EP0936007B1 - Device for filtering and treating molten metal - Google Patents

Description

The present invention relates to a device to filter and process molten metal.

We know from the name EP-A-0 578 517 of the Applicant, on which the preamble of the appended claims is based, a device for filtering and process molten metal, comprising a series of at least minus two mineral filter plates refractory holes with filtration holes for the passage and filtration of the molten metal, these plates being kept at a predetermined distance from each other by peripheral walls of so as to create a cavity between them of which is housed a plate of a material of treatment of said molten metal having such a shape that, seen in the direction of passage of the liquid metal, the plate leaves on the filter plates at least one region not covered.

The region of the first filter plate (upstream) not covered by the material plate treatment has free filtration holes which allow molten metal to enter the cavity, to come into contact with the material of plaque treatment, and to flow around the plate before leaving the cavity through the holes in free filtration of the second filter plate (downstream).

We can see that the molten metal freely crosses the device from the start of the casting, after being in contact with the material of treatment present in the cavity of the device, so that we get a treatment of the molten metal very homogeneous from the beginning and until the end of the casting said metal.

Such a device is adapted to be prefabricated by the based filter supplier end user requirements.

The end user, who is usually a foundry, has two conflicting requirements.

On the one hand, knowing that the weight of the same treatment material must be a known fraction of the weight of molten metal passing through the device during of a predetermined casting operation, the user needs devices containing respective weights different predetermined treatment material constituting a series. Such a series can go, for example in the case of an inoculation material for the spheroidal graphite cast iron, in stages successive 10 grams in 10 grams or 20 grams in 20 grams, from ten grams to 150 grams or more.

In addition, materials of different treatment depending on the nature of the metal in fusion to be treated, these treatment materials different having different densities and being used in different proportions compared the weight of the molten metal to be treated.

On the other hand, and for reasons of standardization of the equipment used, a user wishes to limit the number of devices of different dimensions necessary for meet their needs.

The Applicant was therefore led to study the possibility of placing, in the cavity of the same device for filtering and treating molten metal, different amounts of processing materials different. Certain tests carried out by the Applicant have shown in some cases a decrease in the quality and / or homogeneity of the treatment of molten metal during an operation of casting.

The object of the present invention is to remedy the aforementioned drawbacks of the devices known, and to propose a device of the aforementioned type able to contain different amounts of various processing materials while ensuring quality and the homogeneity of the treatment of molten metal at during a casting operation.

According to a first aspect of the invention, the device of the aforementioned type for filtering and treating molten metal is characterized in that the ratio between the number of free holes in a filter plate located in regions not covered by the plate processing material, on the one hand, and the number total of the holes in said filter plate, on the other share, is not less than 10%, and / or is not greater than 75%, advantageously is not less than 20%, and / or is not more than 65%, and preferably is not less than 35%, and / or is not more than 50%.

We understand that a minimum percentage is required free holes to allow the passage of metal in fusion through the device according to the invention from the start of a casting operation.

We also understand that this percentage of free holes should not be too large: effect that the contact surface of the plate treatment material with molten metal either sufficient to allow regular passage and sufficient treatment material in said metal.

So, by controlling the relationship between the number of free holes and total number of holes of a filter plate, it is possible to introduce, in the cavity of a device of dimensions as many as possible of different weight plates of various materials from treatment without reducing the quality and consistency of the treatment of molten metal. This guarantees a as few as possible of different dimensions.

According to an advantageous version of the invention, the ratio between the volume left free in the cavity by the treatment material plate, on the one hand, and the total volume of said cavity, on the other hand, is not less than 20%, and / or is not more than 80%, advantageously is not less than 30%, and / or is not more than 75%, and preferably not less than 35%, and / or is not greater than 72%.

We understand that a minimum percentage is required of volume left free by the material plate of treatment inside the cavity to allow the passage of molten metal in this free volume at contact of the treatment material from the start and throughout the duration of the casting.

