JP3925149B2 - Continuous heat treatment equipment for thick steel plates. - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment apparatus for thick steel plates used in heat treatment processes such as quenching, annealing, and tempering of thick steel plates.
[0002]
[Prior art]
In the heat treatment processes such as quenching, annealing, and tempering of thick steel plates, when using an induction heating device to rapidly heat the thick steel plates, the material to be treated is a ferromagnetic material at room temperature except for stainless steel. Since an induced current is generated and the surface layer portion is heated more rapidly than the inside of the steel plate, it is necessary to consider the following points.
(1) It is necessary to prevent deformation due to heat distortion by minimizing the heating temperature difference between the front and back surfaces of the steel sheet. When the material to be treated is deformed in a solenoid induction heating device (hereinafter referred to as an inductor) due to heat distortion, the device may be damaged.
[0003]
This is because, when solenoid type inductors are arranged in series between table rolls as material conveying means and are continuously heated, distortion of the material due to the heating temperature difference between the front and back surfaces and deformation accompanying it can be prevented from passing through the downstream inductor. Not only will it disappear, but it will cause serious defects in quality. A technique for removing this heating strain by arranging a straightening machine such as a leveler has been studied, and there are the following problems.
(1) The distance between the inductors becomes longer by the length of the leveler machine, and the temperature is lowered by a thin material.
(2) Since the leveler generally has more lower rolls than upper rolls, it enters the next heating with the temperature difference between the front and back sides.
(3) If a leveler is arranged for each inductor, the equipment cost increases and it becomes uneconomical.
(2) It is necessary to make the temperature distribution in the plate width direction uniform by minimizing the heating temperature difference between the plate center and the plate edge. FIG. 5 shows that an induced current (sneak current) is generated in the surface layer portion of the plate section corner portion (both in the plate thickness and plate width directions). Since induced current flows from both, Joule heat generation occurs, and the temperature of the edge portion rises. In general, the temperature rises at the edge portion having a width corresponding to about 20 to 100 mm from the edge portion, that is, about 2 to 5 times the plate thickness, and has a great adverse effect on the quality.
[0004]
Conventionally, the following proposals have been made regarding a technique for uniformly heating a material to be processed when a thick steel plate is heat-treated using an induction heating device.
[0005]
Japanese Patent Laid-Open No. 48-25237 discloses a measure for preventing temperature unevenness at the front and rear ends in the longitudinal direction of the plate when a plurality of solenoid induction heating devices are arranged in series.
[0006]
Japanese Patent Laid-Open No. 48-64534 shows that uniform heating of non-uniform thickness cross-section materials can be achieved by alternating heating of low frequency induction heating and high frequency induction heating if heating is performed below the Curie point. Has been.
[0007]
On the other hand, Japanese Patent Application Laid-Open No. 48-25239 discloses a method for cooling a high temperature portion of a plate edge by spraying cooling water to a limited portion of the plate edge as a countermeasure against non-uniform heating in the width direction.
[0008]
[Problems to be solved by the invention]
However, the above prior art has the following problems.
[0009]
First, in the method disclosed in Japanese Patent Laid-Open No. 48-25237, it is not possible to uniformly perform heat treatment on the entire cross section of the plate, and it is impossible to prevent plate deformation due to heating strain and generation of temperature distribution in the plate thickness direction.
[0010]
Further, in the method of Japanese Patent Laid-Open No. 48-64534, if heating is performed below the Curie point, it is possible to raise the temperature of an unequal-thickness cross-section material uniformly by alternating heating of low frequency induction heating and high frequency induction heating. However, when the material to be heated is thin, there is a problem that the temperature cannot be sufficiently increased. In the case of low frequency induction heating in the vicinity of a commercial frequency of about 50 to 200 Hz, as shown in the following formula (1), the heat input power decreases in proportion to the frequency and a current is required to obtain a sufficient magnetic field. It is necessary to take an enormous amount, and there is a lower limit value of the plate thickness that can be heated when the heating frequency is low (for example, when the heating frequency is 200 Hz, the lower limit value is about 17 mm). Difficult to do. Therefore, it is difficult to heat-treat thick steel plates having various thicknesses with this technique.
[0011]
P = π · μ · f · H ² · S · L · Q (1)
Here, P: heating absorption power, μ: permeability, f: frequency, H: magnetic field strength, S: material cross-sectional area, L: material length, Q: absorption coefficient.
