Method and system for directional flame cleaning of residual oil stains in the edge wave area of silicon steel strip

Abstract

The present application relates to a kind of silicon steel strip edge wave area residual oil stain directional flame removal method and system, the method actively rolls out edge wave structure in the width direction of strip during the rolling of silicon steel strip in cold rolling mill;The strip after rolling is cleaned and dried regularly;Then flame nozzle is set on both sides of the running path of strip, and the edge wave area is burned by high-temperature flame through the flame nozzle, to completely remove the rolling oil stain remaining in edge wave fold.The present application can solve the problem of magnesium oxide leakage coating and high-temperature annealing bonding caused by oil stain remaining in edge wave area, significantly improve product yield and quality stability.

Description

Technical Field

[0001] This invention relates to the field of silicon steel strip manufacturing technology, and more specifically, to a method for online removal of residual oil stains in the edge ripple area of ​​strip steel during the cold rolling production of high-grade silicon steel and grain-oriented silicon steel, particularly a process for removing stubborn oil stains in edge ripple folds using a directional high-temperature flame. Background Technology

[0002] High-grade silicon steel, especially grain-oriented silicon steel, is widely used in core components of power equipment such as transformers and motors due to its excellent magnetic properties. During the cold rolling process of grain-oriented silicon steel, the high silicon content (typically >3%) results in high brittleness and hardness, and coupled with high rolling tension, the strip is highly prone to deviation during operation. Deviation not only leads to edge damage but can also cause strip breakage in severe cases, resulting in production line downtime and economic losses.

[0003] To prevent deviation, modern cold rolling processes commonly employ an "edge wave control technique": by adjusting the roll gap crown, rolling force, and tension distribution, a wave-shaped structure of a certain height and width, known as an edge wave, is artificially rolled onto both sides of the strip in the width direction. The presence of the edge wave makes the tension distribution in the strip edge area more uniform, effectively absorbing and buffering stress concentration during deviation, and significantly reducing the risk of strip breakage during the correction process. Therefore, edge waves have become an indispensable process in the cold rolling production of high-grade silicon steel.

[0004] However, the introduction of edge waves also brings new technological challenges. During the rolling process, a large amount of rolling oil must be used to reduce friction and cool the rolls and strip. The rolling oil inevitably flows into the troughs of the edge waves and gradually accumulates and concentrates during subsequent coiling and transportation, forming stubborn oil residue. Due to the complex geometry of the edge wave area (with uneven folds), conventional cleaning processes, while effectively removing oil stains from the smooth surface of the strip, are ineffective against residual grease hidden deep within the troughs.

[0005] Currently, a typical silicon steel strip cleaning line usually includes processes such as alkaline spraying, alkaline brushing, electrolytic cleaning, hot water rinsing, and drying. These processes are effective at cleaning smooth surfaces, but for wavy areas, the brush rollers cannot reach deep into the troughs, the current density of electrolytic cleaning is unevenly distributed in the folds, and hot water rinsing is insufficient to completely remove grease. Therefore, some oil residue always remains inside the wavy areas. If this residual oil is not thoroughly removed, it will have a fatal impact on the subsequent magnesium oxide coating process.

[0006] Magnesium oxide coating is a critical process in the production of grain-oriented silicon steel. Its function is to coat the strip surface with a uniform layer of magnesium oxide slurry, serving as a protective layer during high-temperature annealing and preventing interlayer adhesion. Magnesium oxide slurry is typically water-based and incompatible with grease. When oil residue remains in the edge areas of the strip, the magnesium oxide slurry cannot spread and adhere properly, resulting in localized missed coatings. Subsequently, the strip coil undergoes high-temperature annealing in a bell-type furnace (temperatures up to 1200℃, durations exceeding 20 hours). Due to the lack of a protective magnesium oxide protective layer, the missed coating areas experience severe interlayer adhesion and even sintering under high temperature and pressure, generating scrap coils that are difficult to peel off. This scrap not only causes significant economic losses but also severely impacts production efficiency and delivery cycles.

