A method and system for pre-treating subcutaneous blowholes in a heavy casting during rough machining

Abstract

The application discloses a kind of subcutaneous blowhole pretreatment method and system in large casting rough machining process, belong to large casting processing technical field.Exposed to the gas hole to be handled on the surface of finish machining feature is determined by combining workpiece design parameters after rough milling of milling after clamping and positioning, and the data of subcutaneous blowhole is collected by real-time scanning through detection module integrated in cutter handle, and the gas hole repair is completed by laser welding before finish machining, and the finish machining process is executed after repair review is qualified.The system is composed of clamping and positioning module, numerical control milling module, detection module, laser welding module, reinspection module and control module, and each module linkage realizes integrated operation of processing, detection and repair.The application can avoid secondary clamping and repeated finish machining, improve processing efficiency and dimensional accuracy, ensure consistent performance of base material, and reduce comprehensive production cost.

Description

Technical Field

[0001] This invention relates to the field of large casting processing technology, and more specifically, to a method and system for pre-treating subcutaneous porosity during the rough machining of large castings. Background Technology

[0002] During the casting process of large castings, subsurface porosity defects are easily formed beneath the surface due to factors such as raw material characteristics, fluctuations in pouring process parameters, and poor mold venting conditions. These defects are hidden beneath the surface of the casting and are difficult to detect through conventional visual inspection in the blank state and early stages of machining. They are usually only exposed after all finishing processes are completed and the surface material is removed.

[0003] Currently, the mainstream process for handling subcutaneous porosity in large castings in the industry is as follows: first, complete all finishing processes; then, expose the porosity through visual inspection or non-destructive testing; next, repair the area by welding; and finally, perform a second finishing process to eliminate the welding marks and restore the workpiece to its design dimensions and surface accuracy. This model has a series of significant drawbacks. First, the process is severely redundant, requiring the same processing area to undergo finishing, welding, and then finishing again, significantly increasing the total processing time. This is especially true for large castings, where the time cost of repeated clamping and alignment is extremely high, resulting in low production efficiency. Second, secondary clamping inevitably introduces positioning errors, leading to a loss of machining accuracy and easily causing dimensional deviations or even workpiece scrap. Third, the composition of the welding material is difficult to completely match the base material, resulting in differences in hardness, strength, and corrosion resistance between the repaired area and the surrounding substrate, forming weak points with uneven hardness. Furthermore, welding stress can easily induce cracks, reducing the overall mechanical properties and service life of the workpiece. Fourth, defect detection is severely delayed. When porosity is discovered after finishing, most of the workpiece's value has already been realized. At this point, the difficulty and risk of repair increase dramatically. For porosity located in critical load-bearing parts, the entire casting may become unrepairable, resulting in huge losses. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for pre-treating subcutaneous porosity during the rough machining of large castings. The method includes: clamping and positioning the large casting to be machined on a CNC milling machine; inputting workpiece design parameters to determine the range of the feature surfaces of the workpiece after finishing; starting the CNC milling machine to perform rough milling on the casting; simultaneously, a detection module integrated on the milling cutter holder performs real-time scanning of the interior of the casting below the current milling surface, acquiring the position coordinates, depth dimensions, and diameter dimensions of the subcutaneous pores; the detection module includes an eddy current detection unit and wirelessly transmits the detection data to a control module; the control module receives the detection data and, in conjunction with the workpiece design parameters, calculates the distance from the bottom of each subcutaneous pore to the feature surface of the finished workpiece, and pre-treating pores with a distance less than or equal to a preset safety thickness. The hole is identified as a pore to be treated. The control module moves the laser welding module to the location of the pore and adjusts the laser welding parameters according to the depth and diameter of the pore. Laser welding is then performed to remove the gas from the pore and fill it with molten casting material to form a dense weld layer. The thickness of the weld layer does not exceed the finishing allowance. Argon is used as the shielding gas during the welding process. The area where laser welding has been completed is scanned again to confirm that the pores have been repaired successfully. If there are any unrepaired pores, the laser welding and venting repair process is repeated. After all the pores have been repaired successfully, a CNC milling machine is started to finish the casting, removing the finishing allowance and excess weld layer to ensure that the workpiece meets the design dimensions and accuracy requirements.

