JP4419755B2 - Cold-rolled steel sheet scratch prevention method and cold-rolled steel sheet manufacturing equipment - Google Patents

Description

  The present invention relates to a technique for preventing scratches in a cold-rolled steel sheet and a cold-rolled steel sheet manufacturing facility.

  In general, cold-rolled steel sheets are manufactured by subjecting hot-rolled steel sheets that have been hot-rolled to each step of pickling, cold rolling, electrolytic cleaning, annealing, temper rolling, and recoil. It is done by. In recent years, a continuous annealing line in which the steps of electrolytic cleaning, annealing, and temper rolling are summarized has become mainstream. However, especially in the case of special steels such as SC materials (carbon steel for machine structural use) and SK materials (carbon tool steel materials), the purpose is to spheroidize carbides by heat treatment for a long time at high temperature. Even now, there are many cases where annealing is performed using a batch annealing furnace.

  FIG. 2: is a top view which shows an example of the equipment layout of the annealing-temper rolling-recoil process at the time of using the batch type annealing furnace concerning a prior art. In batch annealing using the batch annealing furnace 1, several stages of electrolytically cleaned coils are stacked on the base, and an inner cover and an annealing furnace are placed thereon, the coil is heated to a certain temperature, and the temperature is maintained for a certain period of time. After that, the annealing furnace is removed, and the coil is cooled and taken out. And after cooling to the temperature which can be charged in the temper rolling line 7 of the next process further in the dehumidification yard 6 etc., it charges in the temper rolling line 7 of the next process. Here, batch annealing is performed by stacking the inner diameter holes in the state of the up coil in the vertical direction. The coil after annealing is conveyed to the dehumidification yard 6 in the up coil state, and the dehumidification yard 6 But they are stacked and cooled. And before charging into the temper rolling line 7, it is common that the down-end 3 raises the hole of the coil inner diameter to the state of the down coil in the lateral direction.

  The steel strip that has been subjected to the temper rolling in the temper rolling line 7 is subjected to surface inspection and the like in the recoil line 8.

  During surface inspection at the recoil line, a wrinkle generated in the width direction of the steel strip was sometimes found. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-119575), when a coil that has been lifted and transported by a lifting magnet used for transporting a coil is landed on an impact when it is landed on a destination location, it is in an uneven state. It is described that the end face of the coil end face is in a state where the end faces are aligned due to an impact at the time of landing, and slip wrinkles (scratches in the width direction) occur on the steel strip surface due to slippage between the steel strip surfaces at that time. . Then, by optimizing the lifting speed of the lifting magnet used for carrying the coil, the impact between the lower surface of the coil of the lifting object and the landing surface can be mitigated, and slip wrinkles in the coil width direction can be reduced.

  Further, when the steel strip is taken out from the entrance side of the temper rolling line, which is the next process of batch annealing, longitudinal scratches (winding creases) may occur due to winding tightening due to tension. This occurs when the exit side winding tension in the electrolytic cleaning process is lower than the temper rolling line entry side delivery tension, but also due to a temperature difference inside and outside the coil during the batch annealing process. Another reason is that the stress inside the coil becomes non-uniform, resulting in loose winding.

For example, in Patent Document 2 (Japanese Patent Laid-Open No. 5-295453), by using a double inner cover and optimizing the cooling rate, the coil internal temperature is made uniform during the heating and cooling processes, and seizure flaws and winding tightening are achieved. It is possible to reduce wrinkles.
JP-A-8-119575 JP-A-5-295453

  However, the steel strip discovered at the time of the surface inspection in the recoil line even if the method described in Patent Document 1 prevents the occurrence of slip flaws when the steel strip coil is conveyed by the lifting magnet. There is a problem that wrinkles generated in the width direction cannot be completely eliminated. Further, the method described in Patent Document 2 has a problem that the production efficiency is lowered because the heating and cooling speeds are limited.

  In recent years, demands on the quality of steel sheet products have become stricter, and scratches on steel strip coils have resulted in the product value of products being impaired. Therefore, the steel plate taken up by the take-up device has a problem in that the yield of the product is lowered because the portion where the scratch exists is cut off.

  The present invention has been made to solve the above-described problems, and provides a cold-rolled steel plate scratch prevention method and cold-rolled steel plate manufacturing equipment capable of preventing the occurrence of scratches in the width direction and longitudinal direction of steel strip coils. The purpose is to do.

  The inventors of the present invention have identified the location where the scratches of the cold-rolled steel sheet are generated and examined the cause of the occurrence.

