WO2015079661A1 - 熱延鋼板およびその製造方法 - Google Patents
熱延鋼板およびその製造方法 Download PDFInfo
- Publication number
- WO2015079661A1 WO2015079661A1 PCT/JP2014/005836 JP2014005836W WO2015079661A1 WO 2015079661 A1 WO2015079661 A1 WO 2015079661A1 JP 2014005836 W JP2014005836 W JP 2014005836W WO 2015079661 A1 WO2015079661 A1 WO 2015079661A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- less
- hot
- steel sheet
- rolled steel
- temperature
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- C21D9/46—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
- C22C38/002—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
- C22C38/02—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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- 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 is a steel pipe used for pipelines, oil well pipes, civil engineering / architecture, etc., particularly as a material for API standard X80 class steel pipe, high strength, low yield ratio and hot rolled steel sheet with excellent stability after processing. And a manufacturing method thereof.
- the steel sheet for line pipe material is required to have not only high strength but also excellent low temperature toughness.
- it is easily affected by crustal deformation.
- the directional deformability ie the yield ratio, is stable and low.
- Patent Document 1 includes C: 0.03 to 0.12 wt%, Si: 0.50 wt% or less, Mn: 1.70 wt% or less, P: 0.025 wt% or less, S: 0.025 wt% or less, and Al: 0.070% or less.
- Hot rolling is performed under the conditions of rolling end temperature: 950 to 1050 ° C and finish rolling temperature: 760 to 800 ° C, cooling is performed at a cooling rate of 5 to 20 ° C / s, and air cooling is performed until reaching 670 ° C.
- a technique for producing a hot-rolled steel sheet by starting and holding for 5 to 20 seconds, then cooling at a cooling rate of 20 ° C./s or more and winding at a temperature of 500 ° C. or less has been proposed.
- Patent Document 1 discloses that the tensile strength is 60 kg / mm 2 or more (590 MPa or more), the yield ratio is 85% or less, the yield ratio is 85% or less, and the fracture surface transition temperature is ⁇ 60 ° C. or less. It is described that a hot-rolled steel sheet having low temperature toughness can be produced.
- the composition is composed of the balance Fe and inevitable impurities
- the structure of the hot rolled steel sheet is bainitic ferrite as the main phase
- the second phase is at least an area ratio of 3.0.
- a technique has been proposed in which the composition contains at least 10% martensite and the bainitic ferrite has an average particle size of 10 ⁇ m or less.
- Patent Document 3 discloses that the main phase of the hot-rolled steel sheet is bainitic ferrite having an average particle size of 10 ⁇ m or less, so that a desired high strength can be ensured after pipe making, and the low temperature toughness is also excellent. It is described that a rolled steel sheet is obtained.
- a low yield ratio can be achieved by forming a structure in which martensite having an area ratio of 3.0% or more is dispersed as the second phase. Furthermore, by defining the composition and structure of the hot-rolled steel sheet as described above, there is little decrease in strength after pipe forming, the yield strength in the 30-degree direction from the rolling direction is 480 MPa or more, and the fracture surface transition temperature of the Charpy impact test. It is described that a low yield ratio high strength hot-rolled steel sheet excellent in low temperature toughness having a low yield ratio of vTrs of ⁇ 80 ° C. or lower and a yield ratio of 85% or lower is obtained.
- Patent Document 1 has a problem that the strength of the hot-rolled steel sheet does not satisfy the X80 class, and that the production efficiency is significantly reduced by including an air cooling process during cooling.
- the technique proposed in Patent Document 2 cannot stably secure the fracture surface transition temperature vTrs ⁇ ⁇ 80 ° C. required for a cold and cold high-temperature toughness material, which has been increasingly demanded in recent years.
- steel with relatively good low-temperature toughness has low strength
- spiral steel pipes with smaller processing strain than ERW steel pipes may not satisfy X80 grade strength.
- the yield ratio varies in the circumferential direction of the pipe, when the external force is applied to the steel pipe due to crustal deformation such as ground subsidence or an earthquake, the yield ratio is low (low yield strength). There is a concern that the steel pipe buckles and deforms due to concentration at the position. Once the steel pipe is buckled, the deformation concentrates on the buckled part, and the part is further deformed, and the steel pipe is easily broken.
- the present invention solves the above-mentioned problems of the prior art, and is suitable as a material for X80 class electric resistance welded steel pipe or a material for X80 class spiral steel pipe, and has high strength, high toughness and low yield ratio characteristics.
- An object of the present invention is to provide a hot-rolled steel sheet having excellent characteristic stability and a method for producing the hot-rolled steel sheet. Specifically, it is a hot-rolled steel sheet having a tensile strength of 650 MPa or more, a yield strength of 555 MPa or more, a yield ratio of 90% or less, and a fracture surface transition temperature (vTrs) of ⁇ 80 ° C. or less in the Charpy impact test.
- Patent Document 3 by making the main phase of the hot-rolled steel sheet into bainitic ferrite having an average particle size of 10 ⁇ m or less, desired high strength can be secured after pipe making, and low temperature toughness is also achieved. An excellent hot-rolled steel sheet can be obtained.
- the second phase of the hot-rolled steel sheet is martensite or bainite, as in the technique proposed in Patent Document 3, the processing strain applied during pipe making is particularly dependent on the circumferential position, such as an electric resistance welded steel pipe. In the case of large differences, the yield ratio after pipe making (after processing) varies greatly in the circumferential direction of the steel pipe.
- the present inventors relate to a hot-rolled steel sheet having a main phase of bainitic ferrite having an average particle diameter of 10 ⁇ m or less, and stably after processing regardless of the amount of processing strain applied.
- the second phase structure to develop the low yield ratio characteristic was studied intensively.
- Residual austenite is a soft structure and is advantageous for lowering the yield ratio of steel.
- the retained austenite gradually transforms from a location with a low C concentration to work-induced martensite, so the yield strength remains relatively low. Can increase tensile strength and keep yield ratio low.
- the present inventors examined the influence of the amount of retained austenite contained in the hot rolled steel sheet as the second phase on the low yield ratio characteristics after processing. As a result, when the retained austenite with a volume fraction of 0.5% or more and 9.5% or less is dispersed as the second phase in the hot-rolled steel sheet, a low yield ratio of 90% or less is obtained in the range of 1-15% working strain. The knowledge that can be achieved. In addition, as a result of transformation of retained austenite to work-induced martensite, it was found that the effect of improving the tensile strength of the hot-rolled steel sheet after processing can be obtained.
- the knowledge that a low yield ratio can be secured stably is obtained.
- the yield ratio can be made almost constant regardless of the amount of processing strain by including martensite together with the retained austenite, but hard martensite is dispersed in baitic ferrite.
- the Bauschinger effect is an effect in which the yield strength is lower than when subjected to processing in the compression direction when subjected to a tensile test after undergoing plastic deformation in a direction opposite to the tensile direction (compression direction).
- the present inventors have the desired structure as described above (basic phase having an average crystal grain size of 10 ⁇ m or less and a volume fraction of 90% or more as a main phase, and a volume fraction as a second phase.
- Study of a simple method for producing hot-rolled steel sheets with a retained austenite of 0.5% to 9.5% and a martensite volume ratio of 0.5% to 9.5%) without reducing production efficiency did.
- the heating condition of the slab, the finish rolling condition, at the center position of the sheet thickness in the cooling process after finishing rolling is finished.
- the continuous cast slab having the composition described in [1] or [2] is cooled to 600 ° C. or lower, and then heated to a temperature range of 1050 ° C. to 1300 ° C. to perform rough rolling and the rough rolling.
- finish rolling with a rolling reduction in the non-recrystallization temperature range of 20% to 85% and a finish rolling end temperature of (Ar 3 -50 ° C) to (Ar 3 + 100 ° C)
- the average cooling rate from the cooling start temperature to 650 ° C at the center position of the sheet thickness is set to 10 ° C / s to 100 ° C / s, and the cooling stop temperature is set to 420 ° C to 650 ° C
- a method for producing a hot-rolled steel sheet, which is wound in a temperature range of 400 ° C. or higher and 650 ° C. or lower and the coil after winding is a coil having a weight of 20 tons or more and a width of 1000 mm or more.
- steel pipes used for pipelines, oil well pipes, civil engineering / architecture, etc. particularly suitable as materials for API standard X80 class steel pipes, high strength, high toughness and low yield ratio characteristics are stable.
- a hot-rolled steel sheet having excellent properties can be obtained by conventional hot-rolling equipment and is extremely useful industrially.
- C 0.030% or more and 0.120% or less C is an important element for securing the strength (tensile strength, yield strength) of hot-rolled steel sheet by forming carbides with Nb, V, Ti and heat. It is an element indispensable for the formation of the second phase (residual austenite and martensite) that is important for reducing the yield ratio of rolled steel sheets.
- the C content needs to be 0.030% or more in order to satisfy desired strength and low yield ratio.
- the toughness of the hot-rolled steel sheet deteriorates due to an excessive increase in carbides.
