JP5801647B2 - High N content stainless steel having excellent surface resistance and method for producing the same - Google Patents

Description

  The present invention relates to a high-N content stainless steel with reduced pinholes generated near the surface of a slab during casting, surface defects generated during rolling due to this, surface defects caused by hot rolling cracks, and the like, and It relates to the manufacturing method.

  In recent years, demands for improving the strength of structural stainless steel have increased. Correspondingly, a steel type has been applied in which nitrogen is added and the strength is improved by its solid solution strengthening action, and at the same time the corrosion resistance is improved.

  In steel types with increased nitrogen concentration, the concentration of nitrogen in the molten steel increases due to segregation during solidification, and pinholes are generated when the solubility is exceeded. When such a pinhole exists, there exists a problem that a pinhole expands at the time of rolling and causes the surface flaw of a product. In addition, the high N-containing stainless steel has a problem that the ductility is lowered and cracking during hot rolling is likely to occur as the strength increases.

  In Patent Document 1, in a method of producing a δ phase in the solidification process and casting stainless steel or high alloy steel having a nitrogen content exceeding the nitrogen solubility in the δ phase, the hydrogen content in the molten steel is less than 10 ppm, A method is disclosed in which the sulfur content is less than 20 ppm. When the hydrogen content exceeds the solubility, hydrogen bubbles are formed, and nitrogen is easily released inside the bubbles, so that pinholes grow as solidification progresses. On the other hand, when the hydrogen content is low, hydrogen bubbles that accept the release of nitrogen gas are not formed. Therefore, even if the nitrogen content is high, pinholes are not easily formed.

  In Patent Document 2, as a result of a detailed investigation of bubbles generated in a cast slab of high Mn / N austenitic stainless steel, the gas in the bubbles greatly increases the nitrogen solubility of the molten steel when the molten steel solidifies in the γ phase. The nitrogen gas released to decrease and the presence or absence of bubbles in the slab are calculated from the ratio of the nitrogen concentration in the molten steel to the nitrogen solubility of the molten steel at the liquidus temperature and the composition of the molten steel. It has been found that these values can be adjusted in order to prevent the generation of bubbles in the slab.

Patent Document 3 is a method of continuously casting a high-N content duplex stainless steel, in which the content of hydrogen as an impurity is 8.3 ppm or less, and the molten steel near the meniscus in the mold is appropriate in a horizontal plane. Electromagnetic stirring is performed in the direction of circulation at a flow rate in the range.
By stirring the molten steel electromagnetically in the vicinity of the meniscus in the mold and stirring the molten steel in front of the solidified shell, liquid components such as hydrogen that tend to concentrate on the liquid phase side of the solidification interface are dispersed, and generation of bubbles is suppressed. The generated bubbles can be separated from the solidification interface to suppress the formation of needle pinholes.

JP 2007-275903 A JP-A-7-90471 JP 2010-52026 A

  The conventional method for preventing the generation of pinholes has the following problems. That is, according to the study by the present inventors, in the method disclosed in Patent Document 1 for investigating the hydrogen content and the sulfur content, there is an allowable range in the nitrogen concentration. It has been found that the generation of pinholes by gas alone is not sufficiently suppressed.

  Further, Patent Document 2 is a finding that mainly suppresses bubbles generated by primary crystal γ solidification, and in a region where the amount of δFe targeted by the present invention is high, the segregation behavior of nitrogen on the front surface of solidification is different. It became clear in the examination of the present inventors that it was not possible.

  Further, Patent Document 3 reduces the hydrogen content with respect to Patent Document 1, and even when electromagnetic stirring is applied, if the nitrogen content is high as described above, pinholes cannot be completely suppressed, It was found that there was an appropriate range of nitrogen concentration.

  The present invention has been made in view of the above problems, and in high-N content stainless steel, by controlling the nitrogen concentration within an appropriate range, the generation and growth of pinholes can be suppressed, and by slab surface grinding. It is an object of the present invention to provide a high N-containing stainless steel excellent in surface resistance that can eliminate or simplify removal of pinhole defects and the like, and can prevent cracking during hot rolling, and a method for producing the same.

