts by weight of hexagonal boron nitride micro powder and add it to 40 parts by solid content of aluminum phosphate inorganic binder solution. Disperse at high speed for 60 minutes at room temperature using a mechanical stirring device to obtain a uniformly mixed ceramic slurry suspension.

[0040] Impregnation and winding: Weigh 60 parts by weight of continuous alumina (Al2O3) ceramic fiber bundles and continuously draw the fiber bundles through the ceramic slurry suspension prepared above for thorough impregnation. Then, use a CNC winding machine to tightly wind the fiber bundles impregnated with inorganic slurry onto the outer surface of a standard molding mandrel at a cross angle, controlling the cumulative thickness of single-layer and multi-layer winding so that the final tube wall thickness is 1 mm.

[0041] Gradient high-temperature sintering: The wound mandrel is transferred into an oven and kept at 80℃ for 2 hours to remove physical moisture from the system. The dried preform is then demolded from the mandrel and transferred to a high-temperature sintering furnace for gradient high-temperature sintering. The specific high-temperature sintering temperature and time are set as follows: the temperature is increased to 400℃ at a rate of 3℃ / min and held for 1 hour to dehydrate the inorganic binder; then the temperature is increased to 1100℃ at a rate of 5℃ / min and sintered for 2 hours to completely sinter and solidify the inorganic matrix and alumina fibers into a ceramic matrix, ensuring a high-temperature resistance limit ≥1500℃.

[0042] Finished product acquisition: After the high-temperature sintering furnace heating process is completed and the material is naturally cooled to room temperature, the fully sintered ceramic-based tubular workpiece is taken out, which yields a high-temperature resistant ceramic-based inner liner tube 8 with a wall thickness of 1mm, which is used as an internal buffer material (i.e., high-temperature resistant ceramic-based inner liner tube 8).

[0043] Examples 1-3: Example 1: This embodiment provides a laser cutting process for thick pipes combined with electrochemical jet slag removal, including the following steps: Tube clamping and insertion of internal buffer material: The 304 seamless stainless steel thick-walled tube is clamped in one go into the three-chuck centering mechanism 2 of the laser tube cutting machine. The high-temperature resistant ceramic-based inner liner tube 8 with a wall thickness of 0.2 mm (i.e., as an auxiliary material) prepared in Example 1 is inserted into the buffer material through the automatic feeding and retrieval mechanism 1. Figure 58) The high-temperature resistant ceramic-based inner liner tube is pushed into the inner cavity of the tube to be cut. The outer wall of the buffer material is controlled to fit tightly against the inner wall of the tube, and the radial gap is controlled to be 0.03mm, so that it completely covers the predetermined laser cutting area.

[0044] Laser cutting of thick pipes: A fiber laser cutting head 7 is used for penetrating cuts. During the cutting process, a three-chuck centering mechanism 2 drives the outer stainless steel thick-walled pipe and the inner buffer liner to rotate synchronously and uniformly. The basic operating parameters for laser cutting are set as follows: laser output power 2000W, cutting axial feed speed 2m / min, pure oxygen as the auxiliary cutting gas, gas ejection pressure maintained at 0.3MPa, and laser focus position set at 0mm on the pipe wall surface. The high-temperature molten slag generated during cutting drips onto the surface of the buffer material, achieving slag reduction at the physical source.

[0045] Switching to the slag removal station from its original position: After the laser cutting action is completed, the fiber laser cutting head 7 servo retracts to the safety avoidance position. The servo mechanism activates, and the buffer liner tube in the inner cavity is completely extracted axially from the processing area through the automatic feeding and recovery mechanism 1. The electrochemical jet slag removal device moves to the original cutting position, and the servo-driven physical sliding isolation sealing door 3, together with the flexible clearance pad 5 on the outer wall of the tube, tightly closes, completely isolating and sealing the processing area, and simultaneously activating the positive pressure air curtain purging device 4.

[0046] Internal and external electrochemical jet descaling: A 10% (w / w) NaNO3 aqueous solution was prepared as the passivation electrolyte. The solution conductivity was tested and controlled to be 7 S / m, and the operating temperature was kept constant at 25℃. The electrochemical jet descaling unit was turned on, and a DC regulated power supply was connected. The stainless steel pipe was connected to the anode, and the internal and external jet titanium alloy nozzles, with an inner diameter of 1.50 mm, mounted on the C-type synchronous linkage cantilever 6, were connected to the cathode. The jet distance from the nozzle to the workpiece surface was adjusted to 1 mm, the processing power supply voltage was set to 150V, and the electrolyte spray pressure was set to 3 MPa. The internal and external nozzles simultaneously sprayed high-pressure electrolyte onto the cut surface and residual slag area, and the descaling processing time was 10 seconds. Utilizing the dual action of fixed-point anodic dissolution and high-speed water jet scouring, the residual slag and burrs on the cut surface were peeled off and dissolved.

[0047] Cleaning, Drying, and Discharge: After the slag removal time is completed, the processing power is automatically cut off and the electrolyte spraying stops. The inner and outer walls of the pipe are rinsed sequentially with clean water, followed by the use of high-pressure compressed air to dry the pipe surface and inner cavity. The physical sliding isolation sealing door 3 opens, the electrochemical slag removal device returns to its initial position, the jaws of the three-chuck centering mechanism 2 release, and the finished pipe, having completed non-destructive slag removal, is directly discharged.

[0048] Example 2: This embodiment provides a laser cutting process for thick pipes combined with electrochemical jet slag removal, including the following steps: Tube clamping and insertion of internal buffer material: The 304 seamless stainless steel thick-walled tube is clamped in one go into the three-chuck centering mechanism 2 of the laser tube cutting machine. The high-temperature resistant ceramic-based inner liner tube 8 (i.e., the tube with a wall thickness of 0.6 mm prepared in Example 2) is inserted into the buffer material via the automatic feeding and retrieval mechanism 1. Figure 5 8) The high-temperature resistant ceramic-based inner liner tube is pushed into the inner cavity of the tube to be cut. The outer wall of the buffer material is controlled to fit tightly against the inner wall of the tube, and the radial gap is controlled to be 0.06mm, so that it completely covers the predetermined laser cutting area.

