US3830669A - Process for manufacturing a cold-rolled high strength steel sheet - Google Patents

Process for manufacturing a cold-rolled high strength steel sheet Download PDF

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Publication number
US3830669A
US3830669A US00368478A US36847873A US3830669A US 3830669 A US3830669 A US 3830669A US 00368478 A US00368478 A US 00368478A US 36847873 A US36847873 A US 36847873A US 3830669 A US3830669 A US 3830669A
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United States
Prior art keywords
steel sheet
steel
cold
strip
rolled
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Expired - Lifetime
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US00368478A
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English (en)
Inventor
T Matsuoka
M Kojima
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Priority claimed from JP5877172A external-priority patent/JPS5347331B2/ja
Priority claimed from JP731006A external-priority patent/JPS5422407B2/ja
Application filed by Sumitomo Metal Industries Ltd filed Critical Sumitomo Metal Industries Ltd
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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
    • 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
    • C21D8/0273—Final recrystallisation annealing

Definitions

  • ABSTRACT A process for manufacturing a cold-rolled high strength steel sheet particularly suitable for fabrication of car body comprising the steps of making a steel comprising 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, 0.01 0.25% Nb, 0.01 0.2% Ti, and the remainder being iron excepting inherent impurities and residual deoxidizing elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, and annealing the steel sheet at a temperature of 620 C to A transfor mation point.
  • the present invention relates to a process for manufacturing a high strength steel sheet having an attractive surface and a high accuracy in thickness. More particularly, the present invention relates to a process for manufacturing a high strength cold-rolled steel sheet particularly suitable for fabrication of car body.
  • the steel sheet used usually for fabrication of passenger car body has generally a thickness of 3.0mm, particularly, 2.3mm or less.
  • high strength steel sheet which is able to industrially produce by hot rolling at present has a lower limit in thickness depending on the desired tensile strength, for example, 1.6 mm for 50 kglmm 2.3 mm for 60 kg/mm and 3.2 mm for 80 kg/mm
  • An object of the present invention is to manufacture a high strength steel sheet having a high tensile strength which can not be obtained by the conventional process, at the limited thickness described above.
  • Another object of the present invention is to provide a high strength steel sheet having a tensile strength of 50 to 100 kg/mm at a thickness of 3 mm, particularly, 2.3 mm or less.
  • a further object of the present invention is to provide a process for manufacturing a high strength steel sheet having a tensile strength of 50 to 100 kg/mm and an attractive surface and a uniform thickness.
  • a still further object of the present invention is to provide a cold-rolling process for manufacturing a steel sheet having the above-mentioned properties.
  • a steel comprising 0.03 0.20% C, 1.6 3.0% Mn, 0.03 06% Si, and remainder of Fe excepting inevitable impurities, if desired additionally containing 0.01 0.25% Nb or 0.01 4 0.2% Ti or Nb and Ti in total amount of 0.01 0.3% is hot rolled to produce a hot rolled steel strip, which is then cold rolled to a steel sheet having a desired thickness, and the steel sheet thus produced, when containing neither of Nb and Ti, is heated to a temperature of 710 C to A transformation point to anneal, and when containing at least one of Nb and Ti, is heated to a temperature of 620 C to A transformation point to anneal, thereby to produce a steel sheet having a tensile strength of 50 to 100 kg/mm and a thickness of 3.2 mm or less.
  • a carbon content less than 0.03 percent does not provide a tensile strength of 50 kg/mm or more, and a carbon content exceeding 0.20 percent decreases the toughness and deteriorates the weldability of the steel.
  • a manganese content less than 1.6 percent does not provide a tensile strength of 50 kg/mm or more, whereas a manganese content exceeding 3.0 percent renders the steel making significantly difficult.
  • Silicon, which is used as a deoxidizer, is difficult to reduce its content to less than 0.03 percent, whereas its content exceeding 0.6 percent increases the brittleness and also deteriorates the weldability of the steel.
  • Niobium and titanium serve to improve the tensile strength of the steel when it is annealed at a temperature of 620 C to A, transformation point.
  • a niobium content less than 0.01 percent does not produce such effect, and its content exceeding 0.25 percent does not effect further improvement.
  • a titanium content less than 0.01 percent does not produce the effect, whereas its content exceeding 0.2 percent renders the ingot making difficult.
  • Nb and Ti can be added in combination, whereupon it is necessary to limit the combined content to a range of 0.01 to 0.3 percent.
  • this steel may generally contain P of not more than 0.03 percent and S of not more than 0.03 percent as allowable impurities, and further may contain Cu of not more than 0.3 percent, Ni of not more than 0.3 percent, Cr of not more than 0.5 percent, Mo of not more than 0.5 percent and B of not more than 0.01 percent. These elements in-amount described above do not adversely affect the tensile strength.
  • a molten steel having the above composition is prepared, and cast into ingot in a conventional manner, whereupon Al killing is desirable.
  • the ingot is then subjected to blooming and hot rolling in a conventional manner to produce a hot rolled strip.
  • This hot rolling is desirably performed at a finishing temperature not lower than 800 C.
  • the hot rolled strip is then subjected to pickling, and thereafter is cold rolled in a conventional manner to a steel sheet having a desired thickness, whereupon a reduction ratio of not less than 30 percent is desirable.
  • the steel sheet thus produced is annealed at a constant temperature. This annealing temperature is necessary to be varied depending on whether Nb and Ti are contained or not.
