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Title:
METAL FILLING ARRANGEMENT FOR CONTINUOUS CASTING EQUIPMENT
Document Type and Number:
WIPO Patent Application WO/2011/056078
Kind Code:
A1
Abstract:
Metal filling equipment for continuous casting mould/s, in particular mould/s for the semi-continuous direct chill (DC) casting of aluminium sheet ingot or slabs of different dimensions, in particular ingot or slabs for rolling thin aluminium sheet or strips. The equipment includes a closed metal filling box or container (10) provided above the mould/s (2). The box receives metal from a holding furnace (not shown) through a launder or metal transfer channel (11 ). The metal flow to the box is controlled by means of a valve device (16), whereby the metal filling box is provided with air evacuating means (20) to obtain elevated metal level inside the box during casting. Metal distributor outlets in the form of insulated pipe stubs (18) are provided for each mould, protruding downwardly from the bottom of the metal filling box (10). With the described metal filling box is obtained improved metal distribution and even metal temperature across the mould/s.

Inventors:
HÅKONSEN, Arild (Erik Hauge allé 12, Sunndalsøra, N-6600, NO)
NÆSS, Jr., Harald (Grøaveien 62, Grøa, N-6612, NO)
IVELAND, Terje (Hoelsandveien 16, Sunndalsøra, N-6600, NO)
FAGERLIE, John Olav (Hjelltrøa 9, Sunndalsøra, N-6600, NO)
Application Number:
NO2010/000403
Publication Date:
May 12, 2011
Filing Date:
November 05, 2010
Export Citation:
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Assignee:
NORSK HYDRO ASA (N-0240 Oslo, NO)
HÅKONSEN, Arild (Erik Hauge allé 12, Sunndalsøra, N-6600, NO)
NÆSS, Jr., Harald (Grøaveien 62, Grøa, N-6612, NO)
IVELAND, Terje (Hoelsandveien 16, Sunndalsøra, N-6600, NO)
FAGERLIE, John Olav (Hjelltrøa 9, Sunndalsøra, N-6600, NO)
International Classes:
B22D11/10; B22D35/04
Domestic Patent References:
WO2009072893A12009-06-11
WO1999032248A11999-07-01
Foreign References:
JPS5835051A1983-03-01
JPS5838645A1983-03-07
US3865175A1975-02-11
US3837614A1974-09-24
Other References:
See also references of EP 2496373A4
Attorney, Agent or Firm:
HOFSETH, Svein (Intellectual Property Department, Hydro Aluminium AS, Oslo, N-0240, NO)
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Claims:
Claims

Metal filling equipment for continuous casting mould/s (2), in particular mould/s for the semi-continuous direct chill (DC) casting of aluminium sheet ingots or slabs of different dimensions, where the metal is transferred from a holding furnace through a launder or metal transfer channel (11) and where the supply of metal is detected and controlled by means of sensor (7, 23), respectively actuator (6, 3) and metal valve device (16)

characterised in that the equipment includes a closed metal filling box or container (10) provided above the mould/s (2), the box receiving metal from the holding furnace through the launder or metal transfer channel (11), the metal flow to the box being controlled by means of the sensor (23) and actuator/valve device (16), whereby the metal filling box is provided with air evacuating means (20) to obtain elevated metal level inside the box during casting and that metal distributor outlets in the form of insulated pipe stubs (18) are provided for each mould, protruding downwardly from the bottom of the metal filling box (10), obtaining improved metal distribution, even metal temperature and metal level control across the moulds.

Equipment according to claim 1,

characterised in that

the metal filling box (10), relative to the casting mould/s, is provided on a separate frame construction.

Equipment according to claim 1 and 2,

characterised in that

each mould (2) is provided with two or more insulated pipe stubs (18).

Equipment according to claims 1-3,

characterised in that

the metal filling box (10) is tiltable in relation to the frame construction and mould/s.

5. Equipment according to claims 1 - 4,

characterised in that

the metal filling box (1) is provided with an easily removable lid (11).

6. Equipment according to claim 5,

characterised in that

the lid (17) is hinged to the metal filling box (10) by means of a hinge arrangement (19).

7. Equipment according to claims 1 - 6,

characterised in that

the casting operation from beginning to end is controlled by means of a programmable logic controller.

Description:
Metal filling arrangement for continuous casting equipment

The present invention relates to metal filling equipment for continuous casting moulds, in particular moulds for the semi-continuous direct chill (DC) casting of aluminium sheet ingot or slabs of different dimensions.

