WO2011030768A1 - Tôle d'acier pour tube de canalisation à haute résistance ayant une excellente ténacité à basse température et tuyau en acier pour tube de canalisation à haute résistance - Google Patents

Tôle d'acier pour tube de canalisation à haute résistance ayant une excellente ténacité à basse température et tuyau en acier pour tube de canalisation à haute résistance Download PDF

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WO2011030768A1
WO2011030768A1 PCT/JP2010/065354 JP2010065354W WO2011030768A1 WO 2011030768 A1 WO2011030768 A1 WO 2011030768A1 JP 2010065354 W JP2010065354 W JP 2010065354W WO 2011030768 A1 WO2011030768 A1 WO 2011030768A1
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steel
temperature toughness
line pipe
segregation
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PCT/JP2010/065354
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English (en)
Japanese (ja)
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卓也 原
泰志 藤城
好男 寺田
豪 鈴木
太郎 村木
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新日本製鐵株式会社
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Priority to CN201080039943.5A priority Critical patent/CN102482744B/zh
Priority to JP2011505304A priority patent/JP5131715B2/ja
Priority to BR112012005189A priority patent/BR112012005189A2/pt
Publication of WO2011030768A1 publication Critical patent/WO2011030768A1/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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • 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
    • C22C38/04—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
    • C22C38/12—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
    • 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
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • 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

  • the present invention relates to a steel plate for a line pipe and a steel pipe for a line pipe, which are excellent in low temperature toughness and are suitable for applications such as oil and natural gas transportation line pipes.
  • Non-Patent Documents 1 and 2 X80 line pipe manufacturing technology
  • X100 tensile strength of 760 MPa or more
  • X120 line pipe manufacturing technology Reports have been made on Patent Documents 1 and 2.
  • these high-strength line pipes are also required to have brittle fracture crack propagation stopping characteristics and high-speed ductile fracture propagation stopping characteristics, and if these issues cannot be solved, they can be put into practical use as line pipes even if steel plates and steel pipes can be manufactured. It is impossible to do.
  • the brittle fracture crack propagation stop property needs to stop brittle fracture even if brittle fracture occurs especially from the circumferential weld that connects the line pipes.
  • the crack propagation speed of brittle fracture will be 350 m / s or more, and brittle fracture may be a long-distance fracture ranging from 100 m to several km. Yes.
  • As a small test for evaluating this brittle fracture crack propagation stop characteristic it is required to have a ductile fracture surface ratio of 85% or more at a specified temperature in DWTT (Drop Weight Tear Test).
  • the high-speed ductile fracture crack propagation stopping characteristic is a phenomenon in which ductile fracture propagates at a high speed of 100 m / s or more for a long distance in the tube axis direction of the steel pipe.
  • This high-speed ductile fracture also has a possibility of long-distance fracture ranging from 100 m to several km, and is regarded as important because of the magnitude of damage assumed.
  • This high-speed ductile fracture has been correlated with the Charpy energy of the steel pipe, and has been prevented by securing this Charpy absorbed energy.
  • the microstructure of the high-strength line pipe is a bainite / martensite-based structure.
  • a method for refining crystal grains in a bainite / martensite-based structure it is known to reduce the pancake thickness.
  • ⁇ 100 ⁇ accumulates on a surface inclined by 40 ° with respect to the rolling surface with the rolling direction as an axis (hereinafter referred to as a 40 ° surface).
  • ⁇ 100 ⁇ is a cleavage plane of iron, and if there is a brittle part such as center segregation, brittle fracture occurs from the brittle part, and brittle fracture propagates all at once to the 40 ° plane where ⁇ 100 ⁇ is accumulated. Therefore, it becomes difficult to shift to ductile fracture.
  • ⁇ 100 ⁇ is a cleavage plane of iron, and if there is a brittle part such as center segregation, brittle fracture occurs from the brittle part, and brittle fracture propagates all at once to the 40 ° plane where ⁇ 100 ⁇ is accumulated. Therefore, it was a big problem that did not shift to ductile fracture.
