Method of producing molten iron for stainless steel production

Abstract

The present invention relates to a method of producing molten iron for stainless steel production. More specifically, the method may comprise the steps of: forming a melt pool by melting iron ore charged into a furnace body by using an electric melting furnace including the furnace body, an electrode rod for generating an arc, a raw material charging port, a slag outlet, and a molten iron outlet; charging chromium ore, nickel ore, a slag regulator, and a reducing agent into an arc generation area between the lower end of the electrode rod and the melt pool, along the central axis of the electrode rod from the upper part of the electric melting furnace; and performing melting and reduction through a reaction between the melt pool and the charged chromium ore, nickel ore, slag regulator, and reducing agent.

Description

Method for manufacturing molten iron for stainless steel production

[0001] The present invention relates to a method for producing molten iron for producing stainless steel directly from iron ore, nickel ore and chromium ore using an electric melting furnace.

[0002] Stainless steel manufacturing methods can be broadly divided into two types: scrap-based and molten iron-based, depending on the raw material used. Compared to scrap-based methods, which rely heavily on scrap and raw material prices, molten iron-based methods offer significant cost advantages. Consequently, major global stainless steel manufacturers have recently adopted this method.

[0003] The manufacturing method of stainless steel using scrap generally involves melting scrap containing essential elements of stainless steel, such as chromium, in an electric furnace and then decarburizing it in a refining furnace. The manufacturing method using molten iron involves preparatory treatment to remove impurities such as silicon and phosphorus from the molten iron from the blast furnace, followed by a decarburization process. Most steel mills that manufacture molten iron using blast furnaces for carbon steel also have converters for decarburization, so decarburization of stainless steel is often performed using converters as well.

[0004] The most challenging aspect of stainless steel manufacturing using molten iron is the need to add a chromium source during the process, as conventional molten iron does not contain the chromium source required for stainless steel production. Typically, chromium sources like ferrochrome are added during the decarburization process, which removes impurities like silicon and carbon. However, converters are self-melting furnaces without an external heat source, requiring a heat source to be secured beforehand. Therefore, methods such as direct reduction of chromium ore to produce chromium molten iron and melting prior to adding the chromium source are currently being used.

[0005] The purpose of the present invention to solve the above-described problem is to provide a method for producing molten iron for stainless steel production, which can produce molten iron for stainless steel production directly from iron ore, chromium ore, and nickel ore using an electric melting furnace, thereby having excellent chromium and nickel recovery rates, reducing production costs and energy consumption, and producing stainless steel more efficiently and environmentally friendly.

[0006] The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0007] In order to achieve the above object, a method for manufacturing molten iron for manufacturing stainless steel according to one embodiment of the present invention may include a step of forming a melt pool by introducing and melting iron ore into an electric melting furnace including a furnace body, an electrode rod for generating an arc, a raw material input portion, a slag outlet, and a wire outlet; a step of introducing chromium ore and nickel ore, a slag conditioner, and a reducing agent from an upper portion of the electric melting furnace along the central axis of the electrode rod into an arc generation region between a lower portion of the electrode rod and the melt pool; and a step of melting and reducing the introduced chromium ore and nickel ore, the slag conditioner, and the reducing agent by reacting the melt pool with the melt.

[0008] In addition, the raw material ore according to one embodiment of the present invention can be input according to the relationship of the following equation (1).

[0009] Formula (1): Nickel ore input X 0.3 ≤ Chrome ore input ≤ Nickel ore input X 0.45

[0010] In addition, the raw material ore according to one embodiment of the present invention may include a step of drying the raw material and a step of pre-reducing the dried raw material before being fed into an electric melting furnace.

[0011] In addition, the preliminary reduction step according to one embodiment of the present invention can be performed at a reduction rate of the raw material ore powder of 20 to 80%.

[0012] Additionally, the slag conditioner according to one embodiment of the present invention may include any one of quicklime (CaO), limestone (CaCO3), or a mixture thereof.

