JPS6237693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for direct heat treatment equipment for steel wire rods, and is designed to accurately cool steel wire rods to a predetermined target temperature.

The hot-rolled high-temperature steel wire is cooled by being brought into direct contact with molten salt, which is a liquid coolant. In this case, the molten salt must also be maintained at a certain temperature because it is required that the cooled steel wire always reach a predetermined target temperature so that the properties of the cooled steel wire are uniform. be.

When the amount of steel wire to be processed is small, the temperature of the molten salt stored in the cooling tank is maintained by heating it with electric heat or by cooling the outer surface of the cooling tank with air. When the amount of heat carried into the molten salt was small due to the small amount of treatment, the temperature of the molten salt could be sufficiently kept constant even by the above-mentioned simple means.

On the other hand, as the amount of steel wire rods processed increases, the amount of heat transferred from the steel wire rods to the molten salt becomes very large, so air cooling alone becomes insufficient in cooling capacity. Therefore, in order to cool a large amount of steel wire, a procedure as shown in FIG. 1 is generally used. That is, as shown in FIG. 1, molten salt 2 is stored in the cooling tank 1,
High temperature steel wire rod 3 that has been hot rolled and transported
In particular, as shown in FIG. 2, it is made into a loop shape and is immersed in the molten salt 2 from the left side of the cooling tank 1 in the figure to be cooled, and is pulled up from the right side of the cooling tank 1. The molten salt 2, which has become high in temperature due to receiving heat from the steel wire 3, is sent to a heat exchanger 5 by a pump 4, where it is cooled, and the cooled molten salt 2 is returned to the cooling tank 1 again. Cooling of the molten salt in the heat exchanger 5 is performed by water 6 supplied to the heat exchanger 5.

According to the equipment shown in FIG. 1, since there is sufficient cooling capacity, a large amount of steel wire rod 3 can be cooled. Furthermore, if the wire diameter and transport speed of the steel wire 3 are constant, and the cooling amount of the heat exchanger 3 is set to a certain value, the temperature of the steel wire 3 immediately after being lifted from the molten salt 2 will be , becomes almost equal to the predetermined target temperature.

However, with the above technology, it is not only difficult to accurately match the temperature of the cooled steel wire 3 with the target temperature, but also when cooling steel wires with different diameters or changing the conveyance speed of the steel wires. In this case, the temperature of the cooled steel wire rod and the target temperature are greatly different. Furthermore, it is difficult to set a plurality of target temperatures and accurately select one of them.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a control device that can accurately cool a steel wire to a predetermined target temperature. The present invention achieves the above object by setting the wire diameter and conveyance speed of the steel wire and a predetermined target temperature, based on a predetermined heat balance equation between the temperature of the steel wire and the temperature of the refrigerant. The basis of its technical philosophy is to calculate the temperature of the refrigerant that is optimal for cooling the steel wire to a target temperature, and to control the refrigerant to the calculated temperature.

Before explaining the present invention, a heat balance equation will be shown in the following equation (1). The cooling tank will be a complete mixing system.

However, α: Heat transfer coefficient between refrigerant (molten salt) and steel wire rod A: Surface area of steel wire rod (function of throughput of steel wire rod, conveyance speed, and wire diameter) C ₁ : Specific heat of steel wire rod C ₂ : Refrigerant (molten salt) ) Specific heat of steel wire W ₁ : Steel wire throughput W ₂ : Refrigerant (molten salt) circulation flow rate T _1I : Temperature of steel wire just before being immersed in refrigerant (molten salt) (assumed to be constant) T _1O : (molten salt) T _2I : Temperature of the refrigerant (molten salt) returned from the heat exchanger to the cooling tank T ₂ : Temperature of the refrigerant (molten salt) in the cooling tank Δtm: Q _L : Heat loss Q ₂ : Amount of cooling by the heat exchanger.

Note that the present invention detects the temperature of the refrigerant and controls the refrigerant so that the detected temperature becomes the temperature calculated based on equation (1). Although it is conceivable to form a control system that performs feedback control of the temperature, it is difficult to control the steel wire to accurately cool it to a predetermined target temperature with such a control system. One reason for this is that since the steel wire is transported in a loop shape and immersed in a refrigerant (molten salt), it is difficult to continuously and accurately detect the temperature of the steel wire. Another reason is that the time it takes for steel wire to pass through the refrigerant is about 10 to 20 seconds, whereas the heat capacity of the cooling tank is large (the temperature of the refrigerant returned from the heat exchanger to the cooling tank is The time constant of the temperature inside the cooling tank relative to changes is about 30 minutes).

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that parts that are the same as those in the prior art are given the same numbers and redundant explanations will be omitted.

FIG. 3 shows a first embodiment of the invention. As shown in the figure, a refrigerant temperature detector 7 is arranged in a cooling tank 1 and detects a temperature T ₂ of a molten salt 2 stored in the cooling tank 1, and transmits the detected value to a refrigerant temperature control device 8.
Send to. The calculation device 9 calculates the wire diameter (d) of the steel wire 3.
When the operating conditions consisting of the conveyance speed (ν) and a predetermined target temperature (temperature T _1O is set to a certain predetermined temperature in equation (1)) are set (input), the heat balance equation (1) described above is Based on this, the optimum temperature of the molten salt 2 for cooling the steel wire rod 3 to the target temperature is calculated. The temperature obtained by this calculation is the temperature T ₂ ' that the temperature T ₂ of the molten salt 2 in the cooling tank 1 should be, or the temperature T _2I of the molten salt returned to the cooling tank 1 from the heat exchanger 5. The power temperature is T _2I '. In other words, the calculation device 9 calculates the following equations (2) and (3) when the operating conditions are set.
Perform the calculation.