  As a result of observing the entire production line of cold-rolled steel sheets, after batch annealing of steel strip coils, when the coil cooled in the dehumidification yard is inserted into the temper rolling line, the state is changed from the up coil state to the down coil state. It was found that a scratch due to lateral misalignment occurred when the coil was raised. Furthermore, the cause of the occurrence is that the coil is loosened due to heat shrinkage during cooling in the dehumidification yard, and the lateral deviation occurs when the coil in which the loosening occurs is raised from the up coil state to the down coil state. Woke up and found that scratches occurred.

  In addition, when the above-mentioned loosening of the winding is expanded in the dehumidification yard, the winding tightening when the steel strip is discharged from the temper rolling line entry side of the next process is increased, and the occurrence of scratches in the longitudinal direction of the steel strip is further increased. I also found out.

  Usually, the charging to the temper rolling line is performed after the outer peripheral temperature of the coil becomes about 40 ° C. or less due to the heat resistance problem of the equipment, the stability problem of the temper rolling, and the like. On the other hand, raising the up coil cooled in the dehumidification yard to the state of the down coil has been performed immediately before charging the temper rolling line. Therefore, conventionally, the up coil cooled in the dehumidification yard is brought into the down coil state after the outer peripheral temperature of the coil is at least 50 ° C. or less.

  On the other hand, as a result of detailed observation of the coil winding looseness during cooling in the dehumidifying yard by the present inventors, when the outer peripheral temperature of the coil is about 80 ° C., the coil I found the fact that the loosening of the rolls was remarkably expanded. Coil loosening expands as the heat shrinkage in the cooling process after batch annealing increases with the progress of cooling, but the meaning of the temperature of 80 ° C. is notably observed as winding looseness. It means that the temperature starts to be about 80 ° C.

  That is, it has been found that if the coil is raised from the up-coil state to the down-coil state when the coil outer peripheral temperature is 80 ° C. or higher and the coil winding is not yet loosened, lateral deviation can be prevented. In addition, when the coil is in a down-coiled state while the winding looseness is not significant, the frictional restraining force between the steel strips due to the coil's own weight acts compared to the state in the up-coiled state, preventing the winding loosening and the longitudinal direction. It was found to be effective in preventing scratches.

The present invention has been made based on the above findings and has the following characteristics.
[1] After annealing in a batch-type annealing furnace and after cooling, after removing the inner cover, the steel strip coil before transporting to the dehumidifying yard has an outer peripheral temperature of the steel strip coil of less than 80 ° C. before, scratch prevention method of cold-rolled steel sheet, which comprises the state of the a Ppukoiru the state of the down coil.
[2 ] The steel strip coil after the annealing in the batch type annealing furnace is provided with a down-ender for changing the steel strip coil from an up-coil state to a down-coil state before transporting the steel strip coil to a dehumidification yard. Manufacturing equipment for cold-rolled steel sheets.

  ADVANTAGE OF THE INVENTION According to this invention, the scratch prevention method of the cold-rolled steel plate which can prevent generation | occurrence | production of the width direction of a steel strip coil and a longitudinal direction scratch, and the manufacturing equipment of a cold-rolled steel plate are provided.

  Hereinafter, an example of the best mode for carrying out the present invention will be described.

  The method for preventing scratches of a cold-rolled steel sheet according to the present invention is a method for preventing a steel strip coil after annealing in a batch-type annealing furnace, before the outer peripheral temperature of the steel strip coil is less than 80 ° C. From the state of the up coil in the vertical direction, the hole in the inner diameter of the coil is changed to the state of the down coil in the horizontal direction.

  Here, the outer peripheral temperature of the steel strip coil can be measured using, for example, a contact-type or non-contact-type thermometer.

  After batch annealing of the steel strip coil, before the outer temperature of the steel strip coil becomes less than 80 ° C., that is, at a temperature of 80 ° C. or higher, the coil winding is not noticeably loose. Scratches caused by lateral misalignment that occurs when the coil is raised by raising the coil in the state, and scratches that occur in the longitudinal direction of the steel strip due to winding tightening when the steel strip is discharged from the entrance side of the temper rolling line as the next process It is possible to greatly reduce the occurrence of.

  The above-mentioned temperature of 80 ° C. means that, as described above, in the steel strip coil that is being cooled, it is a temperature of about 80 ° C. that starts to be observed as winding loosening.

  Here, the timing at which the steel strip coil is raised from the up-coil state to the down-coil state is after the inner cover is removed after cooling in the batch-type annealing furnace and before the conveyance to the dehumidification yard. It is preferable. By preventing the coil temperature from being lowered while being transported to the dehumidification yard, it is possible to prevent unevenness of the coil end surface by repeating the transport with the lifting magnet in the up-coiled state. This is because it is possible to prevent lateral displacement.

  FIG. 1 is a plan view showing an example of an equipment layout when a steel strip coil is raised from an up coil state to a down coil state before being conveyed to the dehumidifying yard.