  • the steel containing only C, Mn and Si should be annealed at a temperature of 710 C to A transformation point, and the steel additionally containing Nb and Ti at a temperature of 620 C to A transformation temperature.
  • An annealing temperature lower than 710 C in the former case will cause the steel to recrystallize and soften during annealing, and also cause carbides to be finely dispersed, thereby rendering it difficult to obtain the desired strength.
  • the latter steel sheet (containing Nb or Ti) can be annealed at a temperature of 620 to 710 C without causing severe softening due to the function of Nb or Ti, thereby allowing the attainment of the desired strength.
  • Such martensite and bainite can be produced by such 690 0:439 a very slow cooling rate as in the batch annealing of the 10 B ;;8 2g? 8 2%; g? cold-rolled steel sheet. 750 68:9, 0:469 250 It is known that a steel havlng such a composition de- 238 g l 32% 8.233 g g 1 scribed above can be heat treated into a structure 111- C 710 1 0:408 5 eluding martensite and bainite phases by means of nor- 730 33.3 88.1 0.378 18.5 malizing.
  • the present invention is character- 22 82 ized in that said martensite and bainite phases can be 690 produced by annealing, not normalizing, of the cold- D 3 18 0-776 rolled Steel F 750 37.5 47.7 0.790 30.5
  • the finished 670 39.3 54.5 0.722 23.8 steel sheet has an attractive surface, and a high a'ccu- 20 E 710 39.2 49.1 0.798 27.5 racy 1n thickness as well as a remarkably improved 730 strength.
  • each of the steels A, B and Example 1 C according to the present invention has an improved v tensile strength exceeding 50 kg/mm as annealed at a Steel having Chemical compositions indicated in temperature of 710 C to A, transformation point. That Table 1 WET? Prepared, wherein Steels A, B and C are is, the steel A indicates a tensile strength exceeding 50 according to the present invention, and steels D and E k as l d at 730 C d hi h d th are for comparison.
  • steels B and C indicate a tensile strength exceeding 50 Table 1 kg/mm as annealed at 710 C and higher, and particuas high as 100 kglmm Steel 7 Chemical Composition, 7: by weight I C Si Mn P S It has been also found that the above carbon steel A 009 0.03 105 M03 0006 containing C of 0.03 to 0.20 percent can further coni B ()8 (m3 251 (1003 (1006 tam one or more of Cu, Ni, Cr, Mo and B 1n amounts C :8 of Cu 0.3%, Ni 0.3%, Cr 0.5%, Mo 0.5% and B E 8: ⁇ ? 8:4 0:005 0:006 0.0l% with the similarly improved tensile strength due to the annealmg.
  • each of the steels was killed by Al and then cast into Example 2 an ingot, and then hot rolled to a strip of a thickness of Steels having compositions indicated in-Table 3 were 2 mm, the hot rolling being finished at 850 C.
  • Each prepared by using a high frequency induction furnace, steel strip was pickled and then cold rolled to a steel wherein steels F through I are according to the present heet. of 5.8 mm 12
  • Table 3 Steel 0 Si Mn P 5 Nb Ti F 0.07 0.10 2.01 0.006 0.012 0.11 o 0.07 0.12 2.52 0.002 0.007 0.19 Invented 11 0.09 0.10 2.83 0.003 0008 0.09 SILCIS J 0.09 0.09 2.77 0.006 0.009 0.19
  • This steel sheet was heated at a temperatureof 670 Each molten steel was killed by Al and then cast into to 750 C for 6 hours followed by a slow cooling at a an ingot, which was hot rolled to a strip of 2 mm thickcooling rate of 25 C/ hr. I ness, wherein the hot rolling being finished at 850 C.
  • FIG. 1 is the graph showing these results. annealing temperatures indicated in Table 4, and after larly the tensile strength of the steel C reaches nearly invention and steels K through Nare for comparison.
  • a process for manufacturing a cold-rolled high strength steel sheet having a tensile strength of 50 to 100 kg/mm characterized by making a steel comprising 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, 0.01 0.25% Nb, 0.01 0.2% Ti, and the remainder being iron excepting inherent impurities and residual deoxidizing elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, and annealing the steel sheet at a temperature of 620 C to A transformation point.
  • a process for manufacturing a cold-rolled high strength steel sheet having a tensile strength of 50 to kg/mm characterized by making a steel comprising 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, and the remainder being iron, excepting inherent impurities and residual deoxiding elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, heating the steel sheet at a temperature of 710 C to A transformation point for at least 2 hours, and slow cooling it for annealmg.
  • a process for manufacturing a cold-rolled high strength steel sheet having a tensile strength of 50 to 100 kg/mm characterized by making a steel comprising 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, at least one elements of0.01 0.25% Nb and 0.01 0.2% Ti, and the remainder being iron excepting inherent impurities and residual deoxidizing elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, heating the steel sheet at a temperature of 620 C to A transformation point for at least 2 hours, and slow cooling it for annealing.
  • a process for manufacturing a cold-rolled high strength steel sheet having a tensile strength of 50 to 100 kg/mm characterized by making a steel consisting of 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, and the remainder being iron excepting inherent impurities and residual deoxidizing elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, heating the steel sheet at a temperature of 710 C to A transformation point, and cooling it at a rate slower than 100 C/hr.
  • a process for manufacturing a cold-rolled high strength steel sheet having a tensile strength of 50 to 100 kglmm characterized by making a steel consisting of 0.03 0.2% C, 1.6 3.0% Mn, 0.03 0.6% Si, 0.01 0.25% Nb or 0.01- 0.2% Ti or 0.01 0.30% Nb plus Ti, and the remainder being iron excepting inherent impurities and residual deoxidizing elements, hot rolling the steel to a hot-rolled strip, cold rolling the strip to a steel sheet having a thickness of 3 mm or less, heating the steel sheet at a temperature of 620 C to A transformation point, and cooling it at a rate slower than 100 C/hr.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
US00368478A 1972-06-13 1973-06-11 Process for manufacturing a cold-rolled high strength steel sheet Expired - Lifetime US3830669A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP5877172A JPS5347331B2 (sv) 1972-06-13 1972-06-13
JP731006A JPS5422407B2 (sv) 1972-12-29 1972-12-29

