JPS6056201B2 - Hot metal processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot metal treatment method, and particularly aims to propose the development results of an advantageous means for removing impurities.

The method for treating hot metal according to the present invention is particularly advantageous in application to the following steelmaking and refining process, and in this case, it is also useful as a pretreatment of hot metal for the refining.

In recent years, standards and requirements for steel components and materials have become extremely strict, and as a result, impurities in steel, especially phosphorus,
There is a lot of interest in how to remove sulfur.

On the other hand, there are strong calls for stabilization of converter blowing, improvement of iron yield, and low-cost operation. Under these circumstances, it has become necessary to review ironmaking and steelmaking methods. For stable converter operation, it is desirable that the charged hot metal has a constant composition. Therefore, it is desirable to perform dephosphorization, desulfurization, and desiliconization before charging into the converter. It is conceivable to desulfurize the carbon at a point when the C content is high and the oxygen potential is low, and then bring it into an oxidized state to perform desulfurization and dephosphorization treatments.

This type of process is usually a combination similar to the multi-stage semi-continuous steel manufacturing process, which causes large heat loss and has many problems in terms of energy conservation. In other words, the purpose of such hot metal pretreatment is to remove phosphorus, sulfur, and silicon, but it is undesirable in terms of heat loss and cost to treat each reaction separately. It is. Therefore, in order to perform these reactions simultaneously, we focused on a bottom-blown converter.

The bottom-blown converter has excellent agitation and can advantageously promote the reaction between metal loose lags, so it has good thermal efficiency and can easily switch between pure oxygen gas and inert gases such as nitrogen or argon whenever necessary. Since this method can be used, we considered applying it to the preliminary treatment of hot metal, and after repeated experiments, we established the method. This invention desilicates hot metal in a bottom-blowing converter or similar blowing/refining vessel by mainly bottom-blowing oxidizing gas, then switching to bottom-blowing non-oxidizing gas to perform desulfurization treatment, and then This hot metal treatment method consists of sequentially proceeding with the process of switching to oxidizing gas again and using it as a carrier gas for blowing and bottom blowing it together with a dephosphorizing agent to perform light decarburization and dephosphorization.

According to this invention, a predetermined C can be achieved by the hot metal treatment according to the method.
After adjusting the composition to , Si, Mn, P, and S, the slag is discharged and charged directly into a bottom-blowing converter (Q-BOP furnace) or a normal top-blowing converter for slag-free blowing. Can be done.

Although the process of the present invention is advantageously carried out using a bottom blowing converter as described above, it goes without saying that similar hot metal vessels having the same blowing function may be used.

The outline of the experiment using a Q-BOP reactor with a reactor capacity of 5 tons is as follows. After the blast furnace hot metal is charged into the Q-BOP furnace, pulverized lime is blown in through the bottom tuyere with pure oxygen gas to raise the temperature and desiliconize it.

At this time, it is not necessary to use lime, but in order to prevent spitting and increase the efficiency of the subsequent desulfurization process, the use of lime showed better results. After this desulfurization process is completed, the carrier gas is switched to N2, and CaO is blown into the furnace through the bottom tuyere to perform desulfurization. In addition, Cac2 is used in this desulfurization process.
It is necessary to remove the slag when using it. After that, the gas is switched to oxygen again and decarburization and dephosphorization are carried out while blowing in a dephosphorizing agent. Through this process, C is 1-3%, Si is trace, Mn is
is in the 0.2% range and P is 0.02-0.03% or S
Results were obtained in the 0.01% range. The hot metal that has undergone such treatment may be charged into a mountain converter or a Q-BOP furnace and subjected to only the decarburization process. A schematic diagram of the case where hot metal preliminary treatment is carried out using a bottom blowing converter using the above method is shown in FIG.

An embodiment according to the above process will now be described. Hot metal tapped from a blast furnace was charged into a 5-ton bottom blowing converter without desulfurization.

The charging amount was 5.5 tons, and the hot metal temperature at the time of charging was 130
0℃, hot metal components are C/4.5%, Si/0.6%, Mn
/0.35%, P/0.117%, and S/0.030%. First, in the desiliconization process, the oxygen supply rate is 2 NI/TO per minute.
CaO was blown at 15k9/Ton with oxygen of n, and this treatment resulted in C/4.2%, Si/0.01%, Mn/0.
30%, P/0.082%, S/0.030%.

Switch to blowing gas N2 and 2N/Ton nitrogen per minute
When aO was injected at 10k9/Ton, the above components were C/
4.2%, Si/0.01%, Mn/0.31%, P/
It became 0.082% and S/0.007%. then 0 again
, Switched to gas CaO7O%, iron ore 20%, Na2C
A dephosphorizing agent of QlO% was added at an oxygen flow rate of 20k9/TOn per minute.
It was injected with 5Nd/Ton.

The final composition after hot metal treatment obtained by this is C/3.8
%, Si/TracelMn/0.20%, P/0.0
It was 17% and S/0.006%. Note that the temperature at this time was 0.degree. In this way, the variation in the hot metal components is reduced, which not only makes it possible to stabilize the subsequent converter blowing process, but also because the contents of the hot metal other than C have already reached the predetermined values. In this case, only decarburization needs to be performed, and at this stage there is almost no need to add CaO to the converter blowing, and even if it is added, it will be less than 10 kg/TOn, so the components that conventionally escaped into the converter slag can be removed. The iron yield improves and the life of the refractories increases by the amount that is eliminated. Although the simultaneous dephosphorization and desulfurization method using soda ash has recently been attracting attention for the hot metal pretreatment described above, in this case, 30k9/TOn of soda ash is required, so even compared to this method, the present invention is inferior. It has many advantages such as low raw material cost and low heat loss.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a steelmaking process in which the present invention is applied to hot metal pretreatment.

Claims (1)

[Claims] 1 The hot metal in a bottom blowing converter or similar blowing vessel is subjected to desulfurization treatment mainly by bottom blowing with oxidizing gas, then switched to bottom blowing with non-oxidizing gas to perform desulfurization treatment, and then oxidized again. A hot metal processing method characterized by sequentially proceeding with the process of switching to a carbonaceous gas and using it as a carrier gas for blowing and bottom-blowing it together with a dephosphorizing agent to perform light decarburization and dephosphorization.