A hot-dip galvanized steel pipe cutting device and cutting method

Abstract

The present application relates to the technical field of steel pipe cutting processing, and particularly relates to a hot galvanized steel pipe cutting device and a cutting method, which comprises a load-bearing frame, the left and right sides of the load-bearing frame are respectively provided with fixed supports and movable lifting supports, a pretreatment mechanism comprises a limiting arc groove which is arranged on the top of the fixed support and corresponds to the curved outer wall of the galvanized pipe, and the fixed support is respectively provided with a corrosion liquid sprayer and a phase change spray cooler, the corrosion liquid sprayer and the phase change spray cooler spray corrosion liquid and phase change material to the galvanized cutting area in sequence. The galvanized cutting area is heated to 280-350 DEG C by using an electromagnetic induction preheater before cutting, and a balanced supporting force is formed near the cutting area, which is especially suitable for high-precision cutting of thin-walled pipes, and the relative movement between the pipe to be cut and the wear-resistant rubber pad is adjusted by the movable lifting support, the load-bearing rotating shaft, the driving gear and the driven rack, so that the galvanized cutting area of the pipe to be cut can be precisely cut.

Description

Technical Field

[0001] This invention relates to the field of steel pipe cutting and processing technology, and in particular to a hot-dip galvanized steel pipe cutting device and cutting method. Background Technology

[0002] Hot-dip galvanized steel pipes are widely used in construction, fire protection, petrochemical and other fields due to their excellent corrosion resistance. During the processing of steel pipes, the cutting process directly affects the subsequent connection quality and service life.

[0003] Existing technologies for steel pipe cutting, such as the steel pipe cutting device with a cooling mechanism disclosed in CN220921112U, aim to reduce the cutting temperature and thermal deformation by setting a water spray cooling mechanism next to the cutting blade. However, it still has the following shortcomings: Hot-dip galvanized steel pipes have a low melting point and poor toughness in the zinc coating. Especially for thin-walled hot-dip galvanized steel pipes, the existing clamping structures are mostly external clamping or simple internal support, which are difficult to provide stable radial support during the cutting process. As a result, the radial cutting force generated during cutting can easily cause the thin-walled pipe to be flattened and deformed. A single medium injection method is difficult to achieve a uniform and controllable distribution of cooling or shaping medium in the circumferential direction of the pipeline, and cannot perform precise thermal management of the cutting area. The instantaneous high temperature generated during cutting can easily cause the galvanized layer to melt, evaporate or oxidize and burn over a large area, which can easily destroy the continuous integrity of the galvanized layer, directly exposing the base metal on the cut end face, making it the preferred starting point for corrosion and severely shortening the service life of the steel pipe. During cutting operations, molten zinc is prone to splashing and re-solidifying on the cut edge or inner wall of the pipe, forming zinc nodules and burrs that are difficult to remove. Such residues not only affect the appearance of the pipe opening, but also cause poor sealing and assembly difficulties during subsequent threading or pipe connection. Simple physical cutting or water cooling cannot solve the problem of zinc adhesion and re-solidification. Summary of the Invention

[0004] The purpose of this invention is to solve the problem in the prior art that it is difficult to accurately cut galvanized steel pipes, which easily leads to deformation of the cut surface. Therefore, this invention proposes a hot-dip galvanized steel pipe cutting device and cutting method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A hot-dip galvanized steel pipe cutting device includes a load-bearing frame, with fixed supports and movable lifting supports respectively installed on the left and right sides of the load-bearing frame. A cutter for cutting the galvanized area of ​​the pipe to be cut is installed on the fixed supports. The fixed support is equipped with a pretreatment mechanism for initially supporting the pipe to be cut and for passivating and protecting the galvanized cutting area. The pretreatment mechanism includes a limiting arc groove opened at the top of the fixed support and corresponding to the curved outer wall of the galvanized pipe. The fixed support is also equipped with a corrosion liquid sprayer and a phase change spray cooler. The corrosion liquid sprayer and the phase change spray cooler spray corrosion liquid and phase change material onto the galvanized cutting area in sequence. The movable lifting support is equipped with a picking mechanism for fixing the pipe to be cut and a coating mechanism for uniformly distributing phase change material and etchant around the galvanized cutting area. The picking mechanism includes a set of curved support blocks that expand from the inside out to support the open end of the pipe to be cut. The picking mechanism also includes a set of driven piston curved clamping blocks that contract from the outside in to clamp the outer wall of the pipe to be cut. The coating mechanism includes an outer gear sleeve and an inner gear telescopic tube that are slidably connected. The outer gear sleeve and the inner gear telescopic tube unfold to form a ring structure that fits on the pipe to be cut. The inner walls of the outer gear sleeve and the inner gear telescopic tube are provided with flexible wear-resistant rubber pads that abut against the galvanized cutting area.

[0006] Preferably, the fixed bracket is fixedly mounted on the load-bearing frame, and the movable lifting bracket is slidably mounted on the load-bearing frame, wherein a second-stage lifting frame for fixing the cutter is slidably mounted on the movable lifting bracket.

[0007] Preferably, an electromagnetic induction preheater facing the limiting arc groove is fixedly installed inside the movable lifting bracket.

[0008] Preferably, the etchant is a weakly acidic complex solution, and the phase change material is a low-temperature phase change microemulsion loaded with nano-graphene particles.

[0009] Preferably, both the corrosive liquid sprayer and the phase change spray cooler are inclined toward the axial direction of the pipe to be cut.

[0010] Preferably, the picking mechanism further includes a hollow rotating shaft rotatably mounted on a movable lifting bracket, a load-bearing disc fixedly connected to the hollow rotating shaft, and a drive boss that extends and retracts in a left-right direction movably disposed on the load-bearing disc.

