Process and apparatus for moulding ingots of ferro-alloys by chill casting in a cooled copper mould

The present invention concerns a process and an apparatus for moulding ingots of ferro-alloys by chill casting in a cooled copper mould. The apparatus comprises: PA1 an ingot mould (1) of copper, which is formed from two mould halves (2), at least one of which comprises a plurality of impressions (10) of the ingots to be moulded, communicating with each other by way of ducts (11, 12) and opening in the upper part by way of an ingate (18), PA1 means (5) for cooling each mould half (2) by a heat exchange fluid, PA1 means (9) for bringing the two mould halves into contact and into sealing relationship, PA1 means for moving the two mould halves away from each other, and PA1 means (7, 8) for guiding the mould halves in their movement away from each other and in their movement of coming into sealing relationship.

The present invention concerns a process and apparatus for moulding ingots 
of ferro-alloys by chill casting in a cooled copper mould. 
When ferro-alloys are used as additive or treatment elements in ferrous 
alloys or metals in the molten state, they are used in the form of crushed 
blocks with a unit weight which may be from some tens of grams to a few 
kilograms. That is the case in particular with alloys based on iron and 
silicon, which are used as additives for example for the production of 
silicon killed steels and as deoxidising agents for steels in general. 
It is known that, irrespective of the type of crusher used, the operation 
of crushing the ferro-silicon produces a relatively substantial quantity 
of fines (from 10 to 15% of the metal used), and the subsequent use 
thereof gives rise to technical and economic problems which as yet have 
not been fully solved. The same also applies in regard to other types of 
ferro-alloys. 
French patent FR-A-No. 1 538 948 (corresponding to U.S. Pat. No. 3 604 494) 
to METALLGESELLSCHAFT A.G. and SUDDEUTSCHE KALKSTICKSTOFFWERKE A.G. 
proposed casting pre-alloys of the ferro-silico-magnesium type in cases 
made of thin sheet metal, which are previously filled to about two thirds 
or three quarters with crushed blocks of the same alloy or an alloy of 
slightly different composition, providing for very rapid cooling and thus 
preventing the sheet metal case from melting. 
It is also known for alloys of the ferro-silico-magnesium family to be cast 
by sand moulding in order to produce inoculating agents for cast irons, in 
the form of shaped portions which are introduced into cavities in the 
runners (that process being referred to as "inoculation in-mould"). 
However, the various processes referred to above are not suited nor can 
they be rendered suitable to economic and massive production of blocks 
from an electric furnace having a continuous production per hour of 
several tonnes, for example a furnace for producing ferro-silicon 
containing 75% of Si, with an output of 16 MW, which produces about 2 T/h 
of alloy. 
The present invention therefore concerns a process which permits the 
moulding of ferro-alloy blocks of a predetermined shape and weight, by 
casting in a cooled copper mould of the liquid metal issuing from the 
production furnace either directly or by being transferred by way of a 
ladle or any intermediate vessel. 
This process is characterised by the following repetitive steps: 
an ingot mould is formed by the juxtaposition in sealed relationship of two 
copper mould halves, one at least of which comprises a plurality of 
impressions of the ingots to be moulded, said impressions communicating 
with each other by way of ducts and opening in the upper part of the mould 
by way of at least one ingate, 
a cooling circuit is established in each mould half by the circulation of a 
heat exchange fluid, 
the liquid ferro-alloy is poured into the ingate until the ingot mould is 
filled, 
the ferro-alloy is left to set and cool to a temperature which is 
200.degree. C. and preferably 300.degree. C. below its solidus 
temperature, and 
the two mould halves are separated for removal of the ingots from the 
mould. 
The invention also concerns an apparatus for carrying out the process 
comprising: 
an ingot mould formed of two mould halves made of copper, one at least of 
which comprises a plurality of impressions of the ingots to be moulded, 
said impressions communicating with each other by means of ducts and 
opening in the upper part by way of an ingate, 
means for cooling each mould half by the circulation of a heat exchange 
fluid, 
means for moving the mould halves towards and away from each other, and 
means for guiding the mould halves in their movements towards and away from 
each other. 
The apparatus may also comprise cooled means for introducing the liquid 
ferro-alloy into the ingate. 
