WO2019026739A1 - 王冠用鋼板、王冠、および王冠用鋼板の製造方法 - Google Patents
王冠用鋼板、王冠、および王冠用鋼板の製造方法 Download PDFInfo
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- WO2019026739A1 WO2019026739A1 PCT/JP2018/027995 JP2018027995W WO2019026739A1 WO 2019026739 A1 WO2019026739 A1 WO 2019026739A1 JP 2018027995 W JP2018027995 W JP 2018027995W WO 2019026739 A1 WO2019026739 A1 WO 2019026739A1
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D41/00—Caps, e.g. crown caps or crown seals, i.e. members having parts arranged for engagement with the external periphery of a neck or wall defining a pouring opening or discharge aperture; Protective cap-like covers for closure members, e.g. decorative covers of metal foil or paper
- B65D41/02—Caps or cap-like covers without lines of weakness, tearing strips, tags, or like opening or removal devices
- B65D41/10—Caps or cap-like covers adapted to be secured in position by permanent deformation of the wall-engaging parts
- B65D41/12—Caps or cap-like covers adapted to be secured in position by permanent deformation of the wall-engaging parts made of relatively stiff metallic materials, e.g. crown caps
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0268—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment between cold rolling steps
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- 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 steel plate for a crown, and more particularly to a steel plate for a crown which can produce a crown excellent in formability and sufficient in pressure resistance even in a beverage having a high carbon dioxide content.
- the present invention also relates to a crown made using the crown steel plate, and a method of manufacturing the crown steel plate.
- the internal pressure may be very high, at least 180 psi (1.241 MPa), and the crown may be deformed to cause leakage of the contents. Therefore, in order to prevent the leakage of the contents, a liner made of resin is mainly attached to the crown as a sealing material, and the adhesion between the mouth and the crown is enhanced. Above all, in a crown used for high GV carbonated drinks, the pressure resistance of the crown is improved by using a soft liner.
- SR Single Reduced steel plate
- the SR steel plate is a steel plate manufactured by performing annealing after further thinning the steel plate by cold rolling and further performing temper rolling.
- the plate thickness of the conventional steel plate for crown is generally 0.22 mm or more, and sufficient pressure resistance and formability are secured by applying SR material made of mild steel used for food and beverage cans and the like. It was possible.
- the demand for thinning of steel sheets for crowns has also increased in order to reduce the cost of the crown.
- the crown manufactured by the conventional SR material lacks the pressure resistance.
- a DR (Double Reduced) steel plate is used, which is cold-rolled again and hardened by work after annealing.
- a center part is squeezed to some extent at the early stage of shaping
- the material of the crown is a steel plate with low material uniformity
- the crown outer diameter and the crown height may be uneven and deviate from the product specification. If the crown outer diameter and the crown height are irregular and deviate from the product specification, there is a problem that the yield when a large number of crowns are manufactured is reduced.
- a crown whose outside diameter and height are out of specification is likely to leak its contents during transportation after it is plugged into a bottle, and has a problem that it does not play a role as a lid.
- Patent Document 1 C: 0.0010% to 0.0060%, Si: 0.005 to 0.050%, Mn: 0.10% to 0.50% by mass. , Ti: 0 to 0.100%, Nb: 0 to 0.080%, B: 0 to 0.0080%, P: 0.040% or less, S: 0.040% or less, Al: 0.1000%
- a steel plate for crowns which contains N: 0.0100% or less, and has a component composition in which the balance is Fe and impurities.
- the crown steel plate further has a minimum r value of 1.80 or more in a direction of 25 to 65 ° with respect to the rolling direction of the steel plate, and is 0 ° or more and less than 360 ° with respect to the rolling direction.
- the average value of the r value in the direction is 1.70 or more, and the yield strength is 570 MPa or more.
- the r value in a predetermined direction is obtained by setting the interstand tension and annealing temperature in secondary cold rolling to a predetermined relationship. Is a value suitable for crown processing.
- the steel plate obtained by this method has large variations in the material, and it is difficult to put it to practical use for beverages with a high carbon dioxide content. It is.
- the present invention has been made in view of the above situation, and is excellent in moldability and can be applied to beverages with high carbon dioxide gas content by using a soft liner even when it is thinned.
- An object of the present invention is to provide a steel plate for a crown capable of producing a crown having sufficient compressive strength.
- Another object of the present invention is to provide a crown made using the crown steel plate, and a method of manufacturing the crown steel plate.
- C 0.0060% or more and 0.0100% or less
- Si 0.05% or less
- Mn 0.05% or more and 0.60% or less
- P 0.050% or less
- 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
- the balance has a component composition consisting of Fe and unavoidable impurities
- It 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 ferrite grain size in the ferrite phase is 7.0 ⁇ m or less
- Yield strength in the rolling direction is 560 MPa or more and 700 MPa or less
- a steel plate for crowns having a difference of 25 MPa or more in yield strength in a 2% strain tensile test in a rolling direction and in tensile test after heat treatment at 170 ° C. for 20 minutes.
- Winding temperature hot rolling process of winding at 550 to 750 ° C.
- a pickling step of pickling after the hot rolling step
- Primary cold rolling step of cold rolling at a rolling reduction of 88% or more after the pickling step
- a continuous annealing step of continuous annealing after the primary cold rolling step
- the secondary cold rolling step of performing cold rolling at a rolling reduction of 10 to 40% In the continuous annealing process, Heating up to a soaking temperature of 660 to 760 ° C., an average heating rate in the temperature range of 600 ° C.
- an average cooling rate primary cooling to a temperature of 1050C / s or more and 450C or less
- an average cooling rate a method for producing a steel plate for crown, which is secondarily cooled to a temperature of 140 ° C. or less at 5 ° C./s or more.
- a crown having a sufficient pressure resistance that can be applied to a beverage with a high carbon dioxide content can be produced by using a soft liner even if the moldability is excellent and the thickness is reduced. It is possible to provide a steel plate for crown that can be made.
- C More than 0.0060% and 0.0100% or less
- the C content is 0.0060% or less
- the ferrite of the steel plate after the secondary cold rolling described later becomes coarse and the formability is deteriorated, and the steel is formed
- the crown outer diameter and crown height become uneven.
- the yield strength difference between 2% strain tension and retension in the rolling direction is less than 25 MPa, and high compressive strength can not be obtained even when a soft liner is used in combination. .
- the C content is more than 0.0100%, the ferrite of the steel plate after secondary cold rolling becomes too fine, the steel plate strength excessively increases, and the formability deteriorates, and the crown diameter and the formed crown The crown height becomes uneven. 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.
- the content of Si is 0.05% or less.
- the content of Si is preferably made 0.004% or more.
- Mn 0.05% or more and 0.60% or less
- the content of Mn is set to 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.
