Apparatus and method for forging

Abstract

An apparatus (1) for the semi-solid state forging of metal objects, comprises an upper half-mold (18; 180), a lower half-mold (16; 160), a furnace (20), furnace pressurizing means suitable for applying pressure to the liquid metal contained in the furnace so as to cause the injection of the liquid metal into a mold cavity (22; 220), at least one air suction duct (28; 280) communicating with the mold cavity and connectable to air suction means (30), a shutter device (32; 320) cooperating with the air suction duct, and a forging actuator (34). At least one portion of the upper half-mold is connected to the forging actuator (34) so as to obtain at least one forging male (36; 360).

Description

"APPARATUS AND METHOD FOR FORGING"DESCRIPTION

[0001] The present invention relates to an apparatus and a method for the semi-solid state forging of metal obj ects .

[0002] From the prior art the process of forging by plastic deformation is known, wherein the metal to be forged is in the solid state and requires the use of a press of great force ; furthermore , it is not possible to make obj ects having cavities and inserts .

[0003] Forging processes and apparatuses are also known, which use a mold formed by an upper hal f-mold that couples to a lower hal f-mold so as to form a mold cavity . The mold cavity is filled with metal in the liquid state by means of low pressure or by gravity .

[0004] In low-pressure forging processes , a furnace containing metal in the liquid state is typically used below the lower half-mold, which is pressuri zed so as to cause the metal to rise into the mold cavity . The forging takes place by means of a forging piston sliding inside the upper hal f-mold which exerts pressure on the metal during solidi fication, which corresponds to the pressure applied to the surface of the metal in the furnace .

[0005] The forging technique employing a forging piston sliding inside the upper hal f-mold entails a lateral forging of the mold cavity, which does not allow to havethe entire piece forged .

[0006] For the known forging techniques , in particular low- pressure and gravity, it is not possible to use aluminum alloys with a silicon percentage lower than 5% .

[0007] It is known, however, that in order to achieve very high mechanical characteristics in terms of breaking load, yield load, elongation and hardness , alloys with a very low percentage of silicon and iron must be used and other elements , such as magnesium, chromium, nickel , copper, must be added .

[0008] The main purpose of the present invention is to provide an apparatus and a method for the semi-solidstate forging of obj ects in brass , bronze , aluminum alloys , including those used for plastic deformation forging, such as magnesium and light alloys and the like , which allows to achieve metal obj ects free from porosity, free from burrs , and with high mechanical characteristics .

[0009] Within this aim, a further purpose of the present invention is to make an apparatus and a method for the semi-solid-state forging of metal obj ects which allows to eliminate , or at least to reduce , the metal riser produced by current forging processes .

[0010] A further purpose of the present invention is to make , in a single forging phase , also a plurality offorged pieces .

[0011] These purposes are achieved with an apparatus according to claim 1 and with a forging method according to claim 11 . The dependent claims describe preferred or advantageous embodiments of the apparatus and method according to the invention .

[0012] The characteristics and advantages of the apparatus and forging method according to the invention will in any case be evident from the following description of preferred embodiments thereof , given by way of example and not limitation, with reference to the accompanying drawings , wherein :

[0013] - Figure 1 is a perspective view of an apparatus for the semi-solid-state forging of metal obj ects , according to the invention, in an embodiment wherein the machine is provided with a single-cavity mold equipped with radial carriages ;

[0014] - Figure 2 is an axial section of the apparatus of Figure 1 , with the mold open and with the radial carriages in the retracted position;

[0015] - Figure 3 is an axial section of the apparatus with the mold open and the radial carriages in the advanced position;

[0016] - Figure 4 is an axial section of the apparatus with the mold closed and in the phase of air suction fromthe mold cavity;

[0017] - Figure 4a is an enlarged view of the mold of the apparatus of Figure 4 ;

[0018] - Figure 5 is an axial section of the apparatus with the mold closed and in the phase of filling the mold cavity;

[0019] - Figure 5a is an enlarged view of the mold of the apparatus of Figure 5 ;

[0020] - Figure 6 is an axial section of the apparatus with the mold closed, the mold cavity fi lled with liquid metal and the liquid metal supply duct closed;

