JP6152837B2 - Cold rolled steel sheet manufacturing method and rolling mill - Google Patents

Description

  The present invention relates to a method for producing a cold rolled steel sheet and a rolling mill that can be preferably used in the production method. More specifically, this invention relates to the technique which can suppress generation | occurrence | production of the ear crack and plate fracture | rupture in the width direction edge part of a cold-rolled steel plate.

  When manufacturing a brittle material such as a cold-rolled steel sheet, especially an electromagnetic steel sheet, the incidence of ear cracking is high in the cold rolling process. This is a cause of lowering the yield. Moreover, the board fracture | rupture resulting from an ear crack may generate | occur | produce. This may lead to a decrease in productivity.

  Further, due to the material flow in the steel plate width direction in the vicinity of the plate end of the material to be rolled, the tensile stress generated due to insufficient elongation in the rolling direction with respect to the center portion of the plate width is caused, resulting in an ear crack.

  As a technique for preventing the occurrence of ear cracks, there is a technique in which a work roll end portion is rolled up and rolled as in Patent Document 1. Thereby, the rolling reduction of the edge part of a to-be-rolled material increases, the tensile stress of the edge part of the width direction is reduced, and it becomes possible to prevent an ear crack even if the to-be-rolled material is a brittle material.

JP-A-62-137110

  However, the tapered work roll is an effective work roll only for brittle materials, and tends to increase edge drop for other steel types. For this reason, the equipment having this tapered work roll is not an appropriate equipment when rolling a plurality of steel types. In addition, when a thin work roll is used to roll a thin material / hard material, the work rolls may come into contact with each other on the outer side in the width direction of the material to be rolled. At that time, since a part of the rolling load is applied to other than the material to be rolled, the rolling reduction with respect to the load is reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a cold-rolled steel sheet and a rolling mill that can prevent the occurrence of ear cracks.

  In order to solve the above problems, the present inventors have conducted intensive research. As a result, the present inventors heated at least a part of the contact region that contacts the end in the width direction of the steel sheet during rolling, and expands at least one of the pair of upper and lower work rolls facing each other across the pass line of the steel sheet. The present invention has been completed by finding that the above problems can be solved by cold rolling a steel sheet with a work roll having the expanded portion and the expanded portion. More specifically, the present invention provides the following.

  1. A method of manufacturing a cold-rolled steel sheet using a rolling mill, wherein at least one of a pair of upper and lower work rolls facing each other across a pass line of the steel sheet, in a contact region that comes into contact with an end in the width direction of the steel sheet during rolling A cold-rolled steel sheet comprising: an expanded portion forming step for heating at least a part to form an expanded portion; and a cold rolling step for cold rolling the steel plate with a work roll having the expanded portion. Manufacturing method.

  2. 2. The method for producing a cold-rolled steel sheet according to 1, wherein in the expanded portion forming step, the expanded portion is formed together with the upper and lower work rolls.

3. The rolling mill has a plurality of stands, and uses a rolling mill having a plurality of stands,
The method for producing a cold-rolled steel sheet according to 1 or 2, wherein the inflating part is formed on a work roll of a final stand.

  4). In the cold rolling step, the region to be heated is in the range of (plate thickness (mm) × 10) mm from the end in the width direction of the steel plate toward the inner side of the steel plate. A method for producing a cold-rolled steel sheet according to item 1.

  5. The rolling mill which has a heating part which heats at least one part of the contact area which contacts the width direction edge part of the said steel plate at the time of rolling at least one of a pair of upper and lower work rolls which opposes across the pass line of a steel plate.

  According to the present invention, a cold-rolled steel sheet can be produced while suppressing the occurrence of ear cracks (cracks at the end of the steel sheet). The present invention is particularly preferably applicable to brittle materials. Examples of the brittle material include electromagnetic steel sheets.

