JPH0660340B2 - Desiliconization and dephosphorization treatment method of hot metal - Google Patents

Description

Detailed Description of the Invention

[Field of Industrial Application] The present invention relates to a treatment method of performing desiliconization and dephosphorization of hot metal almost at the same time. [Prior Art] When performing desiliconization and dephosphorization in a single reaction vessel in the conventional hot metal pretreatment stage, the slag basicity CaO
/ SiO ₂ is about ₂ and the total iron content in iron oxide contained in the slag after dephosphorization (hereinafter abbreviated as T-Fe) is 10%.
Although it is dephosphorized before and after, in order to improve the phosphorus distribution ratio after dephosphorization to obtain a lower concentration of phosphorus, or to perform dephosphorization with a lower basicity, that is, with a smaller amount of quicklime basic unit, it is always necessary. Excess oxygen was supplied to prevent (T-Fe) from decreasing. [Problems to be solved by the invention] By the way, in this method, a corresponding decarburization reaction progresses, the amount of heat necessary for melting scrap in the post-process converter smelting cannot be secured, and the iron yield decreases, and Since the FeO in the slag is operated while it is still high, there is a problem that the wear of the refractory becomes large. The present invention has been made in view of the above problems, desiliconization with less wear of refractory materials, dephosphorization treatment, desiliconization with low phosphorus concentration,
Provided are a method for removing silicon and phosphorus, or a method for removing silicon and phosphorus for the purpose of saving auxiliary materials.

[Means for solving the problem]

