EXTRUSION PROCESS

The present invention relates to an injection device, particularly for aluminum extrusion processes, and to an extrusion process, particularly for the extrusion of aluminum, that can be obtained by means of said injection device.

During the process for extrusion of molten aluminum, it is known in the background art to inject aluminum in the liquid state between two contrarotating casting rollers so as to extrude it while it cools in contact with said rollers in the shape of a slab.

The productivity of this method is tied closely to the rotation rate of the casting rollers, which in turns in turn depends on the cooling rate of the aluminum in contact with their lateral surfaces.

In order to ensure correct cooling, the casting rollers are provided generally with an internal cooling system, typically using water, which allows the cooling of their lateral surfaces and consequently allow the hardening of the liquid aluminum into a slab with a width and a thickness that can vary depending on the specific requirements.

In order to allow the easiest possible shaping of the aluminum, said aluminum must make contact with the casting rollers in its liquid state as much as possible.

The heating of the injector, which is responsible for injecting the liquid aluminum between the two casting rollers, is therefore a fundamental operation.

This heating, which is essential during the initial steps of the process, since in its absence the liquid aluminum would harden before it reached the casting rollers, can occur generally in various ways:

- manually, by means of a flame,

- by injection of hot air (between 500°C and 600°C) by means of fans, - by installation of electrical resistors inside an injector supporting deck.

Extrusion processes of the known type are not free from drawbacks, which include the fact that since the state transition occurs in an uncontrolled environment, the aluminum hardens in the presence of oxygen, which leads to the forming of a layer of oxide both on the casting rollers, reducing the capacity for exchanging heat with the aluminum itself, and on the final product.

In particular, the oxide layer that is generated between the jackets of the casting rollers and the aluminum, by slowing the hardening process, forces the rollers to slow down the rotation rate and therefore leads to a reduction of the productivity level of the entire extrusion process.

Moreover, another drawback of the methods of the known type, linked to the forming of the above-cited aluminum oxide layer, resides in the fact that there are frequent machine downtimes so as to allow the operators to clean the jackets of the casting rollers so as to return the production capacity to its nominal value.

The aim of the present invention is to provide an extrusion process and an injection device that obviate the drawbacks cited above simply and effectively.

This aim, as well as other objects that will become more apparent hereinafter, are achieved by an injection device, particularly for aluminum extrusion processes, comprising at least one injector body adapted to inject liquid metal between two contrarotating casting rollers with parallel axes and at least one supporting deck adapted to support said at least one injector body for its positioning proximate to said casting rollers, so as to be oriented toward the space formed between said casting rollers, characterized in that it comprises means for injecting inert gas which are associated with said supporting deck and adapted to inject inert gas substantially at at least one of the points of contact of said liquid metal with said casting rollers for the hardening of said liquid metal in contact with said casting rollers in the absence of oxygen.

Furthermore, the above-cited aim and objects are achieved by an extrusion process, particularly for the extrusion of aluminum, comprising the injection of liquid metal between two contrarotating casting rollers with parallel axes by using at least one injector body associated with at least one supporting deck to arrange it proximate to said casting rollers in such a manner as to be oriented in the direction of the space formed between said casting rollers, characterized in that it comprises the injection of inert gas substantially at at least one of the points of contact of said liquid metal with said casting rollers for the hardening of said liquid metal in contact with said casting rollers in the absence of oxygen.

Further characteristics and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of the injection device according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a top plan view of the injection device according to the invention, arranged between the casting rollers in an aluminum extrusion process;

Figure 2 is a sectional view of the injection device shown in Figure 1, along the sectional plane II-II;

Figure 3 is an enlarged- scale view of a detail of the injection device shown in Figure 2.

With reference to the cited figures, the injection device, particularly for aluminum extrusion processes, generally designated by the reference numeral 1 , comprises at least one injector body 2, adapted to inject liquid metal, specifically aluminum, between two contrarotating casting rollers 3 and 4 with parallel axes.

Moreover, the device 1 also comprises a supporting deck 5 that is adapted to support the injector body 2 to arrange it proximate to the casting rollers 3 and 4 so as to be oriented in the direction of the space formed between them.

In the proposed embodiment, heating means are associated with the supporting deck 5 and are adapted to supply heat to the injector body 2 so as to keep the metal in the liquid state.

More precisely, said heating means comprise one or more electrical resistors 6 and 7 which are accommodated inside the supporting deck 5 and are controlled manually by the operator so as to manage and control the temperature of the liquid aluminum.

According to the invention, means 8 for injecting inert gas are provided which are associated with the supporting deck 5 and are adapted to inject inert gas, which can be constituted by argon or nitrogen, substantially at at least one of the points of contact of the liquid metal with the casting rollers 3 and 4 for the hardening of said liquid metal in contact with the casting rollers 3 and 4 in the absence of oxygen.

More precisely, the injection means 8 are oriented so as to direct the inert gas within the spaces formed between each one of the lateral surfaces 9 and 10 of the casting rollers 3 and 4 and one end with a converging profile 11 of the injector body 2 such that it is inserted between said lateral surfaces 9 and 10.

Advantageously, the injection means 8 comprise at least one first nozzle 12, which is associated directly with the supporting deck 5 so as to inject the inert gas at a first casting roller 3, and at least one second nozzle 13, which is associated with a supporting bar 14 that is integral with the supporting deck 5 so as to inject the inert gas at a second casting roller 4.

Conveniently, the first nozzle 12 is supplied by a first feeder channel 15 that is provided inside the supporting deck 5 and the second nozzle 13 is supplied by a second feeder channel 16 that is provided inside the supporting bar 14.

More precisely, in order to operate along the entire extrusion width, there is a plurality of first nozzles 12 associated with the supporting deck 5 and supplied by means of the first feeder channel 15 and a plurality of second nozzles 13 associated with the supporting bar 14 and supplied by means of the second feeder channel 16.

Furthermore, means for adjusting the orientation, flow-rate and injection rate of the injection means 8 can be provided.

The extrusion process, particularly for the extrusion of aluminum, that can be provided with the device 1 described above or with other devices that are within the protective scope of the present invention comprises the injection of liquid metal between the two casting rollers 3 and 4 and the injection of inert gas substantially at at least one of the points of contact of the liquid metal with the casting rollers 3 and 4 for the hardening of the liquid metal in contact with the casting rollers 3 and 4 in the absence of oxygen.

In practice it has been found that the injection device, particularly for aluminum extrusion processes, and the extrusion process, particularly for extruding aluminum, according to the invention, fully achieve the intended aim, since they allow the aluminum to harden in the extrusion process in the absence of oxygen.

In this manner, no layer of oxide is formed, so as to ensure an optimum heat exchange between the jackets of the casting rollers and the aluminum.

These advantages lead to an increase in productivity in the order of

6%.

The injection device particularly for aluminum extrusion processes and the extrusion process particularly for extruding aluminum thus conceived are susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

All the details may further be replaced with other technically equivalent elements. In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

The disclosures in Italian Patent Application No. MT2012A001688 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.