- P 0.050% or less
- the upper limit value of P content is set to 0.050%.
- P content in order to make P content less than 0.001%, since de-P cost becomes excessive, it is preferable to make P content into 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 reduce the hot ductility of the steel plate. This effect becomes significant when the S content exceeds 0.050%. Therefore, the S content is made 0.050% or less. On the other hand, in order to make S content into less than 0.005%, since de-S cost becomes excessive, it is preferable to make S content into 0.005% 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 solid solution N in the steel. If the Al content is less than 0.020%, the effect as a deoxidizer is insufficient, causing solidification defects and increasing the steelmaking cost. In addition, when the Al content is less than 0.020%, an appropriate amount of AlN can not be secured at the time of recrystallization of ferrite in annealing, so the standard deviation of ferrite grain size after annealing becomes large, and after secondary cold rolling The ferrite grain size of the steel plate becomes coarse, and the formed crown outer diameter and crown height become uneven. Therefore, the Al content is 0.020% or more.
- the Al content is preferably 0.030% or more.
- the Al content is more than 0.050%, formation of AlN increases, the amount of N contributing to steel plate strength as solid solution N described later decreases, and the steel plate strength decreases. Therefore, the Al content is made 0.050% or less.
- the Al content is preferably 0.045% or less.
- the component composition of the steel plate for crowns in one embodiment of this invention can consist of the said element, Fe of remainder, and an unavoidable impurity.
- the metallographic structure of the steel plate for a crown 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 ferrite grain size in the ferrite phase is 7 It is important that the thickness is less than 0 ⁇ m.
- the region from the depth of 1 ⁇ 4 of the plate thickness to the center of the plate thickness is mainly composed of a ferrite phase, and the remaining part is cementite, and the ferrite phase is preferably 85% by volume or more.
- the standard deviation of the ferrite grain size in the above region is set to 7.0 ⁇ m or less.
- the standard deviation is preferably 6.5 ⁇ m or less.
- the lower limit is not particularly limited, but it is difficult to set the width to less than 5.0 ⁇ m due to fluctuations in manufacturing conditions and the like. Therefore, the standard deviation is preferably 5.0 ⁇ m or more.
- the metal structure of the steel plate for crowns can be evaluated using a structure photograph taken using an optical microscope.
- the specific procedure is as follows. First, a plate thickness cross section parallel to the rolling direction of the crown steel plate is from the plate thickness 1/4 depth position (the position from the surface to the plate thickness direction 1 ⁇ 4 in the above section) to the plate thickness 1/2 position The region is observed with a light microscope to obtain a tissue photograph. The ferrite is then identified by visual judgment using the obtained structure photograph. Thereafter, the structure photograph is subjected to image analysis to determine the grain size of ferrite, and the grain size distribution of ferrite grain size is determined in each visual field to calculate the standard deviation. The value obtained by averaging the standard deviations in 10 fields of view is taken as the standard deviation of the ferrite grain size. More specifically, it can be evaluated by the method described in the examples.
- the said metal structure can be obtained by manufacturing the steel plate for crowns on the conditions mentioned later using the steel slab which has the component composition mentioned above as a raw material.
- the upper limit of the difference in yield strength is not particularly limited, but if the difference in yield strength is excessively large, the steel plate strength excessively increases due to heat treatment, so the shape of the crown becomes uneven when used for a crown. There is a case. Moreover, when many crowns are shape
- the said yield strength difference can be measured by the method according to the test method of the amount of baking and hardening of a coating (BH amount) prescribed
- BH amount a coating
- tensile test pieces of JIS No. 5 size are taken from the steel plate for crown in parallel to the rolling direction of the steel plate.
- a tensile test is performed according to “JIS G3135” using the test piece to measure a 2% pre-strain load. That is, 2% of prestrain is given to a test piece, the load at that time (2% prestrain load: P1) is read, and then the load is removed.
- the pre-strained test piece is subjected to heat treatment at 170 ° C.
- BH amount MPa
- P2 load after heat treatment
- A pre-strain
- the yield strength difference satisfying the above-described conditions can be obtained by using a steel slab having the above-described component composition as a raw material and manufacturing a steel plate for crown under the conditions described later.
- yield strength In the steel plate having the above component composition and structure, high strength, specifically, yield strength of 560 MPa or more can be secured. That is, when used for a crown, the steel plate for crowns is required to have a pressure resistance such that the crown crimped to the mouth of the bottle does not come off due to the internal pressure.
- the plate thickness of the steel plate for crowns used conventionally was 0.22 mm or more, but in thinning to make the plate thickness 0.20 mm or less, particularly 0.18 mm or less, higher strength than before is required .
- the yield strength of the steel plate for crowns shall be 560 MPa or more. In order to ensure a higher compressive strength, it is preferable to set the yield strength to 600 MPa or more. On the other hand, if the yield strength is too high, the crown height is lowered during crown molding and the crown shape becomes nonuniform, so the yield strength is made 700 MPa or less. The yield strength is more preferably 680 MPa or less.
- the yield strength refers to the yield strength in the rolling direction of the crown steel plate. The said yield strength can be measured by the metal material tension test method shown by "JIS Z 2241".
- the plate thickness of the above-mentioned steel plate for crowns is not particularly limited, and can be any thickness. However, from the viewpoint of cost reduction, the plate thickness is preferably 0.20 mm or less, more preferably 0.18 mm or less, and still more preferably 0.17 mm or less. If the plate thickness is less than 0.14 mm, disadvantages in terms of manufacturing cost occur, so the lower limit of the plate thickness is preferably 0.14 mm.
- the manufacturing method of the steel plate for crowns in one embodiment of the present invention is explained.
- the definition of the temperature is based on the surface temperature of the steel plate.
- the average heating rate and the average cooling rate are values obtained by calculation based on the surface temperature of the steel plate.
- the steel plate for a crown in one embodiment of the present invention can be manufactured by sequentially applying the following steps (1) to (5) to a steel slab having the above-described component composition.
- (1) Hot rolling process (2) Pickling process (3) Primary cold rolling process (4) Continuous annealing process (5) Secondary cold rolling process
- a steel adjusted to the above-mentioned component composition is melted by a converter or the like to manufacture a steel slab.
- the steel slab may be produced by any method such as continuous casting, ingot casting, thin slab casting, etc., without being particularly limited, but in order to prevent macrosegregation of components, continuous casting may be used. It is preferable to manufacture.
- the steel slab is subjected to a hot rolling process.
- the steel slab is heated, and the heated steel slab is subjected to hot rolling including rough rolling and finish rolling to form a hot rolled steel sheet, and the hot rolled steel sheet after the finish rolling to a coil Take up.
- (heating) Slab heating temperature 1200 ° C. or more
- the steel slab is reheated to a slab heating temperature of 1200 ° C. or more.
