WO2014087524A1 - 熱延鋼板冷却方法 - Google Patents
熱延鋼板冷却方法 Download PDFInfo
- Publication number
- WO2014087524A1 WO2014087524A1 PCT/JP2012/081670 JP2012081670W WO2014087524A1 WO 2014087524 A1 WO2014087524 A1 WO 2014087524A1 JP 2012081670 W JP2012081670 W JP 2012081670W WO 2014087524 A1 WO2014087524 A1 WO 2014087524A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- hot
- cooling
- rolled steel
- steel sheet
- temperature
- Prior art date
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
- B21B37/76—Cooling control on the run-out table
Definitions
- the present invention relates to a hot-rolled steel sheet cooling method for cooling a hot-rolled steel sheet hot-rolled by a finish rolling mill.
- FIG. 21 is a diagram schematically showing a conventional method for producing a hot-rolled steel sheet.
- a slab S obtained by continuously casting molten steel adjusted to a predetermined composition is rolled by a roughing mill 201, and further finished by a plurality of rolling stands 202a to 202d.
- Hot-rolled steel sheet H having a predetermined thickness is formed by hot rolling with a rolling mill 203.
- this hot-rolled steel sheet H is cooled by the cooling water poured from the cooling device 211, it is wound up by the winding device 212 in a coil shape.
- the cooling device 211 is a facility for performing so-called laminar cooling on the hot-rolled steel sheet H that is generally transported from the finishing mill 203.
- the cooling device 211 injects cooling water as jet water from above in the vertical direction to the upper surface of the hot-rolled steel sheet H moving on the run-out table, and also against the lower surface of the hot-rolled steel sheet H. Then, the hot-rolled steel sheet H is cooled by injecting cooling water as jet water through the pipe laminator.
- Patent Document 1 discloses a technique for preventing a shape defect of a steel plate by reducing a difference in surface temperature between the upper and lower surfaces of the thick steel plate. According to the technique disclosed in Patent Document 1, based on the surface temperature difference obtained by simultaneously measuring the surface temperature of the upper and lower surfaces of the steel sheet with a thermometer during cooling by the cooling device, the upper and lower surfaces of the steel sheet Adjust the ratio of the amount of cooling water supplied to the.
- Patent Document 2 the material to be rolled is cooled by using spray spray between two adjacent stands of the finish rolling mill to start and complete the ⁇ - ⁇ transformation of the material to be rolled.
- a technique for preventing deterioration of the sheet-passability between the two is disclosed.
- Patent Document 3 a steepness meter installed on the exit side of a rolling mill is used to measure the steepness of the steel sheet tip, and the cooling water flow rate is changed in the width direction according to the measured steepness.
- a technique for preventing perforation of a steel sheet is disclosed.
- Patent Document 4 aims at eliminating the wavy plate thickness distribution in the plate width direction of the hot-rolled steel plate and uniforming the plate thickness in the plate width direction, and in the plate width direction of the hot-rolled steel plate.
- a technique for controlling the difference between the maximum heat transfer coefficient and the minimum heat transfer coefficient to fall within a predetermined value range is disclosed.
- the hot-rolled steel sheet H manufactured by the manufacturing method shown in FIG. 21 is, for example, as shown in FIG. 22, a transport roll for a run-out table (hereinafter sometimes referred to as “ROT”) in the cooling device 211.
- a wave shape may be generated in the rolling direction (the arrow direction in FIG. 22). In that case, variation occurs in cooling of the upper surface and the lower surface of the hot-rolled steel sheet H. That is, there is a problem that uniform cooling cannot be performed in the rolling direction due to a cooling deviation caused by the wave shape of the hot-rolled steel sheet H itself.
- Patent Document 5 in a steel plate having a corrugated shape in the rolling direction, in order to uniformize the cooling of the steel plate, the influence of the distance between the upper landing water of the steel plate and the lower table roller is described.
- a technique for making the cooling capacity of the upper cooling and the lower cooling the same so as to minimize is disclosed.
- Japanese Unexamined Patent Publication No. 2005-74463 Japanese Laid-Open Patent Publication No. 5-337505 Japanese Patent Application Laid-Open No. 2005-271052 Japanese Unexamined Patent Publication No. 2003-48003 Japanese Unexamined Patent Publication No. 6-328117
- the cooling method of Patent Document 1 does not consider the case where the hot-rolled steel sheet has a wave shape in the rolling direction.
- the hot-rolled steel sheet H having the corrugated shape described above as shown in FIG.
- the hot-rolled steel sheet H is also in local contact with an apron (not shown in FIG. 22) provided as a support for preventing the hot-rolled steel sheet H from falling between the conveying rolls 220 at the corrugated bottom.
- an apron not shown in FIG. 22
- a portion that is locally in contact with the transport roll 220 and the apron is more easily cooled than other portions by contact heat removal. For this reason, there existed a problem that the hot-rolled steel plate H was cooled unevenly.
- Patent Document 1 considers that the hot-rolled steel sheet is corrugated so that the transport roll or apron and the hot-rolled steel sheet are in local contact, and the contact portion is easily cooled by contact heat removal. Absent. Therefore, there are cases where the hot-rolled steel sheet having the corrugated shape cannot be cooled uniformly.
- Patent Document 2 the technique described in Patent Document 2 is to perform a ⁇ - ⁇ transformation between relatively low hardness (soft) ultra-low carbon steel between the stands of a finish rolling mill, and to achieve uniform cooling. It is not a thing. Further, the invention of Patent Document 2 does not relate to cooling when the material to be rolled has a wave shape in the pressure direction or when the material to be rolled is a steel material called so-called high tensile steel having a tensile strength (TS) of 800 MPa or more. Therefore, when the material to be rolled is a hot-rolled steel plate having a corrugated shape or a steel material having a relatively high hardness, there is a possibility that uniform cooling may not be performed.
- TS tensile strength
- Patent Document 3 the steepness in the width direction of the steel sheet is measured, and the cooling water flow rate of the portion having the high steepness is adjusted. However, if the cooling water flow rate in the plate width direction of the steel plate is changed, it becomes difficult to make the temperature in the plate width direction of the steel plate uniform. Furthermore, Patent Document 3 does not consider the case where the hot-rolled steel sheet has a wave shape in the rolling direction, and as described above, the hot-rolled steel sheet may not be uniformly cooled.
- Patent Document 4 since the cooling of patent document 4 is the cooling of the hot-rolled steel sheet immediately before the finish rolling mill roll bite, it cannot be applied to the hot-rolled steel sheet having a predetermined thickness after finish rolling. Furthermore, Patent Document 4 does not consider the case where a wave shape is formed in the rolling direction of the hot-rolled steel sheet, and as described above, the hot-rolled steel sheet cannot be uniformly cooled in the rolling direction. There is a case.
- the cooling capacity of the upper cooling includes the cooling by the riding water on the upper part of the steel sheet in addition to the cooling by the cooling water supplied to the steel sheet from the upper water injection nozzle. Since this boarding water is influenced by the steepness of the wave shape formed on the steel plate and the plate passing speed of the steel plate, the cooling ability of the steel plate by the boarding water cannot be specified strictly. Then, it is difficult to accurately control the cooling capacity of the upper cooling. For this reason, it is difficult to make the cooling capacity of the upper cooling and the lower cooling the same. Moreover, when the cooling capacity of the upper cooling and the lower cooling is made the same, an example of a method for determining the cooling capacity is illustrated, but a universal determination method is not disclosed. Therefore, the cooling method of patent document 5 may not cool a hot-rolled steel plate uniformly.
- the present invention has been made in view of the above-described problems, and an object thereof is to uniformly cool a hot-rolled steel sheet that has been hot-rolled by a finish rolling mill.
- a hot-rolled steel sheet cooling method includes a hot-rolled steel sheet cooling method in which a hot-rolled steel sheet hot-rolled by a finish rolling mill is cooled in a cooling section provided on the sheet-passing path.
- the vertical heat transfer which is a ratio of the heat transfer coefficient between the upper and lower surfaces of the hot-rolled steel sheet, experimentally determined in advance under the condition that the steepness of the hot-rolled steel sheet and the sheet passing speed are constant values.
- the target is the vertical heat transfer coefficient ratio X1 at which the temperature standard deviation Y is the minimum value Ymin.
- a target ratio setting step that is set as a ratio Xt; and an upper surface cooling heat removal amount of the hot-rolled steel sheet in the cooling section so that a vertical heat transfer coefficient ratio X of the hot-rolled steel sheet in the cooling section matches the target ratio Xt. And at least the amount of heat removed from the bottom surface Having; a cooling control step of controlling one.
- the temperature standard deviation Y falls within a range from a minimum value Ymin to a minimum value Ymin + 10 ° C.
- the vertical heat transfer coefficient ratio X may be set as the target ratio Xt.
- the correlation data is prepared for each of a plurality of conditions having different values of the steepness and the sheet passing speed
- the target ratio Xt may be set based on correlation data corresponding to the measured values of the steepness and the plate passing speed among the plurality of correlation data.
- the correlation data may be data indicating a correlation between the upper and lower heat transfer coefficient ratio X and the temperature standard deviation Y by a regression equation. .
- the regression equation may be derived by linear regression.
- the correlation data may be data indicating a correlation between the upper and lower heat transfer coefficient ratio X and the temperature standard deviation Y in a table.
- a temperature measurement step of measuring the temperature of the hot-rolled steel sheet on the downstream side of the cooling section in time series; and the measurement result of the temperature A temperature average value calculating step of calculating a time-series average value of the temperature based on the temperature; cooling the upper surface of the hot-rolled steel sheet in the cooling section so that the time-series average value of the temperature matches a predetermined target temperature; And a cooling heat removal amount adjusting step for adjusting a total value of the heat removal amount and the bottom surface cooling heat removal amount.
- a temperature measurement step of measuring the temperature of the hot-rolled steel sheet on the downstream side of the cooling section in time series; and downstream of the cooling section A fluctuation rate measuring step of measuring the fluctuation rate in the vertical direction of the hot-rolled steel sheet in a time series at the same location as the temperature measurement location of the hot-rolled steel sheet on the side;
- the temperature of the hot-rolled steel sheet is lower than the average temperature in the range of one or more wave shapes of the hot-rolled steel sheet in a positive region, the amount of heat removal from the upper surface is reduced.
- At least one of the directions in which the amount of heat extracted from the bottom surface cooling increases is determined as the control direction, and when the temperature of the hot-rolled steel sheet is higher than the average temperature, the direction in which the amount of heat extracted from the top surface cooling increases and the surface cooling.
- Reduced heat removal At least one of the direction to be controlled is determined as the control direction, and when the temperature of the hot-rolled steel sheet is lower than the average temperature in a region where the fluctuation speed is negative, When at least one of the directions in which the lower surface cooling heat removal decreases is determined as the control direction, and the temperature of the hot rolled steel sheet is higher than the average temperature, the lower surface cooling heat removal direction and the lower surface cooling heat removal are reduced.
- the cooling section is divided into a plurality of divided cooling sections along the sheet passing direction of the hot-rolled steel sheet, and the temperature measuring step and the In the fluctuation rate measurement step, the temperature and fluctuation rate of the hot-rolled steel sheet are measured in time series at each boundary of the divided cooling section; in the control direction determination step, the heat at each boundary of the divided cooling section is measured.
- the direction of increase / decrease in the amount of cooling heat removal on the upper and lower surfaces of the hot-rolled steel sheet is determined for each of the divided cooling zones; Based on the control direction determined for each of the sections, at least one of the upper surface cooling heat removal amount and the lower surface cooling heat removal amount of the hot-rolled steel sheet in each of the divided cooling sections. It may be performed feedback control or feed forward control to adjust the.
- the hot-rolled steel sheet is placed on the downstream side of the cooling section so that a temperature standard deviation of the hot-rolled steel sheet is allowed. You may have further the post-cooling process which cools a steel plate further.
- the sheet-passing speed of the hot-rolled steel sheet in the cooling section is within a range of 550 m / min or more to a mechanical limit speed or less. It may be set.
- the tensile strength of the hot-rolled steel sheet may be 800 MPa or more.
- the finish rolling mill includes a plurality of rolling stands, and performs auxiliary cooling of the hot-rolled steel sheets between the plurality of rolling stands. You may further have an auxiliary
- the cooling section includes an upper cooling device having a plurality of headers for ejecting cooling water on an upper surface of the hot-rolled steel sheet, A lower cooling device having a plurality of headers for ejecting cooling water on the lower surface of the hot-rolled steel sheet, and the upper surface cooling heat removal amount and the lower surface cooling heat removal amount are adjusted by on / off controlling each header. May be.
- the cooling section includes an upper cooling device having a plurality of headers for ejecting cooling water on the upper surface of the hot-rolled steel sheet, A lower cooling device having a plurality of headers for jetting cooling water on the lower surface of the hot-rolled steel sheet, and the upper surface cooling heat removal amount and the lower surface cooling heat removal amount are the water amount density, pressure and water temperature of each header. May be adjusted by controlling at least one of the following.
- the cooling in the cooling section may be performed in a range where the temperature of the hot-rolled steel sheet is 600 ° C. or higher.
- the upper and lower heat transfer coefficient ratio X which is the ratio of the heat transfer coefficient of the upper and lower surfaces of the hot-rolled steel sheet.
- the temperature standard deviation Y can be minimized by controlling the vertical heat transfer coefficient ratio X to a specific value (that is, the hot rolled steel sheet It was found that it can be cooled uniformly. Therefore, according to the present invention, the temperature standard deviation Y becomes the minimum value Ymin based on the correlation data between the upper and lower heat transfer coefficient ratio X of the hot-rolled steel sheet and the temperature standard deviation Y obtained experimentally in advance.
- the upper and lower heat transfer coefficient ratio X1 is set as the target ratio Xt, and the upper surface cooling heat removal and lower surface cooling of the hot rolled steel sheet are made so that the upper and lower heat transfer coefficient ratio X of the hot rolled steel sheet in the cooling zone matches the target ratio Xt. Because it controls at least one of the heat removal amount, The hot-rolled steel sheet that has been hot-rolled by a finish rolling mill and has a corrugated shape can be uniformly cooled.
