A MACHINE AND A METHOD FOR CASTING A METAL STRIP

Description

[0001] This invention relates to a strip casting machine comprising a cooled and power driven endless belt with side dams, and an arrangement for supplying molten metal to the upper side of a flat and substantially horizontal part of the endless belt. It relates also to a method of casting a metal strip.

[0002] A single belt strip casting machine of this kind is described in WO 93/01015.

[0003] When casting strips, there will usually be edge drops, that is the edges will be thinner, so that the edges must be cut away.

[0004] It is an object of the invention to counteract edge drop and this is accomplished principally by having inwardly inclined side dams. Another object is to permit the casting of thinner strips than has been possible before. To these ends, the invention has been given the characteristics stated in the claims.

[0005] The invention will be described with reference to the accompanying drawings.

Figure 1 is a fragmentary perspective view of a strip casting machine in accordance with the invention,

Figure 2 is a fragmentary longitudinal section through a machine that is somewhat modified from the machine in Figure 1,

Figure 3 is a transverse section taken along line 2-2 in Figure 3, and Figure 4 its a schematic transverse section through a strip cast by a machine described, the width and thickness of the strip being not in scale.

[0006] The machine shown in Figure 1 has a substantially horizontal, water cooled, and power driven belt 11 of a heat conductive material for example copper. The belt 11 has side dams 12, 13 which can be movable with the belt, but which can also be fixed. They can advantageously be movable laterally and fixed in various lateral positions so that strips of various width can be cast. Above the belt, there is a tundish 14 that functions as a distributor of molten metal. It has a number of ceramic nozzles distributed over the entire width of the belt so that they produce several separate jets that meet the belt 11 which moves as indicated by the arrow 15. The orifices should be so located that the molten metal flows out and solidifies as a cast thin continuous strip 29 on the substrate, that is, on the movable belt 11. A container 16, for example a furnace or a ladle, supplies a controlled flow of molten metal to the tundish/distributor 14. The flow out of the container 16 can be regulated in various conventional ways, for example by means of a stopper rod or a sliding gate nozzle.

[0007] The Figures 3 and 4 show a design which is somewhat modified from the design shown in Figure 1. The container is replaced by a rotatable tube 17 of the kind disclosed in WO 9301015. The level of the molten metal in the tube 17 is kept constant by means of a non-illustrated regulator that regulates the supply of molten metal to the tube 17. The tube 17 has an outlet 18 in the form of a slot and the flow out of the tube can be regulated by turning of the tube 17 since such turning changes the ferrostatic pressure that drives the flow out through the slot 18. The tundish 14 has two fixed walls 20, 21 that slows down the flow in the tundish and make the flow laminar before it reaches orifices 22. The endless belt 11 is cooled by a large number of cooling nozzles 23 that eject water jets against the underside of the belt 11 so that the molten metal solidifies on the copper belt into a cast continuous strip.

[0008] Since the endless belt 11 moves fast when the vertical and parallel jets 30 from the orifices 22 of the tundish meet the belt 11 and the molten metal does not wet the belt, the molten metal will not flow backwardly on the belt and a rear dam is therefore not necessary. The molten metal should flow out on the belt 11 into an even layer and the distance between the jets 30 must therefore not be too big. There is no contact between the tundish/distributor 14 and the belt 11 and the side dams 12, 13 of the belt, which is advantageous particularly when a casting is ended or if a casting goes wrong, since the molten metal cannot freeze on the machine and prevent it from being started again. The jets are shown vertical but they can also be inclined. Another tundish/distributor can quickly and easily be exchanged for the one on the machine when one wants to cast strips of another width or one wants to change to a casting process that needs other orifices or another number of orifices since the tundish is neither coupled to the endless belt 11 nor to the container 16 or 17. The number of orifices and their size need to be varied in relation to the combination of strip width, belt velocity, viscosity of the molten metal, and desired thickness of the strip.

[0009] The side dams 12, 13 form inwardly inclined walls. A steel strip 29 is shown in Figure 1, which has been cast with the machine described. Because of the inward inclination of the side dams, the metal surface is horizontal along the lines in which solid matter (the dams), the molten metal, and gas (argon) meet. If the surfaces of the dams should instead be vertical, the surface would bend downwards at the edges since the molten metal does not wet the side dams. The inclined dams in combination with the supply of molten metal in the form of separate jets make the upper surface of the strip very even. It will also be possible to cast thinner strips when the influence of the surface tension is counteracted in this way. The inclination of the side walls of the dams 12,13 should be chosen so that it matches the angle of wetting in order to get a flat surface of the molten metal.

[0010] It should be understood that the figures are schematic and fragmentary. A cover is for example not shown. Such a cover holding a protective atmosphere, e.g. argon, protects the free jets of molten metal and the free surface of the molten metal on the belt from being oxidised.

[0011] The strip casting machine according to the invention can be made in different sizes and for various kinds of metals and alloys. It can for example be suited for fast casting of carbon steel in strip thicknesses down to 6 mm or less and for strip widths of up to 2 metres or more.

Claims

1. A strip casting machine comprising a cooled and power driven endless belt (11) with side walls (12,13), and an arrangement (16,14; 17,14) for supplying molten metal to the upper side of a flat and substantially horizontal part of the endless belt,
characterised in that
the side walls (12,13) have inwardly inclined sides facing the melt so as to match the angle of wetting between the molten metal and the solid matter of the side walls and make the surface of the molten metal flat.

