Austenitic stainless steel with improved low-temperature impact toughness and strength and manufacturing method thereof

Abstract

The present invention provides an austenitic stainless steel with improved low-temperature impact toughness and strength for hydrogen applications, by adjusting the relationship between alloying elements that have a major effect on low-temperature toughness and by ensuring high strength through the addition of sufficient N. [Solution] The austenitic stainless steel of the present invention, with improved low-temperature impact toughness and strength, contains, by weight, C: 0.1% or less (excluding 0), Si: 1.5% or less (excluding 0), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (excluding 0), Mo: 0 to 1.5% or less, Cu: 0 to 1.6% or less, N: 0.1 to 0.3%, with the remainder being Fe and impurities, and is characterized in that the formula (1): 1.7Ni + 410C - 0.9Cr - 100N - 13Si - 1.2Mn + 2Cu - 5.5Mo + 40 is 10 to 35, and the formula (2): (Ni + 0.52Cu + 40(C + N) + 0.7Mn + 45) - (0.48(Cr + Mo + 1.7Si)) - 51 is 0 or greater.

Description

[Technical Field]

[0001] The present invention relates to an austenitic stainless steel having excellent low-temperature toughness in a low-temperature environment such as liquefied hydrogen, and more particularly to an austenitic stainless steel having improved low-temperature impact toughness and strength by controlling the chemical formula and alloy composition, and a method for producing the same. [Background technology]

[0002] In recent years, as the demand for environmentally friendly energy such as hydrogen energy has increased, it has become necessary to develop containers and components for storing hydrogen.

[0003] Generally, hydrogen storage containers can be divided into liquefied hydrogen storage containers and gaseous hydrogen storage containers depending on the form of hydrogen. In particular, liquefied hydrogen storage containers are expected to be used in a variety of fields in the future due to their relatively high storage efficiency. For example, liquefied hydrogen storage containers can be used for long-distance transportation of hydrogen from overseas to domestic locations, and for storing large amounts of hydrogen at hydrogen charging stations and hydrogen production plants.

[0004] The steel materials for such hydrogen storage containers are exposed to temperatures ranging from -253°C to room temperature, so the steel materials must not lose their physical properties at various temperatures. Considering this, hydrogen storage tanks and peripheral equipment are required to prevent a decrease in toughness due to hydrogen and cryogenic temperatures, as well as high mechanical strength and corrosion resistance.

[0005] Therefore, in order to utilize hydrogen resources such as liquefied hydrogen and gaseous hydrogen, there is an increasing need for technology that improves the physical properties of hydrogen storage containers such as hydrogen storage tanks. Summary of the Invention [Problem to be solved by the invention]

[0006] In order to solve the above-mentioned problems, the present invention aims to provide an austenitic stainless steel having improved low-temperature impact toughness and strength for hydrogen applications, by adjusting the relationships between alloying elements that have a major effect on low-temperature toughness to ensure high impact toughness at low temperatures, and at the same time, by adding sufficient N to ensure high strength, and a manufacturing method thereof.

[0007] The problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the austenitic stainless steel of the present invention, which has improved low-temperature impact toughness and strength, contains, by weight%, C: 0.1% or less (excluding 0), Si: 1.5% or less (excluding 0), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (excluding 0), Mo: 0 to 1.5% or less, Cu: 0 to 1.6% or less, N: 0.1 to 0.3%, with the remainder being Fe and impurities, and is characterized in that the formula (1): 1.7Ni + 410C - 0.9Cr - 100N - 13Si - 1.2Mn + 2Cu - 5.5Mo + 40 is 10 to 35, and the formula (2): (Ni + 0.52Cu + 40(C + N) + 0.7Mn + 45) - (0.48(Cr + Mo + 1.7Si)) - 51 is 0 or greater.

[0009] The austenitic stainless steel of the present invention having improved low-temperature impact toughness and strength may be an austenitic stainless steel having improved low-temperature impact toughness and strength, with a -196°C Charpy impact energy of 100 J or more.

[0010] The austenitic stainless steel of the present invention having improved low-temperature impact toughness and strength may be an austenitic stainless steel having improved low-temperature impact toughness and strength and having a yield strength of 280 MPa or more.

