Classifications

• • 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
  • B22D11/12—Accessories for subsequent treating or working cast stock in situ
• • 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
  • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
• • 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
  • B21B1/466—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 non-continuous process, i.e. the cast being cut before rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
  • B21B37/005—Control of time interval or spacing between workpieces
• • 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
  • C21D11/00—Process control or regulation for heat treatments

Definitions

• the invention relates to a method for material flow determination and control of continuously cast slabs, in particular steel slabs by means of temperature tracking and optimization on their transport route between the continuous casting plant and the rolling mill.
• the solidified slab leaving the caster goes through different transport and process routes, each of which leads to different slab temperature profiles. Depending on whether the slab is transported with or without thermal insulation on a roller table, whether one or more slabs are stored in the stack, whether it is an open one
• the convective mixing of the amount of heat contained in the slab and the time-dependent heat emission of the inhomogeneously cooling slab to the respective surrounding medium is calculated using a mathematical-physical model and the result of the calculation, possibly together with the measured surface temperature of the slab, is used to control the material flow in an existing slab tracking system
• a preferred embodiment of the method according to the invention provides that the two-dimensional finite element method is used to calculate the mathematical-physical model. Finite-element calculation methods allow the simulation of a wide variety of processes; it serves to support constructive developments, processing, sales and, in the present case, also the future system operator. The method is often used in design to identify and minimize possible risks through structural mechanical analyzes.
• Simulations based on finite element calculations are often requested by plant operators in the project phase and are included in the contract for the supply of the plant as a fixed part of the contract.
• the two-dimensional finite element method, the finite difference method or a software with formulas derived from off-line studies are used to calculate the mathematical-physical model.
• a universal commercial finite element package can be used in offline studies. This is probably too big and slow online. Therefore, a method (this can also be a finite element method or the finite difference method) should be used, ie programmed, which is specially adapted to the slab geometry (rectangular) and is therefore fast enough.
• the online procedure can be checked with the offline finite element package.
• the temperature-dependent material value density p, the specific heat c P ⁇ , the thermal conductivity ⁇ and scale properties are preferably used as physical parameters of the slab.
• the invention advantageously enables by means of the mathematical-physical model, preferably with a finite element simulation or finite element simulation.
• the mean slab temperatures can be estimated later by measuring the surface temperature.
• the result of the method according to the invention can be used to make statements as to how many hours a specified mean slab temperature is maintained in the finishing line; statements can be made about the entire temperature spectrum in the slab tracking system. It has been shown that the method according to the invention and the one described
• the method is very flexible to use and is suitable for solving the problem according to the invention, for enabling the economical and safe material flow between the continuous casting plant and the rolling mill.
• the invention can replace the previous control of the slabs based on experience and empirical values.
• the systems no longer need to be oversized for safety reasons; because with the method according to the invention it is now possible to determine and master the actual conditions in the material flow between the continuous casting plant and the rolling mill.
• the simulation can be broken down as follows:
• the solidification of the slab in the strand is simulated in the holding pit in order to generate a realistic input temperature profile for the slabs.
• the material density, specific heat and thermal conductivity are temperature-dependent.
• a convective heat exchange also takes place in the liquid phase, but this was not modeled.
• the thermal conductivity was increased by a factor of 100 compared to the solid phase.
• An important boundary condition is the different water cooling in the areas of the primary and secondary cooling zones.
• the temperature range of possible surface temperatures is divided into sections of different heat transfer types (stable film evaporation, unstable area, burn-out point, etc.) because different approaches for the heat transfer value apply to these areas.
• the transition value also depends on the material value of the surface of the cooling body, which in the present case applies in particular to heavily scaled surfaces where the material values of scale are to be used.
• the simulation of the slab stack begins with the introduction of the first slab into the holding pit. After that, the next slab is stacked on the previous one every 60 seconds their own weight the curvature of the top hot slab
• the corresponding elements of this slab are activated and the finite element simulation is already carried out for this slab in the holding pit.
• the second slab follows and the elements of the slab two are activated. This procedure proceeds analogously until the storage of the last cold slab Now the simulation of the entire slab stack in the holding pit begins.
• the essential boundary conditions here are also the heat transfer coefficients between the slab surfaces and the surrounding area. With the exception of the lower contact surface, the surface of the
• the air convection is calculated with special functions, because the heat transfer values of different strengths result for the horizontal and vertical surfaces. At high temperatures, these are still small compared to the heat transfer values of the radiation, but at low temperatures they become dominant. Furthermore, the ambient temperature is calculated by the Wide hall area or the walls of the holding pit on These can be seen from a representative stack but only in a certain solid angle section, in the other solid angle sections there are neighboring stacks that have a similar temperature
• the bottom horizontal surface of the stack is in contact with the hall floor.You could include the hall floor yourself in the Fmite element calculation.You can also simply model the hall floor as a semi-infinite body, which constantly remains at its initial temperature, at which one then time-dependent heat transfer value exists
• the temperature profile can now be determined over the cross section of the slab or the stack of slabs Reintegration into the material flow between the caster and the rolling mill for a steel slab should have an average slab temperature between 500 and 600 ° C.
• the first slab still has the temperature profile corresponding to the exit from the caster.
• the end of the stacking process it can be seen that there is a more homogeneous temperature distribution in the stack if the floor is properly insulated.
• the top slab in the stack loses a relatively large amount of heat in the first hour when the cold slab is laid on, and the bottom slab in the stack cools down considerably over a very short period of time until the floor has an insulating effect.
• the method according to the invention enables economical and safe control of the individual slabs between the continuous casting plant and the rolling mill.
• Control measurements on the surface of the slab taking into account the values obtained by the calculation model, make it easy to deduce the amount of heat and the temperature profile of the slab, provided the corresponding boundary conditions are included. In this way, it can be determined at any location between the continuous casting plant and the rolling mill, and in particular in storage locations, which amount of heat can be allocated to the respective slab and which
• the invention provides the technician involved in the implementation with a means of optimally designing the system so that it is economical to manufacture and operate.

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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)
• Continuous Casting (AREA)
• Metal Rolling (AREA)
• Control Of Metal Rolling (AREA)
• Control Of Heat Treatment Processes (AREA)
• Feedback Control In General (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1997
  • 1997-10-02 DE DE19744815A patent/DE19744815C1/de not_active Revoked
• 1998
  • 1998-09-15 TW TW087115371A patent/TW409083B/zh active
  • 1998-09-22 BR BR9812707-1A patent/BR9812707A/pt not_active Application Discontinuation
  • 1998-09-22 JP JP2000515037A patent/JP2001519474A/ja active Pending
  • 1998-09-22 CN CN98809770A patent/CN1094983C/zh not_active Expired - Fee Related
  • 1998-09-22 KR KR1020007003548A patent/KR20010072534A/ko not_active Application Discontinuation
  • 1998-09-22 WO PCT/DE1998/002915 patent/WO1999018246A1/de not_active Application Discontinuation
  • 1998-09-22 AU AU14328/99A patent/AU1432899A/en not_active Abandoned
  • 1998-09-22 EP EP98958181A patent/EP1019550A1/de not_active Ceased
  • 1998-09-22 CA CA002305401A patent/CA2305401A1/en not_active Abandoned

Non-Patent Citations (1)

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