As a result of intensive studies, it has been found that the above problems can be solved by controlling the nitrogen concentration according to the amount of δFe, and also using electromagnetic stirring, and the present invention has been completed. The following is the contents as described in the claims.
(1) By mass%, C: 0.005% to 0.03%, Si: 0.8% or less, Mn: 0.1% to 7.0%, P: 0.04% or less, S: 0 0.002% or less, Ni: 1.0% to 13.0%, Cr: 17.0% to 26.0%, Al: 0.06% or less, N: 0.10% to 0.30%, Mo 0.05% to 4.0%, Cu; 0.05% to 3.5%, the balance being stainless steel made of Fe and inevitable impurities, the amount of δFe calculated from the above component composition ( %), Nitrogen concentration [% N], and nitrogen solubility [% Neq] of the molten steel at the liquidus temperature satisfy the formula (a) or (b) and exist in the surface layer of the stainless steel 1 mm. high N-containing stainless steel inclusions number than the width 20μm and excellent resistance to surface scratches properties, characterized in that 0.15 pieces / mm ² or less
For 10% <δFe amount,
35 ≦ [% N] / [% Neq] ≦ 50 (a)
When 1% ≦ δFe content ≦ 10%, −3.75 × δFe + 72.5
≦ [% N] / [% Neq] ≦ −3.75 × δFe amount + 87.5 (b)
Here, δFe amount (%) = 2.9 (Cr + Mo + 0.3Si) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18
[% Neq] = 10− ^{(518 / T) −1.063−h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu]
(2) By mass%, C; 0.005% to 0.03%, Si; 0.8% or less, Mn; 0.1% to 7.0%, P; 0.04% or less, S; 0 0.002% or less, Ni; 1.0% to 13.0%, Cr; 17.0% to 26.0%, Al; 0.06% or less, N; 0.10% to 0.35%, Mo 0.05% to 4.0%, Cu; 0.05% to 3.5%, Ta: 0.05 to 0.3%, V: 0.02 to 0.5% And Zr: a stainless steel containing at least one of 0.005 to 0.1%, the balance being Fe and inevitable impurities, the amount of δFe (%) calculated from the above component composition, and the nitrogen concentration [% N] and the nitrogen solubility [% Neq] of the molten steel at the liquidus temperature satisfy the following formula (a) or (b) and exist in the surface layer of the stainless steel 1 mm. High N-containing stainless steel inclusions number of more than 20μm and excellent resistance to surface scratches properties, characterized in that 0.15 pieces / mm ² or less.
For 10% <δFe amount,
35 ≦ [% N] / [% Neq] ≦ 50 (a)
1% ≦ δFe amount ≦ 10%
−3.75 × δFe amount + 72.5 ≦ [% N] / [% Neq]
≦ −3.75 × δFe amount + 87.5 (b)
Here, δFe amount (%) = 2.9 (Cr + Mo + 0.3Si + 0.21Ta + 2.27V + 1.25Zr) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18
[% Neq] = 10− ^{(518 / T) −1.063−h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu] −0.07 [Ta] −0.18 [V] −0.63 [Zr]
(3) A method for producing a high N-containing stainless steel having excellent surface resistance as described in (1) or (2) above, wherein the molten steel satisfies the above component composition and formula (a) or (b) High N content ferritic stainless steel characterized by electromagnetic stirring so that the flow velocity V (cm / sec) of the horizontal swirling flow of the molten stainless steel in the mold is 10 to 30 (cm / sec) Steel manufacturing method.

  According to the present invention, in addition to the adjustment of the components, [% N] / [% Neq] control according to the amount of δFe is performed, and the current applied to the electromagnetic stirrer is adjusted to adjust the level of the molten stainless steel in the mold. By controlling the flow velocity V of the swirl flow, surface layer defects such as pinholes in high-N content stainless steel slabs can be prevented, and slab surface grinding can be omitted or simplified. There is no incidence and product yield can be improved. Further, by adding one or more elements from Ta, V, and Zr, the allowable N amount can be increased, and further increase in strength is possible.

It is a figure which shows the influence of (delta) Fe amount and [% N] / [% Neq] which exert on pinhole production | generation. It is a figure which shows the influence of the molten steel flow velocity by electromagnetic stirring which acts on surface defect generation | occurrence | production.

