KR20210078228A - High yield ratio high strength austenitic stainless steel - Google Patents

Abstract

In accordance with the present specification, disclosed is high-yield ratio and high-strength austenitic stainless steel. In accordance with one embodiment of the disclosed high-yield ratio and high-strength austenitic stainless steel, the austenitic stainless steel includes: no more than 0.15 wt% of C; 0.1-0.25 wt% of N; 0.7-2.0 wt% of Si; 1.5-3.5 wt% of Mn; 16-18 wt% of Cr; 3-5 wt% of Ni; no more than 2 wt% of Cu; no more than 0.02 wt% of Ti; and the remaining of Fe and inevitable impurities. The austenitic stainless steel satisfies no less than 0.29 wt% of C+N, and a value of the following formula (1) can be no less than 10.0 and no more than 13.0. (1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si in the formula (1), Ni, Cr, C, N, Mn, Cu, and Si refer to the content (wt%) of each element.

Description

High yield ratio high strength austenitic stainless steel {HIGH YIELD RATIO HIGH STRENGTH AUSTENITIC STAINLESS STEEL}

The present invention relates to high yield ratio high strength austenitic stainless steel, and more particularly, to high yield ratio high strength austenitic stainless steel with improved yield strength and reduced tensile strength.

In recent years, although relatively expensive, the use of double-glazed glass is gradually increasing due to the advancement of living environment and the development of manufacturing technology due to the improvement of economic power. From large buildings to small shops and private houses, the demand for double-glazed glass is gradually increasing according to the desire of consumers to pursue a more comfortable living environment away from noise.

Double-layer glass is combined with a predetermined gap between two or more sheets of glass, and compared to single-layer glass, it not only minimizes the loss of indoor energy, but also reduces the surface temperature of the inner glass relatively less despite the decrease in external temperature. Dew formation is suppressed. In addition, it is possible to effectively block the transmission of noise between indoors and outdoors due to excellent soundproofing performance.

A window spacer is a structure that maintains an interval between glass in a double-glazed glass in the form of a bar. The gwanbong determines the thickness of the air layer, blocks water vapor, and performs the functions of maintaining the container and mechanical strength of the desiccant. In particular, in order to prevent dew condensation caused by the temperature difference between the inner and outer surfaces of the glass, the inter-bar is mainly composed of a material having excellent thermal insulation properties.

Conventionally, plastic, foam, plastic-metal hybrid material, etc. have been applied as the material of the interstitial rod, but there is a problem in that the strength is weak, the durability is poor, and it is not possible to secure sufficient thermal insulation.

Recently, there has been an attempt to apply austenitic stainless steel, which is stronger in strength and excellent in durability and heat insulation, as a material for interstitial rods. However, austenitic stainless steel has a low yield strength and high tensile strength, so it is vulnerable to distortion of windows and doors. In addition, the austenitic stainless steel is easily deformed due to low yield strength, and there is a problem in that it may be fractured during molding due to high tensile strength.

Korean Patent Laid-Open Publication No. 10-2010-0071619 (published date: June 29, 2010)

In order to solve the above problems, the present invention is to provide a high yield ratio high strength austenitic stainless steel with improved yield strength and reduced tensile strength.

As a means for achieving the above object, the high yield ratio high strength austenitic stainless steel according to an embodiment of the present invention is, by weight, C: 0.15% or less, N: 0.1 to 0.25%, Si: 0.7 to 2.0%, Mn : 1.5 to 3.5%, Cr: 16 to 18%, Ni: 3 to 5%, Cu: 2% or less, Ti 0.02% or less, remaining Fe and other unavoidable impurities, and C + N: 0.29% or more and the value of the following formula (1) may be 10.0 or more and 13.0 or less.

(1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si

In the above formula (1), Ni, Cr, C, N, Mn, Cu, and Si mean the content (% by weight) of each element.

In each high yield ratio high strength austenitic stainless steel of the present invention, the Md30 value according to the following formula (2) may be 17.0 to 21.0 °C.

(2) 551 - 462 (C+N) - 9.2Si - 8.1Mn -13.7Cr - 29 (Ni+Cu) - 18.5Mo

In the above formula (2), C, N, Si, Mn, Cr, Ni, and Cu mean the content (wt%) of each element.