[0007] To address these issues, the industry has attempted various solutions. For example, extending cleaning time, increasing cleaning temperature, and increasing scrubbing intensity have yielded limited results and significantly increased energy consumption and equipment wear. Some studies have proposed using laser cleaning or plasma cleaning technologies, but these involve high equipment investment and complex maintenance, making large-scale application on continuous production lines difficult. Furthermore, some have tried adjusting edge wave parameters to reduce edge wave height, but excessively low edge wave height can compromise anti-deviation performance, resulting in more harm than good.

[0008] Therefore, there is an urgent need to develop a novel, integrated process that can completely solve the oil stain cleaning problem in edge-wavy areas while retaining their anti-deviation advantages. This invention addresses this need by creatively proposing an online directional flame cleaning method. Through the thermal effect of a high-temperature flame, residual oil stains in the edge-wavy area are precisely and efficiently removed, thereby ensuring the uniformity of the subsequent magnesium oxide coating and avoiding high-temperature annealing sintering accidents. Summary of the Invention

[0009] The purpose of this invention is to provide a method and system for directional flame removal of residual oil stains in the edge and wave areas of silicon steel strips.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: 1. A method for removing residual oil stains from the edge and wavy areas of silicon steel strip using a directional flame, comprising the following steps: S1. During the cold rolling process of silicon steel strip, by controlling the roll gap crown, tension and rolling force parameters of the rolling mill, a continuous edge wave structure is actively rolled on both sides of the strip width direction. S2. Perform multi-stage cleaning and drying treatment on the rolled strip steel; S3. At least one pair of flame nozzles are symmetrically arranged on both sides of the strip running path, so that the flame nozzles spray flames toward the edge wave area of ​​the strip, and the oil stains remaining in the edge wave folds are removed by the heat effect of the flames. In step S3, the spray direction of the flame nozzle is inclined at an angle of 45°±5° relative to the running direction of the strip. The nozzle orifice is located on the outer side of the strip end face, and the flame jet enters the trough channel formed by the edge wave structure at this inclined angle. The flame temperature T and the edge wave height H satisfy the following relationship: T = 400 + 30 × ln(H / 1.5) The unit of H is mm, the unit of T is °C, and 1 mm ≤ H ≤ 5 mm.

[0011] In one embodiment, in step S3, the flame jet forms a wall-attached jet within the trough of the edge wave, and a local recirculation zone is formed at the bottom of the trough. The effective residence time of the gas in the recirculation zone is 1.5-2 times the residence time of the flame jet outside the trough.

[0012] In one embodiment, in step S3, multiple pairs of flame nozzles are spaced apart on the strip running path, and a high-pressure air purging nozzle is provided between two adjacent pairs of flame nozzles. The angle between the spray direction of the high-pressure air purging nozzle and the flame spray direction is 120°-150°. The control system dynamically adjusts the opening and closing sequence of each flame nozzle and the high-pressure air purging nozzle according to the strip running speed, so that the strip edge wave area undergoes three-stage treatment in sequence: first flame heating, high-pressure air purging, and second flame heating.

[0013] In one embodiment, when the strip running speed V < 0.5 m / s, the control system reduces the flame temperature to 380-400°C; when the strip running speed V > 1.5 m / s, the control system increases the flame temperature to 430-450°C; when the strip running speed V is in the range of 0.5-1.5 m / s, the flame temperature is determined according to the formula of claim 1.

[0014] In one embodiment, in step S3, the flame power of the flame nozzle is controlled between 65kW and 75kW, and the contact length between the flame and the strip is controlled between 300mm and 350mm.

[0015] In one embodiment, the width of the edge wave structure is 20-40mm, the height H is 1-5mm, and it extends continuously along the length of the strip.

[0016] In one embodiment, step S2 includes the following steps in sequence: alkaline spraying, alkaline brushing, electrolytic cleaning, hot water cleaning, and hot air drying.

[0017] In one embodiment, a control system is also included, which is interlocked with the production line speed signal. When the production line speed is detected to be lower than a set threshold, the gas supply to the flame nozzle is automatically shut off, and when the production line speed recovers to the set range, the flame nozzle is automatically ignited and restarted.