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US (1) US3830669A (sv)
CA (1) CA999221A (sv)
DE (1) DE2330123B2 (sv)
FR (1) FR2187922B1 (sv)
GB (1) GB1438385A (sv)
IT (1) IT985451B (sv)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951696A (en) * 1973-08-11 1976-04-20 Nippon Steel Corporation Method for producing a high-strength cold rolled steel sheet having excellent press-formability
US4033789A (en) * 1976-03-19 1977-07-05 Jones & Laughlin Steel Corporation Method of producing a high strength steel having uniform elongation
US4058414A (en) * 1975-12-30 1977-11-15 Sumitomo Metal Industries, Ltd. Method of making cold-rolled high strength steel sheet
US4159218A (en) * 1978-08-07 1979-06-26 National Steel Corporation Method for producing a dual-phase ferrite-martensite steel strip
US4314862A (en) * 1979-10-16 1982-02-09 Kobe Steel, Ltd. Dual phase high strength cold-rolled steel plate
US4426235A (en) 1981-01-26 1984-01-17 Kabushiki Kaisha Kobe Seiko Sho Cold-rolled high strength steel plate with composite steel structure of high r-value and method for producing same
US4437902A (en) 1981-10-19 1984-03-20 Republic Steel Corporation Batch-annealed dual-phase steel
US5122198A (en) * 1990-06-12 1992-06-16 Mannesmann Aktiengesellschaft Method of improving the resistance of articles of steel to H-induced stress-corrosion cracking
EP0576107A1 (de) * 1992-06-10 1993-12-29 MANNESMANN Aktiengesellschaft Verwendung eines Stahles zur Herstellung von Konstruktionsrohren
CN104028554A (zh) * 2014-03-07 2014-09-10 首钢总公司 一种连退镀锌冷轧钢卷的生产方法
CN107299281A (zh) * 2017-05-16 2017-10-27 唐山钢铁集团有限责任公司 一种低成本650MPa级别高强钢带及其制备方法

