WO2004002656A1

WO2004002656A1 - Casting equipment

Info

Publication number: WO2004002656A1
Application number: PCT/NO2003/000202
Authority: WO
Inventors: Arild HÅKONSEN; Terje Iveland; Harald Naess, Jr.; Ian Wiik; Ulf BERSÅS; Fred Arne Gundersen
Original assignee: Norsk Hydro Asa
Priority date: 2002-06-26
Filing date: 2003-06-18
Publication date: 2004-01-08
Also published as: NO20023101L; NO20023101D0; AU2003280527A1

Abstract

Equipment for casting metal, in particular aluminium ingots for rolling purposes, comprising a casting mould (20) with a mould wall (1) with a heat-resistant, insulating inlet or 'hot-top' (2) for supply of liquid metal (3) and an outlet with cooling devices (4, 11) for cooling the metal to be cast and a movable support (18). The hot-top (2) is arranged at a distance from the wall (1) of the casting mould, the space (6) thus formed is closed at the top by means of a cover or plate (7) so that it is mainly gastight and the space (6) is designed for the supply/removal of any gas or gas mixture under a specific pressure.

Description

Casting Equipment

The present invention concerns equipment for casting metal, in particular aluminium rolling blocks, comprising a casting mould with a heat-resistant, insulating inlet ("hot- top") for supply of liquid metal and an outlet with cooling devices for direct water cooling of the metal to be cast.

The prior art contains casting equipment for casting aluminium rolling ingots in which the metal level is adjusted using a nozzle/float ball or nozzle/pin. One disadvantage of this equipment is that it is impractical to use and requires a lot of preparation between casts. Another disadvantage is that the casting speed is low so that the overall efficiency is low. Further disadvantages of the prior art equipment are that filling is turbulent, which can result in the incorporation of oxide, it is not possible to control the atmosphere above the metal and suspended crystals can occur.

The prior art also contains casting equipment for rolling ingots in which a so-called "hot- top" is used. The use of a hot-top means that several of the above disadvantages can be avoided, among others the low casting speed. This technology can be combined with level casting in which turbulent filling is avoided. However, the solution is associated with several other disadvantages. The mould height during casting cannot be adjusted. High-alloy aluminium cannot be cast and the technology is hard to combine with flexing (a fixed hot-top, not f iberfrax, is implied).

The present invention represents equipment for casting rolling ingots in which the above disadvantages are avoided. The equipment is characterised in that the hot-top is arranged at a distance from the wall of the casting mould and the space that is thus formed is closed at the top so that it is mainly gastight and the space is designed for the supply/removal of any gas or gas mixture under a specific pressure.

The dependent claims 2- indicate the advantageous features of the present invention. The present invention will be described in further detail in the following by means of examples and with reference to the attached drawings, where:

Fig. 1 a), b), c) shows an elevation of two prior art casting moulds, compared with the casting mould in accordance with the present invention.

Fig. 2 shows a perspective view, with one corner cut away, of a casting mould in accordance with the present invention.

Fig. 3 shows, in larger scale, a vertical section of the left half of the same casting mould in accordance with the present invention.

As stated above, Figure 1 a) shows an elevation (schematic diagram) of the left half of a casting mould for casting rolling ingots in which a hot-top, i.e. an insulating, heat- resistant material 2 (fiberfrax), is used between the mould wall 1 and the metal 3. The insulating material 2 extends from the top of the casting mould almost down to the end of the casting mould wall 2, just above the gap 4 for supply of water to cool the metal. The use of a hot-top means that several of the above disadvantages can be avoided, among others the low casting speed. This technology can be combined with level casting in which turbulent filling is avoided. However, the solution is associated with several other disadvantages. The mould height during casting cannot be adjusted. High- alloy aluminium cannot be cast and the technology is hard to combine with flexing (a fixed hot-top, not fiberfrax, is implied).

Figure 1 b) shows another prior art solution in which the metal level in the casting mould is controlled by means of a nozzle/float ball arrangement 5. No insulating material is used in the casting mould here and the metal 3 to be cast hardens almost immediately on contact with the mould wall 1 , just above the water nozzle 4. One disadvantage of this equipment is that, as stated above, it is impractical to use and requires a lot of preparation between casts. Another disadvantage is that the casting speed is low so that the overall efficiency is low. Further disadvantages of the prior art equipment are that filling is turbulent, which can result in the incorporation of oxide, it is not possible to control the atmosphere above the metal and suspended crystals can occur.

