CN100406147C - Horizontal induction heating device and horizontal induction heating system - Google Patents

Abstract

The invention provides a transverse type induction heating apparatus which can prevent the excessive temperature rise of the surface of a plate to be rolled by almost uniformly heating the surface of the plate and the middle of the thickness of the plate at the central portion of the width of the plate to be rolled. In the transverse type induction heating apparatus for heating the plate 1 to be rolled by means of inductors 2, 3 to which electric power is supplied from an AC power source 4, the inductors 2, 3 are arranged on the center line of the width of the plate 1 to be rolled such that the width of the iron cores of the inductors 2, 3 in the direction of the width of the plate to be rolled is smaller than the width of the plate 1 to be rolled. The heating frequency of the AC power source 4 is set such that the depth [delta] of current penetration defined by the following expression (1): [delta]=[rho]/([mu]*f*[pi])}<1/2>, satisfies the following expression (2): 1.0<cosh(tw/[delta])+cos(tw/[delta])}/2<1.03, wherein [delta](m) is a depth of current penetration, [rho]([Omega]/m) is a specific resistance of the plate 1 to be rolled, [mu](H/m) is a permeability of the plate 1 to be rolled, f(Hz) is a heating frequency of the AC power source 4, [pi] is a ratio of the circumference of a circle to its diameter, and tw(m) is a thickness of the plate 1 to be rolled.

Description

Horizontal induction heating device and horizontal induction heating system

technical field

The invention relates to a horizontal induction heating device arranged on a steel hot rolling production line and a horizontal induction heating system composed of multiple horizontal induction heating devices.

Background technique

Conventionally, an electromagnetic induction heating device that heats the entire width of the strip has been used as a reheating means for the center portion of the strip width to be rolled. (For example, refer to JP-A-10-128428).

In this electromagnetic induction heating device, it takes a certain amount of time to fully diffuse the heat energy formed at the high temperature only on the surface due to the skin effect to the inside of the plate and make the surface temperature lower than the temperature at the center of the plate thickness. , so that the temperature distribution in the thickness direction of the plate becomes appropriate.

[Patent Document 1] Japanese Unexamined Patent Publication No. 10-128424 (page 5, FIG. 1 )

Contents of the invention

In the existing electromagnetic induction heating device, the higher the heating frequency is, the more the induced current flows on the surface of the rolled plate, causing excessive temperature rise on the surface.

In addition, the thicker the plate, the greater the overheating of the surface relative to the interior.

Therefore, there is a problem that sufficient time is required to make the temperature distribution in the plate thickness direction appropriate before finish rolling, and the installation place of the heating equipment is also limited.

Furthermore, since the entire width of the board is heated, there is a problem that electric power is wasted unnecessarily when only the central portion of the board width is heated.

In addition, when multiple horizontal induction heating devices are installed in the upper and lower processes of the steel hot rolling production line, the power may trip when the front end of the rolled plate passes through the induction heating device in the previous process.

The present invention is proposed to solve the above problems, and its object is to provide a horizontal induction heating system that heats the surface of the sheet at the center of the width and the center of the thickness of the sheet to be rolled approximately uniformly without excessively heating the surface of the sheet. heating equipment.

Another object of the present invention is to provide a horizontal induction heating system in which multiple horizontal induction heating devices are installed in the upper process to the next process of the steel hot rolling production line. After the front end passes through the induction heating device of the previous process, it can prevent the power from tripping.

In the induction heating method of the horizontal induction heating device of the present application, an inductor composed of an iron core and a coil wound on the iron core is arranged between the rough rolling mill and the finishing mill of the hot steel rolling production line, so that they face each other across the plate to be rolled Opposite, use the inductor powered by AC power to heat the rolled plate conveyed by the conveying roller table,

The core width of the inductor in the width direction of the rolled plate is smaller than the width of the rolled plate, and is arranged on the center line of the rolled plate width, and the current penetration depth is δ( m), the resistivity of the rolled plate is ρ (Ω-m), the magnetic permeability of the rolled plate is μ (H/m), the heating frequency of the AC power supply is f (Hz), and the circumference ratio When π, the plate thickness of the rolled plate is tw (m), the method performs the following heating frequency setting steps:

That is, in order to approximately uniformly heat the surface of the sheet at the center of the sheet width and the center of the sheet thickness of the sheet to be rolled, the heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies The following formula (2),

δ＝{ρ/(μ·f·π)} ^1/2 ...(1)

1.0<{cosh(tw/δ)+cos(tw/δ)}/2<1.03...(2).

