Process for improving external scabbing of head of PQF unit steel pipe

Abstract

The invention relates to the technical field of process improvement, and discloses a PQF unit steel tube head external scabbing improvement process which comprises the following steps: S1, optimizing a borax injection process, and reducing the residual of borax on the head of a capillary tube by adjusting the amount of borax and injection pressure; s2, optimizing roller cooling water logic, canceling head and tail avoidance logic, and ensuring uniform cooling of the surface of the roller; s3, a dynamic temperature monitoring system is introduced, the surface temperature of the roller is monitored in real time, and the cooling water flow is dynamically adjusted according to temperature changes; and S4, an ultrasonic cleaning technology is adopted, the surface of the tubular billet is periodically cleaned in the continuous rolling process, and oxide skin and residues are removed. According to the method, cooling water head and tail avoiding logic is canceled, the cooling water flow is dynamically adjusted by combining an intelligent cooling water system and a machine learning algorithm, the temperature difference of the surface of the roller is reduced to be within + / -5 DEG C from 150 DEG C, the service life of the roller is prolonged to 500 times, and the problem of oxide skin residues caused by uneven cooling is remarkably solved.

Description

Technical Field

[0001] The present invention relates to the technical field of process improvement, and specifically to a process for improving the external scarring of the head of steel pipes in a PQF mill. Background Art

[0002] During the continuous rolling production process of steel pipes, external scarring is a common and difficult problem to solve. External scarring not only affects the appearance quality of steel pipes but may also cause serious problems such as cracks and fractures during the use of steel pipes. In the prior art, the generation of external scarring is mainly controlled by adjusting the borax spraying process and the roll cooling water logic. However, the prior art has the following disadvantages:

[0003] 1. The amount of borax used is too high, and the residual borax accumulates at the head of the mandrel. When the mandrel is inserted, the residual borax is carried into the first stand of the rolling mill and adheres to the head of the mandrel to form scarring.

[0004] 2. The delay of cooling water results in insufficient cooling of the roll surface, residual scale, and discontinuous cooling in the head and tail regions, exacerbating the surface scarring problem. Summary of the Invention

[0005] (I) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a process for improving the external scarring of the head of steel pipes in a PQF mill, which solves the problems in the above background art such as "too high amount of borax used and insufficient cooling of the roll surface caused by the delay of cooling water", etc.

[0007] (II) Technical Solutions

[0008] To achieve the above objectives, the present invention is realized through the following technical solutions: A process for improving the external scarring of the head of steel pipes in a PQF mill, including the following steps:

[0009] S1: Optimize the borax spraying process. By adjusting the amount of borax and the spraying pressure, reduce the residue of borax at the head of the mandrel;

[0010] S2: Optimize the roll cooling water logic, cancel the head and tail avoidance logic, and ensure uniform cooling of the roll surface;

[0011] S3: Introduce a dynamic temperature monitoring system to monitor the surface temperature of the roll in real time and dynamically adjust the cooling water flow according to the temperature change;

[0012] S4: Adopt ultrasonic cleaning technology to periodically clean the surface of the mandrel during continuous rolling to remove scale and residues;

[0013] S5: Introduce surface coating technology to coat a layer of high-temperature resistant and oxidation-proof coating on the surface of the mandrel to reduce the generation of scale;

[0014] S6: Introduce roll surface repair technology to perform on-line repair of the worn roll surface during continuous rolling to ensure a smooth roll surface.

[0015] Preferably, the borax spraying process in S1 specifically includes:

[0016] S101: Reduce the amount of borax from 170 g / m2 to 130 g / m2;

[0017] S102: Increase the spraying pressure from 1.1 bar to 1.3 bar;

[0018] S103: Introduce segmented spraying technology to dynamically adjust the spraying area according to the length of the capillary tube to ensure uniform borax coverage at the head and tail;

[0019] S104: Adopt nitrogen purging means. After spraying borax, purge the inner surface of the capillary tube with nitrogen to remove residual borax. The nitrogen purging pressure is 0.8 bar and the purging time is 3 seconds.

[0020] Preferably, the segmented spraying in S103 specifically includes:

[0021] S1011: Set independent spraying units at the head and tail of the capillary tube respectively, and the distance between the spraying units is 1.5 meters;

[0022] S1012: Dynamically adjust the opening time and spraying intensity of the spraying units according to the length of the capillary tube and the rolling speed. The spraying time is 2 seconds at the head and 3 seconds at the tail;

[0023] S1013: Introduce an intelligent control system to adjust the spraying parameters in real time according to the position of the capillary tube and the spraying effect. The spraying angle is 45° and the spraying coverage range is 90%.