We also understand that this percentage of free volume should not be too large. It takes effect that the contact conditions between the metal in melt and the processing material remain substantially regular and constant throughout the casting time to ensure regular quality, homogeneous, reliable and reproducible treatment of molten metal during this time.

According to a preferred version of the invention, for an inoculation treatment of molten cast iron, the ratio expressed in dm x dry between the weight of the cast metal in kg, on the one hand, and the modulus of the pellet in dm multiplied by the speed of the metal poured inside the filter cavity, expressed in dm / sec, on the other hand, is in the range 70d ± 50%, advantageously in the plate 70d ± 35%, preferably in the range 70d ± 20%, d being the specific mass of the molten metal in kg / dm ³ .

The invention also relates, according to a another aspect of it, the use of a device according to the first aspect of the invention in a molten metal mold casting process comprising the steps of interposing a filter and of a treatment material on the passage of the metal before the entry of said metal into the mold properly said.

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

• la figure 1 est une vue en coupe transversale, suivant I-I à la figure 2, d'un mode de réalisation d'un dispositif suivant la présente invention, ce dispositif contenant, dans sa moitié gauche à la figure, une plaque de matériau de traitement d'une première forme, et dans sa moitié droite à la figure, une plaque de matériau de traitement d'une autre forme ;
• la figure 2 est une vue de dessus du dispositif de la figure 1, la plaque filtrante amont étant enlevée pour la clarté du dessin.

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

• Figure 1 is a cross-sectional view, along II in Figure 2, of an embodiment of a device according to the present invention, this device containing, in its left half in the figure, a plate of treatment material of a first shape, and in its right half in the figure, a plate of treatment material of another shape;
• Figure 2 is a top view of the device of Figure 1, the upstream filter plate being removed for clarity of the drawing.

There is shown in the figures a device 1 to filter and process molten metal.

This device comprises a series of at least two filter plates 2, 3 made of mineral material refractory with holes for filtration holes 4, 4a for the passage and filtration of the molten metal. We have not shown in Figures 1 and 2 that part of the holes 4, 4a of filtration for the sake of clarity of these FIGS.

These plates are kept at a distance predetermined from each other by walls peripherals 5 so as to provide a cavity 6 inside which a plate is housed 7 of a material for treating said molten metal having a shape such that, seen in the direction 8 of the passage of molten metal, plate 7 leaves on the filter plates 2, 3 at least one region 9 no covered.

In the direction of arrow 8 representing at the Figure 1 the direction of passage of the molten metal, the plate 2 is the upstream plate, or upper plate, and the filter plate 3 is the downstream plate, or plate lower.

In the embodiment of Figure 1, each filter plate 2, 3 has peripheral walls lateral 5 projecting towards one another in sparing the cavity 6. In this example, the two filter plates 2, 3 are joined to each other by a seal 15, for example of refractory cement.

Such a device 1 is suitable for use in a molten metal mold casting process comprising the steps of interposing a filter and of a treatment material on the passage of the metal in melting before the entry of said metal into the mold well said.

According to the invention, the ratio R1 between the number of free holes 4a of a filter plate 2, 3 located in regions 9 not covered by the plate 7 processing material, on the one hand, and the number total of the holes 4, 4a of said filter plate 2, 3, on the other hand, is not less than 10%, and / or is not more than 75%.

• R1 n'est pas inférieur à 10% ;
• R1 n'est pas supérieur à 75%.

For the sake of clarity, it should be specified here that this means that the ratio R1 fulfills either one or the other, or all of the two conditions below:

• R1 is not less than 10%;
• R1 is not more than 75%.

Advantageously, the ratio R1 is not less than 20%, and / or is not more than 65%.

Preferably, the ratio R1 is not less than 35%, and / or is not more than 50%.

Similarly, the ratio R2 between the volume left free in the cavity 6 by the plate 7 of processing material, on the one hand, and the total volume of said cavity 6, on the other hand, is not less than 20%, and / or is not more than 80%.

