US20130000798A1 - Steel material excellent in resistance of ductile crack initiation from welded heat affected zone and base material and method for manufacturing the same - Google Patents

Steel material excellent in resistance of ductile crack initiation from welded heat affected zone and base material and method for manufacturing the same Download PDF

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US20130000798A1
US20130000798A1 US13/141,373 US200913141373A US2013000798A1 US 20130000798 A1 US20130000798 A1 US 20130000798A1 US 200913141373 A US200913141373 A US 200913141373A US 2013000798 A1 US2013000798 A1 US 2013000798A1
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ferrite
steel
crack initiation
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rolling
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Teruki Sadasue
Satoshi Igi
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JFE Steel Corp
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JFE Steel Corp
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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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/08—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
    • 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
    • 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
    • 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
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints

Definitions

  • This disclosure relates to steel materials suitable for use in welded structures such as pipelines, bridges, and architectural structures, requiring structural safety and a method for manufacturing the same and particularly relates to one excellent in resistance of ductile crack initiation from welded heat affected zone and a base material.
  • the disclosure is targeted to steel materials for structures having excellent resistance of ductile crack initiation from welded heat affected zone and a base material and having strength of Tensile strength: 490 MPa or more in TS and high toughness of Ductile-brittle fracture transition temperature of Charpy impact test (according to the regulation of JIS Z 2242): vTrs of 0° C. or lower.
  • ductile crack initiates in a stress concentration zone, such as a weld toe, and the generated ductile crack serves as a trigger to cause brittle fracture, resulting in break and fracture of the structures in some cases.
  • Japanese Unexamined Patent Application Publication No. 2008-202119 discloses a high tensile-strength steel material excellent in resistance of ductile crack initiation in which, in the microstructure a steel material surface zone, the ferrite area fraction is 10 to 40%, the bainite area fraction is 50% or more, and the average grain size is 5 ⁇ m or lower.
  • Japanese Unexamined Patent Application Publication No. 2000-3281777 discloses a steel plate excellent in arrestrability and resistance of ductile fracture in which the microstructure is substantially constituted by a ferrite structure, a pearlite structure, and a bainite structure and, when divided into three layers of both surface zones and the central zone in the plate thickness direction of the steel plate, each zone has a specific microstructure.
  • Both the surface zones of the steel plate are constituted by a layer which has 50% or more of a ferrite structure containing ferrite grains in which the equivalent (circle) diameter is 7 ⁇ m or lower and the aspect ratio is 2 to 4 over 5% or more of the plate thickness of each of the structure zones and in which the bainite area fraction of the portion is 5 to 25% or lower.
  • the central zone in the plate thickness direction of the steel plate is constituted by a layer which contains ferrite grains in which the equivalent (circle) diameter is 4 to 10 ⁇ m and the aspect ratio is 2 or lower over 50% or more of the plate thickness and in which the bainite area fraction of the zones is 10% or lower.
  • JP '177 is directed to a steel plate in which three layers having a ferrite/pearlite structure containing ferrite grains different in the aspect ratio are present in the plate thickness direction from the plate surface of the steel plate and further in which a bainite structure which is a hard phase is appropriately dispersed in a soft phase which is the ferrite/pearlite structure.
  • the technique increases the arrestrability by positively forming processed ferrite grains having a high aspect ratio and also appropriately dispersing a bainite structure on each of both the surface zones of the three zones of the steel plate and, in contrast, increases extension characteristics, which are important to ductile fracture at room temperature, by controlling the central zone of the steel plate to have a uniform equiaxed ferrite grain structure and also suppressing a bainite structure, and thus satisfies both opposite characteristics of “arrestrability” and “ductile fracture characteristics” by controlling both the surface zones and the central zone of the steel plate to the three-layer structure.
  • Japanese Unexamined Patent Application Publication No. 2003-221619 is directed to a technique of obtaining deformed ferrite grains on the steel plate surface zone of ferrite/pearlite steel and also controlling the microstructure of the central zone to a uniform equiaxed ferrite grain structure similarly as the technique of JP '177.