- the slab heating temperature is set to 1200 ° C. or more.
- N in the steel is considered to exist mainly as AlN. Therefore, (Ntotal ⁇ (N as AlN)) obtained by subtracting the N amount (N as AlN) existing as AlN from the total amount of N (N total) can be regarded as the solid solution N amount.
- the solid solution N amount is preferably 0.0071% or more, and the solid solution N amount is ensured by setting the slab heating temperature to 1200 ° C. or more.
- the more preferable solid solution N content is 0.0090% or more, and for that purpose, the slab heating temperature may be 1220 ° C. or more.
- the upper limit of the slab heating temperature is preferably 1300 ° C. or less because the effect is saturated even when the temperature exceeds 1300 ° C.
- (Finish rolling) Finishing rolling temperature 870 ° C. or higher
- the finishing temperature in the hot rolling step is less than 870 ° C.
- part of the ferrite of the steel sheet becomes fine, and the standard deviation of ferrite grain size becomes more than 7.0 ⁇ m and formability deteriorates
- the temperature is 870 ° C. or higher.
- raising the finish rolling temperature more than necessary may make it difficult to manufacture thin steel sheets.
- the finish rolling temperature is preferably in a 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 plate becomes coarse, and the standard deviation of the ferrite grain size exceeds 7.0 ⁇ m, and the formability is deteriorated. And as a result, when using for a crown, crown shape becomes non-uniform
- the rolling reduction of the final stand is preferably 12% or more.
- the upper limit of the rolling reduction of the final stand is not particularly limited, but it is preferably 15% or less from the viewpoint of rolling load.
- Winding temperature 550 to 750 ° C
- the coiling temperature in the hot rolling step is less than 550 ° C.
- 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 is deteriorated.
- crown shape becomes non-uniform
- the coiling temperature is higher than 750 ° C., a part of the ferrite of the steel sheet is coarsened, and the standard deviation of the ferrite grain size exceeds 7.0 ⁇ m, and the crown shape becomes nonuniform. Therefore, the winding temperature is set to 750 ° C. or less.
- the winding temperature is preferably 600 ° C. or more and 700 ° C. or less.
- the hot rolled steel sheet after the hot rolling step is pickled.
- the oxide scale on the surface of the hot rolled steel sheet can be removed.
- the pickling conditions are not particularly limited, and may be appropriately set according to a conventional method.
- cold rolling is performed on the hot-rolled steel sheet after the pickling.
- the cold rolling is performed in two divided continuous annealings.
- the rolling reduction in the primary cold rolling process is 88% or more. If the rolling reduction in the primary cold rolling process is less than 88%, the strain applied to the steel sheet by cold rolling decreases, so recrystallization in the continuous annealing process becomes uneven, and the standard deviation of ferrite grain size is 7 .0 ⁇ m or more. As a result, the formability deteriorates, and the crown shape becomes nonuniform when used for a crown. Therefore, the rolling reduction in the primary cold rolling process is 88% or more.
- the rolling reduction is preferably 89 to 94%.
- Continuous annealing process Next, continuous annealing is performed on the primary cold rolled sheet.
- the steel plate after the primary cold rolling step is heated to the soaking temperature, held in a temperature range of 660 to 760 ° C. for a predetermined time, and then primary cooling and secondary cooling are performed.
- the conditions at that time are as follows.
- Average heating rate from 600 ° C. to the soaking temperature 15 ° C./s or less Yield strength in the rolling direction of the steel plate (BH amount) when the average heating rate from 600 ° C. to the soaking temperature is more than 15 ° C./s ) Is less than 25 MPa.
- the average heating rate is set to 15 ° C./s or less.
- the average heating rate is preferably less than 10 ° C./s.
- the average heating rate is preferably 1 ° C./s or more, and more preferably 2 ° C./s or more.
- Holding time 60 seconds or less
- the holding time (soaking time) to be held in the temperature range of 660 to 760 ° C. is 60 seconds or less.
- C contained in the steel plate segregates to ferrite grain boundaries and precipitates as carbides in the cooling process after soaking.
- the holding time is set to 60 seconds or less.
- the lower limit of the holding time is not particularly limited, but if the holding time is less than 5 seconds, the stability when the steel sheet passes the soaking roll may be impaired, so the holding time is 5 seconds. It is preferable to set it as the above.
- Average primary cooling rate 10 ° C./s or more After the soaking, cooling is performed at an average cooling rate of 10 ° C./s or more to a temperature of 450 ° C. (primary cooling stop temperature) (primary cooling). If the average cooling rate (primary cooling average speed) in the primary cooling is less than 10 ° C./s, carbide precipitation is promoted during cooling, the amount of solid solution C contributing to the steel sheet strength decreases, and the yield strength decreases Do. Therefore, the primary cooling average speed is set to 10 ° C./s or more. On the other hand, since the above effect is saturated when the primary cooling average speed is more than 50 ° C./s, the primary cooling average speed is preferably 50 ° C./s or less.
- Primary cooling stop temperature 450 ° C. or less If the cooling stop temperature (primary cooling stop temperature) in primary cooling is higher than 450 ° C., carbide precipitation is promoted after primary cooling, and the amount of solid solution C contributing to steel plate strength decreases , Yield strength is reduced. Therefore, the primary cooling stop temperature is set to 450 ° C. or less.
- the lower limit of the primary cooling stop temperature is not particularly limited, but if the primary cooling stop temperature is less than 300 ° C., not only the carbide precipitation suppressing effect is saturated, but also the steel plate shape at the time of sheet passing deteriorates It may occur. Therefore, the primary cooling stop temperature is preferably 300 ° C. or more.
- Average secondary cooling rate 5 ° C./s or more After the primary cooling, cooling to a temperature (secondary cooling stop temperature) of 140 ° C. or lower at an average cooling rate of 5 ° C./s or higher (secondary cooling). If the average cooling rate (secondary cooling average rate) in the secondary cooling is less than 5 ° C./s, the amount of solid solution C contributing to the steel sheet strength decreases, and the yield strength decreases. Therefore, the secondary cooling average speed is set to 5 ° C./s or more. On the other hand, if the secondary cooling average speed is more than 30 ° C./s, not only the effect is saturated but also excessive cost occurs in the cooling equipment. Therefore, the secondary cooling average speed is preferably 30 ° C./s or less, and more preferably 25 ° C./s or less.
- Secondary cooling stop temperature 140 ° C. or less If the cooling stop temperature (secondary cooling stop temperature) in the secondary cooling is over 140 ° C., the amount of solid solution C contributing to the steel plate strength decreases and the yield strength decreases . Therefore, the said secondary-cooling stop temperature shall be 140 degrees C or less.