[0013] Additionally, the slag conditioner according to one embodiment of the present invention may be added so that the slag basicity (mass ratio of CaO to SiO2) becomes 1.3 to 1.5.

[0014] Additionally, the reducing agent according to one embodiment of the present invention may include any one of coke, coal, ferrosilicon (FeSi), or a mixture thereof.

[0015] In addition, the reducing agent according to one embodiment of the present invention can be injected according to the relationship of the following equation (2).

[0016] Formula (2): Reducing agent input amount ≥ Cr ore input amount + Ni ore input amount) X 0.25 / Carbon content in reducing agent

[0017] In addition, the method may include a step of producing molten stainless steel according to one embodiment of the present invention at a time of 1.5 hours or more and 3 hours or less after inputting raw material ore.

[0018] In addition, the molten stainless steel production molten iron according to one embodiment of the present invention may include, in wt%, Cr: 15% or more, Ni: 7% or more, and C: 1.5% or more.

[0019] In addition, the electric melting furnace according to one embodiment of the present invention may include a furnace body, an electrode rod positioned to be inserted inward from the center of the upper part of the furnace body and generating an arc, a raw material input portion positioned apart from the electrode rod and for inputting raw material ore into the furnace body, a slag discharge port for discharging reduced slag from the furnace body, and a molten stainless steel output port for discharging molten stainless steel pig iron from the furnace body.

[0020] According to one embodiment of the present invention, by directly producing molten iron for stainless steel production from iron ore, chromium ore, and nickel ore using an electric melting furnace, it is possible to easily produce molten iron for stainless steel production, which has excellent chromium and nickel recovery rates, reduces production costs and energy consumption, and enables more efficient and environmentally friendly production of stainless steel.

[0021] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0022] FIG. 1 is a block diagram of a method for manufacturing a molten iron for manufacturing stainless steel according to one embodiment of the present invention.

[0023] Figure 2 is a diagram showing the control range of slag basicity according to one embodiment of the present invention.

[0024] Figure 3 is a schematic diagram of an electric melting furnace for manufacturing a molten iron for stainless steel according to one embodiment of the present invention.

[0025] FIG. 4 is a schematic diagram of a circular electric melting furnace having three electrode rods for manufacturing a molten iron for stainless steel according to one embodiment of the present invention.

[0026] FIG. 5 is a schematic diagram of a rectangular electric melting furnace having six electrode rods for manufacturing a molten iron for stainless steel according to one embodiment of the present invention.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. To clarify the present invention, the drawings may omit portions irrelevant to the description, and the sizes of components may be slightly exaggerated to facilitate understanding.

[0028] Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0029] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0030] The present invention relates to a method for producing molten iron for stainless steel production directly from iron ore, nickel ore, and chromium ore using an electric melting furnace. Furthermore, the present invention relates to a method for producing molten iron for stainless steel production containing iron, nickel, and chromium by melting and reducing raw ore using an electric melting furnace, which is different from the existing method of melting scrap in an electric furnace. According to the present invention, inexpensive chromium ore and nickel ore are used as raw materials, and the intermediate step of processing the ore into a ferroalloy is not required, thereby reducing the production cost and energy consumption of stainless steel, and enabling more efficient and environmentally friendly production of stainless steel.

[0031] The method for manufacturing molten iron for manufacturing stainless steel of the present invention may include the steps of: using an electric melting furnace including a furnace body, an electrode rod for generating an arc, a raw material input portion, a slag outlet, and a wire outlet, introducing and melting iron ore into the furnace body to form a melt pool; introducing chromium ore and nickel ore, a slag conditioner, and a reducing agent from the upper portion of the electric melting furnace along the central axis of the electrode rod into an arc generation region between the lower portion of the electrode rod and the melt pool; and introducing the introduced chromium ore and nickel ore, the slag conditioner, and the reducing agent into the melt pool to melt and reduce the molten iron.