[0021] - Figure 6a is an enlarged view of the mold of the apparatus of Figure 6 ;

[0022] - Figure 7 is an axial section of the apparatus during the forging phase ;

[0023] - Figure 7a is an enlarged view of the mold of the apparatus of Figure 7 ;

[0024] - Figure 8 is an axial section of the apparatus during the opening phase of the mold after forging;

[0025] - Figure 9 is an axial section of the apparatus during the extraction phase of the forged obj ect ;

[0026] - Figures 10- 17 show an apparatus according to the invention provided with a multi-cavity mold, in the forging process phases corresponding to Figures 2- 9 ;

[0027] - Figure 18 is an enlarged view of the mold ofthe apparatus of Figures 10-17.

[0028] In the following description, all directional references (for example, upper, lower, upward, downward, left, right, towards the left, towards the right, at the top, at the bottom, above, below, vertical, horizontal, clockwise and counterclockwise) are used only for identification purposes to assist the reader in understanding the described embodiments and do not create limitations, in particular regarding the position, orientation or use of the described embodiments.

[0029] The connection references (for example, fixed, coupled, connected and the like) must be interpreted broadly and may include intermediate elements between a connection of elements and a relative movement between elements. Therefore, the connection references do not necessarily imply that two elements are directly connected and in a fixed relationship to one another.

[0030] Furthermore, elements common to the different embodiments described will be denoted by the same reference numbers.

[0031] In said drawings, number 1 denotes an apparatus for forging according to the invention as a whole.

[0032] The apparatus 1 comprises a lower press plate 10, an upper press plate 12 and a mold 14; 140.

[0033] On the lower press plate 10 there is arranged alower half-mold 16; 160 of the mold which defines one or more lower impressions 16' ; 160' .

[0034] The upper press plate 12 supports an upper half-mold 18; 180 which defines one or more upper impressions 18' ; 180' .

[0035] Below the lower press plate 10 there is placed a furnace 20 containing metal in the liquid state.

[0036] The upper half-mold 18 and the lower half-mold 16 are mutually couplable to define a mold cavity 22; 220.

[0037] The furnace 20 is connected to the mold cavity 22; 220 by means of a liquid metal supply duct 24.

[0038] The apparatus 1 comprises furnace pressurizing means - not shown - adapted to apply pressure to the liquid metal contained in the furnace 20 so as to cause the injection of the liquid metal into the mold cavity 22; 220 through the supply duct 24.

[0039] To this end, the furnace 20 must preferably be of a hermetic type.

[0040] For example, the pressurization of the furnace is controlled by means of a proportional furnace pressurization valve 26.

[0041] The liquid metal contained in the furnace 20 is heated, for example, by means of electrical resistances.

[0042] For example, the temperature of the metal in the furnace exceeds by at least about 120°C the transitiontemperature of the alloy used from the solid state to the liquid state .

[0043] The apparatus 1 comprises at least one air suction duct 28 ; 280 communicating with the mold cavity 22 ; 220 and connectable to air suction means .

[0044] For example , the air suction means are constituted by a vacuum pump 30 .

[0045] The apparatus 1 further comprises a shutter device 32 ; 320 operable to switch between a first position, in which it allows the passage of air from the mold cavity 22 ; 220 to the air suction duct 28 ; 280 , a second position, in which it hermetically closes the air suction duct 28 ; 280 , and a third position, in which it hermetically closes both the air suction duct 28 ; 280 and the supply duct 24 .

[0046] The apparatus 1 further comprises a forging actuator 34 .

[0047] In one embodiment , the forging actuator 34 is made with a hydraulic cylinder supported by the upper press plate 12 .

[0048] According to an aspect of the invention, at least one portion of the upper hal f-mold 18 ; 180 which forms , together with the lower hal f-mold 16 ; 160 , at least one part of the figure of the obj ect 500 to be forged, is connected to the forging actuator 34 so as to obtain atleast one forging male 36; 360 axially movable, with the mold closed, between a raised filling position and a lowered forging position.

[0049] In other words, the forger element is not, as in the prior art, a piston sliding in the upper half-mold, but it is the upper half-mold itself or a movable portion thereof, which forms at least a part of the figure of the object 500 to be forged, that is, at least a part of the upper impression.

