JPH09111329A - Production of highly clean austenitic stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing a highly clean austenitic stainless steel. SOLUTION: This process for producing the highly clean rare earth elements contg. stainless steel comprises executing the treatment by the following stages 1 to 4:1. Crude molten metal is tapped and is subjected to decarburization oxidation refining, then, to predeoxidation by Si and Mn. 2. The molten metal is deoxidized by specifying Al to >=3.0% and forming CaO-Al2 O3 slag. 3. Al is specified to >=0.3% in all ensuring stages and the molten metal is subjected to killing to confine the total oxygen concn. to <=0.003%. 4. The formation of rare earth oxide is thereafter suppressed by adjusting the rare earth elements to >=0.01%. In this method, the Al-Ca and/or Mg composite deoxidation to specify the Ca and/or Mg to >=0.001% is further usable in the above 2 and 3. As a result, the cleanliness in the smelting process is improved, the degradation in the cleanliness by addition of the rare earth elements is suppressed and the clogging of a nozzle at the time of continuous casting is prevented.

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 a rare earth element-containing austenitic stainless steel which has high cleanliness and can prevent nozzle clogging.

[0002]

2. Description of the Related Art Generally, in order to highly clean molten steel, it is necessary to sufficiently deoxidize it, that is, to add an appropriate amount of deoxidizing element and to float the produced deoxidizing product (inclusions). There is. However, in an austenitic stainless steel containing a rare earth element in an amount of 0.01 wt% or more, when added to molten steel, a large amount of a rare earth oxide is generated, resulting in deterioration of cleanability.

This is because the rare earth element has a very strong affinity with oxygen, so that other oxides around it are reduced to form a rare earth oxide, and the rare earth oxide once generated has a specific gravity close to that of molten steel. , Because it is not floated and separated. Thus, although the rare earth element functions to some extent as a deoxidizer for steel, it deteriorates the cleanliness of steel.

Further, the generated rare earth oxide causes nozzle clogging during continuous casting, which is a serious obstacle in actual operation.

Therefore, in the case of a steel type to which a rare earth element is added, another general deoxidizing element (for example, Al or Si) is added before the addition.
Etc.) are used. However, even in such a case, since the rare earth element has a strong affinity with oxygen, it reduces inclusions and slag and produces a large amount of rare earth oxide in the molten steel. .

[0006] In order to avoid nozzle clogging, rare earth elements may be added into the mold during casting. With this method, although nozzle clogging can be avoided, cleanliness cannot be improved, and rare earth elements cannot be improved. There is a problem such as segregation of.

In the method for smelting an austenitic stainless steel containing a rare earth element, a steel is taken out from a smelting furnace and subjected to oxidative refining for decarburization in a ladle, followed by a desulfurization step and nitrogen addition if necessary. Various processes such as a process, a heating process for maintaining the temperature of molten steel, a deoxidizing process, and a rare earth element adding process are required.

[0008] These steps are generally reduction refining in which a deoxidizing element is added, but there is no particular clear guideline or idea regarding the method and sequence. For example, in the nitrogen addition step, nitrogen gas is blown into the molten steel to obtain a predetermined amount of nitrogen, but in the step, the nitrogen addition yield and the treatment time may be taken into consideration, but the progress of deoxidation should be taken into consideration. I had no idea. Further, when undergoing a plurality of refining steps such as austenitic stainless steel melting, the temperature is raised by blowing oxygen to provide heat, but in this temperature raising step, the total oxygen concentration in the molten steel is substantially In many cases, it was in a high state, and the degree of deoxidation and cleanliness of molten steel at this stage were not considered. Therefore, in the conventional manufacturing method, it is not easy to achieve high cleanliness because a large amount of oxide is generated even if the oxygen concentration is lowered to the desired low oxygen concentration in the subsequent deoxidation step.

