JPS5934214B2 - Method for controlling cooling plate temperature in quenching zone of continuous annealing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling plate temperature control method in a quenching zone of a continuous annealing furnace consisting of a plurality of cooling zones, which is used to continuously cool a strip that has been heated to a soaking temperature in a soaking zone. In particular, the present invention relates to a cooling plate temperature control method for a quenching zone of a continuous annealing furnace that can stably and accurately realize a wide range of cooling conditions.

A continuous annealing furnace for heat-treating a strip 8 such as a copper strip is, for example, as shown in FIG.
, steel strip cleaning device 14, priddle roll 16, entry side louver 18, priddle roll 20, tension device 2
2. Heating zone 24, soaking zone 26, gas jet quenching zone 28
, an overaging zone 30, a cooling zone 32, a prydle row 34, an exit looper 36, a prydle roll 38, a shear 40, a tension reel 42, and the like.

In such a continuous annealing furnace, the quenching zone 28 for continuously cooling the strip heated to the soaking temperature in the soaking zone 26 has a quenching zone 28 as shown in FIG. 2, for example.
This zone division is divided into five zones, the first cooling zone 28-1 to the fifth cooling zone 28-5, and a plenum having a gas nozzle is arranged corresponding to each zone. This is done to cope with fluctuations in cooling conditions when heat-treating.

In such a continuous annealing furnace, a heating zone 24, a soaking zone 2
The steel strip 8 passed through 6 and soaked at a predetermined soaking temperature T8 tunnel is cooled at a predetermined cooling rate CR to a predetermined cooling temperature Tso in a gas jet quenching zone 28, and the copper strip is heated to a predetermined cooling temperature Tso. In the case of soft tin plate or cold rolled steel sheet for drawing,
It passes through the pass line A shown in FIG. 2, undergoes an overaging treatment in an overaging zone 30, and is then cooled in a cooling zone 32 to a temperature 1 at which it can be processed on the exit side.

On the other hand, in the case of a high-tensile steel plate, primary cooling is performed at an intermediate position Bt between the second cooling zone 28-2 and the third cooling zone 28-3, and after that, secondary cooling is performed, and the cooling is performed through the pass line C. It is sent directly out of the furnace.

In the quenching zone of such a conventional continuous annealing furnace, only plate thermometers 50,52 are placed on the inlet and outlet sides, and precise temperature control in the middle of the quenching zone is not performed at all. There wasn't.

However, such plate temperature control based only on the temperature at the outlet of the quenching zone has the disadvantage that there is a large control delay from the cooling start zone, which has the greatest effect on plate temperature, making stable control difficult and having poor accuracy. .

Therefore, it has been difficult to obtain good quality materials for steel types that require strict cooling conditions, ie, plate temperature before and after cooling and cooling rate.

In addition, in the prior art, in addition to the above-mentioned steel sheets, primary cooling to obtain a predetermined material quality in the middle of the quenching zone, such as a high-tensile cold-rolled steel sheet that is completely cooled in the gas jet quenching zone 28, has been proposed. When carrying out secondary cooling to maintain the material quality after that, it was difficult to control the plate temperature with high accuracy.

The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a cooling plate temperature control method for a quenching zone of a continuous annealing furnace that can realize many cooling conditions with high accuracy.

The present invention relates to a cooling plate temperature control method of a quenching zone of a continuous annealing furnace consisting of a plurality of cooling zones, which continuously cools a strip heated to a soaking temperature in a soaking zone. The plate temperature is detected and this determines the type of strip,
The above object is achieved by independently controlling each cooling zone so as to match the set plate temperature on the outlet side of each cooling equalization zone, which is determined in advance from dimensions, cooling conditions, etc.

In addition, the set plate temperature at the exit side of each cooling zone is determined by first determining the heat cycle from the type, size, and cooling conditions of the strip, and then determining the line speed and cooling zone to be used using a line speed determination calculation program. Using,
This is calculated using a rapid cooling zone cooling condition setting calculation program.