- the C content exceeds 0.120%, the carbon equivalent increases, and when such a hot-rolled steel sheet is piped and welded, the toughness of the welded portion deteriorates. Therefore, the C content is 0.030% or more and 0.120% or less. Preferably they are 0.040% or more and 0.090% or less.
- Si 0.05% or more and 0.50% or less
- the upper limit of Si content is 0.50%.
- the lower limit of the Si content is set to 0.05% from the viewpoint of securing X80 grade strength by solid solution strengthening.
- Si content shall be 0.10% or more and 0.35% or less.
- Mn 1.00% or more and 2.20% or less
- Mn is an element necessary for suppressing the formation of polygonal ferrite and ensuring the strength and toughness of the hot-rolled steel sheet.
- Mn is also an element necessary for promoting the formation of the second phase, stably generating retained austenite and martensite, and ensuring the low yield ratio characteristics of the hot-rolled steel sheet.
- the Mn content needs to be 1.00% or more.
- the Mn content exceeds 2.20%, variations in mechanical properties of the hot-rolled steel sheet due to center segregation easily occur and toughness deteriorates.
- the Mn content is 1.00% to 2.20%. Preferably it is 1.40% or more and 2.00% or less.
- the upper limit of P content is 0.025%. Preferably it is 0.018% or less.
- S and N also deteriorate the toughness of the hot-rolled steel sheet, so the S content has an upper limit of 0.0050% and the N content has an upper limit of 0.0060%.
- the S content is 0.0030% or less and the N content is 0.0040% or less.
- the lower limit values of the contents of P, S, and N are each preferably set with the lower limit value of P and N being 0.0010% and the lower limit value of S being 0.0001% in consideration of realistic steelmaking control capability limits. .
- Al 0.005% or more and 0.100% or less
- Al is useful as a deoxidizer for steel, and the Al content is set to 0.005% or more where a deoxidation effect is exhibited.
- the Al content is 0.005% or more and 0.100% or less.
- it is 0.010% or more and 0.050% or less.
- Nb 0.020% or more and 0.100% or less
- Nb is a precipitation strengthening element that is effective for refining crystal grains, and it is necessary to make the Nb content 0.020% or more in order to ensure X80 grade steel pipe strength.
- the Nb content is 0.020% or more and 0.100% or less.
- the Nb content is 0.030% or more and 0.080% or less.
- Mo 0.05% or more and 0.50% or less Mo suppresses the transformation of austenite in the steel sheet into polygonal ferrite and pearlite in the cooling process after the hot rolling when manufacturing the hot rolled steel sheet. It is an effective element for improving strength. Mo is an element necessary for promoting the formation of the second phase (residual austenite and martensite) and ensuring the low yield ratio characteristics of the hot-rolled steel sheet. In order to exhibit such an effect, the Mo content is set to 0.05% or more. However, Mo has strong hardenability, and when its content exceeds 0.50%, excessive austenite and martensite, which are the second phase, are generated excessively and the toughness of the hot-rolled steel sheet is lowered. Therefore, the Mo content is 0.05% or more and 0.50% or less. Preferably it is 0.10% or more and 0.35% or less.
- Ti 0.001% or more and 0.100% or less
- Ti is an element effective for refining crystal grains and is a precipitation strengthening element, and the Ti content needs to be 0.001% or more in order to exhibit the effect.
- Ti content shall be 0.001% or more and 0.100% or less. Preferably it is 0.010% or more and 0.040% or less.
- Cr 0.05% or more and 0.50% or less
- Cr is an element that exhibits the effect of delaying pearlite transformation and the effect of reducing grain boundary cementite in the cooling step after hot rolling when producing a hot-rolled steel sheet.
- Cr is an element necessary for promoting the formation of retained austenite and martensite, which are the second phase, and ensuring the low yield ratio characteristics of the hot-rolled steel sheet.
- the Cr content is set to 0.05% or more. On the other hand, if the Cr content exceeds 0.50%, residual austenite and martensite, which are the second phase, are excessively generated and the toughness of the hot-rolled steel sheet is lowered.
- the Cr content is 0.05% or more and 0.50% or less. Preferably it is 0.10% or more and 0.35% or less.
- Ca 0.0005% or more and 0.0050% or less
- Ca has the effect of improving the toughness of the hot-rolled steel sheet by fixing S and suppressing the formation of MnS.
- the Ca content is set to 0.0005% or more.
- the Ca content is set to 0.0050% or less.
- it is 0.0010% or more and 0.0030% or less.
- V 0.001% to 0.100%
- Cu 0.001% to 0.50%
- Ni 0.001% to 1.00%
- B You may contain 1 type, or 2 or more types chosen from 0.0040% or less.
- V 0.001% or more and 0.100% or less
- V is a precipitation strengthening element.
- the V content is preferably 0.001% or more.
- the V content is preferably 0.001% or more and 0.100% or less. More preferably, it is 0.020% or more and 0.080% or less.
- Cu 0.001% or more and 0.50% or less
- Cu is a hot-rolled steel sheet that suppresses the transformation of austenite in the steel sheet into polygonal ferrite and pearlite during the cooling process after hot rolling when manufacturing hot-rolled steel sheet. It is an element effective for improving the strength. In order to exhibit such an effect, it is preferable to make Cu content 0.001% or more. However, if the Cu content exceeds 0.50%, the hot workability of the steel may be reduced. Therefore, the Cu content is preferably 0.001% or more and 0.50% or less. More preferably, it is 0.10% or more and 0.40% or less.
- Ni 0.001% or more and 1.00% or less
- Ni is a hot-rolled steel sheet that suppresses the transformation of austenite in the steel sheet into polygonal ferrite and pearlite in the cooling process after hot rolling when manufacturing a hot-rolled steel sheet. It is an element effective for improving the strength.
- the Ni content is preferably 0.001% or more. However, if the Ni content exceeds 1.00%, the hot workability of the steel may be reduced. Therefore, the Ni content is preferably 0.001% or more and 1.00% or less. More preferably, it is 0.10% or more and 0.50% or less.
- B 0.0040% or less B is effective in suppressing the ferrite transformation at high temperature and preventing the formation of polygonal ferrite in the cooling process after the finish rolling at the time of producing the hot-rolled steel sheet.
- the B content is preferably 0.0001% or more.
- the B content is preferably 0.0040% or less. More preferably, it is 0.0002% or more and 0.0010% or less.
- components other than the above are Fe and inevitable impurities.
- Inevitable impurities include, for example, Co, W, Pb, Sn, etc.
- the content of these elements is preferably 0.02% or less.
- the hot-rolled steel sheet of the present invention has bainitic ferrite as the main phase, contains martensite and retained austenite as the second phase, has a volume fraction of the main phase of 90% or more, and has an average crystal grain size of the main phase. 10 ⁇ m or less, the martensite volume fraction is 0.5% to 9.5% and the residual austenite volume fraction is 0.5% to 9.5%.
- bainitic ferrite is a structure having a substructure with a high dislocation density and having no cementite precipitated in crystal grains.
- bainite has a lath structure with a high dislocation density, cementite is precipitated in the crystal grains, and polygonal ferrite has a very low dislocation density. Different.
- the main phase of the hot-rolled steel sheet is a fine bainitic ferrite with an excellent balance between strength and toughness.
- desired strength and low temperature toughness are imparted to the hot-rolled steel sheet.
- the volume fraction of bainitic ferrite is preferably 91% or more, and the average crystal grain size of bainitic ferrite is 3.0 ⁇ m or less. It is preferable.
- the present invention contains martensite and residual austenite that lower toughness, when the total volume fraction of martensite and residual austenite is 4.0% or more, the average grain size of bainitic ferrite is set to The thickness is preferably 3.0 ⁇ m or less.
- the volume fraction of bainitic ferrite is preferably 95% or less.
- Bainitic ferrite is preferably finer, but the substantial lower limit of the average grain size is about 1 ⁇ m.
- Residual austenite volume fraction 0.5% or more and 9.5% or less Residual austenite undergoes processing-induced transformation in order from low C concentration due to processing strain during pipe forming, etc., and a wide processing strain range (for example, processing) Increases work hardening ability in the strain range from 1% to 10%. For this reason, tensile strength can be made high compared with yield strength, and it can be set as a low yield ratio. As a result, for example, even when the pipe-forming strain differs at the circumferential position of the pipe, such as an electric resistance welded steel pipe, the low yield ratio characteristic can be stably obtained regardless of the circumferential position. In order to exert such an effect, the volume fraction of retained austenite needs to be 0.5% or more.
- the volume fraction of retained austenite is 2.0% or more.
- the volume fraction of retained austenite exceeds 9.5%, it acts as a propagation path of cracks, and the low temperature toughness of the hot rolled steel sheet deteriorates. Therefore, the volume fraction of retained austenite needs to be 9.5% or less. In order to secure better low temperature toughness, the volume fraction of retained austenite is preferably 5% or less.
