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
  • 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

Definitions

• the invention relates to a process for the production of semi-finished products, in particular steel strip, with dual-phase structure, called DP steel strip for short, and a tensile strength of between 500 and 1000 MPa.
• High-strength steel sheets with good formability, durability of structural and mechanical properties to about 600 0 C are ben ⁇ tigt.ö in many areas
• the sheets should also have the ability to Schmelztauchveredelung.
• steels with an already set dual-phase structure have the disadvantage that heating above 200 ° C., as occurs during or in conjunction with hot-dip finishing, generally results in an undesirable, pronounced yield strength.
• the invention is therefore an object of the invention to provide a method for producing a semifinished product, in particular DP steel strip, which is inexpensive and can be produced with a DP steel strip, which not only has optimized forming properties, but also a temperature resistance to 600 0 C and which is therefore also suitable for hot dip finishing.
• This object is achieved according to the invention with a method for producing semifinished products, in particular steel strip, with dual-phase structure and a tensile strength between 500 and 1000 MPa, which is characterized in that for setting a structure of hard constituents, such as martensite, bainite, carbide with small proportions retained austenite in a ferritic matrix which is largely free of interstitially dissolved elements (IF character), the elements interstitially dissolved in the ferritic matrix, such as carbon and nitrogen, by carbide, nitride or carbonitride-forming alloying elements such as Al, Mo, Nb, Ti, V are tied off.,
• IF character interstitially dissolved elements
• the alloy content of the alloying elements is adjusted stoichiometrically to the ferrite content and to the solubility of carbon and nitrogen at the temperature of a subsequent heating or heat treatment of the DP structure.
• the hot strip is cooled after leaving the finishing scale in the two-phase region to adjust an appropriate amount of retained austenite and then accelerated cooled to a temperature below the martensite start or -Finish temperature.
• the cold strip is heated to adjust a suitable amount of retained austenite in the two-phase region and then accelerated cooled to a temperature below the martensite start or -Finish temperature.
• This heat treatment is preferably carried out in a continuous annealing plant. example
• the N content should be as low as possible and bound by Al and possibly Ti addition.
• a correspondingly increased V content can also be used to bind the nitrogen.
• Table 1 contains some possible chemical compositions.
• Figure 1 shows an example of the cooling curve of a steel sheet after hot rolling to set a dual-phase structure
• Figure 2 shows a typical stress-strain diagram for a DP steel with a low yield ratio ( ⁇ 75%) and without a pronounced yield strength.
• Figure 1 shows the austenite part on the left above the time axis and the core temperature on the right.
• the cooling curve of a steel sheet after hot rolling is shown to set a dual phase structure.
• the aim is a reel temperature of about 200 0 C.
• the solid line shows the Austenitzerfall with increasing cooling time.
• the dashed curve shows - also over the cooling time - the decrease in the core temperature, which is seen accelerated between about 600 0 C and the trapping temperature of 200 0 C accelerated.

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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)

Applications Claiming Priority (2)

Publications (1)

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• 2008
  • 2008-08-08 DE DE102008038865A patent/DE102008038865A1/de not_active Withdrawn
• 2009
  • 2009-08-07 CN CN200980129258.9A patent/CN102105605B/zh not_active Expired - Fee Related
  • 2009-08-07 US US13/058,085 patent/US20110146850A1/en not_active Abandoned
  • 2009-08-07 JP JP2011521437A patent/JP2011530649A/ja active Pending
  • 2009-08-07 EP EP09736097A patent/EP2318556A2/de not_active Ceased
  • 2009-08-07 KR KR1020117002936A patent/KR20110036928A/ko active Search and Examination
  • 2009-08-07 CA CA2732495A patent/CA2732495C/en not_active Expired - Fee Related
  • 2009-08-07 WO PCT/DE2009/001136 patent/WO2010015251A2/de active Application Filing
  • 2009-08-07 BR BRPI0917007A patent/BRPI0917007A2/pt not_active Application Discontinuation
  • 2009-08-07 RU RU2011108570/02A patent/RU2475545C2/ru active

Non-Patent Citations (1)

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