In addition, in the horizontal induction heating system of the present application, multiple horizontal induction heating devices are installed between the upper process and the next process of the hot steel rolling production line. An inductor consisting of an iron core and a coil wound on the iron core is arranged between the rolling mill and the finishing mill so that they face each other across the plate to be rolled. The above-mentioned rolled plate is heated,

The core width of the inductor in the width direction of the rolled plate is smaller than the width of the rolled plate, and is arranged on the center line of the rolled plate width, and the current penetration depth is δ( m), the resistivity of the rolled plate is ρ (Ω-m), the magnetic permeability of the rolled plate is μ (H/m), the heating frequency of the AC power supply is f (Hz), and the circumference ratio When π, the plate thickness of the rolled plate is tw (m), perform the following heating frequency setting steps:

That is, in order to approximately uniformly heat the surface of the sheet at the center of the sheet width and the center of the sheet thickness of the sheet to be rolled, the heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies The following formula (2),

δ＝{ρ/(μ·f·π)} ^1/2 ...(1)

1.0＜{cosh(tw/δ)+cos(tw/δ)}/2＜1.03...(2)

The inductors of multiple horizontal induction heating devices are respectively connected to the AC power supply one by one, and the heating frequency of each AC power supply is set as F1, F2, ... Fn from the last process of the steel hot rolling production line, and K=1.05 When ∼1.20, the heating frequency of each AC power source is set to satisfy the relational expression of F1>F2×K>…>Fn×K ^n-1 .

According to the induction heating method of the horizontal induction heating device of the present application, since the core width of the inductor in the width direction of the rolled plate is smaller than the plate width of the rolled plate, and is arranged on the plate width center line of the rolled plate, The heating frequency is selected so that the current penetration depth δ of the aforementioned formula (1) satisfies the aforementioned formula (2), so that the plate surface and the center of the plate thickness of the rolled plate can be heated approximately uniformly, and the plate can be prevented from Excessive heating of the surface.

In addition, according to the horizontal induction heating system of the present application, it can prevent the power from tripping after the front end of the plate to be rolled passes through the induction heating device in the previous process.

Description of drawings

Fig. 1 is a schematic diagram showing the configuration of a horizontal induction heating device according to Embodiment 1 and the relationship between the distance in the width direction of a rolled plate and the average temperature rise value induced by the device.

Fig. 2 is a diagram showing the ratio (tw/δ) of the plate thickness (tw) to the penetration depth (δ) and the ratio of the heat generation density at the plate surface to the heat density at the center of the plate thickness (plate surface) of the horizontal induction heating device according to Embodiment 1. /Schematic diagram of the relationship between heating density in the center of the plate.

FIG. 3 is an enlarged view of a main part of FIG. 2 .

Fig. 4 is a schematic diagram for explaining heat generation density distribution in the plate thickness direction of a horizontal type and an electromagnetic induction heating device.

Fig. 5 is a schematic diagram illustrating the configuration and operation of a horizontal induction heating device according to Embodiment 2.

Fig. 6 is a schematic diagram showing changes in plate temperature before and after heating by the horizontal induction heating device and the electromagnetic induction heating device according to the second embodiment.

Fig. 7 is a schematic view showing coil wiring of a horizontal induction heating device according to a third embodiment.

Fig. 8 is a schematic view showing the distance and electric loss between the rolled plate, the upper inductor core and the lower inductor core in the horizontal induction heating device according to the third embodiment.

Fig. 9 is a schematic diagram showing the configuration of a horizontal induction heating device according to Embodiment 4.

Fig. 10 is a schematic view showing the temperature rise distribution in the thickness direction of the sheet when the distance between the sheet to be rolled and the inductor core is changed in the horizontal induction heating device according to the fourth embodiment.

11 is a schematic diagram showing the ratio of (heat generation density on the upper surface of the plate)/(heat generation density on the lower surface of the plate) to the ratio of (upper pitch)/(lower pitch) in the horizontal induction heating device according to Embodiment 4.

Fig. 12 is a schematic diagram for explaining the configuration and operation of the horizontal induction heating system according to the fifth embodiment.

