JP2006272354A - Method for controlling thermal crown in hot finishing mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of thermal crown in a hot finishing mill by which the thermal crown can be controlled always appropriately in accordance with a material to be rolled. <P>SOLUTION: A pressure controlling valve 8, a pressure transmitter 9 and a flow meter 10 are respectively attached each the cooling water header 5, 6 for supplying the cooling water to an upper and a lower work rolls 1, 2 of each stand of the hot finishing mill and the pressure of each cooling water header 5, 6 is controlled on the basis of a pressure setting valve from the control panel 11. The pressure setting value is automatically calculated in accordance with the material to be rolled by the control panel 11. In this way, the thermal crown is suppressed by individually adjusting the quantity of the cooling water to each work roll 1, 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermal crown control method in a hot finish rolling mill in which the thermal crown of a work roll of a hot finish rolling mill is controlled to improve the stability of a sheet passing plate.

  In a hot finish rolling mill, a thermal crown in which the roll profile changes due to thermal expansion of the work roll is generated, and if the amount of thermal crown increases, the plate shape is disturbed, and the stability of the plate passing is impaired. The Therefore, as shown in Patent Document 1, Patent Document 2, etc., the cooling water header of the work roll is provided with a water volume adjusting function in the roll width direction, and the center portion of the work roll is cooled more strongly than the both ends so that the thermal crown is formed. Suppression is done.

  However, in the conventional thermal crown control method, it is normal to control the cooling of the upper and lower work rolls evenly. Therefore, the thermal crown is controlled individually for the upper and lower rolls so that the upper and lower roll profiles are precisely matched to the same shape. Was difficult. Also, because the amount of heat input and extraction differs depending on the type of material, the thermal crown also changes when the material changes. However, the conventional thermal crown control method does not adjust the amount of cooling water for each material, but it is done temporarily The cases were also based on experience. For this reason, it is not easy to accurately control the change of the thermal crown due to the change of the material.

Furthermore, with the conventional thermal crown control method, sufficient consideration is given to fluctuations in the coolant pressure due to changes in coolant header pressure when the coolant header nozzle is changed and pressure loss due to secular changes in piping valves. Since the amount of cooling water was not changed, the amount of cooling water changed due to the fluctuation of the cooling water pressure, and the thermal crown could not be appropriately suppressed.
JP-A-7-323316 JP 2000-271625 A

  The present invention solves the above-described conventional problems, allows the thermal crown to be controlled individually for the upper and lower rolls, and allows the thermal crown to be always properly controlled according to the material to be rolled. The main object is to provide a thermal crown control method in a rolling mill. Another object of the present invention is to provide a thermal crown control method in a hot finishing mill that can always properly control the thermal crown by controlling the pressure even when the coolant pressure fluctuates. That is.

  The thermal crown control method in the hot finish rolling mill of the present invention made to solve the above-mentioned problems is applied to each cooling water header that supplies cooling water to the upper and lower work rolls of each stand of the hot finishing mill. A pressure transmitter and a pressure control valve are attached, and the amount of water is adjusted individually by controlling the pressure of each cooling water header based on the pressure setting value from the control panel, thereby suppressing the thermal crown. is there.

  In addition, it is preferable to automatically calculate the pressure setting value from the control panel of each cooling water header according to the material to be rolled, in which case the pressure setting value from the control panel of each cooling water header is It is preferable to calculate as a function of rolling speed, reduction amount, sheet width, carbon equivalent, sheet thickness, rolling pass time, rolling idle time, and water temperature.

  According to the thermal crown control method in the hot finish rolling mill of the present invention, the amount of each cooling water header that supplies cooling water to the upper and lower work rolls of each stand can be individually adjusted, so that the thermal crown is moved up and down. The rolls can be controlled individually, and the upper and lower roll profiles can be precisely matched to the same shape. In addition, by automatically calculating the pressure setting value from the control panel of each cooling water header according to the material to be rolled, optimal control can be performed in consideration of the difference in the amount of thermal crown depending on the material.

  Furthermore, by adjusting the pressure control valve to control the header pressure to a constant level, even if there is a change in header pressure due to a change in the coolant header nozzle or pipe pressure loss due to secular change, etc. The amount of supplied water is not affected, and the thermal crown can always be controlled appropriately.

  In addition, not only can energy-saving operation during idling (non-rolling timing) be controlled by VVVF control of the pump, but when pressure control is performed on one stand, the original pressure is set at VVVF so that no pressure fluctuations occur on other stands. There are advantages such as being able to be controlled uniformly, and being able to control the pressure of all the stands uniformly.

Preferred embodiments of the present invention are shown below.
FIG. 1 is an explanatory diagram of the overall configuration of the present invention, and shows a first stand, a second stand, and a final stand of a hot finishing rolling mill having a number of stands. The steel plate passes through each stand in the right direction as indicated by an arrow, and hot finish rolling is performed.

  Each stand is provided with upper and lower work rolls 1 and 2 and backup rolls 3 and 4. As shown in the figure, cooling water headers 5 and 6 are arranged on the front and rear sides of the upper and lower work rolls 1 and 2 of each stand, respectively. Cooling water is supplied from the main pipe 7 to the cooling water headers 5 and 6, and cooling is performed by jetting the cooling water to the work rolls 1 and 2. Each of the cooling water headers 5 and 6 itself preferably has a structure for controlling a change in the thermal crown in the width direction by providing a water amount adjusting function in the roll width direction as in the conventional product.

