JP2021176980A - Electric furnace steelmaking process - Google Patents

Abstract

To provide an electric furnace steelmaking process capable of satisfactorily discharging slag and reducing the cost of a slag-making material by increasing the amount of metallic aluminum.SOLUTION: In an electric furnace steelmaking process, when chromium-containing steel is refined in an electric furnace, a slag-making material having one or more kinds of lime, chromium-containing slag, chromium-containing dust, or a metal silicon-containing material is added during the melting period. A metal aluminum-containing material is added so that the total amount of Al2O3 of the composition of the produced slag exceeds 20 wt%. Adjustment is performed so that the composition of the produced slag satisfies a desired relation and a molten steel temperature is 1,550°C or higher.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electric furnace steelmaking method for refining chromium-containing steel using metallic aluminum.

In recent years, when refining stainless steel or the like in an electric furnace, it is common to charge Si into the furnace as a heating agent and utilize the heat of oxidation of Si in order to reduce the electric energy at the time of melting. (See, for example, Patent Document 1). This Si is also used as a deoxidizing material during steelmaking, and is generally used in the form of ferroalloys such as FeSi and SiMn. However, since ferroalloys are manufactured through high-temperature processes such as electric furnaces, mass use is not desirable from the viewpoint of energy saving and resource saving. Therefore, instead of ferroalloys such as FeSi and SiMn, it is being studied to use "aluminum dross for steel" defined by JIS G2402 as a heating agent / oxygen scavenger.

This aluminum dross refers to the residue floating on the surface of the molten metal and the residue on the bottom of the furnace when the aluminum or the aluminum alloy is melted, and may be abbreviated as aluminum dross or simply dross. Almidross is rich in metallic aluminum and is known to be granular, powdery and lumpy after cooling.
In addition, "aluminum dross for steel" used as a deoxidizing material refers to a mixture in which the above-mentioned aluminum dross is subjected to processing such as crushing, classification, and particle size adjustment, and the components are adjusted by further blending several types. .. If there is a deficient component after blending, the above-mentioned aluminum dross is also included in the "aluminum dross for steel" after adjusting the components by adding metallic aluminum, aluminum oxide, and other active ingredients. Is done. Furthermore, what has been recovered from aluminum dross is called dross residual ash, and is often treated as a substance different from aluminum dross for steel. However, in this specification, when the dross residual ash contains metallic aluminum, it can be expected to be used as a heating material or a deoxidizing material, and therefore, it is treated as "aluminum dross for steel" in this specification.

By the way, as a method of using a material containing metallic aluminum instead of ferroalloy as a heating agent or an oxygen scavenger when melting chrome-containing steel, for example, the steelmaking method of Patent Document 1 is known.
That is, in the steelmaking method of Patent Document 1, the slag composition produced during melting is CaO: 20 to 40 wt%, SiO ₂ : 25 to 45 wt%, Al ₂ O ₃ : 10 to 20 wt%, CaO / SiO ₂ = 0.6 to. It is adjusted to 1.1 and the molten steel temperature is adjusted to 1550 to 1700 ° C to maintain the same slag melting point, viscosity and slag discharge as when using fluorite.

Japanese Patent No. 3636693

In the method of Patent Document 1, _{the concentration of Al 2} O _{3 in} the slag is 10 to 20 wt%, and the amount of metallic aluminum used is not so large. In other words, in order to reduce the cost of the slag-making material and further reduce the cost of the refining process, a large amount of metallic aluminum should be used, that is, the amount of Al ₂ O ₃ added should exceed 20 wt%. It is preferable to increase the amount of metallic aluminum.

However, if the _{amount of metallic aluminum is increased until the amount of Al 2} O _{3 in} the slag exceeds 20 wt%, the viscosity of the slag may become too high or it may not be able to dissolve, making it difficult to remove the slag. There is. That is, although increasing the amount of metallic aluminum is effective in reducing costs, it may cause a problem in terms of scavenging property.
The present invention has been made in view of the above-mentioned problems, and by increasing the amount of metallic aluminum while maintaining good slag slag removal property, it is possible to reduce the cost without impairing workability and the like. The purpose is to provide the law.

