EP1091818B1 - Method for preparing a casting mould - Google Patents

Description

The present invention relates to a method for prepare a casting mold comprising at least one mold cavity adapted to receive molten metal directed towards said cavity by at least one funnel of casting emerging in a flow channel extending in downstream of the pouring funnel to said cavity, this process being carried out on an automatic machine casting and comprising a preparation step of two mold halves and a step of assembling the two mold halves along a substantially joint plane vertical.

We know automatic casting machines of molten metal, for example machines available on the market under the registered trademark "DISAMATIC" ®.

On such a machine, molds are deposited on a closed circuit transporter on which the mussels pass successively in stations preparation of the two mold halves, assembly of these two halves along a substantially joint plane vertical, pouring molten metal into the mold thus formed, of solidification of the metal cast at inside the mold, disassembling the mold for release the casting or castings.

Many attempts have been made to try to interpose a filter on the passage of molten metal to filter this molten metal before it arrives in the mold cavity.

When it comes to casting hollow parts, it is necessary to set up at least one core in the mold cavity. This setting operation place of the nucleus is relatively long and delicate. he it is easy to install a filter at the same time passage of molten metal in the pouring channel which is generally arranged between the two mold halves.

On the contrary, when no nucleus is necessary, the preparation operations of the two mold halves are very fast, so all attempts to install a filter have resulted in negative results, setting up a filter bringing more disadvantages in terms of machine operating cycle disturbances automatic casting only advantages in terms of improving the internal structure of the cast metal. In other words, industrialists prefer prioritize the productivity of the automatic casting at the cost of a large percentage of parts rejected for defects in the quality of the metal.

DE-U-87 11468 describes a two-part mold prepared according to a process of the aforementioned type. A first half of the mold includes a funnel-shaped recess casting extending to the joint plane and comprising a housing for a filter.

The second half of the mold includes a recess communicating downstream with a flow channel.

In some cases, the filter must be turned on place manually or mechanically in the first half of the mold before the two halves of the mold. Such placement of the filter slows the rate of mold making.

In other cases, the filter can be set place manually after assembly of the mold, which is expensive.

In other cases, finally, it is specified that the filter could in principle be installed mechanically after assembling the mold, but this constitutes a hazardous operation which may damage the filter and the mold.

Furthermore, JP-A-01 266 942 describes a filter which has a protrusion on its downstream face adapted to be housed in a corresponding cavity of the second half of the mold, making it mandatory to put in place of the filter before assembling the two halves of the mold.

There is therefore a need for a process of the type aforementioned allowing to introduce a filter on the passage cast metal without practically reducing the productivity of an automatic casting machine molten metal.

• on aménage dans une première moitié du moule un évidemment formant entonnoir de coulée s'étendant jusqu'au plan joint ;
• on aménage au niveau du plan de joint, à la périphérie dudit évidemment, un logement sensiblement parallèle audit plan de joint et présentant à sa partie supérieure une ouverture supérieure, ledit logement ayant, parallèlement audit plan de joint, des dimensions prédéterminées plus grandes que celles dudit entonnoir et, dans la direction perpendiculaire audit plan de joint, une épaisseur prédéterminée ;
• on aménage dans la seconde moitié de moule un second évidemment ayant au niveau du plan de joint une ouverture de dimensions inférieures aux dimensions correspondantes du logement, cet évidement étant fermé à sa partie supérieure et communiquant vers l'aval avec un chenal de coulée;
• on assemble les deux moitiés de moule le long du plan de joint;
• on introduit dans le logement, sensiblement verticalement à travers l'ouverture supérieure de celui-ci, un filtre qui a des dimensions sensiblement inférieures aux dimensions prédéterminées correspondantes du logement, et qui est adapté à filtrer du métal en fusion de façon telle que du métal en fusion versé dans l'entonnoir traverse ledit filtre puis est canalisé par le second évidement vers le chenal de coulée.