[0005] Compared with existing technologies, the technical effects achieved by this solution are as follows: By simultaneously detecting and judging subcutaneous porosity during rough milling and completing laser welding venting repair of the pores to be treated before finishing, the traditional process of welding after finishing and then reprocessing is broken. This eliminates redundant steps of repeated finishing from the process layout, effectively shortening the overall production cycle of large castings. Detection, repair, and finishing are all completed under the same clamping and positioning, avoiding positioning errors caused by secondary clamping, ensuring the consistency of the overall size and shape accuracy of the workpiece, and reducing the risk of workpiece scrap. Laser welding utilizes the casting matrix material itself to melt and fill the pores, eliminating the need for additional welding wire. This ensures that the composition and properties of the repaired area are consistent with the matrix material, avoiding problems such as uneven mechanical properties and easy cracking caused by differences in welding materials. At the same time, the thickness of the weld layer is controlled within the finishing allowance range, and the excess weld layer can be directly removed in subsequent finishing without additional processing steps, improving processing efficiency while reducing production material and labor costs.

[0006] In one embodiment of the present invention, the detection module moves synchronously with the milling cutter. Each time the milling cutter completes a milling feed, the detection module scans the area below the current milling surface, and the scanning interval is not greater than the milling feed amount. The detection module is also equipped with a surface cleaning unit for removing chips and oil stains from the milling surface.

[0007] Compared with existing technologies, the technical effects achieved by this solution are as follows: the detection module moves synchronously with the milling cutter, and can complete the scanning of subcutaneous pores in the corresponding machining area in sync with the milling feed. This eliminates the need for separate detection stations and strokes, avoids additional overall roughing time, and ensures efficient connection between machining and detection processes. The scanning interval is set to be no greater than the milling feed amount, ensuring complete coverage of the area to be detected below the milled surface, eliminating blind spots, and preventing missed detection of subcutaneous pores due to excessively large scanning intervals. The surface cleaning unit can promptly remove residual chips and oil from the milled surface before detection, reducing interference from external impurities on the detection signal, improving the accuracy of pore location, depth, and diameter detection data, and providing reliable data support for subsequent pore identification and welding repair.

[0008] In one embodiment of the present invention, when performing laser welding to repair the venting of the pores, the laser working mode is selected according to the pore diameter.

[0009] Compared with existing technologies, the technical effects achieved by this solution are as follows: by selecting the appropriate laser working mode according to the size of the pores to be treated, the optimal fusion welding process can be matched for pore defects of different sizes, avoiding the problem that a single laser mode cannot take into account the repair quality of pores of different sizes.

[0010] In one embodiment of the present invention, if the aperture is larger than a preset aperture threshold, pulsed laser welding is used and the pulse frequency is adjusted; if the aperture is smaller than or equal to the preset aperture threshold, continuous laser welding is used and the welding speed is adjusted; the laser welding parameters include laser power, welding speed, spot size and shielding gas flow rate.

[0011] Compared with existing technologies, the technical effects achieved by this solution are as follows: For large pores larger than the preset aperture threshold, pulsed laser welding with adjustable pulse frequency can utilize the intermittent heating characteristics of pulsed lasers to provide sufficient time for gas to rise and escape from the pores during the solidification gap of the molten pool, while inhibiting the growth of pore defects caused by excessive flow of the molten pool, thus improving the venting and filling effect of large-diameter pores; For small pores less than or equal to the preset aperture threshold, continuous laser welding with adjustable welding speed can improve welding efficiency and accelerate the repair process while ensuring sufficient venting; By incorporating laser power, welding speed, spot size, and shielding gas flow rate into the adjustable welding parameters, the welding process can be precisely controlled from multiple dimensions such as energy input, work efficiency, effective range, and molten pool protection, ensuring the quality of welding repair under different working conditions.

[0012] In one embodiment of the present invention, the protective gas is argon with a purity of 99.99%, and the positioning accuracy of the laser welding module is no greater than the preset accuracy.

[0013] Compared with existing technologies, the technical effects achieved by this solution are as follows: Using high-purity argon as the protective gas in the welding process creates a stable inert gas protective layer in the molten pool area during welding, isolating oxygen from the outside air from contacting the molten pool and preventing oxidation of the molten pool metal at high temperatures, thus avoiding the formation of oxide inclusions. Simultaneously, it prevents the molten pool from absorbing gases from the air and forming new porosity defects, ensuring the density and material properties of the weld layer. Furthermore, controlling the positioning accuracy of the laser welding module to meet preset accuracy requirements ensures that the laser welding area precisely corresponds to the location of the porosity to be treated, preventing welding position deviation from damaging the surrounding intact casting substrate. It also ensures that the welding range completely covers the porosity defect area, achieving complete repair of the porosity and improving the accuracy and reliability of the repair operation.

