WO2017111526A1 - 응력부식균열 저항성 및 저온인성이 우수한 저항복비 고강도 강재 - Google Patents

응력부식균열 저항성 및 저온인성이 우수한 저항복비 고강도 강재 Download PDF

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WO2017111526A1
WO2017111526A1 PCT/KR2016/015156 KR2016015156W WO2017111526A1 WO 2017111526 A1 WO2017111526 A1 WO 2017111526A1 KR 2016015156 W KR2016015156 W KR 2016015156W WO 2017111526 A1 WO2017111526 A1 WO 2017111526A1
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resistance
strength
temperature toughness
steel
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PCT/KR2016/015156
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English (en)
French (fr)
Korean (ko)
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장성호
이학철
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주식회사 포스코
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Priority to EP16879393.3A priority Critical patent/EP3395987B1/de
Priority to JP2018532057A priority patent/JP6691217B2/ja
Priority to US16/063,886 priority patent/US20180371588A1/en
Priority to CA3009137A priority patent/CA3009137C/en
Priority to CN201680075892.9A priority patent/CN108431274B/zh
Publication of WO2017111526A1 publication Critical patent/WO2017111526A1/ko

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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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D6/001—Heat treatment of ferrous alloys containing 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
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/06—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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to a high-resistance steel composite with excellent resistance to stress corrosion cracking resistance and low temperature toughness.
  • the steel used for the liquefied gas storage tank varies depending on the type of liquefied gas, but the liquefaction temperature of the gas is generally low temperature (-52 ° C in the case of LPG) at normal pressure, so that the low temperature toughness of the base metal and the weld is excellent. Has been required.
  • liquid ammonia is known to cause stress corrosion cracking (SCC) of steel, and in the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC CODE), oxygen partial pressure, temperature, etc.
  • SCC stress corrosion cracking
  • IRC CODE International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk
  • the Ni content of the steel is limited to 5% or less and the actual yield strength is limited to 440 MPa or less.
  • the stress relief of the weld portion is an important part.
  • a method of removing the weld stress there is a PWHT (Post Welding Heat Treatment) method by heat treatment, and there is a mechanical stress relief (MSR) method for removing stress by adding hydrostatic pressure to the weld.
  • MSR mechanical stress relief
  • the weld stress is removed using the mechanical stress relief (MSR) method, since the deformation due to the hydraulic pressure is applied to the base metal part, the yield ratio of the base material is limited to 0.8 or less.
  • Patent Document 1 has been proposed a technique for adding 6.5 to 12.0% Ni in order to implement excellent low-temperature toughness.
  • Patent Literature 2 has proposed a technique of mixing tempered martensite and bainite by quenching a steel having a specific composition.
  • the present invention has a problem of inferior economic efficiency due to high expensive Ni content, and has a problem that may cause a decrease in stress corrosion cracking (SCC) resistance.
  • SCC stress corrosion cracking
  • Patent Document 3 has been proposed a technique for softening only the surface layer of the steel sheet in order to implement a resistance compounding.
  • this technique can achieve low-temperature toughness and resistance ratio, respectively, it is difficult to obtain the low-temperature toughness and resistance ratio at the same time.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 63-290246
  • Patent Document 2 Japanese Patent Application Laid-Open No. 58-153730
  • Patent Document 3 Japanese Patent Application Laid-Open No. 4-17613
  • One aspect of the present invention is to provide a high-resistance-ratio high-strength steel and its manufacturing method excellent in stress corrosion cracking resistance and low temperature toughness.
  • One aspect of the present invention by weight, carbon (C): 0.02 ⁇ 0.10%, manganese (Mn): 0.5 ⁇ 2.0%, silicon (Si): 0.05 ⁇ 0.5%, nickel (Ni): 0.05 ⁇ 1.0%, Titanium (Ti): 0.005 to 0.1%, Aluminum (Al): 0.005 to 0.5%, Niobium (Nb): 0.005% or less, Phosphorus (P): 0.015% or less, Sulfur (S): 0.015% or less Contains Fe and other unavoidable impurities, microstructure is area%, acicular ferrite is more than 60%, the remainder is bainite, polygonal ferrite, martensite-austenite constituent (MA)
  • the present invention relates to a high-resistance-resistant high-strength steel having excellent stress corrosion cracking resistance and low temperature toughness including at least one phase.