[0011] Preferably, a group of curved support blocks are symmetrically distributed vertically or horizontally on the load-bearing disk, and a group of driven piston curved clamping blocks are symmetrically distributed horizontally or vertically to perform radial reciprocating movement.

[0012] Preferably, a set of the curved support blocks is movably pulled by the drive boss to perform radial reciprocating movement, and a set of the driven piston curved clamping blocks is movably pulled by the drive boss to perform radial reciprocating movement.

[0013] Preferably, the coating mechanism further includes a drive gear and a driven rack that are meshed together. The driven rack is integrally connected with a grooved load-bearing block for slidingly mounting the outer gear sleeve. The outer gear sleeve and the inner gear telescopic tube are concentrically distributed semi-circular ring structures, and both the outer gear sleeve and the inner gear telescopic tube are provided with strong capsules for fixing and embedding wear-resistant rubber pads in their inner walls.

[0014] A cutting method based on a hot-dip galvanized steel pipe cutting device, the cutting method comprising the following steps: Step S1: Place the pipe to be cut on the limiting arc groove of the fixed bracket, extend the curved support block into the opening of one end of the pipe to be cut, control the driving boss to move linearly to pull a set of curved support blocks to expand from the inside to the outside until they abut against the inner wall of the opening end of the pipe to be cut, and at the same time, a set of driven piston curved clamping blocks retract from the outside to the inside until they clamp the outer wall of the pipe to be cut. Step S2: The hollow rotating shaft drives the pipe to be cut to rotate, and at the same time, the electromagnetic induction preheater heats the galvanized cutting area of ​​the pipe to be cut to 280-350°C, so that the zinc-iron alloy layer structure of the galvanized cutting area is relaxed. Step S3: While the pipe to be cut rotates, the upward-moving cutter cuts the galvanized cutting area. At the same time, a weak acid complexing solution is sprayed onto the galvanized cutting area through a corrosion sprayer. The drive gear and driven rack are controlled to move, driving the grooved support block to move closer to the galvanized cutting area. The inner gear telescopic tube is controlled to extend from the outer gear sleeve and form a ring structure around the pipe to be cut. The inflated powerful capsule makes the wear-resistant rubber pad elastically contact the periphery of the galvanized cutting area. The outer gear sleeve and inner gear telescopic tube of the ring structure are controlled to perform periodic reciprocating deflections of less than 180° in the grooved support block. The wear-resistant rubber pad is used to coat the weak acid complexing solution. The phase change spray cooler is not used during the cutting process and is activated after the cutting is completed. Step S4: After cutting, control the drive gear and driven rack to move the control grooved load-bearing block, so that the annular structure is away from the cutting surface. The phase change spray cooler continuously sprays low-temperature phase change microemulsion onto the cutting surface. Then, control the drive gear and driven rack to make the cutting end face correspond to the wear-resistant rubber pad. While controlling the rotation of the pipe to be cut, the wear-resistant rubber pad with periodic reciprocating deflection is used to coat the low-temperature phase change microemulsion for cleaning and passivation.

[0015] Compared with the prior art, the present invention has the following advantages: 1. Before cutting, the present invention uses an electromagnetic induction preheater to heat the galvanized cutting area to 280-350°C, causing structural relaxation of the zinc-iron alloy layer and reducing the risk of brittle fracture during cutting. During the cutting process, a weakly acidic complex solution is sprayed onto the galvanized cutting area through a corrosion sprayer. This solution can preferentially react chemically with the tips of microcracks in the zinc layer, reducing the fracture toughness of the zinc layer. After cutting, a low-temperature phase change microemulsion loaded with nano-graphene particles is sprayed into the area for rapid cooling through a phase change spray cooler. Through the synergistic effect of preheating, chemical corrosion, and phase change rapid cooling, the heat-affected zone is controlled to a very small extent, which helps to reduce the degree of large-area melting and evaporation of the zinc layer and improve the original anti-corrosion performance of the galvanized layer near the cutting end face.

[0016] 2. This invention employs an external gear sleeve and an internal gear telescopic tube to form a retractable concentric semi-circular ring structure, which is flexibly fitted onto the pipe to be cut. Through the cooperation of the first and second driving gears, this ring structure can drive the wear-resistant rubber pad to periodically reciprocate along the circumference of the pipe to be cut, realizing the coating operation of weak acid complex solution and low temperature phase change microemulsion. This ensures that the chemical etching solution can accurately cover the cutting path of the galvanized layer before cutting, causing the zinc layer to undergo brittle cleavage fracture rather than plastic flow during sawing, inhibiting the formation of burrs and zinc nodules, and achieving uniform cleaning and passivation of the cut surface in the post-processing stage.

[0017] 3. This invention achieves synchronous linkage and locking of the inner wall of the pipe opening end to be cut from the inside out and the outer wall of the middle end of the pipe from the outside in by driving the boss linkage curved surface support block and driven piston curved surface clamping block. It forms a balanced support force near the cutting area, which counteracts the radial cutting force generated during cutting, prevents the flattening deformation of the thin-walled hot-dip galvanized steel pipe, and ensures the roundness and dimensional accuracy of the cut. It is especially suitable for high-precision cutting of thin-walled pipes. The relative movement adjustment between the pipe to be cut and the wear-resistant rubber pad is achieved by moving the lifting bracket, the load-bearing rotating shaft, the driving gear and the driven rack, which facilitates the precise cutting of the galvanized cutting area of ​​the pipe after treatment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 2 This is a bottom view of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 3 This is a front view of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 4 This is a schematic diagram of the pretreatment mechanism structure of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 5 This is a schematic diagram of the picking mechanism of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 6 This is a schematic diagram of the locking fixture structure of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 7 This is a schematic diagram of the coating mechanism structure of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 8 This is a cross-sectional view of the coating mechanism structure of a hot-dip galvanized steel pipe cutting device proposed in this invention; Figure 9 This is a schematic diagram of a hot-dip galvanized steel pipe structure.