[0049] Laser cutting of thick pipes: A fiber laser cutting head 7 is used for penetrating cuts. During the cutting process, a three-chuck centering mechanism 2 drives the outer stainless steel thick-walled pipe and the inner buffer liner to rotate synchronously and uniformly. The basic operating parameters for laser cutting are set as follows: laser output power 2000W, cutting axial feed speed 2m / min, pure oxygen as the auxiliary cutting gas, gas ejection pressure maintained at 0.3MPa, and laser focus position set at 0mm on the pipe wall surface. The high-temperature molten slag generated during cutting drips onto the surface of the buffer material, achieving slag reduction at the physical source.

[0050] Switching to the slag removal station from its original position: After the laser cutting action is completed, the fiber laser cutting head 7 servo retracts to the safety avoidance position. The servo mechanism activates, and the buffer liner tube in the inner cavity is completely extracted axially from the processing area through the automatic feeding and recovery mechanism 1. The electrochemical jet slag removal device moves to the original cutting position, and the servo-driven physical sliding isolation sealing door 3, together with the flexible clearance pad 5 on the outer wall of the tube, tightly closes, completely isolating and sealing the processing area, and simultaneously activating the positive pressure air curtain purging device 4.

[0051] Internal and external electrochemical jet descaling: A 15% (w / w) NaNO3 aqueous solution was prepared as the passivation electrolyte. The solution conductivity was tested and controlled to be 10.5 S / m, and the operating temperature was kept constant at 25℃. The electrochemical jet descaling unit was turned on, and a DC regulated power supply was connected. The stainless steel pipe was connected to the anode, and the internal and external jet titanium alloy nozzles with an inner diameter of 2.00 mm, mounted on the C-type synchronous linkage cantilever 6, were connected to the cathode. The jet distance from the nozzle to the workpiece surface was adjusted to 2.5 mm, the processing power supply voltage was set to 200 V, and the electrolyte spray pressure was set to 4.5 MPa. The internal and external nozzles simultaneously sprayed high-pressure electrolyte onto the cut surface and residual slag area, and the descaling processing time was 35 s. Utilizing the dual action of fixed-point anodic dissolution and high-speed water jet flushing, the residual slag and burrs on the cut surface were peeled off and dissolved.

[0052] Cleaning, Drying, and Discharge: After the slag removal time is completed, the processing power is automatically cut off and the electrolyte spraying stops. The inner and outer walls of the pipe are rinsed sequentially with clean water, followed by the use of high-pressure compressed air to dry the pipe surface and inner cavity. The physical sliding isolation sealing door 3 opens, the electrochemical slag removal device returns to its initial position, the jaws of the three-chuck centering mechanism 2 release, and the finished pipe, having completed non-destructive slag removal, is directly discharged.

[0053] Example 3: This embodiment provides a laser cutting process for thick pipes combined with electrochemical jet slag removal, including the following steps: Tube clamping and insertion of internal buffer material: The 304 seamless stainless steel thick-walled tube is clamped in one go into the three-chuck centering mechanism 2 of the laser tube cutting machine. The high-temperature resistant ceramic-based inner liner tube 8 with a wall thickness of 1mm (i.e., as an auxiliary material) prepared in Example 3 is then inserted into the buffer material through the automatic feeding and retrieval mechanism 1. Figure 5 8) The high-temperature resistant ceramic-based inner liner tube is pushed into the inner cavity of the tube to be cut. The outer wall of the buffer material is controlled to fit tightly against the inner wall of the tube, and the radial gap is controlled to be 0.10mm, so that it completely covers the predetermined laser cutting area.

[0054] Laser cutting of thick pipes: A fiber laser cutting head 7 is used for penetrating cuts. During the cutting process, a three-chuck centering mechanism 2 drives the outer stainless steel thick-walled pipe and the inner buffer liner to rotate synchronously and uniformly. The basic operating parameters for laser cutting are set as follows: laser output power 2000W, cutting axial feed speed 2m / min, pure oxygen as the auxiliary cutting gas, gas ejection pressure maintained at 0.3MPa, and laser focus position set at 0mm on the pipe wall surface. The high-temperature molten slag generated during cutting drips onto the surface of the buffer material, achieving slag reduction at the physical source.

[0055] Switching to the slag removal station from its original position: After the laser cutting action is completed, the fiber laser cutting head 7 servo retracts to the safety avoidance position. The servo mechanism activates, and the buffer liner tube in the inner cavity is completely extracted axially from the processing area through the automatic feeding and recovery mechanism 1. The electrochemical jet slag removal device moves to the original cutting position, and the servo-driven physical sliding isolation sealing door 3, together with the flexible clearance pad 5 on the outer wall of the tube, tightly closes, completely isolating and sealing the processing area, and simultaneously activating the positive pressure air curtain purging device 4.

[0056] Electrochemical jet descaling: A 20% (w / w) NaNO3 aqueous solution was prepared as the passivation electrolyte. The solution conductivity was tested and controlled to be 14 S / m, and the operating temperature was kept constant at 25℃. The electrochemical jet descaling unit was turned on, and a DC regulated power supply was connected. The stainless steel pipe was connected to the anode, and the inner diameter titanium alloy nozzles (2.50 mm) mounted on the C-type synchronous linkage cantilever 6 were connected to the cathode. The jet distance from the nozzle to the workpiece surface was adjusted to 4.0 mm, the processing power supply voltage was set to 250V, and the electrolyte spray pressure was set to 6.0 MPa. The high-pressure electrolyte was sprayed synchronously from both the inner and outer nozzles onto the cut surface and residual slag area for 60 seconds. The descaling process utilized the dual effects of targeted anodic dissolution and high-speed water jet scouring to peel off and dissolve the residual slag and burrs on the cut surface.

