JPS6160890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preheating a lower tank of a vacuum degasser.

For example, in the RH type vacuum degassing apparatus, as shown in FIG. 1, a lower tank 4, which has a short lifespan due to contact with molten steel, is replaceably attached to an upper tank 3 by a flange. In addition, 1 is a canopy, 2 is an exhaust gas conduit, and 5 is an immersion pipe.

This vacuum degassing equipment is used to preheat the refractory layer with a gas burner prior to use in order to prevent spalling damage to the refractory layer due to rapid heating, a drop in the temperature of the molten steel being processed, and molten steel adhesion to the refractory layer. is being carried out. The conventional preheating method is to first air dry the lower tank or preheat it at a low temperature of about 200℃, then attach it to the upper tank, and then
This is done by preheating to a high temperature of over 1000℃.

In order to shorten the downtime of the vacuum degasser and improve its operating rate, it is necessary to minimize the preheating time after the lower tank is attached to the upper tank. In other words, since the upper tank is already at a high temperature from previous use, the lower tank should be preheated to as high a temperature as possible before installation, and after the lower tank is installed, the vacuum degassing equipment should be ready for operation immediately. is preferred.

However, if the lower tank is preheated to a high temperature before being attached to the upper tank, the top surface of the refractory layer will become uneven due to thermal expansion, and the airtightness, which is important for vacuum degassing equipment, will of course be lost. There was a problem that parts were severely damaged due to penetration of molten steel and slag.

The purpose of this invention is to keep the top surface of the refractory layer smooth even if the lower tank is preheated to a high temperature, thereby solving the above-mentioned conventional problems. After fixing the presser iron plate by providing a thermal expansion allowance for the refractory layer on the top surface of the refractory layer lined with the refractory layer, preheating is performed.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 2 shows the vicinity of the top surface of the refractory layer of the lower tank 4, where 7 is an outer shell, 6 is a refractory layer made of refractory brick, and 9 is a flange ear.

During preheating, first, on the top surface of the refractory layer 6,
After positioning the presser iron plate 8 with one end placed on the flange ear 9 and fitting the U-shaped locking tool 10 into the joint between the presser iron plate 8 and the flange ear 9, the U-shaped locking tool 10 is The presser iron plate 8 is fixed by pressing with a bolt 11 screwed into the presser plate 8.

A gap is provided between the top end surface of the refractory layer 6 and the presser iron plate 8 to provide an expansion allowance 12 for the refractory layer 6. The size of this expansion allowance 12 is determined as appropriate depending on the material of the refractory layer 6, and is, for example, 10 to 40 mm.
shall be.

The method of fixing the presser iron plate 8 is not limited to the one shown in the figure.
For example, a jack is interposed between the U-shaped locking tool 10 and the flange ear portion 9 instead of the illustrated bolt 11. Alternatively, there is a method of directly tightening the presser iron plate 8 and the flange ear portion 9 with bolts and nuts.

In addition, by increasing the wall thickness of the presser fitting 8 or by incorporating a refrigerant flow pipe (not shown),
Deformation due to high temperatures during preheating may be prevented.

The subsequent steps are not particularly different from the conventional method and are therefore omitted from illustration.

After the top surface of the refractory layer is pressed as described above, a gas burner using, for example, butane gas as fuel is inserted through a part of the cover of the upper open part lined with refractory material to preheat it. The upper limit of the preheating temperature is that the inner peripheral surface of the refractory layer is at least 800℃ or higher,
Preferably the temperature is about 1000 to 1300°C.

After the lower tank has been preheated, the presser foot is released and the lower tank is replaced with the previously used lower tank which has reached the end of its useful life and is attached to the upper tank. After removing the lid, it is preferable to cover the lower tank with a heat insulating board or the like until just before attaching it to the upper tank in order to prevent the lower tank from cooling.

According to this invention, by restraining the preheated lower tank with the presser foot, the top surface of the refractory layer remains at a uniform height even after thermal expansion, and it is possible to connect the preheated lower tank to the upper tank without losing airtightness. can. Since the vacuum degassing device degasses molten steel by reducing the pressure inside the tank, the airtightness of the tank according to the present invention can further improve the throughput of the vacuum degassing device. Furthermore, in the refractory layer, there is almost no gap at the joint between the upper tank and the lower tank, and there is no local damage caused by intrusion of molten steel or slag into the gap. Moreover, since the lower tank can be preheated to a high temperature before being installed in the upper tank, preheating after installation is not required or only a small amount of preheating is required, thus reducing the down time of the vacuum degassing equipment. shortened to width.

By the way, the expansion of the top surface of the refractory layer due to preheating is not necessarily constant in each part and varies depending on the material of the refractory layer, the preheating temperature, etc., so the expansion provided between the top surface of the refractory layer and the presser It is necessary to set the allowance to an appropriate size.

Another embodiment shown in FIG. 3 shows a method that can be effectively carried out without strictly selecting the appropriate size of the expansion allowance, and is a method in which a cushioning refractory material 13 is interposed in the expansion allowance. Specific materials for the cushioning refractory include, for example, ceramic fiber mortar, a mixture thereof, or a layered combination thereof.

According to this method, the expansion of the refractory layer is absorbed by the cushioning refractory material, and even if the expansion margin is not very accurate, the upper end surface of the refractory layer becomes smooth.
Moreover, the inner peripheral surface does not protrude.

As explained above, in this invention, even if the lower tank is preheated to a high temperature, the top surface of the refractory layer is smooth, so that the lower tank can be attached to the upper tank in a high temperature state, and the No preheating is required, or only a short preheating time is sufficient. Therefore, the downtime of the vacuum degassing device due to replacement of the lower tank can be significantly shortened.

It should be noted that the present invention is of course applicable not only to the RH type vacuum degassing apparatus but also to preheating the lower tank of the DH type vacuum degassing apparatus.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the entire RH vacuum degassing equipment.
FIGS. 2 and 3 are longitudinal sectional views showing embodiments of the present invention. 1... Canopy, 2... Exhaust gas pipe, 3... Upper tank, 4... Lower tank, 5... Immersion pipe, 6... Refractory layer, 7... Outer shell, 8... Holder iron plate, 9... Flange ear portion, 10... U-shaped locking tool, 11... Bolt, 12... Expansion allowance, 13... Cushion refractory.

Claims (1)

[Claims] 1. A method for preheating a lower tank of a vacuum degassing device, characterized in that the lower tank is preheated after providing an expansion allowance for the refractory layer on the top end surface of the refractory layer lined in the lower tank.