FR2691654A1 - Molten metal treatment for casting with interposition of filter for filtration - by adding e.g. desulphurising agent, thermogenic, inoculant, spheroidiser, carburising, refining or modifier, and directing metal to filter plates forming cavities - Google Patents

Abstract

The treatment involves the addn. of a material (12), e.g. a desulphurising agent, a thermogenic, an inoculant, a spheroidiser, re carburising, refining and modifying agents or other addn. alloys, to the molten metal and directing the molten metal to the filter (1a) which has plates (2, 2a, 2b) in a refractory mineral material contacting each other and forming cavities (4, 5, 6) for the passage of the molten metal. The filter, which is also new, comprises a series of plates (2, 2a, 2b) of refractory mineral materials that define between them cavities (4, 5) and the plates (2, 2a, 2b) each incorporate a series of holes (3, 3a, 3b) allowing the passage and filtration of the molten metal. The cavities (4, 5) contain the material (12) used to treat the molten metal. USE/ADVANTAGE - The treatment is used for treating molten metals by the addn. of agents e.g. a desulphurising agent, a thermogenic, an inoculant, a spheroidiser, a re carburising, refining or modifying agents or other addn. alloys and ensures that the treatment is regular and homogeneous and the added materials are used fully in the treatment. It also allows the simultaneous filtration of the molten metal.

Description

The present invention relates to a method for treating molten metal during a mold casting operation with the interposition of a filter, this method comprising the step of placing a material for treating said metal before casting the molten metal. a channel holder adapted to guide said metal to the filter,
The invention also relates to a filter for implementing the method according to the invention.

 Usually, the treatment agents are simply placed in the channels for the passage of molten metal, which is tedious.

It is also known to provide for the distribution of products intended for the treatment of metal by interposing the treatment products in destructible sachets which are placed in a recess or a cul-desac of the metal passage channels located before the filter; this process has the disadvantage of not guaranteeing that all the metal comes into contact with the treatment agents,
In fact, due to the turbulence associated with the pouring of the metal into the pouring channels, the destructible sachets are driven from the place where they have been deposited and are pushed upstream into the funnel into which the metal is poured. in fusion. There is then a loss of unused treatment material and rejects castings whose metal is insufficiently treated.

 Furthermore, the molten metal does not come fully into contact with the treatment material, and the metal poured into the mold risks being heterogeneous.

 It is also known to treat liquid metal by placing agglomerated treatment products upstream of the filter using a binder or by pressure and / or sintering and / or molding: here again, there is no the guarantee that all the metal has been treated. In addition, this represents additional manipulation.

 The object of the present invention is to remedy the drawbacks of known methods, and to propose a method of the aforementioned type making it possible to ensure that all of the cast molten metal is treated as regularly and as homogeneously as possible, and that the material is fully used to treat said metal.

 The object of the present invention is also to propose a filter for the implementation of said method.

 According to the invention, the method of the aforementioned type is characterized in that a filter for molten metal is used comprising a series of at least two plates of refractory mineral material in contact with each other by their periphery and defining between one or more cavities, these plates each comprising a series of holes allowing the passage and filtration of the liquid metal, and in that the treatment material is introduced into at least one of the cavities before installing the filter in the mold.

 It is thus certain that the treatment material, retained between two plates, cannot be driven from the cavity by the turbulence linked to the flow of molten metal, and will be entirely used for the treatment of the metal, thus eliminating all risk of scrap castings due to metal processing failure.

 In addition, all of the molten metal passing through the filter is contacted with the treatment material.

This contact is also made in a filter cavity in which the metal flows at a lower speed than that which it has in the channels.

 The Applicant has found that the metal cast according to the process of the invention has a distribution of the treatment product and a treatment homogeneity greater than that obtained with the known processes.

 Without claiming that this is the only possible explanation for this unexpected and surprising result, the Applicant assumes that this is due to the very slow speed of passage of the metal in the cavity of the filter compared to the significantly higher speeds of passage through the holes. plates. this results in an energetic and very regular mixing between the untreated metal arriving at high speed inside the cavity and the already treated metal which remains in this cavity before being evacuated through the holes in the second plate, this mixing extending throughout the duration of the casting.

 This mixing, combined with the fact that the treatment product is trapped inside the cavity and cannot in any case be removed from it, probably explains the very regular distribution of the treatment product in the metal of the casting and the excellent homogeneity of the result of the treatment of said metal inside said part.

 According to another aspect of the invention, the filter targeted by the latter for implementing the aforementioned method according to the first aspect of the invention comprises a series of at least two plates of refractory mineral matter in contact with each other. the others by their periphery and defining between them one or more cavities, these plates each comprising a series of holes allowing the passage and ia filtration of the liquid metal.

 According to the invention, this filter is characterized in that the at least one of the cavities contains a material for the treatment of said metal.

 This allows the preparation of prefabricated filters containing a predetermined dose of treatment product: such filters, very suitable for mass production, facilitate the task of the molding workshops and simplify the problems of inventory management of the products and consumable materials of these workshops.

