WO2020036370A1 - Austenitic stainless steel having improved strength - Google Patents

Austenitic stainless steel having improved strength Download PDF

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WO2020036370A1
WO2020036370A1 PCT/KR2019/009977 KR2019009977W WO2020036370A1 WO 2020036370 A1 WO2020036370 A1 WO 2020036370A1 KR 2019009977 W KR2019009977 W KR 2019009977W WO 2020036370 A1 WO2020036370 A1 WO 2020036370A1
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stainless steel
austenitic stainless
content
improved strength
less
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PCT/KR2019/009977
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French (fr)
Korean (ko)
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이재화
조규진
김영태
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주식회사 포스코
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Priority to FIEP19849274.6T priority Critical patent/FI3822384T3/en
Priority to CN201980065501.9A priority patent/CN112789365B/en
Priority to US17/266,011 priority patent/US20210292877A1/en
Priority to EP19849274.6A priority patent/EP3822384B8/en
Publication of WO2020036370A1 publication Critical patent/WO2020036370A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

Definitions

  • the present invention relates to an austenitic stainless steel, and more particularly, to an austenitic stainless steel having improved strength while maintaining elongation and corrosion resistance.
  • stainless steel refers to steel having strong corrosion resistance because corrosion, which is a weak point of carbon steel, is suppressed.
  • stainless steel is classified according to chemical composition or metal structure. According to the metal structure, stainless steel can be classified into austenitic, ferrite, martensite and dual phase systems.
  • austenitic stainless steel is most commonly used as a steel containing a large amount of chromium (Cr) and nickel (Ni).
  • Cr chromium
  • Ni nickel
  • 316L stainless steel is applied to various industrial fields by securing corrosion resistance and molding properties based on 16-18% Cr, 10-14% Ni, and 2-3% Molybdenum based component system. have.
  • Ni and Mo have problems in terms of price competitiveness due to high material prices, and raw material supply and demand are unstable due to extreme fluctuations in material prices and it is difficult to secure stability of supply prices.
  • 216 stainless steel is basically a steel with 7% or more of Mn added to reduce the Ni content below a certain amount to lower the material price and to ensure the stability of the austenite phase according to the Ni reduction. Cr, 5-7% Ni, 7.5-9% Mn and 2-3% Mo.
  • 216 stainless steel can achieve corrosion resistance similar to that of 316L stainless steel, but due to the addition of a large amount of Mn, a large amount of Mn fume is generated during the steelmaking process.
  • MnS rigid inclusions
  • Duplex stainless steel is a stainless steel having a microstructure in which the austenitic phase and the ferrite phase are mixed. Specifically, the austenitic stainless steel and the ferritic stainless steel are characterized by the presence of about 35 to 65% by volume of the austenitic phase and the ferrite phase, respectively. Indicates both.
  • Duplex stainless steel is getting the spotlight as industrial steel such as desalination equipment, pulp, paper, and chemical facilities that require corrosion resistance with low Ni content and easy to secure high strength with low Ni content while securing corrosion resistance equivalent to 316L stainless steel.
  • Embodiments of the present invention to provide an austenitic stainless steel with improved strength while ensuring elongation and corrosion resistance of the existing 316L stainless steel.
  • Austenitic stainless steel with improved strength according to an embodiment of the present invention, in weight percent, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni : 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, the remainder containing Fe and unavoidable impurities, represented by the following formula (1):
  • the SNL (Solubility of Nitrogen in Liquid) value is more than the content of N.
  • C + N may be 0.5% or less (excluding 0).
  • it may further include at least one of B: 0.001 to 0.005% and Ca: 0.001 to 0.003%.
  • Md 30 value represented by the following formula (2) may satisfy -50 or less.
  • C, N, Si, Mn, Cr, Ni, Cu, Mo means the content (% by weight) of each element.
  • Equation (3) Creq / Nieq ⁇ 1.8
  • the pitting index value represented by the following formula (4) may satisfy 22 or more.
  • the yield strength (0.2 off-set) of the austenitic stainless steel may be 400 to 450 MPa, tensile strength 700 to 850 MPa.
  • the elongation of the austenitic stainless steel may be 35% or more.
  • an austenitic stainless steel with improved strength while ensuring elongation and corrosion resistance of the existing 316L stainless steel.
  • Thermocalc for deriving the SNL (Solubility of Nitrogen in Liquid) value of the austenitic stainless steel according to an embodiment of the present invention. This is a graph to explain the correlation between the calculation result and the regression application value.
  • Austenitic stainless steel with improved strength according to an embodiment of the present invention, in weight percent, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni : 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, the remainder containing Fe and unavoidable impurities, represented by the following formula (1):
  • the SNL (Solubility of Nitrogen in Liquid) value is more than the content of N.
  • Austenitic stainless steel with improved strength according to an aspect of the present invention, in weight%, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni: 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, and the balance includes Fe and unavoidable impurities.
  • the content of C is 0.02 to 0.14%.
  • Carbon (C) is an element effective for stabilizing austenite phase, but when the content is low, it may be added at least 0.02% as an additional austenite stabilizing element is required. However, if the content is excessive, not only the workability is lowered by the solid solution strengthening effect, but also it may adversely affect the ductility, toughness and corrosion resistance by inducing grain boundary precipitation of Cr carbide due to heat affected zone of welded part and latent heat after hot rolled coiling. Therefore, the upper limit can be limited to 0.14%.
  • the content of Si is 0.2 to 0.6%.
  • Si Silicon
  • Si may be added as 0.2% or more as an effective element to improve the corrosion resistance while acting as a deoxidizer during the steelmaking process.
  • Si is an effective element for stabilizing ferrite phase, and when excessively added, it promotes the formation of delta ferrite in the cast slab, which not only decreases the hot workability but also decreases the ductility / toughness of the steel due to the solid solution effect. It can be limited.
  • the content of Mn is 2.0 to 4.5%.
  • Manganese (Mn) is an austenite-stable stabilizing element added in place of nickel (Ni) in the present invention, is effective in improving the cold rolling properties by suppressing the production of organic martensite, solubility of nitrogen (N) during steelmaking process to be described later 2.0% or more may be added as an element to increase.
  • the upper limit can be limited to 4.5% because it may decrease the ductility, toughness and corrosion resistance of the steel as it increases the S-based inclusions (MnS).
  • the content of Ni is 2.5 to 5.0%.
  • Nickel (Ni) is a strong austenite stabilizing element, which is essential to ensure good hot workability and cold workability. In particular, addition of more than 2.5% is essential even if a certain amount or more of Mn is added. However, Ni is an expensive element, which leads to an increase in raw material cost when a large amount is added. Therefore, the upper limit can be limited to 5.0% in consideration of both the cost and efficiency of the steel.
  • the content of Cr is 19 to 22%.
  • chromium (Cr) is a ferrite stabilizing element, it is effective in suppressing martensitic phase formation and is a basic element for securing corrosion resistance required for stainless steel.
  • 19% or more may be added as an element to increase the solubility of nitrogen (N) during the steelmaking process described later.
  • N solubility of nitrogen
  • austenite stabilizing elements such as Ni, Mn, etc.
  • the upper limit can be limited to 22%.
  • the content of P is less than 0.1%.
  • Phosphorus (P) can limit the upper limit to 0.1% as it reduces corrosion resistance and hot workability.
  • the content of S is less than 0.01%.
  • S Sulfur
  • S can limit the upper limit to 0.01% as it lowers the corrosion resistance and hot workability.
  • the content of Cu is 1.0 to 3.0%.
  • Copper (Cu) is an austenite stabilizing element added in place of nickel (Ni) in the present invention, and improves the moldability by improving the corrosion resistance in a reducing environment and reducing the stacking fault energy (SFE). 1.0% or more may be added to fully express this effect. However, if the content is excessive, the upper limit can be limited to 3.0% because not only the increase in material cost but also the hot workability can be lowered.
  • the content of Mo is less than 1.0%.
  • Molybdenum (Mo) is an element effective in improving the corrosion resistance of stainless steel by modifying a passive film.
  • Mo is an expensive element
  • the addition of a large amount of raw materials not only increases the raw material cost but also lowers the hot workability. Therefore, the upper limit may be limited to 1.0% in consideration of cost-efficiency and hot workability of the steel.
  • the content of N is 0.25 to 0.40%.
  • Nitrogen (N) is an effective element for improving corrosion resistance and is a strong austenite stabilizing element. Therefore, nitrogen alloying can reduce the material cost by enabling lower use of Ni, Cu, Mn. 0.25% or more may be added to fully express this effect. However, if the content is excessive, the upper limit can be limited to 0.40% because the workability and formability may be reduced by the solid solution strengthening effect.
  • the content of C + N is 0.5% or less.
  • C and N are effective elements for improving strength, but when the content is excessive, there is a problem of degrading workability, and the upper limit of the total can be limited to 0.5%.
  • the austenitic stainless steel with improved strength according to an embodiment of the present invention may further include one or more of B: 0.001 to 0.005 and Ca: 0.001 to 0.003%.
  • the content of B is 0.001 to 0.005%.
  • Boron (B) is an effective element for suppressing the occurrence of cracks during casting to ensure good surface quality, can be added 0.001% or more. However, if the content is excessive, the surface quality can be reduced by forming nitride (BN) on the surface of the product during the annealing / pickling process, the upper limit can be limited to 0.005%.
  • the content of Ca is 0.001 to 0.003%.
  • Calcium (Ca) is an element that suppresses the formation of MnS steelmaking inclusions generated at the grain boundary when containing high Mn and improves the cleanliness of the product, and may be added at least 0.001%. However, when the content is excessive, the hot workability due to the formation of Ca-based inclusions and the surface quality of the product may be lowered, and the upper limit thereof may be limited to 0.003%.
  • the remaining component of the present invention is iron (Fe).
  • impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, not all of them are specifically mentioned in the present specification.
  • the content of N that can be dissolved within the melt temperature at 1150 ° C. is derived according to the amount of each alloy element (C, Si, Mn, Ni, Cr, Cu, Mo) It was.
  • Thermocalc for deriving SNL (Solubility of Nitrogen in Liquid) value of the austenitic stainless steel according to an embodiment of the present invention. This is a graph to explain the correlation between the calculation result and the regression application value.
  • the limit value of the solid solution of nitrogen in the molten metal was calculated and expressed as "N.”
  • the SNL value is greater than the N content.
  • the SNL value is set higher than the N content to increase the nitrogen solubility limit, it was confirmed that the steelmaking operation of the target alloy component is performed well.
  • Austenitic stainless steels are applied to products requiring a beautiful surface.
  • Bright annealing of cold rolled materials is common for products requiring a beautiful surface.
  • Such bright annealing is performed during the heat treatment process of the stainless steel cold rolled material by performing heat treatment of the stainless steel cold rolled material under a reducing atmosphere (Dew point -40 to -60 ° C) using nitrogen (N 2 ), hydrogen (H 2 ), or the like.
  • N 2 nitrogen
  • H 2 hydrogen
  • Bright annealing using hydrogen is the most common atmosphere gas used for bright annealing, because it is most widely used to suppress discoloration of the surface as well as high heat capacity.
  • the hydrogen atoms penetrated into the surface layer are naturally baked out after a certain time at room temperature for ferrite or martensite phases having a general BCC and BCT structure so that they do not significantly affect physical properties.
  • the amount of martensite phase formed on the surface of the austenitic stainless steel together with the alloying components must be controlled to secure beautiful surface quality and workability through bright annealing.
  • the Md 30 value represented by the following formula (2) satisfies the range of -50 ° C or less.
  • martensite transformation occurs by plastic working at a temperature higher than the martensite transformation start temperature (Ms).
  • Ms martensite transformation start temperature
  • the upper limit temperature which causes phase transformation by such a process is represented by Md value, and is a measure which shows the extent to which phase transformation occurs by processing.
  • the temperature (° C.) at which 50% phase transformation to martensite occurs when 30% strain is given is defined as Md 30 . If the Md 30 value is high, it is easy to form a processed organic martensite phase, whereas if the Md 30 value is low, it can be judged to be a relatively difficult steel type. In general, the Md 30 value is used as an index for determining the austenite stabilization degree of ordinary austenitic stainless steel, and can be calculated through the Nohara regression equation represented by Equation (2).
  • Forming various kinds of phases by the difference in alloy content is because the effect of each alloy component added on the phase balance is different.
  • the degree that each alloy component affects the phase balance can be calculated through Creq and Nieq, and the phase generated at room temperature can be predicted through the Creq / Nieq ratio expressed as in Equation (3) below.
  • Creq Cr + Mo + 1.5 ⁇ Si
  • Nieq Ni + 0.5 ⁇ Mn + 30 ⁇ (C + N) + 0.5 ⁇ Cu.
  • the PREN value was set to 22 or more.
  • a slab having a thickness of 200 mm was prepared through ingot melting, and heated at 1,240 ° C. for 2 hours, followed by hot rolling to prepare a hot rolled steel sheet having a thickness of 3 mm.
  • Example 1 0.104 0.48 2.91 0.005 3.53 20.8 2.1 0.52 0.3 0.404
  • Example 2 0.103 0.49 3.4 0.005 3.35 19.6 1.16 0.39 0.27 0.373
  • Example 3 0.088 0.31 3.41 0.004 3.7 21.7 2.51 0.10 0.34 0.428
  • Example 4 0.035 0.31 3.8 0.006 4.2 21 2.48 0.20 0.33 0.365
  • Comparative Example 1 0.02 0.52 1.4 0.004 10.4 16.6 0.39 2.00 0.018 0.038
  • Comparative Example 2 0.014 0.55 2.4 0.006 2.4 20.3 0.1 1.30 0.2 0.166
  • Comparative Example 4 0.15 0.46 3.8 0.004 3.6 21.6 2.04 0.32 0.35 0.500
  • the mechanical properties were measured using No. 5 test piece specified in Japanese Industrial Standard JIS Z 2201. Specifically, the tensile test was conducted using JIS Z 2201, yield strength (MPa), tensile strength (Tensile Strength, MPa) and elongation (%) measured accordingly are described in Table 2 below. .
  • the comparative example 1 corresponding to the component system of general 316L stainless steel, it shows the structure comprised by the austenite phase and showing PREN value of 22 or more.
  • the mechanical property evaluation results show a yield strength of 220 MPa and a tensile strength of 540 MPa, which are generally applied to materials requiring high strength due to the properties of soft austenitic stainless steels. There is a problem that is difficult to do.
  • Comparative Example 3 in which the content of Ni and Mn was slightly increased compared to Comparative Example 2 and the Creq / Nieq ratio was set to 1.8 or less, a microstructure was observed to form austenitic tissue, and the mechanical properties of Comparative Example 1 It is harder than 316L, and it can be seen that it shows soft physical properties compared to Duplex stainless steel of Comparative Example 2.
  • the Md 30 value is -5 °C, which is highly likely to cause hydrogen embrittlement in the future production of bright annealing materials.
  • the N content is significantly affected by the content of Cr is low, the addition amount of N to 0.21% level, it is not possible to maximize the nitrogen factor of the PREN value, there is a problem that it is difficult to secure the pitting resistance of 316L level.
  • the C + N content is 0.5%, exceeding the upper limit of 0.5% of the present invention, showing hard mechanical properties, and an elongation of less than 35%.
  • the Ni and Mo contents were relatively low, and it was confirmed that the PREN value was more than 22 while securing price competitiveness, and the mechanical property evaluation showed that high strength properties were achieved compared to 316L and good elongation of 35% or more was obtained. It was.
  • Austenitic stainless steel according to the present invention can be used as a substitute material of the existing 316L stainless steel while improving the strength while ensuring elongation and corrosion resistance.

