EP1002884B1 - Plaque d'acier laminee a froid possedant d'excellentes caracteristiques d'aptitude au moulage et de formabilite en panneaux, une bonne resistance a la constriction, plaque d'acier a placage en zinc moule et procede de fabrication de ces plaques - Google Patents
Plaque d'acier laminee a froid possedant d'excellentes caracteristiques d'aptitude au moulage et de formabilite en panneaux, une bonne resistance a la constriction, plaque d'acier a placage en zinc moule et procede de fabrication de ces plaques Download PDFInfo
- Publication number
- EP1002884B1 EP1002884B1 EP98944222A EP98944222A EP1002884B1 EP 1002884 B1 EP1002884 B1 EP 1002884B1 EP 98944222 A EP98944222 A EP 98944222A EP 98944222 A EP98944222 A EP 98944222A EP 1002884 B1 EP1002884 B1 EP 1002884B1
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- steel sheet
- rolled steel
- resistance
- panel
- cold
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- 229910000831 Steel Inorganic materials 0.000 title claims description 126
- 239000010959 steel Substances 0.000 title claims description 126
- 239000010960 cold rolled steel Substances 0.000 title claims description 29
- 238000004519 manufacturing process Methods 0.000 title claims description 17
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 title claims 2
- 239000011701 zinc Substances 0.000 title claims 2
- 229910052725 zinc Inorganic materials 0.000 title claims 2
- 238000000137 annealing Methods 0.000 claims description 21
- 238000005098 hot rolling Methods 0.000 claims description 13
- 229910001335 Galvanized steel Inorganic materials 0.000 claims description 11
- 239000008397 galvanized steel Substances 0.000 claims description 11
- 238000005246 galvanizing Methods 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 9
- 238000005266 casting Methods 0.000 claims description 8
- 238000005097 cold rolling Methods 0.000 claims description 8
- 229910000859 α-Fe Inorganic materials 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 238000001953 recrystallisation Methods 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 3
- 239000010955 niobium Substances 0.000 description 20
- 239000000203 mixture Substances 0.000 description 13
- 230000032683 aging Effects 0.000 description 11
- 239000011572 manganese Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
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- 238000005516 engineering process Methods 0.000 description 5
- 230000001771 impaired effect Effects 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 238000005482 strain hardening Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
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- 230000008018 melting Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
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- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical group [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0426—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0436—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0224—Two or more thermal pretreatments
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
Definitions
- the present invention relates to a cold-rolled steel sheet and a galvanized steel sheet, which are excellent in formability, panel shapeability, and dent-resistance required for an outer panel of a motor car, and a method of manufacturing the same.
- An excellent formability, a satisfactory shape after a panel formation and a high dent-resistance (resistance to local depression) are required for a steel sheet for an outer panel of a motor car.
- the panel formability is evaluated by indexes such as yield strength, elongation, and an n-value (work-hardening index) of the steel sheet.
- the panel shapeability and the dent-resistance are evaluated in many cases by yield strength and the yield strength after the working and the coating-baking treatment. If the yield strength of the steel sheet is weakened, the press formability can be improved. However, the dent-resistance after the panel formation is rendered unsatisfactory.
- a method of manufacturing a BH steel sheet having a excellent deep drawability which is a cold-rolled steel sheet prepared by adding elements capable of forming carbonitrides such as Nb and Ti to a steel having a very low carbon content of about 50 ppm, the addition amount of such an element being not larger than 1 in terms of the atomic ratio of carbon.
- Japanese Patent Publication (Kokoku) No. 60-46166 teaches that a Nb or Ti added low-carbon steel is annealed at a high temperature close to 900°C for manufacturing the particular BH steel sheet.
- Japanese Patent Disclosure (Kokai) No. 61-276928 teaches that an extra low carbon BH steel sheet is manufactured by annealing under a temperature region of about 700 to 850°C.
- JP '166 The technology disclosed in JP '166 is certainly advantageous in that the BH properties and an r-value can be improved.
- the annealing is performed at a high temperature, the rough surface derived from enlargement of the ferrite grains is worried about.
- the steel sheet itself is softened, the yield strength after the press forming and the baking steps is not acceptably high, though high BH properties may be obtained.
- the annealing temperature is relatively low, compared with that employed in JP '166, and, thus, is desirable in the required surface properties and the yield strength.
