JP2964351B2 - Induction heating method for sheet metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an induction heating method for soaking a thin metal sheet to a temperature not lower than the magnetic transformation point.

(Prior art) As a heating device for a thin metal plate, a gas furnace, a heavy oil furnace,
A resistance type electric furnace was mainly used.

On the other hand, in recent years, induction heating of a solenoid coil method has been performed as a method of continuously heating a metal sheet in order to anneal the sheet metal and dry a surface paint of the painted sheet metal. It is used for heating magnetic steel plates.

As shown in FIGS. 7 and 8, a thin metal plate 2 is continuously run inside a solenoid coil 1 in which a water-cooled coil is spirally wound, and a magnetic flux 3 generated from the solenoid coil 1 This is a method in which induction heating is performed by a magnetic flux 3 parallel to the thin plate 2.

In the induction heating by the solenoid coil 1, as shown in FIG. 9, heating from a room temperature to a magnetic transformation point of about 700 ° C. can be performed almost uniformly and efficiently in the sheet width direction.

However, when heated above the magnetic transformation point, 500 mH _Z ~
Requires a high-frequency power source of about 1 MH _Z, on the device is expensive, the conversion efficiency from the commercial frequency power supply to the high-frequency power is uneconomical low.

As a heating method of a thin plate of a non-magnetic material such as an aluminum plate, as shown in FIGS. 10 and 11, inductors 7 and 7 in which a water-cooled coil 6 is wound around a concave groove 5 of a U-shaped iron core 4 are conventionally used. An induction heating method using a transverse coil 8 in which a magnetic flux 3 generated in the vertical direction by both inductors 7 and 7 is vertically penetrated through the metal thin plate 2 by running the metal thin plate 2 during this time is used.

This heating method using the transverse coil 8 can heat a steel sheet from room temperature to about 1000 ° C., but has a drawback that the temperature distribution in the sheet width direction becomes largely non-uniform as shown in FIG. Was.

For this reason, a method in which heating is performed by the solenoid coil 1 from room temperature to the magnetic transformation point and heating is performed by the transverse coil 8 immediately after reaching the magnetic transformation point is considered.

However, in this method, as shown in FIG. 13, when the magnetic transformation point is reached, both ends become non-uniform as shown by a curve a, and this non-uniform part is further enlarged by the subsequent heating by the transverse coil 8. On the exit side, curve b
As shown in FIG.

(Problems to be Solved by the Invention) An object of the present invention is to provide an induction heating method for a thin metal plate which can eliminate the above-mentioned disadvantages and can be uniformly heated to a temperature not lower than the magnetic transformation point by an inexpensive apparatus. Is what you do.

[Constitution of the Invention] (Means for Solving the Problems) The present invention heats a continuously running thin metal plate to a magnetic transformation point with a transverse coil or a solenoid coil,
Then, after heating by a solenoid coil at the magnetic transformation point to equalize the temperature in the sheet width direction, heating is performed by a transverse coil to a temperature higher than the magnetic transformation point.

(Operation) Next, the operation of the method of the present invention will be described.

The metal sheet is continuously conveyed by a conveying roller, and first heated from a room temperature to a magnetic transformation point by a transverse coil or a solenoid coil.

At this time, the temperature distribution in the plate width direction near the magnetic transformation point is slightly nonuniform at both ends.

Thereafter, when the thin metal sheet is maintained at the magnetic transformation temperature by induction heating with a solenoid coil, the temperature distribution in the sheet width direction becomes uniform at the time of passing through the solenoid coil.

Thereafter, when heating is performed to 900 to 1000 ° C. by the transverse coil, the temperature distribution in the sheet width direction at the outlet side can be substantially uniformly heated to both end sides.

In this way, when the thin metal plate reaches the magnetic transformation point, the temperature is kept at the magnetic transformation point temperature with the solenoid coil without increasing the temperature, and the temperature distribution in the sheet width direction is made uniform,
It is important to raise the temperature.

Hereinafter, the present invention will be described in detail with reference to examples shown in the drawings.

FIG. 1 shows an embodiment of the present invention, in which two transverse coils 8, 8 and a solenoid coil 1 and two further transverse coils 8, 8 are arranged in series.

The metal sheet 2 is continuously conveyed by conveying rollers 9, 9, and first heated by the preceding transverse coils 8, 8 from room temperature to a magnetic transformation point.

At this time, the temperature distribution in the sheet width direction at the point A is slightly non-uniform at both ends as shown by the curve A in FIG.
The temperature distribution in the sheet width direction at point B near the magnetic transformation point passing through the second-stage transverse coil 8 is represented by a curve B in FIG.
As shown by, both ends are largely non-uniform.

