TECHNICAL FIELD

The subject-matter of the invention is a hybrid casting shell mould with a sand core, a main sand core, riser system, gating system, and a method for manufacture of the hybrid casting shell mould specifically for the manufacture of high-quality metal alloy castings.

BACKGROUND ART

The most well-known moulds and those made from sand. The manufacturing process for such moulds is equally well-known. According to that process sand moulds are usually made in flasks, and the method of compaction is manual or automated. Compaction is sometimes performed by pressurizing. Industry literature also mentions casting into shell moulds, which consists in pouring a molten alloy into thin-walled moulds made from a synthetic mixture of quartz sand with thermally hardened resin and/or hardener, with the help of a heated, metal pattern plate or a core box.

There is an existing patent claim, registered in Poland under no 326238, titled A Casting Mould and a Method for its Manufacture”, where a flask casting mould consists of two flask halves equipped with transport-aiding components on automatic moulding devices. The flask contains a sand mould with cores, a pouring cup, and a gate. For such moulds to enable complex castings, including aluminium ones, and to avoid costly finishing operations connected with the gate and the pouring cup, and to simultaneously ensure good core venting, the flask has a recess within the parting surface, which spreads at least partially along the length and width of one side of the flask, wherein the recess area contains the outlet of the pouring cup and the gate.

There is an existing patent claim, registered in the USA under no 8,302,668Bl, for a hybrid set of cores for casting, where the said hybrid set of cores for casting includes a ceramic core part, a refractory metal core part and a plate located between the ceramic core part and the refractory core part. The ceramic core part includes a gutter. The refractory core part is in the gutter, which is seen in the examples covered in the patent. AIM OF THE INVENTION

The aim of the invention is to design and develop a new hybrid metal shell mould specifically for the manufacture of high-quality metal alloy castings. And method for the manufacture hybrid metal shell mould, using a special selection of materials and unique stages. The hybrid mould and its manufacture combine several processes using different materials. Those materials and processes combined result in manufacture of completely new mould structures and, thus, castings with better properties, as well as in lowering manufacturing costs. However, the main objectives for the hybrid mould are sand savings through lowering the wall thickness of the mould, lowering the amount of sand in internal circulation, utilization of the metal hybrid shell as a chill and obtaining better quality castings as well as improved surface finish. What is more, it is possible to automate the whole process, therefore lowering the standard cost of manufacture.

DISCLOSURE OF THE INVENTION

The hybrid mould specifically for the manufacture of metal alloy castings, comprises minimum two hybrid parts and a main sand core, characterized in that the hybrid cope and drag respectively comprise a thin metal shell and a shell for the sand core of the mould shell; additionally, the shell has holes for shooting in core sand, gassing of the core and venting the casting, whereby the hybrid cope and drag and the main sand core are connected structurally with a negative draft for holding the main sand core in the mould shell.

Preferably, the thickness of the metal shell is from 4 mm to 80 mm, depending on the building material, the geometry of the casting, but predominantly 8 mm for aluminum alloys.

Preferably, the thickness of the cope and drag sand core shell is from 6 mm to 80 mm and it depends on the casting structure, the geometry of the casting and the alloy type.

Preferably, the negative draft is minimum 1° to keep the sand shell in the metal shell. Preferably, the main sand core contains additional metal chills.