- the cold-rolled sheet manufactured by the conventional method is not sufficiently satisfactory in the surface properties, the resistance to natural aging, and the dent-resistance, which are required for the steel sheet used for an outer panel of a motor car.
- An object of the present invention is to provide a cold-rolled steel sheet and a galvanized steel sheet, which are satisfactory in any of the surface properties, the resistance to natural aging, and the dent-resistance, which are required for the steel sheet used for an outer panel of a motor car, and a method of manufacturing the same.
- the cold-rolled sheet manufactured by the conventional method is not sufficiently satisfactory in the surface properties, the resistance to natural aging, and the dent-resistance, which are required for the steel sheet used for an outer panel of a motor car.
- a cold-rolled steel sheet according to the invention must satisfy several conditions which are not met by Elias et al. As a result, the composition of the obtained cold-rolled steel sheet is enterly different that the one of the invention.
- claim 3 of Elias et al. recites steel having yield strength of about 620 MPa. It concerns a technology relating to Al coated steel sheet which is full hard material. Such a sheet is not formable enough to be used for an outer panel of motorcar, for example.
- the cold-rolled steel sheet according to Elias et al. is manufactured by batch annealing, not by continuous annealing.
- An object of the present invention is to provide a cold-rolled steel sheet and a galvanized steel sheet, which are satisfactory in any of the surface properties, the resistance to natural aging, and the dent-resistance, which are required for the steel sheet used for an outer panel of a motor car, and a method of manufacturing the same.
- the present inventors have conducted an extensive research in an attempt to obtain a cold-rolled steel sheet and a galvanized steel sheet, which are excellent in the surface properties, the resistance to natural aging and the dent-resistance required for the steel used for an outer panel of a motor car, and a method of manufacturing the same.
- the dent-resistance of a panel can be improved by an alloy design with an emphasis placed on the work-hardening behavior in a low strain region in the panel forming step, unlike the prior art in which the dent-resistance required for an outer panel of a motor car is improved by increasing the BH value. It has also been found that good surface properties and resistance to natural aging can be imparted to the steel sheet by positively suppressing the BH value.
- % represents “% by weight”.
- a carbide formed together with Nb affects the work-hardening in a low strain region in panel forming step and contributes to an improvement of the dent-resistance.
- the particular effect cannot be obtained, if the C amount is less than 0.005%. Also, if the C amount exceeds 0.015%, the dent-resistance of the panel is certainly improved. However, the shape of the panel is impaired. It follows that the C amount should fall within a range of between 0.005 and 0.015%. Si: 0.01 to 0.2%
- Si is effective for strengthening the steel. However, if the Si amount is smaller than 0.01%, it is impossible to obtain a capability of the solid solution strengthening. On the other hand, if the Si amount is larger than 0.2%, the surface properties of the steel sheet are impaired. In addition, striped surface defects are generated after galvanizing. Therefore, the Si amount should fall within a range of between 0.01 and 0.2%. Mn: 0.2 to 1.5%
- Manganese serves to precipitate sulfide and to suppress deterioration of the hot ductility. Also, Mn is effective for strengthening the steel. If the Mn amount is less than 0.2%, hot brittleness of the steel sheet is brought about, leading to a low yield. In addition, a high mechanical strength characterizing the steel sheet of the present invention cannot be obtained. Further, Mn, which relates to an improvement in the workability of the steel sheet, is necessary for controlling the morphology of the MnS in the hot rolling step. It should be noted that fine MnS particles are formed by the process of resolution and re-precipitation in the hot rolling step. These MnS particles impair the grain growth of the steel.
- Mn amount should fall within a range of between 0.2% and 1.5%. P: 0.01 to 0.07%
- Phosphorus is most effective for the solid solution strengthening of steel. If the P amount is smaller than 0.01%, however, P fails to exhibit a sufficient strengthening capability. On the other hand, if the P amount exceeds 0.07%, the ductility of the steel sheet is deteriorated. Also, a defective coating is brought about in the step of the alloying treatment during the continuous galvanizing process. It follows that the P amount should fall within a range of between 0.01 and 0.07%. S: 0.006 to 0.015%
- Sulfur if added in an amount exceeding 0.015%, brings about hot brittleness of the steel. If the S amount is smaller than 0.006%, however, the peeling capability of the scale is impaired in the hot rolling step, and surface defects tend to be generated markedly. It follows that the S amount should fall within a range of between 0.006 and 0.015%.
