US3716420A - Hot rolled steel sheets for extra deep drawing - Google Patents

Hot rolled steel sheets for extra deep drawing Download PDF

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US3716420A
US3716420A US00196697A US3716420DA US3716420A US 3716420 A US3716420 A US 3716420A US 00196697 A US00196697 A US 00196697A US 3716420D A US3716420D A US 3716420DA US 3716420 A US3716420 A US 3716420A
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hot rolled
steel sheets
rolled steel
steel
sheets
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US00196697A
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K Matsudo
Y Ikegami
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JFE Engineering Corp
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Nippon Kokan Ltd
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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
    • C21D8/04—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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
    • Y10T29/49988—Metal casting
    • Y10T29/49991—Combined with rolling

Definitions

  • a hot rolled steel sheet having extra deep drawing and press formability propertes comparable to cold rolled steel sheets, wherein the steel is vacuum degassed and has a composition consisting essentially of: 0.0010.020% carbon, less than 0.10% slicon, 0.100.60% manganese, less than 0.020% sulphur, 0.010-0.10% aluminum, 0.02- 20 0.08% titanium, balance iron and incidental impnrities and wherein Ti/C 4 and T/S 2.
  • the steel sheets are hot rolled with a finishing temperature in the range 800- 950 C. and coiled at a temperature in the range 650 C.- 700 C.
  • This invention relates to steel sheets and in particular to hot rolled steel sheets having a relatively 10W tensile strength and excellent press forrnability.
  • a steel consisting essentially of 0.001-0.020% carbon, less than 0.10% silicon, 0.100.60% manganese, less than 0.020% sulphur, 0.010-0.10% aluminum, 0.02- 0.08% titanium, balance iron and incidental impurities, provided always that Ti/C 4 and Ti/S 2.
  • the steel of the present invent is hot rolled at a finishing temperature between 800- 950 C. and coiled at a temperature between 650- 700 C.
  • Silicon is another element which increases the tensile strength of steel sheets and therefore this element is restrcted to amounts below 0.1%.
  • Manganese in an amount in excess of 0.1% is added in order to prevent hot shortness caused by sulphur.
  • the upper limit of manganese must, however, be controlled to EXAMPLE 1
  • Table 2 indicates the chemical composition of steels covered by this invention and Table 3 indicates the manufacturing conditions and mechanical properties upon hot rolling of such steels.
  • the Ti added to hot rolled steel sheets achieve excellent press formability. It has been found that the Ti content must satisfy the ratio Ti/S Z in order to achieve the above noted conditions. In addition, the ratio Ti/C 4 further serves to improve the press formability of the hot rolled steel sheets provided the condition of T/S 2 is also met. For the above reasons, the Ti content is fixed at 0.020.08% hearing in mind its further balance with the carbon and sulphur contents.
  • Aluminum is added. in an amount of 0.010%0.10% in order to facilitate deoxidation and eiect a better Ti yield. Amounts in excess of 0.10% are detrimental to the press formability of the steel sheets, and an amount less than 0.010% lessens the effect of deoxidation.
  • finishing temperature of the rolling is above the Ar transforrnaton temperature, because the press formability rapdly deteriorates below the Ar temperature.
  • the Ar transformation temperature is in the vicinity of 850 C. in the case of sheets of extremely low carbon content and t is difficult to maintain a finishing temperature as high as 850 C. in very thin sheets.
  • the elect of a finishng temperature below the Ar transformation temperature is, at least in part, olset by careful control of the steel composition within the ranges previously discussed.
  • the steels of the present invention range frorn 1.0 to 7.0 mm. thick, the range of finishing temperatures may be between 800 C. and 950 C. In operations, it is desirable to maintain a finishing temperature as high as pos sible above the Ar transformation temperature.
  • the coilng temperature can be less than 650 C. and still provicle an acceptable press formabilty.
  • steels manufactured in accordance with this invention have low tensile strength and excellent press formability.
  • FIG. 1 shows the relation between the notch elongation percentage and the tensile strength respcctively of the products of the present invention and the prior art.
  • FIG. 2 is a microphotograph (100 magnifications) of the structure of a steel plate manufactured by the method of this invention and
  • FIG. 3 is a microphotograph (500 magnifications) of the structure of inclusions.
  • FIG. 1 Differences in notch elongation between steels of this invention and other hot rolled steel sheets for drawing of the same thickness are shown in FIG. 1. It is obvious therefrorn that the press formability of the steel sheets of this invention is far superior to those of the conventional hot rolled steel sheets for drawing, an approach is that of cold rolled steel sheets.
  • FIG. 2 the microphotograph of the ferrte structure of a steel sheet according to this invention shows an ideal formation.
  • FIG. 3 shows that Al O and MnS are closely attached to TN+TS. This gain shows that excellent characteristics may be achieved by products of the present invention.
  • a vacuum degassed steel hot rolled nto sheets for extra deep drawing said steel consisting essentially of: 0.001-0.020% carbon, less than 0.10% silicon, 0.10 0.60% manganese, less than 0.020% sulphur, 0.010- 0.10% aluminum, 0.02 0.08% titanium, balance iron and incidental impurties and whercin Ti/C 4 and Ti/S 2.
  • a steel sheet as claimed in claim 1 wherein said sheet is hot rolled with a finishing temperature within the range of 800-950 C. and coiled at a temperature in the range of 650-700 C. whereby press formability properties are enhanced.
  • a process for producing steel sheets for extra deep Reference5 Cted drawing comprislng vacuum degassing a steel havng a UNITED STATES PATENTS composrtron c0nsrst1ng essentrally of 0.0010.020% carbon, less than 0.10% silicon, 0.100.60% manganese, less 3522110 7/1970 shlmlzu et 14812 than 0.020% sulphur, 0.010-0.10% alumnum, 0.02 3560270 2/1971 Rembold et 14812 5 3,67456 9/1971 Forand, Jr.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical 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 Steel (AREA)