In each high yield ratio high strength austenitic stainless steel of the present invention, the value of Equation (3) below may be 0.5 or more.

(3) 0.227 - 0.00116Md30 + 1.13 (C+N)

In Equation (3), Md30 is a value derived according to Equation (2), and C and N mean content (wt%) of each element.

In each high yield ratio high strength austenitic stainless steel of the present invention, the yield ratio may be 0.5 or more.

In each high yield ratio high strength austenitic stainless steel of the present invention, the yield strength may be 430 MPa or more, and the tensile strength may be 850 MPa or more.

In each high yield ratio high strength austenitic stainless steel of the present invention, the elongation may be 40% or more.

In each high yield-ratio high-strength austenitic stainless steel of the present invention, the austenitic stainless steel is manufactured including cold rolling and then annealing heat treatment, and the yield ratio when the annealing heat treatment temperature is 1000 to 1100 ° C. 0.5 or more.

According to the present invention, it is possible to provide a high yield ratio high-strength austenitic stainless steel by controlling the composition.

More specifically, in the present invention, in addition to controlling the content of each alloying element, controlling the C + N content, the following formulas (1), (2) and (3) to ensure high yield ratio and high strength characteristics At the same time, excellent processability can be secured.

(1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si

(2) 551 - 462 (C+N) - 9.2Si - 8.1Mn -13.7Cr - 29 (Ni+Cu) - 18.5Mo

(3) 0.227 - 0.00116Md30 + 1.13 (C+N)

In addition, according to the present invention, it is possible to secure price competitiveness compared to other steel types by adding Cu and Mn in order to reduce the contents of expensive Ni and Mo and prevent the formation of martensite.

In addition, according to the present invention, since it is possible to secure high yield ratio and high strength characteristics at 1000 to 1100° C., which is a typical annealing heat treatment temperature range of austenitic stainless steel, and secure excellent workability, separate heat treatment temperature control There is an advantage in that the desired physical properties can be achieved only by controlling the component composition without the need.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes preferred embodiments of the present invention. However, the embodiment of the present invention may be modified in various other forms, and the technical idea of the present invention is not limited to the embodiment described below. Further, 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 there is a feature, step, function, component, or a combination thereof described in the specification, and other features It should be noted that it is not intended to preliminarily exclude the existence of elements, steps, functions, components, or combinations thereof.

Meanwhile, 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, certain 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 unscrupulous infringers of the mentioned disclosure.

High yield ratio high strength austenitic stainless steel according to an embodiment of the present invention is, by weight, C: 0.15% or less, N: 0.1 to 0.25%, Si: 0.7 to 2.0%, Mn: 1.5 to 3.5%, Cr: 16 to 18%, Ni 3 to 5%, Cu: 2% or less, Ti 0.02% or less, remaining Fe and other unavoidable impurities.

Hereinafter, the reason for limiting the alloy composition will be described in detail.

C: 0.15 wt% or less

C is an austenite phase forming element, and is an element effective for strength increase by solid solution strengthening. However, when C is added excessively, it forms central segregation and coarse carbide during the steelmaking process, thereby adversely affecting the subsequent hot rolling-annealing-cold rolling-cold rolling annealing process. In addition, C easily combines with a carbide-forming element such as Cr, which is effective for corrosion resistance, at the ferrite-austenite phase boundary, thereby lowering the Cr content around the grain boundary, thereby reducing corrosion resistance.

In the present invention, C is added to improve the yield strength. However, in consideration of the above problem, the upper limit of C added is limited to 0.15% by weight. In order to secure more excellent corrosion resistance, it is more preferable that the upper limit of C is limited to 0.1% by weight.

N: 0.1 to 0.25 wt%

N is an element that greatly contributes to the stabilization of the austenite phase together with Ni in stainless steel, and is one of the elements concentrated in the austenite phase during annealing heat treatment. Therefore, corrosion resistance and strength can be improved by increasing the N content. In consideration of this, in the present invention, N is added in an amount of 0.1% by weight or more.