[0032] Hereinafter, the method for manufacturing the molten iron for manufacturing stainless steel of the present invention will be described in detail.

[0033] First, iron ore is injected into the furnace body and power is applied to melt the iron ore to form a melt pool.

[0034] In the case of a typical electric melting furnace, it takes a long time to raise the temperature of the furnace body to operate. Therefore, in order to raise the temperature for the operation of the furnace body, iron ore with excellent solubility is first fed into the furnace body before feeding the raw material ore, and power is supplied so that the iron ore can be melted by the arc heat generated from the electrode to form a molten pool. At this time, the iron ore is fed only in the first stage for temperature increase during the entire operation time of the furnace body, and the iron ore is fed in an amount that can sufficiently raise the temperature of the furnace body and then maintained at a constant temperature. Preferably, the iron ore is fed in an amount of 70 to 80% of the total capacity of the furnace body to maintain the temperature inside the furnace body at 1500°C or higher, and more preferably, it is fed in an amount of 80% of the total capacity of the furnace body to maintain the temperature inside the furnace body at 2000°C to 3000°C.

[0035] Additionally, to raise the temperature for furnace operation, the furnace body may be preheated using a heat source material with excellent solubility prior to the introduction of the iron ore. For example, scrap that readily dissolves in heat may be used as the heat source material. The scrap introduced in this manner is merely used as a heat source material for furnace body heating and is used for a different purpose from the scrap introduced for the production of conventional stainless steel molten iron.

[0036] That is, before the input of raw material ore, a heat source material with excellent solubility, such as scrap, is input and melted to heat the furnace body, and then iron ore is input to form a molten pool so that the furnace body maintains a constant temperature, thereby preparing the furnace body for operation in advance.

[0037] When heat source material or iron ore is injected to heat the furnace body and power is supplied, an arc is generated from the electrode, and the heat source material or iron ore is melted by the arc heat to form a molten pool. At this time, an arc generation area where an arc is generated is formed between the electrode and the molten pool, and the arc generation area has a temperature of 2000℃ to 3000℃.

[0038] After forming a molten pool within the above-described furnace body, raw material ores, such as chromium ore and nickel ore, are introduced into the furnace body. At this time, it is preferable that the raw material ores are introduced around the electrode rod so that they can reach the lower end of the electrode rod along the central axis of the electrode rod.

[0039] That is, the input portion of the raw material ore is placed close to the electrode rod so that the input raw material ore moves along the central axis of the electrode rod and is supplied to the lower portion of the electrode rod, i.e., the arc generation area.

[0040] The arc generated from the electrode is at a very high temperature of about 2000℃ to 3000℃, so it can easily melt high-melting-point and refractory chromium ore into the slag.

[0041] Chromium ore has a spinel structure and is cast in the form of chromite (Mg,Fe)O·(Cr,Al,Fe)2O3. Due to the characteristics of the spinel structure, it has a strong bonding force and a high melting point. Therefore, it was previously considered impossible to melt and reduce chromium ore using an electric furnace, and thus chromium ore was not used in the production of chromium-enriched steel using an electric furnace.

[0042] However, in the present invention, the temperature of the arc generation area between the electrode and the melting pool is as high as 2000℃ to 3000℃ due to the arc generated from the electrode of the electric melting furnace, so that if raw material ores such as chrome ore and nickel ore are injected into the arc generation area, the raw material ores can be effectively melted and reduced. In particular, in the present invention, by injecting the raw material ore into the arc generation area at a temperature of 2000℃ to 3000℃, the castable chromite structure of the chrome ore can be made into a molten oxide such as MgO, FeO, Al2O3, Cr2O3, etc. using a slag conditioner that imparts slag fluidity as a medium, and then the molten oxide can be reduced by a reducing agent. That is, according to the present invention, it is possible to efficiently melt and reduce chrome ore, which was considered impossible to melt and reduce in a conventional electric furnace, and to manufacture molten iron for manufacturing stainless steel containing chrome and nickel.

