JPH07310109A - Production of stainless steel - Google Patents

Abstract

PURPOSE:To provide a producing method of a stainless steel, by which the production is easily executed without need to provide two furnaces of a smelting reduction furnace and a decarburizing furnace and the recovery of chromium and desulfurization are effectively executed. CONSTITUTION:In a method to recover chromium into molten steel by reducing the chromium oxide in slag with carbon in the molten steel or carbon in a carbon-containing material by bringing recycled chromium oxide-containing slag into contact with the molten steel before blowing for roughly decarburizing and temp.-raising or during the blowing, the heating by plasma-arc is executed before the blowing or after the blowing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing stainless steel using hot metal, scrap, ferroalloy, etc. in a steelmaking furnace such as an argon oxygen decarburization furnace (AOD furnace) and a converter.

[0002]

2. Description of the Related Art The most typical process for smelting stainless steel is to use scrap or ferro-alloy such as Fe-Cr and Fe-Ni as a main raw material, melt this in an electric furnace, and then decarburize with argon oxygen. Furnace (AOD furnace), vacuum oxygen decarburization furnace (VOD furnace), etc. for decarburization and reduction refining.After tapping, Ar injection is performed in a steel pan to clean molten steel and control the temperature, and then continuously. It is a casting machine.

Further, as described in the literature (“Iron and Steel” 1985, vol.71, 180), the hot metal is charged into a bottom-blown converter without using an electric furnace to decarburize it so that it becomes a component of stainless steel. During scraping or before blowing, add scrap or ferroalloy to a predetermined component, and after decarburizing brazing, add ferroalloy such as Fe-Si and shift to the reduction process, and then tap steel. There is also a continuous casting process.

There is also a stainless steel melting process using chromium ore as one of the raw materials. For example, in the literature (“Iron and Steel” 1985, vol.71,1072), AOD furnace was charged with hot metal,
After that, chrome ore and coke are added, so-called smelting reduction is performed, and then slag is removed and normal decarburization refining is performed.

However, the above method has the following problems. (1) Addition of a large amount of Si (often Fe-Si) increases the cost. (2) Since SiO ₂ is generated as a reaction product, a large amount of CaO is required to neutralize it. As a result, a large amount of slag is generated. (3) Since the reduction reaction of chromium oxide with silicon is an exothermic reaction, the temperature rises and the slag has a high fluidity, so that it erodes refractory materials.

Therefore, Japanese Patent Publication No. 38806/1992 proposes a process for returning chromium-containing chromium slag at the final stage of decarburization of crude stainless steel to a smelting reduction furnace to reduce and recover chromium. As a result, the reduction period using Fe-Si can be omitted, and the above problems are solved. Further, when the chromium oxide-containing slag remaining in the decarburizing furnace is reduced and recovered by C in the next charge of molten stainless steel, it is possible if the C in the molten metal is 5% and 1500 ° C or higher.

[0007]

[Problems to be Solved by the Invention] However, Japanese Patent Publication No. 4-38
The method disclosed in Japanese Patent No. 806 has a problem that it cannot be realized without having two furnaces, a smelting reduction furnace and a decarburization furnace.
Further, when the chromium oxide-containing slag remaining in the decarburizing furnace is reduced and recovered by C in the hot metal of the next charge, there is a problem that the Cr ₂ O ₃ reduction rate by C in the molten metal is not sufficient.

Therefore, the applicant of the present patent application filed Japanese Patent Application No. 5-14.
As No. 6167, the final decarburization slag was recycled to the same furnace and the chromium oxide in the slag was reduced and recovered with [C] during the decarburization temperature rise of the next charge of the crude melt, and the Si-containing alloy was added at the final reduction stage to recover chromium. Propose a process to improve the rate.

