JP2844616B2 - Induction heating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device for a conveyed object to be heated.

B. Summary of the Invention The present invention relates to an induction heating apparatus for a conveyed metal object to be heated, wherein a transverse magnetic flux coil is wound around an E-shaped iron core, an outer wall of the iron core is used as a circulating magnetic path, and the inside of the iron core is heated. Is formed in a space that can be conveyed, the coil width and the gap between the coil and the object to be heated are taken into consideration, and the width of the magnetic path at the center of the iron core is set to be optimal. The heat input per area can be increased, and even if the object to be heated is a non-magnetic material, the temperature can be quickly raised with a high heating object.

C. Prior Art In general, when heating a conveyed object made of a metal material, in a combustion furnace (such as a gas furnace), heat absorption (transfer) from the surface of the object is per unit surface area. For example 5.
3W / cm ² degree and for low, for example, the conveying direction to the orthogonal cross-section thickness 12 mm, attempts to elevated temperature an object to be heated stainless steel rectangular to 1200 ° C. at a conveying speed of the line of 12m / min Width 60mm Then, it takes about 12 minutes to raise the temperature, and a furnace length of 144 m is required. As described above, among the objects to be heated, an object having a relatively narrow cross section (that is, a small surface area) requires a longer time and a longer furnace length for heating and heating. It was a problem because I could not do it.

In order to improve the above problems, an induction heating device has been considered. This induction heating device is a method of generating Joule heating by directly generating an induction current in the object to be heated, so that the heat input per unit surface area can be significantly improved compared to combustion furnaces and electric heater furnaces. it can.

D. Problems to be Solved by the Invention However, if the metal material to be heated is a non-magnetic material or a non-magnetic region, the heating efficiency in induction heating is low. (Vertical magnetic flux heating)
The coil efficiency (the power efficiency between the induction heating coil and the object to be heated) when the heating is performed at a low temperature is extremely low as shown below.

When the object to be heated is copper or aluminum: 10 to 25% When the object to be heated is iron or stainless steel: 20 to 35% Since the coil efficiency is extremely low as described above, the power efficiency deteriorates. For this reason, in order to supply necessary power for heating to the object to be heated, the coil must be large, and the configuration of the induction heating equipment is accordingly large, which requires a large space. .

As a result, there are the following problems (1) and (2) when heating a non-magnetic material or a non-magnetic region using a combustion furnace or an induction heating device.

(1) The heating step and the heat treatment cannot be incorporated into the original production line, and must be performed as a separate line (or batch processing).

(2) The production line speed cannot be increased, and the heating process must be incorporated at a lower speed.

The present invention has been made in view of the above circumstances, and increases the coil efficiency even when the object to be heated is a non-magnetic material or a non-magnetic region having a relatively narrow cross-sectional shape. It is an object of the present invention to provide an induction heating device in which the amount of heat input per area is increased to enable rapid heating with high heating efficiency.

E. Means for Solving the Problems The present invention relates to an induction heating apparatus for heating a metal object to be conveyed by a transverse magnetic flux coil, wherein a transverse magnetic flux coil disposed on both surfaces of the object to be heated is provided on an iron core, A circulating magnetic path is formed by contacting the core on both sides of a narrow object to be heated, a gap S between the magnetic paths at the center of the core, a width Wc of the magnetic path at the center of the core, and a coil width W. When the gap G between the coil and the object to be heated is set, the following equation is satisfied.

(S / 2 / Wc) × 1.5 ≦ W / G Also, when the width Ww of the long side in the cross section of the object to be heated and the current penetration depth Δw are set, the following expression is satisfied.

Ww / 3 ≧ Wc ≧ 2.5 × Δw F. Action A circulating magnetic path is formed in the iron core to increase the amount of magnetic flux linked to the object to be heated. Further, the gap between the magnetic passage portions at the center of the iron core and the width of the passage portion are set as in the above equation to increase the amount of magnetic flux interlinked. Further, a portion where the effective current flows as large as possible within the long side surface of the object to be heated is secured, and the entire temperature is equalized, and the generated induced currents are effectively circulated without hindering each other.

G. Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 to 3, reference numeral 11 denotes a conveyed object to be heated, and the object to be heated 11 is made of metal. The object to be heated 11 is configured to pass through a transverse magnetic flux coil 12 arranged in the middle of conveyance, and is heated to a predetermined temperature while passing through the coil 12 and is induction-heated. The transverse magnetic flux coil 12 is composed of coil portions 12a and 12b that are respectively disposed opposite to both surfaces of the object to be heated 11 with the object to be heated 11 interposed therebetween. AC power for heating is supplied from the power supply 13 to the coil units 12a and 12b. The coil portions 12a and 12b of the transverse magnetic flux coil 12 are spirally wound and housed in the iron cores 14a and 14b in order to reduce leakage of magnetic flux and increase heating efficiency.

The iron cores 14a and 14b are formed of members 15a and 15b having a substantially concave cross section perpendicular to the conveying direction of the article 11 to be heated, and serve as a central magnetic path for winding a coil around the center of the members 15a and 15b. Protrusions 16a and 16b are formed in the longitudinal direction of the member. Ridge 16
a and 16b are formed lower than both outer walls of the member. The coil portions 12a and 12b are accommodated in the iron cores 14a and 14b thus formed, and the end faces of the outer walls of both the iron cores 14a and 14b are arranged on both outer sides in the width direction of the object to be heated as shown in FIG. To form a circulating magnetic path.

 Next, the operation of the above embodiment will be described.

Coil sections 12a and 12b of transverse flux coil 12 from power supply 13
Is supplied with AC power, the magnetic flux φ ₁ ,
φ ₂ occurs. For example, the magnetic flux phi ₁ generated as shown by the arrow is the induced current flows in the object to be heated 11 interlinked object to be heated 11 and chains, which are heated. Note that the magnetic flux φ ₂ is
Since it does not link with 11, it does not contribute to induction heating.

As shown in FIG. 4, the induced current flowing through the object to be heated 11 is formed as a portion that flows as widely as possible within the long side surface of the object to be heated 11 so that the entire body is evenly heated. In order that the induced currents interfere with each other and circulate effectively without interfering with each other, the following expression is satisfied.

Ww / 3 ≧ Wc ≧ 2.5 × Δw (1) In the expression (1), Ww is the width of a long side in a cross section orthogonal to the transport direction of the object 11 to be heated, and Wc is a magnetic path in the center of the iron core. The width of the ridges 16a and 16b (shown in FIG. 5), and Δw is the penetration depth of the current in the object to be heated (shown in FIG. 5).

 It is well known that Δw is expressed by the following equation.

Δw: (cm) ρ: intrinsic resistivity (μΩ-cm) f: frequency (Hz) μ: relative magnetic permeability (μ = non-magnetic material and non-magnetic region
1) The left side Ww / 3 ≧ Wc in the above equation (1) is as wide as possible within the long side surface of the object to be heated 11 to secure a portion where an induced current flows effectively, and to achieve a uniform temperature distribution of the whole. In FIG. 5, Wc
If the width is too wide, the part where the induced current flows will decrease,
Secure at least 2/3 or more of Ww (1/3 or more each side). Further, the portion where the induced current does not flow through the object to be heated 11 is preferably as narrow as possible, and its width is preferably in the range of Wc−2Δw.

The right side Wc ≧ 2.5 × Δw of the above equation (1) indicates that the generated induced currents interfere with each other and are effectively circulated inside without obstructing each other. Next, this will be described with reference to FIGS. 6 and 7. State.

6 and 7, when Wc is too narrow (2.5 × Δ
When the currents become narrower than w, the induced currents in opposite directions interfere with each other at the center of the long side, causing a portion that does not flow well, thereby lowering the efficiency. Therefore, the right side of the above equation (1) is satisfied.

If the width Ww of the long side of the object to be heated 11 is too narrow to satisfy the expression (1), the value of Wc is determined between the value on the left side and the value on the right side. In this case, the heating efficiency is slightly reduced.

Next, the ridges 16a, 16b, which are the magnetic passages in the center of the iron core
The relationship between the gap S between the core and the width Wc of the magnetic path in the center of the iron core, and the relationship between the coil width W and the gap G between the coil and the object to be heated will be described with reference to FIG.

