JPH05299164A - Induction heating device - Google Patents

Abstract

PURPOSE:To prevent the collision between a rolled material and a heating coil by determining the upper limit value of the gap allowable for heating based on the approximate function, impedance, power factor, and efficiency obtained by theoretical analyses or experiments and the heating power obtained by the temperature rise command value and rolling information. CONSTITUTION:The rolling information and temperature rise command value DELTAT for a rolled material to be heated are inputted to a heating power calculating circuit 10, and the heating power Pref calculated by the circuit 10 is fed to a gap set value calculating circuit 11. An impedance/power factor/efficiency calculating circuit 12 calculates the impedance Z(g), power factor PF(g), and efficiency n(g) for a gap and inputs these values to a single capacity calculating circuit 13, and its heating output P'max(g) is fed to the circuit 11. The circuit 11 calculates the gate gap set value gref, it is fed to a gap control circuit 14, and upper and lower heating coils 2, 3 are vertically moved to decide the distances to the rolled material. The burning of the coils 2, 3 due to an excessive current is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device used for induction heating a rolled material which is being conveyed through a rolling line.

[0002]

2. Description of the Related Art An induction heating device is used to heat a rolled material while it is being transported through a hot rolling line. The through flux type induction heating device is widely used for heating a metal plate material (non-magnetic material or the like), and is well known to be applied to an edge heater of a hot rolling line.

FIG. 2 is a schematic side view showing a state in which a rolled material is heated by a conventional penetration flux type induction heating device. The upper heating coils 2 and 2 and the lower heating coils 3 and 3 are arranged above and below the rolled material 4 that conveys the rolling line. Upper heating coil 2, 2 and lower heating coil 3,
Each of the three members is arranged so as to be separated from the rolled material 4 by an appropriate length in the conveying direction. Upper heating coil 2, 2 and lower heating coil 3,
Each of the three units is separately connected to the drive control units 1, 1 and 1, 1 so that they can be moved up and down. When heating the rolled material 4, the distance x between the rolled material 4 and the upper heating coils 2 and 2 and the distance y between the rolled material 4 and the lower heating coils 3 and 3, that is, the upper heating coils 2 and 2 are lower. The rolled material 4 is heated by controlling the gap g with the side heating coils 3 and 3 to be an appropriate length and supplying a predetermined heating power to the rolled material 4.

In this type of induction heating apparatus, as the gap g between the upper heating coils 2 and 2 and the lower heating coils 3 and 3 increases, the efficiency, power factor and impedance decrease, and the effective single unit capacity of the heating coil increases. Is reduced. The upper heating coils 2 and 2 and the lower heating coils 3 and 3 need to secure a predetermined distance with respect to the rolled material 4 in order to prevent collision with the rolled material 4 being conveyed, and therefore, the upper heating coils 2 and 2 are provided.
The predetermined distance is selected in consideration of the heating capacities of the lower heating coils 3 and 3. On the other hand, an induction heating device for heating a rolled material is disclosed in, for example, JP-A-53-70063 and JP-A-59-116.
No. 318, respectively.

[0005]

However, since there are cases in which the front and rear end sides of the rolled material are warped or warped in the conveying direction, the rolled material is considered to be warped in consideration of the warped height. It is necessary to increase the distance between the upper heating coil and the lower heating coil. Then, the gap g (see FIG. 2) between the upper heating coil and the lower heating coil becomes large.

Here, g ... Gap between upper heating coil and lower heating coil Z (g) ... Coil impedance of heating coil at gap g (monotonically decreasing function of g) PF (g) ... Gap Power factor when g (monotonic decreasing function of g) η (g) ... Heating efficiency when gap g (monotonic decreasing function of g) V ... Terminal voltage of heating coil I _max ... Maximum allowable current of heating coil P _max (g)… Maximum allowable single unit capacity of heating coil when gap is g P (g)… Active power of heating coil when gap is g I… Current of heating coil P ′ _max (g)… Heating when gap is g Assuming that the heating power received by the rolled material when the maximum allowable single unit capacity of the coil is output, the terminal voltage V of the heating coil is V = Z (g) I ... (1), and the heating power P (g) of the heating coil is It is, P (g) = VIPF ( g) = Z (g) I 2 PF (g) ... (2) , and the heated co Le maximum allowable single machine capacity P _max (g) is of rolled material when outputting _{P max (g) = Z (} g) I 2 max PF (g) ... (3) , and the maximum allowable single machine capacity of the heating coil the heating power is received P _'max (g) is _{P' max (g) = η} (g) Z (g) I 2 max PF (g) ... (4).

