JP2016215247A - Width control method for hot rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a width control method for hot rolling that can stably achieve width reduction by preventing a slab (a material to be rolled) from curving even when a width reduction quantity of the slab is large in a hot rolling line for a steel plate.SOLUTION: The present invention relates to a width control method for hot rolling characterized in that: when a width of a material to be rolled is put in a target range after rolling by a rough rolling machine by performing width reduction of a slab using a width press device and a vertical rolling machine in combination in a hot rolling line where a continuous heating furnace, the width press device, and the rough rolling machine having the vertical roling machine are arranged, a temperature deviation in a width direction of the slab right before the slab is extracted from the continuous heating furnace is found; when the temperature deviation in the width direction of the slab is larger than a predetermined threshold, a pressure reduction quantity of the slab by the width press device is made less than a predetermined reference value or a lower-limit value of a reference range; and a width reduction quantity by the vertical rolling machine is increased to put a width of the rolled material having been roughly rolled within the target range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to width control in hot rolling that enables stable width reduction by preventing bending of a slab when performing width reduction of a slab (rolled material) in a hot rolling line of a steel sheet. Regarding the method.

  In a hot rolling line for steel sheets, a slab of the same width produced by a continuous casting machine is heated in a continuous heating furnace (hereinafter also simply referred to as “heating furnace”) while feeding the slab in the slab width direction. As a device for creating different widths according to the product specifications, a width press device that intermittently rolls down the slab in the plate width direction with a pair of press dies installed in a relative manner in the slab width direction, A vertical roll rolling mill is generally used that continuously rolls down the slab in the sheet width direction (width rolling) with a pair of vertical rolls (roller rolls) installed on the rolling mill in a relative heel direction in the slab width direction. is there.

  In the width reduction by this width press apparatus, the width reduction of about 300 to 350 mm at maximum is usually performed for the slab of about 900 to 2000 mm width, and from the slab cast to the same width by a continuous casting machine, It is possible to manufacture steel plate products with different widths according to product specifications.

  In that case, for example, in the technique disclosed in Patent Document 1, first, the width of the slab is roughly narrowed by a width press device, and then the unevenly deformed portion of the width side surface of the slab is uniformly formed in the longitudinal direction by a vertical roll rolling mill. It is trying to flatten.

  Moreover, as shown in Patent Document 2, in the vertical roll rolling mill, as the width reduction amount increases, the width drop amount of the leading end portion of the material to be rolled (the width of the leading end portion with respect to the width of the steady portion). Therefore, when the amount of width reduction is large, most of the width reduction is generally performed by a width press device.

  However, the shape of the slab used for manufacturing the hot-rolled steel sheet has a large width-to-thickness ratio of about 3 to 10, and the width of the slab in the width press apparatus is about 250 mm or more. A plastic unstable state occurs due to the width reduction in the press machine.

  That is, as shown in FIG. 4, the slab 1 tends to buckle upward or downward, and as shown in FIG. 5, the slab 1 tends to bend in the width direction.

  As a technique for preventing the buckling phenomenon of the slab as shown in FIG. 4, for example, as shown in Patent Document 3, a roll that sandwiches the slab in the vertical direction when performing width reduction with a width press device is used. There are techniques to use as appropriate.

JP 60-141301 A JP 2002-263702 A JP 2011-140056 A

  However, the method described in Patent Document 3 is effective in preventing buckling of the material to be rolled since the slab is restrained by a roll from the up and down direction, but cannot contribute to prevention of bending of the material to be rolled. When a large bend occurs in the material to be rolled, the bend becomes large and hits a guide or the like by a horizontal roll mill of a subsequent rough rolling mill, making rolling difficult.

  Therefore, with regard to the material to be rolled, which is likely to generate a large bend and has a large width reduction amount, the operator visually confirms the material to be rolled after the width reduction in the width press device and finds that the bend is large. Is temporarily stopped, and a treatment for removing the material to be rolled from the rolling line is performed, which has a problem that productivity is hindered.

  The present invention has been made in view of the above circumstances, and in the hot rolling line of a steel sheet, even when the width reduction amount of the slab is large, the bending of the slab is prevented and the width is stably increased. An object of the present invention is to provide a width control method in hot rolling that enables reduction.

