Extrusion method and press with device to heat the leading end of hot aluminium ingots to be extruded

Abstract: Device to heat the leading end of aluminium ingots to be extruded when hot in extruder presses, with chambers containing the ingots arranged turret-wise with their axes parellel, the device being arranged in cooperation with the frontal end part of a chamber (12) which will cooperate with the extruder die, and in correspondence with the position for loading and readying an ingot (13), this position being located immediately upstream of the extrusion position. Method to heat the leading end (14) of a hot aluminium ingot (13) held in a chamber (12) located in a position to load and position an ingot immediately upstream of the extrusion position in a turret-type extrusion press, the leading end (14) being extracted from the chamber (12) and caused to protrude therefrom (12) and being then heated by induction and re-inserted thereafter in the chamber (12) immediately before the chamber (12) is placed in its extrusion position and the ingot (13) is extruded.

Description: This invention concerns a rotary turret extrusion press according to the preamble of claim 1. The invention concerns also an extrusion method according to the preamble of claim 7. A turret extrusion press of this type is disclosed in EP-A-0318631. This extrusion press comprises a turret with chambers, each of which is suitable to contain an ingot; the axes of the chambers lie parallel to each other, and the chambers are arranged symmetrically about an axis of rotation of the turret. Each chamber has its front end suitable to cooperate with the extrusion die when the chamber is in its extrusion position, and each chamber can move from a loading position, in which the ingot is inserted into the chamber, to an extrusion position owing to rotation of the turret. It is known that during the hot extrusion operation the temperature of the ingot rises from about 400°C at the beginning to 500°C at the end. This occurrence requires a greater initial thrust and a lesser final thrust since with an increase of the temperature it is necessary to reduce the extrusion pressure as a consequence. Various arrangements have been studied in trying to keep the extrusion capacity constant, that is to say, in trying to keep the extrusion at a high and optimum value. A first arrangement is to heat the ingot with conventional means to a greater extent in the part which will come in contact with the die at once and then to insert the ingot into the chamber just before the chamber is rotated to take up its extrusion position. This is a good arrangement theoretically but in actual practice entails the drawback that the movement and positioning times are such as to nullify the benefits. A second arrangement consists in cooling the trailing end of the ingot just before it is inserted in the chamber, but this arrangement too has not given good results and is also counterproductive from the point of view of energy. Trials have also been conducted with heating the leading end of the ingot with a burner as that end is inserted into the chamber, but these trials have also given bad results owing to the short length thus heated of the ingot and owing to the embrittlement of the chamber due to the increase of temperature of its walls caused by the heating. The present applicant has now found unexpectedly that it is possible to overcome the shortcomings of the state of the art and to achieve a plurality of advantages by means of the turret extrusion press according to claim 1 and the pertaining method according to claim 7. The dependent claims disclose variants of the idea of the solution. According to the invention a hot ingot is inserted as usual into the chamber. Before that chamber is displaced from its loading position to the extrusion position, the ingot is caused to emerge by a desired length at the side where the chamber will cooperate with the extrusion die. That desired length is then lapped by a heating action obtained by induction for a desired time so as to produce an increase of temperature in that leading end zone of the ingot. When the ingot has been heated enough, it is thrust back into the chamber, and the chamber can be displaced so as to cooperate with the die and the extrusion can be started. The required heating of the leading end of the ingot is thus achieved a moment before that leading end comes into contact with the die and extrusion begins. The attached figure, which is given as a non-restrictive example, shows a possible section of an embodiment of the invention. A device 10 cooperates with a chamber 12 of a rotary chamber press when the chamber 12 is in the station or position for loading an ingot 13. The device 10 cooperates with the frontal part of the chamber 12, namely with the part of the chamber which thereafter is located directly in contact with the extrusion die. The chamber 12 is machined in a turret or rotor 11. Before the chamber 12 is moved from the position for loading the ingot 13 to a position of cooperation with the die for extrusion of the ingot 13, the ingot 13 is extracted forwards so that a tract of its leading end 14 protrudes from the chamber 12. This extraction may be performed by an auxiliary ram 22 or by the means which insert the ingot 13 into the chamber 12. The leading end 14 of the ingot 13 thus cooperate with an induction heater 15, which laps and heats the leading end 14. The induction heater 15 cooperates with a screening shield 17 and is supported and positioned in a container 16, which is held by a support 21 and is resiliently thrust by spring means 18 against the outer periphery of the chamber 12, thus enfolding the leading end 14. When the induction heater 15 has heated the leading end 14 enough, a thrust head 20 driven by a ram 19 displaces the ingot 13 axially until the leading end 14 is positioned wholly within the chamber 12. The thrust head 20 is dimensioned so as to rest on the edge of the chamber 12, thus ensuring that the leading end 14 of the ingot 13 coincides with the frontal face of the chamber 12 or is positioned slightly within the chamber so that the positioning and rotation operations can proceed correctly. The chamber 12 can now be rotated to cooperate with the extrusion die and the extrusion operation can begin. The extrusion operation will take place in optimum or almost optimum conditions owing to such partial heating of the ingot.

