JPS59185715A - Pretreatment of molten iron - Google Patents

Abstract

PURPOSE:To shorten the treatment time, to prevent a temp. loss and to reduce a load on the operation of a converter by bringing dropping molten iron into contact with a flux for refining in the 1st vessel while discharging molten iron into the vessel, and successively discharging the pretreated molten iron into the 2nd vessel. CONSTITUTION:While discharging molten iron 3 from a vessel 1 such as a torpedo car into the 1st vessel 2, a flow 3' of the dropping molten iron is brought into contact with a flux 4 for refining, and the molten iron is pretreated in the vessel 2. The pretreated molten iron is successively discharged into the 2nd vessel 5. At this time, a weir 6 is placed in the vessel 2 to prevent slag from entering the molten iron to be discharged. Furthermore a lower weir 6' may be placed as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pre-treating hot metal. Traditionally, high quality steel has been required, and in order to achieve high quality, in addition to converter blowing, preliminary treatment of hot metal has become essential. It is well known that this is being done. In particular, desulfurization of hot metal has been actively carried out to produce low sulfur steel, and recently active treatment methods for Si and P have been actively developed.

For example, in the out-of-furnace molten iron desulfurization method, injection is performed in the pig iron mixer car or hot metal pot.

Alternatively, a stirring method is used in which a desulfurizing agent such as soda ash, quicklime, or carbide is brought into contact with hot metal.In the desiliconization method, iron oxide, quicklime, etc. Similarly, dephosphorization treatment is carried out by adding a dephosphorizing agent such as quicklime or soda ash to hot metal along with an oxygen source and stirring.

These methods require desulfurization to occur in a near-atomic atmosphere due to the reaction mechanism.
Since desiliconization and dephosphorization are promoted in an oxidizing atmosphere, it is difficult to carry out simultaneous treatment, and desiliconization and dephosphorization reactions under the same conditions also have a tendency for desiliconization to occur preferentially over dephosphorization. In terms of work efficiency, the slag generated during the desiliconization process must be removed before the dephosphorization process takes place, resulting in a long process time and a drop in temperature during the process.

The present invention has been made to advantageously solve these drawbacks, and in the preliminary treatment of molten AC, the process is devised and
Continuous processing makes it easier to remove slag, shorten processing time, prevent temperature loss, prevent slag from flowing into the hot metal, and improve refining handling from the blast furnace to the converter.
The purpose is to reduce the operating load of the converter by charging hot metal into the converter at high temperatures. Its constituent features relate to a hot metal pretreatment method characterized by discharging the hot metal into a first container, bringing the falling hot metal into contact with refining flux within the container, and discharging the hot metal into two containers in sequence.

That is, in the present invention, for example, hot metal is directly transported from the blast furnace to the first
It is discharged into a container or treated during the transportation process from a blast furnace to a converter, for example, using a mixer car, a ladle, etc., and a ladle that receives pig iron from a blast furnace and then charges it to a steelmaking furnace. During the weighing process, the falling energy of hot metal is effectively used as stirring force to perform refining processes such as dephosphorization, desiliconization, and desulfurization.

To describe this more specifically with reference to the drawings, as shown in the figure, while discharging hot metal 3 from a container 1 (such as a pig iron mixing car) to the first container 2, the falling flow 3' of the hot metal and the refining flux 4
The hot metal is brought into contact with the first container z, and the hot metal is pre-treated in the first container z, and the treated hot metal is sequentially discharged into the second container 5.

In this way, the process of discharging hot metal into the first container 2, processing there, and then discharging it to the second container 5 is performed continuously, and a major feature is that the pretreatment is performed while discharging the hot metal. It is. In the first container 2,
As shown in the figure, it is preferable to provide a weir 6 to prevent slag (flux) from being located in the upper part of the second container 5, thereby preventing slag (flux) from being mixed into the discharged hot metal. Also, just before the end of dispensing, slag (flux) is deposited at a position lower than the lower end of weir 6.
Even when the surface reaches the surface, by slightly tilting the first container 2, mixing of slag (flux) can be prevented to a minimum.

The drawing shows, as an example, an upper weir 6 that restricts the movement of slag (flux) floating on the hot metal. This is to ensure sufficient contact between the flux and the refining flux and to prevent the slab (flux) from being mixed into the discharged hot metal.The position, shape, number, etc. of the flux are determined as appropriate depending on the processing. Therefore, depending on the processing target, an upper weir 6' may be provided upright from the bottom of the first container as shown by the dotted line.

