EP0264418B1

EP0264418B1 - Continuous production of alloys

Info

Publication number: EP0264418B1
Application number: EP87902638A
Authority: EP
Inventors: Brian Maddock
Original assignee: Alform Alloys Ltd
Current assignee: Alform Alloys Ltd
Priority date: 1986-05-01
Filing date: 1987-04-30
Publication date: 1991-12-04
Anticipated expiration: 2007-04-30
Also published as: DE3774995D1; WO1987006623A1; GB8610717D0; JPS63503229A; ATE70088T1; ES2028135T3; EP0264418A1; EP0244255A1

Abstract

An apparatus and method are described for the continous production of molten metal alloy. A furnace (1) is used to melt a basic metal of the alloy, and that is transferred to a valve (2). Controlled amounts of at least one alloying metal are fed into the supply of molten metal in valve (2) for combining with the basic metal of the alloy to form a controlled supply of the desired alloy.

Description

The present invention relates to an apparatus for the continuous production of alloys and in particular, though not exclusively, to the production of aluminium alloy continuously.
Molten aluminium alloy is used in a variety of production methods, for example in continuous casting and to supply a "Conform"® extruder. Conventionally a furnace full of pure aluminium is melted, and the molten aluminium doped with the necessary quantities of alloying metals to produce a desired alloy formulation. As a method of producing a large quantity of molten aluminium alloy method is reasonably satisfactory. However, it is quite common to only want to produce a relatively small quantity of a finished product of a particular alloy, for example when using a Conform extruder. The practice in the past has been to produce a furnace full of the desired molten alloy and to use as much as is necessary for a production run and then to discard the rest, with only a limited possibility of recycling. This known technique has resulted in a considerable waste of alloy, and consequently increased the expense of small scale production of products of a particular alloy, to the extent that it may not be worthwhile making only small amounts of a product.
GB-2000195A discloses a process for the continuous production of molten metal alloy comprising a furnace for melting a basic metal of the alloy, means for receiving a controlled supply of molten metal from the furnace means for supplying controlled amounts of at least one alloying metal to the molten metal in the receiving means for combining with the basic metal of the alloy to form a controlled supply of the desired alloy and a feed back control system arranged to control the means for controlling the supply of alloying metal in accordance with data indicative of the composition of the desired alloy. The feedback control system takes samples of the desired molten alloy for analysis during production in order to provide the data indicative of the composition of the desired alloy.
Various problems are experienced with this type of apparatus and process primarily because the data indicative of the composition of the desired alloy is sampled from the molten metal rather than the final output. Because the flow rate of the molten metal can vary suddenly and unpredictably because of surges occurring as the molten metal is introduced accurate measurement of the flow rate is difficult.
It is an object of the present invention to provide an apparatus for the continuous production of molten metal which alleviates the aforementioned disadvantages of the prior art.
The present invention seeks to provide an apparatus for the production of molten alloy metals in controllable quantities.
According to the present invention there is provided an apparatus for the continuous production of metal alloy bar from continuously produced molten metal alloy comprising; a furnace for melting a basic metal of the alloy, means for receiving a controlled supply of molten metal from the furnace, means for supplying controlled amounts of at least one alloying metal to the molten metal in the receiving means for combining with the basic metal of the alloy to form a controlled supply of the desired alloy, a feedback control system arranged to control the means for supplying alloying metal in accordance with data indicative of the composition of the desired alloy, means to continuously form an elongate bar from the supply of the desired alloy, the control system being responsive to sensor means arranged to sense the speed of production of the bar characterised in that the sensor means is provided by a sensor which senses the cross-sectional area of the output bar a and speed sensor which senses the speed of the output bar.
The advantage of the apparatus mentioned above is derived from measuring the speed of production or outflow rate of the desired alloy from the solidified bar. In consequence, the sensors can sense the outflow rate without being susceptible to surges in the molten alloy. Furthermore, the sensors can be compact and relatively accessible for maintenance purposes.
In a preferred embodiment a valve controls the flow of the molten metal from the furnace and the valve assembly forms part of the receiving means and the alloying metal is introduced into the basic metal flowing through the valve, and together they are supplied to an alloying chamber where the alloy is temporarily contained to allow the alloying elements to diffuse uniformly through the basic molten metal.
The alloying metal(s) can be held in a "master" alloy of the basic metal with high concentration(s) of the alloying metal(s).
A preferred embodiment of the invention will now be described by way of example and with reference to the accompanying drawings:

Figure 1 is a schematic section through an apparatus according to the preferred embodiment of the invention; and
Figure 2 is a combination of a part of the diagram of Figure 1 and a block schematic diagram of a control circuit for the apparatus of Figure 1.