Abstract

A HOT ROLLED STEEL SHEET HAVING EXTRA DEEP DRAWING AND PRESS FORMABILITY PROPERTIES COMPARABLE TO COLD ROLLED STEEL SHEETS, WHEREIN THE STEEL IS VACUUM DEGASSES AND HAS A COMPOSITION CONSISTING ESSENTIALLY OF: 0.001-0.020% CARBON, LESS THAN 0.10% SILICON, 0.10-0.60% MANGANESE, LESS THAN 0.020% SULPHUR, 0.010-0.10% ALUMINUM, 0.020.08% TITANIUM, BALANCE IRON AND INCIDENTAL IMPURITIES AND WHEREIN TI/C<4 AND TI/S>2. THE STEEL SHEETS ARE HOT ROLLED WITH A FINISHING TEMPERATURE IN THE RANGE 800950*C. AND COLLED AT A TEMPERATURE IN THE RANGE 650*C.700*C.

Description

HOT ROLLED STEEL SHEE'IS FOR EXTRA LEEF DRAWING F 1973 KAZUO MATSUDO T 2 Sheets-Sheet Filed Nov. 8. 1971 jLFQ9). 13, 1973 KAZUO MATSUDQ TAL 3,716,4Z0
HOT ROLLED STEEL SHEETS FOR EXTRA DEEP DRAWING Filed Nov. 8, 1971 2 Sheets-Sheet 2 United States Patent Patened EIN,
percent YPE1, percent percent Mechanical property ABSTRACI OF THE DISCLOSURE A hot rolled steel sheet having extra deep drawing and press formability propertes comparable to cold rolled steel sheets, wherein the steel is vacuum degassed and has a composition consisting essentially of: 0.0010.020% carbon, less than 0.10% slicon, 0.100.60% manganese, less than 0.020% sulphur, 0.010-0.10% aluminum, 0.02- 20 0.08% titanium, balance iron and incidental impnrities and wherein Ti/C 4 and T/S 2. The steel sheets are hot rolled with a finishing temperature in the range 800- 950 C. and coiled at a temperature in the range 650 C.- 700 C.
Coiling tempera- Directnre, C. tion temperature, C.
This invention relates to steel sheets and in particular to hot rolled steel sheets having a relatively 10W tensile strength and excellent press forrnability.
Heretofore most extra deep drawing steels are produced by cold rolling processes, but snch processes are relatively expensive. It is, therefore, economically advantageous to provide hot rolled sheets for drawing purposes provided press formability equal to that of cold rolled sheets can be achieved in sheets in the range of 1.63.4 mm. thick. For example, a 3.2 mm. thick sheet produced by cold rolling has an approximate notch elongation of 20% but by conventional hot rolling for drawing the notch elongation falls far short of that level. 4
It is, therefore, an object of the present invention to provide a hot rolled steel sheet having a notch elongation of at least 20% A number of proposals have been made concerning provision of hot rolled steel sheets having excellent press formability. Notable among these are vacuurn degassed aluminnm klled steels and desulfurized low manganese aluminum killed steels. Table 1 shows an example of each of the two types of prior art hot rolled steels to- 0 gether with the heat treatments and mechanical properties 5 of such steels.
Applicants have found that similar or superior properties can be achieved in hot rolled steel sheets of 10-70 mm. thick provided such steels, are vacuum degassed and contain a carefully controlled addition of titanium.
Thus, by one aspect of the present nvention there is provided a steel consisting essentially of 0.001-0.020% carbon, less than 0.10% silicon, 0.100.60% manganese, less than 0.020% sulphur, 0.010-0.10% aluminum, 0.02- 0.08% titanium, balance iron and incidental impurities, provided always that Ti/C 4 and Ti/S 2.
By a preferred embodirnent the steel of the present invent is hot rolled at a finishing temperature between 800- 950 C. and coiled at a temperature between 650- 700 C.
Specific reasons for limiting the quantity of the components of the hot rolled steel sheets of this invention are explained in more detail hereafter.
