GB2160455A

GB2160455A - Casting mould

Info

Publication number: GB2160455A
Application number: GB8415838A
Authority: GB
Inventors: Ivan Dimov Nikolov; Dobromir Ivanov Dimov
Original assignee: METALOZNANIE I TECHNOLOGIA NA; Institute po Metaloznanie i Technologia na Metalite
Current assignee: METALOZNANIE I TECHNOLOGIA NA; Institute po Metaloznanie i Technologia na Metalite
Priority date: 1984-06-21
Filing date: 1984-06-21
Publication date: 1985-12-24
Also published as: SE446603B; GB8415838D0; JPS613647A; SE8403150L; FR2566299B1; GB2160455B; CA1221222A; SE8403150D0; FR2566299A1

Abstract

A casting mould for bottom pouring from a sealed chamber (10) with molten metal under the action of a gas pressure difference. The mould comprises respective mould parts (1, 2) forming a casting cavity (3) and a gating system for the supply of molten metal. The gating system comprises a gas-tight runner (4, 41) connected with the mould cavity (3) via an overflow-feed conduit (6) which is gas-permeable during the filling of the mould cavity and becomes gas-tight after the filling. In the overflow-feed conduit there is formed a lining (8) comprising an insert (7) which is provided with through-holes (71). There is a sealing surface (5) by which the casting mould is connected via a seal (12) to a movable feed tube (11), disposed in the sealed chamber (10) with molten metal. <IMAGE>

Description

SPECIFICATION Casting mould This invention relates to a casting mould for bottom pouring (charging) from a sealed chamber with molten metal under the action of gas pressure difference, which can find application in foundries for the production of castings with high physical and mechanical characteristics.

A known casting mould for bottom pouring from a sealed chamber with molten metla under the action of a gas pressure difference (USA Patent No.

2,839,801) comprises shaping blocks, forming a casting cavity, and a gating system, comprising a gas-tight runner, which ends in its bottom end with a seat, in which there is disposed a movable lock which is operated during the removal of the molten metal from the runner. The gas-tight runner is connected to a fixed feed tube, disposed within the sealed chamber with molten metal via a gaspermeable, but metal-tight seal, disposed in the bottom portion of the runner.

A main drawback of the known casting mould lies in the necessity for the movable lock in the gas-tight runner, which requires: a suitable actuating mechanism; the disposition and motion in a surrounding of molten metal, contained in the gating system and the mould cavity; and complex engineering solutions for removal of the movable lock after the solidfication of the casting.

Another drawback of the known casting mould is the location of a seal, by which the gas-tight runner is connected to the feed tube disposed in the sealed chamber with molten metal, and this seal is in direct contact with the molten metal during its flow through the gating system, which results in the reduction of its service life and even its replacement after each casting cycle.

The present invention has therefore been developed primarily, though not exclusively, with a view to provide a casting mould for bottom pouring from a sealed chamber with molten metal under the action of a gas pressure difference, in which there is avoided the necessity for the use of a movable lock in the gas-tight runner, and there is eliminated the possibility of any contact with molten metal of the seal, by which is effected a connection of a feed tube disposed in the sealed chamber with molten metal.

According to the invention there is provided a casting mould adapted for bottom charging under differential pressure action and comprising: shaping blocks which define a casting cavity, and a gating system for supplying molten metal to the casting cavity, in which the gating system comprises: a gas-tight runner which is connected to the casting cavity by means of an overflow system conduit, said conduit being arranged to be gaspermeable during charging of the casting cavity with molten metal and to become substantially gas-tight after filling of the casting cavity has been completed.

In the overflow-conduit (gate) there may be formed a lining conduit, between the shaping blocks and a distance insert, which insert is provided with through-holes. The distance insert may be made of the same material, of which the shaping blocks in the area of the overflow-feed conduit are made.

On the external side of the gas-tight runner there may be formed a sealing surface, by which the casting mould is connected via a seal to a movable feed tube, disposed in a sealed chamber containing molten metal.

A basic advantage of the casting mould, in accordance with the invention, lies in the feature that the presence of the overflow-feed conduit allows the removal of the molten metal from the gating system to the level of the overflow immediately after the filling of the mould cavity, without the necessity of any structural elements; it sufficient for that, that the gas pressure produced in the gating system balances the pressure of the metallostatic column of the molten metal inside the mould cavity in the plane of the overflow.

Another advantage lies in the feature that the overflow-feed conduit may be disposed in a suitable place, according to the configuration of the casting and the requirements of the solidification process; moreover, it is possible to arrange more than one overflow-feed conduit.

