Art
[1]
The invention lean duplex stainless steel, and relates to their preparation, component system of Ni, Mo or the like on minimizing the amount of expensive alloying elements and thermal martensitic transformation and firing the austenite phase to control the organic martensitic transformation phenomenon and ferrite 2 having a phase structure relates to a lean duplex stainless steels and methods for their preparation.
BACKGROUND
[2]
To the general this is a preferred austenitic stainless steel workability and corrosion resistance of iron (Fe) in possession of the metal, chromium (Cr), which contains a nickel (Ni) as the main raw material, molybdenum (Mo) and copper (Cu), etc. there were added the other elements have been developed in a variety of steel grades to fit various applications.
[3]
Although corrosion resistance and workability is excellent austenitic stainless steel is expensive material of Ni, which contains Mo, bar, As an alternative ferritic stainless steel is discussed also, the moldability is not below the austenitic stainless steel has a problem this exists. Because of the impact properties for one or the less the relative forming a rather large amount of molding heat / cold extending plates can be applied also to the ferritic level corrosion resistance due to the operating environment, heat with a ferritic stainless steel and weld deterioration plates as to comply with many restrictions.
[4]
On the other hand, the austenite phase and ferrite phase mixed duplex stainless steel has all the advantages of austenite and ferrite boundaries, there have been developed various types of duplex stainless steel to date.
[5]
U.S. Patent No. 6,096,441 No. (08.01.2000) there-is a "low nickel ferrite having a high tensile elongation of austenitic stainless steel" disclosed. This and the iron in possession of a metal, C: 0.04% or less, Si: 0.4 ~ 1.2%, Mn: 2 ~ 4% or less, Ni: 0.1 ~ 1.0%, Cr: 18 ~ 22%, Cu: 0.05 ~ 4.0%, S: 0.03% or less, P: 0.1% or less, N: 0.1 ~ 0.3%, Mo: 3.0% or less and the other comprising the inevitable impurities, is made in a two-phase of austenite and ferrite, that of the austenite phase 30 to but account for 70%, Creq = Cr (%) + Mo (%) + 1.5Si (%), Nieq = Ni (%) + 0.33Cu (%) + 0.5Mn (%) + 30C (%) + 30N ( a mathematical expression Creq / Nieq 2.3 ~ 2.75 range which is defined as%), IM = 551-805 (C + N) (%) - 8.52Si (%) - 8.57Mn (%) - 12.51Cr (%) --36Ni (%) - 34.5Cu (%) - a mathematical formula IM, defined as 14Mo (%) is characterized in that 40 to 115 range.
[6]
On the other hand, and one of the most widely used duplex stainless steels are used in anti-corrosion environment has AL2205 (UNS S31803 or S32205) having 22% Cr, 5.5% Ni, 3% Mo, 0.16% N components.
[7]
Of the steel have superior corrosion resistance than austenitic of the bar, such as AISI 304, 316 to provide a good corrosion resistance in various corrosive environments.
[8]
However, the duplex stainless steel has a disadvantage competitively priced with other grades falling exists as containing expensive elements such as Ni, Mo bar, as well as the manufacturing cost is raised consumed Ni, Mo, etc.
[9]
Recently, to solve this problem, among the duplex stainless steel, Ni and Mo, such as high-priced alloying elements excluded and, in place of those elements that, by the cost of the alloy elements added in that further enhance the benefits of the alloy cost lean duplex (lean of duplex) has been increasing interest in stainless steel.
[10]
Lean duplex stainless steel is conventional austenitic a Ni content of a note while maintaining the corrosion resistance of 304, equivalent to 316 steel is roughly divided into stainless steel economical and desalination plants, pulp and paper, chemical plant and industrial equipment requiring corrosion resistance and high strength to secure easy It has been in the spotlight as a steel product for use.
[11]
The lean duplex steel for example, and the like S32304 (representative component 23Cr-4Ni-0.13N), S32101 (representative component 21Cr-1.5Ni-5Mn-0.22N), which is standardized in ASTMA240 which is standardized in ASTMA240.
[12]
Lean duplex steel while reducing the manufacturing cost by excluding the expensive element 304, but to secure the corrosion resistance of 304L and 316 steel compared to equivalent or higher level, the time therefore is also when the environment compared to lean duplex lecture using corrosion resistance of over-specification 400 sometimes it requires duplex Steels having the corrosion resistance of the system level occurs.