The present invention, when a CaO-containing substance and an oxygen source are added to hot metal to desiliconize and dephosphorize the hot metal, while spraying a predetermined amount of oxygen gas to the hot metal, the bottom defined by the following formula (1) Blowing stirring power: 1.2 to 10 KW / t is given to the hot metal, and the total iron content in the iron oxide contained in the slag after the treatment is 2.5 to 4%, and a method for desiliconizing and dephosphorizing the hot metal, and When adding a CaO-containing substance and an oxygen source to the hot metal to perform desiliconization and dephosphorization treatment of the hot metal, the bottom to be given to the hot metal defined by the following formula (1) while spraying a predetermined amount of oxygen gas to the hot metal This is a method for desiliconizing and desiliconizing phosphorus of hot metal, characterized in that the blowing stirring power is kept at 1.2 to 10 KW / t at the beginning of the above treatment and kept at 0.5 to 1.1 KW / t at the end of the treatment. Here, Qg: blowing gas amount (Nl / min), T: hot metal temperature (° K), Wm: hot metal weight (t), Ho: blowing depth (m), Tg: gas temperature before blowing (° K) Is. [Operation] The present invention, when performing desiliconization and dephosphorization treatment by CaO-based flux while supplying oxygen, stirring force 1.2 ~ 10K
By maintaining W / t, the total iron content in iron oxide contained in slag (hereinafter abbreviated as T-Fe) is 2.5 to 4%.
However, the initial content of hot metal with a phosphorus content of 0.1% was 13.5 kg / CaO.
It was found that this can be dephosphorized up to 0.015% at about t. The basic principle is as follows. Generally, the dephosphorization reaction of hot metal consists of the following three processes. Phosphorus mass transfer slag in molten iron - above oxidation reaction PO ₄ ^3- of mass transfer, where the oxidation reaction in the slag of phosphorus in molten iron interface, (b) Sugura - higher oxygen potential of the molten iron surface, (2 ) The higher the basicity of the slag, the faster the progress. On the other hand, in dephosphorizing the undesiliconized hot metal, since the slag basicity is as low as about 2, dephosphorization is performed by the effect of the above (a). That is, the slag (T-
By securing Fe) to about 10%, the dephosphorization ability of slag is secured. Based on the above principle of dephosphorization of hot metal, when desiliconizing and dephosphorizing the hot metal, it is necessary to keep the bottom blowing stirring power of the hot metal at 1.2 to 10 KW / t while spraying a predetermined oxygen gas to the hot metal. ,
It was found that T-Fe contained in the slag after the treatment can be 2.5 to 4% and sufficient dephosphorization can be performed. While blowing a predetermined amount of oxygen gas onto the hot metal, bottom-blown CaCO ₃
When strong stirring with CO gas or CO ₂ gas generated from
By spraying oxygen gas, FeO was generated, silicon in the hot metal was oxidized to generate SiO _2, and it was added by means such as charging.
The contact efficiency with CaO-based flux increases and the slag formation progresses. At the same time, by the above-mentioned strong stirring, the hot metal and FeO are sequentially supplied to the slag-hot metal interface, so that the oxygen potential at the slag-hot metal interface is kept high, so that phosphorus in parallel with the silicon in the hot metal is early. It can be efficiently oxidized. From these facts, the phosphorus content of the hot metal after the treatment can be reduced to about 0.015%. When the stirring power of the hot metal is less than 1.2 KW / t, the stirring power becomes weak against the supply of oxygen gas, and FeO in the slag increases. Further, if the stirring power exceeds 10 KW / t, the stirring power is too strong, a large amount of splash is generated, and the loss of Fe content increases, which is not preferable. Next, in order to further reduce phosphorus in the hot metal, it is necessary to keep the oxygen potential high at the final stage of the treatment in which dephosphorization is stagnant. It was found that the means for achieving this can be achieved by reducing the stirring power at the final stage of dephosphorization so as to delay the reduction of slag. It can be carried out in parallel with the means for adjusting the amount of oxygen gas sprayed or the amount of iron oxide charged, which is usually used in combination with this means, and specifically, the amount of oxygen gas sprayed. It is desirable to reduce the amount (soft blow) to promote the generation of FeO. Next, in order to carry out the work of reducing the CaO intensity, C
Even if the amount of aO-based flux input is reduced by 20 to 30% and the basicity is lowered to, for example, about 1.8, the stirring power at the final stage of dephosphorization is reduced in the same manner as described above to maintain a high oxygen potential. It was found that the phosphorus concentration can be reduced to about 0.018%. When the stirring power of the amount of hot metal at the final stage of dephosphorization is less than 0.5 KW / t, the stirring power becomes weak with respect to the supply of oxygen gas, and FeO in the slag increases. Further, when the stirring power exceeds 1.1 KW / t, the oxygen gas consumption increases due to the progress of the decarburization reaction, and it becomes difficult to secure the necessary FeO amount. [Embodiment] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a refining apparatus. Using this apparatus, first, 160 t of hot metal 2 and 5 t of slash 3 are charged into a refining vessel 1. Then, a dephosphorization flux composed of a mixture of massive CaO, massive CaF ₂ , and iron ore was charged from the hopper 6, and at the same time, the dephosphorization flux in the blow tank 5 was changed.
It is blown into the hot metal 2 from the bottom blowing tuyere 4 together with the N ₂ gas, and an acidity jet is blown to the hot metal 2 through the lance 7. Table 1 shows refining conditions of Examples 1, 2 and 3 according to the present invention and a comparative example, and FIG. 2 shows Example 1 and FIG. 3 shows Example 2.
FIG. 4 shows the changes over time in the hot metal components of Example 3 and FIG. 5, respectively. In Example 1, the phosphorus concentration decreased to 0.017% at the CaO basic unit of 17.5 Kg / t, and similarly in Example 2, the phosphorus concentration decreased to 0.018% at the 12.0 Kg / t basic unit. In Example 3, the CaO basic unit is 18.1 kg / t and the phosphorus concentration is 0.017%.
Is. Also, T-Fe contained in the slag after dephosphorization is 3.
It can be reduced to 7% and wear of refractory in the processing furnace can be reduced. On the other hand, in the comparative example, the CaO basic unit was 18.0 kg / t, which was the same level as in Example 3, but the stirring power was weak and the phosphorus concentration after the treatment was 0.024%. As described above, the present invention makes it possible to easily reduce the phosphorus concentration of hot metal not subjected to desiliconization treatment to 0.01% or less with a small amount of CaO. The present invention can be easily applied to all refining vessels as long as it has a mechanism for adjusting the stirring force.
The reduction to 0.5 to 1.1 KW / t is sufficient for about 3 to 4 minutes before the completion of the dephosphorization treatment. Further, as a means for giving stirring,
It is also achieved by blowing a gas such as Ar or N ₂ or a gas generating substance such as CaCO ₃ through a lance or a tuyere. [Advantages of the Invention] As described above, the present invention is to adjust the stirring force applied to the hot metal to secure the dephosphorization ability of the slag and promote the reaction without adding extra flux or the like. In addition, low dephosphorization can be achieved with a small amount of auxiliary raw material, and the raw material cost can be reduced and pretreatment efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example of a refining apparatus, FIG. 2 and FIG.
FIG. 4 and FIG. 4 are graphs showing changes over time in molten iron components in the examples. FIG. 5 is a graph showing changes with time in the comparative example. 1 ... Refining container, 2 ... Hot metal, 3 ... Scrap, 4 ...
… Bottom blowing tuyere, 5 …… blow tank, 6 …… hopper,
7 ... Lance

Claims (2)

[Claims] 1. When a CaO-containing substance and an oxygen source are added to hot metal to perform desiliconization and dephosphorization treatment of hot metal, a predetermined amount of oxygen gas is sprayed onto the hot metal as defined by the following formula (1). A method for desiliconizing and dephosphorizing hot metal, characterized in that a bottom blowing stirring power of 1.2 to 10 KW / t is given to the hot metal and the total iron content in iron oxide contained in the slag after the treatment is 2.5 to 4%. . Here, Qg: blowing gas amount (Nl / min), T: hot metal temperature (° K), Wm: hot metal weight (t), Ho: blowing depth (m), Tg: gas temperature before blowing (° K) 2. When a CaO-containing substance and an oxygen source are added to the hot metal to perform desiliconization and dephosphorization treatment of the hot metal, a predetermined amount of oxygen gas is sprayed onto the hot metal, and is defined by the following formula (1). The bottom blowing agitation force given to the hot metal is
A method of desiliconizing and dephosphorizing hot metal, which is characterized by maintaining 1.2 to 10 kW / t and maintaining 0.5 to 1.1 kW / t at the end of treatment. Here, Qg: blowing gas amount (Nl / min), T: hot metal temperature (° K), Wm: hot metal weight (t), Ho: blowing depth (m), Tg: gas temperature before blowing (° K)