WO2018181450A1 - 鋼板およびその製造方法と王冠およびdrd缶 - Google Patents
鋼板およびその製造方法と王冠およびdrd缶 Download PDFInfo
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- WO2018181450A1 WO2018181450A1 PCT/JP2018/012698 JP2018012698W WO2018181450A1 WO 2018181450 A1 WO2018181450 A1 WO 2018181450A1 JP 2018012698 W JP2018012698 W JP 2018012698W WO 2018181450 A1 WO2018181450 A1 WO 2018181450A1
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- crown
- drd
- steel sheet
- steel
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 163
- 239000010959 steel Substances 0.000 title claims abstract description 163
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 61
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims description 58
- 238000005097 cold rolling Methods 0.000 claims description 44
- 238000005096 rolling process Methods 0.000 claims description 44
- 239000000463 material Substances 0.000 claims description 27
- 238000000137 annealing Methods 0.000 claims description 23
- 238000005098 hot rolling Methods 0.000 claims description 16
- 238000005554 pickling Methods 0.000 claims description 14
- 238000000465 moulding Methods 0.000 abstract description 16
- 239000002245 particle Substances 0.000 abstract description 4
- 230000037303 wrinkles Effects 0.000 description 26
- 230000007547 defect Effects 0.000 description 21
- 238000002791 soaking Methods 0.000 description 18
- 238000010438 heat treatment Methods 0.000 description 16
- 238000000034 method Methods 0.000 description 15
- 230000007423 decrease Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 7
- 230000001771 impaired effect Effects 0.000 description 7
- 238000007747 plating Methods 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 238000004804 winding Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229920006395 saturated elastomer Polymers 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000001953 recrystallisation Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000010306 acid treatment Methods 0.000 description 2
- 235000013361 beverage Nutrition 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 2
- 238000010191 image analysis Methods 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000004080 punching Methods 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 239000005029 tin-free steel Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 235000013334 alcoholic beverage Nutrition 0.000 description 1
- 235000013405 beer Nutrition 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 235000014171 carbonated beverage Nutrition 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 235000014214 soft drink Nutrition 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- 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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Definitions
- the present invention relates to a steel sheet, particularly a high-strength thin steel sheet having excellent formability and a method for producing the same.
- Typical examples of such steel plates include DRD (Drawing and Redrawing) cans formed by combining drawing and redrawing, as well as thin steel plates that serve as crown materials used as stoppers for glass bottles and the like.
- the present invention relates to a crown and a DRD can obtained by forming the steel plate.
- crowns are widely used for narrow-mouthed glass bottles.
- a crown is manufactured by press-molding a thin steel plate, and consists of a disk-shaped part that closes the mouth of the bottle and a bowl-shaped part around it. Seal the jar by caulking.
- Bottles that use crowns are often filled with high internal pressure contents such as beer and carbonated drinks. For this reason, even when the internal pressure increases due to a change in temperature or the like, the crown needs to have high pressure strength so that the crown is not deformed and the sealing of the bottle is not broken. Moreover, even if the strength of the material is sufficient, if the material uniformity of the steel plate used for the crown is low, the shape of the crown is not uniform, and those that are out of product specifications are included. Even if such a poorly shaped crown is caulked to the mouth of the bottle, sufficient sealing performance may not be obtained. Therefore, the steel plate used as the crown material must also be excellent in material uniformity.
- SR (Single Reduced) steel sheet is mainly used for the thin steel sheet used for the crown material.
- annealing is performed and temper rolling is performed.
- the sheet thickness of conventional steel plates for crowns is generally 0.22 mm or more, and sufficient compressive strength and formability are ensured by applying SR material made of mild steel used for food and beverage cans and the like. It was possible.
- the center of the crown is squeezed to some extent in the initial stage of molding, and then the outer edge is molded into a bowl shape.
- the material of the crown is a steel plate with low material uniformity
- the crown manufactured from the steel plate may have irregular outer diameters and heights, which may be out of product specifications. If the outer diameter and height of the crown become uneven, and there are things that deviate from the product specification, there is a problem that the yield when a large number of crowns are manufactured decreases. Furthermore, a crown whose outer diameter and height are out of specification is liable to cause leakage of contents during transportation after being plugged into a bottle, and has a problem that it does not serve as a lid. Even if the outer diameter and height of the crown are within the product specification, if the steel plate strength is low, the crown may be removed due to insufficient pressure strength.
- the steel sheet described in Patent Document 1 uses steel containing 0.0060% or less of C, and has a predetermined relationship between the tension between the stands and the annealing temperature in secondary cold rolling. Value (direction / size) is obtained. Since this method does not control the hot rolling process that affects the formation of the metal structure, the obtained steel sheet has a large variation in material, and is difficult to put into practical use.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a steel plate having sufficient strength and excellent formability even when it is thinned, and a method for manufacturing the steel plate. Furthermore, an object of the present invention is to provide a crown and a DRD can which are adjusted to a predetermined size and shape and have excellent shape stability.
- the inventors diligently studied how to solve the above-mentioned problems, and found that high strength and excellent formability can be imparted by regulating the structure under a predetermined component composition.
- the present invention is derived from this finding, and the gist of the present invention is as follows.
- a DRD can comprising the steel plate according to (1) or (2).
- the present invention it is possible to provide a steel sheet having sufficient strength even when thinned and having excellent material uniformity together with its advantageous manufacturing method. Furthermore, when the steel plate of the present invention is used for, for example, a crown or a DRD can, a crown or a DRD can having no shape distortion can be formed.