- Martensite volume fraction 0.5% or more and 9.5% or less Martensite facilitates the introduction of movable dislocations into the bainitic ferrite and enhances the Bauschinger effect.
- the volume fraction of martensite needs to be 0.5% or more. Preferably it is 2.5% or more.
- the volume fraction of martensite needs to be 9.5% or less.
- the martensite volume fraction is preferably 5% or less.
- the structure of the hot-rolled steel sheet of the present invention may contain pearlite and cementite in addition to the bainitic ferrite, retained austenite and martensite. It is preferable to limit the volume fraction of the structure other than bainitic ferrite, retained austenite and martensite, that is, pearlite and cementite, to 2% or less in total.
- the hot-rolled steel sheet of the present invention which is mainly used as a material for line pipes, preferably has a thickness of 15 mm or more and 30 mm or less.
- the hot-rolled steel sheet of the present invention cools a slab (slab) having the above composition obtained by continuous casting to a predetermined temperature or lower, and then heats it to perform rough rolling and finish rolling, under predetermined conditions. It can be manufactured by accelerating cooling and winding it around a coil having a predetermined weight and width at a predetermined temperature.
- Cooling temperature of continuous cast slab 600 ° C. or less
- the continuous cast slab before ferrite transformation has an austenite structure and is exposed to a high temperature for a long time, so its crystal grains are extremely coarse. For this reason, the coarse austenite crystal is refined by ferrite transformation. For this reason, the continuously cast slab is cooled to 600 ° C. or lower where the ferrite transformation is almost completed. Preferably it is 500 degrees C or less. After that, the continuous cast slab is heated and reversely transformed into austenite, whereby the crystal grains are further refined.
- Heating temperature of continuous cast slab 1050 ° C or higher and 1300 ° C or lower If the slab heating temperature (reheating temperature of continuous cast slab) is lower than 1050 ° C, the precipitation strengthening elements Nb, V and Ti are not sufficiently dissolved, X80 grade steel pipe strength cannot be secured. On the other hand, when the temperature exceeds 1300 ° C, the austenite grains become coarse, resulting in coarsening of the grain size of the bainitic ferrite, resulting in deterioration of the low temperature toughness of the hot rolled steel sheet, and in the cooling and winding process after finishing rolling. Nb precipitates excessively, and the toughness and elongation characteristics of the hot-rolled steel sheet deteriorate. Therefore, the reheating temperature of the continuous cast slab is set to 1050 ° C. or higher and 1300 ° C. or lower. Preferably they are 1150 degreeC or more and 1230 degrees C or less.
- the slab (continuous cast slab) after heating is subjected to rough rolling and finish rolling to be adjusted to an arbitrary plate thickness, but in the present invention, the conditions for rough rolling are not particularly limited.
- Reduction ratio in non-recrystallization temperature range during finish rolling 20% or more and 85% or less.
- finish rolling in the non-recrystallization temperature range (about 930 ° C or less in the case of the steel composition of the present invention)
- Crystals are delayed and strain accumulates, and ferrite (bainitic ferrite) is refined during the ⁇ / ⁇ transformation to improve the strength and toughness of the hot-rolled steel sheet.
- the rolling reduction in the non-recrystallization temperature region during finish rolling is less than 20%, these effects are not sufficiently exhibited.
- the rolling reduction exceeds 85%, the deformation resistance increases and hinders rolling. Therefore, in the present invention, the rolling reduction is set to 20% or more and 85% or less. Preferably they are 35% or more and 75% or less.
- Finishing rolling finish temperature (Ar 3 -50 ° C) or more (Ar 3 + 100 ° C) or less
- the finish rolling finish temperature is set to (Ar 3 -50 ° C) or more.
- the finish rolling finish temperature is lower than (Ar 3 -50 ° C.)
- ferrite transformation occurs inside the steel plate during finish rolling, and polygonal ferrite is partially formed.
- Polygonal ferrite has coarser crystal grains than bainitic ferrite generated during or after the subsequent cooling, and therefore has a mixed grain structure with nonuniform crystal grain sizes. For this reason, desired hot-rolled steel sheet characteristics cannot be obtained.
- the finish rolling finish temperature exceeds (Ar 3 + 100 ° C.)
- the bainitic ferrite crystal grains become coarse and the toughness of the hot-rolled steel sheet deteriorates.
- the finish rolling finish temperature is set within the range of (Ar 3 ⁇ 50 ° C.) to (Ar 3 + 100 ° C.).
- it is (Ar 3 ⁇ 20 ° C.) or more and (Ar 3 + 50 ° C.) or less.
- the finish rolling end temperature is a measured temperature value of the steel sheet surface on the exit side of the finish rolling mill.
- Accelerated cooling is preferably started within 7 s after finishing rolling, and more preferably started within 3 s after finishing rolling. If the time until finish of accelerated cooling after finishing rolling exceeds 7 s, crystal grains may be coarsened, or ferrite transformation may start and polygonal ferrite may be generated.
- Average cooling rate at the center of the plate thickness from the cooling start temperature to 650 ° C: 10 ° C / s or more and 100 ° C / s or less Suppresses the formation of pearlite transformation and polygonal ferrite, and the volume fraction of bainitic ferrite is 90%
- the upper limit of the average cooling rate needs to be 100 ° C./s.
- they are 25 degreeC / s or more and 50 degrees C / s or less.
- Cooling stop temperature at the center of the plate thickness 420 ° C or higher and 650 ° C or lower
- the transformation of austenite in the steel sheet (austenite ⁇ bainitic ferrite transformation) Is not completely completed in the cooling process, and it is necessary to leave untransformed austenite.
- the temperature at which accelerated cooling is stopped needs to be 420 ° C. or higher at the plate thickness center position.
- the cooling stop temperature for accelerated cooling needs to be 420 ° C. or higher and 650 ° C. or lower at the plate thickness center position.
- they are 500 degreeC or more and 590 degrees C or less.
- Winding temperature 400 ° C. or higher and 650 ° C. or lower
- residual austenite and martensite which are the second phase, are generated in the cooling process after coil winding. This requires diffusion of C from the bainitic ferrite transformed after the accelerated cooling process or after cooling has stopped into untransformed austenite.
- the diffusion of C from bainitic ferrite to untransformed austenite and the concentration of C in untransformed austenite suppresses the transformation of untransformed austenite to bainite. Is maintained to room temperature). Whether it becomes martensite or retained austenite depends on the degree of concentration of C, and the portion where C is further concentrated and the Ms point (martensitic transformation start temperature) is below room temperature becomes retained austenite.
- the coil winding temperature needs to be 400 ° C. or higher in order to sufficiently diffuse C and achieve the desired volume fraction of retained austenite and martensite.
- the coil winding temperature needs to be 400 ° C. or higher and 650 ° C. or lower. Preferably they are 480 degreeC or more and 580 degrees C or less.
- all the said winding temperature is the temperature in the plate
- Coil weight after winding 20 tons or more
- Coil width after winding 1000 mm or more
- a part of austenite remaining untransformed is transformed into martensite in the cooling process after coil winding. It is necessary to disperse both retained austenite and martensite as a second phase structure in the hot-rolled steel sheet.
- the cooling rate after coil winding is very important.
- the diffusion rate of C from bainitic ferrite to untransformed austenite is promoted by suppressing the cooling rate after coil winding as much as possible. Is preferred.
- the cooling rate after coil winding is suppressed by defining the coil weight and coil width after winding.
- the coil weight after winding is less than 20 tons or the coil width after winding is less than 1000 mm, the cooling rate of the coil after winding becomes too fast, so the austenite remaining untransformed is stable. C does not concentrate sufficiently, and only martensite is preferentially produced as the second phase. As a result, the amount of retained austenite in the hot-rolled steel sheet becomes insufficient, and the low yield ratio characteristics cannot be stabilized in a wide working strain range.
- the coil cooling rate after winding is preferably 70 ° C./s or less. More preferably, it is 50 ° C./s or less.
- the coil cooling rate after winding is the average cooling rate from 400 ° C. to 390 ° C. on the steel sheet surface.
- the coil temperature measurement position after winding is the center position of the outer circumference of the coil in the coil after winding. The temperature of the coil is measured by selecting a location where no gap is formed between the steel plates due to loose winding, and attaching a thermocouple to the steel plate surface at the center of the width of the outer periphery of the coil.
- the coil cooling rate is defined by the average cooling rate from 400 ° C to 390 ° C.
- the temperature range near 400 ° C is the temperature range where C is most likely to be concentrated in the austenite remaining untransformed. This is because.
- the coil weight after winding is 20 tons or more, and the coil width after winding is 1000 mm or more. Further, the coil weight after winding is preferably 25 tons or more, and the coil width after winding is preferably 1400 mm or more.
- the upper limits of the coil weight and coil width after winding are not particularly limited, but the actual upper limit values are about 40 tons and 2500 mm, respectively, considering the operation results of the rolling equipment.
- the obtained hot-rolled steel sheet (steel strip) is formed by cage roll forming, electric resistance welding is performed, bead grinding is performed on the inner surface side, and then heat treatment is performed only on the welded portion with a post-annealer to perform sizing.