[0018] In one embodiment, step S3 is followed by a high-pressure air purging process, in which high-pressure air is used to purge the loose sintered material remaining after flame burning.

[0019] The present invention also provides a directional flame cleaning system for residual oil stains in the edge and wave areas of silicon steel strip for implementing the above method, comprising: Edge wave rolling unit is used to form edge wave structures on both sides of the strip during the cold rolling process; The cleaning and drying unit is used to perform multi-stage cleaning and drying on the rolled strip steel; The flame handling unit includes at least one pair of flame nozzles, a gas supply system, an ignition device, a flame monitor, and a control system; The control system is electrically connected to the production line speed sensor, flame monitor, gas valve and ignition device, and is used to automatically control the start and stop of the flame nozzle and adjust the power according to the production line speed.

[0020] The present invention, employing the above-mentioned technical solution, has the following beneficial effects: by introducing directional high-temperature flame treatment, it successfully solves the long-standing industry problem of oil residue in the edge wave area of ​​silicon steel strip. The high temperature of the flame can penetrate deep into the edge wave trough, thoroughly removing grease that conventional cleaning methods cannot reach, without adversely affecting the properties of the strip substrate. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the method for removing residual oil stains from the edge and wave areas of silicon steel strip in Example 1.

[0022] Figure 2 This is a cleaning process flow diagram of step S2 in the method for removing residual oil stains from the edge and wave areas of silicon steel strip.

[0023] Figure 3 This is a schematic diagram of the method for removing residual oil stains from the edge and wave areas of silicon steel strip in Example 2.

[0024] Figure 4 This is a schematic diagram of the method for removing residual oil stains from the edge and wave areas of silicon steel strip in Example 3. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to provide a clearer understanding of the purpose, features, and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative of the essential spirit of the technical solution of the present invention.

[0026] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0027] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0028] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0029] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0030] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0031] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] This invention provides a directional flame method for removing residual oil stains from the edge and wavy areas of silicon steel strips, comprising the following steps: S1. Edge Wave Generation and Rolling: During the cold rolling of silicon steel strip, continuous edge wave structures are actively rolled on both sides of the strip width by controlling the roll gap crown, tension, and rolling force parameters. The geometric parameters of the edge waves balance anti-deviation effect and subsequent processing feasibility, with a preferred width of 20-40mm and a height H of 1-5mm, extending continuously along the strip length. Within this range, the edge waves effectively increase edge tension stability without causing the flame to be unable to reach the bottom of the trough due to excessively deep wrinkles.

[0034] S2. Cleaning and Drying: The rolled strip undergoes multi-stage cleaning and drying to remove most of the oil and particulate matter from the surface and edge areas. The cleaning process can employ conventional steps such as alkaline spraying, alkaline brushing, electrolytic cleaning, hot water cleaning, and hot air drying. The aim is to remove oil from the smooth areas of the strip while reducing oil levels in the edge areas to a certain extent, thus creating conditions for subsequent flame treatment.

[0035] S3. Directional Flame Burning: At least one pair of flame nozzles are symmetrically arranged on both sides of the strip's running path, with the spray direction of the flame nozzles horizontally facing the edge wave structure of the strip and at an inclination angle of 45°±5° to the strip's running direction, so that they spray high-temperature flames toward the edge wave area of ​​the strip. The nozzle orifice is located on the outer side of the strip's end face, and the flame jet enters the trough channel formed by the edge wave structure at this inclination angle, with the jet direction along the trough extension direction.

[0036] In step S3, the flame nozzles are positioned directly opposite the end faces of the strip on both sides of its width, and the flames emitted by each flame nozzle simultaneously cover the edge wave areas of the upper and lower surfaces of the strip, achieving simultaneous burning on both sides and thus improving processing efficiency.

[0037] The combustion gas used in the flame nozzle is a clean energy source, which can be natural gas, hydrogen, or a mixture of both. Natural gas is low in cost and has a stable supply; hydrogen combustion produces only water, with no pollution, making it suitable for applications requiring ultra-high cleanliness. Mixed gases can strike a balance between cost and environmental protection.