The invention is particularly suitable for the production of moulded blocks 
of ferro-silicon which have a silicon content of higher than 15% and 
preferably between 40 and 90%, the balance being iron and, as appropriate, 
secondary additive elements such as Al, Ba, Ca, Mn, Ti and Zr.

Hereinafter, the term "ingot mould" will be used to denote the 
subject-matter of the present invention, it being appreciated that that 
term denotes a particular ingot mould in which the metal is introduced in 
a molten state and is removed in the form of multiple ingots of 
predetermined dimensions, shape and weight. 
Each ingot mould 1 comprises two half elements or "mould halves", as 
indicated at 2, of electrolytic copper, preferably of the quality referred 
to as Cu/al (being the designation used in the French standard NF 
A-51.050), each mould half being provided with a cooling circuit for the 
circulation of a heat exchange fluid, comprising a main intake 3 which is 
connected to the fluid supply means, for feeding, in a parallel mode in 
the illustrated embodiment, three branch circuits 4A, 4B, 4C, the outlet 
collector manifolds of which combine at a common outlet. The cooling 
circuits are internal (ducts 5 drilled in the copper block forming the 
mould halves) but they may optionally be external (copper tubes 6 which 
are welded or brazed over their entire length to the outside faces of the 
mould halves). 
Each mould half 2 further comprises sealing contact means to form the ingot 
mould. The mould halves may be brought into contact by for example holding 
one of the mould halves in a fixed position and moving the other mould 
half theretowards, or by moving the two mould halves towards each other, 
either by a guided linear translatory movement or by a rotary movement 
about a common axis forming a pivot means. 
The linear translatory movement may be guided by any known means such as 
guide rods 7 which are slidable in internal calibrated apertures 8 or by 
external sliding means such as grooves and slide members. 
The operation of bringing the mould halves into contact by a rotary 
movement may be performed about a vertical or a horizontal axis. In the 
latter case, the operation of removing the moulded ingots from the mould 
is facilitated by virtue of the fact that the ingots come away from the 
mould and drop into a receiving means, under the effect of their own 
weight. 
The different movements of bringing the mould halves together and moving 
them apart are controlled in known manner by means such as the jacks 9. 
Each mould half comprises the half impressions 10 corresponding to the 
ingots and the connecting ducts 11 and 12. The mould halves may be 
symmetrical (see FIGS. 1, 2 and 3) or asymmetric, as shown at 10B and 10A 
(see FIGS. 4 and 5). One of them may even be reduced to a co-operating 
plate 13 which is flat or which is optionally provided with a raised 
moulding portion 14 having a cooling circuit 5 which permits an increase 
in the area of contact between the cast metal and the ingot mould and 
therefore the speed of cooling and the rate of casting. 
The facing contact surfaces 15 of each mould half are trued and polished so 
as to ensure that a satisfactory fluid-tight seal is formed, under the 
effect of the jacks 9, without the interposition of any sealing member. 
The operation of casting the liquid ferro-alloy in the ingot mould is 
preferably carried out by means of the charging funnel 17. The funnel 17 
may be fixed to and integrated in the actual ingot mould or it may be 
removable and positioned on the pouring gate 18, the contact surfaces also 
being trued and polished. In both cases, the member 17 is also provided 
with a cooling circuit. The ducts and impressions beneath the member 17 
are supplied in the top pouring mode while the others are supplied in the 
bottom pouring mode. The number and the dimensions of the impressions or 
cavities and the ducts are so determined as to ensure total filling before 
the metal begins to set and blocks the feed ducts or runners. 
FIG. 1 shows a view in cross section of an ingot mould having 2.times.3 
impressions or cavities, but that arrangement is given only by way of 
non-limiting example and it could equally well comprise 2.times.2 or 
2.times.4 cavities. 
