JPS605823A - Controlling method of direct heat treating installation for steel wire rod - Google Patents

Abstract

PURPOSE:To control adequately the temp. of a refrigerant even if conveyance of a steel wire rod is interrupted for short time when an operating condition is changed in a method for controlling an installation which subjects the steel wire rod after hot rolling to a direct heat exchange by specifying the control when the conveyance of the steel wire rod is interrupted and resumed. CONSTITUTION:A steel wire rod 1 in a looped state is immersed in a refrigerant, for example, molten salt 3, in a cooling vessel 2 and is thus cooled. The refrigerant 3 heated by the wire rod is circulated between the vessel 2 and a heat exchanger 5 by a pump 4 so as to be subjected to a heat exchange with cooling water 6, by which the refrigerant is cooled. When the final end of a preceding material 1 passes through the vessel 2 owing to a change in an operating condition such as a change in a wire diameter, a calculator 14 applies the target value T2 of the refrigerant temp. in the vessel 2 calculated from the input data for the operating condition of the succeeding material to a temp. control device 7 by which a flow rate adjusting system is controlled until the temperature detected with a detector 8 attains T2. The quantity of the heat extraction is thus decreased as far as possible while the supply of the water to the heat exchanger and the circulation of the refrigerant are continued. When the front end of the succeeding material passes through the vessel 2 and the temp. detected with the thermometer 13 rises to the permissiblemin. temp. or above, the refrigerant temp. T21 on the inlet side of the vessel 2 for the succeeding material calculated by the calculator 14 is applied to the device 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a steel wire direct heat treatment facility installed adjacent to a hot rolling mill, that is, a heat treatment facility that directly catalytically exchanges heat between a rolled steel wire and a refrigerant. Even if the conveyance of steel wire rods is interrupted for a short time due to changes, the temperature of the refrigerant can be appropriately controlled.

Conventionally, in heat treatment methods for steel materials using refrigerants such as molten salt (hereinafter, we will explain using molten salt as an example of refrigerant), the amount of molten salt itself handled was an order of magnitude smaller, so it was difficult to control both heating and cooling of the molten salt. There was no technical problem; heating was performed using an electric heater, and cooling was sufficient by air cooling the outer surface of the cooling tank itself.

However, as the amount of steel processed has increased in recent years, the amount of hot steel carried into the molten salt has become extremely large, and air cooling has become insufficient in its cooling capacity. Therefore, a device for circulating and cooling the molten salt was required in addition to the steel material cooling device.

FIG. 1 shows a direct heat treatment facility for steel wire rods to which the above-described circulation and cooling of molten salt in the heat treatment of steel materials is applied. 1st
In the figure, 1 is a hot-rolled steel wire at about 800°C, which is looped and immersed in a cooling tank 2 as shown in Figure 2, and is heated to a predetermined temperature by a refrigerant, such as a molten salt 3, stored in the cooling tank. For example, it is cooled to a temperature of about 500°C. in this case,
Conversely, the molten salt 3 is heated by the sensible heat of the steel wire 10, so the molten salt 3 is pumped between the cooling tank 2 and the heat exchanger 5 by the pump 4.
The water is circulated and is cooled by exchanging heat with water 6 in a heat exchanger 5.

As a control device for the steel wire direct heat treatment equipment as shown in Fig. 1, a temperature control device as shown in Fig. 3 was proposed in Japanese Patent Application No. 57-2.
It has already been filed as No. 28496.

The temperature control device in FIG. 3 has a heat balance target value T2, which will be described later.
This is a device that controls the molten salt temperature so that it becomes I or T2. Specifically, the operating condition data required to calculate equation (2) or equation (3) t is input to the calculator 12, and TR1 or T is input.
A temperature target value such as 2 is calculated, and this target value is given to the molten salt temperature control device 7 as a set value. In the example of FIG. 3, 7 is a temperature control device for the molten salt at the entrance side of the cooling tank that returns from the heat exchanger 5, and the temperature of the molten salt at the entrance side of the cooling tank detected by the temperature detector 8 is calculated by a computer. Heat exchanger 5
Adjust the setting value of the water supply flow rate control device 9.

This water supply flow rate control device 9 controls the water supply valve 1 so that the water supply flow rate detected by the flow rate detector IO becomes the set value.
Control 1.

