JPS5913566B2 - Induction heating method for metal slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a metal slab induction heating method for heating a metal slab material with a heating device equipped with an induction heating coil.

Generally, in hot rolling lines for steel slab materials, a heating furnace using heavy oil or gas is used to heat the slab material before rolling.

The efficiency of these combustion furnaces tends to decrease for heating above about i,ioo°C.

Therefore, in order to ensure a temperature of 1,200°C or more necessary for hot rolling, energy saving is achieved by induction heating the region of 1,100°C to 1,250°C.

In the conventional induction heating method for metal slabs, as shown in FIG. 1a, each slab 26 heated to T1° C. as shown in FIG. 23 and 28, it is rapidly transferred at a speed of Vo as shown by the solid line A in FIG. 1C and fed into the holding furnace 29.

By making the length of the holding furnace 29 longer than the length of one slab 26, as shown in FIG.
6. It is possible to prevent a drop in the overall temperature.

After the slab 26 has completely entered the holding furnace 29, the slab 26 is moved into the main heating furnace 11 by reducing the speed of the rollers 28, 30, 31 to a low speed of vH as indicated by the dashed line B in FIG. The temperature is raised from 12°C to 13°C.

When the rear end of the slab 26 is transferred from the main heating furnace 11 to the holding furnace 32, by switching the speed of the rollers 31 and 25 to a high speed of vo as indicated by the broken line B shown in FIG. 1C,
The slab 26 is fed into the rolling mill 24 while minimizing its temperature drop.

Note that since the holding furnace 32 is provided to maintain the overall temperature of the slab 26 at 13° C., it is made longer than the length of the slab 26.

The above method is generally employed to shorten the furnace length lH of the main heating furnace 11.

For example, assume that the feed speed of the rollers 28, 30, and 31 is constant at Vo.■o■.

Then, the furnace length becomes lH×1.

Usually, the vH is -10 to 20, so the installation area becomes very large.

As explained above, the furnace length lH when changing the feed speed of the rollers 28, 30, 31 can be determined as follows.

In other words, the time required for soaking the slab 26 from 12°C to 13°C is tH (Sec).
, where the slab removal cycle is ts (SeC) and the slab length is tH Lw (mi), then zH=T4X-i.

In addition, the furnace length lo of the holding furnace 29.32 is generally lo-
:Lw, so the length of the entire furnace including the holding furnace is:
tH lH+21°-=:=Lw(2+ becomes ρ.

Therefore, considering the case where tH=ts, the required furnace length is approximately three times the slab length LW, which has the drawback of increasing the installation area.

This invention makes it possible to downsize the heating device and save energy by reciprocating the metal slab carried into the heating device by a plurality of rollers and heating it to a predetermined temperature. It is an object of the present invention to provide a method for induction heating a metal slab.

The figures will be explained below.

In FIGS. 2 to 4, 1 to 5 are induction heating coils arranged at predetermined intervals, and 6 to 9 are rollers arranged between each of the induction heating coils 1 to 5, It is configured to be driven by a drive motor 10 and capable of reversible operation.

In addition, each of the above-mentioned induction heating coils 1 to 5 and each of the above-mentioned rollers 6 to
9 constitute a heating device 11.

Reference numerals 12 to 16 are AC power sources that supply power to each of the induction heating coils 1 to 5.

Note that each of the induction heating coils 1 to 5 may be configured to be supplied with power from the same power source.

17 to 21 are capacitors for power factor improvement, 22 is a combustion furnace for initial heating, 23 is a plurality of conveying rollers disposed between the heating device 11 and the combustion furnace 22, and 24 is a rolling machine. , 25 is a plurality of rollers for conveyance disposed between the heating device 11 and the rolling mill 24, 26 is a metal slab having a predetermined length Lw, and 27 is a roller for conveyance.

Next, the heating method will be explained.

In FIGS. 2 and 3, the slab 26 heated in the combustion furnace 22 as shown in FIG. The slab 26 is carried in and stopped when the tip of the slab 26 reaches the point X in FIG.

