JPH0718343A - Method for controlling cooling of wire rod in hot-rolling - Google Patents

Abstract

PURPOSE:To shorten the length of a uncooled part with water at the tip part of a wire rod in a hot rolling. CONSTITUTION:After detecting the tip part of the wire rod with steel material detectors 6, 7 arranged at the upstream side of a cooling device 1 for wire rod 16, a cooling water change valve 2 is opened to spout the cooling water. At the fixed time before the tip pat of the wire rod reaches the cooling device 1, the cooling water change valve 2 is closed to stop the cooling water, and thereafter, the cooling of the wire rod 16 is started. By this method, regardless of the length of the rolling pitch, the condition of the cooling water supplying pipe before starting the cooling becomes almost constant and the time from opening of the cooling water change valve 2 to actual spouting of the cooling water from a cooling nozzle becomes also almost constant. Even if the rolling pitch is increased, the uncooled part with the water at the tip part of the wire rod is shortened and the yield is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling cooling of a wire rod in hot rolling.

[0002]

2. Description of the Related Art Generally, in a wire rod rolling line, a wire rod after hot finish rolling is cooled to a predetermined winding temperature by a cooling device having a known structure installed downstream of a finish rolling machine and having a plurality of sets. It is then rolled up into a ring.

In the case of a small-diameter wire rod, if cooling water is present in the cooling device, the passage resistance is large when the tip of the wire passes and it is likely to cause misroll. Therefore, the cooling water is not ejected from the cooling nozzle until the tip of the wire passes through the cooling device, and after the tip of the wire passes through the cooling device, the cooling water switching valve is turned on to start cooling, and the tail end of the wire is A cooling control method is generally performed in which the cooling water switching valve is turned off after passing through the cooling device to complete cooling.

In Japanese Utility Model Publication No. 62-32649, the timing at which the tip of the wire reaches the cooling device is predicted by the equivalent distance set according to the rolling conditions (size, rolling speed, etc.), and the cooling water switching valve is turned on. A method of initiating cooling of the is described. However, in this method, the time from the completion of cooling of the preceding wire to the start of cooling of the subsequent wire changes according to the fluctuation of the rolling pitch. When this time becomes longer, that is, when the rolling pitch becomes longer, the amount of residual cooling water in the cooling water supply pipe decreases, and the time from when the cooling water switching valve is turned on until the cooling nozzle actually ejects becomes longer.

Japanese Patent Laid-Open No. 3-248710 discloses a method of measuring and updating the response delay time of the cooling water switching valve every time. However, even with this method, the cooling water switching valve is turned on.
Although the accuracy of the timing can be improved, it is impossible to correct the influence of the decrease of the residual cooling water amount in the cooling water supply pipe due to the increase of the rolling pitch.

Japanese Utility Model Publication No. 63-6205 proposes a method in which a piston valve is provided in the middle of a cooling water supply pipe to forcibly discharge residual cooling water in the pipe. However, in this method, since the residual cooling water is lost in the cooling water supply pipe, the responsiveness from when the cooling water switching valve is turned on to when the cooling water is actually ejected from the cooling nozzle is deteriorated. In addition, installation of a piston valve is newly required, which increases equipment costs.

[0007]

In the conventional method of predicting the time for the tip of the wire to reach the cooling device and turning on the cooling water switching valve to start cooling the wire, cooling of the preceding material if the rolling pitch fluctuates. The time from the end to the start of cooling the subsequent material changes. Along with this time change, there is a problem that the amount of residual cooling water in the cooling water supply pipe fluctuates, and the time from when the cooling water switching valve is turned on to when the cooling water is actually jetted out varies. This time tended to be longer when the value increased.

Particularly, the finishing rolling speed of the thin wire is 60 to
Since it is performed at a high speed of about 100 m / sec, the length of the wire rod becomes 30 to 50 m even if the time is increased by about 0.5 sec. Since this non-water-cooled portion is generally cut off from the viewpoint of quality, there is a problem that the number of cut rings at the tip of the wire increases and the rolling yield deteriorates. Further, in the method of forcibly discharging the residual cooling water in the cooling water supply pipe, there is a drawback in that equipment such as a piston valve is newly required.

Therefore, according to the present invention, even if the rolling pitch is increased, the time from when the cooling water switching valve is turned on to when the cooling water is actually ejected from the cooling nozzle is made substantially constant, and new equipment such as a piston valve is provided. An object of the present invention is to provide a cooling control method that improves the rolling yield without the need for cooling.

