JPH059593A - Sheet temperature control method for cooling zone of continuous annealing equipment for sheet - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the meandering and drawing of the steel sheet in the cooling zone of the continuous annealing equipment for thin products, and to make the material of the steel sheet obtained by the annealing desired. [Structure] Determine an appropriate temperature difference ΔT between the plate temperature and the furnace temperature so that the total crown tc of the furnace rolls of the slow cooling equipment 3b can be kept within the crown limit value for ensuring the plateability, and at the same time, perform radiant heat transfer. A plate temperature transition prediction calculation of the gradual cooling equipment 3b is performed using a model formula, and it is determined from the calculation result whether or not the outlet plate temperature of the gradual cooling equipment 3b is the target plate temperature determined by the steel plate material. Further, when the determination is true, the temperature difference transition of the slow cooling equipment 3b obtained by the prediction calculation is the appropriate temperature difference Δ
Whether or not it is within the range of T is determined. If this is also true, the outlet plate temperature of the quenching facility 3a and the furnace temperature of the slow cooling facility 3b are determined for the first time, and the cooling capacity control of the quenching facility 3a and the furnace temperature setting control of the slow cooling facility 3b are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling zone plate temperature control method capable of preventing drawing and meandering of a steel plate in continuous annealing equipment for thin materials.

[0002]

2. Description of the Related Art Heating zone 1 as shown in FIG.
2. Furthermore, rapid cooling equipment 3a such as gas jet method and slow cooling equipment 3b such as cooling tube method (# 10A furnace, # 20A
In a continuous annealing equipment having a furnace structure such as a cooling zone 3 consisting of a furnace) and a quenching zone 4, a thin pattern such as tin plate is continuously annealed by taking a heat pattern as shown in FIG.

[0003]

Problems to be Solved by the Invention Although mechanical rolls are usually provided to the furnace rolls in the continuous annealing equipment for the purpose of stable threading, according to the study by the present inventors,
During the actual operation, the amount of roll crown changes in proportion to the difference between the plate temperature and the furnace temperature, causing the steel sheet to meander and throttle in the furnace.

Focusing particularly on the furnace after the heating zone 1, the temperature difference between the plate temperature in the cooling zone 3 and the furnace temperature greatly changes depending on the operating conditions such as the plate thickness and speed, and therefore the meandering of the steel plate in the cooling zone 3 occurs. And the aperture was observed.

The drawing or meandering of these steel plates not only makes them difficult to handle as products by making them scratched, but also leads to plate breakage in the furnace, resulting in large mechanical loss and energy loss.

On the other hand, for thin materials such as tinplate, the outlet plate temperature of the soaking zone 2 and the outlet plate temperature of the cooling zone 3 are determined by the material of the steel plate. Cold equipment
When the furnace temperature control is performed so that there is a temperature difference between the plate temperature and the furnace temperature that does not cause the meandering or throttling of the steel plate described above in 3b, the outlet plate temperature of this cooling zone 3 is a target value determined by the steel plate material. It may be out of the range and a predetermined material may not be obtained.

The present invention was devised in view of the above problems of the prior art, and prevents the occurrence of drawing and meandering of the steel sheet in the cooling zone of the continuous annealing equipment for thin products, and is desirable for the annealed steel sheet. An object of the present invention is to provide a method for controlling the plate temperature of the cooling zone, which is made of a material.

[0008]

Therefore, the plate temperature control method in the cooling zone of the present invention is a cooling zone in which a quenching facility and a slow cooling facility are sequentially arranged, and a plate temperature, a quenching facility outlet plate temperature, a slow cooling facility furnace The roll total crown in the slow cooling facility, which is obtained from the difference between the plate temperature and the furnace temperature, is ensured through the sheet while predicting the plate temperature transition in the slow cooling facility from the temperature, line speed, and model correction coefficient. For controlling the setting of the outlet plate temperature of the quenching equipment and the temperature of the furnace of the slow cooling equipment so as to be within the crown limit value for The basic feature is that the outlet plate temperature of the slow cooling equipment is controlled so as to reach a target plate temperature determined by the steel plate material.

The above-described structure of the present invention was created as a result of intensive study by the present inventors, and the background of the invention will be described below.

As described above, the mechanical crown mc usually attached to the roll in the furnace is calculated by the following equation from the length L and plate width W of the straight portion of the roll and the roll surface average inclination angle θm as shown in FIG. It is calculated as in Equation 1.