[0050] In particular, while the forger piston of the prior art, sliding in the upper half-mold, forms at most the metal riser of the piece to be forged (and therefore not a part of the figure of the piece, which is instead formed by the upper half-mold) , the forging male 36; 360 of the apparatus according to the invention is the part of the upper half-mold 18; 180 that forms the entire internal figure of the piece to be forged. As will be described below, in the embodiment of Figures 1-9, the upper half-mold 18 further comprises radial carriages 60 which form at least a part of the external figure of the piece to be forged.

[0051] When it is in the raised filling position, the forging male 36; 360 is at a height slightly higher than the final position in which it gives the exact shape of the object 500 to be made. In this raised position, themold cavity 22 ; 220 takes a greater volume than that of the obj ect to be made . This greater volume allows the introduction into the mold cavity of a quantity of liquid metal suf ficient to carry out the subsequent forging phase of the obj ect when the metal is in the semi-solid state .

[0052] The lowered forging position is the final position, in which the mold cavity corresponds to the shape of the obj ect to be made .

[0053] In one embodiment , the apparatus 1 comprises a control unit - not shown - operatively connected to the furnace pressuri zing means 26 , to the shutter device 32 ; 320 , to the air suction means 30 and to the forging actuator 34 .

[0054] The control unit is configured, when the mold is closed, to perform the following forging cycle :

[0055] - activate , while the shutter device 32 ; 320 is in the first position, the air suction means 30 for extracting air from the mold cavity and from the supply duct ;

[0056] - when the air has been extracted from the mold cavity and from the supply duct , move the shutter device 32 ; 320 from the first position to the second position;

[0057] - activate the furnace pressuri zing means 26 so as to cause the filling of the mold cavity, while theforging male 36; 360 is in the raised filling position;

[0058] - move the shutter device 32; 320 from the second position to the third position;

[0059] - actuate the forging actuator 34 so as to bring the forging male 36; 360 to the lowered forging position.

[0060] The forging method will in any case be described later in greater detail with reference to the accompanying figures.

[0061] In one embodiment, the air suction duct 28; 280 is obtained in the upper half-mold 18; 180 coaxially to the supply duct 24.

[0062] In other words, the air suction duct 28; 280 faces the supply duct 24, so that the shutter device 32; 320 moves from the second position to the third position by means of its axial translation.

[0063] In one embodiment, the shutter device 32; 320 comprises a shutter cylinder 32' , for example supported by the upper press plate 12.

[0064] In one embodiment, the shutter cylinder 32' has a shutter rod 32"; 320" slidingly housed in the air suction duct 28; 280 and ending with a shutter head 40; 400.

[0065] The shutter head 40; 400 comprises an annular sealing portion 42 adapted to create a seal with the end of the air suction duct 28; 280 open into the mold cavity 22; 220. Furthermore, the shutter head 40; 400 comprisesa tail portion 44 adapted to occlude the end of the supply duct 24 open into the mold cavity 22; 220.

[0066] In one embodiment, the air suction duct 28; 280 ends, towards the mold cavity, with a tapered lateral surface 28' which, when the shutter rod 32"; 320" is in the second or third position, is engaged by the annular sealing portion 42 of the shutter head 40; 400.

[0067] In one embodiment, the air suction duct 28; 280 is made of a tubular element, or jacket, inserted in the upper half-mold 18; 180.

[0068] In one embodiment, the air suction duct 28; 280 communicates with an air extraction tube 50 extending radially into the upper half-mold 18 and connectable to the air suction means 30.

[0069] Furthermore, in one embodiment, between the upper half-mold 18; 180 and the lower half-mold 16; 160, circumferentially around the object to be made, an air suction channel 52 is obtained communicating with the mold cavity by means of a plurality of vent channels 54. Said air suction channel 52 is also connectable to air suction means, for example a vacuum pump 56.

[0070] The presence of the air suction duct 28; 280, open towards the central area of the mold cavity 22; 220, and of the air suction channel 52, which communicates, through the vent channels 54, with the peripheral areasof the mold cavity 22; 220, ensures rapid and effective extraction of all air from the mold cavity and from the liquid metal supply duct, so as to facilitate the subsequent filling of the mold cavity with liquid metal.