[0024] Preferably, the optimization of the roll cooling water logic in S2 specifically includes the following steps:

[0025] S201: Cancel the head and tail avoidance logic and keep the cooling water always on;

[0026] S202: Dynamically adjust the cooling water flow rate of each rolling mill through an intelligent cooling water system according to the roll surface temperature distribution. The cooling water flow rate is 500 L / min;

[0027] S203: Adopt a high-pressure cooling water spraying device to increase the impact force of the cooling water on the roll surface and enhance the cooling effect. The spraying pressure is 10 bar and the spraying angle is 30°.

[0028] Preferably, the intelligent cooling water system in S202 specifically includes a temperature sensor array, a control unit, a flow regulating valve, and a machine learning algorithm introduced. Among them, the temperature sensor array mainly monitors the roll surface temperature of each rolling mill in real time, with a temperature measurement range of 0°C to 800°C and an accuracy of ±1°C. The control unit mainly generates a cooling water distribution plan based on the temperature data. The flow regulating valve mainly adjusts the cooling water flow according to the distribution plan, with a flow regulation range of 0 to 1000 L / min. The machine learning algorithm mainly predicts the change trend of the roll surface temperature based on historical data, optimizes the cooling water distribution plan, and the prediction accuracy is ±5°C.

[0029] Preferably, the dynamic temperature monitoring system in S3 includes an infrared temperature sensor, a data processing unit, an execution unit, and a wireless transmission technology. Among them, the infrared temperature sensor is used to collect roll surface temperature data in real time, with a temperature measurement range of 0°C to 1000°C and a response time of 0.1 second. The data processing unit mainly generates a cooling water flow adjustment instruction based on the temperature data. The execution unit mainly dynamically adjusts the cooling water flow according to the instruction. The line transmission technology mainly realizes the real-time transmission and processing of temperature data, with a transmission distance of 50 meters and a transmission rate of 1 Mbps.

[0030] Preferably, the ultrasonic cleaning technology in S4 includes an ultrasonic generator that generates high-frequency vibration waves with a frequency of 40 kHz and a power of 500 W; a cleaning nozzle that transmits the vibration waves to the surface of the capillary tube, with 4 nozzles and a spacing of 1 meter; a cleaning liquid supply device that provides cleaning liquid to enhance the cleaning effect, with a cleaning liquid flow rate of 10 L / min; and an automatic cleaning control module that automatically adjusts the cleaning frequency and intensity according to the surface state of the capillary tube, with a cleaning frequency of 1 time per minute and a cleaning intensity of 80%.

[0031] Preferably, the surface coating technology in S5 specifically includes that the coating material used is nano-ceramic particles with a particle size of 50 nm and a coating thickness of 10 μm, and an electrostatic spraying process is adopted to ensure that the coating evenly covers the surface of the capillary tube, with a spraying voltage of 50 kV and a spraying distance of 20 cm. In addition, an on-line coating detection technology is introduced to monitor the coating thickness and uniformity in real time to ensure the coating quality, with a detection accuracy of ±0.1 μm.

[0032] Preferably, the on-line coating detection technology in S5 adopts, including but not limited to, a laser thickness gauge, an image processing system, and a feedback control system. Among them, the laser thickness gauge is used to measure the coating thickness in real time, with a measurement range of 0 to 20 μm and an accuracy of ±0.05 μm. The image processing system is used to analyze the coating uniformity, with a resolution of 0.01 mm. The feedback control system adjusts the spraying parameters according to the detection results, and the adjustment response time is 0.5 second.

[0033] Preferably, the roll surface repair technology in S6 specifically includes a laser cladding device, a surface grinding device, and a repair control module. The laser cladding equipment is used to repair the worn roll surface by laser cladding, with a laser power of 2 kW and a cladding speed of 10 mm / s. The surface grinding device is used to grind the repaired roll surface to ensure a smooth surface, with a grinding accuracy of ±0.01 mm. The repair control module automatically adjusts the repair parameters according to the wear condition of the roll surface, with a repair accuracy of ±0.05 mm.