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Abstract

An austenitic stainless steel having improved strength is disclosed. The disclosed austenitic stainless steel comprises, by wt%, 0.02-0.14% of C, 0.2-0.6% of Si, S in an amount less than 0.01%, 2.0-4.5% of Mn, 2.5-5.0% of Ni, 19.0-22.0% of Cr, 1.0-3.0% of Cu, Mo in an amount less than 1.0%, 0.25-0.40% of N, and the balance of Fe and inevitable impurities, wherein the value of solubility of nitrogen in liquid (SNL) expressed by the following relation (1) is greater than or equal to the amount of N. Relation (1): SNL= -0.188- 0.0423×C -0.0517×Si+ 0.012×Mn +0.0048×Ni + 0.0252×Cr -0.00906×Cu +0.00021×Mo, wherein C, Si, Mn, Ni, Cr, Cu and Mo mean the amount (wt%) of the respective elements.

Description

강도가 향상된 오스테나이트계 스테인리스강Austenitic stainless steel with improved strength
본 발명은 오스테나이트계 스테인리스강에 관한 것으로, 특히 연신율 및 내식성을 확보하면서도 강도가 향상된 오스테나이트계 스테인리스강에 관한 것이다.The present invention relates to an austenitic stainless steel, and more particularly, to an austenitic stainless steel having improved strength while maintaining elongation and corrosion resistance.
스테인리스강(Stainless Steel)은 탄소강의 약점인 부식이 억제되어 강한 내식성을 보유한 강재를 칭한다. 일반적으로 스테인리스강은 화학성분이나 금속조직에 따라 분류한다. 금속조직에 따를 경우, 스테인리스강은 오스테나이트(Austenite)계, 페라이트(Ferrite)계, 마르텐사이트(Martensite)계 그리고 이상(Dual Phase)계로 분류할 수 있다. Stainless steel refers to steel having strong corrosion resistance because corrosion, which is a weak point of carbon steel, is suppressed. Generally, stainless steel is classified according to chemical composition or metal structure. According to the metal structure, stainless steel can be classified into austenitic, ferrite, martensite and dual phase systems.
그 중에서도 오스테나이트계 스테인리스강은 크롬(Cr)과 니켈(Ni)을 다량 함유하는 강으로, 가장 일반적으로 사용되고 있다. 예를 들어 316L 스테인리스강의 경우, 16~18%의 Cr, 10~14%의 Ni 그리고 2~3%의 몰리브덴(Mo)을 기반으로 한 성분계로 내식성 및 성형특성을 확보함으로써 다양한 산업분야에 적용되고 있다.Among them, austenitic stainless steel is most commonly used as a steel containing a large amount of chromium (Cr) and nickel (Ni). For example, 316L stainless steel is applied to various industrial fields by securing corrosion resistance and molding properties based on 16-18% Cr, 10-14% Ni, and 2-3% Molybdenum based component system. have.
하지만 Ni 및 Mo의 경우 높은 소재 가격으로 인하여 가격경쟁력 측면에서 문제가 있고, 소재 가격의 극심한 변동에 의해 원료수급이 불안정할 뿐만 아니라 공급가의 안정성 확보가 어려운 상황이다. However, Ni and Mo have problems in terms of price competitiveness due to high material prices, and raw material supply and demand are unstable due to extreme fluctuations in material prices and it is difficult to secure stability of supply prices.
따라서, Ni 및 Mo의 함량을 줄이면서도 종래 316L 스테인리스강 수준의 내식성 및 성형성을 확보하기 위한 연구가 진행되었다. 이러한 316L 스테인리스강의 대체강으로써 Ni을 줄이고 Mn의 함량을 증가시킨 200계 스테인리스강, 예를 들어 216강이 개발되었다. Therefore, research has been conducted to secure the corrosion resistance and formability of the conventional 316L stainless steel while reducing the content of Ni and Mo. As a substitute of 316L stainless steel, 200-based stainless steel, for example, 216 steel, which has reduced Ni and increased Mn content, has been developed.
216 스테인리스강은 기본적으로 Ni 함량을 일정량 이하로 감소시켜 소재가격을 낮춤과 동시에 Ni 감소분에 따른 오스테나이트상의 안정도 확보를 위해 7% 이상 다량의 Mn을 첨가한 강으로, 중량 %로 17.5~22% Cr, 5~7% Ni, 7.5~9% Mn 그리고 2~3% Mo을 함유한다. 216 stainless steel is basically a steel with 7% or more of Mn added to reduce the Ni content below a certain amount to lower the material price and to ensure the stability of the austenite phase according to the Ni reduction. Cr, 5-7% Ni, 7.5-9% Mn and 2-3% Mo.
이러한 성분계 설계에 의해, 216 스테인리스강은 316L 스테인리스강과 유사한 수준의 내식성을 확보할 수 있지만, 다량의 Mn 첨가에 의해 제강공정 중 다량의 Mn 흄 발생으로 인하여 환경적 측면에서 개선이 요구될 뿐만 아니라 제강성 개재물(MnS) 생성 시 제조공정상의 생산성 저하 및 최종 소재의 표면 품질 저하를 초래한다.With this component system design, 216 stainless steel can achieve corrosion resistance similar to that of 316L stainless steel, but due to the addition of a large amount of Mn, a large amount of Mn fume is generated during the steelmaking process. The production of rigid inclusions (MnS) results in reduced productivity in the manufacturing process and in surface quality of the final material.
한편. 316L 스테인리스강 대체강으써 듀플렉스 스테인리스강(Duplex Stainless steel)을 들 수 있다. Meanwhile. An alternative to 316L stainless steel is Duplex Stainless Steel.
듀플렉스 스테인리스강은 오스테나이트 상과 페라이트 상이 혼합된 미세조직을 갖는 스테인리스강으로, 구체적으로 오스테나이트상과 페라이트상이 각각 부피분율로 약 35~65% 존재하여 오스테나이트계 스테인리스강과 페라이트계 스테인리강의 특징을 모두 나타낸다.Duplex stainless steel is a stainless steel having a microstructure in which the austenitic phase and the ferrite phase are mixed. Specifically, the austenitic stainless steel and the ferritic stainless steel are characterized by the presence of about 35 to 65% by volume of the austenitic phase and the ferrite phase, respectively. Indicates both.
듀플렉스 스테인리스강은 316L 스테인리스강과 동등한 내식성을 확보하면서 Ni 함량이 적어 경제적이면서도 고강도의 확보가 용이하여 내식성을 요하는 담수설비, 펄프, 제지, 화학설비 등의 산업설비용 강재로 각광을 받고 있다.  Duplex stainless steel is getting the spotlight as industrial steel such as desalination equipment, pulp, paper, and chemical facilities that require corrosion resistance with low Ni content and easy to secure high strength with low Ni content while securing corrosion resistance equivalent to 316L stainless steel.
특히, 듀플렉스 스테인리스강 중에서도 Ni 및 Mo 등의 고가의 합금원소를 감소시켜 19~23%의 Cr, 1.8~3.5%의 Ni, 0~2%의 Mn 그리고 0.5~1.0%의 Mo로 제한하고 0.16~0.3%의 고질소 첨가를 통해서 낮은 합금 비용의 장점을 더욱 부각시킨 린 듀플렉스(Lean Duplex) 스테인리스강에 관한 연구가 활발히 진행되고 있다. In particular, among the duplex stainless steels, expensive alloying elements such as Ni and Mo are reduced to 19-23% Cr, 1.8-3.5% Ni, 0-2% Mn and 0.5-1.0% Mo, and 0.16 ~ Research on lean duplex stainless steel has been actively carried out, with the addition of 0.3% high nitrogen, further highlighting the advantages of low alloy cost.
하지만 린 듀플렉스 스테인리스강의 경우, 오스테나이트와 페라이트간의 상계면 형성에 기인하여 성형성 및 신미성이 열위해지는 문제가 있다. 따라서, Ni, Mo등을 저감하면서 연신율 및 내식성을 확보하면서도 강도가 향상된 오스테나이트계 스테인리스강의 개발이 요구된다.However, in the case of lean duplex stainless steel, there is a problem in that moldability and aesthetics are inferior due to the formation of a phase interface between austenite and ferrite. Therefore, development of austenitic stainless steel with improved strength while reducing elongation and corrosion resistance while reducing Ni and Mo is required.
본 발명의 실시예들은 기존 316L 스테인리스강 수준의 연신율 및 내식성을 확보하면서도 강도가 향상된 오스테나이트계 스테인리스강을 제공하고자 한다.Embodiments of the present invention to provide an austenitic stainless steel with improved strength while ensuring elongation and corrosion resistance of the existing 316L stainless steel.
본 발명의 일 실시예에 따른 강도가 향상된 오스테나이트계 스테인리스강 은, 중량%로, C: 0.02 내지 0.14%, Si: 0.2 내지 0.6%, S: 0.01% 미만, Mn: 2.0 내지 4.5%, Ni: 2.5 내지 5.0%, Cr: 19.0 내지 22.0%, Cu: 1.0 내지 3.0%, Mo: 1.0% 미만, N: 0.25 내지 0.40%, 나머지는 Fe 및 불가피한 불순물을 포함하고, 하기 식(1)로 표현되는 SNL(Solubility of Nitrogen in Liquid)값이 N의 함량 이상이다.Austenitic stainless steel with improved strength according to an embodiment of the present invention, in weight percent, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni : 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, the remainder containing Fe and unavoidable impurities, represented by the following formula (1): The SNL (Solubility of Nitrogen in Liquid) value is more than the content of N.
식(1): SNL= -0.188- 0.0423×C -0.0517×Si+ 0.012×Mn +0.0048×Ni + 0.0252×Cr -0.00906×Cu +0.00021×MoEquation (1): SNL = -0.188-0.0423 x C -0.0517 x Si + 0.012 x Mn +0.0048 x Ni + 0.0252 x Cr -0.00906 x Cu +0.00021 x Mo
(여기서, C, Si, Mn, Ni, Cr, Cu, Mo은 각 원소의 함량(중량%)을 의미한다.)(C, Si, Mn, Ni, Cr, Cu, Mo means the content (wt%) of each element.)
또한, 본 발명의 일 실시예에 따르면, C+N: 0.5% 이하(0은 제외)일 수 있다.In addition, according to an embodiment of the present invention, C + N: may be 0.5% or less (excluding 0).
또한, 본 발명의 일 실시예에 따르면, B: 0.001 내지 0.005% 및 Ca: 0.001 내지 0.003% 중에서 1종 이상을 더 포함할 수 있다.In addition, according to an embodiment of the present invention, it may further include at least one of B: 0.001 to 0.005% and Ca: 0.001 to 0.003%.
또한, 본 발명의 일 실시예에 따르면, 하기 식(2)로 표현되는 Md30 값이 -50 이하를 만족할 수 있다.In addition, according to an embodiment of the present invention, Md 30 value represented by the following formula (2) may satisfy -50 or less.
식(2): Md30 = 551 -462×(C +N) -9.2×Si -8.1×Mn -13.7×Cr -29×(Ni +Cu) - 8.5×MoEquation (2): Md 30 = 551 -462 x (C + N) -9.2 x Si -8.1 x Mn -13.7 x Cr -29 x (Ni + Cu)-8.5 x Mo
(여기서, C, N, Si, Mn, Cr, Ni, Cu, Mo은 각 원소의 함량(중량%)을 의미한다.)(Here, C, N, Si, Mn, Cr, Ni, Cu, Mo means the content (% by weight) of each element.)
또한, 본 발명의 일 실시예에 따르면, 하기 식(3)을 만족할 수 있다. In addition, according to an embodiment of the present invention, the following formula (3) can be satisfied.
식(3): Creq/Nieq ≤ 1.8 Equation (3): Creq / Nieq ≤ 1.8
(여기서, Creq = Cr +Mo +1.5×Si, Nieq = Ni +0.5×Mn +30×(C +N) +0.5×Cu 이다.)(Creq = Cr + Mo + 1.5 x Si, Nieq = Ni + 0.5 x Mn + 30 x (C + N) + 0.5 x Cu.)
또한, 본 발명의 일 실시예에 따르면, 하기 식(4)로 표현되는 내공식지수 값이 22 이상을 만족할 수 있다. In addition, according to an embodiment of the present invention, the pitting index value represented by the following formula (4) may satisfy 22 or more.
식(4): 내공식지수(PREN) = 16 +3.3Mo +16N -0.5Mn Equation (4): PREN = 16 + 3.3Mo + 16N -0.5Mn
(여기서, Mo, N, Mn은 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, N, Mn means the content (wt%) of each element.)