- an ERW steel pipe having an outer diameter of 16 inches was obtained.
- the method of manufacturing an electric resistance steel pipe using a hot rolled steel sheet has been exemplified.
- the hot rolled steel sheet in the present invention is not limited to an electric resistance welded steel pipe but also adopted in various pipe making methods such as a spiral steel pipe. can do.
- Test specimens were collected from the obtained hot-rolled steel sheet and ERW steel pipe, and subjected to structure observation, tensile test and Charpy impact test. The methods of tissue observation and various tests were as follows.
- the photograph taken as described above is image-analyzed and separated into bainitic ferrite and a structure other than bainitic ferrite, and the area ratio of bainitic ferrite occupying each observation visual field is obtained and obtained at each plate thickness position.
- the average value of the area ratio was defined as the volume fraction of bainitic ferrite.
- the area ratio of pearlite in the observation visual field was obtained, and the average value of the area ratios obtained at each plate thickness position was defined as the pearlite volume fraction.
- the volume fraction of polygonal ferrite was also obtained in the same manner.
- the average grain size of bainitic ferrite was determined as an equivalent circle diameter by image analysis of the structure recognized as bainitic ferrite by image analysis.
- Residual austenite and martensite do not show a clear difference in contrast with a scanning electron microscope. Therefore, first, the total area ratio of the retained austenite and martensite in the observation field is obtained in the same manner as described above, and the average value of the area ratio obtained at each plate thickness position is the total volume fraction of the residual austenite and martensite. did. Subsequently, the volume fraction of retained austenite was obtained by X-ray diffraction, and the volume fraction of martensite was obtained by subtracting the volume fraction of retained austenite from the total volume fraction.
- the volume fraction of retained austenite was determined by the following X-ray diffraction method.
- a test piece for X-ray diffraction was collected in parallel to the plate surface, ground and chemically polished, and the surface of the test piece after polishing was set to a 1/4 position in the plate thickness direction of the steel plate. Then, by using the test piece, the diffraction intensity of (200), (211) plane of ⁇ , (200), (220), (311) plane of ⁇ is obtained by X-ray diffraction method, and the volume fraction of ⁇ is calculated. did.
- the tensile strength TS of hot-rolled steel sheet is 650 MPa or more, the yield strength YS is 555 MPa or more, the yield ratio YR is 90% or less, and the difference ⁇ YR between the 90 ° position and 180 ° position of the ERW steel pipe is less than 10%.
- tensile properties excellent in strength, post-processing property stability, and low yield ratio properties are evaluated as “tensile properties excellent in strength, post-processing property stability, and low yield ratio properties”.
- V notch specimen (length 55mm x height 10mm x width) so that the direction perpendicular to the rolling direction (C direction) is the longitudinal direction from the center of the thickness of the obtained hot-rolled steel sheet 10 mm) was collected and subjected to a Charpy impact test in accordance with the provisions of JIS Z 2242 to obtain a ductile-brittle fracture surface transition temperature (° C.).
- Three specimens were collected for each hot-rolled steel sheet, and the arithmetic average of the ductility-brittle fracture surface transition temperature obtained for the three specimens was calculated as the ductility-brittle fracture surface transition temperature (vTrs) of each hot-rolled steel sheet. It was. A case where vTrs was ⁇ 80 ° C. or lower was evaluated as “good toughness”.
- the hot-rolled steel sheets of the inventive examples were all good in tensile properties (yield strength, tensile strength, yield ratio, ERW steel pipe yield ratio difference) and toughness (low temperature toughness).
- the hot-rolled steel sheet of the comparative example could not obtain sufficient characteristics in either one or both of tensile properties and toughness (low temperature toughness).
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
[1] 質量%で、C:0.030%以上0.120%以下、Si:0.05%以上0.50%以下、Mn:1.00%以上2.20%以下、P:0.025%以下、S:0.0050%以下、N:0.0060%以下、Al:0.005%以上0.100%以下、Nb:0.020%以上0.100%以下、Mo:0.05%以上0.50%以下、Ti:0.001%以上0.100%以下、Cr:0.05%以上0.50%以下、Ca:0.0005%以上0.0050%以下を含有し、残部がFeおよび不可避的不純物からなる組成を有し、ベイニティックフェライトを主相とし、第二相としてマルテンサイトおよび残留オーステナイトを含み、前記主相の体積分率が90%以上、前記主相の平均結晶粒径が10μm以下、前記マルテンサイトの体積分率が0.5%以上9.5%以下、前記残留オーステナイトの体積分率が0.5%以上9.5%以下である組織を有し、降伏比が90%以下、降伏強さが555MPa以上、引張強さが650MPa以上である熱延鋼板。
先ず、本発明熱延鋼板の成分組成の限定理由について説明する。なお、以下の成分組成を表す%は、特に断らない限り質量%を意味するものとする。
Cは、Nb、V、Tiと炭化物を形成することで熱延鋼板の強度(引張強さ、降伏強さ)を確保するために重要な元素であるとともに、熱延鋼板の低降伏比化に重要な第二相(残留オーステナイトおよびマルテンサイト)の生成に欠かせない元素である。本発明の熱延鋼板において、所望の強度、低降伏比を満足するためには、C含有量を0.030%以上とする必要がある。一方、C含有量が0.120%を超えると、炭化物の過剰な増加により、熱延鋼板の靭性が劣化する。また、C含有量が0.120%を超えると、炭素当量が高くなり、このような熱延鋼板を造管・溶接すると溶接部の靭性が劣化する。したがって、C含有量は0.030%以上0.120%以下とする。好ましくは0.040%以上0.090%以下である。
