WO2020085847A1 - Acier austénitique à haute teneur en manganèse pour applications cryogéniques ayant une excellente qualité de surface et une excellente résistance à la fissuration par corrosion sous contrainte, et son procédé de fabrication - Google Patents

Acier austénitique à haute teneur en manganèse pour applications cryogéniques ayant une excellente qualité de surface et une excellente résistance à la fissuration par corrosion sous contrainte, et son procédé de fabrication Download PDF

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WO2020085847A1
WO2020085847A1 PCT/KR2019/014156 KR2019014156W WO2020085847A1 WO 2020085847 A1 WO2020085847 A1 WO 2020085847A1 KR 2019014156 W KR2019014156 W KR 2019014156W WO 2020085847 A1 WO2020085847 A1 WO 2020085847A1
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corrosion cracking
stress corrosion
less
surface quality
manganese steel
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English (en)
Korean (ko)
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김성규
이상현
강상덕
한상호
이운해
한태교
이동호
조원태
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주식회사 포스코
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Priority to CN201980069177.8A priority Critical patent/CN112888805A/zh
Priority to EP19876375.7A priority patent/EP3872213A4/fr
Publication of WO2020085847A1 publication Critical patent/WO2020085847A1/fr

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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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/16—Control of thickness, width, diameter or other transverse dimensions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • 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
    • 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
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium 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 a cryogenic austenitic high manganese steel material and a method of manufacturing the same, suitable for fuel tanks, storage tanks, ship membranes, and transport pipes for storage and transport of liquefied petroleum gas, liquefied natural gas, etc.
  • the present invention relates to an austenitic high-manganese steel for cryogenic temperature and a method for manufacturing the same, which effectively suppresses the formation of surface defects and effectively secures the surface corrosion cracking resistance.
  • Austenitic high manganese (Mn) steel has a high toughness because it is stable and austenite is stable even at room temperature or cryogenic temperature by adjusting the contents of manganese (Mn) and carbon (C), which are elements that increase the stability of austenite. It can be used as a material for fuel tanks, storage tanks, ship membranes, and transport pipes for storage and transportation of liquefied petroleum gas, liquefied natural gas, and the like.
  • Patent Document 1 Republic of Korea Patent Publication No. 10-2015-0075275 (2015.07.03. Public)
  • the present invention by inducing twin formation in a complex environment of corrosion and deformation, it effectively secures stress corrosion cracking resistance, but suppresses the formation of surface defects in steel to effectively secure the surface quality by cryogenic austenitic high manganese. Steel and a method of manufacturing the same can be provided.
  • Austenitic high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, in weight percent, C: 0.4 to 0.5%, Mn: 23 to 26%, Si: 0.05 to 0.5% , Cr: 3 ⁇ 5%, Cu: 0.3 ⁇ 0.7%, S: 0.05% or less, P: 0.5% or less, Al: 0.001 ⁇ 0.05%, B: 0.005% or less, including residual Fe and unavoidable impurities, 95
  • the austenite of area% or more is included as a microstructure, but the stacked defect energy (SFE) represented by the following relational expression 1 satisfies the range of 150 mJ / m 2 or more, and when the cross section is observed using an optical microscope, t / 8 (from the surface)
  • t denotes the product thickness
  • Ni, Cr, C, Si, and Mn mean the weight percent of each component, and if the component is not included, the value means 0
  • the stress corrosion cracking generation time may be 900 hours or more.
  • the steel material, the yield strength is 400MPa or more, Charpy impact toughness at -196 °C may be 41J or more.
  • Austenitic high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, in weight percent, C: 0.4 to 0.5%, Mn: 23 to 26%, Si: 0.05 to 0.5% , Cr: 3 to 5%, Cu: 0.3 to 0.7%, S: 0.05% or less, P: 0.5% or less, Al: 0.001 to 0.05%, B: 0.005% or less, residual Fe and slabs containing unavoidable impurities Reheating in a temperature range of 1000 to 1150 ° C, roughly rolling the reheated slab to provide a rough rolling bar, and finishing rolling the rough rolling bar in a temperature range of 750 to 1000 ° C to provide a hot rolling material.
  • the slab has a stacking fault energy (SFE) represented by the following relational expression 1 in a range of 150 mJ / m 2 or more.
  • SFE stacking fault energy
  • Ni, Cr, C, Si, and Mn mean the weight percent of each component, and if the component is not included, the value means 0
  • R RM and T SR mean rough rolling reduction (mm) and slab reheating temperature (°C), respectively.
  • the hot-rolled hot rolled material may be accelerated to 600 ° C. or less at a cooling rate of 10 ° C./s or more.
  • cryogenic austenitic high-manganese steel material and a method of manufacturing the same, which effectively secures stress corrosion cracking resistance by inducing twin formation in a complex environment of corrosion and deformation.
  • the present invention relates to an austenitic high-manganese steel for high temperature and a method for manufacturing the same, which is excellent in surface quality and stress corrosion cracking resistance.
  • preferred embodiments of the present invention will be described.
  • the embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below.
  • Embodiments of the present invention are provided to those having ordinary skill in the art to further describe the present invention.