[0034] (III) Beneficial effects

[0035] The present invention provides a process for improving the external scarring of the head of a steel pipe in a PQF mill. It has the following beneficial effects:

[0036] (1) When the process for improving the external scarring of the head of a steel pipe in a PQF mill is used, through the combined cooperation of "reducing the amount and increasing the pressure + intelligent segmented spraying", and in combination with the nitrogen purging system, the residual thickness of borax is ≤0.1 mm. In addition, the distance between the segmented spraying units is 1.5 meters and the spraying angle is 45°, so that the uniformity of head and tail coverage is increased to 90%, and the adhesive scarring caused by mandrel contamination is eliminated from the root.

[0037] (2) When the process for improving the external scarring of the head of a steel pipe in a PQF mill is used, by canceling the head and tail avoidance logic of the cooling water, combining the intelligent cooling water system with the machine learning algorithm to dynamically adjust the cooling water flow rate, the temperature difference on the roll surface is reduced from 150°C to within ±5°C, and the roll life is increased to 500 times, significantly improving the problem of scale residue caused by uneven cooling.

[0038] (3) When the process for improving the external scarring of the head of a steel pipe in a PQF mill is used, by introducing a triple protection system of ultrasonic cleaning, nano - coating, and on - line roll repair, the scale residue is reduced by 80%, and the energy consumption per ton of steel is reduced to 52 kWh, comprehensively improving the surface quality and production efficiency of the steel pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic flow chart of the method of the present invention;

[0040] Figure 2 It is a schematic diagram of 170 g / m2 borax amount + 1.1 bar pressure in the present invention;

[0041] Figure 3 It is a schematic diagram of 130 g / m2 borax amount + 1.3 bar in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1 - Figure 3 ,

[0044] Embodiment 1, the present invention provides a process for improving the external scarring of the steel pipe head of a PQF mill, including the following steps:

[0045] S1: Optimize the borax spraying process. By adjusting the borax amount and spraying pressure, reduce the residue of borax at the head of the capillary tube. Specifically, the borax spraying process includes:

[0046] S101: Set the borax amount to 130 g / m2;

[0047] S102: Set the spraying pressure to 1.3 bar;

[0048] S103: Introduce a segmented spraying technology. Dynamically adjust the spraying area according to the length of the capillary tube to ensure uniform borax coverage at the head and tail. Further description, the segmented spraying specifically includes:

[0049] S1011: Set independent spraying units at the head and tail of the capillary tube respectively, and the distance between the spraying units is 1.5 meters;

[0050] S1012: Dynamically adjust the opening time and spraying intensity of the spraying unit according to the length of the capillary tube and the rolling speed. The spraying time is 2 seconds at the head and 3 seconds at the tail;

[0051] S1013: Introduce an intelligent control system. According to the position of the capillary tube and the spraying effect, adjust the spraying parameters in real time. The spraying angle is 45°, and the spraying coverage range is 90%;

[0052] S104: Adopt nitrogen purging means. After spraying borax, purge the inner surface of the capillary tube with nitrogen to remove the residual borax. The nitrogen purging pressure is 0.8 bar, and the purging time is 3 seconds;

[0053] S2: Optimize the roll cooling water logic, cancel the head and tail avoidance logic, and ensure uniform cooling of the roll surface. Specifically, optimizing the roll cooling water logic specifically includes the following steps:

[0054] S201: Cancel the head and tail avoidance logic, and the cooling water is always on;

[0055] S202: According to the surface temperature distribution of the roll, the intelligent cooling water system dynamically adjusts the cooling water flow rate of each rolling mill. The cooling water flow rate is 500 L / min. Further description: The intelligent cooling water system specifically includes a temperature sensor array, a control unit, a flow regulating valve, and the introduction of a machine learning algorithm. Among them, the temperature sensor array mainly monitors the surface temperature of the roll of each rolling mill in real time. The temperature measurement range is from 0°C to 800°C, and the accuracy is ±1°C. The control unit mainly generates a cooling water distribution plan based on the temperature data. The flow regulating valve mainly adjusts the cooling water flow rate according to the distribution plan. The flow regulation range is from 0 to 1000 L / min. The machine learning algorithm mainly predicts the change trend of the roll surface temperature based on historical data, optimizes the cooling water distribution plan, and the prediction accuracy is ±5°C;