2. A machine according to claim 1, characterised in that the endless belt (11) has no rear wall and in that said arrangement (16,14; 17,14) comprises a distributor (14) arranged with a plurality of orifices for pouring molten metal onto the belt.

3. A machine according to claim 2, characterised in that the distributor (14) is a tundish (14) arranged to be supplied with a controlled flow of molten metal from a ladle (16).

4. A method of casting a metal strip by supplying molten metal to a cooled and power driven endless belt (11) while limiting the width of the molten metal by side walls (12,13) on the belt, characterised by pouring molten metal on the endless belt (11) in the space between the side walls (12,13) and choosing the angle of inclination of the side walls (12,13) to the horizontal to match the angle of wetting between the liquid metal and the solid matter of said side walls so that the surface of the molten metal will be flat.

5. A method according to claim 4, characterised in that the molten metal is poured on to the belt (11) in the form of a plurality of free streams (30) which are so close to one another that the molten metal flows out to an even layer on the belt (11).

Ansprüche

1. Bandgussmaschine mit gekühltem und angetriebenem endlosem Band (11) mit Seitenwänden (12,13) und Anordnung (16,14; 17,14) zum Anliefern von geschmolzenem Metall an die obere Seite eines flachen und im wesentlichen horizontalen Teiles des endlosen Bandes, gekennzeichnet dadurch, dass die Seitenwände (12,13) nach innen geneigte Seiten haben, die der Schmelze gegenüberliegen, um mit dem Benetzungswinkel zwischen dem geschmolzenen Metall und dem festen Stoff der Seitenwände zusammenzufallen und die Oberfläche des geschmolzenen Metalls flach zu machen.

2. Maschine nach Anspruch 1, gekennzeichnet dadurch, dass das endlose Band (11) keine Rückwand hat und dadurch, dass besagte Anordnung (16,14;17,14) einen Verteiler (14) mit einer Anzahl von Öffnungen zum Gießen von geschmolzenem Metall auf das Band umfasst.

3. Maschine nach Anspruch 2, gekennzeichnet dadurch, dass der Verteiler (14) ein Tundish (14) ist, der mit einer kontrollierten Strömung von geschmolzenem Metall von einer Pfanne (16) beliefert wird.

4. Methode zum Gießen eines Metallbandes durch Anliefern von geschmolzenem Metall zu einem gekühlten und angetriebenem endlosem Band (11), wobei die Breite des geschmolzenen Metalls durch Seitenwände (12,13) auf dem Band begrenzt wird, gekennzeichnet dadurch, dass geschmolzenes Metall auf das endlose Band (11) in den Raum zwischen den Seitenwänden (12,13) gegossen wird und der Neigungswinkel der Seitenwänden (12,13) in der Horizontale gewählt wird, um mit dem Benetzungswinkel zwischen dem Flüssigmetall und dem Feststoff besagter Seitenwände zusammenzufallen, so dass die Oberfläche des geschmolzenen Metalls flach wird.

5. Eine Methode nach Anspruch 4, gekennzeichnet dadurch, dass das geschmolzene Metall auf das Band (11) in Form einer Mehrzahl von freien Strömen (30) gegossen wird, die einander so nah sind, dass das geschmolzene Metall in einer ebenen Schicht auf das Band (11) fließt.

Revendications

1. Machine de coulée en bande comprenant une chaîne sans fin refroidie et motorisée (11) avec des parois latérales (12,13), et un arrangement (16,14;17,14) pour amener du métal en fusion vers le côté supérieur d'une partie plate et substantiellement horizontale de la chaîne sans fin, caractérisée en ce que lesdites parois latérales (12,13) ont des côtés inclinés vers l'intérieur orienté vers le métal en fusion pour coïncider avec l'angle de mouillage entre le métal en fusion et les substance solides des parois latérales et pour niveler la surface du métal en fusion.

2. Machine selon la revendication 1, caractérisée en ce que la chaîne sans fin (11) n'a pas de paroi postérieure et en ce que ledit arrangement (16,14;17,14) comprend un distributeur (14) disposé avec une pluralité d'orifices pour verser le métal en fusion sur la chaîne.

3. Machine selon la revendication 2, caractérisée en ce que le distributeur (14) est un avant-creuset (14) disposé pour être alimenté avec une circulation contrôlée de métal en fusion d'une poche de coulée (16).

4. Procédé de coulage d'une bande métallique en fournissant du métal en fusion à une chaîne sans fin refroidie et motorisée (11) en limitant la largeur du métal en fusion par des parois latérales (12,13) sur la chaîne, caractérisé par le déversement du métal en fusion sur la chaîne sans fin (11) dans l'espace entre les parois latérales (12,13) et le choix de l'angle d'inclinaison horizontal des parois latérales (12,13) pour coïncider avec l'angle de mouillage entre le métal liquide et les substances solides desdites parois latérales afin que la surface du métal en fusion soit plate.

5. Procédé selon la revendication 4, caractérisé en ce que le métal en fusion est versé sur la chaîne (11) sous forme d'une pluralité de courants libres (30) lesquels sont si près les uns des autres que le métal en fusion sort en formant une couche uniforme sur la chaîne (11).

Drawing