- the lower limit of the secondary cooling stop temperature is not particularly limited, but if the secondary cooling stop temperature is less than 100 ° C., not only the effect is saturated but also excessive cost occurs in the cooling facility. Therefore, the secondary cooling stop temperature is preferably 100 ° C. or more, and more preferably 120 ° C. or more.
- high yield strength can be obtained by performing the second cold rolling (secondary cold rolling) after the continuous annealing. At this time, if the rolling reduction of the secondary cold rolling is less than 10%, sufficient yield strength can not be obtained.
- the rolling reduction of secondary cold rolling exceeds 40%, the anisotropy becomes excessive, and for example, when used for a crown, the uniformity of the crown shape is impaired. Therefore, the rolling reduction of secondary cold rolling is 10% or more and 40% or less. The rolling reduction is preferably more than 15% and 35% or less.
- the cold-rolled steel plate obtained as described above may be subjected to surface treatment (for example, one or both of chemical conversion treatment and plating treatment), if necessary, to obtain a surface-treated steel plate.
- chemical conversion treatment for example, electrolytic chromic acid treatment can be used.
- the method of the said plating process is although it does not specifically limit, For example, electroplating can be used.
- the plating treatment include tin plating, chromium plating, nickel plating and the like.
- coating films, such as printing coating and an adhesion varnish can also be formed arbitrarily.
- the film thickness of surface treatment layers, such as plating is small enough with respect to plate thickness, the influence on the mechanical characteristic of a steel plate is a negligible level.
- the crown in one embodiment of the present invention can be obtained by molding the above-mentioned steel plate for crowns. More specifically, it is preferable to use a crown made of a metal portion made of the steel plate for the crown and a resin liner laminated on the inside of the metal portion.
- the metal portion is composed of a disc-like portion for closing the bottle opening and a bowl-like portion provided around the periphery. Further, the resin-made liner is attached to the disc-like portion.
- the crown can be manufactured, for example, by punching the crown steel plate into a circular blank, forming it by press forming, and then fusing the liner.
- the heat sealing of the liner is carried out, for example, by dripping molten resin onto the disc-like portion on the side in contact with the contents of the crown and pressing the liner-shaped mold to form the liner and simultaneously heat sealing it to the steel plate. It can be carried out. Further, after the crown steel plate is punched into a circular blank and formed by press forming, a resin formed into a shape that is easily adhered to the bottle in advance is attached to a discoid portion on the side in contact with the contents of the crown with an adhesive. You may
- soft resin As resin used for the said resin-made liners, soft resin is used.
- soft resins include polyvinyl chloride, polyolefin, polystyrene and the like.
- the resin liner preferably has an ultra-micro load hardness (HTL) of less than 0.70.
- HTL ultra-micro load hardness
- a liner with an ultra-micro load hardness of less than 0.70 is soft, so it is excellent in adhesion to the bottle opening. Therefore, the compressive strength of the crown can be further improved by using a resin liner having an ultra-micro load hardness of less than 0.70.
- the said ultra-micro load hardness can be measured according to the method as described in "JIS Z2255" (2003). In the said measurement, the test piece cut out from the crown in the state by which the resin-made liners were stuck on the steel plate is used.
- load-unload test is performed using a dynamic micro hardness tester, and using the test force P (mN) and the obtained maximum indentation depth: D ( ⁇ m), the following (2 ) Can be calculated.
- the crown of the present invention is manufactured from a steel plate excellent in material uniformity, and therefore, when used as a crown of a high GV carbonated beverage, it is excellent in pressure resistance as a crown even if it is thinned.
- the crown obtained from the steel plate for crown of the present invention is excellent in uniformity of the crown outer diameter and crown height, the yield in the crown manufacturing process is improved, and the amount of waste emissions associated with crown manufacture is reduced. Have an effect.
- Example 1 First, in order to evaluate the influence of the component composition of the steel sheet, the following test was performed.
- a steel slab having the composition shown in Table 1 was melted in a converter and continuously cast to obtain a steel slab.
- the obtained steel slab was treated to treatments in the hot rolling step, the pickling step, the primary cold rolling step, the continuous annealing step, and the secondary cold rolling step under the conditions shown in Table 2, in order,
- the steel plate of the plate thickness shown in Table 3 was manufactured.
- the photograph of the structure of the crown steel plate was taken using an optical microscope, and the standard deviation of the ferrite grain size in the region from the depth of 1 ⁇ 4 of the thickness to the thickness center was determined from the obtained structure photograph.
- the specific procedure was as follows. First, a plate thickness section parallel to the rolling direction of the crown steel plate was polished and then corroded with a corrosive liquid (3 volume% nital). Then, ten fields of view randomly selected from the area from the 1 ⁇ 4 depth position of the cross section (1 ⁇ 4 position in the cross section to the thickness direction in the cross section) to the 1 ⁇ 2 position of the thickness The tissue photograph was obtained by observation at a magnification of 400 using a light microscope.
- Ferrite was specified by visual judgment using the obtained structure photograph, and ferrite particle size was determined by image analysis. Thereafter, the grain size distribution of ferrite grain size was determined in each visual field, and the standard deviation was calculated. The value obtained by averaging the standard deviations in the 10 fields of view is taken as the standard deviation of the ferrite grain size.
- the image analysis used image analysis software “Stream Essentials” manufactured by Olympus Corporation.
- yield strength difference The difference between the yield strength in the rolling direction (yield strength difference) between the 2% strain tensile test and the tensile test after heat treatment of the above crown steel plate is the paint baking hardening amount (JIS G3135) It calculated
- JIS G3135 paint baking hardening amount
- BH (P2-P1) / A (1)
- N in the steel is considered to exist mainly as AlN. Therefore, a value (Ntotal ⁇ (N as AlN)) obtained by subtracting the N amount (N as AlN) existing as AlN from the total amount of N (N total) is calculated, and this is used as the solid solution N amount.
- the amount of N present as AlN was determined by dissolving the sample in 10% Br in methanol and analyzing the residue.
- the obtained crown steel plate was formed into a crown according to the procedure described below, and the formability of the crown steel plate was evaluated.
- the crown steel plate subjected to heat treatment 210 ° C., 15 minutes
- the value of the standard deviation (mm) was used as an index of formability.
- the said standard deviation is 0.09 mm or less, a crown shape is excellent, and when it exceeds 0.09 mm, it can be said that it is inferior.
- a resin liner was attached to the inside of the disc-like portion of the molded crown to make a crown provided with a resin liner.
- the soft liner which consists of various resin whose ultra-micro load hardness is less than 0.70 was used.
- the pressure resistance strength and the ultra-fine load hardness of the liner were evaluated by the procedure described below.
- the ultra-micro load hardness of the liner was measured according to the method described in "JIS Z2255" (2003). In the said measurement, the test piece cut out from the crown in the state by which the resin-made liners were stuck on the steel plate was used. The test piece is bonded and fixed on the steel plate side with epoxy resin in a state of leveling, and load-unload test is performed using a dynamic microhardness tester (DUH-W201S, manufactured by Shimadzu Corp.) to perform ultra-microload The hardness was measured.