Embodiments of the present invention will be described in detail below with reference to the drawings.

First, in the method of the present invention, a method for determining the set plate temperature on the outlet side of each cooling zone will be explained in detail with reference to FIG.

First, from the dimensions (plate thickness, plate width) and components of the steel plate to be heat-treated in a continuous annealing furnace, heat cycles according to the steel type (heating temperature TSH1 soaking temperature 'f'ss, quenching zone exit temperature TSCI
(high tension primary cooling temperature), 'rsc 1' (high tension 2
Next cooling temperature Tsc-1'), overaging zone exit temperature TSC2
, cooling zone outlet temperature Tsc, 3, soaking time tss, overaging time tc-2, cooling rate range CRMIN~CRMA
X) is determined.

Next, among the line speeds at which the determined heat cycle can be achieved, the line speed Ls at which the production amount is maximized is determined by the line speed determination calculation program, and
The number of zones in which the gas jet quench zone will be used will also be determined.

Specifically, first, the maximum value of the line speed in each section other than the quenching zone 28 is calculated as follows.

That is, the line speed maximum value L SH8 in the heating zone 24
MAX is calculated using the following formula.

In particular, TSH is the outlet side plate temperature of the heating zone 24, D is the plate thickness,
W is the plate width, and A1 to A5 are constants.

In addition, the line speed maximum value LSSSMA in the soaking zone 26
X is calculated using the following formula.

Here, As is the soaking zone length and tss is the soaking time.

Furthermore, the line speed maximum value LSc- in the overaging zone 30
2MAX is calculated using the following formula.

In particular, 1c-2 is the overaging zone length and tc-2 is the overaging time.

Moreover, the maximum line speed value L S C- in the cooling zone 32
3MAX is calculated using the following formula.

Here, 'I''sc 2 is the plate temperature on the exit side of the overaging zone, that is, the plate temperature on the entrance side of the cooling zone, 'rsc 3 is the plate temperature on the exit side of the cooling zone, AI
~A16 is a constant.

From the maximum line speed in each section other than the rapid cooling zone 28 obtained in this way, the common line speed maximum value in each section other than the rapid cooling zone is determined by the following formula SM
Find o.

LSMO=min(LSHsMAXy LSSSMA
X +LsC-2MAX, LSo-3MAX)...-
<5) Next, if the steel type is other than high-strength steel plate, i
= 5, and in the case of a high-tensile steel plate, i = 3, and the cooling rate CR of the rapid cooling zone is calculated using the following formula.

Here, Ai is the total zone extension up to the i-th cooling zone.

The above calculation is repeated while decreasing i until the cooling rate CRo calculated in this manner exceeds the cooling rate lower limit CRmin.

When CRo is smaller than CRmin, the magnitude relationship between CRo and cooling rate upper limit CRMAX is compared.

If CRo is smaller than CRMAX, line speed LS
is determined to be LSMo determined by equation (5) above.

On the other hand, if the cooling rate CRo is lower than the line speed upper limit CRMAX, the line speed LS is determined by the following equation.

Here, α is a control margin and is a constant smaller than 1.

In this way, the line speed LS and the number i of zones used in the rapid cooling zone 28 are determined.

Next, the cooling air volume Qi@ of the used cooling zone, the plenum pressure Pi, and the plate temperature Tso□~i on the outlet side of each cooling zone are calculated by the rapid cooling zone cooling condition setting calculation program.

Specifically, first, the cooling air volume Qi@ of the used cooling zone is calculated using the following equation.

Qi=A3, T8, 10A3□'rso+A33LS-D
+A34 TsI”+ A35 TSO2+ A36
TsITSO+A37(LS-D)2+A38T8□・
LS-D+A39Tso・LS ” D + A4 o
(8) Here, A3□ to A40 are constants.

The plenum pressure Pi is calculated from the cooling air volume Qi obtained in this way using the following equation.

