Metal founding – Means to shape metallic material – United particle type shaping surface
Reexamination Certificate
1999-02-04
2001-04-17
Lin, Kuang Y. (Department: 1722)
Metal founding
Means to shape metallic material
United particle type shaping surface
C164S058100
Reexamination Certificate
active
06216768
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for filtering and treating molten metal.
According to EP-A-0 578 517, a device for filtering and treating molten metal includes a set of at least two filtering plates, consisting of a refractory mineral material and having through-holes for the passage and the filtration of the molten metal, such plates being kept at a certain distance apart by means of peripheral walls so as to provide, between them, a cavity receiving an insert made of a treating material for said molten metal and having such a shape that, as seen in the direction of flow of the liquid metal, the insert leaves at least one uncovered area on the filtering plates.
The area of the first filtering plate (upstream), which is not covered by the insert of treating material, includes free filtering holes, allowing the molten metal to enter the cavity, contact the treating material of the insert and flow around the insert before leaving the cavity through the free filtering holes in the second filtering plate (downstream).
It can therefore be noted that the molten metal flows freely through the device as soon as the casting process begins, after having been brought in contact with the treating material present in the device cavity, with the result that a quite homogeneous treatment of the molten metal can be obtained right from the beginning and up to the end of the casting of said metal.
Such a device is suitable for a prefabrication by the filter supplier, according to the end user's requirements.
However, the end user, as a general rule a foundry, has two conflicting requirements.
On the one hand, based on the fact that the weight of a given treating material must be a known fraction of the weight of the molten metal-flowing through the device during a predetermined casting process, the user requires devices with different predetermined respective weights of treating material, constituting a set. Such a set may range, for instance as regards an inoculating material for the casting of spheroidal-graphite cast iron, from ten grams to 150 grams or more, in successive steps 10 grams by 10 grams, or 20 grams by 20 grams.
Besides, various treating materials are used depending on the nature of the molten metal to be treated, such various treating materials having different densities and being used in different proportions in relation to the weight of the molten metal to be treated.
On the other hand, and on standardisation grounds for the equipment used, the user wants to limit as much as possible the number of devices with various sizes, necessary for meeting his requirements.
Therefore the Applicant has been led to investigate the feasibility of placing, in the cavity of a device used for filtering and treating molten metal, different quantities of various treating materials. Some tests, carried out by the Applicant, have revealed, in certain cases, a decrease in the quality and/or homogeneity of the treatment of molten metal in the course of a casting process.
SUMMARY OF THE INVENTION
It is the object of the present invention to cope with the above-mentioned shortcomings of the known devices and to provide a device of the above-mentioned type, capable of holding various quantities of different treating materials, while nevertheless providing for the quality and homogeneity of the treatment of molten metal in the course of a casting process.
According to a first aspect of the present invention the device of the above-mentioned type, intended for the filtration and the treatment of molten metal, is characterised in that the ratio of the number of free holes in a filtering plate, located in the areas which are not covered by the insert of treating material, on the one hand, to the total number of holes in said filtering plate, on the other hand, is not less than 10% and/or not above 75%, and advantageously not less than 20% and/or not above 65% and, more preferably, not less than 35% and/or not above 50%.
As can be seen, a minimum percentage of free holes is required for allowing the passage of molten metal through the device according to the invention, as soon as a casting process starts.
It will also be easily understood that such percentage of free holes should not be too high: as a matter of fact, the area of the insert of treating material in contact with the molten metal must be great enough for an even and sufficient transfer of the treating material into said metal.
Thus, by controlling the ratio of the number of free holes to the total number of holes in a filtering plate, it is possible to insert into the cavity of a device having preset dimensions, the greatest possible number of inserts with various weights of different treating materials, yet without a decrease in the quality and homogeneity of the treatment of molten metal. It results in the smallest possible number of devices having different dimensions.
According to an advantageous facet of the invention, the ratio of the space not occupied in the cavity by the insert of treating material, on the one hand, to the total volume of said cavity, on the other hand, is not less than 20% and/or not above 80%, and advantageously not less than 30% and/or not above 75% and, more preferably, not less than 35% and/or not above 72%.
It will readily be understood that a minimum percentage of space must remain unoccupied by the insert of treating material inside the cavity, to allow for the flowing of the molten metal in such free space, in contact with the treating material right from the beginning of the casting process and through it.
Yet such percentage of free space should not be too high. In fact, the contact conditions between molten metal and treating material must remain substantially even and steady through the whole casting process for an even, homogeneous, reliable and reproducible quality of the treatment of the molten metal during the whole process.
According to a preferred embodiment of the present invention, for an inoculation treatment of molten cast iron, the ratio, expressed in dm×sec, of the weight in kg of the cast metal, on the one hand, to the module of the insert, in dm, multiplied by the cast metal velocity inside the filter cavity, expressed in dm/sec, on the other hand, is in the order of 70D±50%, advantageously in the order of 70D±35%, and preferably in the order of 70D±20%, D being the density of the molten metal as expressed as a dimensionless ratio of the mass of a predetermined volume of the metal to the mass of the same volume of water.
Another aspect of this invention relates to the use of a device according to the first aspect of the invention, in a method of mould casting a molten metal, comprising the steps of interposing a filter and a treating material on the way of the metal before said metal enters the actual mould.
REFERENCES:
patent: 3658115 (1972-04-01), Ryntz, Jr. et al.
patent: 5603373 (1997-02-01), Daussan et al.
patent: 5690161 (1997-11-01), Daussan et al.
patent: 0 249 897 (1987-12-01), None
patent: 0 578 517 A1 (1994-01-01), None
patent: 62-185859 (1987-08-01), None
Daussan Andre
Daussan Gerard
Daussan Jean
Daussan et Compagnie
Lin Kuang Y.
Young & Thompson
LandOfFree
Device for filtering and treating molten metal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for filtering and treating molten metal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for filtering and treating molten metal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2505393