WO2010114131A1 - 冷延鋼板およびその製造方法 - Google Patents
冷延鋼板およびその製造方法 Download PDFInfo
- Publication number
- WO2010114131A1 WO2010114131A1 PCT/JP2010/056096 JP2010056096W WO2010114131A1 WO 2010114131 A1 WO2010114131 A1 WO 2010114131A1 JP 2010056096 W JP2010056096 W JP 2010056096W WO 2010114131 A1 WO2010114131 A1 WO 2010114131A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- temperature
- less
- ferrite
- annealing
- cold
- Prior art date
Links
Images
Classifications
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0405—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing 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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
- C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/11—Making amorphous 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
- 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
- C21D2211/003—Cementite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Definitions
- the present invention relates to a high-strength cold-rolled steel sheet excellent in workability used for automobile parts and the like and a method for producing the same, and more specifically, a high-strength steel sheet having an improved balance between elongation (total elongation) and stretch flangeability and its It relates to a manufacturing method.
- steel sheets used for automobile frame parts and the like are required to have high strength for the purpose of collision safety and fuel efficiency reduction by reducing the weight of the car body, and excellent forming process for processing into complex frame parts Sex is also required.
- the tensile strength TS is 780 MPa or more, TS ⁇ El is 14000 MPa ⁇ % or more, and TS ⁇ El ⁇ ⁇ is 800,000 MPa ⁇ % ⁇ % or more (more preferably, the tensile strength TS is 780 MPa or more, TS ⁇ El is 15000 MPa ⁇ % or more, TS ⁇ El ⁇ ⁇ is 1000000 MPa ⁇ % ⁇ % or more, more preferably, the tensile strength TS is 780 MPa or more, TS ⁇ El is 16000 MPa ⁇ % or more, and TS ⁇ El X ⁇ is required to be 1200,000 MPa ⁇ % ⁇ % or more).
- Patent Document 1 discloses a high-tensile cold-rolled steel sheet containing 1.6 to 2.5% by mass in total of at least one of Mn, Cr, and Mo and substantially comprising a martensite single-phase structure.
- the hole expansion ratio (stretch flangeability) ⁇ is 100% or more, but the elongation El does not reach 10%, and the above-mentioned required level is satisfied.
- Patent Document 2 discloses a high-tensile steel sheet having a two-phase structure of ferrite with an area ratio of 65 to 85% and the balance tempered martensite.
- Patent Document 3 discloses a high-tensile steel plate having a two-phase structure in which the average crystal grain sizes of ferrite and martensite are both 2 ⁇ m or less and the volume ratio of martensite is 20% or more and less than 60%. .
- the inventions related to these high-tensile steel sheets are characterized by controlling the area ratio of the ferrite and the hard phase, and further controlling the particle size of both phases, but the strain amount in the ferrite, the deformability of the hard phase,
- the technical idea is clearly different from the present invention which is characterized by controlling the distribution state of cementite particles present at the interface between the ferrite and the hard phase.
- an object of the present invention is to provide a high-strength cold-rolled steel sheet with improved formability and a method for producing the same, which improves the balance between elongation and stretch flangeability.
- the invention described in claim 1 % By mass (hereinafter the same for chemical components) C: 0.05 to 0.30%, Si: 3.0% or less (including 0%), Mn: 0.1 to 5.0%, P: 0.1% or less (including 0%), S: 0.010% or less (including 0%), Al: 0.001 to 0.10%, with the balance being composed of iron and inevitable impurities, It contains 10-80% area ratio ferrite, which is a soft phase, Including a retained austenite, martensite, and a mixed structure of retained austenite and martensite in a total area ratio of less than 5% (including 0%), Having the structure of tempered martensite and / or tempered bainite, the balance being the hard phase, In the frequency distribution curve of the Kernel Average Misoration value (hereinafter abbreviated as “KAM value”), The relationship between the ratio X KAM ⁇ 0.4 ° (unit:%) of the frequency at which the KAM value is 0.4 ° or less to the total frequency and the
- Invention of Claim 2 is about the said cold-rolled steel plate, Ingredient composition further Nb: 0.02 to 0.40%, Ti: 0.01-0.20%, V: One or more of 0.01 to 0.20%, [% Nb] / 96 + [% Ti] / 51 + [% V] / 48) ⁇ 48 is 0.01 to 0.20 % To satisfy, The average particle diameter of the ferrite is 5 ⁇ m or less in terms of equivalent circle diameter, A precipitate having an equivalent circle diameter of 20 nm or more existing at the interface between the ferrite and the hard phase, and the distribution state of the precipitate containing one or more of Nb, Ti and V is 5 or less per 1 ⁇ m 2 of the hard phase. It is what.
- the invention described in claim 3 relates to the cold-rolled steel sheet.
- the component composition further contains Cr: 0.01 to 1.0%.
- the component composition further includes one or more of Mo: 0.02 to 1.0%, Cu: 0.05 to 1.0%, and Ni: 0.05 to 1.0%.
- the invention described in claim 5 relates to the cold-rolled steel sheet.
- the component composition further includes Ca: 0.0005 to 0.01% and / or Mg: 0.0005 to 0.01%.
- a steel material having the composition shown in claim 1 is hot-rolled under the following conditions (1) to (4), then cold-rolled, then annealed, and further tempered. It is a manufacturing method of a cold-rolled steel sheet.
- Annealing conditions The temperature range of 600 to Ac1 ° C. is raised in a temperature rising pattern that satisfies both the following formulas I and II, and the annealing heating temperature: [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] to 1000 ° C.
- first cooling rate a cooling rate of 1 ° C./s or more and less than 50 ° C./s until a temperature equal to or higher than 0 ° C.
- second cooling end temperature a temperature below the Ms point
- second cooling rate a cooling rate of 50 ° C./s or less
- tempering holding time 30 seconds or less
- a steel material having the component composition shown in claim 2 is hot-rolled under the following conditions (1) to (4), cold-rolled, then annealed, and further tempered. It is a manufacturing method of a cold-rolled steel plate.
- Annealing conditions The temperature range of 600 to Ac1 ° C.
- annealing heating temperature [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] to Annealing holding time at 1000 ° C .: Hold at 3600 s or less, then quench rapidly from the annealing heating temperature to a temperature below the Ms point at a cooling rate of 50 ° C./s or less, or from the annealing heating temperature to less than the annealing heating temperature At a cooling rate of 1 ° C./s or more and less than 50 ° C./s (referred to as “first cooling rate”) until a temperature of 600 ° C.
- first cooling end temperature first cooling end temperature
- second cooling rate second cooling rate
- the amount of strain in the ferrite is controlled and the deformability is high.
- ferrite which is a soft phase
- tempered martensite and / or tempered bainite which is a hard phase
- the amount of strain in the ferrite is controlled and the deformability is high.
- the present inventors mainly have a high-phase structure having a multiphase structure composed of ferrite that is a soft phase and tempered martensite and / or tempered bainite (hereinafter sometimes referred to as “tempered martensite”) that is a hard phase.
- tempered martensite a multiphase structure composed of ferrite that is a soft phase and tempered martensite and / or tempered bainite (hereinafter sometimes referred to as “tempered martensite”) that is a hard phase.
- the steel sheet of the present invention is based on a multiphase structure similar to those of Patent Documents 2 and 3, and in particular controls the strain amount in ferrite and the deformability of the hard phase. Furthermore, the steel sheet of Patent Documents 2 and 3 is different in that the distribution state of cementite particles precipitated at the interface between the ferrite and the hard phase is controlled.
- ⁇ Ferrite as a soft phase 10 to 80% in area ratio>
- a multiphase steel such as ferrite-tempered martensite
- deformation is mainly handled by ferrite with high deformability.
- the elongation of a multiphase steel such as ferrite-tempered martensite is mainly determined by the area ratio of ferrite.
- the area ratio of ferrite In order to ensure the target elongation, the area ratio of ferrite needs to be 10% or more (preferably 15% or more, more preferably 25% or more). However, since the strength cannot be secured if the ferrite is excessive, the area ratio of the ferrite is 80% or less (preferably 70% or less, more preferably 60% or less).
- the balance between strength and elongation depends not only on the area ratio of ferrite but also on the presence form of ferrite. That is, in a state where the ferrite particles are connected to each other, stress concentrates on the ferrite side having high deformability and only the ferrite bears deformation, so that it is difficult to obtain an appropriate balance between strength and elongation.
- the ferrite particles are surrounded by tempered martensite particles and / or bainite particles, which are hard phases, the hard phases are forcibly deformed. The balance between strength and elongation is improved.
- the existence form of ferrite can be evaluated by, for example, the number of points where a line segment having a total length of 1000 ⁇ m intersects a ferrite grain boundary (interface between ferrite particles) or a ferrite-hard phase interface in a region having an area of 40000 ⁇ m 2 or more. it can.
- the preferable condition of the existence form of ferrite for effectively exerting the above action is (“number of intersections with ferrite grain boundaries”) / (number of intersections with ferrite grain boundaries) + “ferrite-hard phase interface”
- the number of intersections " is 0.5 or less.
- Martensite simply means martensite that has not been tempered
- stress concentrates around it, Since breakage is likely to occur, deterioration of stretch flangeability can be prevented by reducing residual austenite, martensite, and their mixed structure as much as possible.
- the retained austenite, martensite and mixed structure thereof are less than 5% (preferably 0%) in the total area ratio, and the balance is a tempering which is a hard phase.
- the structure is composed of martensite and / or tempered bainite.
- the decrease in elongation due to the presence of strain in the ferrite improves the elongation by increasing the ferrite area ratio and decreases the degree of tempering of the hard phase.
- the balance between strength and elongation can be secured.
- the KAM value is an average value of the amount of crystal rotation (crystal orientation difference) between the target measurement point and the surrounding measurement points, and when this value is large, it indicates that strain exists in the crystal.
- FIG. 1 illustrates a KAM value frequency distribution curve obtained by scanning a certain region with a scanning electron microscope for the steel of the present invention.
- the KAM value frequency distribution curve shows two peaks.
- the first peak with a KAM value near 0.2 ° is due to strain in the ferrite
- the second peak with a KAM value near 0.6 ° is due to strain in the hard phase.
- each peak moves to the high KAM value side.
- the area ratio of ferrite increases, the first peak height increases.