Mark description

1, 8, 17 rolled plate 2, 3, 19a, 20a inductor 2a, 3a, 9a, 10a iron core 2b, 3b, 9b, 9c, 10b, 10c coil 7a, 7b, 18a, 18b, 18c conveying roller table 8 , 17 The plate to be rolled 19 The first induction heating device 20 The second induction heating device

Detailed ways

Embodiment 1

Fig. 1 is a schematic diagram showing the configuration of a horizontal induction heating device according to Embodiment 1 of the present invention and the relationship between the distance in the width direction of a rolled plate and the average temperature rise value induced by the horizontal induction heating device.

Fig. 2 is a diagram showing the ratio (tw/δ) of the plate thickness (tw) to the penetration depth (δ) in the horizontal induction heating device according to Embodiment 1 shown in Fig. 1(a), and the ratio of heat generation density on the plate surface to the plate A schematic diagram showing the relationship between the ratio of heat generation density in the thick center (plate surface/plate center heat generation density), FIG. 3 is an enlarged schematic diagram of the main part of FIG. 2 .

In Fig. 1 to Fig. 3, the plate to be rolled 1 is placed between the rough rolling mill (not shown in the figure) and the finishing mill (not shown in the figure) of the steel hot rolling production line by using the conveying roller table (not shown in the figure). delivery.

Then, a pair (one set) of inductors 2 and 3 are arranged facing up and down so that the rolled plate 1 is interposed therebetween. The inductors 2 and 3 are respectively composed of iron cores 2a and 3a whose core width in the width direction of the rolled plate 1 is smaller than that of the rolled plate 1, and coils 2b and 3b wound on the iron cores 2a and 3a.

The coils 2b, 3b are supplied with high-frequency electric energy from the AC power source 4, and the rolled sheet 1 is induced to be heated by the magnetic flux generated by the iron cores 2a, 3a.

The core width of the inductors 2 and 3 is determined by the heating method, and the value obtained by subtracting 300 mm from the width of the rolled plate 1 is taken now, and the inductors 2 and 3 are set at the width of the rolled plate 1 On the center line, the distance between the width end of the rolled plate 1 and the iron cores 2a, 3a is at least 150 mm or more.

In addition, the so-called "distance from the end of the width of the rolled plate 1 to the iron cores 2a, 3a" refers to the distance between the end of the width of the rolled plate 1 and the iron core 2a in a direction parallel to the surface of the rolled plate 1. Or the distance between the outer surfaces of the core 3a (that is, the distance shown by A or A' in FIG. 1 ).

In this way, it has been confirmed by experiments that the excessive temperature rise at the ends of the plate width is almost eliminated, and at the same time, as shown in FIG. 1( b ), the core width region including the center portion of the plate width is heated.

In addition, the so-called disposing the inductors 2 and 3 on the centerline of the rolled sheet 1 means that the inductors 2 and 3 are arranged on the central part of the strip width so that a part of the iron cores 2a and 3a is on the strip width centerline. , also including disposing the centers of the sensors 2 and 3 to be consistent with the center line of the board width. In a hot steel rolling production line, the width of the rolled plate 1 varies widely, ranging from 600 to 1900 mm.

Therefore, the core width of the cores 2a, 3a of the inductors 2, 3 is preferably set within a range of 300 to 700 mm.

The following formula (1) is a formula for calculating the current penetration depth δ(m) by induction heating in the horizontal induction heating device according to Embodiment 1 of the present invention.

δ＝{ρ/(μ·f·π)} ^1/2 ...(1)

In the formula, ρ is the resistivity (Ω-m) of the rolled sheet 1, μ is the magnetic permeability (H/m) of the rolled sheet 1, f is the heating frequency (Hz) of the AC power supply 4, and π is the circumference ratio.

2 and 3 show the relationship between the ratio of the current penetration depth δ in the formula (1) and the thickness tw of the rolled sheet 1, and the ratio of the heat generation density between the surface of the sheet and the central portion of the sheet thickness.

Here, the ratio of the heating density at the surface of the sheet to the heating density at the center of the sheet thickness can be expressed by the following formula (3) using the sheet thickness tw and the current penetration depth δ of the rolled sheet 1 .

Heating density on the surface of the board/heating density in the center of the board thickness =

{cosh(tw/δ)+cos(tw/δ)}/2...(3)

The temperature distribution in the plate thickness direction before heating is that the temperature on the surface of the plate is lower than the temperature in the center of the plate thickness due to the influence of heat dissipation.

Therefore, by setting the ratio of the heating density on the surface of the plate to the heating density at the center of the plate thickness (ie, the heating density at the surface of the plate/the heating density at the center of the plate thickness) below 1.03, it is possible to perform approximately uniform heating in the direction of the plate thickness and prevent excessive heating on the surface of the plate. heat up.

