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
  • C22C38/02—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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • 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
  • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
  • C21D8/0215—Rapid solidification; Thin strip casting
• • 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
  • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
• • 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
  • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/009—Pearlite
• • 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
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling

Definitions

• High strength steels with good elongation characteristics and Processability are used in the field of vehicle construction, in general steel construction as well as in mechanical and apparatus engineering needed for the production of components that require high forces absorb and in their shape optimally to the each adjusted constructive requirements can be.
• a high-strength, good for these purposes malleable hot strip and a method to his Production are known from EP 0 295 500 B1.
• the for the production of the known hot strip used steel contains besides iron and the production-related unavoidable impurities (in% by weight) 0.15 to less than 0.3% C, 0.5 to 2.0% Si, 0.5 to 2.0% Mn.
• the steel 0.0005 to 0.0100 Ca or 0.005 to 0.050% rare earth metals.
• the known steel is according to EP 0 295 500 B1 in a Hot rolling stand with a hot rolling end temperature hot rolled, with a maximum of 50 ° C from the Ar3 temperature differs.
• the hot strip is on the following to the hot roll relay roller table controlled cooled, the EP 0 295 500 B1 two ways this controlled cooling pretends.
• the band will be at a relatively low level in a first stage Cooling speeds of 15 to 45 K / s and then in one second stage with a raised respectively Cooling cooled, which is between 35 to 80 K / s was.
• the cooling takes place three-stage with cooling rates in the first Stage 50 to 85 K / s, in the second stage 10 to 45 K / s and in the third stage was 35 to 80 K / s.
• the two Variants achieved reel temperatures were between 370 up to 520 ° C.
• Hot-rolled strip produced in this way has one formed from ferrite, retained austenite and bainite Structure.
• the formation of perlite and martensite is included largely suppressed to the formation of retained austenite not to hinder.
• the hot strip produced according to the known method Although has a high strength at high ductility. In practice, however, shows that its production is expensive. Also shows in the case of sudden Strains of high kinetic energies, like them for example, in motor vehicles in an accident typically occur that it is difficult to with the well-known steel the ever increasing Requirements for optimized crash behavior too fulfill. On top of that, conventional manufacturing the known hot strip is expensive.
• the Si and Mn content of the processed steel are included adjusted so that in the received hot strip one for the Achieving the TRIP effect sufficient amount Restaustenit is guaranteed.
• Manganese stabilizes the remaining after the controlled cooling in the steel Austenite.
• the presence of silicon supports on the one hand the formation of ferrite and also improves the Extensibility of the steel.
• the mechanical Properties improving effects causes the Limitation of the Si and Mn contents according to the invention also an improvement of the surface finish of the Hot strips. These effects are especially certain then one, if the sum of the contents of silicon and Manganese 1.5-2.5% by weight, in particular 1.8-2.3% by weight, is.
• TRIP steels contain retained austenite and consequently exhibit the effect of the so-called "TRANSformation Induced Plasticity. "It is essential according to the invention prescribed combination of the procedure over a casting mill and the presence of Ti and / or Nb.
• micro-alloying elements are used in the conventional production via slab casting in the slab excreted and go only partially in the warming of the Slab before hot rolling back into solution.
• these elements remain due to the between the Thin slab production and hot rolling usually in a tunnel furnace in passing heat supply however, until the beginning of hot rolling in solution.
• These Excretions improve the grain refinement of the finished Hotbands and contribute on the one hand to an increase in the Restaustenitanteils and on the other hand to a Stabilization of retained austenite against conversion into Martensite at.
• Produced according to the invention and Composite steel is therefore capable of higher Endure stress.
• the obtained thin slabs run with temperatures in the Range from 850 - 1050 ° C in a tunnel kiln.
• the inlet temperature is not less than 950 ° C to the formation of excreta at this stage to avoid the warm strip production.
• the thin slabs at 1000 - 1200 ° C in Flow annealed In the furnace, the thin slabs at 1000 - 1200 ° C in Flow annealed.
• the tunnel oven temperature is included preferably limited to the range of 1000 - 1050 ° C, to avoid excessive scale formation. To this Way is the lying at about 900 ° C temperature range safely bypassed using it in the invention Steel comes to a precipitation maximum. Instead the micro-alloying elements are kept in solution with the consequence that they are finer and finer in the finished product distributed more homogeneously.
• the residence time in the tunnel furnace on 10 to 60 minutes, preferably 15 to 35 minutes.
