JPH01180915A - Dephosphorizing and molten slag separating method at tapping from converter - Google Patents

Abstract

PURPOSE:To easily dephosphorize a molten steel and to prevent intrusion of molten slag into the molten steel in a ladle during tapping by blowing a dephosphorizing agent by an inert gas from the outside circumferential part of a tap hole into a converter at the time of discharging the molten steel from the converter into the ladle. CONSTITUTION:A hole 7 for discharging the molten steel 3 and a hole 8 for blowing the dephosphorizing agent are provided on the tap hole 2 of the converter. The molten steel 3 is discharged from the molten steel outflow hole 7 of the tap hole 2 into the ladle 5 by tilting the converter 1a and the powdery dephosphorizing agent is simultaneously blown by the inert gas such as N2 or Ar as a carrier gas from the blowing hole 8 into the molten steel 3 into the converter. The molten steel 3 in the converter is dephosphorized by such blowing of the dephosphorizing agent and the molten steel 21 in the upper part of the tap hole 2 is built up by the blowing of the carrier gas, by which the intrusion of the molten slag 4 into the molten steel 3 and the eventual intrusion into the ladle 5 are prevented even just before the end of the tapping. Rephosphorization of the molten steel from the molten slag in the ladle 5 is prevented and the low phosphorus content steel is easily obtd.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to further reinforcing dephosphorization in the converter during the process of tapping steel from the converter, and also to perform separation after the dephosphorization treatment. This invention relates to a method of preventing molten slag from entering molten steel as much as possible.

[Prior art] Hot metal contains a large amount of impurities such as phosphorus and sulfur, but these can be removed through refining reactions such as dephosphorization and desulfurization, or slags with controlled composition can be removed. (hereinafter sometimes referred to as slag) is generated and adjusted to have an appropriate content. In any case, the hot metal after such refining and component adjustment (hereinafter referred to as refining) is transferred to a ladle or the like and subjected to subsequent treatment.

Recently, dephosphorization has been carried out by so-called hot metal pretreatment, which is carried out before the hot metal is sifted into the converter, and the converter mainly performs decarburization and temperature raising. From the perspective of making effective use of the tapping time, which accounts for 40% of the blowing time in the converter, in recent years there have been reports on methods for dephosphorization in the converter during tapping. (Refer to Steel J86-31033).In this technology, injection lances are inserted into the four ports of the converter during tapping, and a dephosphorizing agent is injected through the lances, thereby increasing the dephosphorizing effect and reducing the The aim is to suppress the rephosphorization phenomenon.

However, this technique involves inserting a lance into the converter through the furnace opening immediately after the start of steel tapping to perform dephosphorization treatment, and then removing the lance before the end of steel tapping, which makes the operation complicated. There was a problem with the lack of speed.

On the other hand, at the end of refining (blowing), slag is floating covering the molten steel, and the slag after refining is already a useless substance, and if you consider the subsequent process, it is actually an extremely harmful substance, so after refining, Separating molten steel and slag is an extremely important task.

In other words, if slag is mixed into the molten steel in the ladle due to insufficient slag separation, impurities that were separated and removed from the slag during the refining process may return to the molten steel due to the reducing action of the deoxidizing agent. For example, the phenomenon of rephosphorization in guild steel has a serious effect on the quality of the steel. In addition, in the process after molten steel is taken out into a ladle, etc., in order to perform molten steel treatment such as deoxidation, it is necessary to maintain the molten steel surface in a reducing atmosphere. It is never desirable to mix some slag into molten steel. However, both molten steel and slag have high fluidity due to their high temperatures, and it is extremely difficult to completely separate the two when taking out the molten steel.

