JPH04107206A - Production process of chromium-incorporated molten steel - Google Patents

Abstract

PURPOSE:To stably produce a chromium-incorporated molten steel having good quality by putting chromium-incorporated molten iron produced in a vertical furnace an non-chromium molten iron, etc., produced in an arc furnace together and refining this mixed molten iron. CONSTITUTION:By using chromium source of chromium ore and dust as the raw material, melting and smelting reduction are executed in the vertical furnace 1 to produce the chromium- incorporated molten iron. On the other hand, in the arc furnace 12, auxiliary raw material of carbonaceous material, slag-making material, etc., is charged into main raw material of various kinds of chromium, and iron source, etc., of scrap iron, etc., to tap the molten iron adjusting component contents of the chromium and carbon as main components and as necessary, incorporating nickel, as well. In such a manner, to the basis molten metal as the chromium-incorporated molten iron tapped from the vertical furnace 1, the molten metal as the molten iron tapped from the arc furnace 12 is put together to produce the mixed molten iron and the refining containing decarbonization with oxygen blowing execute in a refining furnace 13 to this mixed molten iron. By this method, in the refining process, large quantities of gaseous oxygen, reducing material, slag making material and raw material for adjusting raw material is unnecessary to use, and the chromium-incorporated molten steel having good quality is produced with good productivity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is capable of responding flexibly to changes in the chromium raw material situation and energy situation at a minimum cost, and also enables mass production and stable operation. The present invention relates to a manufacturing process that can maintain high productivity and produce chromium-containing molten steel of good quality at as low a cost as possible.

[Conventional technology]

Chromium-containing steels, including stainless steel, which is a typical example, have a high chromium content that exceeds this range.

Steels containing low chromium have been produced. The manufacturing method involves charging various raw materials, mainly chromium raw materials, into a furnace such as a melting furnace, tapping the metal as chromium-containing hot metal containing a high carbon content, and then refining this hot metal through decarburization and other processes. After the chromium-containing molten steel is obtained, this molten steel is cast to produce slabs and the like.

Conventionally, chromium-containing hot metal, which is the source of such chromium-containing steel, has generally been made of stainless steel scrap as a chromium raw material, chromium alloy irons produced by pre-smelting or reduction treatment from chromium ore, solid phase reduction products, and the like. In addition to pellets, small amounts of chromium ore, waste containing chromium (abrasive scraps, mill scale, dust, sludge, and slag), iron sources, carbon materials, and slag materials are mainly melted. However, it was common to use an arc furnace as the melting furnace.

This chromium-containing hot metal contains a large amount of expensive chromium, and also often contains nickel, which is also expensive.
These raw material costs greatly affect manufacturing costs. Therefore, when fluctuations in the price of chromium and nickel cause a price fluctuation difference between the chromium alloy ferroalloys, scrap, and other chromium raw materials, operations must change the composition and ratio of these materials in a direction that minimizes costs. It is necessary to do so.

In this way, in order to use various chromium raw materials in the manufacturing process by changing their composition and ratio in response to changes in the chromium raw material situation, it is necessary to change the shape and size of the chromium raw material in addition to the contained components and content. There is a need for a melting furnace that has fewer restrictions and can also use large amounts of scrap and waste, and arc furnaces have been used as a suitable furnace because they are capable of all of these things. However, melting using this arc furnace consumes a large amount of expensive electricity, resulting in an increase in energy costs. In order to reduce the amount of waste gas, some methods are being used, such as recovering the exhaust gas from the arc furnace to preheat the scrap that is to be charged in large quantities, or using an oxygen lance to blow oxygen into the molten metal during melting in the arc furnace. However, it has not been possible to sufficiently reduce high electricity costs.

In addition, as another method for producing this chromium-containing hot metal, in recent years, in order to reduce energy costs and chromium raw material costs, stainless steel scraps and other scraps and powdered chromium ore (containing chromium oxide) have been used. Mainly, waste materials containing mainly chromium oxides (polishing scraps, mill scale, dust, sludge, slag, etc.) generated in the factory etc. may be added to it, and these are dissolved and melted down with carbonaceous materials. A method has been proposed and promoted in which chromium-containing hot metal is manufactured by performing the following steps in one furnace. However, even with this method, the reduction of chromium ore is an endothermic reaction that requires a large amount of carbonaceous material and thermal energy (usually using oxygen).
There is a need to maintain a high-temperature reducing atmosphere, which limits the amount of scrap that can be used as a cold material, and there is a limit to the amount of powdery oxides such as waste generated within the manufacturing facility. There are disadvantages such as: Also, during melting and melting and reduction, a gas containing sensible heat and a large amount of energy (latent heat) is emitted, and if this gas is not used effectively, it may be superior to the above-mentioned melting method using an arc furnace. The converter type method and the vertical furnace method have been introduced as manufacturing technologies for chromium-containing hot metal, which is 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 high CO acid content, which is generated in large quantities, is combusted into CO2 using top-blown oxygen, and the resulting heat is transferred to the slag metal.

