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(11) | EP 3 753 649 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | TUNDISH DAM |
| (57) A dam (20) for insertion into a tundish for use in metal casting comprises a body
(21) of refractory material having opposed faces in contact with the liquid metal
in use, opposed side edges and a lower edge (24), the side and lower edges engaging
inner surfaces of the tundish in use. The dam is characterised by an aperture (23)
extending between the opposed faces in the lower part thereof, the aperture being
closed by a metal plate (25), for example of the same composition as the liquid metal
to be introduced into the tundish. The invention further provides a tundish incorporating
at least one such dam (20) and a method of casting metal using the tundish.
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Field of the Invention
[0001] This invention relates to a dam for insertion into a tundish for metals casting to control the flow of liquid metal in the tundish during the casting operation, to a tundish incorporating at least one such dam, and to a method of casting metal using the tundish.
Background to the Invention
[0002] In the continuous casting of steel a tundish is used between the ladle supplying liquid steel and the mould in order to regulate the flow of metal. The tundish consists of a refractory lined open container (although a refractory lid may be provided) into which the steel is poured from the ladle and from which steel flows to the continuous casting mould(s) through one or more outlets, which may have stoppers or gates to control metal flow. The tundish evens out the steel flow and allows contaminating inclusions to be retained, rather than flowing into the casting. Dams or weirs may be installed in the tundish to modify and control the flow of steel in the tundish. By increasing residence time and reducing velocity, the inclusion separation capacity of the tundish is increased, thereby improving the quality of the cast steel.
[0003] A known dam comprises a body of refractory material having opposed faces in contact with the liquid metal in use, opposed side edges and a lower edge, the side and lower edges engaging inner surfaces of the tundish in use.
[0004] A negative aspect of the use of dams is that they prevent the discharge of all the steel in the tundish, so that at the end of the operation, there may be pockets of steel that are not discharged into the mould, but instead solidify in the tundish and therefore require reprocessing, adding significantly to the cost of production.
Summary of the Invention
[0005] The dam of the invention is characterised by an aperture extending between the opposed faces in the lower part thereof, the aperture being closed by a metal.
[0006] The composition of the plate is suitably chosen according to the temperature and chemistry of the molten metal to ensure compatibility with the process.
[0008] The metal plate has a thickness such that, when exposed to the liquid metal, the plate maintains closure of the aperture until the filling of the tundish is completed. For a tundish used for the casting of steel, a plate thickness of at least 12mm has been found to be suitable.
[0009] The aperture suitably represents about 5% to 20% of the area of the face of the dam, for example 7-8%.
[0010] The metal plate may comprise a plurality of projections on or adjacent to the sides and upper edge thereof to anchor the plate in the refractory material. For example, the projections may comprise V-shaped members welded to the face of the plate at the foot of the V. The metal plate may be located in a mould during formation of the dam in such a manner that the projections are engulfed by refractory cement mix as it fills the mould. After hardening of the refractory mix, the projections are thus embedded in the refractory, securing the metal plate in position.
[0011] The invention also provides a tundish for use in the casting of metal, comprising a refractory lined container having an inlet zone therein for receiving poured molten metal and an outlet for discharging the molten metal into a casting mould, the tundish having located therein between the inlet zone and the outlet at least one dam according to the invention.
[0012] The invention further provides method of casting metal comprising pouring molten metal into the inlet zone of the tundish of the invention and discharging the molten metal from the outlet into a casting mould, wherein after pouring of the metal has been completed the discharge of metal is continued until the metal in the inlet zone has flowed through the apertures in the dams to reach the outlet.
[0013] By reducing the remaining metal in the tundish at the end of the casting process, the invention offers significant cost savings, as less metal requires reprocessing; the reduction in energy consumption also offers environmental benefits.
