JP2803490B2 - Cooling control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling control method used for a continuous hot-dip galvanizing line and various strip transfer lines, and more particularly to a cooling zone comprising a rapid cooling zone and a slow cooling zone. The present invention relates to a cooling control method having a function of appropriately controlling the temperature of a cooling target material in consideration of the cooling capacity of a slow cooling zone in response to a change in the thickness or transfer speed of the cooling target material.

[0002]

2. Description of the Related Art Conventionally, when cooling a strip in a continuous transfer line for continuously transferring the strip, a rapid cooling zone using a cooling gas blow is referred to as GJC (Control Jet Jet).
It is possible to cool the strip to a predetermined temperature by passing through a cooling zone consisting of a so-called Co-oling zone and a slow cooling zone using a cooling tube (hereinafter called a CC (Control Cooling) zone). Is being done.

[0003] In such a continuous transfer line, the cooling capacity differs between the GJC band and the CC band from the viewpoints of uses, functions, and the like. For example, in the case of the GJC band, although the cooling capacity is large, temperature unevenness tends to occur in the width direction of the strip. On the other hand, in the case of the CC band, although the cooling capacity is small, a uniform temperature can be obtained in the width direction and the longitudinal direction of the strip.

Therefore, in this type of strip transfer line, in order to satisfy the cooling conditions of the steel type and to perform uniform cooling, a GJC band is provided in front of the line in consideration of the cooling capacity of each cooling zone. A cooling control method is adopted in which a cooling strip is installed to greatly cool the strip, while a CC band is installed downstream of the line for uniform cooling. As one of them, for example, a cooling control method for a continuous hot-dip galvanizing line has been proposed, and a cooling furnace as shown in FIG. 1 described later is used.

[0005] In the cooling furnace of this plating line, the strip passes through the GJC band constituting the cooling furnace. At this time, a cooling gas is applied to the strip from a cooling gas blow to perform forced convection transfer cooling. Is performed so that the cooling temperature difference of the strip between the entrance side and the exit side becomes about 200 ° C. Subsequently, the strip shifts from the GJC band to the CC band constituting the cooling furnace. Here, mainly by performing radiant heat transfer cooling between the furnace wall and the strip, the temperature difference of the strip between the inlet side and the outlet side becomes GJC band. Cooling is performed so that the cooling capacity is about 100 ° C., which is generally smaller than that of the belt.

[0006]

However, in the above-mentioned CC band, since radiation heat transfer cooling is used, there is a limit on the amount of heat that can be cooled by the lower limit of the furnace temperature. There is a restriction on the amount of cooling heat per unit width (this is called hearth load). Therefore, the upper limit of the amount of cooling heat to be removed in the CC band is determined by the hearth load restriction. On the other hand, in the GJC band, the target plate temperature on the exit side of the GJC band is fixed. As a result, the following problems arise in controlling the cooling temperature of the strip in the continuous transfer line.

That is, when the size of the strip (eg, thickness, width, etc.) or the transfer speed is changed, as described above, the CC
Since there is a restriction on the amount of cooling heat in the band, a so-called plate temperature deviation that deviates from the required cooling temperature on the CC band exit side occurs. Therefore, in order to avoid the deviation of the plate temperature, the operator must think and error the strip transfer speed, sometimes GJC.
It is artificially operated to change the target plate temperature on the banding side, but the efficiency (ton / hr) can not be denied, and the wrong plate temperature also occurs due to an operation error, which adversely affects the product quality. There is a problem giving.

The present invention has been made in view of the above circumstances, and by controlling the plate temperature on the exit side of the GJC band while taking into consideration the cooling calorie characteristics of the CC band, it is possible to change various conditions of the material to be cooled. In addition, an object of the present invention is to provide a cooling control method that enables an optimal cooling calorie operation in the CC band, thereby suppressing the temperature of the cooling band from deviating from the plate temperature, and greatly contributing to the improvement of product quality.

[0009]

In order to solve the above problems, the invention corresponding to claim 1 is a cooling method for cooling a material to be cooled by a GJC band using a cooling gas blow and a CC band using a cooling tube. the control method, a small cooling capacity
Cooling heat characteristics and the transfer speed of the coolant again the CC zone,
The outlet plate temperature of the GJC band having a large cooling capacity is obtained based on the density, specific heat, and material, and the outlet plate temperature of the GJC band is controlled , whereby uniform cooling from the slow cooling zone is performed.
This is a cooling control method for outputting the cooled material .

