JPH0456730A - Vertical slab induction heating furnace - Google Patents

Abstract

PURPOSE:To uniformly heat a slab in its cross direction and to reduce the damage of the hearth when the slab is erected in its cross direction, charged into the furnace from the bottom and heated by allowing a supporting rod for supporting both side ends of the slab and holding slab afloat in the space in the furnace to pierce the side wall of the furnace and making it free to slide. CONSTITUTION:A slab is placed on the vertically movable hearth 3 through a metallic support 2, charged into the furnace 5 by raising the hearth 3, and elevated slightly above a supporting rod 9. The rod 9 is approached to the slab, the hearth 3 is lowered, the slab is supported by the rod 9, and the upper and of the hearth 3 is slightly left in the furnace. Under these conditions, an induction heating coil provided outside the furnace 5 is energized to heat the slab.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an induction heating furnace that heats a steel billet such as a slab to a temperature suitable for rolling when hot rolling the steel billet. This relates to a vertical induction heating furnace in which steel billets are charged vertically into the furnace from the bottom and heated uniformly at a high temperature by induction heating.

<Prior art> Vertical induction heating furnaces are mainly used to uniformly heat steel materials, which have been heated by ordinary continuous heating furnaces, to a higher temperature, as shown in Figure 6. The steel slab 1 is placed on a support hardware 2 with its width oriented vertically, and the steel slab 1 is placed on a lifting device installed below via a hearth 3 that supports the support hardware 2 from below. (not shown) into the furnace body 5 from the lower part of the furnace. The support hardware 2 directly supports the steel billet 1 during the induction heating of the steel billet 1, and after the heating is completed, the steel billet 1 is lowered and taken out of the furnace.

A support metal fitting 2 that comes into direct contact with the steel piece 1 is made of a heat-resistant metal, and a water-cooled vibrator 4 is buried in the lower part of the support metal fitting 2. On the side wall of the furnace body 5, a plurality of induction heating coils 6 are vertically divided and arranged so as to correspond to the steel slabs 1 vertically erected in the width direction. Each induction heating coil 6 is controlled so that the temperature distribution in the width direction of the steel billet charged into the furnace is uniform by inputting electric power individually and independently. 8 indicates a power factor correction capacitor.

<Problem to be solved by the invention> In the vertical induction heating furnace having the above structure, the steel billet l
Heat transfers from the steel plate 1 to the cooling water of the pipe 4 through the support fitting 2 made of heat-resistant metal, and the temperature at the upper end of the steel piece 1 becomes low. In other words, when the steel billet 1 is first heated from a cold state as shown in FIG. It can be seen that heat is taken away from the steel billet 1, which causes insufficient temperature at the lower end of the steel billet 1. This tendency is also seen when the steel material heated in the continuous heating furnace is further heated to a high temperature, and the lower end of the steel slab 1 tends to be under-temperature.

In particular, in induction heating using the induction heating coil 6, the steel piece 1 itself is a heating element, and heat transfer to the support hardware 2 cannot be maintained at a predetermined temperature unless the steel piece 1 itself provides heat guarantee. be. As a measure to maintain the temperature of the steel slab 1, the temperature of the support hardware 2 can be increased by making the support hardware 2 have an insulating structure, or by making the height of the support hardware 2 made of heat-resistant metal very high, thereby reducing heat transfer. It is also possible to do so.

However, even if these measures are taken, the initial heating of the support hardware 2 is from the steel billet I itself, and it is inevitable that the temperature at the lower end of the steel billet I will become low before a steady state is reached. . This is due to the fact that the heat source in induction heating is the steel piece I itself, which is the object to be heated, as described above.

Further, when the steel billet is heated to a particularly high temperature, the scale on the surface of the steel billet melts and the vicinity of the hearth including the support hardware 2 becomes high temperature, resulting in severe damage to the support hardware 2 and the hearth 3.

The present invention solves the above-mentioned problems of the prior art, and when a steel billet is placed vertically in the width direction and charged into the furnace from the lower part of the furnace for induction heating, the steel billet comes in contact with the support hardware, resulting in insufficient temperature. It is an object of the present invention to provide a vertical steel billet induction heating furnace capable of uniformly induction heating the entire steel billet including the lower end of the billet.

Means for Solving the Problems> The present invention provides induction heating coils for steel billets arranged around the furnace side wall, and steel billets vertically oriented in the width direction placed on a hearth that can be raised and lowered. In a vertical induction heating furnace where billets are charged into the furnace from the bottom and heated, the support rods that support both ends of the billet and keep the billet floating in the furnace space can be slid freely through the furnace side wall. This is a vertical billet induction heating furnace characterized by being installed in a vertical steel billet induction heating furnace.

