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
  • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • 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
  • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
  • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
  • B21B3/02—Rolling special iron alloys, e.g. stainless steel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B9/00—Measures for carrying out rolling operations under special conditions, e.g. in vacuum or inert atmosphere to prevent oxidation of work; Special measures for removing fumes from rolling mills

Definitions

• the invention relates to a method for producing a hot strip from a steel having a high manganese content of more than 12 to 30% by weight. Steels of this type are characterized by their particularly high strength.
• a problem in the production and processing of steels which have such high manganese contents is that they have a solidification behavior which differs from the conventional steels intended for deep-drawing applications, such as IF or low-carbon steels. This shows that steels of the type in question which are cast in conventional slab casting have poor forming behavior.
• steels which, in addition to other alloying elements, contain 7% to 27% Mn, can be produced by thin strip casting as a strip close to the end and processed into hot strip.
• the material obtained in this way is particularly suitable for use in the field of automobile body construction.
• the object of the invention is to provide a method which enables the production of steel strips enables that have a good forming behavior despite a high manganese content.
• This object is achieved by a method for producing a hot strip having TWIN and TRIP properties from a steel containing more than 12 to 30% by weight of manganese, in which a melt in a two-roll casting machine is close to the final dimensions of a preliminary strip with a Thickness of up to 6 mm is cast, which is continuously processed into hot strip after the casting by rolling it to the final thickness of the hot strip in a single hot pass.
• high manganese steel is cast into a raw material, the dimensions of which approximate the final dimensions of the hot strip.
• a thin material is produced in the casting process that an essentially uniform solidification is ensured over its entire cross section.
• the hot strip produced from the primary material has TRIP ("Transformation-Induced-Plasticity") and TWIP ("Twinning-Induced-Plasticity”) properties and accordingly has good formability, which it combines with the high strength in a special way suitable for use in body construction.
• the thickness of the material produced should be as small as possible.
• the solidification process can be specifically controlled in a simple manner in the case of a thin cast preliminary product.
• the rate of solidification has a direct influence on the level and distribution of micro segregations. These in turn influence the grain growth and the state of the precipitates occurring during the solidification, such as MnS, A1N and Ti (C, N).
• the fundamentals can be set which decisively influence the further processability and the properties of use of the end product.
• the steel is cast according to the invention in a two-roll casting machine.
• This type of casting machine which is known per se, makes it possible to produce particularly thin pre-material, which closely approximates the final dimension of the hot strip, and whose solidification behavior, in particular its solidification speed and uniformity, leads to an optimal casting structure and, consequently, to an optimized formability.
• the further processing of the primary material into hot strip comprises a controlled cooling immediately following the casting. This enables the primary material emerging from the casting mold to be specifically cooled in such a way that a structure which is optimized for further processing is obtained. As a rule, cooling will take place at a higher cooling rate than cooling in air.
• the mean initial rolling temperature at which the starting material enters the roll stand can be between 1100 ° C and 750 ° C.
• the properties of the hot-rolled strip can also be influenced in a targeted manner by cooling the rolled hot strip in a controlled manner after the hot rolling.
• process the hot strip obtained in accordance with the invention “inline”, for example into a cold strip. In many cases it will possibly be with regard to the following
• Processing steps or properties of the hot strip to be set are expedient if the strip is coiled into a coil in the course of further processing.
• the primary material By further processing the primary material into hot strip at least in sections under a protective gas atmosphere, oxidation of the strip surface and the associated excessive scale formation can be avoided.