• R2 n'est pas inférieur à 20% ;
• R2 n'est pas supérieur à 80%.

This means that the R2 report fulfills either one or the other, or all of the two conditions below:

• R2 is not less than 20%;
• R2 is not more than 80%.

Advantageously, the ratio R2 is not less than 30%, and / or is not more than 75%.

Preferably the ratio R2 is not less than 35%, and / or is not more than 72%.

In a manner known per se, the material of treatment forming the plate 7 is chosen from among desulfurizing, thermogenic, inoculating products, spheroids, refuels, refiners, modifiers, and addition alloys.

In known manner, the weight of the material of treatment ranges from approximately 0.001% to 1% of the weight of molten metal to be treated.

The filtration holes 4, 4a have, in general, a diameter between 1.5 and 3 mm approximately, preferably between 1.8 and 2.5 mm approximately.

The processing material forming the plate 7 is advantageously an inoculating material chosen from the following compounds: iron alloy, magnesium and compounds of magnesium, calcium and its compounds barium, silicon, zirconium, aluminum, rare earths, graphite, carbon, for an inoculation treatment of molten iron.

In the example shown in half left of figures 1 and 2, the plate 7 has in projection on a plane perpendicular to the direction 8 of passage of the metal, an octagonal outer contour 10 and has a central hole 11 whose diameter is greater than that filtration holes 4, 4a.

In the example shown in half right of Figures 1 and 2, the plate 7 has in projection the shape of a circular crown delimited by a outer circular outline 12 whose diameter is slightly less than the width of the cavity which has here a square section, and a circular outline interior 13.

Filter plates 2 and 3 are refractory mineral plates baked in the oven. The holes 4, 4a, which all have the same diameter in the example shown in the figures, could have different diameters on a plate 2, 3 compared to the other plate 3, 2, or on the same plate.

Plates 2, 3 can be manufactured with their holes, by die casting, or by pressure extrusion, then baked.

They can have walls protruding peripherals 5 shown in the figures. They may also not include such walls and be joined to each other by means a peripheral spacer, with two seals such than 15.

The filter plates 2, 3 can have a outside contour of any shape, square like in the example shown, but also round, rectangular or other.

Similarly, the cavity 6 can have an outline interior of any shape adapted to that of the outer contour of the filter plates 2, 3.

The plate 7 of treatment material has for its part an external contour whose shape is adapted to that of the interior contour of the cavity, so that the plate 7 can be introduced into the cavity 6 leaving a number of free holes 4a on the filter plates 2, 3 adapted to allow regular, consistent, effective quality treatment, reliable and reproducible, molten metal for the entire duration of the casting operation.

The values indicated above for the ratio between the number of free holes 4a on a plate filter 2, 3 and the total number of holes 4, 4a of said plate, of course get along in assuming that holes 4, 4a all have the same diameter.

In this case, the ratio between the numbers of respective holes is equal to the ratio between sections of passage of the respective holes, and substantially equal to the ratio between the area of regions 9 no on the one hand, and the total area of the cavity, on the other hand.

So in the example shown in the left half of Figures 1 and 2, we can check, according to the dimensions reproduced as plate 7 of octagonal processing material a, in projection, an area such that the ratio between the area of regions 9 not covered by the plate 7, on the one hand, and the total area of the cavity, on the other hand, is around 41%. By way of consequence, the ratio between the number of free holes and the total number of holes is approximately 41%.

Similarly, in the example shown in the right half of Figures 1 and 2, we can check, according to the dimensions reproduced, that plate 7 of processing material in the shape of a circular crown has, in projection, an area such that the ratio between the area of regions 9 not covered by plate 7, of a park, and the total area of the cavity 6, on the other hand, is around 53%. By way of consequence, the ratio between the number of free holes and the total number of holes is approximately 53%.

We can also verify that the ratio R2 between the volume left free in the cavity 6 by the processing material plate 7, on the one hand, and the total volume of cavity 6, on the other hand, taking into account thicknesses shown for the cavity 6 and the plate 7, is around 61% for the octagonal plate of the left half of the figures, and about 69% for the plate in the shape of a half cylindrical crown right of the figures.