[0014] In one embodiment of the present invention, the re-inspection scanning uses an eddy current re-inspection unit to detect whether there are porosity or crack defects inside the welded area.

[0015] Compared with existing technologies, the technical effects achieved by this solution are as follows: Using an eddy current re-inspection unit to scan and inspect the welded area allows for non-destructive verification of the internal quality of the welded area. This accurately identifies defects such as incompletely filled residual pores, poor fusion, or cracks, ensuring that every pore meets the repair standards. The re-inspection process after repair allows for the timely detection and secondary repair of unrepaired defects, preventing workpieces with internal defects from entering subsequent finishing processes. This also prevents the need for rework due to unsatisfactory repairs discovered after finishing, ensuring the quality stability of the final product and reducing wasted time in subsequent processes.

[0016] This invention also provides a subcutaneous porosity pretreatment system for rough machining of large castings, used to implement the method described in any of the above, comprising: a clamping and positioning module for fixing the casting to be machined; a CNC milling module for rough and finish milling of the casting; a detection module integrated on the milling cutter of the CNC milling module, including a tool holder, a connector, a cutter head, and a built-in detection unit, the built-in detection unit including an eddy current detection unit, a positioning sleeve, a data transmission unit, a quick-change component, and a battery power supply unit; a six-outlet conical spiral guide column is provided at the center inside the cutter head, and spiral diversion channels and water outlet holes are distributed on the outer periphery of the guide column; the connector is provided with mounting holes and limiting... The positioning slot and guide column are connected to the connector through mounting holes and limiting slots, and fixed to the tool holder by positioning pins; the detection module is also equipped with a surface cleaning unit for removing chips and oil stains from the milled surface; the laser welding module is used for laser welding venting repair of the pores to be treated, including a laser generator, welding head, shielding gas supply unit and moving mechanism; the re-inspection module is used for re-inspection scanning of the welding area; the control module is electrically connected to the clamping and positioning module, CNC milling module, detection module, laser welding module and re-inspection module respectively, and is used to receive detection data, input workpiece design parameters, determine whether the pores need to be treated and control the coordinated work of each module.

[0017] Compared with existing technologies, the technical effects achieved by this solution are as follows: This pretreatment system, through the coordinated operation of clamping and positioning modules, CNC milling modules, detection modules, laser welding modules, re-inspection modules, and control modules, constructs a complete process system integrating roughing, online detection, defect judgment, welding repair, quality re-inspection, and finishing. All pretreatment and machining processes can be completed under the same clamping condition, eliminating the need for multi-station transfers and secondary clamping. The detection module is integrated onto the milling cutter and can perform detection operations synchronously with the cutter, eliminating the need for an additional independent detection execution mechanism and simplifying the overall system structure. The conical spiral guide column and water outlet structure inside the milling cutter achieve efficient cooling during the cutting process, improving tool life and milling surface quality. The connection structure of the connector and positioning pin ensures stable connection of all components of the milling cutter and facilitates the assembly and maintenance of the detection module. The overall system structure is rationally laid out, with clearly defined functions for each module, enabling stable pretreatment of subcutaneous porosity during the roughing process of large castings.

[0018] In one embodiment of the present invention, the outer circumference of the six-outlet conical spiral guide column is uniformly distributed with six spiral diversion channels, and six independent water outlets are provided to each cutting edge.

[0019] Compared with existing technologies, the technical effects achieved by this solution are as follows: Multiple spiral flow channels are evenly arranged on the outer circumference of the conical spiral guide column, and correspondingly, multiple independent water outlets are provided leading to each cutting edge. This allows the cooling medium to be evenly distributed to each cutting edge position, ensuring that all cutting edges receive sufficient and uniform cooling, avoiding problems such as accelerated tool wear and chipping due to insufficient local cooling. The spiral flow channel structure extends the flow path of the cooling medium inside the tool, improving the heat exchange efficiency between the cooling medium and the tool substrate, enhancing the overall cooling effect, effectively reducing the contact temperature between the tool and the workpiece during milling, improving the surface quality and dimensional stability of the milling process, and reducing the adhesion of chips to the tool or workpiece surface due to high temperatures, indirectly reducing signal interference from chips to the detection module.

[0020] In one embodiment of the present invention, the control module includes a data processing unit, a judgment unit, a parameter adjustment unit, and a motion control unit, and has a built-in matching database of casting material and laser welding parameters, which is used to automatically match laser welding parameters according to casting material and pore size.

