Disposal method for preventing strip breakage in furnace under sudden power failure condition of annealing furnace

Abstract

The invention discloses a disposal method for preventing strip breakage in a furnace under the condition of sudden power failure of an annealing furnace, and belongs to the technical field of steel smelting. Power supply is recovered after power failure reasons are eliminated, and then the interior of the furnace is cooled according to the quality and specification of strip steel after combustible gas in the furnace is discharged. And after the accumulation condition of the strip steel in the subsequent process is observed, all automatic centering systems in the furnace area are adjusted to be in a centering state, the tension of the strip steel is adjusted, the stacked steel is pulled out, and production is gradually recovered. According to the method, by designing and executing the specific standardized operation process aiming at the steel stacking part, the steel stacking fault can be efficiently and thoroughly eliminated, and chain accidents such as in-furnace strip breakage and equipment damage which are extremely easily caused by the steel stacking problem when a conventional furnace shutdown treatment method is adopted are fundamentally avoided.

Description

Technical Field

[0001] This invention belongs to the technical field of iron and steel smelting, and specifically relates to a method for preventing belt breakage in an annealing furnace in the event of a sudden power outage. Background Technology

[0002] The continuous annealing furnace is a core piece of equipment in the cold-rolled strip steel production process. Its main function is to eliminate the internal stress generated during strip rolling through continuous heating, holding, and cooling processes, thereby improving the strip's microstructure and mechanical properties. This enhances the surface quality, dimensional accuracy, and performance of the strip products, making it a crucial step in ensuring the quality of cold-rolled strip steel. In actual industrial production, continuous annealing furnace production lines require long-term, stable operation. The strip steel is transported at a set high speed and uniform velocity within the furnace, making the entire production system highly dependent on the stability of the power grid. However, the power grid system is affected by various factors such as external environmental interference and line faults. Voltage fluctuations and grid grounding are difficult to completely avoid. Once such grid anomalies occur, they inevitably lead to a complete power outage, loss of tension, and ultimately, a furnace shutdown.

[0003] In the event of a sudden power outage caused by a grid anomaly, the motor's brake is in the open state. The strip steel, operating at high speed and without stable tension, is highly susceptible to collision and folding in the aforementioned areas, resulting in large-scale steel accumulation. In furnaces without a strip breakage detection device (or with a malfunctioning device), this accumulation goes undetected by the operator. Immediately re-tensioning without addressing the accumulated steel will cause the folded portion to tighten further, eventually leading to strip breakage.

[0004] Currently, industry-standard solutions for shutting down continuous cold-rolled annealing furnaces are mostly designed based on conventional shutdown scenarios, failing to adequately consider the unique challenges of sudden power outages. If the conventional procedures used during normal shutdowns are applied to the strip steel after a sudden power outage, not only will existing folding defects remain unaddressed, but the mismatch between the treatment method and the actual condition of the strip can further exacerbate the problem of strip breakage within the furnace. Once the strip breaks, the fractured segments are prone to collisions and jamming with heating elements, guide rollers, and other equipment, resulting in significant scrapping of a large quantity of strip steel and severe damage to the annealing furnace, substantially increasing maintenance costs and time. Furthermore, the escalation of the shutdown disrupts the continuous operation of the production line, causing delays in subsequent production plans, reducing production efficiency, and resulting in significant economic losses and adverse production impacts for the company.

[0005] In summary, existing technologies lack effective methods for handling sudden power outages and shutdowns of cold-rolled continuous annealing furnaces caused by power grid anomalies. These methods cannot avoid the risks of strip folding, breakage, and accident escalation after such shutdowns. Therefore, there is an urgent need to propose a solution that adapts to the scenario of sudden power outages and shutdowns caused by power grid anomalies, in order to ensure the operational stability of cold-rolled continuous annealing furnace production lines and reduce production losses for enterprises. Summary of the Invention

[0006] To address the problem that existing annealing furnaces cannot effectively handle severe steel buildup after a sudden power outage, this invention provides a method for preventing strip breakage inside the furnace during a sudden power outage, thus solving the aforementioned problem.