According to the present invention, the method of the aforementioned type is characterized in that it comprises the following steps:

• a recess is formed in a first half of the mold forming a funnel extending to the joint plane;
• is arranged at the joint plane, at the periphery of said recess, a housing substantially parallel to said joint plane and having at its upper part an upper opening, said housing having, parallel to said joint plane, predetermined dimensions larger than those of said funnel and, in the direction perpendicular to said joint plane, a predetermined thickness;
• a second recess is arranged in the second mold half having at the joint plane an opening of dimensions smaller than the corresponding dimensions of the housing, this recess being closed at its upper part and communicating downstream with a pouring channel;
• the two mold halves are assembled along the joint plane;
• is introduced into the housing, substantially vertically through the upper opening thereof, a filter which has dimensions substantially smaller than the corresponding predetermined dimensions of the housing, and which is adapted to filter molten metal in such a way as metal molten poured into the funnel crosses said filter and is then channeled through the second recess to the pouring channel.

Housing provided in the first half of mold is open at the top and allows an introduction easy and reliable filter in the opening upper of said housing. This accommodation is closed at its periphery by the edges defining the opening of the recess of the second half of the mold. When molten metal arrives in the funnel, this metal in fusion presses the filter against the second half of mold. The filter is thus applied in a way substantially waterproof against the edges of the opening of this second mold half, which forces the metal into fusion to pass through the filter to be filtered before reach the mold cavity. We thus arrive at provide a passage for molten metal allowing to introduce a filter through this passage without disrupt the operation of an automatic casting.

This introduction of the filter can be carried out either during any waiting time of the mold, by example during the duration, a few seconds, of the pouring molten metal into one of the molds previous, or even during a movement of the mold.

There is sufficient clearance between the walls of the recess and those of the filter, to eliminate all risk of the filter jamming when it is inserted, the vibrations of a displacement that can further facilitate this introduction of the filter.

Furthermore, the skilled person was dissuaded provide for the installation of a filter in position substantially vertical with no way to prevent a possible rise of this filter whose density is much lower than that of molten metal, under the effect ferrostatic pressure.

In fact, experience has confirmed that, from the start of pouring the molten metal into the funnel, this molten metal presses the filter against the edges of the second recess, so that the friction against these edges prevent movement of the filter.

According to an advantageous version of the invention, we give the housing and the filter, in section transverse by a plane parallel to the joint plane, respective complementary contours so shaped to automatically center the filter relative to the housing, for example trapezoidal contours having its small base in the lower part.

According to a preferred embodiment, use is made a filter comprising a series of at least two plates refractory filters defining between two adjacent plates a corresponding cavity these plates each comprising a series of holes allowing the passage and filtration of the molten metal, one at fewer cavities containing a material for treating the molten metal in the form of a compressed plate, sintered or molded, the wafer of material treatment having a form such as, seen in the direction passage of molten metal, it leaves on each filter plate at least one region not covered with filtration holes not blocked by said wafer to allow molten metal having entered the cavity to come into contact with the wafer processing material and flow around said plate and then through the holes in filtration of the second filter plate.

Such a filter is known, in particular from the EP-A-0 578 517 and FR 98 01 634 on behalf of the Applicant.

The cavity formed between the two plates is fills with molten metal substantially at the same time than the funnel, which weighs down the filter. This heavier filter, combined with the fact that metal molten present in the funnel presses the filter against the edges of the second recess, there is no no risk of the filter rising due to the ferrostatic pressure.

In addition, the molten metal is not only filtered but also treated in excellent conditions of reliability and homogeneity of the treatment.

According to another aspect of the invention, the mold for casting molten metal according to this invention comprising at least one mold cavity adapted to receive molten metal directed towards said cavity by at least one through-funnel in a channel extending downstream from the funnel to said cavity, a filter being interposed on the passage molten metal, is characterized in that said mold was prepared by implementing the method according to the first aspect of the invention.

Other features and advantages of the present invention will appear in the description detailed below.

