JP6090606B2 - Method for melting reduction of chromium-containing oxides - Google Patents

Description

  The present invention relates to a chromium-containing oxide smelting reduction method for producing a chromium-containing hot metal used for refining stainless steel or chromium-containing steel.

  Until now, in the chrome-containing oxide smelting reduction method, chrome ore has been mainly used as the target of smelting reduction treatment, and the technology aimed at efficiently recovering chromium by improving its reduction rate Many have been reported. In these technologies, chromium-containing oxides other than so-called chromium ore, such as dust, sludge, and slag containing chromium, which are generated during the refining of chrome ore in stainless steel in electric furnaces, are also used for effective resource utilization. To chrome ore as a raw material for smelting reduction.

  As an example of such a chrome-containing oxide smelting reduction method, when performing smelting reduction of chromium-containing oxides such as stainless steel scrap and chrome ore, the smelting reduction temperature is 1500 ° C. or more and [ A technique for obtaining a high reduction rate by adjusting the C concentration so that C] and [Cr] satisfy [C] (mass%) ≧ 4.03 + 0.084 · [Cr] has been proposed (for example, , See Patent Document 1).

JP-A-1-215912

However, since the technique disclosed in Patent Document 1 needs to increase the smelting reduction temperature to 1500 ° C. or higher, it is necessary to increase the basic unit of the heating material, and the refractory used in the smelting reduction furnace. There was a problem that the wear of objects increased. Therefore, it has been required to reduce the basic unit of the heat-generating material and reduce the wear of the refractory by lowering the melting reduction temperature.

  By the way, chromium ore generally has a stable crystal structure called spinel structure composed of trivalent chromium and divalent metal oxide, and in order to melt and reduce such stable chromium oxide, the temperature is high. It is necessary to do. On the other hand, among chromium-containing oxides, raw materials containing chromium oxides, such as chromium-containing dust generated by stainless steel refining and chromium-containing sludge produced from the rolling process of stainless steel, have a different crystal composition from chromium ore, There is a possibility that smelting reduction may proceed without necessarily increasing the temperature. However, it is substantially difficult to manage the crystal structures of the various chromium-containing oxides described above in a process. Actually, in actual operation, when the reduction rate survey was conducted in an operation where the smelting reduction temperature was lowered, there was a risk of poor reduction and an increase in cost.

  As a result of intensive studies in view of the above-mentioned problems of the prior art, the inventors have found that it is desirable to appropriately manage the smelting reduction temperature in advance according to the composition of the chromium-containing oxide, and the present invention. Developed.

  The object of the present invention is to be able to easily calculate the required smelting reduction temperature according to the composition of the chromium-containing oxide to be used, and to use in smelting reduction smelting by suppressing unnecessary temperature rise. To propose a smelting reduction method for chromium-containing oxides that can reduce the amount of the heat-generating material to reduce the cost of the heat-generating material and reduce the refractory cost by lowering the smelting temperature. is there.

In order to achieve the above object, in the present invention, in a smelting reduction method in which a chrome-containing hot metal is produced from a chrome-containing oxide using a smelting reduction furnace, the bath temperature in the smelting reduction furnace is expressed by the following (formula 1): and calculating a smelting reduction temperature T1 and below (equation 2) by more people not high either calculation smelting reduction temperature T2 by, and the smelting reduction process of chromium-containing oxides, characterized in that less than 1500 ° C..
(Formula 1)
T1 (° C.) = 8.58 ×% Cr ₂ O ₃ +1137
(Formula 2)
T2 (° C.) = 8.58 × (% MgO × Mc / Mm +% FeO × Mc / Mf) +1137
Here,% Cr ₂ O ₃ : mass ratio (mass%) of Cr ₂ O ₃ in the chromium-containing oxide,
% MgO: mass ratio (mass%) of MgO in the chromium-containing oxide,
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO.

