KR940009670B1 - Molton metal cooling method - Google Patents

Abstract

A) if a measured temp. of molten steel at 1-2 min. before blowing-in ends is higher than a target value, a falling amount of temp. is determined; B) the direct reduced steel of which Fe/all Fe ratio is over 85 % is injected to molten steel in the amount of within 10-20 kg per ton; C) molten steel is cooled at the blowing-in end.

Description

Molten steel cooling method at the end of converter

1 is a graph showing the change in the [O] _f value according to the elapsed time after the termination of the blow after the cooling by the end of the converter blow.

The present invention relates to a method of cooling molten steel by injecting a coolant at the end of the blowdown at the time of blowing the molten iron.

The molten iron from the blast furnace is charged into the converter through a preliminary treatment step, and the charged molten iron is blown (refined) using the heat generated from the sensible heat of the molten iron and oxygen injection. The blowing process is divided into electrical, middle, and late stages, the end of the blowing is required to precisely control the molten steel component and temperature.

Conventionally, by measuring the sub-Lance at the end of the blowdown for accurate target hitting of the components and temperature of the molten steel at the end of the converter blowdown, the final blowdown pattern is set. At this time, when the temperature is higher than the target value (approximately about 1630-1750 ° C.), a coolant is introduced into the converter. In this case, iron ore, sintered ore, and scrap chooper are mainly used as the coolant.

However, in the case of scrap chopper, hot rolled coils, closed plates, etc. are used by scraping iron so that they can be introduced into the converter through the hopper, so that the cost burden increases, and iron ore or sintered ore is generally used.

However, when iron ore or sintered ore is used as a coolant at the end of the blow (usually 2 minutes before the end of the blow), foaming of slag occurs, and the end point of the steel (hereinafter referred to as [O] _f ) and the temperature is changed to a sub-lance after the blow is finished. There is a problem that it is difficult to secure accurate data during measurement. In particular, the steel [O] _f the ryeonhu take not only very important to predict the final composition of the molten steel is an important factor governing the recovery of deoxidizer and alloy steel used in steel, [O] if _f measurement inaccuracy of the molten steel There is a problem in that it is difficult to determine the component and thus inhibit the component unidentified tapping (direct tapping).

Accordingly, the present invention has been proposed to solve the above problems, and when the temperature of the end of the converter blowdown of the molten iron is higher than the target value, direct reducing iron directly reduced iron ore into the molten steel at the end of the converter blows to cool the molten steel in the converter. In order to provide an accurate method for measuring molten steel at the end of converter blowdown, the objective is to provide accurate measurement.

Hereinafter, the present invention will be described.

The present invention measures the temperature of the molten steel 1-2 minutes before the end of the converter blasting when the molten iron is blown to determine the temperature drop when the molten steel temperature is higher than the target value, the ratio of the amount of metal Fe and the total Fe (hereinafter, "acceleration rate" The present invention relates to a method of cooling molten steel at the end of converter conversion by injecting directly reduced iron having a degree of greater than 85% into molten steel in a range of 10-20 kg / TS.

In the present invention, when the reduced iron is directly introduced into the molten steel as a coolant, the reaction time between the directly reduced iron and the molten steel is short and the temperature and component gradients become unstable when the time is within 1 minute before the end of the blow. In this case, since the furnace reaction becomes long and it is difficult to estimate the accurate furnace situation, it is preferable to add the reduced iron directly for 1-2 minutes before the end of the blow.

When the metallization rate of the direct reduced iron is 85% or less, since the oxygen content in the direct reduced iron increases and generates bubbles by reacting with carbon in the molten steel, the metallization rate is preferably set to 85% or more.

If the input amount of the direct reduced iron is less than 10kg / TS, the temperature control effect of the molten steel is insufficient, and if it is more than 20kg / TS interferes with the converter operation, the input amount of the direct reduced iron is preferably set to 10-20kg / TS. Do.

When directly reducing iron is added to molten steel, 0.7 to 0.9 kg of direct reduced iron is used to cool 1 ton of molten steel at 1 ° C. In addition, unlike the case of using sintered or iron ore when using the direct reduced iron as a coolant, not only does not cause slag forming, but also has a lower cooling capacity than that of sintered or iron ore, so that the temperature of molten steel can be precisely adjusted, and the amount added Because of this, the final tapping volume also increases.

Hereinafter, the present invention will be described in detail through examples.

Example 1

After the completion of the 300Ton converter, the coolant adjusted as shown in Table 1 was added to the molten steel in the converter as shown in Table 2, and the converter was blown, and the cooling capacity was calculated by measuring the temperature of the molten steel. Is shown in Table 2 below. In addition, the amount of [O] _f was measured at 1 minute intervals after the completion of the blowing, and the measurement results are shown in FIG.

TABLE 1

TABLE 2

As shown in FIG. 1, when iron ore or sintered ore is used as a coolant, slag foaming is caused by CO gas generated by reaction of oxygen of Fe ₂ O ₃ in iron ore or sintered ore with [C]. ), It is not possible to obtain an exact value of [O] _f if a certain time (about 6 minutes) has elapsed and it is also difficult to apply an endpoint component model that is normally set as a function value by [O] _f . It can be seen that.

On the contrary, in the case of using direct reduced iron prepared by directly reducing iron ore as in the present invention as the converter coolant (Invention Examples (a) and (b)), the metallization rate of the directly reduced iron is high and the amount of CO gas generated is low, and the scrap chopper It can be seen that the accurate [O] _f value can be obtained within a short time (1-2 minutes) which is almost the same level as (Scrap Chopper), and because the cooling capacity is low, a large amount can be used to increase the tapping amount. have.

Claims (1)

When molten iron current is blown, the temperature of molten steel is measured 1-2 minutes before the end of the current drilling, and when the molten steel temperature is higher than the target value, the temperature drop is determined, and the ratio of metal Fe and total Fe (metalization rate) is 85% or more. Method of cooling the molten steel at the end of the converter blowdown, characterized in that the direct reduction iron is put into the molten steel in the range of 10-20kg per ton of molten steel to cool the molten steel at the end of the converter blowdown.