• la figure 1 est une vue partielle en coupe, suivant un plan perpendiculaire au plan de joint, d'un moule de coulée selon un mode de réalisation de la présente invention ;
• la figure 2 est une vue de dessus du moule de la figure 1 ;
• la figure 3 est une vue partielle en coupe suivant III-III à la figure 1 ;
• la figure 4 est une vue partielle en coupe suivant IV-IV à la figure 1 ;
• la figure 5 est une vue en coupe, suivant V-V à la figure 6 d'un mode de réalisation d'un filtre utilisable dans le moule des figures 1 à 4 ;
• la figure 6 est une vue en coupe, suivant VI-VI à la figure 5 du filtre représenté à ladite figure 5 ;
• la figure 7 est une vue semblable à la figure 1 représentant un autre mode de réalisation de la présente invention ;
• les figures 8A et 8B sont des demi-vues juxtaposées en coupe respectivement suivant VIIIA-VIIIA et VIIIB-VIIIB à la figure 7 ;
• la figure 9 est une vue semblable à la figure 7 d'un autre mode de réalisation de l'invention ;
• la figure 10 est une vue en coupe suivant X-X à la figure 9, le filtre n'étant pas représenté pour la clarté de la figure ;
• la figure 11 est une vue semblable à la figure 1 représentant un autre mode de réalisation de la présente invention ;
• la figure 12 est une vue partielle en coupe suivant XII-XII à la figure 11 ;
• la figure 13 est une vue partielle en coupe suivant XIII-XIII à la figure 11 ;
• la figure 14 est une vue de dessus du mode de réalisation de la figure 11 ;
• la figure 15 est une vue schématique agrandie d'un détail de la figure 14.

In the appended drawings, given only by way of nonlimiting examples:

• Figure 1 is a partial sectional view, along a plane perpendicular to the joint plane, of a casting mold according to an embodiment of the present invention;
• Figure 2 is a top view of the mold of Figure 1;
• Figure 3 is a partial sectional view along III-III in Figure 1;
• Figure 4 is a partial sectional view along line IV-IV in Figure 1;
• Figure 5 is a sectional view, along VV in Figure 6 of an embodiment of a filter used in the mold of Figures 1 to 4;
• Figure 6 is a sectional view along VI-VI in Figure 5 of the filter shown in said Figure 5;
• Figure 7 is a view similar to Figure 1 showing another embodiment of the present invention;
• FIGS. 8A and 8B are half-views juxtaposed in section respectively along VIIIA-VIIIA and VIIIB-VIIIB in FIG. 7;
• Figure 9 is a view similar to Figure 7 of another embodiment of the invention;
• Figure 10 is a sectional view along XX in Figure 9, the filter not being shown for clarity of the figure;
• Figure 11 is a view similar to Figure 1 showing another embodiment of the present invention;
• Figure 12 is a partial sectional view along XII-XII in Figure 11;
• Figure 13 is a partial sectional view along XIII-XIII in Figure 11;
• Figure 14 is a top view of the embodiment of Figure 11;
• FIG. 15 is an enlarged schematic view of a detail of FIG. 14.

Schematically shown in Figures 1 to 4 a casting mold 1 comprising at least one cavity molding 60 (see Figure 11) adapted to receive metal in fusion which is directed towards said cavity 60 by at minus a funnel 2 pouring into a channel 3 pouring extending downstream of the pouring funnel 2 up to said molding cavity 60.

Such a mold 1, adapted to be prepared on a automatic closed circuit casting machine, by example a machine of the type "DISAMATIC" ®, is consisting of two mold halves 1a, 1b, which are assembled against each other along a plane of joint 4 substantially vertical.

• on aménage dans une première moitié 1a du moule 1 un évidement 2 formant entonnoir de coulée 2 s'étendant jusqu'au plan de joint 4 ;
• on aménage au niveau du plan de joint 4, à la périphérie de l'évidement 2, un logement 5 sensiblement parallèle au plan de joint 4 et présentant à sa partie supérieure une ouverture supérieure 6, le logement 5 ayant, parallèlement au plan de joint 4, des dimensions prédéterminées plus grandes que celles dudit entonnoir 2 et, dans la direction 7 perpendiculaire au plan de joint 4, une épaisseur prédéterminée ;
• on aménage dans la seconde moitié 1b du moule 1 un second évidement 8 ayant au niveau du plan de joint 4 une ouverture 9 de dimensions inférieures aux dimensions correspondantes du logement 5, cet évidement 8 étant fermé à sa partie supérieure et communiquant vers l'aval avec un chenal de coulée 3 ;
• on assemble les deux moitiés de moule 1a, 1b le long du plan de joint 4 ;
• on introduit dans le logement 5, sensiblement verticalement à travers l'ouverture supérieure 6 de celui-ci, un filtre 12 qui a des dimensions sensiblement inférieures aux dimensions prédéterminées correspondantes du logement 5 et qui est adapté à filtrer du métal en fusion, de façon telle que du métal en fusion versé dans l'entonnoir 2, traverse le filtre 12 puis est canalisé par le second évidement 8 vers le chenal de coulée 3.

