Production process for improving first-time qualification rate of wind tower steel

Abstract

The application provides a production process for improving the first pass rate of a wind tower steel. The process comprises a steelmaking, continuous casting, rolling, ACC cooling, hot straightening and post-processing procedure. The molten steel composition is controlled through converter smelting, the crystallizer electromagnetic stirring technology is used to optimize the slab structure, and the structure homogenization treatment is performed. The two-stage temperature control rolling is used in the rolling stage, the specific SKI head buckling parameters and the air passing pass are set, and the descaling device is started. The ACC cooling adopts the multi-stage laminar cooling, the nine-roller straightening machine is used for the hot straightening, and the second return straightening is performed on the tail buckling area. The post-processing procedure comprises the cooling bed cooling, laser-flame composite cutting and magnetic powder detection. The application solves the surface quality defects and the plate shape control problem in the traditional process, significantly reduces the pit defects, optimizes the surface quality and the plate shape flatness, significantly improves the product first pass rate, reduces the energy consumption and the production cycle, and improves the weather resistance of the steel plate.

Description

Technical Field

[0001] This invention relates to the field of wind tower steel production technology, specifically to a production process for improving the first-pass yield of wind tower steel. Background Technology

[0002] In the production of heavy plates, wind tower steel, as a typical high-strength structural steel, has always been a key focus of industry technology research in terms of surface quality and plate shape control. In traditional production processes, when wind tower steel is rolled using hot rolling in the heavy plate workshop, the final rolling temperature is generally controlled at a high level, and the final cooling temperature is also maintained in the high-temperature range, with hot straightening machines used for roll gap straightening. However, in actual production, two major technical bottlenecks have been found under conventional process conditions: First, after hot straightening, the steel plate surface is prone to continuous worm-like pitting defects, mainly due to the indentation of iron oxide scale on the steel plate surface at high temperatures and localized stress concentration caused by improper roll gap settings; second, when attempting to improve surface quality by adjusting the hot straightening roll gap parameters, irreversible hard bending deformation occurs in the head area of ​​the steel plate, and small wavy defects in the buckled state cannot be eliminated by conventional straightening. In existing technologies, surface grinding and re-leveling not only reduce production efficiency but also damage the surface integrity of the material, leading to a decline in the overall performance of the product. Therefore, it is urgent to achieve a breakthrough in both quality and efficiency through process innovation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the above-mentioned technical defects and provide a production process to improve the first-pass yield of wind tower steel.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is a production process for improving the first-pass yield of wind tower steel, characterized by comprising the following steps:

[0005] (1) Steelmaking process: Converter smelting is adopted, and the composition of molten steel is controlled to meet the mechanical performance requirements of wind tower steel using a C-Mn-Nb-Ti microalloying system. Deoxidizer is added during the tapping process for deep deoxidation.

[0006] (2) Continuous casting process: The solidification structure of the billet is optimized by using electromagnetic stirring technology in the crystallizer. After the billet is removed from the line, it is immediately placed in the slow cooling pit for homogenization treatment.

[0007] (3) Rolling process:

[0008] a. The roughing stage adopts a two-stage temperature-controlled rolling process, with the initial rolling temperature ≤1100℃ and the final rolling temperature ≥980℃;

[0009] b. In the finishing rolling stage, the inlet mode is used to produce finished products. The penultimate pass is set to the SKI buckle parameter of 15. The last pass is set to the empty pass. The empty pass roll gap setting value exceeds the finished product thickness by 8-12mm.

[0010] c. The mill exit descaling device is started synchronously in the empty passage, with a working water pressure ≥18MPa and equipped with a self-cleaning nozzle;

[0011] (4) ACC cooling process: Multi-stage laminar flow cooling is adopted, with a cooling water ratio of 1.0-1.2 between the upper and lower surfaces and a cooling rate of 15-20℃ / s. After the steel plate leaves the cooling zone, the side air jet knife is activated to blow away the residual water film.

[0012] (5) Hot straightening process: A nine-roller straightener is used, with the roll gap set to the nominal thickness of the steel plate +0-5mm, the straightening temperature 450-550℃, and the straightening force 3500-4000 tons. The tail end upward area is straightened twice.

[0013] (6) Post-processing: After cooling to room temperature on a cooling bed, laser-flame composite cutting process is used to cut to length, and magnetic particle inspection is performed on the cut surface.

[0014] Furthermore, in step (2), the billet slow cooling pit is equipped with a temperature gradient monitoring system, with a thermocouple arranged every 2 meters along the length of the billet to monitor temperature fluctuations ≤ ±10℃ in real time.