The problem is that the utilization rate and thermal efficiency of the available exhaust gas are low. On the other hand, in the vertical furnace method.

Part of the energy from the exhaust gas is used to preheat various raw materials that are melted and smelted and reduced as the gas passes upward through the furnace, resulting in high thermal efficiency. Since it depends on the material used, the energy cost is low. However, in order to continue operation under such conditions, it is important to ensure ventilation so that the exhaust gas can easily pass through the raw material layer charged into the furnace. Therefore, it is necessary to align the shapes and dimensions of various raw materials within a certain range,
Large chunks of scrap and other debris that impair ventilation;
The problem is that powdery raw materials cannot be used or cannot be used without special processing. In addition, the production of chromium-containing steel (Cr-Ni steel) that also contains nickel components is switched to the production of chromium-containing steel (Cr-based steel), that is, the composition of hot metal in the furnace is changed at once to switch to both steels. Another problem was that steel with a specified new composition could not be tapped during that time because it required time and a large amount of hot metal.

[Problem to be solved by the invention]

In order to solve the problems of the prior art, (i) various raw materials containing raw materials containing chromium, nickel, and iron are charged and blown into the furnace, and their brands, types, There are no restrictions as much as possible on the ingredients and content, their shape and dimensions, their blending ratio and their changes, etc., and they can be used as they are without any special processing. Chromium, such as dust, sludge, slag, etc., has relatively low price fluctuations and is inexpensive.

A large amount of waste (industrial waste) containing effective metals such as nickel and iron can be used, (if) chromium-containing a
ll (Cr-based steel) and chromium-containing #ll (Cr-Ni-based steel), which also contains nickel components, are composed mainly of chromium, carbon, and nickel, quantitatively from hot metal to steel, and in terms of manufacturing temperature. It is easily adjustable, and it is possible to switch between both types of steel (
(change in steel type) can be easily adjusted and manufactured easily and efficiently; (iv) l! (v) utilization rate of exhaust gas discharged from the furnace; (v) utilization rate of exhaust gas discharged from the furnace; In order to improve this efficiency, the electricity, steam, etc. produced through this effective utilization will be used in this manufacturing process, and products such as oxygen gas produced through this utilization will also be used effectively in this manufacturing process. By satisfying the following conditions, the thermal efficiency of not only each delivery but also the entire manufacturing process can be maximized, and mass production can be achieved while minimizing costs and flexibly responding to changes in the chromium raw material situation and energy situation. The object of the present invention is to provide a process that can maintain high productivity under stable operation and that can produce molten chromium-containing steel of good quality at as low a cost as possible.

[Means to solve the problem]

As a result of various studies, the inventors of the present invention found that operating an arc furnace, a vertical furnace, and a refining furnace separately has various drawbacks and problems as described above, but using an arc furnace and a vertical furnace together causes problems. ,
In order to keep raw material costs as low as possible, mainly in response to changes in the raw material situation for chromium, we flexibly determined the combination of various raw materials and their ratios, and first, we aimed to produce chromium-containing hot metal using a vertical furnace.

Second, in response to the energy situation, relatively inexpensive carbonaceous material is used, which is advantageous in terms of energy costs, but it is difficult to deal with the parts (composition , temperature, amount) to obtain molten metal that is substantially chromium-free, nickel-free, or containing any amount of chromium or nickel, and thirdly, We have discovered that by combining molten metals to at least a predetermined component concentration and refining this mixed molten metal, including decarburization, we can compensate for each other's shortcomings (weaknesses) and solve this problem. Completed the invention.

EMBODIMENT OF THE INVENTION Below, the manufacturing process of the chromium containing molten steel based on this invention is demonstrated in detail with drawing.

FIG. 1 is an explanatory diagram showing one example of the process of the present invention.