  • JP '619 discloses a method for manufacturing a thick steel plate excellent in arrestrability and ductile fracture characteristics in which the rolling conditions are strictly controlled so that the steel plate surface zone has a specific microstructure.
  • an equivalent plastic strain ⁇ of ⁇ 0.5 in a non-recrystallization temperature zone of Ar 3 transformation point or more and 900° C. or lower is given to a surface layer zone of 0.05 t or more and 0.15 t or lower from both the surfaces in the plate thickness direction.
  • the surface layer zone is cooled to a temperature range of 450 to 650° C. at a cooling rate of 2 to 15° C./s while maintaining the temperature of the central zone defined as t/4 to 3t/4 of the plate thickness at the Ar 3 transformation point or more within a period of time when the residual and cumulative equivalent plastic strain ⁇ r of the surface layer zone satisfies ⁇ r ⁇ 0.5, and subsequently rolling is restarted.
  • the residual and cumulative equivalent plastic strain ⁇ r of 0.35 ⁇ r ⁇ 0.55 is given to the central zone to complete the rolling at the Ar 3 transformation point or more and also the surface layer is recuperated to the Ar 3 transformation point or lower by processing heat and internal sensible heat, and thereafter cooling is performed in such a manner that the average cooling rate is 1 to 10° C./s.
  • JP '119, JP '177 and JP '619 all relate to techniques of forming fine subgrains in austenite to miniaturize the structure after transformation by performing rolling in a non recrystallization zone (fine grain temperature zone) of austenite or performing rolling at a rolling finish temperature Ar 3 or more.
  • FIG. 1 is a view illustrating a ductile crack initiation test method of a welded heat affected zone.
  • FIG. 2 is a view illustrating influence of the area fraction of a hard phase and the average aspect ratio of ferrite on ductile crack initiation of a 1400° C. simulated heat cycle material.
  • FIG. 3 is a view illustrating a ductile crack initiation test method of a base material.
  • FIG. 4 is a view illustrating influence of the area fraction of a hard phase and the average aspect ratio of ferrite on ductile crack initiation of a base material.
  • C is an element having an action of increasing the strength of steel and, particularly, contributes to the generation of a hard phase.
  • a C content of 0.02% or more is required to obtain such an effect.
  • the C content exceeds 0.2%, the ductility or the bending workability are reduced and also the weldability decreases. Therefore, the C content is limited in the range of 0.02 to 0.2%. More preferably, the C content is 0.02 to 0.18%.
  • Si acts as a deoxidizing agent and has an action of forming a solid solution to increase the strength of steel.
  • An Si content of 0.01% or more is required to obtain such an effect.
  • the Si content exceeds 0.5% the toughness is reduced and also the weldability is reduced.
  • Si is limited in the range of 0.01 to 0.5%. More preferably, the Si content is 0.01 to 0.4%.
  • Mn has an action of increasing the strength of steel and also increasing the toughness through an increase in hardenability.
  • An Mn content of 0.1% or more is required to obtain such an effect.
  • Mn content exceeds 2.5% the weldability is reduced. Therefore, Mn is limited in the range of 0.1 to 2.5%. More preferably, the content is 0.5 to 2.0%.
  • the P content is preferably reduced as much as possible, but the content up to 0.05% is permissible. Therefore, the P content is limited to 0.05% or lower. More preferably, the content is 0.04% or lower.
  • the S content is preferably reduced as much as possible. However, the content up to 0.05% is permissible. Therefore, the S content is limited to 0.05% or lower. More preferably, the content is 0.04% or lower.
  • Al is an element that acts as a deoxidizing agent and also contributes to pulverization of crystal grains.
  • an excessive content of Al in a proportion exceeding 0.1% causes a reduction in toughness. Therefore, the Al content is limited to 0.1% or lower. More preferably, the content is 0.05% or lower.
  • N is an element that increases the strength of steel by solid solution strengthening similarly as C.
  • an excessive content of N causes a reduction in toughness. Therefore, the N content is limited to 0.01% or lower. More preferably, the content is 0.005% or lower.