[0019] In the diagram: 1. Load-bearing frame; 2. Fixed bracket; 3. Moving lifting bracket; 4. Pretreatment mechanism; 41. Limiting arc groove; 42. Electromagnetic induction preheater; 43. Corrosion liquid sprayer; 44. Phase change spray cooler; 45. Second-stage lifting frame; 46. Cutter; 5. Picking mechanism; 51. Hollow rotating shaft; 52. Load-bearing disc; 53. Drive boss; 54. Locking fixture; 541. Guide elongated hole; 542. 543. Curved support block; 544. Communicating vessel-like tube; 545. Synchronizing block; 546. Driving piston; 547. Traction rod; 548. Driven piston curved clamping block; 6. Coating mechanism; 61. Drive gear; 62. Driven rack; 63. Groove bearing block; 64. First driving gear; 65. External gear sleeve; 66. Second driving gear; 67. Internal gear telescopic tube; 68. High-strength capsule; 69. Wear-resistant rubber pad. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Reference Figures 1-9 A hot-dip galvanized steel pipe cutting device includes a load-bearing frame 1. Fixed supports 2 and movable lifting supports 3 are respectively installed on the left and right sides of the load-bearing frame 1. A first driver is installed on the load-bearing frame 1 to drive the movable lifting supports 3 to move. The first driver is preferably a servo electric cylinder or a hydraulic cylinder, with its cylinder body fixed to the load-bearing frame 1. The end of the telescopic rod is hinged to the bottom of the movable lifting supports 3, and a linear guide pair is provided between the movable lifting supports 3 and the load-bearing frame 1 to ensure the linear motion accuracy of the movable lifting supports 3 in the left-right direction. This allows the movable lifting supports 3 to move the pipe to be cut in the left-right direction. The vertical telescopic function of the movable lifting supports 3 is achieved by a built-in scissor lift mechanism or screw jack, driven by a servo motor and equipped with a displacement sensor for closed-loop control of the lifting height. A cutter 46 is installed on the fixed supports 2 to cut the galvanized cutting area of ​​the pipe to be cut, performing vertical cutting operations on the pipe during the upward movement.

[0022] The fixed support 2 is equipped with a pretreatment mechanism 4 for initially supporting the pipe to be cut and for passivating the galvanized cutting area. The pretreatment mechanism 4 includes a limiting arc groove 41 located at the top of the fixed support 2 and corresponding to the curved outer wall of the galvanized pipe. The limiting arc groove 41 serves as the initial support reference for the pipe to be cut, and its radius of curvature is adapted to the outer wall of the pipe to be cut, ensuring the radial positioning accuracy of the pipe to be cut during the rotary cutting process. An electromagnetic induction preheater 42 is fixedly installed inside the movable lifting support 3, facing the limiting arc groove 41. The end of the induction coil of the electromagnetic induction preheater 42 extends to the side of the limiting arc groove 41 and is axially aligned with the preset cutting path. Through electromagnetic induction heating, the surface temperature of the galvanized cutting area can be precisely raised to 280-350℃ within 0.5-1.5s. The selection of this temperature range has specific technical significance: it is below the melting point of the zinc layer (about 419℃), but sufficient to cause lattice relaxation and dislocation rearrangement in the zinc-iron alloy layer, reducing its brittleness and thus reducing the tendency to crack during subsequent cutting.

[0023] A corrosion liquid sprayer 43 and a phase change spray cooler 44 are respectively installed on the fixed bracket 2. Both the corrosion liquid sprayer 43 and the phase change spray cooler 44 are inclined towards the axial direction of the pipe to be cut, and are arranged at an angle on the fixed bracket 2, with their nozzle axes intersecting at the preset cutting path. Both the corrosion liquid sprayer 43 and the phase change spray cooler 44 are precision atomizing nozzles with atomized particle size controlled between 20-50μm. The spray pressure is provided by an independent micro pneumatic diaphragm pump, and the pressure is controlled in a closed loop through a proportional pressure regulating valve to ensure precise adjustment of the spraying amount. The corrosion liquid sprayer 43 and the phase change spray cooler 44 spray the corrosion liquid and phase change material sequentially onto the galvanized cutting area. The corrosion liquid is a weakly acidic complexing solution, and the phase change material is a low-temperature phase change microemulsion loaded with nano-graphene particles. The weakly acidic complexing solution has a pH value of 5.5-6.5 and contains a zinc ion complexing agent. It should be noted that: The weakly acidic complex solution contacts the zinc plating layer before the saw blade during the cutting process, and can selectively chemically corrode along the micro-cracks in the cutting process, reducing the fracture toughness of the zinc layer. When the low-temperature phase change microemulsion comes into contact with the high-temperature cutting surface, it undergoes a liquid-gas phase change, absorbing a large amount of latent heat and controlling the width of the heat-affected zone to within 0.5 mm. At the same time, the nano-graphene particles form a self-assembled protective film on the cutting surface, achieving physical passivation.

[0024] Width of heat-affected zone 2.8-3.5 mm 0.3-0.5 mm ↓ 85.7% Area of ​​zinc coating burn 12.6-18.3 mm² 0.5-1.2 mm² ↓ 93.2% Integrity of zinc layer on cut surface There was obvious melting and resolidification, and the zinc-iron alloy layer was broken. Complete structure, clear grain boundaries Significant improvement Rust initiation time in neutral salt spray test 72 h 312 h ↑ 333% It can be seen that the width of the heat-affected zone in the experimental group is only 1 / 7 to 1 / 6 of that in the control group, indicating that the synergistic effect of electromagnetic induction preheating and phase change rapid cooling effectively blocks the heat diffusion path; the burn area of ​​the zinc coating is reduced by more than 93%, proving that the combination strategy of chemical modification and phase change cooling significantly inhibits the melting and evaporation of the zinc layer; the salt spray test results are extended to 312 hours, indicating that the protective effect of the pretreatment mechanism 4 on the cut end face is close to the corrosion protection level of the uncut original pipe.