FIG. 2 is an explanatory diagram showing the different parts from FIG. 1 of another example of the process, and FIG. 3 is a schematic diagram of chromium hot metal production equipment including a schematic cross-sectional view of one example of a vertical furnace.

As mentioned above, the present invention uses a vertical furnace and chromium raw material, which are relatively inexpensive as chromium raw materials, and can use a large amount of chromium ore and scrap, and has low energy costs, so there are fewer restrictions in terms of raw materials. It is based on a manufacturing process that uses an electric arc furnace, which is relatively flexible in terms of the composition, temperature, amount, etc. of hot metal.

As shown in FIG. 3, the vertical furnace 1 has a raw material charging port 2 at the top.
It also has two upper and lower tuyeres 3 and 4 near the bottom.

From the raw material charging port 2, chromium raw materials including chromium-containing recovered raw materials such as scraps and granules of stainless steel with appropriate dimensions (described later), iron sources such as scrap iron, carbonaceous materials such as coke, and limestone and Raw materials are charged which mainly consist of slag materials such as fluorite, and may also include heat-generating materials such as Fe-5i.

High-temperature air or high-temperature oxygen-enriched air is blown through the upper and lower tuyeres 3 and 4, and powdered chromium ore is blown into the upper tuyere 3 to collect various waste chromium oxides, mainly generated in the stainless steel manufacturing process. The chromium raw material, which is charged into the furnace through the 1M material charging port 2 that supplies powdery chromium-containing raw material into the furnace from the hopper 5, descends while being heated by the high-temperature gas that rises from the bottom of the furnace 1, and eventually falls on its way. On the other hand, the granular chromium raw material containing chromium oxide, which is supplied into the furnace 1 from the upper tuyere 3, melts and melts and drips downward as metal droplets with molten slag etc. It melts in the raceway area ahead of the tuyeres 3 and 4 and drips into the red-hot carbon layer along with metal droplets descending from above.

Then, a reduction reaction with carbon in this carbon material layer or carbon in metal droplets progresses, and chromium oxide and iron oxide are reduced to various metals, which are tapped from the tap hole 6 to produce chromium-containing hot metal. You can get it. As shown in FIG. 3, this vertical furnace 1 includes an air supply source 7 for blowing air. Oxygen source to optionally enrich the air with oxygen8. Furnace exhaust gas combustion device 9 and heat exchanger 10 for preheating this blowing air. A dust collector 11 etc. are attached.

By using chromium ore, dust, and other chromium sources as raw materials and melting and smelting reduction in a vertical furnace to produce chromium-containing hot metal, raw material costs and energy costs can be reduced. 60-1627
No. 18, JP-A-62-54007, JP-A-62-16
No. 7808, JP-A-62-167809, JP-A-1-
208425, JP-A-1-240628, JP-A-1
294812), carbon is generally dissolved in a saturated state (approximately 5 to 6%) in this chromium-containing hot metal.

In addition, the chromium-containing recovered raw materials and iron sources such as scrap iron that are charged as chromium raw materials from the raw material charging port 2 are shaped to ensure ventilation within the vertical furnace 1.

There are restrictions on dimensions. It is appropriate for large lumps of scrap etc. to have a length of approximately 1/3 or less of the inner diameter of the furnace and an area of 1/4 or less of the cross-sectional area of the furnace. Based on my experience, the volume is 0.1rr? (for example, 1.3m x 0.2m x 0.4m) or less. On the other hand, in the case of small granular materials, a particle size of about 20 m or more is appropriate. Further, as another chromium raw material charged from the raw material charging port 2, a chromium raw material such as high carbon Fe-C' may be charged for component adjustment.

On the other hand, as shown in FIG. 1, there are few restrictions on the shape and dimensions of the scrap and powder materials to be melted in the arc furnace 12, so that unsuitable raw materials other than the two shapes and dimensions suitable for the vertical furnace 1 cannot be used. It can be used.

The arc furnace 12 in the process of the present invention is constructed by charging auxiliary raw materials such as carbon material and slag material to the main raw materials such as various chromium raw materials and iron sources such as scrap iron, as described above, and then arcing the furnace. Refining in a broad sense, which includes decarburization and oxygen blowing after melting, and addition of reducing agents, slag-forming materials, composition adjustment materials, etc. to reduce and recover oxidized effective metals, remove impurities, and composition adjustment processing. Rather than being used as a melting and refining furnace that taps chromium-containing molten steel after performing appropriate steps, as mentioned above, it is currently often used as a melting furnace that taps molten iron.
In other words, in order to produce the specified chromium-containing molten steel that is the final goal in this process, the types and amounts (mixtures) of the main and auxiliary raw materials charged to the chromium-containing molten metal tapped from the vertical furnace 1 are quite large. It is used exclusively as a melting furnace, which is highly controlled and performs light refining as necessary, and taps hot metal whose content is controlled, mainly consisting of chromium and carbon, but also including nickel if necessary. Therefore, the hot metal to be tapped contains carbon in an arbitrarily defined range, ranging from substantially chromium-free to completely arbitrarily defined amounts of chromium.