[0007] The technical solution of this invention is as follows: A method for preventing belt breakage inside an annealing furnace in the event of a sudden power outage includes the following steps: (1) Confirm the root cause of the power outage and, after resolving the power outage, prepare to restore power to all motors on the production line; (2) Close all burners in the furnace area to prevent the strip from warping due to overheating; (3) Open the venting holes to cool down the atmosphere in the annealing furnace and remove the combustible hydrogen gas from the furnace; (4) Open the fixing pins of the front and rear compensating rollers in the furnace area to prevent the strip from breaking due to excessive tension when it is in a cooling and shrinking state; (5) Cool the furnace to the specified temperature according to the steel grade and specifications of the strip; (6) Observe the steel stacking situation of the strip in each cooling section; (7) Adjust all automatic alignment systems (CPC) of the cleaning section and the inlet looper to the alignment state and switch to manual control mode; (8) Restore the tension of the cleaning section and the inlet looper. After the tension stabilizes, reduce the looper's capacity to below 90%. The capacity here is the ratio of the actual amount of strip steel stored in the looper to the maximum designed storage capacity of the looper. The purpose is to reserve enough space for the strip steel to be re-rolled in the furnace. (9) Adjust all automatic centering systems (CPC) in the furnace area to the centering state and switch to manual control mode; this is to prevent deviation during rewinding; (10) Adjust the tension of the strip steel in the furnace to 2~3KN; (11) The furnace area is tensioned in the order of preheating section, heating section and slow cooling section. After the tension is stable, it is maintained for at least 10 minutes. The purpose of maintaining the tension for at least 10 minutes after the tension is established is to ensure the tension is stable and to avoid the breakage of the belt during the subsequent rewinding or start-up of production. (12) Establish an outlet loop tension of 2KN to eliminate loose strip steel in the outlet loop; (13) Open all the sealing rollers and stabilizing rollers inside the furnace; (14) Tensioning is carried out in the order of rapid cooling section and aging section, and is maintained for at least 10 minutes. Observe whether the steel pile in the rapid cooling section is pulled out. (15) After the stacked strips of each cooling section are completely pulled apart, tension is set up from the final cooling section to the furnace outlet; (16) Switch all automatic alignment systems (CPC) on the production line back to automatic mode; (17) Start production at a speed of 10~15m / min and pull the wavy strip out of the furnace area; strictly control the production speed at 10~15m / min to avoid secondary damage to the wavy strip or stacked strip due to excessive speed. (18) After the strip of steel that has been bent out of the furnace area is pulled out, the furnace area is ignited and heated up to resume production.

[0008] Furthermore, in step (3), when the rapid cooling section is in high hydrogen mode, the focus is on venting the combustible hydrogen gas inside the furnace.

[0009] Furthermore, in step (5), the strip steel includes SPCC, DC01 and above strength grade steels and cold-rolled low-carbon mild steels such as DC03, DC04, DC05, DC06 and DC07.

[0010] Furthermore, in step (5), the relationship between the steel grade, specifications, and furnace cooling temperature of the strip is shown in Tables 1 and 2 below: Table 1 - Relationship between SPCC or DC01 cold-rolled steel sheet specifications and furnace cooling temperature

[0011] Table 2 - Relationship between DC03~DC07 cold-rolled steel sheet specifications and furnace cooling temperature

[0012] Furthermore, in step (6), the focus is on observing the steel stacking situation of the strip in the final cooling section and the water quenching section.

[0013] Furthermore, in step (14), when tension is established in the rapid cooling section and the aging section, tension is strictly prohibited in the final cooling section, the water quenching section and the furnace outlet section.

[0014] Furthermore, in step (14), the stacked strip steel is observed to see whether it has moved or whether the stacked part has been pulled apart through the furnace zone final cooling inspection hole and the water quenching inspection hole; if the stacked strip steel has not moved, the tension is increased to 3~5KN to cause the stacked part to crack, and the tension is stopped after cracking.

[0015] Furthermore, in step (14), if the stacked portion still does not crack after the tension is increased to 3~5KN, the tension should not be increased further.

[0016] The beneficial effects of this invention are as follows: The method provided by this invention addresses the problem of severe steel buildup in specific areas of the furnace during sudden power outages in industrial production. By designing and implementing standardized operating procedures for these areas, this invention efficiently and thoroughly eliminates steel buildup faults, fundamentally avoiding the chain reactions of furnace belt breakage and equipment damage that are easily triggered by steel buildup issues when using conventional furnace shutdown methods. This improvement not only significantly reduces material losses, equipment maintenance costs, and downtime losses caused by sudden power outages, but also significantly improves equipment operational stability and production process continuity, thereby increasing overall production efficiency and creating greater economic benefits for enterprises. It also has broad prospects for industry-wide application. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0018] Example 1 (1) The unit experienced a power outage due to fluctuations in the external grid voltage. After the power outage was resolved, power was restored to all motors on the production line.

