JPS6063305A - Method for producing high-purity pig - Google Patents

Abstract

PURPOSE:To produce stably high-purity pig to be used as a raw material for a high-grade spheroidal graphite cast iron, etc. by oxidizing and removing Si and Mn in the molten pig in a preliminary treatment stage then adding an acid or the like and a flux thereto under mechanical stirring in succession to said oxidation and oxidation-refining elements such as P, S, etc. while suppressing decarburization. CONSTITUTION:Si, Mn, etc. in molten pig are oxidized and removed as a preliminary treatment by using a pan 2 to be used exclusively for said treatment of a KR-OB plant shown in the figure. O2 is charged from a lance 3 into the molten pig and a solid acid and flux (e.g.; >=1 kind among quicklime, CaCl2, etc.) are charged thereto from chutes 4,4 under stirring with an impeller in succession to the above-mentioned treatment and P, S and other elements which are liable to remove into basic slag are oxidation-refined while decarburization is suppressed. The high-purity pig contg., respectively by weight %, >4.0 T.C, <=0.09 Mn, <=0.09 P, <=0.005 S, <=0.009 Ti, <=0.005 As, and <=0.020 SIGMAT (total sum of Ti, Cr, V, As, and Sn) is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing high-purity pig iron used as a raw material for high-grade spheroidal graphite cast iron and the like.

(Prior art) There are two types of pigs that have traditionally been called high-purity pigs: Hanna pig iron, OB
There are imported pig irons and commercially available domestic pig irons such as DuO-8 pig iron, but both of them are pig irons with less spheroidal graphitization inhibiting elements, their chemical composition and mechanical properties. The superiority and inferiority of these are well known. Therefore, the methods for producing high-purity pig iron are as follows: (a) A method of obtaining high-purity pig iron by carefully selecting raw materials such as iron ore to reduce impurities in the hot metal. (For example - Nanna pig iron, Swedish pig iron) @) A method of decarburizing hot metal to the steel region in a pure oxygen top-blowing converter, removing impurities, and then carburizing it to make high-purity iron (
(For example, Japanese Patent Publication No. 46-31654) (C) Out-of-furnace treatment focusing only on some harmful elements) After the hot metal is subjected to preliminary treatment to remove Si and Mn, it is decarburized in a pure oxygen top-blowing converter. Depletion of P without suppressing it.

Method for removing S...DLIO-S pig (e.g. JP-A-53, +s 4112) However, these known manufacturing methods (a), ←) and e; It cannot be said that this method is sufficient for producing stably and in large quantities on an industrial scale. In addition, in the case of method (2), decarburization is suppressed and P is removed.

Although S removal has been carried out, there are limits to suppressing decarburization during blowing in pure oxygen top-blowing converters, and it is difficult to improve as-cast ferrite, which is required for high-purity iron for recent spheroidal graphite cast iron. Therefore, it is impossible to deal with the high carbonization trend (0>4.0%).

Therefore, even in the previously known Hanna pig iron, etc., it is possible to improve the graphite spheroidization ratio or the ferrite area based on the mechanical properties of the spheroidal graphite cast iron using it and the small amount of elements that inhibit spheroidization. There are some problems with the rate.

(Object of the Invention) The present invention is an invention aimed at solving the drawbacks of such conventional methods.

(Structure 1 of the invention) That is, the feature of the present invention is that the amount of carbon necessary for pig iron is entrusted to the carbon in the blast furnace hot metal without carburization, and 3i and Mn are oxidized in the pretreatment process. After removing
Continuously in the same container, gas acid, solid acid, and solvent are added with mechanical stirring to suppress decarburization, and P, S, and other elements that are easily removed in basic slag are oxidized and blown. T
, OS> 4.0wt%* 81 2 g M”
: ≦ 0.09wt%, P: ≦ 0.009
wt%, s: kuo, ooswt%, Ti: 50.0
09w1%.

Aj: (Q.00fX T : ≦0-020wt% is a method for producing high-purity iron for spheroidal graphite cast iron.

Note that ΣT refers to the sum of Ti, or, V, As, and sn.

(Example of the invention) Using the KR-OB equipment schematically shown in Fig. 1, after preliminary treatment based on the method of the present invention, Si and Mn removal treatment using a combination of gas acid and solid acid while stirring with an impeller. Anteroposterior and post-P,
Table 1 shows the chemical composition, temperature, and chemical composition of the pig iron and blowing conditions after S removal treatment.

In FIG. 1, 1 is a freeboard, 2 is a special pot, 3 is a lance for oxygen injection, and 4 is a chute for introducing solid acid and solvent.

*1 Perform component v1c with PE-8i for deoxidation treatment before gunpigment (deoxidation 3i, deMll treatment conditions) K mixing: 18 minutes Oxygen flow rate: 200ON*//IIr (8Nt++'
/', r) Amount of oxidizing agent input: 2900ky (39,2
kp/T) Diffusion ratio = 56% Lance height: △L = 300-400 Bait (de-P, de-S treatment conditions) K-Rin Tei Hayabusa = 18 minutes Oxygen flow rate: 800Nrr? /Hr (3,P Nyy
//T) Oxidizing agent input: 1,125 kr (15,0
Garlic/'r) Solvent: Quicklime 24 to 9/T Fluorite 5 ky/T Rhusium chloride 5 kg/T Commanite 2 Garlic/'r) Lance height 2,900 to 1,000 questions As a comparative example for this, we have already mentioned Table 2 shows examples of the manufacturing method (Japanese Patent Application Laid-Open No. 53-54112).