- FIG. It is explanatory drawing which shows the hot rolling equipment 1 for implement
- FIG. It is a graph which shows the correlation of the up-and-down heat-transfer coefficient ratio X and the temperature standard deviation Y calculated
- a graph showing the relationship between the temperature fluctuation and steepness of a hot-rolled steel sheet H in the ROT cooling of a typical strip in a normal operation shows the upper graph shows the temperature fluctuation with respect to the distance from the coil tip or the fixed point elapsed time.
- the lower graph shows the steepness with respect to the distance from the coil tip or the fixed point elapsed time. It is a graph which shows the relationship between the temperature fluctuation and the steepness of the hot-rolled steel sheet H in the ROT cooling of a typical strip in a normal operation.
- FIG. 6 is a graph showing the relationship between the temperature fluctuation and steepness of the hot-rolled steel sheet H when the upper surface cooling heat removal amount is decreased and the lower surface cooling heat removal amount is increased.
- the steepness of the wave shape of the hot-rolled steel sheet H is a value obtained by dividing the amplitude of the wave shape by the length in the rolling direction for one cycle.
- FIG. It is explanatory drawing which shows the detail of the periphery of the cooling device 14 in the hot rolling equipment 1.
- FIG. It is explanatory drawing which shows the modification of the cooling device. It is explanatory drawing which shows a mode that the temperature standard deviation was formed in the plate width direction of the hot-rolled steel plate H. It is explanatory drawing which shows the hot rolling equipment 2 for implement
- FIG. It is explanatory drawing which shows a mode that the lowest point of the hot-rolled steel plate H contacts the conveyance roll 132.
- FIG. It is a graph which shows the time-dependent change of the temperature of the hot-rolled steel sheet H when the plate-feeding speed of the hot-rolled steel sheet H is low. It is a graph which shows the time-dependent change of the temperature of the hot-rolled steel sheet H when the plate-feeding speed of the hot-rolled steel sheet H is high.
- the finishing mill 113 which can perform cooling between stands. It is explanatory drawing which shows the manufacturing method of the conventional hot-rolled steel plate H. It is explanatory drawing which shows the cooling method of the conventional hot-rolled steel plate H.
- FIG. 1 schematically shows an example of hot rolling equipment 1 for realizing the hot-rolled steel sheet cooling method in the present embodiment.
- This hot rolling facility 1 is a facility intended to continuously roll a heated slab S sandwiched between rolls up and down, thin it to a minimum of 1 mm, and wind it up.
- This hot rolling equipment 1 is rolled in the width direction, a heating furnace 11 for heating the slab S, a width-direction rolling mill 16 that rolls the slab S heated in the heating furnace 11 in the width direction, and the width direction.
- a roughing mill 12 that rolls the slab S from the upper and lower directions to form a rough bar, a finishing mill 13 that continuously hot-rolls the rough bar to a predetermined thickness, and a hot rolling by the finishing mill 13.
- a cooling device 14 that cools the hot-rolled steel plate H that has been finish-rolled with cooling water, and a winding device 15 that winds the hot-rolled steel plate H cooled by the cooling device 14 into a coil shape are provided.
- the heating furnace 11 is provided with a side burner, an axial flow burner, and a roof burner for heating the slab S by blowing out flames to the slab S carried in from the outside through the loading port.
- the slab S carried into the heating furnace 11 is sequentially heated in each heating zone formed in each zone, and further in the soaking zone formed in the final zone, the slab S is evenly heated using a roof burner, A coercive heat treatment is performed to enable conveyance at the optimum temperature.
- the slab S is transferred to the outside of the heating furnace 11 and moves to a rolling process by the roughing mill 12.
- the rough rolling mill 12 allows the slab S that has been conveyed to pass through a gap between cylindrical rotary rolls that are disposed across a plurality of stands. For example, this roughing mill 12 hot-rolls the slab S only by the work rolls 12a arranged up and down in the first stand to form a rough bar.
- the rough bar that has passed through the work roll 12a is further continuously rolled by a plurality of quadruple rolling mills 12b constituted by the work roll and the backup roll. As a result, at the end of the rough rolling step, the rough bar is rolled to a thickness of about 30 to 60 mm and conveyed to the finishing mill 13.
- the finish rolling mill 13 finish-rolls the coarse bar conveyed from the rough rolling mill 12 until the thickness becomes about several mm. These finish rolling mills 13 allow the coarse bar to pass through the gaps between the finish rolling rolls 13a arranged in a straight line over 6 to 7 stands, and gradually reduce them.
- the hot-rolled steel sheet H finish-rolled by the finish rolling mill 13 is conveyed to the cooling device 14 by a conveyance roll 32 described later.
- the cooling device 14 is equipment for applying so-called laminar cooling to the hot-rolled steel sheet H conveyed from the finish rolling mill 13. As shown in FIG. 2, the cooling device 14 has an upper cooling device 14 a that jets cooling water from the upper cooling port 31 to the upper surface of the hot-rolled steel sheet H that moves on the transport roll 32 of the run-out table, The lower side cooling device 14b which injects a cooling water from the lower side cooling port 31 with respect to the lower surface of the hot-rolled steel plate H is provided. A plurality of cooling ports 31 are provided for each of the upper cooling device 14a and the lower cooling device 14b. A cooling header (not shown) is connected to the cooling port 31.
- the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is determined by the number of the cooling ports 31.
- the cooling device 14 may be composed of at least one of an upper / lower split laminar, a pipe laminar, spray cooling, and the like. Further, a section in which the hot-rolled steel sheet H is cooled by the cooling device 14 corresponds to a cooling section in the present invention.
- the winding device 15 winds the hot rolled steel sheet H cooled by the cooling device 14 at a predetermined winding temperature.
- the hot-rolled steel sheet H wound up in a coil shape by the winding device 15 is conveyed outside the hot rolling facility 1.
- the hot-rolled steel sheet cooling method of this embodiment realized by the hot rolling facility 1 configured as described above will be described.
- the hot-rolled steel sheet H hot-rolled by the finish rolling mill 13 is formed with a wave shape whose surface height (wave height) varies in the rolling direction as shown in FIG. ing.
- the influence of the running water which accumulates on the hot-rolled steel sheet H when the hot-rolled steel sheet H is cooled is ignored.
- the hot-rolled steel sheet cooling method of this embodiment has two processes, a target ratio setting process and a cooling control process.
- a target ratio setting process heat transfer between the upper and lower surfaces of the hot-rolled steel sheet H, which has been experimentally determined in advance under the condition that the steepness of the hot-rolled steel sheet H and the sheet passing speed are constant values.
- the temperature standard deviation Y becomes the minimum value Ymin.
- the heat transfer coefficient ratio X1 is set as the target ratio Xt.
- the cooling section is set such that the vertical heat transfer coefficient ratio X of the hot rolled steel sheet H in the cooling section (the section in which the hot rolled steel sheet H is cooled by the cooling device 14) matches the target ratio Xt. At least one of the upper surface cooling heat removal amount and the lower surface cooling heat removal amount of the hot-rolled steel sheet H is controlled.
- the correlation data used in the target ratio setting step is experimentally obtained in advance using the hot rolling facility 1 before actual operation (before actually manufacturing the hot-rolled steel sheet H as a product).
- a method for obtaining correlation data used in the target ratio setting step will be described in detail.
- the upper cooling capacity and the lower cooling capacity are respectively the heat transfer coefficient of the upper surface of the hot rolled steel sheet H cooled by the upper cooling device 14a and the heat transfer of the lower surface of the hot rolled steel sheet H cooled by the lower cooling device 14b. Adjust using the coefficient.
- the temperature difference is a difference between the temperature of the hot-rolled steel sheet H measured by the thermometer on the inlet side of the cooling device 14 and the temperature of the cooling water used in the cooling device 14.
- the amount of heat removed from cooling is the amount of heat removed from the hot-rolled steel sheet H in the cooling device 14, and the difference in temperature between the hot-rolled steel plates H measured by the thermometer on the inlet side and the thermometer on the outlet side of the cooling device 14. And the specific heat of the hot-rolled steel sheet H and the mass of the hot-rolled steel sheet H cooled by the cooling device 14, respectively.
- the heat transfer coefficient of the hot-rolled steel sheet H calculated as described above is divided into the heat transfer coefficients of the upper surface and the lower surface of the hot-rolled steel sheet H.
- These heat transfer coefficients of the upper surface and the lower surface are calculated using, for example, a ratio obtained in advance as follows. That is, the heat transfer coefficient of the hot-rolled steel sheet H when the hot-rolled steel sheet H is cooled only by the upper cooling device 14a and the heat transfer of the hot-rolled steel plate H when the hot-rolled steel plate H is cooled only by the lower cooling device 14b. Measure the coefficient. At this time, the cooling water amount from the upper cooling device 14a and the cooling water amount from the lower cooling device 14b are the same.
- the reciprocal of the ratio between the measured heat transfer coefficient when using the upper cooling device 14a and the heat transfer coefficient when using the lower cooling device 14b is the upper and lower heat transfer coefficient ratio X described later as "1".
- the upper / lower ratio of the cooling water amount of the upper cooling device 14a and the cooling water amount of the lower cooling device 14b is obtained.
- the above-described hot-rolled steel sheet is obtained by multiplying the vertical ratio of the cooling water amount obtained in this way by the cooling water amount of the upper cooling device 14a or the cooling water amount of the lower cooling device 14b when the hot-rolled steel plate H is cooled.
- the ratio of the heat transfer coefficient between the upper surface and the lower surface of H (upper and lower heat transfer coefficient ratio X) is calculated.
- the heat transfer coefficient of the hot-rolled steel sheet H that is cooled only by the upper cooling device 14a and the lower cooling device 14b is used. However, it is cooled by both the upper cooling device 14a and the lower cooling device 14b.
- the heat transfer coefficient of the hot-rolled steel sheet H may be used. That is, the heat transfer coefficient of the hot-rolled steel sheet H when the amount of cooling water of the upper cooling device 14a and the lower cooling device 14b is changed is measured, and the ratio of the heat transfer coefficient is used to determine the upper and lower surfaces of the hot-rolled steel sheet H. The ratio of the heat transfer coefficient may be calculated.
- the heat transfer coefficient of the hot-rolled steel sheet H is calculated, and the upper surface of the hot-rolled steel sheet H is calculated based on the above ratio (upper and lower heat transfer coefficient ratio X) of the heat transfer coefficients between the upper and lower surfaces of the hot-rolled steel sheet H. And the heat transfer coefficient of the lower surface is calculated.
- the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b is each adjusted based on FIG. 3 using the up-and-down heat transfer coefficient ratio X of this hot-rolled steel sheet H.
- the horizontal axis of FIG. 3 represents the ratio of the average heat transfer coefficient of the upper surface of the hot rolled steel sheet H to the average heat transfer coefficient of the lower surface (that is, the same as the vertical heat transfer coefficient ratio X), and the vertical axis represents the hot rolled steel sheet H.
- the standard deviation of temperature between the maximum temperature and the minimum temperature in the rolling direction (temperature standard deviation Y) is shown.
- the vertical heat transfer coefficient ratio X and the temperature standard deviation Y obtained by actually measuring the temperature standard deviation Y of the hot-rolled steel sheet H after cooling while changing the vertical heat transfer coefficient ratio X of the hot-rolled steel sheet H.
- correlation data indicating the correlation with Referring to FIG. 3, the correlation between the temperature standard deviation Y and the upper and lower heat transfer coefficient ratio X is V-shaped, with the temperature standard deviation Y being the minimum value Ymin when the upper and lower heat transfer coefficient ratio X is “1”. It turns out that it is related.
- the steepness of the wave shape of the hot-rolled steel sheet H is a value obtained by dividing the amplitude of the wave shape by the length in the rolling direction for one cycle.
- FIG. 3 shows the correlation between the vertical heat transfer coefficient ratio X and the temperature standard deviation Y obtained under the condition that the steepness of the hot-rolled steel sheet H is 2% and the sheet passing speed is 600 m / min (10 m / sec). It is data.
- the temperature standard deviation Y may be measured during cooling of the hot-rolled steel sheet H, or may be measured after cooling.
- the target cooling temperature of the hot-rolled steel sheet H is a temperature of 600 ° C. or higher, for example, 800 ° C.
- the upper and lower heat transfer coefficient ratio X1 at which the temperature standard deviation Y becomes the minimum value Ymin is set as the target ratio Xt based on the correlation data obtained experimentally in advance as described above.
- This correlation data may be prepared as data (table data) indicating the correlation between the vertical heat transfer coefficient ratio X and the temperature standard deviation Y in a table (table format), or the vertical heat transfer coefficient ratio X and You may prepare as correlation data with the temperature standard deviation Y as data which shows a numerical formula (for example, regression equation).
- the V-shaped line shown in FIG. 3 is substantially linear on both sides across the valley. Therefore, the regression equation may be derived by performing linear regression on this line. If it is a linear distribution, the number of times of confirmation with a test material and the number of times of calibration for predicting calculation can be reduced.
- the minimum value Ymin of the temperature standard deviation Y is searched by using various methods such as a dichotomy method, golden section method, and random search, which are generally known search algorithms.
- the upper and lower heat transfer coefficient ratio X1 at which the temperature standard deviation Y of the hot-rolled steel sheet H is the minimum value Ymin is derived.
- FIG. 4 shows a standard case where different regression lines are obtained across the minimum value Ymin of the temperature standard deviation Y.
- the temperature standard deviations Ya, Yb, Yc at the point c, the point a, the point b, and the middle point c between the points a and b are extracted.
- the middle of the points a and b indicates the point c having a value between the upper and lower heat transfer coefficient ratio Xa at the point a and the upper and lower heat transfer coefficient ratio Xb at the point b.