  In the hot rolling line of the steel sheet, the present inventors have conducted an earnest investigation as to what operation condition caused the bending of the material to be rolled after the width reduction, as shown in FIG. It has been found that when the width reduction amount of the slab by the width press apparatus is large and the temperature deviation in the slab width direction immediately before extraction in the heating furnace is large, the material to be rolled after the width reduction is bent greatly. Here, the temperature deviation in the slab width direction is a difference between the temperature of the slab width end face on the heating furnace charging side and the temperature of the slab width end face on the heating furnace extraction side.

  Moreover, when the transition of the width direction temperature deviation of the material to be rolled after the heating furnace extraction was examined, as shown in FIG. 3, the width direction temperature deviation in the slab width direction temperature deviation immediately before the heating furnace extraction is It turned out that it does not appear easily in the temperature deviation in the width direction of the material to be rolled (bar).

  For this reason, even if the temperature deviation in the width direction of the slab immediately before extraction of the heating furnace is large, it is considered that no bending occurs in the width reduction by the vertical roll mill of the rough rolling mill.

  The present invention has been conceived based on the above findings and has the following characteristics.

  [1] In a hot rolling line in which a continuous heating furnace, a width press apparatus, and a rough rolling mill having a vertical roll mill are arranged, the width reduction of the slab is reduced by using the width press apparatus and the vertical roll mill in combination. When the width of the material to be rolled after rolling with a rough rolling mill is set to the target range, the temperature deviation in the width direction of the slab immediately before extracting the slab from the continuous heating furnace is obtained, and the temperature in the width direction of the slab When the deviation is larger than a predetermined threshold value, the width reduction amount of the slab by the width press device is further reduced below the predetermined reference value or the lower limit value of the reference range, and the width reduction by the vertical roll mill A width control method in hot rolling, characterized in that the amount is increased so that the width of the material to be rolled after rough rolling is within a target range.

  [2] When the temperature deviation in the width direction of the slab immediately before extracting the slab from the continuous heating furnace exceeds a predetermined threshold, the width reduction amount of the slab by the width press device is 250 mm or less. The width control method in hot rolling as described in [1] above.

  According to the present invention, in a hot rolling line for steel sheets, even when the width reduction amount of a slab (rolled material) by a width press apparatus and a vertical roll mill is large, the bending of the slab is prevented and stable. It becomes possible to perform width reduction. As a result, it is possible to prevent the productivity of the hot rolling line from being hindered due to the bending of the slab.

It is a block diagram of the hot rolling line of the steel plate in one Embodiment of this invention. It is the figure which showed the relationship between the width reduction amount of the slab by a width press apparatus, the slab width direction temperature deviation just before extraction with a heating furnace, and bending generation | occurrence | production. It is the figure which showed the relationship between the temperature deviation of the slab width direction just before heating furnace extraction, and the temperature deviation of the bar width direction after rough rolling. It is the figure which showed the buckling phenomenon of the slab. It is the figure which showed the bending phenomenon of the slab.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a hot rolling line for steel plates in one embodiment of the present invention. As shown in FIG. 1, in this hot rolling line, a slab (not shown) heated in a continuous heating furnace (hereinafter also simply referred to as “heating furnace”) 11 is first subjected to width reduction by a width press device 12. After that, the width is further reduced by the vertical roll rolling mill 14 provided in the rough rolling mill 13, and rolling in the horizontal roll rolling mill 15 provided in the rough rolling mill 13 and rolling in the finish rolling mill 16 are performed. Then, it is wound up by the winder 17.

  And the control apparatus (PLC; Programmable logic controller) 22 is a continuous heating furnace 11, the width press apparatus 12, the rough rolling mill 13 (the vertical roll rolling mill 14, the horizontal roll rolling mill 15), the finish rolling mill 16, and winding-up. The machine 17 is controlled, and a control computer (PC; process computer) 21 for controlling the control device 22 is based on the specifications of the material to be rolled, with the width press device 12 and the vertical roll rolling mill 14, It is determined to what extent the width reduction amount is set, and the control device 22 is instructed.

  Incidentally, in the conventional method, although the upper limit value Wu of the width reduction amount by the equipment specifications by the width press device 12 varies depending on the equipment specifications, it is generally set as 300 mm to 350 mm.

  On the other hand, in this embodiment, when the temperature deviation in the width direction of the slab immediately before extracting the slab from the continuous heating furnace 11 is obtained and the temperature deviation in the width direction of the slab is larger than a predetermined threshold value. Reduces the upper limit value of the width reduction amount of the slab by the width press device 12 from a predetermined upper limit value, thereby increasing the width reduction amount by the vertical roll mill 14 due to the insufficient width reduction amount. By doing so, the width of the material to be rolled after rough rolling (after rolling by the horizontal roll mill 15) is set to be within the target range. The slab is heated while being fed with the slab width direction aligned with the slab feed direction of the continuous heating furnace 11.