[0011]

[Equation 1]

Further, due to the difference between the plate temperature T ₁ and the furnace temperature T ₂ , a difference in roll thermal expansion occurs between the roll surface portion in contact with the plate and the roll surface portion exposed to the furnace atmosphere. The difference in expansion caused a so-called heat crown hc, and the actual crown amount of the roll fluctuated to cause meandering and drawing.

The actual crown amount of the roll is expressed as a total crown tc which is the sum of the mechanical crown mc and the heat crown hc. Since the heat crown hc is expressed by the following equation 2, the total crown tc Becomes as shown in Equation 3 (where D is the roll diameter and β is the linear expansion coefficient of the roll).

[0014]

[Equation 2]

[0015]

[Equation 3]

As described above, the difference between the plate temperature T ₁ and the furnace temperature T ₂ in the slow cooling equipment is remarkable at the inlet side of the slow cooling equipment, depending on the outlet plate temperature of the rapid cooling equipment, and T ₁ > T ₂ . Therefore, a positive heat crown hc is generated, and the roll total crown tc becomes large unless the mechanical crown mc is set in consideration of this heat crown hc.

On the other hand, according to the knowledge of the present inventors, when the total crown tc of the furnace rolls becomes larger or smaller than a certain range, the rate of occurrence of drawing and meandering of the steel sheet increases. It is known, and the crown limit value at which these occurrence rates become substantially 0 (hereinafter, this value will be referred to as a crown limit value for securing the plateability, but the present inventors, as an example from experimental examples described below, 0.2 from tc
By setting the total crown tc of each in-furnace roll within the range of 0.4 mm), stable in-reactor threading can be realized.

The temperature difference between the plate temperature T ₁ in the cooling zone and the furnace temperature T ₂ changes depending on the furnace temperature and line speed as shown in FIGS. 2 (a) (b) (c). Roll total crown tc
Also changes.

Therefore, the total crown tc of the rolls in the furnace
Temperature difference (T ₁ −T ₂ ) range ΔT between the plate temperature T ₁ and the furnace temperature T ₂ such that the temperature can be kept within the crown limit value for ensuring the plate passing property.
Then, by controlling the furnace temperature and line speed in the cooling zone so that the temperature difference □ T between the actual plate temperature transition and the furnace temperature in the cooling zone can fall within the above range ΔT, That purpose will be achieved.

However, the actual transition of the plate temperature in the slow cooling equipment is such that if the outlet plate temperature of the immediately preceding quenching equipment is high as shown in FIG. Even if the temperature difference is small, the difference between the plate temperature in the first half and the furnace temperature is large, and it may fall outside the target temperature difference range ΔT.

Therefore, in the case of adjusting the temperature difference #T between the actual plate temperature transition and the furnace temperature by controlling the furnace temperature and the line speed in the cooling zone described above, if the plate temperature at the soaking zone is high, the quenching equipment is preferably installed. It is necessary to control the furnace temperature and the like of the slow cooling equipment described above by lowering the outlet plate temperature as shown in (b) and (c) of FIG.

On the other hand, even when the plate temperature / furnace temperature control capable of suppressing the meandering and throttling of the steel plate is performed in the slow cooling equipment, the outlet plate temperature of the slow cooling equipment is a target plate temperature ( For example, in the case of a thin material such as tin plate, when it deviates from about 400 ° C), it becomes impossible to obtain a desired steel plate material. Therefore, in the above plate temperature / furnace temperature control, it is necessary to make the final plate temperature of the slow cooling equipment the target plate temperature.

Further, if the above-mentioned plate temperature / furnace temperature control is attempted to be carried out with the control of the line speed in the slow cooling equipment,
The line speed is such that the total crown tc of the roll is within the above-mentioned crown limit value for ensuring the threadability, which becomes the operating speed, which is a constraint on the operating efficiency and a bottleneck for low speed operation in an emergency. Therefore, this plate temperature / furnace temperature control must be performed without being restricted by the line speed.

From the above point of view, according to the configuration of the present invention, while predicting the plate temperature transition in the slow cooling equipment using a predetermined model formula is repeatedly performed, the plate temperature transition and the temperature difference between the furnace temperatures ensure the plateability. Is within the crown limit value for, and whether the final plate temperature reaches the target plate temperature determined by the steel plate material, and if all of these judgments are true, then It is intended to operate the furnace under furnace conditions.