Japanese Patent Publication No. Sho 62-39205 discloses a method for producing a high cleanliness steel in which a deoxidizing agent, a flux and a slag modifier are added in the secondary refining of molten steel. However, the examples only describe the case of producing a Si trace low carbon Al killed steel, and this method can be directly applied to the production of an austenitic stainless steel containing a rare earth element having a high affinity with oxygen. Not a thing.
This is due to the increase in oxygen solubility due to Cr in molten steel and the interaction between Ni and Al in steel types containing a large amount of Cr and Ni.
This is because the deoxidizing power of Al generally tends to decrease.

In Japanese Patent Laid-Open No. 63-277708, molten steel and slag are directly stirred after VOD treatment, and SiO ₂ in the slag is mixed.
A method for producing high-cleanliness stainless steel with a content of 10 wt% or less is shown. However, it is not clear whether this method is also effective in the case of austenitic stainless steel to which rare earth elements are added.

[0011]

DISCLOSURE OF THE INVENTION The present invention is to solve the above problems in the production of an austenitic stainless steel containing a rare earth element. The purpose of the present invention is to improve the cleanliness of molten steel in the melting process, to prevent deterioration of cleanliness due to the addition of rare earth elements, and further to prevent nozzle clogging during continuous casting, thereby achieving high quality. An object of the present invention is to provide a manufacturing method capable of achieving both stable operation.

[0012]

In order to achieve high cleaning of austenitic stainless steel containing a rare earth element, the present inventor has carried out pre-deoxidation at a stage before adding a rare earth element and then Al deoxidation. In order to thoroughly perform Al deoxidation or to perform sufficient Al deoxidation, it is most effective to add Ca and / or Mg at the same time as Al deoxidation to perform complex deoxidation and perform high cleaning at the molten steel stage. I found that there is.

The gist of the present invention resides in the following methods (1) and (2) for producing a highly clean rare earth element-containing austenitic stainless steel.

(1) A method for producing an austenitic stainless steel containing a rare earth element, the method comprising the steps of: Hereinafter, this is referred to as a first method of the present invention.

The crude molten metal from the melting furnace is tapped into a ladle, subjected to oxidative refining for decarburization, and then pre-deoxidized with Si and Mn.

Subsequently, the Al concentration is made 0.03 wt% or more, and CaO—Al ₂ O ₃ slag is formed to perform deoxidation.

Throughout the entire refining process thereafter, adjustment is made so that the Al concentration becomes 0.03 wt% or more, and then killing is performed to make the total oxygen concentration 0.003 wt% or less.

After that, rare earth elements containing La and Ce as main components are added to make the concentration 0.01 wt% or more, thereby suppressing the generation of rare earth oxides.

(2) A method for producing an austenitic stainless steel containing a rare earth element, comprising the steps of:
A process for producing a highly clean rare earth element-containing austenitic stainless steel, which is characterized in that the treatment is carried out in steps 1 and 2. Hereinafter, this is referred to as a second method of the present invention. The steps of and are the same as in the case of the first method (1).

The crude molten metal from the melting furnace is tapped into a ladle, subjected to oxidation refining for decarburization, and then pre-deoxidized with Si and Mn.

'Subsequently, the Al concentration is set to 0.03 wt% or more, the Ca and / or Mg concentration is set to 0.001 wt% or more alone or in total, and CaO-Al ₂ O ₃ slag is formed to perform deoxidation.

′ Adjustment is made so that the Al concentration is 0.03 wt% or more and the Ca and / or Mg concentration is 0.001 wt% or more alone or in total over the entire refining process thereafter, and then killing is performed to adjust the total oxygen concentration. 0.003 wt% or less.

After that, rare earth elements containing La and Ce as main components are added so that the concentration thereof is 0.01 wt% or more, thereby suppressing generation of rare earth oxides.

