JP2013099782A - Method for manufacturing steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel plate, which is excellent in production efficiency.SOLUTION: In the method for manufacturing a steel plate by heating and hot-rolling a steel slab to form a steel plate, cooling the steel plate on a cooling bed and conveying it to a shearing line, the method includes measuring the surface temperature of the steel plate at the exit of the cooling bed of which the entrance and the exit are located close to each other, before the steel plate is conveyed to the shearing line; returing the steel plate to the entrance of the cooling bed to be cooled again on the cooling bed, if the surface temperature is not lowered to a temperature necessary for the material characteristics of the steel plate; and during cooling, extracting another steel plate from the exit of the cooling bed to conveyed it to the shearing line.

Description

  The present invention relates to a method for producing a thick steel plate.

  The process of cooling the thick steel plate in the cooling bed is a gentle cooling rate that does not affect the material up to the temperature at which the thick steel plate brought in from the hot rolling process that is the previous process can be passed through the shearing process that is the subsequent process. In this step, uniform cooling is performed without impairing the shape. In addition, the cooling bed is a process having a function as a physical distribution buffer that absorbs the difference in the cooling bed when a difference in processing pitch between the rolling process and the shearing process occurs. Therefore, the cooling floor is required to have an area where the cooling can be performed and to have a function as a distribution buffer.

  In Patent Document 1, the interval between the steel sheets of the cooling floor is widened from the prediction of the future occupancy rate transition of the cooling floor and the actual occupancy ratio of the cooling floor from the position of the steel sheet in the cooling floor, tracking information, and the pitch difference prediction of the preceding and following processes. An automatic control device for a steel sheet cooling bed that automatically determines the operation mode of the cooling bed to be packed or packed is disclosed.

  Patent Document 2 discloses a method of manufacturing a steel plate that can select a cooling bed on which the steel plate is to be transported in accordance with the current production amount of the steel plate in the finishing line.

  In Patent Document 3, in a steel material transport system in which rolled steel materials are sequentially charged into a cooling bed and extracted into a finishing line while being transported and cooled in the cooling bed, a buffer zone is formed on the outlet side of the cooling bed. When the steel material in the cooling bed is cooled below the predetermined temperature, it is extracted to the finishing line without being placed in the buffer zone, and the steel material moved to the buffer zone before the buffer zone trouble or before the buffer zone is still at the predetermined temperature. A method of manufacturing a steel sheet is disclosed in which the steel sheet is placed in a buffer zone when it is not cooled to a certain level and is extracted to a finishing line when a predetermined condition is satisfied.

JP-A-9-108722 JP 2007-61871 A JP 2001-205316 A

  However, the techniques described in Patent Documents 1 and 2 have a problem that only the quality of the steel sheet is considered and the production efficiency in the cooling bed is not considered.

  That is, the techniques described in Patent Documents 1 and 2 only specify the operation method of the cooling bed when cooling the thick steel plate after hot rolling in the cooling bed, and before the shear line as the next step. When the temperature of the thick steel plate is higher than the target value, the steel plate must be allowed to cool on the table before shearing, while the thick steel plate scheduled to be sheared next must wait for the shearing work, The production efficiency was significantly reduced.

  In addition, since the technology described in Patent Document 3 is a linear cooling bed that can be transported in only one direction from the rolling line to the finishing line, there is a next process in which only a steel sheet having a predetermined temperature or less can be received. When the high-temperature finishing materials are continuously hot-rolled, the high-temperature finishing materials stay in the cooling bed until the temperature is lowered to a predetermined temperature or lower, and the cooling bed becomes a neck process in terms of production efficiency.

  An object of this invention is to provide the manufacturing method of the thick steel plate excellent in the production efficiency which solves the said subject.

  The gist of the present invention is as follows.

  [1] Hot-rolling a slab into a thick steel plate, cooling the thick steel plate with a cooling bed, and then shearing with a shearing line, after cooling with the cooling bed and before being sent to the shearing line When the surface temperature is measured and the surface temperature has not dropped to the temperature required for the material properties of the thick steel plate, the thick steel plate is returned to the cooling bed and re-cooled, while the other thick steel plates are cooled. A method for producing a thick steel plate, wherein the steel plate is extracted from the floor and sent to a shearing line.

  [2] In the method of manufacturing a thick steel plate in which the slab is heated and hot-rolled to obtain a thick steel plate, the thick steel plate is cooled in a cooling bed and carried out to a shearing line, the cooling bed inlet and outlet are arranged close to each other. Further, before carrying out the shear line at the outlet of the cooling bed, the surface temperature of the thick steel plate is measured, and when the surface temperature does not decrease to a temperature necessary for the material properties of the thick steel plate, the thick steel plate is Returning to the inlet of the cooling bed, cooling again in the cooling bed, and during that time, another thick steel plate is extracted from the outlet of the cooling bed and carried out to the shearing line. .

  According to the present invention, the thick steel plate having a high temperature before shearing is fed back to the cooling bed, so that the thick steel plate to be sheared next can be sheared, and the production efficiency is improved. In addition, since the cooling is sufficiently performed to the cooling temperature necessary for the material properties of the thick steel plate, the quality of the shear surface of the thick steel plate can be maintained at a certain level.

It is the schematic which shows the manufacturing process of a thick steel plate.

  FIG. 1 is a schematic view showing an example of a manufacturing process of a thick steel plate.

