Metal founding – Means to shape a forming surface – And separate metal casting means
Patent
1996-06-13
1998-11-17
Batten, Jr., J. Reed
Metal founding
Means to shape a forming surface
And separate metal casting means
164323, 164337, 164363, B22C 908, B22D 2709, B22D 4702
Patent
active
058363734
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a mould plant which employs moulds having a vertical parting surface or surfaces, and especially those moulds used for pouring light metals from below.
BACKGROUND ART
It is commonly known that metals, both in the liquid and solid state, when cooled undergo a decrease in volume, a so-called thermal contraction. In moulds, in which there is a non-uniform distribution of heat quantity in the mould cavity after the pouring, and in which for this reason not all the parts of the casting solidify at the same time, this causes the regions of the casting remaining longest in the liquid state to give off liquid metal to compensate for the contraction in the regions of the casting having solidified earlier, this leading to flaws in the casting commonly called "shrinkages", either appearing as depressions in the surface of the casting or as hollows (cavities or micro-shrinkages) within the casting. In order to avoid these faults, the skilled person can take a series of steps, of which the most common is the use of after-feeding reservoirs, i.e. cavities in the mould being filled with metal during the pouring operation and having such dimensions that the metal in them remains liquid longer than the last-solidifying regions of the casting, being connected to these regions through passages with a relatively large cross-sectional area so as to enable them to after-feed these regions with liquid metal during their solidification.
Such after-feeding reservoirs are mainly known in two types, viz. as open feeders or risers, i.e. substantially cylindrical cavities extending from the passage connecting them to the casting to the upper surface of the mould, and as internal or enclosed cavities in the mould, so-called "blind risers", placed in the immediate vicinity of the region of the casting to be fed. Relative to the latter form, the former form exhibits the advantage that the higher metallostatic pressure at the after-feeding location, i.e. the pressure of the "head" or overlying metal column, to a high degree supports the after-feeding by pressing the feeding metal through the connecting passage into the casting, while in the latter form, the pressure diminishes during the after-feeding process. On the other hand, the latter form exhibits the advantage of normally giving a higher metal yield in the casting process, i.e. a lesser quantity of metal to be separated from the castings for subsequent re-melting (recycling), this also reducing the energy consumed for melting.
Compared to moulds with a horizontal parting surface, the top surface of moulds with a vertical parting surface has a relatively small surface area, and for this reason, the latter type of moulds allows only to a low degree the use of open feeders or risers for after-feeding purposes, and thus, for this purpose it is generally necessary to use the above-mentioned "blind risers" with the associated disadvantage mentioned above, i.e. the lesser metallostatic pressure for pressing the after-feeding metal in through the passage to the casting. This disadvantage is additionally noticeable when after-feeding light-metal castings, i.e. castings of aluminium and its alloys or magnesium and its alloys, due to the relatively low specific weight of these metals.
In order to overcome the above problem U.S. Pat. No. 2,568,428 discloses blind risers situated on one or both sides of a mould cavity and being at the top connectable to a source or pressurized gas, the pressure whereof will add to the metallostatic pressure at the bottom of the risers and thereby make the after-feeding more efficient.
DISCLOSURE OF THE INVENTION
Casting of light-metal castings in moulds with vertical parting surfaces is of commercial interest especially by casting of moulds in a string-moulding plant, such as e.g. the "Disamatic" mould-making plant and for this reason, the object of the invention is to provide a mould with which it is possible to avoid the disadvantages referred to above, at the same time providing a possibility of increas
REFERENCES:
patent: 2568428 (1951-09-01), Billiar
patent: 3566952 (1971-03-01), Lane
patent: 3905419 (1975-09-01), Tenner
patent: 4436140 (1984-03-01), Ebisawa et al.
Hansen Preben N.
Jespersen Emil
Mogensen Vagn
Pedersen Steen
Rasmussen Niels W.
Batten, Jr. J. Reed
Georg Fischer Disa A/S
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