JPH0637673B2 - Rigid induction heating furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vertical induction heating furnace for steel slabs, and more particularly, to effectively prevent heat dissipation from the bottom surface of the steel slab during induction heating. The idea is to evenly heat the pieces.

(Prior Art) As a heat treatment for billets that need to be heated at high temperature, such as slag for grain-oriented silicon steel sheets, recently, so-called vertical induction is used in which the billets are heated in an upright state in the width direction. A heating furnace is used.

In such a vertical induction heating furnace, the charging and extraction of the steel pieces into the furnace are generally performed from below the furnace by elevating the elevating beam on which the steel pieces are placed.

FIG. 3 shows the entire vertical induction heating furnace, and FIG. 4 shows the details of the support structure for the steel slab by the elevating beam.

In the figure, numeral 1 is a steel piece, 2 is a furnace wall, 3 is an induction coil,
Reference numeral 4 is a lifting beam. The elevating beam 4 is composed of a support metal 4-1, which is made of heat-resistant metal, a water cooling pipe 4-2 (internal water cooling type), and a fireproof heat insulating material 4-3. The steel piece 1 is placed on the support metal 4-1 and is loaded into the furnace from below by an elevating device (not shown).

Now, as shown in Fig. 4, support hardware made of heat-resistant metal
4-1 are arranged at appropriate intervals along the longitudinal direction of the steel slab and directly contact the steel slab 1 to support it. The support hardware 4-1 is supported by a water-cooled water cooling pipe 4-2. Furthermore, this pipe 4-2 is a support hardware 4-1.
Lined with fireproof insulation 4-3, including a part of
It has a structure that prevents heat transfer to the cooling water as much as possible.

However, such a support structure has the following problems.

That is, in the induction heating furnace, the steel piece itself, which is the object to be heated, is a heating element, so if there is a low-temperature portion around it, heat transfer from the steel piece occurs, and the temperature of the steel piece itself decreases. .

Here, considering the heat transfer based on FIG. 5, it is as follows. When the temperature of the billet 1 rises due to self-heating, heat transfer Q ₁ to the refractory heat insulating material 4-3 occurs with it, and then heat diffusion Q ₂ into the heat insulating material, and further the water cooling pipe 4-2.
Heat transfer Q ₃ to the cooling water occurs via, and becomes stable with the lapse of time, and each part reaches a certain balanced temperature.
What should be noted here is that since the heat source is only the steel piece itself, the steel piece itself must generate heat by compensating for this heat transfer amount.

On the other hand, in the steel slab portion where such heat transfer does not occur, for example, the upper portion of the steel slab, the heat generated by the steel slab directly leads to an increase in the temperature of the steel slab. Therefore, depending on the location,
An imbalance that cannot be ignored occurs in the temperature rise of the billet,
The billet temperature becomes uneven.

As a measure to prevent this, there is an attempt to divide the induction coil in the width direction of the steel piece and individually control each coil 5 to achieve uniform heating in the width direction as shown in FIG. As long as there is a large amount of heat transfer in the lower part of the billet, it is inevitable that the billet has a temperature distribution, and only the minimum temperature can be secured.

(Problems to be solved by the invention) Therefore, in order to prevent uneven temperature distribution, in order to maintain the temperature of the lower part of the steel slab, in other words, the upper part of the ascending / descending beam, the heat transfer from the steel slab is not relied on and another heat source It is necessary to compensate for the heat transfer.

Even in the upper part of the lifting beam, if the induction coil is arranged so that an induction current flows through the support metal object around the heat resistant metal object, which is in direct contact with the steel slab, Since the temperature rises due to self-heating, generation of heat transfer can be suppressed, but such heat generation cannot be expected in the refractory heat insulating material portion between the support metal parts, so that heat transfer is particularly remarkable.

(Means for Solving the Problem) As described above, in order to prevent the transfer of heat from the bottom surface of the steel slab, the heat for maintaining the temperature of the upper part of the lifting device does not depend on the heat input from the steel slab. , You need to expect your own fever. However, most of the constituents of the lifting device are refractory heat insulating materials, and these do not generate self-heating because no induced current flows.