Siの含有量が増加すると、Mn-Si系の非金属介在物を形成し、熱延鋼板を造管・溶接した際に溶接部靭性を悪化させる原因となる。したがって、Si含有量は0.50%を上限とする。一方、Si含有量の下限は、固溶強化によりX80級の強度を確保する観点から0.05%に定める。なお、Si含有量は0.10%以上0.35%以下とすることが好ましい。
Mnは、ポリゴナルフェライトの生成を抑制し、熱延鋼板の強度と靭性を確保するために必要な元素である。また、Mnは、第二相の生成を促進し、残留オーステナイトやマルテンサイトを安定的に生成して熱延鋼板の低降伏比特性を確保するのに必要な元素でもある。これらの効果の発揮には、Mn含有量を1.00%以上とする必要がある。一方、Mn含有量が2.20%を超えると、中心偏析に伴う熱延鋼板の機械的特性のバラツキが発生し易くなるとともに、靭性が劣化する。また、Mn含有量が2.20%を超えると、熱延鋼板の強度が高くなり過ぎることで、伸び特性が低下する等の悪影響が現れるとともに、炭素当量の増加に伴い溶接部靭性が劣化する可能性がある。したがって、Mn含有量は1.00%以上2.20%以下とする。好ましくは1.40%以上2.00%以下である。
Pは、鋼中に不純物として存在するが、偏析し易い元素であり、熱延鋼板の靭性劣化をもたらす。したがって、P含有量は0.025%を上限とする。好ましくは0.018%以下である。
SおよびNも、Pと同様、熱延鋼板の靭性を劣化させるため、S含有量は0.0050%を上限とし、N含有量は0.0060%を上限とする。好ましくは、S含有量は0.0030%以下、N含有量は0.0040%以下である。
なお、P、S、Nの含有量の下限値は、いずれも現実的な製鋼制御能力限界を考慮し、P、Nの下限値を0.0010%、Sの下限値を0.0001%とすることが好ましい。
Alは、鋼の脱酸剤として有用であり、Al含有量は脱酸効果の発現する0.005%以上とする。但し、Al含有量が過剰になると、アルミナ系介在物が生成し、熱延鋼板を溶接する際に溶接部欠陥の原因となる。したがって、Al含有量は0.005%以上0.100%以下とする。好ましくは0.010%以上0.050%以下である。
Nbは、結晶粒の微細化に有効でかつ析出強化元素であり、X80級の鋼管強度を確保するためにはNb含有量を0.020%以上とする必要がある。一方、Nb含有量が過剰になると、熱延鋼板の製造時、後述する巻取り温度域(400℃以上650℃以下)で過剰に析出が生じて靭性が低下するとともに、溶接性を劣化させる。したがって、Nb含有量は0.020%以上0.100%以下とする。好ましくは、Nb含有量は0.030%以上0.080%以下とする。
Moは、熱延鋼板を製造する際、熱間圧延終了後の冷却工程において鋼板中のオーステナイトがポリゴナルフェライトやパーライトに変態するのを抑制し、熱延鋼板の強度向上に有効な元素である。また、Moは、第二相(残留オーステナイトおよびマルテンサイト)の生成を促進し、熱延鋼板の低降伏比特性を確保するのに必要な元素である。このような効果を発現させるために、Mo含有量を0.05%以上とする。但し、Moは、焼入れ性が強く、その含有量が0.50%を超えると、第二相である残留オーステナイトやマルテンサイトを過剰に生成して熱延鋼板の靭性を低下させる。したがって、Mo含有量は0.05%以上0.50%以下とする。好ましくは0.10%以上0.35%以下である。
Tiは、結晶粒の微細化に有効な元素でありかつ析出強化元素であり、その効果の発現にはTi含有量を0.001%以上とする必要がある。一方、Ti含有量が過剰になると、熱延鋼板の溶接性を劣化させる。したがって、Ti含有量は0.001%以上0.100%以下とする。好ましくは0.010%以上0.040%以下である。
Crは、熱延鋼板を製造する際、熱間圧延終了後の冷却工程においてパーライト変態の遅延効果と粒界セメンタイトの低減効果を発現する元素である。また、Crは、第二相である残留オーステナイトおよびマルテンサイトの生成を促進し、熱延鋼板の低降伏比特性を確保するのに必要な元素である。これらの効果を発現させるために、Cr含有量を0.05%以上とする。一方、Cr含有量が0.50%を超えると、第二相である残留オーステナイトやマルテンサイトが過剰に生成して熱延鋼板の靭性を低下させる。また、Cr含有量が過剰になると、熱延鋼板を造管・溶接する際、溶接部に焼き入れ組織を形成して溶接部靭性の劣化を招く。したがって、Cr含有量は0.05%以上0.50%以下とする。好ましくは0.10%以上0.35%以下である。
Caは、Sを固定し、MnSの生成を抑制することで熱延鋼板の靭性を向上させる効果がある。このような効果を発現させるために、Ca含有量を0.0005%以上とする。一方、Ca含有量が過剰になると、Ca系酸化物の形成により熱延鋼板の靭性が低下するため、Ca含有量は0.0050%以下とする。好ましくは0.0010%以上0.0030%以下である。
Vは、析出強化元素であり、これを有効に作用させるためにはV含有量を0.001%以上とすることが好ましい。一方、V含有量が過剰になると、熱延鋼板の製造時、後述する巻取り温度域(400℃以上650℃以下)で過剰に析出が生じて靭性と伸び特性が低下するとともに、溶接性を劣化させるおそれがある。したがって、V含有量は0.001%以上0.100%以下とすることが好ましい。より好ましくは0.020%以上0.080%以下である。
Cuは、熱延鋼板を製造する際、熱間圧延終了後の冷却工程において鋼板中のオーステナイトがポリゴナルフェライトやパーライトに変態するのを抑制するとともに、熱延鋼板の強度向上に有効な元素である。このような効果を発現させるためには、Cu含有量を0.001%以上とすることが好ましい。但し、Cu含有量が0.50%を超えると、鋼の熱間加工性を低下させるおそれがある。したがって、Cu含有量は0.001%以上0.50%以下とすることが好ましい。より好ましくは0.10%以上0.40%以下である。
Niは、熱延鋼板を製造する際、熱間圧延終了後の冷却工程において鋼板中のオーステナイトがポリゴナルフェライトやパーライトに変態するのを抑制するとともに、熱延鋼板の強度向上に有効な元素である。このような効果を発現させるためには、Ni含有量を0.001%以上とすることが好ましい。但しNiは、その含有量が1.00%を超えると、鋼の熱間加工性を低下させるおそれがある。したがって、Ni含有量は0.001%以上1.00%以下とすることが好ましい。より好ましくは0.10%以上0.50%以下である。
Bは、熱延鋼板の製造時、仕上げ圧延終了後の冷却過程において高温でのフェライト変態を抑制し、ポリゴナルフェライトの生成を防止する効果がある。このような効果を発現させるためには、B含有量を0.0001%以上とすることが好ましい。一方、B含有量が過剰になると、熱延鋼板を溶接する際、溶接部に焼入れ組織を形成するおそれがある。したがって、B含有量は0.0040%以下とすることが好ましい。より好ましくは0.0002%以上0.0010%以下である。
本発明の熱延鋼板は、ベイニティックフェライトを主相とし、第二相としてマルテンサイトおよび残留オーステナイトを含み、前記主相の体積分率が90%以上、前記主相の平均結晶粒径が10μm以下、前記マルテンサイトの体積分率が0.5%以上9.5%以下、前記残留オーステナイトの体積分率が0.5%以上9.5%以下である組織を有する。なお、本発明において、ベイニティックフェライトとは、転位密度が高い下部組織を有し、結晶粒内にセメンタイトが析出していない組織である。これに対し、ベイナイトは転位密度の高いラス状組織を有し、結晶粒内にセメンタイトが析出している点で、また、ポリゴナルフェライトは転位密度が極めて低い点で、ベイニティックフェライトとは異なる。
ベイニティックフェライトの平均結晶粒径:10μm以下
本発明においては、熱延鋼板の主相を強度と靭性のバランスに優れた微細なベイニティックフェライトとすることにより、熱延鋼板に所望の強度と低温靭性を付与する。主相であるベイニティックフェライトの体積分率を90%以上とし、該ベイニティックフェライトの平均結晶粒径を10μm以下とすることで、細粒化効果により熱延鋼板の強度と低温靭性を確保することができる。一方、ベイニティックフェライトの体積分率が90%未満になると、第二相の体積分率が大きくなり、亀裂の伝播経路が増加するため、熱延鋼板の低温靭性が劣化する。また、ベイニティックフェライトの平均結晶粒径が10μmを超えると、破面単位が大きくなり靭性が低下する。
残留オーステナイトは造管時等の加工歪により、C濃度の低い箇所から順々に加工誘起変態し、造管にかかる広い加工歪域(たとえば加工歪1%から10%程度までの歪域)で加工硬化能を高める。このため、降伏強さに比較して引張強さを高くすることができ、低降伏比とすることができる。その結果、例えば電縫鋼管のようにパイプ周方向位置で造管歪の異なるような場合でも、周方向位置によらず、安定して低降伏比特性を得ることができる。このような効果を発揮するためには、残留オーステナイトの体積分率を0.5%以上とする必要がある。より好ましくは2.0%以上である。一方、残留オーステナイトの体積分率が9.5%を超えると、亀裂の伝播経路として働き、熱延鋼板の低温靭性が劣化する。したがって、残留オーステナイトの体積分率は9.5%以下とする必要がある。なお、更に良好な低温靭性を確保するためには、残留オーステナイトの体積分率を5%以下とすることが好ましい。
マルテンサイトは、ベイニティックフェライト中に、加工による可動転位の導入をし易くし、バウシンガー効果を高める。この効果を発揮させるためには、マルテンサイトの体積分率を0.5%以上とする必要がある。好ましくは2.5%以上である。一方、マルテンサイトの体積分率が9.5%を超えると、亀裂の伝播経路として働き、熱延鋼板の低温靭性が劣化する。したがって、マルテンサイトの体積分率は9.5%以下とする必要がある。更に良好な低温靭性を確保するためには、マルテンサイトの体積分率を5%以下とすることが好ましい。
本発明の熱延鋼板は、連続鋳造によって得られた上記組成を有するスラブ(鋳片)を、所定の温度以下に冷却したのち、加熱して粗圧延および仕上げ圧延を施し、所定の条件にて加速冷却し、所定温度で、所定の重量および巾を持つコイルに巻き取ることにより製造することができる。
フェライト変態する前の連続鋳造鋳片は、オーステナイト組織であり、高温に長時間さらされているため、その結晶粒は極めて粗大である。このため、この粗大なオーステナイト結晶をフェライト変態させることにより微細化する。このためフェライト変態がほぼ完了する600℃以下まで連続鋳造鋳片を冷却する。好ましくは500℃以下である。なお、その後、連続鋳造鋳片が加熱され、オーステナイトに逆変態することで、更に結晶粒が微細化する。
スラブ加熱温度(連続鋳造鋳片の再加熱温度)が1050℃未満では、析出強化元素であるNb、V、Tiが十分固溶せず、X80級の鋼管強度が確保できない。一方、1300℃を超えると、オーステナイト粒が粗大化し、結果としてベイニティックフェライトの結晶粒径が粗大化し、熱延鋼板の低温靭性が劣化するとともに、仕上げ圧延終了後の冷却・巻取り過程においてNbが過剰に析出し、熱延鋼板の靭性と伸び特性が劣化する。したがって、連続鋳造鋳片の再加熱温度は1050℃以上1300℃以下とする。好ましくは1150℃以上1230℃以下である。
