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
  • B22D11/10—Supplying or treating molten metal
  • B22D11/11—Treating the molten metal
  • B22D11/114—Treating the molten metal by using agitating or vibrating means
  • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/02—Use of electric or magnetic effects
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/08—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like for bottom pouring
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper

Definitions

• the present invention relates to a device for continuous or semicontinuous casting of metals, comprising a stirrer according to the preamble to claim 1.
• a molten metal is supplied to a casting mould, hereinafter designated mould, in which it is cooled and formed into an elongated strand.
• the strand is designated BILLET, BLOOM or SLAB.
• a primary flow of hot, molten metal is supplied to the cooled mould, in which the metal is cooled and at least partially solidifies into an elongated strand.
• the cooled and partially solidified strand then continuously leaves the mould. At the ⁇ point where the strand leaves the mould, it has at least a mechanically self-supporting, solidified casing that surrounds a non-solidified centre.
• the cooled mould is open at two opposite ends in the casting direction and preferably connected to means for supporting the mould and means for supplying coolant to the mould and supporting means.
• the mould is preferably made of a copper-based alloy with good thermal conductivity.
• the molten metal is supplied to the mould via a casting tube . that extends down in to the mould.
• the casting tube preferably extends so far. down into the mould that it projects into the molten metal that exists therein.
• the pri ⁇ mary flow leads downwards in the casting direction, whereas the secondary flow leads from the region of the walls of the mould upwards towards the surface of the metal bath located therein, designated the meniscus, and downwards. In different metal bath, designated the meniscus, and then downwards again.
• the meniscus is covered by a layer consisting of casting powder intended to act as protection against the surrounding atmosphere and to minimize heat losses.
• hot metal flow is allowed to enter into the mould in an uncontrolled manner, the flow will penetrate deep into the cast strand, which probably will have a negative influence on the quality and productivity.
• An uncontrolled hot metal flow in the cast strand may result in encapsulation of non-metallic particles and/or gas occlusions in the solidified strand, or cause casting defects in the inner structure of the cast strand.
• a deep penetration of hot metal flow may also cause a partial remelting of the solidified surface structure so that the melt penetrates the surface layer below the mould, which causes severe disturbances in production and a long downtime for repair.
• Velocity variations caused by oscillating flow in the mould give rise to pressure variations at the meniscus, and, in addition, variations in height arise at the meniscus.
• Velocity variations caused by oscillating flow in the mould give rise to pressure variations at the meniscus, and, in addition, variations in height arise at the meniscus.
• the velocity of flow and hence the turbulence at the meniscus become too high, this leads to slag being drawn down from the casting powder and further down into the solidified strand, and results in an increased risk of cracking due to uneven shell growth.
• the velocity becomes too low at the meniscus there is a risk of temperature differences arising, which may lead to local solidification at the meniscus with ensuing risks of cracking and of slag particles adhering under the shell that is solidifying at the meniscus.
• the object of the present invention is to provide a device for continuous or semicontinuous casting of metals, especially intended for casting of slabs, which contributes to reduce or eliminate the disadvantages mentioned above.
• a device is aimed at which creates an even flow at the meniscus for different speeds of the inflowing melt.
• the metal flow at the meniscus is directed away from the narrow sides of the mould inwards towards the casting tube and uniformly across the whole width of the melt, and, in addition, a homogeneous flow configuration is obtained at the meniscus which provides the lowest turbulence when the flow is uniform across the whole mould width.
• a stirrer placed as previously described a sufficiently large counter-directed meniscus flow is obtained uniformly over the whole width of the casting mould while at the same time the turbulence is restricted.
