Method for efficiently eliminating nodules on roller surface of strip steel continuous annealing furnace at low cost

Abstract

The invention relates to the technical field of steel rolling surface control, and particularly discloses a low-cost and high-efficiency method for eliminating nodules on a roller surface of a strip steel continuous annealing furnace, which comprises the following steps: daily prevention of nodules on a furnace roller: optimizing a strip steel cleaning procedure: partially replacing alkali liquor in a cleaning tank every 24 hours, discharging only one third of the alkali liquor in the cleaning tank, and supplementing new alkali liquor; arranging a production plan; controlling the atmosphere in the furnace; the position of the furnace roller where nodulation occurs is judged according to the face type and the period of the roller mark of the furnace roller; loading a transition coil into a production line, and controlling the temperature of a heating section of an annealing furnace; a deviation rectifying device in the furnace is adjusted to enable the buckled strip steel to swing repeatedly on the surface of the nodulation furnace roller, and nodules on the surface of the furnace roller are scraped off through scraping and grinding; after the buckled transition roll is produced, checking the roll mark or pocking mark condition of the furnace roll by using a subsequent normal steel roll, and if the roll mark or pocking mark condition is not eliminated, continuing to insert the transition roll to grind the roll; according to the method, a prevention method and an emergency method are provided, the furnace roller nodulation is effectively controlled, the effect is better, the cost is lower, and the efficiency is higher.

Description

Technical Field

[0001] This invention relates to the field of steel rolling surface control technology, specifically to a low-cost and efficient method for eliminating nodules on the roll surface of continuous strip annealing furnaces. Background Technology

[0002] The continuous strip annealing furnace is the core equipment of the continuous annealing and continuous hot-dip galvanizing production line. The furnace rolls are the parts that come into direct contact with the strip inside the furnace. When producing strips with high alloy content, such as ultra-high strength steel of 780MPa level and above, or strips with dirty surfaces and iron powder adhering to them, nodules will form on the surface of the furnace rolls. These nodules press onto the subsequent strips, forming furnace roll marks and pitting defects, which affect the surface quality of the strip products and their subsequent use. Since the continuous annealing furnace is a closed high-temperature equipment, personnel cannot enter to process the roll surface at any time. Therefore, once a defect occurs, it will result in a batch of unqualified products. Opening and cleaning the furnace is very costly and delays production time by about a week, resulting in extremely high costs.

[0003] Patent CN 113798981 A discloses a method for rapidly eliminating nodules on the surface of furnace rolls. This method involves controlling the differential rotation of adjacent furnace rolls within the roll group in the nodule area, or the variable-acceleration rotation of a single furnace roll, to induce friction between the strip and the furnace rolls, thus eliminating the nodules online and avoiding furnace start-up. However, the contact between the strip and the furnace rolls is surface contact, which has limited effectiveness in eliminating nodules. In practice, it often requires more than 200 tons of strip to essentially eliminate the nodules, resulting in a significant amount of defects and high costs. Furthermore, this method is only an emergency measure and lacks long-term improvement mechanisms.

[0004] Patent CN 110396574 A also discloses a method for effectively preventing pitting in annealing furnaces. This method optimizes production planning and significantly reduces nodule formation on furnace rolls during production, effectively reducing the occurrence of pitting defects in strip steel, thereby achieving the goals of improving product yield, reducing costs, and increasing production capacity. However, this method only provides a routine improvement method for nodule formation caused by alloy precipitation in high-strength steel, and does not address methods for improving surface cleanliness of conventional products and nodule formation caused by residual iron on furnace rolls, nor does it provide emergency measures for severe nodule formation.

[0005] Patent CN119061340B discloses a method for preparing galvanized strip steel, galvanized strip steel, and automotive outer panels. This method slows down the precipitation of nodules by controlling the hydrogen and oxygen content in the annealing furnace atmosphere within a reasonable range. However, this is a conventional production method in the industry and not a method specifically designed to eliminate nodules. Therefore, there is a need to design a low-cost and efficient method to eliminate nodules on the roll surface of continuous annealing furnaces for strip steel, to solve the problems of inability to control furnace roll nodules in the long term, high cost of emergency treatment, and low efficiency in existing strip steel production. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a low-cost and efficient method for eliminating nodules on the roll surface of a continuous strip annealing furnace.