Further, in the melt reduction method in the case of producing chromium-containing hot metal from chromium-containing oxide using a melting reduction furnace, the mass ratio (mass%) of Cr ₂ O ₃ , MgO, and FeO of the chromium-containing oxide is obtained. From the obtained mass ratio of Cr ₂ O ₃ , MgO, and FeO, A is calculated by the following (formula 4), X is calculated from the following (formula 5), and using the obtained X, the following (formula 3) Based on the above, the calculated smelting reduction temperature T1 is obtained, and the bath temperature in the smelting reduction furnace is made to be not less than the calculated smelting reduction temperature T3 and less than 1500 ° C.
(Formula 3)
T3 (° C.) = 8.58 × X + 1137
(Formula 4)
A = (% MgO × Mc / Mm +% FeO × Mc / Mf)
Here,% MgO: the mass ratio (mass%) of MgO in the chromium-containing oxide,
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO.
(Formula 5)
i) In the case of A ≦% Cr ₂ O ₃
X = A,
ii) if A>% Cr ₂ O ₃
X =% Cr ₂ O ₃ ,
Here,% _Cr 2 _{O 3:} a mass ratio of _Cr 2 _{O 3} in the chrome-containing oxide (mass%).

In the chromium-containing oxide smelting reduction method according to the present invention configured as described above, 30% before the end of the addition of the chromium-containing oxide within the smelting time of the smelting reduction furnace. It is more preferable that the bath temperature during a period corresponding to% is set to be equal to or higher than the calculated smelting reduction temperature T1 and the calculated smelting reduction temperature T2 or higher than the calculated smelting reduction temperature T3. It is considered to be a solution.

  Further, in the chrome-containing oxide smelting reduction method according to the present invention configured as described above, the bath temperature during the period during which the chrome-containing oxide is added within the smelting time of the smelting reduction furnace, T1 + 50 ° C.) or less and (T2 + 50 ° C.) or less is more preferable. More preferably, the Cr mass ratio is 0.5 mass% or more.

  According to the chrome-containing oxide smelting reduction method according to the present invention having the above-described configuration, a good smelting reduction treatment can be performed based on the calculated smelting reduction temperature, and an unnecessary temperature increase can be suppressed. Reduction of the heating material cost and reduction of the refractory cost can be achieved.

It is a graph showing the relationship between the Cr ₂ O ₃ concentration which may take the reduction temperature and the spinel structure in the present invention. It is a graph which shows the carbon material usage-amount in the smelting reduction of chromium-containing oxide in the example of this invention and a prior art example. It is a figure which shows the converter type iron bath type smelting reduction furnace which performs the smelting reduction smelting of the chromium-containing oxide which concerns on this invention.

When the chromium-containing oxide is smelted and reduced using a smelting reduction furnace and the chrome-containing hot metal is smelted, the temperature in the smelting reduction furnace, that is, the bath temperature during smelting reduction is at least at the final stage of smelting reduction smelting. It is necessary that the reduction rate of the chromium-containing oxide be in a sufficiently large range. The temperature dependence of the reduction rate of the chromium-containing oxide is considered to depend on the crystal structure of the chromium-containing oxide.
In particular, according to the knowledge of the inventors, regarding the chromium-containing oxide, it is considered that the abundance ratio of the (Mg, Fe) Cr ₂ O ₄ spinel structure has a great influence on the smelting reduction temperature.
Generally, MgO and FeO is found to take a spinel structure combines with _Cr 2 _{O 3,} stoichiometrically, if excessive than MgO and FeO is _{Cr 2 O 3, Cr 2 O} 3 is All are considered to have a spinel structure. Conversely, if MgO and FeO is less than _{Cr 2 O 3, Cr 2 O} 3 that can not be combined with MgO and FeO is believed to not take a spinel structure.

Based on such estimation, according to the present invention, first, from the MgO, FeO, and Cr ₂ O ₃ concentrations of the chromium-containing oxide that is the object of smelting reduction, the following (Formula 4) and (Formula 5) are used. _The Cr ₂ O ₃ concentration X that can be a ₂ O ₃ spinel is estimated, and the Cr ₂ O ₃ concentration X that can actually be a spinel is calculated based on the thermal mass analysis-differential thermal analysis (TG) of the chromium-containing oxide mixed with the carbon powder. The relationship with the reduction temperature obtained by -DTA) was investigated, and the results shown in FIG. 1 were obtained. As is clear from the results shown in FIG. 1, it was found that the Cr ₂ O ₃ concentration capable of forming a spinel structure and the temperature at which smelting reduction proceeds have a strong correlation as shown in the following (formula 3).

