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
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/62—Quenching devices
  • C21D1/667—Quenching devices for spray quenching
• • 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
  • B21B45/04—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 de-scaling, e.g. by brushing
  • B21B45/08—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 de-scaling, e.g. by brushing hydraulically

Definitions

• the invention relates to a method for reducing and controlling the surface scaling during hot rolling of flat products, in particular hot strips, in which the rolling stock is subjected to water for the purpose of simultaneous cooling.
• the latter is also the cooling process proposed in DE-PS 27 50 718 and the one used to carry it out Load device.
• the spray jet which is produced with the aid of a Laval nozzle from water and compressed air and is referred to as air-water mist, is intended to hit the surface of a hot rolled product at high speed, which means that at the same time, new atmospheric oxygen with this surface ready to react in again and again Touch comes.
• the crumbling of the scale layer resulting from this contact as a result of a thermal shock effect is disadvantageous compared to avoiding or reducing scale formation.
• the method known from DE-OS 4036043 for achieving limited scale formation provides a multi-part cooling unit which encapsulates essential parts of the cooling section in order to largely exclude the access of the ambient air.
• the cooling unit has pressure water pressurization spaces separated by expansion and sealing devices from expansion spaces, into which the cooling water is introduced under pressure and may be suitable for the treatment of wire, but - apart from its complicated structure - it cannot be used for hot wide strip, because such rolled material can be used does not allow the inevitably narrow tolerances of entry and passage into or through the pressure cooling unit to be maintained.
• the invention is based on the object of specifying a method which allows the scale formation to be controlled, in particular reduced, while maintaining the conventional spray water cooling.
• the invention provides that a droplet mist is generated from part of the water (required for the desired cooling) by mechanical fine atomization, with which the surfaces of the rolling stock are enveloped.
• the rolling stock is thus completely covered over a certain section or the entire cooling section by the water mist generated without air supply, so that the entry of atmospheric oxygen is effectively prevented is.
• the droplet mist also envelops the area of water application for cooling purposes, but prevents the water vapor forming there from 'sucking in' air and leading its oxygen to the belt surface.
• the small size of the droplets prevents the development of undesirable turbulence, and the formation of a 'vapor cushion' undesirable in the area of the cooling water impairs further evaporation without adversely affecting the shielding effect of the mist.
• the water mist used according to the invention preference is given to those atomizing nozzles in which water under high pressure, for example 100 bar, is atomized so finely that the droplet size is on average between 10 and 100 ⁇ m, namely approximately 65 ⁇ m, if the atomization is against Atmospheric pressure takes place.
• Additives can be added to the atomizing water which, as evaporation residues on the strip surface, lead to skin that inhibits oxidation.
• Such additives can for example consist of milk of lime, water glass or starch or other organic substances. The latter result in carbon-containing residues which, when deposited on the surface of the rolling stock, have a reducing effect.
• their scaling-impairing effect must be optimized with their influences on liability and compatibility with a stain, which is still provided.
• the rolling stock is sealed against the ambient air on the underside and on the side by means of a half-shell-shaped cover. Furthermore, by means of covers arranged above the rolling stock, the vapor flow triggered by the droplet-mist evaporation can be influenced. Such covers can consist of light grids, which do not restrict the accessibility and observation of the hot strip; they can also be limited to certain sections of the cooling section.
• water curtains are preferably provided on the inlet and outlet sides of the cooling section, which prevent the injector-like entry of air or the floating of the droplet mist; both are driven by the high feed rate of the hot strip running out.
• the "mist" zone extends over a defined section or the entire length of the cooling section, while the spray water for intensive cooling of the hot strip occupies only a relatively short section of this section - or several spaced apart, relatively short sections. It is important that the hot strip is immersed in the droplet mist immediately after leaving the last rolling stand or within a relatively short time and also in the area of the spray water cooling is maintained. The mist atmosphere enveloping the hot strip may only end when it has cooled down to such an extent that practically no further scale formation takes place.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

Families Citing this family (3)

Citations (5)

• 1994
  • 1994-08-31 DE DE19944430856 patent/DE4430856C2/de not_active Expired - Fee Related
• 1995
  • 1995-08-30 WO PCT/EP1995/003407 patent/WO1996006696A1/de not_active Ceased
  • 1995-09-30 TW TW84110235A patent/TW290483B/zh active

Patent Citations (5)

Non-Patent Citations (2)

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