The term "rare earth element" as used herein means La and Ce.
In addition, it refers to lanthanoids such as Nd and Pr and Y (yttrium), and the addition thereof is an alloy containing La and Ce as main components (for example, Misch metal) and / or Y.
Is used. In the following, when expressing the rare earth element concentration, La + Ce
Indicated by

Al concentration, Ca and / or Mg concentration and La
Desirable upper limits of + Ce concentration are 0.2 wt% and 0.005, respectively.
wt% and 0.1 wt%.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION
When roughly classified, it consists of a decarbonation refining process after tapping, and a reduction process mainly performing preliminary deoxidation, deoxidation, and addition of a rare earth element. Therefore, the refining apparatus for carrying out the method of the present invention includes a VOD furnace, an RH vacuum refining apparatus, a blowing apparatus for oxygen and a stirring gas, a vacuum or atmospheric ladle refining apparatus equipped with a cylindrical dipping tube, and the like. For example, an induction melting furnace.

Regarding the first method of the present invention and the reasons for limiting the respective conditions, C: 0.050 to 0.15% in wt% and Si: 0.05 to
0.5%, Mn: 0.3-0.6%, P: 0.04% or less, S: 0.01
%, Cr: 20-30%, Ni: 10-15%, N: 0.1-0.3
%, La + Ce: 0.01 to 0.1%, balance: Fe, with the aim of producing a rare earth element-containing austenitic stainless steel consisting of impurities and impurities, the raw material was melted in an electric furnace, tapped, and then removed using a VOD furnace. The case of performing pot refining will be described as an example.

Oxidative refining of the crude molten steel for decarburization is performed in a VOD furnace to adjust the C concentration to 0.05 to 0.15 wt%, and then preliminary deoxidation (hereinafter referred to as preliminary composite deoxidation) with Si and Mn is performed. Then, the oxygen concentration is preliminarily reduced (step described above). At this time, the method of adding the preliminary composite deoxidizer is not particularly limited,
In order to exert the effect of preliminary composite deoxidation, the Si concentration is 0.
05wt% or more, Mn concentration is preferably 0.3wt% or more. However, from the viewpoint of preventing deterioration of the weldability and creep properties of product materials, the Si concentration is 0.4 wt% or less and the Mn concentration is 0.5 wt% or less.
It is preferably less than wt%.

Next, the above-mentioned deoxidizing step is performed. First, Al is added so that the Al concentration is 0.03 wt% or more, and deoxidation is performed.
The total oxygen concentration in molten steel is desirably reduced to 0.003 wt% or less. If the Al concentration is less than 0.03 wt%, the total oxygen concentration cannot be reduced to the above value or less, and the effect of improving cleanliness is poor. At this time, the more desirable range of Al concentration is
It is 0.05 to 0.1 wt%. If the Al concentration is 0.05 wt%, it can be expected from thermodynamic calculation that the total oxygen concentration is reduced to 0.002 wt% or less. The desirable upper limit of Al concentration is determined from the viewpoint of weldability and creep resistance of the product material.

The main components of the slag at this time are CaO and Al ₂ O ₃
However, the CaO / Al ₂ O ₃ ratio in the range of 1.5-4.0 wt%
It is necessary to form O-Al ₂ O ₃ slag. This lower bound
The reason for setting 1.5 is to reduce the activity of Al ₂ O _{3 in} the slag sufficiently
l This is to exert the effect of deoxidation. At this time, CaO
A more desirable lower limit of the / Al ₂ O ₃ ratio is 3. CaO / Al ₂ O
_{If the 3} ratio is 3 or more, the activity of Al ₂ O ₃ is the lowest in the CaO saturated region, so reduce the total oxygen concentration to 0.002 wt% or less even if the Al concentration is 0.03 wt%. You can On the other hand, when the upper limit of 4 is exceeded, the slag slagification property deteriorates,
Not only does it hinder the operation, but the slag that deteriorates the slag-
It causes a decrease in deoxidation reaction due to molten steel.

