KR102448742B1 - Non-magnetic austenitic stainless steel - Google Patents

Abstract

In the present specification, a non-magnetic austenitic stainless steel is disclosed.
According to an embodiment of the disclosed nonmagnetic austenitic stainless steel, in wt%, C: 0.01 to 0.15%, Si: 0.1 to 3%, P: less than 0.05%, S: less than 0.03%, Mn: 1 to 10 %, Ni: 5 to 15%, Cr: 15.0 to 22.0%, Cu: 2.0% or less, Mo: less than 3.0%, N: less than 0.3%, the remainder contains Fe and unavoidable impurities, and is represented by the following formula (1) The expressed Ni _eq ^' value is 12.5 or more, and may contain less than 0.5% of martensite and residual austenite as a volume fraction.
(1) Ni + Cu + 0.47*Mn + 15*N
In the above formula (1), Ni, Cu, Mn, and N are weight % of each alloy element.

Description

Non-magnetic austenitic stainless steel {NON-MAGNETIC AUSTENITIC STAINLESS STEEL}

The present invention relates to non-magnetic austenitic stainless steel.

Recently, as the use of austenitic stainless steel is expanding in electronic devices, it is spotlighted as a demand for next-generation stainless steel. In particular, the stainless steel frame has superior durability and corrosion resistance compared to existing frame materials. Aesthetics due to the luster and beautiful surface that only metal materials have, further enhance the value of the material. STS 304, a representative austenitic stainless steel type, is unsuitable for parts requiring high non-magnetism because machining-induced martensite (α'-martensite) is generated during cold working to increase the magnetic properties of the material. Therefore, STS 316L steel, which is superior in austenite phase stability with a higher Ni content than that of STS 304, is mainly used for conventional electronic devices.

However, the raw material cost of STS 316L steel is high due to its high Ni content. Accordingly, austenitic stainless steel using relatively inexpensive Mn, Cu and N as an austenite phase stabilizing element to suppress α'-martensite and reduce Ni during cold working has been proposed. Since even a very small amount of martensite contributes greatly to increasing magnetism, it is most important to accurately determine the austenite phase stability.

Patent Document 1 evaluated the austenite phase stability using Md30, which is the temperature at which 50% martensite transformation occurs during 30% cold rolling, using Md30 expressed by the following formula, and disclosed a super non-magnetic soft stainless steel with Md30 of -150 ° C or less. .

Md30(℃) = 551-462(C+N)-9.2Si-8.1Mn-13.7Cr-29(Ni+Cu)-18.2Mo

In the above formula, C, N, Si, Mn, Cr, Ni, Cu, Mo are the content (% by weight) of each alloy element.

In Patent Document 2, the following Ni equivalent value (Ni _eq ) is 19 or more, d ^-1/2 of the average grain size (d, μm) is 0.4 or more, and the magnetic permeability (μ) after cold working of 50% or more is 1.01 or less Disclosed is an austenitic stainless steel.

Ni _eq = Ni+0.6Mn+0.18Cr-0.11Si ² +9.69(C+N)

In the above formula, Ni, Mn, Cr, Si, C, and N are the content (% by weight) of each alloying element.

There is a difference between the contribution of Md30 in Patent Document 1 and the Ni equivalent value in Patent Document 2 to the austenite phase stability for each alloying element, and errors may occur due to the difference between the austenite phase stabilizing elements when designing the alloy composition of austenitic stainless steel. can In addition, Md30 does not consider the magnetic change after cold working, and Ni _eq does not consider the influence of Cu.

Therefore, when designing an austenitic stainless steel component to reduce expensive Ni, it is necessary to design a new alloy component in consideration of the phase stability effects of Mn, Cu, and N, which are representative low-cost austenite stabilizing elements, and non-magnetic properties.

(Patent Document 1) WO2014-050943 A1 (Publication Date: 2014.04.03)

(Patent Document 2) WO2014-133058 A1 (Publication Date: 2014. 09. 03)

WO 2014-050943 A1 (Release date: 2014.04.03) WO2014-133058 A1 (published date: 2014. 09. 03)

In order to solve the above problems, the present invention is to provide a low-Ni austenitic stainless steel having high price competitiveness compared to STS 316L steel and excellent non-magnetic properties.