또한, 본 발명의 일 실시예에 따르면, 상기 오스테나이트계 스테인리스강의 항복강도(0.2 off-set)는 400 내지 450 MPa, 인장강도는 700 내지 850 MPa일 수 있다.In addition, according to an embodiment of the present invention, the yield strength (0.2 off-set) of the austenitic stainless steel may be 400 to 450 MPa, tensile strength 700 to 850 MPa.
또한, 본 발명의 일 실시예에 따르면, 상기 오스테나이트계 스테인리스강의 연신율은 35% 이상일 수 있다. In addition, according to an embodiment of the present invention, the elongation of the austenitic stainless steel may be 35% or more.
본 발명의 실시예에 따르면, 기존 316L 스테인리스강 수준의 연신율 및 내식성을 확보하면서도 강도가 향상된 오스테나이트계 스테인리스강을 제공할 수 있다.According to the embodiment of the present invention, it is possible to provide an austenitic stainless steel with improved strength while ensuring elongation and corrosion resistance of the existing 316L stainless steel.
도 1은 본 발명의 일 실시예에 따른 오스테나이트계 스테인리스강의 SNL(Solubility of Nitrogen in Liquid)값 도출을 위한 성분별 Thermocalc. 계산결과 및 회귀식 적용 값과의 상관관계를 설명하기 위한 그래프이다. 1 is a component-specific Thermocalc for deriving the SNL (Solubility of Nitrogen in Liquid) value of the austenitic stainless steel according to an embodiment of the present invention. This is a graph to explain the correlation between the calculation result and the regression application value.
본 발명의 일 실시예에 따른 강도가 향상된 오스테나이트계 스테인리스강 은, 중량%로, C: 0.02 내지 0.14%, Si: 0.2 내지 0.6%, S: 0.01% 미만, Mn: 2.0 내지 4.5%, Ni: 2.5 내지 5.0%, Cr: 19.0 내지 22.0%, Cu: 1.0 내지 3.0%, Mo: 1.0% 미만, N: 0.25 내지 0.40%, 나머지는 Fe 및 불가피한 불순물을 포함하고, 하기 식(1)로 표현되는 SNL(Solubility of Nitrogen in Liquid)값이 N의 함량 이상이다.Austenitic stainless steel with improved strength according to an embodiment of the present invention, in weight percent, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni : 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, the remainder containing Fe and unavoidable impurities, represented by the following formula (1): The SNL (Solubility of Nitrogen in Liquid) value is more than the content of N.
식(1): SNL= -0.188- 0.0423×C -0.0517×Si+ 0.012×Mn +0.0048×Ni + 0.0252×Cr -0.00906×Cu +0.00021×MoEquation (1): SNL = -0.188-0.0423 x C -0.0517 x Si + 0.012 x Mn +0.0048 x Ni + 0.0252 x Cr -0.00906 x Cu +0.00021 x Mo
(여기서, C, Si, Mn, Ni, Cr, Cu, Mo은 각 원소의 함량(중량%)을 의미한다.)(C, Si, Mn, Ni, Cr, Cu, Mo means the content (wt%) of each element.)
이하에서는 본 발명의 실시 예를 첨부 도면을 참조하여 상세히 설명한다. 이하의 실시 예는 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 본 발명의 사상을 충분히 전달하기 위해 제시하는 것이다. 본 발명은 여기서 제시한 실시 예만으로 한정되지 않고 다른 형태로 구체화될 수도 있다. 도면은 본 발명을 명확히 하기 위해 설명과 관계 없는 부분의 도시를 생략하고, 이해를 돕기 위해 구성요소의 크기를 다소 과장하여 표현할 수 있다.Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are presented to sufficiently convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein but may be embodied in other forms. The drawings may omit illustrations of parts not related to the description in order to clarify the present invention, and may be exaggerated to some extent in order to facilitate understanding.
명세서 전체에서, 어떤 부분이 어떤 구성요소를 "포함"한다고 할 때, 이는 특별히 반대되는 기재가 없는 한 다른 구성요소를 제외하는 것이 아니라 다른 구성요소를 더 포함할 수 있는 것을 의미한다.Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise.
단수의 표현은 문맥상 명백하게 예외가 있지 않는 한, 복수의 표현을 포함한다.Singular expressions include plural expressions unless the context clearly indicates an exception.
이하에서는 본 발명에 따른 실시예를 첨부된 도면을 참조하여 상세히 설명한다. Hereinafter, with reference to the accompanying drawings an embodiment according to the present invention will be described in detail.
본 발명의 일 측면에 따른 강도가 향상된 오스테나이트계 스테인리스강은, 중량%로, C: 0.02 내지 0.14%, Si: 0.2 내지 0.6%, S: 0.01% 미만, Mn: 2.0 내지 4.5%, Ni: 2.5 내지 5.0%, Cr: 19.0 내지 22.0%, Cu: 1.0 내지 3.0%, Mo: 1.0% 미만, N: 0.25 내지 0.40%를 포함하고, 나머지는 Fe 및 불가피한 불순물을 포함한다.Austenitic stainless steel with improved strength according to an aspect of the present invention, in weight%, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni: 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0%, Mo: less than 1.0%, N: 0.25 to 0.40%, and the balance includes Fe and unavoidable impurities.
이하, 본 발명의 실시예에서의 함금성분 함량의 수치 한정 이유에 대하여 설명한다. 이하에서는 특별한 언급이 없는 한 단위는 중량%이다.Hereinafter, the reason for the numerical limitation of the content of the alloying component in the embodiment of the present invention will be described. In the following, the unit is% by weight unless otherwise specified.
C의 함량은 0.02 내지 0.14%이다.The content of C is 0.02 to 0.14%.
탄소(C)는 오스테나이트상 안정화에 효과적인 원소이나, 함량이 낮을 경우 추가적인 오스테나이트 안정화 원소의 첨가가 요구됨에 따라 0.02% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, 고용강화 효과에 의해 가공성을 저하시킬 뿐만 아니라 용접부 열영향부 및 열연 코일링 후 잠열에 기인한 Cr탄화물의 입계 석출을 유도하여 연성, 인성, 내식성 등에 악영향을 미칠 수 있으므로 그 상한을 0.14%로 한정할 수 있다.Carbon (C) is an element effective for stabilizing austenite phase, but when the content is low, it may be added at least 0.02% as an additional austenite stabilizing element is required. However, if the content is excessive, not only the workability is lowered by the solid solution strengthening effect, but also it may adversely affect the ductility, toughness and corrosion resistance by inducing grain boundary precipitation of Cr carbide due to heat affected zone of welded part and latent heat after hot rolled coiling. Therefore, the upper limit can be limited to 0.14%.
Si의 함량은 0.2 내지 0.6%이다.The content of Si is 0.2 to 0.6%.
실리콘(Si)은 제강공정 중 탈산제의 역할을 함과 동시에 내식성을 향상시키는데 효과적인 원소로 0.2% 이상 첨가할 수 있다. 그러나 Si은 페라이트상 안정화에 효과적인 원소로써 과잉 첨가 시 주조 슬라브 내 델타 페라이트 형성을 조장하여 열간가공성을 저하시킬 뿐만 아니라 고용강화 효과에 의한 강재의 연성/인성을 저하시킬 수 있으므로 그 상한을 0.6%로 한정할 수 있다.Silicon (Si) may be added as 0.2% or more as an effective element to improve the corrosion resistance while acting as a deoxidizer during the steelmaking process. However, Si is an effective element for stabilizing ferrite phase, and when excessively added, it promotes the formation of delta ferrite in the cast slab, which not only decreases the hot workability but also decreases the ductility / toughness of the steel due to the solid solution effect. It can be limited.
Mn의 함량은 2.0 내지 4.5%이다.The content of Mn is 2.0 to 4.5%.
망간(Mn)은 본 발명에서 니켈(Ni) 대신 첨가되는 오스테나이트상 안정화 원소로, 가공유기 마르텐사이트 생성을 억제하여 냉간 압연성을 향상시키는데 효과적이고, 후술할 제강 공정 중 질소(N)의 용해도를 증가시키는 원소로 2.0% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, S계 개재물(MnS)의 증가를 초래함에 따라 강재의 연성, 인성 및 내식성을 저하시킬 수 있으므로 그 상한을 4.5%로 한정할 수 있다. Manganese (Mn) is an austenite-stable stabilizing element added in place of nickel (Ni) in the present invention, is effective in improving the cold rolling properties by suppressing the production of organic martensite, solubility of nitrogen (N) during steelmaking process to be described later 2.0% or more may be added as an element to increase. However, if the content is excessive, the upper limit can be limited to 4.5% because it may decrease the ductility, toughness and corrosion resistance of the steel as it increases the S-based inclusions (MnS).
Ni의 함량은 2.5 내지 5.0%이다.The content of Ni is 2.5 to 5.0%.
니켈(Ni)은 강력한 오스테나이트상 안정화 원소로써 양호한 열간 가공성 및 냉간 가공성을 확보하기 위해서는 필수적이다. 특히 일정량 이상의 Mn을 첨가함에도 2.5% 이상의 첨가는 필수적이다. 그러나 Ni은 고가의 원소임에 따라 다량의 첨가 시 원료비용의 상승을 초래한다. 이에, 강재의 비용 및 효율성을 모두 고려하여 그 상한을 5.0%로 한정할 수 있다.Nickel (Ni) is a strong austenite stabilizing element, which is essential to ensure good hot workability and cold workability. In particular, addition of more than 2.5% is essential even if a certain amount or more of Mn is added. However, Ni is an expensive element, which leads to an increase in raw material cost when a large amount is added. Therefore, the upper limit can be limited to 5.0% in consideration of both the cost and efficiency of the steel.
Cr의 함량은 19 내지 22%이다.The content of Cr is 19 to 22%.
크롬(Cr)은 페라이트 안정화 원소이지만 마르텐사이트상 생성 억제에 있어서 효과적이며, 스테인리스강에 요구되는 내식성을 확보하는 기본 원소이다. 또한, 후술할 제강 공정 중 질소(N)의 용해도를 증가시키는 원소로 19% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, 제조비용이 상승하고, 슬라브 내 델타(δ) 페라이트를 형성하여 열간가공성의 저하를 초래함에 따라 Ni, Mn 등의 오스테나이트 안정화 원소의 추가적 투입이 요구되는 문제가 있어 그 상한을 22%로 한정할 수 있다.Although chromium (Cr) is a ferrite stabilizing element, it is effective in suppressing martensitic phase formation and is a basic element for securing corrosion resistance required for stainless steel. In addition, 19% or more may be added as an element to increase the solubility of nitrogen (N) during the steelmaking process described later. However, if the content is excessive, there is a problem that additional input of austenite stabilizing elements such as Ni, Mn, etc. is required as the manufacturing cost increases and delta (δ) ferrite is formed in the slab, resulting in a decrease in hot workability. The upper limit can be limited to 22%.
P의 함량은 0.1% 미만이다.The content of P is less than 0.1%.
인(P)은 내식성이나 열간가공성을 저하시킴에 따라 그 상한을 0.1%로 한정할 수 있다.Phosphorus (P) can limit the upper limit to 0.1% as it reduces corrosion resistance and hot workability.
S의 함량은 0.01% 미만이다.The content of S is less than 0.01%.
황(S)은 내식성이나 열간가공성을 저하시킴에 따라 그 상한을 0.01%로 한정할 수 있다.Sulfur (S) can limit the upper limit to 0.01% as it lowers the corrosion resistance and hot workability.
Cu의 함량은 1.0 내지 3.0%이다. The content of Cu is 1.0 to 3.0%.