[0071] In one embodiment, the air suction duct 28; 280 is connected to the air suction means 30 by means of a first proportional depression valve 30' .

[0072] In one embodiment, the air suction channel 52 is connected to the air suction means 56 by means of a second proportional depression valve 56' .

[0073] The proportional depression valves 30' , 56' are configured so as to ensure that the air is extracted from the mold cavity and from the supply duct, but the liquid metal is not sucked from the furnace.

[0074] In one embodiment, a vacuum control solenoid valve - not shown - connects a single vacuum pump to the air suction duct 28; 280 and to the air suction channel 52.

[0075] In one embodiment illustrated in Figures 1-9, the upper half-mold 18 comprises at least one radial carriage 60 (in the represented example the radial carriages 60 are two, diametrically opposed to one another) which forms, together with the forging male 36, a respective side portion 22' of the mold cavity 22, that is, of the upper impression.

[0076] The radial carriages 60 are used in particular tomake mold cavities provided with undercuts, which would otherwise not be obtainable with an upper half-mold made in one piece.

[0077] In this case, the forging male 36 corresponds to a central portion of the upper half-mold 18, axially movable with respect to the radial carriages 60.

[0078] For example, each radial carriage 60 is movable by means of a respective actuator 62 between an open position, spaced from the forging male to allow extraction of the forged piece, and a closed position, that is, of assembled half-mold, in which it is coupled to the forging male.

[0079] In one embodiment, the lower half-mold 16; 160 has an upper concave surface adapted to house with shape coupling the upper half-mold 18; 180. In this way, the lower half-mold 16; 160 contributes to radially retaining the radial carriages 60 in the closed position also during the forging phase.

[0080] In one embodiment illustrated in Figures 10-18, the upper half-mold 180 is a multi-cavity mold 180' , for the simultaneous making of multiple pieces. Each mold cavity 180' forms a forging male 360. The forging males 360 are connected to a common forging actuator 34.

[0081] In the example of Figures 10-18, the upper half-mold 180 comprises an upper plate 180a to which the forgingmales 360 are connected, for example by means of screws . The upper plate 180a is connected to the forging actuator 34 .

[0082] In one embodiment , the forging males 360 pass through a lower plate 180b of the upper hal f-mold 180 . The lower plate 180b is rigidly connected to the upper press plate 12 . The upper plate 180a with the forging males 360 is therefore slidable with respect to the lower plate 180b between the raised filling position and the lowered forging position .

[0083] In a peripheral portion of the lower plate 180b there are obtained the air suction channel 280 and the upper surfaces of the vent channels 54 . When the upper hal f-mold 180 is coupled to the lower hal f-mold 160 , said peripheral portion of the lower plate of the upper hal fmold is adapted to come into contact with a corresponding peripheral portion of the upper surface of the lower hal f-mold, so as to form the vent channels 54 communicating with the mold cavity .

[0084] The lower plate 180b has a central portion wherein, coaxially to the liquid metal supply duct 24 , at least a lower portion of the air suction duct 280 is obtained, within which the shutter rod 320" is slidingly housed .

[0085] In the example of Figures 10- 18 , the air suction duct 280 is also made of a tubular element 280 ' fixed,for example by means of screws, to the lower plate 180b. An upper portion of said tubular element 280' axially crosses the upper plate 180a.

[0086] In the example of Figures 10-18, the forging males 360 extend around the central portion of the lower plate 180b. When the upper half-mold 180 is coupled to the lower half-mold 160, the central portion of the lower plate 180b forms, with a corresponding central portion of the upper surface of the lower half-mold 160, a central region 220' of the mold cavity 220 which connects and supplies the peripheral regions 220" of the mold cavity that form the figures of the objects to be forged.

[0087] With particular reference to the example of the apparatus of Figures 1-10, the operation of the forging apparatus is as follows.

[0088] At the beginning of the forging cycle (Figure 2) , the forging male 36 may be, as a result of a previous forging cycle, or is brought, to the raised filling position .

[0089] The shutter device 32 is, or is brought, to the first suction position. The radial carriages, if present, are moved from the open position to the closed position (Figure 3) .