- Sol. Al 0.01 to 0.08%
- Aluminum serves to deoxidize the steel and fix N as nitride. If the Al amount is smaller than 0.01%, however, the deoxidation and the fixation of N cannot be achieved sufficiently. On the other hand, if the Al amount is larger than 0.08%, the surface properties of the steel sheet are deteriorated. Therefore, the Al amount should fall within a range of between 0.01 and 0.08%. N ⁇ 0.004%
- Nitrogen is fixed in the form of AlN. If the N amount exceeds 0.004%, however, it is impossible to obtain a desired formability of the steel sheet. Naturally, the N amount should not exceed 0.004%. O ⁇ 0.003%
- Niobium is bonded to C to form fine carbide particles. These fine carbide particles affect the work-hardening behavior in the panel forming step so as to contribute to an improvement in the dent-resistance of the panel. If the Nb amount is smaller than 0.04%, however, it is impossible to obtain the particular effect. On the other hand, if the Nb amount exceeds 0.23%, the panel shapeability such as the spring back and the surface deflection is deteriorated, though the dent-resistance is certainly improved. Naturally, the Nb amount should fall within a range of between 0.04 and 0.23%. ( Nb ⁇ 12 ) / C ⁇ 93 : 1.0 to 3.0
- B 0.0001 to 0.002%
- the grain boundary is strengthened so as to improve the resistance to the secondary working brittleness.
- the ferrite grains are diminished so as to ensure an absolute value of the yield strength and, thus, to improve the dent-resistance.
- the B amount is smaller than 0.0001%.
- the B amount exceeds 0.002%, the yield point is increased and, thus, the panel shapeability is impaired. It follows that the B amount should fall within a range of between 0.0001 and 0.002%.
- a ratio of flow stress ⁇ obtained by a tensile test under the condition that a true strain ⁇ is larger than 0.002 and not larger than 0.096, i.e., 0.002 ⁇ ⁇ ⁇ 0.096, to a 0.2% proof stress ⁇ 0.2 , i.e., ⁇ / ⁇ 0.2 , should fall within a range of between exp( ⁇ ) ⁇ (5.29 ⁇ exp ( ⁇ ) - 4.19) and exp( ⁇ ) ⁇ (5.64 ⁇ exp( ⁇ ) - 4.49).
- the dent-resistance load under the conditions of 2%P0.1, 4%P0.1, 8%P0.1 is as high as 160 to 190N as shown in FIGS. 3 to 5 .
- a steel sheet is formed to a model panel shown in FIG. 2 with strain of 2%, 4% or 8% imparted to the steel sheet, followed by applying a heat treatment at 170°C for 20 minutes. Then, measured is a load required for imparting a residual displacement of 0.1 mm to the model panel.
- the spring back ⁇ (measured for a panel having a strain of 2%) is as large as 7 to 10% so as to impair the panel shapeability, if the ratio ⁇ / ⁇ 0.2 is lower than the lower limit noted above. On the other hand, if the ratio ⁇ / ⁇ 0.2 is higher than the upper limit noted above, the spring back ⁇ is as small as 2 to 5% to improve the panel shapeability.
- the dent-resistance is as low as 140 to 175N. In other words, the dent-resistance cannot be improved.
- the ratio ⁇ / ⁇ 0.2 should fall within a range of between exp( ⁇ ) ⁇ (5.29 ⁇ exp ( ⁇ ) - 4.19) and exp ( ⁇ ) ⁇ (5.64 ⁇ exp( ⁇ ) - 4.49).
- a cold-rolled steel sheet and a galvanized steel sheet excellent in the panel surface properties and the dent-resistance required for the steel used for an outer panel of a motor car can be obtained by controlling the additive components as described in item (1) above and the tensile characteristics as described in item (2) above.
- the steel sheet exhibiting the particular properties can be manufactured as follows.
- steel of the composition given in item (1) above is melted.
- a converter method is generally employed for melting the steel composition, or an electric furnace method can also be employed.
- the slab is heated immediately after the casting, or after the slab is once cooled, for applying a hot rolling.
- the hot rolling is performed under the conditions that the finishing temperature is set at temperature not less than (Ar 3 -100)°C and that the coiling temperature is set at 500°C to 700°C. If the finishing temperature is lower than (Ar 3 -100)°C, 2%P0.1, i.e., the dent-resistance load of the panel imparted with 2% of strain) is as low as 140 to 150N, as shown in FIG.