未再結晶温度域(本発明の鋼組成の場合、約930℃以下)で仕上げ圧延を行うことにより、オーステナイトの再結晶が遅延して歪が蓄積し、γ/α変態時にフェライト(ベイニティックフェライト)が微細化して熱延鋼板の強度および靭性が向上する。ここで、仕上げ圧延時における未再結晶温度域での圧下率が20%未満では、これらの効果が十分に発現しない。一方、上記圧下率が85%を超えると、変形抵抗が増大して圧延に支障をきたす。したがって、本発明では上記圧下率を20%以上85%以下とする。好ましくは35%以上75%以下である。
均質な粒径および組織で圧延を終了するためには、仕上げ圧延終了温度を(Ar3-50℃)以上とする必要がある。仕上げ圧延終了温度が(Ar3-50℃)を下回ると、仕上げ圧延中に鋼板内部でフェライト変態が生じ、一部にポリゴナルフェライトが生成する。ポリゴナルフェライトは、その後の冷却中あるいは冷却後に生成するベイニティックフェライトよりも粗大な結晶粒となるため、結晶粒の大きさが不均一な混粒組織となる。このため、所望の熱延鋼板特性が得られない。一方、仕上げ圧延終了温度が(Ar3+100℃)を超えると、ベイニティックフェライトの結晶粒が粗大化し、熱延鋼板の靱性が劣化する。特に、本発明ではベイニティックフェライトに加えて、靭性に悪影響を及ぼすマルテンサイトおよび残留オーステナイトを含むため、ベイニティックフェライト結晶粒を微細にして靭性を確保する必要がある。したがって、仕上げ圧延終了温度を(Ar3-50℃)以上(Ar3+100℃)以下の範囲内とする。好ましくは(Ar3-20℃)以上(Ar3+50℃)以下である。
なお、上記の仕上げ圧延終了温度は、仕上げ圧延機の出側での鋼板表面の測定温度値である。
パーライト変態およびポリゴナルフェライトの生成を抑制し、ベイニティックフェライトの体積分率を90%以上とし、熱延鋼板の低温靱性を確保するためには、冷却開始温度から650℃までの板厚中央位置の平均冷却速度を10℃/s以上とすることが必要である。但し、この板厚中央位置での上記温度域における冷却速度が大きくなり過ぎると、鋼板表面硬度が上昇し、ラインパイプ用鋼板として適さなくなる。したがって、上記平均冷却速度の上限は100℃/sとする必要がある。好ましくは25℃/s以上50℃/s以下である。
第二相として残留オーステナイトおよびマルテンサイトを組織中に分散させるためには、鋼板中のオーステナイトの変態(オーステナイト→ベイニティックフェライト変態)を冷却過程で完全に完了させず、未変態のオーステナイトを残す必要がある。そのためには、本発明の成分範囲においては、加速冷却を停止する温度を板厚中央位置で420℃以上とする必要がある。一方、加速冷却を停止する温度が650℃を超えると、粗大なポリゴナルフェライト、パーライトが生成され所望の熱延鋼板組織を得ることができない。したがって、加速冷却の冷却停止温度は、板厚中央位置で420℃以上650℃以下とする必要がある。好ましくは500℃以上590℃以下である。
本発明においては、第二相である残留オーステナイトおよびマルテンサイトを、コイル巻取り後の放冷過程で生成する。このためには、加速冷却過程あるいは冷却停止後に変態したベイニティックフェライトから未変態オーステナイトへのCの拡散が必要である。ベイニティックフェライトから未変態オーステナイトへCが拡散し、未変態オーステナイトにCが濃縮することにより、未変態オーステナイトのベイナイトへの変態が抑止され、未変態オーステナイトをマルテンサイトあるいは残留オーステナイト(未変態オーステナイトが室温まで維持された状態)とすることができる。マルテンサイトとなるか、残留オーステナイトとなるかは、Cの濃化度合いにより、Cがより濃化してMs点(マルテンサイト変態開始温度)が室温未満となった部分が残留オーステナイトとなる。
巻取り後のコイル巾:1000mm以上
本発明においては、未変態のまま残存したオーステナイトの一部を、コイル巻取り後の放冷過程でマルテンサイト変態させることにより、熱延鋼板中に第二相組織として残留オーステナイトおよびマルテンサイトの両方を分散させる必要がある。ここで、第二相としての残留オーステナイトおよびマルテンサイトを所望の体積分率で分散させるためには、コイル巻取り後の冷却速度が非常に重要となる。
得られた熱延鋼板(鋼帯)を、ケージロールフォーミングで成形し、電気抵抗溶接を行い、内面側のビード研削を施した後、ポストアニーラにて溶接部にのみ熱処理を施し、サイジングを行うことにより、外径16インチの電縫鋼管とした。
なお、本実施例では、熱延鋼板を用いて電縫鋼管を製造する方法を例示したが、本発明における熱延鋼板は電縫鋼管に限らず、スパイラル鋼管など種々の造管方法にも採用することができる。
得られた熱延鋼板および電縫鋼管から試験片を採取し、組織観察、引張試験およびシャルピー衝撃試験を実施した。組織観察および各種試験の方法は次のとおりとした。
得られた熱延鋼板の板厚中央位置、板厚方向1/4位置、板厚方向3/4位置、表面下1mm位置における微細組織を、走査型電子顕微鏡(倍率:2000倍)を用いて各板厚位置で3視野以上観察および撮像し、ベイニティックフェライト、残留オーステナイト、マルテンサイト、パーライトの体積分率を測定した。なお、得られた熱延鋼板の微細組織を観察した結果、本発明例の熱延鋼板においては、基地組織としてベイニティックフェライト、残留オーステナイト、マルテンサイト、パーライト以外の組織は観察されなかった。
板面に平行にX線回折用試験片を採取し、研削および化学研磨し、研磨後の試験片表面を鋼板の板厚方向1/4位置とした。その後、試験片を用いてX線回折法によりαの(200)、(211) 面、γの(200)、(220)、(311)面の回折強度を求め、γの体積分率を算出した。
得られた熱延鋼板の板幅中央位置から、圧延方向に直交する方向(C方向)が長手方向となるように、平板状の全厚引張試験片(板厚:全厚、平行部長さ:60mm、ゲージ間距離:50mm、ゲージ部幅:38mm)を採取し、ASTM E8M-04の規定に準拠して、室温で引張試験を実施し、引張強さTS、降伏強さYSを測定し、降伏比YR(=YS/TS)を求めた。また、得られた電縫鋼管のシーム位置を0度とした場合の90度位置と180度位置から、パイプをフラットニングした後、鋼管円周方向が長手方向となるように、上記と同形状の引張試験片を採取した。次いで、上記と同条件で引張試験を実施して降伏比を測定し、加工歪の異なる90度位置と180度位置の降伏比の差ΔYRを求めた。熱延鋼板の引張強さTSが650MPa以上、降伏強さYSが555MPa以上、降伏比YRが90%以下であり、電縫鋼管90度位置と180度位置の降伏比の差ΔYRが10%未満である場合を、「強度、加工後特性安定性および低降伏比特性に優れた引張特性」と評価した。
得られた熱延鋼板の板厚中央位置から、圧延方向に直交する方向(C方向)が長手方向となるようにVノッチ試験片(長さ55mm×高さ10mm×幅10mm)を採取し、JIS Z 2242の規定に準拠してシャルピー衝撃試験を実施し、延性-脆性破面遷移温度(℃)を求めた。なお、各熱延鋼板につき試験片を3本採取し、3本の試験片について得られた延性-脆性破面遷移温度の算術平均を各熱延鋼板の延性-脆性破面遷移温度(vTrs)とした。vTrsが-80℃以下である場合を「靭性が良好である」と評価した。
Claims (3)
- 質量%で、
C :0.030%以上0.120%以下、 Si:0.05%以上0.50%以下、
Mn:1.00%以上2.20%以下、 P :0.025%以下、
S :0.0050%以下、 N :0.0060%以下、
Al:0.005%以上0.100%以下、 Nb:0.020%以上0.100%以下、
Mo:0.05%以上0.50%以下、 Ti:0.001%以上0.100%以下、
Cr:0.05%以上0.50%以下、 Ca:0.0005%以上0.0050%以下
を含有し、残部がFeおよび不可避的不純物からなる組成を有し、ベイニティックフェライトを主相とし、第二相としてマルテンサイトおよび残留オーステナイトを含み、前記主相の体積分率が90%以上、前記主相の平均結晶粒径が10μm以下、前記マルテンサイトの体積分率が0.5%以上9.5%以下、前記残留オーステナイトの体積分率が0.5%以上9.5%以下である組織を有し、降伏比が90%以下、降伏強さが555MPa以上、引張強さが650MPa以上である熱延鋼板。 - 前記組成に加えて更に、質量%で、V:0.001%以上0.100%以下、Cu:0.001%以上0.50%以下、Ni:0.001%以上1.00%以下、B:0.0040%以下のうちから選ばれる1種以上を含有する請求項1に記載の熱延鋼板。
- 請求項1または2に記載の組成を有する連続鋳造鋳片を、600℃以下に冷却した後、1050℃以上1300℃以下の温度域に加熱し、粗圧延および該粗圧延に続き未再結晶温度域での圧下率を20%以上85%以下、仕上げ圧延終了温度を(Ar3-50℃)以上(Ar3+100℃)以下の温度域とする仕上げ圧延を施し、該仕上げ圧延終了後、板厚中央位置で冷却開始温度から650℃までの平均冷却速度を10℃/s以上100℃/s以下とし、冷却停止温度を420℃以上650℃以下とする冷却を施し、400℃以上650℃以下の温度域で巻取り、巻取り後のコイルを、重量が20ton以上であり且つ巾が1000mm以上であるコイルとする熱延鋼板の製造方法。
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201480064978.2A CN105793458B (zh) | 2013-11-28 | 2014-11-20 | 热轧钢板及其制造方法 |
EP14866276.0A EP3040439B1 (en) | 2013-11-28 | 2014-11-20 | Hot-rolled steel sheet and method for manufacturing the same |
US15/038,616 US10273554B2 (en) | 2013-11-28 | 2014-11-20 | Hot-rolled steel sheet and method of manufacturing the same |
KR1020167016866A KR101802269B1 (ko) | 2013-11-28 | 2014-11-20 | 열연강판 및 그 제조 방법 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2013-245616 | 2013-11-28 | ||
JP2013245616A JP5783229B2 (ja) | 2013-11-28 | 2013-11-28 | 熱延鋼板およびその製造方法 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2015079661A1 true WO2015079661A1 (ja) | 2015-06-04 |
Family
ID=53198630
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2014/005836 WO2015079661A1 (ja) | 2013-11-28 | 2014-11-20 | 熱延鋼板およびその製造方法 |
Country Status (7)
Country | Link |
---|---|
US (1) | US10273554B2 (ja) |
EP (1) | EP3040439B1 (ja) |
JP (1) | JP5783229B2 (ja) |
KR (1) | KR101802269B1 (ja) |
CN (1) | CN105793458B (ja) |
TW (1) | TWI558823B (ja) |
