JPS5838484B2 - How to suction molten metal processing slag - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suctioning molten metal processing slag to facilitate suction and discharge of slag produced after treating hot metal with a treatment agent.

An object of the present invention is to improve the fluidity of the produced slag and to very easily suction and discharge the produced slag without any adverse effect on hot metal processing.

As is well known, in recent years, the divisional refining of hot metal has become popular.

That is, there are the Si-free theory P-theory S, Si-free and simultaneous removal P theory, S, and so on.

On the other hand, in order to efficiently discharge the slag produced by the reaction between the processing agent and the hot metal components during each treatment, attempts have been made to use a suction type slag cleaner from above.

However, depending on the treatment method in each treatment step, the fluidity of the generated slag is not sufficient, making it extremely difficult to suction and discharge the slag using the slag cleaner, and it has been necessary to use a conventional mechanical discharger.

For example, when solid oxygen is injected below the bath surface during the Si removal process, the T and Fe of the produced slag decrease, and the fluidity of the produced slag deteriorates.

In addition, for example, when CaO is the main component and deP or simultaneous deP, S is performed using solid acid, aeration, or a combination of both, the melting point of the generated slag is high, and especially in the latter case, simultaneous deP, s In both cases, the fluidity of the produced slag is poor because it is necessary to lower T and Fe.

In view of the above points, this invention improves the fluidity of the generated slag and facilitates suction and discharge.

This will be explained in detail below.

(1) Fluidity improver for produced slag Fluidity improvers used in the present invention include, for example, CaF
2. One or more types of sintered ore, fine iron ore, etc. are used.

In this case, the sintered ore contains a suitable amount of SiO2 in addition to iron oxide, which is preferable.

Figure 1 shows the simultaneous dephosphorization of molten iron (1310 to 1320°C) from which Si has been removed using a CaO-based treatment agent and supplying oxygen.
, shows the relationship between suction time and slag removal rate when 200 to 600 kf of various produced slag fluidity improvers are added to 3 to 4 tons of slag after S treatment, and the slag is sucked and discharged. .

In the case of the conventional method in which a slag fluidity improver is not added first, the fluidity of the slag decreases over time due to the temperature drop on the surface of the slag, and only about 40% of the slag can be removed.

On the other hand, when sintered steel and CaF2 are added, the fluidity of the generated slag improves, and when sintered ore is added, the fluidity of the produced slag improves.
%, when CaF2 is added, it is about 90 or so, and when both are added together, it is close to 100, which shows that the slag removal rate is significantly improved.

(2) Timing of addition of fluidity improver In this invention, the timing of addition is extremely important.

That is, the timing of addition is considered to be at the beginning or middle of the treatment process, but at such a time, various troubles will occur in the treatment process as specifically described in the section ``Deficiency''.

For example, during the above-mentioned Si removal process, if CaF2 is added at the initial or middle stage to improve the fluidity of the generated slag, the forming of the generated slag will become intense and the Si removal process will be delayed.
Continuing treatment becomes difficult.

Similarly, during simultaneous deP and S treatment, if CaF2 is added at the initial or middle stage to improve the fluidity of the generated slag, the forming of the generated slag will become intense, resulting in deP and
It becomes difficult to continue S processing.

Further, for example, when deP and S treatment is performed by solidification of the top charge, the deP reaction is hindered.

On the other hand, when sintered ore is added, T and Fe in the treated slag
increases unnecessarily and exceeds the value suitable for S removal (T, Fe 7-8 or less), which not only reduces the S removal efficiency but also reduces the S removal efficiency.
It also gives birth.

As a result of studying how to increase the fluidity of the generated slag to the point where it can be easily discharged without having these problems, we found that fluidity improvers can be used at the end of the treatment process, after treatment, and from the end of the treatment process to after treatment. It has been found that it is sufficient to add it and then perform a slag treatment.

That is, as for CaF2, the fluidity of the generated slag improves in a short time, so if the slag treatment is stopped at that point, extreme forming will not occur.

Furthermore, since the sintered ore is added at the end of the treatment or after the treatment and subjected to the slag treatment, the decrease in treatment efficiency due to the increase in T-Fe in the treated slag can be suppressed to a minimum or to no amount at all.

At the same time, since sintered ore contains 5i02,
This lowers the basicity of the treated slag, but since it is added for a short time, such as at the end of the treatment, there is no need to worry about re-S.

Note that the end of the first half of the process is, but is not limited to, 3 to 5 minutes before the end of the process.

Examples will be described below.

A supplementary explanation will be given below regarding the above embodiment.

Example 1 In Example 1, where CaF2 was added at the beginning of the Si removal process (comparative example), slag forming was severe, and
The treatment had to be interrupted 10 minutes after the treatment.

After the interruption, the Si content of the hot metal decreased to only 0.43%.

On the other hand, in the case where CaF2 was added 3 minutes before the end of the treatment (example of the present invention), the desired Si removal treatment was completed without any slag forming, and 100φ of generated slag could be removed in 11 minutes of suction time. .

Example 2 In Example 2, in which CaF2 was added at the beginning of the simultaneous membrane P and S treatment (comparative example), slag foaming was severe and the treatment was interrupted 8 minutes after the treatment.

After the interruption, the P and S contents of the hot metal were each 0°073%.

It decreased to only 0.021%.

On the other hand, in the case where CaF2 was added 3 minutes before the end of the treatment (example of the present invention), there was no slag forming at all, and the desired P and S removal processes were completed, and the generated slag was removed by 90φ in 10 minutes of suction time. did it.

Example 3 Example 3 is an optimal example of the present invention, in which sintered ore and CaF2 were added together in simultaneous membrane P and S treatment.

As a result, 100% of the generated slag could be removed in 9 minutes of suction time.

[Brief explanation of drawings]

FIG. 1 is a graph showing the suction efficiency of generated slag.

Claims (1)

[Claims] 1. In the method of removing impurities by adding a treatment agent to the hot metal bath, a fluidity improver for the treated slag is added at the end of the treatment or after the treatment, or after the slag treatment by adding a fluidity improver of the treated slag from the end of the treatment to after the treatment. A method for sucking slag from molten metal processing, characterized by sucking and removing slag.