[0012]
In the method of Japanese Patent Laid-Open No. 48-25239, it is considered that a certain amount of effect can be obtained by injecting an appropriate amount of cooling water to the plate edge. However, in the heat treatment of a thick steel plate, the thickness and heating frequency of the material to be heated Depending on the relationship, the overheated edge width and overheating amount change, and accordingly it is difficult to inject cooling water into the edge part without excess or deficiency. If the edge width for jetting water is not appropriate, there arises a problem that the temperature distribution in the width direction is not improved. In addition, problems such as deterioration of surface quality due to jetting of cooling water, sudden change of material, insulation management problem of induction heating device due to use of water, and deterioration of material and transport roll insulation cause spark flaws on the transport roll. There are also problems such as.
[0013]
The object of the present invention is to solve the above-mentioned problems of the prior art, to achieve a uniform temperature distribution in the plate thickness direction and the plate width direction, and to provide a heat treatment apparatus for thick steel plates that does not cause deformation due to heating strain There is to do.
[0014]
[Means for Solving the Problems]
That is, the steel plate heat treatment apparatus of the present invention has the following characteristics.
[0015]
(1) In a steel plate heat treatment apparatus in which a plurality of solenoid type induction heating devices are arranged in series, an internal cooling table roll and an internal cooling type presser roll are vertically opposed to each solenoid type induction heating device exit side. A continuous heat treatment apparatus for thick steel plates, characterized by being installed.
[0016]
(2) In a heat treatment apparatus for thick steel plates in which a plurality of solenoid type induction heating devices are arranged in series, an edge cooling pinch roll comprising internal cooling type upper and lower rolls is installed on the outlet side of each solenoid type induction heating device. A feature of continuous heat treatment equipment for thick steel plates.
[0017]
(3) In a thick steel plate heat treatment device in which a plurality of solenoid induction heating devices are arranged in series, an internal cooling type thick steel plate end face cooling steel roll is installed on the exit side of each solenoid type induction heating device. Continuous heat treatment equipment for thick steel plates.
[0018]
(4) The internal cooling type edge cooling pinch roll is movable in the width direction, and restrains the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. The continuous heat processing apparatus of the described thick steel plate.
(5) In a heat treatment apparatus for thick steel plates in which a plurality of solenoid type induction heating devices are arranged in series, an internal cooling type table roll and an internal cooling type installed on each solenoid type induction heating device exit side A continuous heat treatment apparatus for a thick steel plate, comprising at least one of a presser roll, an edge cooling pinch roll composed of internal cooling type upper and lower rolls, or an internal cooling type thick steel plate end surface cooling saddle roll.
(6) The internal cooling type edge cooling pinch roll is movable in the width direction, and restrains the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. The continuous heat processing apparatus of the described thick steel plate.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a heat treatment apparatus for thick steel plates according to the present invention, FIG. 1 (a) is a side view, and FIG. 1 (b) is an arrow view along the line BB in FIG. 1 (a). FIG.
[0020]
The cooling device of FIG. 1 has an internal water-cooled presser roll 1 that is an upper roll and an internal water-cooled table roll 2 that is a lower roll. The internal water-cooled presser roll 1 is supported by bearings 3a and 3b, and the internal water-cooled table roll 2 is supported by bearings 4a and 4b. The bearings 3a and 3b are held by a lifting device 5, and the lifting and lowering device 5 lifts and lowers the bearings 3a and 3b to raise and lower the internal water-cooled presser roll 1 so that the internal water-cooled presser roll 1 and the internal water-cooled table are lifted. The distance between the rolls 2 and the reduction amount of the internal water-cooled presser roll 1 can be adjusted.
[0021]
Cooling water is supplied to the internal water-cooled presser roll 1 through a bearing 3b. The cooling water flows through the presser roll 1 to cool the roll, and is then drained from the bearing 3a.
[0022]
Cooling water is also supplied to the internal water-cooled table roll 2 through the bearing 4b. The cooling water flows through the table roll 2 to cool the roll, and is then discharged from the bearing 4a.
[0023]
The elevating devices 5a and 5b are for pressing the internal water-cooled presser roll 1 against the upper surface of the thick steel plate 7 and pinching the thick steel plate 7 with an upper roll and a lower roll, and are usually driven by an air cylinder. .
[0024]
Next, the operation and action of the thick steel plate heat treatment apparatus of the above embodiment will be described.
[0025]
In a heat treatment process such as quenching, annealing, and tempering of a thick steel plate, the thick steel plate is continuously heated with a series inductor.
