JP3240623B2 - Pig iron production method - Google Patents

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 pig iron using steel scrap or steel scrap and iron ore as raw materials without using electric power as a heat source for melting. The present invention relates to a method for producing pig iron that can be used for producing high-grade converter steel equivalent steel and special steel by effectively utilizing scrap.

[0002]

2. Description of the Related Art The amount of steel scrap generated is expected to increase at a rate of about 1 million tons annually with the increase in the accumulation of steel materials. As of 2000, the amount of market scrap (city waste) generated was about 40 million tons. It is expected to be 45 tons / year of crude steel production.

[0003] At present, most of commercial wastes are commercialized in electric furnaces. In particular, in recent years, practical use of a so-called mini-mill system, in which scrap or direct reduced iron is melted in an electric furnace, and then continuously cast and rolled, is being studied in order to increase the number of products and reduce costs.

On the other hand, at the integrated steelworks, in order to cope with the above-mentioned increase in scrap and secure an iron source that can cope with fluctuations in crude steel production during the blast furnace consolidation, scrap is melted without using electric power as a heat source for melting. Technology development is progressing.

Approximately two-thirds of city debris are waste debris collected after the end of their service life, and the ratio is increasing year by year.
These wastes often contain many impurities or have unknown chemical composition. In addition, as the consumption structure becomes more sophisticated, for example, market waste of high alloy steel and surface-treated steel is increasing.
That is, the generation of various types of steel scrap containing useful elements or harmful impurity elements is increasing. Table 1 shows the first subcommittee of the Japan Society for the Promotion of Science, 69 Committee on Material Processing,
This is an example of the composition analysis of market wastes cited from Anesaki's report data at the second subcommittee meeting. In particular, shredder waste and bundle waste are high in Cu, Ni and Cr, and tin can waste is Sn.
Is high.

[0006]

[Table 1]

[0007] In order to melt high-grade steel equivalent to converter steel from steel scrap whose type and content of the above-mentioned components are unknown, the treatment of the Trump element is an important issue.

[0008] The following research has been conducted as a method of removing a playing card element by a chemical treatment.

Utilization of difference in melting point: Steel scrap preferentially dissolves and removes non-ferrous metals such as Cu, Sb, and Sn mixed in the scrap in a solid state.

Utilization of evaporation reaction: For example, a scrap of a galvanized steel sheet is heated, and only the Zn is dissolved and evaporated to remove it while the steel sheet remains in a solid state. Alternatively, the steel scrap is made into a liquid state, and P
b, Zn is removed and Cu, Se, Sb, Sn, T
e, Bi, Zn and Ag are removed.

[0011] Use of distribution ratio ... in the steel scrap to a liquid state, for example Sn in strongly reducing smelting using CaO-CaF ₂ based flux, As, Sb, Bi, Pb, the P is shifted in the slag separation Remove.

Use of chlorination reaction: chlorine is brought into contact with the molten scrap to generate metal chloride having a high vapor pressure and remove it in gaseous form.

Use of electrolytic reaction: For example, Sn of Sn plating scrap is removed by electrolysis.

Although it has been shown that many impurity elements can be removed as described above, there are many unsolved problems in terms of processing cost and effective utilization of the removed elements, and only the possibility of a practical process is high. It is.

[0015]

SUMMARY OF THE INVENTION The present invention provides a wide variety of steel scraps without the use of high energy cost electricity.
The task was to develop a practical process for producing pig iron that can be used in the production of various high-grade steels using iron as a source of iron . The specific object of the present invention is to dilute harmful elements in steel scrap to a level that is not harmful, while actively collecting valuable elements and saving expensive ferroalloys,
An object of the present invention is to provide a method for producing the above pig iron at low cost.

[0016]

SUMMARY OF THE INVENTION The present invention relates to a method for producing pig iron using steel scrap as an iron source without using electric power as a heat source for melting, comprising the following steps: Is the gist.

A process of producing hot metal from scrap having a high content of elements other than iron, or scrap and ore , and analyzing Cu, Ni, Cr, Sn, Sb and As in the hot metal, iron ore or other than iron The process of producing hot metal from scrap with low content of the elements, or from scrap and iron ore , and analyzing Cu, Ni, Cr, Sn, Sb and As in the hot metal, depending on the type of steel to be manufactured The process of determining the mixing ratio of the hot metal obtained in the process and the process of mixing the hot metal so that they fall within the chemical composition range of the hot metal.