구리(Cu)는 본 발명에서 니켈(Ni) 대신 첨가되는 오스테나이트상 안정화 원소로, 환원 환경에서의 내식성을 향상시키고 적층 결함 에너지(Stacking Fault Energy, SFE)를 감소시켜 성형성을 향상시킨다. 이러한 효과를 충분히 발현시키기 위해 1.0% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, 소재비용의 상승뿐만 아니라 열간가공성을 저하시킬 수 있으므로 그 상한을 3.0%로 한정할 수 있다.Copper (Cu) is an austenite stabilizing element added in place of nickel (Ni) in the present invention, and improves the moldability by improving the corrosion resistance in a reducing environment and reducing the stacking fault energy (SFE). 1.0% or more may be added to fully express this effect. However, if the content is excessive, the upper limit can be limited to 3.0% because not only the increase in material cost but also the hot workability can be lowered.
Mo의 함량은 1.0% 미만이다.The content of Mo is less than 1.0%.
몰리브덴(Mo)은 부동태 피막(Passive Film)을 개질하여 스테인리스강의 내식성을 향상시키는데 효과적인 원소이다. 그러나 Mo는 고가의 원소임에 따라 다량의 첨가 시 원료비용의 상승을 초래할 뿐만 아니라 열간가공성을 저하시키는 문제점이 있다. 이에 강재의 비용-효율성을 및 열간가공성을 고려하여 그 상한을 1.0%로 한정할 수 있다.Molybdenum (Mo) is an element effective in improving the corrosion resistance of stainless steel by modifying a passive film. However, since Mo is an expensive element, the addition of a large amount of raw materials not only increases the raw material cost but also lowers the hot workability. Therefore, the upper limit may be limited to 1.0% in consideration of cost-efficiency and hot workability of the steel.
N의 함량은 0.25 내지 0.40%이다. The content of N is 0.25 to 0.40%.
질소(N)는 내식성 향상에 효과적인 원소로, 강력한 오스테나이트 안정화 원소이다. 따라서 질소 합금화는 Ni, Cu, Mn의 보다 낮은 사용을 가능하게 함으로써 소재비용을 절감할 수 있다. 이러한 효과를 충분히 발현시키기 위해 0.25% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, 고용강화 효과에 의해 가공성 및 성형성을 저하시킬 수 있으므로 그 상한을 0.40%로 한정할 수 있다.Nitrogen (N) is an effective element for improving corrosion resistance and is a strong austenite stabilizing element. Therefore, nitrogen alloying can reduce the material cost by enabling lower use of Ni, Cu, Mn. 0.25% or more may be added to fully express this effect. However, if the content is excessive, the upper limit can be limited to 0.40% because the workability and formability may be reduced by the solid solution strengthening effect.
C+N의 함량은 0.5% 이하이다.The content of C + N is 0.5% or less.
C 와 N은 강도 향상에 효과적인 원소이나, 그 함량이 과도할 경우, 가공성을 저하시키는 문제가 있어, 그 합계의 상한을 0.5%로 한정할 수 있다. C and N are effective elements for improving strength, but when the content is excessive, there is a problem of degrading workability, and the upper limit of the total can be limited to 0.5%.
또한 본 발명의 일 실시예에 따른 강도가 향상된 오스테나이트계 스테인리스강은, B: 0.001 내지 0.005 및 Ca: 0.001 내지 0.003% 중 1종 이상을 더 포함할 수 있다.In addition, the austenitic stainless steel with improved strength according to an embodiment of the present invention may further include one or more of B: 0.001 to 0.005 and Ca: 0.001 to 0.003%.
B의 함량은 0.001 내지 0.005%이다.The content of B is 0.001 to 0.005%.
붕소(B)는 주조 중의 크랙 발생을 억제하여 양호한 표면 품질을 확보하는데 효과적인 원소로, 0.001% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, 소둔/산세 공정 중 제품 표면에 질화물(BN)을 형성시켜 표면품질을 저하시킬 수 있어 그 상한을 0.005%로 한정할 수 있다.Boron (B) is an effective element for suppressing the occurrence of cracks during casting to ensure good surface quality, can be added 0.001% or more. However, if the content is excessive, the surface quality can be reduced by forming nitride (BN) on the surface of the product during the annealing / pickling process, the upper limit can be limited to 0.005%.
Ca의 함량은 0.001 내지 0.003%이다.The content of Ca is 0.001 to 0.003%.
칼슘(Ca)은 고 Mn 함유 시 입계에 생성되는 MnS 제강성 개재물의 형성을 억제하여 제품의 청정도를 향상시키는 원소로, 0.001% 이상 첨가할 수 있다. 다만 그 함량이 과도할 경우, Ca계 개재물 형성에 기인한 열간가공성 저하 및 제품 표면품질 저하를 초래할 수 있어 그 상한을 0.003%로 한정할 수 있다.Calcium (Ca) is an element that suppresses the formation of MnS steelmaking inclusions generated at the grain boundary when containing high Mn and improves the cleanliness of the product, and may be added at least 0.001%. However, when the content is excessive, the hot workability due to the formation of Ca-based inclusions and the surface quality of the product may be lowered, and the upper limit thereof may be limited to 0.003%.
본 발명의 나머지 성분은 철(Fe)이다. 다만, 통상의 제조과정에서는 원료 또는 주위 환경으로부터 의도되지 않는 불순물들이 불가피하게 혼입될 수 있으므로, 이를 배제할 수는 없다. 이들 불순물들은 통상의 제조과정의 기술자라면 누구라도 알 수 있는 것이기 때문에 그 모든 내용을 특별히 본 명세서에서 언급하지는 않는다.The remaining component of the present invention is iron (Fe). However, in the conventional manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, not all of them are specifically mentioned in the present specification.
오스테나이트 스테인리스강의 가격경쟁력을 확보하기 위해서는 Ni, Mn 등 고가의 오스테나이트 안정화 원소의 함량을 줄여야 하고, 이를 보상할 수 있는 N 첨가량을 예측하는 것이 요구된다. 이를 위해, 각 합금성분을 고려하여 N의 용해한도 계산을 통한 최적의 N 함량 설정이 필요하다. In order to secure the price competitiveness of austenitic stainless steel, it is necessary to reduce the content of expensive austenite stabilizing elements such as Ni and Mn, and to predict the amount of N to be compensated for. For this purpose, it is necessary to set the optimum N content by calculating the dissolution limit of N in consideration of each alloy component.
이에, 상태도 예측 프로그램인 Thermocalc.를 활용하여 각 합금 원소(C, Si, Mn, Ni, Cr, Cu, Mo)의 첨가량에 따라 1150℃에서의 용탕 온도내에 용해될 수 있는 N의 함량을 도출하였다. Thus, by using Thermocalc., A state diagram prediction program, the content of N that can be dissolved within the melt temperature at 1150 ° C. is derived according to the amount of each alloy element (C, Si, Mn, Ni, Cr, Cu, Mo) It was.
도 1은 본 발명의 일 실시예에 따른 오스테나이트계 스테인리스강의 SNL(Solubility of Nitrogen in Liquid)값 도출을 위한 성분별 Thermocalc. 계산결과 및 회귀식 적용 값과의 상관관계를 설명하기 위한 그래프이다. 1 is a component-specific Thermocalc for deriving SNL (Solubility of Nitrogen in Liquid) value of the austenitic stainless steel according to an embodiment of the present invention. This is a graph to explain the correlation between the calculation result and the regression application value.
도 1을 참조하면, 용탕 내 질소가 고용되는 한계값을 계산하여 "N용해한(The.)"로 표기하였다.Referring to FIG. 1, the limit value of the solid solution of nitrogen in the molten metal was calculated and expressed as "N.".
이러한 성분변화에 따른 Thermocalc.의 계산값을 바탕으로 하기 식(1)의 SNL(Solubility of Nitrogen in Liquid) 회귀식을 도출하였다. Based on the calculated value of Thermocalc. According to the component change, the SNL (Solubility of Nitrogen in Liquid) regression equation of Equation (1) was derived.
식(1): SNL= -0.188- 0.0423×C -0.0517×Si+ 0.012×Mn +0.0048×Ni + 0.0252×Cr -0.00906×Cu +0.00021×MoEquation (1): SNL = -0.188-0.0423 x C -0.0517 x Si + 0.012 x Mn +0.0048 x Ni + 0.0252 x Cr -0.00906 x Cu +0.00021 x Mo
도출된 회귀식을 적용할 경우 R(sq)값이 100%로 높은 상관관계에 해당함을 확인하였으며, N 용융 한계값인 SNL(Solubility of Nitrogen in Liquid) 도출을 위한 성분별 Thermocalc. 계산결과와 회귀식의 관계에서 적합성의 확보가 가능함을 확인하였다. When applying the derived regression equation, it was confirmed that the R (sq) value corresponds to a high correlation of 100%, and the component-specific Thermocalc for deriving the solution melting of Nitrogen in Liquid (SNL), which is the N melting limit value. It was confirmed that the suitability can be secured in the relationship between the calculation result and the regression equation.
본 발명의 일 실시예에 따른 강도가 향상된 오스테나이트계 스테인리스강은, SNL 값이 N 함량 이상이다. 이와 같이, SNL 값을 N 함량 보다 높게 설정하여 질소 고용한도를 높일 경우, 목표하는 합금성분의 제강조업이 양호하게 실시되는 것을 확인하였다.Austenitic stainless steel with improved strength according to an embodiment of the present invention, the SNL value is greater than the N content. Thus, when the SNL value is set higher than the N content to increase the nitrogen solubility limit, it was confirmed that the steelmaking operation of the target alloy component is performed well.
오스테나이트계 스테인리스강의 경우 미려한 표면을 요구하는 제품에 적용된다. 미려한 표면을 요구하는 제품의 경우 냉간압연재를 광휘소둔(Bright Annealing)하는 것이 일반적이다. 이러한 광휘소둔은 스테인리스 냉간압연재를 질소(N2), 수소(H2) 등을 이용한 환원성 분위기(Dew point -40 ~ -60℃) 하에서 열처리를 수행하여 스테인리스 냉간압연재의 열처리 과정에서 발생하는 재산화를 방지함으로써, 표면의 색상 및 성상 변화 없이 표면을 밝고 미려하게 유지하는 열처리기술이다. 이러한 광휘소둔에 사용되는 분위기 가스로 수소를 이용한 광휘소둔이 가장 일반적이며, 이는 높을 열용량 뿐만 아니라 표면의 변색을 억제를 위해서 가장 널리 사용되기 때문이다.Austenitic stainless steels are applied to products requiring a beautiful surface. Bright annealing of cold rolled materials is common for products requiring a beautiful surface. Such bright annealing is performed during the heat treatment process of the stainless steel cold rolled material by performing heat treatment of the stainless steel cold rolled material under a reducing atmosphere (Dew point -40 to -60 ° C) using nitrogen (N 2 ), hydrogen (H 2 ), or the like. By preventing reoxidation, it is a heat treatment technology that keeps the surface bright and beautiful without changing the color and appearance of the surface. Bright annealing using hydrogen is the most common atmosphere gas used for bright annealing, because it is most widely used to suppress discoloration of the surface as well as high heat capacity.
일반적인 오스테나이트계 스테인리스강 대비 본 발명과 같이 Ni, Mn 등의 오스테나이트 안정화 원소를 감소시킨 스테인리스강에 있어서, 수소분위기의 광휘소둔 적용 시 고려해야 할 점이 있다. In the stainless steel in which austenitic stabilizing elements such as Ni and Mn are reduced as compared with the general austenitic stainless steel, there are points to be considered in applying bright annealing of the hydrogen atmosphere.