When the δ phase is generated in the solidification process and the nitrogen content exceeds the solubility, nitrogen that cannot be dissolved is discharged from the solidification interface of the solidification shell to the liquid phase side, and nitrogen bubbles are formed at the solidification interface. This forms pinholes while being captured by the solid phase as the solidification interface progresses. Further, when the amount of δFe increases, the γ phase having a high nitrogen solubility that is generated during solidification decreases, so that pinholes are easily generated. This effect is particularly prominent in the region where the amount of δFe expressed by the following formula exceeds 10%. Therefore, it is necessary to adjust the component according to the amount of δFe. If the amount of δFe is less than 1%, solidification starts in the γ phase. The γ phase has a problem that the solid solubility of P and S is smaller than that of the δ phase, and many hot working cracks are generated.
δFe amount (%) = 2.9 (Cr + Mo + 0.3Si) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18

  By magnetically stirring the molten steel near the meniscus in the mold and stirring the molten steel in front of the solidified shell, the solute concentrated on the liquid phase side of the solidification interface can be washed and the formation of pinholes can be suppressed. . Further, by imparting an appropriate molten steel flow, solidification and homogenization can be achieved, and there is an effect that slab surface defects can be suppressed.

FIG. 1 shows the results of investigation by the present inventors on the influence of the amount of δFe and [% N] / [% Neq] on pinhole generation. As shown below, there is an appropriate region of [% N] / [% Neq] depending on the amount of δFe when the amount of δFe is in the range of 1 to 10%, and constant [% N] / It has been found that control should be made within the [% Neq] range. Further, in each δFe amount range, the region where pinhole generation can be suppressed only by [% N] / [% Neq] control, and application of electromagnetic stirring (in FIG. 1, the molten steel flow rate is 20 cm / sec.). ) Was confirmed to be necessary. The occurrence of surface defects such as pinholes was examined by visual observation about a length of about 2 m after grinding the surface of the slab by about 1 mm. Here, the evaluation was divided into ○, ●, and ×. ● indicates that there is no slab surface defect only by controlling [% N] / [% Neq], ○ indicates that the slab surface defect is eliminated by further electromagnetic stirring, and × indicates that surface cutting is required again. .
For 10% <δFe amount,
35 ≦ [% N] / [% Neq] ≦ 50 (a)
1% ≦ δFe amount ≦ 10%
−3.75 × δFe amount + 72.5 ≦ [% N] / [% Neq]
≦ −3.75 × δFe amount + 87.5 (b)
[% Neq] is
[% Neq] = 10- ^{(518 / T) -1.063-h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu]
It is represented by

  In FIG. 1, the range marked with ○ has a high tolerance for nitrogen addition, so that it can fully satisfy the demands for high strength and high corrosion resistance of structural stainless steel, and has high performance, manufacturability and productivity. Are compatible.

  FIG. 2 shows the influence of the molten steel flow rate by electromagnetic stirring on the occurrence of surface defects. Pinholes can be suppressed by electromagnetically stirring the molten steel near the meniscus in the mold in a direction to circulate at a flow rate of 10 cm / sec or more in a horizontal plane. Here, the molten steel in the vicinity of the meniscus means molten steel in a region of 150 to 500 mm downward from the meniscus. Moreover, the flow velocity of the circulating molten steel means the horizontal flow velocity of the circulating molten steel. For example, if the current value during electromagnetic stirring during operation is determined by determining in advance the relationship between the current value during electromagnetic stirring in the mold and the dendrite deflection angle in the cross section of the slab and the solidification speed and molten steel flow rate, The molten steel flow rate can be obtained.

  It is appropriate that the molten steel flow speed circulating around the meniscus in the mold is in the range of 10 to 30 cm / sec. When the molten steel flow rate is less than 10 cm / sec, it is not possible to obtain the effect of cleaning the solute concentrated on the liquid phase side of the solidification interface and the separation effect of bubbles generated at the solidification interface. On the other hand, when the molten steel flow rate increases beyond 30 cm / sec, slab surface flaws such as mold powder entrainment occur due to increased meniscus level fluctuation.

