JP2938535B2 - Manufacturing process of chromium-containing molten steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] The present invention can flexibly respond to changes in the chromium raw material situation and the energy situation in a cost-minimum direction, can mass-produce, and is based on a stable operation. The present invention relates to a production process capable of producing high quality chromium-containing molten steel at low cost while maintaining high productivity.

[Conventional technology]

As chromium-containing steels, steels including high and low chromium exceeding the range of chromium content, including stainless steel, which is a typical example, are manufactured. And, as a method of its production, various raw materials, mainly chromium raw materials, are charged into a furnace such as a melting furnace, and the molten iron is made into chromium-containing hot metal containing a high carbon content. After the resulting chromium-containing molten steel is obtained, the molten steel is cast to produce a slab or the like.

Conventionally, chromium-containing hot metal, which is the source of such chromium-containing steel, is generally made of stainless steel scrap,
Small amounts of chromium ore and chromium-containing waste (abrasive waste, mill scale, dust, sludge, slag, etc.), such as chromium irons, solid-phase reduction products and their pellets, which have been previously refined or reduced from chromium ore. ), Etc., as well as iron sources, carbon materials and slag-making materials, etc., were mainly melted and manufactured, but it was common to use an arc furnace as a melting furnace.

This chromium-containing hot metal contains a large amount of expensive chromium,
Furthermore, since expensive nickel is also contained in many cases, the cost of these raw materials greatly affects the production cost. Therefore, if the price fluctuation of chromium or nickel causes a price fluctuation between the chromium irons, scraps and other chromium raw materials, the operation and the ratio of these compounds and their ratios will be in the direction of minimizing the cost. Needs to be changed. In order to use various chromium raw materials in the production process by changing the composition and the ratio thereof in response to the change of the chromium raw material situation, in addition to the content and content of the chromium raw material, in particular, the shape and size are required. Although a melting furnace which can use a large amount of scraps and wastes is also required with few restrictions, an arc furnace has been used as a suitable furnace which can comprehensively perform such matters. However, melting by this arc furnace consumes a large amount of expensive electric power, and increases energy costs. In order to save energy, there are methods of recovering exhaust gas from the arc furnace and preheating a scrap to be charged in a large amount, or blowing oxygen into the molten metal using an oxygen lance during melting in the arc furnace and heating. However, the power cost has not been sufficiently reduced.

In addition, as another method of producing chromium-containing hot metal, in recent years,
In order to reduce energy cost and chromium raw material cost, mainly stainless steel scrap and other debris and powdered chromium ore (containing chromium oxide)
In addition to this, wastes mainly containing chromium oxides generated in factories and the like (abrasive debris, mill scale, dust, sludge, slag, etc.) may be added. A method of producing chromium-containing hot metal in a furnace has been proposed and promoted. However, also in this method, the reduction of chromium ore is an endothermic reaction, which consumes a large amount of carbon material and thermal energy (usually using oxygen), and is a cold material because it is necessary to maintain a high-temperature reducing atmosphere. There are disadvantages, such as that the amount of scrap used is limited, and that the amount of particulate oxides such as waste generated in the manufacturing plant is limited. Further, when melting and smelting and reducing, a gas having a large amount of energy (latent heat) from sensible heat is discharged, and if the gas is not effectively utilized, it is superior to the melting method using an arc furnace. It can not be said. A converter type system and a vertical furnace system are introduced as the production technology of chromium-containing hot metal characterized by the smelting reduction of chromium ore. Among these, in the converter type system, secondary combustion technology is important, in which exhaust gas with a large amount of CO generated in a large amount is burned into CO ₂ by upper blowing oxygen and the heat is heated to slag metal. The problem is that the utilization rate and thermal efficiency are low. On the other hand, in the vertical furnace system, a part of the energy of the exhaust gas is utilized for preheating various raw materials that are melted and melt-reduced when the gas passes upward in the furnace, and have high thermal efficiency. In addition, since expensive electric power is not used as an energy source and an inexpensive carbon material is used, the energy cost can be reduced. However, in order to continue the operation in such a state, it is important to ensure air permeability so that the exhaust gas easily passes through the raw material layer charged into the furnace. Therefore, it is necessary to make the shape and dimensions of various raw materials within a certain range, and large scraps and other debris and powdery raw materials that deteriorate air permeability cannot be used or must be specially processed. The problem is that they cannot be used. In addition, from the production of chromium-containing steel (Cr-Ni-based steel) containing nickel components,
System production), that is, it is not possible to change the hot metal composition in the furnace all at once to switch between both system steels, and it takes time and the amount of hot metal. That was also a problem.