[0011] The method for producing an austenitic stainless steel having improved low-temperature impact toughness and strength according to the present invention comprises, by weight percent, C: 0.1% or less (0 is excluded), Si: 1.5% or less (0 is excluded), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (0 is excluded), Mo: 0 to 1.5% or less, Cu: 0 to 1.6% or less, N: 0.1 to 0.3%, with the remainder being Fe and impurities, Formula (1): 1.7Ni+410C-0.9Cr-100N-13Si-1.2Mn+2Cu-5.5Mo+40 is 10 to 35; The method is characterized by comprising the steps of hot rolling a slab that satisfies formula (2): (Ni + 0.52Cu + 40(C + N) + 0.7Mn + 45) - (0.48(Cr + Mo + 1.7Si)) - 51 is 0 or greater, and hot rolling annealing the slab at 900 to 1200°C.

[0012] A method for producing an austenitic stainless steel with improved low-temperature impact toughness and strength according to one embodiment of the present invention may be a method for producing an austenitic stainless steel with improved low-temperature impact toughness and strength, in which the stainless steel has a Charpy impact energy at −196°C of 100 J or more.

[0013] A method for producing an austenitic stainless steel with improved low-temperature impact toughness and strength according to one example of the present invention may be a method for producing an austenitic stainless steel with improved low-temperature impact toughness and strength, in which the yield strength of the stainless steel is 280 MPa or more. [Effects of the Invention]

[0014] According to the present invention, by controlling the alloying elements effective for low-temperature impact toughness and strength, and by controlling the relationship between low-temperature toughness and the relationship between strength, and by controlling the N content to 0.1% or more, it is possible to provide an austenitic stainless steel with improved low-temperature impact toughness and strength, having a -196°C Charpy impact toughness value of 100 J or more and a yield strength of 280 MPa or more, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes preferred embodiments of the present invention. However, the embodiments of the present invention can be modified into various other forms, 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 completely explain the present invention to those with average knowledge in the art.

[0016] The terms used in this application are merely used to describe specific examples. Thus, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, it should be noted that the terms "comprise" or "include" 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 preclude the presence of other features, steps, functions, components, or combinations thereof.

[0017] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Therefore, unless clearly defined herein, specific terms should not be interpreted in an overly ideal or formal sense.

[0018] Furthermore, in this specification, the terms "about," "substantially," and the like are used to mean from or close to a numerical value when manufacturing and material tolerances inherent in the stated meaning are given, and are used to prevent unscrupulous infringers from unfairly taking advantage of the contents of the disclosure in which precise or absolute numerical values ​​are stated to aid in the understanding of the present invention.

[0019] According to the present invention, it is possible to provide an austenitic stainless steel with improved low-temperature impact toughness and strength for hydrogen applications, and a manufacturing method thereof, by adjusting the relationship between alloying elements that have a major effect on low-temperature toughness to ensure high impact toughness at low temperatures and simultaneously ensuring high strength through the addition of sufficient N. Specifically, the relationship between the contents of the major elements constituting the alloy and low-temperature toughness can be used to predict the feasibility of use in cryogenic environments. Furthermore, the addition of N can improve austenite stabilization while simultaneously improving strength.

[0020] According to the low-temperature toughness equation, excessive Mn is detrimental to low-temperature toughness, so adding large amounts of Mn requires increasing the Ni content, which has a powerful effect on increasing low-temperature toughness. The more Ni added to an alloy, the more beneficial it is in terms of low-temperature toughness and austenite stabilization, so large amounts can be added when designing an alloy. However, from an economical perspective, it is possible to consider replacing Ni with Mn or N, which are austenite stabilizing elements.

[0021] Precipitation strengthening has a negative effect on low-temperature toughness. Therefore, according to one embodiment of the present invention, N can be added to improve strength through solid solution strengthening rather than precipitation strengthening. However, N has a negative coefficient in the equation related to low-temperature toughness, so it is necessary to take this into consideration when designing an alloy that can minimize the decrease in low-temperature toughness while ensuring sufficient strength improvement. Therefore, in the present invention, the amount of N added is adjusted based on the value of the equation related to low-temperature toughness, expressed by Equation (1), being between 10 and 35, to design a steel grade.