Certainly, in the method of Japanese Patent Application No. 5-146167, Cr ₂ O ₃ in the slag is reduced by C, but it is not necessary to simply add the final decarburization slag into the furnace and reduce it by C. , The C reduction rate is slow and the Cr ₂ O ₃ reduction rate is not sufficient. In other words, although it is necessary to raise the temperature immediately after the start of blowing to the reduction temperature (1500 to 1600 ° C) at which slag turns into slag, the hot metal temperature during pouring is at most 1300 ° C, This is because when the chromium oxide-containing slag is added before the start or immediately after the start of the blowing, the heat removal time due to the addition of the slag increases the heating time to the reduction temperature (1500 to 1600 ° C).

Therefore, it is necessary to reduce the chromium oxide that has not been reduced by C with the Si-containing alloy.
The original goal of reducing alloys may not be fully met. Furthermore, for desulfurization, it is necessary to add a small amount of Si-containing alloy at the final stage of reduction. Further, in this method, the C basic unit for heating is increased, and as a result, there is a concern that the decarburizing and blowing time may be extended.

In the method disclosed in Japanese Patent Laid-Open No. 58-16037, a high chromium alloy is produced by melting a high chromium alloy in a shaft type reactor equipped with a plasma torch using a solid containing chromium as a raw material. Although it is said that alloys can be melted, although the shaft furnace has good thermal efficiency, it is difficult to melt various steel types because the furnace height needs to be increased, the equipment cost is high, and batch processing is difficult. There are problems such as this. In addition, the method is limited to shaft furnaces, and ordinary decarburization furnaces (such as converters or AOD furnaces)
There is no information on how to use plasma heating in.

The object of the present invention is (1) it is not necessary to have two furnaces, a smelting reduction furnace and a decarburization furnace, and (2) the problem of chromium unreduction and desulfurization by only C reduction is solved. 3) Reduce the C intensity and suppress the extension of decarburization blowing time,
(4) To provide a method capable of easily producing various steel types by batch processing.

Specifically, the object of the present invention is to reduce the amount of coke as a heat source, reduce the amount of metallic Si and CaO input, and simultaneously realize the improvement of the Cr reduction rate and the desulfurization rate. Is to provide a method for manufacturing the same.

[0014]

Therefore, the present inventors have
The present invention has been completed by paying attention to the use of plasma in a decarburizing furnace, which has not been conventionally studied, in order to achieve such a subject.

Here, the gist of the present invention is to prepare a chromium oxide-containing slag obtained during the finishing decarburization refining stage of the crude molten steel of stainless steel, and to prepare the slag and the crude decarburization temperature rising blowing before Or, in contact with the molten metal during blowing, recover the chromium oxide in the slag by recovering it in the molten metal by the carbon in the molten metal or the carbon in the carbon-containing material, in which case metal and Raising the slag to improve the reduction efficiency, to the crude molten steel of the molten stainless steel obtained by the crude decarburization temperature-rising blowing, if necessary, add Si-containing alloy for finish reduction and desulfurization, then The method for producing stainless steel is characterized in that slag is discharged and a Cr-containing alloy is added in a predetermined amount to perform final decarburization refining. Here, as the slag containing chromium oxide obtained in the final decarburizing and refining stage, the slag obtained in the final decarburizing and refining final stage is preferable.

According to a preferred embodiment of the present invention, when the temperature of the molten metal and the slag by the plasma arc is raised, the chromium oxide-containing slag generated when decarburizing the crude molten steel of stainless steel by using an inert gas as a carrier gas. Is a method for producing stainless steel, characterized in that the slag powder obtained by crushing and pulverizing the slag is continuously or divided and sprayed onto the surface of the molten metal.

[0017]

Next, the operation of the present invention will be described more specifically. FIG. 1 is a process diagram showing an example of a method for producing stainless steel according to the present invention. In the figure, hot metal prepared separately,
Preferably, the deoxidized P hot metal is recycled with the Cr ₂ O ₃ -containing slag recovered during the precharge finish decarburization refining period. If necessary, they may be dividedly charged or continuously charged. Also, in this case, a pre-charging decarburization furnace (example: converter)
It is also possible to leave the Cr ₂ O ₃ -containing slag of No. 1 and leave the above-mentioned de-P hot metal in it. The hot metal may be discharged in the electric furnace melting method depending on the case.