Brief Description of the Drawings
[0014] In the drawings, which illustrate an exemplary embodiment of the invention:
Figure 1 is a part-sectional perspective view of a tundish containing a pair of dams in accordance with the prior art;
Figure 2 is a rear (relative to the flow direction of steel in the tundish) elevation of a dam according to the invention;
Figure 3 is a front elevation of the dam shown in Figure 2;
Figure 4 is an underneath plan view of the dam;
Figure 5 is a top plan view of the dam;
Figure 6 is a side elevation of the dam; and
Figure 7 is a perspective view of the metal plate used in the dam of Figures 2 to 6.
Detailed Description of the Illustrated Embodiment
[0015] Figure 1 shows, in simplified form, a typical tundish for use in the continuous casting of steel comprises a steel vessel 1 provided with a replaceable refractory lining 2 which may be provided by the use of refractory bricks or boards, or by other means such as the spraying of a refractory slurry or by dry lining using a resin-bonded powder. In the illustrated example, the molten steel is introduced into the tundish 1 adjacent to one end thereof and discharged into the continuous casting mould through an outlet 3 adjacent to the opposite end. While the outlet 3 is shown as a simple hole, means may be provided to control the outlet flow, for example a stopper or an outlet gate.
[0016] In order to ensure that the flow of molten steel from the tundish to the casting mould is optimised, avoiding turbulence and delaying cooling, allowing any inclusions to float, rather than be carried through to the mould, various devices may be mounted within the tundish, such as impact pads at the point at which steel is poured into the tundish from the delivery ladle, as well as weirs and dams to provide an indirect path between the pouring point and the outlet 3. As illustrated in Figure 1, the tundish includes two dams 4 by way of example, but it will be appreciated that in practice the number and positioning of the dams will depend on the size of the tundish and the placement and number of the outlets - there may be more than one outlet for some casting operations. For example, a common tundish may feed more than one mould.
[0017] Referring now to Figure 2 to 6, a dam 20 in accordance with the invention consists of a body 21 of refractory material provided with a pair of steel loops 22 in the upper edge thereof for use in lifting the dam 20 into position in a tundish. An aperture 23 is formed in the dam 20 centrally of the lower edge 24 thereof and extending from one face of the dam to the other. However, the aperture 23 is closed off by a steel plate 25 which is mounted in a recess 26 in the rear face of the dam and is held in place by anchors embedded in the refractory material, as hereinafter described with reference to Figure 7.
[0018] It will be seen from Figures 3, 4 and 5 that the dam is formed with one chamfered side edge 27. This is to accommodate installation in a tundish having a tapered configuration, with steel being poured into a central section of maximum width and then flowing to a plurality of outlets on either side thereof, the width reducing away from the central portion in each direction. Dams will be introduced between the central portion and the outlets on either side thereof, and between adjacent outlets. One longitudinal wall of the tundish will be straight, while the opposite walls will be obliquely angled relative to the longitudinal axis of the tundish. The chamfered edge 27 of each dam 20 will thus fit against the angled wall, the opposite edge engaging the straight wall. It will be appreciated that other configurations of tundish may be used, with the design of the dam being adjusted accordingly.
[0019] In use, the liquid steel is poured into the tundish from the ladle at an inlet zone (which is the point of maximum turbulence) and then overflows the dams 20 when sufficient steel has been introduced, flowing to the outlet(s) from the tundish in a more controlled manner. The contact of the liquid steel with the steel plates 25 in the dams 20 eventually causes the plates to soften and then melt, thereby opening the aperture to flow of steel as well. The plates are selected so that they have a thickness sufficient to delay melting and opening of the apertures until after linear flow of steel to the outlet(s) has been established. In practice, a thickness of about 12mm has been found sufficient, with the aperture 23 having an area of approximately 7-8% of the face of the dam so as to provide adequate flow of steel therethrough without compromising the strength of the dam. In this way, when the casting operation is complete, the residual steel in the tundish can flow through the apertures to the outlet(s) rather than remaining in the tundish inlet zone to solidify as it cools and then requiring reprocessing.
[0020] Figure 7 shows the steel plate 25 before installation into the dam. The plate is provided with a plurality of anchors 30, each on the form of a V-shape formed from steel rod and welded to the face of the plate at locations around three edges thereof, i.e. the top and the two sides. In the formation of the dam, the steel plate 25 is located in a mould with the anchors 30 facing inwardly of the mould and the plate defining the recess 26. A refractory concrete mix is then poured into the mould and allowed to harden with the anchors 30 embedded within the refractory material.