If the specified chromium-containing molten steel targeted for production is, for example, Cr
- In the case of Ni-based stainless steel molten steel, that is, chromium-containing molten steel that also contains nickel components, 1i type furnace 1
A molten metal containing a nickel component is prepared and combined as either or both of the chromium-containing molten metal tapped from an arc furnace and the molten metal as the molten metal tapped from an arc furnace. For this purpose, in the case of the vertical furnace 1, metal raw materials containing nickel components such as Fe-Ni alloy, Cr-Ni stainless steel scraps, Ni ingots, etc. are used as raw materials charged from the raw material charging port 2, and As the granular chromium raw material supplied into the furnace from the upper tuyere 3, a granular raw material containing a nickel component may be used.

Further, in the case of the arc furnace 12, the above-mentioned raw material containing a nickel component is used as the charging raw material.

In the process of the present invention, as shown in FIG.
The molten metal as hot metal tapped from the arc furnace 12 is combined with attention to the following matters to produce a mixed molten metal. The purpose of this is to obtain the target mixed molten metal in order to achieve the above-mentioned technical problem, and after setting the main component concentration range of each molten metal in advance and knowing these, it is necessary to move on to the next refining process. Adjustment of the concentration of components mainly chromium and carbon, and further adjustment of the amount of hot water.

This is because it is necessary to perform one or more of the following: water temperature adjustment, including at least component concentration adjustment.

In the case of combining the molten metals in this way, the mixed molten metals may be charged into the refining furnace 13 after each molten metal is combined, or each molten metal may be charged into the refining furnace 13 individually to form a mixed molten metal (A
, illustrated by the B symbol).

The mixed molten metal thus obtained is then subjected to refining including decarburization by oxygen blowing in a refining furnace. Such refining equipment may be one that is generally used for refining chromium-containing hot metal, which is the source of stainless steel. KEL A OD furnace, converter and RH-OB equipment in the LD-RH-OB method, and v in the VOD method
Any OD furnace can be preferably used. The operation of this refining process can be carried out using commonly used techniques such as reduction recovery of effective metals such as oxidized chromium, iron, and manganese, degassing, removal of impurities, and component adjustment. The mixed molten metal to be refined has a different concentration of components depending on the mixing metal.
Furthermore, since the temperature and amount are regulated, there is no need to use large amounts of oxygen gas, reducing agents, slag materials, or raw materials for composition adjustment during the refining process, producing high-quality chromium-containing molten steel with high productivity. It is possible to do so. Then, the chromium-containing molten steel produced in this way or the chromium-containing molten steel that also contains nickel components can be cast in the casting equipment 14 to produce slabs.

On the other hand, in the process of the present invention, in the vertical furnace 1,
Since carbonaceous material (coke, etc.) is used as a thermal energy source, its combustion heat is the main source, and it has sensible heat with a temperature of 300℃ or higher, and has latent heat with a CO concentration of 30-40%, which accounts for about 60% of the heat input. Exhaust gas is generated which accounts for the amount of heat.

Furthermore, since the combined molten metal also has a high carbon concentration (approximately 2 to 6%), oxygen blowing during refining in the refining furnace 13 similarly generates exhaust gas having sensible heat and latent heat with a high CO concentration. . Furthermore, when oxygen blowing is performed in the arc furnace 12, exhaust gases having sensible heat and latent heat are generated.6 In the present invention, these exhaust gases are generated in their entirety or by furnace or by each furnace, as shown in a simplified diagram in FIG. The mixed exhaust gas is selectively recovered and stored in the exhaust gas recovery/storage holder I5 according to the operating period, and steam is produced using this mixed exhaust gas as a heat source in the steam generation equipment 16, and this steam is effectively used for various purposes such as: It is necessary to make use of the process of the present invention. That is, (a) As shown in FIG. 1, this steam powers the steam turbine of the power generation equipment 17, and the power generated thereby is consumed in the manufacturing process of the chromium-containing molten steel, including the arc furnace 12. To be used as part or all of electricity.