In order to satisfy the above relationship, it is sufficient to select the frequency such that the relationship between the thickness tw of the rolled sheet 1 and the current penetration depth δ satisfies the following formula (2).

1.0＜{cosh(tw/δ)+cos(tw/δ)}/2＜1.03...(2)

In the steel hot rolling production line, the resistivity ρ of the rolled plate 1 treated according to the specified heating temperature is about 120 μΩ-cm, and the relative magnetic permeability is 1.

Therefore, if the heating frequency for the thickness tw of the rolled plate 1 is selected to be an appropriate heating frequency lower than 413Hz when tw=25mm, 287Hz when tw=30mm, and 161Hz when tw=40mm, the heating density on the surface of the plate will affect the thickness of the plate The central heating density ratio is 1.03 or less, which enables approximately uniform heating in the thickness direction of the plate and prevents excessive temperature rise on the surface of the plate.

FIG. 4 is a schematic diagram for explaining the heat generation density distribution in the plate thickness direction of the horizontal induction heating device and the electromagnetic induction heating device.

In the figure, 5 represents the characteristics of the electromagnetic induction heating device, and 6 represents the characteristics of the horizontal induction heating device.

The electromagnetic induction heating device is shown in characteristic 5. Theoretically, the heating density is 0 at the center of the plate thickness, and the heat is concentrated on the surface of the plate.

On the contrary, in the horizontal induction heating device, by appropriately selecting the frequency, as shown in characteristic 6, the distribution of heat generation can be made approximately uniform over the distance in the plate thickness direction.

In Embodiment 1, an example in which a pair (one set) of inductors 2 and 3 are arranged on the center line of the strip width of the rolled sheet 1 has been described, but it is also possible to place more than one inductor along the advancing direction of the rolled sheet 1. Groups (for example, two groups) of inductors 2 and 3 are arranged at the same position in the width direction of the plate or positions shifted left and right, so that they can correspond to the rolled plate 1 of different widths and perform heating according to the optimal heating method.

In addition, in Embodiment 1, the magnetic poles of the inductors 2 and 3 are respectively unipolar. However, it is expected that the same effect can be obtained if two or more poles are used.

Also, in Embodiment 1, an example in which the AC power supply 4 generates high-frequency electric energy has been described, but a commercial power frequency of 50 Hz or 60 Hz can also satisfy the requirement of formula (2).

As described above, in the horizontal induction heating device of this embodiment, the inductors 2, 3 composed of the iron cores 2a, 3a and the coils 2b, 3b respectively wound on the iron cores 2a, 3a are arranged in the steel hot rolling production line. Make them face each other between the rough rolling mill and the finishing mill, and use the inductors 2 and 3 powered by the AC power supply 4 to heat the rolled plate 1 conveyed by the conveying roller table. In the built-in induction heating device, the width of the core of the inductors 2 and 3 in the universal direction of the plate width of the rolled plate 1 is smaller than the plate width of the rolled plate 1, and is arranged on the center line of the plate width of the rolled plate 1, and the current The penetration depth is δ (m), the resistivity of the rolled sheet 1 is ρ (Ω-m), the magnetic permeability of the rolled sheet 1 is μ (H/m), and the heating frequency of the AC power supply 4 is f (Hz) , when the circumference is π and the thickness of the above-mentioned rolled plate is tw (m), the heating frequency of the AC power supply 4 is set so that the current penetration depth δ of the following formula (1) satisfies the following formula (2).

δ＝{ρ/(μ·f·π)} ^1/2 ...(1)

1.0＜{cosh(tw/δ)+cos(tw/δ)}/2＜1.03...(2)

As a result, the horizontal induction heating device according to the embodiment of the present invention can approximately uniformly heat the surface of the sheet to be rolled at the center of the width and the center of the sheet thickness, and prevent excessive temperature rise of the surface of the sheet.

Implementation form 2

Fig. 5 is a schematic diagram illustrating the configuration and operation of a horizontal induction heating device according to Embodiment 2 of the present invention.

As shown in Fig. 5(a), between the rough rolling mill (not shown in the figure) and the finishing mill (not shown in the figure) of the steel hot rolling production line, the rolled plate 8 is conveyed by conveying rollers 7a, 7b.

Then, a pair of inductors 9 and 10 each having two (plural) magnetic poles are arranged to face each other with the rolled sheet material 8 interposed therebetween.