[0021] Compared with existing technologies, the technical effects achieved by this solution are as follows: The control module, through the establishment of a data processing unit, a judgment unit, a parameter adjustment unit, and a motion control unit, can achieve fully automated operation of the entire process, including detection data processing, porosity risk assessment, welding parameter adjustment, and equipment motion control. Each unit has a clear division of labor and smooth connection, completing the entire process from porosity identification to repair execution without manual step-by-step operation, thus improving the system's automation level. Furthermore, the built-in database matching casting materials and laser welding parameters can automatically match the optimal welding parameters according to different casting materials and porosity sizes, avoiding experience differences and operational errors caused by manual parameter setting. This ensures the consistency and stability of the repair process for castings of different batches and materials, while reducing the process experience requirements for operators and improving the system's ease of use and versatility.

[0022] In one embodiment of the present invention, the eddy current detection unit is a low-frequency eddy current probe with a detection depth range of 0 to 4 mm; the re-inspection module includes an eddy current verification unit for detecting the internal density of the welded area.

[0023] Compared with existing technologies, the technical effects achieved by this solution are as follows: The eddy current detection unit uses a low-frequency eddy current probe, which is suitable for detecting subcutaneous porosity in the near-surface area of ​​castings, covering the common depth range of subcutaneous porosity, and has high detection sensitivity for small near-surface pores. It can accurately identify small subcutaneous pore defects and avoid missing small pores. The re-inspection module is equipped with an eddy current verification unit, which uses the same eddy current detection principle as the pre-inspection to perform density detection on the welded area. This ensures the uniformity of detection standards and data caliber, facilitates the comparison and analysis of detection results before and after repair, accurately judges the internal filling quality and defect elimination of the welded area, ensures the accuracy and reliability of the re-inspection results, and provides a stable technical basis for judging the quality of defect repair.

[0024] By adopting the technical solution of the present invention, the following technical effects can be achieved: By simultaneously detecting and determining subcutaneous porosity during rough milling and completing laser welding venting repair of the pores to be treated before finishing, the traditional process of welding after finishing and then performing secondary processing is broken. This eliminates redundant steps of repeated finishing in terms of process layout, effectively shortening the overall production cycle of large castings. Detection, repair, and finishing are all completed under the same clamping and positioning, avoiding positioning errors caused by secondary clamping, ensuring the consistency of the overall dimensions and dimensional accuracy of the workpiece, and reducing the risk of workpiece scrap. Laser welding uses the casting matrix material itself to melt and fill the pores, without the need for additional welding wire, ensuring that the composition and properties of the repaired area are consistent with the matrix material. This avoids problems such as uneven mechanical properties and easy cracking caused by differences in welding materials. At the same time, the thickness of the weld layer is controlled within the finishing allowance range, and the excess weld layer can be directly removed in subsequent finishing without additional processing steps, improving processing efficiency while reducing production material and labor costs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 A schematic flowchart illustrating a method for pretreating subcutaneous porosity during rough machining of large castings, provided by an embodiment of the present invention. Figure 2 This is a schematic diagram of a subcutaneous porosity pretreatment system for rough machining of large castings, provided by an embodiment of the present invention. Figure 3 This is a schematic diagram of the connection structure between the detection module and the milling cutter holder; Figure 4 This is one of the structural schematic diagrams of a milling cutter; Figure 5 for Figure 4 A cross-sectional view along the AA direction; Figure 6 This is the second schematic diagram of a milling cutter.

[0026] Explanation of reference numerals in the attached figures: 1. Clamping and positioning module; 2. CNC milling module; 3. Laser welding module; 4. Re-inspection module; 5. Tool holder; 6. Connector; 7. Tool head; 8. Eddy current detection unit; 9. Positioning sleeve; 11. Quick change component; 12. Battery power supply unit; 13. Six-outlet conical spiral guide column; 14. Spiral diversion channel; 17. Mounting hole; 18. Limiting groove. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention are clearly and completely described. 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.