[0057] Cleaning, Drying, and Discharge: After the slag removal time is completed, the processing power is automatically cut off and the electrolyte spraying stops. The inner and outer walls of the pipe are rinsed sequentially with clean water, followed by the use of high-pressure compressed air to dry the pipe surface and inner cavity. The physical sliding isolation sealing door 3 opens, the electrochemical slag removal device returns to its initial position, the jaws of the three-chuck centering mechanism 2 release, and the finished pipe, having completed non-destructive slag removal, is directly discharged.

[0058] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that in the pipe clamping and internal buffer material insertion steps, the high-temperature resistant ceramic-based inner liner pipe 8 is not pushed in by the automatic buffer material feeding and recycling mechanism 1 (i.e., it is missing as an attachment). Figure 5 The high-temperature resistant ceramic-based inner liner tube 8 has an internal buffer material, and the remaining steps and process parameters are exactly the same as in Example 2.

[0059] Comparative Example 2: Compared with Example 2, the difference is that the internal and external electrochemical jet slag removal steps are removed (that is, after laser cutting, the corresponding electrochemical slag removal hardware equipment such as the internal and external jet titanium alloy nozzles installed on the C-type synchronous linkage cantilever 6 is not activated, and the process directly jumps to the clean water rinsing and drying discharge process). The remaining steps and buffer material configuration are exactly the same as in Example 2.

[0060] Comparative Example 3: Compared with Example 2, the difference is that in the internal and external electrochemical jet slag removal steps, the 15% NaNO3 aqueous solution is replaced with an equivalent NaCl (sodium chloride) aqueous solution, while the remaining steps and process parameters are exactly the same as in Example 2.

[0061] Comparative Example 4: Compared with Example 2, the difference is that in the internal and external electrochemical jet deslagging steps, the processing power supply voltage is significantly increased and set to 350V (exceeding the parameter protection range of 250V), while the remaining process steps and parameters are exactly the same as in Example 2.

[0062] Comparative Example 5: The difference compared to Example 2 is that: the built-in cushioning material (i.e., the attached...) Figure 5 In the preparation process of the high-temperature resistant ceramic-based inner liner tube 8), the special anti-adhesion heat-conducting component, hexagonal boron nitride micro powder, was completely removed (that is, only aluminum phosphate inorganic binder and alumina fiber were used to prepare a ceramic-based inner liner tube with a wall thickness of 0.6 mm through pure two-phase composite preparation). The rest of the buffer material preparation process, the processing steps of Example 2, and the various slag removal process parameters were kept exactly the same.

[0063] Test Examples 1-4: Test Example 1: Analysis of Passivation and Dissolution Mechanisms in Electrolyte Systems In Example 2 and Comparative Example 3, the laser cutting stage was completed using the fiber laser cutting head 7 (corresponding appendix). Figure 6 The cut surface of the thick pipe with slag after laser cutting was used as the research object. Local cross-sections and connected parent materials were extracted to prepare test electrodes, and electrochemical polarization behavior was analyzed at room temperature.

[0064] A 10mm×10mm test block was cut along the cutting edge, retaining the slag-bearing cut surface. After grinding the back and sides of the test block, copper wires were welded on, and then the block was cold-mounted and sealed with epoxy resin, exposing only the slag-bearing cut surface as the test surface. The test surface was rinsed and dried only with deionized water and anhydrous ethanol, without mechanical grinding, to avoid damaging the slag and the original morphology of the laser cutting, and was used as the working electrode.

[0065] A standard three-electrode system was used to connect to the electrochemical workstation, with a saturated calomel electrode as the reference electrode and a large-area platinum sheet as the auxiliary electrode.

[0066] Prepare 15% NaNO3 aqueous solution and 15% NaCl aqueous solution by mass, respectively, and transfer them to the test electrolytic cell to maintain the nominal temperature of the solution at 25℃.

[0067] Immerse the working electrode in the corresponding electrolyte and let it stand for 30 minutes. Monitor the dynamic evolution trend of the open circuit potential until the open circuit potential fluctuations tend to stabilize and the system reaches an approximate steady state.

[0068] The potentiodynamic polarization scanning test program was executed, with the potential scanning range set to -0.8V to +1.2V and the scanning rate controlled at 1mV / s. The microcurrent density response on the working electrode surface under different systems was recorded.

[0069] The polarization data obtained from the test were extracted, and the linear Tafel region in the anodic polarization region and the cathodic polarization region was extracted for extrapolation to obtain the corrosion potential Ecorr and corrosion current density Jcorr. Based on the passivation plateau and the inflection point of rapid current rise in the anodic polarization curve, the passivation initiation potential Epass, the breakdown potential Eb, or the initiation potential of rapid current rise Eonset were identified.

[0070] Table 1. Comparison of electrochemical polarization parameters between Samples of Example 2 and Comparative Example 3 In the potential-current density logarithmic coordinate system polarization curve, after crossing the corrosion potential and approaching the passivation initiation potential, the current density of the curve in Example 2 changes from the activation growth stage to the passivation plateau and remains relatively stable within a certain potential range, showing a low current density plateau with a large span; after crossing the corrosion potential, the current density of the curve in Comparative Example 3 shows a continuous upward trend with the positive shift of the potential, and no obvious passivation characteristics were observed.

[0071] Figure 1 This is a potentiodynamic polarization curve for analyzing the passivation and dissolution mechanism of the electrolyte system of this invention. The solid line in the figure represents the polarization response trajectory of the working electrode of Example 2 (15% NaNO3 system), and the dashed line represents the polarization response trajectory of the working electrode of Comparative Example 3 (15% NaCl system).