[13]
Grades one corresponding to these requirements, there are currently no it is not developed, ferritic stainless steel and DBTT properties are very vulnerable to low impact properties of structural factors, due to the coarsening of the weld HAZ portion organizations challenging the plates used as a problem .
[14]
In addition, by simply reducing the Cr, Ni ingredients in conventional lean duplex steel components if you want to decrease the corrosion resistance, the austenite phase stability is reduced austenite phase phenomenon which is transformed to the martensite phase in the cooling stage at room temperature occurred do. That is, in the 20% Cr or less ferrite phase, is difficult to implement a duplex steel structure having a two-phase structure austenite phase, by reducing the elongation of Marte sites phase material formed in the cooling process cause problems processing is not possible, such as the Tube Mill Process .
[15]
(Patent Document 0001) U.S. Patent No. 6,096,441 No. (2000.8.1).
Detailed Description of the Invention
SUMMARY
[16]
Embodiments of the present invention to minimize the amount of expensive alloy elements such as Ni, Mo of component duplex stainless steels and provide lean duplex stainless steels having a two-phase structure on the austenite phase and the ferrite through the Si, N ingredient is controlled.
[17]
In addition, embodiments of the present invention and securing the elongation to give the austenite phase stability at room temperature, to provide a method for producing lean duplex stainless steel capable of ensuring the corrosion resistance of the ferritic steel universal level.
Problem solving means
[18]
Lean duplex stainless steel in accordance with one embodiment of the present invention is, by weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance includes iron (Fe) and other unavoidable impurities.
[19]
Further, according to one embodiment of the invention, the following formula (1) in the ferrite prediction fraction (Ferrite fraction, FF (%)) is a 60 to 80%, the following formula (2) modified in accordance with the Md according to 30 (Modified Md 30 , a MM (℃)) can be equal to or less than 110 ℃.
[20]
FF (%) = 398-146 * C + 9.07 * Si-0.58 * Mn-22.5 * Cr-416N ------ Eq. (1)
[21]
MM(℃) = 551-[462*(C+N)/(1-0.01*FF)]-9.2*Si-8.1*Mn-13.7*Cr ------ 식(2)
[22]
Further, according to one embodiment of the invention, the chromium (Cr) may include 13.5 to 14.5%.
[23]
Further, according to one embodiment of the invention, the stainless steel may be 13.0 to 16.0 Cr equivalent weight according to the following equation (3).
[24]
Cr eq = Cr + 0.48Si + 1.5Mo ------ Eq. (3)
[25]
Further, according to one embodiment of the present invention, it may include a nickel (Ni) not more than 0.05%.
[26]
Further, according to one embodiment of the invention, the stainless steel has a Ni equivalent weight according to the following formula (4) be equal to or less than 5.0.
[27]
Ni + 18N + 30C + Ni eq 0.1Mn = 0.01Mn- 2 ------ Eq. (4)
[28]
Further, according to one embodiment of the invention, the stainless steel, the elongation may be at least 30%.
[29]
Lean duplex stainless steel producing process according to an embodiment of the present invention includes, by weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr ) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance iron (Fe) and other unavoidable step of hot rolling the lean duplex stainless steel slab containing the impurities, the hot-rolled steel sheet annealing annealing at a temperature of 1,050 to 1,150 ℃ and a step, and the water-cooling method comprising a.
[30]
Further, according to one embodiment of the present invention, the hot rolled steel sheet can be annealed heat treatment for 10 to 60 minutes.
Effects of the Invention
[31]
Embodiments of the present invention can save the resources to minimize or eliminate the alloy components such as Cr, Ni, Mo-component of the duplex stainless steel, it is possible to minimize the manufacturing costs of duplex stainless steels.
[32]
In addition, Si, and can be secured by more than 30% elongation through the N component control increasing the stability of the austenite phase at room temperature, it is possible to ensure corrosion resistance of the ferritic steel universal level.
Brief Description of the Drawings
[33]
1 is a three plug Organization (Schaeffler's diagram) for explaining a lean duplex stainless Steel component according to embodiments of the present invention.