Figures 2 and 3 are schematic explanatory diagrams showing the conventional molten steel extraction work state, and in the figures, 1 indicates a converter, 2 indicates a molten steel discharge port, 3 indicates molten steel 14, slag, and 5 indicates a ladle, respectively. There is. First, in FIG. 2, there is refined molten steel 3 at the bottom side of the converter 1, and slag 4 is floating on the surface of the molten steel 3 so as to cover it. When taking out the molten steel 3, the converter 1 is tilted from the state shown in FIG. 2 by a converter tilting device (not shown) to the state shown in FIG. It flows out through a ladle 5 and is transferred to a ladle 5 or the like. It has been practiced for a long time to tilt the converter in the opposite direction prior to tapping the steel, to discharge only the slag 4 from the spout 10, and then turn it around as shown in Fig. 3 to take out the molten steel. Even in this case, since the slag 4 is not completely discharged by the first tilting, the situation is the same as that of the slag 4 floating on top of the molten steel 3 in some amount in FIG. 3.

In other words, the work of removing molten steel as shown in FIGS. 2 and 3 can be said to be the work of separating molten steel 3 and slag 4. In order to achieve this purpose, it is necessary to accurately grasp the point at which the molten W43 has finished flowing out or the point at which the slag 4 has started flowing out, and then
There are two known methods: one is to block the converter 1, as shown in Figure 2, and the other is to prevent the slag 4 that flows out from entering the ladle 5, but the latter method However, there are problems from the viewpoint of ensuring the prevention of slag contamination and work safety.

On the other hand, as for the former method, various slag cutting methods have been known, such as the sliding nozzle method, slag hole method, projector method, two-piece arget method, siphon method, and one-stopper method. Most of the methods attempt to prevent slag from entering the ladle by mechanically blocking the slag.

However, although these conventional methods can reduce the amount of slag mixed into the ladle, it is not sufficient, and it is desired to further reduce the amount of slag mixed into the ladle. Furthermore, if a large amount of slag gets mixed into the molten steel in the ladle, it is necessary to remove the slag using a slag tracker or the like. Therefore, it goes without saying that these facilities and their maintenance work are necessary, and the greater the amount of slag mixed in, the more complicated the slag removal work. Loss of thermal energy), reduction in iron yield due to co-diversion of molten steel by a slag tracker, etc., or melting damage to large ladle-resistant materials, etc., also occur.

[Problems to be solved by the invention] The present invention solves the above-mentioned technical problems at the time of steel tapping in a converter,
In other words, this was done to solve the problems that dephosphorization processing is complicated and separation of molten steel and slag is extremely difficult, and as is clear from the above purpose, The object of the present invention is to provide a method that can rapidly dephosphorize in a converter during the steel tapping process in the converter, and also reliably separate molten steel and slag.

[Means for Solving the Problems] The present invention that achieves the above object is a method of separating molten steel and slag by discharging molten steel from the molten steel discharge port of a converter where slag is present on the molten steel. In doing this, a dephosphorizing agent supply member having a molten steel discharge hole and a dephosphorizing agent/carrier cass mixture injection hole is attached to the molten steel discharge port, and during tapping, the dephosphorizing agent is supplied through the dephosphorizing agent supply member. A converter that dephosphorizes and separates molten steel and slag by supplying carrier gas and only supplying carrier gas immediately before the completion of tapping, and discharging molten steel while preventing the discharge of slag. This is a method for dephosphorization and slag separation during tapping.

[Effect] The operation of the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic explanatory diagram of a converter configured to carry out the method of the present invention, and its basic configuration is similar to that of the prior art shown in FIG. By adding symbols, duplicate explanations can be avoided. The state of the converter 1a shown in Fig. 1 shows the state of steel tapping, and the basic operations up to this state and during the tapping of the converter have already been described in connection with Figs. 2 and 3. That's right.