As a means for achieving the above object, the non-magnetic austenitic stainless steel according to an embodiment of the present invention is, by weight, C: 0.01 to 0.15%, Si: 0.1 to 3%, P: less than 0.05%, S: Less than 0.03%, Mn: 1 to 10%, Ni: 5 to 15%, Cr: 15.0 to 22.0%, Cu: 2.0% or less, Mo: less than 3.0%, N: less than 0.3%, the remainder being Fe and unavoidable impurities Including, Ni _eq ^' value expressed by the following formula (1) is 12.5 or more, and may include less than 0.5% of martensite and residual austenite as a volume fraction.

(1) Ni + Cu + 0.47*Mn + 15*N

In the above formula (1), Ni, Cu, Mn, and N are weight % of each alloy element.

In addition, each high nitrogen austenitic stainless steel of the present invention may have a δ _ferrite value of 0 or less expressed by the following formula (2).

(2) 0.938 - 0.095*Ni -0.007*Mn - 0.1*Cu -2.05*N

In the above formula (2), Ni, Mn, Cu, and N mean weight % of each element.

In addition, each non-magnetic austenitic stainless steel of the present invention may have a thickness of 5 mm or less, and a magnetic permeability of 1.005 or less.

In addition, each non-magnetic austenitic stainless steel of the present invention may have a thickness of 3.5 mm or less, and a magnetic permeability of 1.01 or less.

In addition, each non-magnetic austenitic stainless steel of the present invention may have a thickness of 2 mm or less, and a magnetic permeability of 1.05 or less.

According to the present invention, expensive Ni is replaced with Mn, Cu and N, which are austenite phase stabilizing elements, and specifically, by controlling the Ni _eq ^' value expressed by the following formula (1) to 12.5 or more, price competitiveness compared to STS 316L steel can provide low-Ni austenitic stainless steels with high, excellent non-magnetic properties.

(1) Ni + Cu + 0.38*Mn + 19.7*N

In the above formula (1), Ni, Cu, Mn, and N are weight % of each alloy element.

In addition, according to the present invention, it is possible to suppress the increase in magnetism due to the δ-ferrite phase by controlling the δ _ferrite value expressed by the following formula (2) to be 0 or less.

(2) 0.938 - 0.095*Ni -0.007*Mn - 0.1*Cu -2.05*N

In the above formula (2), Ni, Mn, Cu, and N mean weight % of each element.

The non-magnetic austenitic stainless steel according to the present invention can secure sufficient non-magnetic properties not only for ordinary hot-rolled annealed materials and cold-rolled materials, but also for ultra-thin materials that have been subjected to a large amount of cold rolling to a total rolling ratio of 60% or more. .

1 is a graph showing the change in the volume fraction (%) of processed organic martensite (α'- martensite) according to Ni _eq '.
2 is a graph showing the change in magnetic permeability (μ) according to the Cu content (wt%) for Ni _eq ' 12.5 or more alloys.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes preferred embodiments of the present invention. However, the embodiments of the present invention may be modified in various other forms, and the technical spirit of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided in order to more completely explain the present invention to those of ordinary skill in the art.

The terms used in this application are only used to describe specific examples. Therefore, for example, a singular expression includes a plural expression unless the context clearly requires it to be singular. In addition, terms such as "comprises" or "comprises" used in the present application are used to clearly indicate that the features, steps, functions, components, or combinations thereof described in the specification exist, and other features It should be noted that it is not intended to be used to preliminarily exclude the existence of elements, steps, functions, components, or combinations thereof.

On the other hand, unless otherwise defined, all terms used herein should be regarded as having the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Accordingly, unless explicitly defined herein, specific terms should not be construed in an unduly idealistic or formal sense. For example, a singular expression herein includes a plural expression unless the context clearly dictates otherwise.

In addition, in this specification, "about", "substantially", etc. are used in or close to the numerical value when manufacturing and material tolerances inherent in the stated meaning are presented, and are used in a precise sense to aid the understanding of the present invention. or absolute figures are used to prevent unreasonable use by unconscionable infringers of the mentioned disclosure.

The austenite phase is a paramagnetic material with a face-centered cubic (FCC) crystal structure, and is generally not magnetic. However, δ-ferrite or α'-martensite produced during hot rolling has a body-centered cubic (BCC) crystal structure and is ferromagnetic. In general, in austenitic stainless steels with low phase stability, α′-martensite is formed when strain is applied above the martensitic transformation initiation temperature (Ms). For this reason, the magnetic permeability of the austenitic stainless steel increases according to α'-martensite generated during deformation, and thus the non-magnetic properties are inferior.