[0022] Furthermore, Mn also has a negative coefficient in the equation relating to low-temperature toughness, so Mn and N must be added in an appropriate ratio. When designing a steel that ensures sufficient low-temperature toughness in an extremely low-temperature environment, it is necessary to design the steel using chemical compositions that give a value of 10 to 35 calculated using the equation relating to low-temperature toughness proposed by the present invention. In the present invention, the amounts of Ni, Mn, and N added were adjusted based on when the value of the equation relating to low-temperature toughness expressed by equation (1) is 10 to 35.

[0023] The present invention can provide an austenitic stainless steel that satisfies both the relationship related to low-temperature toughness and the relationship related to strength, and that has improved low-temperature impact toughness and strength by simultaneously controlling the component ranges of alloying elements.

[0024] The austenitic stainless steel of the present invention with improved low-temperature impact toughness and strength contains, by weight, C: 0.1% or less (0 is excluded), Si: 1.5% or less (0 is excluded), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (0 is excluded), Mo: 1.5% or less, Cu: 1.6% or less, N: 0.1 to 0.3%, and the remainder being Fe and impurities.

[0025] The reasons for limiting the range of each alloying element will be described in more detail below.

[0026] The C content may be 0.1% by weight or less (0 is excluded).

[0027] C is an element that is effective in stabilizing austenite, suppressing delta-ferrite formation, and increasing strength through solid solution strengthening. However, excessive C content can easily combine with carbide-forming elements such as Cr, Ti, and Nb, reducing the corrosion resistance, ductility, and toughness of the base material. Therefore, the C content is preferably 0.1% or less. More preferably, the C content can be 0.019% to 0.23%.

[0028] The Si content may be 1.5% by weight or less (excluding 0).

[0029] Si is an element effective in improving corrosion resistance and solid solution strengthening. However, Si is a ferrite stabilizing element, and if the Si content is excessive, it can form intermetallic compounds such as sigma phases, reducing the ductility and toughness of the base material. Therefore, the Si content is preferably 1.5% or less. More preferably, the Si content can be 0.38% to 0.46%.

[0030] The Cr content may be 16.0 to 23.0 wt %.

[0031] Cr is an alloying element that must be added to stainless steel to improve corrosion resistance, and it is preferable to add 16.0% or more to ensure corrosion resistance. However, if the Cr content is excessive, excess delta-ferrite remains as a ferrite-forming element, reducing hot workability, and the austenite becomes unstable, requiring a large amount of Ni to ensure phase stability, which can increase costs. Therefore, it is preferable to limit the Cr content to 23.0% or less. More preferably, the Cr content can be 16.8% to 21.5%.

[0032] The Ni content may be 5.0 to 12.0 wt %.

[0033] Ni is an austenite stabilizing element. From the viewpoint of austenite stabilization effect and low-temperature toughness, the more Ni is added, the more advantageous the element becomes. Ni is preferably added in an amount of 5.0% or more to suppress the formation of delta-ferrite in the manufacturing process. However, if the Ni content is excessive, the probability of surface defects in the manufacturing process increases, which may lead to increased costs. Therefore, the Ni content is preferably 12.0% or less. More preferably, the Ni content can be 5.0% to 10.4%.

[0034] The Mn content may be 10.0 wt % or less (0 is excluded).

[0035] Mn is an austenite stabilizing element. Mn can replace expensive Ni. Furthermore, since Mn is an important element from the viewpoint of low-temperature toughness, low-temperature toughness cannot be ensured unless Mn and Ni are added in an appropriate ratio. However, if the Mn content is excessive, the low-temperature toughness relationship proposed by the present invention cannot be made equal to or greater than 0 unless Ni is additionally added. However, the addition of expensive Ni may be disadvantageous in terms of cost. Therefore, the Mn content is preferably 10.0% or less. More preferably, the Mn content can be 0.8% to 7.9%.

[0036] The Mo content may be 0 or more than 0 to 1.5% by weight or less. Mo is an element effective in improving the corrosion resistance of stainless steel, and therefore can be selectively added in the present invention. However, if the Mo content is excessive, the ferrite fraction increases, causing a decrease in low-temperature toughness and possibly resulting in a cost disadvantage. Therefore, the Mo content is preferably 1.5% or less. More preferably, the Mo content can be 0% to 0.6%.

[0037] The Cu content may be 0 or more than 0 to 1.6% by weight or less.

