WO2018004297A1 - Plaque d'acier à haute résistance présentant d'excellentes caractéristiques de faible coefficient d'élasticité et une ténacité à basse température et son procédé de fabrication - Google Patents

Plaque d'acier à haute résistance présentant d'excellentes caractéristiques de faible coefficient d'élasticité et une ténacité à basse température et son procédé de fabrication Download PDF

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WO2018004297A1
WO2018004297A1 PCT/KR2017/006956 KR2017006956W WO2018004297A1 WO 2018004297 A1 WO2018004297 A1 WO 2018004297A1 KR 2017006956 W KR2017006956 W KR 2017006956W WO 2018004297 A1 WO2018004297 A1 WO 2018004297A1
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steel sheet
low temperature
less
temperature toughness
ratio
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PCT/KR2017/006956
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English (en)
Korean (ko)
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김우겸
방기현
엄경근
유승호
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주식회사 포스코
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Priority to JP2018566924A priority Critical patent/JP6771047B2/ja
Priority to CN201780039727.2A priority patent/CN109328240B/zh
Priority to EP17820573.8A priority patent/EP3480332B1/fr
Publication of WO2018004297A1 publication Critical patent/WO2018004297A1/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
    • 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
    • C21D1/28—Normalising
    • 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
    • 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
    • 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
    • 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
    • C22C38/02—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
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • 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-strength steel sheet excellent in resistivity ratio and low temperature toughness and a method of manufacturing the same.
  • Steels with resistance yield ratio not only have excellent formability by increasing the difference between yield strength and tensile strength, but also delay the plastic deformation time until fracture can occur and absorb energy in this process to prevent collapse by external force. can do. In addition, even if there is a deformation, it is possible to repair before collapse, thereby preventing damage to property and life due to damage to the structure.
  • the technology of two phase organization of steel was developed. Specifically, the first phase is soft ferrite, and the remaining second phase is martensite, pearlite, or bainite, thereby implementing a resistance ratio.
  • the impact toughness due to the hard two phase and the carbon content is increased for the second phase, so that the toughness of the weld is degraded, thereby causing brittle fracture of the structure at low temperature.
  • Patent Literature 1 has been developed as a technique for securing both resistance ratio and low temperature impact toughness.
  • the microstructure includes 2-10 vol% of MA (martensite / austenite mixed structure) and 90 vol% or more of cyclic ferrite, thereby ensuring resistance ratio and excellent low temperature toughness.
  • Patent Document 1 it is possible to implement a yield ratio of about 0.8 but there is an insufficient problem to secure the seismic characteristics can not implement a sufficient resistance yield ratio.
  • Patent Document 1 Korean Unexamined Patent Publication No. 2013-0076577
  • One aspect of the present invention is to provide a high-strength steel sheet excellent in resistance ratio ratio characteristics and low temperature toughness and a method of manufacturing the same.
  • One aspect of the present invention is by weight, C: 0.03-0.08%, Si: 0.05-0.3%, Mn: 1.0-2.0%, Al: 0.005-0.04%, Nb: 0.005-0.04%, Ti: 0.001-0.02 %, Cu: 0.05-0.4%, Ni: 0.6-2.0%, Mo: 0.08-0.3%, N: 0.002-0.006%, P: 0.01% or less, S: 0.003% or less, including remaining Fe and unavoidable impurities ,
  • the microstructure includes 80 to 92% of ferrite and 8 to 20% of MA (martensite / austenite mixed structure) as an area fraction, and the MA has a resistivity ratio characteristic of 3 ⁇ m or less in average size measured in equivalent diameter and It relates to a high strength steel sheet excellent in low temperature toughness.