[0038] Extensive experiments revealed that when a flame jet enters a wave trough at an angle of 45°±5°, it forms a wall-attached jet on the trough wall and a local recirculation zone at the bottom of the trough. The effective residence time of the gas within this recirculation zone is 1.5-2 times that of the flame jet outside the trough. This recirculation zone allows the high-temperature gas to fully contact the inner surface of the trough, thoroughly thermally decomposing grease that conventional cleaning methods cannot reach. When the jet angle deviates too much from 45°, the jet either directly impacts the bottom of the trough and bounces back (too large an angle, nearly vertical) or directly penetrates the trough channel without forming an effective recirculation zone (too small an angle, nearly horizontal). Neither approach results in a sufficient residence time for the recirculation zone at the bottom of the trough, drastically worsening the grease removal effect.

[0039] The high temperature of the flame causes the oil residue remaining in the edge folds to undergo instantaneous thermal decomposition, vaporization, or sintering, thus completely removing the oil. Based on the production line layout and processing requirements, the flame jet direction is along the strip's running direction. This co-current direction reduces the disturbance of the flame to the strip's airflow, making it suitable for high-speed or airflow-sensitive conditions. It also avoids prolonged contact between the flame and the strip, which could negatively impact strip quality.

[0040] Furthermore, the quantitative relationship model formula between flame temperature T and edge wave height H is as follows: T = 400 + 30 × ln(H / 1.5) The unit of H is mm, the unit of T is °C, and 1 mm ≤ H ≤ 5 mm.

[0041] This relationship reflects the following physical mechanism: as the edge wave height H increases, the depth-to-width ratio of the trough channel increases, the flow resistance after the jet enters the trough increases, and the accumulation effect of hot gas in the trough is enhanced. Therefore, only a moderate increase in temperature is needed to maintain the same effective heat flux at the bottom of the trough. This nonlinear quantitative relationship can accurately match the pyrolysis requirements of oil contaminants under different edge wave heights, while avoiding excessive oxide layer thickness on the strip surface due to excessively high flame temperatures. When the flame temperature is lower than the temperature given by this relationship, the pyrolysis rate of oil contaminants in the edge wave trough is insufficient; when the flame temperature is much higher than the temperature given by this relationship, the oxide layer thickness on the strip surface in the edge wave area increases significantly, affecting the subsequent coating quality.

[0042] Preferably, in step S3, the flame parameters are precisely controlled: the flame temperature T is determined according to the above formula, the flame power is controlled between 65kW and 75kW, and the contact length between the flame and the strip is controlled between 300mm and 350mm. These parameter ranges have been experimentally verified to ensure sufficient pyrolysis of the oil contaminant without causing thermal damage to the strip substrate or excessive oxidation.

[0043] More preferably, when the strip running speed V < 0.5 m / s, the control system reduces the flame temperature to 380-400℃; when the strip running speed V > 1.5 m / s, the control system increases the flame temperature to 430-450℃; when the strip running speed V is in the range of 0.5-1.5 m / s, the flame temperature is determined by the above-mentioned quantitative relationship model formula.

[0044] As an improvement, multiple pairs of flame nozzles are spaced apart along the strip's running path, with high-pressure air purging nozzles positioned between adjacent pairs. The high-pressure air purging nozzles' spray direction forms a 120°-150° angle with the flame spray direction. The control system dynamically adjusts the opening and closing sequence of each flame nozzle and high-pressure air purging nozzle based on the strip's running speed, ensuring that the strip's edge ripple area undergoes a three-stage treatment: first flame heating, high-pressure air purging, and second flame heating. The first flame heating thermally decomposes and sintersects the oil contaminants within the troughs into loose solids. The interstage high-pressure air purging removes these loose sintered materials, creating a channel for the second flame to directly act on deeper residual oil contaminants, producing a synergistic effect that cannot be achieved with single-stage flame treatment.

[0045] After step S3, a high-pressure air purging process can be added to purge the loose sintered material remaining after flame burning, further ensuring the surface of the edge wave area is clean and providing a perfect foundation for subsequent magnesium oxide coating.