[0072] In summary, based on the data in Table 1, the polarization behavior of Example 2 exhibits certain passivation characteristics. In the NaNO3 system, the corrosion potential of the stainless steel cross-section is -0.194V, and the corrosion current density remains at 3.82 × 10⁻⁶. -6 A / cm 2 This indicates that the system can suppress the corrosion and consumption of the background metal within a specific potential range. Considering the electrochemical jet slag removal performed by the nozzle at the end of the C-type synchronous cantilever 6 (corresponding to the attached...), Figure 6 The internal and external electrochemical jet descaling steps in the process need to be carried out under conditions that minimize damage to the base material. The aforementioned low corrosion current characteristics provide a preliminary basis for maintaining the stability of the processed surface. In contrast, the NaCl medium used in Comparative Example 3 caused the anolyte current to continuously increase with the potential, with a rapid rise in current at approximately -0.053V, failing to form an effective stable passivation range. This continuous active dissolution effect increases the probability of local defects such as pitting or corrosion forming on the substrate surface during macroscopic processing.

[0073] In Example 2, the neutral nitrate system influenced the interfacial reaction kinetics of the cut surface. When the applied external potential crossed the corrosion potential and approached the passivation initiation potential, the stainless steel surface tended to enter a low current density state, forming a passivation range with a width of approximately 0.884V. The establishment of this passivation platform is related to the low-damage slag removal mechanism of the process: during the high-pressure water jet flushing and peeling off the large-scale solidified slag on the surface, the exposed fresh metal substrate tends to adsorb oxygen-containing species in the solution, which helps to promote the oxidation process of elements such as Fe, Cr, and Ni on the surface, thereby facilitating the in-situ formation of a protective passivation film. This passivation film remains relatively stable before reaching the +0.912V breakdown threshold, limiting the continuous anodic dissolution of the flat base material area continuously clamped by the three-chuck centering mechanism 2. When the dissolution of a large area of ​​the base material is suppressed, the anodic current is more likely to concentrate in areas with microscopically rougher burrs or residue tips where the film layer is not yet discontinuous. This localized electric field concentration and targeted dissolution effect promotes the preferential removal of surface-attached defects. The balance mechanism between this localized concentrated dissolution and surface chemical passivation film formation improves the surface protection effect of the slag removal process for thick-walled pipes on the underlying substrate to a certain extent, helping to reduce the risk of damage caused by over-processing.

[0074] Test Example 2: Thermal Stability and Anti-Adhesion Mechanism Test of Cushioning Material The high-temperature resistant ceramic-based inner liner tube 8 containing hexagonal boron nitride prepared in Example 2, and the high-temperature resistant ceramic-based inner liner tube 8 without hexagonal boron nitride in Comparative Example 5 were used as research objects to conduct simulations of fiber laser cutting head 7 operation (corresponding to the attached...). Figure 6 Analysis of material stability and interfacial wetting mechanical behavior in high-temperature environment of laser cutting of thick pipes.

[0075] Arc-shaped samples with dimensions of 15mm × 15mm were cut from the walls of the buffer material tubes of Example 2 and Comparative Example 5, respectively. They were placed in an ultrasonic cleaner and cleaned with anhydrous ethanol for 10 minutes to remove surface impurities. They were then subjected to constant weight treatment in a vacuum drying oven at 80°C to serve as substrate test samples. At the same time, a 0.5g standard metal block of 304 stainless steel was prepared as the molten phase.

[0076] Thermogravimetric analysis (TGA) was performed on two sets of substrate samples using a comprehensive thermal analyzer. The test environment was a high-purity argon atmosphere, the heating rate was set to 15℃ / min, and the temperature scan range was continuously heated from room temperature to 1500℃. The mass change data of the samples during the heating process were continuously recorded to evaluate the high-temperature structural maintenance capability of the substrate.

[0077] A 304 stainless steel block was placed in the center of the substrate test sample and then moved into the heating furnace of a high-temperature in-situ contact angle measuring instrument. Under micro-positive pressure argon protection, the furnace temperature was rapidly increased to 1450℃ and held at this temperature for a short period to allow the stainless steel block to fully melt or soften and collapse into droplets. The system automatically identified and recorded the dynamic contact angle evolution trajectory of the droplet-substrate interface during the 60-second isothermal holding period, and the average contact angle within the 55-60 second period of the isothermal holding was taken as the steady-state contact angle.

[0078] After the contact angle test, the furnace body was allowed to cool naturally to room temperature. The sample with solidified stainless steel droplets was transferred to the worktable of a computer-controlled electronic universal testing machine and clamped. A special clamp was used to hook the metal droplets, and a normal tensile force perpendicular to the sample surface was applied at a constant rate of 0.5 mm / min. The critical pull-out load at the moment when the droplets completely detached from the substrate surface and fractured was recorded.

[0079] Table 2. Test results of thermal and interfacial mechanical properties of the buffer material in Example 2 and Comparative Example 5 Note: The steady-state contact angle is the average value of the period from 55 to 60 seconds during the later stage of isothermal holding at 1450℃; the desorption pull-out force after solidification is the critical load recorded at the moment when the molten droplet completely desorbs from the substrate surface. The desorption pull-out force of Example 2 is reduced by approximately 95.3% compared to Comparative Example 5.

[0080] In the dynamic interface evolution record output by the high-temperature in-situ measurement device, the molten stainless steel droplets on the surface of Example 2 tended to stabilize after morphological adjustment in the initial contact stage, forming a near-spherical state with high curvature, and maintained a relatively stable repulsive characteristic during the subsequent heat preservation stage; the molten metal droplets on the surface of Comparative Example 5 showed a spreading trend, the contact angle value gradually decreased with time, and the droplet edge penetrated and wetted into the micropores of the ceramic substrate.

[0081] Figure 2 This is a curve showing the dynamic contact angle evolution at the interface between the buffer material of this invention and molten stainless steel. The solid line in the figure represents the dynamic contact angle evolution trajectory of the surface of Example 2 (containing hexagonal boron nitride ceramic matrix), and the dotted line represents the dynamic contact angle evolution trajectory of the surface of Comparative Example 5 (without hexagonal boron nitride ceramic matrix).