- the dent-resistance of the panel cannot be improved.
- the value of 2%P0.1 is high, i.e., 155 to 165N.
- the value of ⁇ i.e., the spring back amount of the panel imparted with 2% of strain, is as large as 8% to 10%, leading to a poor shapeability.
- the value of Wca i.e., Arithmetic Average Waviness Height; measuring length of 25 mm; average of the values measured at 10 optional points around the apex of the panel
- Wca Arithmetic Average Waviness Height; measuring length of 25 mm; average of the values measured at 10 optional points around the apex of the panel
- the finishing temperature should be not lower than (Ar 3 -100)°C and that the coiling temperature should fall within a range of between 500°C and 700°C.
- the hot-rolled steel band is subjected to pickling, cold-rolling and, then, a continuous annealing.
- galvanizing is applied after the continuous annealing.
- the cold-rolling reduction should desirably be at least 70% in order to improve the deep drawability (r-value) of the steel sheet.
- the annealing should desirably be carried out within a recrystallization temperature region of the ferrite phase.
- the coating employed in the present invention is not limited to continuous galvanizing. Specifically, even if a surface treatment such as coating with zinc phosphate or an electrolytic galvanizing is applied to the steel sheet obtained by the continuous annealing, no problem is brought about in the characteristics of the resultant steel sheet.
- Molten steel of the composition shown in Table 1 were prepared in a laboratory, followed by continuously casting the steel to prepare a slab having a thickness of 60 mm.
- Samples Nos. 1 to 7 shown in Table 1 represent the steel of the composition specified in the present invention, with samples Nos. 8 to 15 denoting the steel for Comparative Examples.
- the slab was treated by a blooming mill to reduce the thickness of the steel sheet to 30 mm, followed by heating the steel sheet at 1050°C for 1.5 hours under the atmosphere for the hot rolling treatment (by roughing mill). After the rough rolling, a finish rolling was applied at 900°C, followed by applying a coiling simulation at 630°C so as to obtain a hot rolled sheet having a thickness of 3 mm.
- the hot rolled steel sheet was pickled, followed by applying a cold rolling to reduce the thickness of the steel sheet to 0.8 mm and subsequently applying a continuous annealing at 840°C for 90 seconds.
- a galvanizing was applied at 460°C, followed by applying an alloying treatment at 530°C.
- 1.0% of temper rolling was applied to the annealed steel sheet or the galvanized steel sheet so as to prepare samples for the experiments. These samples were used for the tensile test (test piece of JIS No.
- the sample was formed into the model panel shown in FIG. 2 (formed at three levels of the forming strain of 2, 4 and 8%). After a heat treatment was applied at 170°C for 20 minutes, the dent-resistance of the panel and the shapeability of the panel were examined.
- the dent-resistance was evaluated under a load of P0.1, in which 0.1 mm of residual displacement was imparted to the panel (in the following description, expressions of 2%P0.1, 4%P0.1 and 8%P0.1 are used for denoting the panel imparted with strain of 2, 4 and 8%, respectively).
- the panel shapeability was evaluated by the spring back amount ⁇ and Wca: Arithmetic Average Waviness Height (JIS B 0610).
- the spring back amount ⁇ was defined by using a curvature radius R' of the panel imparted with 2% of strain and a curvature radius R of the press mold, i.e., ⁇ was defined by (R'/R-1) ⁇ 100.
- ⁇ was not larger than 6%, i.e., ⁇ ⁇ 6%, the evaluation was marked by ⁇ .
- ⁇ was larger than 10%, i.e., ⁇ > 10%, the evaluation was marked by x.
- Wca was not larger than 0.2 ⁇ m, i.e., Wca ⁇ 0.2 ⁇ m, the evaluation was marked by ⁇ .
- Wca was larger than 0.2 ⁇ m but not larger than 0.4 ⁇ m, i.e., 0.2 ⁇ m ⁇ Wca ⁇ 0.4 ⁇ m
- the evaluation was marked by ⁇ .
- Wca was larger than 0.4 ⁇ m and not larger than 0.6 ⁇ m, i.e., 0.4 ⁇ m ⁇ Wca ⁇ 0.6 ⁇ m
- the evaluation was marked by x.
- Table 2 shows the results of measurements and evaluations.
- the value of the elongation El was as large as 41.6% to 45.0%.