  • the chemical compositions described above are basic chemical compositions but one or two or more elements selected from Cu: 0.01 to 2%, Ni: 0.01 to 5%, Cr: 0.01 to 3%, Mo: 0.01 to 2%, Nb: 0.1% or lower, V: 0.1% or lower, Ti: 0.1% or lower, B: 0.01% or lower, Ca: 0.01% or lower, and REM: 0.1% or lower may be further contained according to the desired properties.
  • Cu is an element that has an action of increasing the strength of steel through an increase in hardenability or solid solution.
  • the content of 0.01% or more is required to secure such an effect.
  • the content exceeds 2%, the weldability decreases and also cracks are likely to generate during manufacturing of steel materials. Therefore, when Cu is added, the content is in the range of 0.01 to 2%. More preferably, the content is 0.01 to 1%.
  • Ni is added as required, because Ni contributes to an increase in low temperature toughness, an increase in hardenability, and prevention of hot ductility of Cu when Cu is contained. Such an effect is recognized when Ni is contained in the proportion of 0.01% or more. However, the addition of 5% or more causes a reduction in steel material cost and also a reduction in weldability. Therefore, when Ni is added, the content is in the range of 0.01 to 5%. More preferably, the content is 0.01 to 4.5%.
  • Cr is added as required to increase the strength of steel materials through improvement of hardenability or an increase in tempering softening resistance. Such an effect is recognized when Cr is contained in the proportion of 0.01% or more. In contrast, the addition exceeding 3% reduces weldability and toughness. Therefore, when Cr is added, the content is in the range of 0.01 to 3%. More preferably, the content is in the range of 0.01 to 2.5%.
  • Mo is added as required to increase the strength of steel materials through improvement of hardenability or an increase in tempering softening resistance. Such an effect is recognized when Mo is contained in the proportion of 0.01% or more. In contrast, the addition exceeding 2% reduces weldability or toughness. Therefore, when Mo is added, the content is in the range of 0.01 to 2%. More preferably, the content is in the range of 0.01 to 1%.
  • Nb is an element that precipitates as a carbide or a carbonitride in tempering and increases the strength of steel through precipitation strengthening. Moreover, Nb also has an effect of pulverizing austenite grains during rolling to increase toughness. The content of 0.001% or more is preferable to obtain the effects. However, the content exceeding 0.1% reduces toughness. Therefore, when Nb is added, the content is 0.1% or lower. More preferably, the content is 0.05% or lower.
  • V is an element that precipitates as a carbide or a carbonitride in tempering and increases the strength of steel through precipitation strengthening. Moreover, V also has an effect of pulverizing austenite grains during rolling to increase toughness.
  • the content of 0.001% or more is preferable to obtain the effects. However, the content exceeding 0.1% reduces toughness. Therefore, when Nb is added, the content is 0.1% or lower. More preferably, the content is 0.05% or lower.
  • Ti is added as required because Ti has an effect of pulverizing austenite in a welded heat affected zone to increase toughness.
  • the content of 0.001% or more is preferable to obtain the effect.
  • the addition exceeding 0.1% reduces toughness and also causes a sudden rise of steel material cost. Therefore, when Ti is added, the content is 0.1% or lower. More preferably, the content is 0.05% or lower.
  • B is added as required because B has an effect of increasing hardenability and increasing the strength of steel with a small content thereof.
  • the content is preferably 0.0001% or more to obtain the effect. However, the addition exceeding 0.01% reduces weldability. Therefore, when B is added, the content is 0.01% or lower. More preferably, the content is 0.005% or lower.
  • Ca is added as required because Ca increases the base material toughness by controlling the shape of a CaS inclusion and further increase the toughness of a welded heat affected zone.
  • the content of 0.0001% or more is preferable to obtain the effects. However, the addition exceeding 0.01% reduces toughness due to an increase in the amount of the CaS inclusion. Therefore, when Ca is added, the content is 0.01% or lower. More preferably, the content is 0.009% or lower.
  • REM is an element that increases the toughness of a welded heat affected zone and is added as required.