• the restriction causes the annealing time immediately increase the output of the Casting-rolling plant used according to the invention.
• the Formation of a fine-grained microstructure can also be assisted by the fact that, if the finish rolling is carried out in several passes, the deformation in the last pass of the hot rolling is at least 5%, preferably 15-25%.
• the through the various measures of the invention The achieved fine graininess not only contributes to Deformability, but together with the chemical Composition of processed steel also to Stabilization of the desired Restaustenitanteils at. So hinders the fine distribution of the individual
• the hot strip according to the invention produced hot strip existing phases also in a mechanical way the transformation of the retained austenite into Martensite.
• the hot strip according to the invention has due its not only one in terms of the retained austenite content high chemical but also a high geometric Stability on. This stability of the structure contributes to it in that still finished in produced from the hot strip Component residual austenite may be present.
• the post-warming controlled cooling has also a significant influence on the expression of the Microstructure and mechanical properties of the finished Hot strip. So can be targeted by the cooling the Shares of the individual phases and the strength and Affect elongation properties.
• a first Variant of the invention is the controlled cooling to this purpose, placing the hot strip in a first stage starting from the hot rolling end temperature with a Cooling speed of 70 to 500 K / s on a 600-750 ° C intermediate temperature is cooled, by placing the hot strip in a second stage for 2 to 13 seconds in air cools and by the hot strip then in a third stage with a 30 to 200 K / s amounting cooling speed on a reel temperature is cooled, which is 300 - 530 ° C.
• the highest possible Cooling rate in the first stage of cooling has a positive effect on the hot strip obtained contained Austenitmenge from. Therefore, after one preferred embodiment of this variant of the controlled Cooling the cooling rate in the first stage of the Cooling at least 150 K / s, preferably 300 K / s.
• the duration of the second stage of cooling may be preferred for this purpose be limited to 4 to 8 seconds. Subsequently, will in the third stage the accelerated cooling continued to the formation of perlite and grain growth to suppress.
• Another variant of the invention provides that the controlled cooling takes place in that the hot strip with a cooling rate of 10 to 70 K / s continuously from the hot rolling end temperature to the Reel temperature is cooled. Also in this way lets a hot strip with the invention sought after Create microstructure.
• the cools Hot strip after reeling in the coil continues from.
• the hot strip accelerates after a rest period in the coil is cooled.
• the desired division of the individual phase components adjusts when the accelerated cooling of the coil after a rest period ranging from 2 to 30 starts.
• the cooling by applying the Accelerate coils with a cooling fluid.
• a liquid such as water, or an air stream be used.
• the hot strip produced according to the invention has in each case at least three of the structural components ferrite, bainite, Retained austenite or martensite.
• the sum of the Content of martensite and retained austenite at least 8% be.
• As low as possible martensite contents are sought to reduce carbon loss to the detriment of the To avoid residual austenite. Accordingly sees the Invention that the carbon content of the retained austenite more than 1%. This carbon content leaves For example, determine by X-ray.
• produced hot strip is suitable in special way for use in vehicle construction, in Steel construction, in general machine and apparatus construction as well in shipbuilding.
• the invention is based on Embodiments explained in more detail.
• the steel melts S1, S2, S3 are in a casting-rolling plant to thin slabs with an average thickness 55 mm has been cast in a continuous the casting subsequent process in a tunnel kiln in which they are at average Temperatures of 1050 ° C in the course of an annealing have been subjected. After leaving the oven, the Thin slabs happen a scale washer in which their Surface by applying one under more than 300 bar of sprayed cleaning liquid in the flow has been freed from the tinder.
• the thus cleaned thin slabs are then in one multistage hot roll stand arrived, in which they at a hot rolling end temperature ET in several passes too in each case, a hot strip with a thickness d finished hot rolled have been.
• the hot strip thicknesses d are in Table 2.
• Table 4 shows the relevant process parameters and the thickness d of the hot strips W5 to W10.
• Table 5 contains the corresponding information on the respective tensile strength Rm, uniform elongation Ag, elongation A80 and elongation A5 as well as the respective product of Rm * A5 and Rm * A80.

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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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Publications (2)

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Cited By (8)

Citations (6)

• 2002
  • 2002-08-28 DE DE50208550T patent/DE50208550D1/de not_active Expired - Lifetime
  • 2002-08-28 AT AT02019314T patent/ATE343649T1/de not_active IP Right Cessation
  • 2002-08-28 EP EP02019314A patent/EP1396549B1/fr not_active Expired - Lifetime

Patent Citations (6)

Non-Patent Citations (1)

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