ES2632181T3 - Device and procedure for obtaining semi-solid sludge - Google Patents

Abstract

Equipment for manufacturing metal parts by injection, comprising a vibrating table, a high pressure injector equipment (5) and a device for obtaining semi-solid sludges, characterized in that the device for obtaining semi-solid sludges comprises a crucible (1, 2), which It comprises at least one fixed part (1), which is fixed to the vibrating table, and at least one mobile part (2) that can be attached to the fixed part (1) by means of fixing means (3).

Description

DESCRIPTION

Device and procedure for obtaining semi-solid sludge

Technical Field of the Invention

The present invention relates to a device and a method for obtaining semi-solid sludge, which has application in the metallurgical industry, and more specifically in the field of manufacturing of metal parts 5 by means of any semi-solid state injection process in which use closed vessels for the preparation of materials, preferably to avoid having a non-dendritic structure.

Background of the invention

The conformation of materials by injection in a semi-solid state can be considered as a process halfway between forming by molding and forming in a solid state. Thus, the conformation of 10 aluminum alloys in a semi-solid state is a process that includes elements of several classic forming techniques, such as high pressure injection and squeeze casting and forging.

Among the advantages of forming in a semi-solid state, it is worth mentioning the fact that it allows a great freedom in the design of the mold and a high production speed, as well as a high metallurgical quality and mechanical properties superior to those of permanent mold casting or cast iron injected at high pressure. fifteen

The interest of these techniques of forming in a semi-solid state lies in the need to produce new parts and components with fewer defects and at a lower cost, and is based on the thixotropy that certain materials present, whereby the rheological properties of the materials when they coexist a liquid phase and a spherical solid phase, allow a low viscosity even with solid fractions of 0.6 (as much as one) depending on the rate of deformation of the material. Hence its name in English as rheocasting. twenty

At present, various manufacturing processes are known in semi-solid state that, unlike forged or cast iron processing, allow to obtain a structure of non-dendritic material that allows to reach a material with thixotropic characteristics. For this purpose, different technologies have been developed, including the following:

- Passive agitation. 25

- SRC (Shearing Cooling Rolling) process.

- Ultrasound treatment.

- Treatment by electric shocks.

- Fast solidification methods such as the Osprey procedure.

- Air SlipTM. 30

- SIMA (Strain Induced Melt Activated).

- RAP (Recrystalization and Partial Melting).

- Electromagnetic stirring (MHD).

- New RheoCasting (NRC).

- HITACHI Metals. 35

- Semi Solid Rheocasting (SSR ™).

- Continuous Rheoconversion Process (CRP).

- Direct Thermal Method (DTM).

- Sub Liquidus Casting (SLC ™).

- Swirl Enthalpy Equilibration Device (SEED). 40

- SLC developed by THT Presses.

In several of these technologies, the agitation forces the liquid to be poured into a cylindrical or truncated conical crucible or vessel, and after reaching the semi-dendritic semi-solid structure, the billet must be extracted, that is to say the semi-solid mass, also called, slug or semi-solid mud . At this point in the process there are different problems that have as a negative consequence the fact that oxides are generated in the surface, drag or material that remains 45

adhered to the surface of the vessel. Keep in mind that aluminum alloys oxidize almost immediately upon contact with air.

One of the processes that use vessels for the manipulation of the material is the process called SEED (Swirl Enthalpy Equilibration Device) mentioned above, on which the description of the problem presented by any process that requires a closed vessel for the preparation of the material is based 5 non-dendritic structure material, especially in the case of cylindrical or frustoconical vessels.

The characteristics of the SEED injection process in a semi-solid state are the following:

- It is based on a liquid material (re-fusion).

- Requires a lower degree of control over other techniques.

- Offers a relatively wide process window. 10

- Reduces the tendency of the material to adhere to the mold.

- Wide range of billet weight (2-8 kg).

- Wide range of alloys that can be used:

 - Casting alloys: 319, 356, 357, 514, 206.

 - Forgeable alloys: 6061. 15

A schematic sequence of the current SEED process of manufacturing semi-solid sludge (billet) used in aluminum injection cells, for obtaining customized billets, is shown in Figure 1, and comprises the following sequential steps.

a) Melt aluminum by traditional procedures: melt and pour over maintenance furnace, also called a doser. Next, pour the aluminum onto monobloc cylindrical containers, called 20 crucibles. Each crucible is inclined to favor the spillage and reduce the generation of gases, as can be seen in the crucible of the state of the art that has been represented in Figure 2.

b) Shake the crucibles, usually on a vibrating table, and cool the aluminum until it reaches an adequate globular structure. The solid fraction will be approximately 50% depending on the percentage of Si, depending on the proximity to the eutectic point. 25

c) Optionally, after step b) the semi-solid sludge obtained before demolding can be drained.

d) Remove the crucible from the vibrating table and move it with the billet inside to the container of an HPDC (High Pressure Die Casting) high pressure injector equipment, henceforth the HPDC injector. Then, longitudinally remove the billet, for example in automated equipment by means of an abrupt movement of the robot or by means of an auxiliary piston, and deposit it in the HPDC injector container. At this point it is necessary to bear in mind that the billet cannot be broken to avoid the generation of oxides.

e) Push the billet or semisolid sludge with the HPDC injector piston to fill the steel mold.