Thereafter, when induction heating is performed by the solenoid coil 1, the metal sheet 2 reaches the magnetic transformation point temperature. When the temperature is maintained at this temperature, the temperature distribution in the sheet width direction at the point C passing through the solenoid coil 1 is shown in FIG. , Becomes uniform as shown by the straight line C.

After this, 900-1
When heated to the final temperature of 000 ° C., the temperature distribution in the sheet width direction at point D at the outlet becomes almost uniform to both ends as shown by the curve D in FIG.

Therefore, since the transverse coil 8 is used to heat the magnetic region below the magnetic transformation point and the non-magnetic region beyond the magnetic transformation point, the frequency of the power supply is reduced, and the cost of the apparatus can be reduced.

FIG. 4 shows another embodiment of the present invention. The former solenoid coil 1 has a narrow winding pitch of the coil, the latter solenoid coil 1 has a wide winding pitch of the coil, and three transverse coils 8. Are arranged in series.

The metal sheet 2 is continuously conveyed by the conveying rollers 9, and is first heated from the room temperature to the magnetic transformation point by the former solenoid coil 1.

At this time, the temperature distribution in the sheet width direction at the point A is almost uniform as shown by the curve A in FIG. 6, and the temperature distribution in the sheet width direction at the point B on the exit side near the magnetic transformation point is further improved. The distribution is the sixth
As shown by the curve B in the figure, the temperature slightly increases at both ends.

Thereafter, when the induction heating is performed by the solenoid coil 1 at the subsequent stage, the metal sheet 2 reaches the magnetic transformation point temperature, and when the temperature is maintained at this temperature, the heat radiation on the end side increases, and at the point C passing through the solenoid coil 1 The temperature distribution in the plate width direction becomes uniform as shown by the straight line C in FIG.

After that, the temperature is adjusted to 900 to 100 by the transverse coil 8.
When heated to 0 ° C., the temperature distribution in the sheet width direction at the point D on the outlet side slightly decreases at both ends as shown by a curve D in FIG. 6, but becomes substantially uniform as a whole.

In this device, since the transverse coil 8 is used to heat the non-magnetic region exceeding the magnetic transformation point, the frequency of the power supply is reduced, and the cost of the device can be reduced.

In the above-described embodiment, the structure in which the solenoid coils 1 and 1 are provided in two stages is shown. However, the winding pitch of one solenoid coil 1 is widened on the front side and narrowed on the rear side. You may make it carry out soaking heating at a transformation point.

Further, in the above embodiment, the case where the solenoid coil 1 and the transverse coil 8 are arranged in a horizontal series has been described. However, the solenoid coil 1 and the transverse coil 8 may be arranged in the vertical direction to heat the metal sheet 2 while meandering in the vertical direction.

[Effects of the Invention] As described above, according to the present invention, the temperature distribution in the sheet width direction is made uniform by heating the thin metal sheet heated to the magnetic transformation point with the solenoid coil and maintaining the temperature. Since the non-magnetic region beyond the magnetic transformation point is heated by an inexpensive transverse coil, an inexpensive apparatus can be used to obtain an induction heating method for a metal sheet that can be uniformly heated to a temperature above the magnetic transformation point.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of an induction heating apparatus according to an embodiment of the present invention, FIG. 2 is a graph showing a temperature change of a metal sheet by the apparatus of FIG. 1, and FIG. 3 is a sheet width direction of the metal sheet. FIG. 4 is an explanatory diagram showing a configuration of an induction heating device according to another embodiment of the present invention, FIG. 5 is a graph showing a temperature change of a thin metal plate by the device of FIG. 4, and FIG. FIG. 7 is a graph showing the temperature distribution of the metal sheet in the sheet width direction, FIG. 7 is a front sectional view showing the solenoid coil, FIG. 8 is a side view of FIG. 7, and FIG. Graph showing distribution, FIG. 10 is a front view showing a transverse coil,
FIG. 11 is a side view of FIG. 10, and FIGS. 12 and 13 are graphs showing the temperature distribution in the sheet width direction of a thin metal plate. DESCRIPTION OF SYMBOLS 1 ... Solenoid coil, 2 ... Metal thin plate 3 ... Magnetic flux, 4 ... U-shaped iron core 5 ... Concave groove, 6 ... Water cooling coil 7 ... Inductor, 8 ... Transverse coil 9 ... Conveying roller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-154848 (JP, A) JP-A-2-250285 (JP, A) JP-A 63-91195 (JP, U) JP-A 51- 25805 (JP, Y1) (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 6/10

Claims (1)

(57) [Claims] 1. A continuously running thin metal sheet is heated to a magnetic transformation point by a transverse coil or a solenoid coil.
A method for inductively heating a thin metal sheet, comprising: heating at a magnetic transformation point by a solenoid coil to equalize the temperature in the sheet width direction;