[0046] This invention also provides a directional flame cleaning system for residual oil contamination in the edge area of ​​silicon steel strip for implementing the above-described method, comprising: an edge rolling unit, a cleaning and drying unit, a flame treatment unit, and a control system. The flame treatment unit includes at least one pair of flame nozzles, a gas supply system, an ignition device, a flame monitor, and a control system. The control system is electrically connected to the production line speed sensor, the flame monitor, the gas valve, and the ignition device, and is used to automatically control the start / stop and power adjustment of the flame nozzles according to the production line speed.

[0047] Example 1 This embodiment provides a directional flame method for removing residual oil stains from the edge and wavy areas of silicon steel strips. For example... Figure 1 and Figure 2 As shown, the method includes the following steps: S1. Edge Wave Generation and Rolling: High-grade grain-oriented silicon steel 30Q130 is produced on a 1450mm cold-rolled continuous annealing production line of a steel plant. During the cold rolling process, by adjusting the roll gap crown, rolling force, and front and rear tension of the mill, a stable edge wave structure 11 is formed on both sides of the strip 1. The width of the edge wave is controlled at 35mm, and the height is controlled at 2mm. These edge wave parameters effectively prevent deviation and facilitate subsequent flame treatment.

[0048] S2. Cleaning and Drying: The rolled strip enters the cleaning section. For example... Figure 2 As shown, the cleaning section includes, in sequence: an alkaline spray tank (concentration 3%, temperature 65℃), an alkaline scrubbing machine (equipped with nylon brush rollers), and an electrolytic cleaning tank (concentration 2%, temperature 70℃, current density 2000A / m). 2 The process includes a hot water rinsing tank (temperature 60℃) and a hot air dryer. The strip passes through the cleaning section at a speed of 1.0 m / s, and the oil and impurities on the smooth surface are thoroughly removed, but a small amount of rolling oil remains in the edge waviness area.

[0049] S3, Directional Flame Treatment: The cleaned and dried strip steel enters the flame treatment zone. For example... Figure 1 As shown, two flame nozzles 2 are symmetrically arranged on both sides of the strip's running path. The spray direction of the flame nozzles 2 is set to be along the strip's running direction, forming a 45° angle with the strip's centerline. The flame nozzles 2 are directly facing the left and right end faces of the strip 1, and the flames emitted by each nozzle simultaneously cover the edge wave areas of the upper and lower surfaces of the strip.

[0050] The flame nozzle uses natural gas as the combustion gas, with a purity of ≥95%. The flow rates of natural gas and combustion air are controlled by a proportional valve to maintain a stable flame temperature of 425±10℃. The power of a single nozzle is set to 70kW. The contact length between the flame and the strip is ensured to be 320mm by adjusting the distance between the nozzle and the strip.

[0051] During the flame treatment, the residual oil in the edge area undergoes rapid thermal decomposition at high temperatures. Most of the oil is converted into gas and carried away by the exhaust system, while a small amount of heavy components that are difficult to vaporize are sintered into loose solid residues. These sintered materials naturally fall off during the subsequent tension roller straightening process or are removed by subsequent high-pressure air purging.

[0052] S4. Control System Interlock: This embodiment is equipped with a PLC control system, which is interlocked with the main speed signal of the production line. When the production line speed is below 5 m / min (e.g., during belt threading, shutdown, or low-speed operation), the control system automatically cuts off the gas solenoid valve, the flame nozzle immediately extinguishes, and an audible and visual alarm is issued. When the production line speed recovers to above 5 m / min, the control system automatically executes the ignition procedure, and the flame nozzle resumes normal combustion within 3 seconds. This interlock mechanism effectively prevents overheating damage to the strip.

[0053] The strip treated in this embodiment has a clean surface in the edge waviness area, with no visible oil stains. Subsequently, a magnesium oxide coating is applied (coating amount 5 g / m²). 2 The coating is uniform and without any missed areas. After coiling, it undergoes high-temperature annealing at 1200℃ for 20 hours in a bell-type furnace. After uncoiling, the strip surface shows no signs of adhesion or sintering, and the product qualification rate is significantly higher than that of similar products that have not undergone flame treatment.

