JPS58151410A - Molten iron desiliconizing agent - Google Patents

Abstract

PURPOSE:To pretreat molten iron efficiently and simply by adding a specified amount of CaCO3 to scale or the like to obtain a molten iron desiliconizing agent having a specified grain size and by adding the agent to the molten iron during passing through an iron discharging spout. CONSTITUTION:At least 8-21wt% CaCO3 is added to an iron oxide-base material such as scale, ore or minus mesh from a sintering stage to obtain a molten iron desiliconizing agent composed of grains. All the grains have <=1.0mm. grain size, and grains having 0.1-1.0mm. grain size occupies >=50wt% of all the grains. Molten iron discharged from a blast furnace is desiliconized with the desiliconizing agent during passing through an iron discharging spout. Since slag formed by the desiliconization has high flowability, it can be removed easily through a slag discharging spout placed at the downstream side of the iron discharging spout.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot metal desiliconizing agent for removing silicon from hot metal tapped from a blast furnace while passing through a tap sluice, and particularly to a hot metal desiliconizing agent that has a good desiliconizing effect and a good slag removal property. This invention relates to a desiliconizing agent that produces good desiliconization slag.

In the blast furnace ah! There is a large amount of #l in the hot metal! l1
1 is present, so it is removed by oxidation and heated to a predetermined temperature K.
Mm operation using a converter, etc. is being carried out for the purpose of N ink.

However, in general converter@refining, the purpose is often to dephosphorize in addition to decarburization, and for that purpose, a large amount of slag-forming agent is input and the CaO
Amount of slag produced by 1 b x 1 ton of bath salt m 17104) - 160 k
gK may also be affected. This kind of steelmaking slag is so to speak *
Since it is an II product, many ways to reuse it are being considered in #J, but at present it has reached saturation. Therefore, in addition to the development of application development technology, the basic solution is to suppress the amount of steelmaking slag generated, and desulfurization during dephosphorization is carried out by cutting it from the converter N4#.

There is a shift toward focusing converter refining exclusively on decarburization and temperature raising purposes. This kind of refining not only makes it possible to reduce the yield of slag, but also eliminates the problem of rephosphorization and resulfurization from slag*, and also improves the accuracy of the target carbon content. Steel has the advantage that it also makes it easier to produce ultra-low carbon steel.

Due to the above-mentioned circumstances, it is becoming more and more common to carry out preliminary treatment such as dephosphorization11 (vh so-called furnace refining) prior to refining in a converter, etc. However, there are still desiliconization, dephosphorization, desulfurization, etc. These metallurgical reactions each have different common reaction conditions, and if they are performed all at once, there will be a lot of trouble. Silica reaction 510
When 2 is generated, Ca added as a dephosphorizing agent or desulfurizing agent
The basicity indicated by the ratio to O (CaO/8402) decreases, and desulfurization during dephosphorization becomes insufficient. Therefore, we have no choice but to introduce a large amount of CaO, which leads to an increase in slag formation), which leads to the above-mentioned Seki 11 again! treat For this reason, a method is being considered in which desiliconization is separated from desulfurization and phosphorization, and hot metal is first subjected to desiliconization treatment to remove desiliconization slag, followed by dephosphorization and desulfurization treatment. However, in this method, the out-of-furnace refining is performed in multiple steps, which makes the work complicated and has low productivity. There was a problem in that the temperature of KFi hot metal decreased significantly.

The inventors of the present invention were concerned about such stagnation, and thought that it was necessary to develop a method that could efficiently carry out preliminary treatment of hot metal. I felt that the preliminary treatment could be simplified if desiliconization was performed during the process of tapping the iron via the tap. That is, a skinmer is placed in the path of tapping the tap water via the tap sluice, and first the blast furnace slag is separated. Next, by adding a desiliconizing agent to the bath pig iron in the tap runner and completing the desiliconization while the hot metal is passing through the tap runner, it becomes possible to substantially omit desiliconization equipment and desiliconization time. The purpose of determining the quantity line here is to ensure that the amount of silicon in the hot metal can be sufficiently reduced even when the above-mentioned simplistic method is adopted. However, Figure 1 shows the relationship between hot metal temperature and initial (SI) amount on road dephosphorization, and as is clear from this figure, when the amount of (Si) in hot metal is large, dephosphorization is Therefore, it is extremely important to perform sufficient desiliconization in advance. The only gap is
The purpose is to enable efficient removal of the generated desiliconization slag layer 429 on the downstream side. However, if the removal of the desiliconization slag is insufficient, the basicity of the dephosphorization slag will decrease as mentioned above, and the slag will form an S cliff in the slag drain of the desiliconization slag. If this happens, the subsequent attachment/detachment process itself becomes impossible 111.