[0019] (2) Close all burners in the furnace area to prevent the strip steel from warping due to overheating.

[0020] (3) Open the venting holes to cool the atmosphere in the annealing furnace and at the same time discharge the combustible hydrogen in the furnace.

[0021] (4) Open the fixing pins of the front and rear compensation rollers in the furnace area.

[0022] (5) The steel grade of the strip is DC01, the specification is 0.7×1380mm, and the furnace temperature is reduced to 550℃.

[0023] (6) Observe the steel stacking situation in the rapid cooling section, final cooling section, water quenching section, etc., and focus on observing the steel stacking situation in the final cooling section and water quenching section.

[0024] (7) Set all CPCs in the cleaning section and the inlet looper to the centering state and switch to manual control mode to prevent deviation during rewinding.

[0025] (8) Restore the tension of the cleaning section and the inlet looper. After the tension is restored, reduce the looper amount of the inlet looper to 80% to leave space for the strip steel in the furnace to be re-rolled.

[0026] (9) Set all CPCs in all furnace areas to the centering state and switch to manual control mode to prevent deviation during rewinding.

[0027] (10) Modify the tension of the strip steel in the furnace to 2KN.

[0028] (11) Tensioning is carried out in the furnace area in the order of preheating section, heating section and slow cooling section. After the tension is stable, it is maintained for 10 minutes.

[0029] (12) Establish an outlet loop tension of 2KN to eliminate the loose strip steel in the outlet loop.

[0030] (13) Open all the sealing rollers and stabilizing rollers inside the furnace.

[0031] (14) The rapid cooling section and aging section of the furnace area are set up in sequence and held for 10 minutes. Observe whether the steel pile in the rapid cooling section is pulled out.

[0032] Construction is strictly prohibited in the final cooling section, water quenching section, and furnace outlet section at this time.

[0033] Observing through the final cooling inspection hole and water quenching inspection hole in the furnace area, it was found that the stacked strips had moved and the stacked parts had been pulled apart.

[0034] (15) After the stacked strips in the final cooling section and the water quenching section are completely pulled apart, tension is set up from the final cooling section to the furnace outlet.

[0035] (16) Switch all CPCs on the production line back to automatic mode.

[0036] (17) Start production at a speed of 10 m / min and pull the flaky part out of the furnace area.

[0037] (18) After the part of the gourd is pulled out of the furnace area, the furnace area is ignited and heated up to resume production.

[0038] Example 2 (1) The unit experienced a power outage due to the grounding of the transformer maintenance cable. After the power outage was resolved, power was restored to all motors on the production line.

[0039] (2) Close all burners in the furnace area to prevent the strip steel from warping due to overheating.

[0040] (3) Open the venting holes to cool the atmosphere in the annealing furnace and at the same time discharge the combustible hydrogen in the furnace.

[0041] (4) Open the fixing pins of the front and rear compensation rollers in the furnace area.

[0042] (5) The steel grade of the strip is DC05, the specification is 1.0×1640mm, and the furnace temperature is reduced to 550℃.

[0043] (6) Observe the steel stacking situation in the rapid cooling section, final cooling section, water quenching section, etc., and focus on observing the steel stacking situation in the final cooling section and water quenching section.

[0044] (7) Set all CPCs in the cleaning section and the inlet looper to the centering state and switch to manual control mode to prevent deviation during rewinding.

[0045] (8) Restore the tension of the cleaning section and the inlet looper. After the tension is restored, reduce the looper amount of the inlet looper to 80% to leave space for the strip steel in the furnace to be re-rolled.

[0046] (9) Set all CPCs in all furnace areas to the centering state and switch to manual control mode to prevent deviation during rewinding.

[0047] (10) Modify the tension of the strip steel in the furnace to 3KN.

[0048] (11) Tensioning is carried out in the furnace area in the order of preheating section, heating section and slow cooling section. After the tension is stable, it is maintained for 10 minutes.

[0049] (12) Establish an outlet loop tension of 2KN to eliminate the loose strip steel in the outlet loop.

[0050] (13) Open all the sealing rollers and stabilizing rollers inside the furnace.