 According to an advantageous version of the invention, the filter comprises at least two plates assembled along their periphery by an anointed, the cavity formed between the two plates is filled with powdery treatment material, and the holes in the plates are closed by a film made of a material capable of melting, carbonizing or calcining on contact with the liquid metal to be treated, disposed on the inside or on the outside of each plate.

 The treatment material can thus be easily maintained by such a film insulated in a sealed manner from atmospheric humidity and remain perfectly dry, which allows storage without disadvantage of prefabricated filters.

 Other features and advantages of the invention will become apparent in the description below.

In the appended drawings, given only by way of nonlimiting examples:
- Figure 1 is a sectional view along TI in Figure 2 of a two-stage filter according to a first embodiment of the present invention;
- Figure 2 is a plan view of the filter of Figure 1;
- Figure 3 is a view similar to Figure 1 of a filter having only one cavity;
- Figure E is an enlarged sectional view of a filter according to another embodiment of the present invention;
- Figure 5 is a view similar to Figure 4 showing in two half-views joined two variants of the filter shown in said figure;
- Figure 6 is a sectional view along VI-VI in Figure 7;
- Figure 7 is a top view, in two half-views, the upper plate having been removed, of two variants of another embodiment of the present invention.

 As shown in the figures, the process targeted by the invention for treating molten metal during a mold casting operation with the interposition of a filter 1, la, lb, lc, Id, comprises the step which consists in placing before pouring the molten metal a material 12 for treating said metal at a point in the channel adapted to guide said metal to said filter.

 According to the invention, this process is characterized in that a filter 1, 1a, 1b, 1c, 1d, for liquid metal is used comprising a series of at least two plates 2, 2a, 2b, made of refractory mineral material. contact with each other by their periphery and defining between them one or more cavities 4, 5, 6, these plates 2, 2a, 2b, each comprising a series of holes 3, 3a, 3b, allowing the passage and filtration of the liquid metal, and in that the treatment material 12 is introduced into at least one of the cavities 4, 5, 6, before placing the filter 1, la, lb, Sc, Id, in a mold ( not shown).

 The treatment material 12 is chosen from desulfurizing, thermogenic, inoculating, spheroidizing, recarburizing, refining, modifying products and addition alloys.

 The weight of the treatment material 12 can vary between 0.01% and 1% approximately of the weight of the liquid metal, depending on the nature of the treatment that it is desired to apply.

 The filter 1a shown in FIG. 1 comprises three plates 2, 2a, 2b. The plates 2 and 2a each have a projecting peripheral flange 11 adapted to come into contact with the adjacent plate, 2a, 2b, corresponding which is thus kept at a distance to provide a cavity, respectively 4, 5. The plate 2b does not have such a rim, which would unnecessarily increase the height of the filter 1.

 The upper plate, which is normally placed on the upstream side, is pierced with holes 3, 3a, 3b, of different diameters increasing in this order. The plates 2a, 2b also have holes of equal or different diameters.

The holes in the intermediate plate 2a are staggered with respect to the holes in the end plates 2 and 2b. The holes 3, 3a, 5 may have sections other than circular.

 The plates 2, 2a, 2b are in known manner made of a refractory ceramic mineral material, for example silica, and are capable of withstanding the temperature of the cast metal without deformation.

 The filter 1 shown in Figure 2 has a plate 2 having holes 3 of substantially the same diameter.

 The filter 1b shown in FIG. 3 consists of two plates 2a, the peripheral edges 11 of which are adjacent and joined to one another by a bonding 10. The heights of the flanges It are shown to be identical but could be different. The two plates delimit a cavity 6.

 FIGS. T and 5 on the one hand, 6 and 7 on the other hand, respectively represent a filter lc, ld, consisting of two plates 2a in contact by their peripheral edge II to define a cavity 6.

 As shown in the figures, and according to 1 invention, at least one of the cavities 4, 5, 6 of the filter 1, la, lb, ic, ld contains a material for the treatment of the molten metal to be treated.

 In the embodiment of Figures 1, 3, a and 5, the treatment material 12 is in powder form and is retained by a film 13 of a material capable of melting, carbonizing or calcining on contact with the liquid metal to be treated.

 The particle size of the coating material is chosen according to the treatment conditions that are desired.

 The film 13 of a material capable of melting, carbonizing or calcining on contact with the metal to be treated is for example an aluminum sheet or paper or a plastic film, or even a composite sheet.

 In the embodiment of FIGS. 1 and 3, the treatment material 12 is contained in sachets 7, 7a, 7b, produced with said film 13 and placed in said cavity 4, 5, 6.

 The cavities 4 and 5 of FIG. 1 each contain a sachet, respectively 7, 7a, which partially or almost completely fills the corresponding cavity 4, 5. These sachets 7, 7a can be identical or have different capacities.

 The cavity 6 in FIG. 3 contains a sachet 7b arranged, by way of example, eccentrically in said cavity 6.