1. A dam for insertion into a tundish for use in metal casting, comprising a body (21)
of refractory material having opposed faces in contact with the liquid metal in use,
opposed side edges and a lower edge (24), the side and lower edges engaging inner
surfaces of the tundish in use, characterised by an aperture (23) extending between the opposed faces in the lower part thereof, the
aperture being closed by a metal plate (25).
2. A dam according to Claim 1, wherein the aperture (23) extends to the lower edge (24)
of the dam.
3. A dam according to Claim 1 or 2, wherein the metal plate (25) has a thickness such
that, when exposed to the liquid metal, the plate maintains closure of the aperture
until the filling of the tundish is completed.
4. A dam according to Claim 4, wherein the metal plate (25) is steel and has a thickness
of at least 12mm.
5. A dam according to any preceding claim, wherein the aperture (23) represents 5% to
20% of the area of the face of the dam.
6. A dam according to any preceding claim, wherein the metal plate (25) is located in
a recess (26) surrounding the aperture (23).
7. A dam according to any preceding claim, wherein the metal plate (25) is anchored in
the dam by means of a plurality of projections (30) on or adjacent to the side and
upper edge of the plate, the projections (30) being embedded in the refractory material
(21).
8. A dam according to Claim 7, wherein the projections comprise V-shaped members (30)
each welded to the plate at the foot of the V.
9. A tundish for use in the casting of metal, comprising a refractory lined container
having an inlet zone therein for receiving poured molten metal and an outlet for discharging
the molten metal into a casting mould, the tundish having located therein between
the inlet zone and the outlet at least one dam according to any preceding claim.
10. A method of casting metal comprising pouring molten metal into the inlet zone of a
tundish according to Claim 9 and discharging the molten metal from the outlet into
a casting mould, wherein after pouring of the metal has been completed the discharge
of metal is continued until the metal in the inlet zone has flowed through the apertures
in the dams to reach the outlet.
Amended claims in accordance with Rule 137(2) EPC.
1. A dam for insertion into a tundish for use in metal casting, comprising a body (21)
of refractory material having opposed faces in contact with the liquid metal in use,
opposed side edges and a lower edge (24), the side and lower edges engaging inner
surfaces of the tundish in use, an aperture (23) extending between the opposed faces
in the lower part thereof, the aperture being closed by a metal plate (25), characterised in that the metal plate (25) is anchored in the dam by means of a plurality of projections
(30) on or adjacent to the side and upper edge of the plate, the projections (30)
being embedded in the refractory material (21).
2. A dam according to Claim 1, wherein the aperture (23) extends to the lower edge (24)
of the dam.
3. A dam according to Claim 1 or 2, wherein the metal plate (25) has a thickness such
that, when exposed to the liquid metal, the plate maintains closure of the aperture
until the filling of the tundish is completed.
4. A dam according to Claim 4, wherein the metal plate (25) is steel and has a thickness
of at least 12mm.
5. A dam according to any preceding claim, wherein the aperture (23) represents 5% to
20% of the area of the face of the dam.
6. A dam according to any preceding claim, wherein the metal plate (25) is located in
a recess (26) surrounding the aperture (23).
7. A dam according to any preceding claim, wherein the projections comprise V-shaped
members (30) each welded to the plate at the foot of the V.
8. A tundish for use in the casting of metal, comprising a refractory lined container
having an inlet zone therein for receiving poured molten metal and an outlet for discharging
the molten metal into a casting mould, the tundish having located therein between
the inlet zone and the outlet at least one dam according to any preceding claim.
9. A method of casting metal comprising pouring molten metal into the inlet zone of a
tundish according to Claim 8 and discharging the molten metal from the outlet into
a casting mould, wherein after pouring of the metal has been completed the discharge
of metal is continued until the metal in the inlet zone has flowed through the apertures
in the dams to reach the outlet.