[0082] In summary, according to the data in Table 2, the ceramic matrix composed of aluminum phosphate inorganic binder and alumina fiber exhibits high thermal stability at 1500℃, with the mass retention rates of Example 2 and Comparative Example 5 both exceeding 98%. This similarity in thermogravimetric data indicates that both types of ceramic matrices possess good resistance to weight loss and structural retention under high-temperature inert atmospheres, providing a material basis for withstanding the high-temperature thermal effects during laser cutting. In the actual laser processing area, the molten metal droplets ejected with high-pressure auxiliary gas possess high surface tension and reactivity. When these droplets contact the tube wall buffer layer, the wetting, penetration, and solidification bonding behaviors at the interface are the key mechanisms determining the ease of slag removal. Test observations revealed that when relying solely on refractory materials for barrier treatment, the cooled slag easily forms a strong mechanical interlocking effect with the material surface, often causing localized damage or jamming of the high-temperature ceramic-based inner liner tube 8 during pull-out. Comparative Example 5 illustrates this phenomenon: the contact angle of the molten droplets on the ceramic matrix surface without added hexagonal boron nitride was as low as 78.6°. Under the combined influence of gravity, wetting force, and capillary action, the liquid metal penetrated into the micropores of the ceramic matrix surface. The mechanical interlocking effect after solidification led to an increase in the desorption pull-out force to 45.82 N. Based on the addition of boron nitride... Figure 5 The device and accessories shown Figure 6 In the actual processing of the sealed inner cavity shown in the process flow diagram, the adhesion of this level will be significantly increased. The buffer material is automatically fed in and automatically withdrawn by the recycling mechanism 1 (corresponding to the attached...). Figure 6 The operating resistance during the in-situ switching to the slag removal station step increases the risk of failure.

[0083] After introducing a special two-dimensional layered material into the ceramic system to reconstruct the surface energy state, Example 2 demonstrates a differentiated interface evolution path. When a high-temperature droplet falls onto the surface of the buffer material in Example 2, the hexagonal boron nitride component utilizes its graphite-like layered crystal cleavage properties and low surface free energy to form a low-wetting interface barrier layer on the contact surface. This allows the molten stainless steel to maintain a high-curvature droplet shape under surface tension, achieving a steady-state contact angle of 137.4°. This relatively non-wetting interface state reduces the actual contact area between the droplet and the buffer material, inhibiting the capillary penetration process of liquid metal into the micropores. Due to the limited interface wetting behavior, droplet spreading, pore penetration, and the mechanical interlocking effect after solidification are correspondingly weakened, resulting in a pull-out force in the later stages of the test decreasing to 2.14 N, approximately 95.3% lower than that of Comparative Example 5. The interface bonding force data indicates that this solution has the foundation for physical slag reduction and low-stress extraction, which helps the high-temperature resistant ceramic-based inner lining tube 8 used to hold slag in long, thick-walled pipes to achieve low-resistance exit thanks to the automatic feeding and recovery mechanism 1 of the buffer material after cutting. This facilitates the subsequent electrochemical cleaning process (see attached diagram). Figure 6 The internal and external electrochemical jet deslagging steps provide a processing basis with less adhesion.

[0084] Test Example 3: Comprehensive Evaluation of Pipe Slag Removal Efficiency and Surface Roughness The thick-walled pipes treated with composite anti-adhesion and electrochemical slag removal processes in Example 2, as well as the pipes processed in Comparative Example 6 (with the same buffer barrier layer but only using 150MPa high-pressure water jet physical slag removal) and Comparative Example 7 (without adding a buffer barrier layer and using 15% NaCl solution for electrochemical slag removal), were used as research objects to conduct comprehensive tests on macroscopic slag removal efficiency and microscopic surface morphology.

[0085] A 304 stainless steel pipe with an outer diameter of 60mm, a wall thickness of 8mm, and a length of 1000mm was used as the basic test sample. Laser cutting and subsequent slag removal were performed according to the set processes for each group. This process covered the entire process from the attached... Figure 6 The process involves the clamping of pipes, placement of internal buffer material, and a complete workflow from cleaning and drying to discharge. During this process, the physical sliding isolation sealing door 3, in conjunction with the flexible clearance pad 5 on the outer side of the pipe wall, closes tightly, and combined with the dynamic airflow sealing formed by the positive pressure air curtain blowing device 4, constructs a completely independent composite closed slag removal zone (as shown in the attached diagram). Figure 5 As shown in the figure, this ensures that the surrounding drive mechanism is protected from jet erosion; the actual processing time from the end of cutting to the removal of the pipe from the slag removal station is recorded.

[0086] The solidified slag collected from the bottom of the cleaning tank and the inner cavity of the pipe was dried and weighed using a high-precision analytical balance. The apparent slag removal rate of each test sample was calculated based on the theoretical total slag mass derived from the equivalent kerf volume theory. The apparent slag removal rate was calculated as (actual collected slag mass / theoretical total slag mass) × 100%. The theoretical total slag mass was adjusted based on the kerf width, cutting path length, pipe wall thickness, and the density of 304 stainless steel.

[0087] The test section was cut along the axial direction of the pipe using an electrical discharge wire cutting device and placed in an ultrasonic cleaning tank containing acetone for continuous vibration for 15 minutes to remove surface oil and loose particles. It was then dried by blowing with cold air. This ultrasonic cleaning step is only used to remove oil and non-bonded loose particles before microscopic testing; it is not a secondary slag removal treatment and does not involve additional removal of firmly attached residues.

[0088] The microstructure of the central region of the cut section and the adjacent base material region 5 mm from the edge was scanned using a laser confocal three-dimensional microscope. The measurement area was set to 2 mm × 2 mm, and the arithmetic mean surface roughness Sa and the maximum height Sz of the cut surface within this area were extracted. Five different locations within the same area were randomly selected for repeated measurements, and the arithmetic mean was taken as the final recorded data.

