Non-coated austenitic steel sheet for bipolar plate for alkaline water electrolysis

Abstract

According to the present invention, a non-coated austenitic steel sheet for a bipolar plate for alkaline water electrolysis is provided, the sheet comprising, by wt%, greater than 0% and less than or equal to 0.04% of C, greater than 0% and less than or equal to 0.4% of Si, greater than 0% and less than or equal to 0.5% of Mn, greater than 0% and less than or equal to 2.0% of Cr, 33-40% of Ni, greater than 0% and less than or equal to 4.0% Co, and the balance of Fe and other inevitable impurities, wherein the value of relation (1) is 0.83 or less, the surface roughness Ra value is 0.07-0.25 μm, and excellent corrosion resistance is exhibited in an alkaline environment. Relation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co (In relation (1), Ni, Cr and Co mean the amounts (wt%) of the respective elements.)

Description

Uncoated austenitic steel plate for alkaline electrolysis separator

[0001] The present invention relates to an austenitic steel plate for an alkaline water electrolysis separator having excellent corrosion resistance in an alkaline environment and easy hydrogen generation, and a method for manufacturing the same.

[0002] Recently, efforts are underway to utilize hydrogen, an eco-friendly fuel, to combat global warming. In particular, hydrogen production through electrolysis, which utilizes water electrolysis in conjunction with renewable energy sources, is being considered. Electrolysis methods include high-temperature electrolysis, cation membrane electrolysis, and alkaline electrolysis, with alkaline electrolysis being the most commonly commercialized method.

[0003] An alkaline water electrolysis device is composed of an electrolyte, an anode, a cathode, a separator, a separator, etc. The electrolyte may include a strong base solution, such as a 25% to 30% KOH solution. Therefore, the components included in the alkaline water electrolysis device must utilize materials that are highly corrosion-resistant in strong base solutions.

[0004] Traditionally, pure nickel metal or nickel-coated stainless steel was used as a separator in alkaline water electrolysis devices.

[0005] However, conventional technologies utilize expensive nickel, which reduces their price competitiveness. Furthermore, they suffer from problems such as poor nickel coating, which can degrade overall cell performance. Furthermore, conventional technologies utilize large-area separators, making coating difficult. Furthermore, coating is more difficult when the base material, stainless steel, has good corrosion resistance.

[0006] The purpose of the disclosed invention to solve the above-described problem is to provide an uncoated austenitic steel sheet having excellent corrosion resistance in an alkaline environment and easy hydrogen generation by controlling the alloy composition and surface roughness.

[0007] An uncoated austenitic steel sheet for an alkaline electrolytic separator according to one embodiment of the present invention comprises, in wt%, C: more than 0% and 0.04% or less, Si: more than 0% and 0.4% or less, Mn: more than 0% and 0.5% or less, Cr: more than 0% and 2.0% or less, Ni: 33% to 40%, Co: more than 0% and 4.0% or less, the remainder being Fe and other unavoidable impurities, and has a value of the following formula (1) of 0.83 or less, a surface roughness Ra value of 0.07 ㎛ to 0.25 ㎛, and has excellent corrosion resistance in an alkaline environment.

[0008] Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co

[0009] (In formula (1), Ni, Cr, and Co represent the content (weight%) of each element)

[0010] In addition, the uncoated austenitic steel sheet according to one embodiment of the present invention may have an alkaline environment in which the concentration of [OH-] ions is 0.3 mol to 7.5 mol based on molar concentration.

[0011] In addition, the uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention may have a current density ratio expressed by the following equation (2) of 1.9 or less.

[0012] Equation (2): Current density of uncoated austenitic steel plate for alkaline water electrolysis separator / Current density of pure Ni metal

[0013] In addition, the uncoated austenitic steel plate for the alkaline electrolytic separator according to one embodiment of the present invention has a strength of 25 N / cm 2 The surface contact resistance at a pressure of 40 mΩ·㎠ or less can be achieved.

[0014] In addition, the uncoated austenitic steel plate for an alkaline water electrolysis separator according to one embodiment of the present invention may have a hydrogen generation ratio expressed by the following equation (3) of less than 1.0.

