JPS60169507A - Steel manufacturing method using auxiliary lance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for making steel using hot metal that has been subjected to preliminary treatments such as de-S1, de-P, de-S, etc., and more specifically, the blending ratio of cold iron sources such as scrap. This relates to a method of making steel using hot metal that can increase the amount of steel.

Prior Art In the converter steelmaking method, which is the current method for refining hot metal, generally hot metal is tapped from a blast furnace, transferred by a hot metal pot or a topite power source, charged into a converter, and then transferred to a converter. A large amount of slag-forming agent is added to the hot metal, and oxygen is blown from the top using a lance to remove unnecessary components such as C, Si, p, and s@ from the hot metal. In recent years, this converter steel manufacturing method has been attracting attention from the viewpoints of cost reduction, quality improvement, energy saving, etc. That is, the converter steel manufacturing method has several drawbacks as described below, and improvements to it are desired.

(1) There is a lot of iron loss that escapes as iron oxide to Das I and slag.

(2) Slag-forming agents are often used, which increases the hydrogen concentration in the steel, necessitating primary refining to remove it, and causes problems such as a large amount of heat being carried away due to the slag generated in a large amount of slag. There's a problem.

(3) Since the oxygen potential of the slag is high, the alloy yield is poor due to oxygen in the slag and metal when adding the alloy.

(4) Because the removal of C, Si, P, and S are performed simultaneously in two containers, the efficiency of each reaction is low.

Furthermore, from the point of view of effective energy use, recently there have been many cases in which converter waste is recovered, but this needs to be reconsidered from the following points.

(a) When the collected waste is used for power generation, only about 20% can be used, so the energy use efficiency is low.

(b) Equipment costs are high, such as the need for dust removal equipment.

(C) Converter scum is generated intermittently and a breadfer is required.

Several proposals have been made to address some of these shortcomings and seek correction.

For example, according to Tetsu to Hagane, Vol. 89, No. 15, "Refining characteristics of juvenile slag blowing in a bottom-blown converter," when using low-K slag with the F + ' agent reduced to large + lj,
The combustion of GO generated by Etsubo in the converter is large, and by effectively utilizing the generated heat, it is expected that the scrap ratio will be greatly improved.

Furthermore, Japanese Patent Application Laid-open No. 111-58-73712 discloses that a carbon source and/or a hydrogen source is added to the converter waste in a bottom-blown converter to increase the C01H7 concentration in the converter waste. And it has been small to use the right effect. However, in this publication, oxygen (, 1
(When blowing is performed with
), /(CflCO7)] It has been shown that when X100χ) exceeds 40%, the in-furnace thermal efficiency decreases (Figure 7 of the same publication).

Improving the direction of heat transfer in the furnace, that is, the heat transfer efficiency to molten steel, means increasing the blending ratio of scrap, etc. to hot metal (i.e., reducing the charging hot metal blending ratio).
There were great prospects for this, as it would increase the freedom of choice of iron source, and also reduce costs and save energy.

In order to improve the thermal efficiency of the molten steel, a method has been proposed in which a recarburizing agent is added to the converter. come.

The present invention is a new steel manufacturing method that uses an auxiliary lance (21).
By stably maintaining the secondary combustion rate β in a range exceeding 40% and ensuring that the generated heat is transferred to the molten steel with high heat transfer efficiency, it is possible to increase the blending ratio of the cold heat source. The purpose is to

Structure of the Invention In the present invention, when refining hot metal in a refining vessel using an oxygen lance from a part of the hot metal surface, the depth L of the hot metal surface indentation due to seven blows of oxygen is 80≦L≦400 mm. Oxidation is carried out so that -) S lance and main lance are fed in combination A1 m! :This is a steelmaking method characterized by carrying out refining using an auxiliary lance that delivers oxygen so that the oxygen delivery is 1- or less than 60% of i'r.

action Next, the present invention will be explained in detail.

The reaction and heat transfer mechanism of secondary combustion will be explained based on FIG. 1. FIG. 1 is a schematic cross-sectional view of a refining vessel 1, the interior of which is covered with a refractory 2, into which hot metal (steel) 3 is charged. When the butyric acid discharged from the lance 4 collides with the molten steel 3, iron oxide is generated on a part of the molten steel surface I, and at the slag-molten steel interface, FeO+ C+Fe+CO
In the Dobe slag layer, the reaction ↑ occurs between the CO generated from molten steel and the iron oxide slag FeO.
007 reaction occurs.

