EP0131025A1 - Method and device for casting ingots of ferro-alloys by permanent mould casting into cooled copper chills. - Google Patents

Abstract

The device consists of: an ingot mold (1), made of copper, formed of two half-shells (2), at least one of which has a plurality of hollow imprints (10) of ingot molds, communicating between them by channels (11), (12) and opening, at the top, by an inlet channel (18); cooling means (5) by heat transfer fluid, of each half-shell (2); means (9) for bringing the two half-shells into contact and in sealed relation, means for moving the two half-shells apart; means (7, 8) for guiding the movements away and for sealing the half-shells.

Description

 PROCESS AND DEVICE FOR MOLDING LINGOTINS IN FERRO-ALLOYS BY COATED COPPER SHELL CASTING

The present invention relates to a method and a device for molding ingots of ferro-al bindings by casting in a cooled copper shell.

When they are used as addition or treatment elements in ferrous metals and alloys in the molten state, the ferro-alloys are used in the form of crushed blocks of a unit weight which can range from a few tens from grams to a few kilograms. This is the case, in particular, of alloys based on iron and silicon, used as additives, for example for the manufacture of steels quenched with silicon and, as deoxidants. steels in general.

It is known that crushing ferrosilicon causes, whatever the type of crusher used, a relatively large quantity of fines (from 10 to 15% of the metal used), the subsequent use of which poses technical and economic problems which are still imperfectly resolved. The same is true for other types of ferro-alloys.

In French patent FR-A-1538948 (= US 3604494) in the names of METALLGESELLSCHAFT AG and SÜDDEUTSCHE KALKSTICKSTOFFWERKE AG, it has been proposed to pre-alloys of the ferro-si.lico-magnesium type into thin sheet ferrules, previously filled in about three-quarters or about three-quarters, with crushed blocks of the same alloy - or an alloy of slightly different composition - ensuring very rapid cooling and thus avoiding the melting of the metal shell.

It is also known to cast in the sand mold alloys of the ferro-silico-magnesium family, in order to obtain innoculants for cast irons, in the form of shaped parts which are introduced into housings of casting channels (so-called process "in-mold inoculation"). However, these various processes are neither suitable nor adaptable to an economic and massive production of blocks from an electric oven having a continuous hourly production of several tonnes, for example an oven for the preparation of 75% ferrosilicon. of Si, of 16 MW, which produces approximately 2 T / h of alloy.

The object of the present invention is therefore a method which makes it possible to mold blocks of ferro-alloys of a predetermined shape and weight, by casting in cooled copper shells, of the liquid metal leaving a furnace. preparation, either directly, or through a pocket or any intermediate container.

This process is characterized by the following repetitive steps:

- An ingot mold is formed by juxtaposition, in sealed relationship, of two copper half-shells, at least one of which has a plurality of hollow imprints of the ingots to be molded, said imprints communicating with each other by channels and opening into the upper part of the mold by at least one inlet channel.

- A cooling circuit is established in each half-element by circulation of a heat transfer fluid.

- Liquid ferro-alloy is poured into the inlet channel, until the mold-mold is filled.

- The ferro-alloy is allowed to solidify and cool to a temperature below 200 ° C and preferably 300 ° C to its solidus temperature.

- The two half-elements are separated to cause the ingots to be removed from the mold.

The invention also relates to a device for implementing the method, comprising:

an ingot mold formed from two copper half-shells, at least one of which has a plurality of hollow imprints of the ingots to be molded, communicating with each other by channels and opening, at the top, by a channel d 'Entrance,

means for cooling each half-shell by circulation of a heat transfer fluid, - means for bringing the half-shells together and away,

- Means for guiding the movements of bringing together and away from the half-shells.

The device can also include cooled means for introducing the liquid ferro-alloy into the inlet channel.

The invention is particularly well suited to the production of molded blocks of ferrosilicon having a silicon content of more than 15% and preferably between 40 and 90%, the rest being iron and, where appropriate, elements of secondary additions such as Al, Ba, Ca, Mn, Ti, Zr.

Figures 1 to 5 explain the implementation of the invention: Figure 1 shows, in vertical section, a mold for the implementation of the invention.

Figure 2 is a horizontal section along AA of Figure 1. Figure 3 shows an industrial Itrigotière, with four elements, the opening and closing of which are controlled by jacks. Figures 4 to 5 show two alternative embodiments, in which the half-shells are asymmetrical.

In what follows, we will use the term "mold-mold" to designate the object of the invention, it being understood that this term designates a particular mold in which the metal is introduced in the molten state and extracted in the form multiple ingots, of predetermined size, shape and weight.

