JPH02200716A - Method for dephosphorizing molten iron - Google Patents

Abstract

PURPOSE:To dephosphorize a molten iron in a short period of time by imparting the bottom blowing stirring force of gaseous N2 from a bottom blowing tuyere to the molten iron at the time of blowing oxygen in the presence of basic molten slag and subjecting the molten iron to an oxidation dephosphorization treatment. CONSTITUTION:The molten iron 2 is put into a converter 1 having the bottom blowing tuyere 4 and a top blowing lance 7 and inexpensive steel scrap 3 is added to the molten iron and is melted. Powdery CaCO3 in a tank 5 is blown as a flux together with the gaseous N2 from the bottom blowing tuyere 4 into the converter during this melting and powdery CaO, CaF2 and iron ore in a hopper 6 are simultaneously charged into the converter to form high-basicity molten slag. Gaseous O2 is then blown from the top blowing lance 7 into the converter. The stirring force epsilon defined by equation I is applied to the molten iron 2 by blowing of the gaseous N2 from the bottom blowing tuyere 4 to attain 1.2 to 10kw/t in this case; in addition, the total oxygen feed rate Vo2 given by equation II is adjusted by the lance 7 to 0.8 to 2.5Nm<3>/t/min, by which the dephosphorization treatment is completed within the extremely short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hot metal dephosphorization method that shortens dephosphorization time and improves processing efficiency in hot metal pretreatment.

[Conventional technology]

Conventional techniques for dephosphorizing hot metal include, for example, Japanese Unexamined Patent Publication No. 62i09911, No. 109912, 1.
There are techniques disclosed in publications such as No. 09913.

[Problems to be Solved by the Invention] By the way, the above-mentioned Japanese Patent Application Laid-open No. 109911/1983 discloses that the hot metal has a stirring force of =0. ．． 3-1. It is a technique of dephosphorizing by giving I KW/l, and there are no regulations regarding the total oxygen delivery rate, etc., and it is not intended to improve the efficiency of dephosphorization.

Although JP-A-62-109912 stipulates the total oxygen delivery rate, etc., it does not mention the stirring force applied to the hot metal.

Furthermore, JP-A-62-109913 aims to improve the efficiency of the pretreatment by dividing the pretreatment of hot metal into a desiliconization period and a dephosphorization period and specifying the stirring power and oxygen supply rate of the hot metal. The stirring force 2 is as small as 0.3 to 1.1/l, and like the above technique, it is not intended to improve the efficiency of dephosphorization.

The present invention has been made in view of the above problems, and provides a method for dephosphorizing hot metal that achieves shortening of dephosphorization time and improves the efficiency of preliminary treatment.

[Means for Solving the Problems] The present invention provides a bottom-blowing stirring force to be applied to the hot metal defined by the following formula (1) when dephosphorizing the hot metal by adding a CaO-containing substance and an oxygen source to the hot metal. 2 to 1.2~10KW
/l, total oxygen delivery rate Vo! 0.8~2.5N+1f/l
/mir+.

・・・・・・(1) Blowing gas! (1!/clean in), hot metal temperature (0K), hot metal mold lid (1), blowing depth (m), gas temperature before blowing (0K) Voz = (total oxygen consumption unit 50 □ gas conversion Nr + Z / 1)
/(refining time, m1n).

[For production]

When dephosphorizing hot metal, a fine powder of a CaO-containing substance is blown into the hot metal, or a lump of a CaO-containing substance is added to the hot metal, and a solid oxygen source such as iron ore and gaseous oxygen are added. The total oxygen consumption rate supplied here is the sum of the 02 source supplied as a gas and the 0□ present in the raw material as oxides, etc., and this is converted into the amount of gaseous oxygen, and the total oxygen delivery rate V
By setting O2 in the range of 0.8 to 2.5 Nrrf/l/win and blowing in a gas containing these or a gas generating substance, dephosphorization is carried out while maintaining the bottom blowing stirring power i in the range of 1.2 to 10 KW/l.

Figure 1 shows the relationship between stirring force ε and total oxygen delivery rate Voz,
It is a drawing showing the appropriate range.

When i is less than 1.2 KW/, the stirring force is weak relative to 0□ supply, and therefore FeO in the slag increases. Also 2
However, if the stirring force is 1 OKm/ll, the stirring force is too strong, a large amount of splash occurs, and the loss of Fe content increases, which is not preferable. Therefore, 2 was limited to 1.2 to 10 W/l.

When Voz is less than 0.8 im/l/aiin, 0. Since the stirring force is strong relative to the supply, the dephosphorized P2O is reduced and becomes P again. Also, Vot is 2.5Nrrf/l
If /win is exceeded, 0□ becomes excessive, and in this case, the membrane treatment time is shortened, but since the supplied CaO etc. are not completely dissolved, a large amount of dephosphorizing agent is required, which becomes uneconomical. Therefore, VO2 was limited to 0.8 to 2.5 Nrr'r/l/win.