  • the present invention has been made in view of such circumstances, and low temperature toughness of steel pipes used for line pipes having a structure mainly composed of bainite and martensite, particularly brittle fracture crack propagation stopping characteristics and high-speed ductile fracture. It is an object to improve the crack propagation stop characteristic.
  • the present inventors conducted earnest research on the conditions that should be satisfied by steel materials for obtaining high-strength linepipe steel sheets and high-strength linepipe steel pipes that have excellent tensile strength of 600 MPa or more and low-temperature toughness. It came to invent the steel plate for line pipes and the steel pipe for high-strength line pipes. And even in the structure mainly composed of bainite and martensite, the embrittlement phase such as central segregation is remarkably relaxed, and if the low temperature toughness of the place is improved, the ductile / brittle transition temperature such as DWTT can be lowered. I found it.
  • the gist of the present invention is as follows.
  • Ni 0.01 to 2.0%
  • Cu 0.01 to 1.0%
  • Cr 0.01 to 1.0%
  • Mo 0.01 to 0.60%
  • W 0.01 to 1.0%
  • V 0.01 to 0.10%
  • Zr 0.0001 to 0.050%
  • Ta 0.0001 to 0.050%
  • B 0.0001 to 0.0020%
  • the base material is mass%, C: 0.03-0.08%, Si: 0.01 to 0.5%, Mn: 1.6 to 2.3% Nb: 0.001 to 0.05%, N: 0.0010 to 0.0050%, Ca: 0.0001 to 0.0050% Including P: 0.015% or less, S: 0.002% or less, Ti: 0.001 to 0.030%, Al: 0.030% or less, O: limited to 0.0035% or less, with the balance being Fe and inevitable impurity elements, S / Ca ⁇ 0.5 Satisfied, Maximum Mn segregation degree: 2.0 or less, Nb segregation degree: 4.0 or less, Ti segregation degree: limited to 4.0 or less, Furthermore, A high-strength line pipe excellent in low-temperature toughness characterized by having a ⁇ 100 ⁇ accumulation degree limited to 4.0 or less and a tensile strength of 600 MPa or more with the rolling direction as the axis and tilted by 40 ° on the rolling surface Steel pipe.
  • the segregation degree of Mn, Nb, and Ti is reduced, the increase in the maximum hardness of the central segregation part is suppressed, and it is possible to produce a steel plate for line pipe and a steel pipe for line pipe excellent in low temperature toughness. For example, the industrial contribution is very remarkable.
  • the influence of the maximum M segregation degree on the DWTT ductile fracture surface ratio in the 0.06C-1.9Mn-Ni-Cu-Cr system is shown.
  • the influence of the Nb segregation degree on the DWTT ductile fracture surface ratio in the 0.06C-1.9Mn-Ni-Cu-Cr system is shown.
  • the influence of the Ti segregation degree on the DWTT ductile fracture surface ratio in the 0.06C-1.9Mn-Ni-Cu-Cr system is shown.
  • the present invention relates to an ultra-high-strength line pipe excellent in low-temperature toughness having a tensile strength (TS) of 600 MPa or more. Since the ultra-high-strength line pipe of this strength level can withstand a higher pressure than the conventional mainstream X65, it is possible to transport many gases with the same size. In the case of X65, in order to increase the pressure, it is necessary to increase the wall thickness, which increases the material cost, transportation cost, and local welding construction cost, and the pipeline laying cost significantly increases.
  • TS tensile strength
  • the base metal has high fracture propagation stop characteristics.
  • DWTT drop weight test
  • the structure is basically composed of bainite or martensite. In that case, the steel sheet is cooled from a temperature of Ar3 or higher to obtain a steel plate.
  • ⁇ 100 ⁇ which is a cleavage plane of iron, is accumulated at a position of 40 degrees with respect to the rolling surface with the rolling direction as an axis.