[0028] See Figure 1 This invention provides a method for pretreating subcutaneous porosity during the rough machining of large castings, comprising: Step S1: Clamp and position the large casting to be machined on the CNC milling machine, input the workpiece design parameters, and determine the range of the feature surfaces of the workpiece after finishing. Step S2: Start the CNC milling machine to perform rough milling on the casting. At the same time, the detection module integrated on the milling cutter holder performs real-time scanning on the interior of the casting below the current milling surface, and collects the position coordinates, depth and diameter of the subcutaneous pores. The detection module includes an eddy current detection unit and wirelessly transmits the detection data to the control module. Step S3: The control module receives the detection data and, in conjunction with the workpiece design parameters, calculates the distance from the bottom of each subcutaneous pore to the feature surface of the finished workpiece. Pores with a distance less than or equal to the preset safety thickness are identified as pores to be processed. Step S4: The control module controls the laser welding module to move to the position of the pore to be treated. The laser welding parameters are adjusted according to the depth and diameter of the pore. The pore is then repaired by laser welding to remove gas, so that the gas in the pore is discharged and filled by the molten casting material to form a dense weld layer. The thickness of the weld layer does not exceed the finishing allowance. Argon is used as a protective gas during the welding process. Step S5: Re-inspect the area where laser welding has been completed to confirm that the pores to be treated have been repaired to a qualified standard. If there are pores that have not been repaired to a qualified standard, repeat the laser welding venting repair process. Step S6: After all the pores to be treated have been repaired and are qualified, start the CNC milling machine to perform finishing on the casting, remove the finishing allowance and excess part of the weld layer, so that the workpiece meets the design size and accuracy requirements.

[0029] Specifically, the first step is clamping, positioning, and parameter input. The large casting to be processed is hoisted onto the worktable of the CNC milling machine. The clamping components of the clamping and positioning module hold and fix the casting, completing the workpiece alignment and clamping positioning to ensure that the casting does not undergo relative displacement during subsequent milling, inspection, and welding operations. After clamping, the operator inputs the workpiece's design parameters into the control module, including the position coordinates of each feature surface, the reserved finishing allowance, and dimensional tolerance requirements. The control module calculates and determines the location range of each feature surface of the workpiece after finishing based on the input parameters, which serves as the benchmark for subsequent assessment of porosity exposure risk. Among them, the workpiece feature surface refers to the machined surface of the casting that must ultimately guarantee dimensional accuracy and surface quality, and the finishing allowance refers to the material thickness reserved after rough machining for subsequent finishing removal.

[0030] The second step involves rough milling and simultaneous inspection. The CNC milling module is activated, and the large casting is milled layer by layer according to the preset roughing program to remove most of the machining allowance. During milling, the inspection module integrated on the milling cutter holder moves synchronously with the cutter, following its feed trajectory to perform real-time scanning and inspection of the internal area of ​​the casting below the milled surface. The inspection module has a built-in eddy current detection unit that scans the near-surface area below the milled surface based on the eddy current induction principle, collecting data such as the location coordinates, depth, and diameter of subcutaneous pores within the area. The inspection module also has a built-in data transmission unit that wirelessly transmits the collected inspection data to the control module in real time, eliminating the need for external wiring and preventing cable entanglement during milling. The inspection module also includes a surface cleaning unit with an air-blowing structure that cleans the current milled surface before scanning, removing residual chips, oil, and other impurities to reduce interference with the eddy current detection signal and improve the accuracy of the inspection data. Each time the milling cutter completes a feed stroke, the detection module simultaneously scans the corresponding area. The row spacing of the scan is set to be no greater than the milling feed amount to ensure complete coverage of the detection area below the milled surface, with no blind spots, thus preventing missed detection of subcutaneous pores.

[0031] The third step is the assessment of the risk of porosity exposure. After receiving the porosity detection data transmitted by the detection module, the data processing unit of the control module, combined with the workpiece design parameters entered in the first step, calculates the distance from the bottom of each detected subcutaneous porosity to the corresponding feature surface after finishing. The judgment unit of the control module compares the calculated distance with the preset safety thickness: if the distance is less than or equal to the preset safety thickness, it is determined that the porosity will be exposed on the workpiece feature surface after subsequent finishing and material removal, and it is marked as a porosity to be treated; if the distance is greater than the preset safety thickness, it is determined that the porosity will not be exposed on the feature surface after finishing and will not affect the final surface quality and performance of the workpiece, and it is marked as a porosity that does not require treatment and will not be repaired. The preset safety thickness is the thickness threshold that ensures a sufficiently dense matrix remains under the surface of the workpiece after finishing, and it can be set according to the usage requirements and machining accuracy requirements of the casting. Specifically, the preset safety thickness can be 3mm.