The present study has begun to solve the above-mentioned problems, and has shown that a high desiliconization effect can be achieved simply by passing ## pig iron flowing down through the bath pigtails. We have been conducting intensive research in an attempt to obtain a desiliconizing agent that can generate desiliconizing slag that can be removed.

Kibatazaki was completed as a result of such research, and its composition is a hot metal desiliconization agent for desiliconizing hot metal tapped from a blast furnace during the extraction process. In addition to iron ore and substances mainly composed of iron oxides, such as sifter generated in the sintering process, there are
and the grain melt loss is 0.1 to 1. The gist is that it contains 50% or more of the Off value and the total amount is 1.0W or less.

First, in the present invention, KCaCO is used together with SCA-V as a desiliconizing agent.
3 is used, but when it is thrown into the hot metal in the hot metal gutter, it gets caught up in the hot metal at the curved p angle in the drop part of the hot metal gutter. And (1), 5i-s@ in the bath iron by C-type reaction
Caco3 undergoes thermal decomposition at the same time as #trend and releases CO gas, which passes through the desiliconization slag layer and escapes into the atmosphere. .

IF@g03+8 ($1) Tomi j18i0g+4F・
1112FI110+(Sゑ)-8i02+2Fe
By the way, the desiliconized slag rises to the surface of the generated hot metal, but it bubbles on the l#aIM surface and shows a haze, reducing the apparent fluidity.
aW7A, it becomes difficult to discharge the slag from the drainage gutter which is branched to the downstream side. However, when CaCO3 containing CaCO3 is used as a desiliconizing agent, as mentioned above, the C generated during melting is
When the O slag penetrates the desiliconization slag layer, an antifoaming effect is exerted and foaming is suppressed. As a result, a decrease in the fluidity of the desiliconized slag and abrasion solidification of the surface layer are suppressed, and the desiliconized slag maintains a high level of slag excretion. Desilicated slag C807
As the 810g ratio decreases, the melting point and viscosity increase and F11I
! The fluidity of sug decreases. Just like the above-mentioned CO
In order to effectively exhibit the effect of suppressing foaming due to the generation of the gas mentioned above, it is necessary to contain a small amount of CaCO3 (more than 8% by weight). At the same time, the basicity of the slag becomes too small, and the first problem occurs in which the amount of MIS in the bath iron becomes MltO and migrates into the slag. There are a lot of things, and then the drop of silica is removed.
As basicity increases, melting point and viscosity increase, and %C
a) The temperature decreases due to the heat of decomposition of CO30, and the amount of C0g gas generated exceeds 111, cooling the slag, and the fluidity decreases on the contrary. Moreover, since the SCA-A10X* ratio, which is the main component of the desiliconizing agent, decreases and the desiliconizing effect decreases, (the acO30 content must be kept below 21%. Incidentally, Figure 2 cA), ( 1, (0 is a graph showing the influence on the sludge drainage property (slag O fluidity in sludge @) when the cacos content rate during demolition is taken into account, and these graphs also The significance of caco3 overflow is described in Japanese books.Especially when cooling the normal AM pig iron discharged from the blast furnace, the
By using a desiliconizing agent that combines CO3, the sludge removal performance can be dramatically improved. tt4 0CI in the strict sense
The optimum content of CO3 is preferably determined by the amount of (St) in the hot metal and the removal rate of the main paddle, and the most preferable is the amount of CO3 generated x 9
FK) base qtd 0.8-0.5 and null* K C
a. Determine the CO3 content rate.

Fluorite and cryolite are known to lower the melting point of each dan slag and increase its fluidity, but one! ! Also in FM4, it is extremely effective to add am fluorite or cryolite as a V&solvent. However, adding 11 JK is economically wasteful, and furthermore, fluorine, which is harmful to dissolved and reactive fK, is generated, so its content must be kept below 6 weight qII.

