JPH0658193B2 - Vertical induction heating furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an induction heating furnace for heating a steel material to a temperature suitable for rolling when hot-rolling the steel material. The present invention relates to a vertical induction heating furnace which is charged from the lower part of the furnace into the furnace and uniformly heated at high temperature by induction heating.

<Prior Art> A vertical induction heating furnace is used for heating a steel material once heated by an ordinary continuous heating furnace to a higher temperature and uniformly. As shown in FIG. Is placed on the support hardware 2 in a state where the width direction is vertical, and the steel material 1 is an elevating device (not shown) installed below through the support pipe 3 that supports the support hardware 2 from the lower side. ) Is charged into the furnace body 5 from the lower part of the furnace. The support hardware 2 supports the steel material 1 as it is during induction heating of the steel material 1, and after heating is completed, the steel material 1 is lowered and taken out of the furnace.

The support hardware 2 that is in direct contact with the steel material 1 is made of heat-resistant metal, and the support pipe 3 has a water-cooled structure and is lined with a fireproof heat insulating material 4 so that the heat transfer to the cooling water is prevented as much as possible. Has become. On the side wall of the furnace body 5, a plurality of induction heating coils 6 are divided and arranged in the vertical direction so as to correspond to the steel material 1 whose width direction is upright. Each induction heating coil 6 is individually and independently supplied with electric power so that the temperature distribution in the width direction of the steel material 1 charged in the furnace is controlled to be uniform. Reference numeral 7 is a power source for supplying electric power to the induction heating coil 6, and 8 is a power factor improving capacitor.

<Problems to be Solved by the Invention> In the vertical induction heating furnace having the above structure, the steel material 1
Through the support metal 2 made of heat-resistant metal to the cooling water of the support pipe 3, the lower end temperature of the steel material 1 becomes low. That is, when the steel material 1 is first heated from the cold as shown in FIG. 4, the temperature distribution in the width direction of the steel material 1 depends on the heat transfer to the cooling water in the support pipe 3 and the temperature rise of the support metal fitting 2. It can be seen that the heat of No. 1 is taken away, which causes a temperature shortage at the lower end of the steel material 1. This tendency is also seen when heating the steel material heated by the continuous heating furnace to a higher temperature,
The temperature of the lower end of the steel material 1 is likely to be insufficient.

Particularly, in the induction heating by the induction heating coil 6, the steel material 1 itself is a heating element, and the heat transfer to the support hardware 2 cannot be maintained at a predetermined temperature unless the steel material 1 itself guarantees heat. As a measure for maintaining the temperature of the steel material 1, the support hardware 2 has a heat-insulating structure, or the height of the support metal 2 made of heat-resistant metal is extremely increased to raise the temperature of the support hardware 2 and reduce heat transfer. It is also possible.

However, even if these measures are taken, it is unavoidable that the temperature of the lower end side of the steel material 1 is still low by the time the steel material 1 itself heats the support hardware 2 for the first time. This is because the heat source in the induction heating is the steel material 1 itself to be heated as described above.

The temperature transition of the support hardware 2 is shown in FIG. It is clear that the induction heating treatment and the standby of the steel material 1 are not in the same pattern, and the temperature of the support hardware 2 largely changes due to the length of the standby time between the heating treatments. This is because the temperature of the support hardware 2 is maintained by the heat transfer from the steel material 1 during heating, the heat source disappears when the heat treatment is finished, and the temperature decreases due to the heat transfer to the water cooling pipe 3.

In particular, if the waiting time between the processes is short as indicated by (a) in FIG. 5, the temperature of the support hardware 2 becomes high. This means that the temperature difference between the steel material 1 and the support hardware 2 becomes smaller,
Since the heat transfer to the support hardware 2, that is, the heat removal of the steel material 1 becomes small, the decrease of the steel material temperature is prevented. Steel 1 is forced to operate with large temperature fluctuations as shown in Fig. 5.
The temperature of the contact portion between the support metal 2 and the support metal 2 varies during each heating, which causes variations in the size and shape of the steel material, resulting in a large loss in product yield.

The present invention solves the above-mentioned problems of the prior art, and when the steel material is put up and down in the width direction and charged into the furnace from the lower part of the furnace for induction heating, the temperature tends to be insufficient because it is in contact with the support hardware. It is an object of the present invention to provide a vertical induction heating furnace capable of uniformly induction heating the entire steel material including the lower end of the steel material.

<Means for Solving the Problem> In order to achieve the above object, the temperature of the support metal may be maintained within a predetermined temperature range below the upper limit of the heat resistant temperature thereof to prevent cooling of the steel material as much as possible. At this time, the heat source required to maintain the temperature of the support metal is not guaranteed by the heat generated by the steel itself as in the conventional case, but it is possible to prevent the temperature drop of the steel material if the heat is guaranteed by another heat source. Is.

What should be noted here is that the support metal itself is also a heat-resistant metal and is made of an induction heating element, so the support metal made of this heat-resistant metal is positively heated by induction and taken away by the cooling water of the support pipe. You just have to guarantee the heat. The present invention has been made based on such a viewpoint, and the gist thereof is as follows. That is, the present invention, the induction heating coil for steel material is divided and arranged in the vertical direction of the furnace side wall, and the hot steel material standing vertically in the width direction is placed on the heat-resistant metal support hardware that can be raised and lowered from the furnace lower portion. In a vertical induction heating furnace that is charged into the furnace and heated to a high temperature, a support metal object induction heating coil is separately arranged on the furnace side wall adjacent to the lower side of the steel material induction heating coil divided in the vertical direction, A vertical induction heating furnace, characterized in that power is supplied to the induction heating coil for the support hardware to independently control the coil and the temperature is maintained within a predetermined temperature range not higher than the heat resistant upper limit temperature of the support hardware. Is.

