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
• • 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
  • B22D11/108—Feeding additives, powders, or the like

Definitions

• the present invention relates to the continuous casting of metals and in particular of steel.
• the invention relates to the supply and the deposition of a layer of a granular material of a more or less fine particle size on the surface of the liquid metal in a continuous casting mold.
• This material has the particular functions of thermally insulating the molten metal bath, of capturing the non-metallic inclusions which settle out of the liquid metal, of avoiding the reoxidation of the metal, and of ensuring the heat ingot mold / product transfers. and the lubrication of the walls of the mold.
• This material is usually called “covering powder”, and, for convenience, it will hereinafter be called “powder”, it being understood that its particle size and the shape of the grains can vary widely.
• This powder melts on contact with the liquid metal and infiltrates between the metal and the walls of the mold, thus playing the role of lubricant.
• the amount of this contribution varies according to the characteristics of the powder and those of the casting installation and of the metal cast.
• the consumption of powder can vary during casting as a function of the various operating parameters, and in particular the temperature of the cast metal.
• This conduit opens into the mold above the surface of the cast metal, at a distance therefrom corresponding to the desired thickness of powder, in the solid or molten state.
• a such a device is described in particular in document EP 473521.
• This device makes it possible to ensure an automatic supply of powder, because when the thickness of the latter tends to decrease, the powder flows in the conduit by gravity until the upper level of the layer reaches the level of the discharge port of the conduit, interrupting the flow.
• this takes advantage of its ability to spread substantially uniformly over the entire section of the ingot mold while taking advantage of the characteristics of the grain materials which are deposited in heaps at the outlet of the supply duct. .
• the continuous casting mold is overhung by the distributor, which is only a few tens of cm away. It is therefore not possible to install the powder feed hopper above the ingot mold and in the immediate vicinity thereof.
• the duct must be inclined relative to the horizontal by an angle not exceeding a few tens of degrees. This slight inclination, imposed by the local conditions of congestion of the pouring zone, is an obstacle to a good sliding of the powder inside the duct, which therefore risks clogging. This risk exists especially when using a powder with a fine particle size, less than 100 ⁇ m.
• the powders most suited to the start-up phases of the casting are precisely powders of small particle size
• the object of the invention is to provide an installation for the automatic distribution by gravity of covering powder in a continuous ingot mold, which can operate reliably both with powders of small particle size (less than 100 ⁇ m) than with powders of larger particle size.
• the subject of the invention is a feed device for the simple gravity deposition of a layer of granular material on the surface of a liquid metal contained in a continuous casting ingot mold, comprising a hopper containing said granular material, and connected to a supply duct comprising a portion inclined at a non-zero and non-right angle to the horizontal, and the lower discharge end of which is permanently open and is located above said surface of the metal in the mold at an equal distance or slightly greater than a nominal thickness of the layer of said material, characterized in that, on at least part of said inclined portion, said supply duct is constituted by a rectilinear tube, and in that it comprises means for imparting a rotational movement to said straight tube around its axis, and means for connecting the ends of said straight tube to the remainder of said conduit allowing said rotational movement.
• the invention consists in imparting a rotation about its axis to at least a portion of the part of the supply duct which is inclined relative to the horizontal. This creates agitation within the powder which minimizes the risk of clogging, and allows the use of fine particle size powders even when the configuration of the continuous casting machine locally requires a relatively small inclination of the conduit.
• FIG. 1 which shows schematically, in longitudinal section, the upper part of a continuous casting mold equipped with a device for feeding granular material according to the invention, also seen in longitudinal section;
• FIG. 2 which shows schematically a variant of the device for rotating the rectilinear tube included in the previous device.
• FIG. 1 a continuous casting ingot mold 1 supplied with liquid metal 2, in a conventional manner, by supply means, not shown, such as a distributor and a submerged nozzle.
• the liquid metal 2 sees its solidification initiated there by the formation of a solid crust 3 against the walls 4 of the mold 1, vigorously cooled by an internal circulation of water.
• On the surface of the liquid metal 2 is a layer of covering powder 5 which melts on contact with the metal 2, forming a liquid film 6 of slag which flows gradually towards the walls 4 of the mold 1, infiltrates between them and the solid crust 3 and plays a role of lubricant there.
• a continuous consumption of powder 5 and this must be replaced permanently to ensure a substantially constant thickness of the powder layer 5.
• the powder 5 is supplied from a hopper 7 to which is connected a supply conduit 8.
• the admission of the powder 5 into this conduit 8 is controlled by a valve 32.
• the terminal part of this conduit 8 is constituted by a bent tubular part 9 made of a rigid material and resistant to relatively high temperatures prevailing above the mold 1. The steel is quite suitable for this use.
• the lower end 10 of this bent tubular part 9 is permanently open and is held (by means which will be described later) above the surface of the liquid metal 2, at a distance d therefrom. This distance d is equal to or slightly greater than a set thickness of the layer of powder 5 and of slag 6.