  In FIG. 1, a region A is a region where a batch type annealing furnace group is installed, a region B is a region where a dehumidification yard is installed, and a region C is a region where a temper rolling line and a recoil line are installed. Each of the regions A, B, and C forms an independent region by air conditioning or the like, and a transport carriage 5 is installed between the regions to carry out and carry in the steel strip coil.

  In FIG. 1, the steel strip coil after annealing in the batch type annealing furnace 1 is cooled in the furnace, and after the inner cover is removed, it is conveyed to the downender 3 by the lifting magnet crane 2 in the state of the up coil. . The down-ender 3 performs an operation for raising the steel strip coil placed in the up-coil state to the down-coil state.

  At this time, in the down-ender 3, an operation for raising the steel strip coil to the state of the down coil is performed before the outer peripheral temperature of the steel strip coil becomes less than 80 ° C.

  The steel strip coil raised in the down coil state by the down-ender 3 is placed on the transport cart 5a that moves back and forth between the region A and the region B in the state of the down coil by the crane 4a. The steel strip coil placed on the transport carriage 5a and carried into the region B is stored in a designated position in the dehumidifying yard 6 by the crane 4b while also being in a down coil state.

  The steel strip coil stored in the dehumidifying yard 6 is cooled to a temperature at which temper rolling in the next process can be performed, and then the carriage 4b moves back and forth between the region B and the region C in the down coil state by the crane 4b. It is put on. The steel strip coil loaded on the conveyance carriage 5b and carried into the region C is charged into the entrance side of the temper rolling line 7 of the next process by the crane 4c while keeping the state of the down coil.

  The steel strip discharged from the steel strip coil in the down coil state inserted on the entrance side of the temper rolling line 7 is subjected to temper rolling in the temper rolling line. On the exit side, it is recoiled in the state of a down coil and is carried out.

  In the present invention, in the down-ender 3, the steel strip coil is raised to the down coil state before the outer peripheral temperature of the steel strip coil is less than 80 ° C., and thereafter, the conveyance is performed in the down coil state. Therefore, it is possible to greatly reduce the occurrence of scratches generated in the longitudinal direction of the steel strip due to winding tightening when the steel strip is paid out from the entrance side of the temper rolling line. This is presumably because, when the loosening of the coil is not remarkable, the frictional restraining force between the steel strips due to the weight of the coil acts and the expansion of the loosening can be prevented.

  The steel strip coil carried out to the exit side of the temper rolling line 7 is charged into the recoil line 8 of the next process by the crane 4c while being in the state of a down coil. In the recoil line 8, surface inspection of the steel strip is performed.

  Hereinafter, as an example of the present invention, in the equipment layout shown in FIG. 1, before the outer temperature of the steel strip coil is less than 80 ° C. in the downender 3, the steel strip coil is raised from the up coil state to the down coil state, After that, the result of examining the scratch occurrence rate in the steel strip surface inspection in the recoil line 8 when transporting in the down coil state is shown.

  Moreover, as a comparative example according to the conventional method, in the equipment layout shown in FIG. 2, immediately after the steel strip coil is batch-annealed, immediately before the coil cooled in the dehumidification yard is inserted into the temper rolling line (the outer peripheral temperature of the coil is about 50). (° C.) shows the result of examining the scratch occurrence rate in the steel strip surface inspection in the recoil line 8 when the coil is raised from the up coil state to the down coil state.

  In the present invention example, the rate of occurrence of scratches in the width direction and the longitudinal direction was about 1.2%, whereas in the comparative example, the rate of occurrence of scratches in the width direction and the longitudinal direction was About 6.5%.

  As described above, it was confirmed that the occurrence rate of the scratch in the width direction and the longitudinal direction is remarkably reduced by using the method of the present invention.

It is a top view which shows an example of the equipment layout in the case of raising a steel strip coil from the state of an up coil to the state of a down coil before conveyance to the dehumidification yard based on this invention. It is a top view which shows an example of the equipment layout of the annealing-temper rolling-recoil process at the time of using a batch type annealing furnace concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Batch type annealing furnace 2 Lifting magnet crane 3 Down-ender 4 Crane 5 Carriage cart 6 Dehumidification yard 7 Conditioning rolling line 8 Recoil line

Claims (2)

After completion of cooling by annealing in a batch type annealing furnace, after removing the inner cover, before the outer peripheral temperature of the steel strip coil is less than 80 ° C., the steel strip coil before being transported to the dehumidification yard , scratch prevention method of cold-rolled steel sheet, which comprises the state of the a Ppukoiru the state of the down coil. A cooling apparatus comprising a down-ender for changing the steel strip coil from an up-coiled state to a down-coiled state before transporting the steel strip coil after being annealed in a batch-type annealing furnace to a dehumidifying yard. Production equipment for rolled steel sheets.

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