  • another aspect of the present invention is by weight, carbon (C): 0.02 ⁇ 0.10%, manganese (Mn): 0.5 ⁇ 2.0%, silicon (Si): 0.05 ⁇ 0.5%, nickel (Ni): 0.05 ⁇ 1.0%, Titanium (Ti): 0.005 to 0.1%, Aluminum (Al): 0.005 to 0.5%, Niobium (Nb): 0.005% or less, Phosphorus (P): 0.015% or less, Sulfur (S): 0.015%
  • nickel (Ni): 0.05 ⁇ 1.0% nickel
  • Titanium (Ti): 0.005 to 0.1% 0.005 to 0.1%
  • It relates to a stress corrosion cracking resistance and low-temperature toughness high strength steels excellent manufacturing method comprising the step of cooling to a temperature below 300 °C after the finish rolling.
  • the present invention by controlling the alloy composition and the microstructure, there is an effect that can provide a high-resistance-ratio high-strength steel and excellent method for stress corrosion cracking resistance and low temperature toughness.
  • Figure 2 is a microstructure of 1 / 4t part of the steel sheet of A-5 of Comparative Example It is the photograph (1- (1) of FIG. 1) observed with the optical microscope.
  • Figure 3 is a microstructure of 1 / 4t part of the steel sheet of the invention A-1 It is the photograph (1- (2) of FIG. 1) observed with the optical microscope.
  • Figure 4 is a microstructure of 1 / 4t part of the steel sheet of A-6 of Comparative Example It is the photograph (1- (3) of FIG. 1) observed with the optical microscope.
  • the present inventors have recognized that it is difficult to improve both ammonia stress corrosion cracking resistance and low temperature toughness, and studied in depth to solve this problem.
  • the stress-ratio crack resistance and the low-temperature toughness high strength steel having excellent low temperature toughness are% by weight, carbon (C): 0.02 to 0.10%, manganese (Mn): 0.5 to 2.0%, and silicon (Si): 0.05 to 0.5%, nickel (Ni): 0.05 to 1.0%, titanium (Ti): 0.005 to 0.1%, aluminum (Al): 0.005 to 0.5%, niobium (Nb): 0.005% or less, phosphorus (P) : 0.015% or less, sulfur (S): 0.015% or less, containing the remaining Fe and other unavoidable impurities,
  • Microstructure is the area%, acicular ferrite (Acicular Ferrite) is more than 60%, the rest includes at least one phase of bainite (Bainite), Polygonal Ferrite (Martensite-Austenite constituent).
  • the content of each component means weight%.
  • C is the most important element for securing basic strength, it needs to be contained in steel within an appropriate range, and in order to obtain such an addition effect, it is preferable to add C 0.02% or more.
  • the C content is less than 0.02%, it is not preferable because it can lead to a decrease in yield ratio with a drop in strength.
  • the C content exceeds 0.10%, there is a problem that the yield strength upper limit that can cause ammonia stress corrosion cracking (SCC) is generated a large amount of low-temperature transformation phase, such as bainite.
  • SCC stress corrosion cracking
  • the content of C is preferably limited to 0.02 to 0.10%. More preferably, it is 0.05 to 0.08%.
  • Si has the effect of strengthening the strength by solid solution strengthening effect, and is an element that is also usefully used as a deoxidizer in the steelmaking process.
  • the Si content is less than 0.05%, the deoxidation effect and the strength improving effect may be insufficient.
  • the Si content is more than 0.5%, there is a problem in lowering the low temperature toughness and at the same time deteriorating the weldability.
  • the content of the silicon is preferably limited to 0.05 ⁇ 0.5%. More preferably, it is 0.05 to 0.3%.
  • Manganese contributes to the ferrite grain refinement and is a useful element for enhancing strength by solid solution strengthening.
  • the Mn content is preferably limited to 0.5 to 2.0%. More preferably, it is 1.0 to 1.5%.