As a result, the molten iron oxide and CO
A slag forming layer 5 in a gas-liquid mixed state consisting of and GO is formed. In other words, contrary to what is called secondary combustion, it occurs within this slag forming layer 5, and the heat from the high-temperature slag is supplied. ρ"6, and is transmitted to the molten steel by forced convection caused by bottom-blowing stirring by the gas blown in from the blower blade 117. Therefore, the present invention is based on this secondary combustion mechanism, and is transmitted to the molten steel by ]: From the lance 4, oxygen is sent for the purpose of removing carbon and oxidizing iron, and from the auxiliary lance 8, the purpose is to burn the CO in the slag foaming layer 5 formed in the molten copper. The main purpose is to supply oxygen.The reason why an auxiliary lance is necessary in the present invention will be described below.

That is, in order to increase the secondary combustion rate with only one lance, it is necessary to increase the lance height. However, beyond a certain range 1. When this happens, the secondary combustion rate becomes low. 1) The distance and time it takes for oxygen from the transformer to reach the molten steel becomes longer, and the slag forming layer is formed on the way, so that the oxygen effectively reaches the molten steel and causes a decarburization reaction. This is thought to be due to the fact that the probability of the generated GO reacting with oxygen in the slag forming layer and the gas phase 9 increases. As a result, only Lance has 2
Attempting to reduce the secondary combustion rate results in the following disadvantages.

(1,) When the -secondary combustion rate β is in the range β>40%, the efficiency of heat transfer to molten steel is significantly reduced. The reason for this is 2/! X,
This appears to be because combustion occurs in a part of the slag-forming layer rather than within the slag-forming layer.

(J) When secondary combustion occurs, the decarburization oxygen efficiency decreases and the blowing time becomes longer.

The inventor of the present invention has discovered that by using the auxiliary lance 8, these drawbacks can be overcome. In other words, the ten lances are set at seven points within a range that does not reduce the heat transfer efficiency, and the auxiliary lances send oxygen directly into the slag forming layer, burning the CO in the slag forming layer E' and forming the slag. By transferring heat to the melt 411 by forced convection through bottom-blown stirring, low thermal efficiency can be prevented. In addition, since it functions in conjunction with the auxiliary lance, the decarburization oxygen train -1/ in the -1 lance is kept stable without lowering, and only the secondary combustion rate is controlled. Increasing the power to the maximum level becomes the IIf ability.

The secondary combustion anti-1 core can be expressed as 10 stations of CO in general) → CO7 or high 1 flll! Then, the CO7 solution 14\ reaction begins to occur. Fire'+, ntiA degree is reported to be about 2400-2600°C (Automa-LionΔm5t).
er+Jam 5ession, March 1965, In
terna-tional Cant, on Iro
n and 5teel making). Therefore, the temperature inside the slag forming layer increases to 2,500 yen due to the combustion of CO.
It is thought that the temperature will be around °C. From this temperature, secondary combustion 3
J'l-j< is 1.Equitically speaking, about 60% of 1 odor is considered to be the maximum limit.

Next, the reason for the numerical limitation of the present invention will be explained.

) For Nirans, it is necessary to increase the secondary combustion rate.
- The depth L of the dent in the hot water surface due to blown oxygen should be 80≦L≦400mm (preferably. When expressed in terms of depth, that is, the depth of the dent in the hot water surface, L<8.
If the condition is 0 mm, more CO gas burns in the 11 part gas layer than in the slag forming layer, so the specific gravity of radiation heat transfer from the slag body becomes higher than that of convection heat transfer in the slag forming layer. V has a low toe.

On the other hand, lower the lance height to reach 400m.
Under the conditions of m, secondary combustion hardly occurs and jM
'+ It becomes the same as converter operation. Furthermore, under these conditions, spitting and dust generation lt+ also increase, which becomes a factor in deterioration of yield.

From the above-1, the oxygen supply conditions for 1:, 5;
m is i[/like.

The secondary combustion rate β due to this transformer alone is 40% as described above.

