EP0131025B1 - Method and device for casting ingots of ferro-alloys by permanent mould casting into cooled copper chills - Google Patents

Abstract

PCT No. PCT/FR84/00005 Sec. 371 Date Sep. 6, 1984 Sec. 102(e) Date Sep. 6, 1984 PCT Filed Jan. 6, 1984 PCT Pub. No. WO84/02668 PCT Pub. Date Jul. 19, 1984.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: 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), means (5) for cooling each mould half (2) by a heat exchange fluid, means (9) for bringing the two mould halves into contact and into sealing relationship, means for moving the two mould halves away from each other, and means (7, 8) for guiding the mould halves in their movement away from each other and in their movement of coming into sealing relationship.

Description

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

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 with 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 deoxidizers of steels in general.

It is known that the crushing of 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-1,538,948 (= US 3,604,494) to the names of METALLGESELLSCHAFT AG and SÜDDEUTSCHE KALKSTICKSTOFFWERKE AG, it has been proposed to pre-alloys of the ferro-silico-magnesium type in thin sheet ferrules , previously filled to about two-thirds or 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 sheet metal shell.

In patent US-A-2 308 448 which serves as a basis for the preambles of independent claims 1 and 2, a device for casting metal balls is described, in a cooled ingot mold, consisting of two removable symmetrical parts. The footprints are supplied with liquid metal from a central channel and bypass channels. The disadvantage principle is that a significant proportion of the cast metal, which fills the channel and the bypass channels, must be recycled.

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 the runners (process says "in-mold inoculation").

However, these various processes are neither suitable nor adaptable to an economic and massive production of blocks from an electric furnace having a continuous hourly production of several tonnes, for example an furnace for the preparation of 75% ferrosilicon If, of 16 MW, which produces approximately 2 T / h of alloy.

The object of the present invention is therefore a process which makes it possible to mold blocks of ferro-alloys of a predetermined shape and weight, by casting in a cooled shell, of the liquid metal leaving an elaboration furnace, either directly, or through a pocket or any intermediate container, and in such a way that almost all of the cast metal is effectively recovered in the form of blocks of predetermined shape and weight.

This process is characterized in that all the mold cavities are fed in series, and in that the temperature of the mold, the latter being made of copper, is maintained, at all points, below 200 ° C., by cooling effective, and a quick release of the cast ingots, as soon as solidification has started.

• un dispositif de moulage de lingotins en ferro-alliages, pour la mise en oeuvre du procédé selon la revendication 1, comportant une lingotière-moule (1), formée de deux demi-coquilles (2) dont l'une au moins comporte une pluralité d'empreintes en creux (10) des lingotins à mouler, des moyens de refroidissement (4), (5) par fluide caloporteur, de chaque demi-coquille (2), des moyens de mise en contact et en relation étanche des deux demi-coquilles, des moyens d'éloignement des deux demi-coquilles, des moyens de guidage des mouvements d'éloignement et de mise en relation étanche des demi-coquilles, caractérisé en ce que la lingotière est en cuivre et en ce que toutes les empreintes (10) sont disposées en série.

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

• a device for molding ingots of ferro-alloys, for implementing the method according to claim 1, comprising an ingot mold-mold (1), formed of two half-shells (2) of which at least one has a plurality of hollow impressions (10) of the ingots to be molded, of the cooling means (4), (5) by heat transfer fluid, of each half-shell (2), of the means of contacting and in sealed relation of the two half -shells, means for separating the two half-shells, means for guiding the movements of distance and for sealing the half-shells in tight relation, characterized in that the ingot mold is made of copper and in that all of the imprints (10) are arranged in series.

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

Particularly advantageous embodiments of the device for implementing the method according to the invention are the subject of dependent claims 3 to 5.

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

• La figure 1 représente, en coupe verticale, une lingotière pour la mise en oeuvre de l'invention.
• La figure 2 est une coupe horizontale, selon AA de la figure 1.
• La figure 3 représente une lingotière industrielle, à quatre éléments, dont l'ouverture et la fermeture sont commandées par des vérins.
• Les figures 4 à 5 représentent deux variantes d'exécution, dans lesquelles les demi-coquilles sont dissymétriques.

FIGS. 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 in Figure 1.
• FIG. 3 represents an industrial ingot mold, 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 all that follows, we will use the term "mold-mold" to designate the subject 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 / A1 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), which collectors exit on a common exit. The cooling circuits 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 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 one another, 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 fall under their own weight in a receiving means.

The various movements of approaching 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), sufficient sealing 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 footprints located under the funnel are supplied “in fall”, the others being supplied “at source”. The number and size of cavities and channels are determined 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 nonlimiting example, and it could as well include 2 x 2 or 2 x 4 thereof.

• 1) par le choix du métal constituant les lingotières-moules dont la conductivité thermique doit être aussi élevée que possible, ce qui oriente le choix vers le cuivre électrolytique dit Cu/a1 défini par la norme NF A 53 100 (conductivité thermique à 20° = 400 à 412 W.m^-1.K^-1) ou du cuivre faiblement allié tel que le «CUPRONICS» (marque déposée de la société TREFIMETAUX) (365 W.m-¹.K-¹) ou le CuZr 0,15 à 0,15% de zirconium (350 à 370 W.m-^I.K-¹), ou tout autre alliage à base de cuivre ayant une conductivité thermique au moins égale à 300 W.m-'.K-';
• 2) par la mise en place d'un circuit de refroidissement très efficace, le fluide caloporteur étant de l'eau à la température ambiante, qui permet d'éviter, en tous points, une élévation de la température du cuivre au-dessus de 200°C et réduire ainsi à une vitesse négligeable le grossissement des grains de cuivre (recristallisation) qui est la principale cause de dégradation des lingotières;
• 3) par le choix du rapport
  
  à une valeur au moins égale à 6 et, de préférence, comprise entre 10 et 25;
• 4) par un démoulage extrêmement rapide des lingotins, de façon que la lingotière ait pour seule fonction de solidifier au moins la partie externe des lingotins jusqu'à une température inférieure de 200 à 300°C au point de solidus de l'alliage, le refroidissement jusqu'à l'ambiante s'effectuant ensuite, spontanément, hors de la lingotière, en un temps quelconque qui n'a plus d'importance.