According to the invention, the method for preparing a casting mold 1 is characterized in that it comprises the following steps:

• is provided in a first half 1a of the mold 1 a recess 2 forming a funnel 2 extending to the joint plane 4;
• is provided at the joint plane 4, at the periphery of the recess 2, a housing 5 substantially parallel to the joint plane 4 and having at its upper part an upper opening 6, the housing 5 having, parallel to the joint plane 4, predetermined dimensions larger than those of said funnel 2 and, in the direction 7 perpendicular to the joint plane 4, a predetermined thickness;
• there is provided in the second half 1b of the mold 1 a second recess 8 having at the joint plane 4 an opening 9 of dimensions smaller than the corresponding dimensions of the housing 5, this recess 8 being closed at its upper part and communicating downstream with a runner 3;
• the two mold halves 1a, 1b are assembled along the joint plane 4;
• is introduced into the housing 5, substantially vertically through the upper opening 6 thereof, a filter 12 which has dimensions substantially smaller than the corresponding predetermined dimensions of the housing 5 and which is adapted to filter molten metal, so such as molten metal poured into the funnel 2, passes through the filter 12 and is then channeled through the second recess 8 towards the pouring channel 3.

The filter 12 is any known filter, for example example a refractory material filter (ceramic) drilled with holes for the passage of molten metal.

The dimensions of the housing and those of the filter are predetermined to take into account the tolerances of manufacturing and games necessary to allow a easy and reliable insertion of filter 12 into the housing 5.

The funnel 2 is preferably defined for direct the molten metal across its width and substantially the entire height of the filtering zone of the filter, for example the area with holes for the passage of molten metal.

In the example shown in Figures 1 to 4, the second recess 8 alone constitutes a first section of the runner 3 and extends substantially vertically down beyond the lower seat 10 of the housing 5. It opens into a second section 11 the runner which is arranged at least in part in the first half of mold 1, which is suitable directing molten metal to the mold cavity 60 of mold 1.

The second section 11 could also extend horizontally on one side, or on each side, of the second housing 8, or following a layout and a any direction, towards said cavity.

The second section 11 of the runner 3 can obviously be spanned by the two halves 1a, 1b of the mold 1 on either side of the joint plane 4.

To facilitate the introduction and implementation place of the filter 12 in the housing 5, the housing 5 and to filter 12, in cross section through a plane parallel to the joint plane 4, contours respective complementary shaped so automatically center the filter 12 relative to the housing 5.

As shown in Figure 3, we give the filter 12, in cross section through a parallel plane in the joint plane 4, a contour having the shape of a trapezoid having its small base in the lower part. This substantially trapezoidal shape can be limited to the lower part of housing 5 and filter 12.

The same can be done for housing 5.

In addition, or alternatively, the housing 5 and to filter 12, in cross section through a plane parallel to the joint plane 4, contours respective complementary having a lower seat respective 10, 13 concave.

Such a concave seat can have a shape rounded, or a tapered dihedral shape, like shown schematically at 13a in Figure 3.

The essential condition to respect is that the filter is positioned automatically inside the housing 5, with sufficient precision for the filter 12, pressed against the peripheral edges of the opening 9 of the second recess 8, covers by its peripheral contour all the edges of the opening 9 to force all the molten metal poured into the funnel 2 to pass through the filter 12 to be directed then by the first section 8 and by the second section 11 of the flow channel 3 towards the cavity of molding, as shown schematically by the arrow 31 in the figure 1.

There is shown in Figure 3, in solid lines, the respective contours of the housing 5 and of the filter 12, and dashed the outline of the funnel 2 at the housing 5. This makes the edges appear lower 5a, 12a, lateral 5b, 5c; 12b, 12c and upper 12d respectively of the housing 5 and of the filter 12, on their faces parallel to the joint plane 4.