- X KAM ⁇ 0.4 ° is the ratio of the frequency with a KAM value of 0.4 ° or less to the total frequency
- V ⁇ is the area ratio of ferrite
- X KAM 0.6 to 0 .8 ° is the ratio of the frequency with a KAM value of 0.6 to 0.8 ° to the total frequency.
- X KAM ⁇ 0.4 ° that is, the ratio of the frequency with a KAM value of 0.4 ° or less to the total frequency is considered to be a function of the amount of strain in the ferrite and the area ratio of the ferrite. by dividing by the area ratio V alpha, it is obtained as an index representing the amount of strain in ferrite. As the amount of strain in the ferrite increases, the first peak position moves to the high KAM value side, and X KAM ⁇ 0.4 ° / V ⁇ decreases.
- X KAM ⁇ 0.4 ° / V ⁇ is set to 0.8 or more (preferably 0.9 or more, more preferably 1.1 or more). In other words, if X KAM ⁇ 0.4 ° is 30% or more, it means that 20% or more of ferrite with a small strain exists.
- X KAM 0.6 to 0.8 ° , that is, the ratio of the frequency with the KAM value of 0.6 to 0.8 with respect to the total frequency indicates the amount of the hard phase having high deformability. If the ratio is 10% or more, the amount of the hard phase and the deformability are sufficient to ensure a balance between strength, elongation and stretch flangeability. On the other hand, if the ratio exceeds 20%, the amount of the hard phase becomes too large, so that elongation cannot be secured.
- a preferable range of X KAM 0.6 to 0.8 ° is 12 to 18%, and a more preferable range is 13 to 16%.
- coarse cementite particles having an equivalent circle diameter of 0.1 ⁇ m or more are limited to 3 or less, preferably 2.5 or less, more preferably 2 or less per 1 ⁇ m 2 of the hard phase. .
- each test steel sheet was mirror-polished, corroded with a 3% nital solution to reveal the metal structure, and then a scanning type with a magnification of 2000 times for approximately 5 fields of 40 ⁇ m ⁇ 30 ⁇ m area.
- An electron microscope (SEM) image was observed and the area of the ferrite was determined by measuring 100 points per field of view by a point calculation method.
- region containing cementite was made into the hard phase by image analysis, and the remaining area
- the area ratio of each phase was computed from the area ratio of each area
- N ⁇ / (N ⁇ + N ⁇ -TM ) means that there are few regions where ferrite particles and ferrite particles are continuous, that is, ferrite particles are not continuous and are surrounded by a hard phase. It is shown that.
- Component composition of the steel sheet of the present invention C: 0.05 to 0.30% C is an important element that affects the area ratio of the hard phase and the amount of cementite precipitated in the hard phase and affects the strength, elongation, and stretch flangeability. If it is less than 0.05%, the strength cannot be secured. On the other hand, if it exceeds 0.30%, in addition to the large amount of distortion during quenching, the amount of cementite increases and the dislocation is difficult to recover, indicating that the dislocation is lost and the hard phase has improved deformability.
- the evaluation formula X KAM 0.6 to 0.8 ° ⁇ 10% cannot be obtained. If the tempering conditions are increased to a high temperature or a long time so as to satisfy this evaluation formula, the cementite becomes coarse, and the strength and stretch flangeability cannot be secured.
- the range of C content is preferably 0.10 to 0.25%, more preferably 0.14 to 0.20%.
- Si 3.0% or less (including 0%) Si has an effect of suppressing the coarsening of cementite particles during tempering, and is a useful element that contributes to both elongation and stretch flangeability. If it exceeds 3.0%, the formation of austenite at the time of heating is inhibited, so that the area ratio of the hard phase cannot be ensured and stretch flangeability cannot be ensured.
- the range of Si content is preferably 0.50 to 2.5%, more preferably 1.0 to 2.2%.
- Mn 0.1 to 5.0% Mn contributes to both elongation and stretch flangeability by increasing the deformability of the hard phase, in addition to having the effect of suppressing the coarsening of cementite during tempering, similar to Si. In addition, by increasing the hardenability, there is an effect of expanding the range of production conditions for obtaining a hard phase. If the content is less than 0.1%, the above effects cannot be sufficiently exhibited, so that it is impossible to achieve both elongation and stretch flangeability. On the other hand, if it exceeds 5.0%, the reverse transformation temperature becomes too low and recrystallization becomes impossible. And the balance of growth cannot be secured.
- the range of Mn content is preferably 0.50 to 2.5%, more preferably 1.2 to 2.2%.
- P 0.1% or less P is inevitably present as an impurity element and contributes to an increase in strength by solid solution strengthening, but segregates at the prior austenite grain boundaries and embrittles the grain boundaries to increase stretch flangeability. Since it deteriorates, it is made 0.1% or less. Preferably it is 0.05% or less, More preferably, it is 0.03% or less.
- S 0.010% or less S is also unavoidably present as an impurity element, forms MnS inclusions, and becomes a starting point of cracks when expanding holes, thereby reducing stretch flangeability. .
- S is 0.005% or less, More preferably, it is 0.003% or less.
- N 0.01% or less N is also unavoidably present as an impurity element and lowers the elongation and stretch flangeability by strain aging, so the lower one is preferable, and the content is made 0.01% or less.
- Al 0.001 to 0.10%
- Al is added as a deoxidizing element and has the effect of making inclusions finer. Moreover, it combines with N to form AlN and reduces the solid solution N that contributes to the occurrence of strain aging, thereby preventing elongation and stretch flangeability from being deteriorated. If it is less than 0.001%, solute N remains in the steel, so strain aging occurs, and elongation and stretch flangeability cannot be secured. On the other hand, if it exceeds 0.1%, the formation of austenite during heating is inhibited. The area ratio of the hard phase cannot be secured, and the stretch flangeability cannot be secured.
- the steel of the present invention basically contains the above components, with the balance being substantially iron and impurities.
- the tensile strength TS is 780 MPa by containing at least one of Nb, Ti, and V within the following ranges and performing the following structure control.
- TS ⁇ El is 16000 MPa ⁇ % or more
- TS ⁇ El ⁇ ⁇ is 1200,000 MPa ⁇ % ⁇ % or more.
- Nb 0.02 to 0.40%
- Ti 0.01 to 0.20%
- V 0.01 to 0.20%
- ⁇ 48 0.01 to 0.20%> Nb
- Ti and V form fine MX type compounds (generic name for carbide, nitride and carbonitride), and the fine MX type compounds are particles that pin the growth of austenite during heating during annealing. By acting, it contributes to the refinement of ferrite grains, and the stretch flangeability is enhanced by refining the structure after hot rolling.
- ⁇ Average diameter of ferrite 5 ⁇ m or less in equivalent circle diameter>
- the average particle diameter of ferrite is 5 ⁇ m or less, preferably 4 ⁇ m or less, more preferably 3.5 ⁇ m or less in terms of equivalent circle diameter.
- the average particle diameter of a ferrite is so preferable that it is small, it is very difficult to obtain a fine structure with an equivalent circle diameter of less than 0.2 ⁇ m, and the practical lower limit is 0.2 ⁇ m with an equivalent circle diameter.
- ⁇ Distribution state of precipitates present in the hard phase in contact with the ferrite interface is a precipitate having an equivalent circle diameter of 20 nm or more, and includes one or more of Nb, Ti and V: 1 ⁇ m of the hard phase 5 or less per 2 >
- Precipitates containing Nb, Ti, and V such as NbC, TiC, and VC have very high rigidity and critical shear stress compared to the parent phase, so the precipitate itself is not easily deformed even if the periphery of the precipitate is deformed. Therefore, when the size is 20 nm or more, a large strain is generated at the interface between the parent phase and the precipitate, and the breakage occurs.
- stretch flangeability can be improved by restricting the existence density of coarse Nb, Ti, and V-containing precipitates.
- the number of equivalent precipitates having a circle equivalent diameter of 20 nm or more and including one or more of Nb, Ti and V is 5 or less per 1 ⁇ m 2 of the hard phase, preferably It is limited to 3 or less, more preferably 2 or less.
- Cr 0.01 to 1.0% Cr is a useful element that can improve stretch flangeability by suppressing the growth of cementite. If the addition is less than 0.01%, the above-described effects cannot be exhibited effectively. On the other hand, if the addition exceeds 1.0%, coarse Cr 7 C 3 is formed, and the stretch flangeability deteriorates. Resulting in.
- [Preferred production method of the steel sheet of the present invention (part 1)]
- steel having the above composition is melted and formed into a slab by ingot forming or continuous casting, and then hot-rolled.
- the finish rolling finish temperature is set to Ar 3 or higher, and after cooling appropriately, winding is performed in the range of 450 to 700 ° C.
- pickling is performed and then cold rolling is performed.
- the cold rolling rate (hereinafter also referred to as “cold rolling rate”) is preferably about 30% or more.
- annealing conditions As annealing conditions, the temperature range of 600 to Ac1 ° C. was raised with a stay time of (Ac1-600) s or more, and the annealing temperature was [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] to 1000 ° C. Holding time: After holding for 3600 s or less, quench immediately from the annealing heating temperature to a temperature below the Ms point at a cooling rate of 50 ° C./s or from the annealing heating temperature to a temperature of 600 ° C. or more below the annealing heating temperature.
- first cooling rate a cooling rate of 1 ° C./s or more and less than 50 ° C./s to (first cooling end temperature)
- second cooling end temperature a temperature below the Ms point
- the annealing heating temperature is less than [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] ° C., the amount of transformation to austenite is insufficient during annealing heating, so that the amount of hard phase that transforms from austenite during subsequent cooling cannot be secured. On the other hand, heating exceeding 1000 ° C. is industrially difficult with existing annealing equipment.
- a preferable upper limit of the annealing heating temperature is [(1 ⁇ Ac1 + 9 ⁇ Ac3) / 10] ° C.
- a preferred lower limit of the annealing and heating holding time is 60 s. By increasing the heating time, strain in the ferrite can be further removed.
- the annealing heating temperature is Ac3 to 1000 ° C
- the annealing heating temperature is 1 to 50 ° C / s, cooled to 550 ° C or more and 650 ° C or less, and then over 50 ° C / s to the Ms point or less. Rapid cooling is preferred. If the temperature is 550 ° C. or lower, bainite may be formed and the characteristics may be deteriorated. If the temperature is 650 ° C. or higher, the ferrite fraction may be too small to secure the characteristics.