[0032] The fourth step is laser welding for venting and repair. After determining the porosity of the current milled layer, the motion control unit of the control module sends a motion command to the laser welding module, controlling the moving mechanism of the laser welding module to move the welding head to a position directly above the porosity to be treated. The positioning accuracy meets the preset accuracy requirements, ensuring that the welding area corresponds perfectly with the porosity. Subsequently, the parameter adjustment unit of the control module retrieves the corresponding optimal welding parameters from the built-in matching database based on the depth and diameter of the porosity and the material of the casting. These parameters include laser power, welding speed, spot size, and shielding gas flow rate. The corresponding laser working mode is selected according to the porosity size: for larger porosities, a pulsed laser welding mode is used, adjusting the corresponding pulse frequency to utilize the intermittent heating characteristics of the pulsed laser to ensure that the gas in the porosity has sufficient time to rise and escape, while suppressing the flow of the molten pool that could cause the porosity to enlarge; for smaller porosities, a continuous laser welding mode is used, adjusting the appropriate welding speed to balance the solidification speed of the molten pool and the rising speed of the bubbles, improving repair efficiency while ensuring thorough venting. During the fusion welding process, the shielding gas supply unit continuously outputs high-purity argon gas, forming an inert protective atmosphere in the molten pool area to prevent oxidation of the molten metal and avoid the inhalation of gas that would create new pores. After the laser beam irradiates the pore area, the high temperature melts the casting matrix material. The gas inside the pores expands due to heat and rises to escape. The molten matrix material fills the voids in the original pores, and after cooling, forms a dense fusion weld layer. During the fusion welding process, the thickness of the fusion weld layer is strictly controlled to not exceed the remaining finishing allowance at that location, ensuring that weld marks can be completely removed in subsequent finishing processes and will not remain on the final surface of the workpiece.

[0033] Specifically, the laser welding module is linked with the CNC milling machine and the detection module. The control module achieves synchronous positioning with a positioning accuracy of no more than 0.05mm, ensuring that the position of the laser welding corresponds perfectly with the position of the pores to be treated. The welding parameters are adaptively adjusted according to the casting material and the size of the pores, with the laser power being 1000-5000W, the welding speed being 5-20mm / s, the spot size being 0.5-2mm, and the protective gas flow rate being 5-15L / min.

[0034] Step 5: Post-repair verification and secondary repair. After the fusion welding repair of a single area or batch of pores, the re-inspection module moves above the fusion welding area and performs a secondary scan inspection using the eddy current verification unit. This checks for residual pores, cracks, incomplete fusion, or other defects within the fusion welding area, confirming that the pores have been completely vented and densely filled, meeting the repair qualification standard. If the re-inspection reveals unrepaired pore defects, the control module will readjust the fusion welding parameters and control the laser fusion welding module to perform a secondary fusion welding repair on that area. After the repair is completed, another re-inspection is performed until the area passes the inspection.

[0035] Step 6, finishing process. After all the pores in the rough machining layers have been repaired and qualified, and all rough machining processes have been completed, the CNC milling module performs finishing machining on the large casting according to the preset finishing program. It removes the finishing allowance reserved in the rough machining layer by layer, as well as the excess part of the weld layer, so that the dimensions and form and position tolerances of the workpiece meet the design requirements, and completes the entire machining process.

[0036] See Figures 2-6 This embodiment also provides a subcutaneous porosity pretreatment system for rough machining of large castings, used to implement the above-mentioned pretreatment method. The specific structure of the system is as follows: The system includes a clamping and positioning module 1, a CNC milling module 2, a detection module, a laser welding module 3, a re-inspection module 4, and a control module.

[0037] The clamping and positioning module 1 includes a worktable and multiple clamping components. The base is fixedly installed on the worktable of the CNC milling machine. The clamping components can adjust the position and clamping force according to the shape of the casting to firmly clamp the casting on the worktable, ensuring that the casting does not undergo relative displacement during the entire process of milling, inspection and welding, and realizing the precise clamping and positioning of the casting.

[0038] The CNC milling module 2 includes a CNC milling machine body and a CNC spindle. The milling cutter is mounted on the CNC spindle and can rotate under the spindle drive and complete the feed motion according to the preset machining program to realize rough milling and finish milling of large castings.