  • MA martensite / austenite mixed structure
  • another aspect of the present invention is by weight, C: 0.03-0.08%, Si: 0.05-0.3%, Mn: 1.0-2.0%, Al: 0.005-0.04%, Nb: 0.005-0.04%, Ti: 0.001 to 0.02%, Cu: 0.05 to 0.4%, Ni: 0.6 to 2.0%, Mo: 0.08 to 0.3%, N: 0.002 to 0.006%, P: 0.01% or less, S: 0.003% or less, remaining Fe and unavoidable impurities Heating the slab including 1050 to 1200 ° C;
  • T is a value measured in mm of the thickness of the hot rolled steel sheet.
  • the present invention can be applied not only to shipbuilding and marine structural steel fields but also to industrial fields requiring molding and seismic characteristics.
  • Test No. 1 is a photograph taken with a scanning electron microscope (SEM) of the microstructure of Test No. 1 as an example of the invention.
  • the present inventors are able to secure a yield ratio of about 0.8 in the prior art, but it is possible to secure a certain degree of moldability, but it is not possible to implement a sufficient resistance ratio, recognizing that there is an insufficient problem of securing seismic characteristics, and solved this. In order to study deeply.
  • the base material lacks the hardness difference from the MA as an ecuous ferrite, MA It was found that the phase was formed at grain boundaries and the MA size was coarse to achieve sufficient resistance ratio.
  • the microstructure of the base material is made of ferrite, and the fine MA phase is uniformly distributed in the ferrite grain boundary and the inside of the grain, so that a resistivity ratio of 0.65 or less can be secured. It was confirmed that the control to include, and came to complete the present invention.
  • High-strength steel sheet having excellent resistance ratio and low temperature toughness is a weight%, C: 0.03 ⁇ 0.08%, Si: 0.05 ⁇ 0.3%, Mn: 1.0 ⁇ 2.0%, Al: 0.005 ⁇ 0.04%, Nb: 0.005 to 0.04%, Ti: 0.001 to 0.02%, Cu: 0.05 to 0.4%, Ni: 0.6 to 2.0%, Mo: 0.08 to 0.3%, N: 0.002 to 0.006%, P: 0.01% or less, S: 0.003% or less, including the remaining Fe and inevitable impurities,
  • the microstructure includes 80 to 92% of ferrite and 8 to 20% of MA (martensite / austenite mixed structure) in an area fraction, and the MA has an average size of 3 ⁇ m or less measured in a circular equivalent diameter.
  • C is an element that causes solid solution strengthening and exists as carbonitride by Nb to secure tensile strength.
  • Si serves to deoxidize molten steel by assisting Al, and is added to secure yield strength and tensile strength.
  • the Si content is less than 0.05%, the above effects are insufficient.
  • the Si content is more than 0.3%, the impact property may be degraded by coarsening of the MA, and the welding property may be degraded.
  • Mn contributes greatly to the strength increasing effect by solid solution strengthening and is an element that helps to form bainite.
  • the Mn content is less than 1.0%, the above effects are insufficient. On the other hand, excessive addition may cause a decrease in toughness due to the formation of MnS inclusions and segregation of the central portion, so the upper limit is 2.0%.
  • Al needs to be added 0.005% or more as a major deoxidizer of steel. However, when added in excess of 0.04%, the effect is saturated and may cause low temperature toughness by increasing the fraction and size of Al 2 O 3 inclusions.
  • Nb is an element that suppresses recrystallization during rolling or cooling by precipitation of solid solution or carbonitride, thereby making the structure fine and increasing the strength.
  • the Nb content is less than 0.005%, the above effects are insufficient.
  • the Nb content is more than 0.04%, there is a problem that can lower the toughness of the base metal and the toughness after welding.
  • Ti combines with oxygen or nitrogen to form precipitates, thereby inhibiting coarsening of tissues and contributing to miniaturization and improving toughness.
  • Cu is a component that does not significantly reduce the impact characteristics, and thus improves strength by solid solution and precipitation. In order to sufficiently improve the strength, it should be contained in 0.05% or more, but when the Cu content is more than 0.4%, surface cracks of the steel sheet due to Cu thermal shock may occur.