[0010]

The present invention is a method for controlling the cooling of a wire rod in hot rolling which can advantageously eliminate the above-mentioned conventional drawbacks, and the gist thereof is (1) hot finishing of the wire rod. In cooling after rolling, after the wire rod tip has passed through the steel material detector upstream of the cooling device and before a certain time before reaching the cooling device, the cooling water switching valve is turned on and cooling water is ejected from the cooling nozzle in the cooling device. After that, a dummy injection cycle in which the cooling water switching valve is turned off to stop the cooling water is inserted, and after the wire rod reaches the cooling device and the passage is completed, cooling of the wire, that is, main injection is started. .

(2) When the time (rolling pitch) from the trailing edge of the preceding material to the leading edge of the following material passing is equal to or less than the time from the start of dummy injection to the start of main injection, The main injection of the preceding material and the start of the dummy injection of the following material are omitted, and the main injection of the preceding material and the dummy injection of the following material are continued.

[0012]

First, the conventional method will be described with reference to FIG. In the conventional cooling control method (the method of Japanese Utility Model Publication No. 62-32649, etc.), the timing at which the steel material detector (6) installed upstream of the finish rolling mill detects the wire rod tip and passes through the cooling device (1) Is predicted, an ON signal is output to the cooling water switching valve (2) to start cooling the wire. In this case, the mechanical response delay (about 0.2 to 0.3 sec) of the cooling water switching valve is measured in advance and a signal is output in consideration of this. After that, the temperature of the wire is measured by the winding thermometer (14) during cooling, and the amount of cooling water is controlled by the flow rate control valve (3) so that the winding temperature becomes constant by feedback, feedforward, or a combination thereof. When the tail end of the wire passes through the cooling device, the cooling water switching valve (2) is turned off to stop the jet of cooling water and complete the cooling of the wire. After that, the cooling water switching valve (2) is turned off and the cooling water is not jetted until the tip of the succeeding material reaches the cooling device and starts cooling. FIG. 2 schematically shows the relationship between the passage of time and the amount of cooling water according to the conventional control method.

Next, the control method of the present invention will be described with reference to FIG. FIG. 4 shows only one set of the cooling device (1), the cooling water switching valve (2), the flow control valve (3) and the cooling water flow meter (4) for the sake of easy understanding, but these are generally used. Multiple sets of equipment are installed.

After the cooling of the preceding material is completed, an ON signal is output to the cooling water switching valve (2) at the time when the front end of the succeeding material passes through the steel material detector (6) or after a certain time has passed after passing the steel material detector (6) to cool the material. Cooling water switching valve (2) that ejects cooling water from the cooling nozzle in the state where there is no wire rod in the device (1) and a certain time before the tip of the wire rod reaches the cooling device (usually set to the same as the rolling pitch). Turn off the cooling water by sending an OFF signal to.

Then, the tip of the succeeding material reaches the cooling device.
Cooling of the wire is started from the time when the wire passes. As a result, even if the residual cooling water in the cooling water supply pipe (5) is reduced due to a leak of a valve or the like while the cooling water switching valve (2) is OFF and becomes unfilled, the actual cooling water is cooled. The cooling water is supplied to the cooling water supply pipe (5) to fill the inside thereof with a certain amount of time before the start of the cooling water, and the residual amount of the cooling water is substantially constant.

Therefore, the state inside the cooling water supply pipe (5) before the cooling of the wire is kept stable regardless of the length of the rolling pitch, so that an ON signal is issued to the cooling water switching valve (2). The time from when the cooling water is actually ejected from the cooling nozzle is substantially constant. FIG. 3 schematically shows the relationship between the elapsed time and the amount of cooling water according to the method of the present invention.

[0017]

EXAMPLE An example of the present invention will be described with reference to FIG. In FIG. 1, a steel material detector (6) installed before the finish rolling mill (11) and a steel material detector (6) installed between the first intermediate rolling mill group (9) and the second intermediate rolling mill group (10) ( 7) and a cooling device (1) installed on the downstream side of the finishing rolling mill group (11)
And a cooling water switching valve (2) for controlling the supply and stop of cooling water through the cooling water supply pipe (5), a flow control valve (3) for controlling the amount of cooling water, a cooling water flow meter (4) and these 1 shows a wire rolling line consisting of a cooling controller (15) for processing and controlling signals.

In the cooling device (1), a plurality of cooling nozzles having a known structure are arranged, and in the case of this embodiment, five boxes are installed. Further, six sets of the cooling water switching valve (2), the flow rate control valve (3), and the cooling water flow meter (4) are installed. Generally, a plurality of sets of these devices are installed in this way, but the effects of the present invention can be exhibited by performing the same control for each cooling device.