• the primary material is kept under the protective gas atmosphere at least up to its entry into the roll stand.
• Steels used according to the invention can contain up to 3.5% by weight, in particular up to 3% by weight, of silicon in addition to further alloying elements. In addition, they can have up to 3.5% by weight, in particular up to 3% by weight, of aluminum. In steels of the type processed according to the invention, iron and aluminum or iron and silicon form intermetallic phases which occur below the thermoforming temperature and are stable up to room temperature.
• FIG. 1 shows the structure of a device for producing a hot strip in a schematic side view, Diagram the temperature profile over the processing time of the pre-strip and hot strip in a device according to FIG. 1,
• Image 1 an enlarged section through the
• the figure shows schematically the structure of a device 1 for producing a hot strip W, which comprises a casting device 2, a first cooling section 3, a roll stand 4, a second cooling section 5 and a reel device 6.
• a melt S contained in a tundish 7 of a composition explained below in detail is converted into a preliminary strip V in the casting gap 10 formed between two casting rolls 8, 9 cast.
• the cast pre-strip V leaves the casting gap 10 in a continuous conveying process with a thickness that can be varied between less than 1 mm and 6 mm.
• the sliver V On its way to the rolling stand 4, the sliver V is cooled in a controlled manner in the first cooling section 3 below the outlet of the casting gap 10 and closely adjacent to it, using a cooling medium applied to its surfaces.
• the conveyor section covered by the thin strip V between the exit of the casting gap 10 and the roll stand 4 is surrounded by a housing 11 in which a protective gas atmosphere is maintained. In this way, contact of the belt surface with the oxygen in the ambient air is avoided.
• the thin strip V runs into the rolling stand 4 with a rolling start temperature AT and is rolled in one pass to its final thickness.
• the hot strip W is again brought to the reel temperature HT in a controlled manner with a suitable cooling medium, with which it is finally in the reel device
• the attached diagram shows the roll starting temperature AT, the roll end temperature ET and the reel temperature HT over the processing time after casting in the range that can be set depending on the composition and the desired properties of the hot strip to be produced on a device constructed according to the figure , Appropriate temperature control along a predetermined limit curve with subsequent isothermal holding, rolling and quenching allows the fine-grained structure of the hot strip to freeze after it leaves the rolling stand, so that the good performance properties of the hot strip are retained after hot rolling. Especially when the temperature profile of the pre and hot strip approximates the lower limit curve shown in the diagram, this effect can be achieved.
• the melt S cast in the exemplary embodiment had an Mn content of 20% by weight, a C content of 0.003% by weight, a sulfur content of 0.007% by weight and an Si content of 3%. 0% by weight, an Al content of 3.0% by weight and the balance iron.
• Figure 1 shows an enlarged section through the edge area
• Figure 2 shows an enlarged section in the same way through the central area of a hot strip produced from this steel in the device shown in the figure. It can be seen that the strip has a dendritic structure which consists of austenite and a presumably carbon-containing second phase. Towards the core of the tape there is a clear fine-tuning of the structure.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Metal Rolling (AREA)
• Continuous Casting (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2000
  • 2000-12-06 DE DE10060948A patent/DE10060948C2/de not_active Expired - Fee Related
• 2001
  • 2001-12-06 JP JP2002548196A patent/JP3836793B2/ja not_active Expired - Fee Related
  • 2001-12-06 AT AT01991793T patent/ATE267269T1/de active
  • 2001-12-06 AU AU2002231664A patent/AU2002231664A1/en not_active Abandoned
  • 2001-12-06 US US10/433,729 patent/US20040074628A1/en not_active Abandoned
  • 2001-12-06 WO PCT/EP2001/014306 patent/WO2002046480A1/fr active IP Right Grant
  • 2001-12-06 CZ CZ2003-1558A patent/CZ304928B6/cs not_active IP Right Cessation
  • 2001-12-06 DE DE50102363T patent/DE50102363D1/de not_active Expired - Lifetime
  • 2001-12-06 ES ES01991793T patent/ES2221659T3/es not_active Expired - Lifetime
  • 2001-12-06 PL PL362508A patent/PL196538B1/pl unknown
  • 2001-12-06 EP EP01991793A patent/EP1341937B1/fr not_active Expired - Lifetime
  • 2001-12-06 CN CN01816434.XA patent/CN1236076C/zh not_active Expired - Fee Related
• 2007
  • 2007-04-27 US US11/796,245 patent/US20070199631A1/en not_active Abandoned

Non-Patent Citations (1)

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