- tempering conditions As the tempering conditions, the temperature after the annealing cooling to the tempering heating temperature: from 420 ° C. to less than 670 ° C. is heated at a heating rate exceeding 5 ° C./s, and [tempering heating temperature ⁇ 10 ° C.] to tempering heating temperature.
- the heating rate or cooling rate is 5 ° C./s or less, cementite nucleation / growth occurs during heating or cooling, and coarse cementite is formed, so that stretch flangeability cannot be secured.
- the tempering heating temperature is less than 420 ° C.
- the strain in the ferrite or hard phase is large, and it becomes impossible to secure the stretch and stretch flangeability.
- the tempering heating temperature is 670 ° C. or higher or the tempering holding time exceeds 30 s, the strength of the hard phase is insufficient, and the strength of the steel sheet cannot be secured, or cementite becomes coarse and stretch flangeability deteriorates.
- the preferred range of the tempering heating temperature is 450 ° C. or more and less than 650 ° C., the more preferred range is 500 ° C. or more and less than 600 ° C., the preferred range of the tempering holding time is 10 s or less, and the more preferred range is 5 s or less.
- the [annealing condition] stipulates that “the temperature range of 600 to Ac1 ° C. is raised with a stay time of (Ac1-600) s or more” It is more preferable to raise the temperature in the temperature range of 600 to Ac1 ° C. with a temperature rising pattern that satisfies both the following formulas I and II.
- the other production conditions are the same as those described above [Preferred production method of the steel sheet of the present invention (part 1)].
- the cold rolling rate in the cold rolling was “preferably about 30% or more” in the above-mentioned [Preferred production method of the steel sheet of the present invention (part 1)].
- the present inventors promote the recovery and recrystallization of ferrite by annealing for a long time before reverse transformation during annealing in the above-mentioned [Preferred production method of steel sheet of the present invention (part 1)].
- the temperature range of 600 to Ac1 ° C. was raised with a stay time of (Ac1-600) s or more”.
- cementite precipitated during cooling after melting of the steel material or cooling after hot rolling may remain in the structure of the steel sheet before annealing.
- cementite remaining in the steel sheet structure becomes coarse when the temperature rises during annealing, and this coarsened cementite is brought in until after the tempering process, which may deteriorate the stretch flangeability of the steel sheet after the heat treatment. I understood it.
- the recrystallization rate X is used as an index that quantitatively represents the degree of ferrite recovery and recrystallization
- cementite is used as an index that quantitatively represents the degree of cementite coarsening.
- the particle radius r was adopted, and first, the effects of the treatment temperature and treatment time on these indices were investigated.
- the recrystallization rate X is expressed by the following formula 1 as a result of examining the effects of the recrystallization temperature and time using a material in which the initial dislocation density ⁇ 0 is changed by changing the cold rolling rate. I found out that I can do it.
- Formula 1: X 1 ⁇ exp [ ⁇ exp ⁇ A 1 ln (D Fe ) + A 2 ln ( ⁇ 0 ) ⁇ A 3 ⁇ ⁇ t n ] (Here, A 1 , A 2 , A 3 , n: constant)
- the correlation between the initial dislocation density ⁇ 0 and the cold rolling rate [CR] was investigated using steel sheets cold-rolled at 20 to 80% on various steel materials. As a result, it was found that it can be expressed by the following formula 3.
- B 1 1.54 ⁇ 10 15
- the recrystallization rate was calculated using the definition formula of ( ⁇ 180Hv).
- 180Hv in the above definition formula is the lowest hardness that does not soften any more when heat treatment is performed by sequentially extending the holding time in the state where the holding temperature is the highest, and it is sufficiently annealed and re-applied. This corresponds to the hardness of the state where crystallization is completed and completely softened.
- Formula 1 and Formula 4 are formulas when T is constant, these formulas are changed to a temperature T (t) as a function of time t so that they can be applied to the temperature raising process, Equations I and II were derived by transforming them to integrate in the residence time between 600 and Ac1 ° C.
- the relationship between the recrystallization ratio X and cementite particle radius r calculated using the formulas I and II and the mechanical properties of the steel sheet after heat treatment (annealing + tempering) was investigated. From the results of the investigation, as a more preferable annealing condition, the value of TS ⁇ E1 ⁇ ⁇ of the steel plate after heat treatment is more than 1500,000 MPa ⁇ % ⁇ %, which is higher than the desired level described in the above [Background Art] section. As a result of obtaining the combination of r, X ⁇ 0.8 and r ⁇ 0.19 were obtained.
- the hot rolling was finished at a finish rolling finish temperature: 900 ° C. or higher, and then the cooling time to 550 ° C. was cooled at [(finish finish finish temperature ⁇ 550 ° C.) / 20] s or less. Then, it winds at winding temperature: 500 degrees C or less.
- the MX type compound After preventing the precipitation of MX type compound during hot rolling, the MX type compound is finely precipitated in the heating process during the subsequent annealing, so that the structure can be refined without becoming the starting point of fracture. Can improve the stretch flangeability.
- ⁇ Finish rolling finish temperature 900 ° C. or higher>
- finish rolling finish temperature is less than 900 ° C.
- the MX type compound is precipitated during hot rolling, and the precipitate grows and becomes coarse in the heating process during the subsequent annealing, and the stretch flangeability deteriorates.
- ⁇ Winding temperature 500 ° C. or less>
- the winding temperature exceeds 500 ° C., precipitates are formed or coarsened during winding, and stretch flangeability deteriorates.
- cold rolling rate (hereinafter also referred to as “cold rolling rate”) is preferably about 30% or more. Then, after the cold rolling, annealing and further tempering are performed.
- annealing conditions As annealing conditions, the temperature range of 600 to Ac1 ° C. was raised with a stay time of (Ac1-600) s or more, and the annealing temperature was [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] to 1000 ° C. Holding time: After holding for 3600 s or less, quench immediately from the annealing heating temperature to a temperature below the Ms point at a cooling rate of 50 ° C./s or from the annealing heating temperature to a temperature of 600 ° C. or more below the annealing heating temperature.
- first cooling rate a cooling rate of 1 ° C./s or more and less than 50 ° C./s to (first cooling end temperature)
- second cooling end temperature a temperature below the Ms point
- the annealing heating temperature is less than [(8 ⁇ Ac1 + 2 ⁇ Ac3) / 10] ° C., the amount of transformation to austenite is insufficient during annealing and heating, and the amount of hard phase that transforms from austenite during subsequent cooling cannot be secured. On the other hand, heating exceeding 1000 ° C. is industrially difficult with existing annealing equipment.
- a preferable upper limit of the annealing heating temperature is [(1 ⁇ Ac1 + 9 ⁇ Ac3) / 10] ° C.
- a preferred lower limit of the annealing and heating holding time is 60 s. By increasing the heating time, strain in the ferrite can be further removed.
- the annealing heating temperature is Ac3 to 1000 ° C
- the annealing heating temperature is 1 to 50 ° C / s, cooled to 550 ° C or more and 650 ° C or less, and then over 50 ° C / s to the Ms point or less. Rapid cooling is preferred. If the temperature is 550 ° C. or lower, bainite may be formed and the characteristics may be deteriorated. If the temperature is 650 ° C. or higher, the ferrite fraction may be too small to secure the characteristics.
- tempering conditions As the tempering conditions, the temperature after the annealing cooling to the tempering heating temperature: from 420 ° C. to less than 670 ° C. is heated at a heating rate exceeding 5 ° C./s, and [tempering heating temperature ⁇ 10 ° C.] to tempering heating temperature. Time (tempering holding time) existing in the temperature region between: After 20 s or less, it may be cooled at a cooling rate of more than 5 ° C./s.
- the heating rate or cooling rate is 5 ° C./s or less, cementite nucleation / growth occurs during heating or cooling, and coarse cementite is formed, so that stretch flangeability cannot be secured.
- the tempering heating temperature is less than 420 ° C.
- the strain in the ferrite or hard phase is large, and it becomes impossible to secure the stretch and stretch flangeability.
- the tempering heating temperature is 670 ° C. or higher or the tempering holding time exceeds 20 s, the strength of the hard phase becomes insufficient, and the strength of the steel plate cannot be secured.
- the preferred range of the tempering heating temperature is 450 ° C. or more and less than 650 ° C., the more preferred range is 500 ° C. or more and less than 600 ° C., the preferred range of the tempering holding time is 10 s or less, and the more preferred range is 5 s or less.
- the [annealing conditions] stipulates that “the temperature range of 600 to Ac1 ° C. is raised with a stay time of (Ac1-600) s” It is more preferable to raise the temperature in the temperature range of 600 to Ac1 ° C. with a temperature raising pattern that satisfies both the following formulas I ′ and II ′.
- the other production conditions are the same as those described above [Preferred production method of the steel sheet of the present invention (part 3)].
- the cold rolling rate in the cold rolling was set to “30% or more” in the above [Preferred production method of the steel sheet of the present invention (part 3)], but in this example, the initial dislocation density described later is used. This is the range in which the expression 7 representing the relationship is established, and is in the range of 20 to 80%).
- more preferable annealing conditions are not only to promote recovery / recrystallization of ferrite but also to the structure of the steel sheet before annealing. It is necessary to adopt a temperature rising pattern that promotes recovery and recrystallization of ferrite while preventing coarsening of the cementite remaining therein.
- C 0.17%, Si: 1.35%, Mn: 2.0%, Nb: 0%, Ti: 0.04%, V: 0%
- the actual cold-rolled steel sheet (sheet thickness: 1.6 mm) that has been cold-rolled at a cold rolling rate of 36% (before annealing and tempering) and the actual cold-rolled steel sheet with a cold rolling rate of 36% are further cooled.
- Two types of cold-rolled steel sheets that were cold-rolled to a cold rolling rate of 60% were used as test materials.
- the recrystallization rate was calculated using the definition formula of ( ⁇ 180Hv).
- 180Hv in the above definition formula is the lowest hardness that does not soften any more when the heat treatment is performed by sequentially extending the holding time in the state where the holding temperature is the highest, and it is sufficiently annealed and re-applied. This corresponds to the hardness of the state where crystallization is completed and completely softened.