- the temperature standard deviation Yd at the point d between the points a and c is extracted. Then, it is determined whether the temperature standard deviation Yd is closer to Ya or Yc. In the present embodiment, Yd is close to Yc.
- the temperature standard deviation Ye at the point e between the points c and d is extracted. Then, it is determined whether the temperature standard deviation Ye is closer to Yc or Yd. In the present embodiment, Ye is close to Yd.
- Such calculation is repeated to specify the minimum point f (minimum value Ymin) of the temperature standard deviation Y of the hot-rolled steel sheet H. In order to specify the practical minimum point f, the above-described calculation may be performed, for example, about 5 times. Alternatively, the range of the upper and lower heat transfer coefficient ratio X to be searched may be divided into 10, and the above-described calculation is performed in each range to specify the minimum point f.
- the upper and lower heat transfer coefficient ratio X may be calibrated by using a so-called Newton method.
- the deviation between the vertical heat transfer coefficient ratio X with respect to the actual temperature standard deviation Y value and the vertical heat transfer coefficient ratio X at which the temperature standard deviation Y becomes zero is obtained.
- the vertical heat transfer coefficient ratio X1 (Xf in FIG. 4) at which the temperature standard deviation Y of the hot-rolled steel sheet H is the minimum value Ymin is derived.
- the relationship between the V-shaped temperature standard deviation Y and the upper and lower heat transfer coefficient ratio X it is easy to obtain a regression function for each of them by the least square method or the like.
- the vertical heat transfer coefficient ratio X1 at which the temperature standard deviation Y of the hot-rolled steel sheet H becomes the minimum value Ymin is “1”. Therefore, when the correlation data as shown in FIG. 3 is obtained, in order to minimize the temperature standard deviation Y, that is, to cool the hot-rolled steel sheet H uniformly, in the target ratio setting process during actual operation, The ratio Xt is set to “1”. In the cooling control step, the upper surface cooling of the hot-rolled steel sheet H in the cooling section is made so that the vertical heat transfer coefficient ratio X of the hot-rolled steel sheet H in the cooling section matches the target ratio Xt (that is, “1”). At least one of the amount of heat and the amount of heat extracted from the bottom surface cooling is controlled.
- the cooling capacity of the upper cooling device 14a and the lower cooling device may be made equal by adjusting the cooling capacity of 14b equally.
- the numerator is the heat transfer coefficient on the upper surface of the hot-rolled steel sheet H
- the denominator is the heat transfer coefficient on the lower surface of the hot-rolled steel sheet H.
- the condition that the temperature standard deviation Y becomes the minimum value Ymin is “A”, and the standard deviation from the minimum value as will be described later. The difference between the two is within 10 ° C., that is, the condition that the operation is suitable is “B”, and the condition that is trial-and-error to obtain the above-described regression equation is “C”.
- the evaluation is “A”, that is, the vertical heat transfer coefficient ratio X1 at which the temperature standard deviation Y of the hot-rolled steel sheet H is the minimum value Ymin is “1”.
- the temperature standard deviation Y of the hot-rolled steel sheet H is at least within the range from the minimum value Ymin to the minimum value Ymin + 10 ° C., variations in yield stress, tensile strength, etc. can be suppressed within the production allowable range. Can be cooled uniformly. That is, in the above target ratio setting step, based on the correlation data obtained experimentally in advance, the vertical heat transfer ratio X in which the temperature standard deviation Y is within the range from the minimum value Y to the minimum value Ymin + 10 ° C. is set as the target ratio Xt.
- the allowable manufacturing range is a range in which the temperature standard deviation Y of the hot-rolled steel sheet H is within the minimum value Ymin + 10 ° C. from the minimum value Ymin.
- a straight line extends in the horizontal axis direction from the point on the vertical axis where the temperature standard deviation Y becomes the minimum value Ymin + 10 ° C. Then, two intersections between the straight line and the two regression lines on both sides of the V-shaped curve are obtained, and the target ratio Xt may be set from the vertical heat transfer coefficient ratio X between the two intersections.
- the temperature standard deviation Y can be set within the range from the minimum value Ymin to the minimum value Ymin + 10 ° C. by setting the vertical heat transfer coefficient ratio X having an evaluation of “B” as the target ratio Xt.
- the vertical heat transfer coefficient ratio X coincide with the target ratio Xt, it is easiest to operate the cooling water density of at least one of the upper cooling device 14a and the lower cooling device 14b. Therefore, for example, in FIG. 3 and FIG. 4, the value of the horizontal axis is read as the upper and lower water density ratio, and the hot rolled steel sheet H with respect to the upper and lower ratio of the water density on both sides sandwiching the same point above and below the average heat transfer coefficient.
- the regression equation of the temperature standard deviation Y may be obtained.
- the points that are equal above and below the average heat transfer coefficient are not necessarily equal points above and below the cooling water density, so it is better to perform a slightly wider test to obtain the regression equation.
- the above correlation data is prepared for each of a plurality of conditions having different values of the steepness level and the sheet passing speed, and in the target ratio setting step, among the plurality of correlation data, the steepness level at the time of actual operation.
- the target ratio Xt may be set based on correlation data corresponding to the measured value of the plate passing speed.
- the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is adjusted (the upper surface cooling heat removal amount and the lower surface cooling heat removal amount of the hot rolled steel plate H are controlled.
- the inventors of the present application have made extensive studies on the characteristics of the temperature standard deviation Y generated by cooling in a state where the wave shape of the hot-rolled steel sheet H is generated, and as a result, have clarified the following.
- the temperature of the hot-rolled steel sheet H is controlled to a predetermined target temperature (temperature suitable for winding). Need to maintain the quality. Therefore, in the target ratio setting process and the cooling control process described above, based on the temperature measurement process for measuring the temperature of the hot-rolled steel sheet H on the downstream side of the cooling section (that is, the cooling device 14) in time series and the measurement result of the temperature.
- the temperature average value calculating step for calculating the time series average value of the temperature and the upper surface cooling heat removal amount and the lower surface cooling of the hot-rolled steel sheet H in the cooling section so that the time series average value of the temperature coincides with a predetermined target temperature.
- a cooling heat removal amount adjustment step for adjusting the total value of the heat removal amount may be newly added.
- a thermometer 40 for measuring the temperature of the hot-rolled steel sheet H which is arranged between the cooling device 14 and the winding device 15 as shown in FIG. Can do.
- the temperature measurement at the position determined in the rolling direction of the hot-rolled steel sheet H by the thermometer 40 is performed on the hot-rolled steel sheet H conveyed from the cooling device 14 to the winding device 15 at a certain time interval (sampling). Time interval data is obtained at intervals).
- the temperature measurement region by the thermometer 40 includes the entire width direction of the hot-rolled steel sheet H.
- the sampling time of each temperature measurement result is multiplied by the sheet feeding speed (conveying speed) of the hot-rolled steel sheet H
- the position in the rolling direction of the hot-rolled steel sheet H from which each temperature measurement result is obtained can be calculated. That is, by multiplying the time at which each temperature measurement result is sampled by the sheet passing speed, it becomes possible to link the time series data of the temperature measurement result to the position in the rolling direction.
- the time series average value of the temperature measurement result is calculated using the time series data of the temperature measurement result. Specifically, every time a certain number of temperature measurement results are obtained, an average value of the temperature measurement results for the certain number may be calculated. Then, in the cooling heat removal amount adjustment step, the upper surface cooling heat removal amount and the lower surface cooling of the hot-rolled steel sheet H in the cooling section so that the time-series average value of the temperature measurement results calculated as described above coincides with the predetermined target temperature. Adjust the total value with heat removal.
- the shape meter 41 measures the shape of the same measurement position as the thermometer 40 defined on the hot-rolled steel sheet H (hereinafter, this measurement position may be referred to as a fixed point).
- the shape means the height or fluctuation component of the wave pitch by using the movement amount of the hot-rolled steel sheet H in the passing direction as the fluctuation amount in the height direction of the hot-rolled steel sheet H observed by the fixed point measurement. This is the steepness obtained by the line integral.
- the shape measurement region includes the entire region in the width direction of the hot-rolled steel sheet H, similarly to the temperature measurement region.
- FIG. 5 shows the relationship between the temperature fluctuation and the steepness of the hot-rolled steel sheet H cooled in the ROT of a typical strip in a normal operation.
- a region A in FIG. 5 is a region before the strip front end portion shown in FIG. 13 is bitten by the coiler of the winding device 15 (a region having a bad shape because there is no tension).
- a region B in FIG. 5 is a region after the end of the strip is bitten by the coiler (a region where the wave shape is changed flat due to the influence of the unit tension). It is desired to improve a large temperature fluctuation (that is, temperature standard deviation Y) generated in the region A where the shape of the hot-rolled steel sheet H is not flat.
- the inventors of the present application have conducted intensive experiments with the goal of suppressing an increase in the temperature standard deviation Y in the ROT, and as a result, have obtained the following knowledge.
- FIG. 6 shows the temperature fluctuation component with respect to the same shape steepness of the cooling in the ROT of a typical strip in a normal operation as in FIG.
- This temperature fluctuation component is a residual obtained by subtracting a time-series average of temperature (hereinafter sometimes referred to as “average temperature”) from the actual steel plate temperature.
- the average temperature may be averaged over a range of one or more wave shapes of the hot-rolled steel sheet H.
- the average temperature is in principle the average of the range in units of cycles.
- it has been confirmed by the operation data that the average temperature in the range of one cycle is not significantly different from the average temperature in the range of two cycles or more. Therefore, it is only necessary to calculate an average temperature in a range of at least one waveform.
- the upper limit of the corrugated range of the hot-rolled steel sheet H is not particularly limited, but preferably an average temperature with sufficient accuracy can be obtained if it is set to 5 cycles. Further, even if the range to be averaged is not a cycle unit range, an acceptable average temperature can be obtained if it is in the range of 2 to 5 cycles.
- the wave shape of the hot-rolled steel sheet H is a region where the fluctuation rate measured at a fixed point is positive.
- the temperature of the hot-rolled steel sheet H temperature measured at a fixed point
- the temperature of the hot-rolled steel sheet H is lower than the average temperature in the range of one cycle or more, at least one of the direction in which the upper surface cooling heat removal amount decreases and the direction in which the lower surface cooling heat removal amount increases.
- the control direction Is determined as the control direction, and when the temperature of the hot-rolled steel sheet H is higher than the average temperature, at least one of the direction in which the upper surface cooling heat removal amount increases and the direction in which the lower surface cooling heat removal amount decreases is determined as the control direction. To do. Further, when the temperature of the hot-rolled steel sheet H is lower than the above average temperature in the region where the fluctuation rate measured at a fixed point is negative, the direction in which the upper surface cooling heat removal amount increases and the direction in which the lower surface cooling heat removal amount decreases.
- the direction in which the upper surface cooling heat removal amount decreases and the direction in which the lower surface cooling heat removal amount increases. Is determined as a control direction, and when the temperature of the hot-rolled steel sheet H is higher than the above average temperature, at least one of the direction in which the upper surface cooling heat removal amount increases and the direction in which the lower surface cooling heat removal amount decreases is controlled. Determine as direction. Then, when at least one of the upper surface cooling heat removal amount and the lower surface cooling heat removal amount of the hot-rolled steel sheet H in the cooling section is adjusted based on the control direction determined as described above, as shown in FIG. And it turned out that the temperature fluctuation which generate
- the temperature measurement process for measuring the temperature (temperature at a fixed point) of the hot rolled steel sheet H on the downstream side of the cooling section in time series, and the hot rolled steel sheet H Fluctuation rate measurement process that measures the variation rate in the vertical direction of the hot-rolled steel sheet H at the same location (fixed point) as the temperature measurement location, and the amount of heat removed from the top surface and the bottom surface based on the temperature measurement result and the variation rate measurement result
- An adjustment step may be newly added.
- the fluctuation speed at the fixed point of the hot-rolled steel sheet H is a positive region, and the fixed temperature of the hot-rolled steel sheet H with respect to the average temperature at the fixed point of the hot-rolled steel sheet H.
- the temperature of the hot rolled steel sheet H is higher than the above average temperature Determines at least one of the direction in which the upper surface cooling heat removal amount increases and the direction in which the lower surface cooling heat removal amount decreases as the control direction.
- this control direction determination step when the temperature of the hot-rolled steel sheet H is lower than the average temperature in the region where the fluctuation speed is negative, the upper surface cooling heat removal amount and the lower surface cooling heat removal amount are increased.
- the direction of decreasing the upper surface cooling heat removal amount and the direction of increasing the lower surface cooling heat removal amount are determined. At least one is determined as a control direction. Even in this cooling method, it is necessary to adjust the upper surface cooling heat removal amount and the lower surface cooling heat removal amount while achieving the control target of making the upper and lower heat transfer coefficient ratio X of the hot rolled steel sheet H in the cooling section coincide with the target ratio Xt. There is.
- the cooling header connected to the cooling port 31 of the upper cooling device 14a and the cooling port 31 of the lower cooling device 14b When adjusting the cooling capacity of the upper cooling device 14a and the cooling capacity of the lower cooling device 14b, for example, the cooling header connected to the cooling port 31 of the upper cooling device 14a and the cooling port 31 of the lower cooling device 14b.
- Each of the cooling headers connected to may be controlled on and off. Or you may control the cooling capacity of each cooling header in the upper side cooling device 14a and the lower side cooling device 14b. That is, you may adjust at least one of the water quantity density of the cooling water injected from each cooling port 31, a pressure, and water temperature.
- the cooling headers (cooling ports 31) of the upper cooling device 14a and the lower cooling device 14b may be thinned out to adjust the flow rate and pressure of the cooling water injected from the upper cooling device 14a and the lower cooling device 14b.
- the cooling capacity of the upper cooling device 14a before thinning out the cooling header is higher than the cooling capacity of the lower cooling device 14b, it is preferable to thin out the cooling header constituting the upper cooling device 14a.