In order to solve the above problems, the electric furnace steelmaking method of the present invention takes the following technical measures.
That is, the electric furnace steelmaking method of the present invention has one or more of lime, chromium-containing slag, chromium-containing dust, and metallic silicon-containing substances in the melting period when refining chromium-containing steel in an electric furnace. Along with the addition of the slag-making material, the metallic aluminum-containing material was added so that the total amount _{of Al 2} O _{3 in the produced slag composition exceeded 20 wt%, and 0.25 ≤ CaO / SiO 2 was added during the composition of the produced slag.} It is characterized in that the relationship of ≤1.24, 0.50≤ (CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ ) is established, and the molten steel temperature is adjusted to 1550 ° C. or higher.

It should be noted that preferably, the metallic aluminum-containing material is aluminum dross, aluminum ash, aluminum scrap, aluminum alloy scrap, aluminum-containing iron scrap, a mixture of metallic aluminum and aluminum oxide, a briquette containing metallic aluminum and aluminum oxide, and metallic aluminum. It is preferable to have any one or more of the granules containing aluminum oxide and aluminum oxide.

According to the electric furnace steelmaking method of the present invention, by increasing the amount of metallic aluminum while maintaining good slag slag removal property, it is possible to reduce the cost without impairing workability and the like.

It is a figure which summarized the relationship between the basicity and the parameter which shows the ratio of a liquid phase / solid phase about Experimental Examples 1-10.

Hereinafter, embodiments of the electric furnace steelmaking method according to the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, in the electric furnace steelmaking method of the present embodiment, when refining chromium-containing steel in an electric furnace, the slag-making material and metallic aluminum are contained before the raw material is melted, during the melting period when the raw material is melted, or after melting. Chromium-containing steel is smelted while adding a substance and adjusting the molten steel temperature to 1550 ° C or higher.

As the slag-making material, one or two or more selected from lime, chromium-containing slag, chromium-containing dust, and metallic silicon-containing material are used. Further, the metallic aluminum-containing material is _{added so that Al 2} O ₃ having a slag composition to be produced exceeds 20 wt% in terms of weight concentration with respect to the weight of the slag to be produced. Further, the above-mentioned slag-making material and metallic aluminum-containing material need to be added so that the composition of the produced slag satisfies the following formulas (1) and (2).

0.25 ≤ CaO / SiO ₂ ≤ 1.24 ・ ・ ・ (1)
0.50 ≤ (CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ ) ・ ・ ・ (2)
_{In addition, CaO, SiO 2} , MgO, MnO, Al ₂ O ₃ , and Cr ₂ O ₃ in the formulas (1) and (2) determine the concentration of each oxide in the slag composition to be produced. It is shown by the weight concentration with respect to the weight.

Hereinafter, the electric furnace steelmaking method of the present invention will be described in detail.
The chrome-containing steel refined by the electric furnace steelmaking method of the present invention is a steel type containing chrome such as chrome steel containing so-called stainless steel, nickel chrome molybdenum steel, chrome molybdenum steel, nickel chrome steel, and nickel steel. These chromium-containing steels are obtained by melting raw materials such as scrap in an electric furnace and refining them so as to have a composition corresponding to the steel type. After the raw material is dissolved, in other words, the above-mentioned slag-making material and the metallic aluminum-containing material are added during the dissolution period of the raw material.

The slag-making material contains one or more selected from lime, chromium-containing slag, chromium-containing dust, and metallic silicon-containing substances. That is, the slag-making material contains lime and metallic silicon-containing substances that form slag in the melted raw material, and chromium-containing slag and chromium-containing dust that stably promote refining by replenishing chromium.
The metallic aluminum-containing material is _{added as a reducing agent or a heating agent for reducing Cr 2} O ₃ and returning Cr (metal Cr) to the molten steel. This metallic aluminum-containing material includes aluminum dross, aluminum ash, aluminum scrap, aluminum alloy scrap, aluminum-containing iron scrap, a mixture of metallic aluminum and aluminum oxide, briquettes containing metallic aluminum and aluminum oxide, and metallic aluminum and aluminum oxide. Those having one kind or two or more kinds selected from the containing granules are preferably used. That is, the metallic aluminum-containing material is added to recover (refin) the metallic chromium by reducing the chromium oxide with the contained metallic aluminum.