[Problems to be solved by the invention]

In order to solve the above-mentioned problems of the prior art, the present invention provides: (i) various kinds of raw materials including a raw material containing nickel and iron, including chromium, and charged and blown into a furnace; Ingredients and contents, their shapes and dimensions, mixing ratios and their changes, etc., are as unrestricted as possible and can be used without special processing. (Ii) Inexpensive chromium ore and expensive chromium and nickel alloys A large amount of scrap (industrial waste) containing effective metals such as chromium, nickel, and iron such as dust, sludge, slag, etc. (Iii) Chromium-containing steel (Cr-based steel) and chromium-containing steel (CR-Ni-based steel) that also contain nickel components can be used from hot metal to steel mainly in chromium, carbon, and nickel. Quantitative It can be easily adjusted in terms of manufacturing temperature, and it is easy to switch between both steels (change of steel type), and it can be easily and efficiently manufactured. (Iv) Expensive electric power as a manufacturing process The energy use ratio of cheaper carbon materials (for example, coke) can be increased as much as possible to perform melting and smelting reduction of the various raw materials. (V) Improve the utilization rate of exhaust gas discharged from the furnace and make effective use of it. Each furnace is designed to utilize the electric power, steam, etc. produced by the process in the production process, and to effectively use the product such as oxygen gas produced by the utilization in the production process. Of course, the thermal efficiency of the whole manufacturing process can be increased as much as possible, and by satisfying each condition of, it is possible to flexibly respond to fluctuations in the chromium raw material situation and energy situation in the direction of cost minimization and mass production is possible. Also it is possible to maintain high productivity under a stable operation, and to provide a process that can be manufactured at as low as possible cost molten steel good quality chromium-containing steel of natural.

[Means for solving the problem]

As a result of various studies, the present inventors have found that operating the arc furnace, the vertical furnace, and the refining furnace separately has various disadvantages as described above and causes problems.However, when the arc furnace and the vertical furnace are used in combination, In order to reduce the raw material cost as much as possible mainly in response to the fluctuations of the chromium raw material situation, the blending of the various raw materials and their ratios are flexibly determined. First, the production of chromium-containing hot metal using a vertical furnace is attempted. The use of relatively inexpensive carbonaceous materials in accordance with the energy situation is advantageous in terms of energy costs, but the parts (component, temperature, The amount of the molten metal is substantially chromium-free or nickel-free or a molten metal containing an arbitrary amount of chromium or nickel by using such an arc furnace with a small amount. Predetermined component concentration So as to align with hot water, and completed the present invention by investigating that can solve the complement if connexion the object disadvantages (weaknesses) in due connexion mutually to refining including further decarburization the mixture melt.

Hereinafter, the manufacturing process of the chromium-containing molten steel according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing one example of the process of the present invention, FIG. 2 is an explanatory view showing a process different from that of FIG. 1, and FIG. 3 is a schematic sectional view of one example of a vertical furnace. It is the schematic of the chrome hot metal manufacturing equipment containing.

In the present invention, a large amount of relatively inexpensive chromium ore and scrap can be used as the chromium raw material as described above, and the energy cost is low. It is based on a manufacturing process that uses an arc furnace that is relatively flexible in terms of the composition, temperature, amount, etc. of the hot metal to be pigged.

As shown in FIG. 3, the rigid furnace 1 has a raw material charging inlet 2 at an upper part and two upper and lower tuyeres 3, 4 near a lower part.
From the raw material charging port 2, a chromium raw material including a chromium-containing recovered raw material such as scrap or granular material having an appropriate range (described later) of stainless steel, an iron source such as scrap iron, a carbon material such as coke, and a limestone The raw material which is mainly made of slag making material such as fluorite and may also add a heating material such as Fe-Si is charged, and high-temperature air or high-temperature oxygen-enriched air is blown from the upper and lower two-stage tuyeres 3,4. From the upper tuyere 3, powdery and granular chromium ore, which is mainly a chromium oxide-containing powdery chromium ore generated in a stainless steel manufacturing process or the like, is supplied from the hooper 5 into the furnace. The chromium raw material charged into the furnace from the raw material charging inlet 2 descends while being heated by the high-temperature gas rising from below in the furnace 1, and then melts and melts in the middle of the metal, accompanied by molten slag and the like. Drops downward as drops. On the other hand, the powdery and granular chromium raw material containing chromium oxide supplied into the furnace 1 from the upper tuyere 3 is melted in the raceway region ahead of the tuyere 3, 4 and red-hot with the metal droplets descending from above. Is dropped in the carbon material layer.
The reduction reaction with the carbon in the carbonaceous material layer or the carbon in the metal droplets proceeds, and chromium oxides and oxidized droplets are reduced to each metal. You get it. As shown in FIG. 3, the vertical furnace 1 has an air supply source 7 for blowing air, an oxygen supply source 8 for enriching the air as necessary, and preheating the blowing air. Exhaust gas combustion device 9, heat exchanger 10, dust collection device 11 and the like are provided.