[0026]
The material is cooled while the full width roll is being reduced by a cooling device comprising an internal water-cooled presser roll 1 and an internal water-cooled table roll 2 shown in FIG.
[0027]
By cooling while rolling down the roll, the heating temperature difference between the front and back surfaces of the steel sheet can be minimized, and deformation due to heating strain can be prevented. It also has the effect of reducing the heating temperature difference between the plate center and the plate edge.
[0028]
FIG. 2 shows the relationship between the thickness of a thick steel plate and the soaking time required to soak the thick steel plate having the thickness, using a cooling device using an internal water-cooled presser roll and an internal water-cooled table roll. It shows the results of examining the case of cooling while rolling down and the case of not using a cooling device. Here, the soaking time is the time required for the high-temperature steel plate surface layer and the low-temperature steel plate interior to reach the same temperature in the plate thickness direction due to heat transfer. According to this, when cooling with roll cooling by the above-described cooling device, the steel plate surface can be cooled in the same manner by roll contact heat transfer, so the steel plate with a thickness of 50 mm must be heated by natural air cooling. The place that takes 20 seconds can be shortened by about 2 seconds. As a result, the heat treatment time can be shortened or the equipment can be made compact by shortening the distance between the inductors.
[0029]
Furthermore, by forcibly lowering the surface temperature of the steel sheet, the heating increase in the next inductor can be set large, so that rapid heating can be performed.
[0030]
Moreover, FIG. 3 shows the result of investigating the relationship of the temperature difference of the steel plate temperature with the width center position at a certain width direction position of the thick steel plate, and the steel plate temperature difference with the width center position becomes closer to the edge part of the steel plate. Although it becomes large, the effect of reducing the temperature difference in the width direction can be obtained by the roll contact heat transfer, particularly as the edge portion is approached, by cooling while lowering the roll pressure from above and below.
[0031]
FIG. 4 shows another embodiment of the heat treatment apparatus for thick steel plates of the present invention, FIG. 4 (a) is a side view, and FIG. 4 (b) is an arrow along the line BB in FIG. 4 (a). FIG.
[0032]
The cooling device of FIG. 4 has a pinch roll A composed of rolls 8 and 9 for cooling the upper edge and for cooling the lower edge. The upper edge cooling roll 8 is supported by bearings 10a and 10b, and the lower edge cooling roll 9 is supported by bearings 11a and 11b. The bearings 10a and 10b are held by the elevating device 5. The elevating device 5 elevates and lowers the bearings 10a and 10b to elevate and lower the upper edge cooling roll 8, thereby cooling the upper edge cooling and the lower edge cooling. The interval between 8 and 9 and the amount of rolling down of the upper edge cooling roll can be adjusted. The lifting device 5 is supported by a frame 13, and the frame 13 is moved on the fixed base 14 by a moving mechanism 12 that allows the frame to move in the steel plate width direction. FIG. 4B shows one end portion in the plate width direction, but the other end portion has the same structure.
[0033]
One or more sets of such pinch rolls A are arranged in the steel sheet feed direction on the outlet sides of the plurality of inductors arranged in series. Although one set is provided here, two or more sets may be provided. In the present embodiment, the internal water-cooled presser roll 1 and the internal water-cooled table roll 2 are already arranged opposite to each other between the inductors, and the upper edge cooling and lower edge cooling rolls 8 and 9 are further arranged. A pinch roll A is arranged. The pinch roll A is disposed between the internal water-cooled presser roll 1, the internal water-cooled table roll 2, and the subsequent inductor disposed opposite to each other, but the internal water-cooled presser roll 1 disposed opposite to the preceding inductor. And an internal water-cooled table roll 2.
[0034]
Cooling water is supplied to the internal water-cooling upper edge cooling roll 8 through a bearing 10b. The cooling water flows through the upper edge cooling roll 8 to cool the roll, and is then drained from the bearing 10a.
[0035]
Cooling water is also supplied to the internal water-cooled lower edge cooling roll 9 through a bearing 11b. The cooling water flows through the lower edge cooling roll 9 to cool the roll, and is then discharged from the bearing 11a.
[0036]
The elevating devices 5a and 5b are for pressing the upper edge cooling roll 8 to the upper edge of the thick steel plate 7 and pinching the thick steel plate 7 with the upper roll and the lower roll, and are usually driven by an air cylinder. .
[0037]
The moving mechanism 12 moves the frame 13 in the width direction, and the upper edge cooling roll 8 and the lower edge cooling roll 9 restrain the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. Is for.
