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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
  • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • 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
• • 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
• • 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

• the present invention relates to an Fe—Mn—Al—Si light steel and steel strip or sheet steel having good cold formability and high strength.
• the present invention relates to a method of producing strips from such a steel and particularly suitable uses of such a steel.
• a light steel used for producing car body parts and for low-temperature use is known from German Patent 197 27 759 C2. It contains, in addition to Fe, 10% to 30% Mn, 1% to 8% Al, and 1% to 6% Si, the sum of the contents of Al and Si not exceeding 12%.
• the carbon content, if any, is in the impurity range.
• the known light steel has >7% to 27% Mn, >1% to 10% Al, >0.7% to 4% Si, ⁇ 0.5% C, ⁇ 10% Cr, ⁇ 10% Ni, and ⁇ 0.3% Cu. Furthermore, the steel may contain N, V, Nb, Ti and P, the sum of these elements not to exceed 2%.
• the light steel known from European Patent Application 1 067 203 A1 also contains carbon, in a range from 0.001 to 1.6%.
• this steel has, besides Fe, 6-30% Mn, ⁇ 6% Al, ⁇ 2.5% Si, ⁇ 10% Cr, ⁇ 10% Ni, and ⁇ 5% Cu.
• the steel may contain V, Ti, Nb, B, Zr, and rare earths, the sum of their contents not exceeding 3%.
• the known steel may also contain P, Sn, Sb, and As, the sum of the contents of these elements not to be greater than 0.2%.
• Well-formable steels having higher strengths are also necessary for the manufacture of components which are provided with teeth or comparable shaped elements. These components are typically gear parts provided with inner or outer teeth. These may be produced cost effectively and with high dimensional accuracy through flow forming.
• a method for producing gear parts through flow forming is known from German Patent 197 24 661 C2.
• a blank is produced from a microalloyed, high-strength structural steel, which has a lower yield point of at least 500 N/mm 2 , from a sheet.
• This blank is then cold formed into the gear through flow forming.
• the sheet material is reformed up to the limit of its forming ability.
• a surface of the workpiece provided with the teeth is hardened without heat deformation while essentially maintaining the temperature.
• the object of the present invention is, proceeding from the related art described above, to provide a light steel and/or a steel strip or sheet steel produced therefrom having good formability and good strength which may also be easily produced at an industrial scale.
• a method of producing a steel strip or sheet steel and preferred uses for the steel are to be indicated.
• a light steel which has the following composition (in weight-percent): C: ⁇ 1.00% Mn: 7.00-30.00% Al: 1.00-10.00% Si: >2.50-8.00% Al + Si: >3.50-12.00% B: >0.00- ⁇ 0.01% as well as alternately Ni: ⁇ 8.00% Cu: ⁇ 3.00% N: ⁇ 0.60% Nb: ⁇ 0.30% Ti: ⁇ 0.30% V: ⁇ 0.30% P: ⁇ 0.01%
• the remainder is Fe and unavoidable impurities.
• the impurities include sulfur and oxygen in this case.
• the targeted addition of boron leads to significant improvement of the properties and producibility in steels according to the present invention.
• the content of boron contained in the steel according to the present invention causes reduction of the yield point, through which the formability is significantly improved.
• the favorable influence of the alloy on the mechanical-technological properties of steel according to the present invention may be reinforced even further if the carbon content is 0.10-1.00 weight-percent, i.e., if at least 0.10 weight-percent carbon is detectable in the steel according to the present invention.
• steel according to the present invention and/or steel strip or sheet steel produced therefrom has a significantly lower ⁇ r value than sheet steel known from the related art of the species discussed here.
• cold-rolled steel strips and steel sheets having the composition according to the present invention are distinguished by comparatively low yield points, improved stretch formability at elevated hardening exponents (n value), elevated deep drawing quality (r value), and lower planar anisotropy ( ⁇ r value) as well as an elevated product of yield point and elongation.
• n value hardening exponents
• r value elevated deep drawing quality
• ⁇ r value lower planar anisotropy
• the tensile strength of steel strips and steel sheets according to the present invention is at least 680 MPa.
• the product of tensile strength and elongation is at least 41,000 MPa.
• the yield point of steel sheets and strips according to the present invention does not exceed 520 MPa.
• steels according to the present invention, and/or sheets and strips produced therefrom have an extraordinarily high uniform elongation of 20% up to more than 45%. n values of up to 0.7 are achieved.
• Sheet steels according to the present invention are additionally especially suitable for producing non-magnetic components if they have a purely austenitic microstructure.
• the steels according to the present invention maintain their strength even at especially low temperatures. As such, they are particularly suitable for producing components used in cryoengineering, such as containers or pipes for cryoengineering.
• the positive effects of boron in the steel used according to the present invention may be achieved especially reliably if the boron content is 0.002 weight-percent to 0.01 weight-percent, particularly 0.003 to 0.008 weight-percent.
• the C content which lies in the range from 0.1% to 1.0%, also ensures improved producibility of sheet steel and steel strip according to the present invention.
• the formation of intermetallic phases is suppressed due to the presence of carbon. Cracks and instabilities in the strip edge region, which arise in steel strips produced from the known steels, are thus significantly reduced, the instabilities especially being reduced with increasing C content.