Si is contained in the CaO--Al ₂ O ₃ slag as described above.
Since O ₂ becomes an impurity, the desirable concentration of SiO ₂ inevitably mixed in the slag is less than 10 wt%, and more desirably 5 wt% or less. When the content is 10 wt% or more, Al reduces SiO ₂ in the slag, increases the total oxygen concentration and Si concentration in the molten steel, and impairs the Al deoxidizing effect. If it is 5 wt% or less, substantially no increase in total oxygen concentration and Si concentration occurs.

20 Wt% for promoting slag formation (slag formation)
Addition of CaF ₂ below, 20 wt% or less of MgO for protection of refractories
Is allowed in each case. Such control of the slag composition is performed by pre-composite deoxidation, then once slagging if necessary, and then taking into account the Al ₂ O ₃ concentration generated by deoxidation, while producing quick lime, fluorspar, dolomite, etc. A slag agent may be added.

Next, the above steps are performed. That is, the Al concentration is adjusted to 0.03 wt% or more over the entire refining process thereafter, and then killing is performed to reduce the total oxygen concentration to 0.003 wt% or less.

However, after the above steps are completed, if necessary or necessary, nitrogen is added from a bubbling lance or the like, and molten steel heating by oxygen blowing (hereinafter referred to as Al heating) to compensate for temperature decrease is performed. To do.

When these treatments are carried out, after that step, when they are not carried out, after the above-mentioned steps, appropriately.
Al concentration in molten steel is 0.03 wt% or more by adding Al, preferably
It is necessary to adjust it to be 0.05 wt% or more. The reason for this is to prevent an increase in the total oxygen concentration in the molten steel due to oxygen from the surroundings in the steps of nitrogen addition and Al heating.

At this time, if the Al concentration is 0.05 wt% or more, the total oxygen concentration in the molten steel can be suppressed low.
Furthermore, maintaining the Al concentration at a higher level makes it easier to adjust and control the Al concentration. Further, if the Al concentration is increased when nitrogen is added, the solubility of nitrogen is increased, the nitrogen yield is improved, and the processing time can be shortened.

Further, in order to secure sufficient cleanliness by setting the total oxygen concentration to 0.003 wt% or less, the killing time is set before the final step of adding the rare earth element. The reason for this is
This is because the Al ₂ O ₃ -based inclusions generated by the Al deoxidation are floated and removed, and at the same time, the slag-induced inclusions and the reoxidation-induced inclusions that are caused by the above-mentioned nitrogen addition and Al heating are also floated and removed.

The killing time required for floating removal varies depending on the molten steel amount and ladle shape, but as a simple index, the time per cube root of the unit molten steel amount (t: ton) (s: seconds)
Can be given by The desired killing time is 150 s
/ (T ^1/3 ) or more, more preferably 200 s / (t ^1/3 ).
That is all. That is, the total oxygen concentration is 150 times the killing time.
If s / (t ^1/3 ) or more, 0.003 wt% or less, 20
If it is 0 s / (t ^1/3 ) or more, it can be reduced to 0.002 wt% or less.

Next, the above-mentioned step of adding the rare earth element is performed to make the La + Ce concentration 0.01 wt% or more. As the rare earth element, Y (yttrium) can be selected in addition to the lanthanoid, and when adding Y, an alloy containing La and Ce as main components (for example, misch metal) and / or Y is used. Such rare earth element addition process and La + Ce
When the concentration is set, the production of rare earth oxides in molten steel can be suppressed.

As described above, if the total oxygen concentration in the molten steel is lowered and the rare earth element is added in a state of high cleanliness, the formation of these oxides caused by the rare earth element having a strong affinity for oxygen is suppressed to the minimum. Therefore, it is possible to avoid deterioration of the cleanliness of the slab and further avoid manufacturing inconveniences such as nozzle clogging.

The upper limit of the La + Ce concentration to which the method of the present invention can be applied is about 0.1 wt% although it varies depending on the steel type.

Next, the second method of the present invention will be described.