Moulds of the above type includes a mould frame with a pair of facing side walls and a pair of facing end walls, the walls defining a mould with an upwardly open inlet for the supply of metal and a downwardly facing outlet provided with a starter block on a movable support to extend the ingot to be cast and which prior to each casting closes the downwardly facing opening. The equipment further includes means for cooling the metal during casting.

When casting sheet ingot with the above DC moulds, metal is usually supplied to the mould from a holding furnace by means of a launder or open supply channel. The furnace is tilted depending on the number of casting moulds, casting velocity etc. and thereby the amount of metal required to maintain the level in the launder is supplied in a controllable manner. The metal level in the casting mould on the other hand is commonly controlled by means of a spout and stopper where the stopper in turn is activated and controlled by a float (Early solution) or an electric actuator.

This known type of transfer and metal filling equipment is encumbered with disadvantages, among other things poor metal distribution and oxide formation due to turbulent melt flow.

From EP-A- 995523 is known a filling system for continuous casting equipment for aluminium sheet ingot where metal is transported to the casting mould from an furnace by means of a launder system and where a measuring apparatus for determining a metal melt level and a through flow regulator to control the metal supply in the mould depending on the difference of a pre-described theoretical value progression and the measured time-dependent metal melt level. The measuring apparatus consists of two physically different working measuring systems each with a separate sensor fixed in a predetermined position with respect to the mould.

Further, the applicants own EP-B1 1648635 shows a low pressure continuous casting system where metal is transported from a holding furnace to the mould via a closed siphon type channel and where the metal level is controlled in the mould such that the metallostatic pressure is basically zero in the solidification zone.

With the present invention is provided a metal filling equipment for continuous casting moulds, in particular equipment for the semi-continuous direct chill (DC) casting of aluminium sheet ingots or slabs which is cheap and simple to manufacture and use and which has excellent metal distribution, is reliable as regards metal level control and has low maintenance costs. The equipment may easily be adapted to existing casting moulds (retrofit installations) as well as greenfield installations. The invention is characterized by the features as defined in the attached independent claim 1.

Preferred embodiments of the invention are further defined in the attache dependent claims 2 - 6 The invention will be described in further detail in the following by way of example and with reference to the figures, where:

Fig. 1 shows a schematic view of a filling apparatus and mould for casting sheet ingot of the conventional type with spout and stopper, seen in perspective,

Fig. 2 shows a cross section along one of the moulds of the same apparatus as shown in Fig. 1 , Fig. 3 shows a perspective view of a casting apparatus with four mould and with a filling arrangement according to the present invention,

Fig. 4 shows a cross section of the casting apparatus and filling arrangement along of one of the moulds shown in Fig. 3,

Figs. 5 - 11 show the same as in Fig. 4, but in smaller scale and in a sequence from start to end of a casting operation. A conventional known apparatus 1 for casting aluminium sheet ingot may, as is shown in Figs. 1 and 2, consist of one or more moulds 2. An insulated launder or channel (not shown) is provided to transport hot liquid aluminium metal 8 from a holding furnace (not shown) to an insulated 9 distributor launder 3 provided above the moulds 2. Metal is, during casting, supplied to the moulds 2 through a spout 5 and stopper 4 arrangement. The opening and closing of the stopper 4 and thereby the amount of metal supplied to the moulds 2 is accomplished by an actuator 6 on the basis of signals from a metal level detector 7, striving to maintain the metal level in the mould at a desired constant height. The disadvantage with this conventional spout and stopper casting equipment is further discussed above.

The present invention is based on a quite different solution which will be further described in the following.

Figs. 3 and 4 shows casting equipment 1 according to the invention including four casting moulds 2 for sheet ingot. Each mould 2 is equipped with indirect and direct water cooling arrangements (not shown) and are provided in a common frame construction (neither not shown). In stead of an open launder as described above, the equipment is provided with a closed metal filling box or container 10. The box 10 is preferably provided on a separate frame construction (not shown) above the moulds 2. For each mould metal distributor outlets in the form of insulated pipe stubs 18 are protruding downwardly from the container 10. To obtain good metal distribution and even temperature in the moulds, preferably at least two pipe stubs 18 are provided for each mould. A Iid17 is further provided in a sealing relation on top of the filling box 10 and is attached to it by means of a hinge 19 to obtain easy access for cleaning and maintenance. Metal is supplied to the filling box 10 by means of a launder 1 from a holding furnace (not shown) and is admitted to the filling box through an inlet being controlled by a valve device 16 in the form of a stopper plug (spindle) 14 and seat 5. The stopper 14 of the valve device 16 is in turn controlled by means of an electrically driven actuator 13 based on signals from a PLC control device (see later section).

