JPH0226928Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The technical contents described in this specification regarding a slab induction heating furnace are related to eliminating problems caused by accumulation of scale in the furnace during processing of slabs in the heating furnace. The aim is to propose development results.

(Background Art) Induction heating furnaces are beginning to be used for hot rolling of slabs. In this heating furnace, if the slab is placed horizontally, scale will accumulate on the induction coil and elute downward, causing damage to the bricks, or in severe cases, making it difficult to transport the slab. Therefore, the vertical type, which performs induction heating with the slab in an upright position, is rather common. Even in this case, scale formation during heating is of course unavoidable.

In order to suppress the amount of scale generated, the atmosphere in the heating furnace is controlled to lower the oxygen concentration, which is a so-called sealed method.

In other words, the amount of scale generated is mainly determined by the ambient temperature and
This is because it is determined by the residence time and oxygen concentration.

Regarding both the ambient temperature and residence time, it is necessary to heat the slab to a temperature that is sufficiently uniform for hot rolling, and it is necessary to sufficiently dissolve the various additive elements precipitated in the steel. The lowest value is determined based on the following. On the other hand, the oxygen concentration in the furnace generally does not have any adverse effect on quality and operation no matter how low the value is, and the amount of scale formation can be suppressed by reducing the concentration as much as possible.

That is, the reason why induction heating furnaces are designed to be sealed is to lower the oxygen concentration in the atmosphere inside the furnace to reduce the amount of scale produced.

(Problems) However, scale already adheres to the surface of the slab when it is placed in the furnace, and a small amount of scale is unavoidable even during heating under controlled atmosphere. Even when using a conventional sealed induction heating furnace, the molten scale generated during heating to a surface temperature of It adheres and accumulates on the walls, hindering the self-supporting of the slabs, worsening airtightness, and even damaging the lower furnace wall, making it difficult to operate in which multiple slabs are heated continuously. In addition, additional furnace maintenance costs were required.

(Purpose of the invention) The purpose of this invention is to solve the problems caused by the adhesion and falling of scale and molten scale as described above, and to enable continuous and smooth induction heating.

(Structure of the device) This device uses a vertical induction heating furnace that heats slabs in an upright position during hot rolling. A pair of bottom doors are provided facing both sides of the skid to open and close the lower part of the induction heating furnace, and each bottom door is provided with a processing gutter for receiving fallen scale, and a discharge for removing scale is provided in each bottom door. This is a vertical slab induction heating furnace equipped with a device.

Now, FIGS. 1A and 1B show examples of vertical slab induction heating furnaces according to two ideas, individually illustrated for the slab heating state and the scale removal state. In the figure, 1 is the heating coil, 2 is the slab, and 3 is the furnace body. , 4 is a skid, 5 is a pair of bottom doors, 6 is an operating cylinder for opening and closing the skid, 7 is a skid support beam, 8 is a scale treatment gutter, 9 is a header for high-pressure water or gas injection, 10 is a header for header 9. The lifting cylinder, 11, is a scale back. Here, the skid 4 supports the slab 2 in an upright position with its upper surface that is slightly narrower than the thickness of the slab, and is provided with a side slope that expands downward to smoothly guide the fall of scale and molten scale. It is accommodated in the processing gutter 8.

The pair of bottom doors 5 are horizontally slidable and openable, and the processing gutter 8 is disposed on the bottom doors.

It is preferable that the bottom door 5 is provided with a heat-resistant packing (not shown) that maintains airtightness between the sliding portion of the furnace body 3 and the side surface of the skid 4 or its support beam 7 to seal the furnace body 3.

In this way, scales and molten scales generated during heating in the state shown in FIG. 4 and its support beam 7, and then, during transportation to the hot rolling process, the scale is discharged from the processing gutter 8 by jetting high-pressure water or gas.

As shown in FIG. 2A, the scale is discharged by adjusting the header 9 from the header lifting cylinder 10 to the processing gutter 8 when the bottom door 5 is in the open retracted position, and removing the scale in the gutter from the scale bag 11.
It is washed away towards the.

Of course, this scale discharge may be performed by a mechanical mechanism such as a spatula movable along the processing gutter 8 as shown in FIG. 1 in the diagram
3 and 14 are pinions and racks used to drive the brush 12, 15 is a drive motor, and 16 is a guide rod.

As mentioned above, it is preferable to apply this idea to a sealed system, which is because the amount of scale generated according to the furnace time is determined by using the slab surface temperature and atmospheric oxygen concentration as parameters, as shown in Figure 3. As shown, the higher the surface temperature, the more significant the influence of oxygen concentration becomes.

(Example) In order to heat a hot rolling slab of size 250 mm thickness x 1000 mm width x 10000 mm length to a slab surface temperature of 1280°C, a sealed vertical slab induction heating furnace shown in Fig. 1 was used. Using.

The slab 2 manufactured by the continuous casting machine is held on the skid 4 in an upright position, that is, with the side surface facing downward and the plane vertical, using a turning machine, and is charged upward into the furnace body 3 with the bottom door 5 open. Then, the bottom door 5 is hermetically closed by its opening/closing operating cylinder 6, and after the atmosphere in the furnace is adjusted, the heating coil is energized to perform heating.

The surface temperature of slab 2 reached 1280 after being in the furnace for about 90 minutes.
℃, and the temperature at the center of the thickness reached approximately 1240°C.At this time, the bottom door 5 was opened to extract the heated slab 2, which was returned to the horizontal position using the turner and supplied to the rolling line.

At the time of extraction of the heating slab 2, the scale that had fallen into the processing gutter 8 was discharged and cleaned, and the next charging was made to wait.

(Effects of the invention) According to this invention, the scale received in the treatment gutter can be discharged whenever induction heating of the slab is completed, making it possible to continuously and smoothly heat the slab. All problems caused by accumulation and stagnation have been resolved.

[Brief explanation of the drawing]

Figure 1 shows the operation of the vertical slab heating furnace and
2 is a diagram illustrating a scale discharge procedure, and FIG. 3 is a graph showing the relationship between the time in the furnace and the amount of scale produced. 1... Heating coil, 2... Slab, 3... Furnace body, 4...
Skid, 5...bottom door, 8...processing gutter, 9, 12...
Scale removal equipment (header, brush).

Claims (1)

[Claims for Utility Model Registration] 1. In a vertical induction heating furnace for heating slabs in an upright position during hot rolling, the top surface of the skid, which supports the slab in an upright position, is made narrower than the thickness of the slab; A vertical slab induction heating furnace is provided with a pair of bottom doors that open and close the bottom of the induction heating furnace facing both sides of the skid, and each bottom door is provided with a processing gutter to catch fallen scales. 2. The vertical slab induction heating furnace according to claim 1, wherein the treatment gutter is equipped with a discharge device for removing scale.