Since electronic device parts are usually manufactured in the form of final products by cold working at room temperature, it is important to control so that α'-martensite is not formed when cold working austenitic stainless steel. Accordingly, when designing an austenitic stainless steel component to reduce expensive Ni, it is necessary to design a new alloy component that considers the phase stability effects and nonmagnetic properties of Mn, Cu and N, which are representative low-cost austenite stabilizing elements.

The following Md30 is mainly known as a conventional austenite phase stability index.

Md30(℃) = 551-462(C+N)-9.2Si-8.1Mn-13.7Cr-29(Ni+Cu)-18.2Mo

In the above formula, C, N, Si, Mn, Cr, Ni, Cu, Mo are the content (% by weight) of each alloy element.

Md30 represents the temperature at which 50% martensite volume ratio appears during 30% cold rolling. It is advantageous for comparing the relative phase stability between alloys when designing components, but it is difficult to estimate the exact content of α'-martensite. In addition, considering that the α'-martensite transformation is further promoted as the amount of cold rolling increases, there is a limit in being used as an accurate index for ultra-thin materials requiring a large amount of cold rolling of 60% or more using only the above index.

The following Ni _eq can be mentioned as another phase stability index.

Ni _eq = Ni+0.6Mn+0.18Cr-0.11Si ² +9.69(C+N)

In the above formula, Ni, Mn, Cr, Si, C, and N are the content (% by weight) of each alloying element.

In the Ni _eq equivalent, it is difficult to evaluate the phase stability of an austenitic stainless steel containing Cu because Cu, which is an inexpensive and efficient austenite stabilizing element to be utilized in the present invention, is not considered.

As described above, Md30 and Ni _eq are difficult to evaluate the phase stability of the high nitrogen austenitic stainless steel to be developed in the present invention. Ni _eq ^' expressed by the following formula (1) was derived by analyzing the content of α'-martensite formed during cold working of austenitic stainless steel with excitation.

(1) Ni + Cu + 0.47*Mn + 15*N

In the above formula (1), Ni, Cu, Mn, and N are the content (% by weight) of each alloy element.

When Ni _eq ^' of Formula (1) according to the present invention is 12.5 or more, α′-martensite transformation can be suppressed. In particular, it was confirmed that the permeability of 1.05 or less can be secured when the Cu content is 2.0 wt% or less.

In addition, the inventors of the present invention, through analysis of alloys having various component systems, if the δ- _ferrite value expressed by the following formula (2), which means the δ-ferrite volume fraction, is 0 or less, austenite single phase during hot rolling at 1250°C was confirmed to be obtainable.

(2) 0.938 - 0.095*Ni -0.007*Mn - 0.1*Cu -2.05*N

In the above formula (2), Ni, Mn, Cu, and N mean weight % of each element.

Non-magnetic austenitic stainless steel according to an embodiment of the present invention is, by weight, C: 0.01 to 0.15%, Si: 0.1 to 3%, P: less than 0.05%, S: less than 0.03%, Mn: 1 to 10 %, Ni: 5 to 15%, Cr: 15.0 to 22.0%, Cu: 2.0% or less, Mo: less than 3.0%, N: less than 0.3%, the remainder may include Fe and unavoidable impurities. Hereinafter, the reason for limiting the component range of each alloy element will be described below.

The content of C is 0.01 to 0.15% by weight.

C is a low-cost austenite stabilizing element, and effectively suppresses the formation of a ?-ferrite phase. In addition, C is an interstitial element and improves the yield strength of the steel by the solid solution strengthening effect. To this end, in the present invention, C is added in an amount of 0.01% by weight or more. However, if the content of C is excessive, carbides such as Cr ₂₃ C ₆ in the heat affected zone (HAZ) are precipitated at grain boundaries during welding, and there is a risk of sensitization that reduces the ductility, toughness and corrosion resistance of the steel. Accordingly, in the present invention, the content of C is managed to 0.15% by weight or less.

The content of Si is 0.1 to 3% by weight.