Increases in carbon content cause increases in carbide precipitation which are in turn detrimental to the press formability of the steel. In the steel of the present invention, therefore, the carbon content is reduced as much as TABLE 1 Het rolling conditions Composition (percent) by weight nlelsstof Finshing s ee s, 81 Mn S N2 S01Al mm. r 0.332 0.018 0.017 0.0029 0.043 3 2 0.01 0.18 0.010 0.012 0.0030 0.016 3.2
NOTEEIN represents notch elongation in a notch tenslle test which turnishes a reliable standard for evaluatng press formability of thin sheets.
Items Degassed A1 killed steel 3 possible by vacuum degassing s as to achieve higher press formability. 0.001% carbon is the practical lower limit of decarbonization by vacuum degassing and the upper limit of 0.020 represents the point above which the tensile strength of the steel rises sharply because of TiC precipitation.
Silicon is another element which increases the tensile strength of steel sheets and therefore this element is restrcted to amounts below 0.1%.
Manganese in an amount in excess of 0.1% is added in order to prevent hot shortness caused by sulphur. The upper limit of manganese must, however, be controlled to EXAMPLE 1 Table 2 indicates the chemical composition of steels covered by this invention and Table 3 indicates the manufacturing conditions and mechanical properties upon hot rolling of such steels.
TABLE 2 Percent b w h less than 0.6% because manganese works, hke carbon and C y silicon, t0 increase the tensile strength of the steel. Si Tr Sulphur is mantained at a level of less than 0.020% Mn 0.20 because larger amounts affect the cleanlrness of the steel P 0 011 and adversely afiect the press formability beca se of the S 0012 formation of MnS. (10.040 Titanium is added to the steel because it C0nverts MnS 5,51 1 from an A type to a C type impuri y. An A type incluson 20 T 0 03 P v m 0r impur1ty 1S defined as one WhlCh 1s plastically deformed Ti/C 3 7 by workjng, and a C type inclusion is defined as one which T/S 2.5
'IABLE 3 Hot: rolling conditions C.) Finishing Coling Skin- Test Mechanical pmperty Thickness of plates tempertempcrpass, direc- YP, IS, E1, YPE1, E1N, AI, (mm.) ature ature percent tien lrg.lmm. kg./rnmfl percent percent percent kg.lmm 2 NOTE AI=Agng index.
is scattered at random throughout the matrix and which is not plastically defined by working. The C type inclusion is less detrimental to press formability, and at the same time produces solid solution of sulphur to some extent through the formation of TiN thereby serving to decrease MI1S-type sulfides extending in the direction of rolling. Thus, the Ti added to hot rolled steel sheets achieve excellent press formability. It has been found that the Ti content must satisfy the ratio Ti/S Z in order to achieve the above noted conditions. In addition, the ratio Ti/C 4 further serves to improve the press formability of the hot rolled steel sheets provided the condition of T/S 2 is also met. For the above reasons, the Ti content is fixed at 0.020.08% hearing in mind its further balance with the carbon and sulphur contents.
Aluminum is added. in an amount of 0.010%0.10% in order to facilitate deoxidation and eiect a better Ti yield. Amounts in excess of 0.10% are detrimental to the press formability of the steel sheets, and an amount less than 0.010% lessens the effect of deoxidation.
In order to achieve the desired mechanical properties in the hot rolled steel sheets for extra deep drawing, the heat treatrnent steps must be controlled Within the temperature ranges previously discussed.
