JPS6360816B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a method for cooling a metal strip, such as a steel strip, in a cooling zone of a continuous annealing furnace. (Prior art) When continuously annealing a steel plate, the steel plate is heated and soaked to a temperature higher than the recrystallization temperature and then cooled to 400°C at a cooling rate of 70 to 200°C/s to achieve cold rolling with excellent drawability. It is known that steel plates and high-strength steel plates can be produced. As a method for performing this cooling with compact equipment at low cost, the most excellent method is to bring the steel plate into contact with a cooling roll through which a cooling medium is passed, as shown in Figure 3.
There is an invention described in the publication No. In FIG. 3, 1 is a group of cooling rolls 7a to 7.
3 is an inlet plate temperature control device installed on both sides of the steel plate 1, 4 is a control valve that adjusts the flow rate of cooling gas to the plate temperature control device 3, and 5 is an inlet steel plate. Width direction plate thermometer, 6 is cooling roll group 7a~
7e is a non-cooled roll provided on the inlet side, 9 is a non-cooled roll also provided on the exit side, and 10 is an exit side steel plate width direction plate thermometer. The cooling rolls 7a, 7c, and 7e in the cooling roll group are moved by cooling roll moving devices 8a, 8c, and 8e belonging to the cooling rolls, respectively.
In the figure, it can move freely in the vertical direction, and by this movement, the contact length between the steel plate 1 and each cooling roll of the cooling roll groups 7a to 7e can be changed. Reference numeral 12 is a calculator, into which the steel plate temperatures on the inlet and outlet sides measured by plate thermometers 5 and 10 are introduced, and from the deviation between these temperatures and the target steel plate temperature, A control value to be introduced into a control device that controls the flow rate regulating valve 4 and the cooling roll moving devices 8a, 8c, and 8e is calculated. FIG. 4 shows cooling rolls 7a, 7c, and 7e in order to change the contact length between the cooling roll and the steel plate in order to obtain a target temperature pattern in the method shown in FIG.
The figure shows the state in which it has been lowered to the position indicated by the broken line. In this method, the contact length l is the entrance side plate temperature T _io to the cooling zone (cooling roll group), the outlet side plate temperature T _put , the plate thickness t,
It is a function of line speed v. l=f(T _io , T _put , t, v) For example, if the speed is reduced from the state where the sheet is being threaded at the maximum line specification speed as shown in Figure 3, the speed will be reduced as shown in Figure 4. , cooling rolls 7a, 7
If the contact length is to be shortened by lowering c and 7e and the speed is to be increased, the reverse operation is performed. When the contact length is small, the cooling roll and the steel plate tend to slip, especially when the line accelerates or decelerates, so the contact length cannot be made extremely small, and some parts of the cooling roll must be in a non-contact state, and then when the line accelerates or the plate thickness increases, the maximum contact length of the rolls in contact is determined by mechanical constraints, so the non-contact state is Certain rolls must be brought into contact again. At that time, in order to prevent scratches from forming on the steel plate, the steel plate is stopped once and the cooling roll is pushed into the steel plate before it starts running. The shape of the steel plate may collapse,
There was a problem in that the plate temperature fluctuations became extremely large, making it impossible to stably manufacture steel plates. (Problems to be Solved by the Invention) An object of the present invention is to change the contact length between the metal strip and the individual cooling rolls when cooling the metal strip using a group of cooling rolls in the cooling zone of a continuous annealing furnace. The object of the present invention is to provide a method for cooling a metal strip in a cooling zone of a continuous annealing furnace, which solves the above-mentioned problems when controlling cooling using a continuous annealing furnace and achieves a wide range of cooling controllability. (Means for Solving the Problems) The above-mentioned object of the present invention is to prevent the metal strip from running when switching the cooling roll into contact with the metal strip in the cooling zone of a continuous annealing furnace equipped with a group of cooling rolls. This is achieved by synchronizing the circumferential speed of the cooling roll with the feeding speed of the metal strip and bringing them into contact without stopping the running of the metal strip. In other words, in order to set the outlet plate temperature as the target temperature,
When changing the contact length between the cooling roll and the metal strip, if the winding angle of the metal strip on each cooling roll is less than the limit angle at which slip occurs, for example, 15 degrees or less, multiple Remove the book completely from the strip (no contact)
If cooling is insufficient, the number of cooling rolls used will be increased, but the contact and separation of the cooling rolls while running is based on the amount and speed of movement of the cooling rolls. To do this, the cooling roll is driven by an electric motor, and is rotated in a non-contact state so that the circumferential speed is the same as the steel plate running speed, and then moved to a contact state to cool the steel plate. Prevents scratches from forming. According to the present invention, even when the line speed increases or the plate thickness increases, the cooling roll can be pushed into the steel plate without stopping the running of the strip, so the shape of the steel plate can be changed. It has become possible to produce steel plates stably, with no crumbling or fluctuations in plate temperature. [Example] Table 1 and FIG. 1 show examples of control according to the conventional method and the present invention.
This prevents yield deterioration due to deformation of the steel plate shape and material failure due to deviation from the target plate temperature, making it possible to produce stable steel plates. Figure 1 A shows the total winding angle of the cooling roll when passing a steel plate (0.5 x 1000mm) at a line speed of 120mpm to achieve a target temperature pattern of 650℃ for the input plate temperature and 400℃ for the exit plate temperature. This shows the state where the angle is 120°. Figure 1 B shows that when the plate thickness changes to 0.8 mm,
In order to achieve the same target temperature as described above, the cooling rolls 7a and 7e are brought into contact with the steel plate, and the winding angle of each cooling roll is set to 200° C. in total. FIG. 2 shows an embodiment of the present invention. Each cooling roll is provided with an electric motor 13a-13g and a tachometer 14a-14g for detecting the roll speed, making it possible to synchronize the running speed of the metal strip with the speed of the cooling roll.

[Table] (Effects of the Invention) According to the present invention, a wide range of cooling control capabilities can be obtained without deteriorating the yield due to deformation of the steel plate or fluctuations in plate temperature, so it is extremely beneficial industrially. It's large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of equipment for implementing the present invention, and FIGS. 3 and 4 are diagrams showing a conventional cooling roll group. FIG. 3 is a diagram showing a method of cooling a metal strip. DESCRIPTION OF SYMBOLS 1... Steel plate, 3... Inlet side plate temperature control device, 4... Flow rate adjustment valve, 5... Inlet side steel plate direction plate thermometer, 6... Uncooled roll, 7a to 7e... Cooling roll group, 8a, 8c,
8e... Cooling roll transition mechanism, 9... Non-cooling roll, 10... Output side steel plate width direction plate thermometer, 11... Control device, 12... Computer, 13a to 13g... Electric motor, 1
4a-14g...Tachometer.

Claims (1)

[Claims] 1. In the cooling zone of a continuous annealing furnace equipped with a group of cooling rolls, when switching the cooling roll into contact with the metal strip, the circumferential speed of the cooling roll is increased without stopping the running of the metal strip. A method for cooling a metal strip in a cooling zone of a continuous annealing furnace, characterized in that the metal strip is brought into contact in synchronization with the traveling speed of the metal strip.