WO2011162135A1 - 形状凍結性に優れた冷延薄鋼板およびその製造方法 - Google Patents

形状凍結性に優れた冷延薄鋼板およびその製造方法 Download PDF

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WO2011162135A1
WO2011162135A1 PCT/JP2011/063626 JP2011063626W WO2011162135A1 WO 2011162135 A1 WO2011162135 A1 WO 2011162135A1 JP 2011063626 W JP2011063626 W JP 2011063626W WO 2011162135 A1 WO2011162135 A1 WO 2011162135A1
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cold
less
rolled
steel sheet
thin steel
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PCT/JP2011/063626
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English (en)
French (fr)
Japanese (ja)
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太郎 木津
英子 安原
藤田　耕一郎
重宏 ▲高▼城
花澤　和浩
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Ｊｆｅスチール株式会社
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Priority to CN201180031182.3A priority Critical patent/CN102947476B/zh
Priority to KR1020127033254A priority patent/KR101479391B1/ko
Priority to MX2012013968A priority patent/MX336858B/es
Publication of WO2011162135A1 publication Critical patent/WO2011162135A1/ja

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—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
    • C21D8/0421—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 characterised by the working steps
    • C21D8/0436—Cold 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
    • C21D8/04—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
    • C21D8/0421—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 characterised by the working steps
    • C21D8/0442—Flattening; Dressing; Flexing
    • 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
    • C21D8/0447—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 characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing
    • 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
    • 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
    • C22C38/04—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
    • C22C38/28—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
    • 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

Definitions

  • the present invention relates to a cold-rolled thin steel sheet suitable for structural members such as electrical appliances, office equipment, and automobile members, and particularly suitable for members requiring high dimensional accuracy after press forming.
  • the present invention relates to a cold-rolled thin steel sheet having excellent freezing properties.
  • the “thin steel plate” is a steel plate having a thickness of 0.2 to 2.0 mm, and includes a steel plate and a steel strip.
  • Patent Document 1 discloses that the average value of the X-ray random intensity ratio of ⁇ 100 ⁇ ⁇ 011> to ⁇ 223 ⁇ ⁇ 110> orientation group is 3.0 or more and ⁇ 554 ⁇ ⁇ 225>, ⁇ 111 ⁇ ⁇ 112>, ⁇ 111 ⁇ ⁇ 110> Three crystal orientations of X-ray random intensity ratio of the average value of 3.5 or less to develop a texture with a specific orientation, further rolling direction A ferritic thin steel sheet having excellent shape freezing properties, mainly bending, in which at least one of the r value and the r value perpendicular to the rolling direction is 0.7 or less is described. The steel sheet described in Patent Document 1 is markedly improved in bend formability, has a small amount of springback, and is excellent in shape freezing, mainly bending.
  • Patent Document 2 has a structure in which an island-like structure including martensite is dispersed in a ferrite matrix, the surface average roughness Ha is 0.4 to 1.8 ⁇ m, and the PPI value is 80 or more at a 0.5 ⁇ m count level.
  • the object of the present invention is to solve the problems of the prior art and propose a cold-rolled thin steel sheet having excellent shape freezing property and a method for producing the same.
  • the present inventors have intensively studied various factors affecting the shape freezing property.
  • the present inventors consider that the defective shape of the product (member) at the time of press molding is caused by the elastic strain introduced at the time of press molding being released when the product (member) is taken out from the press mold, We focused on the proportional limit of the steel sheet.
  • the proportional limit is the limit of stress that can maintain a proportional relationship with strain when an external force is applied to the elastic body. While the stress is small, Hooke's law holds, so a proportional relationship is seen.
  • Steel plates having various proportional limits were prepared, parts of a predetermined shape were formed by press forming, and the shape freezing property after forming was investigated. As a result, it was found that the proportional limit of the steel plate needs to be reduced to 150 MPa or less in order to ensure the desired excellent shape freezing property.
  • the proportional limit of the steel plate is 150 MPa or less, the increase in the opening amount X is small and excellent shape freezing property can be maintained, but if the proportional limit of the steel plate exceeds 150 MPa and becomes large, the opening amount X Increases rapidly and the shape freezing property is remarkably lowered.