When the gap g becomes larger than the equation (2), the coil impedance Z (g) decreases and the power factor
Since PF (g) decreases, the heating power P (g) of the heating coil decreases. Also, according to equation (3), when the gap g increases, the coil impedance Z (g) decreases and the power factor PF (g) increases.
Is decreased, the heating power P _max is decreased. Further, when the gap g becomes larger from the formula (4), the coil impedance Z (g), the power factor PF (g) and the heating efficiency η are decreased, so that the heating power P ′ _max (g) received by the rolled material is decreased. ..
This reduces the heating capacity. If the terminal voltage V of the heating coil is more than a predetermined value from the equation (1), the impedance Z (g) of the heating coil decreases as the gap g increases, so that the current I of the heating coil becomes excessive. There is.

In order to solve such a problem, it is considered that the warp height of the rolled material is detected by an image device and the distance between the end of the rolled material and the heating coil, that is, the gap is selected accordingly. However, since the setting of the gap in the middle portion of the rolled material depends only on the plate thickness of the rolled material, the gap becomes improper and heating capacity becomes excessive or insufficient. Further, since the gaps on the front and rear end sides of the rolled material in the conveying direction are focused only on the collision prevention, it is impossible to secure an appropriate heating capacity. Further, since the current constraint condition of the heating coil is not taken into consideration when selecting the gap, if an attempt is made to heat with a large gap, there is a problem that an excessive current may flow in the heating coil and burn the heating coil. is there.

On the other hand, JP-A-53-70063 and JP-A-59-116.
The induction heating device shown in each publication of No. 318 is a structure for heating the rolled material to an optimum temperature by moving the induction heating coil for heating the rolled material in a direction perpendicular to the conveying direction of the rolled material. However, it does not mean that the heating coil is moved up and down to maintain an appropriate gap with respect to the rolled material to ensure an appropriate heating capacity. In view of such problems, it is an object of the present invention to provide an induction heating device that vertically moves a heating coil with respect to a rolled material, appropriately controls the facing distance thereof, and appropriately heats the rolled material.

[0010]

An induction heating apparatus according to the present invention is an induction heating apparatus for heating a rolled material by arranging heating coils on the upper surface side and the lower surface side of the rolled material, and the information of the rolled material and rolling A first arithmetic circuit that calculates heating power based on a temperature rise command value of the material, a second arithmetic circuit that calculates impedance, power factor, and efficiency corresponding to the gap between the rolled material and the heating coil, and the second arithmetic circuit Based on the calculation result of the circuit, between the rolled material and the heating coil, the third calculation circuit for calculating the maximum allowable power obtained by the current upper limit value of the heating coil and the output of the first calculation circuit and the output of the third calculation circuit And a gap control circuit that controls the position of the heating coil according to the gap setting value calculated by the fourth calculation circuit.

[0011]

The heating power P _ref for heating the rolled material is P _ref = vtρCBe ^{0.025 / B} ΔT × 10 ³ [kW] / edge on one side of the rolled material according to the information of the rolled material to be heated and the temperature rise command value ΔT. (5) (however, v = rolling material speed [m / s] C = specific heat [kJ / kg
° C] ρ = specific gravity [T / m ³ ] B = temperature increase distribution parameter t = rolled material thickness [m]) By comparing the equations (4) and (5), the upper limit value of the gap g such that P ′ _max (g) ≧ P _ref (6) is obtained, and g _ref ≦ g (P _ref ) = P The gap setting value g _ref is calculated so as to be ′ _max ⁻¹ (P _ref ). The heating coil is controlled so as to _{achieve the} determined gap set value g _ref . As a result, an appropriate gap can be obtained between the rolled material and the heating coil, and the rolled material can be appropriately heated.