• a further improvement of the strip edge quality is achieved by adding boron. As a result, strip edge instabilities may be almost completely avoided through the combined addition of C and B.
• an input stock such as slabs, thin slabs, or strip, made of a steel according to the present invention having the composition described above
• the hot strip is hot rolled at hot rolling final temperatures of at least 800° C. and coiled at lower temperatures according to the present invention
• the positive effect of the carbon and, in particular, of the boron described is used to its full extent.
• boron and carbon produce higher tensile strength and yield point values in strips hot rolled in this range with fracture elongation values which are still acceptable.
• the hot rolling final temperature increases, tensile strength and yield point are reduced, while the elongation values increase.
• the desired properties of the steel strip may be influenced easily and in a targeted way.
• the hot strip produced according to the present invention is distinguished by good usage properties. If thinner sheets or strips are to be produced, the hot strip may be cold rolled to cold strip after the coiling, the cold rolling advantageously being performed at a reduction of 30% to 75%.
• the cold strip obtained is subsequently preferably subjected to annealing, the annealing temperatures to be between 600° C. and 1100° C.
• the annealing may be performed in this case in the hood in the temperature range from 600° C. to 750° C. or continuously in the annealing furnace at temperatures from 750° C. to 1100° C.
• a further, particularly advantageous use of steel according to the present invention, and/or steel strips and sheets produced therefrom, is the production of cold-formed components through flow forming.
• blanks are produced from the steel, which are then finished by flow forming. Due to its special property profile, steel according to the present invention, and/or sheet blanks produced therefrom, are particularly suitable for this purpose.
• a microstructure which is purely austenitic or which comprises a mixture of ferrite and austenite with components of martensite may result in the steel according to the present invention as a function of the composition.
• the steels according to the present invention may therefore be formed significantly better. They compact significantly more strongly in the course of cold forming than the known high-strength microalloyed or multiphase steels used for production through flow forming. Thus, depending on the cold forming, component strengths in the range from 1400 N/mm 2 to 2200 N/mm 2 may be achieved. Additional hardening of the components produced after the cold forming may therefore be dispensed with. It also has a favorable effect in regard to the intended purpose, in particular for the production of toothed gear components, if the steels used according to the present invention for their production have their density reduced due to the high content of light elements, such as Si and Al.
• a steel composed and constituted according to the present invention is used, then heat treatment or surface hardening of the flow formed component may be dispensed with.
• the danger of distortion and scaling caused in the related art by these additional processing steps therefore no longer exists if a steel according to the present invention is used to produce toothed elements subjected to localized strong stress in use.
• the steel according to the present invention allows cost-effective production of light, heavy-duty, and dimensionally stable components through cold forming, in particular flow forming.
• Steels A to E of the compositions concerned are melted and cast into slabs. Subsequently, the slabs are preheated to a temperature of 1150° C. The preheated slabs are then hot rolled and subsequently coiled.
• Respective hot rolling final temperatures ET and coiler temperatures HT and the respective properties of tensile strength R m , yield point R e , A 50 elongation, uniform elongation A g1 , and n value of the hot strips obtained are indicated in Table 2.
• Table 2 ET HT R e R m Steel [°C.] [° ] [N/mm 2 ] [N/mm 2 ] A 50 [%] A gl [%] n
• all variants of sheet steels according to the present invention are especially suitable for the production of car body components, especially for the outer panels of an automobile body, of wheels for vehicles, in particular motor vehicles, of non-magnetic components, of containers used in cryoengineering, of internally or externally hydroformed components, of tubes which are particularly intended for the production of high-strength engine parts, such as camshafts or piston rods, of components intended for protection against pulsed stresses, such as bombardment, or protective elements, such as armor plates, or body armor for human or animal bodies.
• Heavy-duty gear parts which are distinguished by low weight and good usage properties, without requiring additional heat treatment for this purpose, may also be produced from steel sheets according to the present invention.

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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)

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• 2001
  • 2001-06-13 DE DE10128544A patent/DE10128544C2/de not_active Expired - Fee Related
• 2002
  • 2002-06-13 WO PCT/EP2002/006480 patent/WO2002101109A1/de active IP Right Grant
  • 2002-06-13 ES ES02732754T patent/ES2292762T5/es not_active Expired - Lifetime
  • 2002-06-13 AT AT02732754T patent/ATE370258T1/de active
  • 2002-06-13 EP EP02732754A patent/EP1309734B2/de not_active Expired - Lifetime
  • 2002-06-13 JP JP2003503854A patent/JP4227010B2/ja not_active Expired - Fee Related
  • 2002-06-13 KR KR10-2003-7001684A patent/KR100536645B1/ko active IP Right Grant
  • 2002-06-13 CN CNB028018923A patent/CN1215188C/zh not_active Expired - Fee Related
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  • 2002-06-13 US US10/344,192 patent/US20030145911A1/en not_active Abandoned
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