  • Ni is an important element for facilitating cross slip of dislocations at low temperatures, improving impact toughness, improving hardenability, and improving strength. To achieve this effect, Ni is preferably added at least 0.05%. However, when the Ni content is more than 1.0%, it may cause ammonia stress corrosion cracking (SCC), and the manufacturing cost may also increase due to the high cost of Ni relative to other hardenable elements.
  • SCC stress corrosion cracking
  • the Ni content is preferably limited to 0.05 to 1.0%. More preferably, it is 0.2 to 0.5%.
  • Nb is known to have an effect of refining austenite by inhibiting recrystallization of austenite because Nb precipitated very finely in the form of NbC when reheated to a high temperature.
  • the yield strength may be excessively increased, and thus the yield strength may be exceeded, which may cause ammonia stress corrosion cracking (SCC). Therefore, Nb is preferably controlled at 0.005% or less. More preferably, it is 0.003% or less.
  • Titanium can greatly improve low-temperature toughness by forming oxides and nitrides in steel to suppress grain growth upon reheating, and is effective for miniaturizing welded microstructures.
  • the titanium content is preferably 0.005 to 0.1%. More preferably, it is 0.01 to 0.03%.
  • Aluminum is a useful element for deoxidizing molten steel, which needs to be added at 0.005% by weight or more. However, if the content exceeds 0.5% by weight it is not preferable because it causes nozzle clogging during continuous casting. Therefore, the aluminum content is preferably 0.005 to 0.5%. More preferably, it is 0.005 to 0.05%.
  • Phosphorus is an element that causes grain boundary segregation in the base metal and the welded part, which causes the problem of embrittlement of the steel, and thus it is necessary to actively reduce it.
  • the load of the steelmaking process is intensified, and the above-mentioned problem does not occur significantly when the phosphorus content is less than 0.015%, so the upper limit thereof is limited to 0.015%, more preferably 0.010% by weight. .
  • Sulfur (S) is an element that causes MgS and the like to cause thermal embrittlement and thus greatly impairs impact toughness. Therefore, the sulfur (S) is preferably controlled as low as possible, so the content is limited to 0.015% by weight or less, and more preferably 0.005% by weight. do.
  • 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, all of them are not specifically mentioned in the present specification.
  • the microstructure of the steel of the present invention is the area%, acicular ferrite (60% or more), the rest of the bainite (Bainite), polygonal ferrite (Polygonal Ferrite), MA (Martensite-Austenite constituent) at least one phase It includes.
  • the area fraction of acicular ferrite is preferably 60% or more.
  • the tensile strength and the low temperature impact toughness may be inferior, and thus the microstructure of the steel of the present invention may not include pearlite.
  • the acicular ferrite may have a size of 30 ⁇ m or less as measured by a circular equivalent diameter. If the size exceeds 30 ⁇ m, impact toughness may be inferior.
  • bainite is preferably granular bainite and upper bainite.
  • the bainite area fraction is preferably 30% or less. If the bainite area fraction exceeds 30%, it is necessary to limit the bainite fraction as it may exceed the upper limit of yield strength (440 MPa) that can cause ammonia stress corrosion cracking (SCC).
  • the said MA phase is 10 area% or less, and the magnitude
  • Martensite-Austenite constituent (MA) is also known as iconic martensite.
  • the toughness of the base material and the welded part tends to be greatly reduced, so it is necessary to limit the fraction and size of the MA phase.
  • the steel material of the present invention that satisfies the above condition may have a yield ratio (YS / TS) of 0.85 or less, preferably 0.8 or less.
  • the steel material may have excellent tensile strength of about 490 MPa or more, for example, about 510 to 610 MPa.
  • the upper limit of the steel yield strength does not exceed the upper limit of the yield strength for generating ammonia stress corrosion cracking (SCC) to 440MPa or less, it may be excellent in ammonia stress corrosion cracking (SCC) resistance.
  • the impact transition temperature of 1 / 4t portion in the thickness direction of the steel material can be excellent in low temperature toughness of -60 °C or less.
  • t means the thickness of the steel.
  • the steel has a thickness of 6mm or more, preferably 6 to 50mm.
  • the steel of the present invention can secure both high strength, resistance ratio, excellent low temperature toughness and ammonia stress corrosion cracking (SCC) resistance.