- the steel sheet according to the present invention is in mass%, C: more than 0.0060% and 0.0100% or less, Si: 0.05% or less, Mn: 0.05% or more and 0.60% or less, P: 0.050. %: S: 0.050% or less, Al: 0.020% or more and 0.050% or less, N: 0.0070% or more and 0.0140% or less, with the balance being Fe and inevitable impurities It has a composition and has a ferrite phase in a region from a depth of 1 ⁇ 4 of the plate thickness to the center of the plate thickness, and the standard deviation of the ferrite grain size in the ferrite phase is 7.0 ⁇ m or less.
- the "%" display regarding a component shows "mass%".
- the C content is 0.0060% or less
- the ferrite of the steel sheet after the secondary cold rolling described later becomes coarse and the formability deteriorates.
- the outer diameter and the height of the formed crown are not uniform.
- wrinkles are generated in the flange portion when the DRD can is formed, resulting in a poorly shaped can.
- the C content exceeds 0.0100%, the ferrite of the steel sheet after the secondary cold rolling becomes too fine, the steel sheet strength is excessively increased, and the formability deteriorates, for example, when used for a crown Further, the outer diameter and height of the molded crown are not uniform. Similarly, when it is used for a DRD can, for example, wrinkles are generated in the flange portion when the DRD can is formed, resulting in a poorly shaped can. Therefore, the C content is more than 0.0060% and 0.0100% or less. Preferably, the C content is 0.0065% or more and 0.0090% or less.
- Si 0.05% or less
- the Si content is 0.05% or less.
- the Si content is preferably 0.004% or more. More preferably, it is 0.01% or more and 0.03% or less.
- Mn 0.05% or more and 0.60% or less
- the Mn content is 0.05% or more.
- the Mn content is set to 0.60% or less.
- the Mn content is 0.10% or more and 0.50% or less.
- the steel sheet is hardened and the corrosion resistance is lowered. Further, the standard deviation of the ferrite grain size after annealing exceeds 7.0 ⁇ m and the formability deteriorates. For example, when used for a crown, the uniformity of the outer diameter and height of the crown is impaired. When used for cans, it leads to shape defects that cause wrinkles in the flanges during DRD can molding. Therefore, the upper limit of the P content is 0.050%. Further, in order to make P less than 0.001%, the removal P cost becomes excessive, so the content of P is preferably made 0.001% or more.
- S 0.050% or less S combines with Mn in a steel plate to form MnS, and precipitates in a large amount to lower the hot ductility of the steel plate. This effect becomes significant when the S content exceeds 0.050%. Therefore, the upper limit of the S content is 0.050%. Further, in order to make S less than 0.005%, the removal S cost becomes excessive, so the S content is preferably made 0.004% or more.
- Al 0.020% or more and 0.050% or less
- Al is an element to be contained as a deoxidizing agent, and forms N and AlN in the steel to reduce the solid solution N in the steel. If the Al content is less than 0.020%, the effect as a deoxidizer becomes insufficient, causing solidification defects and increasing the steelmaking cost. Also, if the amount of Al is less than 0.020%, an appropriate amount of AlN cannot be ensured during recrystallization of ferrite during annealing, so the standard deviation of the ferrite grain size after annealing increases, and after secondary cold rolling The ferrite of the steel sheet becomes coarse and the formability deteriorates.
- the uniformity of the outer diameter and height of the crown is impaired, and when used for a DRD can, for example, it leads to a shape defect that causes wrinkles in the flange portion during DRD can molding.
- the Al content exceeds 0.050%, the formation of AlN increases, the amount of N contributing to the steel sheet strength as solute N described later decreases, and the steel sheet strength decreases. Is 0.050% or less.
- the Al content is 0.030% or less and 0.045% or less.
- N 0.0070% or more and 0.0140% or less
- the ferrite of the steel sheet after the secondary cold rolling becomes coarse and the formability deteriorates.
- the outer diameter and height of the molded crown are not uniform, and the amount of N that contributes to the steel sheet strength as solute N described later is reduced, and the steel sheet strength is reduced.
- wrinkles are generated in the flange portion when the DRD can is formed, resulting in a poorly shaped can.
- the N content exceeds 0.0140%, the ferrite of the steel sheet after the secondary cold rolling becomes too fine, the steel sheet strength is excessively increased and the formability deteriorates, for example, when used for a crown.
- the uniformity of the outer diameter and height of the crown is impaired.
- the N content is 0.0085 or more and 0.0125% or less. More preferably, it is over 0.0100%.
- the balance other than the above components is Fe and inevitable impurities.
- the metal structure of the steel sheet according to the present invention has a ferrite phase at least in a region from a depth of 1 ⁇ 4 of the plate thickness to the center of the plate thickness, and the standard deviation of the ferrite grain size in the ferrite phase is 7 It is important that the thickness is 0.0 ⁇ m or less.
- the metal structure of the steel sheet of the present invention is preferably composed mainly of a ferrite phase, the balance being cementite, and the ferrite phase being 85% by volume or more. More preferably, it is 90% or more. That is, when the ferrite phase is less than 85% by volume, breakage tends to occur starting from hard cementite during processing, and formability deteriorates.
- the standard deviation of the ferrite grain size in the ferrite phase in the region from at least a quarter of the plate thickness to the center of the plate thickness is set to 7.0 ⁇ m or less. That is, when the standard deviation of the ferrite grain size exceeds 7.0 ⁇ m, the formability deteriorates. For example, when used for a crown, the outer diameter and height of the crown after molding become non-uniform, and the pressure strength decreases. At the same time, the yield when manufacturing the crown decreases. Similarly, when it is used for a DRD can, for example, wrinkles are generated in the flange portion when the DRD can is formed, resulting in a poorly shaped can. Preferably, the standard deviation of the ferrite grain size is not more than 6.5 ⁇ m.