  • a surface positioned at 40 degrees with respect to the rolling surface with the rolling direction as an axis is referred to as a “40 ° surface”.
  • integration degree the ratio of ⁇ 100 ⁇ accumulation compared to this random case.
  • FIGS. 1 to 3 show the influence of the maximum segregation degree of Mn, Ti and Nb on the DWTT ductile fracture ratio in the 0.06C-1.9Mn—Ni—Cu—Cr system. It was found that when the maximum Mn segregation degree, Ti segregation degree, and Nb segregation degree decrease, the DWTT ductile fracture surface ratio decreases remarkably. In particular, when the maximum Mn segregation degree was 2.0 or less, the Ti segregation degree was 4.0 or less, and the segregation degree of Nb was 4.0 or less, the DWTT ductile fracture surface ratio significantly increased. Thus, the inventors consider the reason why the DWTT ductile fracture ratio is remarkably improved by decreasing the maximum Mn segregation degree, Ti segregation degree, and Nb segregation degree as follows.
  • the degree of segregation of Mn increases, the Mn concentration in that region increases. Therefore, the hardenability of the center segregation portion is increased, and the hardness is greatly increased as compared with the normal portion.
  • the hardness in that region is increased, the low temperature toughness, specifically the fracture occurrence characteristics, is significantly reduced. Therefore, the fracture easily occurs from the center segregation, and the brittle fracture progresses on the 40 ° plane.
  • the maximum Mn segregation degree decreases, the increase in the hardness of the center segregation part is suppressed, and the resistance value of fracture increases.
  • the maximum Mn segregation degree is the maximum Mn amount of the central segregation portion relative to the average Mn amount excluding the central segregation portion of the steel plate and the steel pipe.
  • the Nb segregation degree and the Ti segregation degree are the average Nb amount (Ti amount) averaged at the center segregation portion relative to the average Nb amount (Ti amount) excluding the center segregation portion of the steel plate and the steel pipe.
  • the Mn concentration distribution of the steel sheet and the steel pipe is measured by EPMA (Electron Probe Micro Analyzer) or CMA (Computer Aided Micro Analyzer) capable of image processing the measurement result by EPMA.
  • EPMA Electro Probe Micro Analyzer
  • CMA Computer Aided Micro Analyzer
  • the Nb segregation degree and the Ti segregation degree are measured by EPMA or CMA, respectively.
  • the numerical value of the maximum Mn segregation degree varies depending on the probe diameter of EPMA (or CMA).
  • the present inventors have found that the segregation of Mn can be properly evaluated by setting the probe diameter to 2 ⁇ m.
  • the Nb segregation degree and the Ti segregation degree it was found that the segregation can be properly evaluated by setting the probe diameter to 2 ⁇ m.
  • the maximum value cannot be accurately determined. Therefore, the average value of the measurement data, that is, the average maximum value in the thickness direction is determined.
  • inclusions such as MnS, TiN, and Nb (C, N) are present, the maximum Mn segregation degree, Ti segregation degree, and Nb segregation degree are apparently increased. Shall be evaluated.
  • C is an element that improves the strength of steel, and as an effective lower limit, addition of 0.03% or more is necessary.
  • the C content exceeds 0.08%, the formation of carbides is promoted and the low temperature toughness of the central segregation part is impaired, so the upper limit is made 0.08% or less.
  • the upper limit of C it is preferable to make the upper limit of C amount into 0.07% or less.
  • Si is a deoxidizing element and needs to be added in an amount of 0.01% or more. On the other hand, if the Si content exceeds 0.5%, the toughness of the weld heat affected zone (HAZ) is lowered, so the upper limit is made 0.5% or less.
  • Mn is an element that improves strength and toughness, and needs to be added in an amount of 1.6% or more. On the other hand, if the amount of Mn exceeds 2.3%, the low temperature toughness and the HAZ toughness of the center segregation part are lowered, so the upper limit is made 2.3% or less. In order to suppress the low temperature toughness deterioration of the center segregation part, the upper limit of the Mn content is preferably set to 2.0% or less.