[0015] Equation (3): Hydrogen generation amount of uncoated austenitic steel plate for alkaline water electrolysis separator / Hydrogen generation amount of pure Ni metal

[0016] According to another embodiment of the present invention, a method for manufacturing an uncoated austenitic steel sheet for an alkaline water electrolysis separator comprises the steps of: manufacturing a slab containing, in wt%, C: more than 0% and 0.04% or less, Si: more than 0% and 0.4% or less, Mn: more than 0% and 0.5% or less, Cr: more than 0% and 2.0% or less, Ni: 33% to 40%, Co: more than 0% and 4.0% or less, the remainder being Fe and other unavoidable impurities, and having a value of Equation (1) below of 0.83 or less; reheating the slab and hot-rolling it to manufacture a hot-rolled steel sheet; and solution-heat treating the hot-rolled steel sheet.

[0017] Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co

[0018] (In formula (1), Ni, Cr, and Co represent the content (weight%) of each element)

[0019] In addition, a method for manufacturing an uncoated austenitic steel sheet for an alkaline water electrolysis separator according to another embodiment of the present invention may include a step of cold rolling and re-solution heat treatment after the step of solution heat treatment.

[0020] In addition, in the method for manufacturing an uncoated austenitic steel plate for an alkaline electrolytic separator according to another embodiment of the present invention, the reheating can be performed at 1150 to 1350°C for 150 to 240 minutes.

[0021] In addition, in a method for manufacturing an uncoated austenitic steel sheet for an alkaline electrolytic separator according to another embodiment of the present invention, the solution heat treatment and re-solution heat treatment steps can be performed at 800 to 900°C for 100 to 200 seconds.

[0022] In addition, a method for manufacturing an uncoated austenitic steel plate for an alkaline electrolytic separator according to another embodiment of the present invention may further include a step of controlling the surface roughness of the steel plate obtained by the solution heat treatment to Ra: 0.07 µm to 0.25 µm.

[0023] An uncoated austenitic steel sheet according to one embodiment of the present invention has excellent corrosion resistance in an alkaline environment and is easy to generate hydrogen.

[0024] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0025] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0026] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense.

[0027] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0028] Unless otherwise specifically stated herein, percentages indicating the content of each element are based on weight.

[0029] An uncoated austenitic steel sheet for an alkaline water electrolysis separator according to one embodiment of the present invention may include, in wt%, C: more than 0% and 0.04% or less, Si: more than 0% and 0.4% or less, Mn: more than 0% and 0.5% or less, Cr: more than 0% and 2.0% or less, Ni: 33% to 40%, Co: more than 0% and 4.0% or less, the remainder being Fe and other unavoidable impurities. Hereinafter, the reasons for numerical limitations on the alloying component content in the present invention will be described.

[0030] The content of C (carbon) may be greater than 0% and less than or equal to 0.04%.

[0031] C is an element that degrades steel quality by forming carbides. Its content can be controlled to extremely low levels through various decarburization processes. However, performing ultra-low-carbon decarburization processes can increase process costs. Considering this, the C content may be between 0% and 0.04%.

[0032] The content of Si (silicon) may be greater than 0% and less than or equal to 0.4%.

[0033] Silicon (Si) is an essential element added for deoxidation during alloy refining. Therefore, adding Si facilitates deoxidation during refining, thereby reducing oxygen content and facilitating inclusion control. However, excessive Si addition can degrade steel quality due to inclusions. Considering this, the Si content may be greater than 0% and less than 0.4%. Specifically, the Si content may be between 0.1% and 0.3%.

[0034] The content of Mn (manganese) may be greater than 0% and less than or equal to 0.5%.

[0035] Mn is an effective element for strengthening solid solutions and improving hot workability. In particular, Mn can be used as a deoxidizer together with silicon during alloy refining. However, excessive Mn content can lead to the formation of sulfides such as MnS, which can deteriorate corrosion resistance. Considering this, the Mn content may be greater than 0% and less than 0.5%. Specifically, the Mn content may be between 0.2% and 0.4%.

[0036] The content of Cr (chromium) may be greater than 0% and less than or equal to 2.0%.

[0037] Cr can dissolve at 0 V compared to a hydrogen electrode in an alkaline environment. Therefore, if Cr is included, corrosion resistance may be reduced in an alkaline environment. However, since Cr is an essential element added in the stainless steel manufacturing process, additional costs may be incurred for removing Cr introduced from sources such as metal. Taking this into account, the Cr content may be greater than 0% and less than or equal to 2.0%. Specifically, the Cr content may be 0.02% to 2.0%. Specifically, the Cr content may be 0.02% to 1.5%.

[0038] The content of Ni (nickel) can be 33% to 40%.