(Example〕 Embodiments of the present invention will be described based on the drawings.

FIG. 2 is a side cross-sectional view of the converter equipment. First, 16 ot hot metal 2 containing 5i-0.34% which has not been subjected to desiliconization treatment and 5i-0.34% hot metal 2. The OL scrap 3 was charged into the converter l, and the flux (CaCOz) in the blow tank 5 was blown to 0.09 Nn (/l/cod iri) from the bottom blowing tuyere 4.
．． It was continuously blown into the hot metal 2 for about 8 minutes at a rate of 7 kg/l. By this blowing, the no.l during dephosphorization and desiliconization treatment is
H? * ibki”i = 4.5 XW/lc hold t,
k. , ゎ is co! due to the decomposition of CaC0, shown in (2) 2 below! This is an example of securing stirring energy by utilizing gas generation.

CaC0,-+ CaO+ C(h ・・
...” (2) At the same time as the blowing started, the flux in the hopper 6 (lumped CaO-18, 2 kg/l, lumped CaFzf, 7 kg/l) and iron ore 16.7 kg
8 was put into hot metal 2. Also, at the same time as the Franks blowing started, a 2.0Nr oxygen gas jet was applied via lance 7.
The film was sprayed for 8 minutes at a ratio of rr8/#lin to remove phosphorus from the silicon film. In this case, Voz is 1.6Nrrr
/l/1IIin.

FIG. 3 shows changes over time in the hot metal components of this example.

As shown in the figure, the phosphorus concentration in the hot metal decreased from 0.095% to 0.019% in 8 minutes from the start of blowing.

The hot metal temperature before and after treatment is 1355°C and 1355°C, respectively.
There was almost no change at 360″C.

FIG. 4 shows a comparative example of changes in hot metal components over time.

In the comparative example, SiO,,3, which was not subjected to desiliconization treatment
157 tons of hot metal containing 4% 2 and 5. Ot's Scrap 3
was charged into the converter 1, and 0.09Nrr was released from the blow tank 5.
Dephosphorization flux C with f/l/win N2 gas
7 kg/l of aO3 was injected. At the same time as dephosphorization Franks injection starts, oxygen gas jet x7 is released from lance 7.
．． Spray at a rate of 8Nrrf/l/mlri for 12 minutes, and at the same time dephosphorization flux in hopper 6 (lumped Ca06.7 kg/l, lumped CaFz 2.Ok
g/l) and 8.3 kg/l of iron ore were charged into hot metal 2. In this comparative example, Vor=0.9Nrrf/l/wi
However, it took 12 minutes to reduce the phosphorus concentration to 0.020% or less. Also, before and after processing? 8 pig temperatures are 1 each
375°C and 1345°C.

In the present invention, as a method of maintaining the stirring force i, N,
Ar may be blown in from the lance 7 or the tuyere 4, or other means such as blowing in a gas generating substance may be used. Furthermore, in order to keep Vo in the optimum range, it is possible to adjust the addition rate of 0□ gas or to continuously add oxidizing substances such as iron ore. Can be supplied via.

[Effects of the Invention] As explained above, the present invention can shorten the desiliconization and dephosphorization treatment time to about 8 minutes, as shown in the embodiment, by controlling the stirring force of hot metal and the total oxygen feeding rate. Therefore, the temperature after dephosphorization can be maintained at 1290° C. to 1350° C. without causing unnecessary decarburization, and dephosphorization can be stably performed to a low concentration. In addition, this method does not require equipment costs because it can be carried out using a converter, bead car, pot, etc. as the reaction vessel, and the consumption of refractories etc. is reduced by reducing heat loss and reaction time. The pretreatment efficiency can be improved by accelerating the reaction.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the appropriate range of dephosphorization treatment, Figure 2 is a side sectional view of an example of a converter equipment, Figure 3 is a graph showing changes in hot metal components over time in Examples, and Figure 4 is a comparative example. It is a graph showing the change over time. 1... Converter, 2... Hot metal, 3... Scrap, 4
...Bottom blowing grain 1.5...Blow tank, 6...
Hopper, 7... Lance agent Patent attorney Masamitsu Aki Sawa and 1 other person π1 figure Seri 5 figure VO2 (Nm/l/m1n) 7i'' figure ellipse time P81 (minutes)

Claims (1)

[Scope of Claims] When dephosphorizing the hot metal by adding a CaO-containing substance and an oxygen source to the hot metal, the bottom blowing stirring power ■ defined by the following formula (1) is 1.2 to 10 KW. /t, total oxygen delivery rate Vo_2 0.8 to 2.5Nm^3/t/min
A method for dephosphorizing hot metal, characterized by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) Here, Q_g: Blowing gas amount (Nl/min), T: Hot metal temperature (°K), Wm: Hot metal weight (t), Ho: Blowing depth (m), T_g; Gas temperature before blowing (°K) Vo_2 = (total oxygen consumption unit, O_2 gas equivalent Nm^3/
t)/(refining time, min)