Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
  • B21B45/0203—Cooling
  • B21B45/0209—Cooling devices, e.g. using gaseous coolants
  • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
  • B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
• • 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
  • B21B1/22—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 plates, strips, bands or sheets of indefinite length
  • B21B1/30—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 plates, strips, bands or sheets of indefinite length in a non-continuous process
  • B21B1/32—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 plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work
  • B21B1/34—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 plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work by 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

Definitions

• the invention relates to a method for producing hot strip and sheet metal on a production plant, consisting of a continuous casting plant for slabs with a thickness between 100 and 180 mm and with an exit temperature from the
• FFM Flexible Fiat Mill
• the temperature of the slab after leaving the continuous casting plant is usually between 1000 ° C and 1150 ° C and decreases during transport to the heating furnace on the roller table.
• the direct hot use in the heating furnace takes place at temperatures between 750 and 950 ° C.
• the slab is heated evenly across thickness, width and length to material-dependent temperatures between 1050 and 1280 ° C.
• Characteristic of the hot application is the fact that before the first forming in the rolling mill there is no or only a slight austenite-ferrite / per-lit transformation in the area close to the surface over the slab thickness if the surface temperatures change the transition temperatures during transport of the __
• the method of hot use saves heating energy and time during the heating process compared to cold use.
• the described method of hot use has proven itself for steels with a copper content of less than 0.3%. With higher copper contents in the steel, the copper released during the scale formation in the heating furnace accumulates at the grain boundaries of the primary austenite. Depending on the copper content, the heating temperature and scaling, these copper deposits at the grain boundaries can lead to material separations in the form of network-like cracks during the forming in the rolling mill.
• EP 0686702 A1 it is proposed to solve the problem that also occurs in thin slab casting and rolling plants that the surface of the 40 - 70 mm thick thin slabs be lowered in a cooling section downstream of the continuous casting plant to temperatures below the Ar 3 temperature in such a way that in a near-surface area of at least 2 mm depth there is at least a 70% structural transformation of the austenite into ferrite / pearlite with reorientation of the austenite limits after reheating in the roller hearth furnace.
• An average surface temperature should not fall below the martensite threshold of the respective material quality during cooling in the cooling section.
• AIN precipitates during hot use are given as the cause of cracks in the rolling stock when rolling aluminum-quenched steels with 0.008-0.030% N and 0.03-0.25% Pb. Rapid cooling of the near-surface boundary layer of the blooms with structural transformation in the bainite region is recommended to suppress the AIN excretions. The rapid cooling takes place between the continuous caster and the heating furnace.
• the device for rapid cooling is located between the continuous caster and the heating furnace.
• a material-specific control and regulation of the cooling device is provided.
• the described prior art has in common that the actual causes, processes or mechanisms that lead to cracks and material separations when using the hot insert in the process line continuous casting plant - heating / equalizing furnace - rolling mill have not yet been clearly clarified. It is possible to combine ⁇ several named causes.
• the prior art proposes rapid cooling of the surface layer of the continuous casting material near the surface below the transition temperature with subsequent tempering by the heat flowing from the core. The risk of the surface temperature sometimes falling below the martensite threshold is present in all the patents mentioned, as shown in FIG. 1a with the solid line representing the prior art.
• Fig. 1a shows the course of the surface temperature over time.
• the devices for rapid cooling are proposed in the prior art locally between the continuous casting plant and the heating furnace or compensating furnace.
• the partial conversion of the near-surface boundary layer into ferrite / pearlite is associated with a refinement and reorientation of the austenite limits after reheating, as can also be seen in FIGS. 1b and 2 on the course of the solid line representing the prior art.
• the object of the present invention is to ensure that steels with higher contents of Cu, Al and N can also be processed in a combined hot strip / sheet metal production plant of the generic type described. According to the invention, it is proposed that between the continuous caster and the heating furnace only the surface layer of the previously descaled slab near the surface is formed in-line, recrystallized during and after the forming and then in several stages to a temperature below the A r3 - __
• Cooling point is cooled and temporarily held until the structural transformation of the recrystallized fine-grained austenite in the ferrite / pearlite is completed.
• the slab is formed with a total decrease of 5-15% and with a diameter-optimized rolling gap ratio l d / h m of less than 0.8.
• the rolling speed corresponds to the casting speed.
• the region of the continuous casting material near the surface in the roll gap of the respective stand of the rolling unit recrystallizes partially to completely dynamically, depending on the forming conditions.
• a partial to complete static recrystallization of the deformed surface layer of the rolling stock near the surface takes place.
• the temperature curve of the surface layer near the surface is shown in FIG. 1a with the dashed line.
• the dynamic and static recrystallization results in grain refinement of the surface layer near the surface (see FIG. 1b, dashed line), ie the coarse-grained primary austenite has changed into a rolled fine-grained structure.
• the intensity of the cooling section consisting of several nozzle groups is controlled and regulated so that the surface temperature of the slab neither reaches the bainite area nor falls below the martensite threshold of the respective material quality.
• control and regulating systems control the media pressure of the nozzle groups of the cooling section as a function of the respective slab thickness and casting speed, the average temperature of the surface layer near the surface, while observing the cooling temperature and time necessary for a 100% structural change, as well as the bainite start temperature and the martensite start temperature regulate the respective material quality.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Control And Other Processes For Unpacking Of Materials (AREA)
• Thermotherapy And Cooling Therapy Devices (AREA)
• Diaphragms For Electromechanical Transducers (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (10)

Cited By (1)

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Family Cites Families (8)

• 1998
  • 1998-09-14 DE DE19843200A patent/DE19843200C1/de not_active Expired - Fee Related
• 1999
  • 1999-09-08 AT AT99969051T patent/ATE230315T1/de active
  • 1999-09-08 RU RU2001106994/02A patent/RU2224605C2/ru not_active IP Right Cessation
  • 1999-09-08 ES ES99969051T patent/ES2186438T3/es not_active Expired - Lifetime
  • 1999-09-08 CN CNB998108987A patent/CN1142038C/zh not_active Expired - Fee Related
  • 1999-09-08 US US09/787,158 patent/US6451136B1/en not_active Expired - Fee Related
  • 1999-09-08 EP EP99969051A patent/EP1112128B1/fr not_active Expired - Lifetime
  • 1999-09-08 DE DE59903924T patent/DE59903924D1/de not_active Expired - Lifetime
  • 1999-09-08 CA CA002344423A patent/CA2344423C/fr not_active Expired - Fee Related
  • 1999-09-08 AU AU11492/00A patent/AU1149200A/en not_active Abandoned
  • 1999-09-08 WO PCT/DE1999/002866 patent/WO2000015362A1/fr active IP Right Grant

Non-Patent Citations (1)

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