  • the present inventors diligently studied various factors affecting the proportional limit of the steel sheet in order to stably manufacture the steel sheet having the proportional limit described above. As a result, it was found that the proportional limit can be easily reduced by subjecting a steel sheet mainly composed of a ferrite phase having a relatively large crystal grain size to temper rolling using a roll having a small surface roughness. Next, experimental results that serve as a basis for the above-described knowledge will be described.
  • composition of 0.040% C-0.01% Si-0. 20% Mn-0.01% P-0.01% S-0.04% Al-0.003% N-balance Fe in mass% A cold-rolled annealed plate (thickness: 0.8 mm) having a structure composed of a ferrite single phase with an average crystal grain size of 10 ⁇ m was subjected to temper rolling with a rolling elongation of 1%. In temper rolling, various rolling rolls having a surface roughness Ra adjusted to 0.2 to 2.5 ⁇ m were used. A JIS No. 5 test piece was taken from each temper-rolled steel sheet so that the tensile direction was the rolling direction, and a tensile test was performed to determine the proportional limit of each steel sheet.
  • the proportional limit was obtained by performing a tensile test at a tensile speed of 1 mm / min using a tensile test piece in which a strain gauge having a length of 5 mm was attached to both sides of the parallel part.
  • the proportional limit is defined as a point at which the inclination starts to decrease as the stress increases due to the relationship between the inclination ( ⁇ / ⁇ ) of the stress-strain curve and the stress ( ⁇ ).
  • the obtained results are shown in FIG. 4 in relation to the proportional limit of the steel plate and the roll surface roughness Ra of the used roll.
  • roll surface roughness Ra was measured based on the prescription
  • FIG. 4 shows that the proportional limit of the steel sheet easily becomes 150 MPa or less when temper rolling is performed using a rolling roll having a roll surface roughness Ra of 2.0 ⁇ m or less.
  • the present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows. (1) By mass%, C: 0.10% or less, Si: 0.05% or less, Mn: 0.1 to 1.0%, P: 0.05% or less, S: 0.02% or less, A composition comprising Al: 0.02 to 0.10%, N: less than 0.005%, the balance consisting of Fe and inevitable impurities, and a structure mainly composed of a ferrite phase having an average crystal grain size d: 5 to 30 ⁇ m; A thin steel sheet obtained by subjecting a thin steel sheet having a surface roughness Ra to temper rolling using a rolling roll having a surface roughness Ra of 2.0 ⁇ m or less, and having a proportional limit of 150 MPa or less. Excellent cold rolled steel sheet.
  • the steel material is subjected to a hot-rolling step and a cold-rolling step in order to obtain a cold-rolled plate, and the cold-rolled plate is subjected to an annealing step to obtain a cold-rolled annealed plate.
  • the annealing step is performed on the cold-rolled sheet, annealing temperature: After heating for 30 s or more at a temperature in the range of 730 to 850 ° C., an annealing treatment is applied to cool to a temperature of 600 ° C.
  • a rolling roll having a surface roughness Ra of 2.0 ⁇ m or less is used, and the temper rolling elongation is d / 20 to d / 5 corresponding to the average crystal grain size d ( ⁇ m) of the cold-rolled annealed sheet.
  • % Cold rolled thin steel sheet excellent in shape freezing property characterized by being subjected to temper rolling to a range of% and producing a cold rolled thin steel sheet having a proportional limit of 150 MPa or less.
  • the cold-rolled sheet is annealed at a temperature in the range of 730 to 850 ° C. and 600 ° C. or less at an average cooling rate of 5 ° C./s or more.
  • the manufacturing method of the cold-rolled thin steel plate characterized by making it the annealing-hot-dip galvanization process process which cools to the temperature of this and performs hot-dip galvanization.
  • a cold-rolled thin steel sheet having a proportional limit of 150 MPa or less can be manufactured at low cost and stably, and the shape freezing property of the formed member can be remarkably improved, thereby producing a remarkable industrial effect.
  • C 0.10% or less
  • the content of C exceeding 0.10% makes ferrite grains finer, promotes the formation of cementite, makes it difficult to lower the proportional limit, increases hardenability, and lowers the temperature. Promotes the formation of the transformation phase, increases strength and decreases ductility. For this reason, C was limited to 0.10% or less. In addition, Preferably it is 0.05% or less. In the present invention, it is not necessary to limit the lower limit of the C content, but excessive reduction leads to an increase in production cost, so 0.0010% or more is preferable.