"Scrap having a high content of elements other than iron" in the above-mentioned process includes scraps of special steel containing a large amount of alloying elements, scraps of zinc-plated or tin-plated surface-treated steel, and the like. . In addition, scraps (so-called city waste) whose type and amount of contained elements, including impurities, are unknown are also included in this category.

On the other hand, the term "scrap having a low content of elements other than iron" used in the first step refers to scrap (so-called in-site scrap) generated in the steel making and rolling steps in an ironworks, and is mainly used. It is made of carbon steel and has not been subjected to surface treatment or the like.

In the practice of the present invention, the production of hot metal in the step and the production of hot metal in the step may be performed in the same furnace with different charges, but it is preferable to use different furnaces. desirable. The molten iron manufacturing furnace used at this time may be of any type as long as it does not use electric power as a heat source for melting. For example, the following hot metal manufacturing method is suitable.

Method of producing hot metal in process (a) Method of making iron using 100% market waste in a cupola furnace (b) Using a converter type furnace equipped with a bottom blow tuyere and top blow lance
Method of making iron using 100% commercial waste (c) A method in which coke and an iron source are filled in layers in a cylindrical furnace, and flammable gas is blown from the tuyere to melt and reduce. In this method, hot metal can be produced using market waste and iron ore (further, Mn ore, Cr ore, Ni ore, etc.).

(B) Method of making iron using 100% iron ore in a blast furnace (b) Method of making iron using 100% in-plant waste (b) according to the above method (b) C) In the method described in (c) above, ironmaking is performed using in-house waste and iron ore, etc. as iron sources.Here, market waste mainly refers to waste waste, and is used for industrial machinery and building steel. For example, automotive exterior steel sheets and the like, and scrap generated in the plant refers to steel scrap with low impurities generated at the integrated steelworks. Mn ore, Cr ore, and Ni ore are used to manufacture pig iron for special steel.

The above methods (b) and (c) are based on the proposal of the present applicant, and the outline of the method for producing hot metal is as follows.

The method (b) (see, for example, Japanese Patent Application Laid-Open No. Sho 62-47417) uses a reaction vessel having a gas blowing tuyere at the bottom of the furnace and a lance above the furnace, into which coke is first charged. I do. And after igniting by blowing O ₂ into the furnace,
This is a method in which scrap is charged and the scrap is dissolved and refined by injecting O ₂ while charging carbon material.

In the method (c) (for example, see JP-A-1-290711 and JP-A-2-221309), an opening for discharging gas in the furnace and an opening for charging a raw material are provided on the upper part of the furnace wall. A cylindrical furnace having a taphole and a primary tuyere at the lower part and a secondary tuyere at the upper part in the furnace is used. Then, a coke packed layer is formed from the furnace bottom to the level including the primary tuyere, and a packed layer of scrap and iron ore, or scrap and Mn is formed thereon, up to the level including the secondary tuyere.
Ore, Cr ore, ore rich in Mo or Ni, or Mn,
A filling layer made of at least one oxide of Cr, Mo or Ni is formed. Thereafter, dissolved scraps and ores by blowing primary tuyeres and secondary tuyeres from burning-supporting gas (0 ₂ -containing gas) is a method for refining.

[0026]

FIG. 1 is a block diagram showing the steps performed when the method of the present invention is carried out using two furnaces. As shown, the first
The furnace is charged with scrap (or scrap of unknown chemical composition) having a high content of elements other than iron, or the scrap and ores (iron ore, Mn ore, Cr ore, etc.).
Then, hot metal is manufactured by the various methods described above. This hot metal naturally has a high content of elements other than iron, including impurities, and cannot normally be used as hot metal in converters or the like as it is.

On the other hand, the second furnace is charged with scrap having a low content of elements other than iron, such as the above-mentioned in-site waste, or the scrap and iron ore to produce hot metal.
Here, hot metal may be produced using only iron ore as an iron source without using scrap.

What is obtained in this way is hot metal with a low content of elements other than iron and low impurities.