Note that power is supplied to each of the coils 1 to 5 until one end of the slab 28 reaches the tip of the induction heating coil 1.

After the slab 26 is stopped at the point X, the rollers 6 to 9 are reversed to produce the result shown in FIG.

The slab 26 is moved back at a speed of , and the other end of the slab 28 is
Stop when the point is reached.

Furthermore, the rollers 6 to 9 are rotated in the normal direction to +■H shown in FIG.
Move forward at a speed of and stop at point X.

By repeating the above operation, the slab 26 will reciprocate between the X point and the Y point within the heating device 11.

As a result, the temperature of the slab 26 is raised from the temperature T2°C when it is carried into the heating device 11 to the predetermined heating temperature T3°C.

Here, when a take-out command is received, the roll is sent to the rolling mill 24 by the rollers 6 to 9 and 25 at a speed of VH shown in FIG.

If there is no extraction command after the specified cycle, each coil 1
It is also possible to maintain the temperature at 13°C by lowering the power supplied to ~5 to a predetermined value.

According to the method described above, the total length zH of the heating device 11
In FIG. 3, LH=LW-+-LX)-+2X.

Here, Lw is the length of the slab 26, and LXY is the length of each roller 6.
~9 The distance corresponding to the pitch LP between each other is about 1,000
~1,500mm.

In addition, the pitch LP satisfies LP<Lw/2, and even if the end of the slab 26 hangs around the rollers 6 to 9 at high temperatures, it will not contact the refractory of the heating device 11, and the roller 6 to 9 are set so that they can be sent sequentially.

X is a margin necessary to compensate for the temperature drop at both ends of the slab 26, and is usually 100 to 300 mm, depending on the size and shape of the slab 26.

For example, if LW=4,000mm, LH=5.2
00~6.100 Since it's my friend, LH-1, 3~1.
5.times.LW, which means that the furnace length can be approximately 1/2 that of the conventional method.

In the above method, the slab 26 is reciprocated between LXY by making the non-heating time of each roller 6 to 9 equal to the heating time of each coil 1 to 5. This is to uniformly heat the entire 26.

In the above embodiments, the method of heating a slab material before rolling has been described, but similar effects can be expected when applied to a long metal material such as a rod, plate, or plate.

According to this invention, the metal slab carried into the heating device is reciprocated within the heating device by a plurality of rollers and heated to a predetermined temperature, thereby achieving miniaturization and reducing the installation area. I can do it.

Moreover, since heating can be performed to a predetermined temperature without providing a holding furnace as in the conventional case, energy saving can be achieved.

[Brief explanation of drawings]

Figure 1a is a block diagram showing the configuration of a rolling line applying the conventional induction heating method for metal slabs. Figure 1a shows the temperature of the metal slab when it is on each roller in Figure 1a. FIG. 1C is an explanatory diagram showing the slab feed speed corresponding to the position of each roller in FIG. , Fig. 3 is a configuration diagram showing the main part configuration of Fig. 2, Fig. 4 is a single line diagram of Fig. 3, and Fig. 5 a shows the temperature of the metal slab when it is on each roller of Fig. 2. FIG. 5 is an explanatory diagram showing the slab feeding speed corresponding to the position of each roller in FIG. 2. In the figure, 1 to 5 are induction heating coils, 6 to 9 are rollers, 11 is a heating device, and 26 is a metal slab. Note that the same reference numerals in each figure indicate gaps or corresponding parts, respectively.

Claims (1)

[Claims] 1. Inside a heating device consisting of a plurality of induction heating coils arranged at predetermined intervals and a plurality of rollers arranged between the induction heating coils and capable of reversible operation. Induction heating of a metal slab, characterized in that a metal slab is brought in and heated to a predetermined temperature by reciprocating the inside of the heating device with the roller while induction heating the metal slab with the heating coil. Method. 2. The method of induction heating a metal slab according to claim 1, wherein the heating device is larger by a predetermined length than the total length of the metal slab and the distance between the two rollers. 3. The induction heating method for a metal slab according to claim 1 or 2, wherein the induction heating coil is configured such that the applied power can be adjusted.