The details of the structure of the present invention will be described below based on the description of the following embodiments.

[0026]

EXAMPLES Hereinafter, specific examples of the method of the present invention will be described.

The inventors of the present invention continuously anneal the furnace configuration shown in FIG. 10 (however, the quenching equipment 3a is a gas jet cooling configuration, and the slow cooling equipment 3b is a # 10A furnace and # 20A furnace configuration). Performed continuous annealing of tin plate steel using equipment,
At that time, the plate temperature of the cooling zone 3 was controlled based on the method of the present invention.

First, in a continuous annealing facility constructed separately from the above facility as an experimental facility, each in-furnace roll having the specifications shown in Table 1 below was installed to have a sheet thickness of 0.15 to 0.6 mm and a sheet width of 610.
Strip stripping of ~ 1100 mm was performed.

[0029]

[Table 1]

In this experiment, it was confirmed that throttling occurred in the cooling zone, so the present inventors also examined the heat crown amount of the roll in each furnace.

As a result, it was found that the heat crown of the furnace roll in each furnace was obtained by the following equation. Heating zone: hc = −9.53 × 10 ⁻⁴ (T ₁ −T ₂ ) −0.025 Soaking zone: hc = −1.40 × 10 ⁻³ (T ₁ −T ₂ ) +0.002 Cooling / quenching zone: hc = − 1.65 × 10 ^-3 (T ₁ -T ₂ ) -0.
006

Further, in these furnaces, the strip generation rate in the cooling zone was examined, and the results shown in FIG. 4 were obtained.

In FIG. 4, the strip occurrence rate is represented by the plate width W.
The (represented by the broken line) also shows the corresponding relationship with the plate width W and the plate thickness when the diaphragm is simultaneously generated (the part surrounded by a frame). In this way, in the cooling zone (width W
It can be seen that the strip occurrence rate increases as the value becomes larger.

On the other hand, the inventors of the present invention changed the rolls in the furnace in the experimental furnace (provided that the changed rolls had the same material and diameter as those of the rolls before the change, and had the same heat crown as that of the roll before the change). Amount of heat crown was obtained), and the total crown of the furnace roll in each furnace was 0.2 to 0.4 mm over 1 to 4 steps as shown in Fig. 5 (a) (b) (c) (d). A mechanical crown was added to each roll to fit within the range.

The maximum total crown amount of the in-furnace roll and the strip drawing rate in the cooling zone in each step were examined, and the results shown in FIG. 6 were obtained. As shown in Fig. 6, the total crown of the furnace rolls in this cooling zone is set to 0.
By setting it in the range of 2 to 0.4 mm, it was possible to greatly reduce the squeezing rate of the strip.

In setting the total crown tc as described above, it must be noted that there is a further restriction from the roll surface roughness Rz. That is, the roll surface roughness Rz is related to the meandering correction coefficient α and the friction coefficient μ that determine the meandering correction ability, and the set value of the total crown tc is that when the roll surface roughness Rz is 20. However, if Rz is less than 15, the roll life is short, and clogging occurs, and the meandering correction ability is significantly reduced.
On the other hand, when the roughness Rz exceeds 25, the metal band, particularly the strip, is prominently prone to flaws, and there is a concern that biting flaws may be caused due to a defective convex portion of the roughness. Therefore, the condition is that the roll surface roughness Rz is within the above range.

Furthermore, the setting of the total crown tc value is obtained when the roll surface roughness Rz is 20 as described above, and therefore the roughness Rz is obtained within this range. , The roll surface roughness R as described above
When z changes in the range of 15 to 25, it cannot be said that all of the meandering / diaphragm can be suppressed by the above setting of only the total crown tc.

Therefore, the inventors of the present invention added the above-mentioned experimental furnace to the table 2 below.
Each in-core roll of the specifications shown in (these rolls were of the same material and diameter as the above-mentioned recombining rolls, but several types of mechanical crowns with different average tilt angles θm of the crown slope surface part were used. (Prepared and different surface roughness Rz was used as shown in Table 2), and strips having a plate width of 900 mm were passed.

[0039]

[Table 2]

FIG. 7 shows that the rolls having different mechanical crowns mc and surface roughness Rz are exchanged a plurality of times in each of the experimental furnaces, and after each exchange, the strips and the meandering of the strip generated in these furnaces are generated. The results when examining the situation are shown. When the roll crown amount is expressed by the total crown tc obtained by adding the heat crown hc of each furnace to the mechanical crown mc of each roll, the total crown tc and the roll surface roughness are shown. The result clearly shows the influence on the occurrence of meandering / throttle due to the relationship with the degree Rz.