[0038]
Next, the operation and action of the thick steel plate heat treatment apparatus of the above embodiment will be described.
[0039]
In a heat treatment process such as quenching, annealing, and tempering of a thick steel plate, the thick steel plate is continuously heated with a series inductor.
[0040]
The internal water-cooling type edge cooling rolls shown in Fig. 4 are arranged facing the front side and the back side of each inductor on the exit side, and the edge cooling roll is brought into contact only with the edge overheated part, and edge cooling is performed by contact heat transfer. I do.
[0041]
It is preferable that the internal cooling type edge cooling roll is movable in the width direction according to the thickness of the thick steel plate and restrains the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. At this time, the edge cooling roll, which is the edge cooling range, and the lap length of the steel plate width, the width of the overheated part may be measured with a width direction thermometer, and the lap amount is determined for each material. The overheated portion of the edge portion may be estimated by solving a two-dimensional heat conduction equation. In order to cool by contact heat transfer, it is necessary to sufficiently cool the roll and ensure a sufficient temperature difference with respect to the material.
[0042]
In the present invention, the temperature is made uniform by cooling the overheated steel sheet, but a method of heating the width direction uniformly can be considered by devising the characteristics of the inductor as described below. However, both have demerits and poor feasibility.
(1) In order to make the plate thickness / penetration depth (t / δ) constant, the heating frequency is changed for each plate thickness of the material to be heated.
[0043]
In order to increase the manufacturing range, it is necessary to change the power capacitor for impedance matching and the inverter oscillation voltage of the large-capacity induction heating device in order to change the resonance frequency, and the device design is difficult.
(2) When the heating frequency cannot be changed, it is necessary to prepare a large number of heating devices having different frequencies, which greatly increases the number of inductors. In addition, when the rational arrangement cannot be achieved or when the edge temperature distribution is controlled by combining a plurality of heating frequencies, it is necessary to perform a large amount of very complicated calculations, resulting in an increase in system cost.
(3) Demagnetization of the edge portion by an auxiliary coil such as a magnetic concentrator (flux diverter) not only makes the inductor a complicated structure but also reduces the total heating efficiency. It is not suitable for high power.
[0044]
FIG. 6 shows another embodiment of the heat treatment apparatus for thick steel plates according to the present invention. FIG. 6 (a) is a front view and FIG. 6 (b) is a plan view.
[0045]
The cooling device of FIG. 6 has two thick steel plate end face cooling rolls 15. The heel roll 15 is supported by bearings 16a and 16b. The bearings 16a and 16b are supported by a frame 13, and the frame 13 is moved on the fixed base 14 by a moving mechanism 12 that allows the frame to move in the steel plate width direction. FIG. 6 shows one end in the plate width direction, but the other end also has the same structure.
[0046]
Cooling water is supplied to the inner water-cooled thick steel plate end face cooling saddle roll 15 through a bearing 16a. The cooling water flows through the saddle roll 15 to cool the roll, and is then drained from the bearing 16b.
[0047]
The moving mechanism 12 moves the frame 13 in the width direction and pushes the thick steel plate end surface cooling saddle roll 15 into contact with the end surface of the thick steel plate 7.
[0048]
Next, the operation and action of the thick steel plate heat treatment apparatus of the above embodiment will be described.
[0049]
In a heat treatment process such as quenching, annealing, and tempering of a thick steel plate, the thick steel plate is continuously heated with a series inductor.
[0050]
An internal cooling type thick steel plate end surface cooling saddle roll shown in FIG. 6 is brought into contact with the end surface of the thick steel plate to cool each inductor outlet side.
[0051]
When induction heating a thick steel plate, according to FIG. 5, it is known that the end surface of the plate is heated at the same penetration depth as the center in the width direction. This means that the plate end surface is heated from both the plate width direction and the plate thickness direction, which means that the temperature is higher than any part in the steel plate, and end surface cooling is necessary to prevent overheating. It is shown that. Therefore, a great effect can be obtained by removing heat by bringing the hard roll into contact with the end face of the thick steel plate.
[0052]
In the embodiment shown in FIG. 6, two or more hard rolls can be arranged in series in the steel plate traveling direction at the same time, and a role as a side guide (material centering function) can be provided by pressing the end face of the thick steel plate. In an actual inductor, when heating a steel plate that is sufficiently wide with respect to the solenoid width, the infinite distance in the width direction is not satisfied, so the magnetic flux at the end of the inductor (width and vertical directions) also contributes to the end heating. Must be taken into account.