Si acts as a deoxidizer during the steelmaking process and improves the corrosion resistance of steel. To this end, in the present invention, Si is added in an amount of 0.1 wt% or more. However, when the content of Si is excessive, intermetallic compounds such as δ-ferrite phase and sigma phase are formed during casting, and there is a risk that the hot workability, ductility and toughness of the steel may be inferior. Accordingly, the content of Si in the present invention is managed to 3% by weight or less.

The content of P is less than 0.05% by weight, and the content of S is less than 0.03% by weight.

P and S are harmful elements that lower the corrosion resistance and hot workability of steel, so keep the content as low as possible. In the present invention, the content of P is limited to less than 0.05% by weight, and the content of S is limited to less than 0.03% by weight.

The content of Mn is 1 to 10% by weight.

Mn is an austenite phase stabilizing element and is effective in suppressing the formation of α'-martensite. In addition, Mn is cheaper than Ni and improves the cold workability of steel. For this purpose, in the present invention, Mn is added in an amount of 1 wt% or more. However, if the content of Mn is excessive, inclusions (MnS) that deteriorate the hot workability, ductility and toughness of the steel are formed in large amounts. In consideration of this, the content of Mn in the present invention is limited to 10% by weight or less.

The content of Ni is 5 to 15% by weight.

Ni is a powerful element that stabilizes the austenite phase. In addition, since Ni suppresses the formation of a δ-ferrite phase and improves hot workability and cold workability, Ni is added in an amount of 5 wt% or more in the present invention. The more Ni is added, the easier it is to suppress the formation of α'-martensite at low temperature, but since it is an expensive element, the content of Ni is limited to 15% by weight or less in the present invention in order to reduce raw material cost.

The content of Cr is 15.0 to 22.0% by weight.

Cr is an essential element to secure corrosion resistance. In addition, Cr increases the solubility of N to facilitate the manufacture of high-nitrogen austenitic stainless steel, and suppresses the formation of α'-martensite. For this purpose, Cr is added in an amount of 15.0 wt% or more in the present invention. However, if the content of Cr is excessive, δ-ferrite phase and the formation of carbonitrides such as Cr ₂ N and Cr ₂₃ C ₆ may be promoted to reduce corrosion resistance. In consideration of this, the content of Cr in the present invention is limited to 22.0% by weight or less.

The content of Cu is 2.0% by weight or less.

Cu is an element that stabilizes the austenite phase, and is effective in improving cold workability by suppressing the formation of α'-martensite, and improving the corrosion resistance of steel materials in a reducing environment. However, if the content of Cu is excessive, there is a risk that the hot workability may be deteriorated due to the solidification and segregation of Cu. In consideration of this, the content of Cu in the present invention is limited to 2.0% by weight or less.

The content of Mo is less than 3.0% by weight.

Mo is an effective element for improving the corrosion resistance of stainless steel. However, since Mo is an expensive element and causes an increase in raw material cost, and reduces cold workability when added in a large amount, the content of Mo in the present invention is limited to less than 3.0% by weight.

The content of N is less than 0.3% by weight.

N is the cheapest element among the austenite phase stabilizing elements, and N is an interstitial element that improves the strength and corrosion resistance of steel through solid solution strengthening. However, if the content of N is excessive, since hot workability and cold workability are deteriorated, the content of N in the present invention is limited to less than 0.3% by weight.

The remaining component of the present invention is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be mixed in the normal manufacturing process, this cannot be excluded. Since these impurities are known to anyone skilled in the art of manufacturing processes, all details thereof are not specifically mentioned in the present specification.

In the non-magnetic austenitic stainless steel of the present invention according to the above-mentioned bar, the formation of α'-martensite is suppressed. The non-magnetic austenitic stainless steel according to an example may contain less than 0.5% of martensite and residual austenite by volume fraction.

The non-magnetic austenitic stainless steel according to the present invention can secure sufficient non-magnetic properties not only for ordinary hot-rolled annealed materials and cold-rolled materials, but also for ultra-thin materials that have been subjected to a large amount of cold rolling to a total rolling ratio of 60% or more. . The non-magnetic austenitic stainless steel according to an example may have a magnetic permeability of 1.005 or less when the thickness is 5 mm or less. The non-magnetic austenitic stainless steel according to an example may have a magnetic permeability of 1.01 or less when the thickness is 3.5 mm or less. The non-magnetic austenitic stainless steel according to an example may have a magnetic permeability of 1.05 or less when the thickness is 2 mm or less.