In addition, by performing electromagnetic stirring as described above, the floating of inclusions mixed in the mold is promoted. As the particle size of the inclusion is larger, the floating by stirring is promoted, so that the coarse inclusion remaining in the steel surface layer after casting is reduced. Therefore, the high N content stainless steel of the present invention has few surface defects due to pinholes and few coarse inclusions in the vicinity of the steel surface after hot rolling. Therefore, it can be used as an index of whether or not the molten steel flow control of the present invention is properly performed. As a result of the investigation, it was found that the number of inclusions having a width of 20 μm or more present in the surface layer of 1 mm after hot rolling was 0.15 / mm ² or less by giving the molten steel the proper flow of the present invention. The conditions for hot rolling in the present invention may be the same as in the conventional method, the heating temperature is 1100 to 1200 ° C., the rolling finishing temperature is 900 to 980 ° C., the subsequent cooling is air cooling, and the reduction ratio is 4 to 18. It ’s fine. About cooling, it can also change into water cooling suitably. Moreover, since the said inclusion number is not influenced by the annealing after hot rolling, the presence or absence of annealing does not ask | require.

The reason for limiting the component composition (mass%) according to the present invention will be described together with the action of each element. C is a strong austenitizing element and strengthens the solid solution, so 0.005% or more is added. However, if the content is increased, carbide is generated and the corrosion resistance is deteriorated.

  Since Si is an element that acts as a deoxidizer during the melting of stainless steel, it is added in an amount of 0.1% or more. In the present invention, it is necessary to control it to 0.8% or less from the viewpoint of ensuring hot workability. is there.

  Mn is a deoxidizer and has an effect of improving hot workability, and is an element effective for fixing S as MnS and preventing the occurrence of red hot brittleness due to the formation of FeS. And Moreover, Mn can increase the solubility of N. However, if contained in a large amount, the refractory melting loss during melting will increase and the corrosion resistance will deteriorate, so the content is made 7.0% or less. Preferably it is 0.5 to 5.5%.

  P is an impurity in the steelmaking process, but if it is contained in a large amount, hot workability is impaired, so the upper limit is made 0.04% or less. On the other hand, since extremely reducing the content leads to an increase in cost, the lower limit is preferably made 0.001%.

  S lowers the hot workability, easily causes cracking defects during hot rolling, and deteriorates the corrosion resistance. Therefore, the content is made 0.002% or less. On the other hand, since extremely reducing the content leads to an increase in cost, the lower limit is preferably made 0.001%.

  Cr is a basic element of stainless steel and contributes to improvement of corrosion resistance and oxidation resistance. Cr is an effective element that can increase the solubility of N. However, since the influence on the amount of δFe varies depending on the concentration level, the Cr concentration is set to 17.0 to 26.0% in order to stably control the amount of δFe in the present invention. Preferably it is 22.0 to 26.0%.

  Ni is an element having an effect of improving the corrosion resistance and toughness of steel, so it is set to 1.0% or more. However, Ni is also expensive, so it is set to 13.0% or less.

  Al acts as a deoxidizer. However, if a large amount of Al is contained, harmful hard oxides are generated and surface defects occur during rolling. Therefore, the upper limit of Al is 0.06%. The lower limit of Al is not particularly defined, but 0.003% or more is preferable.

  N is an element having an action contributing to stabilization of austenite and the like, and at the same time is an element effective for improving the strength, and is controlled to 0.1% to 0.30%. Moreover, when adding 1 or more types from Ta, V, and Zr mentioned later, it is possible to increase the upper limit of N content to 0.35%.

  Mo is not a scale that is an effective element for improving corrosion resistance, but has an effect of solid solution strengthening and is added in an amount of 0.05% or more. However, if it exceeds 4.0%, the hot workability deteriorates rapidly, so it is controlled to 4.0% or less.

  Cu is an austenite stabilizing element and is an element having an action of improving corrosion resistance, so 0.05% or more is added. Preferably it is 0.1% or more. However, if contained in a large amount, the hot workability is impaired, so the content is made 3.5% or less. The balance consists of Fe and inevitable impurities.