For example, when used as a reducing agent aluminum metal inclusions refining stainless steel such as chromium-containing steel, metallic aluminum by reducing Cr ₂ O _3, metallic aluminum itself is oxidized to Al ₂ O _3, Al ₂ in the slag O ₃ concentration increases. Here, if the addition of auxiliary raw materials that generate CaO and SiO ₂ in the slag, such as FeSi and SiMn, is suppressed and the amount of metallic aluminum-containing material added is increased (increased), the cost is reduced because the expensive auxiliary raw materials are reduced. It can reduce, save energy, and save resources.

That is, in the electric furnace steelmaking method of the present invention, in order to exert cost reduction, energy saving, and resource saving effects, the amount of metallic aluminum content is increased so that the total amount _{of Al 2} O _{3 in the slag exceeds 20 wt%.} It has become.
Further, when refining by the electric furnace steelmaking method of the present invention, it is necessary to set the melting temperature to 1550 ° C. or higher in order to melt the steel. The melting temperature is preferably higher than 1550 ° C, more preferably 1600 ° C, which is higher than 1800 ° C.

As described above, when a metallic aluminum-containing material is added in place of the conventional auxiliary material that produces Ca O _{and SiO 2 in the slag, the metallic aluminum-containing material is added so that Al 2 O 3} in the slag exceeds 20 wt%. Under the condition of adding a large amount, it is possible to reduce the cost as compared with the case of using the above-mentioned conventional auxiliary raw materials.
However, even if cost reduction is possible, if the generated slag cannot be eliminated, it is insufficient as a refining method. In this regard, if a _{large amount of metallic aluminum-containing material is added until Al 2} O ₃ in the slag exceeds 20 wt%, there is a concern that the eutectic portion having a low melting point is reduced and the fluidity of the slag is deteriorated.

Therefore, in the electric furnace steelmaking method of the present invention, the composition of the refined slag is controlled in order to surely discharge the produced slag. Specifically, the composition control of this slag is the condition that "the slag produced at the above-mentioned melting temperature is melted" and "the produced slag has a viscosity that allows sufficient discharge". It means controlling the slag to a composition that satisfies both of the conditions.

Hereinafter, the two conditions for controlling the composition of the slag described above will be described.
In order to obtain a viscosity that allows the produced slag to be sufficiently discharged, it is indispensable to control the composition in _{which the CaO-SiO 2 compound has a low melting point region at the above-mentioned dissolution temperature.} That is, the temperature of the molten steel in contact with the slag must be 1550 ° C or higher as described later, and even in that case, the above-mentioned basicity (CaO / It is necessary to control the slag of SiO ₂ ) to the composition as shown in the formula (1).

0.25 ≤ CaO / SiO ₂ ≤ 1.20 ・ ・ ・ (1)
In addition, the applicant actually showed in both the phase diagram and the experiment that slag can be discharged if the basicity (CaO / SiO ₂ ) satisfies the composition range of 0.25 ≤ CaO / SiO _{2 ≤ 1.20.} I have confirmed to.
Further, when the above-mentioned basicity (CaO / SiO ₂ ) decreases (decreases), scavenging becomes possible, but the viscosity becomes too small and the time required for scavenging increases. Therefore, the lower limit of the basicity is preferably 0.25 or more, preferably 0.3 or more, more preferably 0.40 or more, and further preferably (most preferably) 0.60 or more.

Furthermore, when the basicity (CaO / SiO ₂ ) increases, the time required for scavenging decreases, but the amount of CaO used increases, so the amount of slag generated and the refining cost increase. Therefore, the upper limit of basicity (CaO / SiO ₂ ) is preferably 1.24 or less, preferably 1.20 or less, more preferably 1.15 or less, and further preferably 1.10 or less.
It is known that the slag produced by refining chrome-containing steel such as stainless steel described above is roughly classified into CaO-SiO ₂ type compounds and MgO-Al ₂ O ₃ -Cr ₂ O ₃ type compounds. Here, MnO is also present in the slag, but MnO generally takes the form of being dissolved in a compound of the _{MgO-Al 2} O _3- Cr ₂ O _{3 system.} Therefore, MnO can be treated in the same way as _{MgO-Al 2} O _3- Cr ₂ O _{3 compounds.}

Next, the solubility of these compounds will be examined using a phase diagram. As a result of examining the phase diagram, it was found that the CaO-SiO ₂ system compound has a liquid phase in a specific composition range and can be dissolved even at a low melting point of 1600 ° C. or lower. On the other hand, it was found that MgO-Al ₂ O _3- Cr ₂ O ₃ compounds have a solid phase in any composition range and cannot be dissolved even if the composition state is changed. In other words, MgO-Al ₂ O _3- Cr ₂ O ₃ compounds are solid-phase over the entire composition range and cannot be melted at a low melting point of 1600 ° C or lower.