The inductors 9 and 10 are composed of iron cores 9a and 10a whose core width in the width direction of the rolled plate 8 is smaller than that of the rolled plate 8, and coils 9b, 9c, 10b, and 10c wound on the respective magnetic poles.

Each coil 9b, 9c, 10b, 10c is supplied with high-frequency electric energy from an AC power source (not shown in the figure), and the rolled plate 8 is induced to be heated by the magnetic flux generated by the magnetic poles of each iron core 9a, 10a.

Like Embodiment 1, the core width of the inductors 9, 10 is equal to or less than the value obtained by subtracting 300 mm from the width of the rolled plate 8, and the cores 9a, 10a are arranged on the center line of the rolled plate 8.

In the above-mentioned configuration, the frequency (that is, the heating frequency) according to the AC power supply (not shown in the figure) is 150 Hz, the thickness of the rolled plate 8 is 40 mm, the conveying speed is 60 mpm, and the average temperature rise is 20 ° C. During heating, as shown in FIG. 5( c ), the surface of the plate being heated and the center of the plate thickness rise approximately uniformly.

Here, in the electromagnetic induction heating device, when the electromagnetic coil is used to heat the rolled plate under the same conditions as the horizontal type, when the rolled plate passes through the electromagnetic coil, the center of the plate thickness hardly rises in temperature, while the surface of the plate heats up significantly. .

Compared with the set value of 20°C as the average temperature rise value, the surface of the plate is instantaneously (rapidly) excessively heated to 52°C, which is about 2.6 times.

As shown in Figure 5(b), the heat distribution of the rolled sheet 8 spreads from the position facing the inductors 9, 10, and reaches the conveyor rollers 7a, 7b arranged before and after the inductors 9, 10 depending on the situation.

Therefore, there is a possibility that sparks may be generated at contact points with the conveying roller tables 7a and 7b by the current flowing through the rolled sheet material 8 .

In order to prevent the occurrence of the above phenomenon, for example, electric insulating materials such as ceramic coatings are used to coat the surfaces of the conveying roller tables 7a, 7b to prevent the current flowing on the rolled plate 8 from flowing into the conveying roller tables 7a, 7b.

FIG. 6 is a schematic view showing changes in plate temperature before and after heating by a horizontal induction heating device and an electromagnetic induction heating device.

With the electromagnetic induction heating device, it takes more than 20 seconds to reach the set humidity of 20°C on the surface of the board and the center of the thickness of the board, and the conveying speed is 60 mpm, which is converted into a distance of 20 m.

In contrast, this can be achieved within seconds with a horizontal induction heating device.

Implementation form 3

Fig. 7 is a schematic view showing coil wiring of a horizontal induction heating device according to Embodiment 3 of the present invention.

In Fig. 7, the AC power supply 4 is the same as that of the first embodiment, and the rolled sheet 8 and inductors 9 and 10 are the same as those of the second embodiment.

In FIG. 7(a), the coils 9b, 9c, 10b, and 10c of the inductors 9, 10 are connected in series, and connected to the AC power supply 4 and the matching capacitor 11 in parallel.

In addition, in FIG. 7(b), the coils 9b and 9c of the inductor (upper inductor) 9 arranged above the rolled plate 8 are connected in series, and the coils 10b and 10c of the inductor (lower inductor) 10 arranged below are connected in series. connected in series.

Then, the upper coils 9 b and 9 c of the rolled sheet 8 and the lower coils 10 b and 10 c are connected in parallel to the AC power supply 4 .

As shown in Figure 7(a), when the coils 9b, 9c, 10b, and 10c of the inductors 9, 10 are all connected in series, even if the inductors 9, 10 are not symmetrically arranged on the upper and lower sides of the rolled plate 8, the coils will flow through all the coils. The currents of 9b, 9c, 10b, and 10c are also the same, and the electric losses of the respective inductors 9, 10 are equal.

On the other hand, as shown in FIG. 7(b), when the coils 9b, 9c of the inductor 9 and the coils 10b, 10c of the inductor 10 are connected in parallel, since the impedance of the coil near the side of the rolled plate 8 becomes smaller, the flow Too much current, so the electrical loss of the inductor near the rolled plate 8 side becomes larger.

FIG. 8 is a schematic diagram showing the relationship between the distance between the iron cores of the rolled plate 8 , the upper inductor 9 , and the lower inductor 10 , and the electric loss.