[0056] S203: Adopt a high-pressure cooling water spraying device to increase the impact force of the cooling water on the roll surface and enhance the cooling effect. The spraying pressure is 10 bar, and the spraying angle is 30°;

[0057] S3: Introduce a dynamic temperature monitoring system to monitor the roll surface temperature in real time and dynamically adjust the cooling water flow rate according to the temperature change. Specifically, the dynamic temperature monitoring system includes an infrared temperature sensor, a data processing unit, an execution unit, and a wireless transmission technology. Among them, the infrared temperature sensor is used to collect the roll surface temperature data in real time. The temperature measurement range is from 0°C to 1000°C, and the response time is 0.1 second. The data processing unit mainly generates a cooling water flow rate adjustment instruction based on the temperature data. The execution unit mainly dynamically adjusts the cooling water flow rate according to the instruction. The wireless transmission technology mainly realizes the real-time transmission and processing of the temperature data. The transmission distance is 50 meters, and the transmission rate is 1 Mbps;

[0058] S4: Adopt ultrasonic cleaning technology to periodically clean the surface of the capillary tube during continuous rolling to remove oxide scale and residues. Specifically, the ultrasonic cleaning technology includes an ultrasonic generator that generates high-frequency vibration waves with a frequency of 40 kHz and a power of 500 W; a cleaning nozzle that transmits the vibration waves to the surface of the capillary tube. The number of nozzles is 4, and the spacing is 1 meter; a cleaning liquid supply device that provides cleaning liquid to enhance the cleaning effect. The cleaning liquid flow rate is 10 L / min; an automatic cleaning control module that automatically adjusts the cleaning frequency and intensity according to the surface state of the capillary tube. The cleaning frequency is 1 time per minute, and the cleaning intensity is 80%;

[0059] S5: Introduce the surface coating technology to coat a layer of high-temperature resistant and oxidation-proof coating on the capillary tube surface to reduce the formation of oxide scale. Specifically, the surface coating technology includes using nanoscale ceramic particles with a particle size of 50 nm as the coating material, a coating thickness of 10 μm, and adopting an electrostatic spraying process to ensure that the coating evenly covers the capillary tube surface. The spraying voltage is 50 kV, and the spraying distance is 20 cm. In addition, introduce the on-line coating detection technology to monitor the coating thickness and uniformity in real time to ensure the coating quality. The detection accuracy is ±0.1 μm. The on-line coating detection technology includes but is not limited to a laser thickness gauge, an image processing system, and a feedback control system. The laser thickness gauge is used to measure the coating thickness in real time, with a measurement range of 0 to 20 μm and an accuracy of ±0.05 μm. The image processing system is used to analyze the coating uniformity with a resolution of 0.01 mm. The feedback control system adjusts the spraying parameters according to the detection results, and the adjustment response time is 0.5 seconds;

[0060] S6: Introduce the roll surface repair technology to perform on-line repair on the worn roll surface during continuous rolling to ensure the roll surface is smooth. Specifically, the roll surface repair technology includes a laser cladding device, a surface grinding device, and a repair control module. The laser cladding equipment is used to perform cladding repair on the worn roll surface, with a laser power of 2 kW and a cladding speed of 10 mm / s. The surface grinding device is used to grind the repaired roll surface to ensure the surface is smooth, with a grinding accuracy of ±0.01 mm. The repair control module automatically adjusts the repair parameters according to the wear condition of the roll surface, and the repair accuracy is ±0.05 mm.

[0061] The experimental results are as follows:

[0062] Index Example 2 Example 3 Example 1 Scab rate 30％ 12％ ≤1％ Roll life 200 times 300 times 500 times Energy consumption per ton of steel 58 kWh 55 kWh 52 kWh Borax residue 0.5 mm 0.3 mm ≤0.1 mm

[0063] From the above experimental results, it is concluded that the tail coverage defect in Example 3 is solved by "reducing the amount and increasing the pressure + intelligent segmented blowing", the 150°C temperature difference in Example 2 is eliminated by dynamic temperature control, the oxide scale residue is reduced by 80% (as Figure 3 shown), and the double protection of ultrasonic + nano coating further reduces the scar rate by 91.7% compared with Example 3.