- Equations I ′ and II ′ were derived by transforming into an integral form with a residence time between 600 and Ac1 ° C.
- the relationship between the recrystallization ratio X and the cementite particle radius r calculated using the formulas I ′ and II ′ and the mechanical properties of the steel sheet after the heat treatment (annealing + tempering) was investigated. From the results of the investigation, as a more preferable annealing condition, the value of TS ⁇ E1 ⁇ ⁇ of the steel plate after heat treatment is 1800000 MPa ⁇ % ⁇ % or more, which exceeds the desired level described in the above [Background Art] section. As a result of obtaining the combination of r, X ⁇ 0.8 and r ⁇ 0.19 were obtained.
- Example 1 Steels having the components shown in Table 1 below were melted to produce 120 mm thick ingots. This was hot rolled to a thickness of 25 mm, and then hot rolled again to a thickness of 3.2 mm. After pickling this, it cold-rolled to 1.6 mm in thickness to make a test material, and heat-treated on the conditions shown in Table 2 and Table 3.
- Steel No. 1 to 32 and 35 were heated from 600 ° C. to T1 (° C.) (however, 600 ° C. ⁇ T1 ⁇ Ac1) as a temperature rising pattern from 600 ° C. to Ac1 during annealing at a predetermined temperature rising rate. Thereafter, it is held for a certain time at T1, and thereafter, T1 to Ac1 are heated at a predetermined temperature increase rate.
- tensile strength TS, elongation El, and stretch flangeability were measured.
- the tensile strength TS and elongation El were measured in accordance with JIS Z 2241 by preparing No. 5 test piece described in JIS Z2201 with the long axis perpendicular to the rolling direction.
- stretch flangeability performed the hole expansion test according to the iron continuous standard JFST1001, and measured the hole expansion rate, and made this the stretch flangeability.
- steel no. 1, 2, 7, 11, 14, 16-21, 24, 25, 27-36 all have a tensile strength TS of 780 MPa or more, TS ⁇ El of 14000 MPa ⁇ % or more, and TS ⁇ El ⁇ ⁇ .
- TS tensile strength
- steel No. in particular. Nos. 32, 33, 35 and 36 satisfy both X ⁇ 0.8 and r ⁇ 0.19, which are the recommended conditions of the above-mentioned [Preferred production conditions of the present invention (Part 2)], in the temperature rising pattern during annealing. Therefore, TS ⁇ E1 ⁇ ⁇ satisfies a level of more than 1500,000 MPa ⁇ % ⁇ %, far exceeding the desired level, and a high-strength cold-rolled steel sheet having an excellent balance of mechanical properties was obtained.
- steel No. which is a comparative example. 3 to 6, 8 to 10, 12, 13, 15, 22, 23, and 26 are inferior in at least one of TS ⁇ E1 and TS ⁇ E1 ⁇ ⁇ .
- steel No. 3 to 6 and 8 to 10 do not satisfy at least one of the requirements for defining the structure of the present invention because the annealing condition or the tempering condition is out of the recommended range, and TS ⁇ El, TS ⁇ El ⁇ ⁇ At least one of them is inferior.
- steel No. No. 15 is inferior in TS ⁇ E1 ⁇ ⁇ because the C content is too high and the amount of coarsened cementite particles increases too much.
- Example 2 Steels having the components shown in Table 6 below were melted to produce 120 mm thick ingots. This was hot rolled to a thickness of 25 mm, and then hot rolled again to a thickness of 3.2 mm. After pickling this, it cold-rolled to 1.6 mm in thickness to make a test material, and heat-treated on the conditions shown in Table 7 and Table 8.
- Steel No. 1 to 35 as a temperature rising pattern from 600 ° C. to Ac1 during annealing, after heating from 600 ° C. to T1 (° C.) (where 600 ° C. ⁇ T1 ⁇ Ac1) at a predetermined temperature rising rate, This is held for a certain time at T1, and then heated from T1 to Ac1 at a predetermined rate of temperature increase.
- tensile strength TS, elongation El, and stretch flangeability were measured.
- the tensile strength TS and elongation El were measured in accordance with JIS Z 2241 by preparing No. 5 test piece described in JIS Z2201 with the long axis perpendicular to the rolling direction.
- stretch flangeability performed the hole expansion test according to the iron continuous standard JFST1001, and measured the hole expansion rate, and made this the stretch flangeability.
- Steel No. 1, 2, 10, 13 to 17, 20, 22, 23, 26, 27, 30 to 36 all have a tensile strength TS of 780 MPa or more, TS ⁇ El of 16000 MPa ⁇ % or more, and TS ⁇ El
- TS ⁇ El A high-strength cold-rolled steel sheet having an excellent balance between elongation and stretch flangeability, in which ⁇ ⁇ satisfies 1200000 MPa ⁇ % ⁇ % or more, was obtained.
- steel No. which is a comparative example. 3 to 9, 11, 12, 18, 19, 21, 24, 25, 28, 29 are inferior in at least one of TS, TS ⁇ E1 and TS ⁇ E1 ⁇ ⁇ .
- steel No. 3 to 9, 11 and 12 do not satisfy at least one of the requirements for defining the structure of the present invention because the annealing condition or the tempering condition is out of the recommended range, and TS ⁇ El, TS ⁇ El ⁇ ⁇ At least one of them is inferior.
- steel No. No. 21 is inferior in TS ⁇ E1 and TS ⁇ E1 ⁇ ⁇ because the C content is too high and the amount of coarsened cementite particles increases too much.
- TS ⁇ E1 and TS ⁇ E1 ⁇ ⁇ are ferrite grains, although they are acceptable levels at the level of Example 1 described above. It is slightly inferior to other examples that satisfy the conditions of 5 ⁇ m or less.
- the present invention can be applied to cold-rolled steel sheets used for automobile parts and the like.
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)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
質量%で(以下、化学成分について同じ。)、
C:0.05~0.30%、Si:3.0%以下(0%を含む)、Mn:0.1~5.0%、P:0.1%以下(0%を含む)、S:0.010%以下(0%を含む)、Al:0.001~0.10%を含み、残部が鉄および不可避的不純物からなる成分組成を有し、
軟質相であるフェライトを面積率で10~80%含むとともに、
残留オーステナイト、マルテンサイト、および、残留オーステナイトとマルテンサイトの混合組織を、面積率の合計で5%未満(0%を含む)含み、
残部が硬質相である、焼戻しマルテンサイトおよび/または焼戻しベイナイトからなる組織を有し、
Kernel Average Misorientation値(以下、「KAM値」と略称する。)の頻度分布曲線において、
全頻度に対する、該KAM値が0.4°以下の頻度の比率XKAM≦0.4°(単位:%)と、フェライトの面積率Vα(単位:%)との関係が、XKAM≦0.4°/Vα≧0.8を満たすとともに、
全頻度に対する、前記KAM値が0.6~0.8の頻度の比率XKAM=0.6~0.8°が10~20%であり、かつ、
前記フェライトと界面を接する硬質相中に存在する、円相当直径0.1μm以上のセメンタイト粒子の分散状態が、該硬質相1μm2当たり3個以下である