[0043] It is preferable that the above raw material ores, chromium ore and nickel ore, be input according to the relationship of the following equation (1).

[0044] Formula (1): Nickel ore input X 0.3 ≤ Chrome ore input ≤ Nickel ore input X 0.45

[0045] In general, for the production of Fe-Cr-Ni stainless steel, the molten iron must contain at least 15% Cr, at least 7% Ni, and at least 1.5% C. In order to satisfy these compositions, in the present invention, it is preferable to input the raw material ores, chromium ore and nickel ore, according to the relationship of the above equation (1).

[0046] In addition, the above raw material ore, chromium ore, is Cr2O in weight% based on dry ore components. 3: It is preferable to contain 40% of Ni, 12% of FeO, 8% of MgO, and the remainder of CaO, MgO, Al2O3, and SiO2. In addition, nickel ore preferably contains 3% to 4% of Ni and 40% to 60% of Fe by weight based on dry ore components, although this varies depending on the type of ore.

[0047] In addition, the above raw material ore may further include a step of drying the raw material before being fed into an electric melting furnace and a step of pre-reducing the dried raw material.

[0048] The step of drying the above raw material can be performed using a rotary hearth furnace (RHF), a rotary kiln (RK), etc., and the preliminary reduction can be controlled so that the reduction rate of the raw material ore is 20 to 80%. If the reduction rate of the raw material ore is less than 20% during the preliminary reduction, the effect of improving the dissolution rate within the furnace due to the preliminary reduction cannot be observed, and if it exceeds 80%, the effect of improving the dissolution rate within the furnace and the raw material recovery rate compared to the reduction rate may be minimal.

[0049] Additionally, when the raw material ores, chrome ore and nickel ore, are injected into the furnace, a slag conditioner and a reducing agent can be injected together.

[0050] The above slag conditioner serves to impart fluidity to the slag, and quicklime (CaO), limestone (CaCO3), etc. can be used. At this time, the basicity of the slag (mass ratio of CaO to SiO2) needs to be controlled to a level where the viscosity is low and the Cr2O3 solubility is low, making reduction easy in terms of the slag properties.

[0051] Fig. 2 shows the slag basicity control range. As shown in Fig. 2, when the basicity of the slag increases, the solubility of Cr2O3 decreases. However, if the slag basicity increases excessively, CaCr2O4 is precipitated, which increases viscosity and makes reduction difficult. Therefore, considering this, it is preferable to add the slag conditioner so that the basicity of the slag (mass ratio of CaO to SiO2) is controlled to be between 1.3 and 1.5, and more preferably, it is added so that it is controlled to be 1.4.

[0052] In addition, when ferrosilicon (FeSi) or silicon carbide (SiC) is used as the reducing agent, the slag may become low-basic, and the problem of slag volume increasing as the lime input is increased to control the slag basicity may occur. Therefore, in the present invention, it is preferable to use a carbon-based reducing agent such as coke or coal as the reducing agent. However, if the reduction is not effective and there is a problem with the furnace, a reducing agent such as ferrosilicon may be used.

[0053] It is preferable that the above reducing agent be added according to the relationship of the following equation (2).

[0054] Formula (2): Reducing agent input amount ≥ Cr ore input amount + Ni ore input amount) X 0.25 / Carbon content in reducing agent

[0055] The more the amount of the reducing agent is added, the better, and it is preferable to add more than the relationship presented in the above equation (2) for the recovery rate of the raw material ores, chrome ore and nickel ore.

[0056] As described above, when raw material ores such as chrome ore and nickel ore are supplied to the arc generation area between the lower part of the electrode rod and the molten pool in the furnace body or the high temperature area near it, and a slag conditioner that imparts fluidity to the slag together with SiO2, Al2O3, etc. contained in the chrome ore and nickel ore are added to the furnace body, the chrome ore and nickel ore are melted into the slag by the arc heat generated between the electrode rod and the molten pool, and the molten chrome ore and nickel ore are reduced by the reducing agent and slag conditioner added to the furnace body.