[0039] The detection module is integrated and installed on the milling cutter, specifically including a tool holder 5, a connector 6, a cutter head 7, and a built-in detection unit. The upper end of the tool holder 5 is connected to the CNC spindle, and the lower end is connected and fixed to the cutter head 7 via the connector 6. The connector 6 has mounting holes 17 and limiting grooves 18. The cutter head 7 is positioned and assembled with the connector 6 through the mounting holes 17 and limiting grooves 18, and is further fixed to the tool holder 5 by a positioning pin to ensure a stable connection and prevent loosening during milling. The built-in detection unit is integrated inside the tool holder 5 and the connector 6, including an eddy current detection unit 8, a positioning sleeve 9, a data transmission unit, a quick-change assembly 11, and a battery power supply unit 12. The eddy current detection unit 8 uses a low-frequency eddy current probe to detect subcutaneous pores in the near-surface area below the milled surface; the positioning sleeve 9 is used to fix the installation position of the eddy current detection unit 8 to ensure detection position accuracy; the data transmission unit is used to wirelessly transmit the collected detection data to the control module; the quick-change component 11 facilitates the quick disassembly, assembly, maintenance, and replacement of the detection module; the battery power supply unit 12 provides power to the various electronic components of the detection module, eliminating the need for external power lines. The detection module is also equipped with a surface cleaning unit, which uses an air blowing structure to clean chips and oil stains from the milled surface, improving detection accuracy.

[0040] A conical spiral guide column is located at the center of the cutter head 7. Multiple spiral diversion channels 14 are evenly distributed around the outer circumference of the guide column, corresponding to multiple independent water outlets. Each water outlet leads to a different cutting edge of the cutter head 7. The cooling medium enters the guide column from inside the tool holder 5, is evenly diverted by the spiral diversion channels 14, and is then sprayed out from each water outlet to cool the cutting edge and the machining area. The spiral flow channel structure extends the flow path of the cooling medium, improves the heat exchange efficiency of the cooling medium, ensures uniform cooling of each cutting edge, and improves tool life and milling surface quality.

[0041] The laser welding module 3 includes a laser generator, a welding head, a shielding gas supply unit, and a moving mechanism. The moving mechanism is linked to the motion system of the CNC milling machine, enabling precise movement of the welding head within the processing range and positioning it at the location of the pores to be treated. The laser generator produces the laser beam required for welding, which is focused onto the workpiece surface through the welding head. The shielding gas supply unit delivers argon shielding gas to protect the molten pool during the welding process. Both the laser generator and the moving mechanism are controlled by a control module, allowing adjustment of laser parameters and movement position according to instructions.

[0042] The re-inspection module 4 has a built-in eddy current verification unit, which adopts the same eddy current detection principle as the pre-inspection unit. It is used to scan and inspect the area after welding, check the internal density of the welding area, and determine whether there are defects such as residual porosity, cracks, and lack of fusion.

[0043] The control module is electrically connected to the clamping and positioning module 1, CNC milling module 2, detection module, laser welding module 3, and re-inspection module 4, and specifically includes a data processing unit, a judgment unit, a parameter adjustment unit, and a motion control unit. The data processing unit receives and processes the porosity detection data transmitted from the detection module, calculating the relative position of the porosity to the finished surface. The judgment unit determines whether the porosity needs treatment based on the calculation results. The parameter adjustment unit adjusts the laser welding parameters according to the porosity size and casting material. The motion control unit controls the position and movement of each moving part, achieving coordinated operation of all modules. The control module has a built-in database matching casting materials and welding parameters, storing the optimal welding process parameters for different casting materials and porosity sizes, which can be automatically retrieved for matching. Simultaneously, the control module can store and record all detection data, welding parameters, and re-inspection results, facilitating production traceability and subsequent process optimization.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for pretreating subcutaneous porosity during rough machining of large castings, characterized in that, include: The large casting to be processed is clamped and positioned on a CNC milling machine. The workpiece design parameters are input, and the range of the feature surfaces of the workpiece after finishing is determined. The CNC milling machine is started to perform rough milling on the casting. At the same time, the detection module integrated on the milling cutter holder performs real-time scanning of the interior of the casting below the current milling surface, and collects the position coordinates, depth and diameter of the subcutaneous pores. The detection module includes an eddy current detection unit and wirelessly transmits the detection data to the control module. The control module receives the detection data and, in conjunction with the workpiece design parameters, calculates the distance from the bottom of each subcutaneous pore to the feature surface of the finished workpiece, and determines pores whose distance is less than or equal to the preset safety thickness as pores to be processed. The control module controls the laser welding module to move to the position of the pore to be treated, and adjusts the laser welding parameters according to the depth and diameter of the pore. The laser welding is used to repair the pore by venting, so that the gas in the pore is discharged and filled by the molten casting material to form a dense weld layer. The thickness of the weld layer does not exceed the finishing allowance. Argon is used as a protective gas during the welding process. The area where laser welding has been completed is re-inspected and scanned to confirm that the pores to be treated have been repaired to a qualified standard. If there are pores that have not been repaired to a qualified standard, the laser welding venting repair is repeated. After all the pores to be treated have been repaired to a qualified standard, the CNC milling machine is started to perform finishing machining on the casting, removing the finishing allowance and excess part of the weld layer, so that the workpiece meets the design size and accuracy requirements.