A component analysis is performed to confirm the chemical composition of the hot metal produced in each of the first furnace and the second furnace. For hot metal for converter equivalent steel and stainless steel, C, S
Most of i, Mn, P, S, Ti, Al, Pb, Bi, etc. are oxidized and removed in the oxidizing and refining process at the steelmaking stage, so the elements to be analyzed are Cu, Ni, Cr, Sn, Sb, and As. It may be an element. In addition,
Mixing hot metal with low C content and ordinary hot metal causes bumping due to rapid CO generation reaction.
It is desirable that the above two types of hot metal satisfy C ≧ 1.7%.

Next, based on the component analysis values of the two types of hot metal, the combined molten metal ratio x (= 0) is set so as to satisfy the impurity element standard value or alloy element content standard value of the product steel product to be manufactured. ~ 1) is adjusted to obtain W tons of hot metal.

Tables 2 and 3 show examples of the influence of impurity elements and allowable upper limit values of ordinary steel and austenitic stainless steel, and Table 5 shows the allowable upper limit values of impurity elements of typical converter-melted steel. This is an example (the source is the same as Table 1). Based on such a standard value, the molten metal is mixed so as to have a hot metal component suitable for producing these steels.

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

Next, the method of calculating the ratio of the mixed hot water will be specifically described.

As shown in Table 5, the impurity element analysis values of the hot metal smelted in the first and second hot metal manufacturing furnaces in FIG. 1 are respectively β _i weight% and α _i weight%, and the product specification value is γ. _i weight%
And

Then, the minimum molten metal ratio x satisfying the following equation (1) for all impurity elements i (i = Cu, Ni, Cr, Sn, Sb, As) was calculated, and the first molten iron (1) was calculated. −x) W
Tons, 2nd hot metal xW tons combined hot water.

Xα _i + (1−x) β _i ≦ γ _i (1) Thereby, the harmful elements in the steel scrap can be kept within the product specifications.

For example, when smelting the steel types shown in Table 6, Cu, Ni and Cr are valuable alloying elements , but these can be recovered from steel scrap and the amount of expensive ferromagnetic iron used can be reduced. be able to. When the alloying element composition of the assorted hot water is less than the standard value, ores and scraps containing known valuable alloying elements whose analytical components are known are preferentially charged during the decarburization and refining period of the assembling hot metal, and It is desirable to increase the alloy element content to a level that satisfies the value.

[0040]

[Table 5]

[0041]

[Table 6]

Hereinafter, the effects of the present invention will be described specifically with reference to examples.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first and second hot metal production furnaces used are the converter type cylindrical furnaces disclosed in the above-mentioned JP-A-1-290711 or JP-A-2-221309.

The main specifications of the furnace are as follows.

Furnace dimensions: 1.5 m in diameter, 3.6 m in height from furnace bottom to furnace mouth, internal volume 6.0 m ³ Primary tuyere: Upper side wall 0.8 m from furnace bottom, 4 wings installed at 90 ° intervals Secondary wings Mouth: Four upper walls 1.4 m from the furnace bottom, four at 90 ° intervals Tapping hole: One at the center of the furnace bottom Drainage port: One on the upper side wall 1.0 m from the furnace bottom Table 7 shows the chemical compositions of iron ore and chromium ore.

In-house steel scrap in the table is a crop end generated from a slab for a thin plate at an integrated steel mill. In addition,
Since the market scrap contains industrial machine chips, cutting chips, tinplate, and bolts and nuts, the analysis component values as shown in Table 7 are unknown.

[0047]

[Table 7]

In the first hot metal production furnace, commercial scrap 514 is used.
kg / T (514 kg per ton of pig iron produced… the same applies hereafter),
723 kg / T of iron ore was charged, and in the second hot metal production furnace, 478 kg / T of in-house steel scrap and 723 kg / T of iron ore were charged to produce hot metal. Table 8 shows the component analysis values of each hot metal.

[0049]

Example 1 A molten metal was prepared to obtain hot metal for producing converter steel having the product specifications shown in Table 8.

From the hot metal analysis values of the first furnace and the second furnace shown in Table 8, impurity harmful elements i = Cu, Ni, Cr, Sn, Sb and As, the combined hot water ratio x _i satisfying the above-mentioned formula (1) is as follows. (2-a) to (2-
f) As shown in the equation.