In Fig. 8, (a) shows the situation that the distance between the iron cores of the upper and lower inductors 9, 10 and the rolled plate 8 is equal to 90 mm, and (b) shows the distance between the iron core of the upper inductor 9 and the rolled plate 8. The spacing is 50mm, the spacing between the iron core of the lower inductor 10 and the rolled plate 8 is 130mm, and the connection of the coils 9b, 9c, 10b, 10c is shown in Figure 7 (a), (c) indicates the situation of the upper and lower induction The distance between the devices 9, 10 and the rolled sheet 8 is the same as (b), and the coils 9b, 9c and the coils 10b, 10c are connected in parallel as shown in Fig. 7(b).

FIG. 8 shows the results of comparison under the condition that the average temperature rise of any rolled sheet material 8 is the same.

When the distances between the iron cores 9a, 10a of the upper and lower inductors 9, 10 and the rolled plate 8 are equal, then as shown in Fig. 8(a), the electric losses of the iron cores 9, 10 are equal.

The difference is that, as shown in Figure 7(a), when the upper coils 9b, 9c and the lower coils 10b, 10c are connected in series, even if the inductors 9, 10 are not symmetrically arranged to the rolled plate 8, due to the The same current flows through all the coils 9b, 9c, 10b, and 10c, so the electric losses of the respective inductors 9, 10 are almost the same.

In addition, as shown in FIG. 7(b), when the upper coils 9b, 9c and the lower coils 10b, 10c are connected in parallel, as shown in FIG. 8(c), the loss on the side of the inductor 9 with a smaller pitch becomes larger. , and such as the connection shown in Fig. 7(a), the loss is large.

As mentioned above, when the upper coils 9b, 9c and the lower coils 10b, 10c are connected in parallel, because the coils 9b, 9c on the side close to the rolled plate 8 have more current flowing, the inductor 9 close to the side Electric loss increases, and the cooling capacity of the coil is insufficient, so it is possible to limit the current flowing in the coil and limit the temperature rise of the rolled plate 8

On the contrary, as shown in FIG. 7( a ), by connecting all the coils 9 b , 9 c , 10 b , and 10 c in series, the electric losses of the respective inductors 9 , 10 can be made almost the same.

Embodiment 4

Fig. 9 is a schematic diagram showing the configuration of a horizontal induction heating device according to Embodiment 4 of the present invention.

In Fig. 9, the sheet to be rolled 8, the inductors 2 and 3, and the AC power supply 4 are the same as those in the first embodiment.

In FIG. 9 , a trolley 12 capable of moving in the width direction of the sheet material 1 to be rolled is disposed. Each inductor 2, 3 is disposed on the trolley 12 opposite to the rolled plate 1 through the middle of the lifting means 13, 14, and each can be lifted and lowered separately.

The coils 2a, 3a of the inductors 2, 3 are connected to the AC power supply 4 through the matching capacitors 15, 16 arranged on the trolley 12. Also, the matching capacitors 15 and 16 may be provided separately from the trolley 12 .

In the above-mentioned horizontal induction heating device, by using the lifting means 13, 14 to move the inductors 2, 3 arranged on the upper and lower sides of the rolled plate 1, the inductors 2, 3 and the rolled plate 1 can be adjusted freely. spacing between.

Fig. 10 is a diagram showing the distribution of temperature rise in the thickness direction of the steel plate 1 when the distance between the steel plate 1 and the cores 2a, 3a of the inductors 2, 3 disposed vertically is changed in the horizontal induction heating device according to the fourth embodiment. schematic diagram.

If the upper and lower spacings are different, no matter whether the upper and lower coils 2b, 3b are connected in series or in parallel, there is a tendency that the plate surface on the side with the smaller spacing will heat up more.

Fig. 11 is a schematic diagram showing the ratio of (heat generation density on the upper surface of the plate)/(heat generation density on the lower surface of the plate) to the ratio of (upper pitch)/(lower pitch) in the horizontal induction heating device according to Embodiment 4.

In Fig. 11, if the distance between the upper and lower sides is different, the surface temperature of the side plate with the smaller distance rises more.

In this way, when the upper and lower distances are different, the temperature rise of the rolled plate 1 in the thickness direction is different, so according to the thickness of the rolled plate 1, the position of each inductor 2, 3 is adjusted by the lifting means 13, 14, so that the upper and lower The spacing is the same, so that the same temperature rise occurs on the upper and lower sides of the plate.