It is a figure which shows typically the stand which is a part of rolling mill, (a) is a front view, (b) is a side view. It is an enlarged view which shows the A section of FIG. 1 typically. It is a figure showing typically the case where it has a plurality of stands. It is a figure which shows typically the case where the highest position of an expansion | swelling part and the width direction end of a steel plate are not matched.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

FIG. 1 schematically shows a stand 1 which is a part of a rolling mill used in the present invention. Fig.1 (a) is a front view, (b) is a side view. FIG. 2 schematically shows an enlarged view of part A of FIG. In addition, a rolling mill provided with the stand shown in FIG. 1 is an example of the rolling mill of this invention.

  The stand 1 includes a work roll 10, an intermediate roll 11, a backup roll 12, and a heating device 13. The heating device 13 corresponds to a heating unit.

  As shown in FIG. 1, the stand 1 includes a work roll 10, an intermediate roll 11, and a backup roll 12 that are opposed to each other across the pass line of the steel plate S. When the steel plate S is conveyed between the work rolls 10, the steel plate S is rolled.

  As shown in FIG. 1, the heating device 13 is installed near the work roll 10 of the stand 1. The heating device 13 heats the work roll 10 at a position corresponding to the end in the width direction of the steel sheet S. Here, the heating method employed by the heating device 13 is typically induction heating. However, if a desired region on the surface of the work roll 10 can be expanded, other heating methods such as burner heating can be used. Also good.

  The “end in the width direction of the steel sheet S” is an area that affects the occurrence of ear cracks, and refers to the range of (thickness (mm) × 10) mm from the end in the width direction of the steel sheet S toward the inside of the steel sheet. Here, the plate thickness means the plate thickness on the entry side. In the present invention, the heating device 13 only needs to be able to heat at least a part of the end portion in the width direction of the steel plate S, and may heat a region including other than the end portion in the width direction of the steel plate S.

  As shown in FIG. 1, the heating device 13 is preferably provided on both of a pair of work rolls 10 facing each other across the pass line of the steel sheet S.

  The stand 1 preferably has a slide mechanism (not shown) that slides the heating device 13 in the width direction of the steel plate.

  The stand 1 preferably has an expansion amount control mechanism (not shown). The expansion amount control mechanism is for controlling the size of the expansion portion 100 described later, which is formed on the surface of the work roll 10 by the heating device 13, and specifically, as the expansion amount control mechanism, expansion is performed. Examples include a mechanism for switching the heating device 13 between ON and OFF while measuring the amount, and a mechanism for cooling when the heating amount is too large while measuring the expansion amount. Further, in cold tandem rolling, the coolant is normally injected toward the work roll 10, but this coolant injection control mechanism may be used as an expansion amount control mechanism to prevent overheating of the work roll 10. .

  The stand 1 preferably has a thermometer (not shown) for monitoring the surface temperature of the work roll 10. In particular, a thermometer that can measure the temperature of the region heated by the heating device 13 is more preferable.

  The rolling mill of the present invention may have a plurality of stands. In the case of having a plurality of stands, it is preferable that the heating device 13 is disposed at least on the final stand. In the case of a rolling mill having a plurality of stands, it is preferable to have the heating device 13 only in the final stand. In addition, the schematic diagram in the case of having a plurality of stands is shown in FIG.

Method for producing cold-rolled steel sheet The method for producing a cold-rolled steel sheet of the present invention can be carried out using the rolling mill shown in FIG. The manufacturing method of the cold-rolled steel sheet of this invention has an expansion part formation process and a cold rolling process.

  The expanded part forming step is to heat at least a part of a contact region that contacts the end in the width direction of the steel sheet S during rolling, at least one of the pair of upper and lower work rolls 10 facing each other across the pass line of the steel sheet S, It is a process of forming an inflating part.