Next, the abundance ratio of the solid-phase MgO-Al ₂ O _3- Cr ₂ O ₃ compound and the liquid phase _{Ca O-SiO 2} compound at the above-mentioned dissolution temperature is contained in the slag. The applicant examined whether the slag itself could be dissolved if this was the case (how much the liquid phase should be increased).
As a result, it was found that the slag dissolves when the concentration ratio of the CaO-SiO _{2 system compound to the MgO-Al 2} O ₃ -Cr ₂ O _{3 system compound is 0.50 or more.}

As described above, since MnO is _{dissolved in the MgO-Al 2} O _3- Cr ₂ O ₃ system compound, it is different from MgO in the state diagram of the MgO _{-Al 2} O ₃ -Cr ₂ O _{3 system.} It can be treated as an equivalent.
The relationship derived from the above is the following equation (2).
(CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ ) ≧ 0.50 ・ ・ ・ (2)
Here, the liquid phase / solid phase ratio (liquid phase ratio) described on the left side of the above formula (2) is preferably 0.55 or more, more preferably 0.60 or more. Further, even if the liquid phase / solid phase ratio (liquid phase ratio) is increased, the amount of dissolution increases and it becomes easier to discharge, so that the upper limit value is not specified in the formula (2). However, if the liquid phase / solid phase ratio is made too large, the amount of slag generated increases and the refining cost also increases. Therefore, even if the workability is improved, it is not preferable from the viewpoint of the overall cost. From this, the upper limit of the liquid phase / solid phase ratio (liquid phase ratio) described on the left side of the above formula (2) is preferably 1.80 or less, more preferably 1.70 or less, still more preferably 1.30 or less, and most. It is preferably 1.0 or less.

From the above results, _{the values of "CaO / SiO 2} " and "(CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ )" are related to equations (1) and (2). By adding a metal-aluminum-containing material to chrome-containing steel together with a slag-making material and refining at a molten steel temperature of 1550 ° C or higher, the composition of the slag is optimized and good slag removal property is obtained. It is judged that the amount of metallic aluminum can be increased to 20 wt% or more while maintaining the slag, and both the improvement of slag slag discharge property and the reduction of the cost of slag-making material can be achieved at the same time.

Next, the action and effect of the electric furnace refining method of the present invention will be described in detail with reference to Examples and Comparative Examples.
The experiments for Examples and Comparative Examples were carried out at 10 levels of "Experimental Example 1" to "Experimental Example 10". Of "Experimental Example 1" to "Experimental Example 10", "Experimental Example 5", "Experimental Example 6", and "Experimental Example 10" correspond to Comparative Examples, and the remaining "Experimental Example 1" to "Experimental Example 10" 4 ”and“ Experimental Example 7 ”to“ Experimental Example 9 ”correspond to Examples.

In addition, "Experimental Example 1" to "Experimental Example 10" are those in which an experiment (evaluation) was performed according to any one of (Experimental Method 1) to (Experimental Method 3) shown below. Specifically, "Experimental Example 1" to "Experimental Example 6" are conducting experiments according to Experimental Method 1, and "Experimental Example 7" to "Experimental Example 9" are conducting experiments according to Experimental Method 2. In addition, "Experimental Example 10" is an experiment conducted according to the experimental method 3.