[0007] The technical solution adopted by this invention to solve its technical problem is: a low-cost and efficient method for eliminating nodules on the roll surface of a continuous annealing furnace for strip steel, comprising the following steps:

[0008] S1. Daily prevention of furnace roller nodule formation:

[0009] S11. Optimize the strip steel cleaning process: Replace part of the alkaline solution in the cleaning tank every 24 hours, drain only one-third of the alkaline solution from the cleaning tank and replenish with new alkaline solution.

[0010] S12. Arrange production plans;

[0011] S13. Control the atmosphere inside the furnace;

[0012] S2. Emergency treatment of furnace roller nodules:

[0013] S21. Determine the location of the furnace roller where nodules occur based on the surface and cycle of the furnace roller imprint;

[0014] S22. Load the transition roll into the production line and control the temperature of the heating section of the annealing furnace.

[0015] S23. After monitoring the movement of the wavy strip to the position of the nodulation furnace roller through the production line HMI screen or the camera inside the annealing furnace, adjust the correction device inside the furnace to make the wavy strip swing repeatedly on the surface of the nodulation furnace roller, and scrape off the nodules on the surface of the furnace roller.

[0016] S24. After the transition coil of the swivel is produced, use the subsequent normal steel coil to check the furnace roll marks or pits. If they are not eliminated, continue to insert transition coils for grinding.

[0017] Specifically, in step S11, the density of residual iron contaminants in the cleaning tank is higher than that of the alkaline solution, and the contaminants settle at the bottom of the cleaning tank. Only one-third of the alkaline solution is discharged from the bottom of the cleaning tank to eliminate the residual iron contaminants in the cleaning tank.

[0018] Specifically, the effective alkali concentration in the cleaning tank after alkali solution replacement is ≥95%; the oil content in the alkali immersion circulation tank is less than 3g / L; the oil content in the electrolytic cleaning circulation tank is less than 2g / L; the iron content in the alkali immersion circulation tank is less than 100mg / L; and the iron content in the electrolytic cleaning circulation tank is less than 40mg / L. The reflectivity of the cleaned strip steel is tested using a reflectivity meter to ensure that the surface reflectivity of the cleaned strip steel is controlled above 90%.

[0019] Specifically, the production plan in step S12 is as follows: when producing high-strength steel of grade 780MPa and above or other strip steel with a Mn mass percentage content greater than 1.6%, the single continuous production shall not exceed 300 tons, and then the production of low-carbon steel with a Mn mass percentage content less than 0.5% shall not be less than 500 tons.

[0020] Specifically, in step S13, the furnace atmosphere is controlled to induce the oxidation and precipitation of Mn and Si elements in the strip steel; the strip steel running speed is 90mpm~200mpm; the furnace pressure in the heating section is 2.0hPa~4.0hPa; the H2 content in the furnace is 3.0%~6.0% by mass fraction; the O content in the furnace is ≤20ppm by parts per million; and the dew point temperature is ≤-35℃.

[0021] Specifically, the transition roll in step S22 weighs 30-50 tons, is made of CQ grade material, has a thickness of 0.6-0.8 mm, and a width of 500-1000 mm equal to the length of the furnace roll body.

[0022] Specifically, after the 100m head of the transition coil enters the heating section of the annealing furnace, the temperature of heating section 1 is increased, causing the strip temperature to rise, while the temperature of heating section 2 and the soaking section is decreased. The strip temperature is 50~100℃ higher than the furnace temperature of heating section 2, causing the transition coil to warp.

[0023] Specifically, in step S23, the wavy strip is wrinkled and contacts the furnace roller in a multi-line contact manner at a large angle to the axial direction of the furnace roller. When the wavy strip swings left and right, it produces a scraper-like effect, repeatedly scraping and grinding along the axial direction of the furnace roller.