[0025] A second-stage lifting frame 45 for fixing the cutter 46 is slidably mounted on the movable lifting support 3. In some embodiments, a second driver is provided on the movable lifting support 3 to drive the second-stage lifting frame 45 to move vertically, so that the cutter 46 cuts the pipe to be cut during the upward movement. The second driver is preferably a combination of a ball screw and a servo motor, wherein the ball screw is vertically mounted on the movable lifting support 3, and the second-stage lifting frame 45 cooperates with the ball screw through a nut seat. The servo motor drives the ball screw to rotate, causing the cutter 46 to move upward at a uniform speed along the vertical guide rail. Its feed speed and the rotational linear speed of the pipe to be cut are linked and matched by a CNC system to ensure the stability of the cutting process.

[0026] The mobile lifting support 3 is equipped with a picking mechanism 5 for fixing the pipe to be cut and a coating mechanism 6 for uniformly distributing phase change material and etchant around the galvanized cutting area. The picking mechanism 5 achieves high rigidity and low deformation clamping of the thin-walled hot-dip galvanized steel pipe through a composite transmission design of hollow rotating shaft 51, load-bearing disc 52, drive boss 53, and locking fixture 54. The inner support and outer clamping are linked and controlled by the same drive source to form a self-balancing mechanism of radial force.

[0027] The picking mechanism 5 includes a hollow rotating shaft 51 rotatably mounted on the movable lifting bracket 3. The movable lifting bracket 3 is equipped with a servo motor for driving its rotational movement. The servo motor is connected to the hollow rotating shaft 51 through a synchronous pulley pair or a gear pair. A rotary encoder is installed at the end of the hollow rotating shaft 51 for real-time feedback of speed and rotation angle to achieve closed-loop control.

[0028] In some embodiments, the hollow channel inside the hollow rotating shaft 51 allows corrosion liquid or coolant pipelines to pass through, enabling precise liquid supply to the galvanized cutting area. The inner wall of the hollow channel is coated with a polytetrafluoroethylene anti-corrosion layer, and the pipeline interface uses a rotary sealing joint to ensure continuous liquid supply during rotation.

[0029] A load-bearing disc 52 is fixedly connected to the hollow rotating shaft 51, serving as the mounting base for the locking fixture 54. A drive boss 53, capable of sliding and extending laterally, is movably mounted on the load-bearing disc 52. The drive boss 53 slides and extends along the axial direction (left-right direction) of the load-bearing disc 52, and its front end has a flared curved surface that mates with the inner wall of the curved support block 542. The extension and retraction of the drive boss 53 is driven by a miniature servo cylinder mounted on the back of the load-bearing disc 52, which is connected to the drive boss 53 via a floating joint.

[0030] The load-bearing disc 52 is provided with a locking fixture 54 driven by a drive boss 53 for radial movement adjustment. The locking fixture 54 includes a set of guide elongated holes 541 symmetrically opened at both ends of the load-bearing disc 52, and a kind of communicating vessel tube 543 located on the other two sides of the load-bearing disc 52. The communicating vessel tube 543 is filled with hydraulic medium, preferably hydraulic oil or grease. The communicating vessel tube 543 is a closed cavity structure, and its inner wall is honed with a surface roughness Ra≤0.4μm. Both the active piston 545 and the driven piston curved surface clamping block 547 are equipped with combined sealing rings to ensure that the hydraulic medium transmits pressure without leakage. A curved support block 542, which expands outward from the inside to support the open end of the pipe to be cut, is slidably installed in the guide hole 541. When the drive boss 53 extends forward, its trumpet-shaped curved surface engages with the trumpet-shaped curved surface of the curved support block 542, forcing a set of symmetrically arranged curved support blocks 542 to expand radially outward along the guide hole 541 until they contact the inner wall of the open end of the pipe to be cut. By utilizing the principle of inclined plane force amplification, the axial thrust is converted into radial expansion force, achieving self-centering internal support for the open end of the pipe to be cut. The outer wall of the curved support block 542 is covered with a polyurethane elastic layer with a Shore A hardness of 60-70 to avoid rigid contact with the inner wall of the pipe to be cut, which could cause scratches to the galvanized layer. A set of driven piston curved surface clamping blocks 547, which retract from the outside to the inside to clamp the outer wall of the pipe to be cut, are slidably installed in the outer opening of the communicating vessel tube 543. The inner wall of the curved surface support block 542 is provided with a trumpet-shaped curved surface that matches the driving boss 53. A synchronizing block 544 is fixedly connected to the outer wall of the driving boss 53. An active piston 545 that matches the driven piston curved surface clamping block 547 is slidably installed in the inner opening of the communicating vessel tube 543. A traction connecting rod 546 is pin-connected between the synchronizing block 544 and the active piston 545.

[0031] When the active piston 545 is pulled inward, the hydraulic medium pressure in the communicating vessel-like pipe 543 increases, pushing the driven piston curved surface clamping block 547 to contract radially inward along the outer opening, clamping the outer wall of the middle end of the pipe to be cut. Utilizing Pascal's principle, the minute displacement of the active piston 545 is amplified into a uniform clamping force of the driven piston curved surface clamping block 547, avoiding synchronization errors caused by multi-point independent driving, ensuring dynamic balance of internal and external clamping forces on the same axial section, and effectively counteracting the radial cutting force during cutting. The inner wall of the driven piston curved surface clamping block 547 is also covered with a polyurethane elastic layer, and its clamping surface has axial grooves to expel any air or impurities that may be present during clamping, ensuring clamping reliability.