However, since the solubility of N may change depending on the content of Mn added, it is necessary to control the content. When the N content exceeds 0.25% by weight in the Mn range of the present invention, blowholes and pinholes occur during casting due to excess nitrogen solubility, resulting in surface defects of the product and edge cracks during rolling. There is a problem induced. In consideration of this, the upper limit of N is preferably limited to 0.25% by weight.

Si: 0.7 to 2.0 wt%

Since Si improves corrosion resistance when added, it may be added in an amount of 0.7 wt% or more in the present invention. However, Si is a ferrite phase stabilizing element and has a problem of increasing magnetic permeability, and when its content is excessive, it promotes precipitation of intermetallic compounds such as σ phase, thereby reducing mechanical properties and corrosion resistance. The upper limit of is limited to 2.0% by weight.

Mn: 1.5 to 3.5 wt%

Mn is an element that controls molten metal fluidity, a deoxidizer, and increases nitrogen solubility, and can replace expensive Ni as an austenite phase forming element. In consideration of this, in the present invention, Mn is added in an amount of 1.5 wt% or more.

However, when Mn is excessively added, there is a problem of reducing corrosion resistance by forming sulfide inclusions (MnS), etc., so the upper limit of Mn in the present invention is preferably limited to 3.5 wt%.

Cr: 16 to 18 wt%

Cr is the most important element for improving the corrosion resistance of stainless steel. In order to ensure sufficient corrosion resistance, Cr may be added in an amount of 16 to 18% by weight in the present invention.

Ni: 3 to 5 wt%

Ni is an austenite phase stabilizing element and is essential to ensure good hot workability and cold workability. In particular, even when a certain amount of Mn is added, an addition of 3 wt% or more is essential. However, since Ni is an expensive element, it causes an increase in raw material cost when added in a large amount. Therefore, the upper limit is set to 5% by weight.

Cu: 2 wt% or less

Cu is an austenite phase stabilizing element, and is an effective element for softening a material. However, there is a problem of causing hot brittleness as well as an increase in material cost when a large amount of Cu is added. Accordingly, the upper limit of Cu in the present invention is limited to 2% by weight.

Ti: 0.02 wt% or less

Ti plays a role in increasing the yield strength by forming TiC. However, when Ti is excessively added, the upper limit of Ti is limited to 0.02% by weight, because TiN may be excessively crystallized to cause clogging of the playing nozzle or defects in inclusions.

The remaining component 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 the impurities are known to any person skilled in the art of a conventional manufacturing process, all details thereof are not specifically mentioned in the present specification.

The alloy composition of the stainless steel of the present invention may further limit the relationship between them as follows, in addition to limiting the content of each alloying element to the above-described conditions.

The yield ratio means the ratio of the yield strength of the steel divided by the tensile strength. In order to achieve the desired high yield ratio of the present invention, the tensile strength should be lowered while increasing the yield strength. As the yield ratio increases, the deformability of the material decreases. Hereinafter, the means of the present invention for improving the yield ratio will be described in detail.

C+N: 0.29% by weight or more

C and N, as interstitial elements, have an effect of solid-solution strengthening of steel when added. According to an example of the present invention, the yield strength can be improved by controlling the C + N content to 0.29 wt % or more in order to secure a desired high yield ratio.

Yield strength index: 10.0 or more and 13.0 or less

The inventors of the present invention satisfy the above C + N content range, and if the yield strength index value expressed by the following formula (1) is controlled in an appropriate range, a high yield ratio can be secured while the yield strength and tensile strength can be improved found

Equation (1) below is an expression for the energy that affects the dislocation behavior of steel. The lower the value of Equation (1), the more difficult the dislocation movement. The required stress is reduced.

(1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si

In the above formula (1), Ni, Cr, C, N, Mn, Cu, and Si mean the content (% by weight) of each element.

According to an example of the present invention, the value of Equation (1) may be 10.0 or more and 13.0 or less. If the value of Equation (1) is less than 10.0, a phase transformation behavior occurs, and there is a risk that the yield ratio may be lowered due to a decrease in yield strength and an increase in tensile strength. When the value of Equation (1) exceeds 13.0, plastic deformation becomes easy and there is a fear that the yield strength may be lowered.