  • Nb is an element that forms carbides and nitrides and contributes to improvement in strength. In order to obtain the effect, it is necessary to add 0.001% or more of Nb. However, if Nb is added excessively, the degree of segregation of Nb increases, and the accumulation of Nb carbonitrides is invited, resulting in a decrease in HIC resistance. Therefore, in the present invention, the upper limit of the Nb amount is 0.05% or less.
  • N is an element that forms nitrides such as TiN and NbN.
  • the lower limit of the N amount is 0.0010% or more. Is necessary.
  • the upper limit of the N amount is set to 0.0050% or less.
  • toughness etc. are requested
  • P is an impurity, and if the content exceeds 0.015%, the HIC resistance is impaired, and the toughness of the HAZ decreases. Therefore, the upper limit of the P content is limited to 0.01% or less.
  • S is an element that generates MnS that extends in the rolling direction during hot rolling, and lowers the low-temperature toughness. Therefore, in the present invention, it is necessary to reduce the amount of S, and the upper limit is limited to 0.0020% or less. In order to improve toughness, the S content is preferably 0.0010% or less. The smaller the amount of S, the better. However, it is difficult to make it less than 0.0001%. From the viewpoint of production cost, the lower limit is preferably made 0.0001% or more.
  • Ti is an element that is usually used for grain refinement as a deoxidizer or nitride-forming element.
  • Al is a deoxidizing element. However, in the present invention, when the addition amount exceeds 0.030%, an accumulation cluster of Al oxide is confirmed, so the content is limited to 0.030% or less. When toughness is required, the upper limit of Al content is preferably set to 0.017% or less. Although the lower limit of the amount of Al is not particularly limited, it is preferable to add Al in an amount of 0.0005% or more in order to reduce the amount of oxygen in the molten steel.
  • O is an impurity, and the upper limit is limited to 0.0035% or less in order to suppress oxide accumulation and improve low-temperature toughness.
  • the upper limit value of the O amount is preferably 0.0030% or less.
  • the optimum upper limit of the amount of O is 0.0020% or less.
  • Ca is an element that generates sulfide CaS, suppresses the generation of MnS that extends in the rolling direction, and contributes significantly to the improvement of low-temperature toughness. If the addition amount of Ca is less than 0.0001%, the effect cannot be obtained, so the lower limit is made 0.0001% or more. On the other hand, if the Ca content exceeds 0.0050%, oxides accumulate and the low temperature toughness is impaired, so the upper limit is made 0.0050% or less.
  • the ratio of S / Ca is an important index. MnS produces
  • one or more elements among Ni, Cu, Cr, Mo, W, V, Zr, Ta, and B may be added as elements for improving strength and toughness. it can.
  • Ni is an element effective for improving toughness and strength, and in order to obtain the effect, addition of 0.01% or more is necessary. However, addition of 2.0% or more reduces weldability. Therefore, the upper limit is preferably set to 2.0%.
  • Cu is an element effective for increasing the strength without reducing toughness, but if it is less than 0.01%, there is no effect, and if it exceeds 1.0%, cracking is likely to occur during heating of the steel slab or during welding. To do. Therefore, the content is preferably 0.01 to 1.0% or less.
  • Cr Cr is effective to improve the strength of the steel by precipitation strengthening. Addition of 0.01% or more is effective, but if added in a large amount, the hardenability is increased, the bainite structure is generated, and the low temperature toughness is lowered. Let Therefore, the upper limit is preferably 1.0%.
  • Mo is an element that improves hardenability and at the same time forms carbonitrides and improves strength. To obtain the effect, addition of 0.01% or more is preferable. On the other hand, when Mo is added in a large amount exceeding 0.60%, the cost increases, so the upper limit is preferably made 0.60% or less. Moreover, since the low temperature toughness may decrease when the strength of the steel increases, the preferable upper limit is made 0.20% or less.