Table 2 Example (mill scale treatment conditions) of the method for producing high purity iron for spheroidal graphite cast iron (JP-A-53-54112) KR stirring: 20 minutes Mill scale addition amount: 40 g/T (Converter blowing Refining conditions) Lance height: △L = 3.0~4.0 fi Oxygen flow rate: 3000~800ONnI/Hr (37Ni/T
) Interruption, etc. 2 hard blows, 2 interruptions Solvent: Quicklime 20 kr/T Dolomite 15 kr/T Fluorite 1.5 kf/T Blowing time = 30 minutes Blowing method of JP-A-53-54112 So s:, p.

Stirring to remove S and other impurities is performed using an oxygen dient, followed by hard blowing, and then a soft blower is used to remove slag from the slag necessary for the deP reaction (FeO produces slag to proceed with the molten metal deP reaction. (Do the Zoronogu turn to make it happen) Tsume 9, pardock 41 is hot metal (S
Along with the oxidation of i), the hot metal [C] is also inevitably burned.

Furthermore, in the blowing method, a total of three re-drivings are required: between the preliminary treatment and the converter, between the converter and the steel receiving ladle, and between the steel receiving ladle and the hot metal ladle. Semi-compensation for the temperature drop at the time of redriving is performed in a converter, and as can be seen in the example in Table 2, hot metal [Si] is left after preliminary treatment with mill scale as a heat source. In the blowing method of 1983-54112, a high temperature of approximately 1470°C is required when the converter blows off.
The heat produced by combustion in I) is also used.

However, leaving hot metal [St:+] means removing P.
, high basicity (OaQ/sio,
) This increases the amount of Si02 in the slag, which increases the amount of quicklime used and the resulting increase in the amount of slag, which also causes an increase in the cost of secondary materials and energy. It has become.

On the other hand, in the case of the present invention, stirring is performed mechanically using an impeller, solid acid is used in combination with the slag (Fed) necessary for deP, and furthermore, by using aeration, the slag-hot metal In addition to providing auxiliary stirring during the process, the amount used for producing the slag (Fed) is minimal, and since soft blowing is performed throughout, the amount of decarburization is also small.

In addition, the present invention performs preliminary treatment from receiving hot metal to pig iron in the same container.

Since all processes are carried out including P removal, S removal treatment, and the pig iron casting machine, there is no need for a reidle for heat compensation. - There is no need for residual (Si) after preliminary treatment, which reduces auxiliary raw material costs and energy costs. It is possible to reduce the cost by approximately 4,900 yen/T.

(Effect of the invention) As shown in the examples in Table 1,
(after treatment) at 1280°C, as stated in JP-A-53-54112
The temperature is 190° lower than the 1470°C when the converter shuts down.

Furthermore, as shown in the example of FIG. 2, the amount of decarburization during the deP and S deprocessing is 0.23% in the present invention, compared to JP-A-53-54.
The decarburization amount of 1120 is 0.9%, which is about 3.9 times higher, and it is impossible to obtain a blowstop of 0>4.0% with such blowing method.

In addition, Table 3 shows the mechanical properties of brackish graphite cast iron using the currently commercially available high-purity pig iron and the high-purity pig iron of the present invention, respectively.
Further, their chemical components are shown in Table 4.

Table 3 Characteristic values for spheroidal graphite cast iron As shown in Table 4, the high-purity pig iron produced by the present invention has a higher carbon content and extremely lower content of graphite spheroidization-inhibiting elements than conventional pig iron. , Mn.

P is also low, and it can be seen that the spheroidal graphite cast iron using this has the best impact properties and ferrite area ratio in the low temperature range, as shown in Table 3. As described above, the present invention improves the drawbacks of the conventional methods and is a method for producing high-purity pig iron that is extremely inexpensive, industrially stable, and suitable for mass production.

[Brief explanation of drawings]

FIG. 1 shows an outline of the Ni-O-OB equipment used in the embodiment of the present invention. Figure 2 shows the present invention and JP-A-53-54112.
This shows the carbon content in hot metal in the valley treatment process. 1...Free board, 2...Special pot, 3...Lance for oxygen injection, 4...Chute for introducing solid acid and solvent, agent Masamitsu Akizawa, patent attorney, and 2 others

Claims (1)

[Claims] (1) A preliminary treatment step to oxidize and remove 3i, Mn, etc.
Gas acid, solid acid, and solvent are added to the hot metal that has undergone this process while continuously stirring it mechanically to suppress decarburization.
Manufactures high-purity pig iron for spheroidal graphite cast iron, which is characterized by performing the process of oxidizing and blowing other elements that are easily removed in basic slag in the same container, resulting in a high-purity pig component with the chemical composition shown below. how to. High purity piglet component (wt%) T, 0 > 4.0 6H I Si - Mn ≦ 0.09 P ≦ 0009 S ≦ 0005 Ti < 0.009 AS ≦ 0.005 *2ΣT ≦0.020 *l Adjustable due to the nature of foundry pig iron. *2 Ti, Cr, v, and AS are elements that inhibit graphite spheroidization.
. Refers to the total of 8 units.