- a dynamic microhardness tester DH-W201S, manufactured by Shimadzu Corp.
- Measurement conditions are test force P: 0.500 mN, loading speed: 0.142 mN / s, holding time: 5 seconds, temperature: 23 ⁇ 2 ° C., humidity: 50 ⁇ 5%, made of diamond with an interval of 115 ° A triangular cone indenter was used.
- the evaluation results of each item are as shown in Table 3.
- the steel plates 1 to 22 had a yield strength in the rolling direction of not less than 560 MPa and a standard deviation of the crown height of not more than 0.09 mm, and the crown formability was good.
- No. 1 which does not satisfy the requirements of the present invention. Since the steel sheet of 23 to 25 contains too much C, the standard deviation of ferrite grain size becomes more than 7.0 ⁇ m, and as a result, the crown formability is inferior such that the standard deviation of crown height is more than 0.09 mm. It was
- the 29 steel plates had an excessively high Mn content, so the standard deviation of ferrite grain size was more than 7.0 ⁇ m, and as a result, the crown formability was inferior such that the standard deviation of crown height was more than 0.09 mm. .
- the evaluation results of each item are as shown in Table 5.
- the steel plates 39, 42, 44, 46, 47, 51 to 54, 57, 58, 62, 63, 65, 68, 69 have a yield strength in the rolling direction of 560 MPa or more and a standard deviation of crown height of 0.. It was 09 mm or less, the crown moldability was good, and the pressure resistance was good.
- No. 1 which is a comparative example.
- Steel plates 40, 48, 49, 60, 61, 67, 70 have slab heating temperatures, soaking holding times, primary cooling average speeds, secondary cold rolling reductions, secondary cooling average speeds, primary cooling stop temperatures, It has been found that the yield strength in the rolling direction is reduced because at least one of the next cooling stop temperatures is outside the scope of the present invention.
- No. 1 which is a comparative example. Since the steel plates of 52, 57, 66 had an average heating rate too high, the yield strength difference was less than 25 MPa, and the pressure resistance was inferior.
- No. 1 which is a comparative example.
- the steel sheet of 71 to 76 has a component composition outside the range of the present invention, and any of the secondary cooling average speed, the secondary cooling stop temperature, and the secondary cold rolling reduction ratio is outside the range of the present invention.
- the standard deviation of the ferrite grain size was more than 7.0 ⁇ m, and the standard deviation of the crown height was more than 0.09 mm, and the crown formability was inferior.
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Abstract
Description
また、本発明は、前記王冠用鋼板を用いて作成された王冠、および前記王冠用鋼板の製造方法に関する。
また本発明は、前記王冠用鋼板を用いて作成された王冠、および前記王冠用鋼板の製造方法を提供することを目的とする。
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、残部がFeおよび不可避的不純物からなる成分組成を有し、
板厚の1/4の深さから板厚中心までの領域にフェライト相を有し、前記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、
圧延方向における降伏強度が560MPa以上700MPa以下であり、
圧延方向の2%ひずみ引張試験における降伏強度と、170℃で20分の熱処理後の引張試験における降伏強度の差が25MPa以上である、王冠用鋼板。
上記1に記載の成分組成を有する鋼スラブを、1200℃以上のスラブ加熱温度に加熱し、仕上圧延温度:870℃以上、最終スタンドの圧下率:10%以上の条件で熱間圧延したのち、巻取り温度:550~750℃で巻取る熱間圧延工程と、
前記熱間圧延工程後に酸洗する酸洗工程と、
前記酸洗工程後に、圧下率:88%以上で冷間圧延する一次冷間圧延工程と、
前記一次冷間圧延工程後に、連続焼鈍する連続焼鈍工程と、
前記連続焼鈍工程後に、圧下率:10~40%で冷間圧延を行う二次冷間圧延工程とを有し、
前記連続焼鈍工程においては、
660~760℃の均熱温度まで、600℃から前記均熱温度までの温度域における平均加熱速度:15℃/s以下の条件で加熱し、
次いで、660~760℃の温度域に60秒以下の保持時間保持し、
前記保持後、平均冷却速度:10℃/s以上で450℃以下の温度まで一次冷却し、
引き続き、平均冷却速度:5℃/s以上で140℃以下の温度まで二次冷却する、王冠用鋼板の製造方法。
[成分組成]
本発明の一実施形態における王冠用鋼板は、上記成分組成を有することが重要である。そこで、まず本発明において王冠用鋼板の成分組成を上記のように限定する理由を説明する。なお、成分の説明における「%」は、特に断らない限り「質量%」を意味する。
C含有量が0.0060%以下であると、後述する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、成形した王冠外径および王冠高さが不均一となる。また、C含有量が0.0060%以下であると、圧延方向における2%ひずみ引張と再引張との降伏強度差が25MPa未満となり、軟質なライナーを併用しても高い耐圧強度が得られない。一方、C含有量が0.0100%超であると、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、成形した王冠外径および王冠高さが不均一となる。そのため、C含有量は0.0060%超0.0100%以下とする。好ましくは、C含有量は0.0065%以上0.0090%以下とする。