We have also shown in Figure 4, in lines solid, the outline of the opening 9 of the second recess 8 and in dashes the corresponding position of the contour of the filter 12. This makes the lower edges appear 9a, lateral 9b, 9c and upper 9d of the opening 9, and the lower edges 12a, lateral 12b, 12c and upper 12d of the filter 12, on their respective parallel faces on the joint plane 4.

We note that during its introduction into the housing 5 through the upper opening 6, the filter 12 a its lateral edges 12b, 12c guided on one side by the edge corresponding 5b, 5c of the housing 5, on the other side by the corresponding edge 9b, 9c of the second recess 9.

During the casting of molten metal, the edges 12b, 12c, 12d of the filter are pressed against the edges correspondents 9b, 9c, 9d of the opening 9 of the second recess 8, while its seat 13 rests on all its length on the seat 10 of the housing 5, so that force all molten metal through the filter 12.

In the example shown diagrammatically in FIGS. 5 and 6, we uses a filter 12 comprising a series of at least two filter plates 14, 15 made of refractory material defining between two adjacent plates 14, 15 a corresponding cavity 16. These filter plates 14, 15 each have a series of filtration holes 17 allowing the passage and filtration of the metal into fusion, at least one of the cavities 16 containing a material for processing molten metal. The plaques 14, 15 are for example fired ceramic plates in the oven, especially around 1400 ° C, if the metal to to deal with is cast iron or steel.

Preferably a material of treatment in the form of a compressed plate 18, sintered or molded, the wafer 18 of material treatment having a form such as, seen in the direction 19 passage of molten metal, it leaves on each filter plate 14, 15 at least one region 20 no covered with filtration holes 17 no closed by said plate 18 to allow the metal molten having entered cavity 16, crossing the first filter plate 14, to come into contact with the material for processing the wafer 18 and flow around said wafer 18, then through the filtration holes 17 of the second filter plate 15.

We usually choose the material of treatment among desulfurizing and thermogenic products, inoculants, spheroids, vermiculants, recarburants, refiners, modifiers, and addition alloys.

We use a known weight of material of treatment between approximately 0.001% and approximately 2% the weight of the molten metal to be treated.

We choose the dimensions of the plate 18 parallel to the joint plane 4 and the thickness of this wafer, so that the processing material is absorbed completely or substantially completely by the liquid metal during the entire casting time of the molten metal, this absorption occurring so substantially regular throughout the duration of this casting.

Figures 5 and 6 show, by way of non-limiting examples, in the left half of these two figures, a section plate substantially octagonal which leaves in each of the four corners of the cavity 16 an uncovered region 20 comprising uncoated filtration holes 17, shown at solid lines in Figure 6.

This octagonal plate can present in its center a hole 21 of any diameter.

We have represented, on the right side of Figures 5 and 6, a substantially section plate circular also leaving in each of the four corners of the cavity 16 an uncovered region 20.

The circular section insert can also present, for example in the center, a hole (not shown) of any diameter.

For the clarity of Figures 5 and 6, we have shown that part of the filtration holes 17, which have a diameter advantageously between 1.5 and 4 mm, preferably between 2 and 3mm, of the order of 2.5 mm. The number of holes 17 is obviously calculated so that the holes 17 constitute a total section of passage of molten metal compatible with casting imperatives.

In the example shown in these figures, each filter plates 14, 15 has on one side a peripheral edge 22, and the two plates 14, 15 are joined together along their edges respective peripherals 22, after introduction of the plate 18 in the cavity, by a seal 23.

In the embodiments shown in Figures 7 to 15, the housing 5 and / or the mold 1 are provided with means for creating friction forces opposing the buoyancy exerted by metal molten on filter 12 when said molten metal press the filter 12 against the edges 9a, 9b, 9c, 9d of opening 9.

In the embodiment shown in Figures 7 and 8, the housing 5 extends substantially vertically, along a plane 33 inclined downwards and downstream, in the direction 19 of passage of the metal in fusion, of a predetermined small angle A compared to the vertical plane.

In other words, the lower end 5a of the housing 5 is more advanced in direction 19 than the upper end 5d of said housing.

In the example shown, the housing 5 is, at less in its lower part, formed in the second half 1b of the mold 1.

In general, this housing 5 is arranged to facilitate the realization of both halves 1a, 1b of the mold 1, while allowing support edges of the filter 12 on the edges of the opening 9 under the thrust of molten metal poured into funnel 2.