[0015] Furthermore, in step (3)b, the empty passage secondary roll gap is collected in real time by the PLC system and a 10mm deviation value is automatically added.

[0016] Furthermore, in step (3)b, a laser leveling instrument is added before the empty passageway to detect the warping height of the steel plate in real time and provide feedback to adjust the SKI parameters with an adjustment accuracy of ±0.5mm.

[0017] Furthermore, in step (4), a side shielding device is configured, the shielding width is 5-8% of the width of the steel plate, and the cooling manifold is equipped with an infrared temperature sensor to dynamically adjust the water flow.

[0018] Furthermore, in step (5), the upper four rollers of the straightener are active drive rollers, and the lower five rollers are driven rollers. The difference in linear speed of the drive rollers is controlled within the range of ±0.1m / s.

[0019] Furthermore, in step (2), the temperature of the billet slow cooling pit is controlled at 200-250℃, and the surface temperature gradient of the billet is ≤15℃ / m after the slow cooling is completed.

[0020] Furthermore, in the composite cutting process described in step (6), the laser cutting power is 4-6kW, the oxygen purity of the flame cutting is ≥99.6%, and the cut surface is treated with a grinding wheel after cutting.

[0021] Furthermore, in step (6), fluorescent magnetic powder is used for magnetic particle testing, the magnetic suspension concentration is 1.5-2.0 mL / 100 mL, and the magnetization current is 3-5 times the thickness of the steel plate.

[0022] The advantages of this invention compared to the prior art are:

[0023] Compared with existing technologies, this invention fundamentally solves the problem of mutual constraints between surface quality defects and plate shape control in traditional processes through systematic synergistic innovation of rolling process and hot straightening technology. Its core advantages are as follows: First, it innovatively proposes a linkage control between the setting rules for the secondary roll gap in the empty passage during the rolling stage and the descaling and water spraying strategy. This significantly reduces the problem of uneven temperature gradient distribution in the final rolling, suppresses the intrusion of iron oxide scale and stress concentration from the source, and greatly reduces the incidence and depth of pitting defects on the steel plate surface, completely avoiding the damage to material integrity caused by surface grinding. Second, it develops dynamic roll gap compensation technology in the hot straightening stage. Based on the morphology and temperature field distribution characteristics of the steel plate, it establishes a real-time feedback roll gap adjustment mechanism, which accurately compensates for the warping and wave deformation of the steel plate head and tail while eliminating surface pitting, successfully achieving simultaneous optimization of surface quality and plate flatness. Finally, through the deep integration of the parameter system, the entire process significantly improves the first-pass yield of products without relying on additional equipment modifications and subsequent rework processes, while simultaneously reducing energy consumption and production cycle. Furthermore, the process optimization fundamentally improves the weather resistance of the steel plate. This technology system breaks through the technical bottleneck of efficient production of wind tower steel and provides a process innovation path that is both universal and economical for the field of high-strength steel. Attached Figure Description

[0024] Figure 1 This is a flowchart of a production process for improving the first-pass yield of wind tower steel according to this application.

[0025] Figure 2 This is a picture showing the cleaning effect of the wind tower steel before the optimization process.

[0026] Figure 3 The diagram shows the effect of optimizing the production process for improving the first-pass yield of wind tower steel according to the method described in this application. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings.

[0028] The following is in conjunction with the appendix Figure 1 - Appendix Figure 3 The following will further illustrate specific embodiments of the present invention. Identical components are indicated by the same reference numerals.

[0029] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0030] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] Example 1

[0032] This embodiment provides a production process to improve the first-pass yield of wind tower steel. The specific implementation steps are as follows:

[0033] (1) Steelmaking process

[0034] The steel is smelted in a 300-ton converter, with the composition controlled to meet the microalloying requirements of 0.12-0.18% C, 1.2-1.5% Mn, 0.02-0.04% Nb, and 0.008-0.015% Ti. Deep deoxidation is performed using a silicon-calcium alloy during tapping, maintaining the oxygen activity in the molten steel at ≤15 ppm. Argon blowing and stirring at the bottom of the ladle lasts for at least 8 minutes to ensure uniform composition.

[0035] (2) Continuous casting process

[0036] A 320mm thick billet was cast using an arc-shaped continuous casting machine. The electromagnetic stirring current in the crystallizer was 450A at a frequency of 2.5Hz. Immediately after casting, the billet was placed in a slow cooling pit, where the temperature was controlled at 230±10℃ for at least 48 hours. K-type thermocouples were placed every 2 meters along the length of the billet in the slow cooling pit to monitor temperature fluctuations within ±8℃. After treatment, the surface temperature gradient of the billet was ≤12℃ / m, and the central equiaxed crystal ratio increased to 42%.

