JPS6257694B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) This specification relates to a method and apparatus for preventing heat buckling of a cold rolled thin steel sheet that often occurs during heat treatment of a cold rolled thin steel sheet by a continuous annealing method. The technical content described in is included in the field of technology to which continuous annealing of cold rolled steel sheets belongs.
In particular, we will present the development results of a procedure for appropriately detecting signs of heat buckle generation behavior during the annealing process and a control means that can immediately respond to the detected information.

(Problem) Thin steel sheets used for forming using presses, such as processed steel sheets for automobiles, need to be soft materials suitable for forming. Relief will be given.

The so-called box annealing method was once common for this type of annealing, but because the time required for annealing was extremely long, productivity, economic efficiency, and product quality were affected. It is well known that continuous annealing equipment has been developed in recent years, and its superiority has gradually become clearer. That's right.

However, at present, the continuous annealing method is not superior to the conventional box annealing method in all aspects, and there are still many problems that need to be improved.

One of them is the problem of transportability during continuous annealing of cold-rolled thin steel sheets to be treated (hereinafter simply referred to as steel sheets).

First of all, currently most continuous annealing equipment is vertical.
During the process, the steel plate is transported under the support of upper and lower hearth rolls and is exposed to various thermal environmental conditions such as heating, soaking, and cooling.

At this time, temperature differences tend to occur in the steel plate in the width direction,
Meandering is likely to occur due to deformation caused by thermal stress due to the difference in thermal expansion, and uneven tension distribution between the hearth rolls due to vibration of the steel plate.

If this meandering occurs, normal conveyance is not possible, so to prevent this, the shape of the hearth roll is generally made into a medium-high narrow body shape or a crown shape to give the hearth roll a self-centering effect.

However, when the degree of non-uniformity of the temperature distribution and tension distribution that causes the meandering described above increases,
Due to the large amount of self-centering, the steel plate undergoes buckling deformation in the width direction, that is, a shape defect called a heat buckle occurs.

When heat buckles occur, not only the commercial value of the product is significantly impaired, but also normal heat treatment operations cannot be maintained, sometimes causing serious problems such as breakage of the steel plate.

Additionally, due to the above reasons, there are restrictions on the thickness and width of the steel plate, as well as the maximum heating temperature, making it difficult to produce high value-added products using the continuous annealing method. This also leads to disadvantages.

Therefore, establishing a method for preventing heat buckles in continuous annealing has become an extremely important issue from both the operational technology of continuous annealing equipment and the production technology of products.

(Prior Art and Its Difficulties) Regarding the above-mentioned problem, the current means of detecting heat buckles is, for example, by installing television cameras at several locations in the continuous annealing equipment and monitoring the images, which is almost the only and best method. It is considered a means.

From a practical point of view, the most effective means of dealing with the occurrence of heat buckles is to detect the signs of heat buckles in the early stages of their occurrence and take immediate measures accordingly. However, there remain problems such as delayed detection, the inability to obtain quantitative information, and the inability to perform automatic control that requires observers, and no proposals for improvements from these perspectives have been found.

In other words, the conventional techniques are far from solving the above-mentioned basic problems, and it is difficult to expect them to be very effective in practical use.

(Objective of the Invention) In view of the problems of the prior art as described above, in order to advantageously eliminate the problem, the signs of heat buckling are automatically and quantitatively detected in the initial stage of occurrence, and based on the detected information. The purpose of this invention is to take optimal and prompt measures, and it not only has the practical advantage of being immediately practical at the current state of the art compared to the prior art, but also has the practical advantage of being able to put it into practical use immediately at the current state of the art. The object of the present invention is to provide a heat buckle detection device and a method for preventing heat buckles in continuous annealing, which are convenient for matching the heat buckles in continuous annealing and have excellent applicability and expandability.

(Structure of the Invention) The above object can be advantageously achieved by a procedure and a structure based on the following matters.