According to the present invention, the recycled chromium oxide-containing slag is placed in contact with the molten metal which is hot metal in this manner, and the reduction of chromium by C is performed during the coarse decarburizing temperature-rising blowing. However, prior to that, during that period, and after that, heating by the plasma arc is performed. The state at this time is schematically shown in FIG. An appropriate number (three in the illustrated example) of plasma torches 10 are provided to heat the molten metal 12. The molten metal, which was approximately 1200 to 1300 ° C. when the chromium oxide-containing slag was charged, is thereby heated to approximately 1450 to 1550 ° C. in a short time of approximately 5 to 10 minutes. During the heating period by the plasma torch 10, it is preferable to continue the inflow of the stirring gas of O ₂ + Ar gas from the tuyere 14 at the bottom of the molten metal. Reference numeral 16 represents a slug.

In the present invention, the reason why the heating by the plasma torch 10 is employed in the coarse decarburizing temperature rising blowing is as follows. That is, in order to reduce Cr ₂ O ₃ in the final decarburization slag with C in the molten metal, the reduction temperature (15
It is necessary to raise the temperature as soon as possible after the start of blowing up to 00-1600 ℃. However, as mentioned above, the hot metal temperature during pouring is at most 13
The temperature is about 00 ° C, and when the chromium oxide-containing slag is added before or immediately after the start of blowing, the heat removal due to the addition of slag increases the heating time to the reduction temperature (1500 to 1600 ° C).

However, since the slag 16 can be heated by heating with the plasma torch 10, the temperature of the slag can be increased as compared with the conventional method even if the molten iron is below the conventional reduction temperature (1500 to 1600 ° C.). Therefore, the reduction time can be shortened. After the heating is completed, the plasma torch 10 is pulled up, a normal oxygen top-blowing lance is charged, and coarse decarburizing temperature rising blowing is performed.

Further, in the conventional method, the carbon concentration in the molten iron decreases at the final stage of reduction, so that [Cr] in the molten metal is oxidized at the oxygen supply fire point, resulting in a marked reduction in the reduction rate. Therefore, in the final stage of reduction, a method of reducing or eliminating the rate of oxygen transfer to suppress the oxidation of [Cr] in the molten metal is taken. However, in that case, the temperature of the molten iron is lowered, so that the time for the treatment for lowering or zeroing the acid transfer rate is limited. Therefore, there is a limit to the improvement of the reduction rate.

Therefore, if the plasma torch 10 is used for heating to reduce or reduce the acid transfer rate at the final stage of the reduction, the reduction rate can be maintained while preventing the decrease in molten iron temperature. It can be greatly improved.

FIG. 2 (b) schematically shows how the coarse decarburizing temperature rising blowing at this time is carried out. During the blowing by the upper blowing lance 20, stirring from the tuyere 14 at the bottom of the furnace is performed. Gas (O ₂ + A
r) is still being blown in. Coarse decarburization temperature rising blowing is
It may be carried out in the same manner as the blowing of stainless steel in a normal converter, and there is no particular limitation in the present invention. Therefore,
The top blowing gas may be any conventional one such as O ₂ , O ₂ + N ₂ or O ₂ + Ar.

At this time, C used as a reducing agent is [C] contained in the molten metal, or carbon (C) contained in carbon-containing materials such as coke, char or anthracite to be introduced at the time of decarburization. May be After the completion of the coarse decarburization temperature-rising blowing, the chromium oxide concentration in the slag is generally 4 to 15%, the melt composition is C: 0.1 to 1%, and S: 0.01 to 0.07%.

The crude molten steel containing a few% of [Cr] thus obtained is subjected to finish reduction treatment and then to finish decarburization, as shown in FIG. Partially oxidizes into the slag.