By using such a raw material containing a chromium source such as chromium ore and dust and melting and melting and reducing it in a vertical furnace to produce chromium-containing hot metal, the raw material cost and the energy cost are reduced (Japanese Patent Application Laid-Open No. 60−162718
JP-A-62-54007, JP-A-62-167808, JP-A-62-167808
2-167809, JP-A-1-208425, JP-A-1-240628
No., JP-A-1-294812). Generally, carbon is dissolved in a saturated state (about 5 to 6%) in the molten metal that is the chromium-containing hot metal.

The chromium-containing recovered raw material as the chromium raw material charged from the raw material charging inlet 2 and the iron source such as scrap iron are used in the vertical furnace 1.
There are restrictions on the shape and dimensions in order to ensure the air permeability inside. It is appropriate that the massive scrap etc. have a length of about 1/3 or less of the inner diameter of the furnace and an area of 1/4 or less of the inner cross-sectional area of the furnace. experience are those based on if Shimese at a volume of about 0.1m ³ (for example 1.3m × 0.2m × 0.4m) below. Conversely, in the case of a small granular material, a particle size of about 20 mm or more is appropriate. Further, a chromium raw material such as high-carbon Fe-Cr or the like may be charged as another chromium raw material to be charged from the raw material charging inlet 2 for component adjustment.

On the other hand, as shown in FIG. 1, in the arc furnace 12, there are few restrictions on the shape and size of scraps and granular materials to be melted, so that unsuitable raw materials other than the shapes and sizes suitable for the vertical furnace 1 are used. Can be used.

In the arc furnace 12 in the process of the present invention, an auxiliary material such as a carbon material or a slag-making material is charged into a main material such as an iron source such as various chromium materials and scrap iron as described above, and an arc furnace is used. Oxygen blowing including decarburization after dissolving in, and reducing and recovering oxidized effective metal by adding reducing material, slag material and component adjusting material, removal of impurities, component adjusting process etc. Is not used as a smelting and refining furnace for tapping molten steel containing chromium after appropriately performing it, but is often used as a melting furnace for tapping molten iron as described above. In other words, in order to produce the desired target chromium-containing molten steel in this process, the type and amount (mixing) of the main and auxiliary raw materials to be charged with respect to the chromium-containing hot metal tapped from the vertical furnace 1.
When it is adjusted to a considerable extent, it is used exclusively as a melting furnace to perform light refining as needed, and produces hot metal with a controlled content of mainly chromium and carbon and, if necessary, nickel. I do. Accordingly, the hot metal to be tapped contains a predetermined range of carbon that can be arbitrarily determined, and may include chromium-free substantive droplets or chromium that contains a large amount of chromium in a completely arbitrary predetermined range.

If the target chromium-containing molten steel to be manufactured is, for example, Cr
-In the case of molten steel of stainless steel of Ni-based steel, that is, chromium-containing molten steel containing a nickel component, as the molten metal that is chromium-containing hot metal that taps from the vertical furnace 1 and the molten iron that taps from the arc furnace, As one or both of the molten metal and the molten metal that also contains a nickel component, the molten metal is produced and adjusted to form a combined molten metal. In the case of the vertical furnace 1, a metal raw material containing a nickel component, such as Fe—Ni alloy, Cr—Ni stainless steel scrap, Ni
In some cases, a bullion press is used, and a powdered or granular material containing a nickel component is used as a powdered or granular chromium raw material supplied into the furnace from the upper tuyere 3. In the case of the arc furnace 12, the above-mentioned raw material containing a nickel component is used as a charging raw material.