  • Ni is an element that can improve strength and toughness at the same time as the increase in content is not great, and is an element that helps to form bainite by decreasing the Ar3 temperature.
  • the Ni content is less than 0.6%, the above effects are insufficient. On the other hand, when the Ni content is more than 2.0%, the manufacturing cost may increase and the weldability may deteriorate.
  • Mo is an austenite stabilizing element that affects the amount of MA and plays a large role in improving the strength. It is also an element that prevents a drop in strength during heat treatment and helps to form bainite.
  • N is an element that forms a precipitate with Ti, Nb, Al and the like to make the austenite structure fine when the slab is heated to help improve strength and toughness.
  • the N content is less than 0.002%, the above effects are insufficient.
  • the N content is more than 0.006%, it causes surface cracking at high temperatures, forms precipitates, and the remaining N may exist in an atomic state to reduce toughness.
  • P may cause grain boundary segregation as impurities and cause the steel to be withdrawn. Therefore, it is important to control the upper limit and it is preferable to control it to 0.01% or less.
  • S as an impurity, mainly combines with Mn to form MnS inclusions, which are factors that inhibit low-temperature toughness. Therefore, it is important to control the upper limit, and in order to secure low temperature toughness, it is preferable to control S to 0.003% or less.
  • 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 high strength steel sheet having excellent resistivity ratio properties and low temperature toughness includes 80 to 92% of ferrite and 8 to 20% of MA in an area fraction, and the average of the MAs is measured by the equivalent diameter.
  • the size is 3 micrometers or less.
  • the fraction of microstructure means an area fraction unless otherwise specified.
  • Ferrite is to ensure basic toughness and strength, preferably 80% or more.
  • the upper limit is preferably 92%.
  • the ferrite does not contain an acicular ferrite. This is because the epoxy ferrite has a small hardness difference from the MA, and thus a sufficient resistance ratio cannot be secured.
  • the MA is less than 8%, it is difficult to secure a resistance ratio of 0.65 or less. If the MA is more than 20%, the impact toughness may be lowered and the elongation may be reduced. In addition, when the average size measured by the equivalent circular diameter of MA is more than 3 ⁇ m, MA is mainly formed in the grain boundary, it is difficult to ensure a uniform distribution and resistance ratio of MA.
  • unavoidable phases may be included in addition to the above-described ferrite and MA, but are not excluded.
  • pearlite of 1 area% or less may be included.
  • a plurality of straight lines are drawn up and down or left and right on a microstructure photograph having a size of 100 ⁇ m ⁇ 100 ⁇ m, and at this time, 5 to 13 MAs may be present on each line.
  • MA which mainly causes breakage, is present in the grain boundary, and when the above conditions are satisfied, the MA is evenly distributed in the grain boundary and inside the grain, which is advantageous in securing a resistance ratio.
  • the ratio of the MA present in the ferrite grains and the MA present in the grain boundary may be 1: 3 to 1:10.
  • the ratio refers to the ratio of the number of MA, because by satisfying the ratio can be uniformly distributed so that the MA present in the ferrite grains becomes 0.5 to 5 area%.
  • the ferrite may have an average size of 20 ⁇ m or less as measured by a circle equivalent diameter. If the average size of the ferrite is more than 20 ⁇ m it may be difficult to secure sufficient toughness and strength.
  • the steel sheet according to the present invention is normalized heat treatment
  • the microstructure of the steel sheet before the normalizing heat treatment may be 50 ⁇ 90 area% of bainite.
  • the microstructure of the steel sheet before the heat treatment is bainite with carbides present therein, it is possible to distribute MA evenly in the grain boundary and inside the grain after heat treatment. Therefore, the microstructure of the steel sheet before the heat treatment is preferably 50 to 90 area%. Do.
  • the steel sheet according to the present invention has a yield ratio of 0.5 to 0.65, the low temperature impact characteristics at -40 °C may be 100J or more. Yield ratio is 0.65 or less to increase the difference between yield strength and tensile strength, not only excellent formability, but also delay the time of plastic deformation until fracture can occur and absorb energy in this process to prevent collapse by external force can do.