  • W is an element effective for improving strength, and is preferably added in an amount of 0.01% or more, more preferably 0.05% or more. On the other hand, if W exceeding 1.0% is added, the toughness may be lowered, so the upper limit is preferably made 1.0% or less.
  • V is an element that forms carbides and nitrides and contributes to the improvement of strength. In order to obtain the effect, addition of 0.01% or more is preferable. On the other hand, addition of V exceeding 0.10% may cause a decrease in low-temperature toughness, so the upper limit is preferably made 0.10% or less.
  • Zr, Ta: Zr and Ta are elements that form carbides and nitrides as well as V and contribute to the improvement of strength. In order to obtain the effect, 0.0001% or more is preferably added. On the other hand, if Zr and Ta are added excessively over 0.050%, the low temperature toughness may be lowered, so the upper limit is preferably made 0.050% or less.
  • B is an element that segregates at the grain boundaries of the steel and contributes significantly to improving the hardenability. In order to obtain this effect, 0.0001% or more of B is preferably added. Further, B is an element that generates BN, lowers the solid solution N, and contributes to the improvement of the toughness of the weld heat affected zone. Therefore, addition of 0.0005% or more is more preferable. on the other hand. When B is added excessively, segregation to the grain boundary becomes excessive, and the low temperature toughness may be lowered, so the upper limit is preferably made 0.0020%.
  • one or more of REM, Mg, Zr, Ta, Y, Hf, and Re may be included.
  • REM is an element added as a deoxidizer and a desulfurizer, and 0.0001% or more is preferably added. On the other hand, if added over 0.010%, a coarse oxide is formed, which may reduce the HIC property and the toughness of the base material and HAZ. The preferable upper limit is 0.010% or less.
  • Mg is an element added as a deoxidizing agent and a desulfurizing agent.
  • a fine oxide is generated and contributes to improvement of HAZ toughness.
  • 0.0001% or more of Mg is preferably added, and 0.0005% or more is more preferably added.
  • the upper limit of the amount of Mg is 0.010% or less.
  • Y, Hf, Re Y, Hf, and Re are elements that, like Ca, generate sulfides, suppress the generation of MnS elongated in the rolling direction, and contribute to the improvement of HIC resistance.
  • 0.0001% or more of Y, Hf, or Re is preferably added, and more preferably 0.0005% or more.
  • the upper limit is preferably made 0.0050% or less.
  • the maximum Mn segregation degree, the Nb segregation degree, and the Ti segregation degree are 2.0 or less, 4.0 or less, and 4.0 or less, respectively.
  • the maximum Mn segregation degree is 2.0 or less, the increase in hardness of the center segregation part is suppressed, and the low temperature toughness of the center segregation part is improved. Further, when the Nb segregation degree is 4.0 or less, the production of accumulated Nb (C, N) is suppressed, and when the Ti segregation degree is 4.0 or less, the production of accumulated TiN is suppressed, both of which are the central segregation part. It is possible to prevent the deterioration of the low temperature toughness.
  • the maximum Mn segregation degree is the maximum Mn amount of the central segregation part relative to the average Mn amount excluding the central segregation part of the steel plate and steel pipe, and the Mn concentration distribution of the steel plate and steel pipe is determined by EPMA or CMA with a probe diameter of 2 ⁇ m. Can be measured and determined. The same applies to the degree of Nb segregation and the degree of Ti segregation.
  • the Nb concentration distribution and the Ti concentration distribution were measured by EPMA or CMA with a probe diameter of 2 ⁇ m, respectively, and the average Nb excluding the central segregation part of the steel plate and steel pipe.
  • the average Nb amount averaged at the center segregation part with respect to the amount (Nb segregation degree), the average maximum Ti amount at the center segregation part with respect to the average Ti amount excluding the center segregation part of the steel plate and steel pipe (Ti segregation degree) Is to be sought.