The present inventors have further investigated the influence of the additive element, and found that when one or more of Ta, V, and Zr are added, pinhole formation can be particularly suppressed and the productivity is improved. did. The test was conducted by changing the test conditions for each element in various ways, and the effect was that the addition of the element increased the amount of δFe and the nitrogen solubility [% Neq] of the molten steel at the liquidus temperature as shown in the following formula. I found out that it was caused by In particular, an increase in nitrogen solubility [% Neq] of molten steel at the liquidus temperature is a notable finding, which means that it is possible to further increase the strength by increasing the nitrogen concentration. .
In order to obtain this effect, it is necessary to add at least one of Ta, V, and Zr at Ta: 0.05%, V: 0.02%, and Zr: 0.005%. On the other hand, if the addition exceeds the upper limit, hot workable cracks are generated due to high strength and the cost is increased, so the upper limits are Ta: 0.3%, V: 0.5%, Zr: 0.1, respectively. %.
δFe amount (%) = 2.9 (Cr + Mo + 0.3Si + 0.21Ta + 2.27V + 1.25Zr) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18
[% Neq] = 10- ^{(518 / T) -1.063-h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu] −0.07 [Ta] −0.18 [V] −0.63 [Zr]

  Hereinafter, the effects of the present invention will be described with reference to examples, but the present invention is not limited to the conditions shown in the examples.

  After preparing high N-containing stainless steel with the chemical composition shown in Table 1 and Table 2 with the balance consisting of Fe and inevitable impurities in a vacuum induction melting furnace, manufacture a slab with a 170 × 800 mm mold test continuous caster. went.

  The surface of the slab having a thickness of 163 mm after casting was ground by about 1 mm with a grinder, and the number of pinholes and powder entrainment was visually measured. Note that the measurement was performed over the entire surface of 2 m.

  It was confirmed that the number of pinholes generated was significantly reduced by performing electromagnetic stirring in the mold as compared with the case where the stirring was not performed.

  The slab was hot-rolled to 10 mm at a heating temperature of 1180 ° C. and a finishing temperature of 950 ° C., cooled to room temperature by air cooling, and then visually inspected on the surface of the steel sheet to confirm the occurrence of surface defects. Here, the evaluation was divided into ○, Δ, and ×. ○ indicates that there is no problem as a product, Δ indicates that care is required by surface cutting, and × indicates that the product is unacceptable and cannot be used.

Further, the inclusions in the vicinity of the surface layer were investigated by measuring the number of inclusions having a width of 20 μm or more in the range of 1 mm surface layer in the C cross section after the hot rolling. The observation area was 200 mm ² .

  The state of occurrence of defects in the slab and steel plate was evaluated as described above. Almost no slab surface defects were found in the steel of the present invention, no defects were found in the steel sheet, and all were good. In addition, it can be seen that in Reference Examples 16 to 18, defects in the slab and the steel plate did not occur without using electromagnetic stirring, and the amount of coarse inclusions on the surface layer increased because electromagnetic stirring was not performed.

  In comparison, the comparative steel 19 had pinholes because [% N] / [% Neq] was too high relative to the δFe value. Since the comparative steel 20 had a δFe value that was too low, galling due to hot working cracks occurred. In comparative steel 21, the molten steel flow velocity in the mold was low, and pinholes were generated. In addition, coarse inclusions on the surface layer are increasing. Since the comparative steel 22 had a molten steel flow velocity in the mold that was too high, powder entrainment occurred. Since C was too high in the comparative steel 23, the amount of δFe was low, and galling due to hot work cracking occurred. Since comparative steel 24 was too high in Si, galling due to hot working cracks occurred. Since the comparative steel 25 had Mn too low, [% N] / [% Neq] was large and pinholes were generated. Since P was too high in the comparative steel 26, hot work cracks were generated. Since the comparative steel 27 had too high S, the hot work cracks were generated. Since comparative steel 28 was too high in Ni, the amount of δFe was low, and galling due to hot working cracks occurred. Since the comparative steel 29 had too low Cr, [% N] / [% Neq] was large and pinholes were generated. Since the comparative steel 30 was too high in Al, galling caused by inclusions occurred. Since N was too high in the comparative steel 31, [% N] / [% Neq] was also large and pinholes were generated. Since the comparative steel 32 has too high Mo, lashes due to hot working cracks occurred. Since the comparative steel 33 was too high in Cu, the hot work cracks were prone to occur.