<Operation> As described above, the support metal induction heating coil is separately installed, and the support metal can be heated to a predetermined temperature range below the heat-resistant upper limit temperature, so that the heat guarantee for the lower end of the steel material is surely performed. It is possible to achieve uniform heating of the steel material. The heating of the support metal by induction heating is preferably maintained at a predetermined temperature near the upper limit of heat resistance.

If overheated, the strength of the support metal made of heat-resistant metal will be insufficient and the supporting function of the steel material will deteriorate, and in some cases it may lead to melting, which may cause a major operation accident, so the temperature of the support metal is set separately. It is important to control by the induction heating coil for the support hardware. Thus, the performance of the vertical induction heating furnace can be greatly improved.

<Example> An example of the present invention will be described below with reference to FIG. The same components as those shown in the conventional example are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, a plurality of induction heating coils 6 for steel materials are arranged in the vertical direction of the side wall of the furnace body 10 in the same manner as in the conventional example, but the existing structure is arranged in the vertical direction in a divided manner. An induction heating coil 9 for support hardware is separately arranged on the furnace side wall of the furnace body 5 that is adjacent to and below the induction heating coil 6 for steel material. Reference numeral 10 is a power source for supplying electric power to the induction heating coil 9 for support hardware, and 11 is a power factor improving capacitor.

The induction heating coil for support hardware 9 is arranged at a position corresponding to the upper ends of the support hardware 2 and the support pipe 3 supporting the steel material 1 charged in the furnace. The power power can be controlled independently by 10 and the power factor improving capacitor 11.

The power supplied to the induction heating coil 9 for the support hardware is mainly controlled by the temperature of the support hardware 2, and the temperature of the support hardware 2 is measured so that the support hardware 2 is maintained within a predetermined temperature range below the heat resistant temperature. Controlled. When the vertical induction heating furnace is operated in the same pattern during steady-state heating, the temperature inside the furnace and the steel material 1 and the support hardware 2 are also patterned, so based on this pattern, induction heating for the support hardware is performed in advance. It is also possible to determine the input power pattern of the coil 9 and control according to this pattern.

FIG. 2 shows the temperature transition of the support hardware 2 and the transition of the input power when the support hardware 2 is induction-heated by the support metal induction heating coil 9. During the period in which the steel material 1 is induction-heated by the induction heating coil 6 for steel material, the support hardware 2 is heated by the induction heating coil 9 for support hardware, and the heat resistant upper limit temperature θmax of the support hardware 2 is increased.
It is of course possible to prevent the temperature drop at the lower end of the steel product 1 by maintaining the temperature range between the upper limit target value θmax and the lower limit target value θmin, which are the following predetermined temperature ranges, and reducing the temperature difference between the steel product 1 and the support hardware 2. However, electric power is supplied to the induction heating coil for support hardware 9 so that the support hardware 2 can be held between the predetermined temperature ranges θmax and θmin even during the waiting period between heating. This lower limit target value θmin is determined so as not to exceed θmax when heating is restarted.

In FIG. 2, since the standby period before heating is short at the timing, there is a danger that the temperature of the support hardware 2 will exceed the upper limit target value θmax. Therefore, the input power of the support hardware induction heating coil 9 should be turned off. Is shown. In this case, even if the induction heating coil 9 for support hardware is cut, heat transfer from the steel material 1 and the induction heating coil 6 for steel material
As a result, the temperature of the support hardware 2 is rising.

By controlling the electric power applied to the induction heating coil 9 for the support hardware as described above, the temperature rise amount of the steel material 1 can be increased by about 50 ° C compared with the conventional one and the temperature variation can be reduced from 40 ° C to 20 ° C. I was able to.

<Effects of the Invention> As described above, according to the present invention, it is possible to increase the absolute value of the lower end temperature of the steel material that comes into contact with the support hardware, so that the variation in the temperature of the steel material that comes into contact with the support hardware is reduced, A steel material having a good size and shape can be manufactured with good yield.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a vertical induction heating furnace according to an embodiment of the present invention, FIG. 2 is a graph showing changes in temperature and input power of a support metal object according to the present invention, and FIG. 3 is a conventional example. FIG. 4 is a schematic longitudinal sectional view of a vertical induction heating furnace, FIG. 4 is a graph showing a temperature distribution in the width direction of a steel material according to a conventional example, and FIG. 5 is a graph showing a temperature transition of the steel material according to the conventional example. 1 ... Steel material, 2 ... Support hardware, 3 ... Support pipe, 4 ... Fireproof heat insulating material, 5 ... Furnace body, 6,9 ... Induction heating coil, 7,10 ... Power supply, 8,11 ... … Capacitor.

Claims (1)

[Claims] 1. An induction heating coil for steel material is vertically arranged on a side wall of a furnace, and a hot steel material whose vertical width direction is vertically placed is placed on a heat-resistant metal support hardware which can be raised and lowered, and the furnace is heated from the bottom of the furnace. In a vertical induction heating furnace that is charged into and heated to a high temperature, a support hardware induction heating coil is separately disposed on the furnace side wall adjacent to the lower side of the steel material induction heating coil that is divided and arranged in the vertical direction. A vertical induction heating furnace, characterized in that power is applied to the induction heating coil for support hardware to control it independently so as to be maintained within a predetermined temperature range below the heat resistant upper limit temperature of the support hardware.