JPS6356294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for cooling a metal strip, and in particular to a method for cooling a metal strip using a gas jet cooling device and a cooling roll in a cooling zone in a continuous annealing facility.

(Prior art) When continuously annealing a metal strip, for example, a steel strip, a plurality of cooling rolls with a coolant flowing through the inner peripheral surface of the body are installed in the cooling zone of the continuous annealing equipment, and the cooling roll group is A commonly used method is to cool the steel strip by bringing it into contact with each other (for example, Japanese Patent Application Laid-open No. 80208/1983).
This roll cooling method allows rapid cooling of the steel strip.

(Problem to be Solved by the Invention) In the above cooling method, the contact time of the steel strip with the cooling roll is a few seconds, so if the contact state of the steel strip with the cooling roll changes even slightly, the temperature of the steel strip will change. The non-uniform distribution results in a defective shape, and if the contact with the cooling roll is continued with this defective shape, the contact condition will become even worse and the defective shape will be amplified. Particularly in roll cooling, if the metal strips are not in uniform contact on the first cooling roll, this tendency is amplified on subsequent cooling rolls.

The present invention solves these problems, allows the metal strip to come into uniform contact with the cooling roll, and makes it possible to uniformly distribute the temperature of the strip after the cooling roll and perform stable cooling without causing shape defects. The purpose is to provide a possible cooling method.

(Means and effects for solving the problems) The above object is achieved by the following cooling method of the present invention. That is, in a method of cooling a metal strip by bringing the metal strip into contact with a plurality of cooling rolls, a gas jet cooling device divided in the width direction of the strip is installed adjacent to the entrance side of the first roll of the cooling rolls. In addition, this method of cooling a metal strip is characterized in that the gas jet air volume of each division unit of the gas jet cooling device is individually controlled, and the supply pressure of the gas jet cooling device is maintained constant.

The present invention will be explained in detail below.

FIG. 1 shows an example of an embodiment of the present invention, and shows a cooling roll section in a cooling zone of a continuous annealing furnace. In the figure, reference numeral 12 denotes a plurality of cooling rolls disposed in a roll cooling section, and the cooling roll 12 is a rotating body having a water-cooled structure in which cooling water flows through the inner circumferential surface of the body. 1 is a metal strip that is cooled by contacting the cooling roll 12, and 2 is a gas jet cooling device provided on the inlet side of the roll cooling section, that is, close to the first cooling roll.

FIG. 2 shows details of the gas jet cooling device 2 and its piping system. The gas jet cooling device 2 is composed of a large number of cooling gas blowing boxes 2a that are divided in the width direction of the strip 1, and the blowing air volume of each box can be adjusted individually. That is, a branch pipe 11 is connected to each box 2a, and these branch pipes 11
are collected in the main pipe 10, and the main pipe 10
is connected to the furnace shell 3 via a blower 5 and a heat exchanger 4. 6 is a main damper provided in the main pipe 10, 9 is a control valve provided in each branch pipe 11, 7 is a valve provided in the bypass pipe 13 provided in the main pipe 10, and 8 is a pressure detection provided in the main pipe 10. , which communicates with the bypass valve 7. Note that each branch pipe 11 branches into a corresponding box 2a with the strip 1 in between.

In the present invention, the gas jet cooling device 2 is disposed on the entrance side of the roll cooling section and close to the first cooling roll, and the reason for this is that the gas jet cooling device 2 improves the tension distribution in the strip width direction. This is to ensure uniform contact with the first cooling roll through the . That is, since the high temperature part of the strip has a low tension and the low temperature part has a high tension, it is possible to change the tension distribution by changing the plate temperature distribution immediately before the first cooling roll.

σ = αE・ΔT However, α: linear expansion coefficient, E: elastic modulus, ΔT: temperature difference, σ: tension Therefore, in the present invention, the plate temperature on the exit side of the roll cooling section is not uniform in the width direction. In some cases, the strip is not in uniform contact with the cooling roll, which means that the tension distribution is uneven, so if you increase the amount of cooling gas in the cooling box of the gas jet cooling device at the position corresponding to the high temperature area, good.