• the duct 8 When the valve 9 is open, the duct 8 is permanently supplied with powder 5 so as to be kept loaded, and the powder 5 pours by simple gravity into the mold 1 until the layer thus formed comes to close off the lower end 10 of the bent tubular part 9, thus interrupting the arrival of powder.
• This phenomenon continues continuously during the casting, as the powder 5 is consumed, the thickness of which is present in the mold 1 is thus kept constant.
• the bent tubular part 9 which terminates it is connected, at its upstream end, to a rectilinear tube 11.
• This tube must be rigid, heat resistant, and present on its internal surface a coefficient of friction with the powder 5 as low as possible to allow easy descent powder 5.
• Steel, in particular stainless steel, here again, is a material which is particularly suitable for constituting it.
• the tube 11 is itself connected to the remaining part of the conduit 8.
• the internal diameter of the tube 11 is of the same order of magnitude as that of the assembly of the conduit 8 and of the bent tubular part 9, namely of the order of 2 to 6 cm.
• the installation also comprises means for holding the longitudinal axis of the tube 11 in a position such that it makes a non-zero and non-right angle ⁇ with the horizontal, and means for putting the tube it rotating around this axis.
• these holding means comprise a telescopic bracket 12 fixed to a base 13 made integral with the upper edge 14 of the ingot mold 1.
• This bracket in the example (not limiting) shown, comprises a vertical rod 15 fixed rigidly to the base 13, a tubular rod 16 fixed to the vertical rod 15 by an articulation 17 making it possible to tilt the tubular rod 16.
• Inside the tubular rod 16 can slide a rod 18, the depth of penetration into the tubular rod 16 can be adjusted and kept constant by a key 19 or any other equivalent means.
• This rod 18 is, on the one hand, rigidly connected by a lateral rod 20 to the bent tubular part 9 constituting the terminal part of the conduit, 8.
• the rod 18 carries at its free end a motor 21 (by electric or pneumatic example) printing on an axis 22 a speed of rotation chosen by the operator.
• This axis 22 carries at its free end a roller 23, whose outer surface is maintained in contact with the outer wall of the straight tube 11, and whose shape (frustoconical in the example shown) is suitable for this purpose.
• the roller 23 is made of a material having a high coefficient of friction with the material constituting the straight tube 11, for example rubber if the straight tube 11 is made of steel. The result obtained by this configuration is that the rotation of the roller 23, driven by the axis 22 of the motor 21, causes by friction the rotation of the straight tube 11 around its longitudinal axis.
• This rotation takes place at an angular speed depending on the speed of rotation of the roller 23 and the respective dimensions of the roller 23 and of the straight tube il. These are chosen so that the angular speed of rotation of the straight tube 11 is of the order, for example, of 1 t / min. To guarantee good friction between the roller 23 and the straight tube 11, it can also be provided to roughen the external surface of the straight tube 11 in the area where it is likely to be in contact with the roller 23. As has been said, the effect of this rotation of the straight tube 11 is to create, within the powder 5 which it contains, permanent agitation which eliminates the risks of clogging of the straight tube 11.
• the angle ⁇ of inclination of the axis of the rectilinear tube 11 and the distance d between the end 10 of the bent tubular part 9 and the surface of the liquid metal 2 in the ingot mold 1 are adjusted in combination by the operator, which can act on the one hand on the insertion depth of the rod 18 in the tubular rod 16, and, on the other hand, on the orientation given to the tubular rod 16 by the articulation 17.
• the duct 8, in its part located upstream of the rectilinear tube 11, has means of articulation, or is made over at least a portion of its length in a flexible material.
• Figure 1 there is shown an installation which is such that, with the angle ⁇ and the distance d chosen, the bent tubular part 9 is found perpendicular to the surface of 1 • liquid steel 2 in the mold 1, but this feature is not at all mandatory.
• connections between the straight tube 11 and the conduit 8 on the one hand, and the bent tubular part 9 on the other hand, must be designed to allow easy rotation of the straight tube 11. This assumes that the powder 5 cannot constitute a hinders this rotation.
• these connections can be provided by seals 24, 25 each comprising a bearing integral with the straight tube 11 or the element to which it is connected.
• seals 24, 25 each comprising a bearing integral with the straight tube 11 or the element to which it is connected.
• the downstream end 26 of the conduit 8 is inserted into the upstream end 27 of the straight tube 11, and opens downstream of the seal 24;
• FIG. 2 shows a possible variant of the mode of driving the rectilinear tube in rotation 11.
• the roller 23 of the previous example it is a pinion 30 which the axis 22 of the motor 21 carries, and this pinion is meshed on a frustoconical ring gear 31 secured to the external wall of the straight tube 11.
• the minimum value the angle ⁇ of inclination of the straight tube 11 depends on the characteristics of the powder 5, but a value of 20 to 30 ° is sufficient to ensure a regular fall of the usual fine powders whose particles have an average size of less than 100 ⁇ m.
• the length of the straight tube 11 it depends on the geometry of the continuous casting installation on which the device according to the invention is mounted. But it is quite obvious that it is advantageous for this rectilinear rotary tube 11 to represent a large fraction of the path taken by the powder 5 between the hopper 7 and the ingot mold 1, at least of the non-vertical portion of this path in which, without it, one could encounter problems of flow of the powder 5.
• this device is primarily designed to dispense powders 5 of fine particle size, it is perfectly compatible with the use of powders 5 of coarser particle size. Likewise, it can be installed on installations for the continuous casting of metals other than steel.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9453507