Tables 1 and 2 summarize, in Examples 1 to 17, the characteristics of tests carried out by the applicant on a private and confidential basis. These tables indicate for each filter, the length L, the width l, the height h of the filter and the radius Ø of the holes, all in millimeters, the weight in grams of the patch, for each filter, the front surface a, in mm ² , the number of holes b, the diameter of the holes c, the passage surface d in mm ² for all the holes, for the filter cavity, the surface e of the cavity in mm ² , the height f of the cavity in mm, the volume g of the cavity in mm ³ , for the pellet of treatment material, its diameter h in mm, its height i in mm, its front surface j in mm ² , its total developed surface k in mm ² , its volume l in mm ³ , its module M = l / k in dm, the number n of the chamber holes plugged by the patch, the ratio R1 of the number n of plugged holes compared to the total number b of the holes filter, the surface p not blocked by the patch, in mm ² , the ratio R1 = p / e in%, the free volume r in mm ³ occupied by the patch (r = g-1), the ratio R2 e n% between the volume r left free in the cavity by the patch, and the total volume g of this cavity (R2 = r / g).

Examples 5 and 6 did not give totally satisfactory results, and are at the origin the lower limit equal to 10% for the ratio R1, as well as the lower limit, equal to 20% for the R2 report. The most difficult cases, in which several identical pieces are poured at the same time or not in cells distributed around the casting from the same mold, made it possible to determine the lower and upper limits of the ranges advantageous and preferred for the two ratios R1 and R2.

Tables 1 and 2 show that the material treatment is advantageously in the form of a plate or patch with module M, or relationship between the volume and the total developed surface of said plate or tablet, is an increasing function of the weight of said pellet.

Table 2 shows that module M of the pastille is greater than at least 0.0050 dm, preferably at least 0.0100 dm, preferably at at least 0.0150 dm.

However, the weight of processing material is a known proportion of the weight of the metal cast in a casting operation. In a given mold and with a given filter, the casting time is appreciably proportional to the weight of the molten metal to be poured and to treat.

Table 3 groups together 6 examples 21 to 26 for each of which the characteristics of a filter and a corresponding tablet.

As the ratio between the weight of the material treatment and the weight of the molten metal to be treated may vary within certain limits around a average percentage, the same pellet of material treatment and the same filter can be used to weights of cast metal included in a certain range on either side of a weight of cast metal way. Under these conditions, the casting time is substantially proportional to the weight of the metal cast at treat.

Table 3 therefore indicates, for each of the 6 examples of filters and tablets, a weight range of cast metal and a range of casting times.

The Applicant Interested in the Report R3 defined as the ratio between the weight of cast metal to be treated, on the one hand, and on the other hand, the treatment material tablet module multiplied by the speed of the metal poured into the filter.

The module of the patch is defined by the ratio M between volume and developed surface total of this patch.

Furthermore, the speed of the metal cast at the inside of the filter is equal to the ratio between the weight of cast metal on the one hand, and on the other hand, the chamber surface multiplied by the casting time and by the specific mass d of the molten metal.

t égale le temps en secondes

V(p) égale le volume de la pastille en dm³

So we have R3 equal S (p) xdx S (c) x (t) / V (p) where S (p) equals the total developed surface of the pellet in dm ² , d equals the specific weight of the molten metal, S (c) equals the frontal area of the filter cavity, in dm ²

t equals time in seconds

V (p) equals the volume of the tablet in dm ³

So we have S (c) R3 = S (c) xtxd M (p)

The value of the R3 ratio obtained for the average casting time in each of the 6 examples.

We can see a grouping of values of this R3 ratio around 70d, which is quite surprising.