In addition to these sequential stages represented in Figure 1, it is necessary to verify that there are no aluminum residues left in the crucible and if necessary it is necessary to clean them more vigorously to eliminate them. These aluminum remains can be oxides that deteriorate the next piece to be obtained in the process. Likewise, 35 standard stages of crucible preparation must be carried out, including cleaning, heating, etc. On the other hand it is necessary to mount and hold the crucible on the vibrating or stirring table, and it is necessary to apply by lubricating spray, usually boron nitride, on the crucible.

It is also convenient to carry out an auxiliary process for the preparation of the crucibles, which includes applying lubricant on the crucibles with a brush or gun, similar to how the paint is applied, and subsequently dried in the oven. Depending on the lubricant products, the application layers will be between 3 and 5, and logically, the application frequency varies depending on the applied layers.

As mentioned above and it becomes clear, all these stages, with the time and cost involved, are aimed at preventing the generation of oxides on the surface of the sludge and crucibles or vessels, as well as trawlers or material that sticks to the surface of the vessels. Four. Five

Description of the invention

A first aspect of the present invention relates to an equipment for manufacturing metal parts by injection as defined in claim 1.

A second aspect of the invention relates to a process for obtaining semi-solid sludges as defined in claim 4.

In the manufacturing processes of semi-solid sludges of the prior art, molten aluminum is poured into a monobloc cylinder or crucible, which is a container of refractory material that is used to melt a very high temperature material, while in accordance with the invention, the crucible is formed by two parts or 5 shells, which are molds in which metal objects are melted, by injection of molten metal, preferably semi-cylindrical, that is to say the invention proposes a crucible container in two halves. In this way, the demoulding of the semi-solid or billet is carried out transversely instead of longitudinally. In this way, the risks of breaking the billets when unmolding are eliminated and the billet is totally or partially adhered to the crucible. The crucible cleaning processes are also significantly reduced. 10

The crucible according to the invention comprises two half-shells or parts. A semi-pin fixed to the vibrating table and a semi-mobile movable. It is envisaged that there will be means for fixing the mobile shell to the fixed and to the vibrating table that allow the configuration of the crucible for pouring and solidification and that logically allow the mobile shell to be separated for demolding. According to a preferred embodiment, the fixing means are composed of a tilting clamp mounted articulated on the vibrating table and which can be coupled 15 on a perimeter flange of the movable half-tooth. Obviously, this is a concrete embodiment but this fixation could be done in multiple ways.

In demolding, the mobile shell is separated from the fixed shell and the billet is in the mobile shell that is moved to the injector piston. This movement can be done using a robot or any other type of automated installation. twenty

Description of the drawings

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description. By way of illustration and not limitation, the following has been represented: 25

Figure 1 shows a schematic view of the sequence of operations comprising an injection process in a semi-solid state of the art.

Figure 2 shows an elevation view of a crucible of the state of the art that can be used in the process represented in Figure 1.

Figure 3.- Shows a schematic view of the sequence of operations comprising an embodiment of the process for obtaining semi-solid sludge according to the invention.

Figure 4.- Shows an elevation detail of a bicoquilla crucible, comprising a fixed part and a moving part, comprising an embodiment of the device for obtaining semi-solid sludges of the invention.

Preferred Embodiment of the Invention

In view of the aforementioned figures, it can be seen that in one of the possible embodiments of the invention, one of the processes using vessels for handling the material is the process called SEED (Swirl Enthalpy Equilibration Device) mentioned above, in which based on the description of an embodiment of the invention, however, the invention is extensive and applicable to any process that requires closed vessels for the preparation of the material in a non-dendritic structure, especially cylindrical or frustoconical.

The invention comprises a crucible container in two halves usable in the manufacture of metal parts by means of any semi-solid injection process (e.g. SEED) in which closed vessels are used for the preparation of materials, preferably of non-dendritic structure.

The differences between the two types of crucibles, monobloc and bicoquilla, are the following:

The bicoquilla container must have uniform thicknesses in order to ensure a balanced heat evacuation that guarantees the uniformity of the globular structure throughout the entire billet. There are clear geometric differences between both types of containers because the bicoquilla container needs spaces to implant clamping systems between half-shells, clamping with the shaking table and claw-holder to manipulate the moving half-shell.