According to this, when Rz · tc is in the range of 3.2 to 9.0, there is no meandering / throttle, and the result is that the plate is stably threaded.

When the rolls in the furnace of the slow cooling equipment within the above range are replaced by the mechanical crowns mc, the product of the mechanical crowns mc and the roll surface roughness Rz is 1.4 ≦ Rz · mc ≦ 5.5. Become.

The meandering correction ability of the mechanical crown mc of the roll is mainly determined by the average inclination angle θm of the roll, but in addition, the ratio W / L of the width W of the metal strip to the length L of the straight portion is W / L. Is also affected by. According to the experiments conducted by the present inventors, when the value of W / L is less than 1.3, the metal strip comes into contact with the roll in a substantially planar manner (that is, the mechanical crown amount becomes small), and the thread is wound by the crown roll. The effect cannot be obtained and the meandering is likely to occur. On the other hand, when the value of W / L exceeds 2.4, the mechanical crown becomes large and the occurrence rate of the diaphragm increases. Therefore, when setting the above-mentioned total crown tc value, etc., it is necessary to pay sufficient attention to this W / L value.

From the above-mentioned background, the inventors of the present invention determined the total crown tc value of the rolls in the furnace which can be kept within the crown limit value for ensuring the threadability. On the other hand, with respect to the mechanical crown mc of each furnace roll of the slow cooling equipment 3b in the equipment for carrying out the method of the present invention described above, a value that seems to be appropriate at the beginning is set as a default value, and the furnace roll is adjusted accordingly. Each setting was performed. Therefore, initially, from the above-mentioned total crown tc value and the mechanical crown mc default value, the plate temperature T ₁ such that the total crown tc of these rolls during continuous annealing falls within the crown limit value is calculated by the above-mentioned formula 3. The temperature difference from the furnace temperature T ₂ was obtained, and was set as the proper temperature difference ΔT (Note that the mechanical crown mc must be excluded from the proper temperature difference ΔT in the plate temperature prediction calculation described later and the furnace temperature setting at that time. If the temperature is slow or the outlet plate temperature of the slow cooling equipment 3b does not reach the target plate temperature, the default value is reset and the appropriate temperature difference ΔT is also reset).

Next, the following number 4 for the # 10A furnace of the slow cooling equipment 3b
And the radiant heat transfer model equation [Ts: plate temperature (° K), Tzji: furnace temperature (j = 1 heating zone, j
= 2 soaking zone, j = 3, 4 cooling zones), V: Line speed (m /
h), h: plate thickness (m), other: model correction coefficient]
Using, the predictive calculation of the change dTs of the plate temperature per unit time dx in the slow cooling equipment 3b (note that the line speed V is already determined from the line operating rate in the normal mode,
It is not changed by the furnace temperature / plate temperature control of this embodiment described later).

[0046]

[Equation 4]

[0047]

[Equation 5]

The model formulas of the above equations (4) and (5) are repeated a predetermined number of times (the number of times corresponding to the length of the furnace), and as shown in FIG.
The amount of change in plate temperature (change in plate temperature) can be calculated. # 10A shown on the right side of the figure
In order to obtain the furnace outlet plate temperature, the furnace inlet plate temperature on the left side of the figure is required, and in the # 10A furnace of the slow cooling facility 3b, it corresponds to the outlet plate temperature of the rapid cooling facility 3a. Therefore, in the first calculation, the outlet plate temperature of the quenching equipment 3a is substituted as Ts in the model formula of the equation (4). Further, since the furnace temperature Tzji to be initially substituted into these model formulas is a prediction calculation, a temporary furnace temperature is set as a default value for each furnace and then substituted. Then, as described above, the predetermined number of times of prediction calculation is performed to obtain the # 10A furnace outlet plate temperature and the # 20A furnace outlet plate temperature (the # 10A furnace outlet plate temperature is the value obtained when the # 20A furnace plate temperature transition prediction calculation is performed. At the time of the very first calculation, substitute it as the inlet plate temperature for Ts of the model formula of this equation 5).

When the # 20A furnace outlet plate temperature of the slow cooling equipment 3b has a large error with respect to the target plate temperature (400 ° C. in this embodiment) determined as the material of this tin plate according to the equation 5, The temporary furnace temperature is changed, and the calculations by the model formulas of Formulas 4 and 5 are repeated again to re-estimate the plate temperature transition.