[0057] At this time, the slag including the chromium ore and nickel ore should not be collected at the outer edge of the furnace body, but should be melted by the contact reaction of the molten pool, slag, reducing agent, chromium ore and nickel ore with each other near the electrode rod, and should be reduced in a short time by the reducing agent. Since the concentration of chromium and nickel in the molten pool increases depending on the retention time in the furnace body, it is preferable to extract when the chromium and nickel have reached an appropriate concentration. In consideration of this, it is preferable to extract at least 1.5 hours after the input of raw materials, and preferably between 1.5 and 3 hours, for the recovery of chromium and nickel.

[0058] The molten iron for manufacturing stainless steel of the present invention manufactured as described above may contain, in wt%, Cr: 15% or more, Ni: 7% or more, and C: 1.5% or more. Generally, the components of stainless steel include, in wt%, Cr: 18% to 20%, Ni: 8% to 10%. Therefore, if only one of the components of Cr and Ni is high, a situation may arise where excessive input of ferrochrome or ferronickel must occur to adjust the components in the decarburization process, which is a process after the electric melting furnace, and operation may be difficult due to the cooling effect of this alloy iron. Considering this, it is preferable that Cr and Ni be contained in an amount of 15% and 7% or more at the same time, and not exceed 20% and 10%, respectively. In addition, since C acts as a heat source in the decarburization process, it should be contained in an amount of 1.5% or more, and if it exceeds 5%, the time required for decarburization increases and the molten steel temperature increases excessively, which may cause a vicious cycle where coolant must be added again.

[0059] In addition, the molten iron for manufacturing the above stainless steel can be manufactured into Fe-Cr-Ni stainless steel through a subsequent decarburization process, a secondary refining process, a continuous casting process, etc.

[0060] Hereinafter, a method for manufacturing a molten iron for manufacturing stainless steel according to one embodiment of the present invention will be described with reference to the drawings.

[0061] FIG. 1 is a block diagram of a method for manufacturing molten iron for manufacturing stainless steel according to an embodiment of the present invention, FIG. 3 is a schematic diagram of an electric melting furnace for manufacturing molten iron for manufacturing stainless steel according to an embodiment of the present invention, FIG. 4 is a schematic diagram of an electric melting furnace having a circular structure with three electrode rods for manufacturing molten iron for manufacturing stainless steel according to an embodiment of the present invention, and FIG. 5 is a schematic diagram of an electric melting furnace having a rectangular structure with six electrode rods for manufacturing molten iron for manufacturing stainless steel according to an embodiment of the present invention.

[0062] Referring to FIG. 1, a molten iron for manufacturing stainless steel according to one embodiment of the present disclosure can be manufactured by introducing and melting iron ore into a furnace body of an electric melting furnace to form a melt pool, introducing chromium ore and nickel ore, a slag conditioner and a reducing agent into the furnace body, and then melting and reducing the introduced chromium ore and nickel ore, the slag conditioner and the reducing agent by reacting them with the melt pool.

[0063] Also, referring to FIGS. 3 to 5, an electric melting furnace (1) for manufacturing molten iron for stainless steel according to one embodiment of the present disclosure includes a furnace body (10), an electrode rod (20) positioned at the center of the furnace body (10) and generating an arc, a raw material input portion (30) spaced apart from the electrode rod (20) and for feeding raw material ore into the furnace body (10), a slag discharge port (40) for discharging reduced slag from the furnace body (10), and a discharge port (50) for discharging molten stainless steel molten iron from the furnace body (10).