  • Si 0.05% or less
  • Si is an element that stabilizes ferrite, promotes the concentration of C in the ferrite, facilitates the formation of cementite, martensite, and the like, and contributes to the promotion of hardening. From the viewpoint of improving the property, it is preferable to reduce as much as possible. Moreover, Si forms Si oxide on the surface during annealing, and adversely affects surface properties, chemical conversion properties, plating properties, and the like. For these reasons, Si is limited to 0.05% or less. In addition, More preferably, it is 0.03% or less.
  • Mn 0.1 to 1.0%
  • Mn is an effective element that forms MnS and prevents hot cracking due to S, and is preferably contained according to the amount of S contained. In order to obtain such an effect, the content of 0.1% or more is required.
  • Mn is a solid solution that increases the strength of the steel and improves the hardenability and contributes to the refinement of crystal grains. A large amount of Mn causes the formation of low-temperature transformation phases such as martensite. It is difficult to promote or refine the ferrite grains to reduce the proportional limit, and to significantly reduce ductility and deteriorate workability. Such a tendency becomes prominent when the content exceeds 1.0%. For this reason, Mn was limited to the range of 0.1 to 1.0%. In applications where better workability is required, the content is desirably 0.5% or less.
  • P 0.05% or less
  • P is contained as an inevitable impurity in the steel, but has the effect of segregating at the grain boundaries and reducing the grain boundary strength. For this reason, although it is preferable to reduce as much as possible in this invention, 0.05% is accept
  • S 0.02% or less
  • S is an element that remarkably deteriorates the ductility of hot steel and induces hot cracking to significantly deteriorate the surface properties. Further, S forms coarse sulfides and lowers the ductility and toughness of steel. For this reason, it is preferable to reduce S as much as possible, but if it is up to about 0.02%, it is acceptable. Therefore, S is limited to 0.02% or less. In addition, Preferably it is 0.01% or less.
  • Al acts as a deoxidizer for steel, has the effect of improving the cleanliness of the steel, and has the effect of strongly fixing N and suppressing age hardening by N. In order to obtain such an effect, a content of 0.02% or more is required. On the other hand, inclusion exceeding 0.10% leads to deterioration of surface properties such as an increase in the amount of inclusions due to the formation of alumina. For this reason, Al was limited to the range of 0.02 to 0.10%. In addition, Preferably it is 0.05% or less.
  • N Less than 0.005% N is a solid solution that contributes to increasing the strength of the steel and has a tendency to increase the proportional limit. When it is contained in a large amount, it causes hot cracking of the slab, and the surface properties of the slab Although it is an element which has a tendency to deteriorate and it is desirable to reduce it as much as possible in the present invention, it is acceptable if it is less than 0.005%. For this reason, N was limited to less than 0.005%.
  • the above-mentioned components are basic components.
  • One or more selected from 0003 to 0.0030%, Cr: 0.1 to 1.0%, and Mo: 0.1 to 1.0% can be selected and contained.
  • Nb 0.010% or more
  • B 0.0003% or more
  • Cr 0.1% or more
  • Mo 0.1% or more
  • Ti 0.005 to 0.08%
  • Nb 0.010 to 0.030%
  • B 0.0003 to 0.0030%
  • Cr 0.1 to 1.%. It is preferable to limit to 0% and Mo: 0.1 to 1.0%, respectively.
  • the balance other than the components described above consists of Fe and inevitable impurities.
  • the thin steel sheet of the present invention has the above-described composition and further has a structure mainly composed of a ferrite phase having an average crystal grain size of 5 to 30 ⁇ m.
  • “mainly” refers to a case where the volume ratio with respect to the entire tissue is 95% or more, preferably 98% or more, more preferably 100%.
  • the second phase other than the main phase is cementite, pearlite, bainite, or the like.
  • the second phase has a volume ratio of 5% or less. When the amount of the second phase exceeds 5%, the steel plate becomes hard and formability (workability) decreases.
  • the average crystal grain size of the ferrite phase is less than 5 ⁇ m, the grain boundaries increase, so the strain during temper rolling is concentrated especially at the triple boundary of the grain boundaries, and the dislocations tend to become tandals. Tend to increase.