Si含有量が高すぎると、Cと同様の理由により、王冠外径および王冠高さの均一性が損なわれる。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。
Mn含有量が0.05%を下回ると、S含有量を低下させた場合でも熱間脆性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含有量が高すぎると、Cと同様の理由により、王冠外径および王冠高さの均一性が損なわれる。よって、Mnの含有量は0.60%以下とする。好ましくは、Mn含有量は0.10%以上0.50%以下である。
P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超となり、王冠高さが不均一となる。よって、P含有量の上限値は0.050%とする。また、P含有量を0.001%未満とするためには脱Pコストが過大となるため、P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含有量は0.050%以下とする。一方、S含有量を0.005%未満とするためには脱Sコストが過大となるため、S含有量は0.005%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であり、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粒径が粗大となり、成形した王冠外径および王冠高さが不均一となる。そのため、Al含有量は0.020%以上とする。Al含有量は0.030%以上とすることが好ましい。一方、Al含有量が0.050%超であると、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。そのため、Al含有量は0.050%以下とする。Al含有量は0.045%以下とすることが好ましい。
N含有量が0.0070%未満であると、二次冷間圧延後の鋼板のフェライト粒径が粗大となり、成形した王冠外径および王冠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。さらに、圧延方向における2%ひずみ引張と再引張との降伏強度差が25MPa未満となり、軟質なライナーを併用しても高い耐圧強度が得られない。一方、N含有量が0.0140%超であると、二次冷間圧延後の鋼板のフェライト粒径が微細となりすぎて、成形した王冠外径および王冠高さが不均一となる。そのため、N含有量は0.0070%以上0.0140%以下とする。N含有量は、0.0085%以上0.0125%以下とすることが好ましく、0.0100%超0.0125%以下とすることがより好ましい。
本発明に係る王冠用鋼板の金属組織は、少なくとも、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、前記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以下であることが肝要である。
まず、王冠用鋼板の圧延方向に平行な板厚断面を、板厚1/4深さ位置(上記断面における、表面から板厚方向に1/4の位置)から板厚1/2位置までの領域に渡って光学顕微鏡で観察して組織写真を得る。次いで、得られた組織写真を用いて、フェライトを目視判定により特定する。その後、前記組織写真を画像解析してフェライトの粒径を求め、各視野でフェライト粒径の粒度分布を求めて、標準偏差を算出する。10視野における標準偏差を平均した値をフェライト粒径の標準偏差とする。より具体的には、実施例に記載の方法で評価することができる。
本発明に係る鋼板の機械的性質として、圧延方向における2%ひずみ引張試験と熱処理後の引張試験との降伏強度差(以下、単に「降伏強度差」という場合がある)が25MPa以上であることが肝要である。すなわち、前記降伏強度差が25MPa未満であると、該鋼板を用いて多数の王冠を製造し、耐圧試験を行った場合に、耐圧強度の低い王冠が散見されることになり、王冠を製造する際の歩留りが低下する。そのため、前記降伏強度差は25MPa以上とする。前記降伏強度差は30MPa以上とすることが好ましい。
BH=(P2-P1)/A ・・・(1)
以上の成分組成および組織を有する鋼板では、高い強度、具体的には560MPa以上の降伏強度を確保することができる。すなわち、王冠用鋼板には、王冠に用いた際に、瓶の口にかしめた王冠が内圧によって外れない耐圧強度を備えることが求められる。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。
上記王冠用鋼板の板厚は特に限定されず、任意の厚さとすることができる。しかし、コストダウンの観点からは、板厚を0.20mm以下とすることが好ましく、0.18mm以下とすることがより好ましく、0.17mm以下とすることがさらに好ましい。なお、板厚が0.14mmを下回ると、製造コスト面での不利が生じるので、板厚の下限は0.14mmとすることが好ましい。
次に、本発明の一実施形態における王冠用鋼板の製造方法について説明する。なお、以下の説明において、温度の規定は鋼板の表面温度を基準とする。また、平均加熱速度および平均冷却速度は、鋼板の表面温度を基に計算して得られた値とする。
(1)熱間圧延工程
(2)酸洗工程
(3)一次冷間圧延工程
(4)連続焼鈍工程
(5)二次冷間圧延工程
まず、上記の成分組成に調整した鋼を転炉などで溶製し、鋼スラブを製造する。前記鋼スラブは、特に限定されることなく、連続鋳造法、造塊法、薄スラブ鋳造法など、任意の方法で製造することができるが、成分のマクロ偏析を防止するために連続鋳造法で製造することが好ましい。
次に、前記鋼スラブを熱間圧延工程に供する。前記熱間圧延工程では、前記鋼スラブを加熱し、加熱された前記鋼スラブに粗圧延と仕上圧延からなる熱間圧延を施して熱延鋼板とし、前記仕上圧延後の熱延鋼板をコイルに巻取る。
スラブ加熱温度:1200℃以上
前記加熱においては、前記鋼スラブを1200℃以上のスラブ加熱温度まで再加熱する。前記スラブ加熱温度が1200℃未満であると、強度を確保するために必要な固溶N量が減少し、強度が不足する。そのため、スラブ加熱温度は1200℃以上とする。
仕上圧延温度:870℃以上
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し、王冠用に供した場合に、王冠形状が不均一となるため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。
熱間圧延工程における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%未満であると、鋼板のフェライトの一部が粗大化し、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。そしてその結果、王冠用に供した場合に王冠形状が不均一となる。したがって、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より小さくするためには、最終スタンドの圧下率を12%以上とすることが好ましい。一方、最終スタンドの圧下率の上限は特に限定されないが、圧延荷重の観点からは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℃未満であると、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。そしてその結果、王冠用に供した場合に王冠形状が不均一となる。そのため、巻取温度は550℃以上とする。一方、巻取温度が750℃より高いと、鋼板のフェライトの一部が粗大化し、フェライト粒径の標準偏差が7.0μm超となって、王冠形状が不均一となる。そのため、巻取温度は750℃以下とする。巻取り温度は600℃以上700℃以下とすることが好ましい。
次いで、上記熱間圧延工程後の熱延鋼板を酸洗する。酸洗により、前記熱延鋼板の表面の酸化スケールを除去することができる。酸洗条件は特に限定されず、常法に従って適宜設定すればよい。
圧下率:88%以上
まず、上記酸洗後の熱延鋼板に対して一次冷間圧延を施す。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が88%未満であると、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、フェライト粒径の標準偏差が7.0μm超となる。その結果、成形性が悪化し、王冠用に供した場合に王冠形状が不均一となる。そのため、一次冷間圧延工程の圧下率は88%以上とする。前記圧下率は、89~94%とすることが好ましい。