The Cr ₂ O ₃ concentration after finish reduction is preferably 2 to 10%. In order to perform the reduction of Cr ₂ O ₃ oxide more completely, the amount of metallic Si input must be increased,
If the amount of Si added is increased, it becomes necessary to add more CaO accordingly, and the melting loss of refractory due to the rise in molten steel temperature cannot be avoided.

As described above, according to the present invention, the chromium oxide-containing slag is recycled for use in the next charge crude decarburizing temperature rising blowing step, and at that time, rapid heating is performed prior to the start of decarburization. Plasma heating is also used for this purpose. After finishing decarburization, the steel is tapped and stainless steel is produced as in the conventional case. If necessary, you may perform refining outside a furnace suitably.

It is necessary to recycle the slag containing chromium oxide generated when decarburizing the crude molten steel of the stainless steel at the time of decarburization after the next charge, depending on the carbon in the molten metal or the carbon-containing material such as coke. Reduces chromium oxide,
It is preferable for omitting the metal Si or reducing the usage amount.

As described above, according to the present invention, adding the chromium oxide-containing slag all at once or continuously or in a divided manner while heating the molten metal and the slag by the plasma arc promotes the reduction reaction during the temperature rise. By increasing the rate of temperature increase to the reduction temperature to lengthen the melting and reduction time of chromium oxide during decarburization heating, the high melting point Cr ₂ O ₃ -containing slag can be easily melted, and even after that temperature is reached To reduce the C basic unit and shorten the decarburization time by maintaining the above value, improving the reduction rate and the reduction rate.

The plasma torch which can be raised and lowered is used in accordance with the method of the present invention because a large amount of slag is used and a large amount of CO or CO ₂ gas is generated, so that a slag forming or sloping phenomenon occurs. This is because it may damage the torch. Therefore, in the present invention, it is necessary to lower the plasma torch in the range where the temperature at the beginning of the process is low and to use it, and to raise the plasma torch in the range where the temperature rises and the reduction proceeds sufficiently to prevent melting loss.

In the latter half of the reduction period, Cr ₂ O _{3 in the} slag is also used.
Since the reduction of OH and the temperature have risen sufficiently, the rate of acid transfer can be reduced or even reduced to zero. Normally, at this time, the slag foaming transitions to a low level, so even if the plasma torch is lowered, heating can be performed without damaging the torch.

Further, in a preferred embodiment of the present invention, the chromium oxide produced when decarburizing the crude molten steel of stainless steel by using the inert gas as a carrier gas while being entrained in the plasma jet generated from the plasma torch installed in the refining furnace The contained slag is collected and crushed, and the slag powder obtained by crushing is continuously or divided and sprayed onto the surface of the molten metal to improve the heat adhering efficiency to the slag and further enhance the heating effect by the plasma torch. be able to. Next, the operation and effect of the present invention will be described more specifically by way of examples.

[0033]

【Example】

(Comparative example) Desulfurized pig iron 65T was charged into an upper-bottom blowing converter and recovered at the end of the finish decarburization period of stainless steel (composition:
T.Cr = 20%, T.Fe = 3%, CaO / SiO ₂ = 1.4, MgO = 5
%, Al ₂ O ₃ <10%), 6000 kg, coke 4000 kg, lime 574 kg, and bottom-blown Ar gas 17 Nm ³ / min,
While blowing oxygen from the top blowing lance at 146 Nm ³ / min,
Blown for 41 minutes.

After decarburization to a predetermined carbon concentration [C] = about 1.0% and stopping the feeding of acid, the chromium concentration in the molten iron is [% Cr] = 1.
It became 3% and the reduction rate was 70%. After this, Fe-Si (composition:
400 kg of Si = 75% and the balance Fe) were added. The temperature after the addition of Fe-Si was 1614 ° C, the slag basicity was 1.5, and [% Cr] = 1.71%.