[0053]
FIG. 7 is an explanatory diagram showing that heat deviation occurs in the steel plate because the magnetic path lengths at both ends of the thick steel plate are different on the left and right. A centering function is necessary for induction heating of thick steel plates to prevent such uneven heat.
[0054]
As described above, in the present invention, the internal cooling type table roll and the internal cooling type presser roll as shown in FIG. 1 are installed so as to face each other, and the internal cooling type upper and lower rolls as shown in FIG. The apparatus provided with the pinch roll for edge cooling and the apparatus provided with the internal cooling type thick steel plate end face cooling saddle roll as shown in FIG. 6 may be used in combination depending on the purpose, or alone. It may be used.
[0055]
【The invention's effect】
The temperature distribution in the plate thickness direction and plate width direction is made uniform using a high-efficiency induction heating device, and from the thin to the thick, the plate is heated at the end of heating without generating deformation, warping or meandering due to heat distortion of the material. Uniform heating with extremely high accuracy can be realized in the thickness and width direction.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a heat treatment apparatus for thick steel plates according to the present invention, FIG. 1 (a) is a side view, and FIG. 1 (b) is an arrow along the line BB in FIG. 1 (a). FIG. 2 is a graph showing the relationship between the thickness of a thick steel plate and the soaking time required to soak the thick steel plate having that thickness. FIG. 3 shows the position in the width direction of the thick steel plate, The graph which shows the result of having investigated the relationship between the steel plate temperature in the center position of a width | variety, and the temperature difference of the steel plate temperature in a certain width direction position. FIG. 4 shows other embodiment of the heat processing apparatus of the thick steel plate of this invention. 4 (a) is a side view, and FIG. 4 (b) is an arrow view along the line BB in FIG. 4 (a). FIG. 5 also shows a plate cross-section corner (both in the plate thickness and plate width directions). FIG. 6 shows another embodiment of the heat treatment apparatus for a thick steel plate according to the present invention, FIG. 6 (a) is a front view, and FIG. 6 shows that an induced current (sneak current) is generated in the surface layer portion. b) is an explanatory view showing that produce Hen'netsu the steel sheet for the magnetic path length of both end portions of the plan view FIG. 7 steel plates are different on the left and right [code Description]
DESCRIPTION OF SYMBOLS 1 Presser roll 2 Table roll 3a Bearing 3b Bearing 4a Bearing 4b Bearing 5 Lifting device 5a Lifting device 5b Lifting device 6 Solenoid induction heating device (inductor)
7 Thick Steel Plate 8 Edge Cooling Roll 9 Edge Cooling Roll 10a Bearing 10b Bearing 11a Bearing 11b Bearing 12 Moving Mechanism 13 Frame 14 Fixed Base 15 Thick Steel Plate End Surface Cooling Roll 16a Bearing 16b Bearing

Claims (6)

In a thick steel plate heat treatment device in which multiple solenoid induction heating devices are arranged in series, an internal cooling table roll and an internal cooling presser roll are installed facing each other on the outlet side of each solenoid induction heating device. A continuous heat treatment apparatus for thick steel plates. In a thick steel plate heat treatment apparatus in which a plurality of solenoid type induction heating devices are arranged in series, an edge cooling pinch roll comprising internal cooling type upper and lower rolls is installed on the outlet side of each solenoid type induction heating device. Continuous heat treatment equipment for thick steel plates. In a thick steel plate heat treatment apparatus in which a plurality of solenoid induction heating devices are arranged in series, an internal cooling type thick steel plate end face cooling saddle roll is installed on the outlet side of each solenoid induction heating device. Continuous heat treatment equipment . The thickness of claim 2, wherein the internal cooling type edge cooling pinch roll is movable in the width direction and restrains the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. Steel plate continuous heat treatment equipment . In the heat treatment apparatus for thick steel plates in which a plurality of solenoid type induction heating devices are arranged in series, on the outlet side of each solenoid type induction heating device, an internal cooling type table roll and an internal cooling type presser roll installed facing each other vertically, An apparatus for continuous heat treatment of a thick steel plate, comprising at least one of an edge cooling pinch roll comprising internal cooling type upper and lower rolls or an internal cooling type thick steel plate end face cooling saddle roll.   6. The thickness according to claim 5, wherein the internal cooling type edge cooling pinch roll is movable in the width direction and restrains the edge portion of the thick steel plate with a width corresponding to 2 to 5 times the plate thickness. Steel plate continuous heat treatment equipment.

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