Family Applications (1)

Country Status (14)

Families Citing this family (6)

Family Cites Families (1)

• 1993
  • 1993-11-30 FR FR9314487A patent/FR2713116B1/fr not_active Expired - Fee Related
• 1994
  • 1994-11-07 WO PCT/FR1994/001281 patent/WO1995015234A1/fr not_active Application Discontinuation
  • 1994-11-07 JP JP7515437A patent/JPH08506278A/ja active Pending
  • 1994-11-07 CZ CZ952004A patent/CZ200495A3/cs unknown
  • 1994-11-07 CA CA002155021A patent/CA2155021A1/fr not_active Abandoned
  • 1994-11-07 PL PL94309697A patent/PL309697A1/xx unknown
  • 1994-11-07 BR BR9406074A patent/BR9406074A/pt not_active Application Discontinuation
  • 1994-11-07 CN CN94190930A patent/CN1116414A/zh active Pending
  • 1994-11-07 AU AU81101/94A patent/AU8110194A/en not_active Abandoned
  • 1994-11-07 EP EP95900194A patent/EP0680392A1/fr not_active Ceased
  • 1994-11-08 TW TW083110318A patent/TW274063B/zh active
  • 1994-11-11 ZA ZA948954A patent/ZA948954B/xx unknown
• 1995
  • 1995-07-28 KR KR1019950703130A patent/KR960700113A/ko not_active Application Discontinuation
  • 1995-07-28 FI FI953616A patent/FI953616A/fi not_active Application Discontinuation

Non-Patent Citations (1)

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