[0089] Table 3. Comprehensive test results of slag removal efficiency and surface quality in the examples and comparative examples In the cross-sectional profile data acquired by laser confocal microscopy, the microscopic undulations of Example 2 were relatively uniform, and no abnormal peaks or valleys were observed; the surface of Comparative Example 6 showed randomly distributed large-scale protrusions, corresponding to stubborn slag that was difficult to peel off between microscopic pores; the profile baseline of Comparative Example 7 was accompanied by irregular depressions, reflecting that the local metal matrix had undergone uneven dissolution.

[0090] Figure 3 This is a representative two-dimensional cross-sectional microscopic contour height distribution diagram of the pipe cutting section of the present invention, used to show the typical morphological differences of each group; Sa and Sz in Table 3 are the statistical parameters of three-dimensional surface scanning within a 2mm×2mm area. In the figure, the solid line represents the contour undulation trajectory of the pipe cutting section of Example 2, the dashed line represents the contour undulation trajectory of the pipe cutting section of Comparative Example 6, and the dotted-dash line represents the contour undulation trajectory of the pipe cutting section of Comparative Example 7. In order to clearly present the morphological characteristics of each group, the contour baselines of Comparative Example 6 and Comparative Example 7 have been appropriately offset longitudinally on the Y-axis in the figure.

[0091] In summary, based on the data in Table 3, Example 2 achieved a good balance between slag removal time and surface morphology control, with an apparent slag removal rate of 97.6% and a cross-sectional roughness Sa maintained at 4.21 μm. In actual laser cutting of thick-walled pipes, the bottom metal is prone to slag formation due to molten pool hydrodynamic instability. This interfacial bonding state between the solidified phase and the ceramic matrix significantly affects subsequent cleaning efficiency. Although Comparative Example 6 used the same high-temperature resistant ceramic-based inner liner 8 as a buffer layer, subsequent slag removal relied solely on the physical impact kinetic energy of the high-pressure water jet.

[0092] Under this setup, although the roughness (0.35 μm) of the adjacent base material region remained close to the original surface, when faced with stubborn slag in a state of microporous interlocking, the lack of electrochemical anodic dissolution assistance provided by the hardware mounted on the C-type synchronous linkage cantilever 6 resulted in insufficient removal capability of the single physical impact method, making it difficult to break the deep mechanical anchorage. This led to an actual slag removal rate of only 81.4%, with the remaining large-scale slag blocks increasing the cross-sectional area Sz to 92.7 μm and resulting in a processing time consumption of approximately 38.5 minutes. When an electrolyte containing free chloride ions was introduced to intervene in the slag removal, the processing time of Comparative Example 7 was shortened to 19.1 minutes, and the overall slag removal efficiency improved. However, under the condition of no buffer barrier layer and the use of NaCl electrolyte, the base material surface was more prone to activation dissolution and local pitting corrosion. Although this system accelerated the peeling off of the slag root, it caused obvious local corrosion characteristics in the originally flat adjacent base material region, increasing its roughness Sa to 1.84 μm. This slag removal method, which involves damage to the base material, increases the risk of subsequent pressure or flow failure in the pipe fittings.

[0093] Compared to processing paths that rely solely on physical impact or carry the risk of activated corrosion, the processing operation in Example 2 of this scheme utilizes a non-wetting barrier layer formed during the cutting stage to weaken the basic adhesion of slag. Combined with the anodic passivation effect under a neutral nitrate system, this constructs a selective dissolution and stripping mechanism. In the actual electrochemical cleaning process (corresponding to Appendix 2),... Figure 6 In the internal and external electrochemical jet slag removal steps, it can be observed that a passivation film can be quickly established on the large-area exposed base material surface under the action of an electric field, thereby inhibiting excessive longitudinal consumption of the metal substrate. The roughness of the adjacent base material of this sample is maintained at 0.38 μm, which is close to that of Comparative Example 6 treated with high-pressure water jet and significantly lower than that of Comparative Example 7 of the NaCl system, indicating that the system has a good protective effect on the slag-free area. In contrast, the edges of the slag with rough morphology and damaged barrier layer are more prone to local electric field concentration due to geometric protrusions and film discontinuity, which promotes preferential dissolution of the slag root, reduces the interfacial bonding strength, and eventually leads to desorption. This synergistic effect of interfacial wetting regulation and electrochemical passivation mechanism reduces the dependence on single physical impact kinetic energy and also reduces the risk of electrochemical corrosion in large-area base material areas. The above test data reflect that the process can quickly complete the cleaning of the inner cavity of the pipe within 14.3 minutes, and the micro-profile fluctuation of the cross-section converges, providing favorable conditions for the surface quality stability of thick-walled pipes during subsequent service.

[0094] Test Example 4: Corrosion Resistance Test of Finished Pipes After Processing The finished pipes treated with the composite anti-adhesion and electrochemical slag removal process in Example 2, the processed pipes of Comparative Example 6 (with the same buffer barrier layer but only using 150MPa high-pressure water jet physical slag removal), and the processed pipes of Comparative Example 7 (without adding a buffer barrier layer and using 15% NaCl solution for electrochemical slag removal) were compared (i.e., the pipes were not fully treated with the composite anti-adhesion and electrochemical slag removal process). Figure 6 The process shown is used as the research object to evaluate its electrochemical corrosion resistance under simulated service environment.

[0095] Axial specimens measuring 10mm × 10mm × 5mm were cut from the pipe sections and adjacent base material areas after the slag removal process was completed in each group. Copper wires were welded to the back of the specimens, and then they were cold-mounted and encapsulated with epoxy resin, leaving only a 100mm² area exposed. 2 The slag-cleaned surface is used as the working surface for electrochemical testing. This working surface includes the cut section and the continuous area of ​​the adjacent base material within 5 mm from the cut edge, and the proportion of the exposed area of ​​each group of samples is consistent.

[0096] The non-test surfaces and packaging edges of the sample were lightly trimmed with 240-mesh, 600-mesh, and 1200-mesh silicon carbide sandpaper to remove edge burrs. The slag-cleaning surface, which serves as the working surface for electrochemical testing, was not mechanically polished to maintain the original surface state after different slag removal processes. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 3 minutes, dried with cold air, and placed in a desiccator for later use.