[0064] The above furnace body (10) may have a circular (see FIG. 4) or rectangular (see FIG. 5) structure, may be manufactured from a heat-resistant material to withstand high temperature and corrosive environments, and may be coated with a refractory material on the inside of the furnace body (10) to prevent reaction with the raw material ore. In addition, a gas discharge port (60) for exhausting exhaust gas may be provided on one side of the furnace body (10).

[0065] The above electrode rod (20) is positioned to be inserted into the furnace body (10) from the center of the upper part of the electric melting furnace (1) and is connected to a power supply. The electrode rod (20) is made of a conductive material such as C and generates arc heat when power is applied and electricity passes through it. The electrode rod (20) may include multiple electrodes, such as three or six, as needed. The power supply supplies power to the electrode rod (20) to generate arc heat, and melts and reduces the raw material ores, chrome ore and nickel ore, by the generated arc heat. At this time, the power supply can use any electric source, such as a generator or a power grid.

[0066] When the above electric melting furnace (1) is operated, power is supplied to the electrode rod (20) inserted into the furnace body (10), and as electricity passes through the electrode rod (20), arc heat is generated. The raw material ores, chromium ore and nickel ore, which are introduced into the furnace body (1) are melted by the arc heat generated in this way, and by reacting with a carbon-based reducing agent, molten iron for manufacturing molten stainless steel containing C and saturated Fe, Ni, and Cr can be manufactured. After the reaction is completed, the slag is discharged through the outlet (40), and the molten iron for manufacturing molten stainless steel is discharged through the outlet (50) and can be manufactured into stainless steel through steelmaking processes such as decarburization, secondary refining, and continuous casting.

[0067] Hereinafter, the present invention will be described in more detail through examples. However, the description of these examples is intended only to illustrate the implementation of the present invention and is not intended to limit the present invention. This is because the scope of the present invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0068] Example

[0069] The following example was carried out using a circular electric melting furnace having three electrode rods as shown in Fig. 4 and capable of holding 10 tons of molten iron.

[0070] Two days before feeding the raw materials, chrome ore and nickel ore, into the electric melting furnace, two tons of scrap were placed on the floor of the furnace as a heat source and power was supplied to melt the scrap by the arc heat of the electrodes. Next, to raise the temperature for furnace operation, direct reduction iron (DRI), manufactured by directly reducing iron ore, and coke as a reducing agent were mixed and fed at a rate of one ton per hour for melting. Iron ore was fed to form a total melt pool of eight tons inside the furnace, and the temperature was maintained until it exceeded 1500℃.

[0071] Next, 350 kg of chrome ore, 1 ton of nickel ore, 700 g of quicklime (CaO) as a slag conditioner, and 350 kg of coke as a reducing agent were prepared, and then slowly introduced from the top of the furnace body along the central axis of the electrode through the raw material inlet, and the introduced chrome ore, nickel ore, slag conditioner, and reducing agent were brought into contact with the molten pool to melt and reduce, thereby manufacturing molten iron for manufacturing stainless steel. Then, the molten iron in the furnace body was drawn out once every 3 hours, and the chrome ore, nickel ore, slag conditioner, and reducing agent were introduced again, thereby gradually increasing the concentration of chrome and nickel contained in the molten iron for manufacturing stainless steel.

[0072] The concentrations of Cr, Ni, and C in the molten iron for stainless steel production according to the input time of chromium ore and nickel ore, which are raw ores, during the production of the molten iron for stainless steel production are measured and shown in Figure 6.

[0073] As shown in Fig. 6, it was found that the molten iron for manufacturing molten stainless steel manufactured according to the present invention contains Cr, Ni and C in the molten iron to be suitable for use in manufacturing stainless steel, and must be drawn out at least 1.5 hours after the input of raw materials.

[0074] In addition, the components of the molten stainless steel production molten iron produced after operating the electric melting furnace for 24 hours were analyzed, and the results are shown in Table 1 below.