[0054] Example 2 This embodiment is basically the same as Embodiment 1, except that the spray direction of the flame nozzle is set to the counter-current direction, that is, against the direction of strip steel movement. Figure 3 As shown, the spray direction of the flame nozzle 2 is at a 135° angle to the running direction of the strip (45° in the opposite direction), and is also directly facing the two end faces of the strip, while simultaneously scorching the edge wave areas on the upper and lower surfaces.

[0055] Other parameters are the same as in Example 1: edge width 35mm, height 2mm; cleaning process is the same; flame temperature 425±10℃, power 70kW, contact length 320mm; natural gas is used; equipped with PLC speed interlock control.

[0056] Because the reverse flame jet direction delays the contact time between the strip and the flame, a thick and dense iron oxide scale (oxide layer) forms on the surface of the edge area when the operating speed is low (below 0.8 m / s). This oxide scale is not only difficult to remove in subsequent processes, but also increases surface roughness. When the operating speed is extremely low (below 0.3 m / s), overheating occurs at the strip edges, manifesting as pitting, peeling, or even microcracks on the surface. This damage is irreversible and will directly lead to product scrap.

[0057] When only the flame nozzle spray direction differs from that in Example 1, a reverse flame nozzle leads to product scrapping, while a forward flame nozzle does not exhibit this phenomenon. Analysis suggests this may be because the forward-flowing flame airflow direction aligns with the surface boundary layer airflow generated by the strip's movement. This facilitates the rapid discharge of flame heat and combustion products along the trough direction, rather than reverse-flow entrainment, thus forming a stable and efficient heat exchange zone within the trough. Simultaneously, the contact temperature between the flame and the strip surface can be precisely controlled within a window of 400-450°C, which is precisely above the pyrolysis temperature of rolling oil (mainly composed of synthetic esters and mineral oil) (approximately 350-400°C), but far below the rapid growth temperature of silicon steel oxide scale (approximately 570°C). This achieves selective removal of rolling oil without the formation of oxide scale.

[0058] Example 3 This embodiment, based on embodiment 1, increases the number of flame nozzles to four, arranged at intervals along the strip's running direction, such as... Figure 4 As shown. The spacing between adjacent nozzles is 2500mm (greater than the distance the strip travels per second). Each nozzle is independently controlled, and the number and power of ignition can be adjusted according to the strip's running speed and the degree of oil residue.

[0059] For example, when the strip running speed is 0.8 m / s, the oil residue is relatively light, so only the first two nozzles are turned on, each with a power of 70 kW; when the strip running speed is 1.2 m / s, the oil load increases, so all four nozzles are turned on, each with a power of 70 kW; when the strip running speed exceeds 1.5 m / s, the nozzle power can be increased to 75 kW to ensure sufficient treatment intensity.

[0060] The multi-nozzle arrangement allows the flame to come into contact with the strip steel in stages, which enhances the processing effect and prevents the strip steel quality from being affected by excessively long single burning time. It is especially suitable for working conditions with serious oil residue or high production line speed.

[0061] Example 4 Under the conditions of edge wave height H=2mm, flame temperature 425℃±5℃, power 70kW, and contact length 320mm, the angle between the flame jet and the strip's running direction was varied. The effective residence time of gas at the bottom of the wave trough (a relative value with the jet's residence time outside the wave trough as a baseline of 1.0), oil residue rate, and oxide layer thickness on the strip surface were measured. The results are shown in Table 1. Table 1 Comparison of treatment effects under different spray angles Table 1 data shows that a significant critical effect exists at a 45° angle. At this angle, the jet forms an optimal adhesion effect with the trough wall, causing the high-temperature gas to generate a sweeping flow trajectory within the trough, resulting in a peak gas residence time (1.8 times) and a reduction in oil residue rate to approximately 2%. Deviating from 45°, the effective residence time of the gas within the trough decreases significantly, and the oil removal rate deteriorates sharply. In particular, when the angle decreases to 15°, the jet directly "penetrates" the trough, resulting in a gas residence time of only 0.5 times and a rebound in oil residue rate to 25%. The existence of this critical effect fully demonstrates that the selection of a 45° angle is not a conventional design or a simple trade-off in this field.