In order to produce steel sheets f0r extra deep drawing having excellent press formability, it is desirable that finishing temperature of the rolling is above the Ar transforrnaton temperature, because the press formability rapdly deteriorates below the Ar temperature. However, the Ar transformation temperature is in the vicinity of 850 C. in the case of sheets of extremely low carbon content and t is difficult to maintain a finishing temperature as high as 850 C. in very thin sheets. I-Iowever, the elect of a finishng temperature below the Ar transformation temperature is, at least in part, olset by careful control of the steel composition within the ranges previously discussed. Because the steels of the present invention range frorn 1.0 to 7.0 mm. thick, the range of finishing temperatures may be between 800 C. and 950 C. In operations, it is desirable to maintain a finishing temperature as high as pos sible above the Ar transformation temperature. On the other hand, the coilng temperature can be less than 650 C. and still provicle an acceptable press formabilty. Be-
As is clear from this example, steels manufactured in accordance with this invention have low tensile strength and excellent press formability.
In order to more clearly illustrate the differences between the steels of the present invention and other hot rolled steel sheets for drawing of the same thickness, reference is made to the accompanying drawings in 40 which:
FIG. 1 shows the relation between the notch elongation percentage and the tensile strength respcctively of the products of the present invention and the prior art.
FIG. 2 is a microphotograph (100 magnifications) of the structure of a steel plate manufactured by the method of this invention and FIG. 3 is a microphotograph (500 magnifications) of the structure of inclusions.
Differences in notch elongation between steels of this invention and other hot rolled steel sheets for drawing of the same thickness are shown in FIG. 1. It is obvious therefrorn that the press formability of the steel sheets of this invention is far superior to those of the conventional hot rolled steel sheets for drawing, an approach is that of cold rolled steel sheets.
As shown in FIG. 2, the microphotograph of the ferrte structure of a steel sheet according to this invention shows an ideal formation. FIG. 3 shows that Al O and MnS are closely attached to TN+TS. This gain shows that excellent characteristics may be achieved by products of the present invention.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A vacuum degassed steel hot rolled nto sheets for extra deep drawing, said steel consisting essentially of: 0.001-0.020% carbon, less than 0.10% silicon, 0.10 0.60% manganese, less than 0.020% sulphur, 0.010- 0.10% aluminum, 0.02 0.08% titanium, balance iron and incidental impurties and whercin Ti/C 4 and Ti/S 2.
2. A steel sheet as claimed in claim 1 wherein said sheet is hot rolled with a finishing temperature within the range of 800-950 C. and coiled at a temperature in the range of 650-700 C. whereby press formability properties are enhanced.
5 3. A process for producing steel sheets for extra deep Reference5 Cted drawing comprislng vacuum degassing a steel havng a UNITED STATES PATENTS composrtron c0nsrst1ng essentrally of 0.0010.020% carbon, less than 0.10% silicon, 0.100.60% manganese, less 3522110 7/1970 shlmlzu et 14812 than 0.020% sulphur, 0.010-0.10% alumnum, 0.02 3560270 2/1971 Rembold et 14812 5 3,67456 9/1971 Forand, Jr. 14812 0.08% titanium, balance iron and incidental mpurties and wherein T/C 4 and T/S 2, hot rolling said steel W AYL AND T ALL A P nto sheets 1.0-7.0 rnm. thick with a rolling finishing S nmary Exammer temperature in the range of 800950 C. and coling said U.S. C1. X.R.
steel sheet at a temperature in the range 650700 C. 10 148-12.1 36
US00196697A 1970-12-19 1971-11-08 Hot rolled steel sheets for extra deep drawing Expired - Lifetime US3716420A (en)