- the ferrite microstructure is corroded with a corrosive liquid (3% by volume nital) after polishing a cross section in the plate thickness direction parallel to the rolling direction of the steel plate, and the plate thickness is 1 with an optical microscope over 10 fields of view at 400 ⁇ magnification. / 4 Observe the region from the depth position (in the cross section, 1/4 position of the plate thickness in the thickness direction from the surface) to 1/2 position of the plate thickness, and use the microstructure photograph taken with an optical microscope Is determined by visual judgment, and the particle size of the ferrite is determined by image analysis.
- the particle size distribution of the ferrite grain size is obtained for each field of view, the standard deviation is calculated, and the value obtained by averaging the standard deviations of the 10 fields of view is taken as the standard deviation of the ferrite grain size.
- Olympus Corporation's image analysis software “Stream Essentials” was used for the image analysis.
- the desired metallographic structure is adjusted by adjusting the component composition, adjusting the heating temperature in the hot rolling process, the finishing rolling temperature, the rolling reduction and winding temperature of the final stand, adjusting the rolling reduction of the primary cold rolling, and continuously. It can be obtained by adjusting the cooling rate in the annealing process and adjusting the rolling reduction in the secondary cold rolling process. Details of the manufacturing conditions will be described later.
- a high strength specifically a yield strength of 560 MPa or more
- the steel plate of the present invention is required to have a pressure strength that prevents the crown crimped on the mouth of the bottle from being removed by the internal pressure when the steel plate is used, for example.
- the steel plate for crowns that has been used conventionally has a thickness of 0.22 mm or more, but in order to reduce the thickness to 0.20 mm or less, particularly 0.18 mm or less, higher strength is required than before. .
- the yield strength of the steel sheet is less than 560 MPa, it is impossible to give sufficient pressure resistance to the thin crown as described above.
- the yield strength needs to be 560 MPa or more. Furthermore, in order to ensure sufficient pressure resistance, the yield strength is preferably 600 MPa or more. If the yield strength is too high, the crown height becomes low at the time of crown molding and the crown shape becomes non-uniform, so the yield strength in the rolling direction is preferably 700 MPa or less. More preferably, it is 600 MPa or more and 680 MPa or less.
- yield strength can be measured by a metal material tensile test method shown in “JIS Z 2241”.
- a steel material (steel slab) having the above composition is heated at 1200 ° C. or higher, the finish rolling temperature is 870 ° C. or higher, and the rolling reduction of the final stand is 10% or higher.
- the holding time is 60 seconds or less, and the temperature is cooled to 450 ° C.
- the temperature specification is based on the surface temperature of the steel sheet.
- the average cooling rate is a value obtained by calculation based on the surface temperature. For example, the average cooling rate from the soaking temperature to a temperature range of 450 ° C. or less is ((soaking temperature ⁇ (temperature range of 450 ° C. or less)) / cooling time from the soaking temperature to (temperature range of 450 ° C. or less) ).
- the “temperature range of 450 ° C. or lower” in the above equation means a cooling stop temperature in the temperature range.
- the molten steel is adjusted to the above chemical components by a known method using a converter or the like, and then, for example, a slab by a continuous casting method is used as a steel material.
- Step material heating temperature 1200 ° C or higher
- the heating temperature of the steel material in the hot rolling process is set to 1200 ° C. or higher.
- the heating temperature is less than 1200 ° C.
- the amount of solute N necessary for securing strength in the present invention is reduced and the strength is lowered, so that the heating temperature is 1200 ° C. or higher.
- N in the steel is mainly present as AlN. Therefore, the total amount of N (Ntotal) minus the amount of N present as AlN (NasAlN) is subtracted (Ntotal ⁇ (NasAlN)). The amount of dissolved N was considered.
- the solute N amount is preferably 0.0071% or more, and can be ensured by setting the steel material heating temperature to 1200 ° C. or more.
- a more preferable amount of solute N is 0.0090% or more.
- the heating temperature of the steel material is preferably 1220 ° C. or more. Even if the steel material heating temperature exceeds 1300 ° C., the effect is saturated, so 1300 ° C. or less is preferable.
- the finishing temperature in the hot rolling process is less than 870 ° C.
- a part of the ferrite of the steel sheet becomes fine, and the standard deviation of the ferrite grain size exceeds 7.0 ⁇ m and the formability deteriorates.
- the finishing temperature is 870 ° C. or higher.
- raising the finish rolling temperature more than necessary may make it difficult to produce a thin steel sheet.
- the finish rolling temperature is preferably in the temperature range of 870 ° C. or more and 950 ° C. or less.
- the rolling reduction of the final stand in the hot rolling process is 10% or more.
- the rolling reduction of the final stand is less than 10%, a part of the ferrite of the steel sheet becomes coarse, and the standard deviation of the ferrite exceeds 7.0 ⁇ m, and the formability deteriorates. Then, for example, when it is used for a crown, the crown shape becomes non-uniform, and when it is used for a DRD can, for example, it leads to a shape defect in which a wrinkle is generated in the flange portion at the time of DRD can molding. Therefore, the rolling reduction of the final stand is 10% or more.
- the rolling reduction of the final stand is preferably 12% or more.
- the upper limit of the rolling reduction of the final stand is preferably 15% or less from the viewpoint of rolling load.
- Winding temperature 550-750 ° C
- the winding temperature is set to 550 ° C. or higher.
- the coiling temperature is higher than 750 ° C.
- a part of the ferrite of the steel sheet becomes coarse, and the standard deviation of the ferrite exceeds 7.0 ⁇ m.
- the crown shape becomes non-uniform.
- the coiling temperature is 750 ° C. or lower.