Therefore, as a result of intensive studies to solve the above problems, the inventors have found that in order to perform heat compensation, a self-heater is generated near the upper surface of the refractory heat insulating material between the supporting hardware by an induced current. It is sufficient to arrange them. Especially, in this case, if properly combined with the heat resistance of the refractory insulation, it is possible to suppress heat transfer (loss heat) to the pipe cooling water as much as possible, and at the same time, the part of the refractory insulation that faces the steel slab. It was found that the temperature of slab can be kept high and the heat transfer from the slab to the refractory insulation can be suppressed, and the decrease of the slab temperature can be effectively prevented.

According to the present invention, a plurality of support metal fittings which are arranged at intervals along the longitudinal direction of the steel slab and directly mount the steel slab in an upright state in the width direction, and an inner portion which respectively supports the support metal fittings A lower charging furnace equipped with a water-cooled support pipe and a refractory insulation surrounding all of the support pipe and a part of the support hardware. The vertical induction heating furnace is characterized in that it has a heating element that generates heat by induction heating in a region near the upper layer surface.

The present invention will be specifically described below.

FIG. 1 shows the structure of a vertical induction heating furnace according to the present invention, in which reference numeral 6 is a heating element embedded in the upper layer portion of the refractory heat insulating material 4-3. The heating element 6 may be any one that can raise the temperature of the refractory heat insulating material by being heated and can withstand the temperature reached in combination with the heat input from the steel slab, and is generally used for a support metal object. The refractory metals used are suitable, but other materials such as carbon bricks can be used.

The size of the heating element may be determined according to the required temperature of the fireproof / heat insulating material, and the required temperature can be easily obtained experimentally and empirically here.

(Example) In the place shown in FIG. 1, as a heating element, thickness: 30
Using a cobalt-based refractory metal of mm, the target temperature was set to 1300 ° C and the billet was heated.

FIG. 2 shows the results of examining the temperature distribution of the cross section AA ′ as seen from the arrow after the heat treatment. The figure also shows the results of an investigation on the temperature distribution when heat treatment was performed according to the conventional method without using a heating element. The amount of electric power input to the billet is the same.

As is clear from the figure, when the heating element is arranged, the temperature drop in the refractory heat insulating material portion is remarkably reduced as compared with the case where the heating element is not arranged.

In terms of the amount of power input, the amount of power input to the steel slab is the same, but the amount of heat generated by the heating element, that is, the amount of heat consumed to maintain the refractory insulation at a high temperature, naturally leads to an increase in power consumption. There is. However, considering the improvement in quality and yield due to elimination of the low temperature part of the billet, there is a sufficient effect.

(Effect of the Invention) Thus, according to the present invention, it is possible to effectively prevent the heat dissipation from the lower surface of the steel piece during the induction heating of the steel piece and realize the uniform heating of the steel piece.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a steel slab support elevating / lowering device according to the present invention, FIG. 2 is a temperature distribution diagram after heat treatment of a cross section AA ′ in FIG. 1, and FIG. Overall view of the vertical induction heating furnace, FIG. 4 is a detailed view of the support structure, FIG. 5 is a view showing heat transfer from the bottom of the steel slab in the conventional vertical induction heating furnace, and FIG. FIG. 1 is a vertical sectional view of a vertical induction heating furnace having a split induction coil. 1 ... Steel piece, 2 ... Furnace wall 3 ... Induction coil, 4 ... Support beam 4-1 ... Support hardware, 4-2 ... Water-cooled pipe 4-3 ... Fire-resistant insulation, 5 ... Split Coil 6 ... Heating element

Claims (1)

[Claims] 1. A plurality of support metal fittings, which are arranged at intervals along the longitudinal direction of the steel slab and are directly placed in a state where the steel slab is erected in the width direction thereof, and the support metal fittings are respectively supported. A lower-charge furnace that has an internal water-cooled support pipe and a refractory insulation that surrounds all of this support pipe and a part of the support hardware. Having a heating element that generates heat by induction heating near the upper surface of the material,
A vertical induction heating furnace characterized by that.