[0039] Ni is an essential element for ensuring corrosion resistance in alkaline environments. Considering this, the Ni content can exceed 33%. However, Ni is an expensive element, and excessive addition can reduce price competitiveness. Considering this, the upper limit for Ni content may be 40%.

[0040] The content of Co(cobalt) may be greater than 0% and less than or equal to 4.0%.

[0041] Cobalt (Co), along with nickel (Ni), is a very stable element in alkaline environments and is effective in increasing corrosion resistance. However, Co is an expensive element, and excessive addition may reduce price competitiveness. Considering this, the Co content may be greater than 0% and less than or equal to 4.0%. Specifically, the Co content may be greater than or equal to 0.01% and less than or equal to 4.0%, and more specifically, greater than or equal to 0.01% and less than or equal to 2.0%. Specifically, the Co content may be between 0.01% and 1.5%.

[0042] The remaining component of the present invention is iron (Fe). However, during the typical manufacturing process, unintended impurities from raw materials or the surrounding environment may inevitably be mixed in, and thus cannot be excluded. Since these impurities are readily apparent to anyone skilled in the art of typical manufacturing, their full details are not specifically discussed in this specification.

[0043] An uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention may have a value of the following equation (1) of 0.83 or less.

[0044] Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co

[0045] In Equation (1), Ni, Cr, and Co represent the content (weight%) of each element.

[0046] Ni, Cr, and Co are elements that can directly affect corrosion resistance in an alkaline environment. Therefore, the disclosed invention aims to provide an austenitic steel sheet with improved corrosion resistance in an alkaline environment by controlling the value of formula (1) composed of Ni, Cr, and Co to 0.83 or less. Specifically, in the uncoated austenitic steel sheet for an alkaline water electrolysis separator according to an embodiment of the present invention, the value of formula (1) may be -1 to 0.83, more specifically 0.001 to 0.83, and even more specifically 0.003 to 0.8. Within the above range, the uncoated austenitic steel sheet can realize a current density equivalent to or improved upon that of pure Ni metal, while further improving alkali resistance and corrosion resistance.

[0047] An uncoated austenitic steel sheet for an alkaline electrolytic separator according to one embodiment of the present invention has a surface roughness Ra value of 0.07 µm to 0.25 µm. In the present invention, the surface roughness means the arithmetic mean roughness (Ra), and further, the surface roughness here is the surface roughness in a direction 90° to the cold rolling direction.

[0048] When the surface roughness is lower than 0.07㎛, the amount of hydrogen generated is lower than that of pure Ni due to increased contact resistance, and when the surface roughness is higher than 0.25㎛, hydrogen is adsorbed on the separator, inhibiting the hydrogen generation reaction, thereby reducing the amount of hydrogen generated.

[0049] In an uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention, the alkaline environment may have a concentration of [OH-] ions of 0.3 mol to 7.5 mol based on molar concentration.

[0050] An uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention may have a current density ratio expressed by the following equation (2) of 1.9 or less.

[0051] Equation (2): Current density of uncoated austenitic steel plate for alkaline water electrolysis separator / Current density of pure Ni metal

[0052] The current density ratio refers to the value obtained by dividing the current density of the uncoated austenitic steel sheet for an alkaline electrolysis separator by the current density of pure Ni metal. Therefore, when the current density ratio is 1.0, it can be evaluated that it has the same level of corrosion resistance as pure Ni metal. On the other hand, the current density may appear lower as the corrosion resistance increases in an alkaline environment. In addition, the lower the current density ratio is than 1.0, the better the corrosion resistance is than pure Ni metal. In this respect, the lower limit of the current density ratio expressed by the above formula (2) may be 0.001, specifically 0.01, more specifically 0.1, and even more specifically 0.5. Within the above range, the uncoated austenitic steel sheet for an alkaline electrolysis separator according to an embodiment of the present invention can implement more advantageous physical properties for use as a material for electrolysis batteries such as high-temperature electrolysis, cation membrane electrolysis, and alkaline electrolysis. In addition, it can further increase productivity and reduce costs in achieving the desired properties.

[0053] In addition, the current density ratio expressed by the above formula (2) may be 1.9 or less. Specifically, the current density ratio may be 0.001 to 1.9, more specifically, 0.1 to 1.5, even more specifically, 0.5 to 1.07, and even more specifically, 0.8 to 1.07.