Hereinafter, the present invention will be described in more detail through examples. However, it is necessary to note that the following examples are only intended to illustrate the present invention in more detail and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and matters reasonably inferred therefrom.

{Example}

After heating an ingot having the composition shown in Table 1 at 1250° C. for 2 hours, hot rolling was performed to a thickness of 5 mm. After hot rolling, solution heat treatment was performed at 1150° C. for 10 minutes, followed by water cooling to prepare a hot rolled annealed material (HR material). The prepared hot-rolled annealed material (HR material) was cold-rolled at a reduction ratio of 30% and 60%, respectively, to prepare a 3.5mm thick cold rolled material (30% CR material) and a 2mm thick cold rolled material (60% CR material).

Alloy composition (wt%) C Si Cr Ni Mn Cu Mo N Invention Example 1 0.029 0.34 21.1 9.4 1.50 1.00 0.50 0.22 Invention Example 2 0.030 0.35 20.0 9.4 1.46 0.00 0.51 0.21 Invention example 3 0.030 0.87 20.6 12.0 1.02 0.00 0.00 0.22 Invention Example 4 0.030 1.08 20.4 12.0 1.06 0.00 0.00 0.18 Invention Example 5 0.030 0.45 17.3 14.5 1.33 0.00 2.55 0.05 Invention example 6 0.019 0.51 18.1 12.1 1.95 0.00 0.00 0.00 Invention Example 7 0.020 0.52 17.9 10.9 2.06 0.99 0.00 0.00 Invention Example 8 0.019 0.51 17.9 10.0 2.02 2.00 0.00 0.00 Invention Example 9 0.016 0.49 18.1 7.8 5.80 0.00 0.00 0.15 Invention example 10 0.022 0.49 17.9 7.1 6.30 1.00 0.00 0.15 Comparative Example 1 0.022 0.50 16.5 10.0 1.02 0.00 1.96 0.03 Comparative Example 2 0.019 0.51 17.9 9.0 2.06 2.87 0.00 0.00 Comparative Example 3 0.019 0.51 18.1 8.0 1.96 4.05 0.00 0.00 Comparative Example 4 0.020 0.48 18.0 8.9 2.03 2.04 0.00 0.00 Comparative Example 5 0.018 0.50 18.0 5.0 6.21 2.05 0.00 0.15 Comparative Example 6 0.017 0.51 18.1 6.0 5.90 2.05 0.00 0.16 Comparative Example 7 0.018 0.50 18.2 5.0 5.75 2.92 0.00 0.14

The non-magnetic properties were evaluated for the manufactured hot-rolled annealed material (HR material) and cold-rolled material (30% CR material, 60% CR material), and the results are shown in Table 2.

In Table 2, α'- martensite volume fraction (%) was prepared as a 1.5 mm thick plate-shaped specimen according to ASTM E8M, and then the prepared specimen was stretched at a low speed, and the fractured cross section was measured using XRD. The δ-ferrite volume fraction (%) was measured using a ferrite scope.

Ni _eq ' was derived by substituting the alloy composition of Table 1 into Equation (1) below.

(1) Ni + Cu + 0.47*Mn + 15*N

In the above formula (1), Ni, Cu, Mn, and N are the content (% by weight) of each alloy element.

δ _ferrite was derived by substituting the alloy composition of Table 1 into Equation (2) below.

(2) 0.938 - 0.095*Ni -0.007*Mn - 0.1*Cu -2.05*N

In the above formula (2), Ni, Mn, and N mean wt% of each element.

The magnetic permeability (μ) was measured in the thickness direction for the HR material, 30% CR material, and 60% CR material.