Preferably, the building material for the metal shell is an aluminium alloy, steel, cast steel, cast iron, copper, or brass. The method for the manufacture of a hybrid mould specifically for metal alloy castings characterized in that by this that for a given casting, the mould is designed and made as a metal shell in two parts: the cope and the drag; then, the two sand core shell mould components are made, the cope and the drag; the casting pattern and the cope and drag metal shells are placed on a pattern plate, core sand is shot inside under a pressure between 0.5 MPa and 12 MPa and, depending on the complexity of the structure, the geometry of the casting the area between the pattern, metal shell and the core sand shot inside is hardened by a gas blow under a pressure between 0.5 MPa and 12 MPa or hot air of a temperature between 20°C to 120°C depending on the binder used, and when the sand has hardened, the pattern is removed, whereby the sand core shell cope and drag are made up by the hybrid mould parts the cope and drag , subsequently, depending on the casting structure, when making the sand core shell cope and drag, metal chills are placed inside of them , and next, the riser cores and the sprue core are made from core sand; after that, when all the parts are made, i.e., the hybrid cope, hybrid drag, main sand core, riser cores and sprue core, they are set into place with casting adhesives, or using an interference fit, or they are clamped to form a complete hybrid mould using standard clamps.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject of the invention is shown in drawings, where Fig. 1 shows a longitudinal section of the hybrid mould, Fig. 2 shows the top view of the hybrid mould, Fig. 3 cross sections in a bottom view of the hybrid mould, Fig.4 an isometric projection of the hybrid mould.

MODE FOR CARRYING OUT THE INVENTION

The hybrid mould specifically for the manufacture of metal alloy castings, according to the invention, comprises minimum two parts, thin metal shell cope and drag (1, 2) sand core shell cope and drag (5, 6) for the mould shell, and a main sand core (3), additionally, the shell (1, 2) has holes ( 13) for shooting in core sand, gassing of the core and venting the casting, whereby the metal shell cope (1 ) and the sand core shell cope (5) form a hybrid — the mould cope (1, 5); and the metal shell drag (2) and the sand core shell (6) form a hybrid — the mould drag (2, 6), whereas the mould cope (1 , 5) and the mould drag (2, 6) and the main sand core (3) are structurally connected with a negative draft (15), which holds the main sand core (3) in the shell thus creating a hybrid mould, where the thickness of the metal shell (1, 2) is from 4 mm to 80 mm, depending on the building material, the geometry of the casting but predominantly 8 mm for aluminum alloys, the thickness of the cope and drag sand core shell (5, 6) is from 6 mm to 80 mm and it depends on the casting structure and the alloy type, the negative draft (15) is minimum 1° and it hold the main sand core (3) in the mould core shell (1, 5) and the mould drag (2, 6); the main sand core (3) for the mould has additional metal chills fitted; the building materials for the metal shell (1 , 2) are aluminium alloys, steels, cast steels, cast irons, copper, or different types of brass, whereas the example shows a steel mould made; prototype parts have been cast and trial runs performed.

The method for the manufacture of a hybrid mould specifically for metal alloy castings is characterised by this that for a given casting (4), the mould is designed and made as a metal shell in two parts: the cope (1 ) and the drag (2); then, the two sand core shell mould components are made, the cope (5) and the drag (6); the pattern (14) for the casting (4), and the cope and drag metal shells (1 or 2) are placed on a pattern plate, core sand is shot inside through holes (13) under a pressure between 0.5 MPa and 12 MPa and, depending on the complexity of the structure, the geometry of the casting the area between the pattern (14), metal shell and the core sand shot inside is hardened by a gas blow under a pressure between 0.5 MPa and 12 MPa or hot air of a temperature between 20°C to 120°C depending on the binder used, and when the sand has hardened, the pattern (14) is removed, whereby the sand core shell (5 or 6) with the metal shell (1 or 2) form the hybrid components of the mould: the cope (1, 5) and the drag (2, 6), and, subsequently, depending on the casting (4) structure, when making the sand core shell cope (5) and drag (6), metal chills are placed inside of them, and next, the riser cores (10, 11) and the sprue core (12), the main sand core (3) are made from core sand; after that, when all the parts are made, i.e., the hybrid cope (1, 5), hybrid drag (2, 6), the main sand core (3), riser cores (10, 11) and sprue core (12), they are set into place with casting adhesives, or using an interference fit, or they are clamped to form a complete hybrid mould using standard clamps.

The hybrid mould prepared in such a way is ready to be filled with a metal alloy.