The angle A is for example from 7 ° to 8 ° approximately by compared to the vertical.

Thus, and as shown schematically in Figure 7, the thrust 34 directed substantially horizontally, exerted by the molten metal on the inlet face 35 of the filter 12 has a component 36 perpendicular to this face inlet 35 which presses the filter 12 against the edges of opening 9, and a component 37 parallel to this entry face and directed downwards, which presses the filter 12 against the lower seat 10.

We see that in the example of figure 7, the opening 9 is limited in its lower part by a dam 41 whose face facing the filter 12 forms the lower edge 9a on which the edge rests lower 12a of filter 12.

In the embodiment of Figures 9 and 10, the second half 1b of the mold 1 has a tongue central unit 38 extending from the rear face 39 of the second recess 8 in the opposite direction to direction 19 of passage of the metal, and having a front face 40 on which is supported by the filter 12, over the entire height or any part of the height of the recess 8.

The tongue 38 thus separates the second recess 8 in two parts 8a, 8b which extend in a manner any one, or in a single channel 11 directed towards the bottom, as shown in Figure 9, in two separate channels (not shown) extending from any way to a single mold cavity or to several separate mold cavities.

The bearing face 40 of the tongue 38 is in the plane comprising the edges 9a to 9d of the opening 9, and constitutes not only a bearing surface, but also an additional friction surface between filter 12 and mold 1.

In the embodiment of FIGS. 11 to 14, we have spared at least one, in this case, each of the longitudinal walls substantially vertical 51, 52 of the housing 5 a curved part 53, 54 projecting inwards from said housing 5 towards the other wall 52, 51, so as to create a slight throttle adapted to guide and center the part bottom of the filter 12 which passes through this constriction during the introduction of said filter 12 into the housing 5.

The convex parts 53, 54 have their faces respective upper 53a, 54a which forms an angle progressive with the corresponding wall 51, 52, of so as to cooperate with the angles necessarily rounded bottom corners 55, 56 of filter 12 for ensure progressive guidance then progressive tightening said filter as said filter enters deeper into the cavity 5.

The corresponding clamping forces exerted by the convex parts 53, 54 on the walls longitudinal adjacent 57, 58 of the filter 12 create friction forces opposing Archimedes' thrust exerted by the molten metal on the filter 12.

We can of course vary at will the dimensions of the curved parts 53, 54 according to the values of friction forces that we want to obtain.

We can also, if we want to avoid a reduction of said friction forces in the case a slight displacement of the filter 12 upwards in the case of a trapezoidal shape of said filter 12, household these convex parts 53, 54 on vertical sections 57a, 58a of the walls 57, 58 of said filter 12, as shown schematically in Figure 15.

It will be noted, in Figures 11, 13 and 14, that the dam 41 constituting the lower edge 9a of the opening 9 on which the lower edge 12a rests of the filter 12, in this example consists of a bridge 42 formed in the lower part of the recess 8 on all or part of the width occupied by the holes in the filter 12, and extending in direction 19 to the bottom of the recess 8 which is separated into two channels.

For the simplicity of the figures, there is shown in Figures 11 to 15 of the bulging parts 53, 54 in the case of a vertical housing 5. We can obviously spare these bulging parts in the case of an inclined housing of the type shown in Figures 7 to 10, and associate with will these bulging parts with a dam 41 and / or a tab 38.

Of course, the present invention is not limited to the embodiments which we have just describe, and we can bring to these many changes and modifications without leaving the domain of the invention.

The process described above is obviously applicable both to molds without inner core than molds with inner core.

Claims (13)

1. Method for preparing a casting mould (1) comprising at least one moulding cavity (60) adapted to receive molten metal directed to the said cavity (60) by at least one pouring basin (2) opening out into a casting spout (3) extending downstream of the pouring basin (2) as far as the said cavity (60), this method being used on an automatic casting machine and comprising a step of preparing two mould halves (1a, 1b) and a step of joining the two mould halves (1a, 1b) along a substantially vertical joint face (4), characterised in that it comprises the following steps:

   a recess (2) forming a pouring basin (2) extending as far as the joint face (4) is provided in a first half (1a) of the mould (1);