WO (1) | WO2015079661A1 (ja) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2017221690A1 (ja) * | 2016-06-22 | 2017-12-28 | Jfeスチール株式会社 | 厚肉高強度ラインパイプ用熱延鋼板、ならびに、厚肉高強度ラインパイプ用溶接鋼管およびその製造方法 |
CN108474090A (zh) * | 2015-12-24 | 2018-08-31 | 株式会社Posco | 低屈强比高强度钢材及其制造方法 |
JP6587041B1 (ja) * | 2019-02-19 | 2019-10-09 | 日本製鉄株式会社 | ラインパイプ用電縫鋼管 |
WO2022075027A1 (ja) * | 2020-10-05 | 2022-04-14 | Jfeスチール株式会社 | 電縫鋼管およびその製造方法 |
Families Citing this family (28)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6070642B2 (ja) * | 2014-06-20 | 2017-02-01 | Jfeスチール株式会社 | 高強度でかつ低温靭性に優れた熱延鋼板およびその製造方法 |
CN104264054B (zh) * | 2014-09-19 | 2017-02-22 | 宝山钢铁股份有限公司 | 一种550MPa级的耐高温管线钢及其制造方法 |
EP3296415B1 (en) | 2015-07-27 | 2019-09-04 | JFE Steel Corporation | High-strength hot-rolled steel sheet and method for manufacturing the same |
EP3381577B1 (en) | 2015-11-25 | 2020-01-08 | JFE Steel Corporation | Hot-rolled steel sheet and method for manufacturing same |
JP6519024B2 (ja) * | 2016-05-31 | 2019-05-29 | Jfeスチール株式会社 | 低温靭性に優れた低降伏比高強度熱延鋼板の製造方法 |
CN106435369B (zh) * | 2016-11-29 | 2018-08-07 | 武汉钢铁有限公司 | 一种含Cr的低温韧性优异的正火态耐蚀风电钢及生产方法 |
JP6565890B2 (ja) * | 2016-12-20 | 2019-08-28 | Jfeスチール株式会社 | 低温靭性に優れた低降伏比高強度熱延鋼板の製造方法 |
US11603571B2 (en) * | 2017-02-17 | 2023-03-14 | Jfe Steel Corporation | High-strength hot-rolled steel sheet and method for producing the same |
KR101998952B1 (ko) * | 2017-07-06 | 2019-07-11 | 주식회사 포스코 | 재질편차가 적고 표면품질이 우수한 초고강도 열연강판 및 그 제조방법 |
CN111094612B (zh) * | 2017-11-24 | 2021-09-03 | 日本制铁株式会社 | 热轧钢板及其制造方法 |
KR102020415B1 (ko) * | 2017-12-24 | 2019-09-10 | 주식회사 포스코 | 저항복비 특성이 우수한 고강도 강재 및 그 제조방법 |
JP6572963B2 (ja) | 2017-12-25 | 2019-09-11 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
EP3733879B1 (en) * | 2018-01-30 | 2021-11-17 | JFE Steel Corporation | Steel material for line pipes, production method for same, and production method for line pipe |
JP6635232B2 (ja) * | 2018-01-30 | 2020-01-22 | Jfeスチール株式会社 | ラインパイプ用鋼材およびその製造方法ならびにラインパイプの製造方法 |
CN110643894B (zh) * | 2018-06-27 | 2021-05-14 | 宝山钢铁股份有限公司 | 具有良好的疲劳及扩孔性能的超高强热轧钢板和钢带及其制造方法 |
EP3831971B1 (en) * | 2018-07-31 | 2023-03-15 | JFE Steel Corporation | High-strength hot-rolled plated steel sheet |
JP6693606B1 (ja) * | 2018-08-23 | 2020-05-13 | Jfeスチール株式会社 | 角形鋼管およびその製造方法並びに建築構造物 |
WO2020039979A1 (ja) * | 2018-08-23 | 2020-02-27 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
KR102175575B1 (ko) * | 2018-11-26 | 2020-11-09 | 주식회사 포스코 | 연신율이 우수한 고강도 열연강판 및 그 제조방법 |
DE102019122515A1 (de) * | 2019-08-21 | 2021-02-25 | Ilsenburger Grobblech Gmbh | Verfahren zur Herstellung von hochfesten Blechen oder Bändern aus einem niedrig legierten, hochfesten bainitischen Stahl sowie ein Stahlband oder Stahlblech hieraus |
CN111155035A (zh) * | 2020-02-17 | 2020-05-15 | 本钢板材股份有限公司 | 一种大角度晶界特厚规格x80管线钢及其制备方法 |
CN111304516B (zh) * | 2020-03-05 | 2021-05-28 | 中天钢铁集团有限公司 | 一种高强度高低温冲击韧性吊钩用非调质钢及生产工艺 |
US20230151468A1 (en) * | 2020-04-22 | 2023-05-18 | Thyssenkrupp Steel Europe Ag | Hot-Rolled Flat Steel Product and Method for the Production Thereof |
CN114107794B (zh) * | 2020-08-31 | 2023-08-11 | 宝山钢铁股份有限公司 | 一种980MPa级超低碳马氏体加残奥型超高扩孔钢及其制造方法 |
CN113549824A (zh) * | 2021-06-29 | 2021-10-26 | 武汉钢铁有限公司 | 一种热连轧极限厚度规格高强管线钢板卷及其制造方法 |
MX2024005780A (es) * | 2021-11-12 | 2024-05-27 | Nippon Steel Corp | Hoja de acero laminada en caliente, hoja de acero revestida por inmersion en caliente y metodo para producir hoja de acero laminada en caliente. |
JPWO2023214472A1 (ja) * | 2022-05-06 | 2023-11-09 | ||
KR20240098720A (ko) | 2022-12-21 | 2024-06-28 | 주식회사 포스코 | 강판 및 그 제조방법 |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63227715A (ja) | 1987-03-17 | 1988-09-22 | Kawasaki Steel Corp | 低温靭性に優れた低降伏比高張力ラインパイプ用熱延鋼板の製造方法 |
JP2006299413A (ja) | 2005-03-24 | 2006-11-02 | Jfe Steel Kk | 低温靭性に優れた低降伏比電縫鋼管の製造方法 |
JP2006299414A (ja) * | 2005-03-24 | 2006-11-02 | Jfe Steel Kk | 低温靭性に優れた低降伏比電縫鋼管の製造方法 |
JP2010196165A (ja) * | 2009-01-30 | 2010-09-09 | Jfe Steel Corp | 低温靭性に優れた極厚高張力熱延鋼板およびその製造方法 |
JP2012172256A (ja) | 2011-02-24 | 2012-09-10 | Jfe Steel Corp | 低温靭性に優れた低降伏比高強度熱延鋼板およびその製造方法 |
JP2012188731A (ja) * | 2011-02-24 | 2012-10-04 | Jfe Steel Corp | 低温靭性に優れた低降伏比高強度熱延鋼板およびその製造方法 |
JP2013204103A (ja) * | 2012-03-29 | 2013-10-07 | Jfe Steel Corp | 耐座屈性能に優れた低温用高強度溶接鋼管とその製造方法および耐座屈性能に優れた低温用高強度溶接鋼管用鋼板の製造方法 |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU2783795A (en) | 1994-07-08 | 1996-02-09 | Ipsco Inc. | Twin-roll caster and rolling mill for use therewith |
JP3589071B2 (ja) | 1998-03-24 | 2004-11-17 | 住友金属工業株式会社 | 溶接性、強度および靱性に優れた極厚形鋼の製造法 |
WO2002101112A2 (en) | 2001-06-06 | 2002-12-19 | Nippon Steel Corporation | High-strength hot-dip galvanized steel sheet and hot-dip galvannealed steel sheet having fatigue resistance, corrosion resistance, ductility and plating adhesion, after severe deformation, and a method of producing the same |
JP5151008B2 (ja) * | 2005-03-29 | 2013-02-27 | Jfeスチール株式会社 | 耐hic性および溶接部靱性優れる耐サワー高強度電縫鋼管用熱延鋼板およびその製造方法 |
JP4164537B2 (ja) | 2006-12-11 | 2008-10-15 | 株式会社神戸製鋼所 | 高強度薄鋼板 |
CA2844718C (en) | 2009-01-30 | 2017-06-27 | Jfe Steel Corporation | Thick high-tensile-strength hot-rolled steel sheet having excellent low-temperature toughness and manufacturing method thereof |