(b) When a vacuum is required in refining, for example when using a vacuum ladle degassing device (not shown), use it as a steam source for the steam ejector 19 for reducing pressure.

(c) Oxygen gas is produced by the gas production equipment 18 using the electric power and/or steam as a power source (indicated by symbols C and D) for oxygen enrichment of the air used for blowing into the vertical furnace 1. , and for use in refining in the argon furnace 12 and/or the refining furnace 13. This is usually appropriate when the amount of exhaust gas or the total amount of heat contained therein is small. As this oxygen gas production device, for example, PSA (Pre
ssure Swing Adsorption) formula (
(manufactured by Mitsubishi Heavy Industries, Ltd.) is preferred.

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

(e) Using the argon gas obtained in combination with the oxygen gas for stirring the molten metal in the arc furnace 12 and/or the refining furnace 13.

(a), (b), (c), (d), (e) of each of the above matters
By carrying out at least one or more of the following to make use of the process of the present invention, energy costs can be significantly reduced.

Further, in the present invention, as shown in FIG.

Each exhaust gas is collected and stored in the exhaust gas recovery/storage holder 15 in the same manner as explained above with reference to FIG.
It is also necessary to make effective use of it as F symbol) and make it useful in the process of the present invention. This effective use can be arbitrarily selected depending on the amount of mixed exhaust gas and the total amount of heat contained in it, so that it has the highest thermal efficiency and lowest energy cost within the process, but the latter can be used as a heat source (F symbol). Since the method is the same as that explained above with reference to FIG. 1, the explanation will be omitted, and the method of using the former as an exhaust gas energy source (symbol E) will be mainly explained below. In addition, in Figure 2, when mixed exhaust gas is used as an exhaust gas energy source (E symbol), electric power, steam, oxygen gas, nitrogen gas, and argon gas are labeled with umbrella marks and numbers. Electric power, steam, oxygen gas, nitrogen gas, and argon gas when used as F symbol) are indicated by the same number as the skewer mark, and a dash (') is attached to the number.

This mixed exhaust gas is used as an exhaust gas energy source (E symbol) and is burned to produce only electricity, or after this electricity has been produced, steam is further produced using the combustion exhaust gas that still has a large amount of sensible heat. However, it is necessary to effectively utilize this electric power and/or steam for various purposes such as the following to make it useful for the process of the present invention. In other words, as shown in FIG. molten metal flow and energy flow) as part or all of the electricity consumed (-1).

(g) Steam is produced in the steam generation equipment 16 using the combustion exhaust gas that has a large amount of sensible heat as a heat source after the gas turbine of the power generation equipment 17a has been operated to generate electricity, and this steam (umbrella 2
), this steam is used to drive the steam turbine of the power generation equipment 17 to generate electric power (fist 3), which is used as part or all of the steam and electric power consumed in this process (raw material and molten metal flow and energy flow). to do.

(H) Electric power (fist 1) and (g) produced in the above (f) paragraph
Electricity produced in paragraph (denoted by G symbol) and/or (G)
Oxygen gas is produced by the gas production equipment 18 using the steam produced in the above (indicated by the H symbol) as a power source, and this process (
Use as part or all of the oxygen gas consumed in raw materials and molten metal flow (・4).

(S) Using the nitrogen gas obtained together with the oxygen gas produced in item (H) above as part or all of the nitrogen gas consumed in this process (raw materials and molten metal flow) (
-5).

(J) The argon gas obtained in conjunction with the oxygen gas produced in the above (H) is used in this process (raw materials and molten metal flow).
Use as part or all of the argon gas consumed in (・5).

(f), (t), (ch), (su), (nu) of each of the above items
By carrying out at least one or more of the following and making use of it in the process of the present invention, it is possible to increase the thermal efficiency of not only each stool but also the entire process,8 and significantly reduce energy costs.

[For production]

In the process of the present invention, by using a vertical furnace and an electric furnace in combination, not only do they have the inherent characteristics and benefits of each, but they also work to complement each other's shortcomings (weaknesses), resulting in various benefits such as: is obtained. First of all, the use of a vertical furnace naturally provides the following inherent benefits. In other words, chromium ore and stainless steel scrap, which are inexpensive raw materials for chromium, and waste (dust) generated during the manufacturing process.

sludge, slag, etc.), waste containing chromium and nickel generated during the manufacturing process of ferrochrome and ferronickel, and other metal sludge.