That is, from the results shown in FIG. 1, the following (Expression 3), (Expression 4), and (Expression 5) can be derived.
(Formula 3)
T3 (° C.) = 8.58 × X + 1137
(Formula 4)
A = (% MgO × Mc / Mm +% FeO × Mc / Mf)
Here,% MgO: mass ratio of MgO in chromium-containing oxide (mass%)
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO.
(Formula 5)
i) In the case of A ≦% Cr ₂ O ₃
X = A,
ii) if A>% Cr ₂ O ₃
X =% Cr ₂ O ₃ ,
Here,% _Cr 2 _{O 3:} a mass ratio of _Cr 2 _{O 3} in the chrome-containing oxide (mass%).

Therefore, the equation (Equation 4), on the basis of (Equation _{5), Cr 2 O 3,} MgO -containing chromium oxide is reduced object, the mass ratio of FeO of _Cr 2 _{O 3} that can take a spinel structure Obtain the mass ratio X, obtain the calculated smelting reduction temperature T1 from the mass X based on (Equation 3), and proceed the reduction of the chromium-containing oxide by setting the bath temperature during smelting reduction to the calculated smelting reduction temperature T3 or higher. In other words, the chromium-containing oxide is melt-reduced at a lower melting-reduction temperature than before by adding the chromium-containing oxide at a temperature of at least T3 and less than 1500 ° C. It is considered possible. In addition, as a preferred embodiment, regarding the timing of at least T3 or more in the smelting reduction, “30% before the end of the addition of the chromium-containing oxide in the smelting reduction furnace refining time” It can be. This is because if the above control is carried out only during that period, the reduction of the chromium oxide sufficiently proceeds at the end point of the smelting reduction smelting, and there is no problem with desulfurization from the molten iron.

  Here, the “period in which the chromium-containing oxide is added” means that the chromium-containing oxide is added last from the time when the chromium-containing oxide is first added in the acid feeding period of the smelting reduction smelting. It means the period up to the point of time, and when there is a period during which no chromium-containing oxide is added, the period during which no chromium-containing oxide is added is also included. Also, the bath temperature in the smelting reduction furnace may be a value measured by an immersion-type consumable thermocouple, but it can be accurately estimated from the material balance and heat balance in the furnace, so usually this estimated value is used, Based on the measured value, a value obtained by similarly estimating the time-dependent change in bath temperature from the time of measurement is used.

By the way, in the case of said ii) from which it is thought that all the chromium oxides in chromium-containing oxide take a spinel structure from the above, the melting reduction temperature, ie, the bath temperature in a melting reduction furnace, is the following ( By setting the calculated smelting reduction temperature T1 or higher according to the formula 1), a favorable smelting reduction treatment is possible.
(Formula 1)
T1 (° C.) = 8.58 ×% Cr ₂ O ₃ +1137
Here,% Cr ₂ O ₃ : mass ratio (mass%) of Cr ₂ O ₃ in the chromium-containing oxide.

On the other hand, the content of chromium oxide having a spinel structure in the chromium-containing oxide is considered to be a value determined stoichiometrically from the content ratio of MgO and FeO in the chromium-containing oxide. In this case, by setting the bath temperature in the smelting reduction furnace to be equal to or higher than the calculated smelting reduction temperature T2 according to the following (Equation 2), good smelting reduction treatment is possible.
(Formula 2)
T2 (° C.) = 8.58 × (% MgO × Mc / Mm +% FeO × Mc / Mf) +1137
Here,% MgO: the mass ratio (mass%) of MgO in the chromium-containing oxide,
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO.

  Further, by comparing (Equation 1), (Equation 2), and (Equation 5), it is found that T1 ≧ T2 in the case of i) and T1 <T2 in the case of ii). I understand. Therefore, in the case of ii) in which T1 <T2, the bath temperature in the smelting reduction furnace is set to the calculated smelting reduction temperature T1 or more, and in the case of i) in which T1 ≧ T2, the bath temperature in the smelting reduction furnace is Good smelting reduction treatment is possible by setting the calculated smelting reduction temperature T2 or higher, that is, by setting the bath temperature in the smelting reduction furnace to the higher one of the calculated smelting reduction temperature T1 and the calculated smelting reduction temperature T2. It is. As described above, in both cases i) and ii), the bath temperature in the smelting reduction furnace is equal to or higher than the calculated smelting reduction temperature T1 according to (Equation 1) or the calculated melting according to (Equation 2). By setting the reduction temperature to be equal to or higher than T2, a good smelting reduction treatment is possible.