The values in Table 3 corresponding to an inoculation treatment of molten cast iron, and taking into account the limits of the ranges considered for the casting weight or the casting time, the applicant was led to take as a criterion for determining the geometry of the pellets on the one hand and filters on the other hand, the rule according to which the ratio R3 expressed in dm x sec, between the weight P of the cast metal, in kg on the one hand, and the module M of the tablet in dm multiplied by the speed of the metal poured inside the filter chamber expressed in dm / sec, on the other hand, is in the range of 70d ± 50%, advantageously in the range 70d ± 35%, of preferably in the range 70d ± 20%, d being the specific mass of the molten metal in kg / dm ³ .

The plaintiff also sought to see if she could not define a specific criterion of geometric dimensions of the pellet considered alone.

She therefore gathered in table 4 twelve examples 31 to 42 of pellets whose weights range from 10g to 110g, choosing for several weights from disc, two clearly different geometries one corresponding to a relatively small diameter and at a relatively large thickness, the other at a relatively large diameter associated with a lower height.

The applicant was interested in a first ratio R4 defined as being equal to the square root of the weight of the pellet divided by the module M of it.

The plaintiff was thus taken to conclude that the treatment material pellet is advantageously dimensioned in such a way that the ratio R4 between the square root of its weight P in grams, on the one hand, and its module M in decimeters, on the other hand, is between 80 and 280, advantageously between 100 and 260, preferably between 120 and 250.

At the same time, the plaintiff also interested in the value of the R5 ratio, which is the ratio between the cube root of the weight P of a pellet, in grams, on the one hand, and its module M in decimeters on the other hand.

She was led to define as a criterion for sizing of the pellets, the rule that the ratio R5 is usefully between 50 and 170, advantageously between 60 and 160, preferably between 75 and 130.

The ranges thus indicated for the R5 report are narrower than those indicated above for the R4 report. This can probably be explained by the fact that the ratio R5 is a dimensionless number because its numerator, the cube root of weight, is proportional to the cube root of the volume, and can express themselves in decimeters, as its denominator, the module M.

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 as defined by the appended claims.

In particular, examples 21 to 26 and 31 to 42 relate to known treatments for the inoculation of liquid iron, whatever the quality of the iron sighting, gray cast iron, vermicular cast iron, spheroidal graphite or other.

POIDS
P
(g) Ø
(mm) h
(mm) M
(dm) R4
√P/M R5
³√P/M EX 31 10 25,4 7,5 0,0236 134 91,3 EX 32 10 30 6 0,0214 148 100,6 EX 33 20 38,1 6,3 0,0237 189 114,5 EX 34 20 25,4 17 0,0363 130 74,8 EX 35 30 38,1 9 0,0306 179 101,5 EX 36 30 46 6,5 0,0253 216 122,8 EX 37 40 50,8 8,6 0,0321 197 106,5 EX 38 40 38,1 14,8 0,0416 152 82,2 EX 39 60 50,8 12,3 0,0414 187 94,5 EX 40 60 38,1 21 0,0499 155 78,4 EX 41 80 46 16 0,0472 189 91,3 EX 42 110 56 15 0,0482 218 99,4 R4 = √P/M   R5 = ³√P/M The device according to the invention can of course be used for the treatment of other molten metals, in particular aluminum and its alloys, light alloys in general, other ferrous and non-ferrous metals.

WEIGHT
P
(G) Ø
(Mm) h
(Mm) M
(Dm) R4
√ P / M R5
³ √P / M EX 31 10 25.4 7.5 0.0236 134 91.3 EX 32 10 30 6 0.0214 148 100.6 EX 33 20 38.1 6.3 0.0237 189 114.5 EX 34 20 25.4 17 0.0363 130 74.8 EX 35 30 38.1 9 0.0306 179 101.5 EX 36 30 46 6.5 0.0253 216 122.8 EX 37 40 50.8 8.6 0.0321 197 106.5 EX 38 40 38.1 14.8 0.0416 152 82.2 EX 39 60 50.8 12.3 0.0414 187 94.5 EX 40 60 38.1 21 0.0499 155 78.4 EX 41 80 46 16 0.0472 189 91.3 EX 42 110 56 15 0.0482 218 99.4 R4 = √P / M R5 = ³ √P / M