With this new vessel architecture (crucible), one of the half-shells is permanently attached to the vibrating table (stirring) and the other will be mobile. The mobile will have three positions:

1st position: Subject to the table and the other half-face at the time of pouring. fifty

2nd position: After it is released, transporting and depositing the billet on the HPDC injector container.

3rd position: Cleaning and preparation of the next cycle.

The semi-mobile mobile has a kind of grip plate that allows it to be grasped and manipulated by robot, manipulator or manually. Taking into account that the thicknesses must be uniform in the container, an insulator is inserted between the moving half-shell and the grip plate. Ideally. This grip plate must go in the upper part of the container, at a height that liquid aluminum / billet never reaches. 5

The bottom of the half-shells that comes into contact with the stir table can be opened or closed as appropriate because the drain hole is not required.

The cleaning process is much simpler in the bicoquilla system because the mobile half-face approaches the cleaner-lubricator head that is always accessible and in the same position.

The bicoquilla system does not require a lot of lubrication because the transverse demoulding of the semi-cruisers is very easy because it already has a natural demoulding. To the extent that we need less lubrication, the thickness of the oxide layer that surrounds the billet is less and the risk of displacing said oxides to the part in the mold filling is less.

The resulting process is as follows:

A) Melt aluminum by traditional procedures: melt and pour over maintenance furnace (also called a dispenser).

- Pour the aluminum on cylindrical bicoquilla containers (crucibles). The crucible tilts to favor spillage and reduce gas generation.

B) Shake the bicoquilla crucibles (on a vibrating table) and cool the aluminum until it reaches an adequate globular structure. The solid fraction will be approximately 50% depending on the percentage of Si (proximity 20 of the eutectic point).

C) Rotate the crucible until it is horizontal and separate the semi-mobile fork so that the billet is in it to transport it to the HPDC injector container.

D) Depositing the billet on the container is reduced to turning the half-shell and dropping the billet by rolling-gravity. Push the semi-solid billet with the piston of the HPDC injector to fill the steel mold. 25

Also, the process includes the following auxiliary stages:

- Standard process of preparation of crucibles: clean, heat and lubricate.

- Operation of assembling and fastening the crucible on the vibrating table (mixer).

The crucible container in two halves (half-shells) allows transverse demoulding of the billet and consequently

- Simplifies the lubrication process and reduces the thickness of the oxide layer generated on the skin of the billet. 30

- Eliminates the risks of breakage of the billets.

- Eliminates the risks that the skin of the billet is adhered to the container. Increase the quality of the pieces, the number of deteriorations is reduced.

By eliminating the longitudinal extraction of the billet, we reduce the risk that the billet is adhered to the crucible (totally or partially) reducing the interruptions caused by insufficient lubrication. In addition to the 35 interruptions, the cleaning processes of the container are significantly reduced, especially when the skin is adhered to the crucible.

The transport and discharge of the billet to the HPDC injector container is simplified and the risks of breaking the billet are reduced. This advantage will be more important as the size of the billets increases.

An important part of the lubrication and preparation processes of the crucibles are eliminated. The process becomes more linear and more efficient. As well as prior verification that there is no residue left in the crucible and the need to remove them.

Claims (6)

1.- Equipment for manufacturing metal parts by injection, comprising a vibrating table, a high pressure injector equipment (5) and a device for obtaining semi-solid sludges, characterized in that the device for obtaining semi-solid sludges comprises a crucible (1, 2 ), comprising at least one fixed part (1), which is fixed to the vibrating table, and at least one mobile part (2) that can be attached to the fixed part (1) by means of fixing means (3). 5 2. Equipment according to claim 1, wherein the fixing means (3) consist of an articulated clamp that allows the movable part (2) to be fixed to the fixed part (1). 3. Equipment according to any of the preceding claims, comprising a fixed part (1) and a moving part, both of semi-cylindrical configuration. 4. Procedure for obtaining semi-solid sludge, characterized in that it comprises using the equipment according to any of claims 1 to 3. 5. Method according to claim 4, comprising: A) melting aluminum and pouring said molten aluminum into the crucible formed by at least one movable part (2) and at least one fixed part (1), tilting the crucible to favor the spillage and decrease the generation of gases, B) stir the crucible and cool the aluminum, 15 C) rotate the crucible until it is horizontal and separate the movable part (2) so that a solid mass (4) obtained is housed in said movable part (2) for transport to a high pressure injector equipment (5), Y D) deposit the semi-solid mass (4) on the container of the high pressure injector equipment (5) by rotating the movable part (2) dropping said semi-solid mass (4) due to gravity, and pushing the semi-solid mass (4) with the piston of the high pressure injector equipment (5). twenty 6. Method of forming materials comprising obtaining semi-solid mud by the method according to any of claims 4 and 5.