  • the content is preferably 0.0001% or more to obtain the effect. However, the addition exceeding 0.1% causes a reduction in toughness. Therefore, when REM is added, the content is 0.1% or lower. More preferably, the content is 0.05% or lower.
  • REM is a general term of Y, Ce and the like that are rare earth elements and the addition amount as used herein refers to the total amount of these rare earth elements.
  • the steel material has a microstructure in which the structure at the 1 ⁇ 4 position of the plate thickness contains ferrite and a hard phase, the area fraction of the hard phase is 50 to 90%, and the average aspect ratio of the ferrite grain size is 1.5 or more.
  • the area fraction of the hard phase is lower than 50% and exceeds 90% or the aspect ratio of the ferrite grain size is lower than 1.5, there is a possibility that ductile crack initiation occurs.
  • the upper limit of the average aspect ratio of the ferrite grain size does not need to particularly specify and is 5 or lower in view of the capability and the like of a rolling mill.
  • the area fraction of the hard phase is more preferably 52 to 90% and the average aspect ratio of the ferrite grain size is more preferably 1.6 or more.
  • the average aspect ratio is more preferably 1.7 or more.
  • the yield ratio (or Y/T ratio) of a base material decreases, and the strain concentration in a stress concentration zone is eased even in the base material as it is or even after a simulated heat cycle of simulating the welded heat affected zone. Such an effect is not obtained in the case of a single phase of ferrite or a single phase of a hard phase.
  • the structure of the surface of a steel plate (1 mm position from the plate surface) contains ferrite and a hard phase, in which the area fraction of the ferrite exceeds 40% and is more preferably 50% or more.
  • the average aspect ratio of the ferrite grain size exceeds 2.
  • the hard phase is bainite, martensite, or a bainite/martensite mixed structure and contains 5% or lower, in terms of area fraction, of an island martensite (M-A constituent) (MA).
  • FIG. 2 illustrates the results of examining the resistance of ductile crack initiation using a simulated heat cycle specimen of a welded zone (highest heating temperature of 1400° C.). As illustrated in FIG. 2 , when the area fraction of the hard phase of the base material is 50 to 90% and the average aspect ratio of the ferrite thereof is 1.5 or more, ductile crack initiation is not observed also after the simulated heat cycle.
  • a simulated heat cycle time for reaching the highest heating temperature: 6 s, cooling rate from the highest heating temperature to room temperature: 40° C./s
  • FIG. 1 illustrates the specimen shape and the test conditions.
  • the sample material (specimen 1 ) to which the simulated heat cycle was given, in which a single through-thickness edge notch is introduced with the length of 3 mm in the plate thickness direction into the center of a simulated heat cycle zone 2 of the sample material (specimen 1 ) was fixed with clamps 5 , then a tensile load (arrow 6 ) was applied to 0.6 mm in terms of displacement of a clip gage 3 between knife-edges 4 that are screwed, the load was removed, and then the specimen was ground to the central zone and mirror polished. Then, the presence of crack initiation at the notch tip was evaluated. The case where the ductile crack from the notch bottom was 50 ⁇ m or more was defined as crack initiation.
  • FIG. 4 illustrates the results of examining the influence of the microstructure of the base material exerted on the resistance of ductile crack initiation.
  • the area fraction of the hard phase of the base material is 50 to 90% and the average aspect ratio of the ferrite is 1.5 or more, ductile crack initiation is not accepted.
  • FIG. 3 illustrates the specimen shape and the test conditions.
  • the sample material (specimen 1 ) in which a single through-thickness edge notch is introduced into the center was fixed with clamps 5 , then a tensile load (arrow 6 ) was applied to 0.8 mm in terms of displacement of a clip gage 3 between knife-edges 4 that are screwed, the load was removed, and then the specimen was ground to the central zone and mirror polished. Then, the presence of crack initiation at the notch tip was evaluated. The case where the ductile crack from the notch bottom was 50 ⁇ m or more was defined as crack initiation.
  • the aspect ratio refers to the ferrite grain size in the rolling direction (major axis)/the ferrite grain size in the plate thickness direction (minor axis) in a cross section parallel to the rolling direction.