[0054] An uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention has a strength of 25 N / cm 2 The surface contact resistance may be 40 mΩ·㎠ or less at a pressure of . The higher the surface contact resistance, the more hydrogen may be adsorbed on the surface of the separator, which may inhibit the hydrogen generation reaction. Therefore, the present invention is characterized by a surface contact resistance of 25 N / cm 2The surface contact resistance of pure Ni is controlled to 40 mΩ·㎠ or less at the pressure.

[0055] An uncoated austenitic steel plate for an alkaline electrolysis separator according to one embodiment of the present invention may have a hydrogen generation ratio expressed by the following equation (3) of less than 1.0.

[0056] Equation (3): Hydrogen generation amount of uncoated austenitic steel plate for alkaline water electrolysis separator / Hydrogen generation amount of pure Ni metal

[0057] Meanwhile, since the uncoated austenitic steel plate for an alkaline water electrolysis separator according to one embodiment of the present invention does not undergo a separate coating, the problem of cell performance degradation due to a defective coating layer may not occur, and since a large-area coating process is not performed, the price competitiveness is excellent.

[0058] Next, a method for manufacturing an uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention will be described.

[0059] A method for manufacturing an uncoated austenitic steel sheet for an alkaline water electrolysis separator according to one embodiment of the present invention may include the steps of manufacturing a slab containing, in wt%, C: more than 0% and 0.04% or less, Si: more than 0% and 0.4% or less, Mn: more than 0% and 0.5% or less, Cr: more than 0% and 2.0% or less, Ni: 33% to 40%, Co: more than 0% and 4.0% or less, the remainder Fe and other unavoidable impurities, and having a value of the following formula (1) of 0.83 or less; a step of reheating the slab and hot-rolling it to manufacture a hot-rolled steel sheet; and a step of solution-heat-treating the hot-rolled steel sheet.

[0060] The above slab may have a value of equation (1) below of 0.83 or less.

[0061] Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co

[0062] In Equation (1), Ni, Cr, and Co represent the content (weight%) of each element.

[0063] Specifically, the value of the above formula (1) may be -1 to 0.83, more specifically 0.001 to 0.83, and even more specifically 0.003 to 0.8.

[0064] The reason for the component range of each alloy composition and the numerical limitation of formula (1) is as described above, and each manufacturing step is described in more detail below.

[0065] After manufacturing a slab satisfying the above alloy composition and formula (1), it can undergo a series of reheating, hot rolling, and solution heat treatment processes.

[0066] First, the above slab can be reheated at 1150°C to 1350°C for 150 to 240 minutes and then hot rolled.

[0067] By reheating at 1150℃ to 1350℃ and hot rolling, coarse precipitates generated during slab manufacturing can be redissolved and internal crystal grains can be controlled to an appropriate size.

[0068] A hot-rolled steel sheet can be manufactured by hot rolling, and then solution heat treatment can be performed at 800°C to 900°C for 100 to 200 seconds.

[0069] In addition, the manufactured hot-rolled steel sheet can be cold rolled to produce a final product, and after cold rolling, it can be solution heat treated again at 800°C to 900°C for 100 to 200 seconds.

[0070] During cold rolling, the surface roughness can be controlled according to the roll roughness, and the surface roughness (Ra) value of the uncoated austenitic steel sheet can be 0.07㎛ to 0.25㎛.

[0071] Additionally, the uncoated austenitic steel sheet may have a surface contact resistance of 40 mΩ·㎠ or less, and the ratio of hydrogen generation in a water electrolysis environment may be less than 1.0 compared to pure Ni.

[0072] In addition, the method for manufacturing an uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention may further include a step of controlling the surface roughness of the steel plate obtained by the solution heat treatment to Ra: 0.07 ㎛ to 0.25 ㎛.

[0073] Meanwhile, the method for manufacturing an uncoated austenitic steel plate for an alkaline electrolytic separator according to one embodiment of the present invention does not perform a separate Ni coating process, and therefore has excellent productivity and price competitiveness.

[0074]

[0075] Hereinafter, the present invention will be described in more detail through examples. However, the description of these examples is merely intended to illustrate the implementation of the present invention and is not intended to limit the present invention. This is because the scope of the present invention is determined by the matters set forth in the claims and matters reasonably inferred therefrom.

[0076] {Example}

[0077] For the various alloy composition ranges shown in Table 1 below, slabs measuring 150x150x280 mm were manufactured by melting in a vacuum melting furnace. The slabs were reheated at 1240°C and then hot-rolled to a thickness of 3 mm to manufacture hot-rolled steel sheets. The hot-rolled steel sheets were solution-heat treated at 850°C to manufacture specimens.