[0051] (14) The rapid cooling section and aging section of the furnace area are set up in sequence and held for 10 minutes. Observe whether the steel pile in the rapid cooling section is pulled out.

[0052] Construction is strictly prohibited in the final cooling section, water quenching section, and furnace outlet section at this time.

[0053] When inspecting the final cooling inspection holes and water quenching inspection holes in the furnace area, it was observed that the stacked strips had not moved and the stacked parts had not been pulled apart. When the tension was increased to 5KN, the stacked parts were pulled apart.

[0054] (15) After the stacked strips in the final cooling section and the water quenching section are completely pulled apart, tension is set up from the final cooling section to the furnace outlet.

[0055] (16) Switch all CPCs on the production line back to automatic mode.

[0056] (17) Start production at a speed of 15 m / min and pull the curved part out of the furnace area.

[0057] (18) After the part of the gourd is pulled out of the furnace area, the furnace area is ignited and heated up to resume production.

[0058] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preventing belt breakage inside an annealing furnace in the event of a sudden power outage, characterized in that, Includes the following steps: (1) Confirm the root cause of the power outage and, after resolving the power outage, prepare to restore power to all motors on the production line; (2) Close all burners in the furnace area to prevent the strip from warping due to overheating; (3) Open the venting holes to cool down the atmosphere in the annealing furnace and remove the combustible hydrogen gas from the furnace; (4) Open the fixing pins of the front and rear compensation rollers in the furnace area; (5) Cool the furnace to the specified temperature according to the steel grade and specifications of the strip; (6) Observe the steel stacking situation of the strip in each cooling section; (7) Adjust all automatic alignment systems of the cleaning section and the inlet looper to the alignment state and switch to manual control mode; (8) Restore the tension of the cleaning section and the inlet looper, and after the tension stabilizes, reduce the looping volume of the inlet looper to below 90%; (9) Adjust all automatic centering systems in the furnace area to the centering state and switch to manual control mode; (10) Adjust the tension of the strip steel in the furnace to 2~3KN; (11) Tension the furnace area in the order of preheating section, heating section and slow cooling section, and maintain the tension for at least 10 minutes after it stabilizes; (12) Establish an outlet loop tension of 2KN to eliminate loose strip steel in the outlet loop; (13) Open all the sealing rollers and stabilizing rollers inside the furnace; (14) Tensioning is carried out in the order of rapid cooling section and aging section, and is maintained for at least 10 minutes. Observe whether the steel pile in the rapid cooling section is pulled out. (15) After the stacked strips of each cooling section are completely pulled apart, tension is set up from the final cooling section to the furnace outlet; (16) Switch all automatic alignment systems on the production line back to automatic mode; (17) Start production at a speed of 10~15m / min and pull the curved strip steel out of the furnace area; (18) After the strip of steel that has been bent out of the furnace area is pulled out, the furnace area is ignited and heated up to resume production.

2. The treatment method as described in claim 1, characterized in that, In step (3), when the rapid cooling section is in high hydrogen mode, the focus is on venting the combustible hydrogen gas inside the furnace.

3. The treatment method as described in claim 1, characterized in that, In step (5), the strip steel includes SPCC cold-rolled steel sheet or DC01 cold-rolled steel sheet.

4. The treatment method as described in claim 1, characterized in that, In step (5), the strip steel includes DC03 cold-rolled steel plate, DC04 cold-rolled steel plate, DC05 cold-rolled steel plate, DC06 cold-rolled steel plate or DC07 cold-rolled steel plate.