[0064] Example Two

[0065] Based on Example One, the following technical means will be adopted in this example:

[0066] In the borax spraying process, a borax amount of 170 g / m2 + a pressure of 1.1 bar (as Figure 2 shown) is used, without segmented spraying, the head and tail coverage is uneven, and there is a 0.5 mm borax layer remaining after nitrogen purging;

[0067] The cooling system adopts a head-and-tail avoidance mode, the cooling water is delayed by 4 seconds to start, and the temperature difference on the surface of the roll reaches 150°C;

[0068] In surface treatment, ultrasonic cleaning and coating technologies are not adopted, and the roll is repaired offline after wear, with an accuracy of ±0.1 mm.

[0069] The experimental results are as follows in the table:

[0070] Index Value Head scab rate 30％ Roll life 200 passes of rolling Energy consumption per ton of steel 58 kWh Thickness of borax residue 0.5 mm

[0071] From the above experimental results, it is known that borax mechanical adhesion causes mandrel contamination, uneven cooling leads to thermal fatigue cracks in the roll, and the residual area of scale accounts for 40%.

[0072] Example 3

[0073] Based on Example 1, the following technical means will be adopted in this example:

[0074] In the borax spraying process, a borax amount of 150 g / m2 + a pressure of 1.1 bar is adopted, and basic segmented spraying is introduced (1.5 seconds at the head / 2 seconds at the tail);

[0075] In the cooling system, the avoidance delay is shortened to 2 seconds, and roll temperature monitoring is added (without dynamic adjustment);

[0076] In addition, low-frequency ultrasonic cleaning and micron-level coating are added. Among them, the parameters of low-frequency ultrasonic cleaning are selected as 30 kHz and 60% intensity, and the micron-level coating is selected as 50 μm, without on-line detection.

[0077] The experimental results are as follows in the table:

[0078]

[0079]

[0080] From the above experimental results, it is known that the borax coverage at the tail is still uneven (residual rate 25%), the response delay of the cooling system leads to 30% local scale residue, and the poor coating uniformity leads to unstable anti-oxidation effect.

[0081] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for improving the external scarring of the head of steel pipes in a PQF mill, characterized in that: It includes the following steps: S1: Optimize the borax injection process. By adjusting the amount of borax and the injection pressure, reduce the residue of borax at the head of the capillary tube; S2: Optimize the roll cooling water logic. Cancel the head and tail avoidance logic to ensure uniform cooling of the roll surface; S3: Introduce a dynamic temperature monitoring system to monitor the roll surface temperature in real time and dynamically adjust the cooling water flow according to the temperature change; S4: Adopt ultrasonic cleaning technology to periodically clean the surface of the capillary tube during continuous rolling to remove scale and residues; S5: Introduce surface coating technology to coat a layer of high-temperature oxidation-resistant coating on the surface of the capillary tube to reduce the formation of scale; S6: Introduce roll surface repair technology to perform on-line repair of the worn roll surface during continuous rolling to ensure the smoothness of the roll surface.

2. The improved process for external scarring on the head of steel pipes in a PQF mill unit according to claim 1, characterized in that: The specific borax injection process in S1 includes: S101: Reduce the amount of borax from 170 g / m2 to 130 g / m2; S102: Increase the injection pressure from 1.1 bar to 1.3 bar; S103: Introduce segmented injection technology to dynamically adjust the injection area according to the length of the capillary tube to ensure uniform borax coverage at the head and tail; S104: Adopt nitrogen purging means. After injecting borax, purge the inner surface of the capillary tube with nitrogen to remove the residual borax. The nitrogen purging pressure is 0.8 bar and the purging time is 3 seconds.

3. A process for improving the external scarring at the head of steel pipes in a PQF mill unit according to claim 2, characterized in that: The segmented injection in S103 specifically includes: S1011: Set independent injection units at the head and tail of the capillary tube respectively, and the distance between the injection units is 1.5 meters; S1012: Dynamically adjust the opening time and injection intensity of the injection unit according to the length of the capillary tube and the rolling speed. The injection time is 2 seconds at the head and 3 seconds at the tail; S1013: Introduce an intelligent control system to adjust the injection parameters in real time according to the position of the capillary tube and the injection effect. The injection angle is 45° and the injection coverage is 90%.