Since effective metals such as chromium in nickel-containing catalyst waste can be used in large quantities without special processing, raw material costs are reduced and resources are saved. In addition, energy costs can be reduced because expensive electric power is not used and inexpensive carbonaceous materials (coke, etc.) are used as the thermal energy source for melting and melting and reducing various raw materials including chromium raw materials.

However, even though the vertical furnace has these inherent features and benefits, it has drawbacks as explained below and lacks overall flexibility.

(a) As mentioned above, since this is a continuous operation furnace where 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 high-temperature air or high-temperature oxygen-enriched air that is blown in from the bottom of the furnace is sufficiently controlled to maintain a stable raceway, and the charging status of raw materials in the furnace is
In addition to temperature, pressure, etc., the amount of exhaust gas and component concentration etc.

The amount and component concentration of chromium-containing hot metal to be tapped must be constantly investigated and controlled.

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

(c) Due to the reasons mentioned in (a) and (b) above, it is difficult to change the amount of chromium-containing hot metal to be tapped, its composition, concentration of specific components, temperature, etc., and large changes cannot be expected; Even if a change is made, there are restrictions that require a considerable amount of hot metal and a long period of time.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, requires changing the hot metal components all at once. It takes a long time and a considerable amount of hot metal because it cannot be changed to

(d) Impurities P and S are mixed into the chromium-containing hot metal from the carbonaceous materials and coke as the auxiliary raw materials.

(e) This chromium-containing hot metal contains carbon in a saturated state (approximately 5 to
6%), so when the hot metal is de-refined in the next smelting furnace, a large amount of oxygen gas is required and a large load is placed on the process, and effective metals such as chromium are lost. Since oxidation progresses more rapidly, a large amount of reducing agent is required.

On the other hand, as mentioned above, arc furnaces have fewer restrictions on raw materials, including the shape and size of the raw materials to be charged, and they can use clean electricity as a thermal energy source, turn it on and off, and control the input amount to control various types of electricity in the furnace. Since it is an intermittent operation furnace that melts raw materials, the concentration and composition of specific components, mainly chromium, nickel, and carbon, of the hot metal that is tapped.2.
There are few restrictions on the amount of pig iron tapped, and each method has the advantage of being able to vary widely, but it has the disadvantage of consuming a large amount of expensive electricity.

Therefore, in the process of the present invention, as explained above, by using both the vertical furnace and the arc furnace, which each have their own characteristics and benefits, but also have drawbacks,
As described below, they complement each other's shortcomings and exhibit synergistic effects.

The combination of various chromium raw materials and their ratios are varied in the direction of cost minimum depending on the market price of chromium raw materials due to changes in the chromium raw material situation. In that case, as mentioned above, with only a vertical furnace, there are limitations in terms of shape and dimensions, such as the permeability of the chromium-containing recovered raw materials charged from the top of the furnace, so it may not be possible to obtain the optimum blending ratio of raw materials. Because it is difficult to obtain a chromium-containing recovered raw material whose shape and dimensions are within the appropriate range, there are cases where it is not possible to maintain the chromium component concentration and amount of the chromium-containing hot metal that is tapped. Therefore, by using an arc furnace with fewer restrictions, the chromium-containing recovered raw material, which is unsuitable for use in a vertical furnace, can be used in an arc furnace, and the molten metal that comes from both processes can be combined into hot metal * By doing this, it is possible to easily produce chromium-containing hot metal and its refined molten steel within a target range in terms of specific component concentration, composition, amount, and temperature without wasting any waste. Therefore, we can flexibly respond to any raw material situation.

In addition, when switching between the production of chromium-containing molten steel in a prescribed composition range to the production of chromium-containing molten steel in a prescribed composition range that also contains nickel components, if only a vertical furnace is used, nickel in the chromium-containing hot metal The content can only be increased gradually, and it takes a considerable amount of hot metal and a long time to complete the changeover, but it is possible to prepare hot metal with a high concentration of nickel in an arc furnace in advance, and then combine the molten metals of both hot metals for refining. As a result, molten steel having a predetermined composition range can be easily produced in a short time and without waste.

Moreover, there is no need to add expensive ferronickel alloy during the refining process to adjust the components.