In the subsequent description the apparatus of the preferred embodiment will be described being used in conjunction with a "Conform"® extruding apparatus. A typical alternative to "Conform"® extrusion apparatus would be a continuous casting maschine.
Figure 1 shows a preferred embodiment of the invention, wherein a molten aluminium alloy is produced and supplied to a "Conform" extruding apparatus. A furnace 1 is connected through a mixing and flow control valve 2 to an alloying chamber 3, which valve has an upperr port 2a. A conveying apparatus 4 is arranged to supply a molten alloy from the alloying chamber 3 into a Conform apparatus 5. A sluice gate 6 controls run-off from the alloying chamber 3 to a run-off 7.
In the preferred embodiment aluminium A is melted in the furnace 1 and rung into the mixing control valve 2. A "Master Alloy" B in rod form is also supplied into the mixing control valve 2 through port 2a, to be melted by the molten aluminium A. The molten alloy mixture runs into the alloying chamber 3 where the alloying metals in the "Master Alloy" diffuse throughout the basic aluminium metal to produce a consistent alloy of desired composition. The "Master Alloy" rod B is of known alloy composition and is continuously fed into the mixing control valve 2 to produce the desired output alloy.
As can be better seen in Figure 2 the feeding of the "Master Alloy" B is controlled by a pair of rollers 10. The speed of rotation of the rollers 10 is controlled by a control circuit 20. A sensor 8 detects the area of the extrusion output from the Conform extruder 5 to provide an area input A to control circuit 20 and a speed sensor 9 provides an input V related to the speed of production of the extrusion material. In addition the control circuit 20 is supplied with input data giving the required alloy composition and the composition of the master alloy B which is to be added to the basic molten aluminium A. From the data supplied thte control circuit 20 controls the feed rolls 10 to provide the maste alloy rod at an appropriate rate to produce the desired output alloy.
At termination of extrusion with a particular alloy the valve 2 is closed shutting off flow of aluminium from the furnace 1 and the master alloy B is no longer supplied. The remaining, relatively small quantity of alloy in the mixing control valve 2 and alloying chamber 3 is run-off through run-off 7 by opening the sluice gate 6. It will be appreciated that only a relatively small volume of alloy is run-off. Production of an alloy of differing composition can then begin, with the appropriate data being provided to the control circuit 20.
In some circumstances it may be advantageous to agitate the alloy mixture in the alloying chamber 3 to ensure the consistence of the alloy. This may be done by means of a metal mechanical or an electromagnetic stirer.
Althrough the described embodiment makes use of a master alloy in rod form it would be possible to use pellets or granular master alloy for feeding to the basic aluminium metal. In such alternative case it would be obviously necessary to replace the feed rolls 10 with some means for regulating the supply of master alloy appropriate to the form of alloy material being used.
An example of production of one alloy will now be described for the purposes of illustration only.
The control circuit 20 is supplied with data such as:-

(1) extrusion speed V,
(2) extrusion croos section area A, which together with the extrusion speed V enables it to calculate the volume or weight per minute flowing through the valve,
(3) alloy composition required, and
(4) composition of alloying rod or pellets.

Typical alloying calculation:
extrusion speed 30 metres per minutes,
cross section area 100 sq mm,
weight per minute $= \frac{30 x 100 x 2.7}{1000} = 8.1 Kg/min,$
bath purity 99.8% aluminium,
composition of alloying pellets say
A1 50%, Si 25%, Mg 25% (master alloy),
for 6063 Alloy (A1 Mg Si.6)
Hence wire or pellets would be added at the rate of 192 grams per minute to create 6063 from high purity aluminium.
weight/metre 6mm master alloy = 65 gm.m
master alloy rod speed $= \frac{192}{65} = 2.95 m/minute$
If, for the sake of example the extrusion speed were suddenly reduced to 10 metres per minute, the control system would reduce the master alloy rod speed to 0.98 m/min to maintain the correct alloy composition.

Claims

1. An apparatus for the continuous production of metal alloy bar from continuously produced molten metal alloy comprising; a furnace (1) for melting a basic metal of the alloy, means (2) for receiving a controlled supply of molten metal from the furnace, means (10) for supplying controlled amounts of at least one alloying metal to the molten metal in the receiving means (2) for combining with the basic metal of the alloy to form a controlled supply of the desired alloy, a feedback control system arranged to control the means (10) for supplying alloying metal in accordance with data indicative of the composition of the desired alloy, means (5) to continuously form an elongate bar from the supply of the desired alloy, the control system being responsive to sensor means (8, 9) arranged to sense the speed of production of the bar characterised in that the sensor means (8,9) is provided by a sensor (8) which senses the cross-sectional area of the output bar and a speed sensor (9) which senses the speed of the output bar.

2. An apparatus as claimed in claim 1, wherein a valve (2) controls the flow of the molten basic metal from the furnace (1) and the valve assembly forms parts of the receiving means (2) and the alloying metal is introduced into the basic metal flowing through the value (2), and the valve (2) is connected to an alloying chamber (3) where the alloy is temporarily contained to allow the alloying elements to diffuse uniformly through the basic molten metal.