In the second method, in order to perform more effective deoxidation and obtain high cleanliness, the Al concentration is set to 0.03 wt% or more in each step after the preliminary composite deoxidation performed in the same manner as described above, and Ca and / or Mg are added as in each step after the above step 'to maintain a predetermined Ca and / or Mg concentration and obtain a complex deoxidizing effect with Al.

The composite deoxidizing effect with Al can be obtained by adjusting the Ca and / or Mg concentrations alone or in total to 0.001 wt% or more. The desirable upper limit of Ca and / or Mg concentration is 0.005 wt%. This composite deoxidizing effect is saturated and does not increase when the upper limit value of 0.005 wt% is exceeded in either case of Ca or Mg alone or in the case of combined use of Ca and Mg.

In particular, when Ca is used, the deoxidation product has a low melting point and is likely to be aggregated and enlarged, so that an effect of promoting floating can be expected secondarily.

In each step after the preliminary composite deoxidation, Al
If the concentration is 0.05 wt% or more, the yield at the time of adding Ca and / or Mg is improved, and if the concentration is solely or at least 0.001 wt%, the effect of complex deoxidation with Al is enhanced, In addition, further improvement of deoxidation and high cleaning can be obtained.

The method of adding Ca and Mg is not particularly limited. For example, it is possible to use a general method such as adding in Ca-Si alloy, Ni-Mg alloy or the like in a lump or wire form.

If necessary, Ca and Mg in the steel can be finally removed by evaporation from the molten steel. That is, inclusions are floated, absorbed by slag and removed to the outside of molten steel to obtain a sufficiently high cleanliness, and when there is no particular need for material properties, during vacuum processing and bottom-blown Ar stirring, etc. Evaporate by adding steps and remove as appropriate.

Also in the second method of the present invention, the Si and Mn concentrations after the preliminary composite deoxidation, the composition of the CaO-Al ₂ O ₃ slag after the composite deoxidation, the killing time before the addition of the rare earth element and La +
The upper limit of the Ce concentration may be exactly the same as in the case of the first method of the present invention.

[0050]

[Example] C: 0.050 to 0.15% by weight%, Si: 0.1 to 0.5
%, Mn: 0.3 to 0.6%, P: 0.04% or less, S: 0.01% or less, Cr: 22 to 24%, Ni: 10 to 11%, N: 0.21 to 0.23%,
La + Ce: A production test of a rare earth element-containing austenitic stainless steel having a target component of 0.01 to 0.05% was carried out as follows.

(Test 1) Undeoxidized molten steel (C: 0.05 to 0.15 wt%, Si: 0.02 to 0.1 wt%, Mn) simulating the state after decarburization with Ar sealed using a 2t high frequency induction furnace : 0.1
~ 0.3 wt%, N: 0.01 wt% or less, La + Ce: None, others have the above composition, temperature: 1550 to 1650 ° C) and synthetic slag, with or without preliminary composite deoxidation by Si and Mn, Al
Each treatment step of deoxidation (addition of Al), addition of nitrogen by bubbling (320 Nl / min, about 10 minutes), and oxygen blowing simulating Al heating (120 Nl / min, about 5 minutes) were performed.

Thereafter, 155 to 470 s / (t ^1/3 ) is subjected to killing so that the La + Ce concentration of the misch metal mainly containing La and Ce (hereinafter referred to as REM) becomes 0.01 to 0.05 wt%. So added.

Next, in an Ar atmosphere, it was cast into a mold by top pouring through a trough and a nozzle to obtain a 2t steel ingot.

In each of the above steps, the maximum and minimum values of Al concentration before REM addition after reaching the steel ingot after Al deoxidation, slag composition, total oxygen concentration and cleanliness before REM addition, steel ingot The total oxygen concentration and cleanliness were investigated. Table 1 shows the evaluation of Al concentration, slag composition, total oxygen concentration (T. [O]) and cleanliness.