On the other hand, when the outlet plate temperature of the # 20A furnace of the slow cooling equipment 3b obtained by this prediction calculation falls within a predetermined error with respect to the target plate temperature, the plate temperature at that time becomes the preset furnace temperature, In addition, the plate temperature at each position of the furnace at that time is a quasi-plate temperature transition required.

Then, the difference between the quasi-plate temperature transition and the quasi-set furnace temperature is determined as a temperature difference transition □ T, which is the above-mentioned appropriate temperature difference Δ.
When it is larger than T, the outlet plate temperature of the quenching equipment 3a to be substituted at the very beginning of the formula 4 is changed, and the prediction calculation of the plate temperature transition by the radiant heat transfer model formulas 4 and 5 is performed again from the beginning. Start.

Further, the temperature difference transition □ T is an appropriate temperature difference ΔT.
When the temperature falls within the range, the semi-set furnace temperature at that time is determined as the set furnace temperature, and the semi-plate temperature transition at that time is determined as the official plate temperature transition. At the same time, the outlet plate temperature of the quenching equipment 3a set in the first prediction calculation is determined as the outlet plate temperature to be controlled.
Based on these determinations, the cooling capacity of the gas jet of the rapid cooling equipment 3a is controlled to adjust the outlet plate temperature of the equipment 3a, and the furnace temperature setting control of the slow cooling equipment 3b is performed.

The processing of this embodiment is shown in a flow chart in FIG.

When the control is carried out based on the above settings, the drawing and meandering of the steel sheet in the slow cooling equipment 3b will not occur, and the desired material of the steel sheet after the annealing treatment can be obtained. become.

[0055]

As described in detail above, according to the plate temperature control method of the present invention, in the cooling zone of the continuous annealing equipment for thin products, the occurrence of drawing or meandering of the steel plate is suppressed without being restricted by the line speed. As a result, stable operation of the annealing equipment becomes possible, and a desired material for the steel sheet obtained after annealing can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a mechanical crown, a heat crown, and a total crown of furnace rolls provided in a continuous annealing facility.

FIG. 2 is a graph showing a relationship among an inlet plate temperature, a furnace temperature, and a line speed, which influence the plate temperature control.

FIG. 3 is a graph showing the state of plate temperature transition in the slow cooling facility by adjusting the plate temperature at the exit of the rapid cooling facility.

FIG. 4 is a graph showing a strip occurrence rate in a cooling zone.

FIG. 5 is a graph showing the total crown amount of each roll when the in-furnace roll of the experimental furnace is replaced with a roll provided with a mechanical crown in consideration of the heat crown amount.

FIG. 6 is a graph showing the squeezing occurrence rate of the maximum total crown at each step in the previous figure.

FIG. 7 is a graph showing a stable threading area defined by a product of roll surface roughness and total crown in this experimental furnace in which rolls have been rearranged.

FIG. 8 is a graph showing the prediction calculation result of the plate temperature transition by the radiant heat transfer model formula of the # 10A furnace of the slow cooling facility.

FIG. 9 is a flowchart showing the processing progress of the present embodiment.

FIG. 10 is an explanatory view showing an example of a furnace configuration of continuous annealing equipment for thin products.

FIG. 11 is a graph showing a heat pattern when continuous annealing of a thin material such as a tin plate is performed.

[Explanation of symbols]

 1 heating zone 2 soaking zone 3 cooling zone 3a rapid cooling equipment 3b slow cooling equipment 4 rapid cooling zone

Claims (1)

Claims: 1. A cooling zone in which a quenching facility and a slow cooling facility are arranged in sequence, and the slow cooling is performed based on the plate thickness, the quenching facility outlet plate temperature, the slow cooling facility furnace temperature, the line speed, and the model correction coefficient. While performing the predictive calculation of the plate temperature transition in the equipment, the total roll in-furnace crown of the slow cooling equipment, which is obtained from the difference between the plate temperature and the furnace temperature, can be kept within the crown limit value for ensuring the stripability. In addition to the setting control of the outlet plate temperature of the rapid cooling equipment and the setting of the furnace temperature of the slow cooling equipment, the setting of the furnace temperature of the slow cooling equipment is performed by the outlet plate temperature of the slow cooling equipment. Is controlled so as to reach a target plate temperature determined by the material of the steel plate.