  Here, when the temperature deviation in the width direction of the slab immediately before extraction from the continuous heating furnace 11 is obtained, the control computer 21 calculates the temperature of the furnace acquired to calculate the input / output heat due to the atmosphere in the continuous heating furnace 11. Using the results and the form factor calculated from the slab arrangement to calculate the heat input and output due to thermal radiation from the slab in the heating furnace 11, numerical calculation (sequential calculation) of the three-dimensional heat conduction equation Immediately before the extraction, the temperature Tc of the slab width end face on the heating furnace 11 charging side and the temperature Te of the slab width end face on the heating furnace 11 extraction side are calculated, and the temperature deviation ΔT in the slab width direction is expressed by the following equation (1): Ask.

    ΔT = | Tc−Te | (1)

  Note that Tc and Te may be calculated by numerical calculation of the two-dimensional heat conduction equation by representing a specific position in the longitudinal direction of the slab.

  Further, Tc and Te may be calculated by actually measuring the temperature of the slab.

  When ΔT exceeds a predetermined threshold, the control computer 21 sets the upper limit value Wut of the width reduction amount by the width press device 12 as the reference value (or the width reduction amount based on the equipment specifications of the width press device 12). The lower limit value of the reference range) is set to a value smaller than Wu. For example, if the reference range of the width reduction amount based on the equipment specifications of the width press device 12 is 300 mm to 350 mm, Wu = 300 mm and Wut <300 mm.

  At this time, when the width of the material to be rolled (bar) is within the target range with the originally planned width reduction amount by the vertical roll rolling mill 14, the width reduction amount by the vertical roll rolling mill 14 is initially planned. However, if the width of the material to be rolled (bar) does not fall within the target range with the amount of width reduction by the vertical roll mill 14 originally planned, the control computer 21 In order to compensate for the shortage of the width reduction amount, the width reduction amount by the vertical roll mill 14 is increased and set.

  In this way, when the temperature deviation in the slab width direction immediately before extraction of the heating furnace 11 is high and the width reduction amount of the width press device 12 is large, the width press device 12 is likely to cause slab bending. It is possible to prevent the bending of the slab while reducing the width reduction amount and setting the bar width after the rough rolling to the target range.

  Examples of the present invention are shown below.

  In the example of the actual data shown in FIG. 2, it has been found that if the temperature deviation ΔT in the slab width direction immediately before extraction of the heating furnace 11 exceeds 55 ° C., a trouble due to the bending of the slab occurs. Set as. And the upper limit Wut of the width reduction amount of the width press apparatus 12 when (DELTA) T exceeded the threshold value 55 degreeC was set as 250 mm.

  In this way, when the width reduction amount by the width press device 12 and the width reduction amount by the vertical roll mill 14 are set, the bending of the slab that has occurred conventionally is completely eliminated, and the productivity of the hot rolling line by the bending of the slab is eliminated. It was possible to prevent the inhibition.

DESCRIPTION OF SYMBOLS 1 Slab 11 Continuous heating furnace 12 Width press apparatus 13 Rough rolling mill 14 Vertical roll rolling mill 15 Horizontal roll rolling mill 16 Finishing rolling mill 17 Winding machine 21 Control computer 22 Control apparatus

Claims (2)

  In a hot rolling line in which a continuous heating furnace, a width press apparatus, and a rough rolling mill having a vertical roll mill are arranged, the width reduction of the slab is performed by using both the width press apparatus and the vertical roll mill, When setting the width of the material to be rolled after rolling with a rough rolling mill to the target range, the temperature deviation in the width direction of the slab immediately before extracting the slab from the continuous heating furnace is obtained, and the temperature deviation in the width direction of the slab is determined in advance. If the threshold is larger than the predetermined threshold, the width reduction amount of the slab by the width press device is further reduced below the predetermined reference value or the lower limit value of the reference range, and the width reduction amount by the vertical roll mill is increased. A width control method in hot rolling, characterized in that the width of the material to be rolled after rough rolling is set to a target range.   When the temperature deviation in the width direction of the slab immediately before extracting the slab from the continuous heating furnace exceeds a predetermined threshold, the width reduction amount of the slab by the width press device is 250 mm or less. A width control method in hot rolling according to 1.

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