As shown in FIG. 1, a steel material detector (7) is installed between the first intermediate rolling mill group (9) and the second intermediate rolling mill group (10) to cool the steel material detector (7) and the cooling. When rolling a φ5.5 mm wire rod at 60 m / sec in a wire rod rolling line with a distance of about 90 m from the device (1), the wire rod passes between the steel material detector (7) and the cooling device (1). About 2 hours
It will be 1 sec. Here, the cooling water jetting time (α in FIG. 3) of the dummy jet is set to 5 seconds, and the tip of the wire rod is the cooling device (1).
If the time until the OFF signal is output to the cooling water switching valve (2) before reaching (3) (β in Fig. 3) is 3 seconds, the cooling water switching is performed 13 seconds after the wire tip passes the steel material detector (7). It suffices to issue an ON signal to the valve (2). The steel material detector (6) installed immediately in front of the finishing rolling mill group (11) has a short distance to the cooling device (1), and control using it cannot cope with time.

The time from when the tip of the wire passes the steel material detector (7) to when an ON signal is output to the cooling water switching valve (2) can be adjusted depending on the rolling size and the like. Further, it is convenient to set the time during which the OFF signal is sent to the cooling water switching valve (2) before the tip of the wire reaches the cooling device (1) to coincide with the normal rolling pitch.

The rolling pitch (Tp, Tp2 in FIG. 3) can be measured by measuring the time taken for the leading edge of the succeeding material to pass after the tail edge of the preceding material has passed through the steel material detector (7). be able to. When the time is set as described above, the dummy injection proposed in the present invention is not performed when the rolling pitch is within 3 seconds. Further, when the rolling pitch is within 8 seconds, the jetting time of cooling water (α in FIG. 3) becomes shorter than 5 seconds. Further, it is possible to perform the dummy injection only when the rolling pitch becomes longer than a certain time depending on the operating condition.

The steel material detector (7) used for this control is
It is also possible to replace with a steel material detector installed in the looper or repeater section installed between rolling mill groups or a steel material detector installed for control of crop shear, etc. do not have to.

[0023]

As described above, according to the present invention, the amount of residual cooling water in the cooling water supply pipe is controlled to be stable before the cooling of the wire is started. The time from when the switching valve is turned on to when the cooling water is actually jetted from the cooling nozzle is substantially constant, there is little variation in the length of the unwater-cooled portion at the tip of the wire rod, the rolling yield is improved, and the effect is great. It is a thing.

Further, the cooling control method of the present invention does not require addition of new equipment and can be carried out only by remodeling the control system, so that it can be applied to an existing line at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a wire rod rolling line for carrying out the present invention in one embodiment.

FIG. 2 is a graph showing time-series changes in the amount of cooling water according to a conventional cooling control method.

FIG. 3 is a graph showing time-series changes in the amount of cooling water according to the cooling control method of the present invention.

FIG. 4 is a block diagram schematically showing a wire rod rolling line on which a conventional cooling control method is implemented.

[Explanation of symbols]

1: Cooling device having a cooling nozzle 2: Cooling water switching valve 3: Flow rate control valve 4: Cooling water flow meter 5: Cooling water supply pipe 6: Steel material detector 7: Steel material detector 8: Rough rolling mill group 9: No. 1 Intermediate Rolling Mill Group 10: Second Intermediate Rolling Mill Group 11: Finishing Rolling Mill Group 12: Pinch Roll 13: Laing Head 14: Winding Thermometer 15: Cooling Control Device 16: Wire Rod 17: Heating Furnace

Claims (2)

[Claims] 1. A method for cooling a wire rod after hot finish rolling,
After the wire rod tip passes through the steel material detector upstream of the cooling device, and before a certain time before reaching the cooling device, the cooling water switching valve is turned on and the cooling water is ejected from the cooling nozzle in the cooling device.
Inserting a dummy injection cycle that stops the cooling water by turning off the cooling water switching valve and reaching the cooling device at the tip of the wire,
A method of controlling cooling of a wire rod in hot rolling, which comprises cooling the wire rod after completion of passage, that is, starting main injection. 2. The preceding material when the time (rolling pitch) from the trailing edge of the preceding material to the leading edge of the following material passing is equal to or less than the time from the start of dummy injection to the start of main injection 2. The method for controlling cooling of a wire rod in hot rolling according to claim 1, wherein the main injection of the preceding material and the start of dummy injection of the subsequent material are omitted and the main injection of the preceding material and the dummy injection of the subsequent material are continued.