[0055]

[Table 1]

The evaluation of the total oxygen concentration is x (impossible) if it exceeds 0.003 wt%, and ○ if 0.002 wt% or more and less than 0.003 wt%
(Good) and less than 0.002 wt% were marked as ◎ (excellent). The cleanliness was evaluated as follows: x (impossible) if inclusion index exceeds 1, 0.5
-1 (good), less than 0.5 ◎ (excellent). The inclusion index is obtained by dividing the number of inclusions per unit area by the number of inclusions per unit area, which is a reference in the present steel type. Regarding the number of samples per unit area, the number of polished samples was measured by an optical microscope (magnification 100 times) for each inclusion diameter, and the weighted number of the inclusions was divided by the test area.

As shown in Examples 1 to 4 of Table 1, pre-composite deoxidation was performed with Si and Mn, and Al was used during the subsequent steps.
As a result of adjusting the concentration to be 0.03 wt% or more, the CaO / Al ₂ O ₃ ratio of slag to be 1.5 or more, and the SiO ₂ concentration to be less than 10 wt%, RE
Both the cleanliness before and after the addition of M became good.

On the other hand, as shown in Comparative Example 5, when the preliminary composite deoxidation was not carried out, it was difficult to stabilize the Al concentration thereafter. As shown in Comparative Examples 6 and 7, when the Al concentration was less than 0.03 wt% in the steps after the preliminary composite deoxidation,
The cleanliness before and after the addition of REM was impossible. As shown in Comparative Example 8, the CaO / Al ₂ O ₃ ratio of the slag during Al deoxidation was 1.
When it was less than 5, the cleanliness before and after the addition of REM was impossible. As shown in Comparative Example 9, Si in the slag during deoxidation of Al
When the O ₂ concentration was 10 wt% or more, the cleanliness was not good, especially after adding REM. In Comparative Example 10, since the killing time before the addition of REM was not sufficiently secured, the total oxygen concentration was 0.00
Exceeded 3 wt%. As a result, especially the cleanliness after REM addition became impossible.

(Test 2) Using a 38t electric furnace-VOD process or an 80t electric furnace-VOD process, VOD
Undeoxidized molten steel decarburized in a furnace (C: 0.05 to 0.15 wt%, Si: 0.
02-0.05wt%, Mn: 0.1-0.3wt%, N: 0.01wt% or less, La + Ce: None, others are the same composition as above, temperature: 16
The production test of the rare earth element-containing austenitic stainless steel having the same target composition as the above was carried out by using (00 to 1650 ° C.).

After the preliminary composite deoxidation with Si and Mn, the slag was once removed and a slag was added to form a slag, and a predetermined amount of Al was added for deoxidation. Thereafter, nitrogen was added in two batches, and Al was heated during that period to maintain the molten steel temperature.

During this period, Al was appropriately added to secure the Al concentration. Furthermore, killing was carried out under specified conditions before the addition of REM. After killing, misch metal was added to adjust the range of La + Ce concentration to 0.01 to 0.05 wt%. Then, it was cast into a slab shape by continuous casting.

In the above test, the Al concentration after Al deoxidation and the slag composition, the nozzle clogging condition during casting, the total oxygen concentration in the slab and the cleanliness were investigated.

Table 2 shows evaluations of Al concentration, slag composition, presence / absence of nozzle clogging, total oxygen concentration (T. [O]) and cleanliness. The evaluation method is the same as in the case of test 1.

[0064]

[Table 2]

As shown in Examples 1 to 4 in Table 2, when all the conditions defined in the present invention or desirable conditions are satisfied, continuous casting is possible without causing nozzle clogging, and the slab cleanliness is good. Met. This is because the cleanliness was improved before the addition of REM.

On the other hand, as shown in Comparative Examples 5 and 6, when the conditions defined in the present invention or the desirable conditions were not satisfied, nozzle clogging occurred and the entire amount could not be continuously cast, and the slabs that could be cast were The cleanliness was also unacceptable. This is a result of deterioration of cleanliness before addition of REM, and the results obtained in the above-mentioned Test 1 and Test 2 will be further explained with reference to FIG.