Each mold-ingot mold (1) consists of two half-elements, or "half-shells" (2) made of electrolytic copper, preferably of so-called Cu / al quality (designation according to French standard NF A-51.050), each half -shell being provided with a coolant cooling circuit, comprising a main inlet (3) connected to the fluid supply means, supplying, in parallel in this case, three derived circuits (4A), (4B), (4C), whose outlet collectors gather on a common outlet. The circuits cooling are internal [channels (5) drilled in the copper block forming the half-shells], but may possibly be external [copper tubes (6), welded or brazed over their entire length on the external faces of the half -shells].

Each half-shell (2) further comprises means for sealingly contacting to form the mold-mold. The contacting can be carried out by maintaining, for example, a fixed half-shell and bringing the other together, or even by moving the two half-shells towards each other, either by a movement of guided linear translation, either by a rotational movement around a common axis forming a hinge.

The linear translation can be guided by any known means such as guide rods (7) sliding in internal calibrated orifices (8), or by external sliding means such as grooves and slides.

The contacting by rotation can take place around a vertical or horizontal axis. In the latter case, the release is facilitated by the fact that the ingots are detached from the mold and falling under their own weight in a receiving means.

The various movements of bringing together and moving away the half-shells are controlled in a known manner by means such as the jacks (9).

Each half-shell comprises the half-cavities (10) corresponding to the ingots and to the connecting channels (11, 12). The half-shells can be symmetrical (fig. 1, 2, 3) or asymmetrical (10B) (10A) (fig. 4 and 5). One of them can even be reduced to a flat counter-plate (13) or, optionally, provided with a raised imprint (14) with cooling circuit (5) which makes it possible to increase the contact surface between the cast metal and the ingot mold, therefore, the cooling rate and the rate of casting.

The facing bearing faces (15) of each half-shell are erected and polished so as to ensure, under the action of the jacks (9), a sufficient seal without the interposition of any seal.

The liquid ferro-alloy is poured into the mold preferably by means of the funnel (17). This part can be fixed and integrated into the mold itself, or removable, and placed on the inlet orifice (18), the bearing faces also being erected and polished. In either case, the funnel is also provided with a cooling circuit. The channels and cavities located under the funnel are supplied "in fall", the others being supplied "at source". The number and size of the cavities and channels are determined so as to ensure complete filling before the metal begins to solidify and closes the supply channels.

FIG. 1 represents a section of an ingot mold with 2 x 3 imprints, but this arrangement is given by way of non-limiting example, and it could as well include 2 x 2 or 2 x 4 thereof.

The problem which had to be solved for the implementation of the invention was as follows: it was necessary, at the same time, to ensure a rate of casting fast enough to follow the production of a large modern furnace producing ferrosilicon, or other ferro-alloy, without immobilizing an excessive quantity of copper in the form of a high number of ingot molds, and ensuring a sufficiently long lifespan for the ingot molds so that the amortization of their cost does not increase significantly sensitive the cost of ingots compared to the price of ferrosilicon poured into buns of several tonnes, then crushed and ground. This result was obtained: 1) by the choice of the metal constituting the molds molds whose thermal conductivity must be as high as possible, which directs the choice towards electrolytic copper called Cu / al defined by standard NF A 53.100 (thermal conductivity at 20 ° = 400 to 412 W / mK) or low-alloy copper such as "CUPRONICS" (registered trademark of TREFIMETAUX) (365 W / mK) or CuZr 0.15 to 0.15% zirconium (350 to 370 W / mK), or any other copper-based alloy with thermal conductivity at least equal to 300 W / mK;

2) by setting up a very efficient cooling circuit, the heat transfer fluid being water at ambient temperature, which makes it possible to avoid, in all points, a rise in the temperature of the copper above 200 ° C and thus reduce at a negligible speed the magnification of the copper grains (recrystallization) which is the main cause of degradation of the ingot molds;

3 °) by the choice of the report at a value at least equal to 6 and preferably between 10 and 25. 4 °) by an extremely rapid demolding of the ingots, so that the ingot mold has the sole function of solidifying at least the external part of the ingots up to at a temperature of 200 to 300 ° below the point of solidus of the alloy, cooling down to ambient s. 'then performing, spontaneously, out of the mold, in any time that no longer matters.

EXAMPLE OF IMPLEMENTATION.