  • the average crystal grain size of the ferrite phase exceeds 30 ⁇ m and the crystal grains become coarse, unevenness called orange peel becomes prominent at the time of press molding, the surface property of the member is lowered, and the proportional limit is reduced. It becomes difficult to introduce necessary movable dislocations near the grain boundaries. For this reason, the average crystal grain size of the ferrite phase is limited to 5 to 30 ⁇ m.
  • the cold-rolled thin steel sheet of the present invention is a thin steel sheet obtained by subjecting a thin steel sheet having the above composition and the above structure to temper rolling using a rolling roll having a surface roughness Ra of 2.0 ⁇ m or less.
  • the surface roughness Ra of the rolling roll used for temper rolling is coarser than 2.0 ⁇ m, the strain introduced during temper rolling is concentrated on the surface layer of the steel sheet, and uniform strain can be introduced in the sheet thickness direction. In other words, the desired proportional limit cannot be reduced. For this reason, in this invention, it decided to perform the temper rolling which uses the rolling roll whose surface roughness Ra is 2.0 micrometers or less to the thin steel plate which has the above-mentioned composition and the above-mentioned structure.
  • a steel material is sequentially subjected to a hot rolling process, a cold rolling process, and an annealing process to obtain a cold rolled annealing sheet.
  • the steel material to be used is in mass%, C: 0.10% or less, Si: 0.05% or less, Mn: 0.1 to 1.0%, P: 0.0.
  • a steel material having a composition including more than seeds and the balance Fe and inevitable impurities is used.
  • the manufacturing method of the steel material is not particularly limited, but the molten steel having the above composition is melted by a conventional melting method such as a converter, and a steel material such as a slab by a conventional casting method such as a continuous casting method.
  • the steel material casting method is desirably an intermittent casting method in order to prevent macro segregation of components, but there is no problem with the ingot casting method or the thin slab casting method.
  • a hot rolling process and a cold rolling process are sequentially performed on the steel material having the above composition to obtain a cold rolled sheet.
  • the hot rolling process is not limited as long as the steel material is heated, subjected to hot rolling, and then subjected to a winding process to produce a hot-rolled sheet having a desired dimension and shape. Absent.
  • the obtained hot-rolled sheet is subjected to a cold-rolling step to obtain a cold-rolled sheet.
  • the hot rolled sheet is pickled and then cold rolled to obtain a cold rolled sheet.
  • any conventional pickling method can be applied.
  • the cold rolling should just be made into the cold-rolled board of a predetermined dimension shape, and all the normal cold rolling conditions can be applied.
  • the annealing process is a process in which the cold-rolled sheet is subjected to an annealing process of heating to a temperature of 600 ° C. or less at an average cooling rate of 5 ° C./s after heating the cold rolled sheet at a temperature in the range of 730 to 850 ° C. for 30 s or more.
  • a cold-rolled annealed plate having a structure mainly composed of a ferrite phase having an average crystal grain size d: 5 to 30 ⁇ m is obtained.
  • the annealing temperature is less than 730 ° C., it is difficult to complete recrystallization of ferrite processed by cold rolling, and coarse ferrite grains having an average crystal grain size of 5 ⁇ m or more cannot be secured.
  • the annealing temperature is higher than 850 ° C., the transformation to austenite proceeds and transforms to fine ferrite during cooling, or transforms to a low temperature transformation phase, and the ferrite fraction decreases. Therefore, the annealing temperature is preferably limited to a temperature in the range of 730 to 850 ° C.
  • the holding (heating) time at the annealing temperature is preferably 30 s or more.
  • the upper limit of the heating time is not particularly limited, but is preferably about 200 s or less from the viewpoint of productivity.
  • the cooling after annealing in the annealing step is preferably performed from the annealing temperature to 600 ° C. or less at an average cooling rate of 5 ° C./s or more.
  • the cooling rate after annealing is less than 5 ° C./s on average, the growth of ferrite grains is promoted, and a ferrite structure having a desired grain size range cannot be obtained.
  • it is not necessary to limit the upper limit of the cold rolling rate after annealing but special cooling equipment is required for rapid cooling with rapid cooling exceeding 30 ° C./s, so cooling at 30 ° C./s or less. It is preferable to cool at a rate. If the cooling stop temperature exceeds 600 ° C.