- the value of ⁇ YPel was 0% in any of the samples of the present invention.
- the spring back amount ⁇ and the Waviness Height Wca were small, i.e., 3% to 5% and 0.09 ⁇ m to 0.17 ⁇ m, respectively, supporting a good panel shapeability.
- the dent-resistance P0.1 of the panel imparted with strains of 2%, 4% and 8% was as high as 158N to 193N.
- the steel samples Nos. 8 to 15 each having a composition failing to fall within the range specified in the present invention, did not satisfy simultaneously the formability, the shapeability, and the dent-resistance.
- each of Comparative Samples Nos. 8 and 9 exhibited a 2% BH as high as 33 MPa to 42 MPa and a ⁇ YPel of 0.9% to 2.2%, indicating that these samples were not satisfactory in the resistance to natural aging.
- the dent-resistance P0.1 under strains of 2% to 8% was found to be 165N to 193N, supporting a high dent-resistance.
- Comparative steel sample No. 10 was high in the elongation El and the r-value, and low in ⁇ and Wca, supporting that this sample was satisfactory in each of formability and shapeability.
- the dent-resistance load P0.1 under strains of 2% to 8% was as low as 148 to 172N.
- Comparative steel sample No. 11 was high in ⁇ 0.2 , which was 265 MPa to 270 MPa, supporting that this sample was satisfactory in dent-resistance.
- a molten steel having a composition of steel sample No. 2 of the present invention shown in Table 1 was prepared by melting and casting in a laboratory, followed by casting the molten steel to prepare a slab having a thickness of 50 mm.
- the slab was treated by a blooming mill to reduce the thickness of the steel sheet to 25 mm, followed by heating the steel sheet at 1250°C for 1 hour under the atmosphere and subsequently applying a hot rolling treatment to reduce the thickness of the steel sheet to 2.8 mm.
- the finishing temperature and the coiling temperature in the hot rolling treatment were changed within ranges of 770°C to 930°C and 450°C to 750°C, respectively.
- Example 1 The mechanical characteristics and the panel characteristics of the thin steel sheet thus prepared were examined as in Example 1. Table 3 shows the results.
- the finishing temperature for each of steel samples Nos. 1 to 3 of the present invention was lower than (Ar 3 -100)°C.
- each of these steel samples exhibited a low P0.1 under strains of 2% to 8%, i.e., 139N to 159N, and a high Wca, i.e., 0.35 ⁇ m to 0.40 ⁇ m, indicating that these steel samples were poor in the dent-resistance and in the shapeability. Further, the r-value for these steel samples was as low as 1.69 to 1.77.
- the coiling temperature for each of steel samples Nos. 7 and 12 was lower than 500°C. Also, each of these steel samples exhibited a high ⁇ 0.2 value, i.e., 243 MPa and 248 MPa, respectively, supporting a good dent-resistance.
- the ⁇ value was as high as 8% and the Wca value was as high as 0.30 ⁇ m, indicating that these steel samples were poor in the panel shape.
- the coiling temperature for each of steel samples Nos. 11, 15 and 18 was higher than 700°C.
- each of these steel samples exhibited a low ⁇ 0.2 value, i.e., 210 MPa to 216 MPa, and such a low ⁇ value of 2%.
- the Wca value was as high as 0.42 ⁇ m to 0.43 ⁇ m.
- the dent-resistance load was low in each of these steel samples.
- each of steel samples Nos. 4-6, 8-10, 13, 14, 16 and 17, which fell within the scopes specified in the present invention in respect of the finishing temperature and the coiling temperature was found to be satisfactory in each of the formability, the dent-resistance and the shapeability.