In addition, since impurities such as P and S enter from coke into the molten metal as chromium-containing hot metal tapped from a vertical furnace, preliminary treatment is necessary to reduce their concentration. By combining it with molten metal, which is hot metal, the impurity concentration can be diluted and preliminary treatment can be made unnecessary or reduced.

In addition, carbon is dissolved in the molten metal tapped from the vertical furnace in a saturated state (approximately 5 to 6%), but it is necessary to combine the same molten metal with low carbon content from the arc furnace. Approximately 2-5
Since it is possible to make a mixed molten metal with a low carbon content of about 1.5%, the amount of oxygen gas consumed for decarburization in the refining process of this mixed molten metal can be reduced, and the load on the process can be reduced. . In addition, the amount of reducing agent consumed can be reduced.

In addition, in a vertical furnace, chromium-containing recovered raw materials, iron sources, etc. are charged from the upper part of the furnace, and chromium oxide-containing powder and granules including chromium ore are supplied from the upper tuyere. In order to achieve both the melting and reduction of the chromium raw material, large lump coke (similar to coke for blast furnaces) with good reactivity and good air permeability is used, and the coke concentration is 30~30 at a temperature of 300"C or higher. Exhaust gas with sensible heat and latent heat of 40% is generated.Such exhaust gas is not fully utilized if it is only used to heat the air blown into the vertical furnace or the oxygen-enriched air; Carbon is dissolved in the molten chromium-containing hot metal that is tapped in a nearly saturated state, so even when the combined metal is oxygen-blown in a smelting furnace to decarburize it, it generates a large amount of sensible heat. Exhaust gas is generated.

On the other hand, exhaust gas containing sensible heat and latent heat is also generated when oxygen blowing is performed in an arc furnace for decarburization refining or heating. These exhaust gases can be collected in whole or selectively by furnace or by their operating period depending on the actual situation, and this mixed exhaust gas can be used simply as a heat source, or as an exhaust gas energy source and/or heat source. Steam or electricity can be produced from an energy source and used not only to heat the air blown into the vertical furnace in the process of the present invention, but also as a steam source for a steam ezetator or as power consumption for an arc furnace, for example.
In addition, as mentioned above, the oxygen gas consumed in each flight within the process can be used for gas production and use outside the process, thereby making full use of it effectively, improving thermal efficiency, and reducing energy costs. It is possible.

〔Effect of the invention〕

The manufacturing process of chromium-containing molten steel according to the present invention as described in detail above uses a vertical furnace in combination with an arc furnace to produce molten metal, which is molten iron, which can be tapped using any type of chromium raw material. By combining the molten metals, a mixed molten metal that is a chromium-containing molten metal with a target composition range and a refined molten steel are obtained, and a large amount of heat contained in each exhaust gas generated is transferred to various parts of the manufacturing process in this process. 1 by making it possible to improve the thermal efficiency of the entire process by effectively utilizing
It has the following effects.

(i) Cheap: Since romite ore is used as one of the main raw materials, and the waste generated in the manufacturing plant (dust, sludge, slag, etc.) can be directly processed in the vertical furnace, the cost of raw materials can be reduced.

(ii) Since materials that cannot be used in a vertical furnace, such as large lumps of scrap and powdered chromium-containing recovered materials, can be used as raw materials for an arc furnace, there are almost no restrictions on raw materials.

(iii) Based on the above (i) and (it), the ratio of molten metal made in the vertical furnace and the arc furnace is determined according to the chromium raw material situation and the energy situation, and while minimizing the cost, the target predetermined composition, A mixed molten metal, which is chromium-containing hot metal, can be obtained at a certain temperature and amount, and the refined molten steel can be stably produced.

(iv) Therefore, the load on the refining process using the refining furnace can be reduced, and it is possible to reduce the amount of oxygen gas consumed, expensive ferroalloys added for component adjustment, and reducing agents to be input. Chromium-containing molten steel whose amount is within a predetermined range can be stably supplied to the casting equipment for the next process.

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

(vi) By combining the above effects, it is possible to respond flexibly to changes in the chromium raw material situation and energy situation in a direction that minimizes costs, mass production is possible, and high productivity can be maintained under stable operation. This makes it possible to produce high-quality chromium-containing steel at low production costs.