- the cooling capacity thus adjusted is used to inject cooling water onto the upper surface of the hot-rolled steel sheet H from the upper cooling device 14a, and to inject cooling water onto the lower surface of the hot-rolled steel plate H from the lower cooling device 14b.
- the steel plate H is uniformly cooled.
- the correlation data shown in FIG. 3 is obtained by fixing the sheet passing speed of the hot-rolled steel sheet H to 600 m / min has been described. Furthermore, although the details will be described later, the present inventors have intensively studied. As a result, it has been found that the hot-rolled steel sheet H can be made more uniform if the sheet passing speed is set to 550 m / min or more.
- the cooling of the hot-rolled steel sheet H by the cooling device 14 is preferably performed in the range from the finish rolling mill outlet temperature to the temperature of the hot-rolled steel sheet H up to 600 ° C.
- the temperature region where the temperature of the hot-rolled steel sheet H is 600 ° C. or higher is a so-called film boiling region. That is, in this case, the so-called transition boiling region can be avoided and the hot-rolled steel sheet H can be water-cooled in the film boiling region.
- the transition boiling region when cooling water is sprayed onto the surface of the hot-rolled steel sheet H, a portion covered with a vapor film and a portion where the cooling water is directly sprayed onto the hot-rolled steel plate H are formed on the surface of the hot-rolled steel plate H. Mixed.
- the hot-rolled steel sheet H cannot be cooled uniformly.
- the hot-rolled steel sheet H in the film boiling region, since the hot-rolled steel sheet H is cooled in a state where the entire surface of the hot-rolled steel sheet H is covered with the vapor film, the hot-rolled steel sheet H can be uniformly cooled. Therefore, the hot-rolled steel sheet H can be cooled more uniformly in the range where the temperature of the hot-rolled steel sheet H is 600 ° C. or more as in this embodiment.
- the temperature standard deviation Y of the hot-rolled steel sheet H increases as the wave shape steepness of the hot-rolled steel sheet H increases. That is, as shown in FIG. 10, the temperature standard deviation Y increases according to the steepness (sensitivity of the steepness) as the vertical heat transfer coefficient ratio X increases from “1”.
- the relationship between the vertical heat transfer coefficient ratio X and the temperature standard deviation Y is represented by a V-shaped regression line for each steepness.
- the sheet passing speed of the hot rolled steel sheet H is constant at 10 m / sec (600 m / min).
- the temperature standard deviation Y of the hot-rolled steel sheet H is increased. That is, as shown in FIG. 12, as the vertical heat transfer coefficient ratio X increases from “1”, the temperature standard deviation Y increases in accordance with the plate passing speed (the sensitivity of the plate passing speed).
- the relationship between the vertical heat transfer coefficient ratio X and the temperature standard deviation Y is represented by a V-shaped regression line for each plate passing speed.
- the steepness of the wave shape of the hot-rolled steel sheet H is constant at 2%.
- the vertical heat transfer coefficient ratio X of the hot-rolled steel sheet H is fixed in advance, and the steepness is changed stepwise from 3% to 0%, for example, as shown in FIG. Table data indicating a correlation with the temperature standard deviation Y after cooling of the steel plate H is obtained. Then, the temperature standard deviation Y with respect to the steepness z% of the actual hot-rolled steel sheet H is corrected to a temperature standard deviation Y ′ with respect to a predetermined steepness by an interpolation function. Specifically, when the predetermined steepness is set to 2% as the correction condition, the temperature standard deviation Yz ′ is calculated by the following equation (1) based on the temperature standard deviation Yz at the steepness z%.
- the steepness gradient ⁇ in FIG. 9 may be calculated by the least square method or the like, and the temperature standard deviation Yz ′ may be calculated using the gradient ⁇ .
- Yz ′ Yz ⁇ 2 / z (1)
- the steepness may be corrected to a predetermined steepness
- the temperature standard deviation Y may be derived from the regression equation.
- Table 3 shows the temperature standard deviation Y of the hot-rolled steel sheet H when the vertical heat transfer coefficient ratio X is changed as shown in FIG. 10 with respect to the steepness in FIG.
- the value obtained by subtracting 3.5 ° C. (difference of standard deviation from the minimum value) and the evaluation of each temperature standard deviation Y are shown.
- the display and evaluation criteria for the upper and lower heat transfer coefficient ratio X in Table 3 are the same as those in Table 1 and will not be described.
- the temperature standard deviation Y of the hot-rolled steel sheet H corresponding to the steepness can be derived.
- the evaluation in Table 3 is “B”, that is, the ratio of the vertical heat transfer coefficient that the difference of the standard deviation from the minimum value of the hot-rolled steel sheet H is within 10 ° C.
- X can be set to 1.1.
- the sheet passing speed is changed stepwise from 5 m / sec (300 m / min) to 20 m / sec (1200 m / min), and each sheet passing speed and the hot rolled steel sheet H are changed.
- Table data indicating a correlation with the temperature standard deviation Y after cooling is obtained. Then, the temperature standard deviation Y with respect to the sheet passing speed v (m / sec) of the actual hot rolled steel sheet H is corrected to a temperature standard deviation Y ′ with respect to a predetermined sheet passing speed by an interpolation function.
- the temperature standard is expressed by the following formula (2) based on the temperature standard deviation Yv at the sheet passing speed v (m / sec).
- Deviation Yv ′ is calculated.
- the gradient ⁇ of the sheet feeding speed in FIG. 11 may be calculated by the least square method or the like, and the temperature standard deviation Yv ′ may be calculated using the gradient ⁇ .
- Yz ′ Yv ⁇ 10 / v (2)
- the plate passing speed may be corrected to a predetermined plate passing speed, and the temperature standard deviation Y may be derived from the regression equation.
- Table 4 shows the temperature standard deviation Y and the temperature standard deviation of the hot-rolled steel sheet H when the vertical heat transfer coefficient ratio X is changed as shown in FIG. 12 with respect to the sheet passing speed in FIG.
- the temperature standard deviation Y of the hot-rolled steel sheet H corresponding to the sheet passing speed can be derived.
- the evaluation in Table 4 is “B”, that is, the vertical heat transfer is such that the difference of the standard deviation from the minimum value of the hot rolled steel sheet H is within 10 ° C.
- the coefficient ratio X can be set to 1.1.
- the change in the temperature standard deviation Y with respect to the ratio of the vertical heat transfer coefficient can be quantitatively and accurately evaluated even when the steepness and the sheet passing speed of the hot-rolled steel sheet H are not constant. can do.
- the temperature and wave shape of the hot-rolled steel sheet H cooled by the cooling device 14 are measured, and the cooling capacity of the upper cooling device 14a and the cooling capacity of the lower cooling device 14b are determined based on the measurement result. You may adjust. That is, the cooling capacity of the upper cooling device 14a and the lower cooling device 14b may be feedback controlled.
- thermometer 40 that measures the temperature of the hot-rolled steel sheet H and a shape meter 41 that measures the wave shape of the hot-rolled steel sheet H are provided between the cooling device 14 and the winding device 15. And are arranged.
- the temperature and shape of the hot-rolled steel sheet H in the plate are measured at the same point by the thermometer 40 and the shape meter 41, and measured as time series data.
- the temperature measurement region includes the entire region in the width direction of the hot-rolled steel sheet H.
- the shape indicates the amount of fluctuation in the height direction of the hot-rolled steel sheet H observed by fixed point measurement.
- the shape measurement region includes the entire region in the width direction of the hot-rolled steel sheet H, similarly to the temperature measurement region.
- the fluctuation rate at the fixed point of the hot-rolled steel sheet H is a positive region, and the fixed-point of the hot-rolled steel sheet H with respect to the average temperature at the fixed point.
- the temperature standard deviation Y can be reduced by reducing the upper cooling capacity (upper surface cooling heat removal amount).
- the temperature standard deviation Y can be reduced by increasing the lower cooling capacity (lower surface cooling heat removal amount). If this relationship is utilized, in order to reduce the temperature standard deviation Y, it becomes clear which cooling capacity of the upper cooling device 14a or the lower cooling device 14b of the cooling device 14 should be adjusted.
- the increase / decrease direction (control direction) of the upper cooling capacity (upper surface cooling heat removal amount) and the lower cooling capacity (lower surface cooling heat removal amount) to reduce the temperature standard deviation Y is determined, and the vertical heat transfer coefficient ratio X is adjusted. can do. Further, based on the magnitude of the temperature standard deviation Y, the vertical heat transfer coefficient ratio X can be determined so that the temperature standard deviation Y falls within an allowable range, for example, the range from the minimum value Ymin to the minimum value Ymin + 10 ° C. .
- the method for determining the upper and lower heat transfer coefficient ratio X is the same as that in the above embodiment described with reference to FIGS.
- the ratio of the cooling water amount density (cooling water amount density ratio) is set within ⁇ 5% with respect to the cooling water amount density ratio at which the temperature standard deviation Y is the minimum value Ymin.
- this allowable range does not necessarily include the same upper and lower water density.
- the cooling capacity of the upper cooling apparatus 14a and the lower cooling apparatus 14b can be feedback controlled to adjust the cooling capacity to an appropriate cooling capacity qualitatively and quantitatively. Can be improved.
- the cooling section in which the hot-rolled steel sheet H is cooled may be divided into a plurality of, for example, two divided cooling sections Z1 and Z2 in the rolling direction.
- a cooling device 14 is provided in each of the divided cooling zones Z1 and Z2.
- a thermometer 40 and a shape meter 41 are provided at the boundary between the divided cooling zones Z1 and Z2, that is, downstream of the divided cooling zones Z1 and Z2.
- the cooling section is divided into two divided cooling sections, but the number of divisions is not limited to this and can be arbitrarily set.
- the cooling section may be divided into 1 to 5 divided cooling sections.
- the temperature and the wave shape of the hot-rolled steel sheet H on the downstream side of the divided cooling zones Z1 and Z2 are measured by the thermometers 40 and the shape meters 41, respectively. And based on these measurement results, the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b in each division
- the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is feedback-controlled based on the measurement results of the thermometer 40 and the shape meter 41 on the downstream side, and the upper surface cooling heat removal amount and At least one of the bottom surface cooling heat removal amount is adjusted.
- the cooling capacity of the upper cooling device 14a and the lower cooling device 14b may be feedforward controlled based on the measurement results of the thermometer 40 and the shape meter 41 on the downstream side, Alternatively, feedback control may be performed. In any case, at least one of the upper surface cooling heat removal amount and the lower surface cooling heat removal amount is adjusted in the divided cooling zone Z2.
- the method for controlling the cooling capacity of the upper cooling device 14a and the lower cooling device 14b based on the measurement results of the thermometer 40 and the shape meter 41 is the same as that in the above embodiment described with reference to FIGS. Therefore, detailed description is omitted.
- the hot-rolled steel sheet H can be cooled more uniformly.
- the measurement results of the thermometer 40 and the shape meter 41 are used.
- at least one of the steepness of the wave shape of the hot-rolled steel sheet H and the sheet passing speed may be used.
- the temperature standard deviation Y of the hot-rolled steel sheet H corresponding to at least the steepness or the sheet passing speed is corrected by the same method as in the above-described embodiment described with reference to FIGS.
- FIG. 15 shows an example of a state in which wave shapes having different amplitudes are formed in the sheet width direction of the hot-rolled steel sheet H by medium elongation.
- the temperature standard in the plate width direction is formed. The deviation can be reduced.
- FIG. 16 schematically shows an example of the hot rolling facility 2 in another embodiment.
- This hot rolling facility 2 is a facility intended to continuously roll a heated slab S sandwiched between rolls and to roll it down to a minimum thickness of 1.2 mm.
- This hot rolling facility 2 is rolled in the width direction, a heating furnace 111 for heating the slab S, a width-direction rolling mill 116 that rolls the slab S heated in the heating furnace 111 in the width direction, and the width direction.
- a roughing mill 112 that rolls the slab S from above and below to form a rough bar, a finishing mill 113 that continuously hot-rolls the rough bar to a predetermined thickness, and a hot rolling by the finishing mill 113.
- a cooling device 114 that cools the hot-rolled steel sheet H that has been finish-rolled with cooling water, and a winding device 115 that winds the hot-rolled steel plate H cooled by the cooling device 114 into a coil shape.
- the heating furnace 111 is provided with a side burner, an axial flow burner, and a roof burner for heating the slab S by blowing out flames with respect to the slab S carried in from the outside through the loading port.
- the slab S carried into the heating furnace 111 is sequentially heated in each heating zone formed in each zone, and further, in the soaking zone formed in the final zone, by heating the slab S evenly using a roof burner, A coercive heat treatment is performed to enable conveyance at the optimum temperature.
- the slab S is transferred to the outside of the heating furnace 111 and moves to a rolling process by the rough rolling mill 112.
- the slab S conveyed from the heating furnace 111 passes through a gap between cylindrical rotary rolls arranged over a plurality of stands.
- the rough rolling mill 112 hot-rolls the slab S with only the work rolls 112a disposed up and down in the first stand to form a rough bar.
- the coarse bar that has passed through the work roll 112a is further continuously rolled by a plurality of quadruple rolling mills 112b each composed of a work roll and a backup roll.
- the rough bar is rolled to a thickness of about 30 to 60 mm and conveyed to the finishing mill 113.
- the structure of the rough rolling mill 112 is not limited to what was described in this embodiment, The number of rolls etc. can be set arbitrarily.
- the finish rolling mill 113 finish-rolls the rough bar conveyed from the rough rolling mill 112 until the thickness becomes about several mm. These finish rolling mills 113 allow the coarse bars to pass through the gaps between the finish rolling rolls 113a arranged in a straight line over 6 to 7 stands, and gradually reduce them.
- the hot-rolled steel sheet H finish-rolled by the finish rolling mill 113 is transported to the cooling device 114 by a transport roll 132 (see FIG. 17).
- the rolling mill provided with the above-described pair of finish rolling rolls 113a arranged in a straight line is also referred to as a so-called rolling stand.