[34]
Figure 2 is a photograph as measured with a transmission electron microscope (TEM) of the microstructure lean duplex stainless steels in accordance with one embodiment of the present invention.
[35]
Figure 3 is a lean duplex stainless steels stress according to an embodiment of the present invention - a graph illustrating a correlation between the elongation.
[36]
4 is a formula showing the potential value lean duplex stainless steels in accordance with one embodiment of the invention the chart.
Best Mode for Carrying Out the Invention
[37]
Lean duplex stainless steel in accordance with one embodiment of the present invention is, by weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance includes iron (Fe) and other unavoidable impurities.
Mode for the Invention
[38]
Hereinafter will be described in detail with reference to the accompanying drawings, an embodiment of the present invention. The following examples will be presented to fully convey the scope of the invention to those of ordinary skill in the art. The present invention is not limited to the embodiments described herein may be embodied in different forms. Figures may be somewhat exaggerated to express the size of the components, for clarity, not shown, and a portion not related to the description in order to clarify the invention.
[39]
Lean duplex stainless steel in accordance with one embodiment of the present invention is, by weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance includes iron (Fe) and other unavoidable impurities.
[40]
The amount of carbon (C) 0.05 to 0.1%. Carbon (C) is an effective element to increase the material strength by solid solution strengthening in the austenite phase forming elements. Carbon (C) is to be added is less than 0.05% In order to contribute to the austenite phase stability. Then, carbon (C), when too much is added, the material to form a segregated and coarse carbides of the heart during manufacture, after the step of hot rolling-invading an adverse effect on the cold-rolled annealing process, the ferrite-annealing-cold rolling austenite phase boundary because the carbide, such as available chromium (Cr) in the corrosion-forming elements and easily coupled in reducing corrosion by lowering the chromium (Cr) content of around grain boundaries, the addition in the range of 0.1% or less desirable in order to maximize the corrosion resistance Do.
[41]
The amount of silicon (Si) is from 2.0 to 4.0%. Silicon (Si) is an element which is enriched in the ferrite during annealing heat treatment in the ferrite-forming elements. The content of the lean duplex stainless steel, chromium (Cr) in accordance with embodiments of the present invention lower than a conventional lean duplex stainless steels, it is preferable to add 2.0% to 4.0% in order to ensure proper ferrite phase fraction. However, if the addition of silicon (Si) more than 4.0%, thereby lowering the workability and impact properties by rapidly increasing the hardness of the ferrite phase. Therefore, it is desirable to limit the content of silicon (Si) is 2.0 to 4.0%.
[42]
The amount of manganese (Mn) is 4.0 to 8.0%. Manganese (Mn) is an element for increasing the adjustment, a deoxidizer and a nitrogen solubility melt fluidity, the austenite-forming elements. Manganese (Mn) is added to replace the expensive nickel (Ni). If the manganese (Mn) is less than 4%, the austenite stability is degraded at normal temperatures and is transformed into martensite during the cooling process is difficult to maintain a two-phase structure. If the manganese (Mn) is more than 8%, and the percentage of control is difficult to excessive percentage of austenite phase. Therefore, it is desirable to limit the content of manganese (Mn) to 4.0 to 8.0%.
[43]
The amount of chromium (Cr) is 13.0 to 15.0%. Chromium (Cr) is preferable to minimize the manufacturing cost reduction aspect of duplex stainless steels, conventional limit to less than 15% so as to lean out of the duplex stainless steel components range. However, it is preferred to add more than 13% for securing the corrosion resistance of duplex stainless steels. Therefore, it is desirable to limit the content of chromium (Cr) 13.0 to 15.0%. More preferably, the lean duplex stainless steel may comprise chromium (Cr) 13.5 to 14.5%.
[44]
The amount of nitrogen (N) 0.05 to 0.15%. Nitrogen (N) is one of the elements that are concentrated in the austenite phase when an element which contributes to stabilize austenite phase with nickel (Ni), the annealing heat treatment in duplex stainless steels.
[45]
Thus, by increasing the content of nitrogen (N), but could seek to Incidentally, corrosion resistance and improved strength, because the employment of the nitrogen (N) can be varied according to the content of the added manganese (Mn), the content control this is necessary.