- they are 600 degreeC or more and 700 degrees C or less.
- pickling is preferably performed.
- the pickling is not particularly limited as long as the surface scale can be removed.
- the cold rolling is performed in two steps with the annealing interposed therebetween.
- Primary cold rolling reduction 88% or more
- the rolling reduction in the primary cold rolling process is 88% or more.
- the strain imparted to the steel sheet by cold rolling decreases, so recrystallization in the continuous annealing process becomes non-uniform and the standard deviation of ferrite is over 7.0 ⁇ m.
- the moldability deteriorates.
- the rolling reduction in the primary cold rolling process is set to 88% or more. More preferably, the content is 89 to 94%.
- the soaking temperature in the continuous annealing step is 660 to 760 ° C.
- the soaking temperature is higher than 760 ° C., it is easy to cause troubles such as a heat buckle during continuous annealing, which is not preferable.
- the ferrite grain size of the steel sheet is partially coarsened, the standard deviation of the ferrite is over 7.0 ⁇ m, for example, when used for a crown, the crown shape becomes non-uniform, for example, when used for a DRD can, This leads to a shape defect in which wrinkles are generated in the flange part during DRD can molding.
- the annealing temperature is less than 660 ° C., the recrystallization becomes incomplete, the ferrite grain size of the steel sheet becomes partly fine, and the standard deviation of the ferrite grain size exceeds 7.0 ⁇ m.
- the crown shape becomes non-uniform, and when used for a DRD can, for example, it leads to a shape defect that causes wrinkles in the flange portion when the DRD can is formed. Therefore, the soaking temperature is 660 to 760 ° C. Preferably, the temperature is 680 to 730 ° C.
- the holding time when the soaking temperature is in the temperature range of 660 to 760 ° C is 60 seconds or less.
- C contained in the steel sheet segregates to the ferrite grain boundary, precipitates as carbides in the cooling process in the continuous annealing process, reduces the amount of solute C contributing to the steel sheet strength, and yield. Strength decreases.
- the holding time when the soaking temperature is in the temperature range of 660 to 760 ° C. is set to 60 seconds or less.
- the holding time is less than 5 seconds, the stability when the steel plate passes through the soaking roll is impaired, and therefore the holding time is preferably 5 seconds or more.
- Pre-cooling Cooling to 450 ° C or less at an average cooling rate of 10 ° C / s or more
- After the soaking it is cooled to a temperature range of 450 ° C. or lower at an average cooling rate of 10 ° C./s or higher.
- the average cooling rate is less than 10 ° C./s
- carbide precipitation is promoted during cooling, the amount of solute C contributing to the steel plate strength is reduced, and the yield strength is reduced.
- a shape defect that causes wrinkles in the flange portion at the time of forming the DRD can results.
- an average cooling rate since said effect will be saturated when an average cooling rate exceeds 50 degrees C / s, it is preferable that an average cooling rate shall be 50 degrees C / s or less.
- carbide precipitation is promoted after the former stage cooling, the amount of solute C contributing to the steel sheet strength is reduced, and the yield strength is lowered.
- a steel plate is used for, for example, a DRD can, a shape defect in which wrinkles are generated in the flange portion when the DRD can is formed is caused.
- the cooling stop temperature in the pre-cooling after soaking is less than 300 ° C., not only the carbide precipitation suppression effect is saturated, but the steel plate shape deteriorates when passing and the steel plate cannot be cooled uniformly, for example, crown
- the crown stop shape is uneven. It is preferable to set it to 300 degreeC or more.
- the average cooling rate in the subsequent cooling is preferably 30 ° C./s or less. More preferably, it is 25 ° C./s or less.
- the average cooling rate in the subsequent cooling is preferably 30 ° C./s or less. More preferably, it is 25 ° C./s or less.
- it is cooled to 140 ° C. or lower. If it exceeds 140 ° C., the amount of solute C that contributes to the strength of the steel sheet decreases, and the yield strength decreases.
- a steel plate is used for, for example, a DRD can, a shape defect in which wrinkles are generated in the flange portion when the DRD can is formed is caused.
- the cooling stop temperature is less than 100 ° C., the effect is saturated, and an excessive cost is generated in the cooling facility. More preferably, it is 120 ° C. or higher.
- the steel sheet of the present invention can obtain high yield strength by the second cold rolling after annealing. That is, when the rolling reduction of secondary cold rolling is less than 10%, sufficient yield strength cannot be obtained.
- the rolling reduction of secondary cold rolling exceeds 40%, for example, when the steel sheet is used for a crown, the uniformity of the crown shape is impaired.
- the rolling reduction of secondary cold rolling shall be 10% or more and 40% or less. More preferably, the rolling reduction of secondary cold rolling is more than 15% and 35% or less.
- the cold-rolled steel sheet obtained as described above is then subjected to plating treatment such as tin plating, chromium plating, nickel plating, etc., for example, by electroplating on the surface of the steel sheet, if necessary, to form a plating layer.
- plating treatment such as tin plating, chromium plating, nickel plating, etc.
- electroplating on the surface of the steel sheet, if necessary, to form a plating layer.
- the steel sheet of the present invention can have sufficient strength and excellent material uniformity even if it is thinned. Therefore, the steel sheet of the present invention is particularly suitable as a material for crowns or DRD cans.
- the crown of the present invention is formed using the steel plate described above.
- the crown is mainly composed of a disk-shaped part that closes the mouth of the bottle and a bowl-shaped part provided around the disk-shaped part.
- the crown of the present invention can be formed by press molding after punching the steel plate of the present invention into a circular blank. Since the crown of the present invention is manufactured from a steel sheet having sufficient yield strength and excellent material uniformity, it has excellent pressure resistance as a crown even when it is thinned, and has an outer diameter and high crown. Since the uniformity of the height is excellent, the yield in the crown manufacturing process is improved, and the amount of waste generated by the crown manufacturing is reduced.