Next, a second aspect of the present invention relates to a GJC band using a cooling gas blow and a CC using a cooling tube.
In the cooling control method of cooling the material to be cooled by the band, the maximum hearth load of the CC band is set in advance, and when the cooling heat amount of the material to be cooled passing through the CC band is equal to or less than the maximum hearth load, the CC band The GJ is approximately proportional to the hearth load.
The temperature of the outlet side plate of the C zone is controlled. On the other hand, when the amount of cooling heat of the material to be cooled passing through the CC zone exceeds the maximum hearth load due to changes in various conditions of the material to be cooled, it is set in advance. This is a cooling control method for obtaining the outlet plate temperature of the GJC band based on the obtained maximum hearth load and controlling the outlet plate temperature of the GJC band. In addition, the maximum hearth load, in the radiant heat transfer cooling furnace
This is the constraint load of the heat that can be cooled, and the unit is [Kcal / hr · m
]. This is the restriction value of the amount of cooling heat in the unit plate width direction.

[0011]

According to the first aspect of the present invention, by taking the above-described means, it is possible to take into consideration the change in the cooling calorie characteristic of the CC band having a small cooling capacity and various conditions of the material to be cooled.
Since the exit side plate temperature of the JC band is determined, insufficient cooling of the CC band can be covered, and deviation of the plate temperature can be suppressed.

Next, the invention according to claim 2 is characterized in that when the amount of cooling heat of the material to be cooled passing through the CC band is less than the maximum hearth load, the outlet plate of the GJC band is proportional to the CC band hearth load. The temperature is controlled, and the C
When the amount of cooling heat of the coolant passing through the C zone exceeds the maximum hearth load, GJC is the amount of heat that cannot be removed in the CC band.
By lowering the temperature of the outlet side plate of the band, it is possible to perform a stable operation in an optimum state in the CC band having a small cooling capacity, so that it is possible to prevent the plate temperature from falling off, and to obtain a high quality material to be cooled. . The present invention is particularly effective when controlling the temperature of the sheet on the cooling outgoing side with high precision, as in a hot-dip galvanizing line.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cooling control method according to the present invention will be described below.

As for the cooling zone in which the GJC band and the CC band are combined, it is necessary to perform the cooling control while paying sufficient attention to the cooling calorie characteristic of the CC band having a small cooling capacity. Therefore, the present invention is implemented based on the following control method and knowledge.

(1) First, the control method is divided into two based on the cooling calorie characteristics of the CC band in order to effectively operate the CC band having a small cooling capacity. One of them is C
It is effective use up to the upper limit of the cooling heat capacity (maximum hearth load) of the C band, and the other one is the upper limit value that restricts the cooling heat amount of the CC band, that is, measures when the maximum hearth load is exceeded. You need to think.

Therefore, in the GJC band, the outlet plate temperature of the GJC band is set so as to be proportional to the hearth load of the CC band up to the upper limit of the cooling heat amount of the CC band. On the other hand, when the maximum hearth load in the CC band is exceeded, the cooling heat amount cannot be removed in the CC band. At this time, in the GJC band, the plate temperature on the GJC band outlet side is reduced by the cooling heat amount not removed in the CC band. By lowering, a control method that covers the amount of cooling heat is implemented.

(2) Next, when the strip size and the transfer speed are changed, the target plate temperature on the GJC band needs to be changed in order to set the plate temperature on the CC band side to a constant target value. At this time, G, which is in the process of cooling the cooling furnace,
It is important to be able to operate in a wide allowable temperature range of the JC band outlet side plate.

Incidentally, in the hot-dip galvanizing line, for example, the sheet temperature on the CC band side is about ± 10 ° C., whereas the sheet temperature on the GJC band side is about ± 40 ° C. Has a temperature range. Therefore, in the strip transfer line, the GJC band and the CC band are regarded as one cooling furnace, and there is no problem in the material of the strip even if the plate temperature on the GJC band outlet side is controlled.

Therefore, the method of the present invention implements the cooling control method as described in the above (1) based on the knowledge of the above (2). At this time, the plate temperature on the exit side of the GJC band is changed to the cooling heat amount of the CC band. In addition to the characteristics, it is determined from the following relational expression including the transport speed, density, specific heat, etc. of the strip.

That is, when determining the sheet temperature on the exit side of the GJC band, the cooling heat quantity Q [kcal / h] of the strip passing through the CC band is determined based on the sheet thickness, the sheet width, and the transfer speed of the strip.
r], and if the cooling heat amount Q of the CC band is equal to or less than the maximum hearth load Qmax [kcal / hr · m], a plate having a cooling heat amount substantially proportional to the cooling capacity (ton / hr) of the CC band. Set the temperature. That is, when cooling heat quantity per unit width Q / W [kcal / hr · m] ≦ hearth load Qmax [kcal / hr · m], _TGJ = _TCC + (K / _Cp ) ...... 1) Determine the GJC band exit side plate temperature T _GJ (° C.) from the following relational expression.