[0024] The present invention has the following beneficial effects:

[0025] The present invention provides a low-cost and efficient method for eliminating nodules on the roll surface of continuous strip annealing furnaces. This method is not only for nodules caused by alloy precipitation in high-strength steel, but also provides a method for preventing nodules on furnace rolls caused by residual iron in strip steel. It includes both preventive and emergency methods, and can effectively control nodules on furnace rolls in the long term with better results.

[0026] This invention presents a low-cost and efficient method for eliminating nodules on the roll surface of continuous annealing furnaces for strip steel. The enhanced cleaning effect requires only one-third replacement of the cleaning alkali solution, resulting in lower costs. A reflectivity meter is used to inspect the cleaned strip steel, ensuring controllable cleaning performance.

[0027] This invention presents a low-cost, high-efficiency method for eliminating nodules on the surface of continuous annealing furnace rolls of strip steel. The method involves online grinding of the furnace rolls without the need for furnace start-up. It utilizes controllable curved strip steel to scrape and grind the rolls, ensuring line contact between the curved strip and the roll surface. This avoids the adhesion and compression of nodules on the roll surface during surface-contact grinding. Only one roll of strip steel is needed to scrape away the nodules, whereas other techniques using normal strip steel with speed difference grinding typically require around 10 rolls. This method is more efficient, saving grinding time to produce more high-value-added, high-strength steel products. It is a low-cost, high-efficiency method.

[0028] The present invention provides a low-cost and efficient method for eliminating nodules on the roll surface of a continuous strip annealing furnace. The control of the furnace roll only requires adjusting the correction device and does not require artificially creating speed differences, thus avoiding the risk of strip breakage caused by abnormal fluctuations in furnace tension. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the curved strip steel and furnace rollers.

[0030] In the diagram: 1-furnace roller; 2-curved strip steel; 3-nodule. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, a low-cost and efficient method for eliminating nodules on the roll surface of a continuous strip annealing furnace includes two main parts: daily prevention of nodules on the furnace rolls and emergency treatment of nodules on the furnace rolls.

[0033] Daily methods to prevent nodule formation on furnace rollers:

[0034] 1. Optimize the strip steel cleaning process to remove residual oil and iron from the surface of cold-hardened strip steel, reducing the formation of nodules caused by residual iron being carried into the annealing furnace. Partially replace the alkaline solution in the cleaning tank every 24 hours, draining only one-third of the solution and replenishing with fresh alkaline solution. Since residual iron and other contaminants have a high density and settle at the bottom of the tank, draining only one-third of the cleaning solution from the bottom is sufficient to eliminate residual iron contaminants, effectively controlling the cost of changing the cleaning tank solution. Ensure an effective alkali concentration ≥95%; the oil content in the alkali immersion circulating tank needs to be less than 3g / L; the oil content in the electrolytic cleaning circulating tank needs to be less than 2g / L; the iron content in the alkali immersion circulating tank needs to be less than 100mg / L; and the iron content in the electrolytic cleaning circulating tank needs to be less than 40mg / L. Use a reflectivity meter to test the strip steel after cleaning, ensuring the surface reflectivity of the cleaned strip steel is controlled above 90%.

[0035] 2. Make reasonable production plans. When producing high-strength steel of grade 780MPa and above or other strip steel with Mn mass percentage content greater than 1.6%, the single continuous production shall not exceed 300 tons, and the subsequent production of low-carbon steel with Mn mass percentage content less than 0.5% shall not be less than 500 tons.

[0036] 3. Control the furnace atmosphere within a reasonable range to reduce the oxidation and precipitation of elements such as Mn and Si in the strip steel. The strip steel running speed is 90mpm~200mpm, the furnace pressure in the heating section is 2.0hPa~4.0hPa, the H2 content in the furnace is 3.0%~6.0% by mass fraction, the O content in the furnace is ≤20ppm by parts per million, and the dew point temperature is ≤-35℃.

[0037] Emergency treatment methods for furnace roller nodule formation:

[0038] 1. Determine the location of the furnace roller 1 where nodules occur based on the surface and cycle of the roller imprint on the furnace roller 1.

