JPH0225411B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting a vacuum degassing tank heating device, and particularly to a method for connecting a vacuum degassing tank heating device using an electric resistance heating element provided in a RH type or DH type vacuum degassing tank. Regarding connection method.

In the RH type or DT type vacuum degassing tank,
Prior to vacuum processing in the tank by sucking up molten steel from the ladle, it is necessary to preheat the tank, and in order to prevent the temperature of the molten steel from dropping during vacuum processing, there is a A heating device is provided in which a pair of graphite connecting members is buried, an electric resistance heating element is removably connected by pressure bonding between the graphite connecting members, and heating is performed by passing a large current through the electric resistance heating element. . The details of this heating device and the conventional technology will be explained in the case of an RH type vacuum degassing tank with reference to the attached drawings.

FIG. 1 is a sectional view showing the entire RH type vacuum degassing tank. Ladle 4 containing molten steel 2 to be degassed
is conveyed below the vacuum degassing tank 6 and lifted, and the rising pipe 8 and downcomer pipe 10 provided at the bottom of the degassing tank 6 are immersed in the molten steel 2. Degassing tank 6
is exhausted from the upper exhaust pipe 12, and the inside of the tank is maintained in a vacuum. Ar gas blowing pipe 1 in the middle of riser pipe 8
When an inert gas such as Ar is blown into the ladle 4, the molten steel 2 in the ladle 4 rises through the riser pipe 8, is degassed in the tank, and then flows back into the ladle 4 through the descender pipe 10. By repeating this rising and falling of the molten steel 2, the degassing process is performed.

A heating device 16 for the degassing tank 6 using an electric resistance heating element, which is an object of the present invention, is provided slightly above the top level of the molten steel 2 in the tank. The details of its configuration are shown in FIG. That is, a graphite connecting member 20 consisting of a stay 20A and a connector 20B is provided embedded and fixed between one brick wall 18A of opposing refractory brick walls 18A and 18B, and a connecting member 20 made of graphite is provided between one of the brick walls 18A and the other refractory brick wall 18B.
A graphite connection member 20 called a slidable stick 20A is provided at the tip of the graphite connecting member 20, and an electric resistance heating element 22 called a stub is fixed to the tip of the stub 20A.
The ends of the poles 20A and 20B are fitted and connected to the opposite ends of the poles 20B, and the longer pole side stakes 20A are used to connect the electrical resistance heating element 22 to the short poles of the poles 20B by crimping using a crimping device (not shown). There is.

The electrical resistance heating element 22 configured as above
Electricity of 200 to 1500 kwh is applied, a large current is passed through the red-hot heating element 22, and the refractory bricks in the degassing tank 6 before degassing treatment are heated by radiation, convection, and heat transfer, and the molten steel 2 in the tank is heated. In addition to preventing adhesion, heating is continued during the degassing process to prevent the temperature of the molten steel 2 from decreasing due to the degassing process.

The heating device for a vacuum degassing tank having the above-mentioned configuration and operation is designed to prevent oxidative wear and tear of the graphite heating element 22 and the graphite connecting member 20 due to oxygen mixing into the tank during the degassing process. In addition to consumption due to carburization of the molten steel splash and breakage due to the impact of falling objects such as refractory bricks, there is also damage caused by improper connection when the heating device is set up, and the so-called "blow-up" caused by metal and molten refractory materials flowing down the tank walls. The heating device suffers local melting damage due to the dripping, which significantly shortens its lifespan.

In the conventional connection method when setting up the heating device, the fitting part of the tip of the stub 22 and the connector 20B is machined with high accuracy so that they fit tightly, but if there is a small gap in this joint part, As shown in FIG. 3, an arc is generated at the joint between the tip of the stub 22 and the cutter 20B, and local melting damage gradually expands, making heating impossible. In addition, due to the above-mentioned "sloping", a localized melted part 24 as shown in Fig. 4 may be generated in the carote 20B. This is an unavoidable result.

An object of the present invention is to provide an effective connection method that can extend the life of a vacuum degassing tank heating device in view of the fact that the conventional connection method of the vacuum degassing tank heating device has a shortened life as described above.

The gist of the present invention is as follows. That is, a pair of graphite connecting members embedded between opposing refractory brick walls in a vacuum degassing tank;
In the method for connecting a vacuum degassing tank heating device comprising an electric resistance heating element which is removably crimped and connected between the graphite connecting members, carbon is attached to the connecting portion between the graphite connecting member and the electric resistance heating element. This is a method for connecting a vacuum degassing tank heating device, characterized in that a kneaded carbon member whose main component is a substance is used.

The heating device connection method according to the present invention eliminates the conventional pressure bonding by precision machining of the tip of the stub 22 and the fitting part of the connector 20B, and connects the graphite connecting member 20 and the electric resistance heating element 22. It is characterized by the use of a kneaded carbon member whose main component is carbon material.

As a kneaded carbon member containing a carbon material as a main component, it is desirable to use a kneaded material of a carbon material such as graphite or anthracite and a binder such as a phenol resin or tarpitz. The above-mentioned carbon kneading substance is interposed or applied to the joint between the cutter 20B and the stub 22 shown in FIG. Furthermore, in the case of the state of the joint as shown in FIG. 4, the locally eroded portion 24 may be filled with the carbon kneaded substance.