[0097] The measurement was performed using a three-electrode electrochemical testing system. The resin-encapsulated tubular sample was used as the working electrode, the saturated calomel electrode (SCE) was used as the reference electrode, and a platinum sheet with an area of ​​20 mm × 20 mm was used as the auxiliary electrode. The test medium was 3.5% NaCl solution, and the test temperature was controlled at 25 ± 1 ℃ by a constant temperature water bath.

[0098] The working electrode was immersed in the test medium for open-circuit potential (OCP) monitoring. Steady state was considered reached when the potential fluctuation was less than 2 mV within 30 minutes. Subsequently, potentiodynamic polarization curve scanning was performed. The scanning range was set to -0.4 V to +1.0 V relative to the open-circuit potential, with a scanning rate of 1 mV / s. The system continuously recorded the corresponding data of polarization current density and potential. Due to differences in the open-circuit potential of each group of samples, the absolute potential range corresponding to the actual scan was converted based on the stable open-circuit potential of each sample. Figure 4 The representative potential-log current density polarization curves are shown in Table 4. The specific electrochemical parameters are as described in Table 4.

[0099] Table 4. Potentiodynamic polarization test parameters of each group of pipe surfaces in 3.5% NaCl solution In the potentiodynamic polarization data collected by the electrochemical workstation, Example 2 maintained a low and stable passivation current density over a relatively wide potential range until the potential increased to 0.412V, at which point the current density increased significantly. The trend of the anodic polarization curve of Comparative Example 6 was similar to that of Example 2, but the current fluctuation in its passivation range was relatively obvious, and the pitting potential was detected earlier. Comparative Example 7 showed that the overall anodic polarization curve shifted towards higher current density and negative potential. After passing -0.083V, the current rose rapidly, and no obvious stable passivation region was observed.

[0100] Figure 4This is a representative potentiodynamic polarization curve of the pipe surface processed according to the present invention in a 3.5% NaCl solution, used to compare the polarization characteristics of the pipe after different slag removal processes. In the figure, the solid line represents the polarization curve trajectory of the pipe surface processed in Example 2, the dashed line represents the polarization curve trajectory of the pipe surface processed in Comparative Example 6, and the dotted-dash line represents the polarization curve trajectory of the pipe surface processed in Comparative Example 7. To conform to the layout requirements of the patent specification, the graphics are distinguished by differences in grayscale and line type, and the annotation boxes in the figures are placed in the blank areas of the figure to reduce the overlap between the annotation boxes and the curve trajectories.

[0101] Summary: Based on the data in Table 4, the electrochemical stability exhibited by the samples in the subsequent simulated service environment differed significantly after undergoing different slag removal processes. The self-corrosion potential of the sample in Example 2 remained stable at -0.223V, and its self-corrosion current density was controlled at 0.46μA / cm². 2 This indicates a low tendency for spontaneous active dissolution on the material surface. This maintenance of corrosion resistance is strongly correlated with the anodic passivation protection under the neutral nitrate system during processing. In contrast, Comparative Example 7, under conditions of no buffer layer and slag removal using NaCl electrolyte, showed a negative shift in its self-corrosion potential to -0.438V, while the self-corrosion current density increased to 5.12 μA / cm². 2 This is approximately 11.1 times that of Example 2, which to some extent reflects that localized activation dissolution or electrochemical damage occurred on the substrate surface during the initial cleaning process. Even in Comparative Example 6, which had a buffer layer but was subsequently subjected to only high-pressure water physical impact, its electrochemical parameters (-0.245V, 0.61μA / cm) were significantly lower. 2 Although the 0.338V was better than Comparative Example 7, it still showed a slight degradation compared to Example 2. This is related to the local mechanical stress concentration or uneven morphology caused by the large-scale slag peeling process.

[0102] A deeper investigation of polarization characteristics reveals that the pitting potential or rapid current rise potential (Ep) of each sample better reflects its resistance to localized passivation film rupture under specific service environments. Example 2 exhibits a pitting potential of 0.412V, indicating good resistance to localized corrosion in a chloride-containing simulated service medium. From a technical mechanism perspective, this is mainly attributed to the selective dissolution mechanism implemented in a neutral nitrate system. This mechanism facilitates anodic passivation of the large-area exposed non-slag-bearing substrate surface, forming or maintaining a passivation film primarily composed of chromium-rich oxides, thereby reducing the likelihood of chloride-induced localized corrosion. In contrast, Comparative Example 7 shows a significant drop in its rapid current rise potential to -0.083V. This indicates that under conditions of no buffer barrier layer and slag removal using NaCl electrolyte, the natural passivation system on the substrate surface is damaged to some extent, forming localized active sites. These localized active sites are more likely to induce a rapid rise in anodic current during service testing, leading to instability of the surface protective film at a lower potential during polarization.

[0103] This series of electrochemical response data reflects the surface micro-evolution of the finished pipe after manufacturing. Although slag removal efficiency is an important indicator of processing speed, residual local defects or chemical corrosion products can alter the surface energy state of the material and disrupt the original uniformity of the surface structure. Example 2 of this solution combines a non-wetting barrier interface with a neutral electrochemical passivation process, which not only helps achieve low-resistance and efficient slag desorption but also reduces the risk of localized over-corrosion to a certain extent, allowing thick-walled pipes to undergo further processing. Figure 6 Throughout the process, from the high-temperature melting and cutting of the fiber laser cutting head 7, the stable transmission of the three-chuck centering mechanism 2, and the electrochemical cleaning process within the composite isolation and splash-proof zone, to the final cleaning, drying, and unloading steps, the working surface still exhibits good service corrosion resistance stability. These observations also provide experimental reference and data basis for evaluating the service corrosion resistance of long-length, thick-walled stainless steel pipe fittings in chlorine-containing corrosive media.