- the DRD can of the present invention is formed using the steel plate described above.
- the DRD can be formed by punching the steel sheet of the present invention into a circular blank and then performing drawing and redrawing. Since the DRD can made of the steel plate of the present invention has a uniform shape and does not deviate from the product standard, the yield in the DRD can manufacturing process is improved, and the amount of waste generated in the DRD can manufacturing is reduced. Have.
- Steel slabs were obtained by containing the component composition shown in Table 1, with the balance being made of Fe and unavoidable impurities in a converter and continuously cast.
- the steel slab obtained here was subjected to hot rolling at the slab heating temperature, finish rolling temperature, and winding temperature shown in Table 2. After this hot rolling, pickling was performed. Next, primary cold rolling was performed at the rolling reduction shown in Table 2, and continuous annealing was performed under the continuous annealing conditions shown in Table 2, followed by secondary cold rolling at the rolling reduction shown in Table 2.
- the obtained steel sheet was continuously subjected to electrolytic chromic acid treatment to obtain tin-free steel.
- the steel sheet obtained in accordance with the above was subjected to a heat treatment equivalent to paint baking at 210 ° C. for 15 minutes and then subjected to a tensile test.
- the tensile test was performed according to “JIS Z 2241” using a JIS No. 5 size tensile test piece, and the yield strength in the rolling direction was measured.
- the heat treatment equivalent to this paint baking does not affect the steel plate material before the heat treatment.
- the obtained steel sheet was subjected to a heat treatment equivalent to paint baking at 210 ° C. for 15 minutes, and then formed into a DRD can, and the DRD can formability was evaluated. That is, using a circular blank having a diameter of 158 mm, drawing and redrawing were performed, a DRD can having an inner diameter of 82.8 mm and a flange diameter of 102 mm was formed, and DRD can moldability was evaluated. In the evaluation, a sample in which three or more fine wrinkles are visually observed in the flange portion was evaluated as “x”, and a sample in which the fine wrinkles in the flange portion were two or less locations was evaluated as “good”. The evaluation results are shown in Table 2.
- the steel sheets of Nos. 1 to 22 which are examples of the present invention have a yield strength in the rolling direction of 560 MPa or more and a standard deviation of the crown height of 0.09 mm or less, and the crown formability is good. I understand. Furthermore, the number of wrinkles generated in DRD can molding was 2 or less, and the DRD can moldability was also good.
- Steel plates No. 26 to 28 have too little C content, so the standard deviation of ferrite grain size exceeds 7.0 ⁇ m, the standard deviation of crown height exceeds 0.09 mm, and the crown formability deteriorates. I understood.
- the No. 29 steel plate contains too much Mn, so the standard deviation of ferrite grain size exceeds 7.0 ⁇ m, the standard deviation of crown height exceeds 0.09 mm, and the crown formability deteriorates.
- Steel slabs were obtained by containing a component composition of 5, 9, 18, 21, 28, 29, and 31 with the balance being made of Fe and unavoidable impurities in a converter and continuously cast.
- the steel slab obtained here was hot-rolled at the slab heating temperature, finish rolling temperature, and coiling temperature shown in Table 3. After hot rolling, pickling was performed. Next, primary cold rolling is performed at the rolling reduction shown in Table 3, and the soaking temperature, soaking time, precooling average speed, precooling cooling stop temperature, precooling average cooling speed, and postcooling cooling stop temperature shown in Table 3 are used. Continuous annealing was performed, followed by secondary cold rolling at the rolling reduction shown in Table 3.
- the obtained steel sheet was continuously subjected to electrolytic chromic acid treatment to obtain tin-free steel.
- steel plate No. which is an example of the present invention.
- Steel sheets of 40, 43, 45, 47, 48, 52 to 55, 58, 59, 63, 64, 66, 69, 70, 71 have a high yield strength in the rolling direction of 560 MPa or more and a standard crown height. The deviation was 0.09 mm or less, and the crown moldability and DRD can moldability were good.
- steel plate No. which is a comparative example.
- Steel plates of 42, 44, 46, 51, 57, 60, 65, 67, 73, 74 are slab heating temperature, final stand reduction ratio of hot rolling, winding temperature, primary cold rolling rate, soaking temperature.
- Any one of the pre-stage cooling stop temperature, the post-stage cooling average speed, the post-stage cooling stop temperature, and the secondary cold rolling reduction is outside the range of the present invention, so that the yield strength in the rolling direction is reduced or the standard deviation of the ferrite grain size is 7 It was found that the standard deviation of the crown height exceeded 0.09 mm and the crown moldability deteriorated, and the DRD can moldability also deteriorated.
