JP2005179727A - Method for controlling sheet temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a sheet temperature of a steel strip which enters a pot in a facility for hot-dip-galvanizing the steel strip. <P>SOLUTION: This controlling method employs a preset control method for a portion of the steel sheet in a predetermined length from a stepped point in a reverse direction to a transportation direction, and a feedback control method for a portion except the above portion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to plate temperature control when a steel strip enters a pot in a hot dip galvanizing facility.

  In the hot dip galvanizing facility, it is desirable that the steel strip is cooled to a uniform temperature (plate temperature) over the entire surface of the steel strip when entering the molten zinc in the pot. The reason is that uniformizing the plate temperature makes the quality, including the amount of molten zinc plating, uniform over the entire surface of the steel strip.

  Conventionally, control for making the plate temperature uniform in the longitudinal direction (conveying direction) and the width direction of the steel strip, that is, the entire surface of the steel strip has been performed by a feedback control method. FIG. 2 is a block diagram of the apparatus used for the control, in which the longitudinal plate temperature control means 21 or the width direction plate temperature control means 23 inputs the plate temperature or the like from the thermometer 46 or the width direction plate temperature measurement means 47. Then, a parameter for controlling the amount of air supplied from the air supply port 45 is output, and feedback control for equalizing the plate temperature is performed. More specifically, the longitudinal plate temperature control means 21 controls the opening degree of the cooling fan number control means 22 and the damper 42 that determines the amount of air supplied from the cooling fan 42, and the longitudinal plate temperature control means 21 Control to equalize the temperature. The control is stabilized by the temperature controller 31 to which the plate temperature is input and the pressure controller to which the air supply pressure is input from the pressure detection means 43. Further, the width direction plate temperature control means 23 outputs the opening degree of the damper 44 that relatively sets the air supply amount of each of the plurality of air supply ports 45, and performs control to equalize the plate temperature in the width direction. . Note that the control in the longitudinal direction and the width direction refer to the feedback control condition table 11 storing the target plate temperatures stratified by the steel strip components and dimensions.

Patent Document 1 is one form of the above feedback control, and as the width direction plate temperature measuring means 47, one of the transport rolls as shown in FIG.
JP-A-8-92712

  Since the footback control is performed while monitoring the actual plate temperature, there are few conditions to set in advance and the accuracy is high, but the response of the plate temperature control is not sufficient at the stepped point of the steel strip. For this reason, it has been impossible to achieve uniform plate temperature over several tens of meters from the stepped point in the direction opposite to the direction in which the steel strip is conveyed. In the hot dip galvanizing equipment, steel strips are welded and continuous for transport, but the joints where the components and dimensions (thickness and width) change discontinuously and the cooling behavior of the steel strip changes are stepped. It is called a point.

  An object of the present invention is to provide a plate temperature control method capable of making the plate temperature uniform over a predetermined length from the stepped point.

  The present invention is a method for controlling the temperature of a steel strip entering a pot in a hot dip galvanizing facility for a steel strip, wherein the portion of the steel strip extending from a stepping point to a predetermined length is opposite to the direction of conveyance. The above problems have been solved by a method for controlling the plate temperature of the steel strip, which is preset control and is feedback control except for the above-mentioned part.

  With the steel strip plate temperature control method of the present invention, the response delay is eliminated by preset control in the part extending from the stepped point to the predetermined length, and feedback control is performed in other parts. The advantage of feedback control that can be controlled while monitoring the steel sheet was also obtained, and a uniform plate temperature could be achieved over the entire surface of the steel strip.

  The best mode for carrying out the plate temperature control of the present invention will be described with reference to FIGS.

  Note that the same members and the same components as those in the conventional plate temperature control already described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted here.

  In the plate temperature control method of the present invention, first, it is determined whether or not the control part is a stepped point. In the case of FIG. 1, the control part refers to the part of the steel sheet facing the air supply port 45 of the steel strip. When a plurality of air supply ports 45 are arranged in the width direction as shown in FIG. 1, the positions are in the longitudinal direction. This determination corresponds to step S1 in FIG. 3 which is a control flow. If the control part is a stepped point, the preset control S12 is performed on a part extending from the stepped point to a predetermined length. Otherwise, feedback control S11 is performed. In the present invention, if the part to be controlled is a stepped point, the control condition is immediately switched to the preset control condition, so that the delay in control response at the stepped point is eliminated.

  After the preset control is started, the control part is switched to the feedback control when it is determined that the control part is a part of the steel strip separated from the stepped point by a predetermined length in the direction opposite to the conveyance direction (step S2 in FIG. 3). ). The predetermined length is generally several tens of meters, but it varies depending on the nature of the stepped point, the discontinuity of the components and dimensions (thickness / width), and is determined in advance by experiments. For example, a steel strip having a stepped point is transported and operated, and a control method similar to that of the present invention is carried out with various provisional predetermined lengths. It is determined as Sasa. For the necessary types of stepping points, respective predetermined lengths are determined and stored in the feedback control condition table l1.

  These switching operations are performed by the control switching means 52 shown in FIG. A stepped point or a position having a predetermined length from the stepped point necessary for switching determination is obtained from tracking information of the process computer. The control switching means 52 shown in FIG. 1 shows a state in which preset control is being performed, and the switch 52b in the control switching means 52 is in a connection state on the preset control condition table 51 side. The predetermined length that changes depending on the nature of the stepped point is stored in the preset control condition table 51 in FIG. On the other hand, when performing feedback control, the switches 52a and 52b in the control switching means 52 are connected to the feedback control condition table 11 side.

  In the present invention, whether or not the part to be controlled is a stepped point is used to determine whether or not the control method is switched, and is immediately switched to a preset appropriate control condition, so that the problem of control response delay at the stepped point is solved. Further, since the control is switched to the feedback control after the predetermined length has elapsed, the advantage of the feedback control that can be controlled while monitoring the actual plate temperature can be enjoyed.

It is a typical block diagram for demonstrating plate | board temperature control of the steel strip in this invention. It is a schematic diagram for demonstrating the plate temperature control of the conventional steel strip. It is a control flowchart for demonstrating plate | board temperature control of the steel strip in this invention.

Explanation of symbols

1 Steel strip
11 Feedback control condition table
21 Plate temperature control means
22 Fan number control means (for cooling fan)
23 Width direction plate temperature control means
31 Temperature controller
32 Pressure controller
41 Cooling fan
42, 44 damper
43 Pressure detection means
45 Air inlet
46 Thermometer
47 Width direction plate temperature measuring means (Temperature measuring roll)
51 Preset control condition setting table
52 Control switching means

Claims (1)

In a steel strip hot dip galvanizing facility, a steel plate temperature control method for entering a pot,
The part of the steel strip extending from the step point to a predetermined length in the direction opposite to the conveying direction is preset control,
A method for controlling the plate temperature of the steel strip, wherein feedback control is performed except for the portion.

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