Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B39/02—Feeding or supporting work; Braking or tensioning arrangements, e.g. threading arrangements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B39/02—Feeding or supporting work; Braking or tensioning arrangements, e.g. threading arrangements
  • B21B39/12—Arrangement or installation of roller tables in relation to a roll stand

Definitions

• a hot rolling mill comprises, between the last mill stand and the final wind-up reel, a runout table where the rolled strip is cooled down from the rolling temperature, 900- 850°C, to the final temperature, 550-600°C, at the reel.
• the runout table may amount to about 100 m.
• the runout table according to the prior art consists of a roller table with a large number of rolls which are each driven by their own motor.
• the intention of the present invention is to replace parts of the roller table, counting from the wind-up reel and backwards towards the last mill stand, by a linear motor consisting of a multi-pole, multi-phase stator winding with an associated laminated steel core and wherein the strip functions as the "rotor" of the linear motor.
• the first zone which the strip enters starts directly after the last mill stand and will here ⁇ inafter be referred to as a transport zone. This is a rela ⁇ tively short zone. Then comes a zone where the strip is actively cooled by cooling agents of various kinds. This zone will consequently be referred to as a cooling zone.
• the third and last zone between the active cooling zone and the wind-up reel will hereinafter be referred to as a final zone. A certain amount of cooling of the strip because of the surrounding agents will also take place when the strip passes through the final zone.
• CONFIRMATION COPY out table is to fulfil, as well as the problems which may arise in this connection, will first be described.
• the hot-rolled strip while being propelled from the last mill stand to the wind-up reel, is to be cooled so its temperature is reduced by approximately 300°C.
• This cooling is for the most part performed by spraying with large quantities of water within the cooling zone. The water spraying may influence the strip both from below and from above.
• the optimum rolling speed of the rolling mill is determined, inter alia, by the thread speed that can be maintained along the runout table.
• the thread speed that can be maintained along the runout table.
• the speed is too high, there is a risk of the strip rising from the rollers and hence of losing traction force in the forward direction.
• Particularly sensitive is the region within the last part of the final zone where the head end of the strip has a tendency of lifting upwards. It is also important that the speed of the strip along the whole runout table be kept constant .
• the propulsion device used that is, the roll table according to the state of the art, is to trans ⁇ port the strip with a tension from the rolling mill to the wind-up reel.
• the propulsion device is to retain the strip such that it lies flat on the roll table.
• the propulsion device should maintain the rolled strip centred on the roller table. For the above reason, the propulsion device should exert both a pulling force and a centring force on the strip as well as hold up the strip by way of a lifting force.
• the strip normally turns into scrap with ensuing time expenditure for preparing new strip to be rolled.
• Japanese patent application No. 63-205892 (22) of 26 Feb. 1988 describes a device in which one or more of the rollers in the roll table are replaced by a special type of roller with built-in permanent magnets or electromagnets which exert an attractive force on the strip, preventing the free end from rising.
• the surface of these rollers is coated with a non-magnetic and non-conducting material.
• a similar prin ⁇ ciple is presented also in SU 1486199 Al.
• US 4,407,438 describes a roll table for hot-rolled strips comprising one or more linear driving elements located between two consecutive rollers intended to achieve a travelling force field on the front end of the strip.
• the field is adapted to have a force component at right angles to the direction of movement of the strip in order to adjust and center the strip on the roll table, all according to the patent specification; that is, it is not a question of a device for propelling hot-rolled strip but only for centralizing the strip on the runout table.
• the rolled strip leaves the last mill stand and enters the transport zone, it has, as mentioned above, a tempera ⁇ ture of 850 - 900°C, that is, it is in an austenitic phase state and is thus practically to be regarded as a non- magnetic material.
• that part of the strip which is within the transport zone may serve as a "rotor" in a linear motor although the lifting force is small.
• the strip material nearest the outer surfaces will first be cooled such that the tem- perature drops past the Curie point of the material, which lies at about 625°C for currently used materials, and these parts of the strip are transformed into a ferritic phase state.
• the strip material During the further passage of the strip within the cooling zone, the remaining cross section of the strip material gradually changes from an austenitic to a ferro ⁇ magnetic material.
• the strip material largely from the beginning of the cooling zone and when passing through the final zone up to the wind-up reel, is to be regarded as a ferromagnetic material and may thus consti- tute the "rotor" in a linear motor, where both a lifting and a pulling force on the strip may be obtained.
• the production in a hot rolling mill may vary greatly. Normally, however, the thickness of the strip is between 1.5 and 16 mm and the width of the strip is between 0.6 and 1.5 m.
• the pulling force per surface unit is normally between 5 and 17 N/mm*-- and the transport speed is between 1.5 and 15 m/s.
• the invention comprises replacing that part of a conven ⁇ tional roll table, which comprises the whole of or parts of the cooling zone and the final zone, by the stator part of a linear motor. It should thus be designed to be able to raise the strip from the base such that an "air gap" is formed between the thermal protection covering the stator of the linear motor and the strip, and to be able to provide a pulling force in the strip and hence achieve a speed of the strip which coincides with the speed of the strip within the transport zone, and to be able to centre the strip on the roll table, and finally, to give the leading end such a force component that, at the end of the final zone, that is, before entering the wind-up reel, it does not rise.
• the accompanying figure shows the runout table in a hot rolling mill from the last mill stand 1 to the wind-up reel 2.
• the rolled strip 4 runs on a first propulsion device in the form of conventional rollers 5 which are each driven by a motor (not shown) .
• a second propulsion device within the whole of or parts of the cooling zone 6 and the final zone 7 in the form of a linear motor consisting of a stator 8 and the moving strip leads the strip to the wind-up reel.
• the air gap of the linear motor is shown at 10.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Linear Motors (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (4)

Cited By (1)

Citations (2)

• 1994
  • 1994-11-28 SE SE9404107A patent/SE504520C2/sv not_active IP Right Cessation
• 1995
  • 1995-11-27 EP EP95939462A patent/EP0794842A1/en not_active Withdrawn
  • 1995-11-27 WO PCT/SE1995/001417 patent/WO1996016752A1/en not_active Application Discontinuation
  • 1995-11-27 JP JP8518671A patent/JPH10509918A/ja active Pending

Patent Citations (2)

Non-Patent Citations (1)

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