  • Austenitic high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, in weight percent, C: 0.4 to 0.5%, Mn: 23 to 26%, Si: 0.05 to 0.5% , Cr: 3 to 5%, Cu: 0.3 to 0.7%, S: 0.05% or less, P: 0.5% or less, Al: 0.001 to 0.05%, B: 0.005% or less, residual Fe and unavoidable impurities .
  • Carbon (C) is an effective element for stabilizing austenite in steel and securing strength by solid solution strengthening. Therefore, the present invention can limit the lower limit of the carbon (C) content to 0.4% in order to secure low-temperature toughness and strength. That is, when the carbon (C) content is less than 0.4%, the yield strength may be lowered, the austenite stability is lowered, ferrite or martensite is formed, and the low-temperature toughness may be lowered. On the other hand, when the carbon (C) content exceeds a certain range, excessive carbide may be formed upon cooling after rolling, and the present invention may limit the upper limit of the carbon (C) content to 0.5%. Therefore, the carbon (C) content of the present invention may be 0.4 to 0.5%.
  • Manganese (Mn) is an important element that plays a role in stabilizing austenite. Therefore, the present invention can limit the lower limit of the manganese (Mn) content to 23% to achieve this effect. That is, since the present invention includes 23% or more of manganese (Mn), it is possible to effectively increase austenite stability, thereby suppressing the formation of ferrite, ⁇ -martensite, and ⁇ '-martensite, thereby effectively securing low-temperature toughness. You can. On the other hand, when the manganese (Mn) content is more than a certain level, the effect of increasing the austenite stability is saturated, while excessive manufacturing cost is greatly increased, and surface oxidation may be deteriorated due to excessive internal oxidation during hot rolling. The upper limit of the silver manganese (Mn) content may be limited to 26%. Therefore, the manganese (Mn) content of the present invention may be 23 to 26%.
  • Silicon (Si) is an element that is indispensably added in trace amounts as a deoxidizer, such as aluminum (Al).
  • a deoxidizer such as aluminum (Al).
  • silicon (Si) is excessively added, an oxide is formed at a grain boundary to reduce high temperature ductility, and there is a fear that surface quality may be lowered by causing cracks, etc., so that the present invention has an upper limit of the silicon (Si) content. It can be limited to 0.50%.
  • an excessive cost is required to reduce the silicon (Si) content in the steel, so the present invention can limit the lower limit of the silicon (Si) content to 0.05%. Therefore, the silicon (Si) content of the present invention may be 0.05 to 0.50%.
  • Chromium (Cr) is an element that contributes to the increase in strength through solid solution strengthening in austenite.
  • Cr Cr
  • the present invention can limit the lower limit of the chromium (Cr) content to 3% to achieve this effect.
  • the present invention may limit the upper limit of the chromium (Cr) content to 5%. Therefore, the chromium (Cr) content of the present invention may be 3 to 5%.
  • Copper (Cu) is an austenite stabilizing element and is an element that stabilizes austenite together with manganese (Mn) and carbon (C), and is an element contributing to the improvement of low-temperature toughness.
  • copper (Cu) is a very low solid solution in carbide and has a slow diffusion in austenite, it is concentrated at the interface between austenite and carbide to surround the nucleus of fine carbide to further diffuse carbon (C). It is an element that effectively suppresses the formation and growth of carbides. Therefore, the present invention can limit the lower limit of the copper (Cu) content to 0.3% to achieve this effect.
  • the present invention may limit the upper limit of the copper (Cu) content to 0.7%. Therefore, the copper (Cu) content of the present invention may be 0.3 to 0.7%.
  • the present invention can actively suppress the upper limit of the sulfur (S) content
  • the upper limit of the preferred sulfur (S) content may be 0.05%.
  • Phosphorus (P) 0.5% or less
  • Phosphorus (P) is an element that is easily segregated and causes cracking during casting or degrades weldability. Therefore, the present invention can actively suppress the upper limit of the phosphorus (P) content, the upper limit of the preferred phosphorus (P) content may be 0.5%.
  • Aluminum (Al) is a representative element added as a deoxidizer. Therefore, the present invention can limit the lower limit of the aluminum (Al) content to 0.001%, more preferably the lower limit of the aluminum (Al) content to 0.005% to achieve this effect.
  • aluminum (Al) may form precipitates by reacting with carbon (C) and nitrogen (N), and the hot workability may be deteriorated by these precipitates, and the present invention provides an upper limit of the aluminum (Al) content. It can be limited to 0.05%.
  • the upper limit of the more preferable aluminum (Al) content may be 0.045%.
  • Boron (B) is an element that contributes to the improvement of surface quality by suppressing grain boundary destruction through strengthening of grain boundaries. Therefore, the present invention may add boron (B) to achieve this effect, the lower limit of the more preferred boron (B) content may be 0.0001%. However, when boron (B) is excessively added, there is a fear that toughness and weldability may be deteriorated due to the formation of coarse precipitates, and the present invention may limit the upper limit of the boron (B) content to 0.005%.
  • the austenite-based high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to an aspect of the present invention, may contain residual Fe and other unavoidable impurities.
  • unintended impurities may be inevitably mixed from the raw material or the surrounding environment, and thus cannot be excluded. Since these impurities are known to anyone skilled in the art, they are not specifically mentioned in this specification. In addition, addition of effective ingredients other than the above composition is not excluded.