Claims

1. A laser cutting and electrochemical jet slag removal process for thick pipes, characterized in that, Includes the following steps: The thick-walled tube is clamped in the three-chuck centering mechanism (2). The high-temperature ceramic matrix liner tube (8) made of high-temperature alumina fiber reinforced ceramic matrix composite material is pushed into the inner cavity of the thick-walled tube by the buffer material automatic feeding and recycling mechanism (1). The outer wall of the buffer material is controlled to fit with the inner wall of the thick-walled tube and the radial gap is 0.03 to 0.10 mm, completely covering the predetermined laser cutting area. The thick-walled pipe is cut by a fiber laser cutting head (7). The thick-walled pipe and the buffer material rotate synchronously and uniformly. The high-temperature molten slag generated drips onto the surface of the buffer material, forming a cut and residual molten slag area. After the laser cutting action is completed, the buffer material is completely removed from the processing area along the axial direction by the automatic feeding and recycling mechanism (1). The electrochemical jet slag removal device is moved to the original cutting position, and the physical sliding isolation sealing door (3) is closed. The flexible clearance pad (5) on the outer wall of the pipe completely isolates and seals the processing area and opens the positive pressure air curtain blowing device (4). A NaNO3 aqueous solution with a mass fraction of 10-20% is used as the passivation electrolyte. The thick-walled pipe is connected to the anode. The inner and outer jet nozzles on the C-type synchronous linkage cantilever (6) of the electrochemical jet slag removal device are connected to the cathode. The electrolyte injection pressure is controlled at 3.0-6.0 MPa, and the DC regulated power supply voltage is controlled at 150-250V. The inner and outer jet nozzles synchronously spray high-pressure electrolyte onto the cut surface and the residual slag area.

2. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 1, characterized in that, In the penetration cutting, the operating parameters are set as follows: laser output power is 2000W, cutting axial feed speed is 2m / min, pure oxygen is used as auxiliary cutting gas and the gas ejection pressure is maintained at 0.3MPa, and the laser focus position is set on the surface of the pipe wall.

3. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 1, characterized in that, In the high-pressure electrolyte spraying process, the solution conductivity is controlled to be 7-14 S / m, and the operating temperature is kept constant at 25℃; the jet distance from the inner and outer jet nozzles to the workpiece surface is adjusted to 1.0-4.0 mm, and the continuous slag removal processing time is 10-60 s.

4. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 3, characterized in that, After spraying high-pressure electrolyte, the processing power is automatically cut off and the electrolyte spraying is stopped. The inner and outer walls of the pipe are rinsed with clean water in sequence. High-pressure compressed air is turned on to dry the surface and inner cavity of the pipe. The physical sliding isolation sealing door (3) is opened, the electrochemical slag removal device returns to the initial position, the chucks of the three chuck centering mechanism (2) are released, and the finished pipe with non-destructive slag removal is directly discharged.

5. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 1, characterized in that, The high-temperature resistant ceramic-based inner liner (8) is made from raw materials comprising the following parts by weight: 5-10 parts of hexagonal boron nitride micro powder; 30-40 parts of aluminum phosphate inorganic binder solution (based on solid content); 50-60 parts of continuous alumina ceramic fiber bundles.

6. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 5, characterized in that, The preparation method of the high-temperature resistant ceramic-based inner liner (8) includes the following steps: The hexagonal boron nitride micro powder was added to the aluminum phosphate inorganic binder solution based on solid content, and the mixture was dispersed at high speed using a mechanical stirring device at room temperature to obtain a uniformly mixed ceramic slurry suspension. The continuous alumina ceramic fiber bundle is continuously drawn through the ceramic slurry suspension for full impregnation. A CNC winding machine is used to tightly wind the fiber bundle impregnated with inorganic slurry onto the outer surface of a standard forming mandrel at a cross angle. The cumulative thickness of single-layer and multi-layer winding is controlled so that the final tube wall thickness is 0.2-1mm, thus obtaining a preform. The entire molded core is moved into an oven and kept at a constant temperature to remove physical moisture from the system. The dried preform is then demolded from the core and moved into a high-temperature sintering furnace for gradient high-temperature sintering, so that the inorganic matrix and alumina fiber are completely sintered and solidified into a ceramic matrix.

7. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 6, characterized in that, In the gradient high-temperature sintering, the specific high-temperature sintering temperature and time are set sequentially as follows: The inorganic binder was dehydrated at high temperature by heating to 400℃ at a heating rate of 3℃ / min and holding at that temperature for 1 hour. Then, the temperature was further increased to 1100℃ at a heating rate of 5℃ / min and sintered at that temperature for 2 hours.

8. The thick-tube laser cutting combined with electrochemical jet slag removal process according to claim 6, characterized in that, In the high-speed dispersion, the time is 60 minutes; During the overall transfer into the oven for constant temperature maintenance, the operating conditions were to maintain a constant temperature of 80°C for 2 hours.

9. A laser cutting and electrochemical jet slag removal device for thick pipes, characterized in that, include: The three-chuck centering mechanism (2) is used to clamp and drive the thick-walled pipe to rotate synchronously and uniformly in one operation. The automatic feeding and recycling mechanism (1) for feeding and recycling the buffer material, namely the high temperature resistant ceramic-based inner liner (8), into and out of the inner cavity of the pipe to be cut. Fiber laser cutting head (7) is used for penetrating cutting of thick-walled pipes; The electrochemical jet deslagging unit includes internal and external jet nozzles and a DC regulated power supply installed on a C-type synchronous linkage cantilever (6); A physical sliding isolation sealing door (3), a flexible clearance pad (5), and a positive pressure air curtain blowing device (4) are used to completely isolate and seal the processing area.

10. The thick-tube laser cutting combined with electrochemical jet slag removal device according to claim 9, characterized in that, The inner and outer jet nozzles are made of titanium alloy, and the inner diameter of the inner and outer jet nozzles is 1.50 to 2.50 mm. The DC regulated power supply is connected to the stainless steel pipe at the anode and to the inner and outer jet nozzles at the cathode.

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