Here, T _CC (° C.): CC band target plate temperature,
K: constant (proportional constant between cooling calorific value and ton / hr), ρ
_Fe [kg / m ³ ]: Strip density, C _p [k cal / kg
K]: Specific heat of the strip. On the other hand, if the cooling heat amount Q in the CC band exceeds the maximum hearth load Qmax [kcal / hr · m], the cooling heat amount is set to Qmax, and the plate temperature on the exit side of the GJC band is determined. That is, when the cooling heat Q / W per unit width [k cal / hr · m] > hearth load Qmax of [k cal / hr · m] , T GJ = T CC + {Qmax / (t · v · ρ _Fe · C _p )｝ (2) The plate temperature T _GJ (° C.) on the GJC outgoing side is determined from the following relational expression. However, Qmax [kcal / hr · m]: hearth load,
t [m]: plate thickness, v [m / hr]: transfer speed.

Therefore, by employing the above cooling control method, when the cooling heat of the strip passing through the CC band is less than the maximum hearth load, the GJC band outlet side is proportional to the hearth load of the CC band. The upper limit of the amount of cooling heat to be removed in the CC band when the cooling heat of the strip in the CC band exceeds the maximum hearth load due to changes in conditions such as the strip size and transfer speed, etc. In other words, the maximum hearth load is set, and the GJC band exit side plate temperature is set. Therefore, even in the CC band having a small cooling capacity, stable operation can be performed under the optimum conditions. And the temperature in the strip width direction can be made uniform to obtain a high-quality strip.

Next, an apparatus to which the above-described cooling control method is applied will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of a cooling furnace used for a hot-dip galvanizing line and other continuous strip transfer lines, and FIG. 2 is a diagram showing a configuration of a cooling temperature control device including the cooling furnace.

That is, the cooling furnace has a GJC band and C
The guide rolls 1,... Are arranged in the GJC band and the CC band with a required positional relationship in the GJC band and the CC band. A transfer line is formed so as to form a meandering shape. Thermometers 3 and 4 are installed on the outlet sides of the GJC band and the CC band, respectively. Reference numeral 5 denotes a furnace shell representing the shape of the furnace.

Next, a cooling temperature control device including a cooling furnace includes:
As shown in FIG. 2, gas blows 11 and 11 are installed on the entrance side and the exit side of the GJC band, respectively, and a cooling gas medium sent from the outside via pressure regulating valves 21 and 21 is supplied to the gas blows 11 and 11 respectively. Strip 2 using
In the meantime, cooling tubes 12 and 12 are arranged on the entrance side and the exit side on the CC band side, respectively.
Similarly, a cooling medium sent from the outside via the flow control valves 31 and 31 is passed through the cooling tubes 12 and 12 to perform radiation transmission cooling.

The cooling temperature control device 20 has a combination of cascade control and feedforward control.
More specifically, the strip size and the transfer speed, which are the disturbance elements, are taken in, and the necessary calculations such as the above equations (1) and (2) and other necessary calculations are performed using other necessary parameters and constants. A target plate temperature calculator 30 using a process computer or the like for obtaining a target plate temperature in the CC band, and a GJC band side target plate temperature obtained by the target plate temperature calculator 30 and a GJC band exit side thermometer 3 detected. A temperature controller 22 for calculating a GJC band exit side target pressure by performing an adjustment operation such as PI or PID based on a deviation from the GJC band exit side detected temperature, and a CC band side target similarly obtained by the target plate temperature calculation unit 30. Plate temperature and CC
There is provided a flow controller 32 for performing, for example, a PI or PID adjustment operation based on a deviation from the CC outlet detection temperature detected by the outlet thermometer 4 to obtain a CC outlet target flow rate.

Further, the cooling temperature control device is required based on the target pressure and the discharge pressure from the pressure detectors 23 and 24 provided in the cooling gas medium supply passages on the inlet and outlet sides of the GJC band. Pressure controllers 25 and 26 for outputting pressure operation signals, and flow rate detectors 33 and 34 provided in the cooling medium supply passages on the inlet and outlet sides of the target flow rate and the CC band.
Flow rate controllers 35 and 36 for outputting required flow rate operation signals based on the detected flow rates from the pressure controllers 25 and 26 are provided, and the pressure control valves 21 and 21 are controlled based on the pressure control signals from the pressure regulators 25 and 26. Operating, while the flow controllers 35, 36
The flow control valves 31, 31 are operated based on a flow control signal from the controller.