[0032] Finite element analysis software was used to simulate and analyze the radial deformation of thin-walled hot-dip galvanized steel pipe under cutting conditions. The comparison objects were the traditional three-jaw self-centering chuck external clamping method and the internal and external linkage clamping method of the pick-up mechanism 5, with the same radial cutting force of 500N applied.

[0033] Maximum radial deformation 0.28 mm 0.07 mm Distribution of Deformation Regions Concentrated between the clamping point and the cutting point Evenly distributed on both sides of the cutting point Roundness error of the cut rear end face 0.15-0.22 mm 0.03-0.06 mm Thin-walled tube flattening phenomenon Ellipticization exists (visible in some samples). none It is known that traditional external clamping methods rely solely on radial clamping force to provide frictional damping. Under cutting force, the pipe to be cut is prone to bending deformation, resulting in skewed or elliptical cuts. The curved support block 542 forms an internal rigid support at the open end of the pipe to be cut, and the driven piston curved clamping block 547 forms an external circumferential constraint at the middle of the pipe. Together, they form a double-support point on both sides of the cutting point, which helps improve the bending stiffness of the galvanized cutting area. With the use of the picking mechanism 5, the perpendicularity tolerance of the cutting end face is improved from 0.3mm / 100mm in the traditional method to 0.05mm / 100mm.

[0034] The coating mechanism 6 includes a drive gear 61 and a driven rack 62 meshing together. The drive gear 61 is rotatably mounted on a movable lifting bracket 3. A drive motor for driving the drive gear 61 is mounted on the movable lifting bracket 3. This drive motor is a servo motor and is connected to the drive gear 61 via a planetary reducer to provide sufficient torque and achieve precise position control of the axial feed. The driven rack 62 is slidably mounted on the movable lifting bracket 3. A grooved support block 63 is integrally connected to the driven rack 62. A first drive gear 64 is rotatably mounted inside the grooved support block 63. A roller guide rail is provided between the driven rack 62 and the movable lifting bracket 3 to reduce friction and ensure feed straightness. A first micro motor for driving the first drive gear 64 is mounted on the grooved support block 63. An angle sensor is mounted on the output shaft end of the first micro motor to control the deflection angle of the external gear sleeve 65. Furthermore, an external gear sleeve 65, which meshes with the first driving gear 64, is movably fitted inside the grooved load-bearing block 63. The outer wall of the external gear sleeve 65 is provided with an arc-shaped rack segment that meshes with the first driving gear 64. The external gear sleeve 65 and the grooved load-bearing block 63 are slidably supported by an arc-shaped guide rail or a ball bearing guide sleeve. A second driving gear 66 is rotatably mounted inside the open end of the external gear sleeve 65. A second micro motor for driving the rotation of the second driving gear 66 is provided on the external gear sleeve 65. The second micro motor is also a stepper motor or a servo motor. In some embodiments, it is driven by the second driving gear 66 through a worm gear mechanism. The self-locking characteristic of the worm gear prevents the internal gear telescopic tube 67 from accidentally retracting in the non-driving state. Furthermore, the outer gear sleeve 65 is movably fitted with an inner gear telescopic tube 67 that meshes with the second driving gear 66. The outer wall of the inner gear telescopic tube 67 is also provided with an arc-shaped rack section that meshes with the second driving gear 66. The inner gear telescopic tube 67 and the outer gear sleeve 65 are connected by an embedded arc-shaped guide rail to ensure the coaxiality of the telescopic movement.

[0035] The outer gear sleeve 65 and the inner gear telescopic tube 67 are concentrically distributed semi-circular ring structures. Each of the outer gear sleeve 65 and the inner gear telescopic tube 67 has a high-pressure capsule 68 inside its inner wall. The high-pressure capsule 68 is an inflatable elastic bladder, and its interior is connected to an external air source via an air passage. The air passage is equipped with a precision pressure reducing valve and a high-speed switching valve to independently control the inflation pressure of the two high-pressure capsules 68, thereby achieving differentiated adjustment of the deformation degree. The outer gear sleeve 65 and the inner gear telescopic tube 67 unfold to form a ring structure that fits onto the pipe to be cut. The inner walls of the outer gear sleeve 65 and the inner gear telescopic tube 67 are provided with flexible, wear-resistant rubber pads 69 that abut against the galvanized cutting area through the high-pressure capsules 68. The wear-resistant rubber pads 69 are made of microporous polyurethane material, and their surface has a microporous structure that can adsorb and store the coating medium, achieving uniform release during wiping. The wear-resistant rubber pads 69 are attached to the surface of the high-pressure capsules 68 facing the pipe, for contacting and coating the medium.

[0036] During the coating process, the outer gear sleeve 65, driven by the first drive gear 64, performs a periodic reciprocating deflection motion (deflection angle less than 180°), which drives the annularly distributed wear-resistant rubber pads 69 to perform a wiping coating on the outer wall of the pipe to be cut. This motion, combined with the rotational motion of the pipe to be cut driven by the hollow rotating shaft 51, forms a composite motion, enabling the coating medium to achieve circumferential full coverage of the galvanized cutting area.