(1) When a cold-rolled steel plate is continuously heat-treated by passing it through a continuous annealing furnace that includes a heating zone, a soaking zone, a cooling zone, or an overaging treatment zone in the order of processing steps, the steel plate Detecting the presence or absence of heat buckles in the steel plate during the heat treatment by detecting the distance to the steel plate at each detector using a distance detector installed at at least one position in the conveyance path. Heat treatment control method in a continuous annealing furnace (first invention ).

(2) A continuous annealing device having a heating zone, a soaking zone, a cooling zone, or an overaging treatment zone, and at least one of the locations in the conveyance path of the steel plate that is passed through the device and subjected to continuous heat treatment. At least one excitation coil that generates an alternating magnetic flux with a constant distribution, which is placed close to the steel plate at a location, and a detection coil that detects the rate at which the magnetic flux from the excitation coil changes in accordance with the distance to the steel plate. A heating zone temperature control device, a soaking zone temperature control device, and a cooling zone cooling rate control device are equipped with three distance detectors, and according to the size of the heat buckle of the steel plate determined from the distance detected by the distance detector, , a heat treatment control device in a continuous annealing apparatus (second invention) having a control means for operating at least one of a steel plate conveyance speed control device and a steel plate tension control device.

In addition, it is recommended as an embodiment that distance detectors be placed in each of the heating zone, soaking zone, and cooling zone, so that even more precise control can be performed.

The procedure of the first invention makes it possible to quickly detect signs of heat buckling and take immediate action to reliably prevent heat buckling, and the mechanism of the second invention can be effectively used to implement the method of the first invention. It is clear that it can be done.

The specific contents of the above invention will be explained in detail by taking the illustrated continuous annealing apparatus as an example.

As shown in FIG. 1, this continuous annealing apparatus includes a heating zone 12, a soaking zone 14, a cooling zone 16, and a heating zone 12, a soaking zone 14, a cooling zone 16, and
It mainly consists of an overaging treatment zone 18 and is provided with drive rolls 20 for conveying the steel plate 10 to be treated.

Also, an atmosphere thermometer 22 for detecting the atmospheric temperature in the heating zone 12, an atmosphere thermometer 24 for detecting the atmospheric temperature in the soaking zone 14, and an atmosphere thermometer 24 for detecting the atmospheric temperature in the soaking zone 14, and a conveyance speed of the steel plate 10 at the entrance side of the heating zone 12 are provided. Steel plate conveyance speed detector 26 for detection and overaging treatment zone 18
A steel plate conveying speed detector 28 for detecting the conveying speed of the steel plate 10 on the exit side of the heating zone 1 is further provided.
Heating zone temperature control device 3 for controlling the temperature of 2
0, a soaking zone temperature control device 32 for controlling the temperature of the soaking zone 14, and a steel plate 1 in the cooling zone 16.
By controlling the cooling rate control device 34 for controlling the cooling rate of 0, the overaging zone temperature control device 36 for controlling the temperature of the overaging zone 18, and the rotational speed of the drive roll 20. Steel plate 1
Steel plate conveying speed control device 38 for controlling the conveying speed of 0 and the steel plate 10 in the heating zone 12
a tension control device 40 for controlling the tension of the steel plate 10 in the soaking zone 14, a tension control device 42 for controlling the tension of the steel plate 10 in the cooling zone 16, and a tension control device 42 for controlling the tension of the steel plate 10 in the cooling zone 16. 44
and a tension control device 46 for controlling the tension of the steel plate 10 in the overaging treatment zone 18.

In particular, in this example, near the exit side of the heating zone 12, the steel plate 1 is placed at each predetermined position extending in the width direction of the steel plate 10.
The distance to 0 is detected, and the size of the heat buckle on the steel plate 10 to be processed is detected from the size of the distance at each position. For example, a distance detector P _a including two or three detection coils (described later), a steel plate thermometer T _a for measuring the surface temperature of the steel plate 10 near the distance detector P _a , and a A similar distance detector P _b and a steel plate thermometer T _b are installed near the entrance side of the tropical zone 14 , and a similar distance detector P _c and a steel plate thermometer T _c are installed near the outlet side of the soaking zone 16 . A similar distance detector P _d and steel plate thermometer T _d are provided near the exit side.