  • the austenite-based high-manganese steel for cryogenic properties which has excellent surface quality and stress-bushion crack resistance according to an aspect of the present invention, has an alloy component so that the stacked defect energy (SFE) represented by the following relational expression 1 satisfies a range of 150 mJ / m 2 or more.
  • the content of can be controlled.
  • Ni, Cr, C, Si, and Mn mean the weight percent of each component, and if the component is not included, the value means 0
  • the inventors of the present invention have conducted an in-depth study of the mechanism for generating stress corrosion cracking, and when controlling the stacked defect energy (SFE) defined by the relational expression 1 to a certain level or more, twin formation in a stress and corrosion environment It was found that the resistance to stress corrosion cracking can be effectively improved by inducing.
  • SFE stacked defect energy
  • a slip band or a slip step is formed on the surface because the electric potential acts and deformation occurs, and the stress corrosion cracking that develops into a crack occurs due to the accelerated local corrosion
  • the high-manganese steel material of the present invention is a relational formula 1 Since the stacked defect energy (SFE) indicated by is controlled to 150 mJ / m 2 or more, twins are formed in a stress and corrosion environment, thereby ensuring excellent stress corrosion cracking resistance.
  • SFE stacked defect energy
  • the austenitic high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, is subjected to stress corrosion cracking when immersed in a 25% NaCl solution at 100 ° C after applying stress at a yield strength level. It is possible to secure excellent stress corrosion cracking resistance with an occurrence time of 900 hours or more.
  • the austenite-based high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, contains at least 95% by area of austenite as a microstructure, and when sectional observation is performed using an optical microscope, The number of surface flaws formed at a depth of 10 ⁇ m or more from the surface may be 0.0001 or less per unit area (mm 2 ) with respect to the cross-sectional area from the surface to the point t / 8 (where t means product thickness).
  • the austenite-based high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to an aspect of the present invention, actively suppresses surface defect formation on the product surface through strict process condition control as described below. , By effectively securing the surface quality, it is possible to omit subsequent processes such as a grinding process, thereby effectively securing economic efficiency and productivity.
  • an austenitic high-manganese steel for cryogenic properties with excellent surface quality has a yield strength of 400 MPa or more and a Charpy impact toughness of 41 J or more at -196 ° C, so liquefied petroleum gas, liquefaction requiring cryogenic properties It is possible to provide an austenitic high manganese steel material particularly suitable for materials such as fuel tanks for storage and transportation of natural gas, storage tanks, ship membranes, and transport pipes.
  • Austenitic high-manganese steel for cryogenic properties which has excellent surface quality and stress corrosion cracking resistance according to one aspect of the present invention, in weight percent, C: 0.4 to 0.5%, Mn: 23 to 26%, Si: 0.05 to 0.5% , Cr: 3 to 5%, Cu: 0.3 to 0.7%, S: 0.05% or less, P: 0.5% or less, Al: 0.001 to 0.05%, B: 0.005% or less, residual Fe and slabs containing unavoidable impurities Reheating in a temperature range of 1000 to 1150 ° C, roughly rolling the reheated slab to provide a rough rolling bar, and finishing rolling the rough rolling bar in a temperature range of 750 to 1000 ° C to provide a hot rolling material.
  • the slab has a stacking fault energy (SFE) of 150 mJ / m 2 or more represented by the following relational expression 1 Can be satisfied
  • Ni, Cr, C, Si, and Mn mean the weight percent of each component, and if the component is not included, the value means 0
  • R RM and T SR mean rough rolling reduction (mm) and slab reheating temperature (°C), respectively.
  • the hot-rolled hot rolled material may be accelerated to 600 ° C. or less at a cooling rate of 10 ° C./s or more.
  • the description of the steel composition of the slab will be replaced by the description of the steel composition of the austenitic high manganese steel described above.
  • the description of the stacking fault energy (SFE) of the slab is also replaced with the description of the stacking fault energy (SFE) of the austenitic high-manganese steel described above.
  • Slabs provided with the above-described steel composition can be uniformly heated in a temperature range of 1000 to 1150 ° C.
  • the thickness of the slab provided in the slab reheating step may be about 250 mm, but the scope of the present invention is not necessarily limited thereto.
  • the lower limit of the slab reheating temperature may be limited to 1000 ° C. in order to prevent excessive rolling loads in subsequent hot rolling.
  • the higher the heating temperature the easier the hot rolling is secured, but the higher the manganese (Mn) content, the higher the temperature may cause grain boundary oxidation when heated, and the present invention limits the upper limit of the slab reheating temperature to 1150 ° C. You can.
  • a re-heated slab may be roughly rolled with a rough rolling bar, and the hot rolling process may be performed by finishing rolling the rough rolling bar at a temperature range of 750 to 1000 ° C to provide a hot rolled material.
  • the high temperature of the hot rolling finish rolling also lowers the deformation resistance, so that the ease of rolling is secured, but the higher the finish rolling temperature causes the surface quality to decrease due to grain boundary oxidation, so the finish rolling temperature of the present invention is 750 to 1000 ° C. Can be limited.