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FR (1) FR2117866B1 (en)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001052A (en) * 1971-09-30 1977-01-04 Kawasaki Steel Corporation Hot-rolled low-carbon steel strip with an excellent press-workability capable of forming smooth pressed surface and a method of making the same
US4026729A (en) * 1974-12-05 1977-05-31 Nippon Kokan Kabushiki Kaisha Method of making a soft steel sheet by continuous annealing
US4046597A (en) * 1976-12-09 1977-09-06 Nippon Steel Corporation Vibration damping steel material and process for producing the same
US4144379A (en) * 1977-09-02 1979-03-13 Inland Steel Company Drawing quality hot-dip coated steel strip
US4576656A (en) * 1982-10-08 1986-03-18 Kawasaki Steel Corporation Method of producing cold rolled steel sheets for deep drawing

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55152125A (en) * 1979-02-23 1980-11-27 Torrington Co Bearing cup and production thereof
CA1259827A (en) * 1984-07-17 1989-09-26 Mitsumasa Kurosawa Cold-rolled steel sheets and a method of manufacturing the same
DE3803064C2 (en) * 1988-01-29 1995-04-20 Preussag Stahl Ag Cold rolled sheet or strip and process for its manufacture
CA1331852C (en) * 1988-02-09 1994-09-06 Nobuhiko Sakai Process for preparing alloyed-zinc-plated titanium-killed steel sheet having excellent deep-drawability
DE59009505D1 (en) * 1989-05-09 1995-09-14 Preussag Stahl Ag METHOD FOR PRODUCING COILBREAK-FREE HOT RIBBON AND AGING-RESISTANT FIRE-GALVANIZED COLD RIBBON.
DE19547181C1 (en) * 1995-12-16 1996-10-10 Krupp Ag Hoesch Krupp Mfg. cold-rolled, high strength steel strip with good shapability
FR2742769B1 (en) * 1995-12-20 1998-01-16 Lorraine Laminage COLD-ROLLED STEEL WITH GOOD WELDING AND BRAZING ABILITY

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001052A (en) * 1971-09-30 1977-01-04 Kawasaki Steel Corporation Hot-rolled low-carbon steel strip with an excellent press-workability capable of forming smooth pressed surface and a method of making the same
US4026729A (en) * 1974-12-05 1977-05-31 Nippon Kokan Kabushiki Kaisha Method of making a soft steel sheet by continuous annealing
US4046597A (en) * 1976-12-09 1977-09-06 Nippon Steel Corporation Vibration damping steel material and process for producing the same
US4144379A (en) * 1977-09-02 1979-03-13 Inland Steel Company Drawing quality hot-dip coated steel strip
US4576656A (en) * 1982-10-08 1986-03-18 Kawasaki Steel Corporation Method of producing cold rolled steel sheets for deep drawing

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AU451296B2 (en) 1974-08-01
IT940594B (en) 1973-02-20
DE2155620A1 (en) 1972-07-06
JPS5241209B1 (en) 1977-10-17
DE2155620B2 (en) 1974-05-16
GB1333280A (en) 1973-10-10
FR2117866A1 (en) 1972-07-28
AU3655571A (en) 1973-06-14
CA939937A (en) 1974-01-15
FR2117866B1 (en) 1974-03-29

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