[0039] 2. A 30-50 ton transition coil is loaded into the production line. This transition coil is made of CQ grade material with a thickness of 0.6-0.8 mm. If it is too thin, the strip is prone to breakage; if it is too thick, it is difficult to produce warping. The width is the length of the furnace roll 1 minus (500-1000) mm. If it is too narrow, it is difficult to grind the entire roll surface; if it is too wide, it is prone to deviation and poses a risk. After the first 100m of the transition coil enters the heating section of the annealing furnace, the temperature of heating section 1 is increased to raise the strip temperature, while the temperature of heating section 2 and the soaking section is decreased. This results in the strip temperature being 50-100℃ higher than the furnace temperature of the subsequent heating section 2. If the temperature difference is too small, warping will not occur; if the temperature difference is too large, it will be difficult to control. If the temperature is too high, the strip will come into contact with the subsequent furnace rolls, which have a relatively lower temperature, and warping will occur under the action of thermal stress.

[0040] 3. After monitoring the movement of the wavy strip to the position of the furnace roller 1 with nodules 3 through the production line HMI screen or furnace camera, adjust the furnace correction device to make the wavy strip 2 swing repeatedly on the surface of the nodule furnace roller 1. The wavy strip 2 is wrinkled and contacts the furnace roller 1 in a multi-line contact at a large angle to the furnace roller axis. When it swings left and right, it produces a scraper-like effect, repeatedly scraping and grinding the nodules 3 on the surface of the furnace roller 1 along the axial direction.

[0041] 4. After the transition coil of the swivel is produced, use the subsequent normal steel coil to check the furnace roll 1 for the presence of roll marks or pits. If the marks are not eliminated, continue to insert transition coils for grinding.

[0042] Example 1

[0043] After producing 320 tons of high-strength steel HC780DPD+Z on a continuous hot-dip galvanizing production line, the line switched to DX51D+Z for regular production. Roller marks were found on the center of the upper surface. Based on the cycle and surface of the roller marks, the location was pinpointed to the guide roller in the slow cooling section of the annealing furnace. Manually adjusting the guide roller in the slow cooling section to repeatedly move the strip on the guide roller failed to eliminate the roller marks in the furnace. Subsequently, a DX51D+Z transition coil with a thickness of 0.7mm and a width of 1300mm was loaded, raising the plate temperature in the heating section to 830℃ and the furnace temperature in the soaking section to 760℃, causing warping. Then, the guide roller in the slow cooling section was manipulated to move the warped strip back and forth on the surface of the guide roller in the slow cooling section. After the transition coil scraped the guide roller in the slow cooling section, no more roller marks were found on the surface of the strip in subsequent normal production.

[0044] Example 2

[0045] After producing 300 tons of high-strength steel CR950 / 1180MS continuously on the continuous annealing production line, the line switched to DC01 for regular production. Pitting was found on the entire strip surface. The location was pinpointed to the tension roller in the soaking section of the annealing furnace by analyzing the roller marking cycle and surface type. Manually adjusting the soaking section's correction device to repeatedly move the strip across the tension roller failed to eliminate the pitting. Subsequently, a 0.6mm thick, 1500mm wide SPCC transition coil was loaded, raising the temperature in the heating section to 850℃ and the soaking section furnace temperature to 770℃, causing warping. The soaking section correction device was then manipulated to move the warped strip back and forth across the surface of the tension roller. After the transition coil scraped the tension roller in the soaking section, no further pitting was found on the surface of the strip in subsequent normal production.