<Function> As described above, in the present invention, the copper piece supporting rods that are slidably provided through the furnace side wall support both the top and bottom ends of the steel piece and float the steel piece in the furnace space. It is now possible to hold the state. Therefore, there is no need to directly support the steel piece with support hardware or the hearth during heating of the steel piece, and heat loss from the bottom of the steel piece to the support hardware or hearth is greatly reduced. Furthermore, since the support hardware and the hearth can be moved away from the high-temperature parts of the furnace, the temperature rise can be reduced, and damage caused by melting and falling of scale on the surface of the steel billet can also be reduced.

Next, the present invention will be explained in more detail with reference to Examples.

<Embodiment> FIGS. 1 and 2 are diagrams of the main parts of an embodiment of the present invention, and FIG. 3 shows a diagram of the main parts of a conventional example for reference.

In the conventional example shown in FIG. 3, a steel slab 1 is directly supported in a furnace by a supporting stand constituting a hearth 3.

The first example shows a state in which the lower parts of both ends of the steel slab 1 are held floating in the furnace space by support rods 9 having L-shaped support portions at the tips.

FIG. 2 shows a state in which both ends of a steel billet I are sandwiched between two support rods 9 and held floating in the furnace space.

It is preferable that the apparatus shown in FIG. 1 be applied to steel slabs with a weight of 20 tons or less and a width/length ratio of 0.8 or more. Further, it is preferable that the apparatus shown in FIG. 2 is applied to a steel billet having a weight of 10 tons or less and a width/length ratio of 0.5 or more.

Next, FIG. 4 shows the procedure for supporting a slab steel piece.

First, in Figure 4 (al), the hearth 3 where the slab can be raised and lowered
At this time, the support rod 9 is retracted to the vicinity of the furnace wall of the induction heating furnace 5. As shown in Fig. 3), the slab is loaded into the furnace 5 by raising the hearth 3, and the lower end of the slab is raised to a position slightly above the support rod 9. Here, the rod 9 is brought close to the slab as shown in (C). Next, set the hearth 3 (
The slab is lowered as shown in d) so that the slab is supported by 2 and the upper end of the hearth 3 is slightly pooled in the furnace.

In the state shown in FIG. 4(d), electricity is started to be applied to the induction heating coil provided outside the induction heating furnace 5 to perform heating.

The inside of the furnace is sealed by the furnace wall 5 and the hearth 3, and heating can be performed with the atmosphere inside the furnace being a non-oxidizing atmosphere.The slab supporting skid 2 on the hearth 3 is also spaced apart from the slab, so the lower end It is possible to prevent temperature fluctuations from occurring. Also,
By setting the induction heating coil at a position where it can heat the support rod 9, it is possible to reduce temperature unevenness due to the support rod 9 as much as possible.

By the way, size 220 thickness x 1000 width x 10000
A steel billet slab of 17 tons in length is supported in the manner shown in Figures 1 and 3, and the temperature of the slab at the widthwise position of the slab when heated from an initial temperature of 20'C to 500'C is 5. As shown in the figure.

It can be seen that when heating was performed using the conventional method, the temperature at the bottom of the steel billet located below the furnace dropped dramatically, whereas in the method of the old invention, the steel billet was heated almost uniformly at the top and bottom in the width direction.

<Effects of the Invention> The steel billet support device of the present invention enables uniform heating in the width direction of the steel billet, and also reduces damage to the hearth.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the present invention apparatus, FIG. 3 is an explanatory diagram of the conventional apparatus, and FIGS. 4(a) to (dl are explanatory diagrams showing the slab charging procedure using the present invention apparatus, Figure 5 is a graph showing the position in the width direction of the steel billet and the temperature of the steel billet, Figure 6 is a schematic diagram of an induction heating furnace, and Figure 7 is a graph showing the temperature distribution in the width direction of the steel billet.・Steel piece, 3... Hearth floor, 5... Furnace wall, 7... Power supply, 9... Support rod. 2... Support hardware, 4... Cooling pipe, 6... Induction heating coil, 8... Capacitor, Fig. 2 Lower part of the furnace

Claims (1)

[Claims] Induction heating coils for steel billets are placed around the furnace side wall,
In a vertical billet induction heating furnace, billets with their widths upright are placed on a hearth that can be raised and lowered and heated by being charged into the furnace from the bottom of the furnace. A vertical steel billet induction heating furnace characterized in that a support rod for holding the billet floating in the furnace space is slidably provided through the furnace side wall.