[0075] ClassificationCr concentrationNi concentrationC concentrationComposition of molten iron for manufacturing molten stainless steel15.4%5.5%2.1%

[0076] As shown in Table 1 above, it was confirmed that the molten iron for manufacturing molten stainless steel manufactured according to the present invention contained Cr, Ni, and C at levels suitable for manufacturing stainless steel, and from these results, it was found that it would be possible to manufacture stainless steel using the molten iron for manufacturing stainless steel manufactured according to the present invention.

[0077] Although the embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be implemented by a person having ordinary skill in the art to which the disclosed invention pertains without departing from the gist claimed in the claims.

[0078] (Explanation of symbols)

[0079] 1: Electric melting furnace 10: Furnace body

[0080] 20: Electrode rod 30: Raw material inlet

[0081] 40: Exit port 50: Exit port

[0082] 60: Gas outlet

Claims

1. A step of forming a melt pool by introducing and melting iron ore into the furnace body using an electric melting furnace including a furnace body, an electrode rod for generating an arc, a raw material input portion, an outlet, and a discharge port; A step of injecting chrome ore and nickel ore, slag conditioner and reducing agent from the upper part of the electric melting furnace along the central axis of the electrode rod into the arc generation area between the lower part of the electrode rod and the molten pool; and A step of melting and reducing by reacting the above-mentioned input chrome ore and nickel ore, slag conditioner and reducing agent with the molten pool; A method for manufacturing a molten iron for manufacturing stainless steel, comprising:

2. In paragraph 1, A method for manufacturing molten iron for manufacturing stainless steel, wherein the above chromium ore and nickel ore are input according to the relationship of the following equation (1). Equation (1): Nickel ore input X 0.3 ≤ Chrome ore input ≤ Nickel ore input X 0.45 3. In paragraph 1, A method for producing molten iron for manufacturing stainless steel, comprising a step of drying the raw materials and a step of pre-reducing the dried raw materials before feeding the above chromium ore and nickel ore into an electric melting furnace.

4. In paragraph 3, A method for manufacturing molten iron for manufacturing stainless steel, wherein the above preliminary reduction step is performed at a reduction rate of 20 to 80% of the raw material ore powder.

5. In paragraph 1, The above slag conditioner is quicklime (CaO), limestone (CaCO 3 ) or a method for producing a molten iron for manufacturing stainless steel comprising any one of these mixtures.

6. In paragraph 1, The above slag conditioner is a slag basicity (SiO 2 A method for manufacturing molten iron for manufacturing stainless steel, wherein the molten iron is added so that the mass ratio of CaO to molten iron is 1.3 to 1.

5.

7. In paragraph 1, A method for producing molten iron for manufacturing stainless steel, wherein the reducing agent comprises any one of coke, coal, ferrosilicon (FeSi) or a mixture thereof.

8. In paragraph 1, A method for manufacturing a molten iron for manufacturing stainless steel, wherein the reducing agent is added according to the relationship of the following equation (2). Equation (2): Reducing agent input amount ≥ Cr ore input amount + Ni ore input amount) X 0.25 / Carbon content in reducing agent 9. In paragraph 1, A method for manufacturing molten iron for manufacturing stainless steel, comprising a step of producing molten iron for manufacturing the molten stainless steel 1.5 hours to 3 hours after inputting raw material ore.

10. In paragraph 1, A method for producing molten iron for manufacturing stainless steel, wherein the molten iron for manufacturing the above molten stainless steel contains, in weight %, 15% or more of Cr, 7% or more of Ni, and 1.5% or more of C.

11. In paragraph 1, The above electric melting furnace comprises a furnace body, an electrode rod positioned to be inserted inward from the center of the upper part of the furnace body and generating an arc, a raw material input portion positioned apart from the electrode rod and for inputting raw material ore into the furnace body, a slag discharge port for discharging reduced slag from the furnace body, and a discharge port for discharging molten stainless steel pig iron from the furnace body. A method for manufacturing molten stainless steel pig iron.

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