In the process of the present invention, as shown in FIG. 1, the molten metal as the molten metal from the arc furnace 12 is compared with the molten metal as the molten metal from the arc furnace 12 with respect to the base metal, which is the molten chromium-containing molten metal from the rigid furnace 1. The mixed hot water is mixed to produce a mixed molten metal. that is,
In order to obtain the target mixed molten metal in order to achieve the above technical problem, the main component concentration range of each molten metal is set in advance, and after knowing these, chromium and chromium for transferring to the next refining process are set. This is because the adjustment of the concentration of the component mainly composed of carbon, the adjustment of the amount of hot water, and the adjustment of the temperature of the hot water require at least one or more items including the adjustment of the concentration of the component.

In the case of mixing the molten metal in this way, the mixed molten metal may be charged into the refining furnace 13 after the molten metal is mixed, or each molten metal may be charged into the refining furnace 13 to obtain a mixed molten metal (A, B
Symbol).

The mixed molten metal thus obtained by the combination is then subjected to refining including decarburization by oxygen blowing in a refining furnace. As such a refining device, for example, a device generally used for refining chromium-containing hot metal which is a source of stainless steel may be used, but a converter and a vacuum ladle degassing device in the LD-VAC method, AO
AOD furnace in method D, converter and RH-OB in LD-RH-OB method
Either the apparatus or the VOD furnace in the VOD method can be preferably used. The operation of this refining process is based on oxidized chromium, iron,
Reduction and recovery of an effective metal such as manganese, degassing, removal of impurities, component adjustment, etc. can be performed by a generally used technique, but as described above, the mixed molten metal to be refined has its component concentration, Furthermore, since the temperature and amount are adjusted, it is not necessary to use a large amount of oxygen gas, reducing materials, slag-making materials, or raw materials for component adjustment in the refining process, and it produces chromium-containing molten steel with good productivity and good quality. You can do it. Then, the chromium-containing molten steel or the chromium-containing molten steel that also contains the nickel component produced in this manner can be cast by the casting facility 14 to produce a cast slab.

On the other hand, in the process of the present invention, in the rigid furnace 1, since carbon material (coke or the like) is used as a thermal energy source, it has sensible heat at a temperature of 300 ° C. or more mainly due to its combustion heat and CO concentration of 3%.
Exhaust gas having a latent heat of 0 to 40% and accounting for about 60% of the heat input during the heat input is generated. In addition, the combined molten metal has a high carbon component concentration (approximately 2 to 6%).
Similarly, exhaust gas having sensible heat and latent heat with high CO concentration is generated by oxygen blowing during refining at 13. Further arc furnace 12
Also, when oxygen is blown, exhaust gas having sensible heat and latent heat is generated. In the present invention, as shown in FIG. 1 in a simplified manner, all of these exhaust gases are selectively collected and stored in an exhaust gas collection and storage holder 15 for each furnace or for each operation period of each furnace. It is necessary to produce steam using this mixed exhaust gas as a heat source, and to effectively utilize the steam for the following various items to be useful in the process of the present invention. (A) As shown in FIG.
Operating the 17 steam turbines and using the electric power generated by the operation as part or all of the electric power consumed in the process for producing the chromium-containing molten steel including the arc furnace 12.

(B) When a vacuum is required for refining, for example, when using a vacuum ladle degasser (not shown), use as a steam source of the steam ejector 19 for decompression.

(C) Oxygen gas is produced by the gas production equipment 18 using the electric power and / or steam as a power source (illustrated by C and D symbols), and is used for enriching oxygen used for blowing in the vertical furnace 1. And refining used in the arc furnace 12 and / or the refining furnace 13. This matter is usually appropriate when the amount of exhaust gas or the total amount of heat contained is small. As this oxygen gas production apparatus, for example, PSA (Pressure Swing Adsorp)
tion) formula (manufactured by Mitsubishi Heavy Industries, Ltd.) is preferred.

(D) Nitrogen gas obtained in combination with the oxygen gas is blown into the molten metal in the arc furnace 12 and / or the refining furnace 13 and used for nitriding and / or stirring the molten metal.

(E) The argon gas obtained in combination with the oxygen gas is used for stirring the molten metal in the arc furnace 12 and / or the refining furnace 13.

(A), (b), (c), (d),
By performing at least one or more of (e) and making use of the process of the present invention, energy costs can be significantly reduced.