Thereafter, the slag was discharged, and 21 T of ferrochrome (composition: Cr = 60%, Si = 2.7%, C = 6%, balance Fe) was discharged.
, 1.8T of quicklime was added for decarburization. Temperature after decarburization is 1700 ℃, slag basicity is 1.5, [% Cr] = 13
%Met.

(Example 1) The slag (composition: T.Cr = 20%, T.Fe = 3) collected at the end of the finish decarburization period of stainless steel by charging dephosphorized iron 65T into an upper-bottom blowing converter. %, CaO / SiO ₂ = 1.
4, MgO = 5%, Al ₂ O ₃ <10%) 6000 kg, coke
After adding 2000kg and quick lime to the 360kg furnace, from the bottom tuyeres
Blowing was carried out for 34 minutes while stirring with Ar gas (flow rate 17 Nm ³ / min).

At that time, as shown in FIG. 2 (a), three non-transfer type plasma torches (each having 1 MW output) were lowered by an elevating device in a state in which the upper blowing acid was stopped prior to the blowing. The plasma was ignited and the plasma was heated for 8 minutes.
After that, raise the plasma torch to turn off the plasma,
Instead, as shown in Fig. 2 (b), the blowing lance was lowered to start the acid feeding to perform the decarburization treatment.

After decarburization to a predetermined carbon concentration [C] = 1.0% and then stopping the feeding of acid, the chromium concentration in the molten iron is [% Cr] = 1.
It was 68% and the reduction rate was 91%. After this, Fe-Si (composition:
200 kg of Si = 75% and the balance Fe) were added. The temperature after the addition of Fe-Si was 1635 ° C, the slag basicity was 1.5, and [% Cr] = 1.75%.

Then, the slag is discharged and the ferrochrome is added to 21
Finishing decarburization was performed by adding 1.8 T of T 2 and quicklime.
After decarburization, the temperature is 1700 ℃, slag basicity is 1.5, [% C
r] = 13.1%.

(Example 2) Chromium oxide-containing slag (composition: T.Cr = 20%, T), which was prepared by charging dephosphorized pig iron 65T into an upper-bottom blowing converter and previously recovered at the end of the finish decarburization period of stainless steel .Fe ＝
3%, CaO / SiO ₂ = 1.4, MgO = 5%, Al ₂ O ₃ <10%)
After adding 6000 kg, 2000 kg of coke, and 360 kg of quick lime into the furnace, rough decarburization temperature rising blowing was performed for 34 minutes while stirring with Ar gas (flow rate 17 Nm ³ / min) from the bottom blowing tuyere.

After that, as shown in FIG. 2 (a), the top blowing acid is stopped and the top blowing lance is raised, and three non-transfer type plasma torches (each 1 MW output) are lowered by the lifting device, The plasma was ignited and the plasma was heated for 8 minutes.

After the above treatment, the carbon concentration was [C] = 1.0%, the chromium concentration in the molten iron was [Cr] = 1.67%, and the reduction rate was 90%.
% Advanced. After this, 200 kg of Fe-Si was added. Fe-
Temperature after addition of Si is 1635 ℃, slag basicity is 1.5, [% Cr]
= 1.76%.

After that, the slag was discharged, and 21 T of ferrochrome and 1.8 T of quicklime were added to the same as above to perform a final decarburization treatment. The temperature after decarburization was 1700 ° C, the slag basicity was 1.5, and [% Cr] = 13.1%.

Example 3 The slag (composition: T.Cr = 20%, T.Fe = 3) collected at the end of the finish decarburization period of stainless steel was prepared by charging dephosphorized pig iron 65T into an upper-bottom blowing converter. %, CaO / SiO ₂ = 1.
4, MgO = 5%, Al ₂ O ₃ <10%) 5350 kg, coke
After adding 2000kg and quick lime to the 360kg furnace, from the bottom tuyeres
Blowing was carried out for 34 minutes while stirring with Ar gas (flow rate 17 Nm ³ / min).