  After the slab is heated to a predetermined temperature in the heating furnace 1, the thick steel plate manufactured by hot rolling to a predetermined thickness by the hot rolling mill 2 is conveyed to the cooling bed 4 through the cooling device 3 and cooled to the predetermined temperature. Is done.

  The cooling bed 4 includes a first cooling bed 4a and a second cooling bed 4b, and the first cooling bed 4a and the second cooling bed 4b are connected by a transport roll table 4c. The steel plate that has been cooled is transported to the shearing line 5 via the transport route 4d and sheared to a predetermined product size.

  Conventionally, in order to improve the production efficiency of thick steel plates, it has been performed to automatically carry in and out the thick steel plates having various dimensions and materials to and from the cooling floor. As a result, when the thick steel plate cooled in the cooling bed was once placed on the line and transported to the shearing line which is the next process, it was found that the surface temperature of the thick steel plate was not cooled to the temperature necessary for securing material properties. However, since the next material had already arrived and could not be returned to the cooling bed, it had to be allowed to cool on the shear line. As a result, the shearing operation of the next material could not be performed, resulting in a decrease in production efficiency.

  Therefore, in the present invention, the surface temperature of the thick steel plate is measured before the shearing line (cooling bed outlet 4g), and if it is not cooled to the temperature required for the material properties of the thick steel plate, cooling is performed from the cooling bed outlet 4g. It returned to the cooling bed 4 again through the circulation route 4e to the floor inlet 4f, and it was made to cool. In the present invention, the cooling floor inlet 4f and the cooling floor outlet 4g are close to each other, and the circulation route 4e including the transfer table is disposed. Therefore, the thick steel plate can be easily returned to the cooling floor. In the meantime, the next material was extracted from the cooling bed outlet 4 g and carried to the shearing line 5 so that the shearing operation could be continued.

  The 1st cooling floor 4a is a buffer zone which detours a thick steel plate in order to cool a thick steel plate, and a thick steel plate is conveyed by a carrier chain and a walking beam (not shown). Further, the thick steel plate is transported from the first cooling floor 4a to the second cooling floor 4b by the transport roll table 4c. The second cooling bed 4b has the same structure as the first cooling bed 4a, and the steel plate is conveyed toward the cooling bed outlet 4g. Further, since the circulation route 4e composed of the conveyance rolls connecting the cooling bed outlet 4g and the cooling bed 4f is provided, the first cooling bed 4a and the second cooling bed 4b are connected in a loop by the conveyance roll table 4c and the circulation route 4e. The

  As a result, the thick steel plates in the first cooling bed 4a and the second cooling bed 4b can be circulated. Conventionally, when the cooling bed can be transported in only one direction, In contrast to the cooling method that only had to stop the conveyance until the temperature became lower than the predetermined temperature, the undercooled thick steel plate can be returned to the cooling floor to be cooled. It can be transferred to the shearing process.

  As a result, there was no thick steel plate waiting on the shear line, and the production efficiency was improved.

  Using SS400 thick steel plate having a product size of 30.1 mm in thickness, 2472 mm in width, and 20200 mm in length, the shearing efficiency and the state of care of the steel plate were examined. The results are shown in Table 1.

Ｎｏ．１〜Ｎｏ．５は発明例で、冷却不良となった一連の鋼板について冷却床への逆送を可能とする本数を段階的に増加させて剪断能率（生産能率）と剪断後の鋼板手入率（鋼板品質）を比較した。Ｎｏ．６は比較例であり、冷却床への逆送を行なわなかったものである。冷却床への逆送本数を増やして、十分冷却し、且つ他の鋼板を先に剪断した方が剪断能率（生産能率）、鋼板手入率（鋼板品質）ともに良好な結果が得られた。

No. 1-No. No. 5 is an example of the invention, in which the number of steel plates that have been poorly cooled is increased step by step to increase the number of steel plates that can be fed back to the cooling floor, and the shear efficiency (production efficiency) and the steel sheet care rate after shearing (steel quality) ). No. 6 is a comparative example in which the reverse feed to the cooling bed was not performed. When the number of sheets fed back to the cooling bed was increased to sufficiently cool and the other steel plates were sheared first, good results were obtained in terms of both shear efficiency (production efficiency) and steel plate maintenance rate (steel plate quality).

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Hot rolling mill 3 Cooling device 4 Cooling bed 4a 1st cooling bed 4b 2nd cooling bed 4c Conveyance roll table 4d Conveyance route 4e Circulation route (conveyance roll table)
4f Cooling bed inlet 4g Cooling bed outlet 5 Shear line

Claims (2)

  The slab is hot-rolled into a thick steel plate, and after cooling the thick steel plate in the cooling bed, the surface temperature of the thick steel plate before being sent to the shearing line after being cooled in the cooling bed is cooled. Measure and if the surface temperature has not dropped to the temperature required for the material properties of the steel plate, return the steel plate to the cooling bed and re-cool, while extracting other steel plates from the cooling bed And then sending it to a shearing line.   In the manufacturing method of a thick steel plate in which the slab is heated and hot-rolled to obtain a thick steel plate, the thick steel plate is cooled in a cooling bed and carried out to a shearing line, the cooling bed inlet and outlet are arranged close to each other. At the exit of the floor, before carrying out the shear line, measure the surface temperature of the thick steel plate, and if the surface temperature has not decreased to the temperature required for the material properties of the thick steel plate, the thick steel plate is removed from the cooling floor. A method for producing a thick steel plate, wherein the method returns to the inlet and cools again in the cooling bed, during which another thick steel plate is extracted from the outlet of the cooling bed and carried out to a shear line.

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