이는 광휘소둔 시 수소의 침투에 의해 최종 소재가 수소취성 결함에 따른 가공성 열위의 문제점이 발생할 가능성이 높다는 점이다. 상기의 Ni, Mn 등 오스테나이트 안정화 원소가 감소된 스테인리스강의 경우, 최종 광휘소둔 이전 냉간압연 시 응력유기 또는 가공유기 마르텐사이트가 표층부를 중심으로 형성되며, 이러한 표층부에 형성된 마르텐사이트상은 광휘소둔 시 열처리에 의해 오스테나이트상으로 변태되기 이전에 불활성 가스인 수소원자와 접하게 되고, 이러한 수소원자는 일부 마르텐사이트상 내부로 침투하게 된다. 광휘소둔에 의해 기존의 응력유기 또는 가공유기 마르텐사이트가 오스테나이트상으로 상변태함에 따라 내부에 침투된 수소원자는 바깥으로 배출되지 못하고 표층부에서 원자 상태로 갇혀버리게 된다. This is due to the penetration of hydrogen during bright annealing, the final material is likely to cause a problem of workability inferior due to hydrogen embrittlement defects. In the case of stainless steel having reduced austenite stabilizing elements such as Ni and Mn, stress organic or processed organic martensite is formed around the surface layer part during cold rolling before final bright annealing, and the martensite phase formed on the surface layer part is heat treated during bright annealing. By contact with the hydrogen atom which is an inert gas before being transformed into the austenite phase, the hydrogen atom penetrates into some martensite phase. As the conventional stressed or processed organic martensite phase transformation by a bright annealing, the hydrogen atoms penetrated into the austenite phase cannot be discharged to the outside, but are trapped in the atomic state at the surface layer.
이렇게 표층부에 침투한 수소원자는 일반적인 BCC 및 BCT 구조인 페라이트 혹은 마르텐사이트 상에 대해서는 상온에서 일정시간이 경과한 후 자연적으로 베이크 아웃(bake-out)되어 물성에 큰 영향을 미치지 않게 된다.The hydrogen atoms penetrated into the surface layer are naturally baked out after a certain time at room temperature for ferrite or martensite phases having a general BCC and BCT structure so that they do not significantly affect physical properties.
반면, 표층부 마르텐사이트상이 광휘소둔에 의해서 오스테나이트상으로 상변태 하였을 경우, 즉 FCC의 격자구조 내에 수소원자가 존재할 경우에는, 상온에서 상당 시간이 경과할지라도 수소원자의 자연적 베이크 아웃이 원활하지 못하고 장기간 소재 내에 존재하게 된다.On the other hand, when the surface martensite phase is transformed into an austenite phase by bright annealing, that is, when hydrogen atoms exist in the lattice structure of the FCC, even though a considerable time passes at room temperature, the natural bake-out of hydrogen atoms is not smooth and the material is long-term. Will exist within.
이러한 수소원자는 수소취성을 일으키는 인자로 알려져 있으며, 일부 가공 또는 변형에 의해서 소재 내에 갇혀있던 수소원자들은 수소분자(gas)의 상태로 변화하게 되고, 일정 압력에 도달할 경우, 일정 하중 하에서 크랙의 기점으로 작용하여 연신율의 저하를 일으킨다.These hydrogen atoms are known to cause hydrogen embrittlement, and the hydrogen atoms trapped in the material by some processing or deformation are changed into the state of hydrogen molecules, and when a certain pressure is reached, cracks of a crack under a certain load It acts as a starting point, causing a decrease in elongation.
따라서 Ni 및 Mn이 상대적으로 낮은 오스테나이트계 스테인리스강의 경우, 합금성분과 함께 추가적으로 가공경화에 의해 표면에 형성되는 마르텐사이트상의 생성량을 제어해야만 광휘소둔을 통해 미려한 표면품질 및 가공성을 확보할 수 있다. Therefore, in the case of austenitic stainless steels having relatively low Ni and Mn, the amount of martensite phase formed on the surface of the austenitic stainless steel together with the alloying components must be controlled to secure beautiful surface quality and workability through bright annealing.
이에, 본 발명의 일 실시예에 따른 강도가 향상된 오스테나이트계 스테인리스강은 하기 식 (2) 로 표현되는 Md30 값이 -50℃ 이하의 범위를 만족한다.Thus, in the austenitic stainless steel with improved strength according to an embodiment of the present invention, the Md 30 value represented by the following formula (2) satisfies the range of -50 ° C or less.
식(2): Md30 = 551 -462×(C +N) -9.2×Si -8.1×Mn -13.7×Cr -29×(Ni +Cu) - 8.5×MoEquation (2): Md 30 = 551 -462 x (C + N) -9.2 x Si -8.1 x Mn -13.7 x Cr -29 x (Ni + Cu)-8.5 x Mo
오스테나이트계 스테인리스강은, 마르텐사이트 변태 개시온도(Ms) 이상의 온도에서 소성가공에 의해 마르텐사이트 변태가 발생한다. 이러한 가공에 의해 상변태를 일으키는 상한 온도는 Md 값으로 나타내며, 가공에 의해 상변태가 일어나는 정도를 나타내는 척도이다. In the austenitic stainless steel, martensite transformation occurs by plastic working at a temperature higher than the martensite transformation start temperature (Ms). The upper limit temperature which causes phase transformation by such a process is represented by Md value, and is a measure which shows the extent to which phase transformation occurs by processing.
특히, 30% 변형을 부여할 때 마르텐사이트로의 상변태가 50% 일어나는 온도(℃)를 Md30 라고 정의한다. Md30 값이 높으면 가공유기 마르텐사이트상의 생성이 쉬운 것에 반해, Md30 값이 낮으면 가공유기 마르텐사이트상의 생성이 상대적으로 어려운 강종으로 판단할 수 있다. 일반적으로 Md30 값은 통상의 오스테나이트계 스테인리스강의 오스테나이트 안정화도를 판단할 수 있는 지표로 사용되며, 상기 식(2)로 표현되는 Nohara 회귀식을 통해서 연산될 수 있다.In particular, the temperature (° C.) at which 50% phase transformation to martensite occurs when 30% strain is given is defined as Md 30 . If the Md 30 value is high, it is easy to form a processed organic martensite phase, whereas if the Md 30 value is low, it can be judged to be a relatively difficult steel type. In general, the Md 30 value is used as an index for determining the austenite stabilization degree of ordinary austenitic stainless steel, and can be calculated through the Nohara regression equation represented by Equation (2).
합금성분 함량 차이에 의해 다양한 종류의 상을 형성하는 것은 첨가된 각각의 합금성분이 상 밸런스에 미치는 영향이 다르기 때문이다. Forming various kinds of phases by the difference in alloy content is because the effect of each alloy component added on the phase balance is different.
각 합금성분이 상 밸런스에 영향을 미치는 정도를 Creq 및 Nieq를 통해 계산할 수 있으며, 하기의 식(3)와 같이 표현되는 Creq/Nieq 비를 통해 상온에서 생성되는 상을 예측할 수 있다. The degree that each alloy component affects the phase balance can be calculated through Creq and Nieq, and the phase generated at room temperature can be predicted through the Creq / Nieq ratio expressed as in Equation (3) below.
식(3): Creq/NieqFormula (3): Creq / Nieq
여기서, Creq = Cr +Mo +1.5×Si, Nieq = Ni +0.5×Mn +30×(C +N) +0.5×Cu 이다.Here, Creq = Cr + Mo + 1.5 × Si, Nieq = Ni + 0.5 × Mn + 30 × (C + N) + 0.5 × Cu.
즉 Creq/Nieq 비가 낮을 경우에는, 상대적으로 오스테나이트 안정화도가 높아 상온에서 오스테나이트 단상 형성이 가능한 반면, Creq/Nieq 비가 높은 경우에는, 오스테나이트 안정화도가 낮아 페라이트 상이 국부적으로 형성될 가능성이 높다. In other words, when the Creq / Nieq ratio is low, the austenite stabilization is relatively high at room temperature. However, when the Creq / Nieq ratio is high, the austenite stability is low and the ferrite phase is likely to be locally formed. .
본 발명자들은 다양한 합금성분에 대해서 Creq/Nieq비를 적용하여 검토한 결과, Creq/Nieq비가 1.8 이하인 경우 오스테나이트 단상 기지조직의 형성이 가능한 것을 확인하였다. As a result of examining the application of the Creq / Nieq ratio to various alloy components, the present inventors confirmed that the formation of the austenite single phase matrix was possible when the Creq / Nieq ratio was 1.8 or less.
스테인리스강의 내식성을 평가하는 기준으로 다양한 방법이 활용되고 있으나, 합금성분에 대한 변별력을 간단히 검토하는 방법으로 내공식지수(PREN) 의 활용을 들 수 있다. Various methods are used to evaluate the corrosion resistance of stainless steel, but the PREN can be used as a method of simply examining the discriminating power of alloy components.
PREN은 일반적으로 Cr, Mo, N이 영향을 미치는 것으로 활용되나, Mn의 함량이 상대적으로 높은 강종의 경우 Mn의 영향도 고려할 필요가 있어, 본 발명에서는 하기 식(4) 성분 관계식을 도출하였다. In general, PREN is used to influence Cr, Mo, and N. However, in the case of steel grades having a relatively high Mn content, it is necessary to consider the influence of Mn.
일반적으로 사용되는 고내식 316L 스테인리스강의 합금 성분계를 하기식에 적용할 경우, 약 22의 값을 나타낸다. 이에 본 발명에서는 316L 스테인리스강 대비 동등 수준 이상의 내식성을 확보하고자, PREN 값을 22 이상으로 설정하였다. When the alloy component system of the high corrosion resistance 316L stainless steel generally used is applied to the following formula, the value of about 22 will be shown. Therefore, in the present invention, in order to secure corrosion resistance at least equal to that of 316L stainless steel, the PREN value was set to 22 or more.
식(4): 내공식지수(PREN) = 16 +3.3Mo +16N -0.5MnEquation (4): PREN = 16 + 3.3Mo + 16N -0.5Mn
이하, 실시예를 통하여 본 발명을 보다 상세하게 설명하고자 한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
하기 표 1에 나타낸 다양한 합금 성분범위에 대하여, 잉곳(Ingot) 용해를 통해 200mm 두께의 슬라브를 제조하고, 1,240℃에서 2시간 동안 가열한 후 열간압연을 실시하여 3mm 두께의 열연강판을 제조하였다. For the various alloy component ranges shown in Table 1 below, a slab having a thickness of 200 mm was prepared through ingot melting, and heated at 1,240 ° C. for 2 hours, followed by hot rolling to prepare a hot rolled steel sheet having a thickness of 3 mm.
CC SiSi MnMn SS NiNi CrCr CuCu MoMo NN C+NC + N
실시예 1Example 1 0.1040.104 0.480.48 2.912.91 0.0050.005 3.533.53 20.820.8 2.12.1 0.52 0.52 0.30.3 0.404 0.404
실시예 2Example 2 0.1030.103 0.490.49 3.43.4 0.0050.005 3.353.35 19.619.6 1.161.16 0.39 0.39 0.270.27 0.373 0.373
실시예 3Example 3 0.0880.088 0.310.31 3.413.41 0.0040.004 3.73.7 21.721.7 2.512.51 0.10 0.10 0.340.34 0.428 0.428
실시예 4Example 4 0.0350.035 0.310.31 3.83.8 0.0060.006 4.24.2 2121 2.482.48 0.20 0.20 0.330.33 0.365 0.365
비교예 1Comparative Example 1 0.020.02 0.520.52 1.41.4 0.0040.004 10.410.4 16.616.6 0.390.39 2.00 2.00 0.0180.018 0.038 0.038
비교예 2Comparative Example 2 0.014 0.014 0.55 0.55 2.4 2.4 0.0060.006 2.4 2.4 20.3 20.3 0.1 0.1 1.30 1.30 0.2 0.2 0.166 0.166
비교예 3Comparative Example 3 0.10.1 0.380.38 3.83.8 0.0060.006 3.43.4 17.217.2 1.451.45 0.10 0.10 0.210.21 0.310 0.310
비교예 4Comparative Example 4 0.150.15 0.460.46 3.83.8 0.0040.004 3.63.6 21.621.6 2.042.04 0.32 0.32 0.350.35 0.500 0.500
이후 1,150℃에서 1분간 용체화 처리를 실시한 후, 미세조직 관찰 및 다양한 기계적 물성에 대한 평가를 진행하였다. After 1 minute solution treatment at 1,150 ℃, the microstructure observation and evaluation of various mechanical properties were carried out.