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1071072A (en) * 1975-12-19 1980-02-05 General Motors Corporation Formable high strength low alloy steel
FR2419332A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable contenant du niobium et possedant une bonne soudabilite
FR2419333A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable au niobium
JPS5927370B2 (ja) * 1980-07-05 1984-07-05 新日本製鐵株式会社 プレス加工用高強度冷延鋼板
FR2525709B1 (fr) * 1982-04-22 1986-04-04 Ugine Aciers Vis et boulons en acier a hautes caracteristiques mecaniques et procede d'elaboration de ces vis et boulons
FR2525503B1 (sv) * 1982-04-22 1984-07-13 Ugine Aciers

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3110635A (en) * 1961-07-24 1963-11-12 Lukens Steel Co Normalized alloy steels
US3496032A (en) * 1965-11-30 1970-02-17 Yawata Seitetsu Kk Process for the production of coldrolled steel plate having good shape-fixability
US3673007A (en) * 1968-11-29 1972-06-27 Japan Steel Works Ltd Method for manufacturing a high toughness steel without subjecting it to heat treatment
US3761324A (en) * 1971-01-18 1973-09-25 Armco Steel Corp Columbium treated low carbon steel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3110635A (en) * 1961-07-24 1963-11-12 Lukens Steel Co Normalized alloy steels
US3496032A (en) * 1965-11-30 1970-02-17 Yawata Seitetsu Kk Process for the production of coldrolled steel plate having good shape-fixability
US3673007A (en) * 1968-11-29 1972-06-27 Japan Steel Works Ltd Method for manufacturing a high toughness steel without subjecting it to heat treatment
US3761324A (en) * 1971-01-18 1973-09-25 Armco Steel Corp Columbium treated low carbon steel

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951696A (en) * 1973-08-11 1976-04-20 Nippon Steel Corporation Method for producing a high-strength cold rolled steel sheet having excellent press-formability
US4058414A (en) * 1975-12-30 1977-11-15 Sumitomo Metal Industries, Ltd. Method of making cold-rolled high strength steel sheet
US4033789A (en) * 1976-03-19 1977-07-05 Jones & Laughlin Steel Corporation Method of producing a high strength steel having uniform elongation
US4159218A (en) * 1978-08-07 1979-06-26 National Steel Corporation Method for producing a dual-phase ferrite-martensite steel strip
US4314862A (en) * 1979-10-16 1982-02-09 Kobe Steel, Ltd. Dual phase high strength cold-rolled steel plate
US4426235A (en) 1981-01-26 1984-01-17 Kabushiki Kaisha Kobe Seiko Sho Cold-rolled high strength steel plate with composite steel structure of high r-value and method for producing same
US4437902A (en) 1981-10-19 1984-03-20 Republic Steel Corporation Batch-annealed dual-phase steel
US5122198A (en) * 1990-06-12 1992-06-16 Mannesmann Aktiengesellschaft Method of improving the resistance of articles of steel to H-induced stress-corrosion cracking
EP0576107A1 (de) * 1992-06-10 1993-12-29 MANNESMANN Aktiengesellschaft Verwendung eines Stahles zur Herstellung von Konstruktionsrohren
CN104028554A (zh) * 2014-03-07 2014-09-10 首钢总公司 一种连退镀锌冷轧钢卷的生产方法
CN104028554B (zh) * 2014-03-07 2016-03-30 首钢总公司 一种连退镀锌冷轧钢卷的生产方法
CN107299281A (zh) * 2017-05-16 2017-10-27 唐山钢铁集团有限责任公司 一种低成本650MPa级别高强钢带及其制备方法

Also Published As

Publication number Publication date
DE2330123B2 (de) 1974-09-12
CA999221A (en) 1976-11-02
IT985451B (it) 1974-11-30
FR2187922A1 (sv) 1974-01-18
GB1438385A (sv) 1976-06-03
FR2187922B1 (sv) 1977-07-29
DE2330123A1 (de) 1974-01-10

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