[0078] Classification Alloy composition (weight %) CSiMnCrNiCoExample 10.010.10.150.02330.02Example 20.010.10.150.1234.70.01Example 30.0110.10.150.1360.01Example 40.0110.150.2.0.4936.20.01Example 50.0150.150.30.136.10.3Example 60.020.160.350.136.31.0Example 70. 0170.20.30.1362.0Example 80.020.20.32.0404.0Example 90.020.20.32.0402.0Comparative Example 10.0150.10.1518100.01Comparative Example 20.0180.150.20.5331.0Comparative Example 30.030.20.180.9736.20.01Comparative Example 40.0250.230.31.98360.01Comparative Example 50.0130.30.354.0360.01

[0079] Table 2 below shows the values ​​of Equation (1) and the current density ratio. The values ​​of Equation (1) were calculated using Equation (1) below.

[0080] Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co

[0081] In Equation (1), Ni, Cr, and Co represent the content (weight%) of each element.

[0082] The current density ratio was calculated and expressed as follows.

[0083] Current density ratio = (Current density of uncoated austenitic steel sheet with improved corrosion resistance in alkaline environments / Current density of pure Ni metal)

[0084] The above current density was measured by applying a voltage of 0.4 V versus a standard hydrogen electrode for 6 hours in a 30% KOH solution to the specimen and pure Ni metal.

[0085] Meanwhile, the current density may be lower as corrosion resistance in an alkaline environment increases. Furthermore, if the current density ratio is 1.0, the metal exhibits corrosion resistance equivalent to that of pure Ni metal, and if the current density ratio is lower than 1.0, the metal exhibits corrosion resistance superior to that of pure Ni metal.

[0086] Classification formula (1) Current density Non-example 10.78 1.04 Example 20.45 0.97 Example 30.11 0.98 Example 40.4 10.99 Example 50.08 1.0 Example 60.03 0.95 Example 70.10.84 Example 80.8 0.99 Example 90.8 11.07 Comparative example 122.74 8.17 Comparative example 21.2 11.95 Comparative example 30.84 2.02 Comparative example 41.8 2.11 Comparative example 53.62 3.8

[0087] Referring to Table 2, Examples 1 to 9 satisfied the alloy composition, formula (1), and manufacturing method presented in the disclosed invention. Therefore, Examples 1 to 9 satisfied a current density ratio of 1.9 or less. That is, Examples 1 to 9 can be evaluated as having improved corrosion resistance in an alkaline environment. However, Comparative Examples 1 and 5 had too high a Cr content, and Comparative Example 1 had too low a Ni content. Therefore, Comparative Examples 1 and 5 did not satisfy the formula (1) value of 0.83 or less. Therefore, Comparative Examples 1 and 5 did not satisfy a current density ratio of 1.9 or less. That is, Comparative Examples 1 and 5 had very poor corrosion resistance in an alkaline environment.

[0088] Comparative Examples 2 to 4 satisfied the alloy composition, but did not satisfy the value of Formula (1) of 0.83 or less. Therefore, Comparative Examples 2 to 4 did not satisfy the current density ratio of 0.8 to 1.9 or less. In other words, Comparative Examples 2 to 4 had poor corrosion resistance in an alkaline environment.

[0089] Table 3 below shows the contact resistance and hydrogen generation ratio by surface roughness for the above examples and comparative examples. The contact resistance is 25 N / cm based on pure Ni. 2It is a value measured at the pressure of , and the hydrogen generation ratio is a value obtained by manufacturing an actual separator and operating the electrolysis device. The area of ​​the separator is 46cm. 2 The operating temperature was 60℃, the applied current was 30A, and the electrolyte was 25 wt% KOH, and it was evaluated by operating for 100 hours.

[0090] The hydrogen generation ratio is the ratio of the hydrogen generation amount of the uncoated austenitic steel sheet used in the present invention to the hydrogen generation amount of pure Ni under the same conditions.

[0091] Surface roughness was calculated as the arithmetic mean roughness (Ra) in the 90° direction to the rolling direction of the cold-rolled steel sheet in accordance with JIS B 0601.