2. The method for pretreating subcutaneous porosity during rough machining of large castings according to claim 1, characterized in that, The detection module moves synchronously with the milling cutter. Each time the milling cutter completes a milling feed, the detection module scans the area below the current milling surface, and the scanning interval is no greater than the milling feed amount. The detection module is also equipped with a surface cleaning unit for removing chips and oil stains from the milled surface.

3. The method for pretreating subcutaneous porosity during rough machining of large castings according to claim 1, characterized in that, When performing laser welding to repair venting of pores, select the laser working mode according to the pore diameter.

4. The method for pretreating subcutaneous porosity during rough machining of large castings according to claim 3, characterized in that, If the aperture is larger than the preset aperture threshold, pulsed laser welding is used and the pulse frequency is adjusted. If the aperture is less than or equal to the preset aperture threshold, continuous laser welding is used and the welding speed is adjusted. The laser welding parameters include laser power, welding speed, spot size, and shielding gas flow rate.

5. The method for pretreating subcutaneous porosity during rough machining of large castings according to claim 1, characterized in that, The protective gas is argon with a purity of 99.99%, and the positioning accuracy of the laser welding module is no greater than the preset accuracy.

6. The method for pretreating subcutaneous porosity during rough machining of large castings according to claim 1, characterized in that, The re-inspection scan uses an eddy current re-inspection unit to detect whether there are porosity or crack defects inside the welded area.

7. A subcutaneous porosity pretreatment system for rough machining of large castings, used to implement the method as described in any one of claims 1 to 6, characterized in that, include: Clamping and positioning module (1) is used to fix the casting to be processed; The CNC milling module (2) is used for roughing and finishing milling of castings; The detection module is integrated on the milling cutter of the CNC milling module (2), including a tool holder (5), a connector (6), a cutter head (7) and a built-in detection unit. The built-in detection unit includes an eddy current detection unit (8), a positioning sleeve (9), a data transmission unit, a quick-change assembly (11) and a battery power supply unit (12). The cutter head (7) has a six-outlet conical spiral guide column (13) at its center, and spiral diversion channels (14) and water outlet holes are distributed on the outer periphery of the guide column; The connector (6) is provided with mounting holes (17) and limiting grooves (18). The six-outlet conical spiral guide column (13) is connected to the connector (6) through the mounting holes (17) and the limiting grooves (18), and is fixed to the knife handle (5) by positioning pins. The detection module is also equipped with a surface cleaning unit for removing chips and oil stains from the milled surface; The laser welding module (3) is used to perform laser welding to repair the pores to be treated, including a laser generator, welding head, shielding gas supply unit and moving mechanism; The re-inspection module (4) is used to perform re-inspection scanning on the fusion welding area; The control module is electrically connected to the clamping and positioning module (1), the CNC milling module (2), the detection module, the laser welding module (3) and the re-inspection module (4), respectively, and is used to receive detection data, input workpiece design parameters, determine whether the pores need to be treated and control the coordinated work of each module.

8. The subcutaneous porosity pretreatment system for rough machining of large castings according to claim 7, characterized in that, The outer circumference of the six-outlet conical spiral guide column (13) is evenly distributed with six spiral diversion channels (14), and six independent water outlets are provided to each cutting edge.

9. The subcutaneous porosity pretreatment system for rough machining of large castings according to claim 7, characterized in that, The control module includes a data processing unit, a judgment unit, a parameter adjustment unit, and a motion control unit, and has a built-in database for matching casting materials with laser welding parameters, which is used to automatically match laser welding parameters according to the casting material and porosity.

10. The subcutaneous porosity pretreatment system for rough machining of large castings according to claim 7, characterized in that, The eddy current detection unit (8) is a low-frequency eddy current probe with a detection depth range of 0 to 4 mm; The re-inspection module (4) includes an eddy current verification unit for detecting the internal density of the welded area.

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