Thereafter, as shown in FIG. 2 (a), the top blowing acid is stopped, the top blowing lance is raised, and three non-transfer type plasma torches (each 1 MW output) are lowered by the lifting device, The plasma was ignited and the plasma was heated for 8 minutes.
At that time, a total of 650 kg of the molten slag heated in the plasma jet was sprayed onto the surface of the molten steel.

The carbon concentration after the above treatment was [C] = 1.0%, the chromium concentration in the molten iron was [Cr] = 1.72%, and the reduction rate was 93%.
% Has advanced. After this, 100 kg of Fe-Si was added. Fe
-Si addition temperature is 1635 ℃, slag basicity is 1.5, [% C
r] = 1.78%.

After that, the slag was discharged, and 21 T of ferrochrome and 1.8 T of quick lime were similarly added to carry out a final decarburization treatment. The temperature after decarburization is 1700 ℃, and the slag basicity is 1.5.
, [% Cr] = 13.1%.

(Example 4) The slag (composition: T.Cr = 20%, T.Fe = 3) collected at the end of the finish decarburization period of stainless steel was prepared by charging dephosphorized pig iron 65T into a top-bottom blowing converter. %, CaO / SiO ₂ = 1.
4, MgO = 5%, Al ₂ O ₃ <10%) 5350 kg, coke
After adding 2000kg and quick lime to the 360kg furnace, from the bottom tuyeres
Blowing was carried out for 34 minutes while stirring with Ar gas (flow rate 17 Nm ³ / min).

After that, as shown in FIG. 2 (a), the top-blown acid was stopped and the top-blown lance was raised, and three non-transfer type plasma torches (each 1 MW output) were lowered by an elevating device to generate plasma. Was ignited and plasma heating was performed for 8 minutes.
At that time, a total of 650 kg of the molten slag heated in the plasma jet was sprayed onto the surface of the molten steel.

After the above treatment, the carbon concentration was [C] = 1.0%, the chromium concentration in the molten iron was [Cr] = 1.75%, and the reduction rate was 95%.
% Has advanced. Since the reduction rate was greatly increased, the subsequent addition of Fe-Si was omitted.

Thereafter, the slag was discharged, and 21 T of ferrochrome and 1.8 T of quick lime were similarly added to perform a final decarburization treatment. The temperature after decarburization is 1700 ℃, and the slag basicity is 1.5.
, [% Cr] = 13.1%.

(Embodiment 5) A slag (composition: T.Cr = 20%, T.Fe = 3%, CaO /) which was charged at the end of the finishing decarburization period of stainless steel by charging deoxidized pig iron 65T into AOD SiO ₂ = 1.4,
MgO = 5%, Al ₂ O ₃ <10%) 6000 kg, coke 1000
After adding 360 kg of quick lime and 360 kg of quick lime into the furnace, blowing was performed for 34 minutes while blowing O ₂ -Ar gas from the dipping tuyere on the side wall of the AOD furnace body.

At that time, from the beginning of blowing to 20 minutes, FIG. 2 (a)
As shown in Fig. 3, a plasma jet generated from three non-transfer type plasma torches (1 MW output each) was jetted onto the molten steel surface and heated.

As a result, the reduction rate of Cr ₂ O _{3 in} the slag was higher from the beginning of blowing compared with the case where plasma heating was not used, and after the end of acid transfer, the carbon concentration [% C] = 1.0 and the chromium in molten iron was reduced. The concentration [% Cr] was 1.66, and a reduction rate of 90% was obtained.

After that, 200 kg of Fe-Si was added. The temperature after adding Fe-Si is 1635 ° C, the slag basicity is 1.5, and [% Cr] = 1.
It was 76%. After that, the slag was discharged, and 21 T of ferrochrome and 1.8 T of quick lime were also added to finish decarburization. The temperature after decarburization is 1700 ° C and the slag basicity is 1.
5, [% Cr] = 13.1%.