A copper ingot mold Cu / 1 was produced, according to the invention, comprising a central central block (20) fixed, provided with internal water cooling circuits (5) and four half-shells (21), (22 ), (23), (24), movable separately (or simultaneously) under the action of the jacks (9) and each having its own cooling circuit. Each half-shell corresponds to six imprints (10) connected by channels (11) (12), which are filled, by a funnel (17) in cooled copper. Each of the 24 cavities corresponds to an ingot of approximately 550 grams, plus the rods formed by the connecting channels, and the counterweights, which corresponds to approximately 14 kg of ferrosilicon per operation, each casting cycle being able to be reduced to 90 seconds, which then break down as follows:

Casting ................................................. .................... 15 seconds

Solidification of FeSi 75 ...................................... 15 " Ingot cooling to around 900 ° C (solidus to 1208 ° C) ...................... 15 seconds

Cooling of the shells after opening and unmolding the hot ingots .................. 30 "

Opening and closing times of molds and molds and idle times ........................... 20 "or an hourly production of 15 x 40 = 600 kilos. Four of these ingot molds are therefore sufficient to mold ingots the total production of a ferrosilicon-75 furnace of 2.4 T / h (~ 20 MW). After four months of continuous use, they remain in normal operating condition.

The implementation of the invention is susceptible of a certain number of variants, in particular with regard to: 1 °) the shape of the soft ingot molds which can either be formed of two symmetrical half-elements, or of asymmetrical half-elements (fig. 4 and 5), 2 °) the nature of the cast metal. If the invention is particularly suitable for alloys based on iron and silicon, it may be suitable without any modification of its principle to different alloys, for example based on iron and manganese, or manganese and silicon. However, its advantage is particularly evident in the case of metals the grinding of which results in significant quantities of fines which are difficult to use or to recycle, 3 °) the shape, dimensions and unit weight of the ingots, which may vary, depending of the intended use, within very wide limits, it being understood that the shape is subject to the need for spontaneous and very rapid release from the opening of the mold-mold and that the minimum unit weight is most often , imposed by economic considerations.

Claims

1 ° / - Method for molding ingots of ferro-alloys, characterized by the following repetitive steps:

- A mold-mold is formed by juxtaposition in sealed relation of two copper half-shells, at least one of which has in hollow a plurality of mold ingots imprints, said imprints communicating with each other by channels and opening out to the upper part of the mold-mold by at least

- an entry channel,

a cooling circuit is established in each half-shell by circulation of a heat transfer fluid, which maintains the temperature of the ingot at all points at a temperature not exceeding 200 ° C.,

- the liquid ferro-alloy is poured into the inlet channel, until the mold-mold is filled, - the ferro-alloy is allowed to solidify and cool down to a temperature of -200 ° C. and, preferably, 300 ° C below its point of solidus,

- The two half-shells are separated to cause the ingots to be removed from the mold.

2 ° / - Device for implementing the molding process according to claim 1, characterized in that it comprises:

- an ingot mold (1), made of copper, formed of two half-shells (2) at least one of which has a plurality of recesses (10) of the ingots to be molded, communicating with each other by channels ( 11), (12) and opening, at the top, by an inlet channel (18),

- cooling means (4), (5) by heat transfer fluid, of each half-shell (2), - means for bringing the two half-shells into contact and in sealed relation,

- means for removing the two half-shells,

- Means for guiding the movement away and sealingly connecting the half-shells. 3 ° / - Device according to claim 2, characterized in that the two half-shells (2) have symmetrical imprints (10).

4 ° / - Device according to claim 2, characterized in that the two half-shells have indentations (10A) asymmetrical.

5º / - Device according to claim 2, characterized in that at least one of the half-shells has imprints (14) in relief.

6 ° / - Device according to any one of claims 2 to 5, characterized in that it further comprises a cooled means (17) for introducing the liquid ferro-alloy into the inlet channel.

7º / - Device according to any one of claims 2 to 6, characterized in that it is made of electrolytic copper of Cu / al quality, according to standard NF A 53.100 having a thermal conductivity between 400 and 412 W / mK .

8 ° / - Device according to any one of claims 2 to 6, characterized in that it is made of low alloy copper having a thermal conductivity at least equal to 300 W / mK.

9 ° / - Device according to any one of claims 2 to 8, characterized in that the cooling means is formed by internal channels (5) in the half-shells.

10 ° / - Device according to any one of claims 2 to 8, characterized in that the cooling means is formed by tubes (6) welded over their entire length on the outer face (s) of the half-shells.

11º / - Device according to any one of claims 2 to 10, characterized in that the ratio of the mass of copper forming the mold-mold to the mass of ferro-alloy cast is at least equal to 6 and, preferably, between 10 and 25.