Furthermore, in the smelting reduction treatment in which chromium-containing oxides are added, by reducing the bath temperature in the smelting reduction furnace to less than 1500 ° C., the amount of heat taken away from the system as sensible heat of exhaust gas is reduced, and the thermal efficiency As a result, it is possible to reduce the amount of carbon dioxide (heat raising material) used and to reduce CO ₂ emissions. For this purpose, it is desirable to further reduce the bath temperature in the smelting reduction furnace, and it is desirable to set it to (T1 + 50 ° C.) or less and (T2 + 50 ° C.) or less, or (T3 + 50 ° C.) or less. Considering the controllability of the bath temperature, the bath temperature is not less than T1 or not less than T2, and is not more than (T1 + 50 ° C.) and not more than (T2 + 50 ° C.), thereby reducing the chromium-containing oxide and improving the thermal efficiency. Is possible at a higher level. At this time, it is not always necessary to control this temperature range throughout the entire period of the smelting reduction treatment in which the chromium-containing oxide is added, and the average bath temperature during the smelting reduction treatment period in which the chromium-containing oxide is added. By controlling the temperature within the above temperature range, both reduction of the chromium-containing oxide and improvement in thermal efficiency can be achieved at a high level.

  In the method for melting and reducing chromium-containing oxides according to the present invention as described above, the T.O. The Cr mass ratio is preferably 0.5 mass% or more. T. in chromium-containing oxides. When the Cr mass ratio is 0.5 mass% or more, smelting at low temperature for a long time may cause chromium oxide to accumulate in the slag in the furnace, and the chromium-containing oxide according to the present invention This is because it is desirable to apply the smelting reduction method. For the same reason, T.O. The higher the Cr mass ratio is, the more effective the application of the chromium-containing oxide smelting reduction method according to the present invention is, and it is more than 1.0 mass%, more preferably more than 2.0 mass%, and still more preferably, It is preferable to exceed 3.0 mass%.

  In addition, FIG. 3 is a figure which shows an example of the converter type iron bath type smelting reduction furnace which performs the smelting reduction smelting of the chromium-containing oxide which concerns on this invention. In the example shown in FIG. 3, the iron bath smelting reduction furnace facility 1 includes a furnace body 2, an upper blowing lance 3, and an ore charging lance 4. In addition, the furnace body 2 includes an iron skin 5, a refractory 6, and a bottom blowing tuyere 7. Furthermore, an oxidizing gas supply pipe 8 is connected to the upper blowing lance 3, and an ore transport pipe 9 is connected to the ore charging lance 4. In the iron bath smelting reduction furnace facility 1 described above, the oxidizing gas 13 is blown from the top blowing lance 3 into the molten metal 10 in the furnace body 2 and the slag 11 thereabove, and the ore 12 is fed from the ore charging lance 4. A charcoal material to be used as a fuel and a slagging material for adjusting the slag composition are charged using a charging device (not shown) installed on the furnace. Hereinafter, examples using the above-described converter type iron bath smelting reduction furnace will be described.

<Example 1>
Smelting reduction smelting of chromium-containing oxides was actually performed in a converter type iron bath smelting reduction furnace of 1 charge 150 t shown in FIG. The components of the chromium-containing oxides <1> and <2> used in the experiment are obtained by chemical analysis, and the calculated smelting reduction temperature T1, which is an index obtained by (Equation 1), and the index obtained by (Equation 2) Table 1 shows the results of calculating the calculated smelting reduction temperature T2, the value of A calculated by (Equation 4), and the calculated smelting reduction temperature T3 as an index obtained by (Equation 3). Table 2 shows the operating conditions for this purpose. Chromium-containing oxide <1> is chromium ore, and uses a powdery (average particle size: about 200 μm) material containing 50 mass% or more of Cr ₂ O ₃ and is charged from the furnace through an ore charging lance. Added at. Chromium-containing oxide <2> is dust collection dust generated during refining of stainless steel, and is a powder having a Cr ₂ O ₃ content of about 15 mass% and the same particle size as that of chromium-containing oxide <1>. In the same manner as the chromium-containing oxide <1>, it was added into the furnace from the ore charging lance.