  • Steel containing the above components is made into a steel slab by continuous casting after melting in the steel making process, and the steel slab is reheated and subjected to thick plate rolling to obtain a steel plate.
  • the steel plate is rolled by setting the reheating temperature of the steel slab to 1000 ° C. or more, setting the reduction ratio in the recrystallization temperature region to 2 or more, and reducing the reduction ratio in the non-recrystallization region to 3 or more.
  • water cooling is performed. It is preferable that the water cooling start temperature is set at a temperature equal to or higher than the Ar3 point and the water cooling stop temperature is set to 250 to 600 ° C. If the water cooling stop temperature is less than 250 ° C., cracking may occur.
  • the average prior austenite particle size can be made 10 ⁇ m or less.
  • the measurement method of the average prior austenite particle size conforms to the measurement method of ASTM E112. If the rolling reduction is performed with the reduction ratio in the recrystallization temperature range of less than 2 and the reduction ratio in the non-recrystallization range of less than 3, the average prior austenite grain size cannot be made 10 ⁇ m or less. When the average prior austenite grain size is 10 ⁇ m or more, the DWTT ductile fracture surface ratio of 85% cannot be satisfied. Therefore, the average prior austenite particle size was set to 10 ⁇ m or less.
  • the recrystallization temperature range is a temperature range where recrystallization occurs after rolling, and is generally over 900 ° C. for the steel components of the present invention.
  • the non-recrystallization temperature range is a temperature range in which recrystallization and ferrite transformation do not occur after rolling, and is generally 750 to 900 ° C. for the components of the steel of the present invention.
  • Rolling in the recrystallization temperature range is called recrystallization rolling or rough rolling
  • rolling in the non-recrystallization temperature range is called non-recrystallization rolling or finish rolling.
  • the maximum hardness of center segregation can be reduced to 400 Hv or less by starting water cooling from a temperature of Ar 3 ° C. or higher and setting the water cooling stop temperature to 250 ° C. or higher. Further, when the water cooling stop temperature is set to 400 ° C. or higher, similarly, the hard martensite after transformation is partially decomposed, and the hardness can be suppressed to 350 Hv or lower. Further, if the water-cooling stop temperature is too high, the strength is lowered, so that it is necessary to add a large amount of alloy, and therefore 600 ° C. or less is preferable.
  • the Mn concentration distribution of the steel plate and the steel pipe was measured by EPMA or CMA with the center segregation portion having a probe diameter of 2 ⁇ m, and the measurement location was hit in a grid pattern with a load of 25 g at a pitch of 0.5 mm. The maximum load is shown.
  • the steel plate was formed into a tubular shape by C press, U press, and O press, end surfaces were tack welded, main welding was performed from the inner and outer surfaces, and then expanded to obtain a steel pipe.
  • submerged arc welding was adopted for this welding.
  • Tensile test pieces, DWTT pieces, and macro test pieces were collected from the obtained steel plates and steel pipes and subjected to respective tests.
  • DWTT was performed according to API5L3.
  • the segregation degree of Mn, Nb, and Ti was measured by EPMA using a macro test piece.
  • the segregation degree was measured by EPMA with a probe diameter of 2 ⁇ m and a measurement area of total thickness ⁇ 20 mm width.
  • the Vickers hardness of center segregation was measured according to JIS Z 2244. Vickers hardness was measured at a site where the load was 25 g and the Mn concentration was highest in the distribution of Mn concentration in the thickness direction measured by EPMA.
  • Table 2 shows the thickness of the steel sheet, the maximum Mn segregation degree, the Nb segregation degree, the Ti segregation degree, the maximum hardness of the central segregation part, the tensile strength, and the ductile fracture surface ratio determined by DWTT.
  • Table 3 shows the thickness of the steel pipe, the heat input amount of the main welding, and the ductile fracture surface ratio determined by DWTT.
  • the maximum Mn segregation degree, the Nb segregation degree, the Ti segregation degree, and the maximum hardness of the central segregation part of the steel pipe are the same as those of the steel sheet, and the tensile strength of the steel pipe is about 10% larger than that of the steel sheet.