- a cooling device 142 that performs cooling between the stands (auxiliary cooling) during finish rolling is provided between the rolling rolls 113a arranged over 6 to 7 stands (that is, between the rolling stands). Has been placed.
- FIG. 16 shows a case where the cooling devices 142 are arranged at two locations in the finishing mill 113, but this cooling device 142 may be provided between all the rolling rolls 113a. The structure provided only in a part may be sufficient.
- the cooling device 114 is a facility for cooling the hot-rolled steel sheet H conveyed from the finish rolling mill 113 by nozzle laminator or spray. As shown in FIG. 17, the cooling device 114 has an upper cooling device 114a for injecting cooling water from the upper cooling port 131 to the upper surface of the hot-rolled steel sheet H moving on the transport roll 132 of the run-out table, On the lower surface of the hot-rolled steel sheet H, a lower cooling device 114b for injecting cooling water from the lower cooling port 131 is provided. A plurality of cooling ports 131 are provided for each of the upper cooling device 114a and the lower cooling device 114b. A cooling header (not shown) is connected to the cooling port 131.
- the cooling capacity of the upper cooling device 114a and the lower cooling device 114b is determined by the number of the cooling ports 131.
- the cooling device 114 may be composed of at least one of upper and lower split laminar, pipe laminar, spray cooling, and the like.
- the cooling header connected to the cooling port 131 of the upper cooling device 114a and the lower cooling device 114b may be on / off controlled respectively. Or you may control the operation parameter of each cooling header in the upper side cooling device 114a and the lower side cooling device 114b. That is, at least one of the water density, pressure, and water temperature of the cooling water ejected from each cooling port 131 may be adjusted.
- the cooling headers (cooling ports 131) of the upper cooling device 114a and the lower cooling device 114b may be thinned out to adjust the flow rate and pressure of the cooling water injected from the upper cooling device 114a and the lower cooling device 114b.
- the cooling capacity of the upper cooling device 114a before thinning out the cooling header is higher than the cooling capacity of the lower cooling device 114b, it is preferable to thin out the cooling header constituting the upper cooling device 114a.
- the winding device 115 winds the hot-rolled steel sheet H cooled by the cooling device 114 at a predetermined winding temperature.
- the hot-rolled steel sheet H wound in a coil shape by the winding device 115 is transported outside the hot rolling facility 2.
- the hot-rolled steel sheet H in which a corrugated shape whose surface height (wave height) fluctuates in the rolling direction is formed is performed, As described above, the hot-rolled steel sheet H is made uniform by appropriately adjusting the water density, pressure, water temperature, etc. of the cooling water injected from the upper cooling device 114a and the cooling water injected from the lower cooling device 114b. Can be cooled. However, especially when the sheet passing speed of the hot-rolled steel sheet H is slow, the time for which the hot-rolled steel sheet H and the transport roll 132 and the apron 133 are in contact with each other is long, and the transport roll 132 and apron of the hot-rolled steel sheet H are increased. Since the contact portion with 133 is easily cooled by contact heat removal, the cooling becomes uneven. The cause of this non-uniform cooling will be described below with reference to the drawings.
- the corrugated bottom of the hot-rolled steel sheet H may locally contact the transport roll 132.
- the apron 133 may be provided as a support for preventing that the hot-rolled steel plate H falls between the conveyance rolls 132 adjacent along a rolling direction.
- the corrugated bottom portion of the hot-rolled steel sheet H locally contacts the transport roll 132 and the apron 133.
- the part that locally contacts the transport roll 132 and the apron 133 is more easily cooled than the other part due to contact heat removal. For this reason, the hot-rolled steel sheet H is cooled unevenly.
- the time during which the hot-rolled steel sheet H locally contacts the transport roll 132 and the apron 133 becomes longer.
- the portion (the portion surrounded by the dotted line in FIG. 19A) where the hot-rolled steel sheet H locally contacts the transport roll 132 and the apron 133 is more easily cooled than the other portions.
- the rolled steel sheet H is cooled unevenly.
- the contact time is shortened.
- the hot rolled sheet steel H in the sheet passing plate is lifted from the sheet conveying roll 132 and the apron 133 due to repulsion due to contact between the hot rolled sheet steel H and the conveying roll 132 and the apron 133.
- the hot-rolled steel sheet H is lifted from the transport roll 132 and the apron 133 due to the repulsion due to the contact, and the hot-rolled steel sheet H and the transport roll 132 Since the contact time and the number of times of contact with the apron 133 are reduced, the temperature drop due to the contact becomes negligibly small.
- the hot-rolled steel sheet H can be cooled more uniformly as shown in FIG. 19B.
- the inventors have found that the hot-rolled steel sheet H can be cooled sufficiently uniformly by setting the sheet passing speed to 550 m / min or more.
- the lowest point of the hot-rolled steel sheet H is conveyed regardless of the height of the corrugated shape. Since it comes in contact with the roll 132 and the apron 133, increasing the sheet passing speed regardless of the height of the wave shape is effective for uniform cooling.
- the hot-rolled steel sheet H will be in the state which floated from the conveyance roll 132 or the apron 133 if the plate-feeding speed of the hot-rolled steel sheet H is set to 550 m / min or more, cooling water is supplied to the hot-rolled steel sheet H in this state. Even if it injects, there is no boarding water on the hot-rolled steel sheet H as in the prior art. Therefore, it is possible to avoid the hot-rolled steel sheet H from being unevenly cooled due to the riding water.
- the sheet passing speed of the hot-rolled steel sheet H in the cooling section is set to 550 m / min or more, the wave shape whose wave height varies periodically in the rolling direction. It is possible to cool the hot-rolled steel sheet H having a more uniform temperature.
- the plate-passing speed of the hot-rolled steel sheet H is better as it is higher, it is impossible to exceed the mechanical limit speed (for example, 1550 m / min). Therefore, the sheet feeding speed of the hot-rolled steel sheet H in the cooling section is substantially set within a range from 550 m / min or more to a mechanical limit speed or less.
- the operation upper limit speed (for example, 1200 m / min) is set from 550 m / min or more. min) is preferably set within a range up to or below.
- the hot-rolled steel sheet cooling method described with reference to FIGS. 1 to 14 may be combined with a high speed setting (set within a range from 550 m / min or more to a mechanical limit speed or less). .
- the steel sheet is a hot-rolled steel sheet H having a high tensile strength (particularly a steel sheet called so-called high tensile steel having a tensile strength (TS) of 800 MPa or more and a practical upper limit of 1400 MPa).
- TS tensile strength
- the sheet passing speed of the hot-rolled steel sheet H in the cooling device 114 is kept low, when the corrugated shape is formed on the hot-rolled steel sheet H, as described above, the hot-rolled steel sheet H, the transport roll 132, the apron 133, Due to the local contact, the contact portion is easily cooled by contact heat removal, and uneven cooling is performed.
- the inventors of the present application in the finishing mill 113 of the hot rolling facility 2, for example, cooled between a pair of finish rolling rolls 113a (that is, rolling stands) provided over, for example, 6 to 7 stands (so-called rolling stands). It was found that by performing (cooling between stands), the processing heat generation can be suppressed, and the sheet feeding speed of the hot-rolled steel sheet H in the cooling device 114 can be set to 550 m / min or more.
- the inter-stand cooling will be described with reference to FIG.
- FIG. 20 is an explanatory diagram of the finishing mill 113 capable of performing inter-stand cooling.
- the finish rolling mill 113 is provided with a plurality (three in FIG. 20) of rolling stands 140 including a pair of finish rolling rolls 113a and the like arranged in a straight line.
- the cooling device 142 which is the equipment which performs nozzle cooling by a laminar or a spray is provided, and inter-stand cooling is performed with respect to the hot-rolled steel sheet H between the rolling stands 140. It is possible.
- the cooling device 142 includes an upper cooling device 142 a that ejects cooling water from the upper side through a cooling port 146 to the hot rolled steel plate H conveyed in the finish rolling mill 113, and a lower surface of the hot rolled steel plate H. And a lower cooling device 142b for ejecting cooling water from the lower side.
- a plurality of cooling ports 146 are provided for each of the upper cooling device 142a and the lower cooling device 142b.
- a cooling header (not shown) is connected to the cooling port 146.
- the cooling device 142 may be composed of at least one of upper and lower split laminar, pipe laminar, spray cooling, and the like.
- the finish rolling mill 113 having the configuration shown in FIG. 20, particularly when the tensile strength (TS) of the hot-rolled steel sheet H is 800 MPa or more, processing heat generation of the hot-rolled steel sheet H is suppressed by performing inter-stand cooling. . Thereby, it is possible to keep the sheet passing speed of the hot-rolled steel sheet H in the cooling device 114 at 550 m / min or more. Therefore, the contact portion is easily cooled by contact heat removal due to local contact between the hot-rolled steel sheet H and the transport roll 132 or the apron 133, which has been a problem when cooling is performed at a conventional low plate speed. Therefore, the hot-rolled steel sheet H can be cooled sufficiently uniformly.
- TS tensile strength
- the hot-rolled steel sheet H is cooled by the cooling device 114 in a range where the temperature of the hot-rolled steel sheet H is 600 ° C. or higher.
- the temperature region where the temperature of the hot-rolled steel sheet H is 600 ° C. or higher is a so-called film boiling region. That is, in this case, the so-called transition boiling region can be avoided and the hot-rolled steel sheet H can be cooled in the film boiling region.
- the transition boiling region when the cooling water is sprayed on the surface of the hot-rolled steel sheet H, the surface covered with the vapor film on the surface of the hot-rolled steel sheet H, the part where the cooling water is directly sprayed on the hot-rolled steel sheet H, Are mixed.
- the hot-rolled steel sheet H cannot be cooled uniformly.
- the hot-rolled steel sheet H in the film boiling region, since the hot-rolled steel sheet H is cooled in a state where the entire surface of the hot-rolled steel sheet H is covered with the vapor film, the hot-rolled steel sheet H can be uniformly cooled. Therefore, the hot-rolled steel sheet H can be cooled more uniformly in the range where the temperature of the hot-rolled steel sheet H is 600 ° C. or more as in this embodiment.
- the present inventor conducted a cooling experiment on the hot-rolled steel sheet as an example. It was.
- Example 1 The hot-rolled steel sheet on which a plate thickness of 2.5 mm, a width of 1200 mm, a tensile strength of 400 MPa, and a steepness of 2% was formed was cooled by changing the sheet passing speed in the cooling device. Specifically, the sheeting speed is changed to 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min, and 650 m / min, and the hot-rolled steel sheet is cooled 20 times at each sheeting speed. I went one by one.
- CT temperature fluctuation amount the average value of the standard deviation of temperature fluctuation was computed using the temperature measurement result.
- Table 3 The results of evaluating the calculated CT temperature fluctuation amount are shown in Table 3 below. As an evaluation standard, when the CT temperature fluctuation amount is larger than 25 ° C., it is evaluated that it is not uniformly cooled, and when the CT temperature fluctuation amount is 25 ° C. or less, it is uniformly cooled. evaluated.
- Example 2 A hot-rolled steel sheet having a plate thickness of 2.5 mm, a width of 1200 mm, a tensile strength of 800 MPa and a steepness of 2% is cooled between stands so that the exit side temperature of finish rolling is 880 ° C. Cooling was carried out by changing the plate feeding speed. Specifically, the sheeting speed is changed to 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min, and 650 m / min, and the hot-rolled steel sheet is cooled 20 times at each sheeting speed. I went one by one.
- CT temperature fluctuation amount the average value of the standard deviation of temperature fluctuation was computed using the temperature measurement result.
- Table 4 The results of evaluating the calculated CT temperature fluctuation amount are shown in Table 4 below. Note that the evaluation criteria are the same as in the case of Example 1, and cooling between stands is not performed only when the plate passing speed is 400 m / min.
- the CT temperature fluctuation amount is not sufficiently reduced (higher than 25 ° C.) even when cooling between the stands is performed, and the hot-rolled steel sheet The uniform cooling is not sufficiently performed.
- the sheet feeding speed was 550 m / min or more, the CT temperature fluctuation amount was suppressed to 25 ° C. or less, and it was found that the hot-rolled steel sheet was uniformly cooled.
- the CT temperature fluctuation amount is suppressed even for a hot rolled steel sheet having a relatively high hardness (tensile strength of 800 MPa). That is, in addition to setting the sheeting speed during cooling of the hot-rolled steel sheet to 550 m / min or more, it is uniform for all steel materials, particularly steel materials with high hardness, by carrying out inter-stand rolling with a finish rolling mill. It became clear that it was possible to cool.