On top of the lid is provided a vacuum valve 20 with a hose connector (not shown) for connection to a vacuum source, whereby the hollow space 24 of the box may be set with a pressure (vacuum) below the atmospheric pressure.

The filling box as such is hinged to the frame construction at the connection 21 with the launder 1 and is thereby tiltable upwards in relation to the casting moulds 2 (see later section).

A dam or gate closure 22 is provided in the launder 11 up-stream of the filling box to hold back the metal from the holding furnace in an initial phase of the casting operation. Further, a metal level detector 23 is provided in relation to the mould/s to detect the metal level providing signals to a Programmable Logic Control (PLC - not shown) that controls the complete casting operation from beginning to end.

The filling box as described above may be designed to supply metal to one, two or more casting moulds 2. However, only one detector 23 for detecting the metal level in the moulds and only valve device for the control of the metal flow to the metal fillings box and the moulds is needed for the filling operation. Thus the equipment according to the invention is quite simple and cheap to manufacture and operate.

How the filling box according to the invention works will be further explained in the following. Figs. 5 - 13 show in cross sections of one of the moulds with the filling box 10 according to the invention in a sequence from the start to the end of a casting operation. Fig. 5 shows the initial starting point of a casting operation where the mould 2 is ready for casting as the mould starter block 25 is in its upper position resting against the mould wall 26. The holding furnace (not shown) is already tilted whereby liquid melt is filled in the launder 11 and is closed off by the dam 22 being in a lower position. Fig. 6 shows a further step where the dam 22 of the launder 11 is lifted and the stopper 14 for the valve device 16 is open to enable metal entering the filling box 10. As can be seen from this figure, the metal starts filling up the starter block 25 and the level in the box 10 is raised to the lower end of the metal distributor pipe stubs 8. At this point the pressure outside the box 10 and inside it is the same, atmospheric pressure. As soon as the metal level, detected by the level sensor 23, raises above the end of the pipe stubs 18, the PLC initiates opening of the vacuum valve 20 and air is evacuated from the hollow space of the filling box 0. By further opening the stopper 4, the metal level will now raise inside the filling box to a desired level above the level in the launder 1 1 to obtain sufficient charge and even distribution of metal to the moulds. The desired metal level in the mould/s is maintained and controlled by the flow of metal through the valve device 16 and stopper 14, as well as the pressure inside the metal filling box 10.

As soon as the metal 27has reached its upper desired level the starter block 25 at the same time starts moving downwards as is shown in Fig. 7, and the cast aluminium ingot 28 is formed by solidification of the melted metal 27.

Referring further to Fig. 8, by the time the ingot 28 is approaching its final length, the stopper 14, based on signals from the PLC, closes and the metal flow to the filling box 10 is stopped. At the same time the vacuum inside the filling box is cotrolled such that the pressure inside the box approaches atmospheric pressure. The PLC is programmed to calculate when to close the stopper 14 in relation to the remaining metal in the filling box 10 and the needed amount of metal to complete the casting operation such that no melt is left in the filling box or pipe stubs 18 when the ingot is fully cast.

Upon completion of the casting operation, the metal being left in the launderl 1 is tapped to a crucible through a hole in the launder, as shown in Fig. 9, by removing a plug therein (not shown), or preferably, the melt is transferred back to the furnace. After tapping of most of the metal from the launder, the filling box 10 is tilted upwards about the hinge connection 21 as shown in Fig. 10 and the remaining metal is tapped from the launder as well as the filling box as the stopper 14 now also is opened. By doing this the filling box is drained such that freezing of metal in and around the piping stubs is prevented.

Fig. 1 shows the final position of the equipment after casting and prior to a new casting operation where the lid 17 is opened about the hinge 19 and the filling box is ready for cleaning and inspection and possible maintenance. The equipment as described above has several advantages:

- No oxide formation due to turbulence in the melt flow.

- Even temperature in the mould/s due to improved metal supply and metal distribution in the moulds.

- Only one metal level detector and one activator and metal valve device required, thereby reducing equipment manufacturing cost and simple metal supply and level control.

- Metal freezing at the start and end of casting operation is avoided.

The invention as defined in the claims is not delimited to the examples shown in the figures and described above. Thus the metal filling box may be designed to supply metal to more or less than four casting moulds. Further the lid 17 may not be hinged to the equipment, but may be just lifted off after each casting operation.