(Example 6) Dephosphorized pig iron 65T was charged into an AOD furnace, and slag recovered at the end of the finish decarburization period of stainless steel (composition: T.Cr = 20%, T.Fe = 3%, CaO / SiO ₂ = 1.4,
MgO = 5%, Al ₂ O ₃ <10%) 5350 kg, coke 1000
After adding 360 kg of quick lime and 360 kg of quick lime into the furnace, blowing was performed for 34 minutes while blowing O ₂ -Ar gas from the dipping tuyere on the side wall of the AOD furnace body.

At that time, from the beginning of blowing to 20 minutes, the total amount of the above-mentioned slag heated in the plasma jet generated from three non-transfer type plasma torches (output of 1 MW each) was 650.
Injection into the surface of molten steel.

As a result, the reduction rate of Cr ₂ O _{3 in} the slag was considerably higher from the beginning of blowing compared to the case where plasma heating was not used, and after the end of the acid transfer, the carbon concentration [% C] = 1.0 Chromium concentration [% Cr] = 1.75 and reduction rate of 95% was obtained.
The Fe-Si addition was omitted because the reduction rate was very high.

Thereafter, the slag was discharged, and 21 T of ferrochrome and 1.8 T of quick lime were similarly added to perform a final decarburization treatment. The temperature after decarburization is 1700 ℃, and the slag basicity is 1.5.
, [% Cr] = 13.1%. The results of Comparative Examples and Examples 1 to 6 are summarized in Table 1 below.

[0060]

[Table 1]

[0061]

According to the present invention, when chromium oxide is reduced during decarburization, it is possible to maintain the reduction rate at a high value by increasing the molten steel temperature, thereby improving the reduction rate and C
The decarburization time can be shortened by reducing the basic unit.

[Brief description of drawings]

FIG. 1 is a process chart of an example of a method according to the present invention.

2 (a) and 2 (b) are schematic explanatory views of the states of plasma arc heating and top blowing lance blowing in the present invention, respectively.

Claims (3)

[Claims] 1. A chrome-containing slag obtained during the finishing decarburization refining stage of crude molten steel of stainless steel is prepared, and the slag is brought into contact with the molten metal before or during the coarse decarburization temperature rising blowing. In addition, the chromium oxide in the slag is reduced by the carbon in the molten metal or the carbon in the carbon-containing material to be recovered in the molten metal, in which case the plasma and the slag are heated to improve the reduction efficiency. That is, the production of stainless steel, characterized in that the slag is discharged from the crude molten steel of the molten stainless steel obtained by the crude decarburizing temperature-rising blowing, and a predetermined amount of Cr-containing alloy is added to perform final decarburizing refining. Method. 2. A chromium oxide-containing slag obtained during a finish decarburization refining stage of a crude molten steel of stainless steel is prepared, and the slag is brought into contact with a molten metal before or during the coarse decarburization temperature raising blowing or during the blowing. In addition, the chromium oxide in the slag is reduced by the carbon in the molten metal or the carbon in the carbon-containing material to be recovered in the molten metal, in which case the plasma and the slag are heated to improve the reduction efficiency. Then, the Si-containing alloy is added to the crude molten steel of the stainless molten steel obtained by the crude decarburizing temperature-rising blowing to perform finish reduction and desulfurization, and thereafter,
A method for producing stainless steel, characterized in that slag is discharged and a predetermined amount of Cr-containing alloy is added to carry out finish decarburization refining. 3. When the temperature of the molten metal and slag is raised by the plasma arc, the chromium oxide-containing slag produced when decarburizing the crude molten steel of stainless steel is recovered and pulverized by using an inert gas as a carrier gas and pulverized. The method for producing stainless steel according to claim 1 or 2, wherein the slag powder obtained by the method is sprayed continuously or dividedly onto the surface of the molten metal.