  • the steel material is obtained by successively subjecting the steel material of the above-described chemical compositions to a hot rolling process, a water cooling process, or further a tempering process.
  • the hot rolling includes reheating to 1000° C. or more and performing rolling in such a manner that the rolling reduction rate in a temperature range of 900° C. or more is 50% or more and the rolling finish temperature becomes Ar 3 to Ar 3 -50° C.
  • a more preferable rolling finish temperature is lower than Ar 3 to Ar 3 -40° C.
  • the cumulative rolling reduction rate at 900° C. or more is lower than 50%, desired strength and toughness cannot be secured.
  • the rolling finish temperature exceeds Ar 3 , the aspect ratio of ferrite does not reach 1.5 or more.
  • the rolling finish temperature is lower than Ar 3 -50° C., the area fraction of the hard phase obtained by the subsequent water cooling does not reach 50% or more.
  • the water cooling is started at Ar 3 -10° C. to Ar 3 -70° C. immediately after hot rolling, and then the water cooling is terminated at 500° C. or lower.
  • the water cooling start temperature exceeds Ar 3 -10° C.
  • ferrite of lower than 10% in terms of area fraction hard phase exceeding 90% in terms of area fraction
  • the water cooling start temperature is lower than Ar 3 -70° C. or water cooling is not started immediately after (within 300 seconds) hot rolling, ferrite exceeding 50% in terms of area fraction (hard phase not reaching 50% in terms of area fraction) or pearlite, which is not intended to precipitate, precipitates.
  • desired characteristics cannot be satisfied.
  • tempering treatment can be further performed at a temperature of lower than the Ac 1 point.
  • tempering treatment By performing tempering treatment, toughness and ductility increase, and desired strength and toughness can be achieved.
  • the tempering temperature exceeds the Ac 1 point, a large amount of island martensite generates to reduce the toughness.
  • the Ar 3 point and the Ac 1 point can be calculated by the following equation based on the content (% by mass) of each chemical composition:
  • Ar 3 (° C.) 910 ⁇ 310C ⁇ 80Mn ⁇ 20Cu ⁇ 15Cr ⁇ 55Ni ⁇ 80Mo
  • the obtained steel plates were subjected to microstructure observation, a tensile test, a toughness test, a ductile crack initiation test after a simulated heat cycle, and a ductile crack initiation test of base materials.
  • the test methods were performed as described in the following items (1) to (5).
  • V notch specimens were extracted so that the longitudinal direction was in parallel to the rolling direction according to the regulation of JIS Z 2242 (2005), and then the ductile-brittle fracture transition temperature was determined to evaluate the toughness.
  • the specimens were extracted in such a manner that the 1 ⁇ 4 position of the plate thickness when the plate thickness was 20 mm or more or the 1 ⁇ 2 position of the plate thickness when the plate thickness was lower than 20 mm was the center.
  • the specimens were subjected to a simulated heat cycle of a welded heat affected zone in which the highest heating temperature was 760° C., 900° C., 1200° C., and 1400° C. (time for reaching the highest heating temperature: 6 s, Cooling rate from the highest heating temperature to room temperature: 40° C./s) using a Gleeble tester.
  • a single through-thickness edge notch was introduced with the length of 3 mm in the plate thickness direction into the center of the simulated heat cycle zone.
  • the notch processing was carried out by electrical discharge machining, and the notch tip radius was 0.1 mm.
  • a tensile load was applied while gripping the specimens with both right and left ends thereof with a constraint length of 50 mm.
  • the displacement between the knife-edges screwed near the notch was measured with the clip gage.
  • a tensile load was applied to 0.6 mm in terms of clip gage displacement, and then the load was removed. Thereafter, the specimen was ground to the width center and mirror polished. Then, the crack initiation state at the notch bottom was analyzed under a microscope with a magnification of 50 ⁇ . It was defined that the ductile crack initiation occurred when a ductile crack extended in the length of 50 ⁇ m or more from the notch bottom.
  • a single through-thickness edge notch was introduced with the length of 3 mm in the plate thickness direction into the center of the specimens as illustrated in FIG. 3 .