  As shown in FIG. 2, in the work roll 10 heated by the heating device 13, the heated portion is expanded to form the expanded portion 100. For this reason, compared with the case where it does not heat, the rolling reduction of the edge part of the steel plate S can be increased at the time of the cold rolling process mentioned later. As a secondary effect, the expansion portion 100 increases the amount of deformation at the end of the steel sheet S, so that the temperature at the end increases greatly, thereby improving the crack resistance of the steel sheet S itself. Due to these effects, it is possible to effectively prevent the occurrence of ear cracks in the steel sheet S during the cold rolling process described later.

  The size of the expanded portion 100 formed in the expanded portion forming step is not particularly limited, and may be set as appropriate depending on the material and size of the steel sheet S. The optimum size of the expanding portion 100 can be determined by a rolling experiment in a laboratory. For example, when the steel plate S is thin and the steel plate S is hard, the work roll 10 has a large flatness during cold rolling. It cannot be effectively reduced. The size of the expansion unit 100 may be adjusted by changing the output of the heating device 13 or the like.

  In the expanded portion forming step, the expanded portion 100 may be formed in a region including a position in contact with the width direction end of the steel sheet S during cold rolling. However, when the expanded portion 100 and the steel sheet S come into contact with each other on the inner side of the steel sheet width direction end during cold rolling, the rolling reduction other than the width direction end of the steel sheet S also increases during cold rolling. If the rolling reduction other than the end in the width direction is increased, a problem of defective plate thickness may occur. For this reason, it is preferable to form the expansion part 100 which does not contact with a steel plate in parts other than a steel plate width direction edge part so that the rolling reduction of only the width direction edge part may increase at the time of cold rolling.

  In the expanded portion forming step, as shown in FIG. 2, the expanded portion 100 may be formed so as to be in contact with the width direction end of the steel sheet S during the cold rolling step described later from the viewpoint of enhancing the effect of the present invention. preferable. In particular, as shown in FIG. 2, it is preferable that the highest position of the expanding portion 100 corresponds to the width direction end of the steel sheet S. However, when the highest position of the expanded portion 100 is associated with the width direction end of the steel sheet S, when the expanded portion 100 comes into contact with a region other than the width direction end portion during cold rolling, FIG. As shown, it is preferable that the highest position of the inflating portion 100 is outside the width direction end of the steel sheet S.

  In the expansion part forming step, if the rolling mill provided with the heating device 13 is used for both of the pair of work rolls 10 facing each other across the pass line of the steel sheet S, the effect of the expansion part 100 appears from both surfaces of the steel sheet S. . Thereby, it becomes easier to prevent the cracking of the steel sheet.

  If the rolling mill provided with the stand 1 which has the slide mechanism (not shown) which slides the heating apparatus 13 in the width direction in the expansion part formation process is used, the position where the expansion part 100 is formed can be adjusted. Having a slide mechanism is effective when a desired heating location changes due to a change in the plate width or the like of the steel plate S.

  In the expansion portion forming step, it is preferable to use a rolling mill provided with a stand having an expansion amount control mechanism (not shown). If this mechanism is provided, the amount of expansion of the expansion unit 100 can be finely adjusted, and the occurrence of ear cracks can be more easily suppressed.

  In the expanded portion forming step, it is preferable to use a rolling mill provided with a stand 1 having a thermometer capable of measuring the surface temperature of the work roll 10, particularly the surface temperature of the region heated by the heating device 13. By monitoring the surface temperature of the work roll 10 and adjusting the heat supply to the work roll 10, excessive heat supply to the work roll 10 can be avoided. It is preferable to suppress excessive heat supply to the work roll 10 because problems such as reduction in roll surface hardness, cracks, and spalling can be more effectively suppressed.

  When using a rolling mill having a plurality of stands in the expanding portion forming step, the effect of preventing the ear cracking is enhanced by using a rolling mill having the work roll 10 having the heating device 13 in the final stand. This is because the occurrence of ear cracks in the final stand is remarkable. In addition, when the work roll 10 is heated in a stand before the final stand, the plate width end portion may not be sufficiently reduced in the final stand. For this reason, when using the rolling mill which has a some stand, it is desirable to heat the work roll 10 of only the last stand with the heating apparatus 13. FIG.