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Abstract
Description
C:0.0060%超0.0100%以下、
Si:0.05%以下、
Mn:0.05%以上0.60%以下、
P:0.050%以下、
S:0.050%以下、
Al:0.020%以上0.050%以下および
N:0.0070%以上0.0140%以下
を含有し、残部はFeおよび不可避的不純物の成分組成を有し、
板厚の1/4の深さから板厚中心部までの領域にフェライト相を有し、該フェライト相におけるフェライト粒径の標準偏差が7.0μm以下であり、
降伏強度が560MPa以上である鋼板。
鋼素材を1200℃以上で加熱し、仕上げ圧延温度:870℃以上および最終スタンドの圧下率:10%以上の条件にて圧延を施して550~750℃の温度範囲内で巻取る熱間圧延工程と、
前記熱間圧延後の熱延板に酸洗を行う酸洗工程と、
前記酸洗後の熱延板に、圧下率:88%以上の冷間圧延を行う一次冷間圧延工程と、
前記一次冷間圧延後の冷延板を、660~760℃の温度域に60秒以下で保持したのち、10℃/s以上の平均冷却速度で450℃以下の温度域まで冷却し、次いで5℃/s以上の平均冷却速度で140℃以下の温度域まで冷却する焼鈍工程と、
前記焼鈍板に、10%以上40%以下の圧下率で冷間圧延を行う二次冷間圧延工程と、を有する鋼板の製造方法。
まず、鋼板の成分組成における各成分量の限定理由から順に説明する。なお、成分に関する「%」表示は、特に断らない限り「質量%」を示す。
Cの含有量を0.0060%以下とすると、後述の二次冷間圧延後の鋼板のフェライトが粗大となって成形性が悪化し、例えば王冠用に供した場合に、成形した王冠外径および王冠高さが不均一となる。同様に、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生し形状不良の缶となる。一方、C含有量が0.0100%超となると、二次冷間圧延後の鋼板のフェライトが微細となりすぎて鋼板強度が過剰に上昇して成形性が劣化し、例えば王冠用に供した場合に、成形した王冠の外径および高さが不均一となる。同様に、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生し形状不良の缶となる。よって、Cの含有量は0.0060%超0.0100%以下とする。好ましくは、Cの含有量は0.0065%以上0.0090%以下とする。
Siを多く含むとCと同様の理由により、例えば王冠用に供した場合に、王冠の外径および高さの均一性が損なわれ、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。よって、Siの含有量は0.05%以下とする。また、過剰にSiを低下させることは製鋼コストの増大を招くため、Siの含有量は0.004%以上とすることが好ましい。より好ましくは、0.01%以上0.03%以下である。
Mnの含有量が0.05%を下回ると、Sの含有量を低下させても熱間脆化を回避することが困難になり、連続鋳造時に表面割れなどの問題が生じる。よって、Mnの含有量は0.05%以上とする。一方、Mnを多く含むと、Cと同様の理由により、例えば王冠用に供した場合に、王冠の外径および高さの均一性が損なわれ、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。よって、Mnの含有量は0.60%以下とする。好ましくは、Mnの含有量は0.10%以上0.50%以下である。
Pの含有量が0.050%を超えると、鋼板の硬質化や耐食性の低下が引き起こされる。また、焼鈍後のフェライト粒径の標準偏差が7.0μm超となって成形性が悪化し、例えば王冠用に供した場合に、王冠の外径および高さの均一性が損なわれ、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。よって、Pの含有量の上限値は0.050%とする。また、Pを0.001%未満とするには脱Pコストが過大となるため、Pの含有量は0.001%以上とすることが好ましい。
Sは、鋼板中でMnと結合してMnSを形成し、多量に析出することで鋼板の熱間延性を低下させる。Sの含有量が0.050%を超えるとこの影響が顕著となる。よって、Sの含有量の上限値は0.050%とする。また、Sを0.005%未満とするには脱Sコストが過大となるため、Sの含有量は0.004%以上とすることが好ましい。
Alは、脱酸剤として含有させる元素であり、また鋼中のNとAlNを形成し、鋼中の固溶Nを減少させる。Al含有量が0.020%未満であると脱酸剤としての効果が不十分になり、凝固欠陥の発生を招くとともに製鋼コストが増大する。また、0.020%未満のAl量とすると、焼鈍でのフェライトの再結晶時に適切な量のAlNを確保できないため、焼鈍後のフェライト粒径の標準偏差が大きくなり、二次冷間圧延後の鋼板のフェライトが粗大となって成形性が悪化する。すると、例えば王冠用に供した場合に、王冠の外径および高さの均一性が損なわれ、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。一方、Alの含有量が0.050%超となると、AlNの形成が増加して、後述する固溶Nとして鋼板強度に寄与するN量が低減し、鋼板強度が低下するため、Al含有量は0.050%以下とする。好ましくは、Al含有量は0.030%以下0.045%以下である。
Nの含有量を0.0070%未満とすると、二次冷間圧延後の鋼板のフェライトが粗大となって成形性が悪化し、例えば王冠用に供した場合に、成形した王冠の外径および高さが不均一となるとともに、後述する固溶Nとして鋼板強度に寄与するN量が低減し、鋼板強度が低下する。同様に、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生し形状不良の缶となる。一方、N含有量が0.0140%超となると二次冷間圧延後の鋼板のフェライトが微細となりすぎて鋼板強度が過剰に上昇して成形性が劣化し、例えば王冠用に供した場合に、王冠の外径および高さの均一性が損なわれ、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。好ましくは、Nの含有量は0.0085以上0.0125%以下とする。より好ましくは、0.0100%超とする。
以上の成分以外の残部は、Feおよび不可避的不純物とする。