A further preferred advantage lies in the possibility provided for sealing only against a gaseous phase, and this results in a longer life of the seals and reliability in service.

The aforementioned advantages result in an improved yield and utilization of the cast material, an increased output and reliability in service of the casting machines and in the production of high physical and mechanical characteristics of casting.

One embodiment of casting mould according to the invention will now be described with reference to the accompanying drawing, which shows a cross-sectional view of a casting mould.

On the right of a centre line of the mould there is shown a realization of a sand mould, and on the left there is shown a combined metal mould with a sand core. Along this line there is shown a connection to the casting mould of a pressure diecasting machine, which is disclosed in more detail in Bulgarian author's certificate No. 33,467.

The casting mould comprises bottom and top shaping blocks 1, 2, forming a casting cavity 3, and a gating system for supplying the molten metal.

The gating system comprises a gas-tight runner 4, shaped in a tube 41, and this gas-tight runner 4 is connected to the mould cavity 3 via an overflowfeed conduit 6, which is gas-permeable during the filling or charging of the cavity 3 with molten metal, and becomes gas-tight after this cavity has been filled. In the overflow-feed conduit 6 there is arranged a lining conduit 8, formed between the top shaping block 2 of the cavity 3 and a spacer insert 7, the latter being provided with holes 71 for the molten metal to pass through and being made of the same material as that of the top shaping block 2.

On the external side of the gas-tight runner 4 there is provided a sealing surface 5, (shown on the left of the centre line as a radial surface, and on the right as an axial surface). By means of this surface 5, and a seal 12 co-operating therewith, the casting mould is connected to a movable feed tube 11, disposed in a space 101 of a sealed chamber 10 containing molten metal.

When the casting is effected under differential pressure action e.g. under counter-pressure, or in vacuum, the casting mould is disposed in the space 91 of a sealed chamber 9.

When the top shaping block 2 is gas-tight in the zone of the overflow-feed conduit 6, it is possible to do without the distance insert 7, without this changing substantially the technical solution provided by the illustrated embodiment of the invention.

The casting mould operates as follows: After the connection of the casting mould to the movable feed tube 11 by the seal 12, (between the spaces 101 and the mould cavity 3 in the case of low-pressure casting, or between the spaces 101 and 91 in the case of casting under counter-pressure or in vacuum), there is produced a gas pressure difference, so that the mould cavity 3 is then filled with molten metal. Simultaneously, molten metal enters through the holes 71 of the distance insert 7 to the lining conduit 8 where, because of the small thickness, it solidifies quickly and the initially gas-permeable overflow feed conduit 6 forms a gas-tight layer.

After the filling of the cavity 3 with molten metal and the formation of a gas-tight layer in the lining conduit 8, in the space 111 formed between the tube 41 and the movable feed tube 11 there is supplied a gas pressure, by its connection with the space 101 of the sealed chamber 10 with molten metal. As a result of this pressure, the molten metal from the gating system returns to the sealed chamber 10 and its level in the overflow-feed conduit is set to the level of the overflow. The magnitude of this pressure is such that it balances the action of all remaining forces in the plane of the overflow or, if necessary, it provides an additional pressure. After the removal of the molten metal from the gating system, upon retaining the pressure there, or after the solidification of the casting, the mould is removed, the formed casting is taken out, and a new cycle of casting is prepared.

Claims

1. A casting mould adapted for bottom charging under differential pressure action and comprising: shaping blocks which define a casting cavity, and a gating system for suppying molten metal to the casting cavity, in which the gating system comprises: a gas-tight runner which is connected to the casting cavity by means of an overflow system conduit, said conduit being arranged to be gaspermeable during charging of the casting cavity with molten metal and to become substantially gas-tight after filling of the casting cavity has been completed.

2. A casting mould according to claim 1, in which the feed conduit is arranged below an upper one of the shaping blocks and comprises a conduit lining adjacent to an underside of the upper shaping block, and a spacer insert.

3. A casting mould according to claim 2, in which through-holes are formed in said spacer insert.

4. A casting mould according to claim 2 or 3, in which the spacer insert is made of the same material as the upper shaping block.

5. A casting mould according to anyone of the preceding claims, in which an outer surface of the runner is received in sealed manner in a bottom aperture formed in the mould, thereby to connect the casting mould to a sealed chamber for containing molten metal.

6. A casting mould according to claim 5, including a pressure die-casting apparatus connected to the casting mould via said runner.

7. A casting mould according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.