  The cold rolling step is a step of cold rolling the steel sheet S with the work roll 10 having the expanded portion 100. Occurrence of the ear cracks can be effectively prevented by the expanded portion 100 formed in the expanded portion forming step.

  An example of the present invention will be described in the case of performing cold rolling with a cold rolling mill as shown in FIG. The steel sheet was an electromagnetic steel sheet with a plate width of 1000 mm and was cold-rolled from a base plate thickness of 2.0 mm to 0.3 mm with a 6-stage, 4-stand tandem mill, and then the occurrence of ear cracks was investigated. The occurrence rate of the ear crack was calculated by observing the rolled coil and dividing the number of coils in which the ear crack was observed by the number of all the coils.

  The reduction ratio of each stand is 50% for one stand, 40% for 2 stands, 33% for 3 stands, and 25% for 4 stands.

  Table 1 shows the test results. A comparative example is a case where the work roll is not heated in all the stands.

  An example of an invention is a case where a work roll is heated with an induction heating device. In each case, the output of the heating device is changed. If the output of the heating device is small, the amount of expansion of the work roll is small, so the effect of preventing ear cracks is small, and the effect of preventing ear cracks increases as the output is increased. If it exceeds 8 kW, the effect of preventing ear cracks is saturated, and in this embodiment, about 8 kW is considered to be an appropriate output.

  Also, the conditions for heating the upper and lower work rolls, the condition that the heated region is within the range of (plate thickness (mm) × 10) mm from the width direction end of the steel plate to the inner side of the steel plate (heating on the plate path in the table) Width condition), and the condition of heating in the final stand is preferable.

  Inventive Examples 26 to 30 are cases where the heating range is wide among the inventive examples, and the power consumption increases. In terms of large power consumption, Invention Examples 26 to 30 are inferior in manufacturing cost compared to other Invention Examples. Moreover, although the incidence rate of the ear cracks of Invention Examples 26 to 30 is lower than that of the comparative example, it is slightly higher than that in the case where the roll heating width on the plate path is 10 mm.

  From the above test results, it was found that according to the present invention, the occurrence rate of ear cracks is greatly reduced.

DESCRIPTION OF SYMBOLS 1 Stand 10 Work roll 100 Expansion part 11 Intermediate | middle roll 12 Backup roll 13 Heating device S Steel plate

Claims (4)

A method of manufacturing a cold-rolled steel sheet using a rolling mill,
At least one of a pair of upper and lower work rolls facing each other across the pass line of the steel plate, at least a part of a contact region that comes into contact with the widthwise end of the steel plate at the time of rolling, forms an expanded portion. When,
In work roll having the expansion part, have a, a cold rolling step of cold rolling said steel sheet,
In the expanded portion forming step, the heated region is within a range of 3 mm or more (plate thickness (mm) × 10) mm or less from the width direction end of the steel plate to the inside of the steel plate, and the other regions are not heated. A method for producing a cold-rolled steel sheet, wherein:   The method for producing a cold-rolled steel sheet according to claim 1, wherein in the expanded portion forming step, the expanded portion is formed together with the upper and lower work rolls. The rolling mill has a plurality of stands,
The said expansion part is formed in the work roll of the last stand, The manufacturing method of the cold rolled steel sheet of Claim 1 or 2 characterized by the above-mentioned. At least one of a pair of upper and lower work rolls facing each other across the pass line of the steel plate, a heating unit that heats at least a part of a contact region that contacts the widthwise end of the steel plate during rolling,
The heating unit has a heating area within a range of 3 mm or more (plate thickness (mm) × 10) mm or less from the width direction end of the steel plate to the inside of the steel plate, and other heating is not performed. To roll.

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