4. A process for improving the external scarring of the head of a steel pipe in a PQF mill unit according to claim 1, characterized in that: The specific steps for optimizing the roll cooling water logic in S2 include: S201: Cancel the head and tail avoidance logic, and keep the cooling water always on; S202: Dynamically adjust the cooling water flow of each rolling mill through an intelligent cooling water system according to the temperature distribution on the roll surface. The cooling water flow is 500 L / min; S203: Adopt a high-pressure cooling water spraying device to increase the impact force of the cooling water on the roll surface and enhance the cooling effect. The spraying pressure is 10 bar and the spraying angle is 30°.

5. A process for improving the external scarring on the head of steel pipes in a PQF mill set according to claim 4, characterized in that: The intelligent cooling water system in S202 specifically includes an array of temperature sensors, a control unit, a flow regulating valve, and a machine learning algorithm introduced. Among them, the array of temperature sensors mainly monitors the roll surface temperature of each rolling mill in real time. The temperature measurement range is 0°C to 800°C, and the accuracy is ±1°C. The control unit mainly generates a cooling water distribution plan according to the temperature data. The flow regulating valve mainly adjusts the cooling water flow according to the distribution plan. The flow regulation range is 0 to 1000 L / min. The machine learning algorithm mainly predicts the change trend of the roll surface temperature according to historical data and optimizes the cooling water distribution plan. The prediction accuracy is ±5°C.

6. A process for improving the external scarring at the head of steel pipes in a PQF mill unit according to claim 1, characterized in that: The dynamic temperature monitoring system in S3 includes an infrared temperature sensor, a data processing unit, an execution unit, and a wireless transmission technology. Among them, the infrared temperature sensor is used to collect the surface temperature data of the roll in real time, with a temperature measurement range of 0°C to 1000°C and a response time of 0.1 second. The data processing unit mainly generates a cooling water flow adjustment instruction based on the temperature data. The execution unit mainly dynamically adjusts the cooling water flow according to the instruction. The wireless transmission technology mainly realizes the real-time transmission and processing of temperature data, with a transmission distance of 50 meters and a transmission rate of 1 Mbps.

7. A process for improving the external scarring on the head of steel pipes in a PQF mill set according to claim 1, characterized in that: The ultrasonic cleaning technology in S4 includes an ultrasonic generator that generates high-frequency vibration waves with a frequency of 40 kHz and a power of 500 W; a cleaning nozzle that transmits the vibration waves to the surface of the capillary tube, with 4 nozzles and a spacing of 1 meter; a cleaning liquid supply device that provides cleaning liquid to enhance the cleaning effect, with a cleaning liquid flow rate of 10 L / min; An automatic cleaning control module that automatically adjusts the cleaning frequency and intensity according to the surface state of the capillary tube, with a cleaning frequency of 1 time per minute and a cleaning intensity of 80%.

8. A process for improving the external scarring on the head of steel pipes in a PQF mill unit according to claim 1, characterized in that: The surface coating technology in S5 specifically includes that the coating material used is nano-scale ceramic particles with a particle size of 50 nm and a coating thickness of 10 μm, and an electrostatic spraying process is adopted to ensure that the coating evenly covers the surface of the capillary tube. The spraying voltage is 50 kV and the spraying distance is 20 cm. In addition, an on-line coating detection technology is introduced to real-time monitor the coating thickness and uniformity to ensure the coating quality, with a detection accuracy of ±0.1 μm.

9. A process for improving the external scarring of the head of a steel pipe in a PQF mill set according to claim 1, characterized in that: The on-line coating detection technology in S5 adopts, including but not limited to, a laser thickness gauge, an image processing system, and a feedback control system. Among them, the laser thickness gauge is used to measure the coating thickness in real time, with a measurement range of 0 to 20 μm and an accuracy of ±0.05 μm. The image processing system is used to analyze the coating uniformity, with a resolution of 0.01 mm. The feedback control system adjusts the spraying parameters according to the detection results, and the adjustment response time is 0.5 second.

10. A process for improving the external scarring at the head of steel pipes in a PQF mill unit according to claim 1, characterized in that: The roll surface repair technology in S6 specifically includes a laser cladding device, a surface grinding device, and a repair control module. The laser cladding equipment is used to perform cladding repair on the worn roll surface, with a laser power of 2 kW and a cladding speed of 10 mm / s. The surface grinding device is used to grind the surface of the repaired roll to ensure a smooth surface, with a grinding accuracy of ±0.01 mm. The repair control module automatically adjusts the repair parameters according to the wear condition of the roll surface, with a repair accuracy of ±0.05 mm.

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