  • the austenitic high-manganese steel of the present invention contains a large amount of manganese (Mn) having strong oxidizing properties, intergranular oxidation is inevitably caused by temperature limitations of the heating furnace. Even if some of the grain boundary oxidation formed during slab reheating is removed by scale, the remaining part grows as a crack during hot rolling to form a surface defect on the surface of the product, thereby deteriorating the surface quality of the product.
  • Mn manganese
  • the inventors of the present invention have reached the conclusion that it is effective to refine the tissue by heating the slab as quickly as possible to minimize re-crystallization to minimize the growth of grain boundary oxidation remaining on the slab surface during hot rolling.
  • an increase in the strain rate is most effective, and an increase in the strain rate is a factor that can be reached through an increase in the rolling amount of the rough rolling, but minimizes the growth of grain boundary oxidation into cracks when the rolling amount is excessively increased.
  • equipment damage due to excessive rolling load may be a problem.
  • the inventor of the present invention has drawn the following relational expression 2, which controls the rolling load of hot rolling to a threshold value or less while actively suppressing the formation of surface flaws in the product through repeated experiments.
  • the present invention controls the amount of rough rolling in relation to the furnace temperature to a certain range, as in the relational expression 2 above, so that when the temperature of the furnace is high, the amount of rolling reduction in the rough rolling is relatively increased so that intergranular oxidation during hot rolling is surface flaw. Growth can be suppressed, and when the furnace temperature is low, the rolling load applied to the rolling mill during hot rolling can be reduced by relatively reducing the rolling amount of rough rolling, so that the optimum slab heating conditions and hot rolling conditions Can provide
  • the hot-rolled hot rolled material may be accelerated to 600 ° C. or less at a cooling rate of 10 ° C./s or more. Since the austenitic high-manganese steel of the present invention contains 3 to 5% of chromium (Cr) and C, the cooling rate of the hot rolled material is controlled to 10 ° C./s or more to effectively prevent low-temperature toughness degradation due to carbide precipitation. You can. In addition, in normal accelerated cooling, a cooling rate exceeding 100 ° C / s is difficult to implement due to the characteristics of the equipment, and the present invention can limit the upper limit of the cooling rate to 100 ° C / s.
  • Cr chromium
  • the present invention can limit the cooling stop temperature to 600 ° C. have.
  • the austenitic high-manganese steel produced as described above contains 95% by area or more of austenite as a microstructure, and when observed in cross section using an optical microscope, t / 8 from the surface (where t means product thickness)
  • the number of surface flaws formed at a depth of 10 ⁇ m or more from the surface with respect to the cross-sectional area up to the point may be 0.0001 or less per unit area (mm 2 ), and may have a yield strength of 400 MPa or more and a Charpy impact toughness of 41 J or more at -196 ° C. have.
  • the stress corrosion cracking generation time is more than 900 hours, ensuring excellent stress corrosion cracking resistance. can do.
  • a slab having the composition of Table 1 was prepared to a thickness of 250 mm, and prepared through the process conditions of Table 2 to prepare a specimen.
  • Each specimen was prepared by finish rolling in a temperature range of 750 to 1000 ° C, and accelerated cooling to 600 ° C or less at a cooling rate of 10 ° C / s or higher.
  • Impact absorption energy, yield strength, surface flaw formation and stress corrosion cracking properties were evaluated for each specimen, and the results are shown in Table 2.
  • the shock absorption energy was evaluated at -196 ° C using a plate-shaped specimen having a notch of 2 mm according to the standard test method ASTM E23.
  • the tensile test was performed by processing a plate specimen according to the standard test method ASTM E8 / E8M and evaluated by a one-way tensile tester. Depth and number of surface flaws are prepared by cutting specimens in the thickness direction to prepare specimens according to ASTM E112, and then using an optical microscope, the depth of the largest surface flaw in the viewing area and the number of surface flaws greater than 10 ⁇ m per unit area in the viewing area was measured and evaluated.
  • the stress corrosion cracking properties were evaluated by the ASTM G123 standard method as shown in FIG. 2, and the stress was measured by measuring the time at which fracture occurred by immersing in a 25% NaCl solution at 100 ° C after applying stress at the yield strength level to the specimen for testing. .
  • Specimen 1 is a 304 stainless steel specimen, and a slip band is formed under a stress and corrosion environment, so that the stress corrosion cracking resistance can be significantly deteriorated. Specimen 1 did not perform surface quality and low-temperature physical properties measurements, and the results were not described. In the case of the specimens 2 to 5, since it satisfies the limited stacking defect energy (SFE) range of the present invention, it can be seen that twins are formed under a stress and corrosion environment, thereby securing excellent stress corrosion cracking resistance.
  • 1 and 2 are photographs of the results of the stress corrosion cracking test of the specimen 1 and the specimen 4, the crack occurred in the specimen 1, while in the case of the specimen 4 it can be clearly confirmed that the crack did not occur.