Before passing through the inductors 2 and 3, the temperature distribution of the rolled plate 1 in the direction of plate thickness depends on the working condition of heating with gas in the heating furnace and the suction of the slideway (not shown) supporting the rolled plate 1. The temperature distribution tends to be lower in the lower part of the rolled sheet material 1 than in the upper part due to the heat absorbed by the conveying roller table (not shown in the figure) during the conveyance after being pushed out from the heating furnace.

Such a temperature difference between the upper and lower surfaces of the rolled sheet 1 may destabilize the quality of the sheet and affect the machinability.

But, according to above-mentioned structure, because can make each inductor 2,3 up and down with lifting means 12,13, adjust the spacing between each inductor 2,3 and the plate to be rolled 1, by adjusting the spacing below The spacing is smaller than that of the top, and the temperature below the plate rises higher than the top of the plate, so that the upper and lower sides of the plate can form a uniform temperature.

Embodiment 5

Fig. 12 is a schematic diagram for explaining the configuration and operation of a horizontal induction heating system according to Embodiment 5 of the present invention.

The horizontal induction heating system according to the fifth embodiment is characterized in that a plurality of horizontal induction heating devices having the configuration of the first embodiment are arranged from the upper process to the lower process of the hot steel rolling line.

In addition, Fig. 12 shows the situation where the first induction heating device 19 is arranged on the upper process side of the steel hot rolling line, and the second induction heating device 20 is arranged on the lower process side.

In addition, Fig. 12 (a) shows the situation when the front end (plate head) of the rolled plate 17 begins to pass between the inductors 19a of the first induction heating device 19, and Fig. 12 (b) shows the end of the rolled plate 17 (plate tail). ) starts to pass between the inductors 19a of the first induction heating device 19.

In Fig. 12, the plate to be rolled 17 is conveyed from the left side of the figure to the right side of the figure by the conveying roller tables 18a-18c.

The first induction heating device 19 and the second induction heating device 20 are arranged from the previous process along the advancing direction of the rolled sheet 17 .

Moreover, the induction heating devices 19 and 20 have their own AC power sources (not shown in the figure). The frequency of the AC power supply (not shown) connected to the induction heating device 19 of the last process on the production line is set to be F1, and the frequency of the AC power supply (not shown in the figure) connected to the induction heating device 20 of the next process on the production line is established. Shown) the frequency is F2.

Let the frequency of the AC power supply (not shown) connected to the nth induction heating device from the previous process side be Fn, and when K=1.05～1.20, the AC power supply on the previous process side (Figure 1) ) and the frequency of the AC power supply (not shown) on the next process side are set to satisfy the following formula (4).

F1>F2×K>…>Fn×Kn ^-1 ……(4)

In the horizontal induction heating device, the impedance increases in the no-load state where the rolled plate 17 is not located between the upper and lower inductors 19a, 20a.

Therefore, when an inverter that operates following the resonance frequency of the load is used as an AC power supply, the frequency is lower than when there is a load, as shown in FIG. 12 .

When the front end of the rolled plate 17 from the previous process passes through the inductors 19a and 20a, if the heating frequency of the induction heating device 19 on the previous process side is set lower than that of the induction heating device on the next process side If the heating frequency is 20, then the heating frequency of the induction heating device 19 after the front end of the plate passes and the induction heating device 20 of the next process in which the front end of the plate is passing become identical in an instant.

Therefore, there is a possibility that magnetic interference occurs between the adjacent induction heating devices 19 and 20, causing the heating temperature to become unstable or the power supply to trip.

However, by setting the frequency of the AC power supply (not shown) on the upper process side of the production line higher than the frequency of the AC power supply (not shown) on the next process side, it is possible to prevent the rolled plate 17 The front end of the machine passes through the induction heating device 19 on the side of the previous process, resulting in a power trip.

As mentioned above, the horizontal induction heating system according to the embodiment of the present invention is a horizontal induction heating system in which a plurality of horizontal induction heating devices according to Embodiment 1 are installed on a horizontal steel hot rolling production line between the upper process and the next process. Since the inductors of multiple horizontal induction heating devices are connected to the AC power supply one by one, the heating frequency of the above-mentioned AC power supplies is set to F1, F2, ... Fn from the last process of the steel hot rolling production line, and When K=1.05～1.20, the heating frequency of the above-mentioned AC power sources is set to satisfy “F1>F2×K>…>Fn×K ^n-1 ”, so The frequency of the AC power is higher than the frequency of the AC power on the next process side, which can prevent the power trip caused by the front end of the rolled plate passing through the induction heating device on the previous process side.