Md30: 17.0 to 21.0°C

Md30 refers to the temperature at which the martensite phase occurs at a fraction of 50% when the steel is deformed to a true strain of 30%. The higher the Md30 value, the lower the degree of stabilization of the austenite phase, which means that the tendency to form the processing-induced martensite phase during processing increases.

According to the present invention, the degree of stabilization of the austenite phase is increased by downwardly adjusting the Md30 value expressed by the following formula (2), thereby suppressing the tendency to form a processing-induced martensite phase, thereby reducing the tensile strength.

(2) 551 - 462 (C+N) - 9.2Si - 8.1Mn -13.7Cr - 29 (Ni+Cu) - 18.5Mo

In the above formula (2), C, N, Si, Mn, Cr, Ni, and Cu mean the content (wt%) of each element.

According to an example of the present invention, the Md30 value may be 17.0 to 21.0°C. When the Md30 value exceeds 21.0°C, there is a possibility that the processed organic martensite phase is excessively formed, and there is a fear that the tensile strength may increase. If the Md30 value is less than 17.0° C., expensive Ni, etc., which is an austenite phase stabilizing element, must be further added, so that there is a risk of excessive manufacturing cost.

Predicted Yield Ratio: 0.5 or more

The inventors of the present invention derived a regression equation of the yield ratio using Md30 and C+N content as independent variables and yield ratio as dependent variables in order to secure high yield ratio properties with a yield ratio of 0.5 or more. The predicted yield ratio derived by the regression equation is expressed by the following equation (3).

(3) 0.227 - 0.00116Md30 + 1.13 (C+N)

In Equation (3), Md30 is a value derived according to Equation (2) described above, and C and N mean content (wt%) of each element.

According to an example of the present invention, the predicted yield ratio value may be 0.5 or more.

The high yield ratio high strength austenitic stainless steel according to the present invention may be manufactured according to a conventional method for manufacturing austenitic stainless steel. As an example of the manufacturing method, hot rolling-annealing-cold rolling-annealing may be performed. After cold rolling, the annealing heat treatment temperature may be 1000 to 1100° C., and may be air cooled after annealing. In the austenitic stainless steel according to an embodiment of the present invention, martensitic transformation does not occur during air cooling.

The high yield ratio high strength austenitic stainless steel according to the present invention can secure high yield ratio and high strength characteristics by controlling the composition as described above.

The high yield ratio high strength austenitic stainless steel according to an embodiment of the present invention may have a yield ratio of 0.5 or more.

The high yield ratio high strength austenitic stainless steel according to an embodiment of the present invention may have a yield strength of 430 MPa or more, and a tensile strength of 850 MPa or more.

In addition, the high yield ratio high strength austenitic stainless steel according to the present invention can secure high yield ratio and high strength characteristics by controlling the above-mentioned alloy composition, Formulas (1), (2) and (3), and at the same time, excellent machinability can be ensured. The high yield ratio high strength austenitic stainless steel according to an example may have an elongation of 40% or more.

In particular, the high yield-ratio high-strength austenitic stainless steel according to the present invention controls the alloy composition, Formula (1), Formula (2), and Formula (3), so that the annealing heat treatment temperature after cold rolling is 1000 to 1100 ° C. It is possible to secure high yield ratio and high strength characteristics in the temperature range, and at the same time ensure excellent workability. According to an example, the yield ratio may be 0.5 or more, the yield strength may be 430 MPa or more, the tensile strength may be 850 MPa or more, and the elongation may be 40% or more.

According to the present invention, it is possible to secure high yield ratio and high strength characteristics at 1000 to 1100° C., which is the normal annealing heat treatment temperature range of austenitic stainless steel, and at the same time ensure excellent workability. There is an advantage that the desired physical properties can be achieved only by control.

Hereinafter, the present invention will be described in more detail through examples. However, it is necessary to note that the following examples are only for illustrating 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}

Each of the steel types of the invention and comparative examples having the composition shown in Table 1 below were prepared as austenitic stainless steels by hot rolling-annealing-cold rolling-annealing according to a conventional austenitic stainless steel manufacturing method.

Equation (1) of Table 1 is a value derived by substituting the content (wt%) of each alloying element in Equation (1) below, and means the yield strength index.