Supplying coil portions 12a and 12b AC power as described above, effective as shown in Figure 3 the magnetic flux phi ₁ ineffective magnetic flux phi ₂
Occurs. And the effective magnetic flux φ ₁ linked to the object to be heated
And the ineffective magnetic flux φ ₂ that is not chained is φ ₁ ≧ 1.5 × φ ₂
As a condition for increasing the coil efficiency, the following equation (2) should be satisfied.

(S / 2 / Wc) × 1.5 ≦ W / G (2) In the right side of the equation (2), the larger the W and the smaller the G, that is, the larger the value of W / G, the more effective magnetic flux that links. The amount is large. Then, as shown in comparison with FIGS. 9 and 10, as the plate thickness t of the object to be heated increases, the gap S also increases, and in order to maintain high heating efficiency, W on the right side is maintained according to the equation (2). It is necessary to increase the value of / G.

FIG. 11 is a diagram showing that the tip of the magnetic path portion at the center of the iron core and the coil may be at the same level.

In the above embodiment, the case where the coil 3 has a turn is shown. FIG. 12 shows an embodiment in which the coil has 4 turns.
This embodiment shows an example in which the outermost one-turn coils 12aa and 12bb are arranged on both sides in the drawing. 12, the coil width W can be increased.

With the configuration as in the above embodiment, the following effects can be obtained.

When the temperature of the non-magnetic material 11 to be heated is increased to 1200 ° C., the heating time can be reduced to 5 seconds or less per 1 mm in thickness.
The temperature can be raised to ℃, the furnace length can be reduced to 1/10 or less of that of the conventional combustion furnace, and the coil efficiency is as follows.

30 to 60% for copper and aluminum systems, 45 to 75% for iron systems and stainless steel systems H. Effects of the Invention As described above, according to the present invention, the heat input per unit area to the object to be heated can be increased. In addition, even if the object to be heated is a non-magnetic material (non-magnetic region), high coil efficiency can be realized, and rapid heating can be performed with high heating efficiency. For this reason, for example, even if the line has a transfer speed of about 12 m / min, there is an advantage that efficient production can be performed by incorporating steps such as heating and heat treatment in the line.

[Brief description of the drawings]

1 to 3 show one embodiment of the present invention.
FIG. 1 is a plan view when a part of an iron core is removed, FIG. 2 is a side view, FIG. 3 is a sectional view taken along line XX of FIG. 1, and FIGS. 4 to 11 are embodiments of the present invention. FIG. 12 is an explanatory view for explaining the operation of the example, and FIG. 12 is a sectional view showing another embodiment of the present invention. 11: Heated object, 12: Transverse magnetic flux coil, 12a, 12b ...
Coil part, 14a, 14b ... iron core, 15a, 15b ... member, 16a, 16
b ... a ridge.

Claims (2)

(57) [Claims] 1. An induction heating apparatus for heating a metal object to be conveyed by a transverse magnetic flux coil, wherein a transverse magnetic flux coil disposed opposite to both surfaces of the object to be heated is provided on each of the iron cores. A circulating magnetic path is formed by contacting both sides of a narrow object to be heated, and a width of a long side in a cross section of the object to be heated is set to Ww, and a magnetic field is formed in the center of each of the cores. When the width of the passage portion is Wc and the penetration depth of the current in the object to be heated is Δw,
An induction heating apparatus, wherein Ww / 3 ≧ Wc ≧ 2.5 × Δw is satisfied. 2. An induction heating apparatus for heating a metal object to be conveyed by means of a transverse magnetic flux coil, wherein a transverse magnetic flux coil disposed opposite to both surfaces of the object to be heated is provided on each of the iron cores. A circulating magnetic path is formed by contacting both sides of the narrow object to be heated, and the width of the magnetic path formed in the center of each of the iron cores is defined as Wc, and the gap between the magnetic paths is defined as Wc. S, and the coil width is W, and the gap between the coil and the object to be heated is G,
(S / 2 / Wc) × 1.5 ≦ W / G is satisfied.