기계적 특성은 일본 공업규격 JIS Z 2201에 규정되어 있는 5호 시험편을 이용하여 측정하였다. 구체적으로, JIS Z 2201을 활용하여 인장시험을 진행하고, 그에 따라 측정된 항복강도(Yield Strength, MPa), 인장강도(Tensile Strength, MPa) 및 연신율(Elongation, %)을 하기 표 2에 기재하였다. The mechanical properties were measured using No. 5 test piece specified in Japanese Industrial Standard JIS Z 2201. Specifically, the tensile test was conducted using JIS Z 2201, yield strength (MPa), tensile strength (Tensile Strength, MPa) and elongation (%) measured accordingly are described in Table 2 below. .
또한, 상기 표 1의 실시예 4종 및 비교예 4종에 대하여 SNL 연산결과, Md30 연산결과, Creq/Nieq비 연산결과 및 PREN 연산결과를 하기 표 2에 나타내었다. In addition, SNL calculation results, Md30 calculation results, Creq / Nieq ratio calculation results, and PREN calculation results for Example 4 and Comparative Example 4 of Table 1 are shown in Table 2 below.
강종Steel grade N용해한(The.)N dissolved (The.) N 용해한(Reg.)N dissolved (Reg.) Md30(℃)Md 30 (℃) Creq/NieqCreq / Nieq PRENPREN 상 분석Phase analysis 기계적 특성Mechanical properties
YS(MPa)YS (MPa) TS(MPa)TS (MPa) El(%)El (%)
실시예 1Example 1 0.3238 0.3238 0.3244 0.3244 -121 -121 1.2140 1.2140 25.86125.861 AusteniteAustenite 490 490 780 780 44%44%
실시예 2Example 2 0.3067 0.3067 0.3080 0.3080 -60 -60 1.2322 1.2322 23.50723.507 AusteniteAustenite 460 460 760 760 50%50%
실시예 3Example 3 0.3582 0.3582 0.3590 0.3590 -170 -170 1.0914 1.0914 25.76525.765 AusteniteAustenite 510 510 800 800 44%44%
실시예 4Example 4 0.3472 0.3472 0.3488 0.3488 -136 -136 1.1845 1.1845 25.0425.04 AusteniteAustenite 470 470 750 750 42%42%
비교예 1Comparative Example 1 0.2205 0.2205 0.2204 0.2204 -60 -60 1.5585 1.5585 22.78822.788 AusteniteAustenite 220 220 540 540 58%58%
비교예 2Comparative Example 2 0.3230 0.3230 0.3233 0.3233 76 76 2.6076 2.6076 25.82225.822 DuplexDuplex 480 480 700 700 45%45%
비교예 3Comparative Example 3 0.2552 0.2552 0.2556 0.2556 -5 -5 1.1661 1.1661 18.9918.99 AusteniteAustenite 380 380 720 720 54%54%
비교예 4Comparative Example 4 0.3544 0.3544 0.3550 0.3550 -180 -180 1.0507 1.0507 26.35626.356 AusteniteAustenite 530 530 830 830 32%32%
일반적인 316L 스테인리스강의 성분계에 해당하는 비교예 1의 경우, 오스테나이트상으로 구성된 조직을 나타내며, 22이상의 PREN값을 나타내는 것을 확인할 수 있다. 다만 0.25% 미만의 질소가 첨가되어, 기계적 특성 평가 결과 220MPa의 항복강도 및 540MPa의 인장강도를 나타내며, 이는 일반적으로 널리 사용되는 연질의 오스테나이트계 스테인리스강의 물성에 해당하여 고강도를 요구하는 소재에 적용하기 어려운 문제점이 있다. In the case of the comparative example 1 corresponding to the component system of general 316L stainless steel, it shows the structure comprised by the austenite phase and showing PREN value of 22 or more. However, less than 0.25% of nitrogen is added, and the mechanical property evaluation results show a yield strength of 220 MPa and a tensile strength of 540 MPa, which are generally applied to materials requiring high strength due to the properties of soft austenitic stainless steels. There is a problem that is difficult to do.
Creq/Nieq비가 1.8을 초과하는 비교예 2의 경우, 일정 수준이상의 Mo가 첨가됨에 따라 PREN값이 약 26 수준으로 나타나 우수한 내공식 저항성을 나타낸다. 또한, 기계적 특성 평가 결과 480MPa의 항복강도 및 700MPa의 인장강도 그리고 45%의 연신율을 나타내는 것을 확인할 수 있다.In the case of Comparative Example 2 having a Creq / Nieq ratio of more than 1.8, as more than a certain level of Mo is added, the PREN value is about 26, indicating excellent pitting resistance. In addition, it can be seen that the mechanical property evaluation results show a yield strength of 480 MPa, a tensile strength of 700 MPa, and an elongation of 45%.
다만 Ni, N이 상대적으로 모두 낮은 수준의 합금성분계로써 상온 미세조직 관찰 시 오스테나이트상과 페라이트상이 약 5:5를 지니는 Duplex의 조직을 형성하는 것이 확인되었다. 이는 상 밸런스에서 페라이트의 안정화도가 316L 스테인리스강 대비 상대적으로 높은 값을 나타내기 때문이다. Duplex 조직에서는 오스테나이트상과 페라이트상 사이의 계면에서 크랙이 발생할 가능성이 있어, 절곡 등 성형이 요구되는 소재에 적용하기 어려운 문제점이 있다. However, when Ni and N were relatively low alloying systems, it was confirmed that the austenite phase and the ferrite phase formed a duplex structure with about 5: 5 when observed at room temperature microstructure. This is because the stability of ferrite in phase balance is relatively higher than that of 316L stainless steel. In the duplex structure, there is a possibility that cracks may occur at the interface between the austenitic phase and the ferrite phase, and thus there is a problem that it is difficult to apply to a material requiring molding such as bending.
비교예 2 대비 Ni, Mn의 함량을 소폭 상승시키고 Creq/Nieq비를 1.8 이하로 설정한 비교예 3의 경우, 미세조직 관찰시 오스테나이트상으로 구성된 조직을 형성하고, 기계적 물성의 경우 비교예 1의 316L 대비 경질이며, 비교예 2의 Duplex 스테인리스 대비 연질의 물성을 나타내는 것을 알 수 있다.In Comparative Example 3 in which the content of Ni and Mn was slightly increased compared to Comparative Example 2 and the Creq / Nieq ratio was set to 1.8 or less, a microstructure was observed to form austenitic tissue, and the mechanical properties of Comparative Example 1 It is harder than 316L, and it can be seen that it shows soft physical properties compared to Duplex stainless steel of Comparative Example 2.
하지만 Md30 값이 -5℃ 수준으로, 향후 표면이 미려한 광휘소둔재 생산 시 수소취성 발생가능성이 높다. 또한, Cr의 함량에 크게 영향 받는 N의 용해한이 낮아 N의 첨가량이 0.21% 수준으로, PREN값의 질소 팩터를 극대화시킬 수 없어, 316L 수준의 내공식 저항성을 확보하기 어려운 문제가 있다. However, the Md 30 value is -5 ℃, which is highly likely to cause hydrogen embrittlement in the future production of bright annealing materials. In addition, the N content is significantly affected by the content of Cr is low, the addition amount of N to 0.21% level, it is not possible to maximize the nitrogen factor of the PREN value, there is a problem that it is difficult to secure the pitting resistance of 316L level.
비교예 3 대비 N, C, Cr의 함량을 높인 비교예 4의 경우, -180℃ 수준의 Md30 값을 나타냄에 따라 광휘소둔재 제조에 적합하고, Creq/Nieq비를 1.8 이하로 설정함에 따라 오스테나이트 단상 조직의 확보가 가능함을 확인할 수 있다.In the case of Comparative Example 4 in which the contents of N, C and Cr were increased compared to Comparative Example 3, Md 30 at a level of -180 ° C. It can be confirmed that the austenite single-phase structure can be secured by setting the Creq / Nieq ratio to 1.8 or less, suitable for manufacturing the bright annealing material according to the value.
다만, C+N 함량이 0.5%로 본 발명의 상한인 0.5%를 초과하여, 경질의 기계적 물성을 나타내고, 연신율이 35% 미만으로 나타남을 알 수 있다.However, it can be seen that the C + N content is 0.5%, exceeding the upper limit of 0.5% of the present invention, showing hard mechanical properties, and an elongation of less than 35%.
상기 표 2를 참조하면, 본 발명의 실시예 1 내지 4의 경우, -50℃ 이하의 Md30값의 확보가 가능하여 광휘소둔 시 수소취성의 발생가능성이 낮을 뿐만 아니라, 니켈당량(Nieq)과 크롬당량(Creq)의 비(Creq/Nieq)는 모두 1.8이하의 범위를 만족하여 상온에서 오스테나이트 단상 조직의 형성이 가능하다. Referring to Table 2, in Examples 1 to 4 of the present invention, it is possible to secure an Md 30 value of -50 ° C. or lower, which lowers the possibility of hydrogen embrittlement during bright annealing, as well as nickel equivalent (Nieq) and The ratio of chromium equivalent (Creq) (Creq / Nieq) satisfies the range of 1.8 or less so that austenite single phase structure can be formed at room temperature.
뿐만 아니라, Ni 및 Mo 함량이 상대적으로 낮아 가격 경쟁력을 확보하면서도 22이상의 PREN값을 나태는 것이 확인되었으며, 기계적 특성 평가 결과 316L 대비 고강도 특성 구현이 가능함과 동시에 35% 이상의 양호한 연신율 확보가 가능함을 확인하였다.In addition, the Ni and Mo contents were relatively low, and it was confirmed that the PREN value was more than 22 while securing price competitiveness, and the mechanical property evaluation showed that high strength properties were achieved compared to 316L and good elongation of 35% or more was obtained. It was.
이상의 결과로부터 중량%로, C: 0.02 내지 0.14%, Si: 0.2 내지 0.6%, P: 0.1% 미만, S: 0.01% 미만, Mn: 2.0 내지 4.5%, Ni: 2.5 내지 5.0%, Cr: 19.0 내지 22.0%, Cu: 1.0 내지 3.0%, Mo: 1.0% 미만, N: 0.25 내지 0.40%를 포함하고, 나머지는 Fe 및 불가피한 불순물을 포함하는 오스테나이트계 스테인리스강에 대하여 본 발명에 의해 새로이 제안된 가격 경쟁력 및 제강용이성 확보를 위한 SNL(Solubility of Nitrogen in Liquid)값 제어, 오스테나이트상 안정화도 확보를 위한 Md30 값 제어, 미세조직내 오스테나이트상 형성을 위한 Creq/Nieq비 제어 그리고 내식성 확보를 위한 내공식지수(PREN)의 제어를 통하여 기존 316L 스테인리스강 수준의 가공성 및 내식성을 확보하면서도, 가격 경쟁력 및 강도를 향상시킬 수 있는 스테인리스강을 제조할 수 있음을 알 수 있다.From the above results in weight%, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, P: less than 0.1%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni: 2.5 to 5.0%, Cr: 19.0 Newly proposed by the present invention for austenitic stainless steels containing from 22.0%, Cu: 1.0-3.0%, Mo: less than 1.0%, N: 0.25-0.40%, the remainder comprising Fe and unavoidable impurities SNL (Solubility of Nitrogen in Liquid) value control for price competitiveness and steelmaking ease, Md 30 value control for securing austenite phase stability, Creq / Nieq ratio control for forming austenite phase in microstructure, and corrosion resistance Through the control of the PREN, it can be seen that it is possible to manufacture stainless steel that can improve the price competitiveness and strength while securing processability and corrosion resistance of the existing 316L stainless steel.
상술한 바에 있어서, 본 발명의 예시적인 실시예들을 설명하였지만, 본 발명은 이에 한정되지 않으며 해당 기술 분야에서 통상의 지식을 가진 자라면 다음에 기재하는 특허청구범위의 개념과 범위를 벗어나지 않는 범위 내에서 다양한 변경 및 변형이 가능함을 이해할 수 있을 것이다. As described above, the exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and a person skilled in the art does not depart from the concept and scope of the following claims. It will be understood that various changes and modifications are possible in the following.
본 발명에 따른 오스테나이트계 스테인리스강은 연신율 및 내식성을 확보하면서도 강도가 향상되어 기존 316L 스테인리스강의 대채 소재로 활용될 수 있다.Austenitic stainless steel according to the present invention can be used as a substitute material of the existing 316L stainless steel while improving the strength while ensuring elongation and corrosion resistance.