  Under the operating conditions shown in Table 2, for chromium-containing oxides <1> and <2>, the operation at 1560 ° C., which has been actually performed, and the operations in Experiments 1 to 6 in which the smelting reduction temperature was lowered, , Actually implemented. When the dephosphorized hot metal of about 1200 ° C. is charged into an iron bath smelting reduction furnace, oxygen and a carbon material as a heat source are supplied and the temperature is raised, and the iron bath temperature reaches the smelting reduction temperature shown in Table 2 Then, the supply of chromium-containing oxide was started, and the supply rate of chromium-containing oxide was adjusted so that the temperature of the iron bath in the furnace was maintained at the smelting reduction temperature shown in Table 2. At this time, the oxygen supply rate and supply time are set under the same conditions in each test operation. Therefore, the chromium-containing oxide is added by the amount of time required for the temperature increase depending on the melting reduction temperature of each test operation. The length of the period varied from about 65 to 100 minutes. The amount of carbon material supplied is calculated by calculating the amount of carbon material consumed by oxygen in consideration of the amount of oxygen in the chromium-containing oxide in addition to the amount of oxygen in the oxygen gas blown up and bottom. The carbon material was adjusted to remain in a predetermined mass ratio.

  Compare the experimental results. The evaluation of the reduced state is evaluated by T. Performed by Cr concentration. Cr concentration is T.C. The range of Cr ≧ 2.0 mass% was judged as poor reduction. Table 3 shows the results of evaluation with poor reduction as x and good reduction as ◯. Further, the mass ratio of the chromium-containing oxide supply amount and the carbonaceous material supply amount per chromium-containing oxide supply amount is shown in Table 3 as an index with the conventional method being 1. In this case, Experiment 1 and Experiment 2 are indicated by an index that is 1 in the case of the conventional method 1, and Experiments 3 to 6 are indicated by an index that is 1 in the case of the conventional method 2. Here, the mass ratio of the chromium-containing oxide supply amount and the carbonaceous material supply amount per chromium-containing oxide supply amount is the same as that of the smelting reduction furnace from when the molten metal of one charge is charged until the smelting is finished. It is a value calculated using the integrated value of the supply amount in the entire smelting period and the integrated value of each supply amount in this period. From the results shown in Table 3, Experiment 2 in which the chromium-containing oxide <1> was smelted and reduced at a temperature below the index temperature and Experiment 6 in which the chrome-containing oxide <2> was smelted and reduced at a temperature below the index temperature were . It was found that the Cr concentration was high and the reduction was poor. On the other hand, with respect to Experiments 1 and 3 to 5 where the experiment was performed at the index temperature or higher, T.W. The Cr concentration was low and the reduction state was good. Further, in Experiment 1 performed under the condition where the melting reduction temperature in Table 2 was higher than 1500 ° C., the effect of improving the thermal efficiency was small.

  FIG. 2 is a graph showing the amount of carbon material used in the smelting reduction of the chromium-containing oxide in the present invention example (Experiment 3) and the conventional example (conventional method 2). From the result of FIG. 2, it can be seen that due to the effect of lowering the smelting reduction temperature, the amount of the heating carbon material used in the smelting reduction of the same chromium-containing oxide is reduced by about 14%.

  In this experiment, the bath temperature includes the amount of molten iron and slag in the bath during smelting, the amount of carbon supplied to the smelting reduction furnace, the amount of oxygen blown for smelting, Based on the mass balance and heat balance calculated from the amount of chromium oxide, the supply amount of chromium-containing oxide per unit time is adjusted so that the smelting reduction temperature can be kept almost constant by calculating the smelting reduction temperature. It was confirmed by measuring with a thermocouple.

<Example 2>
Under the conditions of Experiment 5, the bath temperature of T3 or higher, that is, T1 or higher or T2 or higher in the period of adding chromium-containing oxide within the smelting time of the converter type iron bath smelting reduction furnace The operation was carried out with the last period being 30% (experiment 5-2) and 25% (experiment 5-3). In the period of the smelting reduction treatment in which other chromium-containing oxides were added, the bath temperature was controlled to about 1250 ° C.

  As a result, T. The Cr concentration was 1.0 mass% in Experiment 5-2 and the reduction was good, but in Experiment 5-3, it was 1.6 mass% and the reduction was apt to be deteriorated. Therefore, it was found that the period for setting the bath temperature to T3 or higher, that is, T1 or higher or T2 or higher is preferably 30% or higher before the end of the addition of the chromium-containing oxide.