• the location of the stirrer also contributes to obtain a good rotation of the melt around the casting tube and the installation of the stirrer is considerably simpler compared with prior art solutions.
• the secondary flow is utilized in an optimum way while at the same time, with the help of the stirrer, it is modified so as to obtain a good symmetrical flow of the melt in the mould including a good horizontal flow of the melt around the casting tube, which promotes an even shell growth while at the same time the amount of inclusions in the finished strand is reduced.
• an optimum flow is meant that the velocity of the melt at the meniscus (the secondary flow) is maintained at a constant level without varying in time while at the same time the velocity of the metal flow (the primary flow) directed downwards from the casting tube is to be kept at as low a level as possible to minimize the risk of inclusions accompanying the melt far down into the solidified strand.
• the dimension of the iron cores of the stirrer in the vertical direction is usually 240-280 mm.
• the iron core is arranged such that its upper part is positioned at a distance away from the meniscus that lies from 50 mm above the surface of the meniscus to 150 mm below said surface.
• the iron core is ar- ranged such that its upper part is positioned at a distance away from the meniscus that lies from 50 mm above the surface of the meniscus to 100 mm below said surface.
• two stirrers are arranged symmetrically around the centre line of the broad sides of the mould and on both sides of said broad sides . Since the iron cores of the stirrers only need to cover part of the width of the cast strand, such a device provides a cost-effective solution since a good rotation of the melt around the casting tube as well as an even velocity profile over the thickness of the width of the cast strand are obtained.
• stir- rers are placed asymmetrically, on respective sides of the long sides of the mould.
• This embodiment provides advantages such as lower weight, lower power consumption and reduced influence of magnetic fields on the surroundings.
• the pole pitch is large, which results in a maximally effective stirrer.
• Figure 1 is an explanatory sketch of the device according to the invention.
• Figure 2 is a top view according to one embodiment of the device according to the invention.
• Figure 3 is an exploded view of a continuous casting device according to the invention.
• Figure 1 shows an explanatory sketch of the invention, comprising a mould 1 enclosing a melt 2 which is supplied to the mould 1 by means of a casting tube 3 lowered into the melt.
• the melt 2 is cooled and a partially solidified strand is formed.
• the strand is then moved continuously out of the mould 1.
• at least one stirrer 4 is arranged which has an iron core and a coil applied around it and, with the iron cores arranged so as not to cover the whole length of the broad sides of the mould but instead at least 50% of the broad sides of the mould and at most 80% of the broad sides of the mould, symmetrically about the centre line 5 of the mould 1 on both sides of the broad sides of the mould.
• the iron cores are arranged such that their upper parts are positioned at a distance from the meniscus that lies from 50 mm above the surface 7 of the meniscus to 195 mm below said surface 7, in order to create a rotating stirring of the melt below the meniscus 7 by means of a period low- frequency travelling field.
• Figure 2 shows an alternative embodiment of the invention, wherein the stirrers 8 are located asymmetrically on respective sides of the broad sides 10 of the mould 9 and arranged such that the upper parts of the iron cores are positioned at a distance from the meniscus that lies from 50 mm above the surface of the meniscus to 195 mm below said surface.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Continuous Casting (AREA)

Applications Claiming Priority (2)

Publications (2)

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Citations (8)

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• 2007
  • 2007-04-25 US US12/298,537 patent/US20090255642A1/en not_active Abandoned
  • 2007-04-25 WO PCT/SE2007/050269 patent/WO2007123485A1/en active Application Filing
  • 2007-04-25 JP JP2009507643A patent/JP2009535216A/ja active Pending
  • 2007-04-25 CN CN2007800111680A patent/CN101410204B/zh not_active Expired - Fee Related
  • 2007-04-25 EP EP07748430A patent/EP2010346A4/de not_active Withdrawn
  • 2007-04-25 RU RU2008141879/02A patent/RU2419508C2/ru not_active IP Right Cessation
  • 2007-04-25 KR KR1020087025099A patent/KR20090016445A/ko not_active Application Discontinuation
• 2012
  • 2012-02-22 US US13/402,144 patent/US20120199308A1/en not_active Abandoned

Patent Citations (8)

Non-Patent Citations (1)

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