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 amount of copper in the form of a high number of ingot molds, and ensuring a lifetime long enough for the ingot molds so that the amortization of their cost does not significantly increase 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 mold-molds whose thermal conductivity must be as high as possible, which directs the choice towards electrolytic copper known as Cu / a1 defined by standard NF A 53 100 (thermal conductivity at 20 ° = 400 to 412 Wm ^-1 .K ^-1 ) or low-alloyed copper such as "CUPRONICS" (registered trademark of the company TREFIMETAUX) (365 Wm- ¹ .K- ¹ ) or CuZr 0.15 to 0, 15% zirconium (350 to 370 Wm- ^I .K- ¹ ), or any other copper-based alloy having a thermal conductivity at least equal to 300 Wm - '. K-';
• 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 extremely rapid demoulding of the ingots, so that the sole function of the ingot mold is to solidify at least the external part of the ingots up to a temperature lower than 200 to 300 ° C. at the point of solidus of the alloy, cooling to ambient then takes place, spontaneously, out of the mold, in any time which no longer matters.

Example of realization

soit une production horaire de 15 x 40 = 600 kilos. Quatre de ces lingotières-moules suffisent donc à mouler en lingotins la production totale d'un four à ferrosilicium-75 de 2,4T/h (- 20 MW). Après quatre mois d'utilisation continue, elles restent en état normal de fonctionnement.A copper ingot mold Cu / 1 was produced according to the invention, comprising a fixed central block (20), provided with internal circuits (5) for water cooling 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 corresponding to six imprints (10) connected together by channels (11), (12), which are filled, by a funnel (17) of cooled copper. Each of the 24 cavities corresponds to an ingot weighing 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:

or an hourly production of 15 x 40 = 600 kilos. Four of these ingot molds are therefore sufficient to mold into 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.

• 1) la forme des lingotières-moules qui peuvent être soit formées de deux demi-éléments symétriques, soit de demi-éléments dissymétriques (fig. 4 et 5),
• 2) la nature du métal coulé. Si l'invention est particulièrement adaptée aux alliages à base de fer et de silicium, elle peut convenir sans aucune modification de son-principe à des alliages différents, par exemple à base de fer et de manganèse, ou de manganèse et de silicium. Mais, son intérêt est particulièrement évident dans le cas de métaux dont le broyage conduit à des quantités importantes de fines difficiles à utiliser ou à recycler,
• 3) la forme, les dimensions et le poids unitaire des lingotins, qui peuvent varier, en fonction de l'utilisation envisagée, dans des limites très larges, étant entendu que la forme est subordonnée à la nécessité d'un démoulage spontané et très rapide dès l'ouverture de la lingotière-moule et que le poids unitaire minimal est, le plus souvent, imposé par des considérations économiques.

The implementation of the invention is susceptible of a certain number of variants, in particular as regards:

• 1) the shape of the molds which can be either formed by two symmetrical half-elements, or by asymmetrical half-elements (fig. 4 and 5),
• 2) the nature of the metal cast. If the invention is particularly suitable for alloys based on iron and silicon, it may be suitable without any modification of its principle for 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 large quantities of fines which are difficult to use or to recycle,
• 3) the shape, dimensions and unit weight of the ingots, which can vary, depending on the intended use, within very wide limits, it being understood that the shape is subject to the need for spontaneous and very rapid demoulding from the opening of the mold and that the minimum unit weight is, most often, imposed by economic considerations.

Claims (5)

1. A process for casting ingots of ferro-alloys of predetermined shape and weight in a cooled ingot mould formed by two separable half-shells of which one at least comprises a plurality of cavities corresponding to the ingots to be cast, characterised in that the cavities are fed in series with the liquid metal and that the temperature of the ingot mould, the mould being of copper, is maintained at all points at lower than 200°C and that the ingots are removed from the mould at a temperature which is 200 to 300°C lower than their solidus point.

2. Apparatus for casting ingots of ferro-alloys, for carrying out the process according to claim 1, comprising an ingot mould (1) formed by two half-shells (2) of which one at least comprises a plurality of cavities (10) corresponding to the ingots to be cast, means (4, 5) for cooling each half-shell (2) by means of a heat exchange fluid, means for bringing the two half-shells into contact and sealing relationship, means for moving the two half-shells apart, means for guiding the movements of the half-shells for moving them apart and bringing them into sealing relationship, characterised in that the ingot mould is of copper and all the cavities (10) are disposed in series.

3. Apparatus according to claim 1, characterised in that it is made of electrolytic copper of quality Cu/a1, in accordance with standard NF A 53 100, having a thermal conductivity of between 400 and 412 W.m^-1.K^-1.

4. Apparatus according to claim 1, characterised in that it is made of weakly alloyed copper having a thermal conductivity of at least 300 W.m-^l.K-¹.

5. Apparatus according to any one of claims 1 to 3, characterised in that the ratio of the mass of copper forming the ingot mould to the mass of cast ferro- alloy is at least equal to 6 and is preferably between 10 and 25.

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