  • Steels 1 to 22 and 32 are examples of the present invention, and these steel sheets have a maximum Mn segregation degree of 2.0 or less, an Nb segregation degree of 4.0 or less, a Ti segregation degree of 4.0 or less, and a central segregation portion.
  • the maximum hardness is 400 Hv or less, and the DWTT ductile fracture surface ratios all satisfy 85% or more. The same applies to steel pipes made of these steel plates.
  • Steels 23 to 31 and 33 to 35 represent comparative examples that are outside the scope of the present invention. That is, either the basic component or the selected element is out of the scope of the present invention, or because S / Ca is 0.5 or more, the ductile fracture surface ratio by DWTT is less than 85%. I understand that.
  • Steel 33 the ⁇ 100 ⁇ accumulation degree on the 40 ° surface exceeds 4.0, and the ductile fracture surface ratio is less than 85%.
  • Steel 34 has a basic component element outside the scope of the present invention, and the degree of ⁇ 100 ⁇ accumulation on the 40 ° plane exceeds 4.0, so the ductile fracture surface ratio is less than 85%.
  • Steel 35 has a segregation degree of Nb and a segregation degree of Ti exceeding 4.0, and a degree of ⁇ 100 ⁇ accumulation on the 40 ° surface exceeds 4.0, so that the ductile fracture surface ratio is 85%. Is below.

Abstract

L'invention porte sur une tôle d'acier pour un tube de canalisation et sur un tuyau en acier pour un tube de canalisation, qui ont une excellente ténacité à basse température et sont des plus appropriés pour un tuyau en acier qui est utilisé pour un tube de canalisation pour le transport de pétrole, de gaz naturel ou similaire. La tôle d'acier pour un tube de canalisation et le tuyau en acier pour un tube de canalisation contiennent respectivement, en % en masse, 0,02-0,08 % de C, 0,01-0,5 % de Si, 1,2-1,8 % de Mn, 0,001-0,10 % de Nb, 0,0010-0,0050 % de N et 0,0001-0,0050 % de Ca, alors que P est abaissé à une valeur inférieure ou égale à 0,01 %, S à une valeur inférieure ou égale à 0,0020 %, Ti à une valeur de 0,001-0,030 %, Al à une valeur inférieure ou égale à 0,030 % et O à une valeur inférieure ou égale à 0,0035 %, le reste étant constitué de Fe et d'impuretés inévitables. La tôle d'acier pour un tube de canalisation et le tuyau en acier pour un tube de canalisation satisfont à la relation S/Ca < 0,5 et ont un degré maximal de ségrégation de Mn inférieur ou égal à 2,0, un degré de ségrégation de Nb inférieur ou égal à 4,0 et un degré de ségrégation de Ti inférieur ou égal à 4,0.