5. The treatment method as described in claim 3, characterized in that, The relationship between the steel grade, specifications, and furnace cooling temperature of the strip is as follows: A. When the strip thickness is ≤0.499mm: the furnace temperature is reduced to 400℃; B. When 0.499mm < strip thickness ≤ 0.61mm: For strip width ≤ 1300mm, the furnace temperature is reduced to 550℃; for strip width ≤ 1500mm, the furnace temperature is reduced to 500℃; for strip width ≤ 1860mm, the furnace temperature is reduced to 400℃. C. When 0.61mm < strip thickness ≤ 0.71mm: For strip widths ≤ 1100mm, the furnace temperature is reduced to 650℃; for strip widths between 1100mm and 1300mm, the furnace temperature is reduced to 600℃; for strip widths between 1300mm and 1500mm, the furnace temperature is reduced to 550℃; for strip widths between 1500mm and 1600mm, the furnace temperature is reduced to 500℃; and for strip widths between 1600mm and 1860mm, the furnace temperature is reduced to 400℃. D. When 0.71mm < strip thickness ≤ 0.81mm: For strip width ≤ 1300mm, the furnace temperature is reduced to 700℃; for strip width ≤ 1500mm, the furnace temperature is reduced to 600℃; for strip width ≤ 1860mm, the furnace temperature is reduced to 550℃. E. When 0.81mm < strip thickness ≤ 1.01mm: For strip widths between 1300mm and 1500mm, the furnace temperature is reduced to 700℃; for strip widths between 1500mm and 1860mm, the furnace temperature is reduced to 600℃. F. When 1.01mm < strip thickness ≤ 1.31mm: For strips with a width of 1500mm < 1860mm, the temperature inside the furnace is reduced to 650℃.

6. The treatment method as described in claim 4, characterized in that, The relationship between the steel grade, specifications, and furnace cooling temperature of the strip is as follows: A. When the strip thickness is ≤0.499mm: For strip width ≤ 1500mm, the furnace temperature is reduced to 400℃; for strip width ≤ 1860mm and 1500mm, the furnace temperature is reduced to 350℃. B. When 0.499mm < strip thickness ≤ 0.61mm: For strip width ≤ 1100mm, the furnace temperature is reduced to 450℃; for strip width ≤ 1600mm, the furnace temperature is reduced to 400℃; for strip width ≤ 1860mm, the furnace temperature is reduced to 350℃. C. When 0.61mm < strip thickness ≤ 0.71mm: For strip width ≤ 1300mm, the furnace temperature is reduced to 500℃; for strip width ≤ 1500mm, the furnace temperature is reduced to 450℃; for strip width ≤ 1860mm, the furnace temperature is reduced to 400℃. D. When 0.71mm < strip thickness ≤ 0.81mm: For strip widths ≤ 1100mm, the furnace temperature is reduced to 600℃; for strip widths ≤ 1300mm and 1100mm, the furnace temperature is reduced to 550℃; for strip widths ≤ 1500mm and 1300mm, the furnace temperature is reduced to 500℃; for strip widths ≤ 1860mm and 1500mm, the furnace temperature is reduced to 450℃. E. When 0.81mm < strip thickness ≤ 0.91mm: For strip widths ≤ 1100mm, the furnace temperature is reduced to 650℃; for strip widths ≤ 1300mm and 1100mm, the furnace temperature is reduced to 600℃; for strip widths ≤ 1500mm and 1300mm, the furnace temperature is reduced to 550℃; for strip widths ≤ 1860mm and 1500mm, the furnace temperature is reduced to 500℃. F. When 0.91mm < strip thickness ≤ 1.11mm: For strip width ≤ 1100mm, the furnace temperature is reduced to 700℃; for strip width ≤ 1500mm, the furnace temperature is reduced to 600℃; for strip width ≤ 1860mm, the furnace temperature is reduced to 550℃. G. When 1.11mm < strip thickness ≤ 1.31mm: For strip widths between 1100mm and 1500mm, the furnace temperature is reduced to 700℃; for strip widths between 1500mm and 1860mm, the furnace temperature is reduced to 600℃. H. When 1.31m < strip thickness ≤ 1.8mm: For strip widths between 1300mm and 1500mm, the furnace temperature is reduced to 700℃; for strip widths between 1500mm and 1860mm, the furnace temperature is reduced to 600℃.

7. The treatment method as described in claim 1, characterized in that, In step (6), the focus is on observing the steel stacking situation of the strip in the final cooling section and the water quenching section.

8. The treatment method as described in claim 1, characterized in that, In step (14), when tension is established in the rapid cooling section and the aging section, tension is strictly prohibited in the final cooling section, the water quenching section and the furnace outlet section.

9. The treatment method as described in claim 1, characterized in that, In step (14), the stacked strip steel is observed to see if it moves or if the stacked part is pulled apart through the furnace zone final cooling inspection hole and water quenching inspection hole. If the stacked strip steel does not move, the tension is increased to 3~5KN to cause the stacked part to crack. After cracking, the tension is stopped from being increased.

10. The treatment method as described in claim 1, characterized in that, In step (14), if the stacked part still does not crack after the tension is increased to 3~5KN, the tension should not be increased further.

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