As shown in detail in FIG. 2, the distance detectors P _a to P _d described above are excited by an AC excitation device E that generates an alternating current of, for example, 5 Hz to 1 MHz, so that constant alternating magnetic fluxes α, β, An exciting coil C that generates γ, δ, and ε is interlinked with the alternating magnetic flux α, γ, or even ε, and a detection coil C〓, C〓, or further C that generates an induced voltage according to the amount of the interlinked magnetic flux. 〓 and 〓 are arranged near the plate surface at intervals in the direction of the plate width W of the steel plate 10, and voltage measuring devices M〓, M〓, which measure the induced voltage of each detection coil and output it to an arithmetic device, or further Connect to M〓.

In the figure, alternating magnetic fluxes β and δ indicate invalid magnetic fluxes that do not interlink with any detection coil, h is the distance between each coil and the plate surface of the steel plate 10, μ is the magnetic permeability of the steel plate 10, and ρ is the steel plate Assuming that the electric resistivity is 10, when the steel plate 10 is within the magnetic field range of the excitation coil C, the detection coil C〓, C〓, or even C〓
, an induced voltage corresponding to the distance h, magnetic permeability μ, and electric resistivity ρ is generated.

If the induced voltages generated in the detection coil C and the detection coil C are V and V, respectively, then the following formula V = f ₁ (h, μ x ρ) ... (1) V = f ₂ (h′, μ×ρ) …(2) V = f(h″, μ×ρ) …(3) It is expressed by the function of (1), (2) or (3) By substituting the equation and eliminating the μ×ρ term, the distance h of the steel plate 10 can be determined.

Here, the AC power frequency of excitation coil C is 5Hz ~
Preferably in the 1MHz range, with a frequency of 1M
Hz, the induced voltage generated in the detection coils C〓, C〓 increases by the magnetic permeability μ and electric resistivity ρ of the steel plate 10.
The degree of dependence on the distance h becomes excessively large, and the resolution for changes in the distance h of the measurement target becomes small.
This is not preferable because measurement accuracy deteriorates, and if this frequency is lower than 5 Hz, it is difficult to ensure responsiveness of the distance detector.

As described above, the detection signals from the distance detectors P _a to _{P d} detect the steel plate 1 in each of the heating zone 12 , soaking zone 14 , cooling zone 16 , and overaging zone 18 .
0, the detection signals of the steel plate thermometers T _a to _{T d} in each of the above bands,
Together with the detection signals of the atmosphere thermometers 22, 24, 26 and the steel plate conveyance speed detector 28, the signals are input to the calculation device M as shown in FIG. Cooling rate control device 34, overaging treatment zone temperature control device 36
The operations of the steel plate conveyance speed control device 38 and the tension control devices 40 to 46 are appropriately controlled by the calculation device M.

Therefore, if the calculation procedure described above is programmed in the arithmetic unit M in advance, the induced voltage V generated in the detection coil C and the induced voltage V generated in the detection coil C or C By transmitting this to the arithmetic device M, the distance h between the excitation coil C and the steel plate 10 to be processed can be measured.

As described above, heat buckles are particularly likely to occur in steel sheets being passed in a continuous annealing device, for example, near the exit side of the heating zone 12, near the entrance side of the soaking zone 14, and near the exit side of the soaking zone 14. By arranging distance detectors in sets of two or three in the width direction of the steel sheet 10 in the vicinity of the exit side of the cooling zone 16, it is possible to Even in the case of heat buckling, signs of heat buckling occurring on the steel plate can be detected quantitatively as distance signals from each distance detector placed in the band, including the degree of heat buckling from the size of the distance, so it is possible to immediately respond to it. countermeasures are easily possible.

That is, by using the above distance detector,
It is possible to quickly and quantitatively measure the occurrence of heat buckles in a non-contact manner, especially when the magnetic permeability μ and electrical resistivity ρ of the steel sheet 10 change due to γ to α transformation during the continuous annealing process. Even if this happens, there is no difference in the width direction of the plate, so the detection of heat buckles will not be affected by this difference.