  • the yield strength of the steel sheet is 350 ⁇ 400MPa, tensile strength may be 600MPa or more.
  • Another aspect of the present invention provides a method for producing a high strength steel sheet having excellent resistance ratio and low temperature toughness, comprising: heating a slab having the above-described alloy composition to 1050 to 1200 ° C; Hot rolling the heated slab to a finish rolling end temperature of 760 to 850 ° C. to obtain a hot rolled steel sheet; Cooling the hot rolled steel sheet to 450 ° C. or less at a cooling rate of 5 ° C./s or more; And a normalizing heat treatment step of heating the cooled hot-rolled steel sheet to a temperature range of 850 to 960 ° C., and then maintaining it for [1.3t + (10 to 30)] minutes.
  • the t is a value measured in mm of the hot rolled steel sheet.
  • the slab having the alloy composition described above is heated to 1050-1200 ° C.
  • the heating temperature is more than 1200 °C austenite grains may be coarsened to lower the toughness, if less than 1050 °C Ti, Nb, etc. are not sufficiently dissolved, the strength may be reduced.
  • the heated slab is hot rolled to a finish rolling end temperature of 760 to 850 ° C. to obtain a hot rolled steel sheet.
  • the rolling temperature of the heat-treated steel is about 850 ⁇ 1000 °C general rolling is applied.
  • Re-crystallization rolling during hot rolling is necessary to refine the austenite grain size, and it is advantageous in terms of physical properties as the rolling reduction per pass increases.
  • Unrecrystallized rolling must be completed at a temperature of at least Ar3 of the steel and is at least about 760 ° C. More specifically, the finish rolling end temperature may be defined at 760 to 850 ° C. If the finish rolling finish temperature is higher than 850 °C, it is difficult to suppress the ferrite-pearlite transformation, if it is less than 760 °C may lead to non-uniformity of the microstructure in the thickness direction, to reduce the reduction in the amount of reduction due to the load load of the rolling roll May not be able to form microstructures.
  • bainite structure is realized through cooling.
  • the initial structure of bainite is for uniform MA distribution after heat treatment.
  • MAs are mainly formed at grain boundaries, while in bainite structures, MAs are formed at both grain boundaries and inside grains.
  • the hot rolled steel sheet is cooled to 450 ° C. or less at a cooling rate of 5 ° C./s or more.
  • Bainite should be implemented to form fine and uniform MA. Cooling finish temperature and cooling rate are important factors for bainite formation.
  • the grain size may become coarse, and coarse carbide may cause coarse MA to be formed after heat treatment, which may lead to a decrease in toughness and more than 50 area% of bainite. Difficult to secure
  • cooling rate is less than 5 °C / s fine structure of the needle-like ferrite or ferrite + pearlite is formed in a large amount may cause a decrease in strength, and after the heat treatment, coarse ferrite + pearlite or second phase rather than the abnormal structure of ferrite + MA There may be a sudden drop in quantity, it is difficult to secure more than 50 area% bainite.
  • the normalizing temperature is less than 850 ° C or the holding time is less than (1.3t + 10) minutes, it is difficult to re-use cementite and pearlite in pearlite, bainite and MA. The remaining hardened phase will remain coarse.
  • the slab was manufactured using continuous casting.
  • the slabs were rolled, cooled, and normalized to heat treatment under the conditions shown in Table 2 to prepare steel sheets.
  • Table 3 below describes the bainite fraction and mechanical properties of the steel sheet before normalizing heat treatment.
  • Table 4 describes the MA fraction of the steel sheet after the normalizing heat treatment, the average MA size, the number of MAs over 100 ⁇ m, and the mechanical properties thereof. In the case of the invention, it was ferrite except for MA, and the average grain size of the ferrite was not described separately as 20 ⁇ m or less.