(1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si

Equation (2) in Table 1 is a value derived by substituting the content (wt%) of each alloying element in Equation (2) below, and means the Md30 value.

(2) 551 - 462 (C+N) - 9.2Si - 8.1Mn -13.7Cr - 29 (Ni+Cu) - 18.5Mo

Equation (3) of Table 1 is a value derived by substituting the Md30 value according to Equation (2) and the content (wt%) of each alloying element in Equation (3) below, and means the predicted yield ratio.

(3) 0.227 - 0.00116Md30 + 1.13 (C+N)

Alloy composition (wt%) Formula (1) Equation (2) Equation (3) C Si Mn Ni Cr Cu Ti N C+N Invention Example 1 0.12 0.84 2.49 3.5 17.2 1.1 0.009 0.17 0.29 11.28 20.1 0.53 Invention Example 2 0.11 0.78 3.5 3.4 17.3 0.5 0.01 0.21 0.32 11.86 17.5 0.57 Comparative Example 1 0.12 0.63 0.89 7 17.4 0.2 0.011 0.05 0.17 12.85 12.3 0.40 Comparative Example 2 0.12 0.61 0.9 6.8 17 0.2 0.011 0.108 0.228 13.75 -3.1 0.49 Comparative Example 3 0.15 0.6 0.9 6.8 17.1 0.2 0.011 0.1 0.25 14.16 -14.6 0.53 Comparative Example 4 0.12 1.98 2 6.1 17.1 0 0.011 0.097 0.217 5.42 5.2 0.47 Comparative Example 5 0.11 1.46 1.53 3.5 17.3 1.5 0.01 0.15 0.26 7.15 23.0 0.49 Comparative Example 6 0.12 1.53 1.54 4.5 17.2 0.5 0.011 0.14 0.26 6.78 23.7 0.49 Comparative Example 7 0.11 1.51 2.41 4.4 17.1 0 0.01 0.15 0.26 6.70 35.6 0.48

The yield strength (MPa), tensile strength (MPa), elongation (%), and yield ratio of each invention example and comparative example were measured according to the annealing heat treatment temperature after cold rolling of the austenitic stainless steel of Table 1, and the results were obtained. Table 2 shows.

In Table 2, yield strength is expressed as 'YS', tensile strength as 'TS', and elongation as 'EL'.

In Table 2, elongation (%) was measured after stretching the specimen at a tensile rate of 20 mm/min until fracture.

Annealing heat treatment temperature 1000℃ 1050℃ 1100℃ YS
(MPa) ts
(MPa) EL
(%) yield ratio YS
(MPa) ts
(MPa) EL
(%) yield ratio YS
(MPa) ts
(MPa) EL
(%) yield ratio Invention Example 1 544.8 1002.2 42.3 0.54 488.3 906.5 50.9 0.54 466 888.8 52.9 0.52 Invention Example 2 588.4 941.2 46 0.63 537.3 889.7 49.9 0.6 521 874.7 51 0.6 Comparative Example 1 430.5 924.6 44.5 0.47 335.1 798.6 55.6 0.42 315.3 801.9 58 0.39 Comparative Example 2 453.3 865.6 47.7 0.52 391 803.3 55.1 0.49 367.2 786.6 58 0.47 Comparative Example 3 525.8 960 41.4 0.55 403.9 811.3 52.8 0.50 374.7 784.4 55.2 0.48 Comparative Example 4 507.2 968.5 46.1 0.52 432.1 882.5 53.2 0.49 404.2 866.7 55.6 0.47 Comparative Example 5 540.4 1082 37.9 0.5 480.4 998.5 49 0.48 458.7 967.1 48.5 0.47 Comparative Example 6 508 1107.8 43.9 0.46 459.2 1008.6 52.3 0.46 425.4 978 54.2 0.43 Comparative Example 7 521.6 1073 46.6 0.49 465.1 989.7 50 0.47 439.8 983.1 51.9 0.45

Referring to the results of Table 2, Inventive Examples 1 and 2 satisfies all of the alloy compositions defined by the present invention, and the value ranges of Equations (1), (2) and (3). As a result, when the annealing heat treatment temperature was 1000 to 1100 ° C., the yield strength was 430 MPa or more, the tensile strength was 850 MPa or more, the yield ratio was 0.5 or more, and the elongation was 40% or more.