[0037] It is worth noting that the two high-pressure capsules 68 inside the outer gear sleeve 65 and the inner gear telescopic tube 67 exhibit different degrees of deformation after inflation—the high-pressure capsule 68 on the outer gear sleeve 65 deforms less, while the high-pressure capsule 68 on the inner gear telescopic tube 67 deforms more. After inflation, they form a semi-circular structure with the same radius, ensuring uniform contact pressure between the wear-resistant rubber pad 69 and the outer wall of the pipe to be cut, regardless of diameter. Specifically, the inflation pressure of the two high-pressure capsules 68 is adjusted separately using a pneumatic proportional valve, controlling the pressure of the high-pressure capsule 68 on the outer gear sleeve 65 at 0.1-0.2 MPa and the pressure of the high-pressure capsule 68 on the inner gear telescopic tube 67 at 0.3-0.5 MPa, using the pressure difference to compensate for the radius change caused by the difference in structural geometry.

[0038] It should be noted that the coating mechanism 6 has three degrees of freedom of motion: Axial feed: The drive gear 61 meshes with the driven rack 62, and the driven rack 62 is integrally connected with the grooved support block 63. By rotating the drive gear 61, the grooved support block 63 is driven to move closer to or away from the galvanized cutting area along the axial direction of the pipe to be cut. The axial feed stroke is protected by soft and hard limit switches installed on the movable lifting bracket 3.

[0039] Circumferential unfolding: The first driving gear 64 is rotatably installed inside the grooved load-bearing block 63. The first driving gear 64 meshes with the rack section on the outer wall of the outer gear sleeve 65, driving the outer gear sleeve 65 to deflect circumferentially within the grooved load-bearing block 63 within a range of ±90°. The angular velocity of this deflection motion is synchronized with the rotational linear velocity of the pipe to be cut through a CNC system to ensure that the wear-resistant rubber pad 69 always maintains a relatively static wiping relationship with the surface of the pipe to be cut during the coating process.

[0040] Radial opening and closing: The outer gear sleeve 65 has a semi-circular ring structure, with a second driving gear 66 rotatably mounted inside its open end. The second driving gear 66 meshes with the rack section on the outer wall of the inner gear telescopic tube 67, driving the inner gear telescopic tube 67 to extend and retract along the arc-shaped track of the outer gear sleeve 65. When the inner gear telescopic tube 67 is fully extended, it forms a complete circular ring structure with the outer gear sleeve 65, surrounding the pipe to be cut. This radial opening and closing action is completed before each cutting cycle. A positioning signal is detected by a microswitch installed on the telescopic path to ensure that the ring structure is closed in place before the coating process can be started.

[0041] Using hot-dip galvanized steel pipes of the same specifications, the control group and the experimental group were coated with a weakly acidic complexing solution on six pairs of galvanized cutting areas using a conventional spray coating method and a coating mechanism, respectively. After coating, samples were taken, and the uniformity of the zinc ion complexing agent residue distribution along the cutting path was detected by energy-dispersive X-ray spectroscopy (expressed as relative standard deviation RSD).

[0042] Average coating thickness 15.2 μm 8.5 μm thickness relative standard deviation 38.6% 6.3% Coating coverage (area) 72% 98% Average height of zinc nodule on the cut rear face 0.35 mm 0.08 mm Maximum length of burrs on the cut rear face 0.52 mm 0.12 mm It can be seen that although the average coating thickness of the coating mechanism 6 is thinner than that of the traditional spraying method, its uniformity (RSD 6.3%) is far superior to that of the traditional spraying method (RSD 38.6%), indicating that the coating medium achieves nanoscale uniform distribution in the cutting area. This effect is due to the combined effect of the wiping coating and the circumferential reciprocating motion of the wear-resistant pad 69. The thinner, more uniform coating reduces medium waste and avoids excessive liquid accumulation from adversely affecting the cutting process. The height of the zinc nodule and the length of the burr on the cut end face decreased by 77% and 77%, respectively, proving that the uniformly coated weakly acidic complex solution effectively reduces the fracture toughness of the zinc layer, achieving brittle cleavage fracture of the zinc plating layer.

[0043] The fixed bracket 2 is fixedly installed on the load frame 1, and the movable lifting bracket 3 is slidably installed on the load frame 1.

[0044] A set of curved support blocks 542 are symmetrically distributed vertically or horizontally on the load-bearing disk 52, and a set of driven piston curved clamping blocks 547 are symmetrically distributed horizontally or vertically to perform radial reciprocating movement. The relative positions of the two are adjusted by the rotational movement of the load-bearing disk 52.

[0045] A set of curved support blocks 542 are movably pulled by the drive boss 53 to perform radial reciprocating movement, and a set of driven piston curved clamping blocks 547 are movably pulled by the drive boss 53 to perform radial reciprocating movement.

[0046] It should be noted that the specific models and specifications of the electromagnetic induction preheater 42 and the cutter 46 need to be selected and determined according to the actual specifications of the device. The specific selection calculation method adopts the existing technology in this field, so it will not be elaborated here.

[0047] The functional principle of this invention can be explained through the following operational methods: First, the pipe to be cut is placed on the limiting arc groove 41 of the fixed bracket 2. A set of curved support blocks 542, which are in a closed state, are extended into the opening at one end of the pipe to be cut. At the same time, a set of driven piston curved clamping blocks 547, which are in an open state, correspond to the middle part of the pipe to be cut. The drive boss 53 is controlled to move linearly to pull the set of curved support blocks 542 from the inside to the outside until they abut against the inner wall of the opening end of the pipe to be cut. At the same time, the drive boss 53 drives the active piston 545 to move in the communicating vessel tube 543 through the synchronization block 544 and the traction connecting rod 546, so that the set of driven piston curved clamping blocks 547 retracts from the outside to the inside until they clamp the outer wall of the middle end of the pipe to be cut. During this process, the displacement of the drive boss 53 is monitored in real time by the displacement sensor. When the curved support block 542 contacts the inner wall of the pipe and the clamping force reaches the preset threshold (indirectly determined by detecting the thrust of the drive boss 53), the drive boss 53 stops moving and maintains a locked position.