  In the present invention, a pressure transmitter 9, a pressure control valve 8, and a flow meter 10 are attached to the cooling water headers 5 and 6 and the main pipe 7 of each stand, respectively. The pressure transmitter 9 and the pressure control valve 8 are connected to the control panel 11 so that the pressures of the cooling water headers 5 and 6 can be controlled based on the pressure set values from the control panel 11. A plurality of pumps 12 are installed at the base of the main pipe 7, but these pumps 12 are controlled by VVVF so that the pressure to the cooling water headers 5 and 6 of each stand does not fluctuate. It is preferable to keep the original pressure of the pressure constant at all times.

  The control panel 11 instructs the pressure control valve 8 of each cooling water header 5, 6 of each stand to set a pressure setting value, performs feedback control based on the actual pressure of the header by the pressure transmitter 9, and each cooling water header 5 , 6 to control the amount of cooling water sprayed to the work rolls 1,2. The amount of cooling water is monitored by the indicated value of the flow meter 10, and is set to issue an alarm when it is below a certain threshold. The amount of cooling water to be supplied to each of the cooling water headers 5 and 6 is determined according to the amount of generated heat as shown in FIG. 2, and the rolling speed and the amount of reduction are the major factors determining the amount of generated heat. In addition, the amount of generated heat depends on the rolling load, pass time, and idle (rolling interval that contributes to heat dissipation).

  That is, the rolling load is affected by the sheet thickness t, the sheet width W, and the carbon equivalent Ceq, and the pass time and idle are affected by the rolling idle I and the rolling pitch Pch. The rolling load increases as the product sheet thickness t decreases. Conversely, the rolling load increases as the sheet width W increases, and the rolling load increases as the carbon equivalent Ceq of the material increases. Further, the longer the rolling idle I, the larger the heat removal, and the larger the rolling pass time, the larger the heat input. In addition, the cooling water temperature T naturally affects the cooling water amount.

ここでａ，ｂ，ｃ，ｄ，ｅ，ｆ，ｇは係数であり、Ｐｉは第ｉスタンドの設定圧力、Ｐｏｉは第ｉスタンドの基準圧力、Ｗは板幅、Ｃｅｑは炭素当量、ｔは板厚、Ｐｓは圧延パスタイム、Ｉは圧延アイドル、Ｔは冷却水温度、△ｈは圧下量、Ｖは圧延速度である。 Therefore, in this embodiment, the control panel 11 automatically calculates the pressure set value according to the material to be rolled. Specifically, data is received from the material condition table, and the pressure set value is calculated by the following equation.

Here, a, b, c, d, e, f, and g are coefficients, Pi is the set pressure of the i-th stand, Poi is the reference pressure of the i-th stand, W is the plate width, Ceq is the carbon equivalent, and t is Sheet thickness, Ps is rolling pass time, I is rolling idle, T is cooling water temperature, Δh is rolling amount, and V is rolling speed.

  The control panel 11 individually sets the pressure for each of the cooling water headers 5 and 6 of each stand based on the above formula, and opens and closes the pressure control valve 8 to control the cooling water amount of each of the work rolls 1 and 2. Suppresses thermal crown. At this time, the cooling water amount of the upper and lower work rolls 1 and 2 on the same stand can be individually controlled to suppress the thermal crowns of the upper and lower work rolls to be the same. In particular, it is important to properly control the amount of cooling water in the outlet header immediately after the rolling tool in order to suppress the thermal crown.

  The amount of cooling water can be individually controlled for each stand. For example, in the case of a 7-stand hot finish rolling mill, the amount of cooling water may be constant from the first stand to the fourth stand, but when the amount of cooling water is sequentially decreased from the fifth stand to the seventh stand, Good results are obtained. In addition, since the high-tensile material has a larger carbon equivalent than the general material, the amount of cooling water from the first stand to the fourth stand is required to be larger than that of the general material, but from the fifth stand to the seventh stand, Equivalent. These are empirical values that depend on the rolling distribution or load distribution, but these empirical values can be incorporated into the coefficients of the above-described arithmetic expression.

  As a result, according to the present invention, by automatically calculating the pressure set value according to the material to be rolled, the roll cooling water amount and the pressure are adjusted, and the optimum control considering the difference in the thermal crown amount depending on the material can be performed. Is possible. Further, since the cooling water amounts of the upper and lower work rolls are individually controlled, it is possible to control the thermal crowns of the upper and lower work rolls to be the same. Furthermore, the feedback control of the actual pressure allows the amount of water supplied to each cooling water header to be kept constant even when there is a pressure loss of the piping due to secular change, and the thermal crown can always be controlled appropriately.

It is a whole explanatory view showing an embodiment of the present invention. It is explanatory drawing of the determinant of the amount of cooling water.

Explanation of symbols

1 Work Roll 2 Work Roll 3 Backup Roll 4 Backup Roll 5 Cooling Water Header 6 Cooling Water Header 7 Main Pipe 8 Pressure Control Valve 9 Pressure Transmitter 10 Flowmeter 11 Control Panel 12 Pump

Claims (4)

  A pressure transmitter and pressure control valve are attached to each cooling water header that supplies cooling water to the upper and lower work rolls of each stand of the hot finishing mill, and the pressure of each cooling water header is set to the pressure set value from the control panel. A thermal crown control method in a hot finish rolling mill, wherein the amount of water is individually adjusted by controlling based on the control to suppress thermal crown.   2. The thermal crown control method for a hot finishing mill according to claim 1, wherein a pressure set value from a control panel of each cooling water header is automatically calculated according to a material to be rolled.   3. The heat according to claim 2, wherein the pressure set value from the control panel of each cooling water header is calculated as a function of rolling speed, sheet width, carbon equivalent, sheet thickness, rolling pitch, rolling idle time, and water temperature. Thermal crown control method in interfinishing mill. The hot finishing mill according to any one of claims 1 to 3, wherein a pump for supplying cooling water to the cooling water headers of all the stands of the hot finishing mill is subjected to VVVF control to control the amount of supplied water. Thermal crown control method.

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