- the present invention makes it possible to manufacture stably a cold-rolled steel sheet and a galvanized steel sheet satisfying the dent-resistance of a panel, the surface shapeability and resistance to natural aging and having a tensile strength of 340 MPa or more, which are required for steels used for an outer panel of a motor car, by specifying the steel composition, the tensile characteristics and the manufacturing conditions. It follows that the present invention is highly valuable in the steel industries and in the motor car industries.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Crystallography & Structural Chemistry (AREA)
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Claims (5)
- Tôle d'acier laminée à froid et présentant d'excellentes aptitudes en termes de formage, de mise en forme de panneau et de résistance au bosselage, comprenant 0,005 à 0,015 % en poids de C, 0,01 à 0,2 % en poids de Si, 0,45 à 1,5 % en poids de Mn, 0,01 à 0,07 % en poids de P, 0,006 à 0,015 % en poids de S, 0,01 à 0,08 en poids de sol. Al, pas plus de 0,004 % en poids de N, pas plus de 0,003 % en poids de O, 0,04 à 0,23 % en poids de Nb, les quantités de Nb et de C satisfaisant la relation donnée dans la formule (1), le reste étant constitué de Fe et d'impuretés inévitables, ladite tôle d'acier laminée à froid satisfaisant la relation donnée dans la formule (2) :
où 0,002 < ε ≤ 0,096, ε représente un étirement réel, σ0,2 représente une limite d'élasticité à 0,2 %, et σ représente un étirement réel par rapport à ε;
et ledit acier ayant une valeur r moyenne satisfaisant la relation : 1,8 ≤ valeur r ≤ 2,2 ; et une résistance à la traction de 340 MPa ou plus. - Tôle d'acier laminée à froid et présentant d'excellentes aptitudes en termes de formage, de mise en forme de panneau et de résistance au bosselage conformément à la revendication 1, comprenant en outre 0,0001 à 0,002 % en poids de B.
- Tôle d'acier recouverte de zinc en fusion présentant d'excellentes aptitudes en termes de formage, de mise en forme de panneau et de résistance au bosselage, qui est obtenue en appliquant une galvanisation à la tôle d'acier laminée à froid définie dans la revendication 1 ou 2.
- Procédé de fabrication d'une tôle d'acier laminée à froid et présentant d'excellentes aptitudes en termes de formage, de mise en forme de panneau et de résistance au bosselage, définie dans la revendication 1 ou 2, comprenant les étapes de :préparation d'un acier en fusion et de coulée continue dudit acier ;application d'un traitement de laminage à chaud de telle sorte qu'un laminage de finition est effectué à (Ar3-100)°C ou plus pour former une bande d'acier laminée à chaud et que la bande d'acier laminée est enroulée à une température de 500 à 700°C ; etapplication continue d'un traitement de laminage à froid à la tôle d'acier laminée à chaud ainsi que d'un traitement de recuit à la bande d'acier laminée à froid, le traitement de recuit étant effectué dans une région de température de recristallisation de la phase de ferrite.
- Procédé de fabrication d'une tôle d'acier galvanisée, ladite tôle d'acier présentant d'excellentes aptitudes en termes de formage, de mise en forme de panneau et de résistance au bosselage, définie dans la revendication 3, comprenant les étapes de :préparation d'un acier en fusion et de coulée continue dudit acier ;application d'un traitement de laminage à chaud de telle sorte qu'un laminage de finition est effectué à (Ar3-100)°C ou plus pour former une bande d'acier laminée à chaud et que la bande d'acier laminée est enroulée à une température de 500 à 700°C ; etapplication continue d'un traitement de laminage à froid à la tôle d'acier laminée à chaud ainsi que d'un traitement de recuit et d'un traitement de galvanisation à la bande d'acier laminée à froid, le traitement de recuit étant effectué dans une région de température de recristallisation de la phase de ferrite.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP09150416A EP2172575A1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminée à froid possédant d'excellentes caractéristiques d'aptitude au moulage et de formabilité en panneaux, une bonne résistance à la constriction, plaque d'acier à placage de zinc moulé et procédé de fabrication de ces plaques |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11678898 | 1998-04-27 | ||