Further, in the present invention, as shown in FIG.
It is also necessary to collect and store the mixed exhaust gas in the storage holder 15 and use it effectively as an energy source (E symbol) and / or a heat source (F symbol) of the mixed exhaust gas to contribute to the process of the present invention. The method of this effective use may be arbitrarily selected according to the mixed exhaust gas amount and the total amount of heat contained therein so as to have the highest thermal efficiency and low energy cost in the process, but the latter heat source (F symbol) may be used. Since the method of use is the same as that described above with reference to FIG. 1, description thereof will be omitted, and the former method of use as an exhaust gas energy source (E symbol) will be mainly described below. In FIG. 2, when the mixed exhaust gas is used as an exhaust gas energy source (E symbol), the same mixed exhaust gas as that obtained by adding an asterisk (*) to electric power, steam, oxygen gas, nitrogen gas, or argon gas is used as a heat source ( F
The power, steam, oxygen gas, nitrogen gas, and argon gas used as symbols are denoted by the same numbers as those marked with an asterisk (*), and the numbers are indicated by a dash (').

This mixed exhaust gas is used as an exhaust gas energy source (E symbol) to burn it to produce only electric power, or to produce steam using the combustion exhaust gas that has finished producing this electric power and has a large amount of sensible heat. However, it is necessary to make effective use of this electric power and / or steam for various matters such as the following to be useful in the process of the present invention. (F) As shown in FIG. 2, the gas turbine of the power generation equipment 17a is operated by the energy source burning the mixed exhaust gas, and the electric power generated by the operation is supplied to the process (the raw material and Use as part or all of the power consumed by the melt flow and energy flow (* 1).

(G) After operating the gas turbine of the power generation facility 17a to complete power generation and using the combustion exhaust gas having a large amount of sensible heat as a heat source, steam is produced by the steam generation facility 16 and this steam (* 2)
In the same manner as above, the power (* 3) obtained by operating the steam turbine of the power generation facility 17 using this steam and generating power is used as part or all of the steam and power consumed in this process (raw material and molten metal flow and energy flow). thing.

(H) The electric power (* 1) manufactured in the item (f) or the electric power (indicated by a G symbol) manufactured in the item (g) and / or the steam (indicated by an H symbol) manufactured in the item (g). ) Is used as a power source to produce oxygen gas by the gas production facility 18 and use it as part or all of the oxygen gas consumed in this process (raw material and molten metal flow) (* 4).

(I) The nitrogen gas obtained in combination with the oxygen gas produced in the above item (h) is used as part or all of the nitrogen gas consumed in this process (raw material and molten metal flow) (* 5).

(G) Argon gas obtained in combination with the oxygen gas produced in the above item (h) is used as part or all of the argon gas consumed in this process (raw material and molten metal flow) (* 5).

(F), (g), (h), (li),
By performing at least one or more of (u) and making the process of the present invention useful, it is possible to increase the thermal efficiency of each furnace as well as the entire process, and to greatly reduce the energy cost.

(Operation)

In the process of the present invention, by using a vertical furnace and an electric furnace together, not only the features and advantages inherent in each of them but also each other act so as to complement each other's disadvantages (weaknesses), and the following various advantages are obtained. Is obtained. First, the use of a vertical furnace naturally offers the following advantages inherently.
That is, waste containing chromium ore or stainless steel scrap which is inexpensive as a chromium raw material and waste (dust, sludge, slag, etc.) generated in the manufacturing process, or chromium or nickel generated in the manufacturing process of ferrochrome or ferronickel. And effective metals can be used in large quantities without special processing of chromium and other effective metals such as metal scraps, nickel-containing catalyst waste materials, etc., so that the cost of raw materials can be reduced and resources can be saved. In addition, since an inexpensive carbonaceous material (such as coke) is used as a thermal energy source for melting and reducing various raw materials including a chromium raw material without using expensive electric power, energy costs can be reduced.

However, vertical furnaces having such essential features and benefits also suffer from the following disadvantages and lack overall flexibility.

(A) As described above, since the furnace is a continuous operation furnace in which gas permeability in the furnace is important, efforts must be made to maintain good furnace conditions while always paying attention to this. In other words, the amount, temperature, pressure, oxygen concentration, etc. of the high-temperature air or high-temperature oxygen-enriched air blown from the lower part of the furnace are sufficiently controlled to maintain a stable raceway, and the charging conditions, temperature, and pressure of the raw materials in the furnace. In addition, the amount and component concentration of chromium-containing hot metal to be tapped, such as the amount of exhaust gas discharged and the concentration of components, must be constantly investigated and controlled.

(B) Therefore, restrictions on the type, composition and ratio, shape and size (necessity of processing) of main raw materials containing effective metals such as nickel, iron, etc., chromium raw materials, and carbon materials in sub-raw materials For example, there are many restrictions on the size of coke, that is, restrictions on various raw materials.