  According to the chrome-containing oxide smelting reduction method of the present invention, an appropriate smelting reduction temperature can be obtained according to the composition of the chrome-containing oxide. The smelting reduction temperature can be calculated easily, and by performing smelting reduction based on the calculated smelting reduction temperature, an unnecessary temperature rise can be suppressed, and the heating material cost can be reduced and the refractory cost can be reduced. Reduction can be achieved.

DESCRIPTION OF SYMBOLS 1 Iron bath type smelting reduction furnace equipment 2 Furnace body 3 Top blowing lance 4 Ore input lance 5 Iron skin 6 Refractory 7 Bottom blowing tuyere 8 Oxidizing gas supply pipe 9 Ore conveying pipe 10 Molten metal 11 Slag 12 Ore 13 Oxidizing property gas

Claims (7)

In the smelting reduction method in which the chrome-containing hot metal is melted from the chrome-containing oxide using a smelting reduction furnace, the bath temperature in the smelting reduction furnace is calculated by the following formula (Equation 1), the calculated smelting reduction temperature T1 and the following (Equation 2 The smelting reduction method for chromium-containing oxides, characterized in that the calculated smelting reduction temperature T2 is not higher than the calculated smelting reduction temperature T2 and is lower than 1500 ° C.
(Formula 1)
T1 (° C.) = 8.58 ×% Cr ₂ O ₃ +1137
(Formula 2)
T2 (° C.) = 8.58 × (% MgO × Mc / Mm +% FeO × Mc / Mf) +1137
Here,% Cr ₂ O ₃ : mass ratio (mass%) of Cr ₂ O ₃ in the chromium-containing oxide,
% MgO: mass ratio (mass%) of MgO in the chromium-containing oxide,
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO. In a smelting reduction method when producing a chrome-containing hot metal from a chrome-containing oxide using a smelting reduction furnace, the mass ratio (mass%) of Cr ₂ O ₃ , MgO, and FeO of the chromium-containing oxide is obtained and determined. From the mass ratio of Cr ₂ O ₃ , MgO, and FeO, A is calculated by the following (formula 4), X is calculated from the following (formula 5), and based on the following (formula 3) using the obtained X. A method for smelting reduction of chromium-containing oxides, characterized in that a calculated smelting reduction temperature T3 is obtained, and a bath temperature in the smelting reduction furnace is set to be equal to or higher than the calculated smelting reduction temperature T3 and lower than 1500 ° C.
(Formula 3)
T3 (° C.) = 8.58 × X + 1137
(Formula 4)
A = (% MgO × Mc / Mm +% FeO × Mc / Mf)
Here,% MgO: the mass ratio (mass%) of MgO in the chromium-containing oxide,
% FeO: mass ratio of FeO in the chromium-containing oxide (mass%),
Mc: Molecular weight of Cr ₂ O ₃ ,
Mm: MgO molecular weight,
Mf: The molecular weight of FeO.
(Formula 5)
i) In the case of A ≦% Cr ₂ O ₃
X = A,
ii) if A>% Cr ₂ O ₃
X =% Cr ₂ O ₃ ,
Here,% _Cr 2 _{O 3:} a mass ratio of _Cr 2 _{O 3} in the chrome-containing oxide (mass%). The bath temperature of the period corresponding to 30% before the end of the addition of the chromium-containing oxide within the smelting time of the smelting reduction furnace is set to the calculated smelting reduction temperature T1 and the calculated smelting reduction temperature T2 . The method for smelting reduction of chromium-containing oxide according to claim 1, characterized in that any one of them is not higher .   The bath temperature in a period corresponding to 30% before the end of the addition of the chromium-containing oxide within the smelting time of the smelting reduction furnace is set to the calculated smelting reduction temperature T3 or more. The method for melting and reducing the chromium-containing oxide according to claim 2.   4. The bath temperature during the addition of the chromium-containing oxide within the smelting time of the smelting reduction furnace is set to (T1 + 50 ° C.) or less and (T2 + 50 ° C.) or less. A method for melting and reducing chromium-containing oxides.   The bath temperature during the period during which the chromium-containing oxide is added within the smelting time of the smelting reduction furnace is set to (T3 + 50 ° C) or less, and the chromium-containing oxide according to claim 2 or 4, Melting reduction method.   T. in the chromium-containing oxide. The method for smelting reduction of a chromium-containing oxide according to any one of claims 1 to 6, wherein the Cr mass ratio is 0.5 mass% or more.

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