[46]
If in manganese (Mn) range of the present invention, nitrogen (N) content exceeds 0.15%, and the like, the blow holes (blow hole) and a pin hole (pin hole) during casting by excess FIG nitrogen employment occurs, the product there are surface flaws and edge cracks during rolling (edge ​​crack) problems that occur. Therefore, it is desirable to limit the content of nitrogen (N) 0.05 to 0.15%.
[47]
For example, the lean duplex stainless steel in accordance with one embodiment of the present invention may include a nickel (Ni) not more than 0.05%. Nickel (Ni) is an element which contributes to stabilize austenite phase, together with the nitrogen (N) in a duplex stainless steel.
[48]
If the amount of nickel (Ni) exceeds 0.05%, there is a problem that the manufacturing cost increases in the amount of the expensive metal of nickel (Ni) increase.
[49]
For example, ferrite prediction fraction (Ferrite fraction, FF (%)) of the lean duplex stainless steel has the following formula (1) according to one embodiment of the present invention are a 60 to 80%, according to the following formula (2) modified Md 30 (modified Md 30 , MM (℃)) has a number equal to or less than 110 ℃.
[50]
FF (%) = 398-146 * C + 9.07 * Si-0.58 * Mn-22.5 * Cr-416N ------ Eq. (1)
[51]
MM(℃) = 551-[462*(C+N)/(1-0.01*FF)]-9.2*Si-8.1*Mn-13.7*Cr ------ 식(2)
[52]
For example, the austenite phase after annealing heat treatment, the transformation phase in the cooling stage in the martensitic, or, in the case of a sudden transformation of the phase transformation during the martensite phase, modified Md according to the formula (2) 30 to greater than 110 ℃, lean duplex stainless steel appears to be less than 30% elongation river, it is specifically highly susceptible processability from about 10 to 15%.
[53]
For example, the stainless steel may be 13.0 to 16.0 Cr equivalent weight according to the following equation (3).
[54]
Cr eq = Cr + 0.48Si + 1.5Mo ------ Eq. (3)
[55]
For example, the stainless steel may be less than the equivalent of Ni according to the following formula (4) 5.0.
[56]
Ni + 18N + 30C + Ni eq 0.1Mn = 0.01Mn- 2 ------ Eq. (4)
[57]
1 is a three plug Organization (Schaeffler's diagram) for explaining a lean duplex stainless Steel component according to embodiments of the present invention.
[58]
1, that is, the lean duplex stainless steel in accordance with one embodiment of the present invention, chromium (Cr) and nickel (Ni) is decreased content of as the Cr equivalent and Ni equivalent weight decreases, the old lean duplex steel than Cr, Ni equivalent is can be seen that located in the lower region.
[59]
In general, this area is the austenite phase stability at room temperature is lowered. Due to this, the processability and the impact characteristics will drop sharply as after annealing heat treatment, transformed into the austenite phase of martensite in the cooling stage.
[60]
However, to suppress the transformation phenomena compensate for the content, and of such low chromium (Cr), nickel (Ni) in the present invention, was to ensure the stability of austenite phase by controlling the content of silicon (Si) more than 2.0%, by controlling the amount of additional nitrogen (N) less than 0.15% was to suppress the martensitic transformation drive force.
[61]
Accordingly, it is possible to secure an elongation of 30% or more by increasing the stability of the austenite phase in the lean duplex stainless steels of the present invention at room temperature, it is possible to ensure corrosion resistance of the ferritic steel universal level.
[62]
Lean duplex stainless steel producing process according to an embodiment of the present invention includes, by weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr ) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance iron (Fe) and other inevitable, and the lean duplex stainless steel slab containing the impurities, hot-rolling, the hot-rolled steel sheet annealing annealing at a temperature of 1,050 to 1,150 ℃ and , water-cooling to prepare a lean duplex stainless steels.
[63]
Lean duplex stainless steel slab of the said composition is a plate can be rolled in the usual manner, the hot-rolled steel sheet may be a thickness of 5 to 20mm.
[64]
For example, the hot-rolled steel sheet is annealed for heat treatment at a temperature of 1,050 to 1,150 ℃ 10 to 60 minutes.
[65]
The component system and under the heat treatment condition is the microstructure without a martensitic phase transformation occurs during the cooling stage the ferrite phase and the second phase structure on the austenite is retained ferrite phase fraction is maintained at 60 to 80% and modified Md 30 is less than 110 ℃ a value may have.