In the converter 1a, a roughly cylindrical dephosphorizing agent supply member 6 is attached to the molten steel discharge port 2, and the molten steel is supplied to the dephosphorizing agent supplying member 6 as shown in FIG. 4 (enlarged sectional view). A discharge hole 7 and a dephosphorizing agent/carrier gas mixture blowing hole 8 (hereinafter simply referred to as a blowing hole) are formed. During tapping, the molten @3 is discharged into the ladle 5 through the molten steel discharge hole 7, and the dephosphorizing agent is introduced into the converter la by the carrier gas through the blowing hole 8.
It is supplied to the molten steel 3 inside. In addition, in the period immediately before the completion of steel tapping, that is, after the dephosphorization agent has been supplied and until the steel tapping is completed,
Only carrier waste is subsequently supplied via the blowing hole 8. The mechanism by which the dephosphorizing agent/carrier gas mixture or the carrier gas alone is supplied is, for example, as shown in Figure 1.
Pressure supply line 11, logic controller (PLC) 12. Dephosphorizing agent storage tank 13. Carrier gas supply line 14. Controller (RC)15. The flow rate is regulated by the solenoid valves V, , V2 and supplied via a line 20 communicating with the blow hole 8. Further, the carrier gas used at this time is Ar.

It is inert scum such as N2.

By supplying the dephosphorizing agent/carrier gas mixture or the carrier gas alone through the dephosphorizing agent supplying member 6 in this way, the dephosphorizing agent supplying member 6 in the converter during steel tapping from the converter.
A bubbling phenomenon occurs in the molten steel 3 in the vicinity, pushing away the slag 4 and exposing the bare hot water 21, so that the slag is removed not only during tapping but also near the end of tapping (when the molten steel is low). Contamination into the ladle is minimized.

Moreover, since the structure for supplying the dephosphorizing agent is simple and does not require a lance or the like as described in the prior art, the dephosphorization process at the time of tapping can be accomplished quickly. In addition, in the final stage (at the end of steel tapping), the slag cutting method as described above is applied,
It is necessary to block the slag that flows out following the molten steel, but in the case of the present invention, it is possible to reliably prevent slag from entering at least until immediately before the end of tapping, and also to prevent slag from entering at the end of tapping. Even if there is some amount, the amount of slag mixed in can be significantly reduced compared to the conventional method.

[Example] The present inventors performed dephosphorization and slag separation using the converter 1a shown in Fig. 1, investigated various items (see Table 1 below), and confirmed the effects of the method of the present invention. did. For comparison, a similar investigation was also conducted regarding the conventional method described in connection with FIGS. 2 and 3.

The results are shown in Table 1, and as is clear from the results, the method of the present invention not only achieves the effect of dephosphorization during the steel tapping process, but also reliably reduces the amount of slag mixed into the ladle. Understand what is possible.

Table 1 [Effects of the Invention] As described above, according to the present invention, by operating according to the configuration described above, dephosphorization during tapping is easier than before, and separation of molten steel and slag is possible. This can be achieved reliably and reduce the amount of slag flowing into the ladle.
Many effects were obtained, including improved iron yield, prevention of rephosphorization, and extended ladle life.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a converter configured to carry out the present invention, FIGS. 2 and 3 are schematic explanatory diagrams showing conventional molten steel extraction work, and FIG. 4 is a dephosphorizing agent supply member 6. FIG. 1.1a... Converter 2... Molten steel outlet 3.
... Molten steel 4 ... Slag 5 ... Ladle
6... Dephosphorizing agent supply member 7... Molten steel discharge hole

Claims (1)

[Claims] When discharging molten steel from the molten steel discharge port of the converter where molten steel exists on the molten steel and separating the molten steel and slag, the molten steel discharge port is equipped with a molten steel discharge hole and a dephosphorizing agent/carrier gas mixture. A dephosphorizing agent supply member having a blowing hole is installed, and during tapping, the dephosphorizing agent is supplied with a carrier gas through the dephosphorizing agent supplying member, and just before the completion of tapping, only the carrier gas is supplied, and the slag is A method for dephosphorization and separation of molten slag during tapping from a converter, characterized in that dephosphorization and separation of molten steel and slag are performed by discharging molten steel while preventing the discharge of molten steel.