Claims: Extrusion press for the extrusion of hot aluminium ingots, the extrusion press comprising a turret (11) with chambers (12) each suitable for containment of an ingot (13), the axes of the chambers (12) being symmetrically arranged around an axis of rotation of the turret (11), each chamber having a frontal end suitable for cooperation with the extrusion die when the chamber (12) is in the extrusion position and each of the chambers (12) being movable from a loading position, in which the ingot (13) is inserted into the chamber (12), into the extrusion position by means of rotation of the turret (11), characterised in that means (22) are provided for displacing the ingot (13) axially within the chamber (12) into the loading position, the means (22) being suitable for positioning the ingot (13) in such a manner that the leading end (14) of the ingot (13) protrudes from the frontal end of that chamber (12), further means (19-20) being provided suitable for returning the ingot (13) from its protruding position into a position in which it is located wholly within the chamber (12) in the loading position, and in that the extrusion press includes a heating device (15) located in front of the frontal end of the chamber (12) in the loading position, the heating device (15) being capable of producing an increase of temperature in the protruding leading end (14) of the ingot (13) contained in that chamber (12), such increase resulting in a temperature of the leading end (14) of the ingot (13) which is higher than the temperature of the remaining part of the ingot (13). Extrusion press as in Claim 1, in which the heating device (15) is conformed as an induction heating body (15). Extrusion press as in Claim 1 or 2, in which the heating device (15) extends in front of the chamber (12) and substantially axially thereto so as to surround the leading end (14) of the ingot (13) protruding from the chamber (12). Extrusion press as in any claim hereinbefore, in which a thrust head (20) able to move axially to the ingot (13) is included axially to the induction heating body (15) and in front of that body (15). Extrusion press as in any claim hereinbefore, in which screening material (17) is included about the induction heating body (15) and outside that body (15). Extrusion press as in any claim hereinbefore, in which the induction heating body (15) is supported by a container (16) resiliently thrust by resilient means (18) against the outer periphery of the chamber (12) surrounding the leading end (14) of the ingot (13). Method to extrude hot aluminium ingots, the hot ingots (13) being held in chambers (12) of a rotatable turret (11), each of the chambers (12) having a frontal end suitable for cooperation with the extrusion die when the chamber (12) is in the extrusion position, a hot ingot (13) being inserted in a chamber (12) when the chamber (12) is in the loading position, the leading end (14) of the hot ingot (13) in the chamber (12) being further heated and the turret (11) being rotated in order to move the chamber (12) with the hot ingot (13) into the extrusion position, the ingot (13) then being extruded, characterised in that the leading end (14) of the hot ingot (13) is extracted from the chamber (12) and caused to protrude from the frontal end of the chamber (12) prior to the further heating of the leading end (14) of the hot ingot (13), the leading end (14) of the hot ingot (13) being further heated by means of induction heating and the leading end (14) of the hot ingot (13) being re-inserted thereafter into the chamber (12) immediately before the chamber (12) is moved into the extrusion position.

Inventors: CRISTIANI GIANCARLO, D ODORICO DANILO, CRISTIANI, GIANCARLO, D'ODORICO, DANILO
Applicants: DANIELI OFF MECC, DANIELI & C. OFFICINE MECCANICHE S.P.A.
Application year: 1990
Main classification: B21C29
IPC codes: B21C33, B21C29