TmI= f (d, v, Tl□) *eJ2)T
! =f (d, V, T10) 11@e formula (3
) where α: molten ρ1 Heat transfer coefficient between salt and wire A: Wire surface area (function of wire throughput, speed, wire diameter) C: Specific heat of wire C2: Specific heat of molten salt W Uni Wire throughput W,: Melting Salt circulation flow rate TII: Shield material temperature on the inlet side of the cooling tank 'rIQ: y Outlet side 〃 T, I: # Inlet side molten salt temperature T2:〃 Inside 〃 QL: Heat loss C2: Cooling amount by heat exchanger d: Line Diameter ■ = Heddle speed However, in the control system shown in Figure 3, the steel wire rod 1 itself is considered as a heating source, so if the conveyance of the steel wire rod 1 is interrupted even for a short time, the control will be incorrect. . That is, when the operating conditions change, for example when the wire diameter changes, there is a vacant time of about several tens of minutes during which the wire rod is not transported due to the roll rearrangement of the wire rod rolling mill. During this time, the twisted wire rod that is the heating source for the cooling tank 2 is gone, so the temperature of the molten salt in the cooling tank drops significantly. FIG. 4 shows an example in which the response of the molten salt temperature in the cooling tank after steel wire ash removal is calculated, assuming that the molten salt temperature at the entrance of the cooling tank is constant. According to this, the temperature drop rate is about 2 to 3°C/min.

In order to prevent the temperature drop mentioned above, it is necessary to eliminate heat removal from the heat exchanger 5. However, if the supply of cooling water is stopped, for example, a problem arises in that the heat exchanger 5 runs dry due to the high temperature molten salt of approximately 400 to 500°C.

Therefore, a minimum amount of heat removal is required to prevent dry cooking), and the molten salt temperature control device 7 must be provided with a limiter for the low flow rate side, that is, a low limiter function. On the other hand, if the circulation of the molten salt 3 is stopped.

A problem such as solidification of the molten salt remaining in the heat exchanger 5 occurs.

It should be noted that if a heating source, such as an electric heater, is provided with a capacity greater than the minimum amount of heat dissipated to prevent dry cooking as described above, the problem of the molten salt temperature drop will be eliminated. However, it is over-specified to always have a large-capacity heater for changing the wire diameter only a few times a day, and at the same time goes against energy conservation.

The present invention is based on the above-mentioned circumstances, and when steel wire processing is stopped for a short time, (a) neither the circulation of the molten salt nor the supply of cooling water is stopped, and (b) the temperature of the molten salt in the cooling tank is not lowered as much as possible. , (C
)・Furthermore, the temperature of the molten salt in the cooling tank can be controlled to a predetermined value as quickly as possible when steel wire processing is restarted.

The purpose is to provide a control method.

The method for controlling the steel wire direct heat treatment equipment of the present invention that achieves this objective is as follows: (1) At the same time as the end of the preceding steel wire (referred to as the preceding material) passes through the cooling tank, the molten salt temperature control system at the entrance of the cooling tank is controlled. As the temperature setting value, the target value of the molten salt temperature in the cooling tank calculated for the steel wire rod to be attached later (referred to as the following material) is set. When the tip of the material passes through the cooling tank and the detected value of the temperature of the molten salt in the cooling tank becomes [target value - allowable control deviation 3 or more], at the same time, the setting value of the molten salt temperature control system on the inlet side of the cooling tank during normal operation is set. The basis of the technical idea is to provide a target value for the molten salt temperature at the entrance of the cooling tank calculated for the trailing material.

The present invention will be explained below with reference to FIGS. 5 and 6.

FIG. 5 shows an example of the construction of a control device that implements the control method of the present invention, and the same members as in FIGS. 1 and 3 are given the same reference numerals to avoid redundant explanation. Reference numeral 13 in the figure is a detector for measuring the temperature of the molten salt in the cooling tank.

In addition to the functions of the calculator 120 shown in FIG. 3, the calculator 14 has the following functions:
Equipped with calculation functions necessary for processing the method of the present invention. That is, calculation of the molten salt temperature T2I on the entrance side of the cooling tank by cutting (2) and calculation of the molten salt temperature T2 in the cooling tank by the MiJ equation (3) are both performed.

Now, assuming that the preceding material is being cooled, the computing unit 14
From there, the target value Tzl on the cooling tank inlet side calculated by inputting the data of the operating conditions regarding the preceding material is given to the cooling tank inlet side molten salt temperature control device 7 as its setting value, and the detector In other words, the water supply flow rate control device 9. Flow rate detector 1
0 and a flow rate adjustment system consisting of a water supply valve 11 is controlled.

When the end of the preceding material passes through the entire cooling tank 2 due to changes in operating conditions such as changing the wire diameter, the computer 14 calculates the target value in the cooling tank (g) based on the input data of the operating conditions regarding the succeeding material. In place of TRI, T2 is given to the temperature control device 7 as its set value. Therefore, the flow rate adjustment system is controlled so that the temperature detected by the detector 8 becomes T2. As a result, while supplying water to the heat exchanger 5 and circulating molten salt,
The amount of heat removed can be suppressed as much as possible. Naori Te
The setting value can be changed from 1 to T2 by an operator manually observing the movement of the heat treatment line, or by using an appropriate detector that detects the passage of the end of the previous month and using the detection signal 10. You can go there automatically if there are other people.