 In the embodiment of FIGS. 4 and 5, the cavity 6 formed between the two plates 2 is filled with pulverulent treatment material 12, and the holes 3 in the plates 2a are closed by a film 13 of the aforementioned type placed on the inner face or on the outer face of each plate 2a.

 In the example of Figure 4, a film 13 is fixed, for example glued, on the inner face of a top plate. Another film 13 is fixed to the outer face of the lower plate, the holes 3 being filled with treatment material 12.

 In the example of FIG. 5, the films 13 are fixed on the interior faces of the plates in the left half-view and on the exterior faces of these plates in the right half-view. The latter case corresponds to the maximum volume of treatment material 12 contained in the filter c.

 In the embodiment of FIGS. 6 and 7, the material 12 for pulverulent treatment is in compressed or sintered form, and is in the form of note plates, 14b or bars. The dimensions of the plates lova, 14b or bars are smaller than the internal dimensions of the cavity 6, so that these plates or bars can be movable inside the cavity 6 from the start of the casting under the action of the turbulence generated by the arrival of molten metal in the cavity 6.

 For example, there is shown in the left half-views a plate 14a of hexagonal outline and in the right half-views a plate 14b of annular shape. Such plates 14a, 14b are for example compressed with a binder such as stearate or the like; it is also possible to agglomerate under high pressure the treatment material 12 prepared for example in crystallized form. The plate 14a has a central hole 15 for the passage of the metal. It could include other holes of various shapes and dimensions.

 The treatment materials may be desulfurization agents, for example magnesium and / or calcium carbide, and / or be thermogenic agents, for example calcium carbide, and / or be inoculation agents and / or post-inoculation, for example based on silicon, ferrosilicon, silicon carbide, calcium, magnesium, lithium, zirconium, carbon, barium, strontium, rare earths, and / or agents spheroidization, for example magnesium and / or rare earths and / or ferrosilicomagnesium, and / or agents of addition alloys, for example alloys of molybdenum, boron, silicon, ferrosilicon, manganese, with chromium, titanium, ferroaluminium, silicomischmetal, recarburising agents, for example based on carbon or graphite, fluxes to modify the structure of the metal, such as sodium, phosphorus, boron, titanium salts , strontium, etc ...

 Of course, the invention is not limited to the embodiments which have just been described, and many modifications and modifications can be made to them without departing from the scope of the invention.

 It is thus possible to replace the compressed or sintered plates or bars with solid molded plates or bars.

Claims (7)

 1. Method for treating molten metal during a mold casting operation with the interposition of a filter (1, la, lb, ic, ld), this method comprising the step which consists in placing the metal before casting melting a material (12) for treating said metal at a point in the channel adapted to guide said metal to the filter, characterized in that a filter (1, la, lb, lc, ld) for molten metal is used comprising a series of at least two plates (2, 2a, 2b) of refractory mineral material in contact with each other by their periphery and defining between them one or more cavities (4, 5, 6), these plates (2, 2a, 2b) each comprising a series of holes (3, 3a, 3b) allowing passage and filtration to the molten metal, and in that r os introduces the material (12) of treatment in at least one of the cavities (4, 5, 6) before placing the filter (1, a, lb, lc, Id) in the mold.  2. Method according to claim 1, characterized in that the treatment material (12) is chosen from desulfurizing, thermogenic, inoculating, spheroidizing, recarburizing, refining, modifying and addition alloys products.  3. Method according to one of claims 1 or 2, characterized in that the weight of the treatment material (12) can vary between 0.01% and about 1% of the weight of the molten metal.  &, liter (1, la, lb, Ic, Id) for molten metal, suitable for implementing the method according to one of claims 1 to 3, this filter comprising a series of at least two spikes ( 2, 2a, 2b) in refractory mineral material in contact with each other by their periphery and defining between them one or more cavities (t, 5, 6X, these plates each comprising a series of holes (3, 3a, 3b) allowing the passage and filtration of the molten metal, characterized in that at least one of the cavities (4, 5, 6) contains a material (i2) for the treatment of said metal.  5. Filter according to claim 4, characterized in that the treatment material (12) is in powder form and is retained by a film (13) of a material capable of melting, carbonizing or calcining on contact with the metal. in fusion to be treated.  6. Filter according to claim 5, characterized in that the treatment material (12) is contained in sachets! 7, 7a, 7b) produced with said film (13) and placed in said cavity (4, 5, 6 ).  7. Filter according to claim 5, comprising at least two plates (2a) assembled ie along their periphery by a seal (10), characterized in that the cavity (6) formed between the two plates (2a) is filled with powder treatment material (12), and in that the holes (3) of the plates (2a) are closed by a film (13) of the aforementioned type placed on the inner face or on the outer face of each plate (2a).  8. Filter according to claim 4, characterized in that the powder treatment material (12) is in compressed or sintered form.  9. Filter according to one of claims 4 or 8, the treatment material (12) being in the form of plates (14a, 14b) or bars, characterized in that the dimensions of said plates (14a, 14b) or bars are smaller than the internal dimensions of the cavity (6) adapted to receive them.