ことを特徴とする冷延鋼板である。
成分組成が、更に、
Nb:0.02~0.40%、
Ti:0.01~0.20%、
V:0.01~0.20%の1種以上を、
[%Nb]/96+[%Ti]/51+[%V]/48)×48が0.01~0.20
%を満足するように含み、
前記フェライトの平均粒径が円相当直径で5μm以下であり、
前記フェライトと前記硬質相の界面に存在する円相当直径20nm以上の析出物であって、Nb、TiおよびVの1種以上を含む析出物の分布状態が、前記硬質相1μm2当たり5個以下としたものである。
成分組成が、更に、Cr:0.01~1.0%を含むものである。
成分組成が、更に、Mo:0.02~1.0%、Cu:0.05~1.0%、Ni:0.05~1.0%の1種以上を含むものである。
成分組成が、更に、Ca:0.0005~0.01%、および/またはMg:0.0005~0.01%を含むものである。
請求項1に示す成分組成を有する鋼材を、下記(1)~(4)に示す各条件で、熱間圧延した後、冷間圧延し、その後、焼鈍し、さらに焼戻しすることを特徴とする伸冷延鋼板の製造方法である。
(1)熱間圧延条件
仕上げ圧延終了温度:Ar3点以上
巻取温度:450~700℃
(2)冷間圧延条件
冷間圧延率:20~80%
(3)焼鈍条件
600~Ac1℃の温度域を、下記式Iおよび式IIをともに満足する昇温パターンで昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(「第1冷却終了温度」という。)まで1℃/s以上50℃/s未満の冷却速度(「第1冷却速度」という。)で徐冷した後、Ms点以下の温度(「第2冷却終了温度」という。)まで50℃/s以下の冷却速度(「第2冷却速度」という。)で急冷する。
(4)焼戻し条件
上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(「焼戻し保持時間」という。):30s以下とした後、5℃/s超の冷却速度で冷却する。
請求項2に示す成分組成を有する鋼材を、下記(1)~(4)に示す各条件で、熱間圧延した後、冷間圧延し、その後、焼鈍し、さらに焼戻しすることを特徴とする冷延鋼板の製造方法である。
(1)熱間圧延条件
仕上げ圧延の終了温度:Ar3点以上
巻き取り温度:450~700℃
(2)冷間圧延条件
冷間圧延率:20~80%
(3)焼鈍条件
600~Ac1℃の温度域を、下記式I’および式II’をともに満足する昇温パターンで昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(「第1冷却終了温度」という。)まで1℃/s以上50℃/s未満の冷却速度(「第1冷却速度」という。)で徐冷した後、Ms点以下の温度(「第2冷却終了温度」という。)まで50℃/s以下の冷却速度(「第2冷却速度」という。)で急冷する。
(4)焼戻し条件
上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(「焼戻し保持時間」という。):30s以下とした後、5℃/s超の冷却速度で冷却する。
上述したとおり、本発明鋼板は、上記特許文献2、3と近似の複相組織をベースとするものであるが、特に、フェライト中の歪量を制御するとともに、硬質相の変形能を制御し、さらにフェライトと硬質相の界面に析出したセメンタイト粒子の分布状態が制御されている点で、上記特許文献2、3の鋼板とは相違している。
フェライト-焼戻しマルテンサイト等の複相組織鋼では、変形は主として変形能の高いフェライトが受け持つ。そのため、フェライト-焼戻しマルテンサイト等の複相組織鋼の伸びは主としてフェライトの面積率で決定される。
強度を確保しつつ脆化を防止するには、フェライトを除く領域を、主としてマルテンサイトおよび/またはベイナイトが焼戻しされた組織(焼戻しマルテンサイトおよび/または焼戻しベイナイトからなる組織)にすることが有効である。その際、残留オーステナイトや焼戻しされていないマルテンサイト(以下、単に「マルテンサイト」の表記は、焼戻しされていないマルテンサイトを意味するものとする。)が存在すると、その周囲に応力が集中し、破壊に至りやすくなるので、残留オーステナイト、マルテンサイトおよびそれらの混合組織をできるだけ少なくすることで伸びフランジ性の劣化を防止できる。
KAM値0.6~0.8°の比率XKAM=0.6~0.8°:10~20%>
複相組織鋼の強度と伸びのバランスは、一般的にフェライト面積率と硬質相の変形能に依存する。一方、フェライト中の歪量は伸びに大きな影響を及ぼし、フェライト面積率が一定の場合、該歪量が大きければ伸びが低下する。
上記のようにKAM値に関する要件を満足させることでフェライトと硬質相の界面での破壊を抑制できた場合、次に破壊の起点になるのは、フェライトと界面を接する硬質相中に析出したセメンタイトになる。このセメンタイト粒子が粗大になると変形時の応力集中が過大となり伸びフランジ性が確保できなくなるので、伸びフランジ性を確保するためには、セメンタイト粒子のサイズと存在密度を制御する必要がある。
まず、各相の面積率については、各供試鋼板を鏡面研磨し、3%ナイタール液で腐食して金属組織を顕出させた後、概略40μm×30μm領域5視野について倍率2000倍の走査型電子顕微鏡(SEM)像を観察し、点算法で1視野につき100点の測定を行ってフェライトの面積を求めた。また、画像解析によってセメンタイトを含む領域を硬質相とし、残りの領域を、残留オーステナイト、マルテンサイト、および、残留オーステナイトとマルテンサイトの混合組織とした。そして、各領域の面積比率より各相の面積率を算出した。
各供試鋼板を鏡面研磨し、さらに電解研磨した後、走査型電子顕微鏡(Philips社製XL30S-FEG)にて、1step 0.2μmで500μm×500μmの領域の電子線後方散乱回折像を測定し、それを解析ソフト(テクセムラボラトリーズ社製OIMシステム)を用いて、各測定点におけるKAM値を求めた。
セメンタイト粒子のサイズおよびその存在密度については、各供試鋼板の抽出レプリカサンプルを作成し、2.4μm×1.6μmの領域3視野について倍率50000倍の透過型電子顕微鏡(TEM)像を観察し、画像のコントラストから白い部分をセメンタイト粒子と判別してマーキングし、画像解析ソフトにて、前記マーキングした各セメンタイト粒子の面積Aから円相当直径D(D=2×(A/π)1/2)を算出するとともに、単位面積あたりに存在する所定のサイズのセメンタイト粒子の個数を求めた。なお、複数個のセメンタイト粒子が重なり合う部分は観察対象から除外した。
各供試鋼板を鏡面に研磨し、3%ナイタール液で腐食して金属組織を顕出させた後、80μm×60μm領域10視野中に、それぞれ50μmの線分を20本引き、それらの線分と交わるフェライト粒界の数Nαおよびフェライト-硬質相界面の数Nα-TMを測定する。そして、フェライトの存在形態の評価指数として、粒界および界面に占めるフェライト粒界の割合Nα/(Nα+Nα-TM)を求める。Nα/(Nα+Nα-TM)の値が小さいということは、フェライト粒子とフェライト粒子が連続している領域が少ないこと、つまり、フェライト粒子が連続せず、硬質相に囲まれていることを示している。
C:0.05~0.30%
Cは、硬質相の面積率および該硬質相中に析出するセメンタイト量に影響し、強度、伸びおよび伸びフランジ性に影響する重要な元素である。0.05%未満では強度が確保できなくなる。一方、0.30%超では焼入れ時に歪みが多量に入ることに加え、セメンタイトの量が多くなり転位が回復しにくくなることから、転位が抜けて変形能が高まった硬質相であることを示す評価式であるXKAM=0.6~0.8°≧10%が得られなくなる。この評価式を満たすように、焼戻し条件を高温ないし長時間化するとセメンタイトが粗大化し、強度や伸びフランジ性が確保できなくなる。
Siは、焼戻し時におけるセメンタイト粒子の粗大化を抑制する効果を有し、伸びと伸びフランジ性の両立に寄与する有用な元素である。3.0%超では加熱時におけるオーステナイトの形成を阻害するため、硬質相の面積率を確保できず、伸びフランジ性を確保できない。Si含有量の範囲は、好ましくは0.50~2.5%、さらに好ましくは1.0~2.2%である。
Mnは、上記Siと同様、焼戻し時におけるセメンタイトの粗大化を抑制する効果を有することに加え、硬質相の変形能を高めることで、伸びと伸びフランジ性の両立に寄与する。また、焼入れ性を高めることで、硬質相が得られる製造条件の範囲を広げる効果もある。0.1%未満では上記効果が十分に発揮されないため、伸びと伸びフランジ性を両立できず、一方、5.0%超とすると逆変態温度が低くなりすぎ、再結晶ができなくなるため、強度と伸びのバランスが確保できなくなる。Mn含有量の範囲は、好ましくは0.50~2.5%、さらに好ましくは1.2~2.2%である。
Pは不純物元素として不可避的に存在し、固溶強化により強度の上昇に寄与するが、 旧オーステナイト粒界に偏析し、粒界を脆化させることで伸びフランジ性を劣化させるので、0.1%以下とする。好ましくは0.05%以下、さらに好ましくは0.03%以下である。
Sも不純物元素として不可避的に存在し、MnS介在物を形成し、穴拡げ時に亀裂の起点となることで伸びフランジ性を低下させるので、0.010%以下とする。好ましくは0.005%以下であり、より好ましくは0.003%以下である。
Nも不純物元素として不可避的に存在し、歪時効により伸びと伸びフランジ性を低下させるので、低い方が好ましく、0.01%以下とする。
Alは脱酸元素として添加され、介在物を微細化する効果を有する。また、Nと結合してAlNを形成し、歪時効の発生に寄与する固溶Nを低減させることで伸びや伸びフランジ性の劣化を防止する。0.001%未満では鋼中に固溶Nが残存するため、歪時効が起こり、伸びと伸びフランジ性を確保できず、一方、0.1%超では加熱時におけるオーステナイトの形成を阻害するため、硬質相の面積率を確保できず、伸びフランジ性を確保できなくなる。
Nb、TiおよびVは、微細なMX型化合物(炭化物、窒化物、炭窒化物の総称)を形成し、この微細なMX型化合物が焼鈍の際の加熱時にオーステナイトの成長をピン止めする粒子として作用することで、フェライト粒の微細化に寄与し、熱間圧延後の組織を微細化することにより、伸びフランジ性を高める。Nb、TiおよびVの各含有量、ならびに、V換算合計含有量が上記各上限値を超えると、粗大なMX型化合物が形成され、伸びフランジ性が劣化するとともに、これらの元素は再結晶を強く抑制する作用を有するため、冷間圧延後、焼鈍の際の加熱時に再結晶が抑制されてXKAM≦0.4°/Vαが0.8未満になり、強度と伸びのバランスが確保できなくなる。一方、Nb、TiおよびVの各含有量、ならびに、V換算合計含有量が上記各下限値を下回ると、上記フェライト粒微細化の効果が十分に得られなくなる。
フェライトを微細化させることによりフェライトと硬質相の界面など応力が集中しやすいサイトの数を増加させて応力を分散させることで、伸びフランジ性が改善される。
NbC、TiC、VCなどのNbやTiやVを含む析出物は、母相に比べて剛性および臨界せん断応力が非常に高いため、析出物の周囲が変形しても析出物自体は変形しにくいため、20nm以上のサイズになると母相と析出物との界面に大きなひずみが生じ、破壊が発生するようになる。このため、20nm以上のNbやTiやVを含む粗大な析出物が多量に存在すると伸びフランジ性が劣化する。したがって、粗大なNbやTiやV含有析出物の存在密度を制限することで、伸びフランジ性を改善することができる。
前記した面積率の測定の際に測定した各フェライト粒の面積から円相当直径を算出して求めた。
析出物のサイズおよびその存在密度については、前記したセメンタイトの測定と同様に、各供試鋼板の抽出レプリカサンプルを作成し、2.4μm×1.6μmの領域3視野について倍率50000倍の透過型電子顕微鏡(TEM)像を観察した。そして、20nm以上の析出物について、FE-TEMに付随のEDXまたはEELSを用いて析出物中にNb、Ti、Vが存在していることを確認したものだけをカウントした。
Crは、セメンタイトの成長を抑制することで、伸びフランジ性を改善できる有用な元素である。0.01%未満の添加では上記のような作用を有効に発揮しえず、一方、1.0%を超える添加では粗大なCr7C3が形成されるようになり、伸びフランジ性が劣化してしまう。
これらの元素は、固溶強化により成形性を劣化させずに強度を改善するのに有用な元素である。各元素とも下限値未満の添加では上記のような作用を有効に発揮しえず、一方、各元素とも1.0%を超える添加ではコストが高くなりすぎる。
これらの元素は、介在物を微細化し、破壊の起点を減少させることで、伸びフランジ性を向上させるのに有用な元素である。各元素とも0.0005%未満の添加では上記のような作用を有効に発揮しえず、一方、各元素とも0.01%を超える添加では逆に介在物が粗大化し、伸びフランジ性が低下する。
本発明の請求項1に記載した冷延鋼板を製造するには、まず、上記成分組成を有する鋼を溶製し、造塊または連続鋳造によりスラブとしてから熱間圧延を行う。熱間圧延条件としては、仕上げ圧延の終了温度をAr3点以上に設定し、適宜冷却を行った後、450~700℃の範囲で巻き取る。熱間圧延終了後は酸洗してから冷間圧延を行うが、冷間圧延率(以下、「冷延率」ともいう。)は30%程度以上とするのがよい。
焼鈍条件としては、600~Ac1℃の温度域を(Ac1-600)s以上の滞在時間で昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(第1冷却終了温度)まで1℃/s以上50℃/s未満の冷却速度(第1冷却速度)で徐冷した後、Ms点以下の温度(第2冷却終了温度)まで50℃/s以下の冷却速度(第2冷却速度)で急冷するのがよい。
逆変態前に高温域に長時間滞在させることでフェライトの回復・再結晶を促進させ、フェライト中のひずみを開放させるためである。
焼鈍加熱時に面積率20%以上の領域をオーステナイトに変態させることにより、その後の冷却時に十分な量の硬質相を変態生成させるためである。