On the other hand, Comparative Examples 1 to 7 did not satisfy the alloy composition or C + N or the value range of Formula (1) or Formula (2) or Formula (3) defined by the present invention. As a result, when the annealing heat treatment temperature was 1000, 1050, 1100 ° C., the yield strength was less than 430 MPa, the yield ratio was less than 0.5, or the elongation was less than 40%.

Comparative Examples 1 to 4 had a C + N value of less than 0.29 wt %, or a value of Formula (1) exceeding 13.0, resulting in low yield strength. As a result, the yield ratio when the annealing heat treatment temperature was 1050 and 1100°C was less than 0.5. In addition, since the value of Formula (2) is less than 17.0, expensive Ni, which is an austenite phase stabilizing element, was added in a large amount in excess of 5 wt%, which is the upper limit of Ni defined by the present invention.

Comparative Examples 5 to 7 had a C+N value of less than 0.29% by weight, and thus the yield strength was low. In addition, since the value of Equation (1) was less than 10.0, the yield strength was lowered, and the tensile strength was increased. In addition, since the value of Equation (2) exceeded 21.0, the degree of stabilization of the austenite phase was lowered and thus the increase in tensile strength could not be suppressed. As a result, the yield ratio at an annealing heat treatment temperature of 1000, 1050, and 1100°C was less than 0.5.

From the above results, it can be seen that according to the present invention, a high yield ratio high strength austenitic stainless steel can be provided by controlling the composition. In addition, according to the present invention, it can be seen that price competitiveness can be secured compared to other steel types by adding Cu and Mn in order to reduce the contents of expensive Ni and Mo and prevent the formation of martensite. In addition, according to the present invention, it is possible to secure high yield ratio and high strength characteristics at 1000 to 1100° C., which is the normal annealing heat treatment temperature range of austenitic stainless steel, and secure excellent workability, so that components without separate heat treatment temperature control It can be seen that there is an advantage in that the desired physical properties can be achieved only by controlling the composition.

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 (7)

By weight%, C: 0.15% or less, N: 0.1 to 0.25%, Si: 0.7 to 2.0%, Mn: 1.5 to 3.5%, Cr: 16 to 18%, Ni: 3 to 5%, Cu: 2% or less , Ti 0.02% or less, the remaining Fe and other unavoidable impurities, and C + N: 0.29% or more,
High yield ratio high strength austenitic stainless steel with a value of formula (1) of 10.0 or more and 13.0 or less:
(1) 5.53 + 1.4Ni - 0.16Cr + 17.1(C+N) + 0.722Mn + 1.4Cu - 5.59Si
In the above formula (1), Ni, Cr, C, N, Mn, Cu, and Si mean the content (% by weight) of each element. According to claim 1,
High yield ratio high strength austenitic stainless steel having an Md30 value of 17.0 to 21.0°C according to the following formula (2):
(2) 551 - 462 (C+N) - 9.2Si - 8.1Mn -13.7Cr - 29 (Ni+Cu) - 18.5Mo
In the above formula (2), C, N, Si, Mn, Cr, Ni, and Cu mean the content (wt%) of each element. 3. The method of claim 2,
High yield ratio high strength austenitic stainless steel with a value of Equation (3) of 0.5 or more:
(3) 0.227 - 0.00116Md30 + 1.13 (C+N)
In Equation (3), Md30 is a value derived according to Equation (2), and C and N mean content (wt%) of each element. According to claim 1,
High yield ratio high strength austenitic stainless steel with a yield ratio of 0.5 or more. According to claim 1,
High yield ratio high strength austenitic stainless steel with a yield strength of 430 MPa or more and a tensile strength of 850 MPa or more. According to claim 1,
High yield ratio high strength austenitic stainless steel with an elongation of 40% or more. According to claim 1,
The austenitic stainless steel is manufactured including cold rolling and then annealing heat treatment, and a high yield ratio high strength austenitic stainless steel with a yield ratio of 0.5 or more when the annealing heat treatment temperature is 1000 to 1100 ° C.