Inventive steels 34 to 42 shown in Table 2 satisfy the preferable ranges of Ta, V, and Zr, so that both casting defects and thick plate defects are good, but comparative steels 43 to 48 are Ta, Since the ranges of V and Zr deviate from the preferred ranges, either casting defects or thick plate defects were inferior. The effects of the present invention were confirmed by the above examples.

Claims (3)

% By mass, C; 0.005% to 0.03%,
Si: 0.8% or less,
Mn: 0.1% to 7.0%,
P: 0.04% or less,
S: 0.002% or less,
Ni: 1.0% to 13.0%,
Cr: 17.0% to 26.0%,
Al; 0.06% or less,
N: 0.10% to 0.30%,
Mo; 0.05% to 4.0%,
Cu: 0.05% to 3.5%,
Stainless steel comprising the balance Fe and inevitable impurities,
The amount of δFe (%) calculated from the component composition, the nitrogen concentration [% N] and the nitrogen solubility [% Neq] of the molten steel at the liquidus temperature satisfy the following formula (a) or (b):
A high N-containing stainless steel excellent in surface resistance, characterized in that the number of inclusions having a width of 20 μm or more present in a surface layer of 1 mm of the stainless steel is 0.15 / mm ² or less.
For 10% <δFe amount,
35 ≦ [% N] / [% Neq] ≦ 50 (a)
1% ≦ δFe amount ≦ 10%
−3.75 × δFe amount + 72.5 ≦ [% N] / [% Neq]
≦ −3.75 × δFe amount + 87.5 (b)
Here, δFe amount (%) = 2.9 (Cr + Mo + 0.3Si) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18
[% Neq] = 10− ^{(518 / T) −1.063−h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu] % By mass, C; 0.005% to 0.03%,
Si: 0.8% or less,
Mn: 0.1% to 7.0%,
P: 0.04% or less,
S: 0.002% or less,
Ni: 1.0% to 13.0%,
Cr: 17.0% to 26.0%,
Al; 0.06% or less,
N: 0.10% to 0.35%,
Mo; 0.05% to 4.0%,
Cu: 0.05% to 3.5%,
Containing
Furthermore, it contains one or more of Ta: 0.05 to 0.3%, V: 0.02 to 0.5%, and Zr: 0.005 to 0.1%,
The balance is stainless steel consisting of Fe and inevitable impurities,
The amount of δFe (%) calculated from the component composition, the nitrogen concentration [% N] and the nitrogen solubility [% Neq] of the molten steel at the liquidus temperature satisfy the following formula (a) or (b): A high N-containing stainless steel excellent in surface resistance, characterized in that the number of inclusions having a width of 20 μm or more present in a surface layer of 1 mm of the stainless steel is 0.15 / mm ² or less.
For 10% <δFe amount,
35 ≦ [% N] / [% Neq] ≦ 50 (a)
1% ≦ δFe amount ≦ 10%
−3.75 × δFe amount + 72.5 ≦ [% N] / [% Neq]
≦ −3.75 × δFe amount + 87.5 (b)
Here, δFe amount (%) = 2.9 (Cr + Mo + 0.3Si + 0.21Ta + 2.27V + 1.25Zr) −2.6 (Ni + 0.3Mn + 0.25Cu + 35C + 20N) −18
[% Neq] = 10− ^{(518 / T) −1.063−h}
T (K) = 1525-86.8 [C] -4.7 [Si] -2.1 [Mn] -34 [P] -40 [S] -0.8 [Cr] -5.1 [Ni ] -3.1 [Mo] -5 [Cu] -36 [N] +273.15
h = 0.13 [% C] +0.048 [% Si] −0.02 [% Mn] +0.059 [% P] +0.007 [% S] +0.007 [% Ni] −0.046 [ % Cr] −0.025 [% Mo] +0.009 [% Cu] −0.07 [Ta] −0.18 [V] −0.63 [Zr] The method for producing a high N-containing stainless steel excellent in surface resistance according to claim 1 or 2 , wherein the molten steel satisfying the component composition and the formula (a) or (b) is cast. A method for producing a high N-containing ferritic stainless steel, characterized by electromagnetic stirring so that a flow velocity V (cm / sec) of a horizontal swirling flow of stainless steel in a mold is 10 to 30 (cm / sec).

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