[0048] Secondly, the hollow rotating shaft 51 is raised by the movable lifting bracket 3, so that the distance between the pipe to be cut and the limiting arc groove 41 is 0.5-1.5cm. This distance setting can avoid interference between the cutter 46 and the limiting arc groove 41 during the cutting process, and also ensure the stability of the pipe during rotation. The specific value is adaptively adjusted according to the diameter and wall thickness of the pipe to be cut. The hollow rotating shaft 51 drives the pipe to be cut to rotate, and at the same time, the electromagnetic induction preheater 42 heats the galvanized cutting area of ​​the pipe to be cut to 280-350℃, which relaxes the zinc-iron alloy layer structure in the galvanized cutting area. The preheating time is controlled by a closed loop with real-time feedback from an infrared temperature sensor. After reaching the set temperature, it is automatically maintained for 3-5 seconds to ensure uniform heat penetration depth.

[0049] Then, while the pipe to be cut rotates, the second-stage lifting frame 45 drives the running cutter 46 to move upward at a uniform speed to cut the galvanized cutting area. At the same time, a weak acid complexing solution is sprayed into the galvanized cutting area by the corrosion sprayer 43. The start and stop of the spray and the feed movement of the cutter 46 are linked by a PLC or CNC system: the spray is started 0.5 seconds before the cutter 46 contacts the pipe wall and the spray stops 1 second after the cut is completed. The drive gear 61 and the driven rack 62 are controlled to move, so that the grooved support block 63 is close to the galvanized cutting area. The inner gear telescopic tube 67 is controlled to extend from the outer gear sleeve 65 and form a ring structure around the pipe to be cut. The inflated strong capsule 68 is used to make the wear-resistant rubber pad 69 elastically contact the periphery of the galvanized cutting area. The outer gear sleeve 65 and the inner gear telescopic tube 67 of the ring structure are controlled to perform periodic reciprocating deflection of less than 180° in the grooved support block 63. The wear-resistant rubber pad 69 is used to coat the weak acid complexing solution. The frequency of the periodic reciprocating deflection is 0.5-2Hz, and the deflection amplitude is ±60°~±90°. This is coordinated with the rotation speed of the pipe to be cut, so that the wear-resistant rubber pad 69 forms a spiral wiping trajectory on the surface of the pipe to be cut, ensuring full circumferential coverage. The phase change spray cooler 44 is not activated during the cutting process, but is activated after the cutting is completed.

[0050] Finally, after cutting, the drive gear 61 and driven rack 62 are controlled to move the cut surface away from the outer gear sleeve 65 and inner gear telescopic tube 67 of the annular structure. A low-temperature phase change microemulsion is continuously sprayed onto the cut surface by the phase change spray cooler 44 for 3-5 seconds. The spray volume is dynamically adjusted by a proportional valve according to the cooling rate requirements of the heat-affected zone. The drive gear 61 and driven rack 62 are then controlled to align the cut end with the wear-resistant pad 69. While controlling the rotation of the pipe to be cut, the periodically reciprocating wear-resistant pad 69 coats the low-temperature phase change microemulsion for cleaning and passivation. The process parameters (frequency, amplitude, duration) for this post-treatment coating are the same as those for the pre-treatment coating, but can be adjusted independently according to actual needs.

[0051] It should be noted that: First, the extension and retraction of the inner gear telescopic tube 67 is achieved through the second driving gear 66. The inner gear telescopic tube 67 moves along the outer gear sleeve 65 in a curved extension and retraction motion. When the two are close to overlapping, it is convenient for the outer gear sleeve 65 to be initially fitted onto the pipe to be cut. When the two form a ring structure, it is convenient for wear-resistant rubber pads 69 to be distributed circumferentially along the galvanized cutting area. Second, after the outer gear sleeve 65 and the inner gear telescopic tube 67 form a ring structure, they reciprocate around the pipe to be cut. The first active gear 64 drives the circumferentially distributed wear-resistant rubber pad 69 to perform periodic deflection motion to coat the weak acid complex solution and low temperature phase change microemulsion on the pipe to be cut, thereby improving the uniformity of their distribution in the galvanized cutting area. The two high-pressure capsules 68 on the inner walls of the outer gear sleeve 65 and the inner gear telescopic tube 67 have different degrees of deformation. During inflation, the high-pressure capsule 68 on the outer gear sleeve 65 deforms less than the high-pressure capsule 68 on the inner gear telescopic tube 67. This allows the two high-pressure capsules 68 to form a semi-circular structure with the same radius, facilitating the circumferential placement of the wear-resistant rubber pad 69 around the pipe to be cut. Precise control of the inflation pressure is achieved by a pneumatic proportional regulating valve assembly integrated in the equipment control cabinet. The outer diameter parameter of the pipe to be cut can be input via a human-machine interface, and the system automatically calculates and outputs the target pressure values ​​for the two high-pressure capsules 68.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A hot-dip galvanized steel pipe cutting device, comprising a load-bearing frame (1), wherein a fixed support (2) and a movable lifting support (3) are respectively arranged on the left and right sides of the load-bearing frame (1), and a cutter (46) for cutting the galvanized cutting area of ​​the pipe to be cut is provided on the fixed support (2), characterized in that: The fixed support (2) is provided with a pretreatment mechanism (4) for initially supporting the pipe to be cut and for passivating and protecting the galvanized cutting area. The pretreatment mechanism (4) includes a limiting arc groove (41) opened at the top of the fixed support (2) and corresponding to the outer wall of the curved surface of the galvanized pipe. The fixed support (2) is provided with a corrosion liquid sprayer (43) and a phase change spray cooler (44). The corrosion liquid sprayer (43) and the phase change spray cooler (44) spray corrosion liquid and phase change material onto the galvanized cutting area in turn. The movable lifting bracket (3) is provided with a picking mechanism (5) for fixing the pipe to be cut and a coating mechanism (6) for circumferentially coating phase change material and corrosion liquid in the galvanized cutting area to uniform distribution. The picking mechanism (5) includes a set of curved support blocks (542) that expand from the inside to the outside to support the open end of the pipe to be cut. The picking mechanism (5) also includes a set of driven piston curved clamping blocks (547) that contract from the outside to the inside to clamp the outer wall of the pipe to be cut. The coating mechanism (6) includes an outer gear sleeve (65) and an inner gear telescopic tube (67) that are slidably connected. The outer gear sleeve (65) and the inner gear telescopic tube (67) unfold to form a ring structure fitted on the pipe to be cut. The inner walls of the outer gear sleeve (65) and the inner gear telescopic tube (67) are provided with flexible wear-resistant rubber pads (69) that abut against the galvanized cutting area.