By the way, the steel plate 10 has a heating zone 12 and a soaking zone 1.
4. By passing through the cooling zone 16 and the overaging treatment zone 18, predetermined heat treatments such as heating, soaking, and cooling are performed. During this heat treatment, emergency response conditions in the event of a heat buckle occurrence, and conditions for preventing heat buckles. By completing the method of calculating the conditions necessary to suppress the occurrence and return to smooth operation, and inputting them into the calculation device M, the steel plate to be treated 1
If a sign of heat buckling is detected at 0, the location and size of the occurrence are immediately detected according to the distance signals transmitted from the distance detectors P _a to P _d , and the optimal method is determined accordingly. The conditions are calculated and the results are used as control signals to control the heating zone temperature control device 30, the soaking zone temperature control device 32, the cooling zone cooling rate control device 34, and the overaging zone control device 36.
And output to the steel plate conveyance speed control device 38, steel plate tension control devices 40 to 46, etc.

Each control device operates in response to this control signal to suppress the generation of heat buckles, and thus the continuous annealing device operating conditions for the entire process can be adjusted to return to normal conditions.

In this embodiment, since distance detectors for detecting signs of heat buckling are provided in the heating zone, soaking zone, and cooling zone, it is possible to precisely detect and prevent heat buckles.

Note that the location and number of distance detectors are not limited to those in the embodiments, but by providing at least one distance detector at a position along the path where the steel plate is conveyed in the continuous annealing furnace, effective heat buckling can be achieved. It is possible to detect and prevent

(Effects of the Invention) As explained above, according to the first invention, troubles due to the occurrence of heat buckles during continuous annealing of cold-rolled thin steel sheets can be prevented, and the operation of a continuous annealing apparatus can be improved. The second invention can be carried out automatically and stably, and the second invention can be used to implement the heat treatment control method in continuous annealing, contributing to increasing its initial effects.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a continuous annealing furnace;
The figure is an explanatory diagram of the heat buckle detection procedure according to the present invention, and FIG. 3 is a block diagram of the control system. 12...Heating zone, 14...Soaking zone, 16...Cooling zone,
C... Excitation coil, C〓, C〓, C〓...Detection coil, P _a - P _d ... Distance detector, 30... Heating zone temperature control device, 32... Soaking zone temperature control device, 34... Cooling zone cooling rate control Apparatus, 38... Steel plate conveyance speed control device, 40-46... Steel plate tension control device.

Claims (1)

[Claims] 1. When a cold-rolled thin steel plate is passed through a continuous annealing furnace that includes a heating zone, a soaking zone, and a cooling zone in the order of treatment steps and is continuously heat-treated, By detecting the distance to the steel plate at each detector using a distance detector installed at at least one position in the conveyance path, the presence or absence of heat buckling of the steel plate during the heat treatment is detected, and the detection signal is detected. 1. A method for controlling heat treatment in continuous annealing, the method comprising controlling at least one of heating zone temperature, soaking zone temperature, cooling zone cooling rate, steel plate conveyance speed, and steel plate tension according to the above conditions to prevent heat buckling. 2. A continuous annealing device having a heating zone, a soaking zone, and a cooling zone, in which cold rolled thin steel sheets are passed through the continuous annealing device and subjected to continuous heat treatment at at least one location in the conveyance path. at least one distance detector consisting of an excitation coil that generates an alternating magnetic flux with a constant distribution and arranged in close proximity to the excitation coil, and a detection coil that detects the rate at which the magnetic flux from the excitation coil changes in accordance with the distance to the steel plate. and a heating zone temperature control device, a soaking zone temperature control device, a cooling zone cooling rate control device, and a steel plate conveyance speed control device according to the size of the heat buckle of the steel plate determined from the distance detected by the distance detector. 1. A heat treatment control device for a continuous annealing device, comprising a control means for operating at least one of the device and the steel plate tension control device. 3. The heat treatment control device according to 2, wherein a distance detector is disposed in each of the heating zone, soaking zone, and cooling zone.