[0090] The upper half-mold 18 is coupled to the lower halfmold 16, maintaining the forging male 36 in the raisedfilling position so as to form a mold cavity 20 having a greater volume than the volume of the object to be made 500 (Figures 4, 4a) .

[0091] The air suction from the air suction duct 28 and, if present, from the air suction channel 52 is then performed, so as to create a vacuum in the mold cavity and in the supply duct.

[0092] At this point (Figures 5, 5a) , the shutter device 32 is translated to the second position, in which it hermetically closes the air suction duct 28.

[0093] Having extracted all the air from the mold cavity and from the supply duct, the furnace pressurizing means are activated so as to fill the mold cavity with the liquid metal coming from the furnace.

[0094] Once the mold cavity has been filled, the shutter device is translated to the third position, in which it hermetically occludes the supply duct (Figures 6, 6a) .

[0095] At this point, the forging actuator is actuated so as to bring the forging male to the lowered forging position (Figures 7, 7a) .

[0096] At the end of the forging phase, the mold can be opened (Figure 8) and the extraction of the forged object 500 can be carried out (Figure 9) .

[0097] It should be emphasized that the air suction phase from the mold cavity and from the supply duct isperformed, thanks to the air suction control solenoid valves , in such a way as to prevent the metal contained in the furnace from rising back into the supply duct until it reaching the mold cavity .

[0098] During semi-solid state forging, the speci f ic pressure on the piece to be forged may be greater than 200 Kg / cm2, for example between 200 and 700 Kg / cm2.

[0099] The temperature of the mold, for example heated by electrical resistances , may vary from 200 to 400 ° C, in order to allow the metal in the mold cavity to maintain the semi-solid state .

[0100] The temperature of the metal in the pressuri zed furnace is preferably about 120 ° C higher than the transition temperature from solid to liquid of the alloy used .

[0101] The operating method of the multi-cavity apparatus 1 of Figures 10- 18 is the same as that described above for the single-cavity apparatus .

[0102] The invention allows to make obj ects with internal cavities and using a much lower force compared to plastic deformation forging .

[0103] It is evident from what has been described above that , unlike the forging methods of the prior art employing a central forger piston, the proposed apparatus and forging method allow to avoid, or signi ficantlyreduce , the formation of the metal ri ser .

[0104] Thanks to the air suction from the mold cavity and from the supply duct , the filling time of the mold cavity is signi ficantly lower compared to other known systems . For example , the filling time of the mold cavity is usually between 10 and 40 seconds , whereas with the apparatus and forging method according to the invention the filling time of the mold cavity can be reduced to less than 10 seconds .

[0105] The signi ficant reduction of the filling time of the mold cavity prevents the thin parts of the piece from solidi fying before forging .

[0106] The proposed apparatus and forging method allow the forging of obj ects in bronze , brass , magnesium, aluminum alloys , including those used for plastic deformation forging, light alloys and the like .

[0107] To the embodiments of the apparatus and forging method according to the invention, an expert in the field, to meet contingent needs , may make modi fications , adaptations and replacements of elements with others functionally equivalent , without departing from the scope of the following claims . Each of the features described as belonging to a possible embodiment may be implemented independently of the other embodiments described .

Claims

CLAIMS1. An apparatus (1) for the semi-solid state forging of metal objects, comprising:- a mold (14) , comprising:- an upper half-mold (18; 180) ,- a lower half-mold (16; 160) , the upper half-mold and the lower half-mold being mutually couplable to define a mold cavity (22; 220) ,- a furnace (20) arranged below the lower half-mold (16;160) and connected to the mold cavity (22; 220) by means of a liquid metal supply duct (24) ; furnace pressurizing means suitable for applying pressure to the liquid metal contained in the furnace so as to cause the liquid metal to be injected into the mold cavity (22; 220) through the supply duct (24) ;- at least one air suction duct (28; 280) communicating with the mold cavity and connectable to air suction means(30) ;- a shutter device (32; 320) operable to switch between a first position, in which it allows the passage of air from the mold cavity (22; 220) to the air suction duct(28; 280) , a second position, in which it hermetically closes the air suction duct (28; 280) , and a third position, in which it hermetically closes both the air suction duct and the supply duct (24) ;- a forging actuator (34) , wherein at least one portion of the upper half-mold forming, together with the lower half-mold, at least one part of the figure of the object to be forged is connected to said forging actuator (34) so as to obtain at least one forging male (36; 360) axially movable, with the mold closed, between a raised filling position, in which the mold cavity takes a greater volume than that of the object to be made, and a lowered forging position, in which the mold cavity corresponds to the shape of the object to be made.