Next, when the conveyance of the trailing material is restarted, the leading end of the trailing material passes through the cooling tank 2, and the temperature of the molten salt in the cooling tank is detected by the force detected by the detector 13. Control deviation] In other words, the target value T of the cooling input side for the trailing material calculated by the calculator 14 on the condition that the temperature has exceeded the allowable minimum temperature.
RI is given as a set value of the temperature control device 7 in place of T8. As a result, the temperature of the detector 8 is controlled to a new T2I. In this case, the passage t of the leading edge of the trailing material required to change the set value from T2 to T or I may be detected by the operator by looking at the processing line, or automatically detected by an appropriate detector. It's okay. Further, the minimum allowable temperature may be monitored by displaying the temperature deviation on a display and having the operator look at fL, or by providing the computing unit 14 with a determination function. ~Here, the reason why the temperature is not lowered to the set value 'tTzI of the temperature control device 7 on the entrance side of the cooling tank until the detected value of the temperature of the molten salt in the cooling tank becomes equal to or higher than the allowable minimum temperature after restarting the melt processing is as follows. be.

That is, if the idle time becomes long and the temperature of the molten salt in the cooling tank drops significantly when wire processing is restarted, the temperature of the molten salt in the cooling tank is raised as quickly as possible by the sensible heat of the wire while suppressing the amount of heat removed by the heat exchanger 5. It's for a reason. Due to the high responsiveness of the temperature of the molten salt in the cooling tank, the decrease in yield can be reduced by lowering the set value, such as TgI, at the same time as wire processing is restarted.

FIG. 6 shows an example of calculating response characteristics when the method of the present invention is applied to the control system shown in FIG. However, in FIG. 6, it is assumed that the in-tank target value of the preceding material is larger than the in-tank target value of the succeeding material. Note that c and :d in FIG. 6 are allowable deviations.

According to FIG. 6, it is inevitable that the temperature of the molten salt in the cooling tank gradually decreases due to the minimum amount of heat removed by the heat exchanger 5 during the short stop period S of wire processing. The temperature drop rate is 0.4~0.6'c compared to the case of
/, the weight became significantly smaller. Furthermore, since the sensible heat of the trailing material is utilized when restarting operation, the molten salt temperature in the cooling tank becomes more responsive, significantly improving yield.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of the wire direct heat treatment equipment, Figure 2 is a perspective view of the wire being transported, Figure 3 is a configuration diagram of the control device for the already proposed wire rod direct heat treatment equipment, and Figure 4 is the conventional wire rod heat treatment equipment. FIG. 5 is a block diagram showing an example of a control device that implements the method of the present invention, and FIG. 6 is a graph of an example of response calculation in the method of the present invention. In the drawing, 1 is steel wire rod, 2 is cooling tank, 3 is molten salt (refrigerant), 4 is pump, 5 is heat exchanger, 6 is cooling water, 7 is cooling tank type 9! The molten salt temperature control device. 8 is a temperature detector, 9 is a water supply flow rate control device, 10 is a hot stone detector, 11 is a water supply valve, 13 is a temperature detector, and 14 is a computing unit. Patent applicant Mitsubishi Heavy Industries Hata Co., Ltd. (1 other person) Patent attorney Shibe Kuishi (1 other person) Figure 1 Figure 2! Continued from page 1 0 Inventor: Noboru Ibara To Kyushu City, 1-1-1 Edamitsu, Hatto-ku, Yawata Steel Works, Nippon Steel Corporation ■Applicant: Nippon Steel Corporation, 2-chome, Otemachi, Chiyoda-ku, Tokyo 6 number 3

Claims (1)

[Claims] A steel wire cooling device that cools hot-rolled f'Lfc copper wire by direct catalytic heat exchange with a refrigerant stored in a cooling tank, and a heat exchanger that cools by circulating the refrigerant between the cooling tank. and a control device for controlling the temperature of the refrigerant supplied from this heat exchanger to the cooling tank, that is, the temperature of the refrigerant at the entrance of the cooling tank to a set value. (::・When the conveyance of the wire rod is interrupted, after the end of the leading wire passes through the cooling tank, the target temperature of the refrigerant in the cooling tank calculated according to the operating conditions of the trailing wire is set by the control device. value, and the conveyance of the steel wire rod is resumed.
After the tip of the trailing material passes through the cooling tank and the detected value of the refrigerant temperature in the cooling tank exceeds the allowable minimum temperature, the setting value of the control device is calculated based on the operating conditions of the trailing material. A control method for direct heat treatment equipment for copper wire, characterized in that a target value of a refrigerant temperature at the entrance of a cooling tank is given.