- the present invention is useful when cooling a hot-rolled steel sheet that has been hot-rolled by a finish rolling mill and has a corrugated shape whose surface height varies in the rolling direction.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Control Of Metal Rolling (AREA)
- Metal Rolling (AREA)
Abstract
Description
すなわち、
(1)本発明の一態様に係る熱延鋼板冷却方法は、仕上圧延機で熱間圧延された熱延鋼板を、その通板経路上に設けられた冷却区間において冷却する熱延鋼板冷却方法であって、予め実験的に前記熱延鋼板の急峻度及び通板速度を一定値とする条件下で求めておいた、前記熱延鋼板の上下面の熱伝達係数の比率である上下熱伝達係数比率Xと前記熱延鋼板の冷却中または冷却後の温度標準偏差Yとの相関関係を示す相関データに基づいて、前記温度標準偏差Yが最小値Yminとなる上下熱伝達係数比率X1を目標比率Xtとして設定する目標比率設定工程と;前記冷却区間における前記熱延鋼板の上下熱伝達係数比率Xが前記目標比率Xtと一致するように、前記冷却区間における前記熱延鋼板の上面冷却抜熱量と下面冷却抜熱量との少なくとも一方を制御する冷却制御工程と;を有する。
従って、本発明によれば、予め実験的に求めておいた、熱延鋼板の上下熱伝達係数比率Xと温度標準偏差Yとの相関データに基づいて、温度標準偏差Yが最小値Yminとなる上下熱伝達係数比率X1を目標比率Xtとして設定し、冷却区間における熱延鋼板の上下熱伝達係数比率Xが上記の目標比率Xtと一致するように、熱延鋼板の上面冷却抜熱量と下面冷却抜熱量との少なくとも一方を制御するので、
仕上圧延機で熱間圧延されて波形状が形成された熱延鋼板を均一に冷却することができる。
この熱間圧延設備1は、スラブSを加熱するための加熱炉11と、この加熱炉11において加熱されたスラブSを幅方向に圧延する幅方向圧延機16と、この幅方向に圧延されたスラブSを上下方向から圧延して粗バーにする粗圧延機12と、粗バーをさらに所定の厚みまで連続して熱間仕上圧延をする仕上圧延機13と、この仕上圧延機13により熱間仕上圧延された熱延鋼板Hを冷却水により冷却する冷却装置14と、冷却装置14により冷却された熱延鋼板Hをコイル状に巻き取る巻取装置15とを備えている。
また、冷却口31には、冷却ヘッダー(図示省略)が接続されている。この冷却口31の個数によって、上側冷却装置14a及び下側冷却装置14bの冷却能力が決定される。なお、この冷却装置14は、上下スプリットラミナー、パイプラミナー、スプレー冷却等の少なくとも一つで構成されていてもよい。また、この冷却装置14によって熱延鋼板Hが冷却される区間が、本発明における冷却区間に相当する。
なお、以下の説明において、仕上圧延機13で熱間圧延された熱延鋼板Hには、図17に示すように、その圧延方向に表面高さ(波高さ)が変動する波形状が形成されている。また、以下の説明において、熱延鋼板Hの冷却時に、その熱延鋼板H上に溜まる乗り水の影響は無視する。実際に、本願発明者による調査の結果、熱延鋼板H上に溜まる乗り水の影響はほとんどないことがわかっている。
詳細は後述するが、目標比率設定工程では、予め実験的に熱延鋼板Hの急峻度及び通板速度を一定値とする条件下で求めておいた、熱延鋼板Hの上下面の熱伝達係数の比率である上下熱伝達係数比率Xと熱延鋼板Hの冷却中または冷却後の温度標準偏差Yとの相関関係を示す相関データに基づいて、温度標準偏差Yが最小値Yminとなる上下熱伝達係数比率X1を目標比率Xtとして設定する。
また、冷却制御工程では、冷却区間(冷却装置14によって熱延鋼板Hが冷却される区間)における熱延鋼板Hの上下熱伝達係数比率Xが上記の目標比率Xtと一致するように、冷却区間における熱延鋼板Hの上面冷却抜熱量と下面冷却抜熱量との少なくとも一方を制御する。
先ず、冷却装置14で熱延鋼板Hを冷却する前に、予め冷却装置14の上側冷却装置14aの冷却能力(上側冷却能力)と下側冷却装置14bの冷却能力(下側冷却能力)をそれぞれ調整する。これら上側冷却能力と下側冷却能力は、それぞれ上側冷却装置14aによって冷却される熱延鋼板Hの上面の熱伝達係数と、下側冷却装置14bによって冷却される熱延鋼板Hの下面の熱伝達係数とを用いて調整する。
また、冷却抜熱量は、熱延鋼板Hの温度差と比熱と質量をそれぞれ乗じた値である(冷却抜熱量=温度差×比熱×質量)。すなわち、冷却抜熱量は冷却装置14における熱延鋼板Hの冷却抜熱量であって、冷却装置14の入口側の温度計と出口側の温度計によってそれぞれ測定される熱延鋼板Hの温度の差と、熱延鋼板Hの比熱と、冷却装置14で冷却される熱延鋼板Hの質量とをそれぞれ乗じた値である。
すなわち、上側冷却装置14aのみで熱延鋼板Hを冷却する場合の熱延鋼板Hの熱伝達係数と、下側冷却装置14bのみで熱延鋼板Hを冷却する場合の熱延鋼板Hの熱伝達係数を測定する。
このとき、上側冷却装置14aからの冷却水量と下側冷却装置14bからの冷却水量を同一とする。測定された上側冷却装置14aを用いた場合の熱伝達係数と下側冷却装置14bを用いた場合の熱伝達係数との比率の逆数が、後述の上下熱伝達係数比率Xを“1”とする場合の上側冷却装置14aの冷却水量と下側冷却装置14bの冷却水量との上下比率となる。
そして、このようにして得られた冷却水量の上下比率を、熱延鋼板Hを冷却する際の上側冷却装置14aの冷却水量又は下側冷却装置14bの冷却水量に乗じて、上述した熱延鋼板Hの上面と下面の熱伝達係数の比率(上下熱伝達係数比率X)を算出する。
また、上述では、上側冷却装置14aのみと下側冷却装置14bのみで冷却される熱延鋼板Hの熱伝達係数を用いたが、上側冷却装置14aと下側冷却装置14bの両方で冷却される熱延鋼板Hの熱伝達係数を用いてもよい。すなわち、上側冷却装置14aと下側冷却装置14bの冷却水量を変更した場合の熱延鋼板Hの熱伝達係数を測定し、その熱伝達係数の比率を用いて熱延鋼板Hの上面と下面の熱伝達係数の比率を算出してもよい。
また、図3は、熱延鋼板Hの波形状の急峻度と熱延鋼板Hの通板速度を一定値とする条件下で、上側冷却装置14aと下側冷却装置14bの冷却能力を調整することにより、熱延鋼板Hの上下熱伝達係数比率Xを変動させながら、冷却後の熱延鋼板Hの温度標準偏差Yを実測して得られた、上下熱伝達係数比率Xと温度標準偏差Yとの相関関係を示すデータ(相関データ)である。
図3を参照すると、温度標準偏差Yと上下熱伝達係数比率Xとの相関関係は、上下熱伝達係数比率Xが“1”の時に温度標準偏差Yが最小値Yminとなる、V字状の関係になっていることが分かる。
なお、熱延鋼板Hの波形状の急峻度とは、波形状の振幅を1周期分の圧延方向の長さで割った値である。図3は、熱延鋼板Hの急峻度を2%とし、通板速度を600m/min(10m/sec)とする条件下で得られた上下熱伝達係数比率Xと温度標準偏差Yとの相関データである。温度標準偏差Yは、熱延鋼板Hの冷却中に測定しても良いし、冷却後に測定しても良い。また、図3において熱延鋼板Hの目標冷却温度は600℃以上の温度であって、例えば800℃である。
次に、a点とc点の真中のd点における温度標準偏差Ydを抽出する。そして、温度標準偏差YdがYa又はYcのどちらの値に近いかを判断する。本実施形態では、YdはYcに近い。
次に、c点とd点の真中のe点における温度標準偏差Yeを抽出する。そして、温度標準偏差YeがYc又はYdのどちらの値に近いかを判断する。本実施形態では、YeはYdに近い。
このような演算を繰り返し行い、熱延鋼板Hの温度標準偏差Yの最小点f(最小値Ymin)を特定する。なお、実用的な最小点fを特定するためには、上述した演算を例えば5回程度行えばよい。また、探索対象の上下熱伝達係数比率Xの範囲を10分割し、それぞれの範囲で上述した演算を行って最小点fを特定してもよい。
そして、冷却制御工程において、冷却区間における熱延鋼板Hの上下熱伝達係数比率Xが上記の目標比率Xt(つまり“1”)と一致するように、冷却区間における熱延鋼板Hの上面冷却抜熱量と下面冷却抜熱量との少なくとも一方が制御されることになる。
具体的には、冷却区間における熱延鋼板Hの上下熱伝達係数比率Xを目標比率Xt(つまり“1”)と一致させるためには、例えば、上側冷却装置14aの冷却能力と下側冷却装置14bの冷却能力を同等に調整することにより、熱延鋼板Hの上面冷却抜熱量と下面冷却抜熱量を等しくすれば良い。
表1は、図3に示した相関データ(つまり、上下熱伝達係数比率Xと温度標準偏差Yとの相関関係)と、各温度標準偏差Yから最小値Ymin(=2.3℃)を差し引いた値(最小値からの標準偏差の差分)と、各温度標準偏差Yの評価を示している。
表1中の上下熱伝達係数比率Xについては、分子が熱延鋼板Hの上面における熱伝達係数であり、分母が熱延鋼板Hの下面における熱伝達係数である。また、表1中の評価(上下熱伝達係数比率Xの条件についての評価)においては、温度標準偏差Yが最小値Yminとなる条件を“A”とし、後述するように最小値からの標準偏差の差分が10℃以内、すなわち操業が好適となる条件を“B”とし、上述した回帰式を得るために試行錯誤的に行った条件を“C”としている。そして、表1を参照しても、評価が“A”となる、すなわち熱延鋼板Hの温度標準偏差Yが最小値Yminとなる上下熱伝達係数比率X1は“1”である。
なお、熱延鋼板Hの温度測定には様々なノイズがあるため、熱延鋼板Hの温度標準偏差Yの最小値Yminは厳密にはゼロにならない場合がある。そこで、このノイズの影響を除去するため、製造許容範囲を、熱延鋼板Hの温度標準偏差Yが最小値Yminから最小値Ymin+10℃以内の範囲としている。
そこで、上述した目標比率設定工程及び冷却制御工程に、冷却区間(つまり冷却装置14)の下流側における熱延鋼板Hの温度を時系列で測定する温度測定工程と、その温度の測定結果に基づいて温度の時系列平均値を算出する温度平均値算出工程と、その温度の時系列平均値が所定の目標温度と一致するように、冷却区間における熱延鋼板Hの上面冷却抜熱量と下面冷却抜熱量との合計値を調整する冷却抜熱量調整工程と、を新たに加えても良い。
これらの新たな工程を実現するために、図13に示すように冷却装置14と巻取装置15との間に配置されている、熱延鋼板Hの温度を測定する温度計40を使用することができる。
ここで、冷却区間における熱延鋼板Hの上下熱伝達係数比率Xを目標比率Xtと一致させるという制御目標を達成しながら、上面冷却抜熱量と下面冷却抜熱量との合計値を調整する必要がある。
具体的に、上面冷却抜熱量と下面冷却抜熱量との合計値を調整する時には、例えば三塚の式等に代表される実験理論式を用いて予め求められた理論値に対して、実際の操業実績との誤差を補正する様に設定した学習値に基づき、冷却装置14に接続される冷却ヘッダーのオンオフ制御を行っても良い。或いは、実際に温度計40で測定された温度に基づいて、上記冷却ヘッダーのオンオフをフィードバック制御又はフィードフォワード制御してもよい。
なお、形状計41は、熱延鋼板H上に定められた温度計40と同一の測定位置(以下では、この測定位置を定点と呼ぶ場合がある)の形状を測定する。ここで、形状とは、定点測定で観測される熱延鋼板Hの高さ方向の変動量に熱延鋼板Hの通板方向の移動量を用いて、波のピッチ分の高さ或いは変動成分の線積分で求めた急峻度である。また、同時に単位時間当たりの変動量、つまり変動速度も求める。さらに、形状の測定領域は、温度の測定領域と同様に、熱延鋼板Hの幅方向の全域を含む。温度測定結果と同じく、各測定結果(急峻度、変動速度等)がサンプリングされた時間に通板速度を乗じると、各測定結果の時系列データを圧延方向の位置に紐付けすることが可能となる。
図5は、通常の操業における代表的なストリップのROT内冷却の熱延鋼板Hの温度変動と急峻度の関係を示している。図5における熱延鋼板Hの上下熱伝達係数比率Xは1.2:1であり、上側冷却能力が下側冷却能力よりも高くなっている。図5の上側のグラフは、コイル先端からの距離或いは定点経過時間に対する温度変動を示し、図5の下側のグラフは、コイル先端からの距離または定点経過時間に対する急峻度を示している。
図5における領域Aは、図13に示すストリップ先端部が巻取装置15のコイラーに噛み込まれる前の領域(張力が無い為、形状が悪い領域)である。図5における領域Bは、ストリップ先端部がコイラーに噛み込まれた後の領域(ユニットテンションの影響で波形状がフラットに変化する領域)である。このような熱延鋼板Hの形状がフラットでない領域Aで発生する大きな温度変動(つまり温度標準偏差Y)を改善することが望まれる。
なお、平均温度は、原則として周期単位での範囲の平均である。また、1周期の範囲の平均温度は、2周期以上の範囲の平均温度と大きな差がないことが操業データによって確認されている。
従って、少なくとも波形状1周期の範囲の平均温度を算出すればよい。熱延鋼板Hの波形状の範囲の上限は特に限定されないが、好ましくは5周期に設定すれば、十分な精度の平均温度を得られる。また、平均する範囲が周期単位の範囲でなくとも、2~5周期の範囲であれば許容できる平均温度を得られる。
また、定点で測定された変動速度が負の領域で、上記の平均温度に対して熱延鋼板Hの温度が低い場合は、上面冷却抜熱量が増加する方向及び下面冷却抜熱量が減少する方向の少なくとも一方を制御方向として決定し、上記の平均温度に対して熱延鋼板Hの温度が高い場合は、上面冷却抜熱量が減少する方向及び下面冷却抜熱量が増加する方向の少なくとも一方を制御方向として決定する。
そして、上記のように決定された制御方向に基づいて、冷却区間における熱延鋼板Hの上面冷却抜熱量及び下面冷却抜熱量の少なくとも一方を調整すると、図7に示すように、図6と比較して、熱延鋼板Hの形状がフラットでない領域Aで発生する温度変動を低減できることがわかった。
また、定点で測定された変動速度が負の領域で、上記の平均温度に対して熱延鋼板Hの温度が低い場合は、上面冷却抜熱量が減少する方向及び下面冷却抜熱量が増加する方向の少なくとも一方を制御方向として決定し、上記の平均温度に対して熱延鋼板Hの温度が高い場合は、上面冷却抜熱量が増加する方向及び下面冷却抜熱量が減少する方向の少なくとも一方を制御方向として決定する。
そして、上記のように決定された制御方向に基づいて、冷却区間における熱延鋼板Hの上面冷却抜熱量及び下面冷却抜熱量の少なくとも一方を調整すると、図8に示すように、図6と比較して、熱延鋼板Hの形状がフラットでない領域Aで発生する温度変動が拡大することがわかった。なお、ここで説明する例でも冷却停止温度を変えてよいという前提にはなっていない。
ここで、制御方向決定工程では、上記のように、熱延鋼板Hの定点での変動速度が正の領域で、熱延鋼板Hの定点での平均温度に対して熱延鋼板Hの定点での温度が低い場合は、上面冷却抜熱量が減少する方向及び下面冷却抜熱量が増加する方向の少なくとも一方を制御方向として決定し、上記の平均温度に対して熱延鋼板Hの温度が高い場合は、上面冷却抜熱量が増加する方向及び下面冷却抜熱量が減少する方向の少なくとも一方を制御方向として決定する。
また、この制御方向決定工程では、上記の変動速度が負の領域で、上記の平均温度に対して熱延鋼板Hの温度が低い場合は、上面冷却抜熱量が増加する方向及び下面冷却抜熱量が減少する方向の少なくとも一方を制御方向として決定し、上記の平均温度に対して熱延鋼板Hの温度が高い場合は、上面冷却抜熱量が減少する方向及び下面冷却抜熱量が増加する方向の少なくとも一方を制御方向として決定する。