冷却中にオーステナイトからフェライトが形成されることを抑制し、硬質相を得るためである。
面積率で50%未満のフェライト組織を形成させることにより、伸びフランジ性を確保したまま伸びの改善が図れるためである。
焼戻し条件としては、上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(焼戻し保持時間):30s以下とした後、5℃/s超の冷却速度で冷却すればよい。
上記〔本発明鋼板の好ましい製造方法(その1)〕ではその[焼鈍条件]において、「600~Ac1℃の温度域を(Ac1-600)s以上の滞在時間で昇温」すると規定したが、600~Ac1℃の温度域を、下記式Iおよび式IIをともに満足する昇温パターンで昇温するのがより好ましい。なお、その他の製造条件は、上記〔本発明鋼板の好ましい製造方法(その1)〕と同様である。ただし、冷間圧延における冷間圧延率は、上記〔本発明鋼板の好ましい製造方法(その1)〕では「30%以上程度とするのがよい」としたが、本例では、後記初期転位密度との関係を表す式3が成立する範囲である、20~80%の範囲とする。
式1:X=1-exp[-exp{A1ln(DFe)+A2ln(ρ0)-A3}・tn]
(ここに、A1、A2、A3、n:定数)
式2:DFe=0.0118exp[-281500/{R(T+273)}](m2/s)
(ここに、T:温度(℃)、R:ガス定数[=8.314J/K・mol])の関係が成り立つことが知られている(例えば、日本鉄鋼協会編、鉄鋼便覧 第3版、I 基礎、丸善、1981年、p.349参照)。
式3:ρ0=B1ln[(-ln{(100-[CR])/100}]+B2
(ここに、B1、B2:定数)
式4:r3―r0 3=A・exp[-Q/{R(T+273)}]・t
(ここに、A、Q:定数)
本発明の請求項2の冷延鋼板、すなわちNb,Ti,Vの1種以上を含有する場合の冷延鋼板を製造するには、まず、上記成分組成を有する鋼を溶製し、造塊または連続鋳造によりスラブとしてから熱間圧延を行う。
熱間圧延条件としては、仕上げ圧延終了温度:900℃以上にて熱間圧延したのち、550℃までの冷却時間:[(仕上げ圧延終了温度-550℃)/20]s以下で冷却を行った後、巻取温度:500℃以下で巻き取る。
仕上げ圧延終了温度が900℃未満では、熱間圧延中にMX型化合物が析出し、その後の焼鈍の際の加熱過程で該析出物が成長して粗大化し、伸びフランジ性が劣化する。
また、仕上げ圧延終了後550℃までの冷却時間が[(仕上げ圧延終了温度-550℃)/20]s超になると、冷却中にフェライト変態が起こり、形成されたフェライト中に析出物が形成され、その後の焼鈍の際の加熱過程で該析出物が粗大化し、伸びフランジ性が劣化する。
また、巻取温度が500℃超になると、巻き取り中に析出物が形成ないし粗大化し、伸びフランジ性が劣化する。
焼鈍条件としては、600~Ac1℃の温度域を(Ac1-600)s以上の滞在時間で昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(第1冷却終了温度)まで1℃/s以上50℃/s未満の冷却速度(第1冷却速度)で徐冷した後、Ms点以下の温度(第2冷却終了温度)まで50℃/s以下の冷却速度(第2冷却速度)で急冷するのがよい。
逆変態前に高温域に長時間滞在させることでフェライトの回復・再結晶を促進させ、フェライト中のひずみを開放させるためである。特に再結晶を遅延させるマイクロアロイ(Nb、TiおよびV)を添加しているため、Ac1点以下の温度域における滞在時間を長時間化する必要がある。
焼鈍加熱時に面積率20%以上の領域をオーステナイトに変態させることにより、その後の冷却時に十分な量の硬質相を変態生成させるためである。
冷却中にオーステナイトからフェライトが形成されることを抑制し、硬質相を得るためである。
面積率で50%未満のフェライト組織を形成させることにより、伸びフランジ性を確保したまま伸びの改善が図れるためである。
焼戻し条件としては、上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(焼戻し保持時間):20s以下とした後、5℃/s超の冷却速度で冷却すればよい。
上記〔本発明鋼板の好ましい製造方法(その3)〕ではその[焼鈍条件]において、「600~Ac1℃の温度域を(Ac1-600)s以上の滞在時間で昇温」すると規定したが、600~Ac1℃の温度域を、下記式I’および式II’をともに満足する昇温パターンで昇温するのがより好ましい。なお、その他の製造条件は、上記〔本発明鋼板の好ましい製造方法(その3)〕と同様である。ただし、冷間圧延における冷間圧延率は、上記〔本発明鋼板の好ましい製造方法(その3)〕では「30%以上程度とするのがよい」としたが、本例では、後記初期転位密度との関係を表す式7が成立する範囲である、20~80%の範囲とする)。
式5:X=1-exp[-exp{A1ln(DFe)+A2ln(ρ0)-A3}・tn]
(ここに、A1、A2、A3、n:定数)
式6:DFe=0.0118exp[-281500/{R(T+273)}](m2/s)
(ここに、T:温度(℃)、R:ガス定数[=8.314J/K・mol])の関係が成り立つことが知られている。
式7:ρ0=B1ln[(-ln{(100-[CR])/100}]+B2
(ここに、B1、B2:定数)
式8:r3―r0 3=A・exp[-Q/{R(T+273)}]・t
(ここに、A、Q:定数)
下記表1に示す成分の鋼を溶製し、厚さ120mmのインゴットを作成した。これを熱間圧延で厚さ25mmにした後、再度、熱間圧延で厚さ3.2mmとした。これを酸洗した後、厚さ1.6mmに冷間圧延して供試材とし、表2および表3に示す条件にて熱処理を施した。
また、伸びフランジ性λは、鉄連規格JFST1001に則り、穴拡げ試験を実施して穴拡げ率の測定を行い、これを伸びフランジ性とした。
下記表6に示す成分の鋼を溶製し、厚さ120mmのインゴットを作成した。これを熱間圧延で厚さ25mmにした後、再度、熱間圧延で厚さ3.2mmとした。これを酸洗した後、厚さ1.6mmに冷間圧延して供試材とし、表7および表8に示す条件にて熱処理を施した。
また、伸びフランジ性λは、鉄連規格JFST1001に則り、穴拡げ試験を実施して穴拡げ率の測定を行い、これを伸びフランジ性とした。
Claims (7)
- 質量%で(以下、化学成分について同じ。)、
C:0.05~0.30%、Si:3.0%以下(0%を含む)、Mn:0.1~5.0%、P:0.1%以下(0%を含む)、S:0.010%以下(0%を含む)、Al:0.001~0.10%を含み、残部が鉄および不可避的不純物からなる成分組成を有し、
軟質相であるフェライトを面積率で10~80%含むとともに、
残留オーステナイト、マルテンサイト、および、残留オーステナイトとマルテンサイトの混合組織を、面積率の合計で5%未満(0%を含む)含み、
残部が硬質相である、焼戻しマルテンサイトおよび/または焼戻しベイナイトからなる組織を有し、
Kernel Average Misorientation値(以下、「KAM値」と略称する。)の頻度分布曲線において、
全頻度に対する、該KAM値が0.4°以下の頻度の比率XKAM≦0.4°(単位:%)と、フェライトの面積率Vα(単位:%)との関係が、XKAM≦0.4°/Vα≧0.8を満たすとともに、
全頻度に対する、前記KAM値が0.6~0.8°の頻度の比率XKAM=0.6~0.8°が10~20%であり、かつ、
前記フェライトと前記硬質相の界面に存在する、円相当直径0.1μm以上のセメンタイト粒子の分散状態が、前記硬質相1μm2当たり3個以下である
ことを特徴とする冷延鋼板。 - 成分組成が、更に、
Nb:0.02~0.40%、
Ti:0.01~0.20%、
V:0.01~0.20%の1種以上を、
[%Nb]/96+[%Ti]/51+[%V]/48)×48が0.01~0.20%を満足するように含み、
前記フェライトの平均粒径が円相当直径で5μm以下であり、
前記フェライトと前記硬質相の界面に存在する円相当直径20nm以上の析出物であって、Nb、TiおよびVの1種以上を含む析出物の分布状態が、前記硬質相1μm2当たり5個以下である
請求項1に記載の冷延鋼板。 - 成分組成が、更に、
Cr:0.01~1.0%
を含むものである請求項1または2に記載の冷延鋼板。 - 成分組成が、更に、
Mo:0.02~1.0%、Cu:0.05~1.0%、Ni:0.05~1.0%の1種以上を含むものである請求項1~3のいずれか1項に記載の冷延鋼板。 - 成分組成が、更に、
Ca:0.0005~0.01%、および/またはMg:0.0005~0.01%を含むものである請求項1~4のいずれか1項に記載の冷延鋼板。 - 請求項1に示す成分組成を有する鋼材を、下記(1)~(4)に示す各条件で、熱間圧延した後、冷間圧延し、その後、焼鈍し、さらに焼戻しすることを特徴とする冷延鋼板の製造方法。
(1)熱間圧延条件
仕上げ圧延終了温度:Ar3点以上
巻取温度:450~700℃
(2)冷間圧延条件
冷間圧延率:20~80%
(3)焼鈍条件
600~Ac1℃の温度域を、下記式Iおよび式IIをともに満足する昇温パターンで昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(「第1冷却終了温度」という。)まで1℃/s以上50℃/s未満の冷却速度(「第1冷却速度」という。)で徐冷した後、Ms点以下の温度(「第2冷却終了温度」という。)まで50℃/s以下の冷却速度(「第2冷却速度」という。)で急冷する。
(4)焼戻し条件
上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(「焼戻し保持時間」という。):30s以下とした後、5℃/s超の冷却速度で冷却する。
- 請求項2に示す成分組成を有する鋼材を、下記(1)~(4)に示す各条件で、熱間圧延した後、冷間圧延し、その後、焼鈍し、さらに焼戻しすることを特徴とする冷延鋼板の製造方法。
(1)熱間圧延条件
仕上げ圧延終了温度:900℃以上
550℃までの冷却時間:[(仕上げ圧延終了温度-550℃)/20]s以下
巻取温度:500℃以下
(2)冷間圧延条件
冷間圧延率:20~80%
(3)焼鈍条件
600~Ac1℃の温度域を、下記式I’および式II’をともに満足する昇温パターンで昇温し、焼鈍加熱温度:[(8×Ac1+2×Ac3)/10]~1000℃にて、焼鈍保持時間:3600s以下保持した後、焼鈍加熱温度から直接Ms点以下の温度まで50℃/s以上の冷却速度で急冷するか、または、焼鈍加熱温度から、焼鈍加熱温度未満で600℃以上の温度(「第1冷却終了温度」という。)まで1℃/s以上50℃/s未満の冷却速度(「第1冷却速度」という。)で徐冷した後、Ms点以下の温度(「第2冷却終了温度」という。)まで50℃/s以下の冷却速度(「第2冷却速度」という。)で急冷する。
(4)焼戻し条件
上記焼鈍冷却後の温度から焼戻し加熱温度:420℃以上670℃未満までの間を5℃/s超の加熱速度で加熱し、[焼戻し加熱温度-10℃]~焼戻し加熱温度の間の温度領域に存在する時間(「焼戻し保持時間」という。):20s以下とした後、5℃/s超の冷却速度で冷却する。
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP10758898.0A EP2415891A4 (en) | 2009-04-03 | 2010-04-02 | COLD-ROLLED STEEL PLATE AND METHOD FOR THE PRODUCTION THEREOF |
US13/258,823 US8840738B2 (en) | 2009-04-03 | 2010-04-02 | Cold-rolled steel sheet and method for producing the same |
CN201080010267.9A CN102341518B (zh) | 2009-04-03 | 2010-04-02 | 冷轧钢板及其制造方法 |
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009-091298 | 2009-04-03 | ||
JP2009091298 | 2009-04-03 | ||
JP2009091297 | 2009-04-03 | ||
JP2009-091297 | 2009-04-03 | ||
JP2009-231680 | 2009-10-05 | ||
JP2009-231681 | 2009-10-05 | ||
JP2009231681A JP4977185B2 (ja) | 2009-04-03 | 2009-10-05 | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板およびその製造方法 |
JP2009231680A JP4977184B2 (ja) | 2009-04-03 | 2009-10-05 | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板およびその製造方法 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010114131A1 true WO2010114131A1 (ja) | 2010-10-07 |
Family
ID=45440664
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2010/056096 WO2010114131A1 (ja) | 2009-04-03 | 2010-04-02 | 冷延鋼板およびその製造方法 |
Country Status (4)
Country | Link |
---|---|
US (1) | US8840738B2 (ja) |
EP (1) | EP2415891A4 (ja) |