[0051] _{0.01x Cu +0.13 (1-x Cu} ) ≦ 0.07 In other _{words, x Cu ≧ 0.50 ··· (2} -a) 0.01x Ni +0.09 (1-x Ni) ≦ 0.05 In other words, x _Ni ≧ 0.50 ··· (2-b) 0.02x Cr +0.14 (1-x Cr) ≦ 0.06 In other _{words, x Cr ≧ 0.67 ··· (2} -c) 0.06 (1-x Sn) ≦ 0.04 In other words, x _Sn ≧ 0.33 ・ ・ ・ (2-d) 0.01 (1-x _Sb ) ≦ 0.02 That is, x _Sb ≧ 0 ・ ・ ・ (2-e) 0.01 (1-x _As ) ≦ 0.02 That is, x _As ≧ 0 ・ ・・ (2-f) From the above equations (2-a) to (2-f), if the ratio of the mixed hot water is set to x = 0.67, all the values of i are satisfied.
t, 3.3 tons of hot metal were combined from the first furnace, then decarburized and refined to produce molten steel. Cr is partially oxidized during decarburization refining.
It was further reduced from 06% to 0.05%, and it was possible to melt converter steel for general hot-rolled steel sheets satisfying the standard value of harmful impurity elements.

[0052]

Example 2 A combination hot metal was prepared to obtain hot metal for production of special steel having the product specifications shown in Table 8.

As in Example 1, valuable elements Cu, Ni and
Cr and impurity elements Sn, Sb, As described above (1)
The combined hot water ratio x _i that satisfies the formula is as shown in the following formulas (3-a) to (3-f).

[0054] _{0.01x Cu +0.13 (1-x Cu} ) ≦ 0.25 In other _{words, x Cu ≧ 0 ··· (3} -a) 0.01x Ni +0.09 (1-x Ni) ≦ 0.15 In other words, x _Ni ≧ 0 ··· (3-b) 0.02x Cr +0.14 (1-x Cr) ≦ 0.40 In other _{words, x Cr ≧ 0 ··· (3} -c) 0.06 (1-x Sn) ≦ 0.04 In other words, x _Sn ≧ 0.33 ・ ・ ・ (3-d) 0.01 (1-x _Sb ) ≦ 0.02 That is, x _Sb ≧ 0 ・ ・ ・ (3-e) 0.01 (1-x _As ) ≦ 0.02 That is, x _As ≧ 0 ・ ・(3-f) From the above equations (3-a) to (3-f), if the ratio of the mixed bath x = 0.33, all the elements are satisfied.
After 3 tons and 6.7 tons of hot metal from the first furnace were combined, decarburization and refining were performed to produce molten steel. However, in this example, the valuable alloying elements Cu, Ni, and Cr components of the assorted hot water did not reach the product specification values, and thus the chemical composition shown in Table 7 above was known for the Cr ore and the steel plate for boilers (the chemical composition shown in Table 6). The crop ends were charged at 10 kg / T and 100 kg / T, respectively, during the decarburization refining and dissolved. The impurity elements of the molten steel after the decarburization refining satisfied the standard values, and it was possible to produce special steel for weathering steel sheets.
Note that Cu and Ni in the molten steel after decarburization were lower than the product specification values, and thus were adjusted by adding Cu and Ni alloy iron after decarburization refining.

[0055]

[Table 8]

[0056]

According to the method of the present invention, pig iron having a target composition can be produced even when steel scrap having a high content of elements other than iron or whose content is unknown is used. Therefore, various scraps of unknown origin are available,
Reuse of the useful elements therein is also possible. The present invention
This has a great effect of coping with a sharp increase in the amount of scrap generated and enabling pig iron to be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating the steps of the method of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yu Ujizawa 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (56) References JP-A-1-287232 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) C22B 1/00-61/00 C21B 3/00 C21B 11/00

Claims (1)

(57) [Claims] 1. A method for producing pig iron using steel scrap as an iron source without using electric power as a heat source for melting, comprising the following steps: The process of manufacturing hot metal from scrap with high content of elements other than iron or scrap and ore and analyzing Cu, Ni, Cr, Sn, Sb and As in the hot metal, iron ore or elements other than iron A process to produce hot metal from scrap with low content or from scrap and iron ore, and to analyze Cu, Ni, Cr, Sn, Sb and As in the hot metal. A step of determining the mixing ratio of the hot metal obtained in the steps of and so as to fall within the chemical composition range, and mixing them.