PCT/JP2010/065354 2009-09-09 2010-09-01 Tôle d'acier pour tube de canalisation à haute résistance ayant une excellente ténacité à basse température et tuyau en acier pour tube de canalisation à haute résistance WO2011030768A1 (fr)

Priority Applications (3)

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CN201080039943.5A CN102482744B (zh) 2009-09-09 2010-09-01 低温韧性优良的高强度管道用钢板以及高强度管道用钢管
JP2011505304A JP5131715B2 (ja) 2009-09-09 2010-09-01 低温靭性に優れた高強度ラインパイプ用鋼板及び高強度ラインパイプ用鋼管
BR112012005189A BR112012005189A2 (pt) 2009-09-09 2010-09-01 chapas de aço para uso em tubos para oleodutos de alta resistência e aço para uso em tubos para oleodutos de alta resistência com excelente tenacidade a baixa temperatura

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JP2009-208324 2009-09-09

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JP2013117055A (ja) * 2011-12-05 2013-06-13 Jfe Steel Corp 大入熱溶接用鋼材およびその製造方法
KR20140095103A (ko) * 2011-12-28 2014-07-31 신닛테츠스미킨 카부시키카이샤 변형 성능과 저온 인성이 우수한 고강도 강관, 고강도 강판 및 상기 강판의 제조 방법
WO2015012317A1 (fr) * 2013-07-25 2015-01-29 新日鐵住金株式会社 Tôle d'acier pour tube de canalisation et tube de canalisation
WO2019077725A1 (fr) * 2017-10-19 2019-04-25 Ｊｆｅスチール株式会社 Tôle d'acier à haute résistance pour tuyau de canalisation résistant à l'acidité et tuyau en acier à haute résistance l'utilisant
JP2020510749A (ja) * 2016-12-23 2020-04-09 ポスコＰｏｓｃｏ 低温での破壊開始及び伝播抵抗性に優れた高強度鋼材及びその製造方法
JP2020066747A (ja) * 2018-10-22 2020-04-30 日本製鉄株式会社 ラインパイプ用電縫鋼管、及び、ラインパイプ用熱延鋼板
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JP2013117055A (ja) * 2011-12-05 2013-06-13 Jfe Steel Corp 大入熱溶接用鋼材およびその製造方法
KR20140095103A (ko) * 2011-12-28 2014-07-31 신닛테츠스미킨 카부시키카이샤 변형 성능과 저온 인성이 우수한 고강도 강관, 고강도 강판 및 상기 강판의 제조 방법
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EP2799567A4 (fr) * 2011-12-28 2015-08-12 Nippon Steel & Sumitomo Metal Corp Tuyau d'acier de haute résistance possédant une excellente ductilité et une ténacité à basse température, feuille d'acier de haute résistance, et procédé pour la production de feuille d'acier
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CN102899559A (zh) * 2012-10-12 2013-01-30 吉林建龙钢铁有限责任公司 石油输送管线钢的制备方法
WO2015012317A1 (fr) * 2013-07-25 2015-01-29 新日鐵住金株式会社 Tôle d'acier pour tube de canalisation et tube de canalisation
KR20150138301A (ko) * 2013-07-25 2015-12-09 신닛테츠스미킨 카부시키카이샤 라인 파이프용 강판 및 라인 파이프
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JP2020510749A (ja) * 2016-12-23 2020-04-09 ポスコＰｏｓｃｏ 低温での破壊開始及び伝播抵抗性に優れた高強度鋼材及びその製造方法
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WO2019077725A1 (fr) * 2017-10-19 2019-04-25 Ｊｆｅスチール株式会社 Tôle d'acier à haute résistance pour tuyau de canalisation résistant à l'acidité et tuyau en acier à haute résistance l'utilisant
CN111247261A (zh) * 2017-10-19 2020-06-05 杰富意钢铁株式会社 耐酸管线管用高强度钢板和使用了该高强度钢板的高强度钢管
EP3674433A4 (fr) * 2017-10-19 2020-07-29 JFE Steel Corporation Tôle d'acier à haute résistance pour tuyau de canalisation résistant à l'acidité et tuyau en acier à haute résistance l'utilisant
JPWO2019077725A1 (ja) * 2017-10-19 2019-11-14 Ｊｆｅスチール株式会社 耐サワーラインパイプ用高強度鋼板およびこれを用いた高強度鋼管
JP2020066747A (ja) * 2018-10-22 2020-04-30 日本製鉄株式会社 ラインパイプ用電縫鋼管、及び、ラインパイプ用熱延鋼板
JP2020066746A (ja) * 2018-10-22 2020-04-30 日本製鉄株式会社 ラインパイプ用鋼材
JP7159785B2 (ja) 2018-10-22 2022-10-25 日本製鉄株式会社 ラインパイプ用鋼材
JP7206793B2 (ja) 2018-10-22 2023-01-18 日本製鉄株式会社 ラインパイプ用電縫鋼管、及び、ラインパイプ用熱延鋼板

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