(C) Due to the reasons of the above items (a) and (b), it is difficult to change the tapping amount, the composition, the specific component concentration and the temperature of the chromium-containing hot metal to be tapped, and a large change cannot be expected. That is, even if it is changed, there is a restriction that a considerable amount of hot metal and a long time are required. Therefore, switching from chromium-containing hot metal that also contains nickel to chromium-containing hot metal, that is, switching to both types of hot metal, cannot simultaneously change the hot metal composition, and therefore requires a long time and a considerable amount of hot metal.

(D) Impurities P and S are mixed in the chromium-containing hot metal from the carbon material and coke as the auxiliary raw material.

(E) The chromium-containing hot metal is saturated with carbon (about 5-
6%), so that when hot metal is decarburized and refined in a refining furnace in the next process, a large amount of oxygen gas is required and a large load must be applied to the process, and chromium and other effective metals must be used. A large amount of reducing agent is required because oxidation proceeds more.

On the other hand, the arc furnace has few restrictions on the raw material surface including the shape and dimensions of the raw material to be charged as described above, and turns on and off clean power as a thermal energy source and controls the amount of input to control various types of furnaces. Since it is an intermittent operation furnace that melts raw materials, there are few restrictions on the concentration and composition of specific components, mainly chromium, nickel, carbon, etc. of hot metal that is tapped, temperature with various heating and heating means, and tapping amount. Each has features and benefits that can be varied greatly, but has the disadvantage of consuming large amounts of expensive power at any time.

Therefore, in the process of the present invention, as described above, the combined use of the solid furnace and the arc furnace, which have the respective characteristics and advantages as described above, but also have the disadvantages, as described below, allows mutual interaction as described below. In addition, the following points are complemented and synergistically expressed.

Due to the change of the chromium raw material situation, the blending of the various chromium raw materials and the ratio thereof are changed in the direction of the cost minimum according to the market price of the various chromium raw materials. In this case, the vertical furnace alone has limitations on the shape and dimensions in terms of gas permeability and the like of the chromium-containing recovered raw material to be charged from the upper part of the furnace as described above, so that the optimum mixing ratio of the raw materials cannot be obtained. It is sometimes difficult to maintain the concentration and amount of chromium component in chromium-containing hot metal to be tapped because it is difficult to obtain chromium-containing raw materials whose shapes and dimensions are within the appropriate range. Therefore, by using an arc furnace with few such restrictions in combination, the chromium-containing recovered raw material that is unsuitable for use in a vertical furnace is used in an arc furnace, and the molten metal, which is the hot metal that comes out of both furnaces, is adjusted to a combined metal. By doing so, it is possible to easily produce a chromium-containing hot metal and its refined molten steel in a target predetermined range even in terms of the specific component concentration, composition, amount and temperature without waste. Therefore, it can respond flexibly to any raw material situation.

In addition, the switch from the production of chromium-containing molten steel having a predetermined composition range to the production of chromium-containing molten steel having a predetermined composition range that also contains a nickel component is performed only when the vertical furnace is used. Although the content can be increased only gradually and it takes a considerable amount of hot metal and a long time to complete the switching, the hot metal with a high nickel component concentration is adjusted in advance in an arc furnace, and the molten metal of both hot metal is combined and refined. Thus, molten steel having a predetermined composition range can be easily manufactured without waste in a short time.

In addition, no expensive ferro-nickel alloy is added in the refining process for adjusting the components.

In addition, since the molten iron as chromium-containing hot metal discharged from a vertical furnace enters from coke of impurities such as P and S, it is necessary to perform a pretreatment to reduce its concentration. By mixing with the molten metal which is the hot metal, the impurity concentration can be reduced and the pretreatment can be made unnecessary or reduced.

In addition, although carbon is dissolved in a saturated state (about 5 to 6%) in the molten metal which is tapped from the vertical furnace, the molten metal having a low carbon content from the arc furnace is combined with the molten metal. About 2
Since the mixed molten metal having a low carbon content of about 5% can be obtained, the amount of oxygen gas consumed in the decarburization refining in the refining process of the mixed molten metal can be reduced, and the load of the process can be reduced. I can do it. And the consumption of the reducing material can be small.

