Apparatus and method for the die casting in the semisolid state of objects made of brass, bronze, alloys of aluminum, magnesium and light alloys and the like
An apparatus for the die casting in the semisolid state of objects made of brass, bronze, alloys of aluminum, magnesium and light alloys and the like, includes an upper die part adapted to be mated with a lower die part, the mating between the upper die part and the lower die part forming a casting cavity, a furnace being arranged below the lower die part and being provided with a duct for feeding liquid metal which connects to the casting cavity. The upper die part is provided with a cavity in which a forging piston can move freely, the piston accommodating internally a flow control plunger, and having, between the upper die part and the lower die part, circumferentially around the part to be cast, a vacuum channel connected to the casting cavity by at least one venting channel.
1. An apparatus for die casting in a semisolid state of objects made of brass, bronze, alloys of aluminum, magnesium and light alloys, the apparatus comprising: a die constituted by an upper die part adapted to be mated with a lower die part, a mating between said upper die part and said lower die part forming a casting cavity, a furnace being arranged below said lower die part and being provided with a feed duct for feeding liquid metal which connects to said casting cavity, said upper die part being provided with a cavity in which a forging piston can move freely, said piston accommodating internally a flow control plunger, and further comprising, between said upper die part and said lower die part, circumferentially around a part to be cast, a vacuum channel connected to said casting cavity by means of at least one venting channel.
2. The apparatus according to claim 1 , wherein said upper die part comprises a channel for connection to a vacuum pump, which connects said vacuum channel to the outside.
3. The apparatus according to claim 1 , wherein said upper die part comprises a sensor for a level of the liquid metal in the casting cavity.
4. The apparatus according to claim 1 , wherein said forging piston comprises a channel for connection to a vacuum, in order to produce vacuum, said vacuum connection channel being arranged at an upper region of said forging piston.
5. The apparatus according to claim 1 , wherein said forging piston comprises air venting channels configured to be occluded by said flow control plunger in its stroke within said forging piston.
6. The apparatus according to claim 1 , wherein said at least one venting channel of said vacuum channel has a zigzag shape.
7. A method for die casting in a semisolid state of objects made of brass, bronze, alloys of aluminum, magnesium and light alloys, by an apparatus according to claim 1 , the method including the following steps:
closing said upper die part onto said lower die part and forming said casting cavity;
by means of said furnace, heating liquid metal contained therein;
creating vacuum in a vacuum channel of the forging piston and making the liquid metal rise in the feed duct to fill the casting cavity;
said vacuum creation step being provided by creating vacuum simultaneously at said vacuum channel of said forging piston and at said vacuum channel of said upper die part, with rise, by syringe effect, of said forging piston;
closing said feed duct by said flow control plunger;
making said forging piston descend in order to perform a forging step; and
opening the die and extracting the part.