   a housing (5) substantially parallel to the said joint face (4) and having a top opening (6) at its top part is provided at the joint face (4), at the periphery of the recess (2), the said housing (5) having, parallel to the said joint face (4), predetermined dimensions greater than those of the said basin (2) and, in the direction (7) perpendicular to the said joint face (4), a predetermined thickness;

   there is provided in the second half (1b) of the mould (1) a second recess (8) having, at the joint face (1), an opening (9) with dimensions less than the corresponding dimensions of the housing (5), this recess (8) being closed at its top part and communicating downstream with a casting spout (3);

   the two halves of the mould (1a, 1b) are joined along the joint face (4);

   there is introduced into the housing (5), substantially vertically through the top opening (6) thereof, a filter (12) which has dimensions substantially less than the corresponding predetermined dimensions of the housing (5) and which is adapted to filter molten metal, so that molten metal poured into the basin (2) passes through the said filter (12) and is then channelled by the second recess (8) to the casting spout (3).
2. Method according to Claim 1, characterised in that there are given to the housing (5) and to the filter (12), in transverse section through a plane parallel to the joint face (4), respective complementary contours shaped so as to automatically centre the filter (12) with respect to the housing (5).
3. Method according to Claim 1 or 2, characterised in that there is given to the filter (12), and where applicable to the housing (5), in transverse section through a plane parallel to the joint face (4), a contour having, at least in its bottom part, the shape of a trapezium having its small base at the bottom.
4. Method according to any one of the preceding claims, characterised in that there are given to the housing (5) and to the filter (12), in transverse section through a plane parallel to the joint face (4), respective complementary contours with a concave bottom seat (10, 13).
5. Method according to any one of the preceding claims, characterised in that the housing (5) and/or the mould (1) are provided with means for creating friction forces opposing the buoyancy exerted by the molten metal on the filter when the said molten metal presses the filter (12) against the edges (9a, 9b, 9c, 9d) of the opening (9).
6. Method according to Claim 5, characterised in that the housing (5) extends in a plane inclined downwards and downstream by a predetermined small angle with respect to the vertical plane.
7. Method according to either one of Claims 5 or 6, characterised in that there is provided, on at least one of the longitudinal walls (51, 52) of the housing (5), a curved part (53, 54) projecting towards the inside of the said housing (5) towards the other wall (52, 51), so as to create a slight contraction adapted to guide the bottom part of the filter (12) which passes through this contraction when the filter (12) is introduced into the housing (5).
8. Method according to one of Claims 5 to 7, characterised in that a central tongue (38) separating the second recess (8) into two parts (8a, 8b) is provided in the second half (1b) of the mould (1).
9. Method according to any one of the preceding claims, characterised in that use is made of a filter (12) comprising a series of at least two filter plates (14, 15) made from refractory material defining a corresponding cavity (16) between two adjacent plates (14, 15), these plates (14, 15) each having a series of filtration holes (17) allowing the passage and filtration of the molten metal, at least one of the cavities (16) containing a material for treating the molten metal.
10. Method according to Claim 9, characterised in that use is made of a treatment material in the form of a compressed, sintered or cast insert (18), the insert (18) of treatment material having a shape such that, seen in the direction (19) of passage of the molten metal, it leaves on each filter plate (14, 15) at least one uncovered region (20) having filtration holes (17) not closed off by the said insert (18) to enable the molten metal which has entered the cavity (16) to come into contact with the treatment material of the insert (18) and to flow around the said insert (18) and then through the filtration holes (17) in the second filter plate (15).
11. Method according to either one of Claims 9 or 10, characterised in that the treatment material is chosen from amongst desulphurising, heat generating, inoculating, spheroidising, vermiculating, recarburising, refining and modifying products, and addition alloys.
12. Method according to any one of Claims 9 to 11, characterised in that use is made of a weight of treatment material of between approximately 0.001% and approximately 2% of the weight of the molten metal to be treated.
13. Casting mould (1) for pouring and casting molten metal, comprising at least one moulding cavity (60) adapted to receive molten metal directed to the said cavity by at least one pouring basin (2) opening out into a casting spout (3) extending downstream of the pouring basin (2) as far as the said cavity, a filter (12) being interposed on the passage of the molten metal, characterised in that the said mould (1) was prepared using the method according to any one of the preceding claims.

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