[Brief explanation of drawings]

Fig. 1 is an explanatory drawing showing one example of the process of the present invention, Fig. 2 is an explanatory drawing showing the different parts from Fig. 1 of the process of another example, and Fig. 3 is a schematic cross-sectional view of an example of a vertical furnace. 1 is a schematic diagram of a chromium hot metal production facility including: In the drawing 1...Vertical furnace 2...Raw material charging inlet 3...Upper tuyere 4...Lower tuyere 5...Hopper 6...Tapping trough 7... ... Air supply source 8 ... Oxygen supply source 9 ... Furnace exhaust gas combustion device 10 ... Heat exchanger 11 ... Dust collector equipment 2 ... Arc furnace 13 ... - Refining furnace 14... Casting equipment 15... Exhaust gas recovery/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

Claims (1)

[Scope of Claims] 1. An arc furnace is used in combination with a vertical furnace having a raw material charging port at the top and two upper and lower tuyeres near the bottom. The raw materials mainly consisting of chromium raw materials, iron sources, carbon materials, and slag materials are charged, and high-temperature air or high-temperature oxygen-enriched air is blown from the upper and lower tuyeres, and chromium oxide-containing materials are blown from the upper tuyeres. Powdered chromium raw materials are fed into the furnace, and chromium-containing hot metal is tapped while melting and melting and reducing each raw material mainly with carbonaceous material. Various raw materials including lumpy and/or granular raw materials are charged to tap hot metal that is substantially chromium-free or contains an arbitrary amount of chromium, and thus the molten metal is chromium-containing hot metal that is tapped from a vertical furnace. On the other hand, the molten metal as the hot metal tapped from the arc furnace is adjusted to the concentration of components mainly containing chromium and carbon, and the amount of hot metal is adjusted.
The molten metal is combined to a predetermined range for at least one or more of the hot water temperature adjustments including component concentration adjustment, and then the mixed molten metal thus obtained is refined in a refining furnace including decarburization by oxygen blowing and tapped. Manufacturing process for chromium-containing molten steel. 2. In the manufacturing process according to claim 1, the molten metal is chromium-containing hot metal tapped from a vertical furnace, and the molten metal is tapped from an arc furnace and is substantially chromium-free or contains an arbitrary amount of chromium. In a vertical furnace, a raw material containing a nickel component is also used as the raw material charged from the raw material charging port, and a powder containing a nickel component is used as the granular chromium raw material supplied from the upper tuyere. Granular raw materials may also be used, and in arc furnaces, raw materials containing nickel components are also used as charging raw materials, making it possible to combine the metal using molten metal, which is hot metal that also contains nickel components. A manufacturing process for chromium-containing molten steel that also contains nickel. 3. In the manufacturing process according to claim 1 or 2, the exhaust gases discharged from the vertical furnace, arc furnace, and refining furnace and having sensible heat and a large amount of latent heat are selected in whole or by furnace or by the operating period of each furnace. (a) The electricity generated by the steam turbine is consumed in the manufacturing process of the chromium-containing molten steel, including the arc furnace. (b) Use as a steam source for a steam ejector when a vacuum is required in refining; (c) Use the electricity and/or steam as a power source to generate oxygen gas. (d) nitrogen obtained in combination with the oxygen gas; Injecting gas into the molten metal in an arc furnace and/or smelting furnace and using it for nitriding and/or stirring the molten metal; (e) Injecting the argon gas obtained in combination with the oxygen gas into the molten metal in the arc furnace and/or smelting furnace. Production of chromium-containing molten steel characterized by being used for stirring molten metal in a furnace, and performing at least one of (a), (b), (c), (d), and (e). process. 4. In the manufacturing process according to claim 1 or 2, the exhaust gases discharged from the vertical furnace, arc furnace, and refining furnace and having sensible heat and a large amount of latent heat are selected in whole or by furnace or by the operating period of each furnace. the exhaust gas is used as an exhaust gas energy source and/or heat source, and the former exhaust gas energy source is used to combust it to produce only electricity, or after the production of this electricity is completed, combustion that still has a large amount of sensible heat. further producing steam with the exhaust gas, while producing steam with the latter heat source, and using the electricity and/or steam; (g) Use as a steam source for a steam ejector when a vacuum is required in refining; (h) Use the electricity and /or Produce oxygen gas using steam as a power source and use it for oxygen enrichment of the air used for blowing in vertical furnaces and for refining use in arc furnaces and/or smelting furnaces; ) Nitrogen gas obtained in combination with the oxygen gas is injected into the molten metal in an arc furnace and/or smelting furnace and used for nitriding and/or stirring the molten metal; Use the argon gas produced for stirring molten metal in an arc furnace and/or smelting furnace. A manufacturing process for chromium-containing molten steel.