JPH08188814A - Production of extremely low phosphorus high nickel-containing iron - Google Patents

Abstract

PURPOSE: To provide a method for effectively producing a pig iron having <=0.002% P and >=4.5% Ni and a steel <=0.001% P and >=9.0% Ni. CONSTITUTION: A preliminary desulfurized pig iron is poured into a desulfurizing furnace 1, and after charging the metallic nickel, the dephosphorized blowing is started, and an nickel oxide is charged at the end stage of blowing after completing silicon-blowing. After completing the dephosphorized blowing, the nickel oxide can be charged to prevent the rephosphorization. Further, after pouring the extremely low phosphorus high nickel-containing molten iron into a decarburizing furnace 2, the metallic nickel is charged and the decarburized blowing is started and the nickel oxide is charged at the end stage of blowing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an iron having an extremely low phosphorus content and a high nickel content, and an extremely low phosphorus content and a high nickel content steel which are produced by using, for example, a converter type dephosphorization furnace and a decarburization furnace. It relates to a manufacturing method. More specifically, in the hot metal stage of the dephosphorization furnace, metallic nickel and then nickel oxide are added to dissolve nickel in the hot metal and dephosphorize it, and a method for producing pig iron, and to the hot metal thus obtained The present invention relates to an inexpensive manufacturing method of low phosphorus and high nickel content steel in which metal nickel and then nickel oxide are charged in a decarburizing furnace to finish and steel is taken out from the converter.

[0002]

2. Description of the Related Art Fe is a method of smelting high-content Ni steel.
-A method of introducing Ni alloy or metallic Ni ingot into a converter (decarbonization furnace), or decarbonization to promote decarburization reaction in molten steel with inexpensive powder or granular Ni oxide as a Ni source. Heyday (
[C] ≥ 0.6%) or at the end of decarburization ([C] ≤ 0.25%) for the purpose of temperature control (JP-A-58-
No. 91114) has been proposed so far.

Fe-Ni alloys and metals are placed in the converter as in the conventional method.
With the method of introducing a Ni lump, a large amount of Ni can be melted, but it was difficult to smelt Ni steel having an extremely low P content and a high content at the time of tapping the converter. That is, a high temperature is required to dissolve Ni, while a low P cannot be achieved at a high temperature.

Even in the method of blowing Ni oxide, the Ni must be melted in an electric furnace to some extent,
It is difficult to melt steel with high Ni content. This is the opposite of the case described above, and low P is possible at low temperatures, but this time, high Ni cannot be achieved.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an extremely low P and high Ni content iron which simultaneously realizes low phosphorus and high Ni, which were conventionally considered to be contradictory to each other. It is to be. Specifically, the object of the present invention is P ≦ 0.002
%, Ni ≧ 4.5%, an effective method for producing pig iron, and yet another object of the present invention is P ≦ 0.001%,
An object of the present invention is to provide an effective manufacturing method of steel with Ni ≧ 9.0%.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies to achieve such an object, and as a result, have focused on realizing extremely low P and high Ni at the stage of P-free hot metal removal. In addition, paying attention to the melting of steel containing extremely low P and high Ni by using the countercurrent refining method (SRP method) with two dephosphorization furnaces and two decarburization furnaces
During the hot metal preliminary dephosphorization treatment (dephosphorization furnace), metallic Ni lumps and then Ni oxide are charged. In particular, it has been found that Ni oxide has an effect of promoting dephosphorization when added at the final stage of dephosphorization blowing. In addition, when performing Ni adjustment and finishing P removal in the subsequent C removal furnace, P removal can be strengthened by introducing Ni oxide in the final stage of blowing even in the C removal furnace, and at the time of tapping the converter. At the stage of, it was found that an extremely low P and high content Ni steel could be melted, and the present invention was completed.

The gist of the present invention is as follows. (1) Preliminary desulfurization pig iron is poured into the dephosphorization furnace, metal nickel is added, dephosphorization blowing is started, and at the final stage of blowing after completion of silicon blowing,
A method for producing pig iron containing ultra-low phosphorus and high nickel, which comprises adding nickel oxide.

(2) After the completion of the dephosphorization blowing in (1) above,
A method for producing pig iron containing extremely low phosphorus and high nickel, in which nickel oxide is added to prevent re-phosphorization. (3) After pouring the ultra-low phosphorus and high nickel-containing hot metal obtained in (1) or (2) above into a decarburizing furnace, charging metallic nickel and starting decarburization blowing, at the end of blowing A method for producing a steel containing extremely low phosphorus and high nickel, which comprises introducing nickel oxide.