[0092] CSiMnCrNiCoRa(um)Contact resistance(mΩ·㎠)Hydrogen generation amountNon-comparative example 10.010.10.150.02330.020.3550.8Comparative example 20.010.10.150.02330.020.25240.9Comparative example 30.010.10.150.02330.020.05570.95Example 10.0110.10.150.1360.010.2281Example 20.0110.10.150.1360.010.13341.2Comparative example 40.0110.10.150.1360.010.04640.85Comparative example 50.020.20.324020.011200.95Example 30.020.20.324040.07381.1Comparative Example 60.020.20.324020.5720.75

[0093] The contact resistance of pure Ni is 25 N / cm 2At a pressure of 40 mΩ·cm2, according to Table 3, it can be confirmed that the contact resistance is lower than that of pure Ni when the surface roughness is 0.07 μm to 0.25 μm. However, when the surface roughness is 0.25 μm or more, the generated hydrogen is adsorbed on the surface of the separator, which has the effect of inhibiting the hydrogen generation reaction, thereby reducing the amount of hydrogen generated. Therefore, when the surface roughness is lower than 0.07 μm, the amount of hydrogen generated is low due to the increase in contact resistance, and when the surface roughness is 0.25 μm or more, the amount of hydrogen generated is low because the hydrogen is adsorbed on the separator, which inhibits the hydrogen generation reaction.

[0094] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the following claims.

Claims

1. In weight%, C: more than 0% but not more than 0.04%, Si: more than 0% but not more than 0.4%, Mn: more than 0% but not more than 0.5%, Cr: more than 0% but not more than 2.0%, Ni: 33% to 40%, Co: more than 0% but not more than 4.0%, the remainder including Fe and other inevitable impurities, The value of equation (1) below is less than or equal to 0.83, The surface roughness Ra value is 0.07㎛ to 0.25㎛, Uncoated austenitic steel plate for alkaline electrolytic separators with excellent corrosion resistance in alkaline environments. Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co (In formula (1), Ni, Cr, and Co represent the content (weight%) of each element.) 2. In claim 1, The above alkaline environment is an uncoated austenitic steel plate for an alkaline water electrolysis separator, in which the concentration of [OH-] ions is 0.3 molar to 7.5 molar in molar concentration.

3. In claim 1, An uncoated austenitic steel plate for an alkaline water electrolysis separator, having a current density ratio of 1.9 or less, as expressed by the following equation (2). Equation (2): Current density of uncoated austenitic steel plate for alkaline water electrolysis separator / Current density of pure Ni metal 4. In claim 1, 25N / cm 2 Uncoated austenitic steel plate for alkaline water electrolysis separator, having a surface contact resistance of 40 mΩ·㎠ or less at a pressure of .

5. In claim 1, An uncoated austenitic steel plate for an alkaline water electrolysis separator, having a hydrogen generation ratio of less than 1.0, as expressed by the following equation (3). Equation (3): Hydrogen evolution amount of uncoated austenitic steel plate for alkaline water electrolysis separator / Hydrogen evolution amount of pure Ni metal 6. A step for manufacturing a slab, which contains C: more than 0% and not more than 0.04%, Si: more than 0% and not more than 0.4%, Mn: more than 0% and not more than 0.5%, Cr: more than 0% and not more than 2.0%, Ni: 33% to 40%, Co: more than 0% and not more than 4.0%, the remainder being Fe and other unavoidable impurities, and having a value of the following formula (1) of not more than 0.83; A step of reheating the above slab and hot rolling it to manufacture a hot rolled steel sheet; and A method for manufacturing an uncoated austenitic steel sheet for an alkaline electrolytic separator, comprising the step of performing a solution heat treatment on the hot-rolled steel sheet. Equation (1): 9.0 - 0.2495 x Ni + 0.9 x Cr - 0.005 x Co (In formula (1), Ni, Cr, and Co represent the content (weight%) of each element.) 7. In claim 6, A method for manufacturing an uncoated austenitic steel plate for an alkaline water electrolysis separator, comprising the steps of cold rolling and re-solution heat treatment after the above-mentioned solution heat treatment step.

8. In claim 6, A method for manufacturing an uncoated austenitic steel plate for an alkaline water electrolysis separator, wherein the above reheating is performed at 1150 to 1350°C for 150 to 240 minutes.

9. In claim 6 or claim 7, A method for manufacturing an uncoated austenitic steel plate for an alkaline water electrolysis separator, wherein the above-mentioned solution heat treatment and re-solution heat treatment steps are performed at 800 to 900°C for 100 to 200 seconds.

10. In claim 7, A method for manufacturing an uncoated austenitic steel plate for an alkaline water electrolysis separator, further comprising a step of controlling the surface roughness of the steel plate obtained by the above-mentioned re-solution heat treatment to Ra: 0.07 ㎛ to 0.25 ㎛.