Next, the particle size structure of the desiliconizing agent is extremely important in obtaining a good desorption rate. That is, in the present invention, desiliconization is carried out in the tap trough without using a special desiliconization furnace, so the fence must be designed to efficiently widen the contact with the hot metal in the tII trough. Particle size of desiliconizing agent #lIF! It is necessary to use a material containing 60 weight or more of 1 to 1.0 m, and a total amount of 1.0 m or less.

However, if the grain size is too large, the desiliconizing agent only floats to the surface of the hot metal flow and becomes entangled deep inside the hot metal flow. The particles are scattered by the external pair fItK formed above the #1 pig iron, which increases the loss of desiliconizing agent and causes the flow of the outflow fR gutter.
seriously pollutes the working atmosphere. By the way, Figure 8 is a graph showing the influence of the particle size composition of a desiliconizing agent (composition is No. 1111) on the desiliconization rate in nine cases (the (Si) content of the raw hot metal is 0). .1 to 0.6, and the amount of desiliconizing agent added is IIθ to 30 kg/).As is clear from this graph, when the particle size of the desiliconizing agent is 1. If it exceeds Om, the desiliconization rate decreases. The desiliconization rate is decreasing even in the case of 0.1 wx Songman containing a large amount of fine particles, but
This is thought to be due to the fact that the actual amount added to the hot metal decreased due to scattering during addition, and in this case, the area around the addition adhesion could be heavily contaminated by the scattering desiliconizing agent powder! ! I was approved.

@1 Table 1 Situation Composition of Silicant Fit (Amount of Electricity) The present invention is roughly constructed as described above.In addition to containing an appropriate amount of caco3 as the CaO component in the desiliconizing agent, the particle size structure is made uniform. By adjusting K, it is possible to efficiently remove silicon in the process of flowing through the tap pipe. Moreover, the generated desiliconization slag has good fluidity, so it can be installed in the downstream equipment of the gutter and easily removed from the slag drainage gutter, thereby reducing the amount of desiliconization slag mixed into the pig iron in the process. As a result, the installation of a desiliconization furnace, etc. and the desiliconization treatment time can be substantially omitted, and the pretreatment equipment and operation can be simplified, and the pretreatment efficiency can be increased. To my delight, it reached number 1.

[Brief explanation of the drawing]

Figure 1 is a graph showing the influence of hot metal tjAM and initial [si] on dephosphorization, Il! Figure 2 (4), (to), (Q is a graph showing the relationship between the CaCO3 content in the desiliconizing agent and slag removal performance μ5 FIIJ is a graph showing the relationship between the particle size structure of the desiliconizing agent and the desiliconizing rate. Application People Kobe Steel Co., Ltd. Silicification CP) Amount of hot metal <Sr> before treatment (X10%) No addition of heavy limestone Addition of calcium carbonate Addition of calcium carbonate (10 to 21%) (Less than 3 to 10%) Figure 3 Hot metal ( Si)C%) Procedural amendment C method]% formula% 1. Indication of the case Showa Sr. Patent Application No. 114188 Showa No. 2. Name of the invention or device 3. Make an amendment Relationship with the patent applicant case Address: 3-18-4 Wakihama-cho, Chuo-ku, Kobe City Agent: Zip code 530 Address: 2-3-7 Dojima, Kita-ku, Osaka Shinko Building Telephone Osaka (06) )
343-2325 (generation) 6, subject of amendment (1) Specification, 7th summer, line 6 O “Datsutsu de attack,” t “Datsutsu (Figure 118 (4) Tsumuishi translation without addition of stone, Oka (2) Expanded Acid Power A/V Tsufu 1G-1111 added, Okaro Expanded Carbonated★fi/
Vum 8-101〉〉,'' I corrected it. (Movement number 1a (A), @, I will correct the difference in the attached sheet. Figure 2 (A) (B) Sludge drainage performance Sludge drainage performance (C) Bad, normal, and good sludge drainage performance

Claims (1)

[Scope of Claim] Mouth) A molten pig iron desiliconization agent for desiliconizing hot metal tapped from a blast furnace while passing through a tap culvert, and a scale. Saponite, sintered ore under sieve 0 @ at least 8 to 2 with iron oxide
Contains 1 weight of caco3, and its particle size is 5! 'b
A desiliconizing agent for hot metal, characterized in that it contains 50 weight or more of Xo, t~1.01, and the total amount is 1.01 or less.