In the preliminary treatment of the present invention, dephosphorization, desiliconization, and desulfurization may be performed in accordance with the component target, and the treatment agent (refining flux) used in this case can be any one that has been used up to now. For example, as a dephosphorizing agent, CaO1CaF2, Ca
A mixture of 0 sentence 2, calcined flux, Na2 CO3, etc. can be used together with a metal oxide (iron oxide, etc.) as an oxygen source, and sintered ore, mill scale, iron oxide, etc. can be used as a desiliconizing agent. can. Furthermore, by adjusting the flux consumption rate, desiliconization and dephosphorization can be performed simultaneously. As a desulfurizing agent, CaC2, CaO, Na2 GO
3 grade flux can be used.

In order to bring the falling hot metal into contact with the refining flux, methods for charging the refining flux into the first container include dividing charging, batch charging, and continuous charging. In addition, a good effect can be obtained if it is placed in the position where the hot metal flow falls.

Next, the present invention will be explained based on examples.

Example 1 Hot metal (component weight%: Ct, 82, Si
O, 43, Mn O, E15, Po, 08?
, So, 0032 residual Fe and impurities, hot metal temperature 138
0°C) in the first container (depth 1500mm, length ?
OCIOmm, width 2000mm, height 80mm in the center of the container
At the same time, flux (component weight %: Ca070.
When 20 kg/l-pig of GaF230) was charged together with mill scale 30 kg/l-pig (split injection every 3 minutes), hot metal (component weight %: C4, 52, SiO, 09
, Mn0038, Po, 003, So, 0021
, residual Fe and impurities, hot metal temperature 131O°C),
It exhibited excellent dephosphorization and desiliconization effects, had a small temperature drop, and the amount of slag in the second container was as small as 20 mm in thickness, so it could be used in the next step of steelmaking and refining without any problems.

Example 2 Hot metal 150 was received in a pig iron mixing car as in Example 1 (component weight %: C4,9B, SiO,51, MnO,52,
PO, +05, So, 044, residual Fe and impurities, hot metal temperature 1350 ° C) were discharged at a rate of 15 t/min using the first container, and CaO was used as a flux.
When 210 kg/l-p+g was charged (in bulk), hot metal in the second container (component weight %: C4,8[
i, SiO, 48, MnO, 50, Po, 100,
So, 00? , residual Fe and impurities, hot metal temperature 1300°C) showed an excellent desulfurization effect.

Example 3 Hot metal having the same composition as in Example 2 (hot metal temperature 1410°C) was discharged into the first container at a rate of 10 t/min, and a mill scale of 23 kg/l-pig was continuously introduced. Component weight %: C4,8?, SiO;07
, Mn0023, PO, O? '2, SO,034
, residual Fe and impurities, hot metal temperature 1365°C) showed an excellent desiliconization effect.

In both examples, the amount of slag in the second container is halved compared to the conventional method of discharging hot metal, and the slag remaining in the first container is moved to the slag pit without leaving the container. It was easy to remove the slag.

In addition, as a comparative example, let us consider the case where hot metal is pretreated in a normal multi-stage process.The process involves receiving the hot metal in a mixer car, desulfurizing it in the mixer car, removing the slag, and transferring the hot metal to a ladle to desiliconize it. When carrying out slag, dephosphorization treatment, and then discharging to the hot metal charging pot, the treatment time alone takes 1 to 2 hours, even if transportation between treatment facilities is not included, and the final The processing temperature also decreases depending on the processing time.

As described in detail above, according to the present invention, significant total effects such as simplification of treatment steps, reduction of treatment time, prevention of temperature loss, and reduction of load on converter operation can be obtained.

[Brief explanation of drawings]

The drawing is an elevational view illustrating an embodiment of the present invention. 1... Container, 2, φ, first container, 3... Hot metal, 3'
... Falling flow of hot metal, 4 ... Flux for refining, 51
@ @Second container, 6.6'...Weir. Patent applicant Nippon Steel Corporation

Claims (1)

[Claims] A hot metal pretreatment method characterized in that while the hot metal is being discharged into a first container, the falling hot metal is brought into contact with a refining flux in the first container, and the hot metal is sequentially discharged into two containers.