α'-Martensite
volume fraction
(%) δ-ferrite
volume fraction
(%) Ni _eq ^' δ _ferrite Permeability (μ) HR materials 30% CR material 60% CR material Invention Example 1 0 0 14.4 -0.51 1.002 1.000 1.002 Invention Example 2 0 0 13.2 -0.39 1.003 1.002 1.004 Invention example 3 0 0 15.8 -0.66 1.003 1.001 1.000 Invention Example 4 0 0 15.2 -0.57 1.003 1.002 1.001 Invention Example 5 0 0 15.9 -0.55 1.004 1.002 1.000 Invention example 6 0 0 13.0 -0.22 1.001 1.002 1.004 Invention Example 7 0 0 12.9 -0.21 1.001 0.997 1.013 Invention Example 8 0 0 12.9 -0.22 1.004 1.000 1.028 Invention Example 9 0 0 12.8 -0.15 1.003 1.006 1.007 Invention example 10 0 0 13.3 -0.18 1.004 1.002 1.005 Comparative Example 1 16.0 0 10.9 -0.08 1.006 1.066 1.616 Comparative Example 2 0 0 12.8 -0.21 1.004 1.020 1.157 Comparative Example 3 0 0 13.0 -0.24 1.106 1.126 1.210 Comparative Example 4 7.0 0 11.9 -0.12 1.061 1.135 1.277 Comparative Example 5 0.5 0 12.2 -0.09 1.039 1.054 1.076 Comparative Example 6 0 0 13.2 -0.2 1.004 0.999 1.008 Comparative Example 7 0 0 12.7 -0.15 1.088 1.084 1.107

Referring to Tables 1 and 2, in Inventive Examples 1 to 10 satisfying the alloy composition and Ni _eq ' and δ _ferrite defined in the present invention, α'-martensite was not formed due to processing deformation. HR material with a thickness of 5 mm or less had a magnetic permeability of 1.005 or less, a 30% CR material with a thickness of 3.5 mm or less had a magnetic permeability of 1.01 or less, and a 60% CR material with a thickness of 2 mm or less had a magnetic permeability of 1.05 or less.

On the other hand, Comparative Example 1 was satisfied with the alloy composition defined in the present invention, but the Ni _eq ' value was less than 12.5. As a result, α'-martensite was excessively formed, so that the α'-martensite volume fraction was 16.0%, the 30% CR material with a thickness of 3.5 mm or less had a magnetic permeability exceeding 1.01, and the 60% CR material with a thickness of 2 mm or less had a magnetic permeability. 1.05 was exceeded.

In Comparative Examples 2 to 7, the Cu content exceeded 2.0 wt%. As Cu is an austenite phase stabilizing element, the more it is added, the more the processing-induced martensite phase is not formed and it is known as an effective element for improving non-magnetic properties. In this case, it was confirmed that the non-magnetic properties were rather inferior.

1 is a graph showing changes in the volume fraction (%) of processed organic martensite (α'-martensite) according to Ni _eq '. Referring to FIG. 1 , it can be seen that the processing-induced martensite volume fraction rapidly increased in the region where the value of Ni _eq ' was 12.5 as the boundary, in the region less than 12.5.

2 is a graph showing the change in magnetic permeability according to the Cu content for the Ni _eq ' 12.5 or more alloy. Referring to FIG. 2 , it can be seen that the magnetic permeability is rapidly increased in the region where the Cu content exceeds 2.0% by weight, bordering on the point where the Cu content is 2.0% by weight.

In the foregoing, exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and those of ordinary skill in the art will not depart from the concept and scope of the following claims. It will be appreciated that various modifications and variations are possible.

Claims (5)

In wt%, C: 0.01 to 0.15%, Si: 0.1 to 3%, P: less than 0.05%, S: less than 0.03%, Mn: 1 to 10%, Ni: 5 to 15%, Cr: 15.0 to 22.0% , Cu: 2.0% or less, Mo: less than 3.0%, N: less than 0.3%, the remainder contains Fe and unavoidable impurities,
Ni _eq ^' value represented by the following formula (1) is 12.7 or more,
Non-magnetic austenitic stainless steels comprising, by volume fraction, less than 0.5% martensite and residual austenite:
(1) Ni + Cu + 0.47*Mn + 15*N
(In the above formula (1), Ni, Cu, Mn, and N are weight % of each alloy element). According to claim 1,
High nitrogen austenitic stainless steel having a δ _ferrite value of 0 or less expressed by the following formula (2):
(2) 0.938 - 0.095*Ni -0.007*Mn - 0.1*Cu -2.05*N
(In the above formula (2), Ni, Mn, Cu, and N mean wt% of each element). According to claim 1,
Non-magnetic austenitic stainless steel with a thickness of 5 mm or less and a magnetic permeability of 1.005 or less. According to claim 1,
Non-magnetic austenitic stainless steel with a thickness of 3.5 mm or less and a magnetic permeability of 1.01 or less. According to claim 1,
Non-magnetic austenitic stainless steel with a thickness of 2 mm or less and a magnetic permeability of 1.05 or less.

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