Industrial Applicability

The present invention is suitable for a horizontal induction heating device and a horizontal induction heating system capable of heating approximately uniformly the surface of the plate at the central part of the width and the center of the thickness of the plate without causing the surface of the plate to rise excessively in temperature.

Claims (10)

1. An induction heating method of a horizontal induction heating device. An inductor composed of an iron core and a coil wound on the iron core is arranged between the rough rolling mill and the finishing mill of the hot steel rolling production line, so that the rolled plate is separated in the middle. opposite to each other, the inductor powered by an AC power supply heats the rolled plate conveyed by the conveying roller table, and it is characterized in that, The core width of the inductor in the width direction of the rolled plate is smaller than the width of the rolled plate, and is arranged on the center line of the rolled plate width, and the current penetration depth is δ( m), the resistivity of the rolled plate is ρ (Ω-m), the magnetic permeability of the rolled plate is μ (H/m), the heating frequency of the AC power supply is f (Hz), and the circumference ratio When π, the plate thickness of the rolled plate is tw (m), the method performs the following heating frequency setting steps: That is, in order to approximately uniformly heat the surface of the sheet at the center of the sheet width and the center of the sheet thickness of the sheet to be rolled, the heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies The following formula (2), δ＝{ρ/(μ·f·π)} ^1/2 ...(1) 1.0<{cosh(tw/δ)+cos(tw/δ)}/2<1.03...(2). 2. induction heating method as claimed in claim 1, is characterized in that, The magnetic poles of the inductor are composed of a plurality of poles. 3. The induction heating method as claimed in claim 1 or 2, characterized in that, The respective coils are connected in series. 4. the induction heating method as claimed in claim 1 or 2, is characterized in that, The structure of each of the inductors is made to be able to move respectively along the thickness direction of the rolled plate by means of lifting means. 5. induction heating method as claimed in claim 3, is characterized in that, The structure of each of the inductors is made to be able to move respectively along the thickness direction of the rolled plate by means of lifting means. 6. the induction heating method as claimed in claim 1 or 2, is characterized in that, At least two groups of the inductors are arranged along the advancing direction of the rolled plate, and the conveying roller table is arranged between the inductors. 7. induction heating method as claimed in claim 6, is characterized in that, The iron cores of the inductors are arranged on the center line of the strip width of the strip to be rolled. 8. The induction heating method as claimed in claim 1, characterized in that, The conveying roller table is coated on its surface with electrical insulating material. 9. induction heating method as claimed in claim 7, is characterized in that, The core width of each of the inductors is less than or equal to the value after subtracting 300mm from the width of the rolled plate, and in a direction parallel to the surface of the rolled plate, the width of the rolled plate The distance between the end and the outer surface of the iron core is greater than or equal to 150mm. 10. A horizontal induction heating system, a plurality of horizontal induction heating devices are arranged between the upper process and the next process of the hot steel rolling production line, and the horizontal induction heating devices are installed in the rough rolling mill of the hot steel rolling production line. An inductor composed of an iron core and a coil wound on the iron core is arranged between the finishing mill and the iron core, so that they face each other across the plate to be rolled. The rolled plate is heated, characterized in that, The core width of the inductor in the width direction of the rolled plate is smaller than the width of the rolled plate, and is arranged on the center line of the rolled plate width, and the current penetration depth is δ( m), the resistivity of the rolled plate is ρ (Ω-m), the magnetic permeability of the rolled plate is μ (H/m), the heating frequency of the AC power supply is f (Hz), and the circumference ratio When π, the plate thickness of the rolled plate is tw (m), perform the following heating frequency setting steps: That is, in order to approximately uniformly heat the surface of the sheet at the center of the sheet width and the center of the sheet thickness of the sheet to be rolled, the heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies The following formula (2), δ＝{ρ/(μ·f·π)} ^1/2 ...(1) 1.0＜{cosh(tw/δ)+cos(tw/δ)}/2＜1.03...(2) The inductors of multiple horizontal induction heating devices are respectively connected to the AC power supply one by one, and the heating frequency of each AC power supply is set as F1, F2, ... Fn from the last process of the steel hot rolling production line, and K=1.05 When ∼1.20, the heating frequency of each AC power source is set to satisfy the relational expression of F1>F2×K>…>Fn×K ^n-1 .

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