  • a method for producing a high-resistance steel sheet having excellent stress corrosion cracking resistance and low temperature toughness comprising: heating a slab having the aforementioned alloy composition to 1000 to 1200 ° C;
  • the slab having the alloy composition described above is heated to 1000 to 1200 ° C.
  • the slab heating temperature is preferably at least 1000 ° C, in order to solidify the Ti carbonitride formed during casting.
  • the slab heating temperature is too low, it is preferable to limit the lower limit to 1000 ° C. because the deformation resistance during rolling is so high that the rolling reduction per pass cannot be largely applied in the subsequent rolling process.
  • the upper limit of the heating temperature is preferably 1200 ° C.
  • the heated slab is rough rolled at a temperature of 1100 ⁇ 900 °C.
  • the rough rolling temperature is preferably limited to 1100 ⁇ 900 °C.
  • the rough rolling may be performed so that the last three passes have a reduction ratio per pass of 10% or more.
  • the rolling reduction per pass is 10% or more and the total cumulative rolling reduction is 30% or more for the last three passes during rough rolling.
  • the recrystallized structure causes grain growth due to the high temperature, but during the last three passes, the grain growth rate is slowed down as the bar is air-cooled in the rolling atmosphere. The rate of reduction of the pass is greatest for the particle size of the final microstructure.
  • the total cumulative reduction rate during rough rolling is preferably set to 30% or more in order to refine the central tissue.
  • finish rolling at a temperature between Ar 3 + 100 ° C. and Ar 3 + 30 ° C. based on the central temperature.
  • the finish rolling temperature is lowered below Ar 3 + 30 ° C, the ferrite grain size becomes too fine, exceeding the upper limit of yield strength (440MPa) that generates ammonia stress corrosion cracking (SCC), and finish at the temperature exceeding Ar 3 + 100 ° C.
  • the finish rolling temperature between Ar 3 + 100 ° C. and Ar 3 + 30 ° C., and the microstructure of the steel sheet manufactured by performing finish rolling under such conditions is a composite structure having the characteristics as described above. Can be.
  • the temperature is cooled to 300 ° C or lower.
  • Cooling is preferably started to cool at a temperature of Ar 3 + 30 °C ⁇ Ar 3 after the finish rolling to cool to 300 °C or less, such as 100 ⁇ 300 °C Finish Cooling Temperature (FCT, Finish Cooling Temperature).
  • FCT Finish Cooling Temperature
  • the cooling finish temperature (FCT, Finish Cooling Temperature) is more than 300 °C, due to the tempering (Tempering) effect may be difficult to implement the resistance ratio by decomposing the fine MA phase, the cooling finish temperature is preferably 300 °C or less.
  • the central cooling rate is 15 ° C./s or more at Bs-10 ° C. to Bs + 10 ° C., and then the central cooling rate is 10-50 ° C./s until 300 ° C. or less.
  • Two stage cooling can be performed as much as possible.
  • the cooling start temperature may be Ar 3 + 30 °C ⁇ Ar 3 .
  • the first stage cooling starts cooling at the temperature of Ar 3 + 30 °C ⁇ Ar 3 after the finish rolling to the Bs-10 °C ⁇ Bs + 10 °C central cooling rate of the steel sheet is 15 °C / s or more, for example 30 °C / It is preferable to cool at a cooling rate of s or more.
  • the two-stage cooling is preferably cooled to a cooling rate of 10 ° C / s ⁇ 50 ° C / s to the central cooling rate of the steel sheet to 300 ° C or less, for example, 100 ⁇ 300 ° C cooling finish temperature after the first stage cooling.
  • the bainite fraction is formed to 30 area% or more to ammonia stress corrosion cracking (SCC Yield strength exceeding the upper limit (440 MPa) for generating a), and there is a possibility of lowering the elongation and impact toughness due to excessive increase in strength.
  • finish rolling was performed to satisfy the difference between the finish rolling temperature and the Ar 3 temperature shown in Table 2 below to obtain a steel plate having the thickness shown in Table 2, and then cooled at various cooling rates through multi-stage cooling. . At this time, the cooling end temperature of one-step cooling was made into Bs temperature of each steel.