  • the average MA size is the average size measured by the diameter of the equivalent circle, and the number of MAs on a 100 ⁇ m line is obtained by drawing 10 straight lines up and down or left and right on a 100 ⁇ m ⁇ 100 ⁇ m microstructure photograph. The average number was described after measuring the number.
  • Table 3 shows the MA fraction, yield ratio and mechanical properties of the steel sheet prepared by the components A ⁇ H, manufacturing conditions 1 to 12.
  • the unit of each element content in Table 1 is weight%.
  • Invention steels A to D are steel sheets satisfying the component range defined by the present invention
  • comparative steels E to H are steel sheets which do not satisfy the component range defined by the present invention.
  • Comparative steel E is higher than C content
  • comparative steel F is lower than Mo content
  • comparative steel G is lower than Mn content
  • comparative steel H is lower than Ni content.
  • test Nos. 11 to 14 which are comparative examples, the manufacturing conditions presented in the present invention were satisfied, but the alloy composition did not satisfy the sufficient yield ratio, and the test Nos. 11 and 14 had an impact toughness of -40 ° C less than 100J. You can see that you are enthusiastic.
  • the MA fraction is higher than the comparative example.
  • Table 3 by securing a high bainite fraction before the normalized heat treatment, carbides in the grains of the initial bainite structure, the grains at the grain boundary are transformed into fine MA.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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Abstract

Un aspect de la présente invention concerne une plaque d'acier à haute résistance présentant d'excellentes caractéristiques de faible coefficient d'élasticité et une ténacité à basse température comprenant, en % en poids : C : 0,03 à 0,08 % ; Si : 0,05 à 0,3 % ; Mn : 1,0 à 2,0 % ; Al : 0,005 à 0,04 % ; Nb : 0,005 à 0,04 % ; Ti : 0,001 à 0,02 % ; Cu : 0,05 à 0,4 % ; Ni : 0,6 à 2,0 % ; Mo : 0,08 à 0,3 % ; N : 0,002 à 0,006 % ; P : 0,01 % ou moins ; S : 0,003 % ou moins ; et le reste étant du Fe et des impuretés inévitables, dans laquelle une microstructure contient, par fraction de surface, 80 à 92 % de ferrite, 8 à 20 % d'une structure mixte martensite/austénite (MA), la MA présentant une dimension moyenne mesurée en tant que diamètre équivalent en cercle de 3 µm ou moins.
PCT/KR2017/006956 2016-07-01 2017-06-30 Plaque d'acier à haute résistance présentant d'excellentes caractéristiques de faible coefficient d'élasticité et une ténacité à basse température et son procédé de fabrication WO2018004297A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2018566924A JP6771047B2 (ja) 2016-07-01 2017-06-30 低降伏比特性及び低温靭性に優れた高強度鋼板及びその製造方法
CN201780039727.2A CN109328240B (zh) 2016-07-01 2017-06-30 低屈强比特性和低温韧性优异的高强度钢板及其制造方法
EP17820573.8A EP3480332B1 (fr) 2016-07-01 2017-06-30 Plaque d'acier à haute résistance présentant d'excellentes caractéristiques de faible coefficient d'élasticité et une ténacité à basse température et son procédé de fabrication

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KR1020160083588A KR101799202B1 (ko) 2016-07-01 2016-07-01 저항복비 특성 및 저온인성이 우수한 고강도 강판 및 그 제조방법
KR10-2016-0083588 2016-07-01

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KR102236852B1 (ko) 2018-11-30 2021-04-06 주식회사 포스코 우수한 저항복비 및 저온인성 특성을 가지는 구조용강 및 그 제조방법
JP7338811B1 (ja) 2022-04-20 2023-09-05 Ｊｆｅスチール株式会社 鋼板およびその製造方法
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CN110373524A (zh) * 2019-07-16 2019-10-25 河钢股份有限公司承德分公司 一种90公斤级焊丝用钢热处理软化工艺
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