In this way, the amount of cooling gas is adjusted by opening and closing the individual control valve 9 of any cooling box, but it is necessary to prevent the wind speed of the box that is not opened or closed from changing and adversely affecting the tension distribution in the width direction. It is necessary to take care that the pressure remains constant even if the gas amount changes. For this reason, in Fig. 2, the pressure in the main pipe 10 is detected by the detector 8, and if there is a fluctuation by comparison with the set pressure, the opening degree of the bypass valve 7 is adjusted to return it to the set pressure. ing.

Examples of the present invention will be given below.

Example 1 A 0.6 x 1007 mm steel strip was passed through a continuous annealing furnace at 148 MPM, and the temperature at the entrance and exit sides of the strip in the roll cooling section was stable as shown in Figure 3 A, but suddenly I was in a bad state. Then, when I opened the No. 10 control valve from 40% to 80%, the condition returned to A.

Example 2 As in Example 1, when the control valve No. 6 was changed from 20% to 90% and the control valve No. 11 was changed from 0 to 60% in the condition shown in FIG. 4B, the condition returned to A. The material and threading speed were 0.8 x 1015 mm and 180 MPM.

In the case of Example 1, this is thought to be due to the influence of the entrance plate temperature distribution becoming ≒15°C higher, but in the case of Example 2, the influence of the entrance side plate temperature distribution is not clear, and is rather thought to be due to a change in the entrance side shape. It will be done.

Example 3 In a case where the gas pressure was not controlled, and as in Examples 1 and 2, the state in Figure 5 A changed to the state in B during operation, so Nos. 3, 4, 11, and 12
Although the valve was changed from 0 to 80% and then 100%, the plate temperature distribution after the roll cooled did not return to the state shown in Figure 5 A, but instead became the state shown in C. The reason for this is considered to be that since gas pressure control is not performed, the gas blowing speed from the control valves No. 5 to No. 10 decreases, and the tension distribution in the width direction is disrupted.

In Example 3, a 0.6 x 1150 mm steel strip was threaded at 120 MPM.

In the present invention, by adjusting the amount of gas blown from the plurality of boxes in the gas jet cooling device in accordance with the shape of the metal strip, the contact of the metal strip with the cooling roll becomes uniform in the width direction, thereby preventing shape defects. I can't close it. Therefore, even if the shape of the metal strip is not flat on the upstream side of the roll cooling section, that is, the tension distribution in the width direction is not uniform, by providing this gas jet cooling device, the cooling roll and gas jet cooling device can be easily connected. By making the tension distribution uniform between the two, uniform cooling in the width direction can be achieved.

Further, in addition to the bypass method of the embodiment shown in FIG. 2, the rotation speed of the blower may be controlled without providing bypass piping.

(Effects of the Invention) As explained above, according to the cooling method of the present invention, the metal strip can be brought into uniform contact with the first cooling roll of the roll cooling section, and the cooling zone in continuous annealing equipment can be cooled most effectively. be carried out in a proper manner.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing one embodiment of the method of the present invention, Fig. 2 is an explanatory diagram showing the gas jet cooling device and its piping system used in the present invention, Fig. 3,
FIG. 4 and FIG. 5 are graphs showing the effects of the present invention in Examples. DESCRIPTION OF SYMBOLS 1... Metal strip, 2... Gas jet cooling device, 2a... Cooling gas blow-off box, 3... Furnace shell,
4...Heat exchanger, 5...Blower, 6...Main damper, 7...Bypass valve, 8...Pressure detector, 9...
Control valve group, 10...Main piping, 11
...Each branch pipe, 12...Cooling roll, 13...Bypass pipe.

Claims (1)

[Claims] 1. A method for cooling a metal strip by bringing the metal strip into contact with a cooling roll, comprising: a gas jet cooling device divided in the width direction of the strip near the entrance side of a first roll of the cooling rolls; 1. A method for cooling a metal strip, comprising: installing a gas jet cooling device; and individually controlling the gas jet air flow rate of each division unit of the gas jet cooling device to maintain a constant supply pressure of the gas jet cooling device.