[0038] Cu is an element useful for stabilizing the austenite phase and can be used to replace expensive Ni. Cu is an element that suppresses martensite formation during forming and increases the stability of austenite. In the present invention, Cu can be added selectively. However, excessive Cu content can form a low-melting-point phase, reducing hot workability and degrading surface quality. Therefore, the Cu content is preferably 1.6% or less.

[0039] Specifically, the Cu content can be 0.1 to 1.6%. Within this range, the effects of suppressing martensite generation, increasing austenite stabilization, and preventing a decrease in hot workability can be further improved. In this case, the surface quality of the stainless steel of the present invention can be further improved. Preferably, the Cu content can be 0.36% to 1.6%.

[0040] The N content may be 0.1 to 0.3% by weight.

[0041] N is an austenite stabilizing element and is also effective in increasing strength through solid solution strengthening. In the present invention, the addition of N can improve strength through solid solution strengthening, rather than precipitation strengthening, which has a negative effect on low-temperature impact toughness. It is preferable to adjust the amount of N added so that the N content is 0.1% or more, based on the case where the low-temperature toughness relationship is 0. However, if the N content is excessive, it may be difficult to ensure that the low-temperature toughness relationship is 10 to 35, making it difficult to ensure both strength and low-temperature impact toughness. Therefore, it is preferable to limit the N content to 0.3% or less. More preferably, the N content can be 0.11% to 0.2%.

[0042] The remaining component of the present invention is iron (Fe). However, in a normal manufacturing process, unintentional impurities may be inevitably mixed in from raw materials or the surrounding environment, and this cannot be excluded. Since these impurities are easily understood by a person skilled in the normal manufacturing process, not all of the contents thereof will be specifically mentioned in this specification.

[0043] An austenitic stainless steel with improved low-temperature impact toughness and strength according to one embodiment of the present invention may have a delta ferrite fraction of 4.0% by volume or less. Specifically, for example, the austenitic stainless steel according to the present invention may have a delta ferrite fraction of 0%, or more than 0% but not more than 4.0%. Within the above range, the austenitic stainless steel according to the present invention can have further improved impact toughness.

[0044] In the present invention, the relational expression relating to low temperature toughness represented by formula (1) is: Formula (1): 1.7Ni+410C-0.9Cr-100N-13Si-1.2Mn+2Cu-5.5Mo+40. When the formula (1) is 10 to 35, the Charpy energy value at −196° C. can be 100 J or more.

[0045] The present invention can ensure low-temperature impact toughness by controlling the Ni content, which corresponds to a positive coefficient in formula (1). However, the present invention must ensure strength as well as low-temperature impact toughness. N is an essential component for improving strength, but it has a negative coefficient in formula (1). Therefore, it must be controlled.

[0046] That is, in order to ensure both low-temperature impact toughness and strength, the present invention controls the contents of Mn and N, which have negative coefficients in formula (1). In particular, the present invention controls the N content to 0.1% or more, thereby ensuring both low-temperature impact toughness and a yield strength of 280 MPa or more.

[0047] The present invention controls the relational expression (1) relating to low-temperature toughness to 10 to 35, thereby ensuring a yield strength of 280 MPa or more while maintaining a Charpy energy value of 100 J or more at −196°C, thereby enabling the production of austenitic stainless steel with improved low-temperature impact toughness and strength.

[0048] In the present invention, the relational expression regarding the strength expressed by the formula (2) is set to 0 or more, Formula (2): (Ni + 0.52Cu + 40(C + N) + 0.7Mn + 45) - (0.48(Cr + Mo + 1.7Si)) - 51. When formula (2) is 0 or greater, the yield strength can be 280 MPa or greater.

[0049] That is, as mentioned above, N is an essential component for improving strength, but it has a negative coefficient in formula (1). Therefore, it is necessary to design the components so that formula (1) is 10 to 35 and formula (2) is 0 or greater. In the present invention, taking this into consideration, the N content can be controlled to 0.1 to 0.3.

[0050] The present invention controls formula (1) to 10 to 35 and formula (2) to 0 or greater, thereby ensuring a yield strength of 280 MPa or greater while maintaining a Charpy energy value of 100 J or greater at -196°C, thereby enabling the production of austenitic stainless steel with improved low-temperature impact toughness and strength.