JP11678898A JP4177478B2 (ja) | 1998-04-27 | 1998-04-27 | 成形性、パネル形状性、耐デント性に優れた冷延鋼板、溶融亜鉛めっき鋼板及びそれらの製造方法 |
PCT/JP1998/004283 WO1999055927A1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminee a froid possedant d'excellentes caracteristiques d'aptitude au moulage et de formabilite en panneaux, une bonne resistance a la constriction, plaque d'acier a placage en zinc moule et procede de fabrication de ces plaques |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP09150416A Division EP2172575A1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminée à froid possédant d'excellentes caractéristiques d'aptitude au moulage et de formabilité en panneaux, une bonne résistance à la constriction, plaque d'acier à placage de zinc moulé et procédé de fabrication de ces plaques |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1002884A1 EP1002884A1 (fr) | 2000-05-24 |
EP1002884A4 EP1002884A4 (fr) | 2006-04-05 |
EP1002884B1 true EP1002884B1 (fr) | 2009-02-25 |
Family
ID=14695722
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98944222A Expired - Lifetime EP1002884B1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminee a froid possedant d'excellentes caracteristiques d'aptitude au moulage et de formabilite en panneaux, une bonne resistance a la constriction, plaque d'acier a placage en zinc moule et procede de fabrication de ces plaques |
EP09150416A Withdrawn EP2172575A1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminée à froid possédant d'excellentes caractéristiques d'aptitude au moulage et de formabilité en panneaux, une bonne résistance à la constriction, plaque d'acier à placage de zinc moulé et procédé de fabrication de ces plaques |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP09150416A Withdrawn EP2172575A1 (fr) | 1998-04-27 | 1998-09-24 | Plaque d'acier laminée à froid possédant d'excellentes caractéristiques d'aptitude au moulage et de formabilité en panneaux, une bonne résistance à la constriction, plaque d'acier à placage de zinc moulé et procédé de fabrication de ces plaques |
Country Status (7)
Country | Link |
---|---|
EP (2) | EP1002884B1 (fr) |
JP (1) | JP4177478B2 (fr) |
KR (1) | KR100345012B1 (fr) |
CN (2) | CN1084797C (fr) |
BR (1) | BR9810485A (fr) |
DE (1) | DE69840595D1 (fr) |
WO (1) | WO1999055927A1 (fr) |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6706125B2 (en) * | 2000-04-24 | 2004-03-16 | Jfe Steel Corporation | Linear shape steel excellent in joint fatigue characteristics and production method therefor |
CA2379698C (fr) * | 2000-05-26 | 2009-02-17 | Kawasaki Steel Corporation | Tole mince en acier lamine a froid et tole mince en acier galvanise presentant une trempabilite au vieillissement des contraintes |
US20030015263A1 (en) | 2000-05-26 | 2003-01-23 | Chikara Kami | Cold rolled steel sheet and galvanized steel sheet having strain aging hardening property and method for producing the same |
KR100473497B1 (ko) * | 2000-06-20 | 2005-03-09 | 제이에프이 스틸 가부시키가이샤 | 박강판 및 그 제조방법 |
JP4513434B2 (ja) * | 2004-07-09 | 2010-07-28 | Jfeスチール株式会社 | コイル内材質均一性に優れた高強度冷延鋼板およびその製造方法 |
KR101042434B1 (ko) * | 2007-10-29 | 2011-06-16 | 현대제철 주식회사 | 냉연강판 및 그의 제조방법 |
JP5056863B2 (ja) * | 2010-01-15 | 2012-10-24 | Jfeスチール株式会社 | 冷延鋼板およびその製造方法 |
CN109715838B (zh) | 2016-09-20 | 2021-08-03 | 蒂森克虏伯钢铁欧洲股份公司 | 用于生产扁钢产品的方法和扁钢产品 |
KR102439914B1 (ko) * | 2016-10-17 | 2022-09-05 | 타타 스틸 이즈무이덴 베.뷔. | 도색 부품용 강 기판 |