[0009]

Next, the method according to the present invention will be described in detail with reference to the accompanying drawings, and its operation will be specifically described.

FIGS. 1 (a) and 1 (b) show an extremely low P and high content Ni iron obtained by applying the method according to the present invention to the hot metal sufficiently desulfurized in the KR desulfurization facility by using the SRP method. That is, it is an explanatory view of a process of melting pig iron and steel respectively.

In FIG. 1 (a), after the pig iron is received, the metal Ni is put into the scrap chute and then the de-P blowing is started. Metal Ni
May be in the form of lumps or powder, or may be a Ni alloy. There is no particular limit to the amount of compounding, but the final goal
It may be appropriately set depending on the Ni content.

The hot metal at this time is preferably desulfurized to S ≦ 0.003%, but is not particularly limited thereto. De-Ping is performed by blowing oxygen into the hot metal. Iron ore may be added if there is a heat margin. In any case, it is sufficient to carry out the de-P treatment under the conventional de-P condition, and there is no limitation. During the de-P blowing, at the end of the blowing after the end of the silicon blowing, Ni oxide is continuously fed from the feeder. Start. It should be noted that “after the completion of silicon blowing” means a state in which Si is traced, but in the case of the present invention, the timing of introducing the Ni oxide may be determined by the blowing time.

According to the present invention, by adding Ni oxide, the hot metal temperature can be kept low, and P removal can be promoted. The Ni oxide may be charged in the form of granules or lumps, but granules are preferable for prompt dissolution and decomposition. When blowing, blowing oxygen gas may be used as a carrier gas.

Further, according to the modified example of the present invention, after completion of the de-P blowing, a small amount of Ni oxide can be added to the de-phosphorized hot metal to suppress re-P, and the molten metal can be discharged. The addition of this additional amount of Ni oxide is for the purpose of preventing re-P, and therefore, after the target P amount is achieved by de-P blowing, for example, the additional amount of Ni oxide may be added at a rate of about 500 kgf per heat. Good.

Thus, according to this aspect, after the hot metal dephosphorization treatment, P ≦ 0.002%, Ni ≧ 4.5%, a low P content and a high P content.
Ni pig iron is obtained. FIG. 1 (b) is a process explanatory view for explaining the decarburization in the decarburization furnace for the de-P molten pig iron obtained as described above. After the metallic Ni lump was added, de-C blowing was started,
After that, in the final stage of blowing, the Ni oxide required to secure the target Ni content is added.

The metal Ni may be charged in the decarburizing furnace in the same manner as in the decarburizing furnace, and the purpose thereof is to secure the amount of dissolved Ni, so that the amount of nickel to be charged may be determined from the target Ni amount. In addition,
The decarburization treatment itself may be carried out by conventional oxygen blowing, and the present invention is not particularly limited. As a solvent, quick lime, fluorspar, light slag, etc. are added simultaneously.

However, in the case of the present invention, since a considerable amount of Ni has already been melted as hot metal, the amount of Ni dissolved in the decarburizing furnace can be reduced as compared with the conventional one, and P desorption is also stable. Since it has been carried out in the above, it is possible to reduce the solvent medium in the decarburizing furnace. As a result, it is possible to reduce the heating agent (FeSi).

In particular, according to the present invention, hot metal preliminary (P removal)
At the treatment stage, it is possible to produce a fairly high Ni content and low P hot metal. It has become possible to easily manufacture low P steel, which was difficult by the conventional method, by using Ni oxide. In order to proceed with dephosphorization in the dephosphorization furnace, it is an important point to lower the dephosphorization treatment temperature.

Therefore, from the final stage of dephosphorization blowing when Si blowing was completed
By continuously adding Ni oxide, the temperature rise can be suppressed. In addition, since the Ni oxide causes a rapid thermal reaction when it decomposes into Ni, it is effective in suppressing a temperature rise and promotes dephosphorization.

Next, in the decarburization furnace, since the P is thoroughly dePed in the deP furnace, it is possible to reduce the amount of solvent used for the deP, and it is possible to have a thermal margin. That is, the heating agent can be reduced. The finish Ni adjustment is performed by introducing metallic Ni prior to decarburization blowing as in the case of the de-P furnace, and then introducing Ni oxide at the final stage of blowing. At that time, the Ni oxide also plays an effective role in removing P. Here, in the preferred embodiment of the present invention, by using the SRP method, extremely low P and high Ni are obtained.
The molten steel containing can be manufactured easily and simply. Next, the function and effect of the present invention will be described more specifically based on Examples.