[0037] (3) Rolling process

[0038] a. The roughing stage adopts a two-stage temperature-controlled rolling process: the first stage is carried out at 1100℃ with three passes of large reduction, and the single pass reduction rate is ≥25%; the second stage is carried out at 1050℃ with two passes of rolling, and the final rolling temperature is controlled at 985-1000℃.

[0039] b. Finishing stage: The inlet mode is used for finished product output. The penultimate pass is set to a SKI head warping parameter of 15, and the last pass is set as a no-pass pass. The PLC system collects finished product thickness data in real time and automatically sets the no-pass roll gap to finished product thickness + 10mm (e.g., 60mm roll gap when producing 50mm steel plates). A laser leveling instrument is added before the no-pass pass; when the detected steel plate head warping height > 3mm, the SKI parameter is automatically adjusted to 18.

[0040] c. Simultaneous start-up of the mill exit descaling device during empty passes: A self-cleaning fan-shaped nozzle is used, with a stable working water pressure of 18.5-19.2 MPa and a single-pass descaling time controlled at 8-12 seconds. Testing shows that the secondary iron oxide scale removal rate is ≥98%.

[0041] (4) ACC cooling process

[0042] Multi-stage laminar flow cooling is implemented using 24 sets of upper and lower cooling manifolds, with the water flow rate on the upper surface set to 1.15 times that on the lower surface. Edge shielding devices are installed, with a shielding width of 6% of the steel plate width (e.g., 294mm shielding for a 4900mm wide steel plate). The cooling rate is controlled at 18±2℃ / s, with a final cooling temperature of 680-720℃. After exiting the cooling zone, side air jets are activated with a compressed air pressure of 0.6MPa, ensuring a residual water film thickness of ≤0.1mm on the steel plate surface after purging.

[0043] (5) Hot straightening process

[0044] A nine-roll straightener is used, with the linear velocity difference between the upper four driving rolls and the lower five driven rolls controlled within ±0.08 m / s. The roll gap is set to nominal thickness + 3 mm (e.g., a 53 mm roll gap for a 50 mm steel plate), the straightening temperature is 485 ± 15℃, and the straightening force is 3800 ± 100 tons. For areas with a tail-end overhang > 5 mm, a secondary straightening is performed, with a straightening reduction of 2-3 mm.

[0045] (6) Post-processing steps

[0046] After the steel plate is cooled to below 80℃ on a cooling bed, a composite cutting process using a 6kW fiber laser and a high-purity oxygen (99.8% purity) flame is employed. The cutting speed is set as follows: 1.2 m / min for the laser cutting section and 0.8 m / min for the flame cutting section. After cutting, the cut surface is treated with a grinding wheel to achieve a roughness Ra≤12.5μm. Finally, fluorescent magnetic particle inspection is performed with a magnetic suspension concentration of 1.8 mL / 100 mL and a magnetizing current set at 4 times the plate thickness (e.g., 200A current for a 50mm plate).

[0047] Example 2

[0048] This embodiment is an optimization based on Embodiment 1:

[0049] Continuous casting slow cooling control: An infrared thermal imaging system is added to the slow cooling pit to scan the surface temperature distribution of the billet every 30 minutes. When the local temperature difference is greater than 15°C, the auxiliary heating device is activated.

[0050] Rolling parameter optimization: A dedicated rolling specification database has been developed to automatically retrieve parameters based on the steel grade code. For example, when producing Q345B wind tower steel, the system automatically matches parameters such as: roughing reduction rate of 28%, finishing SKI value of 15, and empty roll gap of +10mm.

[0051] ACC Dynamic Adjustment: An infrared temperature sensor array is installed in the cooling manifold, with one temperature measurement point every 2 meters. When a local cooling rate deviation >3℃ / s is detected, the water flow rate in the corresponding manifold is automatically adjusted by ±5%.

[0052] Improved straightening process: Develop an intelligent straightening model that uses a plate shape detector to acquire flatness data in real time and dynamically adjust the straightening force (3500-4000 tons) and roll gap (nominal thickness + 0-5mm). For steel plates with a length greater than 12m, implement segmented straightening, with each 4m section as a straightening interval.

[0053] Implementation effect

[0054] This process is used to produce 60mm thick Q345E wind tower steel (specifications 12×4900×26000mm):

[0055] The incidence of heat-induced cradle cap decreased from 37% to 2.8%;

[0056] The pass rate for flatness of the board increased from 63% to 92%, which can increase the annual benefit by about 4.5 million.