Claims (8)

  1. 중량%로, C: 0.02 내지 0.14%, Si: 0.2 내지 0.6%, S: 0.01% 미만, Mn: 2.0 내지 4.5%, Ni: 2.5 내지 5.0%, Cr: 19.0 내지 22.0%, Cu: 1.0 내지 3.0%, Mo: 1.0% 미만, N: 0.25 내지 0.40%, 나머지는 Fe 및 불가피한 불순물을 포함하고,By weight, C: 0.02 to 0.14%, Si: 0.2 to 0.6%, S: less than 0.01%, Mn: 2.0 to 4.5%, Ni: 2.5 to 5.0%, Cr: 19.0 to 22.0%, Cu: 1.0 to 3.0 %, Mo: less than 1.0%, N: 0.25-0.40%, the rest includes Fe and inevitable impurities,
    하기 식(1)로 표현되는 SNL(Solubility of Nitrogen in Liquid)값이 N의 함량 이상인 강도가 향상된 오스테나이트계 스테인리스강.An austenitic stainless steel having an improved strength at which a SNL (Solubility of Nitrogen in Liquid) value represented by the following formula (1) is equal to or greater than N.
    식(1): SNL= -0.188- 0.0423×C -0.0517×Si+ 0.012×Mn +0.0048×Ni + 0.0252×Cr -0.00906×Cu +0.00021×MoEquation (1): SNL = -0.188-0.0423 x C -0.0517 x Si + 0.012 x Mn +0.0048 x Ni + 0.0252 x Cr -0.00906 x Cu +0.00021 x Mo
    (여기서, C, Si, Mn, Ni, Cr, Cu, Mo은 각 원소의 함량(중량%)을 의미한다.)(C, Si, Mn, Ni, Cr, Cu, Mo means the content (wt%) of each element.)
  2. 제1항에 있어서,The method of claim 1,
    C+N: 0.5% 이하(0은 제외)인 강도가 향상된 오스테나이트계 스테인리스강.C + N: Austenitic stainless steel with improved strength of 0.5% or less (excluding 0).
  3. 제1항에 있어서,The method of claim 1,
    B: 0.001 내지 0.005% 및 Ca: 0.001 내지 0.003% 중에서 1종 이상을 더 포함하는 강도가 향상된 오스테나이트계 스테인리스강.B: 0.001 to 0.005% and Ca: 0.001 to 0.003% of the austenitic stainless steel with improved strength further comprising at least one.
  4. 제1항에 있어서,The method of claim 1,
    하기 식(2)로 표현되는 Md30 값이 -50 이하를 만족하는 강도가 향상된 오스테나이트계 스테인리스강.An austenitic stainless steel with improved strength in which Md 30 value represented by the following formula (2) satisfies -50 or less.
    식(2): Md30 = 551 -462×(C +N) -9.2×Si -8.1×Mn -13.7×Cr -29×(Ni +Cu) - 8.5×MoEquation (2): Md 30 = 551 -462 x (C + N) -9.2 x Si -8.1 x Mn -13.7 x Cr -29 x (Ni + Cu)-8.5 x Mo
    (여기서, C, N, Si, Mn, Cr, Ni, Cu, Mo은 각 원소의 함량(중량%)을 의미한다.)(Here, C, N, Si, Mn, Cr, Ni, Cu, Mo means the content (% by weight) of each element.)
  5. 제1항에 있어서,The method of claim 1,
    하기 식(3)을 만족하는 강도가 향상된 오스테나이트계 스테인리스강.Austenitic stainless steel with improved strength that satisfies the following formula (3).
    식(3): Creq/Nieq ≤ 1.8 Equation (3): Creq / Nieq ≤ 1.8
    (여기서, Creq = Cr +Mo +1.5×Si, Nieq = Ni +0.5×Mn +30×(C +N) +0.5×Cu 이다.)(Creq = Cr + Mo + 1.5 x Si, Nieq = Ni + 0.5 x Mn + 30 x (C + N) + 0.5 x Cu.)
  6. 제1항에 있어서, The method of claim 1,
    하기 식(4)로 표현되는 내공식지수 값이 22 이상을 만족하는 강도가 향상된 오스테나이트계 스테인리스강.An austenitic stainless steel with improved strength that satisfies the pitting resistance value of 22 or more represented by the following formula (4).
    식(4): 내공식지수(PREN) = 16 +3.3Mo +16N -0.5Mn Equation (4): PREN = 16 + 3.3Mo + 16N -0.5Mn
    (여기서, Mo, N, Mn은 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, N, Mn means the content (wt%) of each element.)
  7. 제1항에 있어서, The method of claim 1,
    항복강도(0.2 off-set)는 400 내지 450 MPa, 인장강도는 700 내지 850 MPa인 강도가 향상된 오스테나이트계 스테인리스강.Yield strength (0.2 off-set) is 400 to 450 MPa, tensile strength is 700 to 850 MPa enhanced strength austenitic stainless steel.
  8. 제1항에 있어서, The method of claim 1,
    연신율이 35% 이상인 강도가 향상된 오스테나이트계 스테인리스강.Austenitic stainless steel with improved strength at least 35% elongation.
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Families Citing this family (2)