  • a low temperature transformation phase may be formed by subsequent cooling. For this reason, cooling after annealing was decided to cool to 600 ° C. or lower at an average cooling rate of 5 ° C./s or higher. In addition, it is not necessary to prescribe
  • the cold-rolled sheet is annealed at a temperature in the range of 730 to 850 ° C., and the average cooling rate of 5 ° C./s or more is 600 ° C. or less. It is good also as an annealing-hot galvanization process process which cools to temperature and performs hot dip galvanization.
  • a hot dip galvanizing treatment may be performed by continuously dipping in a normal hot dip galvanizing bath near 480 ° C. using a continuous hot dip galvanizing line.
  • a plating layer alloying treatment step may be performed in which the hot dip galvanized layer is an alloyed hot dip galvanized layer.
  • the alloying treatment may be a reheating treatment in a temperature range of 500 ° C. or higher and lower than 600 ° C. according to a conventional method.
  • a cold-rolled annealed plate (plated plate) that has undergone such a hot-rolling step, a cold-rolling step, an annealing step, or an annealing-hot-dip galvanizing treatment step is mainly composed of a ferrite phase having an average crystal grain size of 5 ⁇ m to 30 ⁇ m. It becomes a cold-rolled annealed plate (plated plate) having a texture to be formed. In addition, you may form a chemical conversion treatment film in the obtained cold-rolled annealing board (plating board) further.
  • the cold-rolled annealed plate (plated plate) is then subjected to temper rolling using a rolling roll having a surface roughness Ra of 2.0 ⁇ m or less.
  • the surface roughness Ra of the rolling roll to be used exceeds 2.0 ⁇ m, the proportional limit of 150 MPa or less cannot be stably secured as shown in FIG.
  • the lower limit of the surface roughness Ra of the rolling roll to be used is not particularly limited. However, when the surface roughness Ra of the rolling roll to be used is reduced, the surface roughness of the obtained steel sheet is also reduced, and the frictional resistance of the steel sheet is reduced. Thus, when the coil is wound up, the coil is easily wound and crushed easily. For this reason, it is preferable that surface roughness Ra of the rolling roll to be used shall be 0.2 micrometer or more. In addition, the surface roughness Ra shall use the value measured based on prescription
  • the elongation ratio (temper rolling elongation ratio) R (%) in temper rolling is (0.05 to 0. 0), where d ( ⁇ m) is the average crystal grain size of the cold-rolled annealed sheet as the material to be rolled. 20) It is good to set it as d.
  • the reason is as follows. By applying temper rolling, movable dislocations are introduced and the proportional limit is reduced. However, movable dislocations introduced by temper rolling are likely to be introduced in the vicinity of grain boundaries. Therefore, in order to effectively introduce movable dislocations necessary for reducing the desired proportional limit to the vicinity of grain boundaries, the larger the ferrite grain size, It is necessary to increase the temper rolling elongation.
  • FIG. 5 shows the relationship between the proportional limit (MPa) of the temper-rolled steel sheet and R / d.
  • FIG. 5 shows the result of temper rolling using a steel sheet having an average ferrite grain size d of 5 to 20 ⁇ m and a rolling roll having a surface roughness Ra of 0.2 to 1.8 ⁇ m.
  • FIG. 5 shows that the proportional limit of the steel sheet is 150 MPa or less when R / d is between 0.05 and 0.20.
  • the temper rolling elongation rate R (%) is less than 0.05 d, the rolling amount of the temper rolling is insufficient, the desired movable dislocation cannot be introduced, and the desired low proportional limit cannot be ensured.
  • the amount of reduction exceeds 0.20d, the introduced dislocations are tangled, and the movable dislocation that effectively contributes to the reduction of the proportional limit is insufficient, and a desired low proportional limit cannot be secured.
  • the temper rolling elongation rate R (%) was limited to the range of (0.05-0.20) d corresponding to the ferrite average crystal grain size d.
  • a steel material having the composition shown in Table 1 is heated to 1200 ° C., subjected to hot rolling at a final pass exit temperature of 900 ° C., wound at 550 ° C., and a sheet thickness of 2.6 mm.
  • a hot rolling process was applied.
  • the obtained thin hot-rolled sheet was pickled and then cold-rolled to give a cold-rolled step of forming a cold-rolled sheet having a thickness of 0.8 mm.
  • the obtained cold-rolled sheet was subjected to an annealing process in which annealing treatment was performed under the conditions of annealing temperature, holding time, and cooling rate shown in Table 2 to obtain a thin cold-rolled annealed sheet.