[0051] A method for producing an austenitic stainless steel having improved low-temperature impact toughness and strength according to one embodiment of the present invention comprises, by weight percent, C: 0.1% or less (excluding 0), Si: 1.5% or less (excluding 0), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (excluding 0), Mo: 1.5% or less, Cu: 1.6% or less, N: 0.1 to 0.3%, with the remainder being Fe and impurities, Formula (1): 1.7Ni + 410C - 0.9Cr - 100N - 13Si - 1.2Mn + 2Cu - 5.5Mo + 4010 ~ 35; The method may be a method for producing austenitic stainless steel with improved low-temperature impact toughness and strength, comprising the steps of hot rolling a slab that satisfies formula (2): (Ni+0.52Cu+40(C+N)+0.7Mn+45)-(0.48(Cr+Mo+1.7Si))-51 is 0 or greater, and hot rolling annealing the slab at 900 to 1200°C.

[0052] The alloy composition, formula (1) and formula (2) are as explained in the austenitic stainless steel of the present invention.

[0053] The temperature at the stage of hot rolling annealing after hot rolling is 900 to 1200°C. The annealing temperature affects the release of residual stress and the microstructure. If the annealing temperature is less than 900°C, coarse carbides are generated, which can cause the microstructure to become non-uniform. In addition, Cr is present around the grain boundaries. 23C6 precipitates may be formed, causing intergranular corrosion. If the annealing temperature exceeds 1200°C, the crystal grains may become extremely coarse. In consideration of this, the temperature at the stage of hot rolling annealing is preferably set to 900 to 1200°C.

[0054] The austenitic stainless steel produced by the method for producing austenitic stainless steel with improved low-temperature impact toughness and strength according to the present invention may have a Charpy impact energy of 100 J or more at −196°C and a yield strength of 280 MPa or more at room temperature. The present invention will be described in more detail below through embodiments. However, the description of these embodiments is for illustrative purposes only and does not limit the scope of the present invention. The scope of the present invention is determined by the matters described in the claims and matters reasonably inferred therefrom. [Example]

[0055] Austenitic stainless steels were produced by hot rolling slabs having the alloy compositions shown in Table 1 below and hot rolling annealing at 900 to 1200°C. To confirm the impact toughness at cryogenic temperatures, the Charpy impact energy values ​​at -196°C and yield strength are shown in Table 2 below.

[0056] Charpy impact energy values ​​were measured using ASTM E23 type A test specimens at a temperature of -196°C. Yield strength was measured in air at room temperature.

[0057] Table 1 shows the alloy compositions of the invention examples and comparative examples.

[0058] [Table 1]

[0059] Table 2 below shows formula (1), formula (2), -196°C Charpy impact energy values, and room temperature yield strengths of the invention examples and comparative examples.

[0060] [Table 2] As shown in Tables 1 and 2, Examples 1 to 21 of the present invention satisfy the alloy composition, formula (1), and formula (2) of the present invention. In particular, by controlling the N content to 0.1% or more and formula (1) to 10 to 35, a Charpy impact energy at -196°C of 100 J or more is ensured, while the yield strength is equivalent to 280 MPa or more. In other words, it is possible to ensure austenitic stainless steel with improved low-temperature impact toughness and strength.

[0061] In contrast, Comparative Examples 1, 5, 6, and 7 have Ni contents within the range of the present invention, and have Charpy impact energies of 100 J or more at -196°C. However, the N content is less than 0.1%, which corresponds to a value of formula (2) of less than 0, and it can be confirmed that strength cannot be ensured with a yield strength of less than 280 MPa. This shows that even if the alloy composition of the present invention is satisfied without N, if formulas (1) and (2) are not satisfied, it is not possible to ensure both low-temperature impact toughness and strength.

[0062] In Comparative Examples 2 to 4, the alloy composition of the present invention, particularly the N content, is 0.1% or more, and formula (2) is satisfied as 0 or more, confirming that a yield strength of 280 MPa or more can be ensured. However, formula (1) does not satisfy the range of the present invention, and the -196°C Charpy impact energy is less than 100 J, confirming that low-temperature impact toughness cannot be ensured. This shows that even if the alloy composition, particularly the N content, is ensured to be 0.1% or more and formula (2) is satisfied, if formula (1) does not fall within the range of 10 to 35, low-temperature impact toughness cannot be ensured, and low-temperature impact toughness cannot be ensured at the same time as strength.