2. The apparatus according to claim 1, comprising a control unit operatively connected to the furnace pressurizing means, to the shutter device (32; 320) , to the air suction means (30) , and to the forging actuator (34) and configured, when the mold is closed, to: activate, while the shutter device is in the first position, the air suction means (30) for extracting air from the mold cavity and the supply duct;- move the shutter device (32) from the first position tothe second position;- activate the furnace pressurizing means so as to cause the mold cavity to be filled, while the forging male (36; 360) is in the raised filling position;- move the shutter device (32) from the second position to the third position;- actuate the forging actuator (34) so as to move the forging male to the lowered forging position.

3. The apparatus according to claim 1 or 2, wherein the air suction duct (28; 280) is obtained in the upper halfmold coaxially to the supply duct (24) .

4. The apparatus according to claim 3, wherein the shutter device (32) comprises a shutter cylinder (32' ) having a shutter rod (32"; 320") slidingly housed in the suction duct (28; 280) and ending with a shutter head (40; 400) comprising an annular sealing portion (42) suitable for creating a seal with the end of the suction duct and a tail portion (44) suitable for occluding the supply duct end open into the mold cavity.

5. The apparatus according to claim 3 or 4, wherein the suction duct (28; 280) communicates with an air extraction tube (50) extending radially into the upper half-mold (18; 180) .

6. The apparatus according to any one of the preceding claims, wherein an air inlet channel (52) is obtainedbetween the upper half-mold and the lower half-mold, circumferentially around the object to be made, communicating with the mold cavity by means of a plurality of vent channels (54) and connectable to air suction means (56) .

7. The apparatus according to any one of the preceding claims, wherein the upper half-mold is a multi-cavity mold, wherein each mold cavity forms a forging male (360) , and wherein the forging males are connected to a common forging actuator (34) .

8. The apparatus according to any one of the preceding claims, wherein the upper half-mold comprises at least one radial carriage (60) forming, together with the forging male, a respective side portion (22' ) of the mold cavity (22) , the forging male (36) being axially movable with respect to said at least one radial carriage (60) .

9. The apparatus according to any one of the preceding claims, comprising at least a first proportional depression valve (30' ) for controlling the suction of air from the suction duct (28; 280) .

10. The apparatus according to any one of claims 6-9, comprising at least a second proportional depression valve (56' ) for controlling the suction of air from the suction channel (52) .

11. The apparatus according to any one of the precedingclaims, wherein the forging male (36; 360) is suitable for forming the entire internal figure of the object to be forged.

12. A method for the semi-solid state forging of metal objects by means of an apparatus according to any one of the preceding claims, comprising the steps of: a) positioning the forging male in the raised filling position; b) positioning the shutter in the first suction position; c) closing the upper half-mold onto the lower half-mold by maintaining the forging male in the raised filling position so as to form a mold cavity having a greater volume than the volume of the object to be made; d) performing the air suction so as to create vacuum in the mold cavity and the supply duct; e) moving the shutter device to the second closing position of the suction duct; f) activating the furnace pressurizing means so as to fill the mold cavity with liquid metal from the furnace in the absence of air; g) moving the shutter device to the third closing position of the supply duct; h) actuating the forging actuator so as to move the forging male to the lowered forging position; i) opening the mold;1) carrying out the extraction of the forged object.

13. The method according to claim 12, wherein in step d) , the air suction is carried out so as to prevent the metal contained in the furnace from rising back into the supply duct until it reaches the mold cavity.

14. The method according to claim 12 or 13, wherein the upper half-mold comprises at least one radial carriage, and wherein:- before step c) , the at least one radial carriage is closed so as to form, with the forging male, a portion of the mold cavity;- in step c) of closing the mold, the at least one radial carriage abuts against the lower half-mold;- in step h) , the forging male moves axially with respect to the at least one radial carriage.

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