T ₂ ′= ₁ (d, ν, T _1O ) ...(2) T ₂ ′ _I = ₂ (d, ν, T _1O ) ...(3) And in this example, the calculated temperature T ₂ ′ ,T ₂
Of _I ', only the temperature _T2 ' is sent to the refrigerant temperature control device 8. A refrigerant temperature control device 8 controls the temperature detected by the refrigerant temperature detector 7.
The temperature T ₂ is compared with the temperature T ₂ ′ calculated by the calculation device 9, and the cooling amount control device 10 is controlled so that the temperature T ₂ becomes equal to the temperature T ₂ ′. In other words, the cooling amount control device 10 is controlled by the refrigerant temperature control device 8, so that when the temperature T ₂ is higher than the temperature T ₂ ′, the water supply valve 11 is opened wide to increase the cooling amount of the heat exchanger 5. When the temperature T ₂ is lower than the temperature T ₂ ', the water supply valve 11 is throttled to reduce the cooling amount of the heat exchanger 5. In addition, the reference numeral 12 in the figure is a water supply amount detector, and the detected value of this is inputted to the cooling amount control device 10.

As mentioned above, in this embodiment, the refrigerant 3 in the cooling tank 1
As a result of controlling the temperature of the refrigerant ₂ so that the temperature T 2 of the steel wire rod 2 becomes equal to the optimum temperature T ₂ ' calculated to cool the steel wire rod 2 to the target temperature, the temperature of the steel immediately after being lifted from the refrigerant 3 The temperature of the wire 3 becomes a preset target temperature with high accuracy.

FIG. 4 shows a second embodiment of the invention. In this embodiment, the refrigerant temperature detector 7 is arranged so as to be in contact with the molten salt 2 that is cooled by the heat exchanger 5 and returned to the cooling tank 7, and the temperature T _2I of this molten salt 2
Measure. This temperature T _2I is then sent to the refrigerant temperature control device 8. On the other hand, the computing device 9 sends only the temperature T _2I ′ out of the computed temperatures T ₂ ′ and T _2I ′ to the refrigerant temperature control device 8 . And the temperature T _2I is the temperature T
The temperature of the refrigerant 2 is controlled to be equal to _2I ', and the steel wire 3 is cooled to the target temperature. Note that the first
The same parts as those in the embodiment are given the same numbers, and redundant explanations will be omitted.

FIG. 5 shows a third embodiment of the invention. In this embodiment, a level detector 13 for detecting the water level of the heat exchanger 5 and a level controller 14 are added to the second embodiment.
The amount of cooling of the heat exchanger 5 can be adjusted more accurately.

As specifically explained above with the embodiments, according to the present invention, even if the wire diameter and conveyance speed of the steel wire rod are different, by setting these, the steel wire rod can be accurately cooled to a predetermined target temperature. be able to. Further, the target temperature itself can be set to various values.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a steel wire direct heat treatment equipment, Fig. 2 is a perspective view showing the form of steel wire immersed in a refrigerant, and Figs. FIG. 3 is a schematic configuration diagram illustrating the third embodiment as installed in steel wire direct heat treatment equipment. In the drawing, 1 is a cooling tank, 2 is a molten salt (refrigerant), and 3 is a cooling tank.
is a steel wire, 5 is a heat exchanger, 6 is water, 7 is a refrigerant temperature detector, 8 is a refrigerant temperature control device, 9 is a calculation device,
10 is a cooling amount control device, and 11 is a water supply valve.

Claims (1)

[Claims] 1. A steel wire cooling device that cools a hot rolled hot steel wire by transporting it, immersing it in a liquid refrigerant stored in a cooling tank, and then pulling it up; A control device included in a steel wire direct heat treatment facility that cools the high-temperature steel wire to a predetermined target temperature, the control device comprising a heat exchanger that cools a refrigerant and returns the cooled refrigerant to the cooling tank again, and that cools the high-temperature steel wire to a predetermined target temperature. a refrigerant temperature detector arranged to be immersed in the refrigerant in the cooling tank or in contact with the refrigerant returned from the heat exchanger to the cooling tank to detect the temperature of the refrigerant at the arrangement position; and a steel wire rod. The steel wire rod is cooled to the target temperature based on a predetermined heat balance formula between the temperature of the steel wire rod and the temperature of the refrigerant by setting the wire diameter and conveyance speed of the steel wire rod and the predetermined target temperature. a calculation device that calculates the optimal temperature of the refrigerant, a cooling amount control device that adjusts the cooling amount of the heat exchanger, and a temperature detected by the refrigerant temperature detector and the temperature calculated by the calculation device. A control device comprising: a refrigerant temperature control device that controls the cooling amount control device so that the detected temperature becomes equal to the calculated temperature.