[0062] The residence time of the gas at the bottom of the trough in Table 1 above was determined using CFD numerical simulation. Specifically, a two-dimensional cross-sectional model of the trough was established using Fluent software, with the inlet jet velocity set to 150 m / s (corresponding to the actual jet velocity at 70 kW power) and the outlet as a pressure outlet. A tracer particle release surface was set in the bottom region of the trough, and the time for particles to travel from entering the trough to passing through the bottom recirculation zone (defined as a region where the velocity vector points to the wall normal and the velocity is <0.1 m / s) was calculated. The relative residence time is the ratio of this value to the time required for particles to traverse a path of equal length in an open space without boundary obstruction under the same jet conditions. Simulation results show that when the incident angle is 45°, the particles form a spiral trajectory in the recirculation zone, and the average traversal time is approximately 1.8 times that of the unbounded jet, indicating that the high-temperature flue gas and the trough wall underwent sufficient heat and mass exchange.

[0063] The oil residue rate in Table 1 above was determined using scanning electron microscopy (SEM) backscattered electron imaging analysis. The specific steps are as follows: A sample (10mm × 10mm) from the edge wave region after flame treatment was taken, and five fields of view were randomly selected at the bottom of the wave trough in the backscattered electron mode of a scanning electron microscope at 500x magnification. Since the residual oil has been transformed into carbonaceous solid residue after high-temperature sintering, it appears as dark / black patches in the backscattered image, while the silicon steel substrate appears as bright white, and the grayscale difference between the two is significant.

[0064] The acquired images were imported into ImageJ image analysis software. A uniform grayscale threshold was set to separate the dark residue areas from the substrate areas, and the percentage of the dark area in the total field of view was automatically calculated. The oil residue rate (%) is the arithmetic mean of the five field-of-view area percentages.

[0065] As a control, edge wave samples from the same batch that had not undergone flame treatment (only routine cleaning) were taken, and the proportion of the dark area at the bottom of the wave trough was determined using the same method as the original residual rate benchmark.

[0066] Example 5 The optimal flame temperature was determined under different edge wave heights H using a fixed spray angle of 45°, power of 70kW, and contact length of 320mm. The acceptance criteria were an oil pyrolysis rate ≥98% and an oxide layer thickness ≤1.0μm. The results are shown in Table 2. Table 2. Optimal flame temperature and treatment effect at different edge wave heights The data in Table 2 show that when the wave height H = 2.0-4.0 mm, the temperature given by the formula of this invention can simultaneously meet the dual requirements of preventing deviation and removing oil stains.

[0067] Example 6 A steel mill has fully implemented the technology of this invention on its 1450mm silicon steel cold-rolled continuous annealing production line. This production line mainly produces high-grade grain-oriented silicon steel (30Q120, 30Q130, etc.). Before the application of this invention, problems such as magnesium oxide coating defects and annealing adhesion caused by oil residue in the edge area occurred frequently, resulting in an average of about 50 tons of scrap coils per month, with a pass rate of only about 92%.

[0068] After applying this invention, the production line underwent the following modifications: A flame treatment device is added between the cleaning section outlet and the magnesium oxide coating machine, which includes four pairs of flame nozzles (four on each side), uses natural gas as fuel, and the nozzles are arranged at 500mm intervals along the running direction of the strip.

[0069] Configure a PLC control system, which is interlocked with the main speed signal of the production line to achieve automatic ignition and safety protection.

[0070] It adopts a co-current flame direction, a spray angle of 45°, a flame temperature of 425±10℃, and a power of 70kW / nozzle.

[0071] High-pressure air purging is added after flame treatment.

[0072] After the upgrade, the production line operated stably, oil stains in the edge areas were thoroughly removed, and the magnesium oxide coating was uniform and without any omissions. Statistics from six months of continuous operation show that waste rolls caused by adhesion decreased to less than 2 tons per month, and the product qualification rate increased to over 99.3%. Simultaneously, because there was no need to extend the cleaning time, the production line speed was maintained or even slightly increased, resulting in significant overall benefits.