[0063] Furthermore, in Comparative Example 4, the N content is high at 0.22%, ensuring a very high yield strength of 374.1 MPa, but the Ni content is low, which means that formula (1) does not satisfy the range of 10 to 35, and the -196°C Charpy impact energy is less than 100 J, confirming that low-temperature impact toughness cannot be ensured. This shows that even if the alloy composition, particularly the N content, is ensured to be 0.1% or more and formula (2) is satisfied, if formula (1) does not fall within the range of 10 to 35, low-temperature impact toughness cannot be ensured, and low-temperature impact toughness cannot be ensured at the same time as strength.

[0064] From the examples and comparative examples of the present invention, it can be seen that N is essential for ensuring strength, but in order to ensure low-temperature impact toughness at the same time as strength, it is necessary to control the N content as well as the formula (1) relating to low-temperature toughness, which includes Ni, Mn, etc., to 10 to 35, and to control the formula (2) relating to strength to 0 or more, thereby obtaining an austenitic stainless steel with improved low-temperature impact toughness and strength at the same time.

[0065] The present invention provides an austenitic stainless steel having improved low-temperature impact toughness and strength at the same time by using a chemical composition that can control the relationship between low-temperature toughness and strength. As a result, the austenitic stainless steel of the present invention can reduce the thickness of the material used, which in turn reduces the amount of material used and helps reduce the cost of manufacturing cryogenic tanks.

[0066] Conventional steel materials have relatively excellent low-temperature toughness but low strength, which can lead to thick material thickness when manufacturing cryogenic tanks or structures. The austenitic stainless steel according to the present invention can solve this problem.

[0067] Furthermore, the austenitic stainless steel according to the present invention can be manufactured using methods that include or exclude the previously proposed methods of improving strength by cold working and precipitation, while maintaining or further reducing the reduction in hydrogen embrittlement and low-temperature toughness, and achieving the desired physical properties. Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and it will be understood by those skilled in the art that various changes and modifications can be made without departing from the concept and scope of the claims set forth below.

Claims

1. In weight percent, it contains C: 0.1% or less (0 is excluded), Si: 1.5% or less (0 is excluded), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (0 is excluded), Mo: 0 to 1.5% or less, Cu: 0 to 1.6% or less, N: 0.1 to 0.3%, and the remainder being Fe and impurities, An austenitic stainless steel having improved low-temperature impact toughness and strength, characterized in that the following formula (1) is 10 to 35, and the following formula (2) is 0 or more: Formula (1): 1.7Ni+410C-0.9Cr-100N-13Si-1.2Mn+2Cu-5.5Mo+40 Formula (2): (Ni+0.52Cu+40(C+N)+0.7Mn+45)-(0.48(Cr+Mo+1.7Si))-51

2. 2. The austenitic stainless steel having improved low-temperature impact toughness and strength according to claim 1, characterized in that the Charpy impact energy at -196°C is 100 J or more.

3. 2. The austenitic stainless steel having improved low-temperature impact toughness and strength according to claim 1, characterized in that the yield strength is 280 MPa or more.

4. hot rolling a slab containing, by weight, C: 0.1% or less (excluding 0), Si: 1.5% or less (excluding 0), Cr: 16.0 to 23.0%, Ni: 5.0 to 12.0%, Mn: 10.0% or less (excluding 0), Mo: 0 to 1.5% or less, Cu: 0 to 1.6% or less, N: 0.1 to 0.3%, and the remainder being Fe and impurities, wherein the following formula (1) is 10 to 35 and the following formula (2) is 0 or more; A method for producing austenitic stainless steel with improved low-temperature impact toughness and strength, comprising the step of hot rolling and annealing at 900 to 1200°C. Formula (1): 1.7Ni+410C-0.9Cr-100N-13Si-1.2Mn+2Cu-5.5Mo+40 Formula (2): (Ni+0.52Cu+40(C+N)+0.7Mn+45)-(0.48(Cr+Mo+1.7Si))-51

5. 5. The method for producing austenitic stainless steel with improved low-temperature impact toughness and strength according to claim 4, wherein the stainless steel has a Charpy impact energy at -196°C of 100 J or more.

6. 5. The method for producing austenitic stainless steel with improved low-temperature impact toughness and strength according to claim 4, wherein the yield strength of the stainless steel is 280 MPa or more.

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