  • the microstructure was mirror-polished after taking specimens from 1 / 4t of steel plate, and then corroded with Nital corrosive solution and observed with optical microscope.
  • the fraction of MA phase was mirror-polished after specimens were taken from the 1 / 4t site, corroded with LePera corrosion solution, and then observed with an optical microscope.
  • yield strength, tensile strength, and yield ratio were measured by collecting a JIS No. 4 specimen in a direction perpendicular to the rolling direction from a 1 / 4t portion of the steel sheet and performing a tensile test at room temperature.
  • ammonia stress corrosion cracking (SCC) test was carried out using the test solution and test conditions described in Table 4 by making a proof ring specimen, wherein the stress applied was 80% of the actual yield stress, 720 If no fracture occurred during the time, it was evaluated as passing. If the fracture occurred before 720 hours passed, it was evaluated as failed.
  • SCC ammonia stress corrosion cracking
  • AF, B, PF, and MA mean AF: Acicular Ferrite, B: Bainite, PF: Polygonal ferrite, and MA: Martensite / Austenite.
  • the invention examples satisfying the composition and manufacturing conditions proposed by the present invention not only have high strength and high toughness, but also have excellent resistance to ammonia stress corrosion cracking (SCC).
  • the yield ratio is 0.8 or less, it can be seen that the steel having a resistance yield ratio characteristics.
  • the area percent, acicular ferrite (60% or more), the remainder bainite (Bainite), Polygonal Ferrite (Polygonal Ferrite), MA (Martensite-Austenite constituent) It can be confirmed that the mixed tissue consisting of one or more phases.
  • component composition satisfies the present invention, but in the case of Comparative Examples A-2, A-4, A-6, B-2, B-4 and B-6 where the manufacturing conditions do not satisfy the present invention, Polygonal The ferrite fraction was too high or the ferrite grain size was too coarse to secure tensile strength and low temperature toughness.
  • the production conditions satisfy the present invention, but in the case of Comparative Examples C-1 to F-4 in which the composition of the composition does not satisfy the present invention, the Bainite fraction is too high, the Acicular Ferrite grain size is too small, or MA As the fraction of phase becomes too high, ammonia stress corrosion cracking (SCC) can occur.
  • SCC ammonia stress corrosion cracking
  • the yield strength exceeded the upper limit (440 MPa), resulting in ammonia stress corrosion cracking, and it was not possible to secure a resistance ratio and low temperature toughness.

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PCT/KR2016/015156 2015-12-23 2016-12-23 응력부식균열 저항성 및 저온인성이 우수한 저항복비 고강도 강재 WO2017111526A1 (ko)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP16879393.3A EP3395987B1 (de) 2015-12-23 2016-12-23 Hochfeste stahlplatte mit niedriger streckgrenze und ausgezeichneter spannungsrisskorrosionsbeständigkeit und niedriger temperaturzähigkeit
JP2018532057A JP6691217B2 (ja) 2015-12-23 2016-12-23 応力腐食割れ抵抗性及び低温靭性に優れた低降伏比高強度鋼材及びその製造方法
US16/063,886 US20180371588A1 (en) 2015-12-23 2016-12-23 Low yield ratio and high-strength steel having excellent stress corrosion cracking resistance and low temperature toughness
CA3009137A CA3009137C (en) 2015-12-23 2016-12-23 Low-yield ratio and high-strength steel having excellent stress corrosion cracking resistance and low temperature toughness
CN201680075892.9A CN108431274B (zh) 2015-12-23 2016-12-23 抗应力腐蚀开裂性及低温韧性优异的低屈强比高强度钢材

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KR1020150185496A KR101767778B1 (ko) 2015-12-23 2015-12-23 응력부식균열 저항성 및 저온인성이 우수한 저항복비 고강도 강재
KR10-2015-0185496 2015-12-23

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WO2017111526A1 true WO2017111526A1 (ko) 2017-06-29

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US (1) US20180371588A1 (de)
EP (1) EP3395987B1 (de)
JP (1) JP6691217B2 (de)
KR (1) KR101767778B1 (de)
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