The problem which had to be overcome in order to carry the invention into 
effect was as follows: it was necessary both to provide a fairly high 
casting rate in order to follow the production of a large modern furnace 
producing ferro-silicon or other ferro-alloy, without however thereby 
tying up an excessive amount of copper in the form of a large number of 
ingot moulds, and to ensure that the ingot moulds enjoyed a fairly long 
operating life so that the amortization of the cost thereof does not 
substantially increase the cost of the ingots produced, in relation to the 
cost of the ferro-silicon which is cast in the form of slabs weighing 
several tons, then crushed and ground. That result was achieved: 
(1) by virtue of the choice of material forming the ingot moulds, the 
thermal conductivity of which must be as high as possible, which directs 
the choice towards the electrolytic copper referred to as Cu/al as defined 
by the French standard NF A 53.100 (thermal conductivity at 20.degree.=400 
to 412 W/mK) or the weakly alloyed copper such as "CUPRONICS" (registered 
trade mark of TREFIMETAUX) (365 W/mK) or CuZr 0.15, containing 0.15% of 
zirconium (350 to 370 W/mK), or any other copper-base alloy having a level 
of thermal conductivity which is at least equal to 300 W/mK; 
(2) by virtue of the provision of a highly efficient cooling circuit, the 
heat exchange fluid being water at ambient temperature, which makes it 
possible at all points to avoid an increase in the temperature of the 
copper above 200.degree. C. and thus to reduce to a negligible rate the 
increase in size of the grains of copper (recrystallisation) which is the 
main cause of degradation of ingot moulds; 
(3) by virtue of the selected ratio: 
EQU (mass of copper forming the ingot mould)/(mass of cast ferro-alloy) 
which is selected at a value at least equal to 6 and preferably between 10 
and 25; and 
(4) by virtue of extremely rapid extraction of the ingots from the mould so 
that the only function of the ingot mould is to solidify at least the 
outside part of the ingots down to a temperature which is from 200.degree. 
to 300.degree. below the solidus point of the alloy, cooling to ambient 
temperature then occurring spontaneously, outside the ingot mould, over 
any period of time which is no longer an important factor. 
EMBODIMENT 
An ingot mould was made from copper Cu/al, in accordance with the 
invention, comprising a central fixed block 20 provided with internal 
water cooling circuits 5 and four mould halves 21, 22, 23 and 24 which are 
movable separately or simultaneously by the action of jacks 9, each mould 
half having its own cooling circuit. Each mould half comprises six 
impressions or cavities 10 which are connected by ducts 11 and 12, which 
are filled by means of a cooled copper feeder funnel 17. Each of the 
impressions or cavities 24 corresponds to an ingot weighing about 550 
grams, plus the sprue portions formed by the connecting ducts or runners 
and the feed heads, which corresponds to about 14 kg of ferro-silicon per 
operation, wherein each casting cycle can be reduced to 90 seconds, then 
being broken down as follows: 
Pouring: 15 seconds 
Solidification of FeSi 75: 15 seconds 
Cooling of the ingots to about 900.degree. C. (solidus point at 
1208.degree. C.): 15 seconds 
Cooling of the moulds after opening thereof and removal of the hot ingots: 
30 seconds 
Times for opening and closing the ingot moulds and idle times: 20 seconds 
giving a production per hour of 15.times.40=600 kilos. Four such ingot 
moulds are therefore sufficient to mould in ingot form the total 
production of a ferro-silicon-75 furnace having a capacity of 2.4 T/h 
(.about.20 MW). After four months of continuous use, they are still in the 
normal operating condition. 
The manner in which the present invention is carried into effect may be the 
subject of a certain number of variations, in particular as regards the 
following: 
(1) the form of the ingot moulds which may be formed from two symmetrical 
mould halves or from asymmetric mould elements (see FIGS. 4 and 5), 
(2) the nature of the metal being cast. If the invention is particularly 
well suited to alloys based on iron and silicon, it may also be used 
without any modification to the basic principle thereof with different 
alloys, for example alloys based on iron and manganese, or manganese and 
silicon. However, the attraction of the present invention is particularly 
apparent in the case of metals in which crushing produces substantial 
amounts of fines which are difficult to use or to recycle, and 
(3) the shape, dimensions and unit weight of the ingots which may vary in 
dependence on the use envisaged, within very wide limits, it being 
appreciated that the form of the ingots is subordinate to the necessity 
for spontaneous and very quick extraction of the moulded ingots from the 
mould as soon as the ingot mould is opened, and that the minimum unit 
weight is in most cases imposed by economic factors.