  • the notch processing was carried out by electrical discharge machining, and the notch tip radius was 0.1 mm.
  • the steel plate (Steel type K*) of No. 11 in which the C content does not satisfy the lower limit of our range has low tensile strength.
  • the steel plate (Steel type L*) of No. 12 in which the content of each of C, P, and S exceeds the upper limit of our range has low toughness and has poor ductile crack initiation characteristics of a welded heat affected zone.
  • the steel plate of No. 13 in which the reheating temperature of slab is lower than our and the cumulative rolling reduction rate at 900° C. or more is outside our range has low toughness.
  • the steel plate of No. 14 in which the rolling finish temperature and the water cooling start temperature exceed our range ferrite is not generated, our microstructure is not obtained, and the resistance of ductile crack initiation of a welded heat affected zone is poor.
  • the steel plate (Steel type W*) of No. 28 in which the C content does not satisfy the lower limit of our range has low tensile strength.
  • the steel plate (Steel type X*) of No. 29 in which the content of each of C, P, and S exceeds the upper limit of our range has low toughness.
  • the steel plate of No. 30 in which the reheating temperature of slab is lower than our range and the cumulative rolling reduction rate at 900° C. or more does not satisfy our range has low toughness.
US13/141,373 2008-12-26 2009-12-25 Steel material excellent in resistance of ductile crack initiation from welded heat affected zone and base material and method for manufacturing the same Abandoned US20130000798A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100236015A1 (en) * 2006-09-29 2010-09-23 Dyson Technology Limited Support assembly for a surface treating appliance
EP3276020A4 (en) * 2015-03-27 2018-03-21 JFE Steel Corporation High-strength steel, production method therefor, steel pipe, and production method therefor
US10041158B2 (en) * 2010-04-28 2018-08-07 Nippon Steel & Sumitomo Metal Corporation Multi-phase hot-rolled steel sheet having improved dynamic strength and a method for its manufacture
US10597745B2 (en) 2013-12-11 2020-03-24 Arcelormittal High strength steel and manufacturing method

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09291339A (ja) * 1996-04-23 1997-11-11 Daido Steel Co Ltd 窒化鋼
JP2000282175A (ja) * 1999-04-02 2000-10-10 Kawasaki Steel Corp 加工性に優れた超高強度熱延鋼板およびその製造方法
JP2002069584A (ja) * 2000-09-05 2002-03-08 Nippon Steel Corp 成形性の優れた高強度鋼管およびその製造方法
US20020043305A1 (en) * 2000-08-07 2002-04-18 Exxonmobil Upstream Research Company Weld metals with superior low temperature toughness for joining high strength, low alloy steels
JP2008156751A (ja) * 2006-11-30 2008-07-10 Jfe Steel Kk 板厚方向の脆性亀裂伝播停止特性に優れる板厚５０ｍｍ以上の鋼板およびその製造方法

Family Cites Families (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2585321B2 (ja) * 1987-12-07 1997-02-26 川崎製鉄株式会社 溶接性の優れた高強度高靭性鋼板の製造方法
US5545269A (en) * 1994-12-06 1996-08-13 Exxon Research And Engineering Company Method for producing ultra high strength, secondary hardening steels with superior toughness and weldability
JPH10147846A (ja) * 1996-11-19 1998-06-02 Nippon Steel Corp 疲労強度が高い集合組織制御鋼板およびその製造方法
JPH10306316A (ja) * 1997-04-28 1998-11-17 Nippon Steel Corp 低温靭性に優れた低降伏比高張力鋼材の製造方法
JP3849244B2 (ja) * 1997-09-16 2006-11-22 Ｊｆｅスチール株式会社 繰返し大変形下での延性き裂進展抵抗の優れた鋼材及びその製造方法
US6159312A (en) * 1997-12-19 2000-12-12 Exxonmobil Upstream Research Company Ultra-high strength triple phase steels with excellent cryogenic temperature toughness
DZ2531A1 (fr) * 1997-12-19 2003-02-08 Exxon Production Research Co Procédé de préparation d'une tôle d'acier double phase cette tôle et procédé pour renforcer la résistance à la propagation des fissures.