  • the cooling rate was an average from the annealing temperature to 600 ° C.
  • Some steel sheets were subjected to an annealing-hot dip galvanizing process under the conditions shown in Table 2 instead of the annealing process.
  • a hot dip galvanizing treatment in which the plating bath was continuously immersed in a hot dip galvanizing bath at a temperature of 480 ° C. was performed following the annealing treatment.
  • Some steel sheets were subjected to alloying treatment at the temperatures shown in Table 2 after the hot dip galvanizing treatment.
  • the particle size and the texture fraction were determined.
  • the average crystal grain size of the ferrite phase was determined by a cutting method for an area of 200 ⁇ 200 ⁇ m using an optical microscope (magnification: 100 times).
  • the structure fraction of the ferrite phase was calculated using an image analysis apparatus by capturing two images of a 200 ⁇ 200 ⁇ m region using an optical microscope (magnification: 100 times). The second phase other than ferrite was also observed.
  • Table 2 The structure observation results are also shown in Table 2.
  • the obtained cold-rolled annealed plate (plated plate) was tempered with a temper rolling elongation R (%) shown in Table 2 using a rolling roll having a surface roughness Ra ( ⁇ m) shown in Table 2.
  • the surface roughness Ra of the rolling roll was measured in accordance with the provisions of JIS B 0601-2001.
  • electrogalvanizing treatment was performed after temper rolling.
  • a JIS No. 5 test piece (GL: 50 mm) is sampled from a temper-rolled thin steel sheet (thin-plated steel sheet) so that the test direction is the rolling direction, and a tensile test is performed in accordance with the provisions of JIS Z 2241.
  • Tensile properties (yield strength YS, tensile strength TS, elongation El) were determined. Further, from the obtained thin steel sheet, a JIS No. 5 test piece was sampled so that the test direction was the rolling direction, and a tensile test was performed to obtain a proportional limit. The proportional limit is determined by performing a tensile test at a tensile speed of 1 mm / min using a tensile test piece affixed to strain gauges (gauge length: 5 mm) on both sides of the parallel portion, and the slope of the stress-strain curve ( ⁇ / ⁇ ). It calculated
  • All of the examples of the present invention are thin steel sheets having a structure mainly composed of a ferrite phase having an average crystal grain size of 5 to 30 ⁇ m and a low proportional limit of 150 MPa or less.
  • the proportional limit exceeds 150 MPa.

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PCT/JP2011/063626 2010-06-23 2011-06-08 形状凍結性に優れた冷延薄鋼板およびその製造方法 WO2011162135A1 (ja)

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CN104870678A (zh) * 2012-10-11 2015-08-26 杰富意钢铁株式会社 形状冻结性优异的冷轧钢板及其制造方法
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CN114959491A (zh) * 2022-06-20 2022-08-30 武汉钢铁有限公司 一种采用短流程生产的350MPa级高耐蚀涂镀薄钢板及方法

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KR20150075014A (ko) * 2013-12-24 2015-07-02 주식회사 포스코 압연강판 및 그의 제조방법
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JP6119628B2 (ja) * 2014-02-05 2017-04-26 Ｊｆｅスチール株式会社 比例限が高く、曲げ加工性に優れた高強度冷延薄鋼板およびその製造方法
JP6086078B2 (ja) * 2014-02-05 2017-03-01 Ｊｆｅスチール株式会社 伸びフランジ性に優れた高強度冷延鋼板およびその製造方法
JP6086077B2 (ja) * 2014-02-05 2017-03-01 Ｊｆｅスチール株式会社 加工性に優れた高強度冷延鋼板およびその製造方法
CN105441795B (zh) * 2014-08-22 2017-10-27 上海梅山钢铁股份有限公司 一种led引线框架用低碳冷轧钢板及其生产方法
CN107614722B (zh) * 2015-05-07 2019-08-27 日本制铁株式会社 高强度钢板及其制造方法
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CN104870678A (zh) * 2012-10-11 2015-08-26 杰富意钢铁株式会社 形状冻结性优异的冷轧钢板及其制造方法
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CN114959491A (zh) * 2022-06-20 2022-08-30 武汉钢铁有限公司 一种采用短流程生产的350MPa级高耐蚀涂镀薄钢板及方法

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MX2012013968A (es) 2012-12-17
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MY162617A (en) 2017-06-30

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