Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
  • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0421—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. 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
  • C22C38/12—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
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/041—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing involving a particular fabrication or treatment of ingot or slab
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0421—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing characterised by the working steps
  • C21D8/0436—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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0447—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing characterised by the heat treatment
  • C21D8/0473—Final recrystallisation annealing

Definitions

• Titanium-free steel indicated in EP-A-0421087, is a steel with ultra-low carbon content, i.e. less than 0.007% by weight, wherein the Nb content is very much higher than the content in nitrogen, of the order of 20 times. Nitrogen is therefore in this steel entirely fixed by nitrobutene niobium and, if boron is used, it remains free and not nitrided. Boron is intended to protect the joints from ferritic grains in order to avoid brittleness to the cold deformation. This steel allows the development to obtain a sheet equivalent or close to IF steels (interstitial free) which have coefficients very high drawing depth, but also a very ⁇ r high (strong plane anisotropy).
• EP-0101740 it is proposed to manufacture flat products whose Nb content is less than or equivalent to the N content. Following hot rolling at a final temperature below Ar 3 , rolling when cold and annealed, products are obtained having low mechanical strength properties, sometimes even lower than the usual minimum requirements.
• a niobium steel is manufactured, in which the Nb content must be at least 6 times that of nitrogen.
• the manufacturing process here also includes hot rolling at a final temperature below Ar 3 , cold rolling and annealing, as well as baking after application of varnish.
• the final products obtained have a much higher niobium content, for properties of mechanical resistance that are not much improved.
• EP-B-0400031 finally proposes, by way of comparative example, a titanium-free niobium steel, having a content comprising more than 12 times the N content. Following hot rolling at a temperature final higher than Ar 3 , cold rolling and annealing, a product is obtained which, according to the patent itself, is not suitable for deep drawing, whatever the degrees of reduction used during cold rolling.
• the object of the present invention is to provide a niobium steel having, in terms of properties mechanical on cold-rolled and annealed strips, a favorable compromise between the properties of resistance, such as for example the elastic limit and the breaking load, and the properties of ductility, such as uniform elongation, coefficient total hardening and elongation.
• niobium steel as described at the beginning, characterized in that this steel contains a stoichiometric niobium content less than that of nitrogen and a boron or zirconium content sufficient to fix nitrogen not fixed by niobium.
• This steel has the advantage of being able have a low niobium content, and therefore not to alter the ductility properties of steel, while obtaining a secure fixation and preferably early nitrogen by the simultaneous presence of boron or zirconium and niobium.
• the content in niobium is at most equal to four times the N content, preferably three times the latter.
• the steel contains an Nb content of less than 0.040% by weight, and preferably between 0.005 and 0.030% by weight.
• it contains a boron content between 0.0005 and 0.012% by weight, preferably between 0.0015 and 0.012% by weight, or a zirconium content between 0.020 and 0.080% by weight.
• the carbon content is equal to or greater than 0.010% by weight.
• the amount of Nb can well be relatively small compared to the content carbon which allows obtaining a steel with favorable mechanical properties.
• This process offers the advantage of fixing supplied with nitrogen in the form of boron nitride or of zirconium as well as in the form of carbonitride niobium, and this at a very early stage in the process.
• the simultaneous presence of boron or zirconium and niobium also promotes reduced grain size austenitic during hot rolling.
• the niobium present is advantageously redissolved.
• the final temperature of hot rolling is preferably equal to or less than 900 ° C. It is precisely at this temperature, that is to say between the transformation temperature ⁇ ⁇ ⁇ (AR 3 ) and 900 ° C, that the boron nitrides and the carbon nitrides of Nb precipitate in the process according to the invention, which fixes the nitrogen.
• the maximum temperature mentioned above is not, however, critical and should only be considered as a preferred temperature.
• the reduction rate is of the order of 40 to 85%, preferably 55-80%.
• the niobium steel according to the invention is usually a steel produced by conversion or of electrical production, classic, which is cast in continued.
• This steel must be extra soft, i.e. have an extremely low carbon content, less than 0.100% by weight, reaching up to minimum contents up to 0.020% or more.
• the carbon content will not exceed not less than 0.010% by weight.
• This steel must also be calmed with aluminum with a content of less than 0.080% by weight.
• Nb, B and Zr are calculated mainly as a function of nitrogen present in the steel being processed.
• Nb added is therefore in reality significantly lower stoichiometrically than nitrogen.
• Nitrogen not fixed by niobium is fixed by B or Zr, which allows an addition of Nb lower than what is usually necessary to obtain properties of sufficient mechanical resistance from a niobium steel, titanium free. This minimal addition of Nb makes it possible to maintain good ductility properties. It also offers advantages economical considering the cost not negligible niobium.
• the steel described above is poured into slabs, which are reheated in a conventional oven, for example a traveling beam oven or a pushing oven, for that they reach a higher temperature at heart or equal to 1000 ° C, which is enough to restore solution of the precipitated niobium.
• a conventional oven for example a traveling beam oven or a pushing oven
• the strip is then cooled so controlled and finally wound at a temperature of around from 625 ° C ⁇ 125 ° C.
• the strip After continuous pickling in conventional lines (HC1 or H 2 SO 4 ), the strip is cold re-rolled, with a thickness reduction rate of between 40 and 85%.
• the cold rolled strip is then subjected to recrystallization annealing to give it the mechanical properties required.
• This annealing can take the form of static annealing, for example in a tight or expanded coil, at a temperature of around 620-680 ° C, or in the form of continuous annealing at a temperature of 680-850 ° C.
• Last annealing can be combined or not with a possible recovery by dip coating or other processes.
• a final rolling step is still performed, in the form of a final work hardening, in order to remove the phenomena of "Lüders bands" and ensure good surface roughness as well as flatness of the product.
• Niobium steel with extremely low carbon content without boron.
• Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 50 350 8 12 6 40 6.0 0 50
• Niobium steel according to the invention with addition of boron.
• Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 55 300 7 14 3 50 5.6 4.5 7
• Niobium steel according to the invention with addition of boron.
• Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb 45 270 19 12 6 43 6.0 4.0 12
• Niobium steel with extremely low carbon content with the addition of zirconium.
• Chemical composition (10 -3 %) VS Mn Yes P S Al N 2 B Nb Zr 35 200 5 9 4 47 4.9 0 10 30
• Niobium steels according to the invention offer both mechanical resistance properties well above the lower limits usual and good ductility properties, in therefore providing an entirely favorable compromise for subsequent treatments.
• the niobium steels according to the invention have, on cold-rolled and annealed strips, mechanical properties in the band plane which are significantly independent of management compared to in the sense of rolling as well as a rational contraction in width substantially identical to a contraction rational in thickness. They therefore bring together all conditions for undergoing stamping type treatments difficult and others.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Catalysts (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Heat Treatment Of Steel (AREA)

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• 1997
  • 1997-03-27 BE BE9700270A patent/BE1011066A3/fr not_active IP Right Cessation
• 1998
  • 1998-03-18 AT AT98200844T patent/ATE249528T1/de not_active IP Right Cessation
  • 1998-03-18 PT PT98200844T patent/PT870848E/pt unknown
  • 1998-03-18 ES ES98200844T patent/ES2207787T3/es not_active Expired - Lifetime
  • 1998-03-18 DK DK98200844T patent/DK0870848T3/da active
  • 1998-03-18 EP EP98200844A patent/EP0870848B1/de not_active Revoked
  • 1998-03-18 DE DE69817900T patent/DE69817900T2/de not_active Revoked

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