まず、本発明の鋼板の金属組織は、フェライト相を主体とし残部はセメンタイトであり、フェライト相は85体積%以上であることが好ましい。より好ましくは、90%以上である。すなわち、フェライト相が85体積%未満では、加工時に硬質なセメンタイトを起点に破断が発生し易くなり、成形性が劣化する。
すなわち、フェライト粒径の標準偏差が7.0μm超となると成形性が悪化し、例えば王冠用に供した場合に、成形後の王冠の外径および高さが不均一となり、耐圧強度が低下するとともに、王冠を製造する際の歩留りが低下する。同様に、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生し形状不良の缶となる。好ましくは、フェライト粒径の標準偏差は6.5μm以下である。
すなわち、本発明の鋼板には、例えば王冠に供する場合に、瓶の口にかしめた王冠が内圧によって外れないための、耐圧強度が求められる。従来用いられてきた王冠用鋼板の板厚は0.22mm以上であったが、板厚を0.20mm以下、特に0.18mm以下とする薄肉化にあたっては、従来よりも高い強度が必要となる。鋼板の降伏強度が560MPa未満であると、上記のような薄肉化した王冠に十分な耐圧強度を付与することが不可能である。そのためには、降伏強度は560MPa以上である必要がある。さらに十分な耐圧強度を確保するためには降伏強度は600MPa以上が好ましい。降伏強度が高すぎると王冠成形時に王冠高さが低くなり王冠形状が不均一となるため、圧延方向の降伏強度は700MPa以下が好ましい。より好ましくは600MPa以上680MPa以下である。
本発明の鋼板は、上記成分組成からなる鋼素材(鋼スラブ)を、1200℃以上で加熱し、仕上げ圧延温度が870℃以上で、最終スタンドの圧下率が10%以上とし、550~750℃の温度範囲内で巻取る熱間圧延工程と、前記熱間圧延後に酸洗する酸洗工程と、前記酸洗工程後に、圧下率が88%以上で冷間圧延する一次冷間圧延工程と、前記一次冷間圧延後に、均熱温度が660~760℃の温度域にある保持時間を60秒以下とし、10℃/s以上の平均冷却速度で450℃以下の温度域まで冷却し、5℃/s以上の平均冷却速度で140℃以下の温度域まで冷却する連続焼鈍工程と、10%以上40%以下の圧下率で二次冷間圧延を行うことで製造される。
熱間圧延工程の鋼素材の加熱温度は1200℃以上とする。該加熱温度が1200℃未満であると、本発明において強度を確保するために必要な固溶N量が低減し、強度が低下するため、1200℃以上とする。なお、本発明の鋼組成では鋼中Nは主にAlNとして存在すると考えられるため、Nの総量(Ntotal)からAlNとして存在するN量(NasAlN)を差し引いた(Ntotal-(NasAlN))を固溶N量とみなした。鋼板の圧延方向の降伏強度を560MPa以上とするためには、固溶N量は0.0071%以上であることが好ましく、鋼素材加熱温度を1200℃以上とすることで確保することができる。より好ましい固溶N量は、0.0090%以上であり、そのためには鋼素材加熱温度を1220℃以上とするとよい。鋼素材加熱温度は1300℃超としても効果が飽和するため、1300℃以下が好ましい。
熱間圧延工程の仕上げ温度が870℃未満となると、鋼板のフェライトの一部が細かくなり、フェライト粒径の標準偏差が7.0μm超となって成形性が悪化する。すると、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、仕上げ温度は、870℃以上とする。一方、必要以上に仕上げ圧延温度を高くすることは薄鋼板の製造を困難にする場合がある。具体的には、仕上げ圧延温度は870℃以上950℃以下の温度範囲内とすることが好ましい。
熱間圧延工程の最終スタンドの圧下率は10%以上とする。最終スタンドの圧下率が10%未満となると、鋼板のフェライトの一部が粗大化し、フェライトの標準偏差が7.0μm超となって成形性が悪化する。すると、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、最終スタンドの圧下率は10%以上とする。フェライト粒径の標準偏差を小さくするには最終スタンドの圧下率は12%以上とすることが好ましい。最終スタンドの圧下率の上限は、圧延荷重の観点で15%以下とすることが好ましい。
熱間圧延工程の巻取温度が550℃未満となると、鋼板のフェライトの一部が細かくなり、フェライト粒径の標準偏差が7.0μm超となって成形性が悪化する。すると、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、巻取温度は550℃以上とする。一方、巻取温度が750℃より高くなると、鋼板のフェライトの一部が粗大化し、フェライトの標準偏差が7.0μm超となって、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、巻取温度は750℃以下とする。好ましくは600℃以上700℃以下である。
その後、酸洗を行うことが好ましい。酸洗は、表層スケールが除去できればよく、特に条件を限定する必要はない。
(一次冷間圧延圧下率:88%以上)
まず、一次冷間圧延工程の圧下率は88%以上とする。一次冷間圧延工程の圧下率は88%未満となると冷間圧延で鋼板に付与されるひずみが低下するため、連続焼鈍工程における再結晶が不均一となり、フェライトの標準偏差が7.0μm超となって成形性が悪化する。すると、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、一次冷間圧延工程の圧下率は88%以上とする。より好ましくは89~94%とする。
(均熱温度:660~760℃)
すなわち、連続焼鈍工程における均熱温度は、660~760℃の温度で行う。均熱温度を760℃超とすると、連続焼鈍においてヒートバックルなどの通板トラブルが発生しやすくなり、好ましくない。また、鋼板のフェライト粒径が一部粗大化し、フェライトの標準偏差が7.0μm超となり、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねくことになる。一方、焼鈍温度が660℃未満であると、再結晶が不完全となり、鋼板のフェライト粒径が一部細かくなり、フェライト粒径の標準偏差が7.0μm超となり、例えば王冠用に供した場合に、王冠形状が不均一となり、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。従って、均熱温度は、660~760℃の温度で行うこととする。好ましくは、680~730℃の温度で行う。