[66]
[67]
The present invention through the following embodiments to be described in more detail.
[68]
Invention steel and comparative steel
[69]
To after manufacturing the lean duplex stainless steel slab containing the component in accordance with each of the inventive steels and the comparative steels in Table 1, the rolled steel plate to thereby prepare a steel plate rolled specimen of 10mmt.
[70]
To Table 1, it is shown the composition of the target low-cost grades Steels lean duplex stainless steel of the present invention. In particular, where the chromium to a profound effect on the securing or more corrosion level STS 409 steel (Cr) 13.5 to 14.5%, manganese (Mn) is fixed in a 5.5 to 6.5% range, and silicon (Si), nitrogen (N) given a change in the content it was prepared.
[71]
TABLE 1
C And Mn Cr N
Invention steel 1 0.048 2.47 5.93 13.87 0.051
Invention steel 2 0.048 3.04 6.12 14.02 0.053
Invention steel 3 0.047 3.07 6.1 13.94 0.097
Comparative Steel 1 0.064 1.02 6.01 13.98 0.048
Comparative Steel 2 0.047 1.99 5.87 13.95 0.047
Comparative Steel 3 0.05 4.1 6.08 14.1 0.052
Comparative Steel 4 0.051 3.03 6.04 13.87 0.151

[72]
[73]
It was then held for 30 minutes of rolling the steel plate specimen as the annealing temperature 1,100 ℃ and evaluate after the water cooling, the material, the characteristic change, tensile properties and corrosion resistant properties.
[74]
TABLE 2
Whether martensitic phase transformation Ferrite prediction fraction (%) Modified Md 30 value (℃) Elongation (%) Other
Invention steel 1 × 76.7 94.2 32.5 -
Invention steel 2 × 77.5 73.8 31.9 -
Invention steel 3 × 61.4 109.8 31.2 -
Comparative Steel 1 ○ 59.9 172.4 10.2 -
Comparative Steel 2 × 72.4 136.9 15.3 -
Comparative Steel 3 × 85.5 -53.7 - Brittle fracture occurs
Comparative Steel 4 × 39.6 129.3 30.8 Edge cracks

[75]
[76]
When transformation by observing the structure of the table 2 in the inventive steels 1 to 3 and the comparative steels 1 to 4 determine whether or not the transformation into the martensitic ○, are shown in the non-transformed during ×. In addition, the ferrite fraction and the modified prediction Md 30 value was calculated with reference to the composition and the formula (1), (2) in Table 1. The elongation-related, in the rolling direction at the time of temperature tensile test by sampling the ASTM-sub size tensile specimen is defined as room temperature, to obtain a strain rate 20mm / min, it was carried out a tensile test.
[77]
Figure 2 is a photograph as measured with a transmission electron microscope (TEM) of the microstructure lean duplex stainless steels in accordance with one embodiment of the present invention.
[78]
Figure 2 shows the microstructure of the invention steel 1 of the present invention. Also, without transformation to the factory, the austenite phase of martensite phase in the composition range of the present invention, it can be seen that the retained austenite phase, as shown in picture 2 tissue.
[79]
Table 1 and referring to Table 2, it is less than 1.0% to 2.0% of the content of silicon (Si), austenite phase transformed in the cooling stage in the martensitic, or rapid transformation (modification of the phase transformation during calcination the organic martensite Md 30 due to this exceeds 110 ℃) and confirmed that the elongation, the workability is very vulnerable from 10 to 15%. Further, the silicon (Si) content is in excess of 4.0%, fraction of ferrite phase and due to the hardness brittle fracture is induced during the processing of the specimen is preferably limited to less than 4.0%.
[80]
Therefore, this is, the stability of austenite during maintenance increasing the content of silicon (Si) is 2.0 to 4.0% modified Md 30 is kept below the 110 ℃ is possible elongation of 30% or more to secure workability.
[81]
It is preferable that since the case of nitrogen (N) content silsuyul by rolling edge cracking during bundles exceeds 0.15% degradation, limited to not more than 0.15%.
[82]
Figure 3 is a lean duplex stainless steels stress according to an embodiment of the present invention - a graph illustrating a correlation between the elongation.