CN (1) | CN102341518B (ja) |
WO (1) | WO2010114131A1 (ja) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011179050A (ja) * | 2010-02-26 | 2011-09-15 | Kobe Steel Ltd | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板 |
EP2703512A1 (en) * | 2011-04-25 | 2014-03-05 | JFE Steel Corporation | High-strength steel plate with excellent formability and stability of material properties, and method for manufacturing same |
CN104011242A (zh) * | 2011-12-26 | 2014-08-27 | 杰富意钢铁株式会社 | 高强度薄钢板及其制造方法 |
CN104928590A (zh) * | 2015-06-11 | 2015-09-23 | 北京交通大学 | 一种Mn-Si-Cr低碳贝氏体钢、钎杆及其制备方法 |
US20180016656A1 (en) * | 2015-02-03 | 2018-01-18 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
US20180023160A1 (en) * | 2015-02-03 | 2018-01-25 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
EP2726637B1 (en) | 2011-07-01 | 2018-11-14 | Rautaruukki Oyj | Method for manufacturing a high-strength structural steel and a high-strength structural steel product |
Families Citing this family (33)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5671359B2 (ja) | 2010-03-24 | 2015-02-18 | 株式会社神戸製鋼所 | 温間加工性に優れた高強度鋼板 |
JP5662902B2 (ja) | 2010-11-18 | 2015-02-04 | 株式会社神戸製鋼所 | 成形性に優れた高強度鋼板、温間加工方法、および温間加工された自動車部品 |
JP5667472B2 (ja) | 2011-03-02 | 2015-02-12 | 株式会社神戸製鋼所 | 室温および温間での深絞り性に優れた高強度鋼板およびその温間加工方法 |
JP5636347B2 (ja) | 2011-08-17 | 2014-12-03 | 株式会社神戸製鋼所 | 室温および温間での成形性に優れた高強度鋼板およびその温間成形方法 |
EP2792760B1 (en) | 2011-12-15 | 2018-05-30 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | High-strength cold-rolled steel sheet having small variations in strength and ductility and manufacturing method for the same |
EP2816132B1 (en) * | 2012-02-17 | 2016-11-09 | Nippon Steel & Sumitomo Metal Corporation | Steel sheet, plated steel sheet, method for producing steel sheet, and method for producing plated steel sheet |
JP5860308B2 (ja) | 2012-02-29 | 2016-02-16 | 株式会社神戸製鋼所 | 温間成形性に優れた高強度鋼板およびその製造方法 |
JP5860343B2 (ja) | 2012-05-29 | 2016-02-16 | 株式会社神戸製鋼所 | 強度および延性のばらつきの小さい高強度冷延鋼板およびその製造方法 |
EP3187614A1 (en) | 2012-05-31 | 2017-07-05 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | High strength cold-rolled steel sheet and manufacturing method therefor |
JP5860354B2 (ja) | 2012-07-12 | 2016-02-16 | 株式会社神戸製鋼所 | 降伏強度と成形性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法 |
CN103805840B (zh) * | 2012-11-15 | 2016-12-21 | 宝山钢铁股份有限公司 | 一种高成形性热镀锌超高强度钢板及其制造方法 |
KR101758003B1 (ko) | 2013-04-15 | 2017-07-13 | 신닛테츠스미킨 카부시키카이샤 | 열연 강판 |
US10563279B2 (en) | 2013-08-02 | 2020-02-18 | Jfe Steel Corporation | High strength steel sheet having high Young's modulus and method for manufacturing the same |
JP5728108B2 (ja) * | 2013-09-27 | 2015-06-03 | 株式会社神戸製鋼所 | 加工性および低温靭性に優れた高強度鋼板、並びにその製造方法 |
EP3093359A4 (en) | 2014-01-06 | 2017-08-23 | Nippon Steel & Sumitomo Metal Corporation | Hot-formed member and process for manufacturing same |
WO2015102050A1 (ja) | 2014-01-06 | 2015-07-09 | 新日鐵住金株式会社 | 鋼材およびその製造方法 |
CN104313497A (zh) * | 2014-09-30 | 2015-01-28 | 合肥恒泰钢结构有限公司 | 一种中低碳锰钢 |
CN104294178A (zh) * | 2014-09-30 | 2015-01-21 | 合肥恒泰钢结构有限公司 | 一种渗碳锰钢 |
JP6032298B2 (ja) | 2015-02-03 | 2016-11-24 | Jfeスチール株式会社 | 高強度冷延鋼板、高強度めっき鋼板、高強度溶融亜鉛めっき鋼板および高強度合金化溶融亜鉛めっき鋼板、並びにそれらの製造方法 |
WO2016132549A1 (ja) | 2015-02-20 | 2016-08-25 | 新日鐵住金株式会社 | 熱延鋼板 |
US11401571B2 (en) | 2015-02-20 | 2022-08-02 | Nippon Steel Corporation | Hot-rolled steel sheet |
US10689737B2 (en) | 2015-02-25 | 2020-06-23 | Nippon Steel Corporation | Hot-rolled steel sheet |
WO2016135898A1 (ja) | 2015-02-25 | 2016-09-01 | 新日鐵住金株式会社 | 熱延鋼板 |
US10385419B2 (en) | 2016-05-10 | 2019-08-20 | United States Steel Corporation | High strength steel products and annealing processes for making the same |
US11560606B2 (en) | 2016-05-10 | 2023-01-24 | United States Steel Corporation | Methods of producing continuously cast hot rolled high strength steel sheet products |
CN105925887B (zh) * | 2016-06-21 | 2018-01-30 | 宝山钢铁股份有限公司 | 一种980MPa级热轧铁素体贝氏体双相钢及其制造方法 |
MX2019000576A (es) | 2016-08-05 | 2019-09-02 | Nippon Steel Corp | Lámina de acero y lámina de acero chapada. |
US10889879B2 (en) | 2016-08-05 | 2021-01-12 | Nippon Steel Corporation | Steel sheet and plated steel sheet |
JP6315044B2 (ja) | 2016-08-31 | 2018-04-25 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
JP6372632B1 (ja) | 2016-11-16 | 2018-08-15 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
WO2018147400A1 (ja) * | 2017-02-13 | 2018-08-16 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
CN113166837B (zh) * | 2018-11-29 | 2023-08-01 | 杰富意钢铁株式会社 | 高强度钢板及其制造方法 |
CN115181895B (zh) * | 2021-04-02 | 2023-09-12 | 宝山钢铁股份有限公司 | 1180MPa级别低碳低合金热镀锌Q&P钢及快速热处理热镀锌制造方法 |
Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63293121A (ja) * | 1987-05-25 | 1988-11-30 | Kobe Steel Ltd | 局部延性にすぐれる高強度冷延鋼板の製造方法 |
JP2002161336A (ja) | 2000-09-12 | 2002-06-04 | Nkk Corp | 超高張力冷延鋼板およびその製造方法 |
JP2004232022A (ja) | 2003-01-30 | 2004-08-19 | Jfe Steel Kk | 伸びおよび伸びフランジ性に優れた二相型高張力鋼板およびその製造方法 |
JP2004256872A (ja) | 2003-02-26 | 2004-09-16 | Jfe Steel Kk | 伸びおよび伸びフランジ性に優れる高張力冷延鋼板およびその製造方法 |
JP2004277858A (ja) * | 2003-03-18 | 2004-10-07 | Jfe Steel Kk | 超微細粒組織を有し衝撃吸収特性に優れる冷延鋼板およびその製造方法 |
JP2004359973A (ja) * | 2003-06-02 | 2004-12-24 | Nippon Steel Corp | 耐遅れ破壊特性に優れた高強度鋼板及びその製造方法 |
JP2007302918A (ja) * | 2006-05-09 | 2007-11-22 | Nippon Steel Corp | 穴拡げ性と成形性に優れた高強度鋼板及びその製造方法 |
JP2008144233A (ja) | 2006-12-11 | 2008-06-26 | Kobe Steel Ltd | 焼付硬化用高強度鋼板およびその製造方法 |
JP2009091297A (ja) | 2007-10-09 | 2009-04-30 | Tsujido Kagaku Kk | 抗鬱・抗ストレス剤 |
JP2009091298A (ja) | 2007-10-10 | 2009-04-30 | Asuka Corporation:Kk | 皮膚改善化粧料 |
JP2009231681A (ja) | 2008-03-25 | 2009-10-08 | Citizen Watch Co Ltd | 半導体装置およびその製造方法 |
JP2009231680A (ja) | 2008-03-25 | 2009-10-08 | Panasonic Corp | 基板の表面処理方法および表面処理装置ならびに半導体パッケージの製造方法 |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6709535B2 (en) * | 2002-05-30 | 2004-03-23 | Kobe Steel, Ltd. | Superhigh-strength dual-phase steel sheet of excellent fatigue characteristic in a spot welded joint |
JP4283757B2 (ja) * | 2004-11-05 | 2009-06-24 | 株式会社神戸製鋼所 | 厚鋼板およびその製造方法 |
US8337643B2 (en) * | 2004-11-24 | 2012-12-25 | Nucor Corporation | Hot rolled dual phase steel sheet |