P1=A41XQi2 ・・・・・・・・・
...(9) Here, A4□ is a constant.

Next, the plate temperature TSOI~i on the outlet side of each cooling zone is calculated from the inverse function Ql 1 of the above equation (8).

If the copper strip is made of a material other than a high-tensile steel plate, this completes the calculation of the set temperature.

When the copper strip is a high-tensile steel plate, the cooling air volume Q3 to the third to fifth cooling zones in the rapid cooling zone is further increased.
(a), plenum pressure P3-5, set plate temperature on the outlet side of each cooling zone 'f'so 3~. is calculated using equations (8), (9), and the inverse function of equation (8).

Using the cooling air volume and set plate temperature for each cooling zone calculated in this way, set values are given to the lower control system by a tracking setting program or the like to control the plate temperature.

The above calculations are automatically performed, for example, by a process computer, and are processed on a plurality of types of steel sheets before they are threaded.

Next, a specific example of a rapid cooling zone and its control system to which the present invention is applied will be explained.

In the rapid cooling zone in which the present invention is implemented, as shown in FIG.
The difference from the conventional example is that 4-1 to 54-4 are provided.

The control system in each cooling zone is configured as shown in FIG. 5, and includes a plenum 64 that injects cooling gas supplied from a circulation blower 60, for example, HNX gas at a temperature of 48 to 51° C., from a gas jet nozzle 62. , a suction pipe 66 that sucks the ejected cooling gas again, a water cooler 68 that cools the sucked cooling gas again, and a flow rate adjustment valve 70 such as a damper that adjusts the amount of circulating cooling gas.
A pressure gauge 72 detects the pressure of the cooling gas supplied to the plenum 64, a pressure regulator 74 controls the flow rate regulating valve 70 according to the output of the pressure gauge 72, and the plenum is adjusted based on the calculation results of the program. In addition to initially setting the initial value of the pressure Pi in the pressure regulator 74, the temperature of the copper strip on the plenum outlet side is adjusted according to the output of the plate thermometer 54 disposed on the outlet side of the cooling zone. a computer 76 for feedback-controlling the pressure regulator 74 so as to match the set plate temperature set in , and a computer 76 for directly controlling the plenum pressure in accordance with the output of the plate temperature meter 54 when the computer 76 is not used. It is composed of a temperature controller 78 and a manual setting device 80.

In this control system, the pressure in the plenum 64 is regulated by a flow control valve 70 installed on the inlet side of a cooling gas circulation blower 60 connected to the plenum 64, and the cooling gas is supplied to the steel strip 8.
After being cooled, it is guided to a water cooler 68 via a suction pipe 66, and after being cooled, it is passed through a circulation blower 60 to a plenum 6.
4 and is ejected from the gas jet nozzle 62.

The deviation signal from plate thermometer 54 is also transmitted to computer 76, which changes the set point to change the plenum pressure.

In addition, in the case of manual operation, from the plate thermometer 54 to the temperature controller 78,
A control signal is provided directly to the plenum pressure via a manual setter 80.

First Example 0.5%Cr-1.2%Mn containing A [A high tensile strength steel plate made of killed steel and having a plate thickness of 1.21n11L and a width of 1000mm was heated at a heating temperature TSH and a soaking temperature T'ss of 800°C. High tension primary cooling temperature T'sc 1 in rapidly cooling zone is 27
5℃ High tension secondary cooling temperature T'sc 1/ is 120℃,
According to the calculation according to the present invention, the minimum value of the soaking time tss is 30 seconds and the allowable cooling rate range is 40~b.
0 m/min, cooling air volume ratio Q1-5 is 90%, 1st zone outlet set plate temperature is 510°C, 2nd zone outlet set plate temperature 2
The temperature of the third zone outlet setting plate was 210°C, the fourth zone outlet setting plate temperature was 170°C, and the fifth zone outlet setting plate temperature was 120°C.