JP5919920B2 (ja) | 2011-03-28 | 2016-05-18 | Jfeスチール株式会社 | Si含有冷延鋼板の製造方法及び装置 |
JP5776377B2 (ja) | 2011-06-30 | 2015-09-09 | Jfeスチール株式会社 | 耐サワー性に優れたラインパイプ用溶接鋼管向け高強度熱延鋼板およびその製造方法 |
JP5834717B2 (ja) * | 2011-09-29 | 2015-12-24 | Jfeスチール株式会社 | 高降伏比を有する溶融亜鉛めっき鋼板およびその製造方法 |
JP5900303B2 (ja) | 2011-12-09 | 2016-04-06 | Jfeスチール株式会社 | 鋼板内の材質均一性に優れた耐サワーラインパイプ用高強度鋼板とその製造方法 |
JP2013155390A (ja) * | 2012-01-26 | 2013-08-15 | Jfe Steel Corp | 疲労特性に優れた高強度熱延鋼板およびその製造方法 |
-
2013
- 2013-11-28 JP JP2013245616A patent/JP5783229B2/ja active Active
-
2014
- 2014-11-20 EP EP14866276.0A patent/EP3040439B1/en active Active
- 2014-11-20 US US15/038,616 patent/US10273554B2/en active Active
- 2014-11-20 WO PCT/JP2014/005836 patent/WO2015079661A1/ja active Application Filing
- 2014-11-20 KR KR1020167016866A patent/KR101802269B1/ko active IP Right Grant
- 2014-11-20 CN CN201480064978.2A patent/CN105793458B/zh active Active
- 2014-11-27 TW TW103141182A patent/TWI558823B/zh active
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63227715A (ja) | 1987-03-17 | 1988-09-22 | Kawasaki Steel Corp | 低温靭性に優れた低降伏比高張力ラインパイプ用熱延鋼板の製造方法 |
JP2006299413A (ja) | 2005-03-24 | 2006-11-02 | Jfe Steel Kk | 低温靭性に優れた低降伏比電縫鋼管の製造方法 |
JP2006299414A (ja) * | 2005-03-24 | 2006-11-02 | Jfe Steel Kk | 低温靭性に優れた低降伏比電縫鋼管の製造方法 |
JP2010196165A (ja) * | 2009-01-30 | 2010-09-09 | Jfe Steel Corp | 低温靭性に優れた極厚高張力熱延鋼板およびその製造方法 |
JP2012172256A (ja) | 2011-02-24 | 2012-09-10 | Jfe Steel Corp | 低温靭性に優れた低降伏比高強度熱延鋼板およびその製造方法 |
JP2012188731A (ja) * | 2011-02-24 | 2012-10-04 | Jfe Steel Corp | 低温靭性に優れた低降伏比高強度熱延鋼板およびその製造方法 |
JP2013204103A (ja) * | 2012-03-29 | 2013-10-07 | Jfe Steel Corp | 耐座屈性能に優れた低温用高強度溶接鋼管とその製造方法および耐座屈性能に優れた低温用高強度溶接鋼管用鋼板の製造方法 |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN108474090A (zh) * | 2015-12-24 | 2018-08-31 | 株式会社Posco | 低屈强比高强度钢材及其制造方法 |
CN108474090B (zh) * | 2015-12-24 | 2021-02-12 | 株式会社Posco | 低屈强比高强度钢材及其制造方法 |
WO2017221690A1 (ja) * | 2016-06-22 | 2017-12-28 | Jfeスチール株式会社 | 厚肉高強度ラインパイプ用熱延鋼板、ならびに、厚肉高強度ラインパイプ用溶接鋼管およびその製造方法 |
JPWO2017221690A1 (ja) * | 2016-06-22 | 2018-07-05 | Jfeスチール株式会社 | 厚肉高強度ラインパイプ用熱延鋼板、ならびに、厚肉高強度ラインパイプ用溶接鋼管およびその製造方法 |
US11377719B2 (en) | 2016-06-22 | 2022-07-05 | Jfe Steel Corporation | Hot-rolled steel sheet for heavy-wall, high-strength line pipe, welded steel pipe for heavy-wall, high-strength line pipe, and method for producing the welded steel pipe |
JP6587041B1 (ja) * | 2019-02-19 | 2019-10-09 | 日本製鉄株式会社 | ラインパイプ用電縫鋼管 |
WO2020170333A1 (ja) * | 2019-02-19 | 2020-08-27 | 日本製鉄株式会社 | ラインパイプ用電縫鋼管 |
WO2022075027A1 (ja) * | 2020-10-05 | 2022-04-14 | Jfeスチール株式会社 | 電縫鋼管およびその製造方法 |
JP7081727B1 (ja) * | 2020-10-05 | 2022-06-07 | Jfeスチール株式会社 | 電縫鋼管およびその製造方法 |
Also Published As
Publication number | Publication date |
---|---|
JP5783229B2 (ja) | 2015-09-24 |
US10273554B2 (en) | 2019-04-30 |
JP2015101781A (ja) | 2015-06-04 |
TW201527848A (zh) | 2015-07-16 |
EP3040439A4 (en) | 2016-10-05 |
TWI558823B (zh) | 2016-11-21 |
KR20160090363A (ko) | 2016-07-29 |
KR101802269B1 (ko) | 2017-11-28 |
EP3040439A1 (en) | 2016-07-06 |
US20160289788A1 (en) | 2016-10-06 |
EP3040439B1 (en) | 2018-01-03 |
CN105793458B (zh) | 2017-11-24 |
CN105793458A (zh) | 2016-07-20 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5783229B2 (ja) | 熱延鋼板およびその製造方法 | |
EP3042976B1 (en) | Steel sheet for thick-walled high-strength line pipe having exceptional corrosion resistance, crush resistance properties, and low-temperature ductility, and line pipe | |
RU2518830C1 (ru) | Горячекатаный стальной лист и способ его изготовления | |
JP5561119B2 (ja) | 高圧縮強度耐サワーラインパイプ用溶接鋼管及びその製造方法 | |
US9089919B2 (en) | Welded steel pipe for linepipe with high compressive strength and manufacturing method thereof | |
JP5776398B2 (ja) | 低温靭性に優れた低降伏比高強度熱延鋼板およびその製造方法 | |
EP2264205B1 (en) | High-strength steel plate excellent in low-temperature toughness, steel pipe, and processes for production of both | |
JP6354910B2 (ja) | 厚肉高強度ラインパイプ用熱延鋼板、ならびに、厚肉高強度ラインパイプ用溶接鋼管およびその製造方法 | |
JP5834534B2 (ja) | 高一様伸び特性を備えた高強度低降伏比鋼、その製造方法、および高強度低降伏比溶接鋼管 | |
JP2015190026A (ja) | ラインパイプ用厚肉高強度電縫鋼管およびその製造方法 | |
JP2010084171A (ja) | 圧潰強度に優れた高靱性溶接鋼管およびその製造方法 | |
JP2013049895A (ja) | 高一様伸び特性を備え、かつ溶接部低温靱性に優れた高強度溶接鋼管、およびその製造方法 | |
JP5803270B2 (ja) | 耐圧潰性に優れた高強度耐サワーラインパイプ及びその製造方法 | |
JP6519024B2 (ja) | 低温靭性に優れた低降伏比高強度熱延鋼板の製造方法 | |
JP2015189984A (ja) | 低降伏比高強度高靭性鋼板、低降伏比高強度高靭性鋼板の製造方法および鋼管 | |
JP5640792B2 (ja) | 圧潰強度に優れた高靱性uoe鋼管及びその製造方法 | |
EP3960891B1 (en) | Electric resistance welded steel pipe for linepipe | |
JP2015224374A (ja) | 鋼管杭向け低降伏比高強度電縫鋼管およびその製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 14866276 Country of ref document: EP Kind code of ref document: A1 |
|
REEP | Request for entry into the european phase |
Ref document number: 2014866276 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2014866276 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 15038616 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
ENP | Entry into the national phase |
Ref document number: 20167016866 Country of ref document: KR Kind code of ref document: A |