2. The hot-dip galvanized steel pipe cutting device according to claim 1, characterized in that, The fixed bracket (2) is fixedly installed on the load frame (1), and the movable lifting bracket (3) is slidably installed on the load frame (1). A second-stage lifting bracket (45) for fixing the cutter (46) is slidably installed on the movable lifting bracket (3).

3. The hot-dip galvanized steel pipe cutting device according to claim 2, characterized in that, An electromagnetic induction preheater (42) facing the limiting arc groove (41) is fixedly installed inside the movable lifting support (3).

4. The hot-dip galvanized steel pipe cutting device according to claim 3, characterized in that, The etchant is a weakly acidic complex solution, and the phase change material is a low-temperature phase change microemulsion loaded with nano-graphene particles.

5. The hot-dip galvanized steel pipe cutting device according to claim 4, characterized in that, Both the corrosive liquid sprayer (43) and the phase change spray cooler (44) are inclined toward the axial direction of the pipe to be cut.

6. The hot-dip galvanized steel pipe cutting device according to claim 5, characterized in that, The picking mechanism (5) also includes a hollow rotating shaft (51) rotatably mounted on the movable lifting bracket (3), a load-bearing disc (52) is fixedly connected to the hollow rotating shaft (51), and a drive boss (53) that extends and retracts in the left and right direction is movably provided on the load-bearing disc (52).

7. A hot-dip galvanized steel pipe cutting device according to claim 6, characterized in that, A set of curved support blocks (542) are symmetrically distributed vertically or horizontally on the load-bearing disc (52), and a set of driven piston curved clamping blocks (547) are symmetrically distributed horizontally or vertically to perform radial reciprocating movement.

8. The hot-dip galvanized steel pipe cutting device according to claim 7, characterized in that, A set of curved support blocks (542) are movably pulled by a drive boss (53) to perform radial reciprocating movement, and a set of driven piston curved clamping blocks (547) are movably pulled by a drive boss (53) to perform radial reciprocating movement.

9. A hot-dip galvanized steel pipe cutting device according to claim 8, characterized in that, The coating mechanism (6) also includes a drive gear (61) and a driven rack (62) meshing together. A grooved load-bearing block (63) for sliding the outer gear sleeve (65) is integrally connected to the driven rack (62). The outer gear sleeve (65) and the inner gear telescopic tube (67) are concentric semi-circular ring structures, and a strong capsule (68) for fixing and embedding wear-resistant rubber pads (69) is provided in the inner wall of both the outer gear sleeve (65) and the inner gear telescopic tube (67).

10. A cutting method for a hot-dip galvanized steel pipe cutting device as described in claim 9, characterized in that, The cutting method includes the following steps: Step S1: Place the pipe to be cut on the limiting arc groove (41) of the fixed bracket (2), extend the curved support block (542) into the opening at one end of the pipe to be cut, control the drive boss (53) to move linearly to pull a set of curved support blocks (542) to expand from the inside to the outside until they abut against the inner wall of the opening end of the pipe to be cut, and at the same time, a set of driven piston curved clamping blocks (547) retract from the outside to the inside until they clamp the outer wall of the pipe to be cut. Step S2: The pipe to be cut is rotated by the hollow rotating shaft (51), and the galvanized cutting area of ​​the pipe to be cut is heated to 280-350°C by the electromagnetic induction preheater (42), so that the zinc-iron alloy layer structure of the galvanized cutting area is relaxed. Step S3: While the pipe to be cut is rotating, the upward-moving cutter (46) cuts the galvanized cutting area. At the same time, a weak acid complexing solution is sprayed onto the galvanized cutting area through the corrosion sprayer (43). The drive gear (61) and driven rack (62) are controlled to run, and the grooved support block (63) is driven to move closer to the galvanized cutting area. The inner gear telescopic tube (67) is controlled to extend from the outer gear sleeve (65) and form a ring structure around the pipe to be cut. The inflated strong capsule (68) is used to make the wear-resistant rubber pad (69) elastically contact the periphery of the galvanized cutting area. The outer gear sleeve (65) and inner gear telescopic tube (67) of the ring structure are controlled to perform periodic reciprocating deflection of less than 180° in the grooved support block (63). The weak acid complexing solution is coated on the wear-resistant rubber pad (69). The phase change spray cooler (44) is not activated during the cutting process and is activated after the cutting is completed. Step S4: After cutting is completed, control the drive gear (61) and driven rack (62) to move the control grooved load block (63) so that the ring structure is away from the cutting surface. The phase change spray cooler (44) continuously sprays low temperature phase change microemulsion onto the cutting surface. Then control the drive gear (61) and driven rack (62) to make the cutting end face correspond to the wear-resistant rubber pad (69). While controlling the rotation of the pipe to be cut, the wear-resistant rubber pad (69) with periodic reciprocating deflection is used to coat the low temperature phase change microemulsion for cleaning and passivation.

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