In the vertical furnace, the chromium-containing recovered raw materials and iron source charged from the upper part of the furnace, and the melting and melting of carbonaceous materials and slag-making materials, and the chromium oxide-containing powder containing chromium ore supplied from the upper tuyere In order to perform both the smelting reduction of the chromium raw material well, large lump coke (close to blast furnace coke) with good reactivity and good air permeability is used. % Of exhaust gas with sensible heat and latent heat. It is not sufficient to use such exhaust gas only for heating the air blown into the vertical furnace or the oxygen-enriched air. Furthermore, since carbon is melted in a state close to saturation in the molten chromium-containing hot metal to be tapped from a vertical furnace, a large amount of carbon is melted in the refining furnace for oxygen blowing and decarburization refining. Exhaust gas with sensible heat is generated.

On the other hand, exhaust gas having sensible heat and latent heat is also generated when oxygen is blown in an arc furnace to perform decarburization refining or heating and heating. These exhaust gases can be selectively or totally recovered according to the actual conditions or furnaces or their operation periods, and the mixed exhaust gas can be simply used as a heat source or as an exhaust gas energy source and / or heat source. By producing steam or electric power by an energy source, not only heating the air blown into the vertical furnace in the process of the present invention, but also using it as power consumption of an arc furnace for a steam source of a steam ejector, or the other described above. By using oxygen gas consumed in each furnace in this process for the production of gas and use outside the process, it is possible to make full use of it to improve thermal efficiency and reduce energy costs. Can be done.

〔The invention's effect〕

As described in detail above, the process for producing chromium-containing molten steel according to the present invention is performed by using any chromium raw material in combination with a vertical furnace and an arc furnace, and is a molten metal that is a hot metal that taps from both furnaces. A mixed molten metal, which is a chromium-containing molten metal having a targeted predetermined composition range, and a refined molten steel can be obtained, and a large amount of heat generated by each exhaust gas can be applied to various parts of the manufacturing process in the process. The following effects can be obtained because the thermal efficiency of the entire application process can be improved by effectively utilizing the above.

(I) Inexpensive chromium ore is one of the main raw materials and waste (dust, sludge, slag, etc.) generated in the manufacturing plant
Can be processed in a vertical furnace as it is, thereby reducing raw material costs.

(Ii) Since a material that cannot be used in a vertical furnace such as a large scrap or a powdery chromium-containing material can be used as a raw material for an arc furnace, there is almost no restriction on the raw material.

(Iii) From the above (i) and (ii), the ratio of the molten metal produced by the vertical furnace and the arc furnace is determined in accordance with the chromium raw material situation and the energy situation to achieve the target predetermined composition and temperature while minimizing cost. Thus, a mixed molten metal which is a chromium-containing hot metal having an appropriate amount and amount can be obtained, and the refined molten steel can be stably manufactured.

(Iv) Therefore, the load in the refining process by the refining furnace is reduced, and it becomes possible to reduce the amount of oxygen gas to be consumed, the expensive ferroalloys added for adjusting the components, and the reducing agent to be charged, and The chromium-containing molten steel having a temperature, an amount, etc. within a predetermined range can be stably supplied to the casting equipment in the next step.

(V) By effectively utilizing a large amount of heat of each exhaust gas generated from the vertical furnace, the smelting furnace, and the arc furnace, it is possible to reduce manufacturing costs mainly including energy costs.

(Vi) By combining the above effects, it is possible to flexibly respond to fluctuations in the chromium raw material and energy conditions in a cost-minimum direction, and mass production is possible, while maintaining high productivity under stable operations. Chromium-containing steel of good quality can be produced at low production cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one example of the process of the present invention, FIG. 2 is an explanatory view showing a process different from that of FIG. 1, and FIG. 3 is a schematic sectional view of one example of a vertical furnace. It is the schematic of the chrome hot metal manufacturing equipment containing. In the drawings: 1 Vertical furnace 2 Raw material inlet 3 Upper tuyere 4 Lower tuyere 5 Hopper 6 Tapping gutter 7 Air supply source 8 Oxygen supply source 9 … Furnace exhaust gas combustion device 10… Heat exchanger 11… Dust collection device 12… Arc furnace 13… Refining furnace 14… Casting equipment 15… Exhaust gas collection and storage holder 16… Steam generation equipment 17… Power generation Equipment (steam turbine) 17a …… Power generation equipment (gas turbine) 18 …… Gas production equipment 19 …… Steam ejector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-161020 (JP, A) JP-A-61-147821 (JP, A) JP-A-62-233681 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C21C 5/52 C21C 7/00 C21C 5/28 F27B 1/00-1/28 F27B 3/00-3/28 F27D 13/00 F27D 17/00 C21C 1 / 06