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JP7462439B2 (en) * 2020-03-12 2024-04-05 日鉄ステンレス株式会社 Austenitic stainless steel and calculation method for upper limit of N
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101056235B1 (en) * 2008-11-25 2011-08-11 주식회사 포스코 Prediction of Material Properties of Austenitic Stainless Steel Cold Rolled Products
KR20120091075A (en) * 2009-11-02 2012-08-17 에이티아이 프로퍼티즈, 인코퍼레이티드 Lean austenitic stainless steel
WO2012143610A1 (en) * 2011-04-18 2012-10-26 Outokumpu Oyj Method for manufacturing and utilizing ferritic-austenitic stainless steel
JP2014001422A (en) * 2012-06-18 2014-01-09 Nippon Steel & Sumitomo Metal Austenitic stainless steel plate and manufacturing method for the same
JP2016065296A (en) * 2014-09-26 2016-04-28 エア・ウォーターＮｖ株式会社 Steel ball for game and method for producing the same

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000026428A1 (en) * 1998-11-02 2000-05-11 Crs Holdings, Inc. Cr-mn-ni-cu austenitic stainless steel
JP3696552B2 (en) * 2001-04-12 2005-09-21 日新製鋼株式会社 Soft stainless steel plate with excellent workability and cold forgeability
WO2005073422A1 (en) * 2004-01-29 2005-08-11 Jfe Steel Corporation Austenitic-ferritic stainless steel
KR101467616B1 (en) * 2007-12-20 2014-12-01 에이티아이 프로퍼티즈, 인코퍼레이티드 Corrosion resistant lean austenitic stainless steel
SE533635C2 (en) * 2009-01-30 2010-11-16 Sandvik Intellectual Property Austenitic stainless steel alloy with low nickel content, and article thereof
TWI460293B (en) * 2011-10-21 2014-11-11 Nippon Steel & Sumikin Sst Duplex stainless steel, duplex stainless steel slab, and duplex stainless steel material
ES2885758T3 (en) * 2012-01-20 2021-12-15 Solu Stainless Oy Procedure for the manufacture of an austenitic stainless steel product
CN103627970A (en) * 2013-10-30 2014-03-12 振石集团东方特钢股份有限公司 Vanadium-containing austenitic stainless steel
FI125105B (en) * 2013-11-04 2015-06-15 Outokumpu Oy Austenitic stainless steel with grain boundary corrosion and method of manufacture
KR20150074697A (en) * 2013-12-24 2015-07-02 주식회사 포스코 Low-nickel containing stainless steels
JP6763759B2 (en) * 2015-11-20 2020-09-30 日本精線株式会社 Duplex stainless steel wire with excellent magnetic properties, and magnetic wire mesh products for sieves, net conveyors, or filters
KR101952808B1 (en) * 2017-08-22 2019-02-28 주식회사포스코 Low nickel austenitic stainless steel having excellent hot workability and hydrogen embrittlement resistance

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101056235B1 (en) * 2008-11-25 2011-08-11 주식회사 포스코 Prediction of Material Properties of Austenitic Stainless Steel Cold Rolled Products
KR20120091075A (en) * 2009-11-02 2012-08-17 에이티아이 프로퍼티즈, 인코퍼레이티드 Lean austenitic stainless steel
WO2012143610A1 (en) * 2011-04-18 2012-10-26 Outokumpu Oyj Method for manufacturing and utilizing ferritic-austenitic stainless steel
JP2014001422A (en) * 2012-06-18 2014-01-09 Nippon Steel & Sumitomo Metal Austenitic stainless steel plate and manufacturing method for the same
JP2016065296A (en) * 2014-09-26 2016-04-28 エア・ウォーターＮｖ株式会社 Steel ball for game and method for producing the same

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FI3822384T3 (en) 2023-03-20
KR20200018995A (en) 2020-02-21

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