DE102017103308A1 (de) * | 2017-02-17 | 2018-08-23 | Voestalpine Stahl Gmbh | Verfahren zum Herstellen von Stahlblechen |
KR102322713B1 (ko) * | 2019-12-19 | 2021-11-04 | 주식회사 포스코 | 내열성과 성형성이 우수한 냉연강판 및 그 제조방법 |
WO2021149810A1 (fr) * | 2020-01-24 | 2021-07-29 | 日本製鉄株式会社 | Panneau |
KR102556444B1 (ko) * | 2020-12-29 | 2023-07-18 | 현대제철 주식회사 | 우수한 내덴트 특성을 가지는 내덴트성 냉연강판, 내덴트성 도금강판 및 그 제조방법 |
CN117165845B (zh) * | 2023-04-28 | 2024-04-16 | 鞍钢股份有限公司 | 新能源汽车用340MPa级合金化热镀锌板及其制备方法 |
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US3876390A (en) * | 1971-01-18 | 1975-04-08 | Armco Steel Corp | Columbium treated, non-aging, vacuum degassed low carbon steel and method for producing same |
JPS6046166B2 (ja) * | 1980-11-26 | 1985-10-15 | 川崎製鉄株式会社 | 焼付硬化性を有する良加工性冷延鋼板の製造方法 |
US4504326A (en) * | 1982-10-08 | 1985-03-12 | Nippon Steel Corporation | Method for the production of cold rolled steel sheet having super deep drawability |
JPS5967322A (ja) * | 1982-10-08 | 1984-04-17 | Kawasaki Steel Corp | 深絞り用冷延鋼板の製造方法 |
JPS59177327A (ja) * | 1983-03-25 | 1984-10-08 | Sumitomo Metal Ind Ltd | プレス加工用冷延鋼板の製造法 |
CA1259827A (fr) * | 1984-07-17 | 1989-09-26 | Mitsumasa Kurosawa | Toles d'acier laminees a froid, et methode de fabrication connexe |
JPS6164852A (ja) * | 1984-09-03 | 1986-04-03 | Kawasaki Steel Corp | 面内異方性の極めて少ないプレス加工用非時効性冷延鋼板 |
EP0421087B1 (fr) * | 1989-08-09 | 1994-11-30 | KABUSHIKI KAISHA KOBE SEIKO SHO also known as Kobe Steel Ltd. | Procédé pour la fabrication d'une tôle d'acier |
CA2037316C (fr) * | 1990-03-02 | 1997-10-28 | Shunichi Hashimoto | Toles d'acier a emboutes laminees a froid ou galvanisees par immersion a chaud |
US5690755A (en) * | 1992-08-31 | 1997-11-25 | Nippon Steel Corporation | Cold-rolled steel sheet and hot-dip galvanized cold-rolled steel sheet having excellent bake hardenability, non-aging properties at room temperature and good formability and process for producing the same |
JP2682351B2 (ja) * | 1992-09-30 | 1997-11-26 | 日本鋼管株式会社 | 耐常温時効性の優れた焼付硬化型冷延鋼板の製造方法 |
JP3293339B2 (ja) * | 1994-07-27 | 2002-06-17 | 日本鋼管株式会社 | 加工硬化性に優れた鋼板 |
JP3094804B2 (ja) * | 1994-08-01 | 2000-10-03 | 日本鋼管株式会社 | 表面性状に優れた焼付け硬化型鋼板 |
JPH0860242A (ja) * | 1994-08-17 | 1996-03-05 | Nippon Steel Corp | 製缶性と耐圧強度に優れたdi缶用鋼板の製造方法 |
FR2735148B1 (fr) * | 1995-06-08 | 1997-07-11 | Lorraine Laminage | Tole d'acier laminee a chaud a haute resistance et haute emboutissabilite renfermant du niobium, et ses procedes de fabrication. |
US5853903A (en) * | 1996-05-07 | 1998-12-29 | Nkk Corporation | Steel sheet for excellent panel appearance and dent resistance after panel-forming |
-
1998
- 1998-04-27 JP JP11678898A patent/JP4177478B2/ja not_active Expired - Fee Related
- 1998-09-24 EP EP98944222A patent/EP1002884B1/fr not_active Expired - Lifetime
- 1998-09-24 WO PCT/JP1998/004283 patent/WO1999055927A1/fr active IP Right Grant
- 1998-09-24 BR BR9810485-3A patent/BR9810485A/pt not_active IP Right Cessation
- 1998-09-24 CN CN988066173A patent/CN1084797C/zh not_active Expired - Lifetime
- 1998-09-24 KR KR1019997012339A patent/KR100345012B1/ko not_active IP Right Cessation
- 1998-09-24 EP EP09150416A patent/EP2172575A1/fr not_active Withdrawn
- 1998-09-24 DE DE69840595T patent/DE69840595D1/de not_active Expired - Lifetime
-
2001
- 2001-10-09 CN CNB011362103A patent/CN1138016C/zh not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP2172575A1 (fr) | 2010-04-07 |
CN1261408A (zh) | 2000-07-26 |
CN1138016C (zh) | 2004-02-11 |
BR9810485A (pt) | 2000-09-12 |
EP1002884A1 (fr) | 2000-05-24 |
CN1405352A (zh) | 2003-03-26 |
CN1084797C (zh) | 2002-05-15 |
JP4177478B2 (ja) | 2008-11-05 |
EP1002884A4 (fr) | 2006-04-05 |
KR20010014238A (ko) | 2001-02-26 |
WO1999055927A1 (fr) | 1999-11-04 |
DE69840595D1 (de) | 2009-04-09 |
JPH11310849A (ja) | 1999-11-09 |
KR100345012B1 (ko) | 2002-07-20 |
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