Claims (4)

(57) [Claims] An arc furnace and a vertical furnace having a raw material inlet at an upper part and two upper and lower tuyeres near a lower part are used together. In the vertical furnace, chromium containing chromium-containing recovered raw material is supplied from the raw material inlet. Raw material mainly consisting of raw material, iron source, carbon material and slag material is charged, and high-temperature air or high-temperature oxygen-enriched air is blown from each of the upper and lower two tuyeres, and chromium oxide-containing powder and granules are injected from the upper tuyeres. The chromium raw material is supplied into the furnace, and the chromium-containing hot metal is tapped while melting and smelting and reducing each raw material mainly with the carbonaceous material. And / or adding various raw materials, including powdered and granular raw materials, and tapping molten iron that is substantially chromium-free or containing an arbitrary amount of chromium, and then arcing the molten metal that is chromium-containing hot metal discharged from a vertical furnace. Chrome is used as the hot metal from the furnace At least one of at least one of component concentration adjustment of hot water and carbon, including adjustment of component concentration and adjustment of hot water temperature, is adjusted to a predetermined range, and then the mixed molten metal thus obtained is subjected to oxygen blowing in a refining furnace. A process for producing chromium-containing molten steel, which comprises refining including decarburization and tapping. 2. The manufacturing process according to claim 1, wherein
A vertical furnace as one or both of a molten metal that is a chromium-containing hot metal that is tapped from a vertical furnace and a molten metal that is tapped from an arc furnace and that is substantially chromium-free or containing any amount of chromium. In some cases, a raw material containing a nickel component is also used as a raw material to be charged from a raw material charging inlet, and a powdered and granular raw material containing a nickel component is also used as a fine and granular chromium raw material supplied from an upper tuyere. In the furnace, a raw material containing a nickel component is also used as a charging material, so that a molten metal that is a hot metal also containing a nickel component is used to make a molten metal. Molten steel manufacturing process. 3. The manufacturing process according to claim 1, wherein the exhaust gas having a sensible heat and a large amount of latent heat discharged from the vertical furnace, the arc furnace, and the refining furnace, respectively, is separated into all or each of the furnaces. The following items are selectively collected by operation period, steam is produced using the exhaust gas as a heat source, and the steam is used. (A) The electric power obtained by power generation by a steam turbine is used for the production of chromium-containing molten steel including an arc furnace. (B) use as a steam source of a steam ejector when a vacuum is required in refining, (c) power source using the power and / or steam (D) the oxygen gas is used for oxygen enrichment of air used for blowing in a vertical furnace, and for refining used in an arc furnace and / or a refining furnace. The nitrogen gas obtained in combination with the melted gas in the arc furnace and / or the refining furnace to be used for nitriding and / or stirring the molten metal, and (e) the argon gas obtained in combination with the oxygen gas. It is used for stirring the molten metal in an arc furnace and / or a refining furnace, and is characterized in that it performs at least one of the following items (a), (b), (c), (d), and (e). Chrome-containing molten steel manufacturing process. 4. The manufacturing process according to claim 1, wherein the exhaust gas having a sensible heat and a large amount of latent heat discharged from the vertical furnace, the arc furnace, and the refining furnace, respectively, is separated into all or each of the furnaces. It is selectively recovered according to the operation period, and the exhaust gas is used as an exhaust gas energy source and / or heat source, and is burned by the former exhaust gas energy source to produce only electric power, or after producing this electric power, a large amount of electricity is produced. The following items use steam and / or steam to produce steam with the combustion exhaust gas having heat, while producing steam with the latter heat source, and (f) electricity generated by a gas turbine and / or steam turbine. Use the electric power as part or all of the electric power consumed in the process of producing chromium-containing molten steel including an arc furnace. (G) Steam escaping when a vacuum is required in refining (H) for producing oxygen gas using the electric power and / or steam as a power source, for enriching oxygen used for blowing in a vertical furnace, and for using an arc furnace and / or Or for refining used in a refining furnace, (i) blowing nitrogen gas obtained in combination with the oxygen gas into molten metal in an arc furnace and / or a refining furnace, for nitriding and / or stirring the molten metal (F) using the argon gas obtained in combination with the oxygen gas for stirring the molten metal in an arc furnace and / or a smelting furnace; (f), (g), (h), A process for producing chromium-containing molten steel, characterized by performing at least one of (i) and (nu).