In the above-mentioned (Experimental Method 1), aluminum dross as a metallic aluminum-containing substance was added as a deoxidizing material to molten steel of chrome-containing steel decarburized in an electric furnace, and refining (deoxidizing) was performed. be. This molten steel is obtained by melting scrap of chromium-containing steel charged in an electric furnace, putting a slag-making material such as lime into the furnace, and then decarburizing by oxygen blowing.
Further, the molten steel to which the deoxidizing material is added is melted by energization in an electric furnace and is used for a deoxidizing operation (refining operation). The molten steel during this deoxidizing work (refining work) has a molten steel temperature of 1600 ° C or higher. Then, after melting, a slag removal operation was performed using a derekki (slag scraping means) with firewood attached to the tip, and the slag collected in the slag removal operation was subjected to a quantitative analysis described later. .. Quantitative analysis of slag is performed by crushing the slag into a briquette state using a fluorescent X-ray diffractometer (Rigaku Co., Ltd., "Supermini2000") for CaO, SiO ₂ , Al ₂ O ₃ , MgO, MnO, Cr ₂ O ₃ . Quantitative analysis is being performed.

(Experimental method 2) is a quantitative analysis of the slag obtained in the same manner as the above-mentioned (Experimental method 1) using ICP (inductively coupled spectroscopic analysis).
Specifically, in (Experimental Method 2), scrap is melted in an electric furnace, a slag-making material such as lime is put into the furnace, and then decarburized by oxygen blowing. Aluminidros was added as a deoxidizing material as a contained material, and after energization, steel was discharged to a ladle. In addition, after steel removal, the slag was collected in a slag removal operation in which the slag was removed by tilting the ladle and using a derecki with firewood at the tip, and quantitative analysis of the slag was performed by ICP. The molten steel temperature in the work of (Experimental Method 2) is also 1600 ° C. or higher.

The quantitative analysis performed on the slag in (Experimental Method 2) sets the method according to the type of metal oxide. Specifically, for the quantitative analysis of the content of calcium oxide (CaO), JIS M8221 (1997) "Iron ore-calcium quantification method" was followed. For quantitative analysis of silicon oxide (SiO ₂ ) content, aluminum oxide (Al ₂ O ₃ ) content, magnesium oxide (MgO) content, and manganese oxide (MnO) content, please refer to JIS M8206 ( 2014) According to "Iron ore-ICP issued spectroscopic analysis method". Furthermore, _{regarding the quantitative analysis of the content of dichrome trichrome (Cr 2} O ₃ ), "3 terms and definitions" in the JIS procedure in JIS M8206 (2014) "Iron ore-ICP issued spectroscopic analysis method". "5 abstracts" and "7 devices" to "14.1 Calculation of final results" are quoted as they are, and "6 reagents" are commercially available in place of the stock solution and standard solution described in this item. The analysis was performed with reference to this item by using a chromium standard solution (1000 ppm). Regarding "calculation of 14.2 oxide content", instead of the conversion coefficient described in this item, "1.4615" is used as the conversion coefficient _{from chromium (Cr) to dichromium trioxide (Cr 2} O _3). Is used.

For both (Experimental Method 1) and (Experimental Method 2) described above, "emission property evaluation" is also performed.
In other words, if the slag has hardened to the extent that the slag cannot be discharged and the slag has to be left in the electric furnace after steel removal and the next charge operation has to be carried out, it is considered difficult to remove the slag. The result of "" was set to x. On the other hand, for those that were able to be discharged and the operation of the next charge could be carried out without leaving slag in the electric furnace after steel removal, the result of "removal property evaluation" was evaluated as 〇.

Furthermore, (Experimental Method 3), the composition of the slag _{CaO: 13.5wt%, SiO 2:} 18.2wt%, Al 2 O 3: 21.8wt%, MgO: 23.0wt%, MnO: 9.2wt%, Cr 2 O ₃ : Commercially available reagents are mixed so as to be 14.3 wt%, 25 g of the mixed reagents are put into a platinum crucible, the platinum crucible containing the reagents is charged into an electric furnace, and the temperature is raised to 1650 ° C. 10 It was held for a minute. The reagent kept at 1650 ° C. in this way was discharged on an iron plate, and the discharge property was evaluated.

In this (experimental method 3) "emission property evaluation", when discharging from a platinum crucible on an iron plate in an atmospheric atmosphere, those that could not be discharged on the iron plate are regarded as difficult to discharge and "removability". The result of "evaluation" was marked with x. In addition, the results of the "emission property evaluation" were marked as ◯, assuming that those that could be discharged on the iron plate can be discharged.
The reagents used for mixing are CaO: Fujifilm Wako Pure Chemical Industries (purity: special grade reagent), SiO ₂ : Fujifilm Wako Pure Chemical Industries (purity: special grade reagent), MgO: Fujifilm Wako Pure Chemical Industries (purity: special grade). Reagent special grade), Al ₂ O ₃ : Fujifilm Wako Pure Chemical Industries (purity: Reagent special grade), Cr ₂ O ₃ : Fujifilm Wako Pure Chemical Industries (purity: Reagent 1st grade), MnO: High Purity Chemical Laboratory (Purity: Reagent special grade) Purity: 99.9%).