Next, we will discuss how to reduce the amount of oxygen supplied by the auxiliary lance. Regarding the secondary combustion rate, as mentioned above, 6 is derived from the 'P-FJi theory.
The limit is 0% culm 1;\. In addition, the relationship between the secondary combustion -V and the amount of oxygen sent from the auxiliary lance is (1; 0:, : oxygen sent from the auxiliary lance η1, F
o7); Amount of oxygen sent from the lance, β' Overall secondary combustion rate (
χ), β, represents the secondary combustion rate (χ) when only the 1' lance is used. ), and under the 1-1-lance conditions, 0 β≦
Since it is 40%, the amount of oxygen sent from the auxiliary lance is 1 at most.
．． It is sufficient to secure 60% of the lance oxygen supply 111.

Even if tiβ=0%, β'-60%, Fo; /
Fo7-0.6 (80%); β-40%, f3'=8
0% throat, Fo', /Fo2 ” o, 143 (1
4.3%), and Figure 2 illustrates this relationship. In other words, the IZ limit of FO'y /Fo7 is 60
% and more than that; even if oxygen is supplied, the secondary combustion rate is
Lee 4, high heat transfer efficiency cannot be obtained either. Therefore, it was decided to supply oxygen in such a way that the amount of oxygen supplied by the auxiliary lance was 60% or more of the amount of oxygen supplied by the main lance at a ratio of 1:1.

Note that it is preferable to use a plurality of auxiliary lances.

Next, the present invention will be explained in more detail with reference to examples.

Example 1 The operations shown in Table 1 were carried out using No. 10 in a furnace. As a result, with the conventional method, the depth of depression caused by the main lance was 70 m.
When the diameter is 100 mm, the secondary combustion rate is lower and the heat transfer efficiency is also lower, so the amount of scrap melting abrasive is reduced. In addition, L = 1010011I・constant, and the conventional method in which the amount of oxygen sent from the auxiliary lance is O, and 22ONm'/
In a comparison of the method of the present invention for H (oxygen to soil ratio of 14.7%), the secondary combustion rate of the present method is 40% to 58% compared to the conventional method, which is 18%, almost as per theory. It was also amplified, and the scram ratio increased by 6z.

Example 2 As a result of carrying out the operations shown in Table 2 using 90 in a furnace,
The secondary combustion rate increased by 13% from 18% to 32%, and the scrap ratio increased by 5%.

Effects of the Invention As described above, the present invention is an industrially significant invention that can lower the hot metal blending ratio and increase the degree of freedom in selecting iron sources.

Table 1 Table 2

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the refining vessel. FIG. 2 is an explanatory diagram of the present invention, and is graph 4) showing the relationship between the secondary combustion rate and the feed ratio. l... Refining container, 2... Refractory, 3... Molten steel, 4
...-Main Lance, 5...Slagf-Ming Layer...6
... φ blade supply pipe, 7 ... Bottom blowing waste blowing blade L-J, 8
... Auxiliary lance, 9..." Two-part scum phase. Patent Delta 1 Applicant New 11 Wooden Steel Co., Ltd. Agent Masao Ito, Patent Attorney Figure 1 Figure 2 73 (%) May 9, 1980 Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of Case 1988 Patent Application No. 25179 2, Steel manufacturing method using an auxiliary lance in the name of the invention 3, Relationship with the amended person's case Patent applicant address 3-6ff, Otemachi 2-chome, Chiyoda-ku, Tokyo Name (
665) Shin 11 Wooden Iron Co., Ltd. Representative Takeshi 1) Yutaka 4, Agent 103 Address 2-2-1 Nihonsho, Chuo-ku, Tokyo Sokyodo Building (
Gofukubashi) Detailed explanation of the invention in the specification column 6, contents of Supplement iE (1) Specification *Page 4, line 1 I] "Converter scum" is changed to "111"
"It's a human hearth," Liu said. (2) Page 5, line 2, “1’s cold and heat 0: (” is changed to “l Zentetsu.
:Mi' and t1' +1-.

Claims (1)

[Claims] When refining hot metal in a refining vessel using an oxygen lance from above the hot metal surface, -1- A main lance that supplies oxygen so that the depth L of the hot metal surface depression due to blown oxygen is 80≦L≦400 mm. A steelmaking method characterized in that refining is carried out using auxiliary lances that supply oxygen such that the total amount of oxygen supplied is 60% or less of the amount of oxygen supplied by the main lance.