次に、一次冷間圧延板に、連続焼鈍を行う。前記連続焼鈍工程においては、一次冷間圧延工程後の鋼板を均熱温度まで加熱し、660~760℃の温度域に所定時間保持した後、一次冷却および二次冷却を行う。その際の条件は、以下のとおりとする。
上記連続焼鈍工程における均熱温度(焼鈍温度)が760℃超であると、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る。また、鋼板のフェライト粒径が一部粗大化し、フェライト粒径の標準偏差が7.0μm超となり、王冠形状が不均一となる。一方、均熱温度が660℃未満であると、再結晶が不完全となるため、鋼板のフェライト粒径が一部細かくなる。そしてその結果、フェライト粒径の標準偏差が7.0μm超となり、王冠形状が不均一となる。したがって、均熱温度は、660~760℃とする。均熱温度は、680~730℃とすることが好ましい。
600℃から前記均熱温度までの平均加熱速度が15℃/s超であると、鋼板の圧延方向における降伏強度さ(BH量)が25MPa未満となる。そしてその結果、該鋼板を用いて高GVの炭酸飲料用の王冠を多数製造した場合に、耐圧強度の低い王冠が散見されることになり、王冠を製造する際の歩留りが低下する。そのため、前記平均加熱速度を15℃/s以下とする。前記平均加熱速度は、10℃/s未満とすることが好ましい。一方、前記平均加熱速度が1℃/sより低くしても、効果が飽和するばかりか、加熱設備に過剰なコストが発生する。そのため、前記平均加熱速度は1℃/s以上とすることが好ましく、2℃/s以上とすることがより好ましい。
660~760℃の温度域に保持する保持時間(均熱時間)は60秒以下とする。前記保持時間が60秒を超えると、鋼板に含有するCがフェライト粒界へ偏析して、均熱後の冷却過程で炭化物として析出する。そしてその結果、鋼板強度に寄与する固溶C量が減少し、降伏強度が低下する。そのため、前記保持時間は60秒以下とする。一方、前記保持時間の下限は特に限定されないが、保持時間が5秒未満であると、均熱帯のロールを鋼板が通板する際の安定性が損なわれる場合があるため、保持時間を5秒以上とすることが好ましい。
前記均熱後、10℃/s以上の平均冷却速度で450℃以下の温度(一次冷却停止温度)まで冷却する(一次冷却)。前記一次冷却における平均冷却速度(一次冷却平均速度)が10℃/s未満であると、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量が減少し、降伏強度が低下する。そのため、前記一次冷却平均速度を10℃/s以上とする。一方、前記一次冷却平均速度が50℃/s超であると上記の効果が飽和するため、一次冷却平均速度は50℃/s以下とすることが好ましい。
前記一次冷却における冷却停止温度(一次冷却停止温度)が450℃より高いと、一次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量が減少し、降伏強度が低下する。そのため、前記一次冷却停止温度を450℃以下とする。一方、前記一次冷却停止温度の下限は特に限定されないが、一次冷却停止温度が300℃未満であると、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トラブルが発生するおそれがある。そのため、前記一次冷却停止温度は300℃以上とすることが好ましい。
前記一次冷却後、5℃/s以上の平均冷却速度で140℃以下の温度(二次冷却停止温度)まで冷却する(二次冷却)。前記二次冷却における平均冷却速度(二次冷却平均速度)が5℃/s未満であると、鋼板強度に寄与する固溶C量が減少し、降伏強度が低下する。そのため、前記二次冷却平均速度を5℃/s以上とする。一方、前記二次冷却平均速度が30℃/s超であると、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。そのため、前記二次冷却平均速度は30℃/s以下とすることが好ましく、25℃/s以下とすることがより好ましい。
前記二次冷却における冷却停止温度(二次冷却停止温度)が140℃超であると、鋼板強度に寄与する固溶C量が減少し、降伏強度が低下する。そのため、前記二次冷却停止温度は140℃以下とする。一方、前記二次冷却停止温度の下限は特に限定されないが、二次冷却停止温度が100℃未満であると、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。そのため、前記二次冷却停止温度は100℃以上とすることが好ましく、120℃以上とすることがより好ましい。
圧下率:10~40%
本発明においては、上記連続焼鈍後に二回目の冷間圧延(二次冷間圧延)を行うことによって高い降伏強度を得ることができる。その際、前記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。一方、二次冷間圧延の圧下率が40%を超えると、異方性が過大となり、例えば王冠用に供した場合に王冠形状の均一性を損なう。そのため、二次冷間圧延の圧下率は10%以上40%以下とする。前記圧下率は15%超35%以下とすることが好ましい。
本発明の一実施形態における王冠は、上記王冠用鋼板を成形することによって得ることができる。より具体的には、上記王冠用鋼板からなる金属部分と、該金属部分の内側に積層された樹脂製ライナーとからなる王冠とすることが好ましい。前記金属部分は、瓶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から構成される。また、前記樹脂製のライナーは、前記円盤状の部分に貼付される。
HTL=3.858×P/D2 ・・・(2)
まず、鋼板の成分組成の影響を評価するために、以下の試験を行った。
光学顕微鏡を使用して王冠用鋼板の組織写真を撮影し、得られた組織写真から、板厚の1/4の深さから板厚中心までの領域におけるフェライト粒径の標準偏差を求めた。具体的な手順は、次のとおりとした。まず、王冠用鋼板の圧延方向に平行な板厚断面を、研磨した後、腐食液(3体積%ナイタール)で腐食した。次いで、前記断面の板厚1/4深さ位置(上記断面における、表面から板厚方向に1/4の位置)から板厚1/2位置までの領域から無作為に選んだ10視野を、光学顕微鏡を用いて400倍の倍率で観察して組織写真を得た。得られた組織写真を用いて、フェライトを目視判定により特定し、画像解析によりフェライト粒径を求めた。その後、各視野でフェライト粒径の粒度分布を求めて、標準偏差を算出した。前記10視野における標準偏差を平均した値をフェライト粒径の標準偏差とした。前記画像解析は、オリンパス株式会社製の画像解析ソフトウェア 「Stream Essentials」を使用した。
上記王冠用鋼板に対し、塗装焼付け相当の熱処理(210℃、15分間)を施した後、引張試験を行って、前記王冠用鋼板の、圧延方向における降伏強度を測定した。前記引張試験は、JIS5号サイズの引張試験片を用いて、「JIS Z 2241」に従って行った。なお、前記熱処理は、王冠用鋼板の成分組成に影響しない。
上記王冠用鋼板の、2%ひずみ引張試験と熱処理後の引張試験との間での、圧延方向における降伏強度の差(降伏強度差)を、「JIS G3135」に規定される塗装焼付硬化量(BH量)の試験方法に準じた方法で求めた。まず、前記王冠用鋼板から、該鋼板の圧延方向に平行にJIS5号サイズの引張試験片を採取した。次いで、前記試験片を用いて、「JIS G3135」に準じて引張試験を行って、2%予ひずみ荷重を測定した。すなわち、試験片に予ひずみ2%を与えて、そのときの荷重(2%予ひずみ荷重:P1)を読み取り、その後荷重を除去した。次いで、予ひずみを与えた前記試験片に170℃で20分の熱処理を施し、前記熱処理後に再度引張試験を実施して降伏荷重(熱処理後荷重:P2)を読み取った。P1、P2、および予ひずみ前の試験片平行部断面積(A)を用いて、下記(1)式によりBH量(MPa)を算出した。得られたBH量を、圧延方向における2%ひずみ引張試験と熱処理後の引張試験との降伏強度差とした。
BH=(P2-P1)/A ・・・(1)
上述したように、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。そこで、Nの総量(Ntotal)からAlNとして存在するN量(N as AlN)を差し引いた値(Ntotal-(N as AlN))を算出し、これを固溶N量とした。AlNとして存在するN量は、試料を10%Brメタノール溶液で溶解し、残渣を分析することにより求めた。