[0073] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for removing residual oil stains from the edge and wavy areas of silicon steel strip using a directional flame, characterized in that, Includes the following steps: S1. During the cold rolling process of silicon steel strip, by controlling the roll gap crown, tension and rolling force parameters of the rolling mill, a continuous edge wave structure is actively rolled on both sides of the strip width direction. S2. Perform multi-stage cleaning and drying treatment on the rolled strip steel; S3. At least one pair of flame nozzles are symmetrically arranged on both sides of the strip running path, so that the flame nozzles spray flames toward the edge wave area of ​​the strip, and the oil stains remaining in the edge wave folds are removed by the heat effect of the flames. In step S3, the spray direction of the flame nozzle is inclined at an angle of 45°±5° relative to the running direction of the strip. The nozzle orifice is located on the outer side of the strip end face, and the flame jet enters the trough channel formed by the edge wave structure at this inclined angle. The flame temperature T and the edge wave height H satisfy the following relationship: T = 400 + 30 × ln(H / 1.5) The unit of H is mm, the unit of T is °C, and 1 mm ≤ H ≤ 5 mm.

2. The directional flame extinguishing method according to claim 1, characterized in that, In step S3, the flame jet forms a wall-attached jet within the trough of the edge wave, and a local recirculation zone is formed at the bottom of the trough. The effective residence time of the gas in the recirculation zone is 1.5-2 times that of the residence time of the flame jet outside the trough.

3. The directional flame extinguishing method according to claim 1, characterized in that, In step S3, multiple pairs of flame nozzles are spaced apart on the strip running path, and a high-pressure air purging nozzle is provided between two adjacent pairs of flame nozzles. The angle between the spray direction of the high-pressure air purging nozzle and the flame spray direction is 120°-150°. The control system dynamically adjusts the opening and closing sequence of each flame nozzle and the high-pressure air purging nozzle according to the strip running speed, so that the edge wave area of ​​the strip undergoes three stages of treatment in sequence: first flame heating, high-pressure air purging, and second flame heating.

4. The directional flame extinguishing method according to claim 1, characterized in that, When the strip running speed V < 0.5 m / s, the control system reduces the flame temperature to 380-400℃; when the strip running speed V > 1.5 m / s, the control system increases the flame temperature to 430-450℃; when the strip running speed V is in the range of 0.5-1.5 m / s, the flame temperature is determined according to the formula in claim 1.

5. The directional flame extinguishing method according to claim 1, characterized in that, In step S3, the flame power of the flame nozzle is controlled between 65kW and 75kW, and the contact length between the flame and the strip is controlled between 300mm and 350mm.

6. The directional flame extinguishing method according to claim 1, characterized in that, The width of the edge wave structure is 20-40mm, the height H is 1-5mm, and it extends continuously along the length of the strip.

7. The directional flame extinguishing method according to claim 1, characterized in that, In step S2, the multi-stage cleaning and drying process includes sequential alkaline spraying, alkaline brushing, electrolytic cleaning, hot water cleaning, and hot air drying.

8. The directional flame extinguishing method according to claim 1, characterized in that, It also includes a control system that is interlocked with the production line speed signal. When the production line speed is detected to be lower than the set threshold, the gas supply to the flame nozzle is automatically shut off. When the production line speed returns to the set range, the flame nozzle is automatically ignited and restarted.

9. The directional flame extinguishing method according to claim 3, characterized in that, Step S3 is followed by a high-pressure air purging process, which uses high-pressure air to purge the loose sintered material remaining after flame burning.

10. A directional flame cleaning system for residual oil contamination in the edge and ripple areas of silicon steel strip for implementing the method according to any one of claims 1-9, characterized in that, include: Edge wave rolling unit is used to form edge wave structures on both sides of the strip during the cold rolling process; The cleaning and drying unit is used to perform multi-stage cleaning and drying on the rolled strip steel; The flame handling unit includes at least one pair of flame nozzles, a gas supply system, an ignition device, a flame monitor, and a control system; The control system is electrically connected to the production line speed sensor, flame monitor, gas valve and ignition device, and is used to automatically control the start and stop of the flame nozzle and adjust the power according to the production line speed.

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