Example 1 Degassing tank heating device 1 as shown in FIGS. 3 and 4
6 connection part 20B and stub 22
In the event that it becomes unusable due to the occurrence of an arc between the holes or the occurrence of localized melted parts 24 due to "sloping", a carbon material such as graphite or anthracite is used as the main raw material to replace the worn parts. When this was repaired with a kneaded carbon material that was kneaded with a binder such as phenol resin or tar peach, good electrical conductivity was obtained and its lifespan could be extended. Figures 5, 6, and 7 show stub 22, karotute 20B, and stake 2, respectively.
It is a diagram showing the change in the life of the conventional before repair of 0A and after the repair after application of the present invention. In Figures 5 to 7, n: number of samples, : average lifespan (hr)
δ: Variation In other words, the life of Stub 22 was extended by 15%, the life of Stub 20B was extended by 63%, and the life of Stub 20A was extended by 12.5%.

Example 2 Two hours had passed after the heating device 16 was energized, and as shown in FIG. Once taken out, we prepared a kneaded carbon material with a weight ratio of 50% natural scaly graphite powder, 25% furan resin, and 25% furfuryl alcohol, applied it to the concave part of Karotute 20B, and restarted the electricity supply, and there was no problem inside the tank. Heating could be continued and the product could be used continuously for 56 hours.

Example 3 After 38 hours had elapsed since the start of energization of the heating device, a localized melted part 24 was generated in the cullet 20B due to "sluggishness" as shown in FIG. 4, and continued energization became impossible due to an increase in resistance value. Therefore, when we temporarily stopped the electricity supply, filled the local melted part 24 with the same kneaded carbon material as in Example 2, and restarted the electricity supply, we were able to continue heating the tank without any problems, and the lifespan was reduced to 63 hours. I was able to extend it.

Embodiment 4 When setting up a new heating device 16, there are two cases: one is crimping by simply precision machining the fitting part using the conventional method, and the other is the case where a kneaded carbon member is interposed at the joint part by the connecting method according to the present invention after the same processing. When we investigated the arc generation rate at the mating part as shown in Figure 3 when the application was applied and then crimped, we found that the average rate of arc generation in the case of the conventional method was 9%, but the average rate decreased to 2% after applying the present invention, as shown in Figure 8. It decreased dramatically. Therefore, it has been found that the present invention is also effective when installing a new heating device.

As is clear from the above examples, the present invention is applicable to RH
When connecting a heating device using an electric resistance heating element installed in a vacuum degassing tank such as a type or DH type, the connection part between the graphite connecting member buried between the refractory brick walls in the tank and the electric resistance heating element. By using a kneaded carbon member containing a carbon material as a main component mixed with a binder, the following effects could be achieved.

(b) Reduce the incidence of arcing that occurs at connections,
It was possible to significantly extend the life of the heating device.

(b) The present invention is effective when applied not only when a failure occurs while the heating device is energized, but also when updating a new product, reducing the frequency of arc occurrence in the case of a new product to 1/4 to 1/5 of the conventional rate. was completed.

(c) Even if local erosion occurs due to "sagging" at the connection part of the heating device, energization can be continued by filling the kneaded carbon member.

(d) According to the present invention, the fitting portion between the stub and the connector no longer requires highly precise machining, so machining costs can be reduced.

(E) Conventionally, the stub and the groin were replaced simultaneously as a pair, but with the present invention, it is only necessary to determine the renewal period based on the lifespan of each part, and the unit consumption of each part can be significantly reduced.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the mounting position of the heating device in the RH type vacuum degassing tank, Figure 2 is an enlarged partial cross-sectional view showing the heating device of the vacuum degassing tank, and Figure 3 is a cross-sectional view showing the heating device in the RH type vacuum degassing tank. A schematic cross-sectional view showing an arc-eroded part, FIG. 4 is a schematic cross-sectional view showing a local melt-damage part of Karotsute due to "sloping", and FIGS. 5, 6, and 7 show a stub before and after implementation of the present invention, respectively. FIG. 8 is a diagram comparing the lifespan of the cartridge and the stake, and FIG. 8 is a diagram comparing the arc occurrence rate between the conventional connection method and the connection method according to the present invention for a new heating device. 6...Vacuum degassing tank, 16...Heating device, 18
(18A, 18B)...Fireproof brick wall, 20...
Graphite connection member, 20A...Static, 20B
... Karotute, 22 ... Stub (electrical resistance heating element), 24 ... Locally eroded part.

Claims (1)

[Scope of Claims] 1. A pair of graphite connecting members buried between opposing refractory brick walls in a vacuum degassing tank, and an electric resistance heating element removably crimped and connected between the graphite connecting members. A method for connecting a vacuum degassing tank heating device comprising: a kneaded carbon member containing a carbon material as a main component is used for the connection between the graphite connecting member and the electrical resistance heating element; How to connect the degassing tank heating device. 2. Vacuum degassing tank heating according to claim 1, wherein the kneaded carbon member containing carbon material as a main component is a kneaded material of carbon material such as graphite or anthracite and a binder such as phenolic resin or tarpitch. How to connect the device. 3. The vacuum degassing tank heating device according to claim 1, wherein the kneaded carbon member containing the carbon material as a main component is interposed or applied to the connection portion between the graphite connection member and the electric resistance heating element. How to connect. 4. The vacuum degassing tank heating device according to claim 1, wherein the kneaded carbon member repairs a localized melted portion that occurs at the connection between the graphite connection member and the electric resistance heating element. Connection method.