なお、この冷却方法においても、冷却区間における熱延鋼板Hの上下熱伝達係数比率Xを目標比率Xtと一致させるという制御目標を達成しながら、上面冷却抜熱量と下面冷却抜熱量を調整する必要がある。
また、上側冷却装置14aと下側冷却装置14bの冷却ヘッダー(冷却口31)を間引いて、上側冷却装置14aと下側冷却装置14bから噴射される冷却水の流量や圧力を調整してもよい。例えば、冷却ヘッダーを間引く前の上側冷却装置14aの冷却能力が、下側冷却装置14bの冷却能力よりも上回っている場合、上側冷却装置14aを構成する冷却ヘッダーを間引くことが好ましい。
このため、熱延鋼板Hを均一に冷却することができない。一方、膜沸騰領域では、熱延鋼板Hの表面全体が蒸気膜に覆われた状態で熱延鋼板Hの冷却が行われるので、熱延鋼板Hを均一に冷却することができる。したがって、本実施形態のように熱延鋼板Hの温度が600℃以上の範囲において、熱延鋼板Hをより均一に冷却することができる。
Yz’=Yz×2/z・・・・(1)
この表3における上下熱伝達係数比率Xの表示と評価の基準については、表1の評価と同様であるので説明を省略する。この図10又は表3を用いて、急峻度に応じた熱延鋼板Hの温度標準偏差Yを導出できる。そして、例えば、急峻度を2%に補正する場合、表3における評価が“B”となる、すなわち熱延鋼板Hの最小値からの標準偏差の差分が10℃以内となる上下熱伝達係数比率Xを1.1に設定することができる。
Yz’=Yv×10/v・・・・(2)
この表4における上下熱伝達係数比率Xの表示と評価の基準については、表1の評価と同様であるので説明を省略する。この図12又は表4を用いて、通板速度に応じた熱延鋼板Hの温度標準偏差Yを導出できる。そして、例えば、通板速度を10m/secに補正する場合、表4における評価が“B”となる、すなわち熱延鋼板Hの最小値からの標準偏差の差分が10℃以内となる上下熱伝達係数比率Xを1.1に設定することができる。
また、温度標準偏差Yの大きさに基づいて、その温度標準偏差Yが許容範囲、例えば最小値Yminから最小値Ymin+10℃以内の範囲に収まるように上下熱伝達係数比率Xを決定することができる。この上下熱伝達係数比率Xを決定する方法は、図3及び図4を用いて説明した上記実施形態と同様であるので、詳細な説明を省略する。なお、この温度標準偏差Yを最小値Yminから最小値Ymin+10℃以内の範囲に収めることにより、降伏応力、引張強さなどのバラつきを製造許容範囲内に抑えられ、熱延鋼板Hを均一に冷却できる。
また、かなりのばらつきはあるものの、冷却水量密度比率が、温度標準偏差Yが最小値Yminとなる冷却水量密度比率に対して±5%以内であれば、温度標準偏差Yが最小値Yminから最小値Ymin+10℃以内の範囲に収まる。すなわち、冷却水量密度を用いる場合、冷却水量密度の上下比率(冷却水量密度比率)を、温度標準偏差Yが最小値Yminとなる冷却水量密度比率に対して±5%以内に設定することが望ましい。ただし、この許容範囲は必ずしも上下同水量密度を含むとは限らない。
また、分割冷却区間Z2においては、その下流側における温度計40と形状計41の測定結果に基づいて、上側冷却装置14aと下側冷却装置14bの冷却能力がフィードフォワード制御されてもよいし、或いはフィードバック制御されてもよい。いずれの場合においても、分割冷却区間Z2において、上面冷却抜熱量及び下面冷却抜熱量の少なくとも一方が調整される。
図16は、他の実施形態における熱間圧延設備2の例を模式的に示している。この熱間圧延設備2は、加熱したスラブSをロールで上下に挟んで連続的に圧延し、最小1.2mmまで薄くしてこれを巻き取ることを目的とした設備である。
この熱間圧延設備2は、スラブSを加熱するための加熱炉111と、この加熱炉111において加熱されたスラブSを幅方向に圧延する幅方向圧延機116と、この幅方向に圧延されたスラブSを上下方向から圧延して粗バーにする粗圧延機112と、粗バーをさらに所定の厚みまで連続して熱間仕上圧延をする仕上圧延機113と、この仕上圧延機113により熱間仕上圧延された熱延鋼板Hを冷却水により冷却する冷却装置114と、冷却装置114により冷却された熱延鋼板Hをコイル状に巻き取る巻取装置115とを備えている。
次に、このワークロール112aを通過した粗バーをワークロールとバックアップロールとで構成される複数の4重圧延機112bにより、さらに連続的に圧延する。その結果、この粗圧延工程の終了時に、粗バーは、厚さ30~60mm程度まで圧延され、仕上圧延機113へと搬送されることになる。なお、粗圧延機112の構成は本実施形態に記載したものに限定されず、ロール数等は任意に設定することが可能である。
冷却口131は、上側冷却装置114a及び下側冷却装置114bのそれぞれについて複数個設けられている。また、冷却口131には、冷却ヘッダー(図示省略)が接続されている。この冷却口131の個数によって、上側冷却装置114a及び下側冷却装置114bの冷却能力が決定される。なお、この冷却装置114は、上下スプリットラミナー、パイプラミナー、スプレー冷却等の少なくとも一つで構成されていてもよい。
あるいは、上側冷却装置114aと下側冷却装置114bにおける各冷却ヘッダーの操業パラメータを制御してもよい。即ち、各冷却口131から噴出される冷却水の水量密度、圧力、水温の少なくとも一つを調整してもよい。
また、上側冷却装置114aと下側冷却装置114bの冷却ヘッダー(冷却口131)を間引いて、上側冷却装置114aと下側冷却装置114bから噴射される冷却水の流量や圧力を調整してもよい。例えば、冷却ヘッダーを間引く前における上側冷却装置114aの冷却能力が、下側冷却装置114bの冷却能力よりも上回っている場合、上側冷却装置114aを構成する冷却ヘッダーを間引くことが好ましい。
一方、熱延鋼板Hの通板速度を高速にすると、上記接触時間が短くなる。しかも、通板速度が高速化すると、熱延鋼板Hと搬送ロール132やエプロン133との接触による反発によって、通板中の熱延鋼板Hが、これら搬送ロール132やエプロン133から浮いた状態になる。
また、熱延鋼板Hの通板速度を高速化すると、上記接触による反発によって熱延鋼板Hが搬送ロール132やエプロン133から浮いた状態となることに加え、熱延鋼板Hと搬送ロール132やエプロン133との接触時間や接触回数が減少するため、その接触による温度降下は無視できるほどに小さくなる。
従って、通板速度を高速化することで接触抜熱を抑制することができ、図19Bに示すように、熱延鋼板Hをより均一に冷却することができる。そして、この通板速度を550m/min以上に設定することにより、熱延鋼板Hを十分に均一に冷却できることを発明者らは見出した。
なお、このような知見は、波形状が形成された熱延鋼板Hにおける冷却について得られたものであるが、その波形状の高さに拘らず、熱延鋼板Hの最下点は、搬送ロール132やエプロン133と接触することになるため、波形状の高さに依らずに通板速度を高速化することは、均一な冷却を行うのに有効である。
なお、熱延鋼板Hの通板速度は、高速であるほど良いが、機械的な限界速度(例えば、1550m/min)を越えることは不可能である。従って、実質的に、冷却区間における熱延鋼板Hの通板速度は、550m/min以上から機械的な限界速度以下までの範囲内に設定されることになる。また、実操業時における通板速度の上限値(操業上限速度)が予め定められている場合には、熱延鋼板Hの通板速度を、550m/min以上から操業上限速度(例えば、1200m/min)以下までの範囲内に設定することが好ましい。
勿論、図1~図14を用いて説明した熱延鋼板冷却方法に、通板速度の高速度設定(550m/min以上から機械的な限界速度以下までの範囲内に設定)を組み合わせても良い。
一方、膜沸騰領域では、熱延鋼板Hの表面全体が蒸気膜に覆われた状態で熱延鋼板Hの冷却が行われるので、熱延鋼板Hを均一に冷却することができる。したがって、本実施形態のように熱延鋼板Hの温度が600℃以上の範囲において、熱延鋼板Hをより均一に冷却することができる。
板厚2.5mm、幅1200mm、引張強度400MPa及び急峻度2%の中波が形成された熱延鋼板について、冷却装置での通板速度を変更して冷却を行った。具体的には、通板速度を400m/min、450m/min、500m/min、550m/min、600m/min、650m/minに変更し、各通板速度での熱延鋼板の冷却を20回ずつ行った。
そして、巻き取り時の熱延鋼板の温度を測定し、その温度測定結果を用いて温度変動の標準偏差の平均値(CT温度変動量)を算出した。その算出されたCT温度変動量について評価を行った結果を以下の表3に示す。なお、評価基準としては、CT温度変動量が25℃より大きい場合には、均一に冷却されていないと評価し、CT温度変動量が25℃以下の場合には、均一に冷却されていると評価した。
板厚2.5mm、幅1200mm、引張強度800MPa及び急峻度2%の中波が形成された熱延鋼板について、仕上げ圧延の出口側温度が880℃となるようにスタンド間冷却を行い、冷却装置での通板速度を変更して冷却を行った。具体的には、通板速度を400m/min、450m/min、500m/min、550m/min、600m/min、650m/minに変更し、各通板速度での熱延鋼板の冷却を20回ずつ行った。
そして、巻き取り時の熱延鋼板の温度を測定し、その温度測定結果を用いて温度変動の標準偏差の平均値(CT温度変動量)を算出した。その算出されたCT温度変動量について評価を行った結果を以下の表4に示す。なお、評価基準については上記実施例1の場合と同様とし、通板速度400m/minの場合のみスタンド間冷却を行っていない。
11、111 加熱炉
12、112 粗圧延機
12a、112a ワークロール
12b、112b 4重圧延機
13、113 仕上圧延機
13a、113a 仕上げ圧延ロール
14、114 冷却装置
14a、114a 上側冷却装置
14b、114b 下側冷却装置
15、115 巻取装置
16、116 幅方向圧延機
31、131 冷却口
32、132 搬送ロール
40 温度計
41 形状計
H 熱延鋼板
S スラブ
Z1、Z2 分割冷却区間
Claims (17)
- 仕上圧延機で熱間圧延された熱延鋼板を、その通板経路上に設けられた冷却区間において冷却する熱延鋼板冷却方法であって、
予め実験的に前記熱延鋼板の急峻度及び通板速度を一定値とする条件下で求めておいた、前記熱延鋼板の上下面の熱伝達係数の比率である上下熱伝達係数比率Xと前記熱延鋼板の冷却中または冷却後の温度標準偏差Yとの相関関係を示す相関データに基づいて、前記温度標準偏差Yが最小値Yminとなる上下熱伝達係数比率X1を目標比率Xtとして設定する目標比率設定工程と;
前記冷却区間における前記熱延鋼板の上下熱伝達係数比率Xが前記目標比率Xtと一致するように、前記冷却区間における前記熱延鋼板の上面冷却抜熱量と下面冷却抜熱量との少なくとも一方を制御する冷却制御工程と;
を有することを特徴とする熱延鋼板冷却方法。 - 前記目標比率設定工程では、前記相関データに基づいて、前記温度標準偏差Yが最小値Yminから最小値Ymin+10℃以内の範囲に収まる上下熱伝達係数比率Xを前記目標比率Xtとして設定することを特徴とする請求項1に記載の熱延鋼板冷却方法。
- 前記相関データは、前記急峻度及び前記通板速度の値が異なる複数の条件のそれぞれについて用意されており、
前記目標比率設定工程では、前記複数の相関データの内、前記急峻度及び前記通板速度の実測値に応じた相関データに基づいて前記目標比率Xtを設定することを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記相関データは、前記上下熱伝達係数比率Xと前記温度標準偏差Yとの相関関係を回帰式で示すデータであることを特徴とする請求項3に記載の熱延鋼板冷却方法。
- 前記回帰式は線形回帰によって導出されたものであることを特徴とする請求項4に記載の熱延鋼板冷却方法。
- 前記相関データは、前記上下熱伝達係数比率Xと前記温度標準偏差Yとの相関関係をテーブルで示すデータであることを特徴とする請求項3に記載の熱延鋼板冷却方法。
- 前記冷却区間の下流側における前記熱延鋼板の温度を時系列で測定する温度測定工程と;
前記温度の測定結果に基づいて前記温度の時系列平均値を算出する温度平均値算出工程と;
前記温度の時系列平均値が所定の目標温度と一致するように、前記冷却区間における前記熱延鋼板の前記上面冷却抜熱量と前記下面冷却抜熱量との合計値を調整する冷却抜熱量調整工程と;
をさらに有することを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記冷却区間の下流側における前記熱延鋼板の温度を時系列で測定する温度測定工程と;
前記冷却区間の下流側における前記熱延鋼板の温度測定箇所と同一箇所での前記熱延鋼板の鉛直方向の変動速度を時系列で測定する変動速度測定工程と;
前記熱延鋼板の鉛直方向の上向きを正とした場合において、前記変動速度が正の領域で、前記熱延鋼板の波形状1周期以上の範囲の平均温度に対して前記熱延鋼板の温度が低い場合は、前記上面冷却抜熱量が減少する方向及び前記下面冷却抜熱量が増加する方向の少なくとも一方を制御方向として決定し、前記平均温度に対して前記熱延鋼板の温度が高い場合は、前記上面冷却抜熱量が増加する方向及び前記下面冷却抜熱量が減少する方向の少なくとも一方を前記制御方向として決定し、
前記変動速度が負の領域で、前記平均温度に対して前記熱延鋼板の温度が低い場合は、前記上面冷却抜熱量が増加する方向及び前記下面冷却抜熱量が減少する方向の少なくとも一方を前記制御方向として決定し、前記平均温度に対して前記熱延鋼板の温度が高い場合は、前記上面冷却抜熱量が減少する方向及び前記下面冷却抜熱量が増加する方向の少なくとも一方を前記制御方向として決定する制御方向決定工程と;
前記制御方向決定工程にて決定された前記制御方向に基づいて、前記冷却区間における前記熱延鋼板の前記上面冷却抜熱量及び前記下面冷却抜熱量の少なくとも一方を調整する冷却抜熱量調整工程と;
をさらに有することを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記冷却区間は、前記熱延鋼板の通板方向に沿って複数の分割冷却区間に分割されており、
前記温度測定工程及び前記変動速度測定工程では、前記分割冷却区間の境のそれぞれにおいて前記熱延鋼板の温度及び変動速度を時系列的に測定し;
前記制御方向決定工程では、前記分割冷却区間の境のそれぞれにおける前記熱延鋼板の温度及び変動速度の測定結果に基づいて、前記分割冷却区間のそれぞれについて前記熱延鋼板の上下面の冷却抜熱量の増減方向を決定し;
前記冷却抜熱量調整工程では、前記分割冷却区間のそれぞれについて決定された前記制御方向に基づいて、前記分割冷却区間のそれぞれにおいて前記熱延鋼板の前記上面冷却抜熱量及び前記下面冷却抜熱量の少なくとも一方を調整するためにフィードバック制御又はフィードフォワード制御を行う;
ことを特徴とする請求項8に記載の熱延鋼板冷却方法。 - 前記分割冷却区間の境のそれぞれにおいて前記熱延鋼板の前記急峻度又は前記通板速度を測定する測定工程と;
前記急峻度または前記通板速度の測定結果に基づいて、前記分割冷却区間のそれぞれにおける前記熱延鋼板の前記上面冷却抜熱量及び前記下面冷却抜熱量の少なくとも一方を補正する冷却抜熱量補正工程と;
をさらに有することを特徴とする請求項9に記載の熱延鋼板冷却方法。 - 前記冷却区間の下流側において、前記熱延鋼板の温度標準偏差が許容される範囲に入るように、前記熱延鋼板をさらに冷却する後冷却工程をさらに有することを特徴とする請求項1または2に記載の熱延鋼板冷却方法。