[0046] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0047] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for low cost and efficient elimination of scale build-up on the rolls of a continuous annealing furnace for steel strips, characterized in that, Includes the following steps: S1. Daily prevention of furnace roller nodule formation: S11. Optimize the strip steel cleaning process: Replace part of the alkaline solution in the cleaning tank every 24 hours, drain only one-third of the alkaline solution from the cleaning tank and replenish with new alkaline solution. S12. Arrange production plans; S13. Control the atmosphere inside the furnace; S2. Emergency treatment of furnace roller nodules: S21. Determine the location of the furnace roller where nodules occur based on the surface and cycle of the furnace roller imprint; S22. Load the transition roll into the production line and control the temperature of the heating section of the annealing furnace. S23. After monitoring the movement of the wavy strip to the position of the nodulation furnace roller through the production line HMI screen or the camera inside the annealing furnace, adjust the correction device inside the furnace to make the wavy strip swing repeatedly on the surface of the nodulation furnace roller, and scrape off the nodules on the surface of the furnace roller. S24. After the transition coil of the swivel is produced, use the subsequent normal steel coil to check the furnace roll marks or pits. If they are not eliminated, continue to insert transition coils for grinding.

2. The method of low cost and efficient elimination of scale build-up on the rolls of a continuous annealing furnace for strip steel according to claim 1, characterized in that, In step S11, the density of residual iron contaminants in the cleaning tank is higher than that of the alkaline solution, and the contaminants settle at the bottom of the cleaning tank. Only one-third of the alkaline solution is discharged from the bottom of the cleaning tank to eliminate the residual iron contaminants in the cleaning tank.

3. The method of low cost and efficient elimination of scale build-up on the rolls of a continuous annealing furnace for strip steel according to claim 2, characterized in that, After the alkaline solution in the cleaning tank is replaced, the effective alkaline concentration is ≥95%; the oil content in the alkaline immersion circulation tank is less than 3g / L; the oil content in the electrolytic cleaning circulation tank is less than 2g / L; the iron content in the alkaline immersion circulation tank is less than 100mg / L; and the iron content in the electrolytic cleaning circulation tank is less than 40mg / L. The reflectivity of the strip steel after cleaning is tested using a reflectivity meter to ensure that the surface reflectivity of the cleaned strip steel is controlled above 90%.

4. The method of low cost and efficient elimination of scale build-up on the rolls of a continuous annealing furnace for strip steel according to claim 1, characterized in that, The production plan in step S12 is as follows: when producing high-strength steel of grade 780MPa and above or other strip steel with a Mn mass percentage content greater than 1.6%, the single continuous production shall not exceed 300 tons, and then the production of low-carbon steel with a Mn mass percentage content less than 0.5% shall not be less than 500 tons.

5. The method of low cost and efficient elimination of scale build-up on the rolls of a continuous annealing furnace for strip steel according to claim 1, characterized in that, In step S13, the furnace atmosphere is controlled to induce the oxidation and precipitation of Mn and Si elements in the strip steel; the strip steel running speed is 90mpm~200mpm; the furnace pressure in the heating section is 2.0hPa~4.0hPa; the H2 content in the furnace is 3.0%~6.0% by mass fraction; the O content in the furnace is ≤20ppm by parts per million; and the dew point temperature is ≤-35℃.

6. The method for cost-effectively eliminating nodules on the roll surface of a continuous strip annealing furnace according to claim 1, characterized in that, The transition roll in step S22 weighs 30-50 tons, is made of CQ grade material, has a thickness of 0.6-0.8 mm, and a width of 500-1000 mm equal to the length of the furnace roll body.

7. The method for cost-effectively eliminating nodules on the roll surface of a continuous strip annealing furnace according to claim 6, characterized in that, After the 100m head of the transition coil enters the heating section of the annealing furnace, the temperature of zone 1 of the heating section is increased, causing the temperature of the strip steel to rise. The temperature of zone 2 of the heating section and the soaking section is decreased. The temperature of the strip steel is 50~100℃ higher than the furnace temperature of zone 2 of the heating section, causing the transition coil to warp.

8. The method for cost-effectively eliminating nodules on the roll surface of a continuous strip annealing furnace according to claim 1, characterized in that, In step S23, the wavy strip is wrinkled, and the contact between the wavy strip and the furnace roller is multiple lines that are at a large angle to the axial direction of the furnace roller. When the wavy strip swings left and right, it produces a scraper-like effect, repeatedly scraping and grinding the furnace roller along its axial direction.

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