JP4173603B2 (ja) 1999-05-24 2008-10-29 株式会社神戸製鋼所 アレスト特性および延性破壊特性に優れた鋼板
JP2000345289A (ja) * 1999-06-01 2000-12-12 Nkk Corp オンライン型厚肉耐候性鋼板
TWI290177B (en) * 2001-08-24 2007-11-21 Nippon Steel Corp A steel sheet excellent in workability and method for producing the same
JP2003221619A (ja) 2002-01-31 2003-08-08 Kobe Steel Ltd アレスト特性および延性破壊特性に優れた厚鋼板の製造方法
JP3848211B2 (ja) * 2002-05-31 2006-11-22 株式会社神戸製鋼所 低温靭性に優れた厚鋼板およびその製造方法
JP4341396B2 (ja) * 2003-03-27 2009-10-07 Ｊｆｅスチール株式会社 低温靱性および溶接性に優れた高強度電縫管用熱延鋼帯
JP4670371B2 (ja) * 2004-01-30 2011-04-13 Ｊｆｅスチール株式会社 板厚方向の強度均一性および耐疲労亀裂伝播特性に優れた鋼材の製造方法
JP4956907B2 (ja) * 2005-03-30 2012-06-20 Ｊｆｅスチール株式会社 耐延性き裂発生特性に優れる高強度高変形能厚鋼板とその製造方法
JP4645461B2 (ja) * 2006-01-27 2011-03-09 Ｊｆｅスチール株式会社 耐延性亀裂発生特性と耐疲労亀裂伝播特性に優れた高強度鋼材およびその製造方法
JP2007314819A (ja) * 2006-05-23 2007-12-06 Kobe Steel Ltd 耐疲労亀裂進展性に優れた鋼板
JP4923968B2 (ja) * 2006-11-15 2012-04-25 Ｊｆｅスチール株式会社 耐疲労亀裂伝播特性に優れた鋼材
JP4858221B2 (ja) * 2007-02-22 2012-01-18 住友金属工業株式会社 耐延性き裂発生特性に優れる高張力鋼材
JP4998708B2 (ja) * 2007-02-26 2012-08-15 Ｊｆｅスチール株式会社 材質異方性が小さく、耐疲労亀裂伝播特性に優れた鋼材およびその製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09291339A (ja) * 1996-04-23 1997-11-11 Daido Steel Co Ltd 窒化鋼
JP2000282175A (ja) * 1999-04-02 2000-10-10 Kawasaki Steel Corp 加工性に優れた超高強度熱延鋼板およびその製造方法
US20020043305A1 (en) * 2000-08-07 2002-04-18 Exxonmobil Upstream Research Company Weld metals with superior low temperature toughness for joining high strength, low alloy steels
JP2002069584A (ja) * 2000-09-05 2002-03-08 Nippon Steel Corp 成形性の優れた高強度鋼管およびその製造方法
JP2008156751A (ja) * 2006-11-30 2008-07-10 Jfe Steel Kk 板厚方向の脆性亀裂伝播停止特性に優れる板厚５０ｍｍ以上の鋼板およびその製造方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Machine translation of JP 09291339, 1997. *
Machine translation of JP 2002069584, 2002. *
Machine translation of JP 2008156751, 2008. *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100236015A1 (en) * 2006-09-29 2010-09-23 Dyson Technology Limited Support assembly for a surface treating appliance
US10041158B2 (en) * 2010-04-28 2018-08-07 Nippon Steel & Sumitomo Metal Corporation Multi-phase hot-rolled steel sheet having improved dynamic strength and a method for its manufacture
US10597745B2 (en) 2013-12-11 2020-03-24 Arcelormittal High strength steel and manufacturing method
EP3276020A4 (en) * 2015-03-27 2018-03-21 JFE Steel Corporation High-strength steel, production method therefor, steel pipe, and production method therefor
US10954576B2 (en) 2015-03-27 2021-03-23 Jfe Steel Corporation High-strength steel, method for manufacturing high-strength steel, steel pipe, and method for manufacturing steel pipe

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