Therefore, the prior art without the cooling control method and the cooling temperature control device of the present invention as described above,
When the transfer speed of the strip is increased at time t1 as shown in FIG. 3 (a), despite it is necessary to up the cooling heat, GJC band target plate temperature, since actual temperature is the same, CC zone In this case, the cooling capacity exceeds the upper limit and cooling cannot be performed. For this reason, the actual temperature rises on the CC outlet side, and the sheet temperature deviates.

On the other hand, according to the cooling control method and the cooling temperature control device of the present invention, as shown in FIG. 3B, when the cooling speed of the CC band exceeds the upper limit of the cooling capacity due to the increase of the transfer speed of the strip. by lowering the target plate temperature of GJC exit side, CC home use side plate temperature can Rukoto to follow the target plate temperature eliminates can affect the quality of the strip by changing the transport speed. It goes without saying that the same applies not only to the strip transfer speed but also to changes in the strip size and other disturbance factors.

Next, FIG. 4 shows the transport speed of the strip 85r.
pm constant, and the strip size is a-plate thickness 0.66 × plate width 1280 mm, b-plate thickness 0.81 × plate width 1
It is a figure which shows the relationship between a GJC band target plate temperature and an actual temperature, and a CC band target plate temperature and an actual temperature when it changes in order of 213 mm, a board thickness 0.71, and a board width 1130 mm.

That is, this cooling control changes the CC band target plate temperature every time the strip size is changed, and sets the optimum GJ every time the CC band target plate temperature is changed.
Is to set the C band target plate temperature.
It can be seen that the target plate temperature in the C band is following well,
Optimal operation can be ensured even in the CC band having a small cooling capacity. The present invention can be variously modified and implemented without departing from the gist thereof.

[0032]

As described above, according to the present invention, C
By controlling the temperature of the material to be cooled on the exit side of the GJC band in accordance with the restriction of the amount of cooling heat in the C band, the CC band having a small cooling capacity can be effectively utilized despite various changes in the conditions of the material to be cooled. It is possible to provide a cooling control method that can secure stable cooling calorie operation, suppress the deviation of the plate temperature in the cooling zone, and greatly contribute to the improvement of product quality.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a cooling furnace to which a cooling control method according to the present invention is applied.

FIG. 2 is a configuration diagram of a cooling temperature control device including a cooling furnace to which the method of the present invention is applied.

FIG. 3 is a diagram illustrating a plate temperature state depending on whether or not the method of the present invention is applied.

Fig. 4 CC band and GJ due to strip size change
The figure explaining the change state of the target plate temperature of C zone, and an actual value.

[Explanation of symbols]

2 ... strip (cooled material), 3, 4 ... thermometer, 11 ...
Guy blow, 12: cooling tube, 20: cooling temperature control device, 22: temperature controller, 23, 24: pressure detector, 2
5, 26: pressure controller, 30: target plate temperature calculator, 32
... temperature controllers, 33, 34 ... flow rate detectors, 35, 36 ...
Flow controller.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C21D 11/00-11/00 105 C21D 9/52-9/66

Claims (2)

(57) [Claims] In a cooling control method for cooling a material to be cooled by a rapid cooling zone using a cooling gas blow and a slow cooling zone using a cooling tube, a cooling calorie characteristic and cooling target of the slow cooling zone having a small cooling capacity are provided. Cooling capacity based on material transfer speed, density , specific heat and material
By calculating the outlet plate temperature of the rapid cooling zone having a large force and controlling the outlet plate temperature of the rapid cooling zone , the slow cooling is performed.
A cooling control method, comprising outputting a material to be cooled uniformly cooled from a zone . 2. A cooling control method for cooling a material to be cooled by a rapid cooling zone using a cooling gas blow and a slow cooling zone using a cooling tube, wherein a maximum hearth load of the slow cooling zone is set in advance. when the cooling heat of the coolant that passes through the cold zone is less than said maximum hearth load, to control the delivery side temperature of the quenching zone with a relationship that proportional to Johiyatai hearth load, whereas, the coolant when the cooling heat of the coolant that passes through the slow cooling zone by varying further with the various conditions exceeds the maximum hearth load, out of the quenching zone based on the maximum hearth load preset A cooling control method comprising: obtaining a side plate temperature; and controlling an outlet side plate temperature of the rapid cooling zone.