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  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

Un aspect de la présente invention peut fournir un acier austénitique à haute teneur en manganèse pour des applications cryogéniques et son procédé de fabrication, l'acier austénitique à haute teneur en manganèse pour des applications cryogéniques assurant efficacement une résistance à la fissuration par corrosion sous contrainte par induction de la formation de monocristaux dans des environnements composites de corrosion et de transformation, et assure efficacement une qualité de surface par suppression de la formation de fissures dans la surface de l'acier.
PCT/KR2019/014156 2018-10-25 2019-10-25 Acier austénitique à haute teneur en manganèse pour applications cryogéniques ayant une excellente qualité de surface et une excellente résistance à la fissuration par corrosion sous contrainte, et son procédé de fabrication WO2020085847A1 (fr)

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CN201980069177.8A CN112888805A (zh) 2018-10-25 2019-10-25 表面品质和抗应力腐蚀开裂性优良的超低温用奥氏体高锰钢材及其制造方法
EP19876375.7A EP3872213A4 (fr) 2018-10-25 2019-10-25 Acier austénitique à haute teneur en manganèse pour applications cryogéniques ayant une excellente qualité de surface et une excellente résistance à la fissuration par corrosion sous contrainte, et son procédé de fabrication

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KR10-2018-0128503 2018-10-25
KR1020180128503A KR20200046831A (ko) 2018-10-25 2018-10-25 표면품질 및 응력부식균열 저항성이 우수한 극저온용 오스테나이트계 고 망간 강재 및 그 제조방법

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CN116926443A (zh) * 2022-04-07 2023-10-24 南京钢铁股份有限公司 超低温钢及其热处理工艺和应用

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CN112888805A (zh) 2021-06-01

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