-
前記冷却区間における前記熱延鋼板の通板速度は、550m/min以上から機械的な限界速度以下の範囲内に設定されていることを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記熱延鋼板の引張強度は、800MPa以上であることを特徴とする請求項12に記載の熱延鋼板冷却方法。
- 前記仕上圧延機は複数の圧延スタンドから構成されており、
前記複数の圧延スタンド同士の間で前記熱延鋼板の補助冷却を行う補助冷却工程をさらに有することを特徴とする請求項12に記載の熱延鋼板冷却方法。 - 前記冷却区間には、前記熱延鋼板の上面に冷却水を噴射する複数のヘッダーを有する上側冷却装置と、前記熱延鋼板の下面に冷却水を噴射する複数のヘッダーを有する下側冷却装置とが設けられており、
前記上面冷却抜熱量及び前記下面冷却抜熱量は、前記各ヘッダーをオンオフ制御することによって調整されることを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記冷却区間には、前記熱延鋼板の上面に冷却水を噴射する複数のヘッダーを有する上側冷却装置と、前記熱延鋼板の下面に冷却水を噴射する複数のヘッダーを有する下側冷却装置とが設けられており、
前記上面冷却抜熱量及び前記下面冷却抜熱量は、前記各ヘッダーの水量密度、圧力及び水温の少なくとも一つを制御することによって調整されることを特徴とする請求項1または2に記載の熱延鋼板冷却方法。 - 前記冷却区間での冷却は、前記熱延鋼板の温度が600℃以上の範囲で行われることを特徴とする請求項1または2に記載の熱延鋼板冷却方法。
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020137022932A KR101467724B1 (ko) | 2012-12-06 | 2012-12-06 | 열연 강판 냉각 방법 |
BR112013028835-3A BR112013028835B1 (pt) | 2012-12-06 | 2012-12-06 | Método para o resfriamento da chapa de aço laminada a quente |
JP2013512030A JP5310965B1 (ja) | 2012-12-06 | 2012-12-06 | 熱延鋼板冷却方法 |
PCT/JP2012/081670 WO2014087524A1 (ja) | 2012-12-06 | 2012-12-06 | 熱延鋼板冷却方法 |
US14/111,457 US9186710B2 (en) | 2011-06-07 | 2012-12-06 | Method for cooling hot-rolled steel sheet |
CN201280010631.0A CN103987470B (zh) | 2012-12-06 | 2012-12-06 | 热轧钢板冷却方法 |
EP12873475.3A EP2764932B1 (en) | 2012-12-06 | 2012-12-06 | Method for cooling hot-rolled steel sheet |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/JP2012/081670 WO2014087524A1 (ja) | 2012-12-06 | 2012-12-06 | 熱延鋼板冷却方法 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2014087524A1 true WO2014087524A1 (ja) | 2014-06-12 |
Family
ID=49529543
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2012/081670 WO2014087524A1 (ja) | 2011-06-07 | 2012-12-06 | 熱延鋼板冷却方法 |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP2764932B1 (ja) |
JP (1) | JP5310965B1 (ja) |
KR (1) | KR101467724B1 (ja) |
CN (1) | CN103987470B (ja) |
BR (1) | BR112013028835B1 (ja) |
WO (1) | WO2014087524A1 (ja) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6204204B2 (ja) * | 2014-01-20 | 2017-09-27 | 中国電力株式会社 | ボイラー燃料投入量決定装置 |
JP6176730B2 (ja) * | 2014-02-19 | 2017-08-09 | Kddi株式会社 | クラスタリング装置、方法及びプログラム |
CN106493179B (zh) * | 2016-12-25 | 2018-08-21 | 首钢集团有限公司 | 一种钢板水冷过程头尾过冷区长度计算的方法 |
WO2020162004A1 (ja) * | 2019-02-07 | 2020-08-13 | Jfeスチール株式会社 | 厚鋼板の冷却制御方法、冷却制御装置及び厚鋼板の製造方法 |
CN114653783B (zh) * | 2020-12-22 | 2024-05-10 | 上海飞机制造有限公司 | 一种冲压成形方法 |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH05337505A (ja) | 1992-06-11 | 1993-12-21 | Kawasaki Steel Corp | 熱間圧延における被圧延材の冷却制御方法 |
JPH06328117A (ja) | 1993-05-18 | 1994-11-29 | Nippon Steel Corp | 連続熱間圧延のrot冷却における注水方法 |
JPH0763750B2 (ja) * | 1988-12-28 | 1995-07-12 | 新日本製鐵株式会社 | 熱間圧延鋼板の冷却制御装置 |
JP2003048003A (ja) | 2001-07-31 | 2003-02-18 | Nkk Corp | 熱延鋼板の製造方法 |
JP2005074463A (ja) | 2003-08-29 | 2005-03-24 | Nippon Steel Corp | 厚鋼板の冷却方法 |
JP2005271052A (ja) | 2004-03-25 | 2005-10-06 | Jfe Steel Kk | 熱間圧延方法 |
JP2011073054A (ja) * | 2009-10-02 | 2011-04-14 | Nippon Steel Corp | 熱延鋼板の冷却方法及び冷却装置 |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3480366B2 (ja) * | 1999-05-07 | 2003-12-15 | 住友金属工業株式会社 | 熱延鋼板の巻取温度制御方法 |
CN101489696B (zh) * | 2007-07-19 | 2011-07-06 | 新日本制铁株式会社 | 冷却控制方法、冷却控制装置及冷却水量计算装置 |
EP2361699A1 (de) * | 2010-02-26 | 2011-08-31 | Siemens Aktiengesellschaft | Verfahren zur Kühlung eines Blechs mittels einer Kühlstrecke, Kühlstrecke und Steuer- und/oder Regeleinrichtung für eine Kühlstrecke |
CN102166582B (zh) * | 2010-12-13 | 2013-02-27 | 河北省首钢迁安钢铁有限责任公司 | 一种提高卷取温度控制精度的方法 |
-
2012
- 2012-12-06 BR BR112013028835-3A patent/BR112013028835B1/pt active IP Right Grant
- 2012-12-06 CN CN201280010631.0A patent/CN103987470B/zh active Active
- 2012-12-06 WO PCT/JP2012/081670 patent/WO2014087524A1/ja active Application Filing
- 2012-12-06 KR KR1020137022932A patent/KR101467724B1/ko active IP Right Grant
- 2012-12-06 EP EP12873475.3A patent/EP2764932B1/en active Active
- 2012-12-06 JP JP2013512030A patent/JP5310965B1/ja active Active
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0763750B2 (ja) * | 1988-12-28 | 1995-07-12 | 新日本製鐵株式会社 | 熱間圧延鋼板の冷却制御装置 |
JPH05337505A (ja) | 1992-06-11 | 1993-12-21 | Kawasaki Steel Corp | 熱間圧延における被圧延材の冷却制御方法 |
JPH06328117A (ja) | 1993-05-18 | 1994-11-29 | Nippon Steel Corp | 連続熱間圧延のrot冷却における注水方法 |
JP2003048003A (ja) | 2001-07-31 | 2003-02-18 | Nkk Corp | 熱延鋼板の製造方法 |
JP2005074463A (ja) | 2003-08-29 | 2005-03-24 | Nippon Steel Corp | 厚鋼板の冷却方法 |
JP2005271052A (ja) | 2004-03-25 | 2005-10-06 | Jfe Steel Kk | 熱間圧延方法 |
JP2011073054A (ja) * | 2009-10-02 | 2011-04-14 | Nippon Steel Corp | 熱延鋼板の冷却方法及び冷却装置 |
Non-Patent Citations (1)
Title |
---|
See also references of EP2764932A4 |
Also Published As
Publication number | Publication date |
---|---|
EP2764932A4 (en) | 2015-06-24 |
BR112013028835B1 (pt) | 2022-08-09 |
BR112013028835A2 (pt) | 2017-01-31 |
JP5310965B1 (ja) | 2013-10-09 |
JPWO2014087524A1 (ja) | 2017-01-05 |
CN103987470A (zh) | 2014-08-13 |
KR20140107102A (ko) | 2014-09-04 |
EP2764932A1 (en) | 2014-08-13 |
KR101467724B1 (ko) | 2014-12-01 |
CN103987470B (zh) | 2015-09-09 |
EP2764932B1 (en) | 2018-02-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US9186710B2 (en) | Method for cooling hot-rolled steel sheet | |
JP2008073695A (ja) | 鋼板の冷却方法 | |
JP5310965B1 (ja) | 熱延鋼板冷却方法 | |
JP5310966B1 (ja) | 熱延鋼板冷却装置 | |
US9566625B2 (en) | Apparatus for cooling hot-rolled steel sheet | |
JP3892834B2 (ja) | 厚鋼板の冷却方法 | |
JP5626275B2 (ja) | 熱延鋼板の冷却方法 | |
JP5310964B1 (ja) | 鋼板製造方法 | |
US9211574B2 (en) | Method for manufacturing steel sheet | |
TWI477328B (zh) | 熱軋鋼板冷卻裝置 | |
JP3596460B2 (ja) | 厚鋼板の熱処理方法およびその熱処理設備 | |
JP5278580B2 (ja) | 熱延鋼板の冷却装置及び冷却方法 | |
JP5673370B2 (ja) | 熱延鋼板の冷却方法 | |
JP5644811B2 (ja) | 熱延鋼板の冷却方法 | |
TWI516317B (zh) | 鋼板製造方法 | |
TWI515054B (zh) | 熱軋鋼板冷卻方法 | |
JP2003025008A (ja) | 熱間圧延における被圧延金属材の冷却制御方法 | |
JP2023007380A (ja) | 熱延板の温度予測モデルおよび熱延板の変態エンタルピ予測モデルの生成方法、熱延板の巻取温度予測方法、温度制御方法、製造方法 | |
JP2014155946A (ja) | 熱間圧延方法及び熱間圧延機 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
ENP | Entry into the national phase |
Ref document number: 2013512030 Country of ref document: JP Kind code of ref document: A |
|
ENP | Entry into the national phase |
Ref document number: 20137022932 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2012873475 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 14111457 Country of ref document: US |
|
REG | Reference to national code |
Ref country code: BR Ref legal event code: B01A Ref document number: 112013028835 Country of ref document: BR |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 12873475 Country of ref document: EP Kind code of ref document: A1 |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
ENP | Entry into the national phase |
Ref document number: 112013028835 Country of ref document: BR Kind code of ref document: A2 Effective date: 20131108 |