US7959747B2 (en) * | 2004-11-24 | 2011-06-14 | Nucor Corporation | Method of making cold rolled dual phase steel sheet |
EP2465961B1 (en) * | 2006-07-14 | 2013-12-04 | Kabushiki Kaisha Kobe Seiko Sho | High-strength steel sheets and processes for production of the same |
US8679265B2 (en) | 2007-11-22 | 2014-03-25 | Kobe Steel, Ltd. | High-strength cold-rolled steel sheet |
KR101230742B1 (ko) | 2008-03-07 | 2013-02-07 | 가부시키가이샤 고베 세이코쇼 | 냉간 압연 강판 |
US8460800B2 (en) * | 2009-03-31 | 2013-06-11 | Kobe Steel, Ltd. | High-strength cold-rolled steel sheet excellent in bending workability |
-
2010
- 2010-04-02 WO PCT/JP2010/056096 patent/WO2010114131A1/ja active Application Filing
- 2010-04-02 US US13/258,823 patent/US8840738B2/en not_active Expired - Fee Related
- 2010-04-02 EP EP10758898.0A patent/EP2415891A4/en not_active Withdrawn
- 2010-04-02 CN CN201080010267.9A patent/CN102341518B/zh not_active Expired - Fee Related
Patent Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63293121A (ja) * | 1987-05-25 | 1988-11-30 | Kobe Steel Ltd | 局部延性にすぐれる高強度冷延鋼板の製造方法 |
JP2002161336A (ja) | 2000-09-12 | 2002-06-04 | Nkk Corp | 超高張力冷延鋼板およびその製造方法 |
JP2004232022A (ja) | 2003-01-30 | 2004-08-19 | Jfe Steel Kk | 伸びおよび伸びフランジ性に優れた二相型高張力鋼板およびその製造方法 |
JP2004256872A (ja) | 2003-02-26 | 2004-09-16 | Jfe Steel Kk | 伸びおよび伸びフランジ性に優れる高張力冷延鋼板およびその製造方法 |
JP2004277858A (ja) * | 2003-03-18 | 2004-10-07 | Jfe Steel Kk | 超微細粒組織を有し衝撃吸収特性に優れる冷延鋼板およびその製造方法 |
JP2004359973A (ja) * | 2003-06-02 | 2004-12-24 | Nippon Steel Corp | 耐遅れ破壊特性に優れた高強度鋼板及びその製造方法 |
JP2007302918A (ja) * | 2006-05-09 | 2007-11-22 | Nippon Steel Corp | 穴拡げ性と成形性に優れた高強度鋼板及びその製造方法 |
JP2008144233A (ja) | 2006-12-11 | 2008-06-26 | Kobe Steel Ltd | 焼付硬化用高強度鋼板およびその製造方法 |
JP2009091297A (ja) | 2007-10-09 | 2009-04-30 | Tsujido Kagaku Kk | 抗鬱・抗ストレス剤 |
JP2009091298A (ja) | 2007-10-10 | 2009-04-30 | Asuka Corporation:Kk | 皮膚改善化粧料 |
JP2009231681A (ja) | 2008-03-25 | 2009-10-08 | Citizen Watch Co Ltd | 半導体装置およびその製造方法 |
JP2009231680A (ja) | 2008-03-25 | 2009-10-08 | Panasonic Corp | 基板の表面処理方法および表面処理装置ならびに半導体パッケージの製造方法 |
Non-Patent Citations (3)
Title |
---|
KENTO SAKUMA: "Nippon Kinzoku Gakkai Kaihou", vol. 20, 1981, pages: 247 |
See also references of EP2415891A4 |
TEKKOU BINRAN: "Steel Handbook", 1981, THE IRON AND STEEL INSTITUTION OF JAPAN, MARZEN, pages: 349 |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011179050A (ja) * | 2010-02-26 | 2011-09-15 | Kobe Steel Ltd | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板 |
US9758848B2 (en) | 2011-04-25 | 2017-09-12 | Jfe Steel Corporation | High strength steel sheet having excellent formability and stability of mechanical properties and method for manufacturing the same |
EP2703512A4 (en) * | 2011-04-25 | 2014-12-10 | Jfe Steel Corp | HIGH-RESISTANCE STEEL PLATE WITH EXCELLENT FORMABILITY AND MATERIAL STABILITY AND MANUFACTURING METHOD THEREFOR |
EP2703512A1 (en) * | 2011-04-25 | 2014-03-05 | JFE Steel Corporation | High-strength steel plate with excellent formability and stability of material properties, and method for manufacturing same |
EP2726637B1 (en) | 2011-07-01 | 2018-11-14 | Rautaruukki Oyj | Method for manufacturing a high-strength structural steel and a high-strength structural steel product |
EP2726637B2 (en) † | 2011-07-01 | 2021-12-29 | Rautaruukki Oyj | Method for manufacturing a high-strength structural steel and a high-strength structural steel product |
CN104011242A (zh) * | 2011-12-26 | 2014-08-27 | 杰富意钢铁株式会社 | 高强度薄钢板及其制造方法 |
CN104011242B (zh) * | 2011-12-26 | 2016-03-30 | 杰富意钢铁株式会社 | 高强度薄钢板及其制造方法 |
US20180016656A1 (en) * | 2015-02-03 | 2018-01-18 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
US20180023160A1 (en) * | 2015-02-03 | 2018-01-25 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
US10934600B2 (en) * | 2015-02-03 | 2021-03-02 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
US11035019B2 (en) * | 2015-02-03 | 2021-06-15 | Jfe Steel Corporation | High-strength steel sheet and production method therefor |
CN104928590A (zh) * | 2015-06-11 | 2015-09-23 | 北京交通大学 | 一种Mn-Si-Cr低碳贝氏体钢、钎杆及其制备方法 |
Also Published As
Publication number | Publication date |
---|---|
EP2415891A1 (en) | 2012-02-08 |
CN102341518B (zh) | 2013-04-10 |
US8840738B2 (en) | 2014-09-23 |
US20120012231A1 (en) | 2012-01-19 |
EP2415891A4 (en) | 2014-11-19 |
CN102341518A (zh) | 2012-02-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2010114131A1 (ja) | 冷延鋼板およびその製造方法 | |
JP4977185B2 (ja) | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板およびその製造方法 | |
JP4977184B2 (ja) | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板およびその製造方法 | |
KR102220940B1 (ko) | 강판 및 도금 강판 | |
JP6048580B2 (ja) | 熱延鋼板及びその製造方法 | |
JP6017341B2 (ja) | 曲げ性に優れた高強度冷延鋼板 | |
WO2009110607A1 (ja) | 冷延鋼板 | |
JP5043248B1 (ja) | 高強度焼付硬化型冷延鋼板及びその製造方法 | |
JP5466552B2 (ja) | 伸び、伸びフランジ性および溶接性を兼備した高強度冷延鋼板 | |
WO2014061270A1 (ja) | 高強度冷延鋼板およびその製造方法 | |
JP5126844B2 (ja) | 熱間プレス用鋼板およびその製造方法ならびに熱間プレス鋼板部材の製造方法 | |
JP5860343B2 (ja) | 強度および延性のばらつきの小さい高強度冷延鋼板およびその製造方法 | |
WO2021149676A1 (ja) | 鋼板およびその製造方法 | |
EP3719155B1 (en) | High-strength cold-rolled steel sheet and method for manufacturing same | |
TW201835347A (zh) | 熱軋鋼板及其製造方法 | |
JP6837372B2 (ja) | 成形性に優れた高強度冷延鋼板及びその製造方法 | |
JP2011052295A (ja) | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板 | |
JP5302840B2 (ja) | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板 | |
KR20100076073A (ko) | 강판 및 그 제조 방법 | |
JP5483562B2 (ja) | 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板 | |
CN109642278B (zh) | 热轧钢板 | |
US11186900B2 (en) | High-strength cold rolled steel sheet and method for manufacturing the same | |
JP4867338B2 (ja) | 超高強度鋼板およびその製造方法 | |
WO2010109702A1 (ja) | 冷延鋼板 | |
JP5228963B2 (ja) | 冷延鋼板およびその製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 201080010267.9 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 10758898 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2010758898 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 13258823 Country of ref document: US |
|
WWE | Wipo information: entry into national phase |
Ref document number: 7157/CHENP/2011 Country of ref document: IN |
|
NENP | Non-entry into the national phase |
Ref country code: DE |