[0012]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a schematic block diagram showing the configuration of the induction heating device according to the present invention. Rolling information for rolling material to be heated: rolling material speed v [m / s], specific heat C [kJ / kg
[° C.], specific gravity ρ [T / m ³ ], temperature rise distribution parameter B, rolled material thickness t [m] and temperature rise command value ΔT are input to the heating power calculation circuit 10. The heating power calculation circuit 10 obtains the heating power P _ref for heating the rolled material by the equation (5) based on the input information. Then, the heating power P _ref calculated by the heating power circuit 10 is input to the gap setting value calculation circuit 11.
The impedance / power factor / efficiency calculation circuit 12 calculates the impedance Z (g) as an approximate function form or a table value of the gap g, which is obtained in advance by an offline theoretical analysis or experiment.
, Power factor PF (g) and efficiency η (g) are calculated.

Impedance / power factor / efficiency calculating circuit 12 calculates impedance Z (g), efficiency η (g) and power factor PF
(g) is input to the single-unit capacity calculation circuit 13, and the single-unit capacity calculation circuit 13 calculates the single-unit capacity P _max (g) of the heating coil when the allowable current of the heating coil is maximized by the formula (3). Further, in consideration of heating efficiency, the heating power P ′ _max (g) received by the rolled material at that time is calculated by the equation (4). The heating output P ′ _max (g) calculated by the unit capacity calculation circuit 13 is input to the gap set value calculation circuit 11. Gap setting value calculation circuit
11 compares _Eqs . (5) and (4), and _P'max (g) ≥ P
_Find the upper limit of the gap g such that _ref becomes g _ref ≤
The gap setting value g _ref is calculated so that g (P _ref ) = P ′ _max ⁻¹ (P _ref ).

Actually, the gap setting value g _ref is determined in consideration of the margin of heating capacity and the margin of collision prevention. The gap setting value g _ref calculated by the gap setting value calculation circuit 11 is
It is input to the gap control circuit 14. Gap control circuit 14
Controls the upper heating coils 2 and 2 and the lower heating coils 3 and 3 up and down according to the input gap setting command value g _ref , and positions them individually. At this time, the upper heating coils 2 and 2, the lower heating coils 3 and 3 and the rolled material 4
And the thickness t of the rolled material 4 are (see FIG. 1),
Allocate so that x + y = g _ref −t.

In this way, the approximate function form, the impedance Z (g), and the power factor PF obtained in advance by theoretical analysis or experiment are obtained.
(g), the efficiency η (g), the heating command value ΔT, and the heating power P _ref obtained from the rolling information to obtain the upper limit value of the gap g allowed to perform the predetermined heating. By obtaining the set value g _ref , it becomes possible to set the gap g that is allowable to obtain a predetermined heating capacity,
The heating coil current does not become excessive. And by combining with a warpage detector that detects the warpage of rolled material,
It is possible to prevent the rolled material from colliding with the heating coil.

[0016]

As described in detail above, according to the present invention, it is possible to set the allowable gap for obtaining the predetermined heating capacity. Moreover, an excessive current does not flow in the heating coil. Further, by combining with a warp detector for detecting the warp of the rolled material, it is possible to prevent the rolled material from colliding with the heating coil. Therefore, the present invention is not likely to burn the heating coil due to an excessive current, and it is possible to provide an induction heating device capable of appropriately controlling the distance between the rolled material and the heating coil to appropriately heat the rolled material. Play.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a configuration of an induction heating device according to the present invention.

FIG. 2 is a schematic side view showing a heating state of a rolled material by a conventional induction heating device.

[Explanation of symbols]

 2 Upper heating coil 3 Lower heating coil 10 Heating power calculation circuit 11 Gap setting value calculation circuit 12 Impedance / power factor / efficiency calculation circuit 13 Single unit capacity calculation circuit 14 Gap control circuit

Claims (1)

[Claims] 1. An induction heating apparatus for heating a rolled material by arranging heating coils on the upper surface side and the lower surface side of the rolled material, the heating power is calculated based on the information of the rolled material and a temperature rise command value of the rolled material. Based on a calculation result of the first calculation circuit, a second calculation circuit that calculates the impedance, power factor, and efficiency corresponding to the gap between the rolled material and the heating coil, and the upper limit of the current of the heating coil. A third arithmetic circuit for calculating the maximum allowable power obtained by the value, and a fourth arithmetic circuit for calculating the gap set value between the rolled material and the heating coil by the output of the first arithmetic circuit and the output of the third arithmetic circuit, An induction heating apparatus for rolled material, comprising: a gap control circuit for controlling the position of the heating coil according to the gap setting value calculated by the fourth arithmetic circuit.