[83]
3 shows a graph of the tensile properties invention steel 1 and the comparative steel 2 of the present invention.
[84]
In the rolling direction at the time of temperature tensile test by sampling the ASTM-sub size tensile specimen is defined as room temperature, to obtain a strain rate 20mm / min, it was carried out a tensile test.
[85]
When the content of silicon (Si) less than 2.0%, it was because of the rapid transformation of the strain during the plastic organic martensite it sees that is not possible to secure a desired elongation. Accordingly, it is retained at the austenite phase stability, the content of silicon (Si) is 2.0 to 4.0% increase was found that more than 30% elongation securing are possible.
[86]
4 is a formula showing the potential value lean duplex stainless steels in accordance with one embodiment of the invention the chart.
[87]
Figure 4 is a comparison of the formal potential value, a general purpose ferritic robust STS 409 steel, STS 430 River formula potential values ​​of the final first invention of the present invention graph.
[88]
The inventive steels 1 and the STS 409 steel, STS 430 steel in the 1.0% NaCl solution is shown in Figure 4 to measure the potential of each formula sample. Accordingly, the lean duplex stainless steel in accordance with one embodiment of the present invention could be confirmed by having a corrosion resistant property between the STS 409 steel STS 430 steel.
[89]
In the above-described bar, although the description has been made to exemplary embodiments of the present invention, in the present invention is not limited to those skilled in the art without departing from the spirit and scope of the claims set forth in the following it will be appreciated from the various changes and modifications are possible.
Industrial Applicability
[90]
Lean duplex stainless steel and the manufacturing method thereof according to embodiments of the present invention can be applied to desalination plants, pulp and paper, chemical plants and industrial plants for steel.
[91]
[92]

Claims
[Claim 1]
By weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance iron lean duplex stainless steels that includes (Fe) and other inevitable impurities.
[Claim 2]
The method of claim 1, wherein the following formula (1) ferrite prediction fraction (Ferrite fraction, FF (%)) is a 60 to 80%, the following formula (2) modified Md according to according to 30 (Modified Md 30 , MM (℃ )) lean duplex stainless steels, characterized in that not more than 110 ℃. FF (%) = 398-146 * C + 9.07 * Si-0.58 * Mn-22.5 * Cr-416N ------ formula (1) MM (℃) = 551- [462 * (C + N) / (1-0.01 * FF)] - 9.2 * Si-8.1 * Mn-13.7 * Cr ------ Eq. (2)
[Claim 3]
The method of claim 1, wherein the lean duplex stainless steel the chromium (Cr), characterized in that it comprises 13.5 to 14.5%.
[Claim 4]
According to claim 1, wherein the lean duplex stainless steel as the stainless steel is characterized in that the Cr equivalent in accordance with the following equation (3) of 13.0 to 16.0 in. Cr eq = Cr + 0.48Si + 1.5Mo ------ Eq. (3)
[Claim 5]
The method of claim 1, wherein the lean duplex stainless steel comprises a nickel (Ni) not more than 0.05%.
[Claim 6]
According to claim 1, wherein the lean duplex stainless steel, the stainless steel which is the equivalent of Ni according to the following formula (4), characterized in that not more than 5.0 in. Ni + 18N + 30C + Ni eq 0.1Mn = 0.01Mn- 2 ------ Eq. (4)
[Claim 7]
The method of claim 1, wherein the lean duplex stainless steels, characterized in that at least the stainless steel, the elongation was 30%.
[Claim 8]
By weight%, carbon (C) 0.05 to 0.1%, silicon (Si) 2.0 to 4.0%, manganese (Mn) 4.0 to 8.0%, chromium (Cr) 13.0 to 15.0%, nitrogen (N) 0.05 to 0.15%, the balance iron (Fe) and other unavoidable step of hot rolling the lean duplex stainless steel slab containing the impurities; The hot-rolled steel sheet comprising: annealing heat treatment at a temperature of 1,050 to 1,150 ℃; And a method for producing lean duplex stainless steel comprising the step of water-cooling.
[Claim 9]
The method of claim 8, wherein the method for producing lean duplex stainless steels, which the hot-rolled steel sheet is characterized in that annealing heat treatment for 10 to 60 minutes.