In addition, (Experimental method 1) to (Experimental method 3) all evaluate the relationship between the slag composition and the fluidity of the slag, and these relationships and the effects of the invention do not differ depending on the difference in the experimental methods.
The results of "Experimental Example 1" to "Experimental Example 10" described above are shown in Table 1.

Looking at "Experimental Example 1" to "Experimental Example 4" and "Experimental Example 7" to "Experimental Example 9" _{, when the value of "CaO / SiO 2} " is 0.66 to 1.11, "emission property evaluation" is performed. The result of is ○. However, looking at "Experimental Example 5", "Experimental Example 6", and "Experimental Example 10" _{, when the values of "CaO / SiO 2} " are 1.25 and 1.53, the result of "exhaustivity evaluation" is ×. It has become. From this, it _{can be seen that when the value of "CaO / SiO 2} " is 1.24 or less, preferably 1.20 or less, more preferably 1.15 or less, and further preferably 1.10 or less, the scavenging property can be improved.

Looking at "Experimental Example 1" to "Experimental Example 4" and "Experimental Example 7" to "Experimental Example 9", "(CaO + SiO ₂ ) / (MgO) shown on the left side of the equation (2). The parameter "+ MnO + Al ₂ O ₃ + Cr ₂ O ₃ )" (parameter of liquid phase ratio) is 0.52 to 0.81, and the result of "emission evaluation" is ○. However, looking at "Experimental Example 6" and "Experimental Example 10", _{the parameters of "(CaO + SiO 2} ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ )" are 0.47 and 0.46. The result of "exhaustivity evaluation" is x. From this, when the value of "(CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ )" is 0.50 or more, preferably 0.55 or more, more preferably 0.60 or more, it is excluded. It can be seen that the slag property can be improved.

From the above results, the horizontal axis is _{the value of "CaO / SiO 2} " and the vertical axis is the value of "(CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ )". _{In No. 1, "CaO / SiO 2} " and "(CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr) are included in the area indicated as the "suitable range" in the figure (the range surrounded by the thick solid line). _By adding a metallic aluminum-containing material to chrome-containing steel together with a slag-making material and refining it at a molten steel temperature of 1550 ° C or higher so that a slag having a composition that includes the value of "2 O _{3)" can be obtained.} , The composition of slag can be optimized to maintain good slag removal property, and the amount of metallic aluminum can be increased to 20 wt% or more, achieving both improvement of slag slag removal property and reduction of cost for slag making material. It is judged that it can be done.

It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. In particular, in the embodiments disclosed this time, matters not explicitly disclosed, such as operating conditions, operating conditions, various parameters, dimensions, weights, volumes of components, etc., deviate from the scope normally implemented by those skilled in the art. A value that can be easily assumed by a person skilled in the art is adopted.

Claims (2)

When refining chrome-containing steel in an electric furnace, slag produced by adding slag containing one or more of lime, chrome-containing slag, chrome-containing dust, or metallic silicon-containing material during the melting period. Add the metallic aluminum content so that the total amount of Al ₂ O _{3 in the composition exceeds 20 wt%,}
During the composition of the slag produced,
0.25 ≤ CaO / SiO ₂ ≤ 1.24
0.50 ≤ (CaO + SiO ₂ ) / (MgO + MnO + Al ₂ O ₃ + Cr ₂ O ₃ )
An electric furnace steelmaking method characterized in that the above relationship is established and the molten steel temperature is adjusted to 1550 ° C or higher. The metallic aluminum-containing material contains aluminum dross, aluminum ash, aluminum scrap, aluminum alloy scrap, aluminum-containing iron scrap, a mixture of metallic aluminum and aluminum oxide, briquettes containing metallic aluminum and aluminum oxide, and metallic aluminum and aluminum oxide. The electric furnace steelmaking method according to claim 1, wherein the granulated product has any one type or two or more types.

Images