[0021]

EXAMPLE In this example, 250 tons of hot metal which had been thoroughly desulfurized in a KR desulfurization facility was used as in the conventional method.

Production of P-free hot metal: The processing conditions were set so that the basicity of the P-free furnace was 2.5 and the amount of fluorspar was (CaF ₂ ) = 15%. In the conventional method, the amount of the metallic Ni ingot to be charged into the de-P furnace is unmelted when the amount is increased, so that the maximum [Ni] after hot-P degassing was 2.0%. However, in the present invention, by continuously adding Ni oxide particles continuously from the final stage of de-P blowing to the end of blowing (10 to 20 K / T), it is possible to strengthen the de-P without leaving any residue.

Conventionally, a small amount of iron ore was added, but it did not significantly contribute to P removal. Iron ore
If you can put in about 15 to 20K / T, you can strengthen P removal,
The heat source in the decarburizing furnace is insufficient, and a large amount of the heating agent must be used in the decarburizing furnace.

De-Ping Nickel oxide addition amount and de-Ping at the end of blowing
The correlation with the effect is shown graphically in FIG. Ni per ton of hot metal
It can be seen that [P] ≤ 0.005% can be stably achieved by adding 10 kg or more of O 2.

Manufacture of molten steel: The hot metal that had been deP-treated was then decarburized. The metal Ni powder added prior to the start of decarburization blowing was 35 kg / ton, and was added at the end of blowing.
The amount of Ni oxide was 10 kg / ton.

The decarburization processing conditions and the like were determined according to the conventional method. The results of this example are summarized in the table below. (i) When Ni oxide is not used preferentially in the de-P furnace.
Hot metal [Si] = 0.35% is assumed.

[0027]

[Table 1]

(Ii) When Ni oxide is preferentially used in the P-deoxidation furnace.

[0029]

[Table 2]

In the conventional method, the Ni dissolution in the de-P furnace is 2.0% because it remains undissolved. Further, a small amount of iron ore was added after the final stage of de-P blowing for the purpose of de-P, but the de-P varied. Further, although it is possible to remove P by introducing iron ore to some extent, this method could not be taken because the heat in the decarburization furnace was insufficient.

In the present invention, by using the Ni oxide for the purpose of dissolving Ni and removing P, respectively, the temperature after removal of P and the [C] after removal of P are low, but the [Ni] after removal of P is 4.5. ~
It became possible to perform a large amount of 5.0% and Ni dissolution. De-P
In comparison with the conventional method as well, the deP capacity increased from 0.006 to 0.003%, and it became possible to reduce the cost of smelting Ni steel with low P content and high content in the decarburization furnace. Therefore, it became possible to reduce the FeNi heating material and the solvent. Ni after de-C blowing in total
Since the component can be increased and the P component can be decreased, it is possible to reduce the processing in the next process (for example, RH, LF, etc.).

[0032]

As described above, according to the present invention, P ≦ 0.005% and Ni: 8 to 9 which could not be realized conventionally.
%, An extremely low P and high Ni molten steel can be produced by a relatively simple means, and the practical significance of the present invention is great.

[Brief description of drawings]

1A and 1B are schematic explanatory views of process diagrams of the present invention.

FIG. 2 is a graph showing the relationship between the amount of NiO added after the final stage of de-P blowing and the post-P [P].

Claims (3)

[Claims] 1. A method of pouring preliminary desulfurization pig iron into a dephosphorization furnace, introducing metallic nickel, starting dephosphorization blowing, and introducing nickel oxide at the final stage of blowing after the completion of silicon blowing. A method for producing pig iron containing extremely low phosphorus and high nickel. 2. A method for producing pig iron containing extremely low phosphorus and high nickel, wherein nickel oxide is added to prevent rephosphorization after the completion of the dephosphorization blowing in claim 1. 3. The molten iron containing the ultra-low phosphorus and high nickel content obtained in claim 1 or 2 is poured into a decarburizing furnace, metal nickel is introduced, decarburizing blowing is started, and nickel is added at the final stage of blowing. A method for producing a steel containing extremely low phosphorus and high nickel, which comprises adding an oxide.