Claims (13)

1. A device (1) for filtering and processing molten metal, comprising a series of at least two filter plates (2, 3) of refractory mineral material formed with filtration holes (4, 4a) for the passage and filtration of the molten metal, said plates being held a predetermined distance apart by peripheral walls (5) so as to form between them a cavity (6) inside which is housed a plate (7) of a molten metal processing material having a form such that, considered in the direction (8) of passage of the molten metal, the plate (7) leaves at least one uncovered zone (9) on the filter plates (2, 3), characterised in that the ratio (R1) between the number of free holes (4a) of a filter plate (2, 3) situated in the zones (9) not covered by the processing material plate (7), on the one hand, and the total number of holes (4, 4a) of the said filter plate (2, 3), on the other hand, is not less than 10%, and/or is not more than 75%, advantageously is not less than 20%, and/or is not more than 65%, and preferably is not less than 35%, and/or is not more than 50%.
2. A device according to claim 1, characterised in that the ratio (R2) between the volume left free in the cavity (6) by the processing material plate (7), on the one hand, and the total volume of the said cavity (6), on the other hand, is not less than 20%, and/or is not more than 80%, advantageously is not less than 30%, and/or is not more than 75%, and preferably is not less than 35%, and/or is not more than 72%.
3. A device according to claim 1 or 2, characterised in that the processing material is in the form of a plate or pellet of which the module (M) or ratio between the volume and the total developed surface of said plate is an increasing function of the casting time or of the weight of the molten metal to be processed through the device.
4. A device according to any one of the preceding claims, characterised in that for a molten casting inoculation processing the ratio (R3) expressed in dm x sec, between the weight (P) of the cast metal in kg, on the one hand, and the module (M) of the pellet in dm multiplied by the speed of the cast metal inside the filter chamber, expressed in dm/sec, on the other hand, is within the range of 70 d ± 50%, advantageously in the range of 70 d ± 35%, preferably in the range of 70 d ± 20%, d being the specific mass of the molten metal in kg/dm³.
5. A device according to any one of the preceding claims, characterised in that the module (M) of the pellet is greater than at least 0.0050 dm, advantageously than at least 0.0100 dm, preferably than at least 0.0150 dm.
6. A device according to any one of the preceding claims, characterised in that the processing material pellet is dimensioned so that the ratio (R4) between the square root of its weight (P) in grams, on the one hand, and its module (M) in dm, on the other hand, is between 80 and 280, advantageously between 100 and 260, preferably between 120 and 250.
7. A device according to any one of the preceding claims, characterised in that the processing material pellet is dimensioned so that the ratio (R5) between the cube root of its weight (P) in grams, on the one hand, and its module (M) in dm, on the other hand, is between 50 and 170, advantageously between 60 and 160, preferably between 75 and 130.
8. A device according to any one of the preceding claims, characterised in that the processing material forming the plate (7) is selected from desulphurising, thermogenic, inoculating, spheroidising, recarbonising, refining, and modifying products, and addition alloys.
9. A device according to any one of the preceding claims, characterised in that the weight of the processing material is between 0.001% and 1% approximately of the weight of the molten metal for processing.
10. A device according to any one of the preceding claims, characterised in that the filtration holes (4, 4a) have a diameter of between 1.5 and 3 mm approximately, preferably between 1.8 and 2.5 mm approximately.
11. A device according to any one of the preceding claims, characterised in that the said processing material is an inoculating material.
12. A device according to claim 11, characterised in that the said inoculating material is selected from the following compounds: alloys of iron, magnesium, lithium compounds, strontium compounds, barium compounds, silicon, zirconium, aluminium, rare earths, graphite, carbon.
13. Use of a device according to any one of the preceding claims, in a molten metal mould casting process comprising the steps of interposing a filter and a processing material in the passage of the molten metal before the metal enters the actual mould.

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