Based on this calculation result, when heat treatment was actually performed, the cooling curve at that time was as shown in Figure 6, and a cooling rate of 44°C/sec from 800°C to 275°C was obtained, and the material after annealing was , tensile strength 44 kg/mm2, Q, 2%
Yield strength: 21 kg/mm2, yield elongation: 0%, elongation: 4
A good material with a yield ratio of 1% and a yield ratio of 0.48 was obtained.

Second Example A [Made of guild steel, plate thickness 1.2 mm, plate width 13QO
A cold-rolled steel sheet for drawing of mm is heated at a heating temperature TSH and a soaking temperature T'ss of 800°C, a third cooling zone exit temperature TsC-1' of the rapid cooling zone of 400°C, and an overaging zone exit temperature T'sc.
2 is 350℃, cooling zone outlet temperature 'I'sc 3 is 120
°C, minimum soaking time tss is 30 seconds, overaging time tC
According to the present invention, the minimum value of 2- is 120 seconds and the allowable cooling rate range is 30~b. According to the calculation according to the present invention, the line speed is 75 m/min, the cooling air volume ratio Q1-3 is 60%, and the first zone exit side setting is The plate temperature was 620°C, the second zone outlet side set plate temperature was 490°C, and the third zone outlet side set plate temperature was 400°C.

Based on this calculation result, when heat treatment was actually performed, the cooling curve at that time was as shown in Figure 7, and the temperature was 800℃.
A cooling rate of 34°C/sec from
A good material with 12% yield strength, yield point of 22 kg/mm, yield elongation of 0%, and elongation of 43% could be obtained.

As explained above, according to the present invention, plate temperature control of the gas jet quenching zone can be carried out stably and with high precision, and a wide range of cooling conditions can be handled, which is an excellent effect.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing the overall configuration of a continuous annealing furnace, Fig. 2 is a sectional view showing a conventional quenching zone, and Fig. 3 is a process diagram showing the overall configuration of a continuous annealing furnace. A flowchart showing the procedure for calculating the set plate temperature on the outlet side of the cooling zone,
FIG. 4 is a sectional view showing a quenching zone of a continuous annealing furnace to which an embodiment of the present invention is applied, FIG. 5 is a block diagram showing a control system for each cooling zone in the quenching zone, and FIG. teeth,
FIG. 7 is a diagram showing the cooling curve of the first embodiment according to the present invention, and FIG. 7 is a diagram showing the cooling curve of the second embodiment. 8... Steel strip, 26... Soaking zone, 28... Gas jet quenching zone, 28-1 to 28-6... Cooling zone, 3
0... Overaging zone, 32... Cooling zone, 5
0,52°54.54-1 to 54-4... Plate thermometer, 6
0... Circulation blower, 62... Gas jet nozzle, 64... Plenum, 66... Suction piping, 68... Water cooling cooler, 70...・・・
...Flow control valve, 72...Pressure gauge, 74...
...Pressure regulator.

Claims (1)

[Scope of Claims] 1. A method for controlling the temperature of a cooling plate in a quenching zone of a continuous annealing furnace consisting of a plurality of cooling zones, which continuously cools a strike IJ tube heated to a soaking temperature in a soaking zone. The plate temperature on the exit side of the cooling zone is detected, and each cooling zone is adjusted independently so that this matches the set plate temperature on the outlet side of each cooling zone, which is determined in advance from the type, dimensions, cooling conditions, etc. of the IJ tube. 1. A cooling plate temperature control method in a quenching zone of a continuous annealing furnace. 2. Set plate temperature on the exit side of each cooling zone. First, determine the heat cycle from the strip type, dimensions, and cooling conditions. Then, use the line speed determination calculation program to determine the line speed and cooling zone to be used. 2. A cooling plate temperature control method for a quenching zone of a continuous annealing furnace according to claim 1, wherein the temperature is calculated by a quenching zone cooling condition setting calculation program.