前記均熱後、10℃/s以上の平均冷却速度で450℃以下の温度域まで冷却する。平均冷却速度が10℃/s未満となると、冷却中に炭化物析出が促進されて、鋼板強度に寄与する固溶C量が低減し、降伏強度が低下する。さらに、鋼板を例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。なお、平均冷却速度が50℃/s超となると上記の効果が飽和するため、平均冷却速度は50℃/s以下とすることが好ましい。
また、均熱後の前段冷却における冷却停止温度が450℃超となると、前段冷却後に炭化物析出が促進されて、鋼板強度に寄与する固溶C量が低減し、降伏強度が低下する。さらに、鋼板を例えばDRD缶用に供した場合、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。なお、均熱後の前段冷却における冷却停止温度が300℃未満となると、炭化物析出抑制効果が飽和するばかりか、通板する際の鋼板形状が劣化して鋼板が均一に冷却できなくなり、例えば王冠用に供した場合に、王冠形状が不均一となり、さらに、例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねくため、均熱後の冷却停止温度は300℃以上とすることが好ましい。
前段冷却後の後段冷却では、5℃/s以上の平均冷却速度で前段冷却時の冷却停止温度から140℃以下の温度域まで冷却する。平均冷却速度が5℃/s未満となると、鋼板強度に寄与する固溶C量が低減し降伏強度が低下する。さらに、鋼板を例えばDRD缶用に供した場合に、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。なお、平均冷却速度が30℃/s超となると、効果が飽和するばかりか、冷却設備に過剰なコストが発生するため後段冷却での平均冷却速度は30℃/s以下が好ましい。より好ましくは25℃/s以下である。
後段冷却では140℃以下まで冷却する。140℃超となると、鋼板強度に寄与する固溶C量が低減し、降伏強度が低下する。さらに、鋼板を例えばDRD缶用に供した場合、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。なお、冷却停止温度が100℃未満となると効果が飽和するばかりか、冷却設備に過剰なコストが発生するため100℃以上が好ましい。より好ましくは120℃以上である。
本発明の鋼板は、焼鈍後の二回目の冷間圧延により高い降伏強度を得ることができる。すなわち、二次冷間圧延の圧下率が10%未満であると、十分な降伏強度が得られない。また、二次冷間圧延の圧下率が40%を超えると、例えば鋼板を王冠用に供した場合に王冠形状の均一性を損なう。さらに、例えばDRD缶用に供した場合、DRD缶成形時にフランジ部にしわが発生する形状不良をまねく。よって、二次冷間圧延の圧下率は10%以上40%以下とすることが好ましい。より好ましくは、二次冷間圧延の圧下率は15%超35%以下である。
また、本発明の王冠は、上述した鋼板を用いて成形されるものである。王冠は、主に瓶の口を塞ぐ円盤状の部分と、その周囲に設けられた襞状の部分とから構成される。本発明の王冠は、本発明の鋼板を円形のブランクに打ち抜いた後、プレス成形により成形することができる。本発明の王冠は、十分な降伏強度を有し、かつ、材質均一性に優れた鋼板から製造されるので、薄肉化しても王冠としての耐圧強度に優れており、かつ王冠の外径および高さの均一性が優れているため、王冠製造工程での歩留りが向上し、王冠製造に伴う廃棄物の排出量を減らす効果を有する。
一方、比較例である鋼板No.41、49、50、56、61、68、72の鋼板は、スラブ加熱温度、均熱保持時間、前段冷却平均速度、二次冷間圧下率、後段冷却平均速度、前段冷却停止温度、後段冷却停止温度が本発明範囲を外れるため、圧延方向の降伏強度が低下することが分かった。比較例である鋼板No.62の鋼板は、二次冷間圧下率が高すぎるため、鋼板の異方性が大きくなり、王冠高さの標準偏差が0.09mm超となり王冠成形性が劣化し、またDRD缶成形性も劣化することが分かった。比較例である鋼板No.42、44、46、51、57、60、65、67、73、74の鋼板は、スラブ加熱温度、熱間圧延の最終スタンド圧下率、巻取温度、一次冷間圧延率、均熱保持温度、前段冷却停止温度、後段冷却平均速度、後段冷却停止温度、二次冷間圧下率の何れかが本発明範囲外であるため、圧延方向の降伏強度が低下またはフェライト粒径の標準偏差が7.0μm超となり、王冠高さの標準偏差が0.09mm超となり王冠成形性が劣化し、またDRD缶成形性も劣化することが分かった。
Claims (5)
- 質量%で、
C:0.0060%超0.0100%以下、
Si:0.05%以下、
Mn:0.05%以上0.60%以下、
P:0.050%以下、
S:0.050%以下、
Al:0.020%以上0.050%以下および
N:0.0070%以上0.0140%以下
を含有し、残部はFeおよび不可避的不純物の成分組成を有し、
板厚の1/4の深さから板厚中心部までの領域にフェライト相を有し、該フェライト相におけるフェライト粒径の標準偏差が7.0μm以下であり、
降伏強度が560MPa以上である鋼板。 - 板厚が0.20mm以下である請求項1に記載の鋼板。
- 請求項1または2に記載の鋼板からなる王冠。
- 請求項1または2に記載の鋼板からなるDRD缶。
- 請求項1または2に記載の鋼板の製造方法であり、
鋼素材を1200℃以上で加熱し、仕上げ圧延温度:870℃以上および最終スタンドの圧下率:10%以上の条件にて圧延を施して550~750℃の温度範囲内で巻取る熱間圧延工程と、
前記熱間圧延後の熱延板に酸洗を行う酸洗工程と、
前記酸洗後の熱延板に、圧下率:88%以上の冷間圧延を行う一次冷間圧延工程と、
前記一次冷間圧延後の冷延板を、660~760℃の温度域に60秒以下で保持したのち、10℃/s以上の平均冷却速度で450℃以下300℃以上の温度域まで冷却し、次いで5℃/s以上30℃/s以下の平均冷却速度で140℃以下の温度域まで冷却する焼鈍工程と、
前記焼鈍板に、10%以上40%以下の圧下率で冷間圧延を行う二次冷間圧延工程と、を有する鋼板の製造方法。
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