Figures 1 c), Figure 2 and Figure 3 show the solution in accordance with the present Invention. More precisely, Figure 1 c) shows the^" more fundamental features of the solution. A relatively strong wall 2 (hot-top) of fireproof material is mounted a little way from the mould wall 1 in the casting mould. The distance between the mould wall and the fireproof material can expediently be in the order of 10-100 mm and, above the gap thus formed, is a cover 7 with a supply boss 8 or similar for the supply of gas. A closed space 6 between the hot-top 2 and the mould wall 1 is thus formed. The principle of the solution is that, when metal 3 is added to the casting mould, a metal level 9 is formed in the space 6 that can be controlled by means of the gas pressure in the space by adjusting the gas supply/removal through the supply boss 8.

Details of the solution are shown in Figures 2 and 3 and will be described in the following.

The casting mould (20) in accordance with the present invention comprises a mould wall 1 with, arranged at the bottom of the wall, a water gap 4 or row of holes that extend around the circumference of the casting mould (mould wall). In connection with the water gap 4 is a water compartment 11 or water supply manifold that supplies the water gap with water. The water compartment 11 is fitted to the mould wall 1 by means of a screw connection or similar 12 so that the water compartment also contributes to indirect cooling, i.e. primary cooling of the metal 3 during its casting (preliminary hardening against the wall in the area above the water surface 4).

At its side, the mould wall 1 is fixed to a frame structure 13 (not shown in Figure 2, only suggested in Figure 3) via an adjustable screw connection 14 which makes it possible to adjust the mould wall 1 or its curvature in a longitudinal direction. The hot-top, i.e. the insulating wall material 2, is arranged at a distance, expediently 10-100 mm, from the mould wall 1. For example, the hot-top can be fixed to a superjacent plate 7 that rests on the mould wall 1 and extends around the entire casting mould and thus also forms a tight closure upwards for the space 6 in the casting mould. In connection with the plate 7 are one or more connection bosses 8 for the supply of gas via hoses or similar.

In connection with the plate 7 there are also a pressure sensor 16 (see Figure 2) that registers the gas pressure in the space 6 and a laser meter 15 that registers the metal level inside the casting mould 20. In addition to the components shown in the figures, the solution also comprises a regulating valve connected to the gas supply hose (not shown) for the connection boss 8 that regulates the supply/removal of gas to/from the chamber 6, plus a PLS control unit (not shown) that, on the basis of the metal level measured by the laser meter 15 and the pressure registered by the pressure sensor 16, regulates the supply/removal of gas to/from the chamber 6 via the regulating valve. The casting equipment is so-called semi-continuous casting equipment and also comprises a movable support 18 that moves downwards during each cast.

The starting point for the present invention is the need to be able to control precisely the level in the space between the hot-top 2 and the mould wall 1 in order to achieve consistent casting conditions during the casting operation when casting ingots for rolling. By registering the metal level in the casting mould and the pressure in the space, as stated above, tests show that the PLS unit makes it possible, by controlling the supply/removal of gas via the regulating valve, to control precisely the level 9 in the space 6 and the metal level at the inlet 19 to the casting mould.

Claims

Equipment for casting metal, in particular aluminium ingots for rolling purposes, comprising a casting mould (20) with a mould wall (1) with a heat-resistant, insulating inlet or "hot-top" (2) for supply of liquid metal (3) and an outlet with cooling devices (4, 11) for cooling the metal to be cast and a movable support (18), characterised in that the hot-top (2) is arranged at a distance from the wall (1) of the casting mould, the space (6) thus formed is closed at the top by means of a cover or plate (7) so that it is mainly gastight and the space is designed for the supply/removal of any gas or gas mixture under a specific pressure.

Equipment in accordance with claim 1, characterised in that a pressure sensor (16) is arranged in connection with the space (6) to register pressure.

Equipment in accordance with claim 1 , characterised in that a level meter (15) is arranged in connection with the inlet and/or space (6) of the casting mould to register the metal level (9, 10).

Equipment in accordance with claims 1-3, characterised in that the equipment comprises a PLS control unit that, on the basis of the signals from the level meter(s) (15) and the pressure sensor (16), is designed to control the metal levels (9, 10) during casting.