[0057] The pass rate for magnetic particle testing has increased to 99.3%.

[0058] Tests showed that the steel plate had an impact energy of 68-75J at -40℃, a yield strength of 365-385MPa, and a Z-direction reduction of area of ​​≥55% for resistance to lamellar tearing, fully meeting the requirements of EN 10025 standard.

[0059] Comparative experiment

[0060] Comparative Example 1: Produced using the original export model, without any empty passes, the area of ​​pitted parts after hot straightening reached 15.7%, and the pass rate was only 61.2%.

[0061] Comparative Example 2: After removing the ACC edge shielding device, the steel plate edge showed saddle-shaped deformation, and the proportion of cracks generated during subsequent straightening reached 8.3%.

[0062] Experimental group: Using this patented process, the pass rate reached 93.7%, which is 32.5 percentage points higher than the control group.

[0063] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A production process for improving the first-pass yield of wind tower steel, characterized in that, Includes the following steps: (1) Steelmaking process: Converter smelting is adopted, and the composition of molten steel is controlled to meet the mechanical performance requirements of wind tower steel. A C-Mn-Nb-Ti microalloying system is used. Deoxidizer is added during the tapping process for deep deoxidation. (2) Continuous casting process: The solidification structure of the billet is optimized by using electromagnetic stirring technology in the crystallizer. After the billet is removed from the line, it is immediately placed in the slow cooling pit for homogenization treatment. (3) Rolling process: a. The roughing stage adopts a two-stage temperature-controlled rolling process, with the initial rolling temperature ≤1100℃ and the final rolling temperature ≥980℃; b. In the finishing rolling stage, the finished product is produced using the inlet mode. The penultimate pass is set to a SKI head parameter of 15, and the last pass is set to an empty pass. c. The descaling device at the mill exit is started synchronously during the empty passage, with a working water pressure ≥18MPa and equipped with a self-cleaning nozzle; In step (3)b, the roll gap of the empty pass is collected in real time by the PLC system and the finished product thickness is automatically superimposed with a 10mm deviation value; In step (3)b, a laser leveling instrument is added before the empty passageway to detect the warping height of the steel plate in real time and provide feedback to adjust the SKI parameters with an adjustment accuracy of ±0.5mm. (4) ACC cooling process: Multi-stage laminar flow cooling is adopted, with a cooling water ratio of 1.0-1.2 between the upper and lower surfaces and a cooling rate of 15-20℃ / s. After the steel plate leaves the cooling zone, the side jet knife is activated to blow away the residual water film. This step is equipped with a side shielding device with a shielding width of 5-8% of the steel plate width, and the cooling manifold is equipped with an infrared temperature sensor to dynamically adjust the water flow. (5) Hot straightening process: A nine-roll straightener is used, with the roll gap set to the nominal thickness of the steel plate + 0-5mm, the straightening temperature 450-550℃, and the straightening force 3500-4000 tons. The tail end upward area is straightened twice. (6) Post-processing: After cooling to room temperature on a cooling bed, laser-flame composite cutting process is used to cut to length, and magnetic particle inspection is performed on the cut surface.

2. The production process for improving the first-pass yield of wind tower steel according to claim 1, characterized in that: In step (2), the billet slow cooling pit is equipped with a temperature gradient monitoring system, with a thermocouple arranged every 2 meters along the length of the billet to monitor temperature fluctuations ≤ ±10℃ in real time.

3. The production process for improving the first-pass yield of wind tower steel according to claim 1, characterized in that: In step (5), the upper four rollers of the straightener are active drive rollers, and the lower five rollers are driven rollers. The difference in linear speed of the drive rollers is controlled within the range of ±0.1m / s.

4. The production process for improving the first-pass yield of wind tower steel according to claim 1, characterized in that: In step (2), the temperature of the billet slow cooling pit is controlled at 200-250℃, and the surface temperature gradient of the billet is ≤15℃ / m after the slow cooling is completed.

5. The production process for improving the first-pass yield of wind tower steel according to claim 1, characterized in that: In the composite cutting process described in step (6), the laser cutting power is 4-6kW, the oxygen purity of the flame cutting is ≥99.6%, and the cut surface is treated with a grinding wheel after cutting.

6. A production process for improving the first-pass yield of wind tower steel according to claim 1 or 5, characterized in that: In step (6), fluorescent magnetic powder is used for magnetic particle testing, and the magnetic suspension concentration is 1.5-2.0 mL / 100 mL.

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