FIG. 1 is a diagram showing the influence of the killing time on the cleanliness before the addition of REM in the above-mentioned Test 1 and Test 2. The vertical axis is the cleanliness index, and the standard value =
1 is the case of the acceptance standard for this steel type.

As shown in the figure, the cube root of unit molten steel t ^1/3
If the killing time is less than 150 s, the total oxygen concentration is 0.
Cleanliness is poor because it exceeds 003 wt%. On the other hand, at 150 s or more, the total oxygen concentration is 0.003 wt% or less, so that the cleanliness is good. Furthermore, the total oxygen concentration is 0.002 for 200 s or more.
Since it is less than wt%, the cleanliness is excellent.

(Test 3) When REM was added in the same manner as in Test 2 above, a predetermined amount of Ca and / or Mg was added together with Al in the steps after Al deoxidation, before addition of REM. The effect of Ca + Mg concentration in molten steel on the cleanliness of slabs was investigated. FIG. 2 shows the results.

FIG. 2 is a diagram showing the relationship between the cleanliness of the slab and the Ca + Mg concentration in the molten steel before the addition of REM. The vertical axis represents the cleanliness index, and the reference value = 1 is as described above.

As shown in FIG. 2, when the concentration of Ca + Mg concentration in the molten steel is 10 × 10 ⁻³ wt% or more, the cleanliness of the slab becomes “excellent” of 0.5 or less, and Ca and / or Mg are maintained at a predetermined concentration. It can be seen that this is effective for highly cleaning the slab.

[0072]

EFFECTS OF THE INVENTION According to the method for producing austenitic stainless steel containing a rare earth element of the present invention, the cleanliness of molten steel in the melting process can be dramatically improved, and the cleanliness of the molten steel deteriorates due to the addition of a rare earth element. Can be suppressed.
This makes it possible to prevent nozzle clogging during continuous casting and achieve both high quality and stable operation.

[Brief description of the drawings]

FIG. 1 is the case of Test 1 and Test 2 in Examples,
It is a figure which shows the influence which killing time affects the cleanliness before REM addition.

[Fig. 2] Cleanliness of slabs and molten steel before REM addition
It is a figure which shows the relationship with Ca + Mg concentration.

Claims (2)

[Claims] 1. A method for producing an austenitic stainless steel containing a rare earth element, wherein crude molten steel is taken out from a melting furnace into a ladle and is subjected to oxidative refining for decarburization, followed by Si and Mn. Pre-deoxidation, followed by increasing the Al concentration to 0.03 wt% or more, forming CaO-Al ₂ O ₃ slag to deoxidize, and then the Al concentration is 0.03 wt% throughout the entire refining process.
After adjusting so that the total oxygen concentration is 0.003 wt% or less, the rare earth element containing La and Ce as the main components is added to make the concentration 0.01 wt% or more. , A method for producing a highly clean rare earth element-containing austenitic stainless steel, which is characterized by suppressing generation of rare earth oxides. 2. A method for producing an austenitic stainless steel containing a rare earth element, wherein crude molten steel is taken out from a melting furnace into a ladle and is subjected to oxidative refining for decarburization, followed by Si and Mn. Pre-deoxidized, then continue to have Al concentration of 0.03 ww% or more, Ca
And / or Mg concentration is set to 0.001 wt% or more alone or in total, and CaO-Al ₂ O ₃ slag is formed to deoxidize, and Al concentration is 0.03 over the entire refining process thereafter.
wt% or more, Ca and / or Mg concentration alone or in total
After adjusting the concentration to 0.001 wt% or more, and then performing killing to reduce the total oxygen concentration to 0.003 wt% or less, a rare earth element containing La and Ce as the main components is added to reduce the concentration to 0.
A method for producing a highly clean rare earth element-containing austenitic stainless steel, which is characterized by suppressing the production of rare earth oxides by setting it to 01 wt% or more.