得られた王冠用鋼板を以下に述べる手順で王冠に成形し、前記王冠用鋼板の成形性を評価した。まず、塗装焼付け相当の熱処理(210℃、15分間)を施した前記王冠用鋼板を打ち抜いて、直径37mmの円形ブランクを作成した。前記円形ブランクを、プレス加工して、各王冠用鋼板について20個(N=20)の王冠を成形した。王冠の高さ(王冠天面からスカート下端までの距離)を、マイクロメータを用いて測定し、N=20の王冠高さの標準偏差を算出した。前記標準偏差の値(mm)を成形性の指標とした。なお、前記標準偏差が0.09mm以下であれば王冠形状が優れており、0.09mmを超える場合は劣っているといえる。
上記王冠を市販瓶に打栓し、Secure Pak社製Secure Seal Testerを用いて王冠が外れる内圧を測定し、王冠が外れた内圧を耐圧強度とした。各20個の王冠に耐圧試験を実施して、耐圧強度が180psi(1.241MPa)以上である王冠の数が18個以上であった場合を合格(○)、耐圧強度が180psi(1.241MPa)以上である王冠の数が18未満の場合を不合格(×)とした。
ライナーの超微小負荷硬さを、「JIS Z2255」(2003)に記載の方法に従って測定した。前記測定においては、樹脂製ライナーが鋼板に貼付された状態で王冠から切り出した試験片を用いた。前記試験片を、水平出しをした状態で鋼板側をエポキシ樹脂で接着固定し、ダイナミック微小硬度計(DUH-W201S、島津製作所製)を用いて負荷-除荷試験を実施して超微小負荷硬さを測定した。
HTL=3.858×P/D2 ・・・(2)
上記成形性の試験におけるN=20の王冠高さの標準偏差が0.09mm以下であり、かつ上記耐圧強度の試験における評価結果が合格(○)であった場合を総合評価○とし、前記条件の一方または両方を満たさない場合を総合評価×とした。
次に、製造条件の影響を評価するために、以下の試験を行った。
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、残部がFeおよび不可避的不純物からなる成分組成を有し、
板厚の1/4の深さから板厚中心までの領域にフェライト相を有し、前記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、
圧延方向における降伏強度が560MPa以上700MPa以下であり、
圧延方向の2%ひずみ引張試験における降伏強度と、170℃で20分の熱処理後の引張試験における降伏強度の差が25MPa以上である、王冠用鋼板。 - 板厚が0.20mm以下である、請求項1に記載の王冠用鋼板。
- 請求項1または2に記載の王冠用鋼板を成形してなる王冠。
- 超微小負荷硬さが0.70未満である樹脂製ライナーを有する、請求項3に記載の王冠。
- 請求項1または2に記載の王冠用鋼板の製造方法であって、
請求項1に記載の成分組成を有する鋼スラブを、1200℃以上のスラブ加熱温度に加熱し、仕上圧延温度:870℃以上、最終スタンドの圧下率:10%以上の条件で熱間圧延したのち、巻取り温度:550~750℃で巻取る熱間圧延工程と、
前記熱間圧延工程後に酸洗する酸洗工程と、
前記酸洗工程後に、圧下率:88%以上で冷間圧延する一次冷間圧延工程と、
前記一次冷間圧延工程後に、連続焼鈍する連続焼鈍工程と、
前記連続焼鈍工程後に、圧下率:10~40%で冷間圧延を行う二次冷間圧延工程と
を有し、
前記連続焼鈍工程においては、
660~760℃の均熱温度まで、600℃から前記均熱温度までの温度域における平均加熱速度:15℃/s以下の条件で加熱し、
次いで、660~760℃の温度域に60秒以下の保持時間保持し、
前記保持後、平均冷却速度:10℃/s以上で450℃以下の温度まで一次冷却し、
引き続き、平均冷却速度:5℃/s以上で140℃以下の温度まで二次冷却する、王冠用鋼板の製造方法。
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JP2000248335A (ja) * | 1999-02-26 | 2000-09-12 | Nippon Steel Corp | 靭性に優れた低降伏比型耐火用熱延鋼板及び鋼管並びにそれらの製造方法 |
JP2013133497A (ja) * | 2011-12-27 | 2013-07-08 | Jfe Steel Corp | 伸びフランジ性に優れた高強度熱延鋼板およびその製造方法 |
JP2015137422A (ja) * | 2014-01-24 | 2015-07-30 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
WO2015129191A1 (ja) * | 2014-02-25 | 2015-09-03 | Jfeスチール株式会社 | 王冠用鋼板およびその製造方法ならびに王冠 |
JP2015199987A (ja) * | 2014-04-08 | 2015-11-12 | 新日鐵住金株式会社 | 低温靭性と均一伸びと穴拡げ性に優れた引張強度780MPa以上の高強度熱延鋼板及びその製造方法 |
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JP5434212B2 (ja) * | 2008-04-11 | 2014-03-05 | Jfeスチール株式会社 | 高強度容器用鋼板およびその製造方法 |
JP5810714B2 (ja) * | 2011-07-29 | 2015-11-11 | Jfeスチール株式会社 | 高強度高加工性缶用鋼板およびその製造方法 |
TW201631177A (zh) | 2014-12-26 | 2016-09-01 | 新日鐵住金股份有限公司 | 瓶蓋用鋼板之製造方法及瓶蓋用鋼板 |
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JPS6057023B2 (ja) | 1979-07-25 | 1985-12-12 | 松下電工株式会社 | 防排煙制御装置の断線短絡検出回路 |
JP2000248335A (ja) * | 1999-02-26 | 2000-09-12 | Nippon Steel Corp | 靭性に優れた低降伏比型耐火用熱延鋼板及び鋼管並びにそれらの製造方法 |
JP2013133497A (ja) * | 2011-12-27 | 2013-07-08 | Jfe Steel Corp | 伸びフランジ性に優れた高強度熱延鋼板およびその製造方法 |
JP2015137422A (ja) * | 2014-01-24 | 2015-07-30 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
WO2015129191A1 (ja) * | 2014-02-25 | 2015-09-03 | Jfeスチール株式会社 | 王冠用鋼板およびその製造方法ならびに王冠 |
JP2015199987A (ja) * | 2014-04-08 | 2015-11-12 | 新日鐵住金株式会社 | 低温靭性と均一伸びと穴拡げ性に優れた引張強度780MPa以上の高強度熱延鋼板及びその製造方法 |
Non-Patent Citations (1)
Title |
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See also references of EP3663427A4 |
Also Published As
Publication number | Publication date |
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CA3066880C (en) | 2021-09-07 |
EP3663427B1 (en) | 2021-01-20 |
US11359255B2 (en) | 2022-06-14 |
EP3663427A1 (en) | 2020-06-10 |
AU2018309965B2 (en) | 2020-12-10 |
BR112020001509A2 (pt) | 2020-09-08 |
PH12020500220A1 (en) | 2020-10-19 |
US20200199706A1 (en) | 2020-06-25 |
EP3663427A4 (en) | 2020-06-10 |
JPWO2019026739A1 (ja) | 2019-08-08 |
AU2018309965A1 (en) | 2020-01-02 |
CA3066880A1 (en) | 2019-02-07 |
JP6465265B1 (ja) | 2019-02-06 |
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